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.
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.
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.
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.
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.
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
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.
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.
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.
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.
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
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.
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.
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
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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:Customers might whine if they ask for 10 volts and see 30. Amd that
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. >>
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
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.
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.
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.
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...
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.
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
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.
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
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.
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.
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
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.
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.
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.
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.
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.
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.
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.
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
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.
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.
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.
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.
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.
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.
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.
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
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.
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.
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.
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?
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.
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
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.
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.
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.
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
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 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.
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
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.
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.
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
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
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
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