Analysis and design of a novel single-phase PFC AC-DC step-up/down converter

A novel single-phase power-factor-correction AC-DC step-up/down converter is presented in this paper. This converter is operated in discontinuous conduction mode to achieve purely sinusoidal line current, almost unity power factor, low total harmonic distortion of line current, and step-up/down DC output voltage. The proposed converter employs a coupled-inductor with same winding-turn in the primary and secondary side, which is charged in series during the switch-on period and is discharged in parallel during the switch-off period. Therefore, the discharging time can be shortened. The proposed converter can be operated in larger duty-ratio range than the conventional single-phase PFC buck-boost converter for DCM operation. Thus, the proposed converter is suitable for universal line voltage (90-264 V) and wide output-power range. Moreover, the steady-state analyses of voltage gain and the boundary operating condition are discussed in detail. The selections of coupled-inductor and output capacitor are also presented. Finally, a prototype circuit is built in the laboratory to verify the performance.