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Recent s.s.t.c. work...more-or-less

Original poster: "K. C. Herrick" <kchdlh@xxxxxxx>

Greetings, all-

Increase in age & decrease in smarts is catching up with me but I press ahead haltingly (tho should have quit years ago). I've repeated a fundamental mistake I made in my 1st-&-only working coil, now sadly defunct: I've neglected to shield the 5V-portion of my current electronics. So...I'll have to saw apart the ckt board & put the 5V part in a box.

In the interim (to be extended shortly by a month away in Europe), I've frittered away some more time simulating 2 types of feedback, represented in


The circuits are essentially the same, incorporating a tuned primary, except that one employs feedback (to sustain the oscillation) from the secondary's current and the other, from a (simulated1-turn) pickup coil near the secondary.

Simulation yields the expected "notches" (or rather, one of them) for the case where feedback is taken from the extra coil -- but no notches when it is taken from the secondary-return. Also, in the latter case, spark voltage (and hence power in) is much larger.

Notice that I simulate the spark with the 100K/10 pF switched-load at the right in each drawing, producing waveform-dips at 50 and 90 us respectively. Also, I need a small noise (100 KHz) source to get oscillation going -- V1 in each case. And lastly, both waveforms are at "Probe 1 - NODE" but one happens to be labeled as at S2-N which is the same node.

So... The phase between driving current & voltage is not shifting for secondary-return feedback (because there are no notches--& also, I checked the simulation waveforms) but it does shift, hence making near-zero-current switching difficult or impossible, in the other case.

Is this of any significance to solid-staters? Can I tweak these circuits for more realistic simulation?

I'll be checking the List periodically while I'm away.

Ken Herrick