Analysis of Conducted EMI in Si IGBT plus SiC MOSFET Hybrid Switch Based Converters

A hybrid switch (HyS) is a parallel combination of a large Si IGBT die in parallel with a small SiC MOSFET die. It demonstrates a static and a dynamic performance improvement over a Si IGBT, and is cost-effective compared to a SiC MOSFET. The switching speeds of the switching device characterizes the high-frequency conducted noise emissions. However, the parasitic common-mode capacitances, especially the capacitance between the drain (of the switching device) and the ground (usually a heatsink) provides path for the high frequency noise propagation; hence also characterize the high frequency emissions. For a HyS, the effective area of the package will be significantly larger than the standalone SiC MOSFET and standalone Si IGBT package. This is under the assumption that the Si and SiC dies, within the module, are placed far apart for a complete thermal isolation. Depending on the relative difference of both, the package area and the switching speeds, the EMI emissions for HyS package could he more than SiC package. Hence, comparison of EMI in a HyS, all-Si and all-SiC based converter is presented.