Fast-Convergent Time-Domain Algorithm Based Parameter Optimization for Phase-Shift LLC Converters

LLC resonant converters have drawn growing attention from industries. Time-domain analysis has the advantage of high accuracy, promoting the utilization of resonant tanks. This article proposes a parameter optimization methodology for phase-shift LLC converters based on a fast-convergent time-domain algorithm. The algorithm can be extended to different operating modes, rather than confined to a specific mode. It minimizes the number of iterative variables in the time analysis and reasonably estimates its initial points based on the fundamental harmonic analysis. Thus, accurate results can be obtained much faster than the existing time-domain algorithms. The property of fast convergence makes it easy to quantitatively investigate the power loss characteristics, based on which the parameter optimization methodology is proposed. The methodology guarantees that the converter achieves zero voltage switching for the primary switches and zero current switching for the secondary diodes in the entire operating region. The energy conversion efficiency is improved by reducing the conduction loss and switching loss. The effectiveness of the proposed methodology is verified by a 2-kW experimental prototype, whose peak efficiency is 96.3%.