Modeling and Controlling Strategy of Four-Switch Buck-boost Convertor with Smooth Mode Transitions

Abstract: Four-switch synchronous buck-boost (FSBB) converter is much suitable for battery management system for its characteristic of wide input voltage range, high efficiency, and positive voltage output. A three mode control scheme with two modulation signals and one carrier can be adopted to achieve the smooth transition among modes. Using feed forward voltage mode control, the input voltage information is injected into the control loop to prevent the disturbance effect on the output voltage through making input voltage construct the carrier signal. High efficiency is gained when the converter is operating in pulse skip mode in light load. The operating mode smooth transition and stability could be achieved by modeling the converter and designing the compensation. Finally, a power prototype was fabricated to validate the validity of the control strategy.