Research And Design Of Planar Transformer Based On Half Bridge LLC Resonant Converter

With the continuous development of science and technology,switching power supply has been widely applied in various power electronic equipment,and small and efficient has become the main development goal of switching power supply.By using LLC high efficiency topology and increasing the switching frequency,it is possible to reduce the size of the power supply while ensuring high efficiency.However,the large volume and obvious high-frequency loss of traditional transformer hinder its further development,while the planar transformer has the advantages of good heat dissipation performance,small volume,high current density and easy realization of parameter consistency.Therefore,in order to make planar transformer widely used,this paper will study the optimal design of planar transformer based on the efficient topology of half bridge LLC.Firstly,the working principle and characteristics of LLC resonant converter topology are analyzed in detail,and then the influence of asymmetric leakage inductance of planar transformer applied to the topology on the converter is explained.According to the principle of high-frequency effect of transformer,aiming at the highfrequency loss of planar transformer,the influence of winding thickness and parallel winding on the loss is analyzed through one-dimensional loss model of transformer winding and simulation software.It shows that simply increasing winding thickness and parallel winding can not necessarily reduce the loss.At the same time,by comparing the loss of parallel windings under different structures,it shows that the method of interleaving windings can effectively improve the excess loss in the application of parallel windings.In addition,the leakage inductance of transformer with different winding structure arrangement is compared and analyzed through theoretical calculation,which shows that the winding structure arrangement can effectively improve the leakage inductance of transformer.Secondly,according to the design requirements of converter parameters,the preliminary design of planar transformer is carried out.The selection of magnetic core and the design of primary and secondary winding turns are completed.According to the actual design results,the planar transformer models with four different arrangements of windings are established for simulation research.It shows that the leakage inductance and leakage inductance can be effectively controlled by changing the arrangement of planar transformer windings Symmetry.At the same time,the distribution of current density in different arrangements of primary and secondary sides of planar transformer is analyzed,and it is explained in detail that the current density in windings can be effectively changed by optimizing the arrangement of windings,so as to optimize the loss of planar transformer.Finally,according to the previous theoretical research and simulation analysis,four kinds of planar transformer samples are made for different winding layout structures of planar transformer.The leakage inductance and AC resistance of each transformer are analyzed through experimental test,and then compared with the simulation results,it is proved that the reasonable winding layout can effectively improve the performance parameters of planar transformer.In order to apply the designed transformer to the circuit,an experimental prototype of 240 W half bridge LLC resonant converter is built,and the working performance of planar transformer is verified by experiments.This paper has 68 pictures,7 tables and 80 references.