A Control Strategy With Pulse Skipping and Optimal Trajectory for Efficiency Improvement of Dual-Bridge Series Resonant Converter Under Light-Load or Non-Unity-Gain Conditions

Dual-bridge series resonant converter (DBSRC) is widely employed in high-voltage and high-power applications such as electric vehicle (EV) chargers, power conversion systems (PCS), etc,. However, under light-load or non-unity voltage gain conditions, the DBSRC with traditional single-phase-shift (SPS) modulation exhibits a very small external phase-shift angle. This leads to significant backflow power, which increases both the root-mean-square (RMS) value of the resonant current and the switch turn-off current, consequently lowering the efficiency. To address this issue, a novel control strategy combining pulse skipping modulation (PSM) with optimal trajectory control (OTC) is proposed in this paper. PSM operates in a periodic pattern: within every C switching cycles, only the first E cycles (E < C) are retained for energy transfer, while the driving signals in the rest of (C- E) cycles are skipped. This increases the energy transferred during each pulse-retained cycle, enlarges the external phase-shift angle, and consequently reduces backflow power. Moreover, switching and driving losses are completely eliminated during the pulse-skipped cycles, further improving efficiency. In order to suppress the transient oscillations induced by PSM,OTCisemployed to force the converter to enter steady state trajectory within the first pulse cycle among E consecutive driving signals. Theoretical analysis shows that the proposed control strategy effectively reduces the losses. Finally, a prototype with 200 V input and 12–24 V output is built to verify the proposed strategy. Experimental results demonstrate that, compared to the traditional SPS scheme, the proposed control strategy improves the prototype's efficiency by at least 8% under non-unity gain and light-load conditions.