Re: Solid-state coil (gate xfrmr question)

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

Original poster: "Jan Florian Wagner by way of Terry Fritz <twftesla-at-qwest-dot-net>" <jwagner-at-cc.hut.fi>


> secondary around different ferrite toroids I had lying around.  All have
> the same effect of keeping the coil from putting out as big a spark as when
> the gate is driven directly.  So, if you know what ferrite material to
> select for a core, how big to make it, and how many turns should be
> required, please let me know!

Telephone network pulse transformers work just nicely, at least from 80kHz
to 300kHz where I tested them. It's those small pot-core type ones. Of
course, you have to remove the original windings and place a new pri & sec
there. Turns # depends on core size, secondary turns # depends on
the input voltage - you want 30V..36V on the sec. 
Use two Zeners of 18V each on the output winding, placed antiparallel, as
shown in
  http://www.hut.fi/~jwagner/tesla/SSTC/fullbridge-designer.htm.
no matter what people say about Zeners causing gate signal ringing. I
haven't found this to be true (at least not yet).

Primary turns number boils down to suck and see. I used ~30 turns at 18V
input for my smaller pulse transformers. All depends... 

The pulse xfmr will run well only in a limited frequency range which
might be quite small, say 80kHz...160kHz. Same xfmr doesn't work well at
20kHz or 500kHz, so for other frequencies you have to make another pulse
xfmr.

cheers,
 - Jan

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