Analysis and implementation of a three‐level hybrid dc–dc converter with the balanced capacitor voltages

In this study, a three‐level hybrid dc/dc converter by integrating the full‐bridge circuit, resonant circuit and three‐level flying capacitor circuit is presented to achieve the main advantages of low‐voltage stress of power devices, low circulating loss, low‐voltage ringing on the rectifier diodes and low‐output filter inductor for medium‐voltage dc‐based systems. Two full‐bridge circuits are connected in series to effectively reduce the voltage stress of switches. Half‐bridge resonant circuit shared the lagging‐leg switches of full‐bridge circuit is used and operated at fixed switching frequency to extend the zero‐voltage switching (ZVS) range from low load to full load. Thus, the drawback of narrow ZVS range in the conventional full‐bridge converter is improved. A flying capacitor is adopted to automatically balance input split capacitor voltages in each switching cycle without any additional active components or complexity control scheme. The circulating loss in the full‐bridge circuit is reduced to zero by parallel connection of outputs of full‐bridge circuit and half‐bridge resonant circuits. Finally, the theoretical analysis and performance of the proposed converter are verified by the experiments with a 1.92 kW prototype circuit.