Research On LLC Resonant Converter For Wide Input Voltage

In recent years,with the development of society and technological evolution,the contamination of nature has been growing day by day,and the energy of the earth has gradually run out.The use and exploitation of renewable energy is one of the most operative solutions,so the application of new energy is becoming more and more common.In the fields of new energy power generation,communication power supply and other fields,the output voltage range of the front stage is large.To make the subsequent converter obtain a stable DC voltage,it is necessary to add a appropriate DC converter between the front stage unit and the back stage unit.The full-bridge LLC resonant topology is appropriate for high-power applications and can realize the soft switching of the primary and secondary side transistors under a wide input voltage.It is one of the ideal topologies of the DC/DC converters.This article mainly studies LLC resonant power supply suitable for wide input voltage.This thesis first briefly explained the technical advantages of soft-switching DC converters under the development origin of various fields such as new energy power generation and communication power supplies,and explored the unique advantages of LLC resonant converters.Then the research status of wide-input voltage LLC resonant converter is explained separately from the topological structure and control strategy,which leads to the main content of this paper.The LLC resonant topological structure is classified and compared,and its working principle in the frequency modulation control mode is discussed in detail on the basis of the full-bridge structure.Modeling by fundamental wave analysis method,analyzes its basic characteristics and derives input and output voltage gains and characteristic curves.At the same time,the principle of frequency modulation control is briefly described and the half-bridge and full-bridge structure simulations are built in the MTALAB/Simulink environment based on the frequency modulation strategy to verify the feasibility of the control strategy and analyze the existing problems and drawbacks.Then,on the problems of the resonant converter in the frequency modulation mode,the phase-shifting control strategy is derived,and its working principle is analyzed in detail based on the full-bridge topology.In order to reduce the error,the time domain analysis method is used to analyze its basic characteristics and derive its gain.In order to adapt to the working conditions of wide input voltage,the advantages of the above-mentioned frequency modulation control strategy and phase-shifting control strategy are combined to form a hybrid control strategy,its working principle is analyzed,and the selection of the control mode switching point is discussed in detail.Based on this control strategy,a full-bridge LLC simulation was built to verify that the resonant converter can achieve soft start,stable output and high conversion efficiency within the designed full voltage range.Finally,according to the design and selection of the main components of the resonant circuit,the hardware and software parts of the control system are designed,the prototype is prototyped,and the feasibility and efficiency of the resonant power supply design are verified through experiments.