Equivalent Circuit of Common-Mode Choke Coil Considering with Conversion from Differential-Mode Signal to Common-Mode Disturbance

A common-mode choke coil (CMC) is an essential device for achieving electromagnetic compatibility (EMC). An equivalent circuit considering the common-mode (CM) disturbance converted from differential-mode (DM) signal is needed because the spectrum of telecommunication signals overlaps with the regulated frequency band of the radiated disturbance due to the increase of telecommunication speed in recent years. In this paper, an equivalent circuit of CMC considering the conversion phenomenon is proposed. The admittances were inserted between each terminal of the CMC and the ground for demonstrating the phenomenon. The SPICE model of CMC was represented by the combination of the ABCD chain-parameter-matrices, and the elements of the overall matrix were calculated. The mixed-mode S-parameters were calculated using these elements. The elements of the ABCD matrix and the mixed-mode S-parameters were measured and the admittance values were determined by comparing the calculated data with the measured data. The pulse response calculated by the proposed equivalent circuit was well agreed with the measurement value.