Am 29.03.2010 17:43 schrieb rich12345:
I've seen plenty of windows PC's assume room temperature after their power supplies decided to be a bit too energetic. No POST beeps, no video output. DEAD.
Inside the PSU is a crowbar circuit that shuts down the regulator in case of overvoltage.
The +12V line is compared to a reference voltage, and when it exceeds the limit, a thyristor fires and shorts +12V to Gnd. As all other voltages are tied to +12V by the transformer winding ration, they are shut down, too.
For additional protection you may add a second crowbar circuit to the +5V line.
Patrick