A Structure and Design Method for Magnetic Integration of Current-Fed Dual Active Bridge DC-DC Converters

In this article, a structure and design method for magnetic integration are proposed for current-fed dual active bridge (DAB) dc-dc converters. To ensure maximum power transmission and achieve zero-voltage switching (ZVS), the operating modes are reviewed. Based on these modes, the series inductance and input dc inductance are designed. The proposed magnetic integration structure aims to reduce the number of cores, core volume, and power loss by integrating two input dc inductors, a series inductor, and a transformer into a single core. The series inductor and the primary windings of the transformer are connected in series. Therefore, the series inductor windings and the transformer's primary windings can be integrated, which can reduce the winding length and copper loss. Two variables, namely the number of the secondary winding turns and the height of the transformer's magnetic column, are freely selected. The entire core and printed circuit board (PCB) winding parameters can be calculated based on these two variables. Finally, the optimal set of parameters is chosen from multiple sets of core and PCB winding parameters, achieving the minimum volume and loss. The proposed magnetic integration structure and design method are applied to a 1 kW current-fed DAB dc-dc converter with a switching frequency of 100 kHz, an input voltage ranging from 40 to 60 V, and output voltage of 200 V. The experimental results demonstrate the operating mode, the soft switching performance, and high efficiency.