PMOS tube overvoltage circuit

tags: circuit design schematic diagram power supply hardware engineering embedded hardware overvoltage protection

A simple overvoltage protection circuit can generally be realized by adding a TVS. When there is a momentary high-energy impact externally, it can suppress this energy. Although the power is high, thousands of W can be used, but the suppression time 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 powerless.

So the best way is to design a smart circuit, as follows:

When Vin has a normal input voltage, the Zener tube has no reverse breakdown, and the current of R3 and R4 is basically 0. Vbe=0 of the PNP transistor, that is, the PNP transistor is not conducting. The Vgs of the PMOS transistor Q4 is determined by the voltage divider of the resistors R5 and R6, and the PMOS transistor is turned on, that is, the power supply works normally.

When the Vin input is greater than the normal input voltage, Vin>Vbr at this time, the Zener tube is broken down, and the voltage on it is Vbr. The PNP transistor Q1 is turned on, VCE≈0, that is, Vgs≈0 of the PMOS transistor, the PMOS transistor is not turned on, and the circuit is disconnected, which realizes overvoltage protection.

If the precision requirement is high, of course, a voltage detection IC can also be used to realize voltage monitoring.

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