Re: Sheppard-Talyor circuit up on my website/ low Z construction technique

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

Original poster: "Justin Hays by way of Terry Fritz <twftesla-at-qwest-dot-net>" <pyrotrons2000-at-yahoo-dot-com>

Hi Rob (and All),

I agree with Jan to some extent, putting some kind of clamp on the
transformer primary is probably a wise idea....but...

Only if I interpret the schematic correctly, this topology doesn't
ever hard-switch the primary. So I suppose that since there is no
fast switching of large currents (IN THIS STAGE), there is minimal
voltage spiking (L di/dt) due to uncoupled inductance (leakage L) in
the primary of the transformer. Seems to me that there is a nice
round pump of current fed into the primary versus a hard-switched,
square-wave slam of current. I also suppose that this is the essence
of this topology...low EMI!

So aside from that stage (the output stage I'll call it) the MOSFET's
are no doubt operated as switches, meant to pull current into the
160uH inductance and "release" this current to the rest of the
circuitry. So the MOSFET's are switched quickly here in order to
minimize I^R power loss in the junction....and therefore there will
most likely be large voltage spikes...

So it is here in this stage (where there is high-speed switching of
significant current) that I think there should be clamp diodes. Maybe
even isolation of the MOSFET body diodes (with a series shottky) if
it comes down to it...I've heard the body diodes can create damaging
reverse recovery transients if driven into forward conduction too
hard (from free-wheeling current).

Well, maybe I've missed some things it but hopefully I've got the
main stuff right, the basic workings of the topology and all.
Although I AM starting to wonder if there is hard-switched ANYTHING
here...

Take care,

Justin Hays
KC5PNP
Email: justin-at-hvguy-dot-com
Website: www.hvguy-dot-com