According to the elements of electromagnetic compatibility, the electromagnetic compatibility of the power adapter can be solved from three aspects:

(1) Propagation path of interference signal

(2) Enhance the anti-interference ability of the disturbed body

(3) Reduce the interference signal generated by the interference source

For external anti-interference capabilities, such as surges and lightning strikes, the lightning protection capabilities of AC input and DC output ports should be optimized. The combination method of zinc oxide varistor and gas discharge tube can be used to solve the lightning strike. For electrostatic discharge, use TVS tube and the corresponding grounding protection, increase the distance between the small signal circuit and the housing, etc., or choose a device with antistatic interference to solve. To reduce the internal interference of the power adapter, we should start from the following aspects: pay attention to the single point grounding of the digital circuit and the analog circuit, the single point grounding of the large current circuit and the small current, especially the current and voltage sampling circuit, in order to reduce the coresistance interference and reduce the influence of the ground ring; When wiring, pay attention to the spacing between adjacent lines and the nature of the signal to avoid crosstalk; Reduce ground impedance; Reduce the area surrounded by the high voltage and high current lines, especially the original side of the transformer and the switching tube, the power filter capacitor circuit; Reduce the area surrounded by the output rectifier circuit, the continuous current diode circuit and the DC filter circuit; Reduce the leakage inductance and filter capacitance of the transformer; Filter capacitors with high resonant frequency are used.

External interference caused by the power adapter, such as harmonic current of the power line, power line conduction interference, electromagnetic field radiation interference, can only be solved by reducing the interference method. On the one hand, strengthen the shielding effect of the casing, improve the gap leakage of the casing, and carry out good grounding treatment. On the other hand, it can enhance the design of input/output filter circuit, improve the performance of active power factor compensation (APFC) circuit, reduce the voltage and current change rate of switching tube and rectifier diode, and adopt various soft switching circuit supplement structure and control mode.

In terms of transmission path, appropriate addition of TUS with high anti-interference ability and high-frequency capacitors, ferrite magnetic beads and other components to improve the anti-interference ability of small signal circuits; Small signal circuits that are close to the housing should be treated with appropriate insulation and pressure resistance. The radiator of the power device and the electromagnetic shielding layer of the main transformer should be properly grounded; Ground floor shielding for large area grounding between control units. In the frame of the rectifier, it is necessary to consider the electromagnetic coupling between the rectifiers and the layout of the ground wire of the whole machine to improve the stability of the internal work of the power adapter.

I hope you can solve the above problems smoothly!

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