Single-phase semi-bridge five-level flying-capacitor rectifier

For unity power factor applications such as grid-connected rectifiers, semi-bridge converters offer significant advantages over their full-bridge counterparts because of their reduced active switch count and shoot-through-free phase leg structure. However, semi-bridge rectifiers have intrinsic operating limits which require a trade-off between current distortion and switching ripple. This paper presents a new single-phase semi-bridge flying-capacitor rectifier that significantly improves these limits, with an effective doubling in switching frequency because of the multilevel topology, and the capability to rectify higher input voltages with lower voltage rated, more efficient, devices. For rectifier applications, the new topology offers a better balance between cost and performance than either a diode rectified single phase leg boost PFC, or a full-bridge single-phase five-level flying-capacitor rectifier. Matching simulation and experimental results are presented to fully validate the new converter structure.