Optimized coil arrangement for integrating leakage inductance in high-frequency transformers of dual active bridge converters

Dual Active Bridge (DAB) converters offer bidirectional power flow and soft-switching capabilities, making them attractive for high-frequency power conversion applications. However, the presence of a separate series inductor alongside the high-frequency transformer can limit the converter's power density and efficiency. This paper presents an optimized transformer winding configuration that integrates the required leakage inductance directly within the high-frequency transformer, eliminating the need for an external series inductor. Various coil arrangements are analyzed through finite element simulations using ANSYS Maxwell to evaluate leakage inductance, ohmic losses, and parasitic capacitance. Results show that the vertical coil arrangement achieves the target leakage inductance of 50 μH while minimizing conduction losses and parasitic effects. The optimized transformer winding was experimentally validated on a 150 W DAB converter prototype using a TMS320F28335 DSP for power stage control. Experimental results confirm close agreement with simulations, demonstrating high efficiency (up to 99.1%) and stable soft-switching operation under nominal conditions without current ringing. The proposed winding configuration offers a practical and efficient approach for integrating magnetic components in high-frequency power converters.