How to design overvoltage protection circuit
Time:2022-07-16
Views:1983
A simple overvoltage protection circuit can generally be realized by adding TVs. When there is an instantaneous high-energy impact outside, it can suppress this energy. Although the power is high, thousands of watts can be used, but the time to maintain the suppression is very short. In case the device is damaged or the working voltage is higher than the normal working voltage for a long time, it will be out of power.
So the best way is to design an intelligent circuit, as shown below:
When Vin is under normal input voltage, the zener tube has no reverse breakdown, and the current of R3 and R4 is basically 0. Vbe=0 of PNP triode, that is, PNP triode is not conductive. The VGS of PMOS tube Q4 is determined by the partial voltage of resistors R5 and R6. The PMOS tube is turned on, that is, the power supply works normally.
When Vin input is greater than the normal input voltage, at this time vin>vbr, the regulator tube is broken down, and the voltage on it is VBR. PNP triode Q1 is on, VCE ≈ 0, that is, VGS of PMOS is ≈ 0, PMOS is not on, and the circuit is open, that is, overvoltage protection is realized.
If the accuracy requirements are high, of course, voltage detection IC can also be selected to realize voltage monitoring.
So the best way is to design an intelligent circuit, as shown below:
When Vin is under normal input voltage, the zener tube has no reverse breakdown, and the current of R3 and R4 is basically 0. Vbe=0 of PNP triode, that is, PNP triode is not conductive. The VGS of PMOS tube Q4 is determined by the partial voltage of resistors R5 and R6. The PMOS tube is turned on, that is, the power supply works normally.
When Vin input is greater than the normal input voltage, at this time vin>vbr, the regulator tube is broken down, and the voltage on it is VBR. PNP triode Q1 is on, VCE ≈ 0, that is, VGS of PMOS is ≈ 0, PMOS is not on, and the circuit is open, that is, overvoltage protection is realized.
If the accuracy requirements are high, of course, voltage detection IC can also be selected to realize voltage monitoring.
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