Novel off-line zero-voltage-switching PWM AC/DC converter for direct conversion from AC line to 48 VDC bus with power factor correction

An offline zero-voltage-switching (ZVS) PWM AC-DC power converter for single-stage preregulation in distributed power systems is proposed. The converter provides both input power factor correction and direct conversion from a 110-220-V AC line to a 48-V DC bus with a single power stage. Compared to the conventional two-stage approach (a boost rectifier followed by an offline DC-DC step-down converter), the proposed approach reduces the loss of one power stage. A new simple auxiliary circuit provides the zero-voltage-switching (ZVS) condition to all semiconductor devices without imposing additional voltage and current stresses and loss of PWM capability. The operational principle, analysis, control of the proposed power converter, and simulation results for a 1-kW prototype are presented