反激式开关电源中变压器分布电容产生的共模干扰研究

以反激式变换器为研究对象,在仔细分析了变压器原副边之间分布电容对共模干扰作用的基础上,建立了共模传导干扰耦合通路模型。在考虑了变压器线圈绕组的电位分布的情况下,提出了一种计算变压器初、次级绕组间等效共模寄生电容的方法。根据模型,重点分析了变压器的绕组结构及变压器与外电路的连接方式对系统中的共模干扰产生的影响。最后,提出了一种共模干扰滤波器,并用软件进行了仿真验证。

Analysis on Common-Mode Conducted EMI Caused by Distributed Capacitance of Transformer for Flyback Switched Mode Power Supply

A common-mode conducted EMI model of a flyback converter is built after detailed analysis about the effect of distributed capacitance between the primary and secondary windings of the transformer on common-mode noise. A computational method about equivalent common-mode stray capacitance between the primary and secondary windings of the transformer is proposed after consider the effect of potential distribution along winding turns. Based on the model, more attention is paid on the effect of winding strategy and different ways of connection of transformer with external circuit on common-mode EMI. Finally, in order to reduce common-mode noise, a common-mode filter is introduced. The above analysis is verified by software.