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Re: HV-DC Supply
Re: Doublers
I've had good luck, but you are correct that large
capacitors are needed. At least large omega R C product..
I have done some simulations here today of a doubler circuit
for a 12 kV, 60 ma neon transformer. Some interesting results.
What I have simulated is a half-wave doubler between each end
and the center tap, with outputs in parallel and a common
output capacitor. Looks like a fairly good source of up to
100 mils at 12 kV (which would probably smoke the transformer
in continuous service). The numbers are at work, but what
turns out to happen is this. If the series capacitors for
the doubler are set 0.025 ufd, which is approximately series
resonant with the 265 henries I estimate for each leg, then
the voltage regulation is really surprisingly good, up to
about 100 mils output at least. Only problem is that the
voltage across the series capacitor (and presumably across
the transformer as well, just realized I didn't look at that)
goes way way up at high current outputs.
Bottom line is that this might be a usable approach,
particularly if someone wanted to run a vacuum tube coil
with a pulsed RF source, something I want to try here. By
running the primary circuit from a blocking or squegging
oscillator, should be able to approximate "normal" spark
gap discharge operation, although probably and significantly
lower peak powers. I think 304TL class tubes might put out
perhaps 100 kw peak power at 15 kV plate voltage, but will
have to look at tube characteristics to see. What I plan to
use are VT327A's, which put out at least 25 kW at a couple
of hundred megacycles, and should put out even more at low
frequencies. A pair in parallel might produce interesting
results. No where near the output of a simple, cheap, easy-
to-build spark gap, but still worth playing with. Will
report more later if I ever get the ambition.
In closing, I'm sure the voltage doubler would work
real well up to perhaps 20 ma output, and would have the
center tap at ground, which was the original goal. By the way,
am very much interested in following the results of your
experiments. Please keep up informed!
Regards,
Ed