• dc/dc startup

    From john larkin@21:1/5 to All on Tue Jan 14 07:09:13 2025
    https://www.dropbox.com/scl/fi/3hyvmc3mkvhrk6rc8dt72/P970_DC-DC.jpg?rlkey=npgerceq4t191hnjfd0907v6u&raw=1

    That makes two isolated 56-volt power supplies. But the problem is
    how to start it up.

    I could just slam on the square wave drives and let the TI chip
    current limit until the caps charge up. That might work.

    I was thiking I could start the two half-bridges with in-phase square
    waves and then slowly slide them out to 180 degrees. My FPGA kids
    could do that. That would be a nuisance to Spice.

    We did a similar supply a while back with discrete fets, no current
    limits. Startup made 300 amp spikes that made all sorts of problems.

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  • From Martin Rid@21:1/5 to john larkin on Tue Jan 14 10:19:01 2025
    john larkin <JL@gct.com> Wrote in message:r
    https://www.dropbox.com/scl/fi/3hyvmc3mkvhrk6rc8dt72/P970_DC-DC.jpg?rlkey=npgerceq4t191hnjfd0907v6u&raw=1That makes two isolated 56-volt power supplies. But the problem ishow to start it up.I could just slam on the square wave drives and let the TI
    chipcurrent limit until the caps charge up. That might work.I was thiking I could start the two half-bridges with in-phase squarewaves and then slowly slide them out to 180 degrees. My FPGA kidscould do that. That would be a nuisance to Spice.We did a
    similar supply a while back with discrete fets, no currentlimits. Startup made 300 amp spikes that made all sorts of problems.

    Yea, software softstart.

    Cheers
    --


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  • From john larkin@21:1/5 to martin_riddle@verison.net on Tue Jan 14 08:10:06 2025
    On Tue, 14 Jan 2025 10:19:01 -0500 (EST), Martin Rid <martin_riddle@verison.net> wrote:

    john larkin <JL@gct.com> Wrote in message:r
    https://www.dropbox.com/scl/fi/3hyvmc3mkvhrk6rc8dt72/P970_DC-DC.jpg?rlkey=npgerceq4t191hnjfd0907v6u&raw=1That makes two isolated 56-volt power supplies. But the problem ishow to start it up.I could just slam on the square wave drives and let the TI
    chipcurrent limit until the caps charge up. That might work.I was thiking I could start the two half-bridges with in-phase squarewaves and then slowly slide them out to 180 degrees. My FPGA kidscould do that. That would be a nuisance to Spice.We did a
    similar supply a while back with discrete fets, no currentlimits. Startup made 300 amp spikes that made all sorts of problems.

    Yea, software softstart.

    Cheers

    I think the sliding square wave thing will work, but I have sceptics.

    So how can I Spice two 200 KHz square waves that start in phase and
    slowly crawl to 180 degrees apart? Over a second maybe.

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  • From Jeroen Belleman@21:1/5 to john larkin on Tue Jan 14 20:08:12 2025
    On 1/14/25 17:10, john larkin wrote:
    On Tue, 14 Jan 2025 10:19:01 -0500 (EST), Martin Rid <martin_riddle@verison.net> wrote:

    john larkin <JL@gct.com> Wrote in message:r
    https://www.dropbox.com/scl/fi/3hyvmc3mkvhrk6rc8dt72/P970_DC-DC.jpg?rlkey=npgerceq4t191hnjfd0907v6u&raw=1That makes two isolated 56-volt power supplies. But the problem ishow to start it up.I could just slam on the square wave drives and let the TI
    chipcurrent limit until the caps charge up. That might work.I was thiking I could start the two half-bridges with in-phase squarewaves and then slowly slide them out to 180 degrees. My FPGA kidscould do that. That would be a nuisance to Spice.We did a
    similar supply a while back with discrete fets, no currentlimits. Startup made 300 amp spikes that made all sorts of problems.

    Yea, software softstart.

    Cheers

    I think the sliding square wave thing will work, but I have sceptics.

    So how can I Spice two 200 KHz square waves that start in phase and
    slowly crawl to 180 degrees apart? Over a second maybe.


    Something like below? The squares start off in phase and
    one of them is shifted by V3 to end up in opposition after
    50us. Scale to taste.

    You can control the rise and fall times of the squares by
    adjusting the amplitudes of the sines in the expressions
    for B1 and B2.

    Jeroen Belleman

    ==============================================================
    Version 4
    SHEET 1 1116 680
    WIRE 128 48 128 16
    WIRE 128 80 128 48
    WIRE -128 96 -192 96
    WIRE -80 96 -128 96
    WIRE -192 160 -192 96
    WIRE 128 192 128 160
    WIRE -192 272 -192 240
    WIRE 128 272 128 240
    WIRE 128 304 128 272
    WIRE 128 416 128 384
    FLAG 128 192 0
    FLAG 128 48 out1
    FLAG -192 272 0
    FLAG -128 96 p
    FLAG 128 416 0
    FLAG 128 272 out2
    SYMBOL voltage -192 144 R0
    WINDOW 123 0 0 Left 2
    WINDOW 39 0 0 Left 2
    SYMATTR InstName V3
    SYMATTR Value PWL(0 0 50u {pi})
    SYMBOL bv 128 64 R0
    SYMATTR InstName B1
    SYMATTR Value V=tanh(10*sin(time*2*pi*200k+v(p)))
    SYMBOL bv 128 288 R0
    SYMATTR InstName B2
    SYMATTR Value V=tanh(10*sin(time*2*pi*200k))
    TEXT 272 104 Left 2 !.tran 100u
    TEXT 272 32 Left 2 ;Square waves with controlled phase.
    TEXT 272 64 Left 2 ;Jeroen Belleman - 20250114

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  • From john larkin@21:1/5 to usenet2007nospam@autometer.de on Tue Jan 14 11:07:59 2025
    On Tue, 14 Jan 2025 19:37:28 +0100, Tilmann Reh
    <usenet2007nospam@autometer.de> wrote:

    Am 14.01.2025 um 17:10 schrieb john larkin:
    So how can I Spice two 200 KHz square waves that start in phase and
    slowly crawl to 180 degrees apart? Over a second maybe.

    Let the one have 199.9995 (or 200.0005) kHz.

    Tilmann

    Of course. They can take, say, one second to drift 180 out of phase.

    Thanks.

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  • From Tilmann Reh@21:1/5 to All on Tue Jan 14 19:37:28 2025
    Am 14.01.2025 um 17:10 schrieb john larkin:
    So how can I Spice two 200 KHz square waves that start in phase and
    slowly crawl to 180 degrees apart? Over a second maybe.

    Let the one have 199.9995 (or 200.0005) kHz.

    Tilmann

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    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Jan Panteltje@21:1/5 to JL@gct.com on Tue Jan 14 19:47:16 2025
    On a sunny day (Tue, 14 Jan 2025 07:09:13 -0800) it happened john larkin <JL@gct.com> wrote in <v5vcojt090tpv5h9a3ancgm1r7pc4p6bjc@4ax.com>:


    https://www.dropbox.com/scl/fi/3hyvmc3mkvhrk6rc8dt72/P970_DC-DC.jpg?rlkey=npgerceq4t191hnjfd0907v6u&raw=1

    That makes two isolated 56-volt power supplies. But the problem is
    how to start it up.

    I could just slam on the square wave drives and let the TI chip
    current limit until the caps charge up. That might work.

    I was thiking I could start the two half-bridges with in-phase square
    waves and then slowly slide them out to 180 degrees. My FPGA kids
    could do that. That would be a nuisance to Spice.

    We did a similar supply a while back with discrete fets, no current
    limits. Startup made 300 amp spikes that made all sorts of problems.

    Just drive the thing from some Microchip PIC and use cycle by cycle current limiting
    feedback via curent transformer.
    No weard chip needed.
    Why full bridge?
    One power trahsistor should do.

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    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From john larkin@21:1/5 to jeroen@nospam.please on Tue Jan 14 12:04:40 2025
    On Tue, 14 Jan 2025 20:08:12 +0100, Jeroen Belleman
    <jeroen@nospam.please> wrote:

    On 1/14/25 17:10, john larkin wrote:
    On Tue, 14 Jan 2025 10:19:01 -0500 (EST), Martin Rid
    <martin_riddle@verison.net> wrote:

    john larkin <JL@gct.com> Wrote in message:r
    https://www.dropbox.com/scl/fi/3hyvmc3mkvhrk6rc8dt72/P970_DC-DC.jpg?rlkey=npgerceq4t191hnjfd0907v6u&raw=1That makes two isolated 56-volt power supplies. But the problem ishow to start it up.I could just slam on the square wave drives and let the TI
    chipcurrent limit until the caps charge up. That might work.I was thiking I could start the two half-bridges with in-phase squarewaves and then slowly slide them out to 180 degrees. My FPGA kidscould do that. That would be a nuisance to Spice.We did a
    similar supply a while back with discrete fets, no currentlimits. Startup made 300 amp spikes that made all sorts of problems.

    Yea, software softstart.

    Cheers

    I think the sliding square wave thing will work, but I have sceptics.

    So how can I Spice two 200 KHz square waves that start in phase and
    slowly crawl to 180 degrees apart? Over a second maybe.


    Something like below? The squares start off in phase and
    one of them is shifted by V3 to end up in opposition after
    50us. Scale to taste.

    You can control the rise and fall times of the squares by
    adjusting the amplitudes of the sines in the expressions
    for B1 and B2.

    Jeroen Belleman

    ==============================================================
    Version 4
    SHEET 1 1116 680
    WIRE 128 48 128 16
    WIRE 128 80 128 48
    WIRE -128 96 -192 96
    WIRE -80 96 -128 96
    WIRE -192 160 -192 96
    WIRE 128 192 128 160
    WIRE -192 272 -192 240
    WIRE 128 272 128 240
    WIRE 128 304 128 272
    WIRE 128 416 128 384
    FLAG 128 192 0
    FLAG 128 48 out1
    FLAG -192 272 0
    FLAG -128 96 p
    FLAG 128 416 0
    FLAG 128 272 out2
    SYMBOL voltage -192 144 R0
    WINDOW 123 0 0 Left 2
    WINDOW 39 0 0 Left 2
    SYMATTR InstName V3
    SYMATTR Value PWL(0 0 50u {pi})
    SYMBOL bv 128 64 R0
    SYMATTR InstName B1
    SYMATTR Value V=tanh(10*sin(time*2*pi*200k+v(p)))
    SYMBOL bv 128 288 R0
    SYMATTR InstName B2
    SYMATTR Value V=tanh(10*sin(time*2*pi*200k))
    TEXT 272 104 Left 2 !.tran 100u
    TEXT 272 32 Left 2 ;Square waves with controlled phase.
    TEXT 272 64 Left 2 ;Jeroen Belleman - 20250114

    That's nice. It goes from in-phase to 180 deg and then hangs there;
    the delta-F thing goes up to 180 degrees and then backs down.

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