What is Over Voltage Protection?

Over voltage protection is a power supply feature which shuts down the supply, or clamps the output, when the voltage exceeds a preset level.

Most power supplies use an over-voltage protection circuit to prevent damage to the electronic components. The impact of an over-voltage condition varies from one circuit to the other and ranges from damaging the components to degrading the components and causing circuit malfunctions or fire.
An over-voltage condition might occur in the power supply due faults inside the supply, or from external causes such as those in the distribution lines.

The magnitude and duration of the over-voltage are some of the major considerations when designing an effective protection. The protection involves setting a threshold voltage above which the control circuit shuts down the supply or diverts the extra voltage to other parts of the circuit such as capacitor.

Ideal characteristics of an over voltage protection circuit

Prevent the excess voltage from being applied to the components.
The protection circuit should not interfere with the normal function of the system or circuit. The protection circuit should not load the power supply and cause related voltage drops.
The protection circuit should be able to distinguish between normal voltage fluctuations and harmful over-voltage.
Be fast enough to respond to transient events that can damage the power supply and downstream components.
The OVP method should not to have false trips or undetected real over-voltage conditions. This can be a nuisance in the case of false trips and also dangerous if it is unable to see the real over-voltage conditions.
The over voltage protection circuit may be constructed using discrete components, integrated circuits, mechanical devices such as relays, etc. These can either connected internally or externally depending on the circuits involved.

There are various protection circuit designs, each with its merits, mode of operation, sensitivity, ability, and reliability. The protection can either clamp off the excess voltage, or completely shut down the power supply.