High Frequency Conducted EMI Investigation on Packaging and Modulation for a SiC-Based High Frequency Converter

Silicon carbide (SiC) devices have the advantages of high switching speed and high switching frequency, which can increase the power density, but electromagnetic interference (EMI) will increase along with higher switching frequency thus it can become a challenge for high-frequency converters. In order to clarify the influence factors of EMI noise in SiC converters and find the suppressing method, this paper investigated the conducted EMI in SiC-based high power density electronic systems from two aspects: packaging structures and modulation methods. For packaging investigation, this paper introduced parasitic parameters of power module into EMI analytical model, then defined transfer functions of EMI noise to analyze the influence of parasitic parameters on noise propagation path and further studied the impact of parasitic parameters on noise source by analyzing switching transient and frequency spectrum. Analysis and simulation are carried out based on a hybrid structure SiC power module and discrete SiC devices to verify the analysis. The influence of modulation on EMI is studied by analyzing and comparing two modulations: continuous current modulation (CCM) and triangle current modulation (TCM). To certify the analysis study, two 1.6-kW, 300-kHz switching-frequency synchronous buck converters are designed and tested. One is based on the hybrid packaging power module and the other is based on TO-247 packaged SiC devices, respectively. The result shows that the hybrid packaging module can suppress the common mode (CM) EMI by 10 dB, and has a suppression on differential mode (DM) EMI between 10 and 20 MHz. Moreover, TCM can increase DM EMI in low-frequency range but suppress it in the high-frequency range.