How To Solve The Interference Caused By The Power Adapter

The power adapter may sometimes be interfered by external factors during use, so how should we avoid this interference?

The external interference to the power adapter, such as AC cable harmonic current, AC cable conduction interference, electromagnetic field radiation interference, etc., can only be solved by reducing interference. On the one hand, we can enhance the design of the input/output filter circuit, improve the performance of the active power factor compensation (APFC) circuit, reduce the voltage and current change rate of the switch tube and the rectifier and freewheeling diode, and adopt various soft switching circuit extensions. Make up the structure and control methods; strengthen the shielding effect of the shell, improve the leakage of the gap of the shell, and perform good grounding treatment.

The external anti-jamming capability, such as surge and lightning strike, should optimize the lightning protection capability of the AC input and DC output ports. The lightning strike can be solved by a combination of zinc oxide varistor and gas discharge tube. For electrostatic discharge, use a TVS tube and corresponding grounding protection, increase the distance between the signal circuit and the housing, or select a device with anti-static interference.

To reduce the internal interference of the power adapter, you should start from the following aspects: pay attention to the single point grounding of digital circuits and analog circuits, single point grounding of high current circuits and small currents, especially current and voltage sampling circuits, to reduce common resistance interference, Reduce the influence of the ground ring; pay attention to the distance between adjacent lines and the nature of the signal when distributing the line to avoid mutual interference; reduce the impedance of the ground line; reduce the high-voltage high-current line, especially the primary side of the transformer and the switch tube, power supply filter capacitor The area surrounded by the circuit; reduce the area surrounded by the output rectifier circuit, freewheeling diode circuit and DC filter circuit; reduce the leakage inductance of the transformer and the distributed capacitance of the filter capacitor; use a filter capacitor with a high resonance frequency.

In terms of propagation channels, appropriate addition of high anti-interference ability TUS and high-frequency capacitors, ferrite beads and other components to improve the anti-interference ability of small-signal circuits; small-signal circuits closer to the housing should be added Appropriate insulation withstand voltage treatment, etc.; the radiator of the power device and the electromagnetic shielding layer of the main transformer should be properly grounded; the large-area grounding between each control unit should be shielded with a ground plate; on the rectifier, the electromagnetic coupling and Machine ground wire layout, etc., to improve the stability of the internal work of the power adapter.