This work tends to solve a practical concern of the H-bridge time-sharing multiplexing proposed in [1], which is the mode switching between the line-frequency and the high-frequency power transmission in a single unipolar SPWM cycle. The deficiency of a closed-loop approach based on the hysteretic control is first analyzed, followed by a novel open-loop approach featured by the setting charge-discharge of blocking capacitors using LC-resonance. Furthermore, the experimental result verifies the principle and feasibility of mode switching, and it lays a foundation for constructing future high-density power electronic transformers.
