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Re: Disabling the freewheling diode
Original poster: dhmccauley-at-spacecatlighting-dot-com
> > The reason for this is that the freewheeling current is much less than
> > the current that the MOSFET conducts when it
> > is ON.
> > The Captain
> But, but.... the Schottky diode has to handle the conduction current
> doesn't it?? There is a real cheap source of 30A/40A Schottky diodes
> out there too - any old scrapped computer SMPS has a dual unit
> rectifying its +5V supply. Note that a single dual diode (common
> anode) would serve both upper MOSFETs in an H-bridge arrangement.
No. The FET takes the conduction current, not the series Schottky in
parallel with it. The Rds of the FET is much lower (and less voltage drop)
then the parallel Schottky
diode, therefore, most of the current goes through the FET. On the
otherhand, for reverse freewheeling current, the Schottky diode will
conductor first and take the bulk of
any reverse freewheeling current in the circuit.