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RE: Disabling the freewheling diode
Original poster: "Mccauley, Daniel H" <daniel.h.mccauley-at-lmco-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
> All,
>
> In a SSTC H-bridge, the internal freewheeling diode of the MOSFET is
> disabled by a clever arrangement of external diodes.
> A schottkey diode above the drain keeps the internal diode
> from getting
> forward biased, so that an ultrafast recovery external diode
> can provide
> the path of any reverse EMF from the load.
> Any current passing trough the MOSFET must pass trough the schottkey
> diode.
>
> In a typical design, I see MOSFETS capable of handling 20A continous,
> with a 3 A schottkey diode on top.
>
> Why is the schottkey diode not dimentioned for a similar 20A?
>
> Cheers, Finn Hammer
>
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