A Bridgeless Buck-flyback PFC Converter with High PF and Dead Angles Eliminated

The inherent dead angles of the input line current in buck power factor correction (PFC) converter deteriorate the power factor (PF) and commonly extra switches with high control complexity are required to eliminate these dead angles. Alternatively, this paper proposed a topological solution using a simple single voltage loop control. The proposed switch integrated bridgeless buck-flyback PFC converter operates in buck-flyback mode and can automatically change to flyback mode when the dead angles occur. Bridgeless operation modes of the proposed converter are achieved by dual converter cells and the corresponding PF expression is derived. Besides, the inductors and transformers ratio is analyzed to ensure the high PF (>0.99) and the satisfactory input current harmonics (meet the IEC 61000-3-2 Class D limits) in the 100∽240 Vac input voltage range. The 100 W prototypes of the conventional buck and the proposed converters are built for experimental tests, which confirm the effectiveness of the proposed topology.