中文摘要：

开关电源传导EMI问题一直都备受关注，目前国内外的研究主要还是定性研究，而定量的分析可以更加准确细致的找出传导EMI形成的机理。针对两种典型工作状态下的AC／DC变换器，测试得到了其传导EMI的频域波形．MOSFET漏极与源极间电压波形以及提取了电路中的主要寄生参数，通过对比与定量的分析计算，找出了其传导EMI几处重要峰值形成的原因。最后得出了变压器原边与副边漏感、MOSFET源极与漏极间寄生电容以及MOSFET与散热片之间的寄生电容，是影响开关电源的传导EMI的重要因素。在开关器件导通或者关断时，开关电源的工作状态发生改变．此时漏感或者器件的寄生电容中的剩余能量会引起高频振荡，进而引起了传导EMI尖峰。

英文摘要：

The AC/DC converter under two typical states was studied. Frequency domain waveform of the conducted EMI and the voltage waveform between the drain and the source of MOSFET were tested, and main parasitic parameters in the circuit were extracted. The reason for the formation of the several important peaks of the conducted EMI was found out through comparison and quantitative calculation. It can be concluded that the important factors that affect the conducted EMI of the switching power supply include the leakage inductance of the transformer＇s primary side and secondary side, the parasitic capacitance between the source and the drain of the MOSFET and the parasitic capacitance between the MOSFET and the fins. The work state of the switching power supply changes when the switching device is turned on or off, and the residual energy in the leakage inductance or the parasitic capacitance of the device causes the high-frequency oscillation, and then inducing the peaks of the conducted EMI.