Re: phase locked loop SSTC

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

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

Hi,

>         It strikes me that the loop filter response time is a bit
> swift. Have you tried using a larger time constant?
> 
> Regards,
> Malcolm

[btw, has anyone made a PLL driven SSTC that really works? it'd be
very relieving to hear from someone that he's done it, i.e. that it
has real chances of working properly...]

Tried larger RC (single pole) loop filter, up to 250kOhm (with the
same 1.0 nF). But the same thing happens - streamers grow to 5cm max
and then suddenly zip and streamers turn off completely. An arc to a
screwdriver looks like a short capacitive discharge, and that's it
then. Rectified mains must go down to 0V and then up again to get any
output from the secondary. I'd guess this is an issue with the current
transformer? Although, the signal out is pretty clean... even though
it is a square wave (overdriven and clipped sine wave).

Anyway I've started to suspect - is a phase locked loop of any use in
driving a SSTC at all? 

Because, when driving the TC at some more or less out-of tune
frequency, the current drawn at the primary coil doesn't look like a
sine wave. Instead it reminds more of a square wave at the driver
frequency, except it has a large ripple / mess / "small bits" of sine
wave on it here and there. Or, hmm..., is this really the signal I
should be getting?

I mean if this is the case, and that messy signal is actually ok, then
a phase locked loop wouldn't have any chance detecting the real
resonant freq - because it appears just as that signal mess on top of
the driving square wave waveform, which is "removed"/clipped off by
the input amplifier of the PLL IC... ???

cheers,
  - Jan


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