A Quasi-Switched-Capacitor-Based Bidirectional Isolated DC-DC Converter With High Voltage Conversion Ratio and Reduced Current Ripple

This research introduces a unique bidirectional dc-dc converter specifically developed for energy storage applications. The proposed circuit topology exhibits a high voltage conversion ratio and a reduced current ripple. On the transformer primary side, a quasi-switched-capacitor (QSC) circuit mitigates voltage stress on switching devices and achieves a 3:1 voltage step-down ratio. The proposed transformer-interleaved circuit on the secondary side features the 2:1 voltage conversion ratio and minimizes the battery current ripple without adding extra switching or magnetic components. The 6:1 voltage conversion contributes to a simpler winding structure, smaller transformer size, and lower transformer loss in high voltage gain application. Furthermore, the reduced current ripple leads to lower battery heat generation and smaller filter bank capacitance, making it suitable for high-density design. The implementation of phase shift control, similar to the dual-active-bridge circuit, serves to regulate the circuit's transferred power. A 1-kW, 300-kHz, 380-420-/20-33-V GaN-based circuit prototype is developed and tested. The tested peak efficiency is 98.5% with a power density of 30.42 W/in(3).