An Improved Quadrangle Control Method for Four-Switch Buck-Boost Converter With Reduced Loss and Decoupling Strategy

Four-switch buck-boost (FSBB) converter is widely used in battery applications due to the simple structure and the excellent performance of both voltage step-up and step-down. With the quadrangle control method, FSBB converter can realize zero voltage switching (ZVS) of all power switches, and thus can adapt to the high-frequency trends. However, the conventional quadrangle control method has two problems: 1) the efficiency degradation caused by the large root mean square (RMS) current of the inductor, and 2) the instability caused by the coupling relationship between multiple control variables. In this article, an improved quadrangle control method is proposed to solve the two problems, making FSBB converter a good candidate for high-frequency battery applications. First, the loss analysis is built to determine the relationship between loss and the control variables. Then, the conditions to achieve the minimum loss are obtained. Second, the decoupling compensation strategy is applied to free the coupling relationship to improve the stability. The proposed strategy can achieve three control goals: 1) ZVS of all power switches; 2) minimize the total loss; and 3) stable closed-loop system. Finally, a 1MHz 280W FSBB prototype is built to verify the proposed control method. The prototype achieves all control goals and 98.1% peak efficiency.