EMI Generation Characteristics of SiC and Si Diodes: Influence of Reverse-Recovery Characteristics

Silicon carbide (SiC) Schottky diodes with zero reverse-recovery current (RRC) are perceived as superior due to their reduced switching losses. The absence of reverse-recovery behavior in these devices is also expected to result in reduced electromagnetic interference (EMI), compared with the conventional silicon (Si) PIN diodes. In this letter, the influence of SiC Schottky diodes on EMI generation in hard-switched power converters is investigated. A simplified analytical model enabling the spectral envelope of the diode current waveform to be predicted is presented. Numerical simulations and experimental tests are employed to validate this model. It is found that although the reverse-recovery characteristics are very different between Si diodes and SiC Schottky diodes, the actual improvement with SiC diodes on the spectral content of the diode current waveforms is relatively small except at frequencies around 5 MHz. Factors affecting the EMI performance such as the peak amplitude and the “snappiness” of the RRC are also analyzed. Experimental measurements of the switching current waveforms for both Si diodes and SiC diodes are presented and their frequency spectra are compared.