| The quality of low-voltage auxiliary power supply is closely related to the proper operation of the whole marine system which serves for equipment of communication,navigation and monitoring.For the preceding class of the power supply is not the rectifier but the battery pack,there exists a wide range of input and load in the converter.In order to ensure safety,electrical isolation is required between high voltage side and low voltage side.High conversion efficiency and high power density is necessary out of the limit of temperature and space.For the reasons above,LLC resonant converter is selected for the research and design.Firstly in the dissertation the first harmonic approximation(FHA)equivalent circuit model of LLC resonant converter is established and the DC voltage gain is calculated.Then the relationship between the voltage gain and the parameters is analyzed,on the one hand,by drawing the curves of the voltage gain under different parameters,qualitative analysis of the trends of voltage gain is carried out from the view of circuit theory,on the other hand,simple expression of voltage gain is obtained through normalization and operation region is set by the operation point under extreme situation,parameters which meets the requirement of input and load is calculated.In order to improve the conversion efficiency,the mechanism and the sufficient condition to realize ZVS of the MOSFETs in the whole input range and the whole load range is presented.Since the magnetizing inductance of the transformer will be used in the design and the leakage inductance is ignored,the influence of leakage inductance on resonance parameters and the operation range of the converter is revealed through two-port equivalent circuit model.Finally,according to FHA analysis and ZVS conditions,the design process which meets the requirements of constant output voltage and soft-switching in the full range of input and load and magnetic components is provided.Through the establishment of small-signal equivalent circuit model,transfer function of control to output is derived and the transfer function of compensation unit is obtained through Bode diagram plotted by MATLAB as PFM control parameters,thus completes the LLC resonant converter design.In this thesis,the effects of various parameters on the trends of voltage gain curve of LLC resonant converter presented a wide range of input and load variations LLC resonant converter is analyzed and the complete design method of a resonance parameters with calculation process is proposed.In terms of transformer,damage caused by leakage inductance of the secondary side of the transformer is researched through modeling,and design method of planar transformer whose leakage inductance is relatively low is provided.In terms of control strategy,some recommendations for optimization is proposed.Finally,according to the design method Saber simulation and prototype experiment are conducted.Experiment results show that the design method and calculated parameters have proven to be practical. |
