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500 volt power supply
Started by ●September 24, 2023
Reply by ●October 2, 20232023-10-02
Reply by ●October 2, 20232023-10-02
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Reply by ●October 2, 20232023-10-02
On Sun, 1 Oct 2023 21:27:52 -0700 (PDT), whit3rd <whit3rd@gmail.com> wrote:>On Friday, September 29, 2023 at 12:07:37?PM UTC-7, John Larkin wrote: >> On Fri, 29 Sep 2023 01:53:09 -0700 (PDT), whit3rd <whi...@gmail.com> >> wrote: >> >On Thursday, September 28, 2023 at 7:09:27?PM UTC-7, John Larkin wrote: >> >> On Thu, 28 Sep 2023 13:58:40 -0700 (PDT), Klaus Kragelund >> >> <klaus.k...@gmail.com> wrote: >> > >> >> >I am driving a UV lamp, so I need to deliver a pulse. Possible with a multiplier, but doesn't make it easier >> >> No, the C-W multiplier isn't good for pulsing. Ixys has a 4700 volt >> >> mosfet. A C-W multiplier could make the HV. >> >> >> >> Maybe use a Marx generator? With medium-high voltage mos or SiC fets? >> > >> >Not usually a great idea; at HV, the best switch is photo-SCR. > >> Should work, but might be too slow for some applications. It is a nice >> idea to make high-current HV pulses. Six of these maybe: >> >> https://www.digikey.com/en/products/detail/vishay-semiconductor-opto-division/VOT8125AB-V/9843471 > >Ick; triacs, not SCRs, and you'd have to wire-connect those input pins... I was >thinking more of fibers to a receiver with phototransistor, use PNP and NPN phototransistor to >make an SCR, bias it with a 9V battery at each node, so a single lamp flash can light >up all the nodes at once. That 9V pulse, of course, just goes to the gate of a REAL SCR. > >This one seems thrifty, and does over a kilovolt > ><https://www.digikey.com/en/products/detail/vishay-general-semiconductor-diodes-division/VS-25TTS16SLHM3/9467407> > >The real advantage, though, of photoSCR is in the turnon dI/dt limit; it doesn't have any, >because it turns on full-area when lit. That takes more light than you'd likely push through a fiber, however. >150 A/us is the limit you get for your $2.86Fiber would be great for a giant, megavolt, megabuck, gigawatt-scale Marx, but not what I'd want to put on a PC board. A flashlamp wouldn't couple much light into a glass fiber. It might work into the dreadful plastic audio stuff.
Reply by ●October 2, 20232023-10-02
On Sun, 1 Oct 2023 19:57:13 -0700 (PDT), John Smiht <utube.jocjo@xoxy.net> wrote:>On Sunday, October 1, 2023 at 9:08:19?AM UTC-5, John Larkin wrote: >> On Sun, 01 Oct 2023 05:31:31 GMT, Jan Panteltje <al...@comet.invalid> >> wrote: >> >On a sunny day (Sat, 30 Sep 2023 12:10:06 -0700) it happened John Larkin >> ><j...@997arbor.com> wrote in <2grghi1vnnsmrkbcl...@4ax.com>: >> > >> >>On Sun, 24 Sep 2023 09:18:31 -0700, John Larkin <j...@997arbor.com> >> >>wrote: >> >> >> >>> >> >>>This is pleasingly weird. >> >>> >> >>>https://www.dropbox.com/sh/sif3efs69dxe1mg/AACY0RJGXl4k8CVvauUbJtYFa?dl=0 >> >>> >> >>>Sort of a baseline-boosted multi-auto-transformer voltage-doubler >> >>>flyback. >> >>> >> >>>What's strange is that adding the two snubbers increases the LT spice >> >>>sim speed radically, about 10:1. >> >> >> >>OK, this has become sort of a background hobby, waiting on the >> >>customer to get serious. >> >> >> >>https://www.dropbox.com/scl/fi/60nb1pcrnl17c07tk8xeu/T875_HV_9.jpg?rlkey=9uv466edcuvddmjldgepcyi0u&raw=1 >> >> >> >>All the caps are a part that we have, 100nF 630 volts 1812. Of course >> >>the capacitance plummets as voltage goes up, so the Spice values have >> >>to be adjusted appropriately. C is only 20nF at 500 volts. >> > >> >That much really? Th big caps I use do not change at all I think? >> I measured one. >> >> https://www.dropbox.com/scl/fi/zrrount2a5s7k5bmqh4bu/C-V.jpg?rlkey=3so16njq8md4ccnm610a8mf49&raw=1 > >John, I have worked quite extensively with CW multipliers. Both series and parallel ones. >The nice thing about series multipliers is that the capacitors will see no more than the p-p input voltage. >So I don't think you high voltage ones except to use them at a lower voltage to improve capacitance. >Parallel multipliers are more efficient but do require the higher voltage ( at least on the final stage). > >Good luck with your project and please post its progress here.Thanks.Right, my caps lose most of their capacitance if I use them in parallel mode. 5 or 6 caps in parallel work OK for the final 500 volt filter to ground. My experience with surface-mount film caps has been bad. The Pockels Cell will work in switch mode, so sees zero volts or Vpi (500) volts, and in both cases it's operating on the flat part of the sine-squared curve, so ripple doesn't much matter. The light is blowing up things anyhow. I hope the customer gets serious and I get to actually build this one. The power supply part is no big secret so I'll post any ideas or actual progress. I do find it helpful to discuss this sort of thing.
Reply by ●October 2, 20232023-10-02
On Monday, October 2, 2023 at 10:01:16 AM UTC-5, John Larkin wrote:> On Sun, 1 Oct 2023 19:57:13 -0700 (PDT), John Smiht > <utube...@xoxy.net> wrote: > >On Sunday, October 1, 2023 at 9:08:19?AM UTC-5, John Larkin wrote: > >> On Sun, 01 Oct 2023 05:31:31 GMT, Jan Panteltje <al...@comet.invalid> > >> wrote: > >> >On a sunny day (Sat, 30 Sep 2023 12:10:06 -0700) it happened John Larkin > >> ><j...@997arbor.com> wrote in <2grghi1vnnsmrkbcl...@4ax.com>: > >> > > >> >>On Sun, 24 Sep 2023 09:18:31 -0700, John Larkin <j...@997arbor.com> > >> >>wrote: > >> >> > >> >>> > >> >>>This is pleasingly weird. > >> >>> > >> >>>https://www.dropbox.com/sh/sif3efs69dxe1mg/AACY0RJGXl4k8CVvauUbJtYFa?dl=0 > >> >>> > >> >>>Sort of a baseline-boosted multi-auto-transformer voltage-doubler > >> >>>flyback. > >> >>> > >> >>>What's strange is that adding the two snubbers increases the LT spice > >> >>>sim speed radically, about 10:1. > >> >> > >> >>OK, this has become sort of a background hobby, waiting on the > >> >>customer to get serious. > >> >> > >> >>https://www.dropbox.com/scl/fi/60nb1pcrnl17c07tk8xeu/T875_HV_9.jpg?rlkey=9uv466edcuvddmjldgepcyi0u&raw=1 > >> >> > >> >>All the caps are a part that we have, 100nF 630 volts 1812. Of course > >> >>the capacitance plummets as voltage goes up, so the Spice values have > >> >>to be adjusted appropriately. C is only 20nF at 500 volts. > >> > > >> >That much really? Th big caps I use do not change at all I think? > >> I measured one. > >> > >> https://www.dropbox.com/scl/fi/zrrount2a5s7k5bmqh4bu/C-V.jpg?rlkey=3so16njq8md4ccnm610a8mf49&raw=1 > > > >John, I have worked quite extensively with CW multipliers. Both series and parallel ones. > >The nice thing about series multipliers is that the capacitors will see no more than the p-p input voltage. > >So I don't think you high voltage ones except to use them at a lower voltage to improve capacitance. > >Parallel multipliers are more efficient but do require the higher voltage ( at least on the final stage). > > > >Good luck with your project and please post its progress here.Thanks. > Right, my caps lose most of their capacitance if I use them in > parallel mode. 5 or 6 caps in parallel work OK for the final 500 volt > filter to ground. > > My experience with surface-mount film caps has been bad. > > The Pockels Cell will work in switch mode, so sees zero volts or Vpi > (500) volts, and in both cases it's operating on the flat part of the > sine-squared curve, so ripple doesn't much matter. The light is > blowing up things anyhow. > > I hope the customer gets serious and I get to actually build this one. > > The power supply part is no big secret so I'll post any ideas or > actual progress. I do find it helpful to discuss this sort of thing.Of course you do. So do the rest of us who are interested in electronics. Like you, I do hope your customer comes forth with what you need to continue. I would love to see your progress in your project if it comes to be. Thanks John. John
Reply by ●October 3, 20232023-10-03
On 29-09-2023 04:09, John Larkin wrote:> On Thu, 28 Sep 2023 13:58:40 -0700 (PDT), Klaus Kragelund > <klaus.kragelund@gmail.com> wrote: > >> On Thursday, 28 September 2023 at 17:26:46 UTC+2, John Larkin wrote: >>> On Thu, 28 Sep 2023 14:59:48 GMT, Jan Panteltje <al...@comet.invalid> >>> wrote: >>> >>>> On a sunny day (Wed, 27 Sep 2023 13:34:29 -0700 (PDT)) it happened Klaus >>>> Kragelund <klaus.k...@gmail.com> wrote in >>>> <903144ac-6642-4a3f...@googlegroups.com>: >>>> >>>>> On Wednesday, 27 September 2023 at 17:38:35 UTC+2, Jan Panteltje wrote: >>>>>> On a sunny day (Wed, 27 Sep 2023 08:10:02 -0700) it happened John Larkin >>>>>> <j...@997arbor.com> wrote in <d3h8hitm54oie4gcl...@4ax.com>: >>>>>>> On Wed, 27 Sep 2023 11:44:57 GMT, Jan Panteltje <al...@comet.invalid> >>>>>>> wrote: >>>>>>> >>>>>>>> On a sunny day (Wed, 27 Sep 2023 00:51:10 -0700) it happened John Larkin >>>>>>>> <j...@997arbor.com> wrote in <4bn7hit0n3rmcg855...@4ax.com>: >>>>>>>> >>>>>>>>> On Wed, 27 Sep 2023 05:14:49 GMT, Jan Panteltje <al...@comet.invalid> >>>>>>>>> wrote: >>>>>>>>> >>>>>>>>>> On a sunny day (Tue, 26 Sep 2023 19:35:18 -0700) it happened John Larkin >>>>>>>>>> <j...@997arbor.com> wrote in <mf47hi15db7eq7mp2...@4ax.com>: >>>>>>>>>> >>>>>>>>>>> On Sun, 24 Sep 2023 09:18:31 -0700, John Larkin <j...@997arbor.com> >>>>>>>>>>> wrote: >>>>>>>>>>> >>>>>>>>>>>> >>>>>>>>>>>> This is pleasingly weird. >>>>>>>>>>>> >>>>>>>>>>>> https://www.dropbox.com/sh/sif3efs69dxe1mg/AACY0RJGXl4k8CVvauUbJtYFa?dl=0 >>>>>>>>>>>> >>>>>>>>>>>> Sort of a baseline-boosted multi-auto-transformer voltage-doubler >>>>>>>>>>>> flyback. >>>>>>>>>>>> >>>>>>>>>>>> What's strange is that adding the two snubbers increases the LT spice >>>>>>>>>>>> sim speed radically, about 10:1. >>>>>>>>>>> >>>>>>>>>>> Since I couldn't find a suitable flyback transformer, and I only need >>>>>>>>>>> 500 volts at 10 mA, a flyback/C-W multiplier makes sense. >>>>>>>>>>> >>>>>>>>>>> https://www.dropbox.com/scl/fi/aquzpawfn8mfmfsnx70ra/T875_HV_6.jpg?rlkey=vfs9pexa0rgyxpo7pg1grqlb7&dl=0 >>>>>>>>>> >>>>>>>>>> Do you still need C11 R8 in that circuit? >>>>>>>>> >>>>>>>>> It doesn't need them to work, but there is a big high-Q ring when the >>>>>>>>> fet turns off, and the RC damps it. It would reduce radiated EMI. And >>>>>>>>> it speeds up the simulation some. >>>>>>>> >>>>>>>> Did you scope that? >>>>>>> >>>>>>> All Spice now. I'll build it when the customer gets serious. >>>>>>> >>>>>>>> There is a load of capacitance hanging from the MOSFET drain in that flyback multiplier ciruit >>>>>>>> I would expect it to damp RF oscillations but could be wrong... >>>>>>>> HV diodes have capacitance too.. >>>>>>> >>>>>>> The real circuit will have a lot of inductances too, what with those >>>>>>> long strings of parts. It needs to be built and tested. Dremeled, to >>>>>>> start. >>>>>>> >>>>>>> Here's an old auto-flyback C-W miltiplier prototype. I think that was >>>>>>> 1400 volts. Worked fine. >>>>>>> >>>>>>> https://www.dropbox.com/s/yd19osiwz1z74s4/HV_Proto_2.JPG?rsw=1 >>>>>> Yea, >>>>>> I did a PMT supply this way: >>>>>> http://panteltje.nl/pub/PMT_HV_supply_with_regulator_img_3175.jpg >>>>>> http://panteltje.nl/pub/PMT_HV_supply_componet_side_img_3180.jpg >>>>>> http://panteltje.nl/pub/PMT_regulated_power_supply_diagram_img_3182.jpg >>>>>> >>>>>> It has been in use now for many years, sits with PMT in the cardboard tube on the right, runs on batteries: >>>>>> http://panteltje.nl/pub/gamma_soectrometer_IMG_4505.JPG >>>>>> >>>>>> Of course that is very low power, but for a bit more power, and using a real TV muliplier: >>>>>> https://panteltje.nl/panteltje/pic/sc_pic/ >>>>>> >>>>>> No dremeling, boards are OK when they work.. >>>>>> >>>>>> And old TV circuits.. if you want a few kV there was / is? plenty stuff to be found on ebay. >>>>> For my case, I am working on a 5W 24V to 4.5kV converter. Right now looking to use a flyback topology, with possibly usage of >>>>> CCFL transformer bobbins. >>>>> >>>>> I am thinking about staggering the windings on 2 transformers, so the voltage across the windings will be lower, but still the >>>>> individual transformer needs to handle 4.5kV insulation (functional, not safety) >>>>> >>>>> Due to the limiting power, it could also be tempting to use the capacitive doublers as listed elsewhere in the thread >>>>> >>>>> My worry goes beyond the design, also about corona effects, which comes into play at +kV voltages. Potting is surely needed. >>>> >>>> For a HV transformer, old TV transformers (from the CRT times) may perhaps be an option: >>>> https://www.google.com/search?client=firefox-b-e&q=ebay+horizonatl+TV+output+transformer >>>> 4.5 kV diodes were used for focus in color TV sets... >>>> >>>> >>>> For a flyback, my rule of thumb (I do not use El Tea Spice), is 1 V per turn for DC input. >>>> So 24 turns primary for 24 V DC supply. >>>> The flyback voltage is (70/12) * 24 = 140V positive pulse if positive DC supply. >>>> To get a 4.5 kV pulse you would then wind 4500 / 140 is about 32, multiplied by 24 makes 768 turns. >>>> This for an EI core running at about 15 kHz (math comes from building TV output stages). >>>> 768 turns is not a big deal.. >>>> Spreading the turns over a segmented coil former is a good idea. >>>> If you want to use a voltage multiplier then less turns are needed, use a TV multiplier, those are 'potted' >>>> The 70/12 factor depends on the PWM on/off ratio of the drive you feed into the switch transistor. >>>> I use Microchip PICs for that, it has a PWM unit., hardware comparators that can directly stop the PWM drive >>>> for cycle by cycle current limiting, and ADCs to measure voltage and currents. >>>> Maybe an old TV horizontal output transformer with build in rectifier / multiplier would do. >>>> https://www.ebay.com/b/flyback-transformer/bn_7024744628 >>>> to adapt use 15 kHz and add 24 turns to the core primary? >>>> ... >>>> :-) >>>> >>>> Maybe like this? >>>> https://www.ebay.com/p/1692562663?iid=374326473542 >>>> plenty space for 24 turns thick wire, its a 30 kV DC out, so use less PWM ... or more primary turns >>>> or whatever you can find... on ebay. >>>> >>> High turns ratios can have two problems: voltage breakdown in the >>> insulation, and winding capacitance limiting the flyback ratio. That's >>> where a C-W diode multiplier helps. >> >> I am driving a UV lamp, so I need to deliver a pulse. Possible with a multiplier, but doesn't make it easier > > No, the C-W multiplier isn't good for pulsing. Ixys has a 4700 volt > mosfet. A C-W multiplier could make the HV. > > Maybe use a Marx generator? With medium-high voltage mos or SiC fets? > > Some of the Zetex app notes, for their avalanche transistors, use a > Marx-type circuit. Charge the caps in parallel and discharge them in > series. You only have to trigger one in the string. > > What sort of speed and current do you need? > >I will generate a single pulse, about 5us long, shaped like a half wave sinusoid, at 100kHz repetition frequency. That's why I was looking at flyback, since I can control the voltage delivered simply by adjusting the primary peak current. Power seems to be less than 5W, at 4.5kV peak, duty of let's say 25%. probably below 10mA
Reply by ●October 3, 20232023-10-03
On 2023-09-24, John Larkin <jl@997arbor.com> wrote:> I started simulating with a single 1:5 transformer, but couldn't find > one for sale.I have successfully used power-over-ethernet transformers (Pulse PA1137) for a 12V -> 200V nixie supply. Not sure how they handle 500V. PA1137 is 1:8, PA1138 is 1:3.43 cu Michael -- Some people have no respect of age unless it is bottled.
Reply by ●October 3, 20232023-10-03
On Tue, 3 Oct 2023 09:46:44 +0200, Klaus Vestergaard Kragelund <klauskvik@hotmail.com> wrote:>On 29-09-2023 04:09, John Larkin wrote: >> On Thu, 28 Sep 2023 13:58:40 -0700 (PDT), Klaus Kragelund >> <klaus.kragelund@gmail.com> wrote: >> >>> On Thursday, 28 September 2023 at 17:26:46 UTC+2, John Larkin wrote: >>>> On Thu, 28 Sep 2023 14:59:48 GMT, Jan Panteltje <al...@comet.invalid> >>>> wrote: >>>> >>>>> On a sunny day (Wed, 27 Sep 2023 13:34:29 -0700 (PDT)) it happened Klaus >>>>> Kragelund <klaus.k...@gmail.com> wrote in >>>>> <903144ac-6642-4a3f...@googlegroups.com>: >>>>> >>>>>> On Wednesday, 27 September 2023 at 17:38:35 UTC+2, Jan Panteltje wrote: >>>>>>> On a sunny day (Wed, 27 Sep 2023 08:10:02 -0700) it happened John Larkin >>>>>>> <j...@997arbor.com> wrote in <d3h8hitm54oie4gcl...@4ax.com>: >>>>>>>> On Wed, 27 Sep 2023 11:44:57 GMT, Jan Panteltje <al...@comet.invalid> >>>>>>>> wrote: >>>>>>>> >>>>>>>>> On a sunny day (Wed, 27 Sep 2023 00:51:10 -0700) it happened John Larkin >>>>>>>>> <j...@997arbor.com> wrote in <4bn7hit0n3rmcg855...@4ax.com>: >>>>>>>>> >>>>>>>>>> On Wed, 27 Sep 2023 05:14:49 GMT, Jan Panteltje <al...@comet.invalid> >>>>>>>>>> wrote: >>>>>>>>>> >>>>>>>>>>> On a sunny day (Tue, 26 Sep 2023 19:35:18 -0700) it happened John Larkin >>>>>>>>>>> <j...@997arbor.com> wrote in <mf47hi15db7eq7mp2...@4ax.com>: >>>>>>>>>>> >>>>>>>>>>>> On Sun, 24 Sep 2023 09:18:31 -0700, John Larkin <j...@997arbor.com> >>>>>>>>>>>> wrote: >>>>>>>>>>>> >>>>>>>>>>>>> >>>>>>>>>>>>> This is pleasingly weird. >>>>>>>>>>>>> >>>>>>>>>>>>> https://www.dropbox.com/sh/sif3efs69dxe1mg/AACY0RJGXl4k8CVvauUbJtYFa?dl=0 >>>>>>>>>>>>> >>>>>>>>>>>>> Sort of a baseline-boosted multi-auto-transformer voltage-doubler >>>>>>>>>>>>> flyback. >>>>>>>>>>>>> >>>>>>>>>>>>> What's strange is that adding the two snubbers increases the LT spice >>>>>>>>>>>>> sim speed radically, about 10:1. >>>>>>>>>>>> >>>>>>>>>>>> Since I couldn't find a suitable flyback transformer, and I only need >>>>>>>>>>>> 500 volts at 10 mA, a flyback/C-W multiplier makes sense. >>>>>>>>>>>> >>>>>>>>>>>> https://www.dropbox.com/scl/fi/aquzpawfn8mfmfsnx70ra/T875_HV_6.jpg?rlkey=vfs9pexa0rgyxpo7pg1grqlb7&dl=0 >>>>>>>>>>> >>>>>>>>>>> Do you still need C11 R8 in that circuit? >>>>>>>>>> >>>>>>>>>> It doesn't need them to work, but there is a big high-Q ring when the >>>>>>>>>> fet turns off, and the RC damps it. It would reduce radiated EMI. And >>>>>>>>>> it speeds up the simulation some. >>>>>>>>> >>>>>>>>> Did you scope that? >>>>>>>> >>>>>>>> All Spice now. I'll build it when the customer gets serious. >>>>>>>> >>>>>>>>> There is a load of capacitance hanging from the MOSFET drain in that flyback multiplier ciruit >>>>>>>>> I would expect it to damp RF oscillations but could be wrong... >>>>>>>>> HV diodes have capacitance too.. >>>>>>>> >>>>>>>> The real circuit will have a lot of inductances too, what with those >>>>>>>> long strings of parts. It needs to be built and tested. Dremeled, to >>>>>>>> start. >>>>>>>> >>>>>>>> Here's an old auto-flyback C-W miltiplier prototype. I think that was >>>>>>>> 1400 volts. Worked fine. >>>>>>>> >>>>>>>> https://www.dropbox.com/s/yd19osiwz1z74s4/HV_Proto_2.JPG?rsw=1 >>>>>>> Yea, >>>>>>> I did a PMT supply this way: >>>>>>> http://panteltje.nl/pub/PMT_HV_supply_with_regulator_img_3175.jpg >>>>>>> http://panteltje.nl/pub/PMT_HV_supply_componet_side_img_3180.jpg >>>>>>> http://panteltje.nl/pub/PMT_regulated_power_supply_diagram_img_3182.jpg >>>>>>> >>>>>>> It has been in use now for many years, sits with PMT in the cardboard tube on the right, runs on batteries: >>>>>>> http://panteltje.nl/pub/gamma_soectrometer_IMG_4505.JPG >>>>>>> >>>>>>> Of course that is very low power, but for a bit more power, and using a real TV muliplier: >>>>>>> https://panteltje.nl/panteltje/pic/sc_pic/ >>>>>>> >>>>>>> No dremeling, boards are OK when they work.. >>>>>>> >>>>>>> And old TV circuits.. if you want a few kV there was / is? plenty stuff to be found on ebay. >>>>>> For my case, I am working on a 5W 24V to 4.5kV converter. Right now looking to use a flyback topology, with possibly usage of >>>>>> CCFL transformer bobbins. >>>>>> >>>>>> I am thinking about staggering the windings on 2 transformers, so the voltage across the windings will be lower, but still the >>>>>> individual transformer needs to handle 4.5kV insulation (functional, not safety) >>>>>> >>>>>> Due to the limiting power, it could also be tempting to use the capacitive doublers as listed elsewhere in the thread >>>>>> >>>>>> My worry goes beyond the design, also about corona effects, which comes into play at +kV voltages. Potting is surely needed. >>>>> >>>>> For a HV transformer, old TV transformers (from the CRT times) may perhaps be an option: >>>>> https://www.google.com/search?client=firefox-b-e&q=ebay+horizonatl+TV+output+transformer >>>>> 4.5 kV diodes were used for focus in color TV sets... >>>>> >>>>> >>>>> For a flyback, my rule of thumb (I do not use El Tea Spice), is 1 V per turn for DC input. >>>>> So 24 turns primary for 24 V DC supply. >>>>> The flyback voltage is (70/12) * 24 = 140V positive pulse if positive DC supply. >>>>> To get a 4.5 kV pulse you would then wind 4500 / 140 is about 32, multiplied by 24 makes 768 turns. >>>>> This for an EI core running at about 15 kHz (math comes from building TV output stages). >>>>> 768 turns is not a big deal.. >>>>> Spreading the turns over a segmented coil former is a good idea. >>>>> If you want to use a voltage multiplier then less turns are needed, use a TV multiplier, those are 'potted' >>>>> The 70/12 factor depends on the PWM on/off ratio of the drive you feed into the switch transistor. >>>>> I use Microchip PICs for that, it has a PWM unit., hardware comparators that can directly stop the PWM drive >>>>> for cycle by cycle current limiting, and ADCs to measure voltage and currents. >>>>> Maybe an old TV horizontal output transformer with build in rectifier / multiplier would do. >>>>> https://www.ebay.com/b/flyback-transformer/bn_7024744628 >>>>> to adapt use 15 kHz and add 24 turns to the core primary? >>>>> ... >>>>> :-) >>>>> >>>>> Maybe like this? >>>>> https://www.ebay.com/p/1692562663?iid=374326473542 >>>>> plenty space for 24 turns thick wire, its a 30 kV DC out, so use less PWM ... or more primary turns >>>>> or whatever you can find... on ebay. >>>>> >>>> High turns ratios can have two problems: voltage breakdown in the >>>> insulation, and winding capacitance limiting the flyback ratio. That's >>>> where a C-W diode multiplier helps. >>> >>> I am driving a UV lamp, so I need to deliver a pulse. Possible with a multiplier, but doesn't make it easier >> >> No, the C-W multiplier isn't good for pulsing. Ixys has a 4700 volt >> mosfet. A C-W multiplier could make the HV. >> >> Maybe use a Marx generator? With medium-high voltage mos or SiC fets? >> >> Some of the Zetex app notes, for their avalanche transistors, use a >> Marx-type circuit. Charge the caps in parallel and discharge them in >> series. You only have to trigger one in the string. >> >> What sort of speed and current do you need? >> >> >I will generate a single pulse, about 5us long, shaped like a half wave >sinusoid, at 100kHz repetition frequency. That's why I was looking at >flyback, since I can control the voltage delivered simply by adjusting >the primary peak current. Power seems to be less than 5W, at 4.5kV peak, >duty of let's say 25%. probably below 10mAOne can stuff a bunch of current into an inductor and then dump it into a mostly-capacitive load. That can make a high-voltage half-sine. This boosts 48 volts to 1400v at MHz pulse rates. http://www.highlandtechnology.com/DSS/T850DS.shtml by switching an inductor around. The energy is recovered and returned to the 48v supply after each pulse, which keeps the power dissipation under control. https://www.dropbox.com/scl/fi/lkjg19hvcus9xz8aeecxy/T850_Rev_C.JPG?rlkey=0pitv0zdmb0x1tz0fkw0gj3ob&raw=1 The really tricky stuff is on the bottom of the board, dumping heat into the water-cooled baseplate. At 5 us, you could make a 4KV DC supply and switch that into your load with a high-voltage mosfet. Brute force.
Reply by ●October 3, 20232023-10-03
On 30-09-2023 21:10, John Larkin wrote:> On Sun, 24 Sep 2023 09:18:31 -0700, John Larkin <jl@997arbor.com> > wrote: > >> >> This is pleasingly weird. >> >> https://www.dropbox.com/sh/sif3efs69dxe1mg/AACY0RJGXl4k8CVvauUbJtYFa?dl=0 >> >> Sort of a baseline-boosted multi-auto-transformer voltage-doubler >> flyback. >> >> What's strange is that adding the two snubbers increases the LT spice >> sim speed radically, about 10:1. > > OK, this has become sort of a background hobby, waiting on the > customer to get serious. > > https://www.dropbox.com/scl/fi/60nb1pcrnl17c07tk8xeu/T875_HV_9.jpg?rlkey=9uv466edcuvddmjldgepcyi0u&raw=1 > > All the caps are a part that we have, 100nF 630 volts 1812. Of course > the capacitance plummets as voltage goes up, so the Spice values have > to be adjusted appropriately. C is only 20nF at 500 volts. > > The RCD snubber is nice. It softens the rise at the fet drain and > dissipates less power than a simple RC that damps ringing about the > same. >Isn't the RCD clamp done wrong? Normally you do it like this: https://www.ridleyengineering.com/images/SPM/11/article11_02.jpg
Reply by ●October 3, 20232023-10-03
On Tue, 3 Oct 2023 14:45:43 +0200, Klaus Vestergaard Kragelund <klauskvik@hotmail.com> wrote:>On 30-09-2023 21:10, John Larkin wrote: >> On Sun, 24 Sep 2023 09:18:31 -0700, John Larkin <jl@997arbor.com> >> wrote: >> >>> >>> This is pleasingly weird. >>> >>> https://www.dropbox.com/sh/sif3efs69dxe1mg/AACY0RJGXl4k8CVvauUbJtYFa?dl=0 >>> >>> Sort of a baseline-boosted multi-auto-transformer voltage-doubler >>> flyback. >>> >>> What's strange is that adding the two snubbers increases the LT spice >>> sim speed radically, about 10:1. >> >> OK, this has become sort of a background hobby, waiting on the >> customer to get serious. >> >> https://www.dropbox.com/scl/fi/60nb1pcrnl17c07tk8xeu/T875_HV_9.jpg?rlkey=9uv466edcuvddmjldgepcyi0u&raw=1 >> >> All the caps are a part that we have, 100nF 630 volts 1812. Of course >> the capacitance plummets as voltage goes up, so the Spice values have >> to be adjusted appropriately. C is only 20nF at 500 volts. >> >> The RCD snubber is nice. It softens the rise at the fet drain and >> dissipates less power than a simple RC that damps ringing about the >> same. >> >Isn't the RCD clamp done wrong? > >Normally you do it like this: > >https://www.ridleyengineering.com/images/SPM/11/article11_02.jpg > >There are at least two topologies of an RCD clamp. The one that you show doesn't damp high-frequency ringing after the diode turns off. My diode multiplier chain actually clamps the fet drain swing in both directions, so there is no voltage overload hazard to the mosfet. All that's left is to damp the residual ringing to reduce radiated EMI a bit. A plain RC will damp the ringing but adding the diode reduces damper power dissipation a little.
