Analytical modeling of parasitic capacitances for a planar common mode inductor in EMI filters

EMI filters are essential parts in power converters which is used to reduce the conducted emissions in order to meet with EMC standards. However, the parasitic elements of the passive components in the filters limit their performances on high frequencies. This paper proposes an analytical model for the parasitic capacitances of CM inductors in planar technology. This method, based on analytical multilayered Green´s function, enables to determine the capacitance matrix in 2D configurations. Then an energetic approach is applied for calculating the equivalent parasitic capacitances. The proposed procedure is validated by impedance measurements on several prototypes. The calculated results show good agreement with the measured ones.