为了解决四开关Buck-Boost（four-switch Buck-Boost, FSBB）变换器四边形电感电流控制策略中电感电流有效值和峰值较高的问题，提出了一种电感电流临界连续模式（boundary conduction mode, BCM）控制策略，通过将现有四边形电感电流控制策略中不传输功率的续流阶段缩短至零，以降低电感电流有效值和峰值。首先，分析了FSBB变换器工作模态和电感电流在不同模式下的电流波形；其次，分析了FSBB变换器在全工况实现软开关的约束条件，获得电感电流的取值规则；接着，分析了不同模式下电感电流的变化情况，给出了临界连续模式下的控制方法，在输入输出压差较小时，通过提高第一阶段或第三阶段的占空比来提高输出功率，在输入输出电压压差较大时，使FSBB变换器工作在电感电流临界连续状态，有效地降低电感电流有效值和峰值；最后，搭建仿真模型，结果表明所提BCM控制策略可以实现零电压开通且有良好的动态响应能力。

In order to solve the problem of high effective inductor current and peak value in the quadrilateral inductor current control strategy of four-switch Buck-Boost (FSBB) converter, a boundary conduction mode (BCM) control strategy was proposed, which shortened the freewheeling phase without power transmission to zero in the existing quadrilateral inductor current control strategy, so as to reduce the RMS and peak value of inductor current. Firstly, the current waveforms of the FSBB converter in different modes of working modes and inductor currents were analyzed. Secondly, the constraints of the FSBB converter to achieve soft switching under all working conditions were analyzed, and the value rules of the inductor current are obtained. Then, the variation of inductor current in different modes was analyzed, and the control method in critical continuous mode was given, when the input and output voltage difference was small, increase the output power by increasing the duty cycle of the first or third stage, and when the input and output voltage difference was large, the FSBB converter works in the critical continuous state of inductor current, which effectively reduces the effective value and peak value of inductor current. Finally, a simulation model was built. The results show that the proposed BCM control strategy can achieve zero-voltage turn-on and has good dynamic response ability.