On Wed, 27 Sep 2023 13:34:29 -0700 (PDT), Klaus Kragelund <klaus.kragelund@gmail.com> wrote:>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.I'm doing 24 to 500, also about 5 watts. The C-W multiplier has many virtues. You can use a more reasonable transformer, and lower voltage diodes and caps. An actual CCFL transformer would work, if you can buy them. Turns ratios are in the 50-100 sort of range. Potting is ugly.
500 volt power supply
Started by ●September 24, 2023
Reply by ●September 27, 20232023-09-27
Reply by ●September 27, 20232023-09-27
On Wednesday, September 27, 2023 at 3:57:50 PM UTC-7, John Larkin wrote:> On Wed, 27 Sep 2023 13:34:29 -0700 (PDT), Klaus Kragelund > <klaus.k...@gmail.com> wrote:> >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. > I'm doing 24 to 500, also about 5 watts. > > The C-W multiplier has many virtues. You can use a more reasonable > transformer, and lower voltage diodes and caps. > > An actual CCFL transformer would work, if you can buy them. Turns > ratios are in the 50-100 sort of range. > > Potting is ugly.Yeah, but it's compact and not messy. Oil immersion and SF6 pressure tanks are not compact. A classic auto spark coil with tar is kinda in-between: the tar is an oil, but it's solid enough stuff not to be messy, if contained. Wood for Model T, can for later autos.
Reply by ●September 27, 20232023-09-27
On Wed, 27 Sep 2023 13:34:29 -0700 (PDT), Klaus Kragelund <klaus.kragelund@gmail.com> wrote:>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.Somebody, VMI maybe, sells potted C-W multiplier strings.
Reply by ●September 28, 20232023-09-28
On a sunny day (Wed, 27 Sep 2023 13:34:29 -0700 (PDT)) it happened Klaus Kragelund <klaus.kragelund@gmail.com> wrote in <903144ac-6642-4a3f-bb85-f9c8485eaf03n@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.
Reply by ●September 28, 20232023-09-28
On Thu, 28 Sep 2023 14:59:48 GMT, Jan Panteltje <alien@comet.invalid> wrote:>On a sunny day (Wed, 27 Sep 2023 13:34:29 -0700 (PDT)) it happened Klaus >Kragelund <klaus.kragelund@gmail.com> wrote in ><903144ac-6642-4a3f-bb85-f9c8485eaf03n@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. Old TV flybacks were pie wound to help with both problems. That makes a hand-wound transformer yet nastier; Sloman would love to (have someone else) wind that. There are some cool old parts from CRT TVs but we wouldn't use Ebay parts for production. Even ISDN transformers are hard to get these days. And most of our boards have a component height limit below about 1". I've gravitated to the classic C-W layout with all series strings of caps. That's driven by the poorly-or-never defined C/V behavior of available ceramic caps, which encourages their use at a small fraction of rated voltage. There are lots of cute flyback controller chips that do peak current limiting control. I don't know how much voltage we dare generate on a regular PCB without coating or potting. I'm guessing that 1KV is safe and I know that 7KV isn't.
Reply by ●September 28, 20232023-09-28
On Friday, September 29, 2023 at 1:26:46 AM UTC+10, John Larkin wrote:> On Thu, 28 Sep 2023 14:59:48 GMT, Jan Panteltje <al...@comet.invalidwrote: > >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:<snip>> High turns ratios can have two problems: voltage breakdown in the insulation,But you should be able to organise the windings so that this isn't a problem.> and winding capacitance limiting the flyback ratio.Again, if you organise the windings into enough banks you should be able to get around that problem.> That's where a C-W diode multiplier helps.It certainly can, but it introduces it's own problems.> Old TV flybacks were pie wound to help with both problems. That makes a hand-wound transformer yet nastier; Sloman would love to (have someone else) wind that.I've wound my own transformers and found specialised coil winding firms to do it for me. Hand-winding is a specialised skill and needs specialised machines. Small ones can be pretty cheap. I've yet to get a printed transformer winding made, but I've talked to printed circuit board firms who specialise in that business at trade shows, and there's nothing nasty about going that way> There are some cool old parts from CRT TVs but we wouldn't use Ebay parts for production. Even ISDN transformers are hard to get these days. And most of our boards have a component height limit below about 1".Planar cores intended to be used with printed windings tend to sit pretty close to the board.> I've gravitated to the classic C-W layout with all series strings of caps. That's driven by the poorly-or-never defined C/V behavior of available ceramic caps, which encourages their use at a small fractionof rated voltage. That depends on the ceramic. And there are lots of non-ceramic caps around.> There are lots of cute flyback controller chips that do peak current limiting control.Get the transformer right, then worry about the control electronics. All the cute chips were developed for somebody who was going to buy 100,000 of them and solves their problem perfectly. It's always going to be less suitable for solving your problem.> I don't know how much voltage we dare generate on a regular PCB without coating or potting. I'm guessing that 1KV is safe and I know that 7KV isn't.High voltage on a PCB makes some kind of conformal coating pretty much essential. You don't want some over-confident clown killing themselves by poking it with a screwdriver. Senior managers and people who own the company tend to be very self-confident. -- Bill Sloman, Sydney
Reply by ●September 28, 20232023-09-28
On Wed, 27 Sep 2023 17:24:13 -0700 (PDT), whit3rd <whit3rd@gmail.com> wrote:>On Wednesday, September 27, 2023 at 3:57:50?PM UTC-7, John Larkin wrote: >> On Wed, 27 Sep 2023 13:34:29 -0700 (PDT), Klaus Kragelund >> <klaus.k...@gmail.com> wrote: > >> >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. >> I'm doing 24 to 500, also about 5 watts. >> >> The C-W multiplier has many virtues. You can use a more reasonable >> transformer, and lower voltage diodes and caps. >> >> An actual CCFL transformer would work, if you can buy them. Turns >> ratios are in the 50-100 sort of range. >> >> Potting is ugly. > >Yeah, but it's compact and not messy.It is very slow and expensive and messy. Buying the goo and a shell or mold, mixing, degassing, pouring, curing, cleanup, and then you have a thing that you can't probe or rework. Globbing or coating is also a pain, but not as big a pain. Expensive labor-intensive processes like potting and transformer winding and exotic PCB fab seem to appeal to some people for some strange reason.
Reply by ●September 28, 20232023-09-28
On 28-09-2023 20:55, John Larkin wrote:> On Wed, 27 Sep 2023 17:24:13 -0700 (PDT), whit3rd <whit3rd@gmail.com> > wrote: > >> On Wednesday, September 27, 2023 at 3:57:50?PM UTC-7, John Larkin wrote: >>> On Wed, 27 Sep 2023 13:34:29 -0700 (PDT), Klaus Kragelund >>> <klaus.k...@gmail.com> wrote: >> >>>> 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. >>> I'm doing 24 to 500, also about 5 watts. >>> >>> The C-W multiplier has many virtues. You can use a more reasonable >>> transformer, and lower voltage diodes and caps. >>> >>> An actual CCFL transformer would work, if you can buy them. Turns >>> ratios are in the 50-100 sort of range. >>> >>> Potting is ugly. >> >> Yeah, but it's compact and not messy. > > It is very slow and expensive and messy. Buying the goo and a shell or > mold, mixing, degassing, pouring, curing, cleanup, and then you have a > thing that you can't probe or rework. > > Globbing or coating is also a pain, but not as big a pain. > > Expensive labor-intensive processes like potting and transformer > winding and exotic PCB fab seem to appeal to some people for some > strange reason. > >When you do it large scale, then it's really quite easy and fast, and not that expensive. A lot less expensive, than having to deal with a big transformer and worrying about flashover.
Reply by ●September 28, 20232023-09-28
On Thursday, 28 September 2023 at 16:59:57 UTC+2, Jan Panteltje 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..Yeah, 768 is not bad at all. A couple of months ago I did a E13 with 200 turns, no problem at all.> Spreading the turns over a segmented coil former is a good idea.Yes, that would handle the issue with large voltage differences on the secondary coil, and isolation to the primary> 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.Yeah, so that's a compromise between the voltage on the primary FET during energy delivery and optimum duty-cyle.> 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.I use STM32s :-)> 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.Would be interesting to see the internal construction of that one
Reply by ●September 28, 20232023-09-28
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> > Old TV flybacks were pie wound to help with both problems. That makes > a hand-wound transformer yet nastier; Sloman would love to (have > someone else) wind that.Pie wound, so that's adding on layers instead of across the bobbin?> > There are some cool old parts from CRT TVs but we wouldn't use Ebay > parts for production. Even ISDN transformers are hard to get these > days. And most of our boards have a component height limit below about > 1".I agree, Ebay does not work for production items :-)> > I've gravitated to the classic C-W layout with all series strings of > caps. That's driven by the poorly-or-never defined C/V behavior of > available ceramic caps, which encourages their use at a small fraction > of rated voltage.In any case for the C-W multiplier to work properly, the charging of the caps needs to be kept low.> > There are lots of cute flyback controller chips that do peak current > limiting control. >I am using a microcontroller. Microcontroller and kV design does not sound good, right?> I don't know how much voltage we dare generate on a regular PCB > without coating or potting. I'm guessing that 1KV is safe and I know > that 7KV isn't.Potting or conformal coating is probably needed to avoid carbonization of PCB surface.
