Utilizing the Intrinsic CC/CV Characteristics of a CLLC Converter for Battery Charging with ZVS Operation

In conventional CLLC topologies, CC/CV charging is typically implemented using closed-loop control strategies based on phase shift modulation. This not only increases control complexity but also requires additional voltage and current sensing circuits, thereby raising the overall system cost. To address these issues, this paper proposes a novel CC/CV charging strategy. By analyzing the inherent characteristics of the coupled network, the switching frequencies corresponding to the CC and CV operating points are derived. By jointly applying frequency modulation and phase shift control to the CLLC converter, the system not only realizes CC/CV charging, but also enables the regulation of both the magnitude and the direction of power flow. Furthermore, to improve the system’s efficiency, a fine frequency tuning method is introduced to ensure operation under the critical zero-voltage switching (ZVS) condition. Finally, a 500 W prototype is constructed to validate the effectiveness of the proposed control strategy.