圆环线匝构成的平面共模EMI滤波器的特性研究

平面LC线圈是组成平面EMI滤波器的基本单元,其匝间寄生电容及所用磁心磁导率的非线性对滤波器的高频性能有重要影响。本文首次提出环形平面LC线圈结构,并对矩形和环形平面LC线圈进行了3D有限元仿真,通过对比其特性确定了环形LC线圈作为组成EMI滤波器的基本组成单元,并基于该结构实现了平面共模EMI滤波器。考虑了匝间寄生电容、相邻导体间的互感及有效磁导率的非线性,建立了环形LC线圈的等效集中参数电路,利用节点电压法求解了当其连接成低通滤波器时的插入损耗。基于环形平面LC线圈设计了一台平面共模滤波器样机,计算与实验对比显示,匝间寄生电容和磁导率的非线性对滤波器的高频性能有重要影响。

Characteristics Research for Planar Common Mode EMI Filter Based on Toroidal LC Coil

Planar LC coil is the basic unit constituted planar EMI filter,of which stray capacitance and non-linear permeability of magnetic core have important impact on high-frequency performances of filter.A novel passive integrated structure,the toroidal planar LC coil,is presented firstly,and the 3D finite element simulation of the rectangle and toroidal planar LC coil is done.By comparing the characteristics between them,the toroidal planar LC coil is used as the basic unit,and planar common mode(CM) filter is achieved based on this structure.Distributed parameters such a stray capacitance,magnetic coupling between conductors and non-linear characteristics of the magnetic core are all considered,and then the equivalent lumped parameter circuit is built.The insertion loss is achieved through node voltage method based on the equivalent circuit when it is connected as low-pass filter.A prototype of planar CM filter is implemented based on toroidal planar LC coil.Contrasting calculated results and measured one,it is shown that stray capacitance and non-linear permeability of magnetic core have important impact on high-frequency performances of filter.