The Research and Design of High-efficiency Control Strategy for Four-switch Buck-Boost Converter

The four-switch Buck-Boost (FSBB) converter has applied in data center power supply architecture due to its excellent soft switching characteristic, wide voltage regulation capacity and identical input and output voltage polarity. However, the multi-degree-of-freedom characteristic of the soft-switching control method of the FSBB converter makes its control strategy complex and variable, increasing the difficulty of efficiency optimization. In response to the above issues, a multi-mode high-efficiency control strategy is proposed to improve the conversion efficiency of the FSBB converter in the full-load range. First, the constraint condition of the control variable based on the zero voltage switch (ZVS) of the FSBB converter is obtained, and the value rule of the control variable is determined when the effective value of the inductance current is the lowest. Then, a complete loss model of the FSBB converter is constructed, and a multi-mode high-efficiency control strategy is proposed with the goal of minimizing the total loss and design the control variables through data fitting. Finally, the simulation verification is completed in Simplis and a 300W experimental prototype is designed and manufactured. The test results show that the designed experimental prototype can achieve high conversion efficiency in the full input, output voltage range, and full load range. The highest peak efficiency reaches 98.5%, the highest average efficiency reaches 97.93%, and the switching frequency range is 500 kHz to 1 MHz.