Study of Isolated Single-stage Resonant AC-DC Converter

This paper presents study of Isolated single-stage resonant AC-DC converter. This converter combines the operation of the boost power factor correction (PFC) and the LLC resonant dc-dc converter in a single stage. In compare to two-stage topology this converter the PFC operation and generation of the high frequency pulsating voltage for LLC tank is done with a single H-bridge arrangement. This converter provides an isolated DC output voltage from AC mains with a high power factor through direct power conversion without using the full-wave diode bridge rectifier. Thus the conduction losses are reduced. The switching losses are also reduced by the zero-voltage switching (ZVS) and zero current switching (ZCS) operation of the power switches through the LLC resonance. The DC-link capacitor is not connected directly to the DC-DC stage so capacitance can reduce largely as it do not required to hold the dc voltage with less ripple. Thus we can use a small film capacitor instead of a large Electrolytic capacitor. This converter works in CCM mode with the interleaved operation so the current stress and input current THD are reduced. It has better Electromagnetic interference performance thus the input EMI filler can be eliminated.