ZVS Implementation Analysis and Optimization Design of <i>LLC</i> Converter Based on TDM-DC

To improve the operational efficiency of LLC converters and ensure zero-voltage switching (ZVS) across the entire operating range, this paper proposes an optimized design method based on time-domain analysis. Existing methods typically ignore the current drop during dead time and the influence of parasitic capacitance, resulting in overly optimistic ZVS estimations. To address this issue, a time-domain model with dead time and capacitance consideration (TDM-DC) is derived. Potential operating trajectories are analyzed, and a solver is established. Based on TDM-DC, key factors affecting ZVS implementation are investigated, and a TDM-DC-based design methodology for LLC converters is proposed. Compared to existing methods, the proposed approach verifies higher accuracy and lower computational complexity, enabling its industrial applicability. A 3-kW prototype achieves 97.0% (500W) peak efficiency through optimized parameters. The maximum efficiency improvement after optimization is 4.8%. Experimental results under various conditions match theoretical analysis, demonstrating the LLC converter achieves the required output voltage range while maintaining full-range soft switching.