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

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

Original poster: "Jolyon Vater Cox by way of Terry Fritz <twftesla-at-qwest-dot-net>" <jolyon-at-vatercox.freeserve.co.uk>

Ken,
Is this the sub-circuit you describe?

       sec
        |
        +-1K-+----+----to amplifier
        |        a|    k|    and fets
        c1    D1 D2
        |        k|   a|
        +-----+----+----to ground
Also, could a common-base amplifier like the one below (with centre-tapped
DC supply and no base biasing) similarly be used to generate antiphase
signals for a bridge amp?

              +ve    supply rail
               |
              R1
               |
              +-------Phase 1 to fets
               |
                \
                 |---------+
            e   /            |
sec         |             |
|              |             |
+----------+            |
|              |             |
c1       e  \            |
|               |---------+
|              /             |
|             |              |
+---------------------+----0V (Ground)
              |
             +----------Phase 2 (to fets)
              |
              R2
              |
             -ve supply rail

Finally, would it be possible to use any of these subcircuits to provide
feedback in a PLL self-tuning SSTC as this seems interesting -despite
reported difficulties.

Jolyon.


----- Original Message -----
From: "Tesla list" <tesla-at-pupman-dot-com>
To: <tesla-at-pupman-dot-com>
Sent: Wednesday, November 13, 2002 6:36 PM
Subject: Re: Hvguy-dot-com Feedback SSTC and New Stuff!!!


 > 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
 >
 >
 >