[TCML] Flyback powered TC

[Troy <teslatroy@xxxxxxxxxxxx>]

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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