Re: Flyback Driver PCBs

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: Jan Wagner <jwagner-at-cc.hut.fi> 

Hi,

On Mon, 12 Apr 2004, Tesla list wrote:
 > Original poster: "Jim Mitchell" <electrontube-at-sbcglobal-dot-net>
 >
 > Hello List:
 >
 > After the recent sucsess of my SSTC boards, and my recent experimentation
 > with a high powered flyback driver,  I have decied I'd like to have some
 > flyback driver boards made.
 >
 > The boards would be custom 2 sided boards,  utilizing a half bridge of
 > MOSFETs or IGBTs,  and a variable oscillator and gate drive section.  This
 > would work wonders as a flyback driver and as a GP high frequency generator
 > for different experiments.

If I may advertise a bit ;-) here's my ancient but proven circuit, with
audio modulation (using FM) and mosfet overcurrent protection:
    http://www.hut.fi/~jwagner/tesla/tv-driver/schematics.htm
(works better with higher than car-battery-charger-xfmr voltage supplies,
and forget about the Eagle PCB for the mosfet section, not a good layout)
You're free to try and copy some ideas, if found useful.

 > I recently built an identical flyback driver and it works very good,  I am
 > able to drive flybacks with half wave AC up to 150v or until they start to
 > break down from overvoltage (about 50v in)  and I have been able to get 2"
 > sparks from a single small flyback (a new style DC one).

Those rectified flybacks can give out some very impressive arcs, >8cm is
possible, depending on the flyback. Really tiny ones from portable TVs can
push 5cm. I checked some 230vac TVs and apparently the flybacks take 80V
RF in as default operating specs.

But they have to be run as a flyback, NOT like an ordinary transformer
(e.g. not forced-rail like half/fullbridge or direct 50Hz in) because the
pri mag field support / current supply must collapse to cause the
high output voltage. Anything else would be inefficient (I think ;-)

cheers,
  - Jan

--
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  Helsinki University of Technology
  Dept. of Electrical and Communications Engineering