Wide Voltage Gain Range LLC DC/DC Topologies: State-of-the-Art

LLC resonant converter is a prevalent isolated dc/dc topology due to its high efficiency, high power density, and simple structure. However, it is challenging to optimize the design of conventional LLC converter in wide gain range applications. Therefore, modifications either on the circuit structure or control strategy are necessary to improve its voltage regulation performance. This paper presents a comprehensive overview of recent evolvements of LLC topology in wide voltage gain applications. The broad applications of wide gain LLC converters, which include hold-up operation, wide input voltage range, and wide output voltage range, are investigated. State-of-the-art wide gain LLC solutions are reviewed and classified into four categories. Benefits and constraints of different solutions are addressed in detail. Finally, the circuit selection principles for different application backgrounds are summarized with a comparative study of different configurations.