Design and Implementation of a New Hybrid EMI Filter for DC-DC Converter with SiC MOSFETs

With the advantages of high frequency, high efficiency and high power density of wide bandgap devices, SiC MOSFETs have gained more and more application in DC-DC converters. However, their fast switching speed and parasitic parameters can also introduce the issues of electromagnetic interference (EMI). The traditional methods for EMI suppression focus on the passive EMI filter. However, the passive EMI filter has a large volume and weight for DC-DC converter. In order to improve the power density of power converters, a hybrid EMI filter that combines active and passive filters is proposed in this paper. The active EMI filter is applied to suppress common-mode (CM) noise for the low and middle frequency bands and the passive EMI filter can attenuate the high-frequency EMI noise. The working principle of the proposed hybrid active filter is analyzed in detail. The insertion loss and stability analysis are also investigated. A prototype is built and experiment are carried out. Experimental results, obtained from the EMI test platform and practical DC-DC converter, show good EMI suppression effect.