什么是过电流的保护?

Overcurrent protection is a circuit protection mechanism used to detect and limit current exceeding the set threshold to prevent component damage, safety risks or system instability caused by excessive current. The following is a detailed analysis of overcurrent protection:

1. ‌Basic concept‌
Overcurrent protection monitors the current value and triggers the protection device to operate (such as tripping or alarm) when the current exceeds the preset maximum value, thereby cutting off the fault circuit or reducing the risk. Its application scenarios include:

‌申请电路保护‌: For instantaneous large currents (such as direct contact of wires), 快速响应 (microsecond level) is required.

‌后载保护‌: For continuous over-rated current, an inverse time delay mechanism (such as thermal relay) is usually used.

2. ‌工程原理
‌Current detection‌: Real-time monitoring of current through sampling resistors, current transformers or integrated ICs (such as LT6100).
‌Trigger mechanism‌: 当电流超过设定值时, the relay or circuit breaker operates and the circuit is disconnected.
‌Delay design‌: It is divided into three-stage protection (fast break, time-limited fast break, and time-limited overcurrent), taking into account selectivity and response speed.

3. ‌Implementation method‌
‌Discrete components‌: Such as a simple circuit built with a transistor + sampling resistor, which limits the current by clamping the voltage (例如, a 1A threshold design).
‌Integrated solution‌:
‌PTC resettable fuse‌: The resistance value increases sharply when overcurrent occurs, and it automatically resets after the fault is eliminated.
‌Special protection IC‌: Such as the overcurrent, overvoltage, and overheating multiple protection circuits in the DC power conversion chip.

4. ‌Technical parameters and selection‌
‌Rated current/voltage‌: It needs to match the load requirements (such as 3A~25A, 125/250交流电).
‌Action time‌: Short-circuit protection needs to be ≤40ns, and overload protection can be delayed to seconds.
环境适应性‌: Consider the influence of conductor cross-sectional area and temperature on current carrying capacity.

5. Application Cases

Power system: Three-stage protection covers the entire length of the line and the backup area.

电子设备: 例如, USB interface overcurrent protection prevents the motherboard from burning out.

Industrial motor: Combines multiple protection functions such as stall and phase failure.

The core of overcurrent protection is to balance sensitivity and selectivity, ensuring accurate fault isolation while avoiding false operation.