RE: Terry's DRSSTC - 6000 BPS >:o)

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Original poster: "Jason Judd" <JJudd@xxxxxxxxxxxxxxxx>

Hi Jimmy,
>
> Hehe, cool. On a slightly off topic note, I'm working on
> making a small one too. Nothing new, just for fun. I was
> gonna use the existing uC controller, and existing secondary
> to make it easy. It turns out that the little IGBTs are a bit
> more fussy about early switching than the bricks. The hard
> switching causes huge spikes that kill them when out of tune.
> Primary (or sec) feedback controller is on the way!
>
>
>

Yes, I have given up on a set clock driven arrangement for small IGBTs.
Those spikes are just about impossible to stop. Also at the moment I am
getting gate spikes when the IGBTs switch on that take the gate back to
zero volts for a 100ns or so and start to turn the IGBTs back off. The
spikes are directly related to the DC bus voltage. I have tried several
gate drive transformers and even an optical driver like Terry used, but
still can't get the gate drive right ! The false gate switching causes
so much noise that the logic chips intermitantly latch up.

I might have to try some slower IGBTs other than the IRG4PF50WD ones I
am using.

Jason.