Research On Design And Power Loss Analysis Of Wide-input Intergrated Three-mode LLC Resonant Converter

Distributed power system has numbers of advantages such as flexibility,reliability,electromagnetic compatibility,low power loss,etc.With the density of switching power supply becoming higher and higher,the utilization of resonant circuit by using soft-switching technology is a great way to obtain higher power density.Nowadays,LLC resonant converter is widely used in DC-DC converter topology and it has many advantages.This paper describes the selection of the LLC resonant converter overall topology,working principle and modal analysis.The equivalent circuit of the converter is deduced by using the First Harmonic Approximation and the influence of the magnetic integrated transformer is considered.Working areas applied to different occasions are described according to the voltage gain curve.By using Extended Describing Function Method,the small signal transfer function of the system is obtained,which lays the foundation for parameters selection,closed-loop feedback design and compensator design.In order to deal with the situation that the input voltage is slightly higher than the rated voltage,this paper presents a design method and a compensator design of an integrated three-mode half-bridge LLC resonant converter suitable for a wide voltage range input.Considering the actual situation of the magnetic integrated transformer,the parameters are adjusted.The Type II Compensator coupled with optocoupler is proposed to compensate the loop and generate feedback signal.By analyzing and designing parameters,the closed-loop feedback system achieves ideal control performances.Based on some reasonable assumptions,this paper proposes an improved calculation method of total power loss,which simplifies the power loss model and modifies traditional calculation method of transformer power loss.This method is more practical and suitable for the integrated half-bridge LLC resonant converter.The corresponding power loss model is established to provide an improved calculation method of primary side loss,transformer loss and secondary side loss respectively.After calculation,the theoretical efficiency of the prototype is 90.90%.Finally,electrical model of PFM feedback with Type II Compensator and power loss model at constant frequency are established respectively in PLECS.The abrupt change of voltage is simulated,three working modes are observed and the rationality of compensator design is verified.Power loss analysis model in PLECS is established by coding improved calculation method into thermal description file,the efficiency obtained from simulation is 90.28%.Furthermore,the prototype is designed,the value and selection of important devices are described,the fabricated prototype is tested and the working states of ZVS,resonant network and diode are respectively observed.Through the waveform of actual output voltage,power loss is calculated and efficiency is 90.17%.Comparison of three efficiency results verifies the correctness of the parameter design and power loss calculation.In this paper,a novel parameter design method of a wide-input integrated three-mode LLC resonant converter is proposed.An improved calculation method is given to analyze power loss.A corresponding prototype is designed and produced at last.This paper provides a reference for distributed module power supply.