Research And Design Of High Performance On-Board DC/DC Converter

With the increasingly serious energy exhaustion and environmental degradation,countries around the world are formulating planning strategies for energy reform.In order to adapt to the development of new energy industries and alleviate the problem of emissions from fuel vehicles,the development of electric vehicles has become a research hotspot.The electric vehicle DC/DC converter is an indispensable part of the electric structure of an electric vehicle.It undertakes the energy conversion from high-voltage power batteries to low-voltage batteries to meet the needs of on-board electronic equipment and various auxiliary power supplies.According to the wide range electrical requirements of vehicle DC/DC converters,this thesis designs a 2.5kW high efficiency and high power density vehicle DC/DC converter prototype.First,according to the functions and requirements of vehicle DC/DC converters,the advantages and disadvantages of several commonly used isolated wide-range low-voltage and high-current DC/DC topologies are analyzed,and several topological variants are further analyzed.In this thesis,a Tr-lag diode-clamped phase-shifted full-bridge soft-switching converter is selected as the research object.The timing and switching state of the circuit are calculated in detail,and the soft-switching conditions,duty cycle loss,and synchronous rectification scheme of the circuit are analyzed.Then,the current drop and parasitic oscillation of the converter under the influence of parasitic parameters are analyzed,and the compensation method of the excitation current and the design method of the optimal absorption parameters to widen the soft-switching range of light load are proposed.Secondly,according to the wide range of input and output voltages and high output current requirements of electric vehicle DC/DC converters,the main power parameters of the prototype are designed,and the design process of magnetic components including high current windings is explained in detail.Then the components are selected according to the circuit operating parameters,and the loss calculation and analysis are performed.For the control part of the converter,the small-signal model of the phase-shifted full-bridge circuit topology is modeled.In this thesis,the average current double loop control structure is used to compensate the current inner loop and voltage outer loop respectively,and then a simulation model is established to verify the feasibility and effectiveness of the control parameters.This thesis uses a digital control scheme,introduces the peripheral resource configuration of the digital chip,and explains the program logic flowchart and the implementation of the state machine.Finally,based on the design results above,a 2.5kW experimental prototype was made and debugged,and the test results of the prototype were given.The prototype meets a wide range of voltage requirements.The maximum efficiency of the whole machine reaches 94.8% and the full-load efficiency reaches 92.4%,which meets the design requirements.The experimental results verify the results of various theoretical analyses and illustrate the correctness and effectiveness of the circuit design and control scheme.