An Interleaved Forward/Flyback DC–DC Converter With Bidirectional Capability and Wide Voltage Range Characteristic

This article introduces an interleaved forward/flyback converter designed to achieve high power capability, bidirectional operation, galvanic isolation, and low ripple current. By integrating a coupled inductor and utilizing interleaved operation, the circuit achieves a broad range of voltage gains while effectively reducing ripple current at the switching frequency by a factor of two. The design employs an interleaved two-switch forward topology that operates bidirectionally while requiring fewer switches than conventional dual-active-bridge converters, making it particularly well-suited for applications such as rechargeable energy storage systems. The interleaved structure not only minimizes the size of passive filters but also accommodates a wide range of voltage variations. In addition, the converter operates with zero-voltage switching in forward mode, significantly reducing losses and electromagnetic interference, thereby enhancing overall efficiency. This article provides a detailed examination of the converter's operational principles, including the behavior of inductor currents in continuous, discontinuous, and boundary conduction modes. Furthermore, a comprehensive circuit analysis is presented, outlining voltage and current stresses under both power flow directions. A comparative performance evaluation with similar isolated converters highlights the key advantages and potential limitations of the proposed topology. Finally, experimental validation is conducted using a 3.5 kW prototype, demonstrating an efficiency exceeding 90% in both power flow directions.