反激变压器传导共模EMI特性分析

为了研究反激变压器传导共模EMI特性的问题,在分析反激电源传导共模噪声传输机理基础上,提出了变压器可视为共模滤波器的新观点。通过理论分析变压器的容性效应,明确了影响变压器共模噪声抑制能力的关键因素,优化设计变压器绕组结构,改变原副边绕组间的容性分布参数,可改善变压器的传导共模EMI特性。最后,通过一台反激电源样机进行了实验验证,实验结果表明优化变压器绕制方式或连接方式,可有效抑制电路的共模噪声。

Analysis of conducted common-mode EMI characteristics of flyback transformer

In order to study the characteristics of conducted common mode EMI of flyback transformer,based on the analysis of the transmission mechanism of conducted common-mode noise in flyback power supply,a new viewpoint that transformer can be regarded as common-mode filter was proposed.Through the theoretical analysis of the capacitive effect of transformer,the key factors affecting the common-mode noise suppression ability of transformer were defined.By optimizing the structure of the transformer winding and changing the capacitance distribution parameters between the primary and secondary windings,the common-mode EMI characteristics of the transformer were improved.Finally,a prototype of flyback power supply was tested.The experimental results show that the common-mode noise of the circuit can be effectively suppressed by optimizing the winding mode or connection mode of the transformer.