A Control Map for a Bidirectional PWM Plus Phase-Shift-Modulated Push-Pull DC-DC Converter

In this paper, a bidirectional push-pull converter is investigated with new add-on feature of three-level PWM plus phase-shift (PPS) control scheme, and a control map is proposed to assist converter operation and design in the optimized region. The PPS control strategy is adopted to reduce peak current of the transistors, to increase the input-voltage-variation range and to expand the soft-switching region. A comprehensive analysis of operation principle, transmission capability, and soft-switching operation in 12 different operation modes is presented. Based on the complete analysis, a control map is proposed to assist converter operation that can effectively avoid high-circulating-current regions, low-power-Transmission-capability regions, and hard-switched regions. In the control map, a circuit parameter k is signified and its range is found, beyond which the PPS converter no longer operates normally. The proposed control map and the circuit parameter k are general to all PPS converters, providing a meaningful analyzing method to design and operate all PPS converters. A 30∼48 V/380 V prototype rated at 100-1000 W was built under the guideline. The analysis is verified by both simulation and experimental results.