A new zero voltage switching single stage power factor corrected three level resonant AC/DC converter

This paper presents a new single stage power factor correction (SSPFC) AC/DC converter based on a three level LCC resonant converter topology. The proposed circuit integrates the operation of the boost power factor pre-regulator and the three level resonant DC/DC converter. The proposed control technique for this circuit is based on two control loops: the output voltage is regulated by controlling the switching frequency of the resonant converter, whereas, the DC bus voltage is regulated by means of duty cycle control of the boost part of the converter. This provides a regulated output voltage and a nearly constant DC bus voltage regardless of the loading condition; this in turn allows using smaller switches and consequently having a lower on resistance helping to reduce conduction losses. Zero voltage switching (ZVS) is also achieved for a wide range of loading and input voltage by having a lagging resonant current in addition to the flowing of the boost inductor current through the body diodes of the upper pair of switches in the free wheeling mode. The effectiveness of this method is verified on a 2.3 kW, 48 V converter, input voltage (90-265 Vrms). The converter has a resonant frequency of 770 kHz, and is operated above resonant frequency.