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

Wei-zhong Zhang1, 2, *, Hui-pin Lin3, Yao Zhang2, Ji-min Jin2
1 School of Mechanical Engineering and Automation, Zhejiang SCI-TECH University, Hangzhou 310018, China
2 Department of Electrical Engineering, Zhejiang Institute of Mechanical and Electrical Engineering, Hangzhou 310053, China
3 Department of Electrical Engineering, Zhejiang University, Hangzhou 310027, China

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© 2017 Zhang et al.

open-access license: This is an open access article distributed under the terms of the Creative Commons Attribution 4.0 International Public License (CC-BY 4.0), a copy of which is available at: ( This license permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

* Address correspondence to this author at the School of Mechanical Engineering and Automation, Zhejiang SCI-TECH University, Hangzhou 310018, China; Tel/Fax: (086)0571-87773023; E-mail:


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.

Keywords: Four-switch synchronous buck-boost converter, Wide input voltage range, Three-mode smooth transition, Feed forward voltage mode control, Buck-boost (FSBB), SEPIC.