A Simplified Real-time Digital Control Scheme for ZVS Four-switch Buck-boost with Low Inductor Current

AbstractThe four-switch buck-boost converter (FSBB) is a preferred choice for the dc-dc applications where the step-up and step-down are needed. In order to reduce the inductor size and improve the efficiency, the zero-voltage switch (ZVS) control schemes with four segments inductor current for FSBB had been investigated in numerous publications. Among these ZVS control schemes, the optimized control variable stored as the huge look-up table data achieved minimum RMS inductor current, and the complex real-time calculation was avoided. However, for the purpose of matching the wide input and output voltage ranges, an external flash was needed for storing the look-up table data; and the large time consumption for invoking the data hazard the dynamic performance significantly. To reduce the storage device cost and meet the demand of transient, a simplified real-time control algorithm is proposed by dividing the operation into the defined DCM and CCM operation featuring the minimum RMS inductor current and ZVS operation during the whole voltage range without complex calculation and mode transient. Finally, a 300W dc-dc prototype is built to verify the theoretical analysis and proposed control scheme with a low-cost real-time digital controller.