Efficiency Optimization and Control Strategy of Four-Switch Buck–Boost Converter for Wide Conversion Ratio

An improved control strategy for the four-switch buck–boost (FSBB) converter is proposed to improve the efficiency in a wide conversion ratio and wide loads. The conventional duty-cycle-controlled FSBB converter cannot achieve the zero voltage switching (ZVS) for all the switches while the converter has a dead zone issue. The proposed control strategy is controlled by the duty cycle and phase shift control. The control law is derived from the analytical solution of the optimized current stress with the constraint of the ZVS for all the switches. The working modes in the proposed control strategy can cover the whole load in a wide conversion ratio. Furthermore, the dead zone issue is removed. The modulation surface and output power surface versus the conversion ratio and control variable demonstrate the working modes are switched seamlessly. The control strategy is implemented in the digital controller. Finally, the experimental results verify the higher efficiency and dynamic performance of the control strategy.