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>

Jolyon (& all)-

Comments interspersed...

On Wed, 13 Nov 2002 16:57:00 -0700 "Tesla list" <tesla-at-pupman-dot-com>
writes:
 > 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

Yes, it is.  Xc of C1 would be <<1 K so the 1 K's loading would be
negligible.  Phase-shifted sine wave across C1 & +/- 0.7 V "square" wave
across the diodes.  Capacitor-couple, usually, to the amplifier, of
course.

 > 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
 >

Hmmm...  I don't quite follow it, but I think not.  The "phase 1" FETs
have their gates referred to their sources, of course, which are
connected to the output--so those gates are bobbing up & down with that
output signal.  You have to drive the "top" FETs with something that will
accomodate that, like a transformer or one of those IR "high'side"
IC-drivers.  Except...the latter gave me fits in an earlier v. of my s.s.
coil & I had to get rid of them.  They incorporate a high-impedance
voltage-shifting circuit, apparently, which didn't stand the e.m. field.
At least, that, my conjecture.

The hvguys just use one multi-winding transformer to do the job.  Simple
enough & as has been commented upon in other postings of yesterday &
today, may well be good enough.

 > 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.

Hooh!  I wouldn't trouble myself with a PLL.  Why bother?  Utilizing
either an antenna or, as I do, the secondary's return current, will
provide just the signal you want absent a PLL.  If you provide enough
excess gain in the linear portion of the amplifier, circuit noise will
get oscillations going in nothing flat.

Ken Herrick

[snipped]