Title:research On High Efficiency Multipul Output Fly-Back Converter Based On Planar Transformer

In order to cope with the growing demand for electronic products brought by the continuous development of human society,as well as human’s constant pursuit of personal living standards,more and more electronic products have entered human’s daily life.In recent years,smart home products such as sweeping robot,Internet TV and intelligent air conditioner have become an inseparable part of most families.With the intelligentization of these electronic products,the demand for multiple output auxiliary power supply which can meet different voltage levels is also increasing.The research of multiple output auxiliary power supply with high performance has an important influence in this field.In this paper,isolated multiple output DC/DC converter is studied.Firstly,the multiple output auxiliary power supplies is investigated.The Flyback converter is determined as the main circuit topology.Secondly,in order to improve the efficiency of the multiple output converter and the power density of the system,the principle and the calculation method of the active clamp Flyback converter under DCM are analyzed.At the same time,the causes of the cross regulation of the multiple output converter are deduced and the constraint conditions based on leakage inductor are given.In view of the two sharp problems of the multiple output Flyback converter,such as the cross regulation and high winding loss.In this paper,we design a multiple output planar transformer under a standard core,and solve the above two problems by optimizing the transformer windings.Optimization of winding width and thickness;Multi-winding arrangement optimization.The design of winding width adopts variable width winding to realize the optimal DC impedance of single-layer winding.At the same time,the optimal thickness of the winding is selected according to 1D Dowell.Finally,the width and thickness of the winding meeting the requirements of current density and having the lowest loss.The optimal arrangement of multilayer PCB is constrained by the relationship of leakage inductances so that it can meet the requirement of better cross regulation.In order to verify the rationality of the theory.In this paper,the main circuit model is built based on Simplis software to verify the rationality of hardware circuit parameter design.At the same time,the 3D model of the designed transformer was built based on Maxwell software.The magnetic induction strength B,excitation inductance Lm and leakage inductance Lk of the transformer are analyzed respectively,and the simulation verifies that the winding loss of the transformer.It embodies the superiority of the design theory.On the basis of simulation,the magnetic core is fabricated,and the excitation inductance and leakage inductor values are measured by experiment.Finally,a multiple output active clamp Flyback converter with a total output power of 30W and six outputs is built,which verifies the rationality and correctness of the above theoretical analysis.