Loss Analysis And Efficiency Optimization Of LLC Resonant Converter

With the rapid development of power electronics technology,high input voltage,large change ratio,high switching frequency converter has been widely used in various fields.At the same time,the LLC resonant converter has many advantages,including increasing the switching frequency,reducing the switching stress and switching losses,and reducing the size of the power electronic device,improving the converter efficiency.LLC resonant converter has a research hotBased on the application of high voltage input low voltage output converter,the circuit of the LLC resonant converter,which is based on the four transformer in series input and parallel output,is the study object in this dissertation.The composition of the converter loss is calculated and analyzed in detail.The mathematical model of the converter loss is given to improve converter efficiency.Firstly,with the simulation software ANSYS Maxwell and ANSYS Simplorer,the 3D modeling and simulation of the LLC circuit based on the four-transformer in series input and parallel output and the planar transformer in the circuit are carried out.This paper has completed the optimization design of planar transformer.The PCB copper windings of four symmetrical overlapping structures are compared and analyzed.Based on the simulation results of current density and copper loss,the optimal staggered parallel structure is obtained.The core structure of the middle double gas gap is obtained according to the simulation results of the magnetic field distribution and the iron loss for four different cores.Then,based on the calculation of the converter loss,the parasitic parameters are extracted by ANSYS Q3D.And the optimal design of the parasitic parameters is analyzed and verified.Finally,The effectiveness of the efficiency improvement measures used in this dissertation is verified by a 4kW DC/DC converter with an input of 800V-1000V and an output of 25 V.At the same time,it proved the correctness of the theoretical analysis and the significance of the simulation model...