A New Modulation Strategy for Four-switch Buck-boost Converter with Reduced Freewheeling Current

Abstract

A control method to achieve the minimum freewheeling current of the four-switch buck-boost (FSBB) converter is presented in this paper. Compared with the conventional method, the proposed method can make the best use of the energy stored in the junction capacitance of the boost stage to realize ZVS of the buck stage. Therefore, the soft-switching can be realized under the condition of the minimum freewheeling current and the efficiency is further improved. Based on the ZVS analysis, the minimum freewheeling current and the dead-time under different input conditions are determined. Moreover, the sampling circuit and the control parameter of the proposed method are also illustrated in this paper. Finally, the proposed method is verified on a 1MHz FSBB prototype.