Research On Vehicle Charger Based On GaN Devices And Magnetic Integration Technology

With the development and popularity of electric vehicles,the portable on-board charger technology based on household power supply system is receiving more and more attention.How to achieve high power factor,high efficiency,miniaturization and high power density of on-board chargers is the key problem to be solved.At present,the traditional Si MOSFETs are used as the main power tubes in on-board chargers,and the magnetic elements are usually independent wire-wound magnetic elements,which limit the improvement of the efficiency and power density of on-board chargers.In this thesis,GaN devices and magnetic integrated technology are applied to vehicle chargers,and the following research work has been completed.Firstly,this thesis designs a two-stage vehicle charger based on the totem pole bridgeless PFC converter and CLLLC resonant converter is designed in this thesis,the excellent reverse recovery characteristics of GaN devices are used to make the totempole PFC converter operate in CCM mode,and the fast switching speed of GaN devices is used to increase the operating frequency and reduce the size of the components.Theoretical analysis of the problems caused by the high speed switching of GaN devices is also carried out,and some optimization measures are proposed.In addition,the hardware parameter design,device selection and control strategy design of the front and rear converters are completed respectively,and the feasibility of the design scheme is verified by simulation.Then,the high frequency loss and distribution parameters of the PCB-type planar transformer are analyzed and optimized by combining theoretical calculation and simulation verification,mainly including the optimization of winding structure,air gap structure and distribution capacitance.On this basis,this thesis adopts the planar magnetic integration technology and designs a magnetically integrated planar transformer with controlled leakage inductance,which replaces the resonant inductor of the primary and secondary side of the CLLLC converter and reduces the number and size of components in the CLLLC converter.In addition,the rationality of the design scheme is verified with the help of Ansys Maxwell simulation platform.Finally,the peripheral circuit of the on-board charger and the control program of the whole machine were designed,and the experimental prototype of the 2k W vehicle charger based on GaN devices and magnetically integrated planar transformers was built and experimentally tested.The experimental results show that the parameter design and controller design of the experimental prototype meet the design requirements.The prototype achieves 5A constant current charging and 400 V constant voltage charging with good steady-state and dynamic characteristics and the power factor is above 0.98,the peak efficiency at full load reaches 95.22%.The thesis has 104 pictures,16 tables,and 86 references.