The Effect of Parasitic Elements on EMI Common Mode Filter Insertion Loss

The common mode filter is a commonly used to suppress common mode noise. The parasitic elements within the filter components significantly impact its performance. It is highly valuable to illustrate the effect of these parasitic elements on the insertion loss of the common mode filter. This work proposes an illustration of the effects of filter parasitic element and a design procedure aimed at determining the corner frequencies in the insertion loss characteristic. The required inductance and capacitance necessary are calculated to achieve the design attenuation at the specified frequencies. Parasitic elements are also accounted for through impedance characteristic calculation. Circuit simulation is employed to compute the noise spectrum with filter, which is then validated through experiment verification. This study identifies the four corner frequencies on the insertion loss with non-ideal LC filter model. Through this design procedure, the simulation results closely match the actual EMI measurement.