A
crowbar or
crowbar circuit is an
electrical circuit used to prevent an overvoltage condition of a
power supply unit from damaging the circuits attached to the power supply. It operates by putting a
short circuit across the
voltage source, much as if one dropped a
tool of the same name across the output terminals of the power supply. Crowbar circuits are frequently implemented using a
thyristor (also called an
SCR) or a
trisil or
thyratron as the shorting device. Once triggered, they depend on the
current-limiting circuitry of the power supply or, if that fails, the blowing of the line
fuse or
circuit breaker.
A
crowbar circuit is distinct from a
clamp in that, once triggered, it pulls the voltage below the trigger level, usually close to
ground. A clamp prevents the voltage from exceeding a preset level. Thus, a crowbar will not automatically return to normal operation when the overvoltage condition is removed; power must be removed entirely to stop its conduction.
The advantage of a crowbar over a clamp is that the low holding voltage of the crowbar lets it carry higher fault current without dissipating much power (which could otherwise cause overheating). Also, a crowbar is more likely than a clamp to deactivate a device (by blowing a fuse or tripping a breaker), bringing attention to the faulty equipment.
The power supply is bad. I would not try to fix it.
item, and proceed. Getting a driver update from the Windows Update site.
