Single-Phase Three-Level Flying-Capacitor Buck PFC Rectifier

Abstract-Active pulsating-power-buffering (PPB) is an effective technique to reduce the energy storage requirement of a singlephase power-factor-correction (PFC) rectifier. Existing singlephase solutions with active PPB, however, generally suffer from high voltage stresses, leading to increased power losses as well as the need for high-voltage-rating semiconductor switches. Previous works have been focusing on two-level switching converter configurations, and thus have failed to address the high-voltagestress problem. In this paper, a single-phase three-level flyingcapacitor PFC rectifier with PPB embedded switching is proposed. The flying capacitor not only clamps the voltage stresses of all power devices but also functions as a PPB capacitor. The operating principles, control methods, and design guidelines are detailed and the feasibility of the proposed converter is verified through a 48- W (48-V/1-A) hardware prototype. The proposed rectifier is shown to achieve nearly 50% reduction of the voltage stresses, 72% reduction of the buffering capacitor’s volume and 23.8% reduction of the magnetic core size, as compared to a state-of-theart two-level solution recently proposed. This new approach of formulating single-phase PFC rectifiers with active PPB could dramatically boost the system’s efficiency and power density whilst reducing cost.