Logic overvoltage protection

Logic overvoltage protection

The Logic overvoltage protection circuit is designed to protect the TTL logic ICs with supply voltages of 5 V from overvoltage conditions.

How it work:
Zener diode ZD1 senses the power supply voltage, and if the supply voltage rise above 6 V, Q1 will-turn on. Therefore, Q2 conducts short the rail. Next events depend on the source supply. It will either shut down, go into current-limit or blow its supply fuse. None of these will damage the TTL chips. The rating of Q2 depends on the source supply, and whether it will be required to operate continuously in the event of failure. Its current rating has to be in excess of the source supply.

Logic overvoltage protection parts list:
R1 : 330 ohm
R2 : 47 ohm
R3 : 1K
R4 : 220 ohm
Q1 : BC 107, 2N3704
Q2 : BD132
Q3 : Bc478, 2N3702
Zd1 : 6 V

Power supply is an electronic device that supplies electric energy to an electrical load. The primary function of a power supply is to convert one form of electrical energy to another and, as a result, power supplies are sometimes referred to as electric power converters. Some power supplies are discrete, stand-alone devices, whereas others are built into larger devices along with their loads. Examples of the latter include power supplies found in desktop computers and consumer electronics devices.

Tags: 5 V overvoltage protection Logic overvoltage protection Logic overvoltage protection circuit overvoltage protection circuit TTL overvoltage protection

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