On 12/9/2015 4:35 PM, Brent Brown wrote:
> In the case where the Schottky diode is across the MOSFET, when the MOSFE=
T
> turns off the inductor current continues to flow in the same direction, t=
he Schottky
> diode becomes REVERSE biased (avalanche breakdown, like a zener, relative=
ly
> high voltage, high power dissipation) and current circulates in a loop th=
rough all of
> the components (now including sense resistor and power supply but not inc=
luding
> the MOSFET) as it decays relatively quickly. Probably not the desired/int=
ended
> operation you want the Schottky to perform.
Bingo!  This is what I was not noticing... now it all makes sense.

> This is kind of what I was trying to say earlier on, still not sure if I'=
ve explained it any
> better, hope this helps.
>
> The MOSFET or the Schottky could go into avalanche, which one depends on
> which has the lower breakdown voltage. The one that does will be the one =
that gets
> hot :-)
>
Yep... this I noticed earlier -- that it was one or the other (MOSFET or=20
any schottky across D-S, but always one or the other).

Much thanks,
-Neil.

--=20
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