Re: MOSFET driver killed with no particular reason

Hi again
I forgot something, The boot strap diode must be at least as fast as 200ns.
The boot strap cap should be 1 uf and the ground cap at the anode end of the
fast diode should be at least 10uf.
I hope this is helpful
Ray


<w2kwong@xxxxxxxxxxx> wrote in message
news:1176911909.411398.111240@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
hi to everyone. I mysteriously killed 5 MOSFET half bridge drivers and
wish to see if anyone can help.

I'm making a N-MOSFET H bridge circuit that switch a sine wave output
using unipolar PWM for an inverter project. The gate driver I choose
was IR21834 and I began testing half of the bridge on breadboard
according to the data*** circuit. Connecting input lines manually to
V+ or GND to produce the output, the lower MOSFET would first work,
but it always happened that somehow after changing the circuit such as
connecting driver input here and there or switching the value of
boostrap capacitor, at a random time the chip would go crazy . The
chip would feel hot touch, followed by increase in current drawn, all
of which signifying an internal short circuit. It seems the hide side
circuit is causing problem, since the low side output would usually
still functioning afterwards.

I believe such short circuit behavior can only be caused by shorting
high side output to ground or to V+, and I swear I didn't, nor did I
connect bootstrap diode and capacitor wrongly (I redid the circuit
several times and same error can't happen over and over again). I
thought it might be chip design problem but as I tried chip from other
manufacture, L6388 from ST, the same happened. Now I'm really
threatened as I don't want to kill any more chips. Although I might
find out the reason myself but that would probably take another 10
chips dedicated to destroy, and this is why I ask for help here.

While not expecting direct reasons to the problem, I am REALLY REALLY
glad if someone who have killed MOSFET driver before (for whatever
reasons) to share his/her story, and also tell me what to avoid when
working with drivers, thousands thanks in advance!



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