Full Bridge LLC Hybrid Control Strategy with Wide Input and Output Voltage Range

The LLC resonant converter has gained extensive adoption in recent years, primarily owing to its benefits including high efficiency and high power density. However, the intrinsic electrical traits of the LLC converter fail to accommodate operational requirements involving a broad voltage span for both the input and the output. To tackle the operational scenarios of LLC resonant converters characterized by broad input and output voltage ranges, this study examines the gain properties of LLC subjected to both frequency modulation control and phase shift control techniques, correspondingly, and puts forward a hybrid control approach integrating frequency modulation with phase shift strategy. Through the seamless combination of frequency modulation control and phase shift control within one control loop, the issue of system oscillations occurring during the transition among differing control loops is successfully eliminated. As a result, the voltage gain spectrum of the LLC is substantially widened. A high-power LLC simulation model featuring interleaved and parallel configurations, along with an experimental testing rig, were established. The presented hybrid control strategy, which utilizes frequency modulation and phase shift, was investigated via extensive simulations and empirical testing. The obtained simulation results and experimental data exhibit strong alignment, thereby confirming the accuracy and feasibility of the presented full-bridge LLC hybrid control approach designed for extensive input and output voltage variations.