Unified One-Cycle Control for Fully Digitalized ZVS Four-Switch Buck-Boost Converter During Bidirectional Power Flow Transition

A unified one-cycle control is presented to achieve bidirectional power flow operation for a four-switch buck-boost converter employing fully digitalized control. There is no need for analog comparators or digital-to-analog converters. Based on the new definition of operating modes, modulation can be unified in both the directional operations. One-cycle bidirectional power transition with fully zero-voltage switching (ZVS) can be achieved under various voltage conversion gains. A modified control curve of inductor current is proposed to eliminate the power oscillation during operation, and ZVS can be ensured during the transition. A 450-W prototype using the proposed fully digital control under bidirectional power flow operation is verified successfully.