Research And Design Of LCC Resonant Converter Considering Current Sharing Characteristics

With the emergence of a large number of high-frequency switching devices and the continuous improvement of magnetic material properties,high-frequency operation has become an inevitable trend of DC/DC power modules.The resonant converter has become a popular topology for high-frequency isolated DC/DC power module because its nature soft switching characteristics can greatly reduce switching losses of high-frequency operation.On the other hand,limited by the current and voltage stress of the switching device,the power module operation in parallel is usually employed to increase the power transmission capacity for high power and high current applications.However,in practical applications,the inevitable errors in the parameters of resonant elements directly lead to the difference of voltage gain for each resonant converter,resulting in the current sharing characteristics and system reliability reduction.Therefore,the current-sharing issue of resonant converters has been a hot topic in the power electronic filed.Due to the different application,the current sharing of resonant converter mainly focus on LLC resonant converter topology.However,the research on LCC resonant converter with the same excellent performance is relatively rare.On the other hand,it is found that the current sharing of resonant converters is mainly achieved by adding the additional current sharing circuit of and modifying resonant converter topology.A review of literature shows there is rarely paper pobulished from the perspective of resonant parameter design.Therefore,the LCC resonant converter is selected as the research object in this thesis.By studying the influence of parameters of LCC resonant converter on parallel flow sharing characteristics,the design method of LCC resonant converter considering the current sharing characteristics are proposed.Firstly,the operation characteristics of the traditional efficiency-based LCC resonant converter have been analyzed.However,the current sharing characteristics of the converter in parallel are poor.Based on this,the linear regression function of the current sharing error on the deviation percentage of the resonant value is derived according to the output volt-ampere characteristics of the LCC resonant converter.Based on theoretical analysis,a method for evaluating current sharing characteristic of LCC resonant converter is presented.Then the design objective of the LCC resonant converter considering the current sharing characteristic is clarified,and the design objective is translated into a mathematical optimization issue.Furthermore,a parameter design method of LCC resonant converter with the current sharing characteristics is proposed,and the closed-loop design flow of the resonant parameters is provided.The simulation comparsion with the conventional method of the LCC resonant converter shows the validity of the design method.Finally,two experimental prototypes in parallel with 200V~400V input and 48V/500 W output have been manufactured in the laboratory to demonstrate the effectiveness of the proposed optimization design.The experimental results show that the proposed optimization design method can ensures a less than 5% current sharing error of LCC resonant converters,and effectively improves the operation characteristics of LCC resonant converter in parallel with the allowable 5% resonant parameter error.The experimental results show the feasibility and validty of the optimization design.