Mitigation of conducted EMI in quasi-resonant DC-DC converters by frequency modulation

Abstract

This paper describes the generation of conducted electromagnetic interference (EMI) in quasi-resonant DC-DC power converters (QRC). An EMI mitigation technique using frequency modulation is proposed along with experimental verification. The switching voltage and input current harmonic spectra are modelled in the frequency domain in order to quantify the amount of common mode and differential mode EMI at certain range of frequencies. The switching voltage and input current harmonic spectra are shown to be significantly depressed as a result of switching frequency modulation.