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Old 18th Sep 2018, 11:49 am   #79
Al (astral highway)
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Join Date: Nov 2006
Location: London, UK.
Posts: 3,496
Default Re: Bach with sparks!

Quote:
Originally Posted by Viewmaster View Post

So I injected a sq wave at approx. 250 KHz into the feedback connection and wound up the variac

Nothing.


Then I slowly adjusted the sq wave freq and suddenly hit the sweet spot of the secondary's resonance freq.

Hey Albert, you’re really pulling all the stops out here!


It’s not advisable to bypass the feedback mechanism by injecting a signal here. The purpose of the current transformer that you removed to inject a signal instead is to control the phasing of the breakout as well as to limit instantaenously any overcurrent. Simpler designs place the current transformer in the secondary coil base, more complex ones in the primary coil where it directly delimits the max current in the full bridge/ half bridge with logic circuitry. You can see some SMD logic circuitry on the Chinese board you e posted .

The logic switches in nanoseconds and then only switches on again via flip-flop at an appropriate moment, , whereas if you reach for a switch because you notice something is warm or burning, that’s a timescale millions of times longer.

Anyways, just sayin’

You seem to be enjoying yourself and trying every resource to reach your goal!
Great enthusiasm!

Good luck !
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