A Soft-Switching Bridgeless AC-DC Power Factor Correction Converter

A new soft-switching, bridgeless power factor correction (PFC) boost converter is proposed for power supply and battery charging applications. The converter operates in both pulse width modulation (PWM) mode and resonant mode each switching cycle, and utilizes standard average current mode control. The converter is bridgeless, therefore eliminating the need for a front-end diode bridge rectifier. It operates in continuous conduction mode and achieves zero voltage switching (ZVS) for all switches. The proposed converter also reduces the turn-off losses of the PWM switches, therefore nearly eliminating switching losses. The output diodes operate with controlled di/dt turn-off, which reduces reverse-recovery losses. The PWM switches of the proposed converter can be driven with the same PWM signal, enabling simplified control. The detailed operation of the proposed converter is presented, including the conditions for ZVS operation and a stress analysis for the circuit components. Experimental results are presented for a 650-W prototype at 150-kHz switching frequency, universal ac input, and 400-V dc output. The proposed converter shows about 1% better efficiency and lower device temperatures at full load and 100-V ac input (maximum loss operating point) compared with the conventional hard switched PFC boost converter.