Research And Design Of GaN-based High-efficiency And Low-ripple DC/DC Converters

With the progress of power electronics technology,intelligent electrical appliances have been developing towards miniaturization of high frequency,which not only improves people's living standards,but also puts forward higher requirements for power supply.Requirements of low-voltage high-current power supply,the ripple,efficiency and response speed are more stringent.Therefore,low ripple,high efficiency and fast response power supply has become the focus of the market and researchers.This thesis will design a converter with high efficiency,low ripple and fast response.On the one hand,the application of gallium nitride devices is studied to improve the efficiency;on the other hand,the interleaving topology is adopted to reduce the ripple.Firstly,the characteristics and working principle of gallium nitride devices are studied.Comparing with silicon devices,the advantages of fast switching speed and low switching loss of gallium nitride devices are verified by experiments.The influence of parasitic parameters on switching waveform of gallium nitride devices is studied by simulation method,which can be used to guide the design of hardware circuit.The switching loss models of gallium nitride devices under different load currents were obtained by double pulse experiment and data fitting.In the research of low ripple technology,this thesis adopts interleaved converter to reduce ripple.In this thesis,the principle of interleaved parallel converter is introduced.And the current ripple property of multiphase interleaved parallel converter is analyzed.Also,the thesis analyzes the characteristics of current sharing,and draws the conclusion that the current distribution is affected by the equivalent resistance,input voltage and duty cycle of each phase.In the aspect of control loop design,the system's small signal model is established,and PI controller parameters are designed based on the model.The reliability of control loop design is verified by Matlab/Simulink software simulation.Finally,on the basis of the previous research,an experimental prototype with rated power of 96 W was built based on gallium nitride devices.The converter adopts PCB with minimum power loop to improve the switching waveform.The maximum efficiency of the converter reached 95.5%,a 4.9% improvement over the silicon-based converter with the same load current.The total current ripple is reduced to 64.3% of the current ripple of each phase inductor by a two-phase interleaved structure.The response time of load experiment is 178?s,and the response time of load reduction experiment is 162?s.The correctness of the converter design is verified by experiments.