Simulation and Analysis of Secondary LLC Resonant Converter

This paper centers on the advanced power electronics technology of LLC resonant high-frequency converters, systematically examining their topology and thoroughly investigating their operational performance. Commencing with an overview of the converter's structure, it delves into the key components: the full-bridge inverter network, the resonant tank (comprising resonant capacitors, inductors, and magnetizing inductance), the high-frequency transformer, the full-bridge rectifier network, and the output capacitor. Employing a fundamental wave equivalent model, the paper scrutinizes the circuit behavior of the LLC resonant converter. This model simplifies high-frequency resonances, enabling quantitative analysis of the circuit. It systematically explores the DC voltage gain characteristics under diverse typical operating scenarios, such as full load and light load, revealing the inherent relationships between gain, input voltage, load conditions, and resonant parameters. These insights furnish crucial theoretical guidance for optimized design and efficient control. Building upon this foundation, the paper presents a detailed derivation of the calculation process for circuit resonant parameters, emphasizing their direct impact on overall performance. This provides precise theoretical grounding for attaining the optimal operating condition of an LLC resonant converter in practical applications. Subsequently, the paper utilizes circuit simulation software Ansys for topology simulations. By constructing a highly faithful simulated model mirroring the actual circuit architecture, rigorous verification of the designed circuit parameters is conducted to ensure the model accurately represents real-world circuit operation. Lastly, recognizing the significant influence of the high-frequency transformer on overall converter performance, the paper examines planar transformers specifically used within LLC resonant converters. It outlines design principles, critical parameter selection, optimization strategies, and issues related to matching the transformer with the resonant circuit. These findings offer practical engineering recommendations for achieving efficient synergy between the transformer and resonant circuitry.