A crowbar circuit is an electrical circuit used for preventing an overvoltage or surge condition of a power supply unit from damaging the circuits attached to the power supply. It operates by putting a short circuit or low resistance path across the voltage output (Vo), like dropping a crowbar across the output terminals of the power supply. Crowbar circuits are frequently implemented using a thyristor, TRIAC, 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 tripping the circuit breaker.
- Zener Diode
- Schottky Diode
Crowbar protection is a fail-safe protection system that short-circuits a power supply’s output in the event of a breakdown, such as an overvoltage. Crowbar protection can also refer to a circuit whose primary goal is to blow a fuse by exposing it to excessive current.
Quite a few electronic components. particularly active ones. cannot withstand too high voltages. Preventing costly circuits from dying premature death because the supply voltage has risen too high makes overvoltage protectors no luxury. Such a protector must, of course, act swiftly, otherwise, the deed has been done before it had a chance to act. Therefore. (slow-acting) relays are not suitable for this purpose. The circuit is shown here, a so-called crowbar. contains several fast-acting components. It is intended to be connected to the mains and the appliance to be protected. -The circuit depends, as it were, on brute force: when the supply voltage rises too high. a thyristor short-circuits the output. This means that the too high voltage is immediately removed from the connected appliance and also that fuse F, blows. Brute force, indeed!
The voltage at which the crowbar carry-s into action is set between 5 V and 25 V with P.
The overvoltage value of the circuit depends purely upon the Zener voltage value, and only a few values of the Zener diode are available.
Prevent serious damage to sensitive and expensive electronic equipment