Quasi-Peak Current Control Strategy for Four-Switch Buck–Boost Converter

With the rapid increase of power consumption in data centers, the 48 V power delivery architecture is introduced, where a two-stage dc–dc power conversion solution is commonly adopted. Four-switch buck–boost (FSBB), as a topology with both voltage step-up and step-down capabilities, is very suitable for implementation as a front-end preregulation module. In this article, the quasi-peak current control strategy for FSBB is proposed, with which, FSBB can achieve zero-voltage switch for all power switches in full input voltage and load range. Meanwhile, the proposed strategy can realize automatic and smooth transition between buck and boost state without detecting the input voltage, and the control logic and the control variables remains unchanged so that there is no modulation mode shift. Also, the proposed control strategy can be implemented by high-speed comparators, which saves storage and computational resources of the controller. In addition, the operating principle of the proposed strategy is analyzed and the optimal design process is deduced. The rms current of the inductor is minimized so that the overall efficiency is improved. Finally, a 200 W prototype with input voltage range of 40–60 V and output voltage of 48 V is built, which verifies the effectiveness of the proposed strategy.