Influence of Junction-Capacitance and Dead-Time on Dual-Active-Bridge Actual Soft-Switching-Range: Analytic Analysis and Solution

Dual active bridges (DABs) may lose zero voltage switching (ZVS) operation when the junction capacitance of semiconductors cannot be fully charged or discharged within dead time. The influence above is more serious especially under light load because the switching current is small. The aim of this article is to analyze the influence of the junction capacitance and dead time on the ZVS range of DAB and propose a novel modulation to eliminate the influence. It is concluded that DAB has an inherent non-ZVS region due to the influence of junction capacitance and dead time. Besides, the exact ZVS range of DAB is given when the junction capacitance and dead time are considered. In view of the influence of junction capacitance and dead time, this article proposed a mixed-mode modulation, which enables DAB to avoid operating in non-ZVS region. Finally, a 4.5 kW rated prototype is made and experimental results are presented to verify the previous conclusions. The efficiency with the proposed method can be up to 4% higher under light load than that with the traditional method ignoring nonideal factors.