Wouter van Ooijen wrote...

>Dave Dilatush wrote:
>
>> Your N-channel MOSFETs are being forcibly and rapidly turned off
>> by the ULN2003s but the P-channel MOSFETs are only being turned
>> off by the 4K7 gate-to-source bleeder resistors, which cannot
>> remove gate charge very fast.  
>
>That's sounds OK, but I knew this so in PWM mode the P-FET is on all the
>time, only the (opposite) lower N-FET is switched! And more bizarre: it
>is not the P-FET that is on (conducting) that gets hot, it is the other
>one, who is supposed to be off!

Actually that isn't bizarre-- it's what I'd expect.  What's
happening is that when the PWM signal turns on the N-FET, the
P-FET above it is also turning on because charge is being coupled
to its gate through the drain-to-gate capacitance; and until that
charge can be bled off through the 4K7 resistor to the (+)
supply, the P-FET conducts current.

I stand by what I said before, that I think you need a "stiff"
driver for those P-FETs so they will be forcibly held in the OFF
state when you don't want them on.

Dave D.

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