500 volt power supply...

John Larkin · Sep 26, 2023

On Tue, 26 Sep 2023 12:43:30 +0100, piglet <erichpwagner@hotmail.com>
wrote:

On 24/09/2023 6:59 pm, John Larkin wrote:
On Sun, 24 Sep 2023 13:41:12 -0400, bitrex <user@example.net> wrote:

On 9/24/2023 1:25 PM, John Larkin wrote:
On Sun, 24 Sep 2023 12:38:28 -0400, bitrex <user@example.net> wrote:

On 9/24/2023 12:18 PM, John Larkin 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.

There are bunch of topologies that charge inductors in parallel and
discharge in series, helps take the stress off the switch(es) and don\'t
need huge duty cycles. I have one like that in my filez that\'s like a
Cuk, with a quasi-floating output posted at the end though haven\'t found
a particular use for it yet..

I started simulating with a single 1:5 transformer, but couldn\'t find
one for sale.

24 to 500 is sort of a black hole for flyback transformers. The
\"capacitor charging\" flybacks are either the wrong ratio or too wimpy.

The DRQ127 parts are cool and cheap (under a dollar) and multi-sourced
and pick-and-place compatible, so it makes sense to use four of them.

Inductors charged in parallel and discharged in series does sound
cool, but I\'d expect that to need a lot of parts.

I could also rectify each of my secondaries independently into DC, and
stack those in series. But no big benefit, more parts.

If you have transformers with a dual secondary you can make a boosting
autotransformer-type topology by using the spare secondaries to couple
fluxes, so they act like they\'re all wound on the same core, sort of
like this somewhat silly example:

The DRQ127\'s are 2 widings, 1:1. Handy parts.

What was your 3KV for? I\'m powering a Pockels Cell driver. It\'s only a
moderate number of KHz so I shouldn\'t need a lot of power.

It would be nice to spread-spectrum my supply. That LT chip is fixed
200 KHz. The customer can get whiney about EMI.

Have you measured the inter-winding capacitance of those DRQ127s?

My guess is many tens of pF and if you simulate with that then your
snubber requirements may be quite changed?

piglet

DRQ127, the big one in the DRQ family:

33 uH is 106 pF measuring two shorted windings

1 mH is 432 pF

I\'m not sure how to Spice a distributed capacitance. Maybe put half on
each end?

piglet · Sep 26, 2023

On 26/09/2023 8:22 pm, John Larkin wrote:

I\'m not sure how to Spice a distributed capacitance. Maybe put half on
each end?

Yes, that is exactly what I do!

piglet

John Larkin · Sep 27, 2023

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.

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

https://www.dropbox.com/scl/fi/kada16c6rl4kcx11pq86q/T875_HV_6.asc?rlkey=2u7nvyhxt7lgwd5dr32gpqtqo&dl=0

I like this one because it simulates fast.

The MMBD5004S is a cute little dual HV diode in SOT-23. BAS21S is
similar.

Anthony William Sloman · Sep 27, 2023

On Wednesday, September 27, 2023 at 5:23:13â¯AM UTC+10, John Larkin wrote:

On Tue, 26 Sep 2023 12:43:30 +0100, piglet <erichp...@hotmail.com
wrote:
On 24/09/2023 6:59 pm, John Larkin wrote:
On Sun, 24 Sep 2023 13:41:12 -0400, bitrex <us...@example.net> wrote:
On 9/24/2023 1:25 PM, John Larkin wrote:
On Sun, 24 Sep 2023 12:38:28 -0400, bitrex <us...@example.net> wrote:
On 9/24/2023 12:18 PM, John Larkin wrote:

<snip>

Have you measured the inter-winding capacitance of those DRQ127s?

My guess is many tens of pF and if you simulate with that then your
snubber requirements may be quite changed?

piglet
DRQ127, the big one in the DRQ family:

33 uH is 106 pF measuring two shorted windings

1 mH is 432 pF

I\'m not sure how to Spice a distributed capacitance. Maybe put half on each end?

I got mildly obsessive about it once and split the inductor into three tightly coupled segments and divided up the stray capacitance and tied it to the new nodes..

It didn\'t change the behavior of the simulated circuit at all.

--
Bill Sloman, Sydney

Jan Panteltje · Sep 27, 2023

On a sunny day (Tue, 26 Sep 2023 19:35:18 -0700) it happened John Larkin
<jl@997arbor.com> wrote in <mf47hi15db7eq7mp2nl9mdqgin7acrujdi@4ax.com>:

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.

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?

John Larkin · Sep 27, 2023

On Wed, 27 Sep 2023 05:14:49 GMT, Jan Panteltje <alien@comet.invalid>
wrote:

On a sunny day (Tue, 26 Sep 2023 19:35:18 -0700) it happened John Larkin
jl@997arbor.com> wrote in <mf47hi15db7eq7mp2nl9mdqgin7acrujdi@4ax.com>:

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.

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.

Jan Panteltje · Sep 27, 2023

On a sunny day (Wed, 27 Sep 2023 00:51:10 -0700) it happened John Larkin
<jl@997arbor.com> wrote in <4bn7hit0n3rmcg8551cskijart3cnh9ess@4ax.com>:

On Wed, 27 Sep 2023 05:14:49 GMT, Jan Panteltje <alien@comet.invalid
wrote:

On a sunny day (Tue, 26 Sep 2023 19:35:18 -0700) it happened John Larkin
jl@997arbor.com> wrote in <mf47hi15db7eq7mp2nl9mdqgin7acrujdi@4ax.com>:

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.

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?
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..

John Larkin · Sep 27, 2023

On Wed, 27 Sep 2023 11:44:57 GMT, Jan Panteltje <alien@comet.invalid>
wrote:

On a sunny day (Wed, 27 Sep 2023 00:51:10 -0700) it happened John Larkin
jl@997arbor.com> wrote in <4bn7hit0n3rmcg8551cskijart3cnh9ess@4ax.com>:

On Wed, 27 Sep 2023 05:14:49 GMT, Jan Panteltje <alien@comet.invalid
wrote:

On a sunny day (Tue, 26 Sep 2023 19:35:18 -0700) it happened John Larkin
jl@997arbor.com> wrote in <mf47hi15db7eq7mp2nl9mdqgin7acrujdi@4ax.com>:

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.

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

Jan Panteltje · Sep 27, 2023

On a sunny day (Wed, 27 Sep 2023 08:10:02 -0700) it happened John Larkin
<jl@997arbor.com> wrote in <d3h8hitm54oie4gclhkeetp7ked7svs5jj@4ax.com>:

On Wed, 27 Sep 2023 11:44:57 GMT, Jan Panteltje <alien@comet.invalid
wrote:

On a sunny day (Wed, 27 Sep 2023 00:51:10 -0700) it happened John Larkin
jl@997arbor.com> wrote in <4bn7hit0n3rmcg8551cskijart3cnh9ess@4ax.com>:

On Wed, 27 Sep 2023 05:14:49 GMT, Jan Panteltje <alien@comet.invalid
wrote:

On a sunny day (Tue, 26 Sep 2023 19:35:18 -0700) it happened John Larkin
jl@997arbor.com> wrote in <mf47hi15db7eq7mp2nl9mdqgin7acrujdi@4ax.com>:

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.

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.

Klaus Kragelund · Sep 27, 2023

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.

John Larkin · Sep 28, 2023

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.

whit3rd · Sep 28, 2023

On Wednesday, September 27, 2023 at 3:57:50â¯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.

John Larkin · Sep 28, 2023

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.

Jan Panteltje · Sep 28, 2023

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.

John Larkin · Sep 28, 2023

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.

Anthony William Sloman · Sep 28, 2023

On Friday, September 29, 2023 at 1:26:46â¯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 fraction
of 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

John Larkin · Sep 28, 2023

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.

Klaus Vestergaard Kragelund · Sep 28, 2023

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.

Klaus Kragelund · Sep 28, 2023

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

Klaus Kragelund · Sep 28, 2023

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.

500 volt power supply...

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