Spread-Spectrum Frequency Modulation With Adaptive Three-Level Current Scheme to Improve EMI and Efficiency of Three-Level Boost DCM PFC

Discontinuous conduction mode controlled boosting power-factor-correction (PFC) converters suffer from high differential-mode electromagnetic interference (EMI) and require a large input filter due to high inductor current ripples at a single switching frequency. To remedy the shortcomings, a downward spread-spectrum frequency modulation (SSFM) is proposed in this letter. The SSFM can be used by boosting PFC converters for reduced EMI and improved efficiency. On top of the frequency modulation, a novel adaptive three-level current (ATC) scheme is devised with three-level boost PFC using multilevel capability to obtain further reductions of peak current and EMI amplitude. Analyses and experiments validate that the proposed SSFM and ATC scheme can bring improvements of EMI and efficiency at the cost of increased output-voltage ripple.