Abstract: The quadrangle control method and its improvement scheme in the existing literature can realize ZVS of all switches in noninverting Buck-Boost converter,but it has the following problems:the need to use multidimensional look-up tables or external storage devices,without closed loop control of real-time calculation,large on-state loss,and output voltage fluctuation caused by multimode switching. The proposed three-segment variable frequency ZVS control strategy solves the three problems. Firstly,the circulating current freewheeling link of the inductor current in the quadrilateral control is removed,which significantly reduces the effective value of the inductor current and improves the efficiency. Secondly,without any additional active or passive components,by dividing the entire wide input voltage range into three modes,after independently analyzing the characteristics of each mode,control conditions can be added,and the online realtime closed-loop and minimum conduction loss ZVS of each mode can be realized at the same time. There is no need to use multi-dimensional lookup table and linear interpolation,and the overall control is simple and easy to achieve. Thirdly,a multimode smooth switching control strategy is proposed,which can ensure that the output voltage is always stable before and after the duty cycle of each switch jumps during mode switching. The theoretical basis for division of each mode is provided,and a 500 W experimental prototype is built to verify the effectiveness of the proposed scheme.