Diode Emulation Control for Efficiency Improvement of Dual Active Bridge Converters

The literature suggests discontinuous conduction mode (DCM) operation for efficiency improvement of dual active bridge (DAB) converters. These techniques require zero voltage across the primary side of the transformer to ensure DCM at part load conditions. Hence, these techniques are not implementable in cost-competitive DAB converters with half-bridge circuit on the primary side (cost-effective up to few kWs). This paper proposes diode emulation control (DEC) for DAB with half-bridge circuit on the primary side. The proposed technique ensures DCM at part load with a simple single phase shift control. The DEC is easily implemented with synchronous rectifier ICs, which are simple to use and popularly available. The design of transformer turns ratio and leakage inductance as per proposed technique are also added. The changes required in the closed loop control of the DAB due to diode emulation on secondary side are also highlighted. When compared to the conventional control, the proposed technique achieves up to 2.5 % improvement in efficiency at part load conditions. The proposed technique is experimentally validated with a 440 W laboratory prototype.