Variable Dead-Time Based Novel Soft-Start Method for Dual Active Bridge Converters

Abstract

Effective startup control is critical for the safe and reliable operation of Dual Active Bridge (DAB) converters. Unlike traditional soft-start techniques that rely solely on phase-shift control or fixed dead-time settings, the proposed approach gradually reduces the dead time from a value close to one switching period to the hardware-defined minimum. This enables a smooth buildup of the secondary-side voltage while effectively minimizing voltage overshoot and suppressing inrush current during startup. As a result, the leakage inductor current rises in a controlled manner, ensuring safe and predictable startup behavior. Simulation results demonstrate that conventional startup methods lead to severe voltage overshoot and high inrush currents, whereas the proposed method achieves a gradual voltage rise with well-regulated current profiles. Experimental validation using a 15 kW hardware platform confirms the effectiveness and robustness of the approach under different operating conditions. The proposed technique is simple, hardware-friendly, easily implementable on standard microcontrollers, and applicable to nth - order DAB architecture, making it a versatile solution for enhancing the reliability and safety of DAB converters in practical applications.