Optimal Design and Modulation of Full Bridge LLC Resonant Converter with Wide Voltage Range

Full bridge LLC resonant converters have become the mainstream solution in the field of wide voltage range due to their advantages such as soft switching, simple structure, and wide voltage gain capability. To improve the working efficiency of the full bridge LLC resonant converters with a wide input voltage range, a working modes based iteration (WMI) modeling method is proposed to obtain both dynamic and steady-state waveforms, which exhibits high accuracy and speed, laying the foundation for the parameter and hybrid modulation strategy design. Then, with the purpose of minimize the effective resonant current, a resonant cavity parameter design process is proposed based on traversing parameters with WMI modeling method, thus guiding the selection of circuit key components. Finally, a loss model of the converter is built, and a hybrid optimization modulation strategy is proposed by taking the minimum total loss as the optimization objective. The accuracy and speed of the proposed WMI modeling method is verified by comparing with the MATLAB/Simulink result. With the designed parameters and hybrid modulation strategy, a 97.0% peak efficiency and a 4.8% maximum efficiency improvement are reached on a 125-375V-input and 48V/240W-output prototype.