LIGHTNING PROTECTION CIRCUIT

摘要

A lightning protection circuit comprises a lightning protection device. The lightning protection device comprises a first common mode protecting device (RT2), a second common mode protecting device (RT1, RT3) and a differential mode protecting device (D1, D2). The first common mode protecting device (RT2) is connected between a first power supply output lead (+P) and a common port or between a first power supply input lead and the common port, wherein the first power supply output lead (+P) is a common supply lead connected between a first output port of a Power over Ethernet (PoE) power supply control circuit and an interface region, and the first power supply input lead is a supply lead connected between a first input port of the PoE power supply control circuit and a PoE power supply. The second common mode protecting device (RT1, RT3) is connected between a second power supply output lead (-P1, -P2) and a common port or between a second power supply input lead and the common port or between the first power supply input lead and the second power supply input lead, wherein the second power supply output lead (-P1, -P2) is a supply lead connected between a second output port of the PoE power supply control circuit and the interface region, and the second power supply input lead is a supply lead connected between the second input port of the PoE power supply control circuit and the PoE power supply. The differential mode protecting device (D1, D2) is connected between the first power supply output lead (+P) and the second power supply output lead (-P1, -P2). The lightning protection circuit reduces the number of protecting devices, saves PCB space and decreases the design cost for PoE ports. In addition, as all of the interface regions are connected to the common ports via protecting devices, a relatively large amount of surge energy can be released, achieving a high level of lightning protection.