A Novel Integrated Buck–Flyback Nonisolated PFC Converter With High Power Factor

A novel integrated buck-flyback nonisolated power factor (PF) correction (PFC) converter is proposed in this paper. This new converter is an inherent integration of a buck converter and a flyback converter, which operates in either flyback mode or buck mode according to whether the input voltage is lower or higher than the output voltage. In this way, the dead zones of ac input current in traditional buck PFC converter are eliminated. Therefore, the proposed integrated buck-flyback nonisolated PFC converter can achieve high PF under universal ac input range, and its input current harmonics can easily meet the IEC61000-3-2 Class C limits. The efficiency of the proposed converter is not deteriorated obviously compared to the conventional buck converter. Detailed theoretical analysis and optimal design considerations are presented. A 100-W prototype was built up to verify the theoretical analysis of the proposed integrated buck-flyback nonisolated PFC converter.