A study on conducted EMI in cascaded boost converters with SiC devices

Abstract

Advantages of silicon carbide devices, such as increasing switching frequency while guaranteeing high energy-conversion efficiency and system reliability, increase the demand for these products in power electronics. However, with the increase of switching frequency, electromagnetic interference (EMI) problems become a challenge that needs to be addressed. In this thesis, a comparative study of conducted EMI on SiC power devises is presented with its Si counterparts, an experiment is designed to verify the differences. An electromagnetic interference (EMI) model for a two-stage cascaded boost converter is presented to distinguish its noise sources. Among the noise sources, switching device voltage waveforms were analyzed as the main noise source in the time and frequency domains for both a SiC MOSFET and Si MOSFET. A detailed simulation circuit is constructed through LTspice to perform the EMI simulation. The issues for simulation time step size is discussed. The simulated results closely match the measured results up to 30 MHz. Methods of modifying the switching waveforms to suppress ringing in conjunction with parasitic components are also discussed.