Re: Hvguy-dot-com Feedback SSTC and New Stuff!!!

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

Original poster: "K. C. Herrick by way of Terry Fritz <twftesla-at-qwest-dot-net>" <kchdlh-at-juno-dot-com>

Justin, Aron (& all)-

Comments below...

On Wed, 13 Nov 2002 07:45:38 -0700 "Tesla list" <tesla-at-pupman-dot-com>
writes:
 > Original poster: "Justin Hays by way of Terry Fritz
 > <twftesla-at-qwest-dot-net>" <pyrotrons2000-at-yahoo-dot-com>
 >
 > Hi Ken and All,
 >
 > Ken, thank you for the compliments. We've worked very hard to
 > document our projects, so that others might look and say "cool!".
 > We
 > always enjoy it.
 >
 >  > Justin & Aron, you might look into my notion for using the
 >  > secondary's return current as the source of feedback
 >  > in your self-tuned systems.
 >
 > Hm. So, perhaps use a current-sense resistor, opamp, and
 > comparator?

[snipped]

I'll copy here what I posted a day or so ago:  You feed the [secondary's]
current through a capacitor whose reactance is small at Fr, to ground.
Take the small capacitor voltage, now shifted 90 degrees w/ respect to
the current, and couple it to a pair of back-to-back diodes to ground via
1K or so.  Then amplify the diode voltage & drive the FET(s) with it.
Voila!...a feedback oscillator with the secondary's Fr as the sole
frequency-determining element.  You need enough gain in the [linear part
of the] amplifier so that noise will start the oscillations going.  Or
else, configure it as a weak internally-fed-back oscillator that will
become swamped with the secondary-signal as soon as you turn it on.  And
I add: be sure to get the polarity right, through the amplifying chain,
for positive & not negative feedback.

 >  > And another thing: be wary of having both FETs in each half of
 > the
 > H
 >  > being on at the same time!  You might want a bit of crossover-
 >  > control in the circuit to avoid that.
 >
 > We keep this in the back of our mind, for sure! A commercial design
 > would never use a single gate transformer to directly control four
 > (or two) MOSFET's in a bridge, and we realize that. But, at the
 > same
 > time, it works! I imagine there is some degree of shoot-through
 > current (we should measure it) but it just isn't hurting anything.
 >
[snipped]

I suppose if the FETs don't get hot you're home free; although...it could
be that a humungous short spike is degrading them, over time.

KCH