A high conversion ratio and high-efficiency bidirectional DC-DC converter with reduced voltage stress

A dc-dc converter is proposed to achieve a high voltage conversion ratio for bidirectional power flow applications. The nonisolated topology is optimally designed to integrate both the switched capacitor and coupled inductor techniques for high efficiency. The windings of the coupled inductor are stacked at the low voltage source, which transfers any leakage energy of the coupled inductor directly into the output port and simplifies the clamping circuit. The optimal design keeps the voltage stress on the main switches low for the entire duty cycle operation. Thus, the converter demonstrates the advantage of wide-voltage gain based on common ground and low and steady voltage stress in both buck and boost modes of its operation. Furthermore, the converter can realize zero-voltage switching through the synchronous rectifiers without requiring extra hardware circuitry to enhance conversion efficiency. The operation principle, including the steady-state analysis, dynamic modeling, controller design, efficiency analysis, and optimization, are discussed in detail and verified by the experimental test. The prototype substantiates the theoretical analysis and soft-switching operation. The converter exhibits the capability for load and line regulation and demonstrates a peak efficiency of 96.38% in the boost mode and 95.61% in the buck mode of operation.