RadioBanter - View Single Post - PSUs: current-limiting and crowbarring

Nico Coesel

wrote:

Hi gang,

Is it not feasible to use a crowbar circuit across a PSU's output if
that PSU has a current-limiting feature? I can imagine a situation
arising where an over-voltage causes the crowbar to close, generating a
short-circuit condition which activates the current limiting. The
output will then be stuck at not enough amps to blow the upstream fuse,
but enough current to smoke the crowbar (which is not designed to be
kept conducting for any length of time of course). Is there some way to
have both over-current and over-voltage protection working together in
harmony?
Thanks.

I see no problem. If the crowbar is active, the voltage accross it is
about 0V so power dissipation in the crowbar device is minimal. You
could probably use a SOT23 trenchFET as a crowbar which would be
capable of handling a few amps.

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