Wide-range Input LLC Resonant Converter

The large-scale utilization of traditional fossil energy has brought tremendous development to human society,but also brought very serious environmental pollution problems.In order to achieve sustainable development of energy and society,countries around the world are committed to research and development of new energy sources.New energy sources represented by wind energy,solar energy and hydrogen fuel cells have ushered in historic development opportunities.Compared with traditional energy sources,the application of new energy sources has the disadvantage of unstable output power.There is an urgent need for a wide-range input DC/DC converter to improve output characteristics.Therefore,a high-efficiency DC/DC converter suitable for a wide input voltage range has become Research hotspots.LLC resonant converter has high efficiency and low electromagnetic interference.It can realize zero voltage turn-on(ZVS)of the primary side switch tube and zero current turn-off(ZCS)of the secondary side rectifier diode.The wide-range operation of the resonant converter is studied.In order to broaden the voltage input range of LLC resonant converter,the control method is improved on the basis of full-bridge LLC resonant converter,using a hybrid combination of full-bridge variable-frequency control,fixed-frequency phase-shift control,and half-bridge variable-frequency control.The control mode uses the advantages of each control method to achieve a three-fold ultra-wide input voltage range.The parameter optimization design of the wide-range input LLC resonant converter is carried out,the voltage gain function of the converter under each control mode is derived using the fundamental wave analysis method,and the working range of the hybrid control mode and the control mode switching are designed by using the voltage gain function.Point of choice.On the basis of the above,the small signal modeling of LLC resonant converter is carried out by the extended description function method(EDF)and the closed-loop system compensator is designed.On the basis of theoretical research,the FPGA-based hardware circuit design and control software design are completed.Finally,the simulation verification is carried out in Matlab/Simulink software,and an experimental prototype is designed to experiment with the hybrid control mode of the wide-range input LLC resonant converter.Simulations and experiments have proved the effectiveness and accuracy of the control method in this paper.