L
Lasse Langwadt Christensen
Guest
torsdag den 28. september 2023 kl. 22.58.46 UTC+2 skrev Klaus Kragelund:
how about something crazy, a car ignition coil? ratio about 1:100, isolation good for +20kV
coil-on-plug can be pretty small, if you need access to both ends of the secondary a dual output coil for wasted spark has that
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.
how about something crazy, a car ignition coil? ratio about 1:100, isolation good for +20kV
coil-on-plug can be pretty small, if you need access to both ends of the secondary a dual output coil for wasted spark has that