• Re: power supply discharge

    From legg@21:1/5 to All on Sat Sep 28 09:46:39 2024
    On Fri, 27 Sep 2024 10:01:30 -0700, john larkin <jl@glen--canyon.com>
    wrote:

    On Fri, 27 Sep 2024 16:17:42 +0100, liz@poppyrecords.invalid.invalid
    (Liz Tuddenham) wrote:

    john larkin <JL@gct.com> wrote:

    Given a benchtop power supply, you can turn the voltage up and then
    down, and it goes down. Most have a substantial amount of output
    capacitance, and can be driving an external cap too. So something
    pulls the output down.

    I guess that there are no standards for this, but I've never seen a
    supply that just hangs high when it's cranked down.

    I'm designing some programmable multi-channel power suplies and that
    is one of many tangled issues in the project.

    A DC-coupled audio amplifier chip might work as a fully-controllable >>bi-directional power supply if your current and voltage requirements
    were fairly modest. They have the advantage of being relatively cheap, >>well-protected and very fast (by power supply standards). Some of them >>have the tab at input earth voltage, so they don't require isolation
    from the heat sink.

    Unfortunately, it has to be a switching regulator.

    and this is a surprise because . . . . ?

    RL

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  • From legg@21:1/5 to john larkin on Sat Sep 28 09:44:44 2024
    On Fri, 27 Sep 2024 08:07:29 -0700, john larkin <JL@gct.com> wrote:


    Given a benchtop power supply, you can turn the voltage up and then
    down, and it goes down. Most have a substantial amount of output
    capacitance, and can be driving an external cap too. So something
    pulls the output down.

    I guess that there are no standards for this, but I've never seen a
    supply that just hangs high when it's cranked down.

    I'm designing some programmable multi-channel power suplies and that
    is one of many tangled issues in the project.

    Twiddling the adjustment knob on a bench supply doesn't
    represent a dramatic change - and most adjustible
    supplies don't load their output terminals with a
    lot of capacitance.

    DC coupled programable supplies, or bipolar programmable
    supplies are made to drive loads in the first and third
    quadrants.

    There are issues in the second and fourth quadrants, where
    the supply is expected to absorb power.

    An amplifier driving a pure reactance experiences the same
    losses as driving a dead short.

    RL

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Jan Panteltje@21:1/5 to clive@nowaytoday.co.uk on Sat Sep 28 14:54:54 2024
    On a sunny day (Sat, 28 Sep 2024 15:28:01 +0100) it happened Clive Arthur <clive@nowaytoday.co.uk> wrote in <vd93ph$19pt8$1@dont-email.me>:

    On 27/09/2024 16:07, john larkin wrote:

    Given a benchtop power supply, you can turn the voltage up and then
    down, and it goes down. Most have a substantial amount of output
    capacitance, and can be driving an external cap too. So something
    pulls the output down.

    I guess that there are no standards for this, but I've never seen a
    supply that just hangs high when it's cranked down.

    I'm designing some programmable multi-channel power suplies and that
    is one of many tangled issues in the project.

    My ancient Farnell bench supply has a voltage adjustment pot and moving
    coil voltmeters. The 'up' speed is much quicker than the 'down' speed.

    Same yor my home designed benchtop supply
    Discharge, with no load, (voltage of the output cap) is via the output voltage sensing resistors,
    slower than the charge.
    https://panteltje.nl/panteltje/pic/pwr_pic/power_box_diagram_img_1817.jpg
    https://panteltje.nl/panteltje/pic/pwr_pic/
    Been working great since 2010, used every day,
    also to charge all sort of batteries.

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  • From Clive Arthur@21:1/5 to john larkin on Sat Sep 28 15:28:01 2024
    On 27/09/2024 16:07, john larkin wrote:

    Given a benchtop power supply, you can turn the voltage up and then
    down, and it goes down. Most have a substantial amount of output
    capacitance, and can be driving an external cap too. So something
    pulls the output down.

    I guess that there are no standards for this, but I've never seen a
    supply that just hangs high when it's cranked down.

    I'm designing some programmable multi-channel power suplies and that
    is one of many tangled issues in the project.

    My ancient Farnell bench supply has a voltage adjustment pot and moving
    coil voltmeters. The 'up' speed is much quicker than the 'down' speed.

    --
    Cheers
    Clive

    --- SoupGate-Win32 v1.05
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  • From john larkin@21:1/5 to All on Sat Sep 28 09:13:42 2024
    On Sat, 28 Sep 2024 15:50:44 +0800, Sylvia Else <sylvia@email.invalid>
    wrote:

    On 28-Sept-24 1:00 am, john larkin wrote:
    On Fri, 27 Sep 2024 23:50:21 +0800, Sylvia Else <sylvia@email.invalid>
    wrote:

    On 27-Sept-24 11:07 pm, john larkin wrote:

    Given a benchtop power supply, you can turn the voltage up and then
    down, and it goes down. Most have a substantial amount of output
    capacitance, and can be driving an external cap too. So something
    pulls the output down.

    I guess that there are no standards for this, but I've never seen a
    supply that just hangs high when it's cranked down.

    I'm designing some programmable multi-channel power suplies and that
    is one of many tangled issues in the project.


    Be easy enough to sink current when the output voltage exceeds the set
    point by more than, say, 0.1V.

    But there has to be a limit - connect the PS to your fully charged car
    battery, and set the PS to 10V, and you're not going to see a 10V output >>> any time soon.

    Sylvia.

    Right, the load could be a battery. The user could set the output
    voltage high with some current limit to charge the battery (or some
    giant capacitor), and then set the voltage low.

    What's complicating my life is that the regulator is a half-bridge
    switcher that, in that case, becomes a boost converter, pumping
    backwards into my bulk power supply, which could then blow up. Or if
    the control loop cranks the PWM duty cycle down to zero in a futile
    attempt to reduce the output voltage, it soon shorts the battery.

    Or some yahoo could connect the battery backwards.

    This is actually a nice multidimensional dilemma. I'll be using the
    DRV8962 quad half-bridge, which also constrains things.

    As usual with data sheets, it isn't entirely clear.







    An even more extreme example of two PS connected together with different
    set points shows that no general solution exists, even in theory.

    Yes, a channel-channel short is possible, especially when a pair of half-bridges drive a bidirectional motor coil.


    So it's down to requirements and specifications.

    I am making those up as we go along, but I'd like to make the product
    as good as I reasonably can.



    The reversed polarity battery case is I think usually handled with a
    diode and fuse. The controller can then email a manager pointing out
    that someone needs to be fired.

    Sylvia.

    The TI quad half-bridge has substrate diodes to ground, so a series
    polyfuse may handle the reverse yahoo connection. I'll try that. I'll
    need a gigantic power supply.

    I suppose I should buy the worst series inductor that will work, to
    limit the surge current.

    I'll post some schematic scribbles as it goes along.

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From john larkin@21:1/5 to legg on Sat Sep 28 09:03:01 2024
    On Sat, 28 Sep 2024 09:46:39 -0400, legg <legg@nospam.magma.ca> wrote:

    On Fri, 27 Sep 2024 10:01:30 -0700, john larkin <jl@glen--canyon.com>
    wrote:

    On Fri, 27 Sep 2024 16:17:42 +0100, liz@poppyrecords.invalid.invalid
    (Liz Tuddenham) wrote:

    john larkin <JL@gct.com> wrote:

    Given a benchtop power supply, you can turn the voltage up and then
    down, and it goes down. Most have a substantial amount of output
    capacitance, and can be driving an external cap too. So something
    pulls the output down.

    I guess that there are no standards for this, but I've never seen a
    supply that just hangs high when it's cranked down.

    I'm designing some programmable multi-channel power suplies and that
    is one of many tangled issues in the project.

    A DC-coupled audio amplifier chip might work as a fully-controllable >>>bi-directional power supply if your current and voltage requirements
    were fairly modest. They have the advantage of being relatively cheap, >>>well-protected and very fast (by power supply standards). Some of them >>>have the tab at input earth voltage, so they don't require isolation
    from the heat sink.

    Unfortunately, it has to be a switching regulator.

    and this is a surprise because . . . . ?

    RL

    We always appreciate your valuable insights.

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Bill Sloman@21:1/5 to john larkin on Sun Sep 29 02:19:41 2024
    On 29/09/2024 2:03 am, john larkin wrote:
    On Sat, 28 Sep 2024 09:46:39 -0400, legg <legg@nospam.magma.ca> wrote:

    On Fri, 27 Sep 2024 10:01:30 -0700, john larkin <jl@glen--canyon.com>
    wrote:

    On Fri, 27 Sep 2024 16:17:42 +0100, liz@poppyrecords.invalid.invalid
    (Liz Tuddenham) wrote:

    john larkin <JL@gct.com> wrote:

    Given a benchtop power supply, you can turn the voltage up and then
    down, and it goes down. Most have a substantial amount of output
    capacitance, and can be driving an external cap too. So something
    pulls the output down.

    I guess that there are no standards for this, but I've never seen a
    supply that just hangs high when it's cranked down.

    I'm designing some programmable multi-channel power suplies and that >>>>> is one of many tangled issues in the project.

    A DC-coupled audio amplifier chip might work as a fully-controllable
    bi-directional power supply if your current and voltage requirements
    were fairly modest. They have the advantage of being relatively cheap, >>>> well-protected and very fast (by power supply standards). Some of them >>>> have the tab at input earth voltage, so they don't require isolation
    from the heat sink.

    Unfortunately, it has to be a switching regulator.

    and this is a surprise because . . . . ?

    We always appreciate your valuable insights.

    Don't bother trying to be sarcastic - your language skills aren't up to it.

    --
    Bill Sloman, Sydney

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Bill Sloman@21:1/5 to john larkin on Sun Sep 29 02:31:09 2024
    On 29/09/2024 2:13 am, john larkin wrote:
    On Sat, 28 Sep 2024 15:50:44 +0800, Sylvia Else <sylvia@email.invalid>
    wrote:

    On 28-Sept-24 1:00 am, john larkin wrote:
    On Fri, 27 Sep 2024 23:50:21 +0800, Sylvia Else <sylvia@email.invalid>
    wrote:

    On 27-Sept-24 11:07 pm, john larkin wrote:

    Given a benchtop power supply, you can turn the voltage up and then
    down, and it goes down. Most have a substantial amount of output
    capacitance, and can be driving an external cap too. So something
    pulls the output down.

    I guess that there are no standards for this, but I've never seen a
    supply that just hangs high when it's cranked down.

    I'm designing some programmable multi-channel power suplies and that >>>>> is one of many tangled issues in the project.


    Be easy enough to sink current when the output voltage exceeds the set >>>> point by more than, say, 0.1V.

    But there has to be a limit - connect the PS to your fully charged car >>>> battery, and set the PS to 10V, and you're not going to see a 10V output >>>> any time soon.

    Sylvia.

    Right, the load could be a battery. The user could set the output
    voltage high with some current limit to charge the battery (or some
    giant capacitor), and then set the voltage low.

    What's complicating my life is that the regulator is a half-bridge
    switcher that, in that case, becomes a boost converter, pumping
    backwards into my bulk power supply, which could then blow up. Or if
    the control loop cranks the PWM duty cycle down to zero in a futile
    attempt to reduce the output voltage, it soon shorts the battery.

    Or some yahoo could connect the battery backwards.

    This is actually a nice multidimensional dilemma. I'll be using the
    DRV8962 quad half-bridge, which also constrains things.

    As usual with data sheets, it isn't entirely clear.







    An even more extreme example of two PS connected together with different
    set points shows that no general solution exists, even in theory.

    Yes, a channel-channel short is possible, especially when a pair of half-bridges drive a bidirectional motor coil.


    So it's down to requirements and specifications.

    I am making those up as we go along, but I'd like to make the product
    as good as I reasonably can.

    You usually end up with a better result if you work out what you are
    trying to do before you start designing it - or in your case, slinging
    it together. It's called system engineering.

    When dim newbies post here, we often have to ask them what they are
    trying to do before we can work out how they might solve the problem
    they think they are seeing.

    The reversed polarity battery case is I think usually handled with a
    diode and fuse. The controller can then email a manager pointing out
    that someone needs to be fired.

    The TI quad half-bridge has substrate diodes to ground, so a series
    polyfuse may handle the reverse yahoo connection. I'll try that. I'll
    need a gigantic power supply.

    I suppose I should buy the worst series inductor that will work, to
    limit the surge current.

    By "worst" do you mean cheapest or smallest?

    I'll post some schematic scribbles as it goes along.

    LTSpice simulations tend to include the kind of information that gets
    left out of your pencil sketches.

    --
    Bill Sloman, Sydney

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  • From john larkin@21:1/5 to legg on Sat Sep 28 10:21:46 2024
    On Sat, 28 Sep 2024 09:44:44 -0400, legg <legg@nospam.magma.ca> wrote:

    On Fri, 27 Sep 2024 08:07:29 -0700, john larkin <JL@gct.com> wrote:


    Given a benchtop power supply, you can turn the voltage up and then
    down, and it goes down. Most have a substantial amount of output >>capacitance, and can be driving an external cap too. So something
    pulls the output down.

    I guess that there are no standards for this, but I've never seen a
    supply that just hangs high when it's cranked down.

    I'm designing some programmable multi-channel power suplies and that
    is one of many tangled issues in the project.

    Twiddling the adjustment knob on a bench supply doesn't
    represent a dramatic change - and most adjustible
    supplies don't load their output terminals with a
    lot of capacitance.

    I've measured a few, and got output terminal capacitance of a few
    hundred to maybe 2000 uF.

    People here might measure some random power supplies. I leave them off
    and connect to a 50 ohm sinewave-output function generator and find
    the -3 dB point. One could use a square wave and scope the slopes too.
    Keeping the amplitude low will avoid turning semi junctions on.

    A square wave source driving a cap illustrates C, ESR, and ESL on a
    scope. C-meters don't usually separate the components so trend to lie, especially with big electrolytics.


    DC coupled programable supplies, or bipolar programmable
    supplies are made to drive loads in the first and third
    quadrants.

    There are issues in the second and fourth quadrants, where
    the supply is expected to absorb power.

    An amplifier driving a pure reactance experiences the same
    losses as driving a dead short.

    I don't understand that. An audio amp driving a 1 pF cap or a 1K
    henry inductor would surely cause less amp losses than a short.

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From KevinJ93@21:1/5 to legg on Sat Sep 28 11:56:52 2024
    On 9/28/24 6:44 AM, legg wrote:
    On Fri, 27 Sep 2024 08:07:29 -0700, john larkin <JL@gct.com> wrote:


    Given a benchtop power supply, you can turn the voltage up and then
    down, and it goes down. Most have a substantial amount of output
    capacitance, and can be driving an external cap too. So something
    pulls the output down.

    I guess that there are no standards for this, but I've never seen a
    supply that just hangs high when it's cranked down.

    I'm designing some programmable multi-channel power suplies and that
    is one of many tangled issues in the project.

    Twiddling the adjustment knob on a bench supply doesn't
    represent a dramatic change - and most adjustible
    supplies don't load their output terminals with a
    lot of capacitance.

    DC coupled programable supplies, or bipolar programmable
    supplies are made to drive loads in the first and third
    quadrants.

    There are issues in the second and fourth quadrants, where
    the supply is expected to absorb power.

    An amplifier driving a pure reactance experiences the same
    losses as driving a dead short.

    RL

    Some specialist power supplies for large scale battery testing can
    absorb power and return it to the AC supply.

    https://eepower.com/tech-insights/regenerative-power-supplies-create-lots-of-energy-at-electronica/#

    kw

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From piglet@21:1/5 to john larkin on Sat Sep 28 18:25:47 2024
    john larkin <JL@gct.com> wrote:
    On Sat, 28 Sep 2024 09:44:44 -0400, legg <legg@nospam.magma.ca> wrote:

    On Fri, 27 Sep 2024 08:07:29 -0700, john larkin <JL@gct.com> wrote:


    Given a benchtop power supply, you can turn the voltage up and then
    down, and it goes down. Most have a substantial amount of output
    capacitance, and can be driving an external cap too. So something
    pulls the output down.

    I guess that there are no standards for this, but I've never seen a
    supply that just hangs high when it's cranked down.

    I'm designing some programmable multi-channel power suplies and that
    is one of many tangled issues in the project.

    Twiddling the adjustment knob on a bench supply doesn't
    represent a dramatic change - and most adjustible
    supplies don't load their output terminals with a
    lot of capacitance.

    I've measured a few, and got output terminal capacitance of a few
    hundred to maybe 2000 uF.

    People here might measure some random power supplies. I leave them off
    and connect to a 50 ohm sinewave-output function generator and find
    the -3 dB point. One could use a square wave and scope the slopes too. Keeping the amplitude low will avoid turning semi junctions on.

    A square wave source driving a cap illustrates C, ESR, and ESL on a
    scope. C-meters don't usually separate the components so trend to lie, especially with big electrolytics.


    DC coupled programable supplies, or bipolar programmable
    supplies are made to drive loads in the first and third
    quadrants.

    There are issues in the second and fourth quadrants, where
    the supply is expected to absorb power.

    An amplifier driving a pure reactance experiences the same
    losses as driving a dead short.

    I don't understand that. An audio amp driving a 1 pF cap or a 1K
    henry inductor would surely cause less amp losses than a short.



    Good bench power supplies should have minimal built in output capacitance;
    it compromises current limit performance. Anyone wanting supply decoupling
    caps on their test load is going to have them already at the load side
    anyhow.

    I am a fan of the HP / Harrison Labs supplies of 1960s that have no output
    caps and are stable.

    --
    piglet

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  • From Joerg@21:1/5 to john larkin on Sat Sep 28 22:28:07 2024
    On 9/27/24 8:07 AM, john larkin wrote:

    Given a benchtop power supply, you can turn the voltage up and then
    down, and it goes down. Most have a substantial amount of output
    capacitance, and can be driving an external cap too. So something
    pulls the output down.


    Often the only internal load is the resistive divider for the regulator
    loop feedback.


    I guess that there are no standards for this, but I've never seen a
    supply that just hangs high when it's cranked down.


    I have some. They drop very slowly when there isn't much load on the output.


    I'm designing some programmable multi-channel power suplies and that
    is one of many tangled issues in the project.


    A synchronous buck architecture should work quite well if you need to
    slew fast. I've used that on a driver that had to modulate a hard
    capacitive load at several kHz and above 100V.

    --
    Regards, Joerg

    http://www.analogconsultants.com/

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  • From legg@21:1/5 to All on Sun Sep 29 09:14:42 2024
    On Sat, 28 Sep 2024 11:56:52 -0700, KevinJ93 <kevin_es@whitedigs.com>
    wrote:

    On 9/28/24 6:44 AM, legg wrote:
    On Fri, 27 Sep 2024 08:07:29 -0700, john larkin <JL@gct.com> wrote:


    Given a benchtop power supply, you can turn the voltage up and then
    down, and it goes down. Most have a substantial amount of output
    capacitance, and can be driving an external cap too. So something
    pulls the output down.

    I guess that there are no standards for this, but I've never seen a
    supply that just hangs high when it's cranked down.

    I'm designing some programmable multi-channel power suplies and that
    is one of many tangled issues in the project.

    Twiddling the adjustment knob on a bench supply doesn't
    represent a dramatic change - and most adjustible
    supplies don't load their output terminals with a
    lot of capacitance.

    DC coupled programable supplies, or bipolar programmable
    supplies are made to drive loads in the first and third
    quadrants.

    There are issues in the second and fourth quadrants, where
    the supply is expected to absorb power.

    An amplifier driving a pure reactance experiences the same
    losses as driving a dead short.

    RL

    Some specialist power supplies for large scale battery testing can
    absorb power and return it to the AC supply.

    https://eepower.com/tech-insights/regenerative-power-supplies-create-lots-of-energy-at-electronica/#

    kw

    It's always made more sense in power test gear, if
    you can afford it. It's a penny-pinching part of
    the industry.

    In the loading case, you don't end up contributing much to
    the line, you just draw net losses from processing, so no
    complications for hydro.

    For PV or other energy sources - it's a negotiation that's
    dependent on local supplier and contracted regs.

    RL

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From legg@21:1/5 to john larkin on Sun Sep 29 09:20:56 2024
    On Sat, 28 Sep 2024 10:21:46 -0700, john larkin <JL@gct.com> wrote:

    On Sat, 28 Sep 2024 09:44:44 -0400, legg <legg@nospam.magma.ca> wrote:

    On Fri, 27 Sep 2024 08:07:29 -0700, john larkin <JL@gct.com> wrote:


    Given a benchtop power supply, you can turn the voltage up and then
    down, and it goes down. Most have a substantial amount of output >>>capacitance, and can be driving an external cap too. So something
    pulls the output down.

    I guess that there are no standards for this, but I've never seen a >>>supply that just hangs high when it's cranked down.

    I'm designing some programmable multi-channel power suplies and that
    is one of many tangled issues in the project.

    Twiddling the adjustment knob on a bench supply doesn't
    represent a dramatic change - and most adjustible
    supplies don't load their output terminals with a
    lot of capacitance.

    I've measured a few, and got output terminal capacitance of a few
    hundred to maybe 2000 uF.

    People here might measure some random power supplies. I leave them off
    and connect to a 50 ohm sinewave-output function generator and find
    the -3 dB point. One could use a square wave and scope the slopes too. >Keeping the amplitude low will avoid turning semi junctions on.

    A square wave source driving a cap illustrates C, ESR, and ESL on a
    scope. C-meters don't usually separate the components so trend to lie, >especially with big electrolytics.


    DC coupled programable supplies, or bipolar programmable
    supplies are made to drive loads in the first and third
    quadrants.

    There are issues in the second and fourth quadrants, where
    the supply is expected to absorb power.

    An amplifier driving a pure reactance experiences the same
    losses as driving a dead short.

    I don't understand that. An audio amp driving a 1 pF cap or a 1K
    henry inductor would surely cause less amp losses than a short.

    Capacitors and inductors are as 'short' as their reactance allows.

    Just don't be surprised when it happens - that's all I'm saying.

    RL

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From legg@21:1/5 to erichpwagner@hotmail.com on Sun Sep 29 09:34:42 2024
    On Sat, 28 Sep 2024 18:25:47 -0000 (UTC), piglet
    <erichpwagner@hotmail.com> wrote:

    john larkin <JL@gct.com> wrote:
    On Sat, 28 Sep 2024 09:44:44 -0400, legg <legg@nospam.magma.ca> wrote:

    On Fri, 27 Sep 2024 08:07:29 -0700, john larkin <JL@gct.com> wrote:


    Given a benchtop power supply, you can turn the voltage up and then
    down, and it goes down. Most have a substantial amount of output
    capacitance, and can be driving an external cap too. So something
    pulls the output down.

    I guess that there are no standards for this, but I've never seen a
    supply that just hangs high when it's cranked down.

    I'm designing some programmable multi-channel power suplies and that
    is one of many tangled issues in the project.

    Twiddling the adjustment knob on a bench supply doesn't
    represent a dramatic change - and most adjustible
    supplies don't load their output terminals with a
    lot of capacitance.

    I've measured a few, and got output terminal capacitance of a few
    hundred to maybe 2000 uF.

    People here might measure some random power supplies. I leave them off
    and connect to a 50 ohm sinewave-output function generator and find
    the -3 dB point. One could use a square wave and scope the slopes too.
    Keeping the amplitude low will avoid turning semi junctions on.

    A square wave source driving a cap illustrates C, ESR, and ESL on a
    scope. C-meters don't usually separate the components so trend to lie,
    especially with big electrolytics.


    DC coupled programable supplies, or bipolar programmable
    supplies are made to drive loads in the first and third
    quadrants.

    There are issues in the second and fourth quadrants, where
    the supply is expected to absorb power.

    An amplifier driving a pure reactance experiences the same
    losses as driving a dead short.

    I don't understand that. An audio amp driving a 1 pF cap or a 1K
    henry inductor would surely cause less amp losses than a short.



    Good bench power supplies should have minimal built in output capacitance;
    it compromises current limit performance. Anyone wanting supply decoupling >caps on their test load is going to have them already at the load side >anyhow.

    I am a fan of the HP / Harrison Labs supplies of 1960s that have no output >caps and are stable.

    That goes without saying for linears. SMPAs are increasingly low-cap
    as the conversion frequencies rise.

    Smaller switching amps - think mp3 portables - don't bother filtering
    anything, they juat figure the load will do it for them.

    The $2 regulators from offshore are a role of the dice (or carefull
    visual inspection), whether an output filter is there, or not. Some of
    the cheapest even expect a common + rail.

    I've seen unfiltered high power stuff that lets a lossy LF isolation transformer do the job, but you shouldn't be able to smell (or hear)
    a power supply in operation, if it's properly designed.

    Another instance of 'Why Can't I Do That'.

    You WERE saying 'good', so I expect you're in a different ball park.

    RL

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From john larkin@21:1/5 to erichpwagner@hotmail.com on Sun Sep 29 08:14:09 2024
    On Sat, 28 Sep 2024 18:25:47 -0000 (UTC), piglet
    <erichpwagner@hotmail.com> wrote:

    john larkin <JL@gct.com> wrote:
    On Sat, 28 Sep 2024 09:44:44 -0400, legg <legg@nospam.magma.ca> wrote:

    On Fri, 27 Sep 2024 08:07:29 -0700, john larkin <JL@gct.com> wrote:


    Given a benchtop power supply, you can turn the voltage up and then
    down, and it goes down. Most have a substantial amount of output
    capacitance, and can be driving an external cap too. So something
    pulls the output down.

    I guess that there are no standards for this, but I've never seen a
    supply that just hangs high when it's cranked down.

    I'm designing some programmable multi-channel power suplies and that
    is one of many tangled issues in the project.

    Twiddling the adjustment knob on a bench supply doesn't
    represent a dramatic change - and most adjustible
    supplies don't load their output terminals with a
    lot of capacitance.

    I've measured a few, and got output terminal capacitance of a few
    hundred to maybe 2000 uF.

    People here might measure some random power supplies. I leave them off
    and connect to a 50 ohm sinewave-output function generator and find
    the -3 dB point. One could use a square wave and scope the slopes too.
    Keeping the amplitude low will avoid turning semi junctions on.

    A square wave source driving a cap illustrates C, ESR, and ESL on a
    scope. C-meters don't usually separate the components so trend to lie,
    especially with big electrolytics.


    DC coupled programable supplies, or bipolar programmable
    supplies are made to drive loads in the first and third
    quadrants.

    There are issues in the second and fourth quadrants, where
    the supply is expected to absorb power.

    An amplifier driving a pure reactance experiences the same
    losses as driving a dead short.

    I don't understand that. An audio amp driving a 1 pF cap or a 1K
    henry inductor would surely cause less amp losses than a short.



    Good bench power supplies should have minimal built in output capacitance;
    it compromises current limit performance. Anyone wanting supply decoupling >caps on their test load is going to have them already at the load side >anyhow.

    I am a fan of the HP / Harrison Labs supplies of 1960s that have no output >caps and are stable.

    One of he big linear HP supplies has a few thousand uF at its output,
    and a barrier strip that allows another 5 or 10K more, internal, to be
    strapped in.

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From john larkin@21:1/5 to All on Sun Sep 29 08:23:01 2024
    On Sat, 28 Sep 2024 22:28:07 -0700, Joerg <news@analogconsultants.com>
    wrote:

    On 9/27/24 8:07 AM, john larkin wrote:

    Given a benchtop power supply, you can turn the voltage up and then
    down, and it goes down. Most have a substantial amount of output
    capacitance, and can be driving an external cap too. So something
    pulls the output down.


    Often the only internal load is the resistive divider for the regulator
    loop feedback.


    I guess that there are no standards for this, but I've never seen a
    supply that just hangs high when it's cranked down.


    I have some. They drop very slowly when there isn't much load on the output.

    Customers might whine if they ask for 10 volts and see 30. Amd that
    may be mostly held up by their capacitive load.



    I'm designing some programmable multi-channel power suplies and that
    is one of many tangled issues in the project.


    A synchronous buck architecture should work quite well if you need to
    slew fast. I've used that on a driver that had to modulate a hard
    capacitive load at several kHz and above 100V.

    I'm doing some multichannel non-isolated supplies that will be sync
    buck, using multiple TI DRV8962 chips.

    One problem is that a sync buck can become a boost in the wrong
    direction, and start charging my +48 supply. If it hits, say, 55
    volts, I'll disable the switcher chips, and the outputs can hang. I
    need to discharge the outputs. I'm thinking about 20 mA of depletion
    fet per channel.

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From john larkin@21:1/5 to john larkin on Sun Sep 29 10:21:25 2024
    On Sat, 28 Sep 2024 10:21:46 -0700, john larkin <JL@gct.com> wrote:

    On Sat, 28 Sep 2024 09:44:44 -0400, legg <legg@nospam.magma.ca> wrote:

    On Fri, 27 Sep 2024 08:07:29 -0700, john larkin <JL@gct.com> wrote:


    Given a benchtop power supply, you can turn the voltage up and then
    down, and it goes down. Most have a substantial amount of output >>>capacitance, and can be driving an external cap too. So something
    pulls the output down.

    I guess that there are no standards for this, but I've never seen a >>>supply that just hangs high when it's cranked down.

    I'm designing some programmable multi-channel power suplies and that
    is one of many tangled issues in the project.

    Twiddling the adjustment knob on a bench supply doesn't
    represent a dramatic change - and most adjustible
    supplies don't load their output terminals with a
    lot of capacitance.

    I've measured a few, and got output terminal capacitance of a few
    hundred to maybe 2000 uF.

    People here might measure some random power supplies. I leave them off
    and connect to a 50 ohm sinewave-output function generator and find
    the -3 dB point. One could use a square wave and scope the slopes too. >Keeping the amplitude low will avoid turning semi junctions on.

    Come on guys, quit pontificating and start measuring.

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Sylvia Else@21:1/5 to john larkin on Mon Sep 30 18:42:08 2024
    On 30-Sept-24 1:21 am, john larkin wrote:
    On Sat, 28 Sep 2024 10:21:46 -0700, john larkin <JL@gct.com> wrote:

    On Sat, 28 Sep 2024 09:44:44 -0400, legg <legg@nospam.magma.ca> wrote:

    On Fri, 27 Sep 2024 08:07:29 -0700, john larkin <JL@gct.com> wrote:


    Given a benchtop power supply, you can turn the voltage up and then
    down, and it goes down. Most have a substantial amount of output
    capacitance, and can be driving an external cap too. So something
    pulls the output down.

    I guess that there are no standards for this, but I've never seen a
    supply that just hangs high when it's cranked down.

    I'm designing some programmable multi-channel power suplies and that
    is one of many tangled issues in the project.

    Twiddling the adjustment knob on a bench supply doesn't
    represent a dramatic change - and most adjustible
    supplies don't load their output terminals with a
    lot of capacitance.

    I've measured a few, and got output terminal capacitance of a few
    hundred to maybe 2000 uF.

    People here might measure some random power supplies. I leave them off
    and connect to a 50 ohm sinewave-output function generator and find
    the -3 dB point. One could use a square wave and scope the slopes too.
    Keeping the amplitude low will avoid turning semi junctions on.

    Come on guys, quit pontificating and start measuring.


    At this stage in the process, you seem to have some odd constraints. Why
    the specific h-bridge driver? Why non-isolated?

    Sylvia.

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From legg@21:1/5 to john larkin on Mon Sep 30 08:39:27 2024
    On Sun, 29 Sep 2024 08:23:01 -0700, john larkin <JL@gct.com> wrote:

    On Sat, 28 Sep 2024 22:28:07 -0700, Joerg <news@analogconsultants.com>
    wrote:

    On 9/27/24 8:07 AM, john larkin wrote:

    Given a benchtop power supply, you can turn the voltage up and then
    down, and it goes down. Most have a substantial amount of output
    capacitance, and can be driving an external cap too. So something
    pulls the output down.


    Often the only internal load is the resistive divider for the regulator >>loop feedback.


    I guess that there are no standards for this, but I've never seen a
    supply that just hangs high when it's cranked down.


    I have some. They drop very slowly when there isn't much load on the output.

    Customers might whine if they ask for 10 volts and see 30. Amd that
    may be mostly held up by their capacitive load.



    I'm designing some programmable multi-channel power suplies and that
    is one of many tangled issues in the project.


    A synchronous buck architecture should work quite well if you need to
    slew fast. I've used that on a driver that had to modulate a hard >>capacitive load at several kHz and above 100V.

    I'm doing some multichannel non-isolated supplies that will be sync
    buck, using multiple TI DRV8962 chips.

    One problem is that a sync buck can become a boost in the wrong
    direction, and start charging my +48 supply. If it hits, say, 55
    volts, I'll disable the switcher chips, and the outputs can hang. I
    need to discharge the outputs. I'm thinking about 20 mA of depletion
    fet per channel.

    You might consider overvoltage protection or a (switched ?)
    internal minimum load.There's usuaally some point in the
    control loop that's a good indicator of a pull-down requirement.
    A single ovp or autoload on the input looks likely to serve
    all of your many sync-bucks.

    RL

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From legg@21:1/5 to john larkin on Mon Sep 30 08:59:39 2024
    On Sat, 28 Sep 2024 09:03:01 -0700, john larkin <JL@gct.com> wrote:

    On Sat, 28 Sep 2024 09:46:39 -0400, legg <legg@nospam.magma.ca> wrote:

    On Fri, 27 Sep 2024 10:01:30 -0700, john larkin <jl@glen--canyon.com> >>wrote:

    On Fri, 27 Sep 2024 16:17:42 +0100, liz@poppyrecords.invalid.invalid
    (Liz Tuddenham) wrote:

    john larkin <JL@gct.com> wrote:

    Given a benchtop power supply, you can turn the voltage up and then
    down, and it goes down. Most have a substantial amount of output
    capacitance, and can be driving an external cap too. So something
    pulls the output down.

    I guess that there are no standards for this, but I've never seen a
    supply that just hangs high when it's cranked down.

    I'm designing some programmable multi-channel power suplies and that >>>>> is one of many tangled issues in the project.

    A DC-coupled audio amplifier chip might work as a fully-controllable >>>>bi-directional power supply if your current and voltage requirements >>>>were fairly modest. They have the advantage of being relatively cheap, >>>>well-protected and very fast (by power supply standards). Some of them >>>>have the tab at input earth voltage, so they don't require isolation >>>>from the heat sink.

    Unfortunately, it has to be a switching regulator.

    and this is a surprise because . . . . ?

    RL waveform

    We always appreciate your valuable insights.

    There are certain configurations of self-driven sync rectifier -
    gate drive supplied by actual transformer terminals being
    rectified - that will self-oscillate with no input, when output
    power is present. This pumps output power back through the
    isolation barrier and can be a bitch when parallel redundancy
    is attempted without orring diodes.

    - so your situation is not only present in actively driven
    sync rectifiers.

    Reversible power transfer, however, is not always a curse.
    You just have to be aware of the possibility and make sure
    that it's not actually unsafe to your hardware.

    It can be usefull.

    RL

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From legg@21:1/5 to john larkin on Mon Sep 30 09:14:20 2024
    On Sat, 28 Sep 2024 09:03:01 -0700, john larkin <JL@gct.com> wrote:

    On Sat, 28 Sep 2024 09:46:39 -0400, legg <legg@nospam.magma.ca> wrote:

    On Fri, 27 Sep 2024 10:01:30 -0700, john larkin <jl@glen--canyon.com> >>wrote:

    On Fri, 27 Sep 2024 16:17:42 +0100, liz@poppyrecords.invalid.invalid
    (Liz Tuddenham) wrote:

    john larkin <JL@gct.com> wrote:

    Given a benchtop power supply, you can turn the voltage up and then
    down, and it goes down. Most have a substantial amount of output
    capacitance, and can be driving an external cap too. So something
    pulls the output down.

    I guess that there are no standards for this, but I've never seen a
    supply that just hangs high when it's cranked down.

    I'm designing some programmable multi-channel power suplies and that >>>>> is one of many tangled issues in the project.

    A DC-coupled audio amplifier chip might work as a fully-controllable >>>>bi-directional power supply if your current and voltage requirements >>>>were fairly modest. They have the advantage of being relatively cheap, >>>>well-protected and very fast (by power supply standards). Some of them >>>>have the tab at input earth voltage, so they don't require isolation >>>>from the heat sink.

    Unfortunately, it has to be a switching regulator.

    and this is a surprise because . . . . ?

    RL

    We always appreciate your valuable insights.

    http://ve3ute.ca/query/sync_rec_self-driven.jpg

    RL

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From john larkin@21:1/5 to All on Mon Sep 30 08:33:42 2024
    On Mon, 30 Sep 2024 18:42:08 +0800, Sylvia Else <sylvia@email.invalid>
    wrote:

    On 30-Sept-24 1:21 am, john larkin wrote:
    On Sat, 28 Sep 2024 10:21:46 -0700, john larkin <JL@gct.com> wrote:

    On Sat, 28 Sep 2024 09:44:44 -0400, legg <legg@nospam.magma.ca> wrote:

    On Fri, 27 Sep 2024 08:07:29 -0700, john larkin <JL@gct.com> wrote:


    Given a benchtop power supply, you can turn the voltage up and then
    down, and it goes down. Most have a substantial amount of output
    capacitance, and can be driving an external cap too. So something
    pulls the output down.

    I guess that there are no standards for this, but I've never seen a
    supply that just hangs high when it's cranked down.

    I'm designing some programmable multi-channel power suplies and that >>>>> is one of many tangled issues in the project.

    Twiddling the adjustment knob on a bench supply doesn't
    represent a dramatic change - and most adjustible
    supplies don't load their output terminals with a
    lot of capacitance.

    I've measured a few, and got output terminal capacitance of a few
    hundred to maybe 2000 uF.

    People here might measure some random power supplies. I leave them off
    and connect to a 50 ohm sinewave-output function generator and find
    the -3 dB point. One could use a square wave and scope the slopes too.
    Keeping the amplitude low will avoid turning semi junctions on.

    Come on guys, quit pontificating and start measuring.


    At this stage in the process, you seem to have some odd constraints. Why
    the specific h-bridge driver? Why non-isolated?

    Sylvia.

    What I suggested is that a few people grab their bench power supplies
    and see what sort of output capacitance they have.

    The simplest way is to crank the voltage up and short the ouput and
    see how much it sparks. Or measure the capacitance, even.

    That quad TI driver is cheap and available and seems to have good
    protections. TI makes good stuff and keeps it in production
    approximately forever.

    Non-isolated because that's simple and gets more channels on a small
    board. The launch customer says that power supplies don't usually need
    to be grounded because everything is grounded on an airplane.

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From john larkin@21:1/5 to legg on Mon Sep 30 11:24:16 2024
    On Mon, 30 Sep 2024 08:39:27 -0400, legg <legg@nospam.magma.ca> wrote:

    On Sun, 29 Sep 2024 08:23:01 -0700, john larkin <JL@gct.com> wrote:

    On Sat, 28 Sep 2024 22:28:07 -0700, Joerg <news@analogconsultants.com> >>wrote:

    On 9/27/24 8:07 AM, john larkin wrote:

    Given a benchtop power supply, you can turn the voltage up and then
    down, and it goes down. Most have a substantial amount of output
    capacitance, and can be driving an external cap too. So something
    pulls the output down.


    Often the only internal load is the resistive divider for the regulator >>>loop feedback.


    I guess that there are no standards for this, but I've never seen a
    supply that just hangs high when it's cranked down.


    I have some. They drop very slowly when there isn't much load on the output. >>
    Customers might whine if they ask for 10 volts and see 30. Amd that
    may be mostly held up by their capacitive load.



    I'm designing some programmable multi-channel power suplies and that
    is one of many tangled issues in the project.


    A synchronous buck architecture should work quite well if you need to >>>slew fast. I've used that on a driver that had to modulate a hard >>>capacitive load at several kHz and above 100V.

    I'm doing some multichannel non-isolated supplies that will be sync
    buck, using multiple TI DRV8962 chips.

    One problem is that a sync buck can become a boost in the wrong
    direction, and start charging my +48 supply. If it hits, say, 55
    volts, I'll disable the switcher chips, and the outputs can hang. I
    need to discharge the outputs. I'm thinking about 20 mA of depletion
    fet per channel.

    You might consider overvoltage protection or a (switched ?)
    internal minimum load.There's usuaally some point in the
    control loop that's a good indicator of a pull-down requirement.
    A single ovp or autoload on the input looks likely to serve
    all of your many sync-bucks.

    RL

    An MOV on the bulk supply could limit the reverse-pump excursion until
    the software can notice and shut things down.

    MOVs can gobble a lot of joules, but their clipping is very soggy.

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Joerg@21:1/5 to john larkin on Mon Sep 30 11:49:54 2024
    On 9/30/24 11:24 AM, john larkin wrote:
    On Mon, 30 Sep 2024 08:39:27 -0400, legg <legg@nospam.magma.ca> wrote:

    On Sun, 29 Sep 2024 08:23:01 -0700, john larkin <JL@gct.com> wrote:

    On Sat, 28 Sep 2024 22:28:07 -0700, Joerg <news@analogconsultants.com>
    wrote:

    On 9/27/24 8:07 AM, john larkin wrote:

    Given a benchtop power supply, you can turn the voltage up and then
    down, and it goes down. Most have a substantial amount of output
    capacitance, and can be driving an external cap too. So something
    pulls the output down.


    Often the only internal load is the resistive divider for the regulator >>>> loop feedback.


    I guess that there are no standards for this, but I've never seen a
    supply that just hangs high when it's cranked down.


    I have some. They drop very slowly when there isn't much load on the output.

    Customers might whine if they ask for 10 volts and see 30. Amd that
    may be mostly held up by their capacitive load.



    I'm designing some programmable multi-channel power suplies and that >>>>> is one of many tangled issues in the project.


    A synchronous buck architecture should work quite well if you need to
    slew fast. I've used that on a driver that had to modulate a hard
    capacitive load at several kHz and above 100V.

    I'm doing some multichannel non-isolated supplies that will be sync
    buck, using multiple TI DRV8962 chips.

    One problem is that a sync buck can become a boost in the wrong
    direction, and start charging my +48 supply. If it hits, say, 55
    volts, I'll disable the switcher chips, and the outputs can hang. I
    need to discharge the outputs. I'm thinking about 20 mA of depletion
    fet per channel.

    You might consider overvoltage protection or a (switched ?)
    internal minimum load.There's usuaally some point in the
    control loop that's a good indicator of a pull-down requirement.
    A single ovp or autoload on the input looks likely to serve
    all of your many sync-bucks.

    RL

    An MOV on the bulk supply could limit the reverse-pump excursion until
    the software can notice and shut things down.

    MOVs can gobble a lot of joules, but their clipping is very soggy.


    MOVs are usually cumulative. They can take a certain amount of
    dissipation over their lifetime and then *PHUT* ... POOOF. Like a bank
    account that runs dry.

    --
    Regards, Joerg

    http://www.analogconsultants.com/

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From john larkin@21:1/5 to All on Mon Sep 30 18:49:14 2024
    On Mon, 30 Sep 2024 11:49:54 -0700, Joerg <news@analogconsultants.com>
    wrote:

    On 9/30/24 11:24 AM, john larkin wrote:
    On Mon, 30 Sep 2024 08:39:27 -0400, legg <legg@nospam.magma.ca> wrote:

    On Sun, 29 Sep 2024 08:23:01 -0700, john larkin <JL@gct.com> wrote:

    On Sat, 28 Sep 2024 22:28:07 -0700, Joerg <news@analogconsultants.com> >>>> wrote:

    On 9/27/24 8:07 AM, john larkin wrote:

    Given a benchtop power supply, you can turn the voltage up and then >>>>>> down, and it goes down. Most have a substantial amount of output
    capacitance, and can be driving an external cap too. So something
    pulls the output down.


    Often the only internal load is the resistive divider for the regulator >>>>> loop feedback.


    I guess that there are no standards for this, but I've never seen a >>>>>> supply that just hangs high when it's cranked down.


    I have some. They drop very slowly when there isn't much load on the output.

    Customers might whine if they ask for 10 volts and see 30. Amd that
    may be mostly held up by their capacitive load.



    I'm designing some programmable multi-channel power suplies and that >>>>>> is one of many tangled issues in the project.


    A synchronous buck architecture should work quite well if you need to >>>>> slew fast. I've used that on a driver that had to modulate a hard
    capacitive load at several kHz and above 100V.

    I'm doing some multichannel non-isolated supplies that will be sync
    buck, using multiple TI DRV8962 chips.

    One problem is that a sync buck can become a boost in the wrong
    direction, and start charging my +48 supply. If it hits, say, 55
    volts, I'll disable the switcher chips, and the outputs can hang. I
    need to discharge the outputs. I'm thinking about 20 mA of depletion
    fet per channel.

    You might consider overvoltage protection or a (switched ?)
    internal minimum load.There's usuaally some point in the
    control loop that's a good indicator of a pull-down requirement.
    A single ovp or autoload on the input looks likely to serve
    all of your many sync-bucks.

    RL

    An MOV on the bulk supply could limit the reverse-pump excursion until
    the software can notice and shut things down.

    MOVs can gobble a lot of joules, but their clipping is very soggy.


    MOVs are usually cumulative. They can take a certain amount of
    dissipation over their lifetime and then *PHUT* ... POOOF. Like a bank >account that runs dry.

    What kills MOVs? Integrated joules? Time-temperature?

    I don't expect a lot of joules per event. Just enough energy to keep
    my supply voltage down until a slowish ADC and the software can shut
    the buck switchers down. 15 milliseconds max, maybe.

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Jan Panteltje@21:1/5 to JL@gct.com on Tue Oct 1 06:35:35 2024
    On a sunny day (Mon, 30 Sep 2024 08:33:42 -0700) it happened john larkin <JL@gct.com> wrote in <1rglfj5jebk56bmbna6udrb9trr666uotm@4ax.com>:

    On Mon, 30 Sep 2024 18:42:08 +0800, Sylvia Else <sylvia@email.invalid>
    wrote:

    On 30-Sept-24 1:21 am, john larkin wrote:
    On Sat, 28 Sep 2024 10:21:46 -0700, john larkin <JL@gct.com> wrote:

    On Sat, 28 Sep 2024 09:44:44 -0400, legg <legg@nospam.magma.ca> wrote: >>>>
    On Fri, 27 Sep 2024 08:07:29 -0700, john larkin <JL@gct.com> wrote:


    Given a benchtop power supply, you can turn the voltage up and then >>>>>> down, and it goes down. Most have a substantial amount of output
    capacitance, and can be driving an external cap too. So something
    pulls the output down.

    I guess that there are no standards for this, but I've never seen a >>>>>> supply that just hangs high when it's cranked down.

    I'm designing some programmable multi-channel power suplies and that >>>>>> is one of many tangled issues in the project.

    Twiddling the adjustment knob on a bench supply doesn't
    represent a dramatic change - and most adjustible
    supplies don't load their output terminals with a
    lot of capacitance.

    I've measured a few, and got output terminal capacitance of a few
    hundred to maybe 2000 uF.

    People here might measure some random power supplies. I leave them off >>>> and connect to a 50 ohm sinewave-output function generator and find
    the -3 dB point. One could use a square wave and scope the slopes too. >>>> Keeping the amplitude low will avoid turning semi junctions on.

    Come on guys, quit pontificating and start measuring.


    At this stage in the process, you seem to have some odd constraints. Why >>the specific h-bridge driver? Why non-isolated?

    Sylvia.

    What I suggested is that a few people grab their bench power supplies
    and see what sort of output capacitance they have.

    The simplest way is to crank the voltage up and short the ouput and
    see how much it sparks. Or measure the capacitance, even.

    That quad TI driver is cheap and available and seems to have good >protections. TI makes good stuff and keeps it in production
    approximately forever.

    Non-isolated because that's simple and gets more channels on a small
    board. The launch customer says that power supplies don't usually need
    to be grounded because everything is grounded on an airplane.

    Was watching one of thse 'Mayday' series on German TV yesterday.
    Airplane got hit by lightning, ball ligtning travelled through the cabin, pilots bllided and distracted, did not hear the auto pilot still engaged warning
    started fighting the auto-pilot...
    almost crashed
    Normally auto pilots would dis-engage when you started manual steering Indicator between auto pilot 'on' and auto-pilot 'off'
    was color change from green to white symbol on the instrumenrts that looked like this
    AP<

    Miracle they could see anything after the lightning strike, green and white are very close togeter
    for teevee white is .11 blue .59 green and .3 red.
    Something to take into account if you are writing display code.
    Do you?
    no credits...

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From john larkin@21:1/5 to All on Tue Oct 1 07:53:16 2024
    On Tue, 01 Oct 2024 06:35:35 GMT, Jan Panteltje <alien@comet.invalid>
    wrote:

    On a sunny day (Mon, 30 Sep 2024 08:33:42 -0700) it happened john larkin ><JL@gct.com> wrote in <1rglfj5jebk56bmbna6udrb9trr666uotm@4ax.com>:

    On Mon, 30 Sep 2024 18:42:08 +0800, Sylvia Else <sylvia@email.invalid> >>wrote:

    On 30-Sept-24 1:21 am, john larkin wrote:
    On Sat, 28 Sep 2024 10:21:46 -0700, john larkin <JL@gct.com> wrote:

    On Sat, 28 Sep 2024 09:44:44 -0400, legg <legg@nospam.magma.ca> wrote: >>>>>
    On Fri, 27 Sep 2024 08:07:29 -0700, john larkin <JL@gct.com> wrote: >>>>>>

    Given a benchtop power supply, you can turn the voltage up and then >>>>>>> down, and it goes down. Most have a substantial amount of output >>>>>>> capacitance, and can be driving an external cap too. So something >>>>>>> pulls the output down.

    I guess that there are no standards for this, but I've never seen a >>>>>>> supply that just hangs high when it's cranked down.

    I'm designing some programmable multi-channel power suplies and that >>>>>>> is one of many tangled issues in the project.

    Twiddling the adjustment knob on a bench supply doesn't
    represent a dramatic change - and most adjustible
    supplies don't load their output terminals with a
    lot of capacitance.

    I've measured a few, and got output terminal capacitance of a few
    hundred to maybe 2000 uF.

    People here might measure some random power supplies. I leave them off >>>>> and connect to a 50 ohm sinewave-output function generator and find
    the -3 dB point. One could use a square wave and scope the slopes too. >>>>> Keeping the amplitude low will avoid turning semi junctions on.

    Come on guys, quit pontificating and start measuring.


    At this stage in the process, you seem to have some odd constraints. Why >>>the specific h-bridge driver? Why non-isolated?

    Sylvia.

    What I suggested is that a few people grab their bench power supplies
    and see what sort of output capacitance they have.

    The simplest way is to crank the voltage up and short the ouput and
    see how much it sparks. Or measure the capacitance, even.

    That quad TI driver is cheap and available and seems to have good >>protections. TI makes good stuff and keeps it in production
    approximately forever.

    Non-isolated because that's simple and gets more channels on a small
    board. The launch customer says that power supplies don't usually need
    to be grounded because everything is grounded on an airplane.

    Was watching one of thse 'Mayday' series on German TV yesterday.
    Airplane got hit by lightning, ball ligtning travelled through the cabin, >pilots bllided and distracted, did not hear the auto pilot still engaged warning
    started fighting the auto-pilot...
    almost crashed
    Normally auto pilots would dis-engage when you started manual steering >Indicator between auto pilot 'on' and auto-pilot 'off'
    was color change from green to white symbol on the instrumenrts that looked like this
    AP<

    Miracle they could see anything after the lightning strike, green and white are very close togeter
    for teevee white is .11 blue .59 green and .3 red.
    Something to take into account if you are writing display code.
    Do you?
    no credits...


    I am thinking that nobody here actually has a power supply.

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Joe Gwinn@21:1/5 to john larkin on Tue Oct 1 11:24:34 2024
    On Mon, 30 Sep 2024 18:49:14 -0700, john larkin <JL@gct.com> wrote:

    On Mon, 30 Sep 2024 11:49:54 -0700, Joerg <news@analogconsultants.com>
    wrote:

    On 9/30/24 11:24 AM, john larkin wrote:
    On Mon, 30 Sep 2024 08:39:27 -0400, legg <legg@nospam.magma.ca> wrote:

    On Sun, 29 Sep 2024 08:23:01 -0700, john larkin <JL@gct.com> wrote:

    On Sat, 28 Sep 2024 22:28:07 -0700, Joerg <news@analogconsultants.com> >>>>> wrote:

    On 9/27/24 8:07 AM, john larkin wrote:

    Given a benchtop power supply, you can turn the voltage up and then >>>>>>> down, and it goes down. Most have a substantial amount of output >>>>>>> capacitance, and can be driving an external cap too. So something >>>>>>> pulls the output down.


    Often the only internal load is the resistive divider for the regulator >>>>>> loop feedback.


    I guess that there are no standards for this, but I've never seen a >>>>>>> supply that just hangs high when it's cranked down.


    I have some. They drop very slowly when there isn't much load on the output.

    Customers might whine if they ask for 10 volts and see 30. Amd that
    may be mostly held up by their capacitive load.



    I'm designing some programmable multi-channel power suplies and that >>>>>>> is one of many tangled issues in the project.


    A synchronous buck architecture should work quite well if you need to >>>>>> slew fast. I've used that on a driver that had to modulate a hard
    capacitive load at several kHz and above 100V.

    I'm doing some multichannel non-isolated supplies that will be sync
    buck, using multiple TI DRV8962 chips.

    One problem is that a sync buck can become a boost in the wrong
    direction, and start charging my +48 supply. If it hits, say, 55
    volts, I'll disable the switcher chips, and the outputs can hang. I
    need to discharge the outputs. I'm thinking about 20 mA of depletion >>>>> fet per channel.

    You might consider overvoltage protection or a (switched ?)
    internal minimum load.There's usuaally some point in the
    control loop that's a good indicator of a pull-down requirement.
    A single ovp or autoload on the input looks likely to serve
    all of your many sync-bucks.

    RL

    An MOV on the bulk supply could limit the reverse-pump excursion until
    the software can notice and shut things down.

    MOVs can gobble a lot of joules, but their clipping is very soggy.


    MOVs are usually cumulative. They can take a certain amount of
    dissipation over their lifetime and then *PHUT* ... POOOF. Like a bank >>account that runs dry.

    What kills MOVs? Integrated joules? Time-temperature?

    I don't expect a lot of joules per event. Just enough energy to keep
    my supply voltage down until a slowish ADC and the software can shut
    the buck switchers down. 15 milliseconds max, maybe.

    I think it's integrated joules per cubic centimeter of the MOV
    material. This is discussed in the literature on MOVs for protecting line-powered equipment from pulse overvoltages, such as from nearby
    lightning strikes. <https://www.deltala.com/>

    Joe Gwinn

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From john larkin@21:1/5 to All on Tue Oct 1 09:59:27 2024
    On Tue, 01 Oct 2024 11:24:34 -0400, Joe Gwinn <joegwinn@comcast.net>
    wrote:

    On Mon, 30 Sep 2024 18:49:14 -0700, john larkin <JL@gct.com> wrote:

    On Mon, 30 Sep 2024 11:49:54 -0700, Joerg <news@analogconsultants.com> >>wrote:

    On 9/30/24 11:24 AM, john larkin wrote:
    On Mon, 30 Sep 2024 08:39:27 -0400, legg <legg@nospam.magma.ca> wrote: >>>>
    On Sun, 29 Sep 2024 08:23:01 -0700, john larkin <JL@gct.com> wrote:

    On Sat, 28 Sep 2024 22:28:07 -0700, Joerg <news@analogconsultants.com> >>>>>> wrote:

    On 9/27/24 8:07 AM, john larkin wrote:

    Given a benchtop power supply, you can turn the voltage up and then >>>>>>>> down, and it goes down. Most have a substantial amount of output >>>>>>>> capacitance, and can be driving an external cap too. So something >>>>>>>> pulls the output down.


    Often the only internal load is the resistive divider for the regulator >>>>>>> loop feedback.


    I guess that there are no standards for this, but I've never seen a >>>>>>>> supply that just hangs high when it's cranked down.


    I have some. They drop very slowly when there isn't much load on the output.

    Customers might whine if they ask for 10 volts and see 30. Amd that >>>>>> may be mostly held up by their capacitive load.



    I'm designing some programmable multi-channel power suplies and that >>>>>>>> is one of many tangled issues in the project.


    A synchronous buck architecture should work quite well if you need to >>>>>>> slew fast. I've used that on a driver that had to modulate a hard >>>>>>> capacitive load at several kHz and above 100V.

    I'm doing some multichannel non-isolated supplies that will be sync >>>>>> buck, using multiple TI DRV8962 chips.

    One problem is that a sync buck can become a boost in the wrong
    direction, and start charging my +48 supply. If it hits, say, 55
    volts, I'll disable the switcher chips, and the outputs can hang. I >>>>>> need to discharge the outputs. I'm thinking about 20 mA of depletion >>>>>> fet per channel.

    You might consider overvoltage protection or a (switched ?)
    internal minimum load.There's usuaally some point in the
    control loop that's a good indicator of a pull-down requirement.
    A single ovp or autoload on the input looks likely to serve
    all of your many sync-bucks.

    RL

    An MOV on the bulk supply could limit the reverse-pump excursion until >>>> the software can notice and shut things down.

    MOVs can gobble a lot of joules, but their clipping is very soggy.


    MOVs are usually cumulative. They can take a certain amount of >>>dissipation over their lifetime and then *PHUT* ... POOOF. Like a bank >>>account that runs dry.

    What kills MOVs? Integrated joules? Time-temperature?

    I don't expect a lot of joules per event. Just enough energy to keep
    my supply voltage down until a slowish ADC and the software can shut
    the buck switchers down. 15 milliseconds max, maybe.

    I think it's integrated joules per cubic centimeter of the MOV
    material. This is discussed in the literature on MOVs for protecting >line-powered equipment from pulse overvoltages, such as from nearby
    lightning strikes. <https://www.deltala.com/>

    Joe Gwinn

    Makes sense. It looks like most MOV appnotes assume that it's across
    an AC line, with kilo-amps available. Or lightning bolts.

    I'll get a few and test them at much lower loads.

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Joe Gwinn@21:1/5 to All on Tue Oct 1 16:03:40 2024
    On Tue, 01 Oct 2024 09:59:27 -0700, john larkin <jl@glen--canyon.com>
    wrote:

    On Tue, 01 Oct 2024 11:24:34 -0400, Joe Gwinn <joegwinn@comcast.net>
    wrote:

    On Mon, 30 Sep 2024 18:49:14 -0700, john larkin <JL@gct.com> wrote:

    On Mon, 30 Sep 2024 11:49:54 -0700, Joerg <news@analogconsultants.com> >>>wrote:

    On 9/30/24 11:24 AM, john larkin wrote:
    On Mon, 30 Sep 2024 08:39:27 -0400, legg <legg@nospam.magma.ca> wrote: >>>>>
    On Sun, 29 Sep 2024 08:23:01 -0700, john larkin <JL@gct.com> wrote: >>>>>>
    On Sat, 28 Sep 2024 22:28:07 -0700, Joerg <news@analogconsultants.com> >>>>>>> wrote:

    On 9/27/24 8:07 AM, john larkin wrote:

    Given a benchtop power supply, you can turn the voltage up and then >>>>>>>>> down, and it goes down. Most have a substantial amount of output >>>>>>>>> capacitance, and can be driving an external cap too. So something >>>>>>>>> pulls the output down.


    Often the only internal load is the resistive divider for the regulator
    loop feedback.


    I guess that there are no standards for this, but I've never seen a >>>>>>>>> supply that just hangs high when it's cranked down.


    I have some. They drop very slowly when there isn't much load on the output.

    Customers might whine if they ask for 10 volts and see 30. Amd that >>>>>>> may be mostly held up by their capacitive load.



    I'm designing some programmable multi-channel power suplies and that >>>>>>>>> is one of many tangled issues in the project.


    A synchronous buck architecture should work quite well if you need to >>>>>>>> slew fast. I've used that on a driver that had to modulate a hard >>>>>>>> capacitive load at several kHz and above 100V.

    I'm doing some multichannel non-isolated supplies that will be sync >>>>>>> buck, using multiple TI DRV8962 chips.

    One problem is that a sync buck can become a boost in the wrong
    direction, and start charging my +48 supply. If it hits, say, 55 >>>>>>> volts, I'll disable the switcher chips, and the outputs can hang. I >>>>>>> need to discharge the outputs. I'm thinking about 20 mA of depletion >>>>>>> fet per channel.

    You might consider overvoltage protection or a (switched ?)
    internal minimum load.There's usuaally some point in the
    control loop that's a good indicator of a pull-down requirement.
    A single ovp or autoload on the input looks likely to serve
    all of your many sync-bucks.

    RL

    An MOV on the bulk supply could limit the reverse-pump excursion until >>>>> the software can notice and shut things down.

    MOVs can gobble a lot of joules, but their clipping is very soggy.


    MOVs are usually cumulative. They can take a certain amount of >>>>dissipation over their lifetime and then *PHUT* ... POOOF. Like a bank >>>>account that runs dry.

    What kills MOVs? Integrated joules? Time-temperature?

    I don't expect a lot of joules per event. Just enough energy to keep
    my supply voltage down until a slowish ADC and the software can shut
    the buck switchers down. 15 milliseconds max, maybe.

    I think it's integrated joules per cubic centimeter of the MOV
    material. This is discussed in the literature on MOVs for protecting >>line-powered equipment from pulse overvoltages, such as from nearby >>lightning strikes. <https://www.deltala.com/>

    Joe Gwinn

    Makes sense. It looks like most MOV appnotes assume that it's across
    an AC line, with kilo-amps available. Or lightning bolts.

    I'll get a few and test them at much lower loads.

    For smaller MOVs, I think that the data sheet specifies capacity in
    Joules. I bet this is the max integrated dose, not the pre-event
    limit. Well, the one-event limit as well.

    Joe Gwinn

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From john larkin@21:1/5 to All on Tue Oct 1 14:00:50 2024
    On Tue, 01 Oct 2024 16:03:40 -0400, Joe Gwinn <joegwinn@comcast.net>
    wrote:

    On Tue, 01 Oct 2024 09:59:27 -0700, john larkin <jl@glen--canyon.com>
    wrote:

    On Tue, 01 Oct 2024 11:24:34 -0400, Joe Gwinn <joegwinn@comcast.net>
    wrote:

    On Mon, 30 Sep 2024 18:49:14 -0700, john larkin <JL@gct.com> wrote:

    On Mon, 30 Sep 2024 11:49:54 -0700, Joerg <news@analogconsultants.com> >>>>wrote:

    On 9/30/24 11:24 AM, john larkin wrote:
    On Mon, 30 Sep 2024 08:39:27 -0400, legg <legg@nospam.magma.ca> wrote: >>>>>>
    On Sun, 29 Sep 2024 08:23:01 -0700, john larkin <JL@gct.com> wrote: >>>>>>>
    On Sat, 28 Sep 2024 22:28:07 -0700, Joerg <news@analogconsultants.com> >>>>>>>> wrote:

    On 9/27/24 8:07 AM, john larkin wrote:

    Given a benchtop power supply, you can turn the voltage up and then >>>>>>>>>> down, and it goes down. Most have a substantial amount of output >>>>>>>>>> capacitance, and can be driving an external cap too. So something >>>>>>>>>> pulls the output down.


    Often the only internal load is the resistive divider for the regulator
    loop feedback.


    I guess that there are no standards for this, but I've never seen a >>>>>>>>>> supply that just hangs high when it's cranked down.


    I have some. They drop very slowly when there isn't much load on the output.

    Customers might whine if they ask for 10 volts and see 30. Amd that >>>>>>>> may be mostly held up by their capacitive load.



    I'm designing some programmable multi-channel power suplies and that >>>>>>>>>> is one of many tangled issues in the project.


    A synchronous buck architecture should work quite well if you need to >>>>>>>>> slew fast. I've used that on a driver that had to modulate a hard >>>>>>>>> capacitive load at several kHz and above 100V.

    I'm doing some multichannel non-isolated supplies that will be sync >>>>>>>> buck, using multiple TI DRV8962 chips.

    One problem is that a sync buck can become a boost in the wrong >>>>>>>> direction, and start charging my +48 supply. If it hits, say, 55 >>>>>>>> volts, I'll disable the switcher chips, and the outputs can hang. I >>>>>>>> need to discharge the outputs. I'm thinking about 20 mA of depletion >>>>>>>> fet per channel.

    You might consider overvoltage protection or a (switched ?)
    internal minimum load.There's usuaally some point in the
    control loop that's a good indicator of a pull-down requirement. >>>>>>> A single ovp or autoload on the input looks likely to serve
    all of your many sync-bucks.

    RL

    An MOV on the bulk supply could limit the reverse-pump excursion until >>>>>> the software can notice and shut things down.

    MOVs can gobble a lot of joules, but their clipping is very soggy. >>>>>>

    MOVs are usually cumulative. They can take a certain amount of >>>>>dissipation over their lifetime and then *PHUT* ... POOOF. Like a bank >>>>>account that runs dry.

    What kills MOVs? Integrated joules? Time-temperature?

    I don't expect a lot of joules per event. Just enough energy to keep
    my supply voltage down until a slowish ADC and the software can shut >>>>the buck switchers down. 15 milliseconds max, maybe.

    I think it's integrated joules per cubic centimeter of the MOV
    material. This is discussed in the literature on MOVs for protecting >>>line-powered equipment from pulse overvoltages, such as from nearby >>>lightning strikes. <https://www.deltala.com/>

    Joe Gwinn

    Makes sense. It looks like most MOV appnotes assume that it's across
    an AC line, with kilo-amps available. Or lightning bolts.

    I'll get a few and test them at much lower loads.

    For smaller MOVs, I think that the data sheet specifies capacity in
    Joules. I bet this is the max integrated dose, not the pre-event
    limit. Well, the one-event limit as well.

    Joe Gwinn

    That's probably a single-shot rating, such as to limit the peak
    temperature. So that can be done many times, if it cools off between
    shots.

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Joe Gwinn@21:1/5 to All on Tue Oct 1 17:57:35 2024
    On Tue, 01 Oct 2024 14:00:50 -0700, john larkin <jl@glen--canyon.com>
    wrote:

    On Tue, 01 Oct 2024 16:03:40 -0400, Joe Gwinn <joegwinn@comcast.net>
    wrote:

    On Tue, 01 Oct 2024 09:59:27 -0700, john larkin <jl@glen--canyon.com> >>wrote:

    On Tue, 01 Oct 2024 11:24:34 -0400, Joe Gwinn <joegwinn@comcast.net> >>>wrote:

    On Mon, 30 Sep 2024 18:49:14 -0700, john larkin <JL@gct.com> wrote:

    On Mon, 30 Sep 2024 11:49:54 -0700, Joerg <news@analogconsultants.com> >>>>>wrote:

    On 9/30/24 11:24 AM, john larkin wrote:
    On Mon, 30 Sep 2024 08:39:27 -0400, legg <legg@nospam.magma.ca> wrote: >>>>>>>
    On Sun, 29 Sep 2024 08:23:01 -0700, john larkin <JL@gct.com> wrote: >>>>>>>>
    On Sat, 28 Sep 2024 22:28:07 -0700, Joerg <news@analogconsultants.com>
    wrote:

    On 9/27/24 8:07 AM, john larkin wrote:

    Given a benchtop power supply, you can turn the voltage up and then >>>>>>>>>>> down, and it goes down. Most have a substantial amount of output >>>>>>>>>>> capacitance, and can be driving an external cap too. So something >>>>>>>>>>> pulls the output down.


    Often the only internal load is the resistive divider for the regulator
    loop feedback.


    I guess that there are no standards for this, but I've never seen a >>>>>>>>>>> supply that just hangs high when it's cranked down.


    I have some. They drop very slowly when there isn't much load on the output.

    Customers might whine if they ask for 10 volts and see 30. Amd that >>>>>>>>> may be mostly held up by their capacitive load.



    I'm designing some programmable multi-channel power suplies and that
    is one of many tangled issues in the project.


    A synchronous buck architecture should work quite well if you need to
    slew fast. I've used that on a driver that had to modulate a hard >>>>>>>>>> capacitive load at several kHz and above 100V.

    I'm doing some multichannel non-isolated supplies that will be sync >>>>>>>>> buck, using multiple TI DRV8962 chips.

    One problem is that a sync buck can become a boost in the wrong >>>>>>>>> direction, and start charging my +48 supply. If it hits, say, 55 >>>>>>>>> volts, I'll disable the switcher chips, and the outputs can hang. I >>>>>>>>> need to discharge the outputs. I'm thinking about 20 mA of depletion >>>>>>>>> fet per channel.

    You might consider overvoltage protection or a (switched ?)
    internal minimum load.There's usuaally some point in the
    control loop that's a good indicator of a pull-down requirement. >>>>>>>> A single ovp or autoload on the input looks likely to serve
    all of your many sync-bucks.

    RL

    An MOV on the bulk supply could limit the reverse-pump excursion until >>>>>>> the software can notice and shut things down.

    MOVs can gobble a lot of joules, but their clipping is very soggy. >>>>>>>

    MOVs are usually cumulative. They can take a certain amount of >>>>>>dissipation over their lifetime and then *PHUT* ... POOOF. Like a bank >>>>>>account that runs dry.

    What kills MOVs? Integrated joules? Time-temperature?

    I don't expect a lot of joules per event. Just enough energy to keep >>>>>my supply voltage down until a slowish ADC and the software can shut >>>>>the buck switchers down. 15 milliseconds max, maybe.

    I think it's integrated joules per cubic centimeter of the MOV >>>>material. This is discussed in the literature on MOVs for protecting >>>>line-powered equipment from pulse overvoltages, such as from nearby >>>>lightning strikes. <https://www.deltala.com/>

    Joe Gwinn

    Makes sense. It looks like most MOV appnotes assume that it's across
    an AC line, with kilo-amps available. Or lightning bolts.

    I'll get a few and test them at much lower loads.

    For smaller MOVs, I think that the data sheet specifies capacity in
    Joules. I bet this is the max integrated dose, not the pre-event
    limit. Well, the one-event limit as well.

    Joe Gwinn

    That's probably a single-shot rating, such as to limit the peak
    temperature. So that can be done many times, if it cools off between
    shots.

    In traditional MOVs, I think that there are two limits, max single
    pulse and integral of all pulses to date, with some variations as to
    pulse width. I have these in my house, in the AC power panel.

    For the Delta Lightning Silicon Oxide limiters, they don't seem to
    wear out all that fast, or at all. Maybe time to replace those old
    arrestors in the power panel.

    Joe Gwinn

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Jan Panteltje@21:1/5 to JL@gct.com on Wed Oct 2 06:09:58 2024
    On a sunny day (Tue, 01 Oct 2024 07:53:16 -0700) it happened john larkin <JL@gct.com> wrote in <953ofj1n321ooo3s5ocqq0vd6lhssh49vn@4ax.com>:

    On Tue, 01 Oct 2024 06:35:35 GMT, Jan Panteltje <alien@comet.invalid>
    wrote:

    On a sunny day (Mon, 30 Sep 2024 08:33:42 -0700) it happened john larkin >><JL@gct.com> wrote in <1rglfj5jebk56bmbna6udrb9trr666uotm@4ax.com>:

    On Mon, 30 Sep 2024 18:42:08 +0800, Sylvia Else <sylvia@email.invalid> >>>wrote:

    On 30-Sept-24 1:21 am, john larkin wrote:
    On Sat, 28 Sep 2024 10:21:46 -0700, john larkin <JL@gct.com> wrote:

    On Sat, 28 Sep 2024 09:44:44 -0400, legg <legg@nospam.magma.ca> wrote: >>>>>>
    On Fri, 27 Sep 2024 08:07:29 -0700, john larkin <JL@gct.com> wrote: >>>>>>>

    Given a benchtop power supply, you can turn the voltage up and then >>>>>>>> down, and it goes down. Most have a substantial amount of output >>>>>>>> capacitance, and can be driving an external cap too. So something >>>>>>>> pulls the output down.

    I guess that there are no standards for this, but I've never seen a >>>>>>>> supply that just hangs high when it's cranked down.

    I'm designing some programmable multi-channel power suplies and that >>>>>>>> is one of many tangled issues in the project.

    Twiddling the adjustment knob on a bench supply doesn't
    represent a dramatic change - and most adjustible
    supplies don't load their output terminals with a
    lot of capacitance.

    I've measured a few, and got output terminal capacitance of a few
    hundred to maybe 2000 uF.

    People here might measure some random power supplies. I leave them off >>>>>> and connect to a 50 ohm sinewave-output function generator and find >>>>>> the -3 dB point. One could use a square wave and scope the slopes too. >>>>>> Keeping the amplitude low will avoid turning semi junctions on.

    Come on guys, quit pontificating and start measuring.


    At this stage in the process, you seem to have some odd constraints. Why >>>>the specific h-bridge driver? Why non-isolated?

    Sylvia.

    What I suggested is that a few people grab their bench power supplies
    and see what sort of output capacitance they have.

    The simplest way is to crank the voltage up and short the ouput and
    see how much it sparks. Or measure the capacitance, even.

    That quad TI driver is cheap and available and seems to have good >>>protections. TI makes good stuff and keeps it in production
    approximately forever.

    Non-isolated because that's simple and gets more channels on a small >>>board. The launch customer says that power supplies don't usually need
    to be grounded because everything is grounded on an airplane.

    Was watching one of thse 'Mayday' series on German TV yesterday.
    Airplane got hit by lightning, ball ligtning travelled through the cabin, >>pilots bllided and distracted, did not hear the auto pilot still engaged warning
    started fighting the auto-pilot...
    almost crashed
    Normally auto pilots would dis-engage when you started manual steering >>Indicator between auto pilot 'on' and auto-pilot 'off'
    was color change from green to white symbol on the instrumenrts that looked like this
    AP<

    Miracle they could see anything after the lightning strike, green and white are very close togeter
    for teevee white is .11 blue .59 green and .3 red.
    Something to take into account if you are writing display code.
    Do you?
    no credits...


    I am thinking that nobody here actually has a power supply.

    Na, have so many in many projects,,\
    Not even mentioning all the wallwarts :-)
    I happen to remebmer you use those too to be free from mains rules ..
    CE !

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Jan Panteltje@21:1/5 to joegwinn@comcast.net on Wed Oct 2 06:17:31 2024
    On a sunny day (Tue, 01 Oct 2024 11:24:34 -0400) it happened Joe Gwinn <joegwinn@comcast.net> wrote in <kj4ofj56re4nl4h6qses2erq6fdgl6gbj7@4ax.com>:

    On Mon, 30 Sep 2024 18:49:14 -0700, john larkin <JL@gct.com> wrote:

    On Mon, 30 Sep 2024 11:49:54 -0700, Joerg <news@analogconsultants.com> >>wrote:

    On 9/30/24 11:24 AM, john larkin wrote:
    On Mon, 30 Sep 2024 08:39:27 -0400, legg <legg@nospam.magma.ca> wrote: >>>>
    On Sun, 29 Sep 2024 08:23:01 -0700, john larkin <JL@gct.com> wrote:

    On Sat, 28 Sep 2024 22:28:07 -0700, Joerg <news@analogconsultants.com> >>>>>> wrote:

    On 9/27/24 8:07 AM, john larkin wrote:

    Given a benchtop power supply, you can turn the voltage up and then >>>>>>>> down, and it goes down. Most have a substantial amount of output >>>>>>>> capacitance, and can be driving an external cap too. So something >>>>>>>> pulls the output down.


    Often the only internal load is the resistive divider for the regulator >>>>>>> loop feedback.


    I guess that there are no standards for this, but I've never seen a >>>>>>>> supply that just hangs high when it's cranked down.


    I have some. They drop very slowly when there isn't much load on the output.

    Customers might whine if they ask for 10 volts and see 30. Amd that >>>>>> may be mostly held up by their capacitive load.



    I'm designing some programmable multi-channel power suplies and that >>>>>>>> is one of many tangled issues in the project.


    A synchronous buck architecture should work quite well if you need to >>>>>>> slew fast. I've used that on a driver that had to modulate a hard >>>>>>> capacitive load at several kHz and above 100V.

    I'm doing some multichannel non-isolated supplies that will be sync >>>>>> buck, using multiple TI DRV8962 chips.

    One problem is that a sync buck can become a boost in the wrong
    direction, and start charging my +48 supply. If it hits, say, 55
    volts, I'll disable the switcher chips, and the outputs can hang. I >>>>>> need to discharge the outputs. I'm thinking about 20 mA of depletion >>>>>> fet per channel.

    You might consider overvoltage protection or a (switched ?)
    internal minimum load.There's usuaally some point in the
    control loop that's a good indicator of a pull-down requirement.
    A single ovp or autoload on the input looks likely to serve
    all of your many sync-bucks.

    RL

    An MOV on the bulk supply could limit the reverse-pump excursion until >>>> the software can notice and shut things down.

    MOVs can gobble a lot of joules, but their clipping is very soggy.


    MOVs are usually cumulative. They can take a certain amount of >>>dissipation over their lifetime and then *PHUT* ... POOOF. Like a bank >>>account that runs dry.

    What kills MOVs? Integrated joules? Time-temperature?

    I don't expect a lot of joules per event. Just enough energy to keep
    my supply voltage down until a slowish ADC and the software can shut
    the buck switchers down. 15 milliseconds max, maybe.

    I think it's integrated joules per cubic centimeter of the MOV
    material. This is discussed in the literature on MOVs for protecting >line-powered equipment from pulse overvoltages, such as from nearby
    lightning strikes. <https://www.deltala.com/>

    Joe Gwinn

    Protects my washer:
    https://panteltje.nl/pub/mains_protector_IXIMG_0501.JPG
    https://panteltje.nl/pub/main_protector_IXIMG_0503.JPG
    VDRs with spark gaps.

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From legg@21:1/5 to john larkin on Wed Oct 2 08:10:50 2024
    On Tue, 01 Oct 2024 07:53:16 -0700, john larkin <JL@gct.com> wrote:

    On Tue, 01 Oct 2024 06:35:35 GMT, Jan Panteltje <alien@comet.invalid>
    wrote:

    On a sunny day (Mon, 30 Sep 2024 08:33:42 -0700) it happened john larkin >><JL@gct.com> wrote in <1rglfj5jebk56bmbna6udrb9trr666uotm@4ax.com>:

    On Mon, 30 Sep 2024 18:42:08 +0800, Sylvia Else <sylvia@email.invalid> >>>wrote:

    On 30-Sept-24 1:21 am, john larkin wrote:
    On Sat, 28 Sep 2024 10:21:46 -0700, john larkin <JL@gct.com> wrote:

    On Sat, 28 Sep 2024 09:44:44 -0400, legg <legg@nospam.magma.ca> wrote: >>>>>>
    On Fri, 27 Sep 2024 08:07:29 -0700, john larkin <JL@gct.com> wrote: >>>>>>>

    Given a benchtop power supply, you can turn the voltage up and then >>>>>>>> down, and it goes down. Most have a substantial amount of output >>>>>>>> capacitance, and can be driving an external cap too. So something >>>>>>>> pulls the output down.

    I guess that there are no standards for this, but I've never seen a >>>>>>>> supply that just hangs high when it's cranked down.

    I'm designing some programmable multi-channel power suplies and that >>>>>>>> is one of many tangled issues in the project.

    Twiddling the adjustment knob on a bench supply doesn't
    represent a dramatic change - and most adjustible
    supplies don't load their output terminals with a
    lot of capacitance.

    I've measured a few, and got output terminal capacitance of a few
    hundred to maybe 2000 uF.

    People here might measure some random power supplies. I leave them off >>>>>> and connect to a 50 ohm sinewave-output function generator and find >>>>>> the -3 dB point. One could use a square wave and scope the slopes too. >>>>>> Keeping the amplitude low will avoid turning semi junctions on.

    Come on guys, quit pontificating and start measuring.


    At this stage in the process, you seem to have some odd constraints. Why >>>>the specific h-bridge driver? Why non-isolated?

    Sylvia.

    What I suggested is that a few people grab their bench power supplies
    and see what sort of output capacitance they have.

    The simplest way is to crank the voltage up and short the ouput and
    see how much it sparks. Or measure the capacitance, even.

    That quad TI driver is cheap and available and seems to have good >>>protections. TI makes good stuff and keeps it in production
    approximately forever.

    Non-isolated because that's simple and gets more channels on a small >>>board. The launch customer says that power supplies don't usually need
    to be grounded because everything is grounded on an airplane.

    Was watching one of thse 'Mayday' series on German TV yesterday.
    Airplane got hit by lightning, ball ligtning travelled through the cabin, >>pilots bllided and distracted, did not hear the auto pilot still engaged warning
    started fighting the auto-pilot...
    almost crashed
    Normally auto pilots would dis-engage when you started manual steering >>Indicator between auto pilot 'on' and auto-pilot 'off'
    was color change from green to white symbol on the instrumenrts that looked like this
    AP<

    Miracle they could see anything after the lightning strike, green and white are very close togeter
    for teevee white is .11 blue .59 green and .3 red.
    Something to take into account if you are writing display code.
    Do you?
    no credits...


    I am thinking that nobody here actually has a power supply.

    Larkin's power supply party !

    There are a couple of dozen supplys in this lab,
    of all shapes and sizes - half of them never seen
    on a vendor's shelf.

    Depending on what they're supposed to do, they'll
    have different final capacitive filter stage values.

    You want people running around measuring adjustible
    bench supplies, to compare to your unique low power
    multi-output 'not yet in hardware' figment.

    Get real.

    The standard adjustible (or fixed) linear bench supply, will see
    between 47 and 220uF on their output terminals and a built-in
    loading of between 1/2 and 2W, depending upon that C and it's
    load rating.

    Switchers are all over the map and may self-load as a
    mattwr of policy - but none like to regulate at zero
    load or zero volts - so again between 1/2 and 2W internal
    loading, if the mfrs actually give a damn - unless it's
    a DC-coupled bipolar job, in which case their'll be
    a zoebel network.

    Have a nice day.

    RL

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Chris Jones@21:1/5 to john larkin on Thu Oct 3 00:02:31 2024
    On 30/09/2024 1:23 am, john larkin wrote:
    On Sat, 28 Sep 2024 22:28:07 -0700, Joerg <news@analogconsultants.com>
    wrote:

    On 9/27/24 8:07 AM, john larkin wrote:

    Given a benchtop power supply, you can turn the voltage up and then
    down, and it goes down. Most have a substantial amount of output
    capacitance, and can be driving an external cap too. So something
    pulls the output down.


    Often the only internal load is the resistive divider for the regulator
    loop feedback.


    I guess that there are no standards for this, but I've never seen a
    supply that just hangs high when it's cranked down.


    I have some. They drop very slowly when there isn't much load on the output.

    Customers might whine if they ask for 10 volts and see 30. Amd that
    may be mostly held up by their capacitive load.



    I'm designing some programmable multi-channel power suplies and that
    is one of many tangled issues in the project.


    A synchronous buck architecture should work quite well if you need to
    slew fast. I've used that on a driver that had to modulate a hard
    capacitive load at several kHz and above 100V.

    I'm doing some multichannel non-isolated supplies that will be sync
    buck, using multiple TI DRV8962 chips.

    One problem is that a sync buck can become a boost in the wrong
    direction, and start charging my +48 supply. If it hits, say, 55
    volts, I'll disable the switcher chips, and the outputs can hang. I
    need to discharge the outputs. I'm thinking about 20 mA of depletion
    fet per channel.


    There is no need to concede defeat and disable your switcher chips, just
    turn on a big load instead.

    In variable speed drives for induction motors, the voltage of the DC
    rail and bulk capacitance can also rise when the motor is slowing down
    with a lot of inertia attached to the shaft. They have a switch built
    in, which you are supposed to attach a big load resistor to. When the DC
    rail rises above some threshold, it turns on your external load
    resistor. It cycles on and off to keep the bulk capacitor voltage in an acceptable range.

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Chris Jones@21:1/5 to john larkin on Thu Oct 3 00:04:28 2024
    On 1/10/2024 4:24 am, john larkin wrote:
    On Mon, 30 Sep 2024 08:39:27 -0400, legg <legg@nospam.magma.ca> wrote:

    On Sun, 29 Sep 2024 08:23:01 -0700, john larkin <JL@gct.com> wrote:

    On Sat, 28 Sep 2024 22:28:07 -0700, Joerg <news@analogconsultants.com>
    wrote:

    On 9/27/24 8:07 AM, john larkin wrote:

    Given a benchtop power supply, you can turn the voltage up and then
    down, and it goes down. Most have a substantial amount of output
    capacitance, and can be driving an external cap too. So something
    pulls the output down.


    Often the only internal load is the resistive divider for the regulator >>>> loop feedback.


    I guess that there are no standards for this, but I've never seen a
    supply that just hangs high when it's cranked down.


    I have some. They drop very slowly when there isn't much load on the output.

    Customers might whine if they ask for 10 volts and see 30. Amd that
    may be mostly held up by their capacitive load.



    I'm designing some programmable multi-channel power suplies and that >>>>> is one of many tangled issues in the project.


    A synchronous buck architecture should work quite well if you need to
    slew fast. I've used that on a driver that had to modulate a hard
    capacitive load at several kHz and above 100V.

    I'm doing some multichannel non-isolated supplies that will be sync
    buck, using multiple TI DRV8962 chips.

    One problem is that a sync buck can become a boost in the wrong
    direction, and start charging my +48 supply. If it hits, say, 55
    volts, I'll disable the switcher chips, and the outputs can hang. I
    need to discharge the outputs. I'm thinking about 20 mA of depletion
    fet per channel.

    You might consider overvoltage protection or a (switched ?)
    internal minimum load.There's usuaally some point in the
    control loop that's a good indicator of a pull-down requirement.
    A single ovp or autoload on the input looks likely to serve
    all of your many sync-bucks.

    RL

    An MOV on the bulk supply could limit the reverse-pump excursion until
    the software can notice and shut things down.

    MOVs can gobble a lot of joules, but their clipping is very soggy.


    Due to the cumulative damage that many have warned of, you are better
    off with a power zener, a poewr-zener replacement made with a
    transistor, or a switchable load resistor.

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Liz Tuddenham@21:1/5 to Chris Jones on Wed Oct 2 20:11:05 2024
    Chris Jones <lugnut808@spam.yahoo.com> wrote:

    On 30/09/2024 1:23 am, john larkin wrote:
    On Sat, 28 Sep 2024 22:28:07 -0700, Joerg <news@analogconsultants.com> wrote:

    On 9/27/24 8:07 AM, john larkin wrote:

    Given a benchtop power supply, you can turn the voltage up and then
    down, and it goes down. Most have a substantial amount of output
    capacitance, and can be driving an external cap too. So something
    pulls the output down.


    Often the only internal load is the resistive divider for the regulator
    loop feedback.


    I guess that there are no standards for this, but I've never seen a
    supply that just hangs high when it's cranked down.


    I have some. They drop very slowly when there isn't much load on the >>output.

    Customers might whine if they ask for 10 volts and see 30. Amd that
    may be mostly held up by their capacitive load.



    I'm designing some programmable multi-channel power suplies and that
    is one of many tangled issues in the project.


    A synchronous buck architecture should work quite well if you need to
    slew fast. I've used that on a driver that had to modulate a hard
    capacitive load at several kHz and above 100V.

    I'm doing some multichannel non-isolated supplies that will be sync
    buck, using multiple TI DRV8962 chips.

    One problem is that a sync buck can become a boost in the wrong
    direction, and start charging my +48 supply. If it hits, say, 55
    volts, I'll disable the switcher chips, and the outputs can hang. I
    need to discharge the outputs. I'm thinking about 20 mA of depletion
    fet per channel.


    There is no need to concede defeat and disable your switcher chips, just
    turn on a big load instead.

    In variable speed drives for induction motors, the voltage of the DC
    rail and bulk capacitance can also rise when the motor is slowing down
    with a lot of inertia attached to the shaft. They have a switch built
    in, which you are supposed to attach a big load resistor to. When the DC
    rail rises above some threshold, it turns on your external load
    resistor. It cycles on and off to keep the bulk capacitor voltage in an acceptable range.

    I once had to repair a large CNC milling machine where the load dump
    resistor was on permanently because the controlling transistor had
    failed short-circuit. The resistor was mounted in a cage on the top of
    the control cabinet and the machine eventually switched itself off when
    the radiant heat from the red-hot resistor raised the internal
    temperature of the cabinet to an unsafe value.

    --
    ~ Liz Tuddenham ~
    (Remove the ".invalid"s and add ".co.uk" to reply)
    www.poppyrecords.co.uk

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From john larkin@21:1/5 to lugnut808@spam.yahoo.com on Wed Oct 2 13:31:44 2024
    On Thu, 3 Oct 2024 00:04:28 +1000, Chris Jones
    <lugnut808@spam.yahoo.com> wrote:

    On 1/10/2024 4:24 am, john larkin wrote:
    On Mon, 30 Sep 2024 08:39:27 -0400, legg <legg@nospam.magma.ca> wrote:

    On Sun, 29 Sep 2024 08:23:01 -0700, john larkin <JL@gct.com> wrote:

    On Sat, 28 Sep 2024 22:28:07 -0700, Joerg <news@analogconsultants.com> >>>> wrote:

    On 9/27/24 8:07 AM, john larkin wrote:

    Given a benchtop power supply, you can turn the voltage up and then >>>>>> down, and it goes down. Most have a substantial amount of output
    capacitance, and can be driving an external cap too. So something
    pulls the output down.


    Often the only internal load is the resistive divider for the regulator >>>>> loop feedback.


    I guess that there are no standards for this, but I've never seen a >>>>>> supply that just hangs high when it's cranked down.


    I have some. They drop very slowly when there isn't much load on the output.

    Customers might whine if they ask for 10 volts and see 30. Amd that
    may be mostly held up by their capacitive load.



    I'm designing some programmable multi-channel power suplies and that >>>>>> is one of many tangled issues in the project.


    A synchronous buck architecture should work quite well if you need to >>>>> slew fast. I've used that on a driver that had to modulate a hard
    capacitive load at several kHz and above 100V.

    I'm doing some multichannel non-isolated supplies that will be sync
    buck, using multiple TI DRV8962 chips.

    One problem is that a sync buck can become a boost in the wrong
    direction, and start charging my +48 supply. If it hits, say, 55
    volts, I'll disable the switcher chips, and the outputs can hang. I
    need to discharge the outputs. I'm thinking about 20 mA of depletion
    fet per channel.

    You might consider overvoltage protection or a (switched ?)
    internal minimum load.There's usuaally some point in the
    control loop that's a good indicator of a pull-down requirement.
    A single ovp or autoload on the input looks likely to serve
    all of your many sync-bucks.

    RL

    An MOV on the bulk supply could limit the reverse-pump excursion until
    the software can notice and shut things down.

    MOVs can gobble a lot of joules, but their clipping is very soggy.


    Due to the cumulative damage that many have warned of, you are better
    off with a power zener, a poewr-zener replacement made with a
    transistor, or a switchable load resistor.

    Zeners, even official transzorbs, have a tiny fraction of the joule
    dump capacity of an mov. Ditto transistors.

    A switched resistor would work but is more complex to implement than a
    single mov.

    I'll test some MOVs and see how they behave.

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From john larkin@21:1/5 to lugnut808@spam.yahoo.com on Wed Oct 2 13:36:39 2024
    On Thu, 3 Oct 2024 00:02:31 +1000, Chris Jones
    <lugnut808@spam.yahoo.com> wrote:

    On 30/09/2024 1:23 am, john larkin wrote:
    On Sat, 28 Sep 2024 22:28:07 -0700, Joerg <news@analogconsultants.com>
    wrote:

    On 9/27/24 8:07 AM, john larkin wrote:

    Given a benchtop power supply, you can turn the voltage up and then
    down, and it goes down. Most have a substantial amount of output
    capacitance, and can be driving an external cap too. So something
    pulls the output down.


    Often the only internal load is the resistive divider for the regulator
    loop feedback.


    I guess that there are no standards for this, but I've never seen a
    supply that just hangs high when it's cranked down.


    I have some. They drop very slowly when there isn't much load on the output.

    Customers might whine if they ask for 10 volts and see 30. Amd that
    may be mostly held up by their capacitive load.



    I'm designing some programmable multi-channel power suplies and that
    is one of many tangled issues in the project.


    A synchronous buck architecture should work quite well if you need to
    slew fast. I've used that on a driver that had to modulate a hard
    capacitive load at several kHz and above 100V.

    I'm doing some multichannel non-isolated supplies that will be sync
    buck, using multiple TI DRV8962 chips.

    One problem is that a sync buck can become a boost in the wrong
    direction, and start charging my +48 supply. If it hits, say, 55
    volts, I'll disable the switcher chips, and the outputs can hang. I
    need to discharge the outputs. I'm thinking about 20 mA of depletion
    fet per channel.


    There is no need to concede defeat and disable your switcher chips, just
    turn on a big load instead.


    The customer load could be a giant capacitor bank, or a battery. I
    don't want to short either. And I do want a supply to recover
    gracefully.



    In variable speed drives for induction motors, the voltage of the DC
    rail and bulk capacitance can also rise when the motor is slowing down
    with a lot of inertia attached to the shaft. They have a switch built
    in, which you are supposed to attach a big load resistor to. When the DC
    rail rises above some threshold, it turns on your external load
    resistor. It cycles on and off to keep the bulk capacitor voltage in an >acceptable range.


    Same problem. My fix is to protect our cap with the MOV, and shut off
    the switchers when that voltage gets too high.

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From ehsjr@21:1/5 to john larkin on Wed Oct 2 17:15:38 2024
    On 10/1/2024 5:00 PM, john larkin wrote:
    On Tue, 01 Oct 2024 16:03:40 -0400, Joe Gwinn <joegwinn@comcast.net>
    wrote:

    On Tue, 01 Oct 2024 09:59:27 -0700, john larkin <jl@glen--canyon.com>
    wrote:

    On Tue, 01 Oct 2024 11:24:34 -0400, Joe Gwinn <joegwinn@comcast.net>
    wrote:

    On Mon, 30 Sep 2024 18:49:14 -0700, john larkin <JL@gct.com> wrote:

    On Mon, 30 Sep 2024 11:49:54 -0700, Joerg <news@analogconsultants.com> >>>>> wrote:

    On 9/30/24 11:24 AM, john larkin wrote:
    On Mon, 30 Sep 2024 08:39:27 -0400, legg <legg@nospam.magma.ca> wrote: >>>>>>>
    On Sun, 29 Sep 2024 08:23:01 -0700, john larkin <JL@gct.com> wrote: >>>>>>>>
    On Sat, 28 Sep 2024 22:28:07 -0700, Joerg <news@analogconsultants.com>
    wrote:

    On 9/27/24 8:07 AM, john larkin wrote:

    Given a benchtop power supply, you can turn the voltage up and then >>>>>>>>>>> down, and it goes down. Most have a substantial amount of output >>>>>>>>>>> capacitance, and can be driving an external cap too. So something >>>>>>>>>>> pulls the output down.


    Often the only internal load is the resistive divider for the regulator
    loop feedback.


    I guess that there are no standards for this, but I've never seen a >>>>>>>>>>> supply that just hangs high when it's cranked down.


    I have some. They drop very slowly when there isn't much load on the output.

    Customers might whine if they ask for 10 volts and see 30. Amd that >>>>>>>>> may be mostly held up by their capacitive load.



    I'm designing some programmable multi-channel power suplies and that
    is one of many tangled issues in the project.


    A synchronous buck architecture should work quite well if you need to
    slew fast. I've used that on a driver that had to modulate a hard >>>>>>>>>> capacitive load at several kHz and above 100V.

    I'm doing some multichannel non-isolated supplies that will be sync >>>>>>>>> buck, using multiple TI DRV8962 chips.

    One problem is that a sync buck can become a boost in the wrong >>>>>>>>> direction, and start charging my +48 supply. If it hits, say, 55 >>>>>>>>> volts, I'll disable the switcher chips, and the outputs can hang. I >>>>>>>>> need to discharge the outputs. I'm thinking about 20 mA of depletion >>>>>>>>> fet per channel.

    You might consider overvoltage protection or a (switched ?)
    internal minimum load.There's usuaally some point in the
    control loop that's a good indicator of a pull-down requirement. >>>>>>>> A single ovp or autoload on the input looks likely to serve
    all of your many sync-bucks.

    RL

    An MOV on the bulk supply could limit the reverse-pump excursion until >>>>>>> the software can notice and shut things down.

    MOVs can gobble a lot of joules, but their clipping is very soggy. >>>>>>>

    MOVs are usually cumulative. They can take a certain amount of
    dissipation over their lifetime and then *PHUT* ... POOOF. Like a bank >>>>>> account that runs dry.

    What kills MOVs? Integrated joules? Time-temperature?

    I don't expect a lot of joules per event. Just enough energy to keep >>>>> my supply voltage down until a slowish ADC and the software can shut >>>>> the buck switchers down. 15 milliseconds max, maybe.

    I think it's integrated joules per cubic centimeter of the MOV
    material. This is discussed in the literature on MOVs for protecting
    line-powered equipment from pulse overvoltages, such as from nearby
    lightning strikes. <https://www.deltala.com/>

    Joe Gwinn

    Makes sense. It looks like most MOV appnotes assume that it's across
    an AC line, with kilo-amps available. Or lightning bolts.

    I'll get a few and test them at much lower loads.

    For smaller MOVs, I think that the data sheet specifies capacity in
    Joules. I bet this is the max integrated dose, not the pre-event
    limit. Well, the one-event limit as well.

    Joe Gwinn

    That's probably a single-shot rating, such as to limit the peak
    temperature. So that can be done many times, if it cools off between
    shots.


    As I understand it, it's cumulative. Each time there is an
    event where the MOV operates (ie conducts), some damage is done.
    So for example a 10 joule rated MOV can operate for 10 1 joule
    events or 1 10 joule event, or any combination totaling 10 joules.

    Ed

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From john larkin@21:1/5 to ehsjr on Wed Oct 2 15:28:18 2024
    On Wed, 2 Oct 2024 17:15:38 -0400, ehsjr <ehsjr@verizon.net> wrote:

    On 10/1/2024 5:00 PM, john larkin wrote:
    On Tue, 01 Oct 2024 16:03:40 -0400, Joe Gwinn <joegwinn@comcast.net>
    wrote:

    On Tue, 01 Oct 2024 09:59:27 -0700, john larkin <jl@glen--canyon.com>
    wrote:

    On Tue, 01 Oct 2024 11:24:34 -0400, Joe Gwinn <joegwinn@comcast.net>
    wrote:

    On Mon, 30 Sep 2024 18:49:14 -0700, john larkin <JL@gct.com> wrote:

    On Mon, 30 Sep 2024 11:49:54 -0700, Joerg <news@analogconsultants.com> >>>>>> wrote:

    On 9/30/24 11:24 AM, john larkin wrote:
    On Mon, 30 Sep 2024 08:39:27 -0400, legg <legg@nospam.magma.ca> wrote: >>>>>>>>
    On Sun, 29 Sep 2024 08:23:01 -0700, john larkin <JL@gct.com> wrote: >>>>>>>>>
    On Sat, 28 Sep 2024 22:28:07 -0700, Joerg <news@analogconsultants.com>
    wrote:

    On 9/27/24 8:07 AM, john larkin wrote:

    Given a benchtop power supply, you can turn the voltage up and then
    down, and it goes down. Most have a substantial amount of output >>>>>>>>>>>> capacitance, and can be driving an external cap too. So something >>>>>>>>>>>> pulls the output down.


    Often the only internal load is the resistive divider for the regulator
    loop feedback.


    I guess that there are no standards for this, but I've never seen a
    supply that just hangs high when it's cranked down.


    I have some. They drop very slowly when there isn't much load on the output.

    Customers might whine if they ask for 10 volts and see 30. Amd that >>>>>>>>>> may be mostly held up by their capacitive load.



    I'm designing some programmable multi-channel power suplies and that
    is one of many tangled issues in the project.


    A synchronous buck architecture should work quite well if you need to
    slew fast. I've used that on a driver that had to modulate a hard >>>>>>>>>>> capacitive load at several kHz and above 100V.

    I'm doing some multichannel non-isolated supplies that will be sync >>>>>>>>>> buck, using multiple TI DRV8962 chips.

    One problem is that a sync buck can become a boost in the wrong >>>>>>>>>> direction, and start charging my +48 supply. If it hits, say, 55 >>>>>>>>>> volts, I'll disable the switcher chips, and the outputs can hang. I >>>>>>>>>> need to discharge the outputs. I'm thinking about 20 mA of depletion >>>>>>>>>> fet per channel.

    You might consider overvoltage protection or a (switched ?)
    internal minimum load.There's usuaally some point in the
    control loop that's a good indicator of a pull-down requirement. >>>>>>>>> A single ovp or autoload on the input looks likely to serve
    all of your many sync-bucks.

    RL

    An MOV on the bulk supply could limit the reverse-pump excursion until >>>>>>>> the software can notice and shut things down.

    MOVs can gobble a lot of joules, but their clipping is very soggy. >>>>>>>>

    MOVs are usually cumulative. They can take a certain amount of
    dissipation over their lifetime and then *PHUT* ... POOOF. Like a bank >>>>>>> account that runs dry.

    What kills MOVs? Integrated joules? Time-temperature?

    I don't expect a lot of joules per event. Just enough energy to keep >>>>>> my supply voltage down until a slowish ADC and the software can shut >>>>>> the buck switchers down. 15 milliseconds max, maybe.

    I think it's integrated joules per cubic centimeter of the MOV
    material. This is discussed in the literature on MOVs for protecting >>>>> line-powered equipment from pulse overvoltages, such as from nearby
    lightning strikes. <https://www.deltala.com/>

    Joe Gwinn

    Makes sense. It looks like most MOV appnotes assume that it's across
    an AC line, with kilo-amps available. Or lightning bolts.

    I'll get a few and test them at much lower loads.

    For smaller MOVs, I think that the data sheet specifies capacity in
    Joules. I bet this is the max integrated dose, not the pre-event
    limit. Well, the one-event limit as well.

    Joe Gwinn

    That's probably a single-shot rating, such as to limit the peak
    temperature. So that can be done many times, if it cools off between
    shots.


    As I understand it, it's cumulative. Each time there is an
    event where the MOV operates (ie conducts), some damage is done.
    So for example a 10 joule rated MOV can operate for 10 1 joule
    events or 1 10 joule event, or any combination totaling 10 joules.

    Ed


    I suspect it can dump many 10 joule events suitably spaced, but that's
    not specified. Ten 1-joule shots within, say, 1 second would be
    thermally equivalent to a 10j shot.

    The short-term thermal damage limit is likely different from the
    other, long-term failure mode.

    I ordered a bunch to test.


    “One good test is worth a thousand expert opinions.”
    - Wernher Von Braun

    --- SoupGate-Win32 v1.05
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  • From john larkin@21:1/5 to All on Wed Oct 2 19:43:51 2024
    On Wed, 02 Oct 2024 13:36:39 -0700, john larkin <jl@glen--canyon.com>
    wrote:

    On Thu, 3 Oct 2024 00:02:31 +1000, Chris Jones
    <lugnut808@spam.yahoo.com> wrote:

    On 30/09/2024 1:23 am, john larkin wrote:
    On Sat, 28 Sep 2024 22:28:07 -0700, Joerg <news@analogconsultants.com>
    wrote:

    On 9/27/24 8:07 AM, john larkin wrote:

    Given a benchtop power supply, you can turn the voltage up and then
    down, and it goes down. Most have a substantial amount of output
    capacitance, and can be driving an external cap too. So something
    pulls the output down.


    Often the only internal load is the resistive divider for the regulator >>>> loop feedback.


    I guess that there are no standards for this, but I've never seen a
    supply that just hangs high when it's cranked down.


    I have some. They drop very slowly when there isn't much load on the output.

    Customers might whine if they ask for 10 volts and see 30. Amd that
    may be mostly held up by their capacitive load.



    I'm designing some programmable multi-channel power suplies and that >>>>> is one of many tangled issues in the project.


    A synchronous buck architecture should work quite well if you need to
    slew fast. I've used that on a driver that had to modulate a hard
    capacitive load at several kHz and above 100V.

    I'm doing some multichannel non-isolated supplies that will be sync
    buck, using multiple TI DRV8962 chips.

    One problem is that a sync buck can become a boost in the wrong
    direction, and start charging my +48 supply. If it hits, say, 55
    volts, I'll disable the switcher chips, and the outputs can hang. I
    need to discharge the outputs. I'm thinking about 20 mA of depletion
    fet per channel.


    There is no need to concede defeat and disable your switcher chips, just >>turn on a big load instead.


    The customer load could be a giant capacitor bank, or a battery. I
    don't want to short either. And I do want a supply to recover
    gracefully.



    In variable speed drives for induction motors, the voltage of the DC
    rail and bulk capacitance can also rise when the motor is slowing down
    with a lot of inertia attached to the shaft. They have a switch built
    in, which you are supposed to attach a big load resistor to. When the DC >>rail rises above some threshold, it turns on your external load
    resistor. It cycles on and off to keep the bulk capacitor voltage in an >>acceptable range.


    Same problem. My fix is to protect our cap with the MOV, and shut off
    the switchers when that voltage gets too high.

    Most electrolytic caps just draw more current as the voltage goes up.
    That usually gets serious at around 120% of rated voltage.

    An elec may be as good as a MOV for absorbing joules. And I'll have
    caps anyhow.

    I tested some polymer elecs that suddenly died shorted at
    over-voltage, without warning, but the Panasonics that we use now just
    leak and get hot. No big deal.

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From john larkin@21:1/5 to All on Fri Sep 27 08:07:29 2024
    Given a benchtop power supply, you can turn the voltage up and then
    down, and it goes down. Most have a substantial amount of output
    capacitance, and can be driving an external cap too. So something
    pulls the output down.

    I guess that there are no standards for this, but I've never seen a
    supply that just hangs high when it's cranked down.

    I'm designing some programmable multi-channel power suplies and that
    is one of many tangled issues in the project.

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Sylvia Else@21:1/5 to john larkin on Fri Sep 27 23:50:21 2024
    On 27-Sept-24 11:07 pm, john larkin wrote:

    Given a benchtop power supply, you can turn the voltage up and then
    down, and it goes down. Most have a substantial amount of output
    capacitance, and can be driving an external cap too. So something
    pulls the output down.

    I guess that there are no standards for this, but I've never seen a
    supply that just hangs high when it's cranked down.

    I'm designing some programmable multi-channel power suplies and that
    is one of many tangled issues in the project.


    Be easy enough to sink current when the output voltage exceeds the set
    point by more than, say, 0.1V.

    But there has to be a limit - connect the PS to your fully charged car
    battery, and set the PS to 10V, and you're not going to see a 10V output
    any time soon.

    Sylvia.

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Liz Tuddenham@21:1/5 to john larkin on Fri Sep 27 16:17:42 2024
    john larkin <JL@gct.com> wrote:

    Given a benchtop power supply, you can turn the voltage up and then
    down, and it goes down. Most have a substantial amount of output
    capacitance, and can be driving an external cap too. So something
    pulls the output down.

    I guess that there are no standards for this, but I've never seen a
    supply that just hangs high when it's cranked down.

    I'm designing some programmable multi-channel power suplies and that
    is one of many tangled issues in the project.

    A DC-coupled audio amplifier chip might work as a fully-controllable bi-directional power supply if your current and voltage requirements
    were fairly modest. They have the advantage of being relatively cheap, well-protected and very fast (by power supply standards). Some of them
    have the tab at input earth voltage, so they don't require isolation
    from the heat sink.


    --
    ~ Liz Tuddenham ~
    (Remove the ".invalid"s and add ".co.uk" to reply)
    www.poppyrecords.co.uk

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From john larkin@21:1/5 to Liz Tuddenham on Fri Sep 27 10:01:30 2024
    On Fri, 27 Sep 2024 16:17:42 +0100, liz@poppyrecords.invalid.invalid
    (Liz Tuddenham) wrote:

    john larkin <JL@gct.com> wrote:

    Given a benchtop power supply, you can turn the voltage up and then
    down, and it goes down. Most have a substantial amount of output
    capacitance, and can be driving an external cap too. So something
    pulls the output down.

    I guess that there are no standards for this, but I've never seen a
    supply that just hangs high when it's cranked down.

    I'm designing some programmable multi-channel power suplies and that
    is one of many tangled issues in the project.

    A DC-coupled audio amplifier chip might work as a fully-controllable >bi-directional power supply if your current and voltage requirements
    were fairly modest. They have the advantage of being relatively cheap, >well-protected and very fast (by power supply standards). Some of them
    have the tab at input earth voltage, so they don't require isolation
    from the heat sink.

    Unfortunately, it has to be a switching regulator.

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From john larkin@21:1/5 to All on Fri Sep 27 10:00:20 2024
    On Fri, 27 Sep 2024 23:50:21 +0800, Sylvia Else <sylvia@email.invalid>
    wrote:

    On 27-Sept-24 11:07 pm, john larkin wrote:

    Given a benchtop power supply, you can turn the voltage up and then
    down, and it goes down. Most have a substantial amount of output
    capacitance, and can be driving an external cap too. So something
    pulls the output down.

    I guess that there are no standards for this, but I've never seen a
    supply that just hangs high when it's cranked down.

    I'm designing some programmable multi-channel power suplies and that
    is one of many tangled issues in the project.


    Be easy enough to sink current when the output voltage exceeds the set
    point by more than, say, 0.1V.

    But there has to be a limit - connect the PS to your fully charged car >battery, and set the PS to 10V, and you're not going to see a 10V output
    any time soon.

    Sylvia.

    Right, the load could be a battery. The user could set the output
    voltage high with some current limit to charge the battery (or some
    giant capacitor), and then set the voltage low.

    What's complicating my life is that the regulator is a half-bridge
    switcher that, in that case, becomes a boost converter, pumping
    backwards into my bulk power supply, which could then blow up. Or if
    the control loop cranks the PWM duty cycle down to zero in a futile
    attempt to reduce the output voltage, it soon shorts the battery.

    Or some yahoo could connect the battery backwards.

    This is actually a nice multidimensional dilemma. I'll be using the
    DRV8962 quad half-bridge, which also constrains things.

    As usual with data sheets, it isn't entirely clear.

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Phil Hobbs@21:1/5 to john larkin on Fri Sep 27 19:23:43 2024
    john larkin <jl@glen--canyon.com> wrote:
    On Fri, 27 Sep 2024 23:50:21 +0800, Sylvia Else <sylvia@email.invalid>
    wrote:

    On 27-Sept-24 11:07 pm, john larkin wrote:

    Given a benchtop power supply, you can turn the voltage up and then
    down, and it goes down. Most have a substantial amount of output
    capacitance, and can be driving an external cap too. So something
    pulls the output down.

    I guess that there are no standards for this, but I've never seen a
    supply that just hangs high when it's cranked down.

    I'm designing some programmable multi-channel power suplies and that
    is one of many tangled issues in the project.


    Be easy enough to sink current when the output voltage exceeds the set
    point by more than, say, 0.1V.

    But there has to be a limit - connect the PS to your fully charged car
    battery, and set the PS to 10V, and you're not going to see a 10V output
    any time soon.

    Sylvia.

    Right, the load could be a battery. The user could set the output
    voltage high with some current limit to charge the battery (or some
    giant capacitor), and then set the voltage low.

    What's complicating my life is that the regulator is a half-bridge
    switcher that, in that case, becomes a boost converter, pumping
    backwards into my bulk power supply, which could then blow up. Or if
    the control loop cranks the PWM duty cycle down to zero in a futile
    attempt to reduce the output voltage, it soon shorts the battery.

    Or some yahoo could connect the battery backwards.

    This is actually a nice multidimensional dilemma. I'll be using the
    DRV8962 quad half-bridge, which also constrains things.

    As usual with data sheets, it isn't entirely clear.

    How about a nice diode in series, inside the FB loop, with the pulldown on
    the load side?

    (You thought of that already.) ;)

    Cheers

    Phil Hobbs

    --
    Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC / Hobbs ElectroOptics Optics, Electro-optics, Photonics, Analog Electronics

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Liz Tuddenham@21:1/5 to john larkin on Fri Sep 27 20:19:24 2024
    john larkin <jl@glen--canyon.com> wrote:

    On Fri, 27 Sep 2024 16:17:42 +0100, liz@poppyrecords.invalid.invalid
    (Liz Tuddenham) wrote:

    john larkin <JL@gct.com> wrote:

    Given a benchtop power supply, you can turn the voltage up and then
    down, and it goes down. Most have a substantial amount of output
    capacitance, and can be driving an external cap too. So something
    pulls the output down.

    I guess that there are no standards for this, but I've never seen a
    supply that just hangs high when it's cranked down.

    I'm designing some programmable multi-channel power suplies and that
    is one of many tangled issues in the project.

    A DC-coupled audio amplifier chip might work as a fully-controllable >bi-directional power supply if your current and voltage requirements
    were fairly modest. They have the advantage of being relatively cheap, >well-protected and very fast (by power supply standards). Some of them >have the tab at input earth voltage, so they don't require isolation
    from the heat sink.

    Unfortunately, it has to be a switching regulator.

    Years ago there were power supplies with a linear regulator fed from a thyristor chopper, the voltage to the linear stage being held just above
    the required output. This gave all the benefits of a linear power
    supply without the dissipation.

    Perhaps you could use the switcher to power the audio amplifier?

    ...or were you thinking of using the switcher in reverse to feed excess
    power back into the supply? (That's where dynamotors and rotary
    converters scored.)


    --
    ~ Liz Tuddenham ~
    (Remove the ".invalid"s and add ".co.uk" to reply)
    www.poppyrecords.co.uk

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From john larkin@21:1/5 to pcdhSpamMeSenseless@electrooptical. on Fri Sep 27 16:27:25 2024
    On Fri, 27 Sep 2024 19:23:43 -0000 (UTC), Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:

    john larkin <jl@glen--canyon.com> wrote:
    On Fri, 27 Sep 2024 23:50:21 +0800, Sylvia Else <sylvia@email.invalid>
    wrote:

    On 27-Sept-24 11:07 pm, john larkin wrote:

    Given a benchtop power supply, you can turn the voltage up and then
    down, and it goes down. Most have a substantial amount of output
    capacitance, and can be driving an external cap too. So something
    pulls the output down.

    I guess that there are no standards for this, but I've never seen a
    supply that just hangs high when it's cranked down.

    I'm designing some programmable multi-channel power suplies and that
    is one of many tangled issues in the project.


    Be easy enough to sink current when the output voltage exceeds the set
    point by more than, say, 0.1V.

    But there has to be a limit - connect the PS to your fully charged car
    battery, and set the PS to 10V, and you're not going to see a 10V output >>> any time soon.

    Sylvia.

    Right, the load could be a battery. The user could set the output
    voltage high with some current limit to charge the battery (or some
    giant capacitor), and then set the voltage low.

    What's complicating my life is that the regulator is a half-bridge
    switcher that, in that case, becomes a boost converter, pumping
    backwards into my bulk power supply, which could then blow up. Or if
    the control loop cranks the PWM duty cycle down to zero in a futile
    attempt to reduce the output voltage, it soon shorts the battery.

    Or some yahoo could connect the battery backwards.

    This is actually a nice multidimensional dilemma. I'll be using the
    DRV8962 quad half-bridge, which also constrains things.

    As usual with data sheets, it isn't entirely clear.

    How about a nice diode in series, inside the FB loop, with the pulldown on >the load side?

    (You thought of that already.) ;)

    Cheers

    Phil Hobbs

    Yes. I plan to offer a version of the product as a stepper/torque
    motor driver, in which case two half-bridges become one full bridge,
    and each half-bridge then has to push current in both directons. The
    current measurement has to be bidirectional too.

    I think I can use a polyfuse to handle the backwards yahoo case.

    The klutzy answer to the reverse-pump issue is to measure the prime 48
    volts power supply voltage and, if it gets pumped above 55 or
    something, shut down the TI quad switcher for one second.

    A depletion fet somewhere could discharge an external cap if I shut
    the switcher down.

    I was just talking to a guy who says that big capacitor bank
    discharging is a common requirement. Sometimes they use a resistor on
    a stick.

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Bill Sloman@21:1/5 to john larkin on Sat Sep 28 17:36:46 2024
    On 28/09/2024 3:01 am, john larkin wrote:
    On Fri, 27 Sep 2024 16:17:42 +0100, liz@poppyrecords.invalid.invalid
    (Liz Tuddenham) wrote:

    john larkin <JL@gct.com> wrote:

    Given a benchtop power supply, you can turn the voltage up and then
    down, and it goes down. Most have a substantial amount of output
    capacitance, and can be driving an external cap too. So something
    pulls the output down.

    I guess that there are no standards for this, but I've never seen a
    supply that just hangs high when it's cranked down.

    I'm designing some programmable multi-channel power suplies and that
    is one of many tangled issues in the project.

    A DC-coupled audio amplifier chip might work as a fully-controllable
    bi-directional power supply if your current and voltage requirements
    were fairly modest. They have the advantage of being relatively cheap,
    well-protected and very fast (by power supply standards). Some of them
    have the tab at input earth voltage, so they don't require isolation
    from the heat sink.

    Unfortunately, it has to be a switching regulator.

    https://www.infineon.com/cms/en/product/power/class-d-audio-amplifier-ic/

    There are lots of Class-D - switching - audio amplifier chips. This is
    just the first link Google picked up.

    Switching audio amplifiers have been around for decades now. I've never
    used any of them - discrete MOSFETs were cheaper than integrated parts
    when I last looked, but that was a while ago.

    --
    Bill Sloman, Sydney

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Sylvia Else@21:1/5 to john larkin on Sat Sep 28 15:50:44 2024
    On 28-Sept-24 1:00 am, john larkin wrote:
    On Fri, 27 Sep 2024 23:50:21 +0800, Sylvia Else <sylvia@email.invalid>
    wrote:

    On 27-Sept-24 11:07 pm, john larkin wrote:

    Given a benchtop power supply, you can turn the voltage up and then
    down, and it goes down. Most have a substantial amount of output
    capacitance, and can be driving an external cap too. So something
    pulls the output down.

    I guess that there are no standards for this, but I've never seen a
    supply that just hangs high when it's cranked down.

    I'm designing some programmable multi-channel power suplies and that
    is one of many tangled issues in the project.


    Be easy enough to sink current when the output voltage exceeds the set
    point by more than, say, 0.1V.

    But there has to be a limit - connect the PS to your fully charged car
    battery, and set the PS to 10V, and you're not going to see a 10V output
    any time soon.

    Sylvia.

    Right, the load could be a battery. The user could set the output
    voltage high with some current limit to charge the battery (or some
    giant capacitor), and then set the voltage low.

    What's complicating my life is that the regulator is a half-bridge
    switcher that, in that case, becomes a boost converter, pumping
    backwards into my bulk power supply, which could then blow up. Or if
    the control loop cranks the PWM duty cycle down to zero in a futile
    attempt to reduce the output voltage, it soon shorts the battery.

    Or some yahoo could connect the battery backwards.

    This is actually a nice multidimensional dilemma. I'll be using the
    DRV8962 quad half-bridge, which also constrains things.

    As usual with data sheets, it isn't entirely clear.







    An even more extreme example of two PS connected together with different
    set points shows that no general solution exists, even in theory.

    So it's down to requirements and specifications.

    The reversed polarity battery case is I think usually handled with a
    diode and fuse. The controller can then email a manager pointing out
    that someone needs to be fired.

    Sylvia.

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Jasen Betts@21:1/5 to john larkin on Sun Oct 6 00:56:51 2024
    On 2024-09-27, john larkin <jl@glen--canyon.com> wrote:
    On Fri, 27 Sep 2024 16:17:42 +0100, liz@poppyrecords.invalid.invalid
    (Liz Tuddenham) wrote:

    john larkin <JL@gct.com> wrote:

    Given a benchtop power supply, you can turn the voltage up and then
    down, and it goes down. Most have a substantial amount of output
    capacitance, and can be driving an external cap too. So something
    pulls the output down.

    I guess that there are no standards for this, but I've never seen a
    supply that just hangs high when it's cranked down.

    I'm designing some programmable multi-channel power suplies and that
    is one of many tangled issues in the project.

    A DC-coupled audio amplifier chip might work as a fully-controllable >>bi-directional power supply if your current and voltage requirements
    were fairly modest. They have the advantage of being relatively cheap, >>well-protected and very fast (by power supply standards). Some of them >>have the tab at input earth voltage, so they don't require isolation
    from the heat sink.

    Unfortunately, it has to be a switching regulator.

    how is that different from a class D audio amplifier?

    --
    Jasen.
    🇺🇦 Слава Україні

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Clive Arthur@21:1/5 to Jasen Betts on Sun Oct 6 15:11:21 2024
    On 06/10/2024 01:56, Jasen Betts wrote:
    On 2024-09-27, john larkin <jl@glen--canyon.com> wrote:
    On Fri, 27 Sep 2024 16:17:42 +0100, liz@poppyrecords.invalid.invalid
    (Liz Tuddenham) wrote:

    john larkin <JL@gct.com> wrote:

    Given a benchtop power supply, you can turn the voltage up and then
    down, and it goes down. Most have a substantial amount of output
    capacitance, and can be driving an external cap too. So something
    pulls the output down.

    I guess that there are no standards for this, but I've never seen a
    supply that just hangs high when it's cranked down.

    I'm designing some programmable multi-channel power suplies and that
    is one of many tangled issues in the project.

    A DC-coupled audio amplifier chip might work as a fully-controllable
    bi-directional power supply if your current and voltage requirements
    were fairly modest. They have the advantage of being relatively cheap,
    well-protected and very fast (by power supply standards). Some of them
    have the tab at input earth voltage, so they don't require isolation
    from the heat sink.

    Unfortunately, it has to be a switching regulator.

    how is that different from a class D audio amplifier?

    Audio doesn't go down to DC.

    --
    Cheers
    Clive

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From john larkin@21:1/5 to clive@nowaytoday.co.uk on Sun Oct 6 07:23:52 2024
    On Sun, 6 Oct 2024 15:11:21 +0100, Clive Arthur
    <clive@nowaytoday.co.uk> wrote:

    On 06/10/2024 01:56, Jasen Betts wrote:
    On 2024-09-27, john larkin <jl@glen--canyon.com> wrote:
    On Fri, 27 Sep 2024 16:17:42 +0100, liz@poppyrecords.invalid.invalid
    (Liz Tuddenham) wrote:

    john larkin <JL@gct.com> wrote:

    Given a benchtop power supply, you can turn the voltage up and then
    down, and it goes down. Most have a substantial amount of output
    capacitance, and can be driving an external cap too. So something
    pulls the output down.

    I guess that there are no standards for this, but I've never seen a
    supply that just hangs high when it's cranked down.

    I'm designing some programmable multi-channel power suplies and that >>>>> is one of many tangled issues in the project.

    A DC-coupled audio amplifier chip might work as a fully-controllable
    bi-directional power supply if your current and voltage requirements
    were fairly modest. They have the advantage of being relatively cheap, >>>> well-protected and very fast (by power supply standards). Some of them >>>> have the tab at input earth voltage, so they don't require isolation
    from the heat sink.

    Unfortunately, it has to be a switching regulator.

    how is that different from a class D audio amplifier?

    Audio doesn't go down to DC.

    Audio amps are usually full-bridge, which doesn't reverse pump up the
    power supply under pathological conditions, like a half-bridge can.

    And loudspeakers are very inefficient so don't store much energy and
    as you note don't go down to DC, again storing not much energy.

    A big capacitor bank, or a battery, or a motor can store a lot of
    energy, so there can be a dilemma when the load voltage is higher than
    the supply setpoint.

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From john larkin@21:1/5 to All on Tue Oct 8 17:27:53 2024
    On Tue, 01 Oct 2024 16:03:40 -0400, Joe Gwinn <joegwinn@comcast.net>
    wrote:

    On Tue, 01 Oct 2024 09:59:27 -0700, john larkin <jl@glen--canyon.com>
    wrote:

    On Tue, 01 Oct 2024 11:24:34 -0400, Joe Gwinn <joegwinn@comcast.net>
    wrote:

    On Mon, 30 Sep 2024 18:49:14 -0700, john larkin <JL@gct.com> wrote:

    On Mon, 30 Sep 2024 11:49:54 -0700, Joerg <news@analogconsultants.com> >>>>wrote:

    On 9/30/24 11:24 AM, john larkin wrote:
    On Mon, 30 Sep 2024 08:39:27 -0400, legg <legg@nospam.magma.ca> wrote: >>>>>>
    On Sun, 29 Sep 2024 08:23:01 -0700, john larkin <JL@gct.com> wrote: >>>>>>>
    On Sat, 28 Sep 2024 22:28:07 -0700, Joerg <news@analogconsultants.com> >>>>>>>> wrote:

    On 9/27/24 8:07 AM, john larkin wrote:

    Given a benchtop power supply, you can turn the voltage up and then >>>>>>>>>> down, and it goes down. Most have a substantial amount of output >>>>>>>>>> capacitance, and can be driving an external cap too. So something >>>>>>>>>> pulls the output down.


    Often the only internal load is the resistive divider for the regulator
    loop feedback.


    I guess that there are no standards for this, but I've never seen a >>>>>>>>>> supply that just hangs high when it's cranked down.


    I have some. They drop very slowly when there isn't much load on the output.

    Customers might whine if they ask for 10 volts and see 30. Amd that >>>>>>>> may be mostly held up by their capacitive load.



    I'm designing some programmable multi-channel power suplies and that >>>>>>>>>> is one of many tangled issues in the project.


    A synchronous buck architecture should work quite well if you need to >>>>>>>>> slew fast. I've used that on a driver that had to modulate a hard >>>>>>>>> capacitive load at several kHz and above 100V.

    I'm doing some multichannel non-isolated supplies that will be sync >>>>>>>> buck, using multiple TI DRV8962 chips.

    One problem is that a sync buck can become a boost in the wrong >>>>>>>> direction, and start charging my +48 supply. If it hits, say, 55 >>>>>>>> volts, I'll disable the switcher chips, and the outputs can hang. I >>>>>>>> need to discharge the outputs. I'm thinking about 20 mA of depletion >>>>>>>> fet per channel.

    You might consider overvoltage protection or a (switched ?)
    internal minimum load.There's usuaally some point in the
    control loop that's a good indicator of a pull-down requirement. >>>>>>> A single ovp or autoload on the input looks likely to serve
    all of your many sync-bucks.

    RL

    An MOV on the bulk supply could limit the reverse-pump excursion until >>>>>> the software can notice and shut things down.

    MOVs can gobble a lot of joules, but their clipping is very soggy. >>>>>>

    MOVs are usually cumulative. They can take a certain amount of >>>>>dissipation over their lifetime and then *PHUT* ... POOOF. Like a bank >>>>>account that runs dry.

    What kills MOVs? Integrated joules? Time-temperature?

    I don't expect a lot of joules per event. Just enough energy to keep
    my supply voltage down until a slowish ADC and the software can shut >>>>the buck switchers down. 15 milliseconds max, maybe.

    I think it's integrated joules per cubic centimeter of the MOV
    material. This is discussed in the literature on MOVs for protecting >>>line-powered equipment from pulse overvoltages, such as from nearby >>>lightning strikes. <https://www.deltala.com/>

    Joe Gwinn

    Makes sense. It looks like most MOV appnotes assume that it's across
    an AC line, with kilo-amps available. Or lightning bolts.

    I'll get a few and test them at much lower loads.

    For smaller MOVs, I think that the data sheet specifies capacity in
    Joules. I bet this is the max integrated dose, not the pre-event
    limit. Well, the one-event limit as well.

    Joe Gwinn

    I'm torturing an MOV, a 470KD14. It's rated for 47 volts and 0.1 watt
    and 10 joules.

    At a constant 15 mA, it's at 58.1 volts, which is 0.86 watts. It's
    pretty warm. The voltage seems very stable after 4 hours so far.
    That's about 12K joules.

    It's likely it could do that forever, but the data sheets suggest that
    high power shots can do cumulative damage. I might set up to try that
    somehow.

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From ehsjr@21:1/5 to john larkin on Tue Oct 8 22:34:16 2024
    On 10/8/2024 8:27 PM, john larkin wrote:
    On Tue, 01 Oct 2024 16:03:40 -0400, Joe Gwinn <joegwinn@comcast.net>
    wrote:

    On Tue, 01 Oct 2024 09:59:27 -0700, john larkin <jl@glen--canyon.com>
    wrote:

    On Tue, 01 Oct 2024 11:24:34 -0400, Joe Gwinn <joegwinn@comcast.net>
    wrote:

    On Mon, 30 Sep 2024 18:49:14 -0700, john larkin <JL@gct.com> wrote:

    On Mon, 30 Sep 2024 11:49:54 -0700, Joerg <news@analogconsultants.com> >>>>> wrote:

    On 9/30/24 11:24 AM, john larkin wrote:
    On Mon, 30 Sep 2024 08:39:27 -0400, legg <legg@nospam.magma.ca> wrote: >>>>>>>
    On Sun, 29 Sep 2024 08:23:01 -0700, john larkin <JL@gct.com> wrote: >>>>>>>>
    On Sat, 28 Sep 2024 22:28:07 -0700, Joerg <news@analogconsultants.com>
    wrote:

    On 9/27/24 8:07 AM, john larkin wrote:

    Given a benchtop power supply, you can turn the voltage up and then >>>>>>>>>>> down, and it goes down. Most have a substantial amount of output >>>>>>>>>>> capacitance, and can be driving an external cap too. So something >>>>>>>>>>> pulls the output down.


    Often the only internal load is the resistive divider for the regulator
    loop feedback.


    I guess that there are no standards for this, but I've never seen a >>>>>>>>>>> supply that just hangs high when it's cranked down.


    I have some. They drop very slowly when there isn't much load on the output.

    Customers might whine if they ask for 10 volts and see 30. Amd that >>>>>>>>> may be mostly held up by their capacitive load.



    I'm designing some programmable multi-channel power suplies and that
    is one of many tangled issues in the project.


    A synchronous buck architecture should work quite well if you need to
    slew fast. I've used that on a driver that had to modulate a hard >>>>>>>>>> capacitive load at several kHz and above 100V.

    I'm doing some multichannel non-isolated supplies that will be sync >>>>>>>>> buck, using multiple TI DRV8962 chips.

    One problem is that a sync buck can become a boost in the wrong >>>>>>>>> direction, and start charging my +48 supply. If it hits, say, 55 >>>>>>>>> volts, I'll disable the switcher chips, and the outputs can hang. I >>>>>>>>> need to discharge the outputs. I'm thinking about 20 mA of depletion >>>>>>>>> fet per channel.

    You might consider overvoltage protection or a (switched ?)
    internal minimum load.There's usuaally some point in the
    control loop that's a good indicator of a pull-down requirement. >>>>>>>> A single ovp or autoload on the input looks likely to serve
    all of your many sync-bucks.

    RL

    An MOV on the bulk supply could limit the reverse-pump excursion until >>>>>>> the software can notice and shut things down.

    MOVs can gobble a lot of joules, but their clipping is very soggy. >>>>>>>

    MOVs are usually cumulative. They can take a certain amount of
    dissipation over their lifetime and then *PHUT* ... POOOF. Like a bank >>>>>> account that runs dry.

    What kills MOVs? Integrated joules? Time-temperature?

    I don't expect a lot of joules per event. Just enough energy to keep >>>>> my supply voltage down until a slowish ADC and the software can shut >>>>> the buck switchers down. 15 milliseconds max, maybe.

    I think it's integrated joules per cubic centimeter of the MOV
    material. This is discussed in the literature on MOVs for protecting
    line-powered equipment from pulse overvoltages, such as from nearby
    lightning strikes. <https://www.deltala.com/>

    Joe Gwinn

    Makes sense. It looks like most MOV appnotes assume that it's across
    an AC line, with kilo-amps available. Or lightning bolts.

    I'll get a few and test them at much lower loads.

    For smaller MOVs, I think that the data sheet specifies capacity in
    Joules. I bet this is the max integrated dose, not the pre-event
    limit. Well, the one-event limit as well.

    Joe Gwinn

    I'm torturing an MOV, a 470KD14. It's rated for 47 volts and 0.1 watt
    and 10 joules.

    At a constant 15 mA, it's at 58.1 volts, which is 0.86 watts. It's
    pretty warm. The voltage seems very stable after 4 hours so far.
    That's about 12K joules.

    It's likely it could do that forever, but the data sheets suggest that
    high power shots can do cumulative damage. I might set up to try that somehow.


    Now lower the voltage. At what voltage does the current drop
    to 0?

    Ed

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Bill Sloman@21:1/5 to Clive Arthur on Wed Oct 9 16:22:34 2024
    On 7/10/2024 1:11 am, Clive Arthur wrote:
    On 06/10/2024 01:56, Jasen Betts wrote:
    On 2024-09-27, john larkin <jl@glen--canyon.com> wrote:
    On Fri, 27 Sep 2024 16:17:42 +0100, liz@poppyrecords.invalid.invalid
    (Liz Tuddenham) wrote:

    john larkin <JL@gct.com> wrote:

    Given a benchtop power supply, you can turn the voltage up and then
    down, and it goes down. Most have a substantial amount of output
    capacitance, and can be driving an external cap too. So something
    pulls the output down.

    I guess that there are no standards for this, but I've never seen a
    supply that just hangs high when it's cranked down.

    I'm designing some programmable multi-channel power suplies and that >>>>> is one of many tangled issues in the project.

    A DC-coupled audio amplifier chip might work as a fully-controllable
    bi-directional power supply if your current and voltage requirements
    were fairly modest.  They have the advantage of being relatively cheap, >>>> well-protected and very fast (by power supply standards).  Some of them >>>> have the tab at input earth voltage, so they don't require isolation
    from the heat sink.

    Unfortunately, it has to be a switching regulator.

    how is that different from a class D audio amplifier?

    Audio doesn't go down to DC.

    But class-D audio amps do. They aren't tightly specified at DC, but
    pulse width modulation does work down to DC.

    --
    Bill Sloman, Sydney

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Joe Gwinn@21:1/5 to All on Wed Oct 9 13:40:49 2024
    On Tue, 08 Oct 2024 17:27:53 -0700, john larkin <jl@glen--canyon.com>
    wrote:

    On Tue, 01 Oct 2024 16:03:40 -0400, Joe Gwinn <joegwinn@comcast.net>
    wrote:

    On Tue, 01 Oct 2024 09:59:27 -0700, john larkin <jl@glen--canyon.com> >>wrote:

    On Tue, 01 Oct 2024 11:24:34 -0400, Joe Gwinn <joegwinn@comcast.net> >>>wrote:

    On Mon, 30 Sep 2024 18:49:14 -0700, john larkin <JL@gct.com> wrote:

    On Mon, 30 Sep 2024 11:49:54 -0700, Joerg <news@analogconsultants.com> >>>>>wrote:

    On 9/30/24 11:24 AM, john larkin wrote:
    On Mon, 30 Sep 2024 08:39:27 -0400, legg <legg@nospam.magma.ca> wrote: >>>>>>>
    On Sun, 29 Sep 2024 08:23:01 -0700, john larkin <JL@gct.com> wrote: >>>>>>>>
    On Sat, 28 Sep 2024 22:28:07 -0700, Joerg <news@analogconsultants.com>
    wrote:

    On 9/27/24 8:07 AM, john larkin wrote:

    Given a benchtop power supply, you can turn the voltage up and then >>>>>>>>>>> down, and it goes down. Most have a substantial amount of output >>>>>>>>>>> capacitance, and can be driving an external cap too. So something >>>>>>>>>>> pulls the output down.


    Often the only internal load is the resistive divider for the regulator
    loop feedback.


    I guess that there are no standards for this, but I've never seen a >>>>>>>>>>> supply that just hangs high when it's cranked down.


    I have some. They drop very slowly when there isn't much load on the output.

    Customers might whine if they ask for 10 volts and see 30. Amd that >>>>>>>>> may be mostly held up by their capacitive load.



    I'm designing some programmable multi-channel power suplies and that
    is one of many tangled issues in the project.


    A synchronous buck architecture should work quite well if you need to
    slew fast. I've used that on a driver that had to modulate a hard >>>>>>>>>> capacitive load at several kHz and above 100V.

    I'm doing some multichannel non-isolated supplies that will be sync >>>>>>>>> buck, using multiple TI DRV8962 chips.

    One problem is that a sync buck can become a boost in the wrong >>>>>>>>> direction, and start charging my +48 supply. If it hits, say, 55 >>>>>>>>> volts, I'll disable the switcher chips, and the outputs can hang. I >>>>>>>>> need to discharge the outputs. I'm thinking about 20 mA of depletion >>>>>>>>> fet per channel.

    You might consider overvoltage protection or a (switched ?)
    internal minimum load.There's usuaally some point in the
    control loop that's a good indicator of a pull-down requirement. >>>>>>>> A single ovp or autoload on the input looks likely to serve
    all of your many sync-bucks.

    RL

    An MOV on the bulk supply could limit the reverse-pump excursion until >>>>>>> the software can notice and shut things down.

    MOVs can gobble a lot of joules, but their clipping is very soggy. >>>>>>>

    MOVs are usually cumulative. They can take a certain amount of >>>>>>dissipation over their lifetime and then *PHUT* ... POOOF. Like a bank >>>>>>account that runs dry.

    What kills MOVs? Integrated joules? Time-temperature?

    I don't expect a lot of joules per event. Just enough energy to keep >>>>>my supply voltage down until a slowish ADC and the software can shut >>>>>the buck switchers down. 15 milliseconds max, maybe.

    I think it's integrated joules per cubic centimeter of the MOV >>>>material. This is discussed in the literature on MOVs for protecting >>>>line-powered equipment from pulse overvoltages, such as from nearby >>>>lightning strikes. <https://www.deltala.com/>

    Joe Gwinn

    Makes sense. It looks like most MOV appnotes assume that it's across
    an AC line, with kilo-amps available. Or lightning bolts.

    I'll get a few and test them at much lower loads.

    For smaller MOVs, I think that the data sheet specifies capacity in
    Joules. I bet this is the max integrated dose, not the pre-event
    limit. Well, the one-event limit as well.

    Joe Gwinn

    I'm torturing an MOV, a 470KD14. It's rated for 47 volts and 0.1 watt
    and 10 joules.

    At a constant 15 mA, it's at 58.1 volts, which is 0.86 watts. It's
    pretty warm. The voltage seems very stable after 4 hours so far.
    That's about 12K joules.

    It's likely it could do that forever, but the data sheets suggest that
    high power shots can do cumulative damage. I might set up to try that >somehow.

    I bet that the duty cycle affects the cumulative damage, with smaller
    duty cycles (more powerful pulses, but more widely separated) doing
    more damage than just the cumulative energy.

    I looked at the Yageo 470KD14 MOV datasheet. It does not seem to
    mention any wearout effect. Perhaps they figured the mechanism out
    and remedied it, which would be a good thing.

    But the "surge life" items under "Reliability" on page 9 only does ten
    surges and notes no visible damage, so we have no idea what happens
    beyond that simple surge test's parameters.

    Joe Gwinn

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From john larkin@21:1/5 to ehsjr on Wed Oct 9 12:53:56 2024
    On Tue, 8 Oct 2024 22:34:16 -0400, ehsjr <ehsjr@verizon.net> wrote:

    On 10/8/2024 8:27 PM, john larkin wrote:
    On Tue, 01 Oct 2024 16:03:40 -0400, Joe Gwinn <joegwinn@comcast.net>
    wrote:

    On Tue, 01 Oct 2024 09:59:27 -0700, john larkin <jl@glen--canyon.com>
    wrote:

    On Tue, 01 Oct 2024 11:24:34 -0400, Joe Gwinn <joegwinn@comcast.net>
    wrote:

    On Mon, 30 Sep 2024 18:49:14 -0700, john larkin <JL@gct.com> wrote:

    On Mon, 30 Sep 2024 11:49:54 -0700, Joerg <news@analogconsultants.com> >>>>>> wrote:

    On 9/30/24 11:24 AM, john larkin wrote:
    On Mon, 30 Sep 2024 08:39:27 -0400, legg <legg@nospam.magma.ca> wrote: >>>>>>>>
    On Sun, 29 Sep 2024 08:23:01 -0700, john larkin <JL@gct.com> wrote: >>>>>>>>>
    On Sat, 28 Sep 2024 22:28:07 -0700, Joerg <news@analogconsultants.com>
    wrote:

    On 9/27/24 8:07 AM, john larkin wrote:

    Given a benchtop power supply, you can turn the voltage up and then
    down, and it goes down. Most have a substantial amount of output >>>>>>>>>>>> capacitance, and can be driving an external cap too. So something >>>>>>>>>>>> pulls the output down.


    Often the only internal load is the resistive divider for the regulator
    loop feedback.


    I guess that there are no standards for this, but I've never seen a
    supply that just hangs high when it's cranked down.


    I have some. They drop very slowly when there isn't much load on the output.

    Customers might whine if they ask for 10 volts and see 30. Amd that >>>>>>>>>> may be mostly held up by their capacitive load.



    I'm designing some programmable multi-channel power suplies and that
    is one of many tangled issues in the project.


    A synchronous buck architecture should work quite well if you need to
    slew fast. I've used that on a driver that had to modulate a hard >>>>>>>>>>> capacitive load at several kHz and above 100V.

    I'm doing some multichannel non-isolated supplies that will be sync >>>>>>>>>> buck, using multiple TI DRV8962 chips.

    One problem is that a sync buck can become a boost in the wrong >>>>>>>>>> direction, and start charging my +48 supply. If it hits, say, 55 >>>>>>>>>> volts, I'll disable the switcher chips, and the outputs can hang. I >>>>>>>>>> need to discharge the outputs. I'm thinking about 20 mA of depletion >>>>>>>>>> fet per channel.

    You might consider overvoltage protection or a (switched ?)
    internal minimum load.There's usuaally some point in the
    control loop that's a good indicator of a pull-down requirement. >>>>>>>>> A single ovp or autoload on the input looks likely to serve
    all of your many sync-bucks.

    RL

    An MOV on the bulk supply could limit the reverse-pump excursion until >>>>>>>> the software can notice and shut things down.

    MOVs can gobble a lot of joules, but their clipping is very soggy. >>>>>>>>

    MOVs are usually cumulative. They can take a certain amount of
    dissipation over their lifetime and then *PHUT* ... POOOF. Like a bank >>>>>>> account that runs dry.

    What kills MOVs? Integrated joules? Time-temperature?

    I don't expect a lot of joules per event. Just enough energy to keep >>>>>> my supply voltage down until a slowish ADC and the software can shut >>>>>> the buck switchers down. 15 milliseconds max, maybe.

    I think it's integrated joules per cubic centimeter of the MOV
    material. This is discussed in the literature on MOVs for protecting >>>>> line-powered equipment from pulse overvoltages, such as from nearby
    lightning strikes. <https://www.deltala.com/>

    Joe Gwinn

    Makes sense. It looks like most MOV appnotes assume that it's across
    an AC line, with kilo-amps available. Or lightning bolts.

    I'll get a few and test them at much lower loads.

    For smaller MOVs, I think that the data sheet specifies capacity in
    Joules. I bet this is the max integrated dose, not the pre-event
    limit. Well, the one-event limit as well.

    Joe Gwinn

    I'm torturing an MOV, a 470KD14. It's rated for 47 volts and 0.1 watt
    and 10 joules.

    At a constant 15 mA, it's at 58.1 volts, which is 0.86 watts. It's
    pretty warm. The voltage seems very stable after 4 hours so far.
    That's about 12K joules.

    It's likely it could do that forever, but the data sheets suggest that
    high power shots can do cumulative damage. I might set up to try that
    somehow.


    Now lower the voltage. At what voltage does the current drop
    to 0?

    Ed


    0 is a fuzzy concept.

    I drops 48.2 v at 1 mA, about the same as always, after 62 K joules.

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From john larkin@21:1/5 to All on Wed Oct 9 12:51:32 2024
    On Wed, 09 Oct 2024 13:40:49 -0400, Joe Gwinn <joegwinn@comcast.net>
    wrote:

    On Tue, 08 Oct 2024 17:27:53 -0700, john larkin <jl@glen--canyon.com>
    wrote:

    On Tue, 01 Oct 2024 16:03:40 -0400, Joe Gwinn <joegwinn@comcast.net>
    wrote:

    On Tue, 01 Oct 2024 09:59:27 -0700, john larkin <jl@glen--canyon.com> >>>wrote:

    On Tue, 01 Oct 2024 11:24:34 -0400, Joe Gwinn <joegwinn@comcast.net> >>>>wrote:

    On Mon, 30 Sep 2024 18:49:14 -0700, john larkin <JL@gct.com> wrote:

    On Mon, 30 Sep 2024 11:49:54 -0700, Joerg <news@analogconsultants.com> >>>>>>wrote:

    On 9/30/24 11:24 AM, john larkin wrote:
    On Mon, 30 Sep 2024 08:39:27 -0400, legg <legg@nospam.magma.ca> wrote: >>>>>>>>
    On Sun, 29 Sep 2024 08:23:01 -0700, john larkin <JL@gct.com> wrote: >>>>>>>>>
    On Sat, 28 Sep 2024 22:28:07 -0700, Joerg <news@analogconsultants.com>
    wrote:

    On 9/27/24 8:07 AM, john larkin wrote:

    Given a benchtop power supply, you can turn the voltage up and then
    down, and it goes down. Most have a substantial amount of output >>>>>>>>>>>> capacitance, and can be driving an external cap too. So something >>>>>>>>>>>> pulls the output down.


    Often the only internal load is the resistive divider for the regulator
    loop feedback.


    I guess that there are no standards for this, but I've never seen a
    supply that just hangs high when it's cranked down.


    I have some. They drop very slowly when there isn't much load on the output.

    Customers might whine if they ask for 10 volts and see 30. Amd that >>>>>>>>>> may be mostly held up by their capacitive load.



    I'm designing some programmable multi-channel power suplies and that
    is one of many tangled issues in the project.


    A synchronous buck architecture should work quite well if you need to
    slew fast. I've used that on a driver that had to modulate a hard >>>>>>>>>>> capacitive load at several kHz and above 100V.

    I'm doing some multichannel non-isolated supplies that will be sync >>>>>>>>>> buck, using multiple TI DRV8962 chips.

    One problem is that a sync buck can become a boost in the wrong >>>>>>>>>> direction, and start charging my +48 supply. If it hits, say, 55 >>>>>>>>>> volts, I'll disable the switcher chips, and the outputs can hang. I >>>>>>>>>> need to discharge the outputs. I'm thinking about 20 mA of depletion >>>>>>>>>> fet per channel.

    You might consider overvoltage protection or a (switched ?)
    internal minimum load.There's usuaally some point in the
    control loop that's a good indicator of a pull-down requirement. >>>>>>>>> A single ovp or autoload on the input looks likely to serve
    all of your many sync-bucks.

    RL

    An MOV on the bulk supply could limit the reverse-pump excursion until >>>>>>>> the software can notice and shut things down.

    MOVs can gobble a lot of joules, but their clipping is very soggy. >>>>>>>>

    MOVs are usually cumulative. They can take a certain amount of >>>>>>>dissipation over their lifetime and then *PHUT* ... POOOF. Like a bank >>>>>>>account that runs dry.

    What kills MOVs? Integrated joules? Time-temperature?

    I don't expect a lot of joules per event. Just enough energy to keep >>>>>>my supply voltage down until a slowish ADC and the software can shut >>>>>>the buck switchers down. 15 milliseconds max, maybe.

    I think it's integrated joules per cubic centimeter of the MOV >>>>>material. This is discussed in the literature on MOVs for protecting >>>>>line-powered equipment from pulse overvoltages, such as from nearby >>>>>lightning strikes. <https://www.deltala.com/>

    Joe Gwinn

    Makes sense. It looks like most MOV appnotes assume that it's across
    an AC line, with kilo-amps available. Or lightning bolts.

    I'll get a few and test them at much lower loads.

    For smaller MOVs, I think that the data sheet specifies capacity in >>>Joules. I bet this is the max integrated dose, not the pre-event
    limit. Well, the one-event limit as well.

    Joe Gwinn

    I'm torturing an MOV, a 470KD14. It's rated for 47 volts and 0.1 watt
    and 10 joules.

    At a constant 15 mA, it's at 58.1 volts, which is 0.86 watts. It's
    pretty warm. The voltage seems very stable after 4 hours so far.
    That's about 12K joules.

    It's likely it could do that forever, but the data sheets suggest that
    high power shots can do cumulative damage. I might set up to try that >>somehow.

    I bet that the duty cycle affects the cumulative damage, with smaller
    duty cycles (more powerful pulses, but more widely separated) doing
    more damage than just the cumulative energy.

    I looked at the Yageo 470KD14 MOV datasheet. It does not seem to
    mention any wearout effect. Perhaps they figured the mechanism out
    and remedied it, which would be a good thing.

    But the "surge life" items under "Reliability" on page 9 only does ten
    surges and notes no visible damage, so we have no idea what happens
    beyond that simple surge test's parameters.

    Joe Gwinn

    On page 5, it doesn't say so but I think the curves are parametreized
    on the number of shots, 1 to 1e6.

    I might have to cut over to using mosfets and resistors to dump my
    overshoot energy. MOVs may be too risky longterm. Pity... they are so
    simple.

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Joe Gwinn@21:1/5 to All on Wed Oct 9 16:37:22 2024
    On Wed, 09 Oct 2024 12:51:32 -0700, john larkin <jl@glen--canyon.com>
    wrote:

    On Wed, 09 Oct 2024 13:40:49 -0400, Joe Gwinn <joegwinn@comcast.net>
    wrote:

    On Tue, 08 Oct 2024 17:27:53 -0700, john larkin <jl@glen--canyon.com> >>wrote:

    On Tue, 01 Oct 2024 16:03:40 -0400, Joe Gwinn <joegwinn@comcast.net> >>>wrote:

    On Tue, 01 Oct 2024 09:59:27 -0700, john larkin <jl@glen--canyon.com> >>>>wrote:

    On Tue, 01 Oct 2024 11:24:34 -0400, Joe Gwinn <joegwinn@comcast.net> >>>>>wrote:

    On Mon, 30 Sep 2024 18:49:14 -0700, john larkin <JL@gct.com> wrote: >>>>>>
    On Mon, 30 Sep 2024 11:49:54 -0700, Joerg <news@analogconsultants.com> >>>>>>>wrote:

    On 9/30/24 11:24 AM, john larkin wrote:
    On Mon, 30 Sep 2024 08:39:27 -0400, legg <legg@nospam.magma.ca> wrote:

    On Sun, 29 Sep 2024 08:23:01 -0700, john larkin <JL@gct.com> wrote: >>>>>>>>>>
    On Sat, 28 Sep 2024 22:28:07 -0700, Joerg <news@analogconsultants.com>
    wrote:

    On 9/27/24 8:07 AM, john larkin wrote:

    Given a benchtop power supply, you can turn the voltage up and then
    down, and it goes down. Most have a substantial amount of output >>>>>>>>>>>>> capacitance, and can be driving an external cap too. So something >>>>>>>>>>>>> pulls the output down.


    Often the only internal load is the resistive divider for the regulator
    loop feedback.


    I guess that there are no standards for this, but I've never seen a
    supply that just hangs high when it's cranked down.


    I have some. They drop very slowly when there isn't much load on the output.

    Customers might whine if they ask for 10 volts and see 30. Amd that >>>>>>>>>>> may be mostly held up by their capacitive load.



    I'm designing some programmable multi-channel power suplies and that
    is one of many tangled issues in the project.


    A synchronous buck architecture should work quite well if you need to
    slew fast. I've used that on a driver that had to modulate a hard >>>>>>>>>>>> capacitive load at several kHz and above 100V.

    I'm doing some multichannel non-isolated supplies that will be sync >>>>>>>>>>> buck, using multiple TI DRV8962 chips.

    One problem is that a sync buck can become a boost in the wrong >>>>>>>>>>> direction, and start charging my +48 supply. If it hits, say, 55 >>>>>>>>>>> volts, I'll disable the switcher chips, and the outputs can hang. I >>>>>>>>>>> need to discharge the outputs. I'm thinking about 20 mA of depletion
    fet per channel.

    You might consider overvoltage protection or a (switched ?) >>>>>>>>>> internal minimum load.There's usuaally some point in the
    control loop that's a good indicator of a pull-down requirement. >>>>>>>>>> A single ovp or autoload on the input looks likely to serve >>>>>>>>>> all of your many sync-bucks.

    RL

    An MOV on the bulk supply could limit the reverse-pump excursion until
    the software can notice and shut things down.

    MOVs can gobble a lot of joules, but their clipping is very soggy. >>>>>>>>>

    MOVs are usually cumulative. They can take a certain amount of >>>>>>>>dissipation over their lifetime and then *PHUT* ... POOOF. Like a bank >>>>>>>>account that runs dry.

    What kills MOVs? Integrated joules? Time-temperature?

    I don't expect a lot of joules per event. Just enough energy to keep >>>>>>>my supply voltage down until a slowish ADC and the software can shut >>>>>>>the buck switchers down. 15 milliseconds max, maybe.

    I think it's integrated joules per cubic centimeter of the MOV >>>>>>material. This is discussed in the literature on MOVs for protecting >>>>>>line-powered equipment from pulse overvoltages, such as from nearby >>>>>>lightning strikes. <https://www.deltala.com/>

    Joe Gwinn

    Makes sense. It looks like most MOV appnotes assume that it's across >>>>>an AC line, with kilo-amps available. Or lightning bolts.

    I'll get a few and test them at much lower loads.

    For smaller MOVs, I think that the data sheet specifies capacity in >>>>Joules. I bet this is the max integrated dose, not the pre-event >>>>limit. Well, the one-event limit as well.

    Joe Gwinn

    I'm torturing an MOV, a 470KD14. It's rated for 47 volts and 0.1 watt
    and 10 joules.

    At a constant 15 mA, it's at 58.1 volts, which is 0.86 watts. It's
    pretty warm. The voltage seems very stable after 4 hours so far.
    That's about 12K joules.

    It's likely it could do that forever, but the data sheets suggest that >>>high power shots can do cumulative damage. I might set up to try that >>>somehow.

    I bet that the duty cycle affects the cumulative damage, with smaller
    duty cycles (more powerful pulses, but more widely separated) doing
    more damage than just the cumulative energy.

    I looked at the Yageo 470KD14 MOV datasheet. It does not seem to
    mention any wearout effect. Perhaps they figured the mechanism out
    and remedied it, which would be a good thing.

    But the "surge life" items under "Reliability" on page 9 only does ten >>surges and notes no visible damage, so we have no idea what happens
    beyond that simple surge test's parameters.

    Joe Gwinn

    On page 5, it doesn't say so but I think the curves are parametreized
    on the number of shots, 1 to 1e6.

    Yes, one can certainly read it that way. Probably have to ask Yageo
    how to read those plots, and the underlying physical mechanism.


    I might have to cut over to using mosfets and resistors to dump my
    overshoot energy. MOVs may be too risky longterm. Pity... they are so
    simple.

    How large are the surges and how long will it be to get to 10^6
    surges in total?

    Joe Gwinn

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From john larkin@21:1/5 to All on Wed Oct 9 14:35:47 2024
    On Wed, 09 Oct 2024 16:37:22 -0400, Joe Gwinn <joegwinn@comcast.net>
    wrote:

    On Wed, 09 Oct 2024 12:51:32 -0700, john larkin <jl@glen--canyon.com>
    wrote:

    On Wed, 09 Oct 2024 13:40:49 -0400, Joe Gwinn <joegwinn@comcast.net>
    wrote:

    On Tue, 08 Oct 2024 17:27:53 -0700, john larkin <jl@glen--canyon.com> >>>wrote:

    On Tue, 01 Oct 2024 16:03:40 -0400, Joe Gwinn <joegwinn@comcast.net> >>>>wrote:

    On Tue, 01 Oct 2024 09:59:27 -0700, john larkin <jl@glen--canyon.com> >>>>>wrote:

    On Tue, 01 Oct 2024 11:24:34 -0400, Joe Gwinn <joegwinn@comcast.net> >>>>>>wrote:

    On Mon, 30 Sep 2024 18:49:14 -0700, john larkin <JL@gct.com> wrote: >>>>>>>
    On Mon, 30 Sep 2024 11:49:54 -0700, Joerg <news@analogconsultants.com> >>>>>>>>wrote:

    On 9/30/24 11:24 AM, john larkin wrote:
    On Mon, 30 Sep 2024 08:39:27 -0400, legg <legg@nospam.magma.ca> wrote:

    On Sun, 29 Sep 2024 08:23:01 -0700, john larkin <JL@gct.com> wrote: >>>>>>>>>>>
    On Sat, 28 Sep 2024 22:28:07 -0700, Joerg <news@analogconsultants.com>
    wrote:

    On 9/27/24 8:07 AM, john larkin wrote:

    Given a benchtop power supply, you can turn the voltage up and then
    down, and it goes down. Most have a substantial amount of output >>>>>>>>>>>>>> capacitance, and can be driving an external cap too. So something
    pulls the output down.


    Often the only internal load is the resistive divider for the regulator
    loop feedback.


    I guess that there are no standards for this, but I've never seen a
    supply that just hangs high when it's cranked down. >>>>>>>>>>>>>>

    I have some. They drop very slowly when there isn't much load on the output.

    Customers might whine if they ask for 10 volts and see 30. Amd that
    may be mostly held up by their capacitive load.



    I'm designing some programmable multi-channel power suplies and that
    is one of many tangled issues in the project.


    A synchronous buck architecture should work quite well if you need to
    slew fast. I've used that on a driver that had to modulate a hard >>>>>>>>>>>>> capacitive load at several kHz and above 100V.

    I'm doing some multichannel non-isolated supplies that will be sync
    buck, using multiple TI DRV8962 chips.

    One problem is that a sync buck can become a boost in the wrong >>>>>>>>>>>> direction, and start charging my +48 supply. If it hits, say, 55 >>>>>>>>>>>> volts, I'll disable the switcher chips, and the outputs can hang. I
    need to discharge the outputs. I'm thinking about 20 mA of depletion
    fet per channel.

    You might consider overvoltage protection or a (switched ?) >>>>>>>>>>> internal minimum load.There's usuaally some point in the >>>>>>>>>>> control loop that's a good indicator of a pull-down requirement. >>>>>>>>>>> A single ovp or autoload on the input looks likely to serve >>>>>>>>>>> all of your many sync-bucks.

    RL

    An MOV on the bulk supply could limit the reverse-pump excursion until
    the software can notice and shut things down.

    MOVs can gobble a lot of joules, but their clipping is very soggy. >>>>>>>>>>

    MOVs are usually cumulative. They can take a certain amount of >>>>>>>>>dissipation over their lifetime and then *PHUT* ... POOOF. Like a bank >>>>>>>>>account that runs dry.

    What kills MOVs? Integrated joules? Time-temperature?

    I don't expect a lot of joules per event. Just enough energy to keep >>>>>>>>my supply voltage down until a slowish ADC and the software can shut >>>>>>>>the buck switchers down. 15 milliseconds max, maybe.

    I think it's integrated joules per cubic centimeter of the MOV >>>>>>>material. This is discussed in the literature on MOVs for protecting >>>>>>>line-powered equipment from pulse overvoltages, such as from nearby >>>>>>>lightning strikes. <https://www.deltala.com/>

    Joe Gwinn

    Makes sense. It looks like most MOV appnotes assume that it's across >>>>>>an AC line, with kilo-amps available. Or lightning bolts.

    I'll get a few and test them at much lower loads.

    For smaller MOVs, I think that the data sheet specifies capacity in >>>>>Joules. I bet this is the max integrated dose, not the pre-event >>>>>limit. Well, the one-event limit as well.

    Joe Gwinn

    I'm torturing an MOV, a 470KD14. It's rated for 47 volts and 0.1 watt >>>>and 10 joules.

    At a constant 15 mA, it's at 58.1 volts, which is 0.86 watts. It's >>>>pretty warm. The voltage seems very stable after 4 hours so far.
    That's about 12K joules.

    It's likely it could do that forever, but the data sheets suggest that >>>>high power shots can do cumulative damage. I might set up to try that >>>>somehow.

    I bet that the duty cycle affects the cumulative damage, with smaller >>>duty cycles (more powerful pulses, but more widely separated) doing
    more damage than just the cumulative energy.

    I looked at the Yageo 470KD14 MOV datasheet. It does not seem to >>>mention any wearout effect. Perhaps they figured the mechanism out
    and remedied it, which would be a good thing.

    But the "surge life" items under "Reliability" on page 9 only does ten >>>surges and notes no visible damage, so we have no idea what happens >>>beyond that simple surge test's parameters.

    Joe Gwinn

    On page 5, it doesn't say so but I think the curves are parametreized
    on the number of shots, 1 to 1e6.

    Yes, one can certainly read it that way. Probably have to ask Yageo
    how to read those plots, and the underlying physical mechanism.


    I might have to cut over to using mosfets and resistors to dump my >>overshoot energy. MOVs may be too risky longterm. Pity... they are so >>simple.

    How large are the surges and how long will it be to get to 10^6
    surges in total?

    Joe Gwinn

    That's tricky. Some user might slam a capacitive load or a motor a lot
    of times.

    Here's a Riedon ceramic DPAK 50 ohm resistor. It could absorb at least
    50j, 100 with two in parallel. That would work. They will need a
    mosfet to switch them on when the 48v supply gets over-driven to 58
    maybe.

    https://www.dropbox.com/scl/fi/octctz94vdi4ac4aageit/Dpak-50r-joules.jpg?rlkey=y21a3x8xmkno82ezrb4vefxrr&raw=1

    The Caddock TO-220 resistors have a big metal tab like a mosfet and
    would absorb more joules, but are more expensive. They would be an
    option.

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From ehsjr@21:1/5 to john larkin on Thu Oct 10 15:08:03 2024
    On 10/9/2024 3:53 PM, john larkin wrote:
    On Tue, 8 Oct 2024 22:34:16 -0400, ehsjr <ehsjr@verizon.net> wrote:

    On 10/8/2024 8:27 PM, john larkin wrote:
    On Tue, 01 Oct 2024 16:03:40 -0400, Joe Gwinn <joegwinn@comcast.net>
    wrote:

    On Tue, 01 Oct 2024 09:59:27 -0700, john larkin <jl@glen--canyon.com>
    wrote:

    On Tue, 01 Oct 2024 11:24:34 -0400, Joe Gwinn <joegwinn@comcast.net> >>>>> wrote:

    On Mon, 30 Sep 2024 18:49:14 -0700, john larkin <JL@gct.com> wrote: >>>>>>
    On Mon, 30 Sep 2024 11:49:54 -0700, Joerg <news@analogconsultants.com> >>>>>>> wrote:

    On 9/30/24 11:24 AM, john larkin wrote:
    On Mon, 30 Sep 2024 08:39:27 -0400, legg <legg@nospam.magma.ca> wrote:

    On Sun, 29 Sep 2024 08:23:01 -0700, john larkin <JL@gct.com> wrote: >>>>>>>>>>
    On Sat, 28 Sep 2024 22:28:07 -0700, Joerg <news@analogconsultants.com>
    wrote:

    On 9/27/24 8:07 AM, john larkin wrote:

    Given a benchtop power supply, you can turn the voltage up and then
    down, and it goes down. Most have a substantial amount of output >>>>>>>>>>>>> capacitance, and can be driving an external cap too. So something >>>>>>>>>>>>> pulls the output down.


    Often the only internal load is the resistive divider for the regulator
    loop feedback.


    I guess that there are no standards for this, but I've never seen a
    supply that just hangs high when it's cranked down.


    I have some. They drop very slowly when there isn't much load on the output.

    Customers might whine if they ask for 10 volts and see 30. Amd that >>>>>>>>>>> may be mostly held up by their capacitive load.



    I'm designing some programmable multi-channel power suplies and that
    is one of many tangled issues in the project.


    A synchronous buck architecture should work quite well if you need to
    slew fast. I've used that on a driver that had to modulate a hard >>>>>>>>>>>> capacitive load at several kHz and above 100V.

    I'm doing some multichannel non-isolated supplies that will be sync >>>>>>>>>>> buck, using multiple TI DRV8962 chips.

    One problem is that a sync buck can become a boost in the wrong >>>>>>>>>>> direction, and start charging my +48 supply. If it hits, say, 55 >>>>>>>>>>> volts, I'll disable the switcher chips, and the outputs can hang. I >>>>>>>>>>> need to discharge the outputs. I'm thinking about 20 mA of depletion
    fet per channel.

    You might consider overvoltage protection or a (switched ?) >>>>>>>>>> internal minimum load.There's usuaally some point in the
    control loop that's a good indicator of a pull-down requirement. >>>>>>>>>> A single ovp or autoload on the input looks likely to serve >>>>>>>>>> all of your many sync-bucks.

    RL

    An MOV on the bulk supply could limit the reverse-pump excursion until
    the software can notice and shut things down.

    MOVs can gobble a lot of joules, but their clipping is very soggy. >>>>>>>>>

    MOVs are usually cumulative. They can take a certain amount of >>>>>>>> dissipation over their lifetime and then *PHUT* ... POOOF. Like a bank >>>>>>>> account that runs dry.

    What kills MOVs? Integrated joules? Time-temperature?

    I don't expect a lot of joules per event. Just enough energy to keep >>>>>>> my supply voltage down until a slowish ADC and the software can shut >>>>>>> the buck switchers down. 15 milliseconds max, maybe.

    I think it's integrated joules per cubic centimeter of the MOV
    material. This is discussed in the literature on MOVs for protecting >>>>>> line-powered equipment from pulse overvoltages, such as from nearby >>>>>> lightning strikes. <https://www.deltala.com/>

    Joe Gwinn

    Makes sense. It looks like most MOV appnotes assume that it's across >>>>> an AC line, with kilo-amps available. Or lightning bolts.

    I'll get a few and test them at much lower loads.

    For smaller MOVs, I think that the data sheet specifies capacity in
    Joules. I bet this is the max integrated dose, not the pre-event
    limit. Well, the one-event limit as well.

    Joe Gwinn

    I'm torturing an MOV, a 470KD14. It's rated for 47 volts and 0.1 watt
    and 10 joules.

    At a constant 15 mA, it's at 58.1 volts, which is 0.86 watts. It's
    pretty warm. The voltage seems very stable after 4 hours so far.
    That's about 12K joules.

    It's likely it could do that forever, but the data sheets suggest that
    high power shots can do cumulative damage. I might set up to try that
    somehow.


    Now lower the voltage. At what voltage does the current drop
    to 0?

    Ed


    0 is a fuzzy concept.

    I drops 48.2 v at 1 mA, about the same as always, after 62 K joules.


    Ok, thanks. Looks like it proves your idea. (-:
    Ed

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Joe Gwinn@21:1/5 to All on Thu Oct 10 20:30:50 2024
    On Wed, 09 Oct 2024 14:35:47 -0700, john larkin <jl@glen--canyon.com>
    wrote:

    On Wed, 09 Oct 2024 16:37:22 -0400, Joe Gwinn <joegwinn@comcast.net>
    wrote:

    On Wed, 09 Oct 2024 12:51:32 -0700, john larkin <jl@glen--canyon.com> >>wrote:

    On Wed, 09 Oct 2024 13:40:49 -0400, Joe Gwinn <joegwinn@comcast.net> >>>wrote:

    On Tue, 08 Oct 2024 17:27:53 -0700, john larkin <jl@glen--canyon.com> >>>>wrote:

    On Tue, 01 Oct 2024 16:03:40 -0400, Joe Gwinn <joegwinn@comcast.net> >>>>>wrote:

    On Tue, 01 Oct 2024 09:59:27 -0700, john larkin <jl@glen--canyon.com> >>>>>>wrote:

    On Tue, 01 Oct 2024 11:24:34 -0400, Joe Gwinn <joegwinn@comcast.net> >>>>>>>wrote:

    On Mon, 30 Sep 2024 18:49:14 -0700, john larkin <JL@gct.com> wrote: >>>>>>>>
    On Mon, 30 Sep 2024 11:49:54 -0700, Joerg <news@analogconsultants.com> >>>>>>>>>wrote:

    On 9/30/24 11:24 AM, john larkin wrote:
    On Mon, 30 Sep 2024 08:39:27 -0400, legg <legg@nospam.magma.ca> wrote:

    On Sun, 29 Sep 2024 08:23:01 -0700, john larkin <JL@gct.com> wrote:

    On Sat, 28 Sep 2024 22:28:07 -0700, Joerg <news@analogconsultants.com>
    wrote:

    On 9/27/24 8:07 AM, john larkin wrote:

    Given a benchtop power supply, you can turn the voltage up and then
    down, and it goes down. Most have a substantial amount of output
    capacitance, and can be driving an external cap too. So something
    pulls the output down.


    Often the only internal load is the resistive divider for the regulator
    loop feedback.


    I guess that there are no standards for this, but I've never seen a
    supply that just hangs high when it's cranked down. >>>>>>>>>>>>>>>

    I have some. They drop very slowly when there isn't much load on the output.

    Customers might whine if they ask for 10 volts and see 30. Amd that
    may be mostly held up by their capacitive load.



    I'm designing some programmable multi-channel power suplies and that
    is one of many tangled issues in the project.


    A synchronous buck architecture should work quite well if you need to
    slew fast. I've used that on a driver that had to modulate a hard
    capacitive load at several kHz and above 100V.

    I'm doing some multichannel non-isolated supplies that will be sync
    buck, using multiple TI DRV8962 chips.

    One problem is that a sync buck can become a boost in the wrong >>>>>>>>>>>>> direction, and start charging my +48 supply. If it hits, say, 55 >>>>>>>>>>>>> volts, I'll disable the switcher chips, and the outputs can hang. I
    need to discharge the outputs. I'm thinking about 20 mA of depletion
    fet per channel.

    You might consider overvoltage protection or a (switched ?) >>>>>>>>>>>> internal minimum load.There's usuaally some point in the >>>>>>>>>>>> control loop that's a good indicator of a pull-down requirement. >>>>>>>>>>>> A single ovp or autoload on the input looks likely to serve >>>>>>>>>>>> all of your many sync-bucks.

    RL

    An MOV on the bulk supply could limit the reverse-pump excursion until
    the software can notice and shut things down.

    MOVs can gobble a lot of joules, but their clipping is very soggy. >>>>>>>>>>>

    MOVs are usually cumulative. They can take a certain amount of >>>>>>>>>>dissipation over their lifetime and then *PHUT* ... POOOF. Like a bank
    account that runs dry.

    What kills MOVs? Integrated joules? Time-temperature?

    I don't expect a lot of joules per event. Just enough energy to keep >>>>>>>>>my supply voltage down until a slowish ADC and the software can shut >>>>>>>>>the buck switchers down. 15 milliseconds max, maybe.

    I think it's integrated joules per cubic centimeter of the MOV >>>>>>>>material. This is discussed in the literature on MOVs for protecting >>>>>>>>line-powered equipment from pulse overvoltages, such as from nearby >>>>>>>>lightning strikes. <https://www.deltala.com/>

    Joe Gwinn

    Makes sense. It looks like most MOV appnotes assume that it's across >>>>>>>an AC line, with kilo-amps available. Or lightning bolts.

    I'll get a few and test them at much lower loads.

    For smaller MOVs, I think that the data sheet specifies capacity in >>>>>>Joules. I bet this is the max integrated dose, not the pre-event >>>>>>limit. Well, the one-event limit as well.

    Joe Gwinn

    I'm torturing an MOV, a 470KD14. It's rated for 47 volts and 0.1 watt >>>>>and 10 joules.

    At a constant 15 mA, it's at 58.1 volts, which is 0.86 watts. It's >>>>>pretty warm. The voltage seems very stable after 4 hours so far. >>>>>That's about 12K joules.

    It's likely it could do that forever, but the data sheets suggest that >>>>>high power shots can do cumulative damage. I might set up to try that >>>>>somehow.

    I bet that the duty cycle affects the cumulative damage, with smaller >>>>duty cycles (more powerful pulses, but more widely separated) doing >>>>more damage than just the cumulative energy.

    I looked at the Yageo 470KD14 MOV datasheet. It does not seem to >>>>mention any wearout effect. Perhaps they figured the mechanism out
    and remedied it, which would be a good thing.

    But the "surge life" items under "Reliability" on page 9 only does ten >>>>surges and notes no visible damage, so we have no idea what happens >>>>beyond that simple surge test's parameters.

    Joe Gwinn

    On page 5, it doesn't say so but I think the curves are parametreized
    on the number of shots, 1 to 1e6.

    Yes, one can certainly read it that way. Probably have to ask Yageo
    how to read those plots, and the underlying physical mechanism.


    I might have to cut over to using mosfets and resistors to dump my >>>overshoot energy. MOVs may be too risky longterm. Pity... they are so >>>simple.

    How large are the surges and how long will it be to get to 10^6
    surges in total?

    Joe Gwinn

    That's tricky. Some user might slam a capacitive load or a motor a lot
    of times.

    Unh.


    Here's a Riedon ceramic DPAK 50 ohm resistor. It could absorb at least
    50j, 100 with two in parallel. That would work. They will need a
    mosfet to switch them on when the 48v supply gets over-driven to 58
    maybe.

    <https://www.dropbox.com/scl/fi/octctz94vdi4ac4aageit/Dpak-50r-joules.jpg?rlkey=y21a3x8xmkno82ezrb4vefxrr&raw=1>

    Cute, even in pairs. If two, would stepped response (two MOSFETs) be worthwhile?

    For the record, VFD (Variable Frequency Drive) for three-phase motors
    also have the backdrive problem when stopping. The 2 HP motor and
    lathe chuck being driven have considerable rotational inertia, and can
    store much energy. The objective is to stop in maybe five seconds
    (too fast stresses the motor windings). I have a 100 watt power
    resistor in a ventilated housing above the VFD, which is on the wall
    behind the lathe being powered. It is possible to get that resistor
    to a red glow.


    Joe Gwinn


    The Caddock TO-220 resistors have a big metal tab like a mosfet and
    would absorb more joules, but are more expensive. They would be an
    option.

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From john larkin@21:1/5 to ehsjr on Thu Oct 10 19:01:19 2024
    On Thu, 10 Oct 2024 15:08:03 -0400, ehsjr <ehsjr@verizon.net> wrote:

    On 10/9/2024 3:53 PM, john larkin wrote:
    On Tue, 8 Oct 2024 22:34:16 -0400, ehsjr <ehsjr@verizon.net> wrote:

    On 10/8/2024 8:27 PM, john larkin wrote:
    On Tue, 01 Oct 2024 16:03:40 -0400, Joe Gwinn <joegwinn@comcast.net>
    wrote:

    On Tue, 01 Oct 2024 09:59:27 -0700, john larkin <jl@glen--canyon.com> >>>>> wrote:

    On Tue, 01 Oct 2024 11:24:34 -0400, Joe Gwinn <joegwinn@comcast.net> >>>>>> wrote:

    On Mon, 30 Sep 2024 18:49:14 -0700, john larkin <JL@gct.com> wrote: >>>>>>>
    On Mon, 30 Sep 2024 11:49:54 -0700, Joerg <news@analogconsultants.com> >>>>>>>> wrote:

    On 9/30/24 11:24 AM, john larkin wrote:
    On Mon, 30 Sep 2024 08:39:27 -0400, legg <legg@nospam.magma.ca> wrote:

    On Sun, 29 Sep 2024 08:23:01 -0700, john larkin <JL@gct.com> wrote: >>>>>>>>>>>
    On Sat, 28 Sep 2024 22:28:07 -0700, Joerg <news@analogconsultants.com>
    wrote:

    On 9/27/24 8:07 AM, john larkin wrote:

    Given a benchtop power supply, you can turn the voltage up and then
    down, and it goes down. Most have a substantial amount of output >>>>>>>>>>>>>> capacitance, and can be driving an external cap too. So something
    pulls the output down.


    Often the only internal load is the resistive divider for the regulator
    loop feedback.


    I guess that there are no standards for this, but I've never seen a
    supply that just hangs high when it's cranked down. >>>>>>>>>>>>>>

    I have some. They drop very slowly when there isn't much load on the output.

    Customers might whine if they ask for 10 volts and see 30. Amd that
    may be mostly held up by their capacitive load.



    I'm designing some programmable multi-channel power suplies and that
    is one of many tangled issues in the project.


    A synchronous buck architecture should work quite well if you need to
    slew fast. I've used that on a driver that had to modulate a hard >>>>>>>>>>>>> capacitive load at several kHz and above 100V.

    I'm doing some multichannel non-isolated supplies that will be sync
    buck, using multiple TI DRV8962 chips.

    One problem is that a sync buck can become a boost in the wrong >>>>>>>>>>>> direction, and start charging my +48 supply. If it hits, say, 55 >>>>>>>>>>>> volts, I'll disable the switcher chips, and the outputs can hang. I
    need to discharge the outputs. I'm thinking about 20 mA of depletion
    fet per channel.

    You might consider overvoltage protection or a (switched ?) >>>>>>>>>>> internal minimum load.There's usuaally some point in the >>>>>>>>>>> control loop that's a good indicator of a pull-down requirement. >>>>>>>>>>> A single ovp or autoload on the input looks likely to serve >>>>>>>>>>> all of your many sync-bucks.

    RL

    An MOV on the bulk supply could limit the reverse-pump excursion until
    the software can notice and shut things down.

    MOVs can gobble a lot of joules, but their clipping is very soggy. >>>>>>>>>>

    MOVs are usually cumulative. They can take a certain amount of >>>>>>>>> dissipation over their lifetime and then *PHUT* ... POOOF. Like a bank
    account that runs dry.

    What kills MOVs? Integrated joules? Time-temperature?

    I don't expect a lot of joules per event. Just enough energy to keep >>>>>>>> my supply voltage down until a slowish ADC and the software can shut >>>>>>>> the buck switchers down. 15 milliseconds max, maybe.

    I think it's integrated joules per cubic centimeter of the MOV
    material. This is discussed in the literature on MOVs for protecting >>>>>>> line-powered equipment from pulse overvoltages, such as from nearby >>>>>>> lightning strikes. <https://www.deltala.com/>

    Joe Gwinn

    Makes sense. It looks like most MOV appnotes assume that it's across >>>>>> an AC line, with kilo-amps available. Or lightning bolts.

    I'll get a few and test them at much lower loads.

    For smaller MOVs, I think that the data sheet specifies capacity in
    Joules. I bet this is the max integrated dose, not the pre-event
    limit. Well, the one-event limit as well.

    Joe Gwinn

    I'm torturing an MOV, a 470KD14. It's rated for 47 volts and 0.1 watt
    and 10 joules.

    At a constant 15 mA, it's at 58.1 volts, which is 0.86 watts. It's
    pretty warm. The voltage seems very stable after 4 hours so far.
    That's about 12K joules.

    It's likely it could do that forever, but the data sheets suggest that >>>> high power shots can do cumulative damage. I might set up to try that
    somehow.


    Now lower the voltage. At what voltage does the current drop
    to 0?

    Ed


    0 is a fuzzy concept.

    I drops 48.2 v at 1 mA, about the same as always, after 62 K joules.


    Ok, thanks. Looks like it proves your idea. (-:
    Ed

    I think there is damage at higher pulse energies, as few as a single
    pulse.

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From john larkin@21:1/5 to All on Thu Oct 10 19:06:03 2024
    On Thu, 10 Oct 2024 20:30:50 -0400, Joe Gwinn <joegwinn@comcast.net>
    wrote:

    On Wed, 09 Oct 2024 14:35:47 -0700, john larkin <jl@glen--canyon.com>
    wrote:

    On Wed, 09 Oct 2024 16:37:22 -0400, Joe Gwinn <joegwinn@comcast.net>
    wrote:

    On Wed, 09 Oct 2024 12:51:32 -0700, john larkin <jl@glen--canyon.com> >>>wrote:

    On Wed, 09 Oct 2024 13:40:49 -0400, Joe Gwinn <joegwinn@comcast.net> >>>>wrote:

    On Tue, 08 Oct 2024 17:27:53 -0700, john larkin <jl@glen--canyon.com> >>>>>wrote:

    On Tue, 01 Oct 2024 16:03:40 -0400, Joe Gwinn <joegwinn@comcast.net> >>>>>>wrote:

    On Tue, 01 Oct 2024 09:59:27 -0700, john larkin <jl@glen--canyon.com> >>>>>>>wrote:

    On Tue, 01 Oct 2024 11:24:34 -0400, Joe Gwinn <joegwinn@comcast.net> >>>>>>>>wrote:

    On Mon, 30 Sep 2024 18:49:14 -0700, john larkin <JL@gct.com> wrote: >>>>>>>>>
    On Mon, 30 Sep 2024 11:49:54 -0700, Joerg <news@analogconsultants.com>
    wrote:

    On 9/30/24 11:24 AM, john larkin wrote:
    On Mon, 30 Sep 2024 08:39:27 -0400, legg <legg@nospam.magma.ca> wrote:

    On Sun, 29 Sep 2024 08:23:01 -0700, john larkin <JL@gct.com> wrote:

    On Sat, 28 Sep 2024 22:28:07 -0700, Joerg <news@analogconsultants.com>
    wrote:

    On 9/27/24 8:07 AM, john larkin wrote:

    Given a benchtop power supply, you can turn the voltage up and then
    down, and it goes down. Most have a substantial amount of output
    capacitance, and can be driving an external cap too. So something
    pulls the output down.


    Often the only internal load is the resistive divider for the regulator
    loop feedback.


    I guess that there are no standards for this, but I've never seen a
    supply that just hangs high when it's cranked down. >>>>>>>>>>>>>>>>

    I have some. They drop very slowly when there isn't much load on the output.

    Customers might whine if they ask for 10 volts and see 30. Amd that
    may be mostly held up by their capacitive load.



    I'm designing some programmable multi-channel power suplies and that
    is one of many tangled issues in the project.


    A synchronous buck architecture should work quite well if you need to
    slew fast. I've used that on a driver that had to modulate a hard
    capacitive load at several kHz and above 100V.

    I'm doing some multichannel non-isolated supplies that will be sync
    buck, using multiple TI DRV8962 chips.

    One problem is that a sync buck can become a boost in the wrong >>>>>>>>>>>>>> direction, and start charging my +48 supply. If it hits, say, 55 >>>>>>>>>>>>>> volts, I'll disable the switcher chips, and the outputs can hang. I
    need to discharge the outputs. I'm thinking about 20 mA of depletion
    fet per channel.

    You might consider overvoltage protection or a (switched ?) >>>>>>>>>>>>> internal minimum load.There's usuaally some point in the >>>>>>>>>>>>> control loop that's a good indicator of a pull-down requirement. >>>>>>>>>>>>> A single ovp or autoload on the input looks likely to serve >>>>>>>>>>>>> all of your many sync-bucks.

    RL

    An MOV on the bulk supply could limit the reverse-pump excursion until
    the software can notice and shut things down.

    MOVs can gobble a lot of joules, but their clipping is very soggy. >>>>>>>>>>>>

    MOVs are usually cumulative. They can take a certain amount of >>>>>>>>>>>dissipation over their lifetime and then *PHUT* ... POOOF. Like a bank
    account that runs dry.

    What kills MOVs? Integrated joules? Time-temperature?

    I don't expect a lot of joules per event. Just enough energy to keep >>>>>>>>>>my supply voltage down until a slowish ADC and the software can shut >>>>>>>>>>the buck switchers down. 15 milliseconds max, maybe.

    I think it's integrated joules per cubic centimeter of the MOV >>>>>>>>>material. This is discussed in the literature on MOVs for protecting >>>>>>>>>line-powered equipment from pulse overvoltages, such as from nearby >>>>>>>>>lightning strikes. <https://www.deltala.com/>

    Joe Gwinn

    Makes sense. It looks like most MOV appnotes assume that it's across >>>>>>>>an AC line, with kilo-amps available. Or lightning bolts.

    I'll get a few and test them at much lower loads.

    For smaller MOVs, I think that the data sheet specifies capacity in >>>>>>>Joules. I bet this is the max integrated dose, not the pre-event >>>>>>>limit. Well, the one-event limit as well.

    Joe Gwinn

    I'm torturing an MOV, a 470KD14. It's rated for 47 volts and 0.1 watt >>>>>>and 10 joules.

    At a constant 15 mA, it's at 58.1 volts, which is 0.86 watts. It's >>>>>>pretty warm. The voltage seems very stable after 4 hours so far. >>>>>>That's about 12K joules.

    It's likely it could do that forever, but the data sheets suggest that >>>>>>high power shots can do cumulative damage. I might set up to try that >>>>>>somehow.

    I bet that the duty cycle affects the cumulative damage, with smaller >>>>>duty cycles (more powerful pulses, but more widely separated) doing >>>>>more damage than just the cumulative energy.

    I looked at the Yageo 470KD14 MOV datasheet. It does not seem to >>>>>mention any wearout effect. Perhaps they figured the mechanism out >>>>>and remedied it, which would be a good thing.

    But the "surge life" items under "Reliability" on page 9 only does ten >>>>>surges and notes no visible damage, so we have no idea what happens >>>>>beyond that simple surge test's parameters.

    Joe Gwinn

    On page 5, it doesn't say so but I think the curves are parametreized >>>>on the number of shots, 1 to 1e6.

    Yes, one can certainly read it that way. Probably have to ask Yageo
    how to read those plots, and the underlying physical mechanism.


    I might have to cut over to using mosfets and resistors to dump my >>>>overshoot energy. MOVs may be too risky longterm. Pity... they are so >>>>simple.

    How large are the surges and how long will it be to get to 10^6
    surges in total?

    Joe Gwinn

    That's tricky. Some user might slam a capacitive load or a motor a lot
    of times.

    Unh.


    Here's a Riedon ceramic DPAK 50 ohm resistor. It could absorb at least
    50j, 100 with two in parallel. That would work. They will need a
    mosfet to switch them on when the 48v supply gets over-driven to 58
    maybe.
    <https://www.dropbox.com/scl/fi/octctz94vdi4ac4aageit/Dpak-50r-joules.jpg?rlkey=y21a3x8xmkno82ezrb4vefxrr&raw=1>

    Cute, even in pairs. If two, would stepped response (two MOSFETs) be >worthwhile?

    For the record, VFD (Variable Frequency Drive) for three-phase motors
    also have the backdrive problem when stopping. The 2 HP motor and
    lathe chuck being driven have considerable rotational inertia, and can
    store much energy. The objective is to stop in maybe five seconds
    (too fast stresses the motor windings). I have a 100 watt power
    resistor in a ventilated housing above the VFD, which is on the wall
    behind the lathe being powered. It is possible to get that resistor
    to a red glow.


    Joe Gwinn



    Just like a car in hill country. Power up a slope and fry the brakes
    coming down.

    We have runaway truck lanes here, a side road filled with gravel. A
    big loaded semi doesn't have much engine braking and then smokes the
    brakes.

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From john larkin@21:1/5 to legg on Sat Oct 12 14:42:12 2024
    On Wed, 02 Oct 2024 08:10:50 -0400, legg <legg@nospam.magma.ca> wrote:

    On Tue, 01 Oct 2024 07:53:16 -0700, john larkin <JL@gct.com> wrote:

    On Tue, 01 Oct 2024 06:35:35 GMT, Jan Panteltje <alien@comet.invalid> >>wrote:

    On a sunny day (Mon, 30 Sep 2024 08:33:42 -0700) it happened john larkin >>><JL@gct.com> wrote in <1rglfj5jebk56bmbna6udrb9trr666uotm@4ax.com>:

    On Mon, 30 Sep 2024 18:42:08 +0800, Sylvia Else <sylvia@email.invalid> >>>>wrote:

    On 30-Sept-24 1:21 am, john larkin wrote:
    On Sat, 28 Sep 2024 10:21:46 -0700, john larkin <JL@gct.com> wrote: >>>>>>
    On Sat, 28 Sep 2024 09:44:44 -0400, legg <legg@nospam.magma.ca> wrote: >>>>>>>
    On Fri, 27 Sep 2024 08:07:29 -0700, john larkin <JL@gct.com> wrote: >>>>>>>>

    Given a benchtop power supply, you can turn the voltage up and then >>>>>>>>> down, and it goes down. Most have a substantial amount of output >>>>>>>>> capacitance, and can be driving an external cap too. So something >>>>>>>>> pulls the output down.

    I guess that there are no standards for this, but I've never seen a >>>>>>>>> supply that just hangs high when it's cranked down.

    I'm designing some programmable multi-channel power suplies and that >>>>>>>>> is one of many tangled issues in the project.

    Twiddling the adjustment knob on a bench supply doesn't
    represent a dramatic change - and most adjustible
    supplies don't load their output terminals with a
    lot of capacitance.

    I've measured a few, and got output terminal capacitance of a few >>>>>>> hundred to maybe 2000 uF.

    People here might measure some random power supplies. I leave them off >>>>>>> and connect to a 50 ohm sinewave-output function generator and find >>>>>>> the -3 dB point. One could use a square wave and scope the slopes too. >>>>>>> Keeping the amplitude low will avoid turning semi junctions on.

    Come on guys, quit pontificating and start measuring.


    At this stage in the process, you seem to have some odd constraints. Why >>>>>the specific h-bridge driver? Why non-isolated?

    Sylvia.

    What I suggested is that a few people grab their bench power supplies >>>>and see what sort of output capacitance they have.

    The simplest way is to crank the voltage up and short the ouput and
    see how much it sparks. Or measure the capacitance, even.

    That quad TI driver is cheap and available and seems to have good >>>>protections. TI makes good stuff and keeps it in production >>>>approximately forever.

    Non-isolated because that's simple and gets more channels on a small >>>>board. The launch customer says that power supplies don't usually need >>>>to be grounded because everything is grounded on an airplane.

    Was watching one of thse 'Mayday' series on German TV yesterday.
    Airplane got hit by lightning, ball ligtning travelled through the cabin, >>>pilots bllided and distracted, did not hear the auto pilot still engaged warning
    started fighting the auto-pilot...
    almost crashed
    Normally auto pilots would dis-engage when you started manual steering >>>Indicator between auto pilot 'on' and auto-pilot 'off'
    was color change from green to white symbol on the instrumenrts that looked like this
    AP<

    Miracle they could see anything after the lightning strike, green and white are very close togeter
    for teevee white is .11 blue .59 green and .3 red.
    Something to take into account if you are writing display code.
    Do you?
    no credits...


    I am thinking that nobody here actually has a power supply.

    Larkin's power supply party !

    There are a couple of dozen supplys in this lab,
    of all shapes and sizes - half of them never seen
    on a vendor's shelf.

    Depending on what they're supposed to do, they'll
    have different final capacitive filter stage values.

    You want people running around measuring adjustible
    bench supplies, to compare to your unique low power
    multi-output 'not yet in hardware' figment.

    Get real.

    The standard adjustible (or fixed) linear bench supply, will see
    between 47 and 220uF on their output terminals and a built-in
    loading of between 1/2 and 2W, depending upon that C and it's
    load rating.

    Switchers are all over the map and may self-load as a
    mattwr of policy - but none like to regulate at zero
    load or zero volts - so again between 1/2 and 2W internal
    loading, if the mfrs actually give a damn - unless it's
    a DC-coupled bipolar job, in which case their'll be
    a zoebel network.

    Have a nice day.

    RL

    Some power supplies have enough output capacitance to blow a fuse in a
    DVM on its current range, even if the power suppy is set to a low
    current limit. That's good to know.

    I've ordered fuses for the two DMMs that my old HP6212A just blew up.
    I was testing some MOVs and it was set for 20 mA current limit and
    zapped a couple of 600 mA fuses.

    The quick test is to short a supply and see how loud the spark is.

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)