T02.2 - Design of Fully Soft-Switched Semi-Dual Active DC-DC Converter for Battery Charging Application

Semi-dual active bridge converter (SDABC) is a popular topology for unidirectional power flow applications, due to its cost-effectiveness. However, there is a dip in the efficiency of SDABC at part load conditions. This dip is due to the loss of soft switching property at these conditions. To address this, a design-based approach focusing on transformer turns ratio and leakage inductance is proposed in this digest. The proposed design methodology extends the zero-voltage switching (ZVS) range at low voltage - medium power conditions by proper selection of leakage inductance. The turns ratio is judiciously chosen to achieve ZVS at high voltage - low power conditions. In addition, the discontinuous conduction property of SDABC is explored to reduce circulating current in the transformer under light load conditions. This improves efficiency by reducing conduction loss. The presented analytical results show that the proposed design allows SDABC to achieve soft switching over the entire constant current-constant voltage (CC-CV) charging profile. In addition, efficiency is also improved. This is validated with a 1.5 kW laboratory-developed prototype.