This is the circuit diagram of 5V Regulated Power Supply circuit, featured with over voltage protection. The circuit is based regulator chip 7805; Thyristor SCR 2N1595 and Dioda Zener 1N3997 for overvoltage protection circuit. The 5V regulated power supply is apply 74LS series integrated circuits which has to be really precise and tolerant of voltage transients. These IC’s are simply damaged by brief voltage spikes. A fuse will blow when its electric current rating is exceeded, but requires several hundred milliseconds to respond. This circuit will react in a few microseconds, triggered when the output voltage exceeds the limit of the zener diode. This circuit uses the crowbar process, where a thyristor is employed and short circuits the supply, causing the fuse to blow. This can take spot in just a few microseconds or less, and so provides a lot greater protection than an ordinary fuse. If the output voltage exceed 5.6V, then the zener diode will conduct, switching on the thyristor ...