Assessment of switching frequency impact on the prediction capability of common-mode EMI emissions of sic power converters using unterminated behavioral models

With silicon carbide (SiC) devices increasing in commercial availability, high switching frequency is becoming a general trend to increase the power density of power converters. High switching frequency operation nonetheless exacerbates EMI emissions in a system, for which accurate EMI models of power converters are needed to predict noise and aid in the design of their EMI filters. Accordingly, this paper assesses the effect on the EMI emissions from a higher switching frequency and evaluates the newly proposed unterminated behavioral model (UBM), which can predict the CM noise of power converters in the conducted EMI frequency range using equivalent noise sources and impedances by assessing its capability to predict the EMI noise of high switching frequency SiC power converters. The results obtained show that under high switching frequency, the input and output current spectrum shifts towards the MHz range, which is effectively captured by the equivalent noise sources of the UBM. A high-pass filter can be applied to capture the noise above the system noise floor, ultimately favoring the UBM prediction capacity extending to the whole conducted EMI range. Experimental results of a 3 kW, 300 V DC, SiC three-phase inverter switching at 20-70 kHz are used to demonstrate these findings and validate the analysis conducted.