Re: A question about SSTC tuning

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

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

Hi Ken and all,

> For the amplification, I am just using several 5V CMOS inverting logic
> gates daisy-chained, capacitively coupled and "linearized" using input-
> and feedback-resistors.  The output of the last one of those is
> essentially a rail-to-rail square wave and that then feeds to several
> additional logic gates for phase selection, on-off gating and MOSFET
> drive-generation.

Just as a side note: another one which works quite well is the single
74HC4046 based signal-square-up trick which Gary Johnson presents in his
brilliant Tesla coiling papers at
 http://www.eece.ksu.edu/~gjohnson/
 (chapter 7, tesla coil driver, page 16, stuff around IC U3, and
  also see description of the circuit)

Anyway it probably doesn't matter what method you use. Propagation delay
is likely to be the same anyways and <50ns. :o)
(That's if you don't want to modulate the TC. Otherwise I'd use a
manually tuned VCO with the audio signal injected into the control
voltage.)

But - a controllable signal delay would be nice, to get proper phase.
  http://www.maxim-ic-dot-com/appnotes.cfm/appnote_number/559

That's something I'm trying to figure out right now, i.e. a maximum power
follower which could be added to this simple feedback scheme. Something
that would use a digital (or analog) controlled, automatically adjusting
phase shift which leads to maximum output power! :-)~

If someone already has done this, it'd be interesting to hear your
experiences on how well it works! And how you did it! :)
(or maybe I should buy a copy of Ken's patent? :o) )

 - Jan

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 high voltage at http://www.hut.fi/~jwagner/tesla
 Jan OH2GHR