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[TCML] Flyback powered TC



Hi all,

It's been many years since I've posted to this list... I built my first TC about 15 years ago in my parent's basement when I was a teenager and I used to be active on the pupman list around that time... But in the meantime I've gone to University, moved around, bought a house, and ended up in the UK (originally from Canada).... Now I'm thinking of building a small tesla coil again. In the past I've played with up to about 900w of input power but I've always used NSTs. For my new coil I'm looking at something much smaller and lighter. My plan is to build a SGTC with a flyback transformer for the primary supply.

I have a good beefy old style AC flyback (not one of the internally rectified ones...) that I've run on a mazzilli zvs circuit for long periods of time at 250w input power without any detectable heating in the mosfets, ferrite or coils. I'm planning on potting the whole thing in thermally conductive high-voltage silicone potting material to get a nice compact brick that gives me about 15kv out from 12vd in. I was thinking of building a small ARSG with a pwm controlled DC motor to adjust the breakrate.

So... The question is.. Should I build this like a regular tesla coil with an NST or should I DC rectify the output from the flyback? I was thinking that the flyback runs at around 20khz, which to me implies that my breakrate would have to be extremely high or I would be wasting the power and stressing the caps / transformer. But if I rectified it to DC then the breakrate could be anything.... But I'm I'm supplying a constant (ish) dc charging current to the capacitor when the gap fires and the energy is dumped into the primary it seems to me this constant supply would cause a problem with the ringing of the primary circuit unless it were somehow disconnected from the capacitor while it is ringing.

Is this correct? How can I handle that? Would an AC blocking inductor work? Could I put a filter capacitor on the dc output of the Flyback to smooth the wave and then put an inductor in between that and the main tank capacitor so that the DC passes through the inductor to charge the cap, but on gap fires and the HF ringing starts the inductor presents a high impedance to that signal to effectively cut the tank circuit from the charging supply until it is exhausted? Would this work?

Cheers,
Troy.


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