The power adapter may sometimes be interfered by external factors during use, so how should we solve this interference?
External interference to the power adapter, such as power line harmonic current, power line conduction interference, electromagnetic field radiation interference, etc., can only be solved by reducing the interference. On the one 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 switch, rectifier and freewheeling diode, and adopt various soft switching circuit extension structures and control modes; On the other hand, strengthen the shielding effect of the housing, improve the gap leakage of the housing, and conduct good grounding treatment.
For external anti-interference capability, such as surge and lightning strike, the lightning protection capability of AC input and DC output ports shall be optimized. The combination of zinc oxide varistor and gas discharge tube can be used to solve the lightning stroke. For electrostatic discharge, TVs tube and corresponding grounding protection shall be used to increase the distance between large and small signal circuits and chassis, or devices with anti-static interference shall be selected to solve the problem.
To reduce the internal interference of power adapter, we should start from the following aspects: pay attention to the single point grounding of digital circuit and analog circuit, and the single point grounding of large current circuit and small current circuit, especially current and voltage sampling circuit, so as to reduce the common resistance interference and the influence of grounding ring; Pay attention to the spacing between adjacent lines and the signal nature during wiring to avoid crosstalk; Reduce ground wire impedance; Reduce the area surrounded by high-voltage and high current lines, especially the primary side of transformer, switch tube and power filter capacitor circuit; Reduce the area surrounded by the output rectifier circuit, the freewheeling diode circuit and the DC filter circuit; Reduce the leakage inductance of transformer and the distributed capacitance of filter capacitor; Filter capacitor with high resonance frequency shall be adopted.
In terms of transmission path, Tus, high-frequency capacitor, ferrite bead and other components with high anti-interference ability shall be appropriately added to improve the anti-interference ability of small signal circuit; The small signal circuit close to the casing shall be provided with appropriate insulation and withstand voltage treatment; The radiator of the power device and the electromagnetic shielding layer of the main transformer shall be properly grounded; Large area grounding between control units is shielded by grounding plate; On the rectifier frame, the electromagnetic coupling between rectifiers and the ground wire arrangement of the whole machine shall be considered to improve the internal working stability of the power adapter.
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