By means of a graft scheme, a buck-boost cell and a wide range diagonal half-bridge flyback cell are combined to create a novel single-stage high power factor correction (HPFC) diagonal half-bridge flyback ac/dc converter in this paper. When both of the two cells operate in discontinuous conduction mode, the proposed converter exhibits high power factor and low bulk capacitor voltage stress independent of the load variations. Based on the Loss-Free Resistor (LFR) model, a new technique, referred to as ac-dc balancing method, is also proposed. It is useful to determine the dc values, voltage ripples, and phase angle shifts of the bulk capacitor and output voltage of the converter. Moreover, the component values are well designed according to the operation conditions and design specifications of the converter. Finally, a prototype of the proposed converter with output voltage 48 V and power 100 W is built to test the theoretical analysis. It is successfully validated by IsSpice simulations and experimental results.
