A Review of Topologies, Principles of Operation, and Modulation Strategies for Bidirectional LLC Resonant Converters

The resonant converters have wide applications and advantages, such as smooth switching operation, electrical isolation, low electromagnetic interference (EMI), low harmonic pollution, magnetic integration, wide output ranges, low voltage stress, and high operating frequency. In addition, these converters can handle higher power density, achieve high efficiency, and work at high frequencies ranging from kHz to MHz, thus reducing passive components. In order to achieve this, it is imperative to familiarize oneself with the diverse topologies in switching, rectification, mathematical models, and auxiliary components. Therefore, this article meticulously examines and presents an array of topologies, switching modes, rectification modes, mathematical models, and switching strategies. These aspects are also summarized in comparative tables. Finally, the article concludes that the most used topology is the full bridge. Similarly, in rectification, the full-bridge configuration is preferred due to its low complexity in bidirectionality. Also, PWM modulation is preferred for its ease of implementation.