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 that require a tradeoff between current distortion and switching ripple. This paper presents a new single-phase semi-bridge flying-capacitor (FC) rectifier that significantly improves this tradeoff, with effective doubling in switching frequency because of the multilevel topology, and the capability to rectify higher output 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 rectifier followed by a single-phase-leg three-level boost power factor corrector (PFC) or a full-bridge single-phase five-level FC rectifier. Matching simulation and experimental results are presented to fully validate the new converter structure.