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
Led
Zd1 : 6 V
psu

Recent Posts

Universal Battery Charger for Charging up to 18V Cell

This universal battery charger has regulated output voltage which can be adjusted as you need.…

5 years ago

Auto Switch-Off Power Supply (Variable Output 3.7V to 8.7V)

Here is the auto switch-off power supply which will turn off itself when there is…

6 years ago

High Voltage, Low Current Power Supply (2000VDC from 15VDC)

This is a high voltage, low current power supply capable to deliver 2000VDC output from…

6 years ago

15V 1A Regulated Symmetrical Power Supply

This is the easy built 15V 1A regulated symmetrical power supply capable to deliver stabilized…

7 years ago

12V / 3A Regulated Power Supply

Here we provide a powerful 12V / 3A regulated power supply circuit. Of course the…

7 years ago

How To Repair Computer Power Supply

If the power supply is damaged or does not work, the computer also will not…

7 years ago