Estimation of Minimum Dead Time to Counter Resonance Mistuning in DAB-SRC for DCX Operation

A DC transformer (DCX) is a dc-dc converter that operates at a fixed voltage conversion ratio, enabling optimized and simplified power converter design. This paper explores the use of a dual-active-bridge series resonant converter (DAB–SRC) topology, in which both bridges are actively switched with symmetric gate signals near the series resonant frequency to achieve uncontrolled, bidirectional DCX operation. It is observed that this topology inherently compensates for resonance mistuning—arising from practical non-idealities—through a counter-balancing mechanism that occurs during the dead time between switching transitions. This paper investigates and models this counterbalancing phenomenon and develops analytical expressions to predict the minimum dead time required for two key cases: stable operation and complete zero-voltage switching (ZVS). The resulting models express the dead time as a function of resonance mistuning and load current, providing a practical framework for designing SRCs that operate as mistuning-tolerant, bidirectional DCXs without the need for feedback control. The proposed models are validated using experimental data collected from a hardware prototype operating at input voltages up to 50 V and power levels up to 200 W. The predicted dead times closely match the measured values, with an error of less than 15%.