Design Method of an Integrated Transformer for a Two-Phase Interleaved Flyback PFC Rectifier

Universal serial bus power delivery (USB PD 3.1) is a widely-applied standard for a lot of electronic device charging. In 2021, USB PD 3.1 was announced with a variable output of 5 V to 48 V and a maximum output power of 240 W. A multi-phase flyback rectifier is capable of power factor correction, galvanic isolation, and wide output voltage range, and is proposed as an alternative topology for USB PD. However, the number of magnetic components increases with the number of phases, which can lead to lower power density. This paper proposes the design of a non-coupled integrated transformer for a two-phase interleaved flyback rectifier to reduce the size and number of magnetic components. The independent operation of the integrated transformer in two phases was verified using a 240-W two-phase interleaved flyback PFC rectifier at 100 kHz switching frequency operating at discontinuous conduction mode.