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RE: Re: hvguy-dot-com new flyback driver

Original poster: "by way of Terry Fritz <twftesla-at-qwest-dot-net>" <rob-at-pythonemproject-dot-com>

When I was a kid, I perfected a flyback circuit that worked with a single
2N3055.  The key was putting an inductor (couple of mH?) directly from base
to emitter to suck the charge out of the base during turn off.  I used 20
turns of secondary on the bottom rung of the flyback, and 2 turns of
tickler coil connected via a cap to the base.  This was an oscillator.  You
start the oscillation by hitting a button which spikes the base line, then
its free running.  I used to be able to flash over and incinerate the
biggest flybacks from the 70's, with about 30V Vcc.  This circuit was very
efficient since the L-C high pass character of the tickler circuit pulsed
the transistor with a very short width.  Rob.

ps.  I'd love to build one of these again, but those old flybacks are
no-where to be found except in landfills

>----- Original Message -----
>From: "Tesla list" <tesla-at-pupman-dot-com>
>To: tesla-at-pupman-dot-com
>Sent: Wed, 01 May 2002 11:31:56
>Original poster: "Jan Wagner by way of Terry Fritz
><twftesla-at-qwest-dot-net>" <jwagner-at-cc.hut.fi>
>> SCHEMATICS and info of our new driver can be
>found at www.hvguy-dot-com,
>> at the very top, just under the blue laser title
>Looks nice! :) And seems to work quite well too!!!
>Hey, I got an additional tip (==cost reduction) for
>the gate drive: you
>can use a single CD4049 (hex inverter, costs maybe
>10 cents??) to replace
>the four transistors in the gate drive.
>  http://student.fortlewis.edu/~gwdurland/4049.html
>It works stunningly well for this single mosfet
>drive, and the gate
>signal looks superbly clean. Just connect a couple
>of outputs from your
>CD4049 together, and connect the mosfet gate to
>(I use a setup exactly like that to drive four 20V
>mosfets that in
>their turn drive a beefy gate drive transformer.
>Works beautifully.)
>One question about the protection diodes around the
>mosfet: what are they
>for? I may be mistaken but I thought that the
>voltage spike on the mosfet
>is always positive (ok I never measured...), so the
>mosfet intrinsic
>diode/bipolar transistor never conducts, thus,
>doesn't need to be
>disabled?  ;o) You could save some bucks by leaving
>out the FR and
>schottky diodes? Or?
>A reverse diode accross the flyback primary helps
>hugely agains voltage
>spikes, but, it will get a bit hot so a heat sink
>is necessary. Some 
>TO-220 packaged ultrafast diode would be best for
>It's called a "flyback diode" in this flyback
>transformer setup.
>Umm yeah and a final note: arcs from flybacks with
>internal rectifier +
>cap are by far the longest. 6-7cm. It's sure worth
>trying out! :)
> - Jan
> high voltage at http://www.hut.fi/~jwagner/tesla