Universal input voltage, unity power factor, high efficiency flyback rectifier with regenerative snubber

This paper presents a single phase rectifier having wide input voltage capability (208 Vac - 480 Vac), high efficiency and near unity power factor operation. The converter uses two IGBT switches arranged in a flyback topology. A regenerative snubber is used to transfer turn-off energy to the load, thus allowing soft-switching where the IGBT is the most inefficient because of its tail current. The converter operates mostly in continuous current mode and charge control is used to generate the single PWM signal needed by the power section. A very efficient post-regulator (two-input buck) is used to tightly regulate the output voltage with minimal impact on overall efficiency. Output voltage is regulated at 320 Vdc, and nominal output power is 1000 W. Experimental results show near-unity power factor (0.999), low current THDi of 4% obtained at 2% of line voltage THDv. The efficiency obtained exceeds 90% under worst-case operation (lowest input voltage (208 Vac) and load changing from 50% to its nominal value). Circuit topology and snubber operation are presented, and experimental results showing the performance of the converter are discussed.