A Selective Common Mode Noise Mitigation Method Using Phase-Shifted Modulation for Four-Switch Buck-Boost DC/DC Converter

Wide bandgap power devices can work at higher switching frequencies compared to silicon competitors. It helps reduce the volume of passive components but brings more serious electromagnetic interference (EMI) noise issue. The increased noise filtering requirements may restrict the power density improvement. This article discusses the conducted EMI issue and noise filtering in the four-switch buck-boost (FSBB) dc/dc converter. The differential mode and common mode (CM) noise models embedded with noise source features are derived and analyzed. It is found that modifying the spectral distribution of the CM noise is a challenge when the duty cycles are fixed by voltage gain. Inspired by the CM model, a phase-shifted modulation method is proposed to achieve selective CM noise mitigation. The recommended operating range and the implementation process are presented. The theoretical modeling and the proposed method are verified through an FSBB converter with 48 V input and 100 kHz switching frequency, and experimental results validate that the proposed method can achieve 30% volume reduction of the CM filter.