A Novel Simplified Time Domain Analysis-Based Synchronous Rectification Strategy for LLC Converter Featuring Real-Time Full-Range Operation

Model-based synchronous rectification (SR) approach for $LLC$ converters offers significant advantages, such as low cost, high scalability, and elimination of additional losses, as no high-frequency signal sampling is required. However, the performance of model-based SR approach heavily depends on the accuracy of the underlying model. Moreover, given that the $LLC$ converters operate in various modes, each necessitating a different model, it is crucial to identify the operating mode to apply the appropriate model. An inaccurate model or failure to recognize the operation mode may lead to degraded SR performance and even risk of system instability. In this article, a novel model-based SR strategy via simplified time domain analysis is proposed, which is integrated with both SR timing online algorithm and operation mode online recognition algorithm. Unlike the existing model-based SR strategies, all the results are calculated online in the proposed SR strategy without relying on fitting curves, and the proposed SR strategy is available under all typical $LLC$ converter operating mode. Both simulation and experiment are carried out for validation. The results demonstrate an overall SR timing error of less than 0.6%, along with a maximum efficiency improvement of 0.34% compared to existing model-based strategies.