Modeling and design of the EMI filter for DC-DC SiC-converter

This paper focuses on the design of EMI filter for a power converter used Silicon Carbide power devices (SiC-JFET and SiC diode). The DC-DC converter used in this study is a buck converter which has operating frequency of 100 kHz and the turn-on and turn-off times of the JFET are equal to ten nanoseconds. It is well known that the switching times have a direct link to the spectrum of the EMI sources. Thus, in order to reduce the conducted emissions induced by the SiC-converter, it´s necessary to add an EMI filter in order to compliance the EMC standard. In this study, a design method of the EMI filter based on the simulation approach is proposed. For this, a high frequency model based on the electrical equivalent circuit of the filter which takes into account of all impedances of the system is proposed. However, values of the different elements of this model are determined by a new approach. The improvement provided by this model is important in high frequencies (above 1 MHz) taking into account the measured impedances of different propagation paths of the common mode currents of the system. The conducted emissions measured without and with the obtained EMI filter show the effectiveness of the proposed design method.