Power Adapter Lightning Strike Design Collection

　　Lightning strikes are a common physical phenomenon and the main source of voltage stress for power adapters. Improper protection will cause power damage or restart, which will affect the normal operation of electronic equipment. Therefore, the power adapter must meet the lightning strike voltage level requirements defined by safety standards.

　　In this issue, the core technology team will share with you the lightning strike standard, lightning strike experimental configuration, differential mode and common mode interference path analysis and design principles.

　　In general, a surge voltage of ±1kV~±6kV is applied to the AC line. The test source is the AC line of the equipment under test (EUT) and the ground point of the system enclosure. During the test, the EUT is directly exposed to the surge energy and must be intact. After the lightning test is completed, it can continue to work normally.

　　There are two modules inside the lightning strike generator, namely the decoupling network and the coupling network. The function of the decoupling network is to isolate the lightning strike energy applied by the coupling network to the phase line of the EUT from the phase line of the power supply. The role of the coupling network is to apply the ideal lightning strike wave to the phase line of the EUT through the coupling capacitor.

　　As shown in Figure 3: The coupling energy of the differential mode lightning strike is transferred between the phase lines L and N of the EUT. From Figure 4, it can be found that the coupling energy of the common mode lightning strike is transferred between the phase lines L(N) and PE of the EUT.

　　Since different actual circuit configurations will have different effects on the differential mode lightning strike analysis of the system, we will make a brief analysis of the impact of differential mode lightning strikes through the circuit in the above figure.

　　The differential-mode lightning strike energy passes through the coupling network, enters the phase lines L and N of the EUT, the fuse F1, and the pressure-sensitive MOV1 to form a loop 1, which generates a differential-mode current 1;

　　After the differential mode lightning strike energy is attenuated through circuit 1, it forms circuit 2 through thermistor RT1, rectifier bridge, and electrolytic capacitor EC1, generating differential mode current 2;

　　After the differential mode lightning strike energy is attenuated by loops 1 and 2, the differential mode inductance L1 and the electrolytic capacitor EC2 form a loop 3, and a differential mode current 3 is generated.

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