8. High Efficiency Current-Fed Dual Active Bridge DC–DC Converter with ZVS Achievement Throughout Full Range of Load Using Optimized Switching Patterns

For current-fed dual active bridge bidirectional DC–DC converters, all the possible switching patterns are summarized in view of the combinations of both side PWM duty cycles and phase shift angle. A control strategy is proposed for the current-fed dual active bridge converter to operate with the optimized patterns. The equivalent duty cycle of the secondary side is smaller than that of the primary side by a fixed value, which is optimized based on the soft switching achievement and the circulating current minimization. The closed-loop control is easy to be implemented since there are only two independent variables, one-side duty cycle and the phase shift angle. With the proposed control, zero-voltage switching (ZVS) can be achieved for all power switches throughout full range of load even at no load condition. The typical working modes with the proposed control are given. The optimal design of the system parameters including the fixed time delta and dead time is illustrated. The effectiveness of the proposed control is verified by the experimental results of a 1 kW laboratory prototype.