Enhanced Bidirectional <i>CLLC</i> Resonant Converter With Improved Efficiency and Wide Voltage Range: Analytical Design, Simulation, Comparison, and Prototyping

This paper presents a novel topology for a bidirectional DC-DC converter based on a CLLC resonant circuit. The proposed design offers significant advancements in three key areas: a wide voltage gain range, improved efficiency, and reduced switching stress. It builds upon the well-established bidirectional CLLC converter by incorporating a third winding on the transformer’s secondary side. This modification is complemented by the addition of a full-bridge with two series capacitors. This innovative integration not only enhances switch performance and mitigates stress but also preserves the advantageous characteristics of the conventional CLLC converter. Notably, it enables exceptional voltage gain adaptability across a broad spectrum of switching frequencies. The paper delves into a thorough analysis of the proposed converter’s operational principles for both forward and reverse power flow directions. This analysis provides a comprehensive understanding of the converter’s unique structural features, and its voltage gain behavior. Additionally, the paper explores the parameter design process, offering valuable insights for optimizing the converter’s performance. Finally, experimental results obtained from a 1 kW prototype validate the effectiveness of the proposed design, showcasing its superior efficiency and wide voltage gain range.