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Re: BEWARE of dead gate drive IC that still works
Original poster: "Marco Denicolai by way of Terry Fritz <twftesla-at-qwest-dot-net>" <marco.denicolai-at-tellabs-dot-com>
Thanks for the warning. It really sounds like a possibly deep pitfall.
Tesla list wrote:
> Original poster: "Justin Hays by way of Terry Fritz <twftesla-at-qwest-dot-net>"
> Say like, for instance, just speculating, this didn't really happen
> to me now ; ), that your gate isolation transformer kicked back into
> the chip and fried it. Oops. I swear some 12V zener diodes literally
> jumped out of my parts drawers and soldered themselves onto my board
> after that happened ; )
Sorry, did the 12V zeners eventually prevent the damage or not? Did you
try varistors (a way faster than "usual" zeners)?
> Obviously, applying Vcc and removing it is a must. So something has
> to be added to protect the chip. I'm thinking a couple of
> back-to-back zeners. Other methods slow down the rise and fall times
> of the output waveform (which is ultra-critical 'cause it controls my
> H-bridge running at 1.5kW!)
You'll find a tradeoff between switching losses (requiring a fast
switching time) and transients + chip mortality (with a benefit from
slower switching time).
If you are going to use a bootstrap power supply (not a floating DC/DC
converter or such) let me know, because I've got a couple of problems
I'd like to warn you of.