A series fuse say 1/4 amp fast acting followed by a 1N400x reverse biased diode would seem to be the simplest solution. The fuse should be heavy enough for max peak load, but still blow in a reverse power situation.

KF4HAZ - Lonnie Underwood

----- From: "Wouter van Ooijen" <wouter@
> A customer let the smoke out of a H-bride motor driver I made for him,
> so now I want to add reverse-power protection. My standard anti-parallel
> 1N4004 won't do much good when connected to a lead accu, so I am
> considering a series diode (1N4004, or a schottky). But now the back-emf
> from the motor, which is fed to the power rail by the 4 diodes, has
> nowhere to go. What is the solution to this? A big zener on the power
> rail, for let's say 150% of the maximum power supply? If so, which
> wattage would be needed? Or maybe a consensator? If you, what capcity
> and what type? Or are there other solutions, maybe with a polyfuse?
> 
> Wouter van Ooijen
> 
> -- -------------------------------------------
> Van Ooijen Technische Informatica: www.voti.nl
> consultancy, development, PICmicro products
> docent Hogeschool van Utrecht: www.voti.nl/hvu

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