New Bidirectional 2-Level Buck-Boost PFC Topology Using Bidirectional Blocking Semiconductors

This paper presents a new bidirectional PFC buck-boost topology designed for the use of bidirectional blocking semiconductors. One advantage of the circuit is that the minimum DC voltage can be halved to the amplitude of the grid voltage compared to conventional PFC stages. Typical two-stage converters, such as on-board chargers and solar inverters, can therefore often be designed as single-stage because no further adaptation to the DC voltage is required. Another advantage is that the switching losses are significantly reduced compared to the classical 2-level topology because the switching voltage is always lower than the DC voltage. The current only ever flows through one semiconductor, resulting in low conduction losses. The requirements for the four semiconductors are analyzed and an extension of the circuit with flying capacitors is presented. The circuit concept is validated using a 1 kW prototype designed for the American 120 V 60 Hz grid with an antiserial-connected unidirectional blocking 600 V 70 m Ω GaN enhancement-mode power transistor.