Bridgeless Star Power Factor Correction Architecture

Two-stage bridgeless power factor correction (PFC) architecture is widely used in high-power AC/DC applications. However, the bridgeless PFC front-end of the two-stage architecture often encounters challenges such as high switching losses in Continuous Conduction Mode (CCM) or high conduction and magnetic losses in Critical Conduction Mode (CRM) and other soft-switching modes. These challenges limit the overall system's efficiency and power density. This article presents a patent-pending semi-single-stage bridgeless Star PFC architecture. It allows simultaneous soft switching and CCM operation of the front-end bridgeless PFC rectifier, resulting in high-efficiency and high-density AC/DC system design. Simultaneous soft switching and CCM operation of the front-end bridgeless PFC rectifier is made possible by smartly ‘borrowing’ the inductor/transformer current from the second-stage DC/DC back-end to create Zero Voltage Switching (ZVS) conditions for all switches in the PFC front-end. The architecture maintains the operation of the second-stage DC/DC back-end, and enjoys similar control simplicity to that in conventional two-stage PFC architecture. The merits of the proposed architecture are validated through a 240-W GaN-based laboratory prototype, achieving a full-load efficiency of 96.1%. Additionally, it boasts an impressive power density of 50W/in³ uncased.