Optimal Trajectory Control for CLL Resonant Converters Under Large‐Signal Load Transients

ABSTRACT With the growing demand for fast transient response in high‐frequency power supplies, CLL resonant converters have garnered significant attention due to their wide‐range soft‐switching (zero‐voltage/zero‐current switching, ZVS/ZCS) features. However, owing to the high‐order nonlinearity of these converters, conventional linear proportional‐integral (PI) control exhibits sluggish dynamics, severe voltage fluctuations, and prolonged settling times under large‐signal step‐load transients. To address these limitations, this paper presents an optimal trajectory control (OTC) strategy tailored specifically for CLL resonant converters. To mitigate analytical complexity, the inherent three‐dimensional state variables of the system are reduced to a normalized two‐dimensional (2‐D) state‐plane model. Utilizing this framework, state trajectory transitions during step‐load changes are analyzed, thereby deriving explicit mathematical expressions for the optimal pulse width required to achieve an instantaneous controller response. Finally, an experimental prototype is constructed to evaluate the performance of the proposed OTC in comparison with conventional PI control. Both simulation and experimental results demonstrate that the proposed OTC strategy significantly shortens the voltage settling time and suppresses transient overshoots, thereby fully validating its effectiveness in enhancing the dynamic performance of CLL resonant converters.