Research On Current Sharing Technology Of Multi-channel LLC Resonant Converter

In recent years,LLC resonant converter has been widely favored by power electronics researchers because of its excellent soft switching characteristics,high efficiency and high power density.With the maturity of LLC resonant technology,LLC resonant converter is superior to other resonant converter topologies in terms of low loss,easy magnetic integration and easy to implement soft switching characteristics,making the LLC resonant topology become the first choice for DC/DC power applications.But in high power applications,a single module LLC still has a number of deficiencies.The parallel power supply mode of multiple LLC modules can not only retain the advantages of high efficiency and low consumption of the LLC resonant converter,but also solve the power capacity problem of a single module.However,due to the limitations of the existing manufacturing process,the component parameters of the parallel modules in actual operation are not completely consistent,which causes a problem of uneven current distribution.Therefore,parallel current sharing technology is the key to realize multi-channel LLC parallel power supply.In this paper,the LLC half-bridge resonant converter is taken as an example to study two current sharing strategies for multi-channel LLC parallel connection.Firstly,this paper expounds the research status of LLC resonant converter,and introduces the research results of LLC parallel technology and current sharing technology in recent years.Then the different resonant transformation topologies are introduced,and their advantages and disadvantages are compared.The LLC resonant converter studied in this paper is derived.Taking the half-bridge LLC resonant converter as an example,the working characteristics of the resonant network are analyzed,and the fundamental equivalent model is established.The voltage gain curve and the design of the basic resonant network parameters are given.Secondly,a half-bridge LLC resonant circuit simulation model is designed and built to analyze the influence of voltage difference and output current on the difference of the parameters of different resonant cavity components.The parallel simulation experiment is carried out to verify the influence of the difference of different resonant components on the output current distribution of the parallel system.The simulation results verify the difference of the resonant cavity components that affect the uneven distribution of the parallel operating current of the resonant circuit.Thirdly,the phase shift current sharing strategy is introduced.The basic principle of the phase shift current sharing strategy is analyzed in detail.The relationship between the phase shift angle and the voltage gain is derived,and the principle and feasibility of the control strategy are analyzed.Then,the simulation experiments of two-way LLC half-bridge resonant transformation in parallel with the same phase are carried out to verify the current sharing effect.Finally,a multi-channel LLC resonant converter topology sharing a resonant capacitor and a resonant inductor is introduced for the case where multiple LLC halfbridge resonant converters are connected in parallel.The effect of these two parameter errors on voltage gain and current distribution is reduced by the parallel connection of resonant inductors or resonant capacitors.After the simulation experiment and hardware experiment verification,this passive current sharing strategy can effectively control the current error within 5%.