A ZCS-ZVS Strategy For Low Impedance Dual Active Bridges in MHz range

At low voltage-to-current ratios and high frequencies, the dual active bridge can suffer significant turn-off losses on the high-current side and typical design rules can lead to inductances on the same order as parasitics, introducing significant unpredictability and loss. In this paper, we analyze the circuit behavior when the parasitic inductance of switching loops approaches the leakage inductance and propose operating the dual-active (half) bridge in boundary conduction mode, where the inductor current returns to zero before switching. This control achieves ZCS on the high-current side and ZVS on the high-voltage side, mitigating the effect of parasitic inductance and reducing switching loss. Operation over a wide power range is provided by burst-mode control. Experimental results verify the efficacy of the proposed strategy on a 1MHz 40W DAHB GAN converter which achieves 600 W/in<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> power density and 93% efficiency.