A ZCS bi-directional flyback DC/DC converter using the leakage inductance of the coupled inductor

This paper describes a zero-current-switched (ZCS) bi-directional flyback DC/DC converter. The methodology is based on replacing the output diode in the existing flyback converter with a controlled switch, acting as either a synchronous rectifier or a main power control switch in the corresponding power flow operation. By adding an auxiliary winding in the coupled inductor, a bi-directional switch, and a capacitor, the hard-switched design can be converted into a soft-switched one. The technique utilizes the leakage inductance in the flyback coupled inductor to achieve the ZCS of all switches in both power flow directions, leading to reduced switching losses, stresses, and electromagnetic interference. No extra active or passive voltage clamp circuits are required to suppress the voltage stress on the switches. The operating principles of the converter and experimental results are presented.