Over Current Protection is the action of a current protection device when the current exceeds a predetermined maximum value. When the current flowing through the protected component exceeds the preset value, the protection device will act and use timing to ensure the selectivity of the action, causing the circuit breaker to trip or issue an alarm signal.

Many electronic devices have a rated current. Once the device exceeds the rated current, it will burn out. Therefore, these devices are equipped with a current protection module. When the current exceeds the set current, the device automatically loses power to protect the device, which is called overcurrent protection. For example, the USB interface on the computer motherboard usually needs to be protected from burning out by USB overcurrent protection.

The overcurrent protection device protects the circuit by disconnecting the device when the current reaches a value that would cause an excessive or dangerous increase in conductor temperature. Most overcurrent protection devices respond to short-circuit or ground fault current values and overload situations. In the event of a phase to phase short circuit fault or abnormal increase in load in the power grid, or a decrease in insulation level, the current will suddenly increase and the voltage will suddenly decrease. Overcurrent protection is the setting of the operating current of a current relay based on the requirements of line selectivity. When the fault current in the circuit reaches the operating value of the current relay, the current relay will act according to the selective requirements of the protection device, selectively cut off the fault line, and activate the time relay through its contacts. After a predetermined delay, the time relay contacts close, the circuit breaker trip coil is connected, the circuit breaker trips, and the faulty circuit is cut off. At the same time, the signal relay acts, the signal board falls, and the light or sound signal opens. When unexpected situations such as load short circuit, overload, or control circuit failure occur, it can cause excessive current to flow through the switching transistor in the voltage regulator, thereby increasing the power consumption and heating of the transistor. If there is no overcurrent protection device, a high-power switching transistor may be damaged.