Research On Four-coil Magnetic Resonance Coupling Wireless Power Transfer Circuit Excited By A Class-de RF Power Amplifier

In recent years,compared with the wired power transmission,wireless power transmission(WPT)technology has developed rapidly because of its cleanliness,applicability,security,and convenience.Among them,the technology of high transmission power long-distance WPT is a hot research topic at present,which is widely concerned by scholars.Among the existing technologies,four-coil magnetic resonance coupling WPT(MRC-WPT)technologr is suitable for long-distance wireless transmission,and the class-DE radio-frequency power amplifier(RFPA)has the characteristics of high-power and high-efficiency at megahertz,so that the combination of two technologies will be a beneficial attempt to realize high-power long-distance WPT technology.Therefore,the design method and operating principle of the four-coil MRC-WPT circuit excited by the class-DE RFPA are focused in this thesis.Firstly,according to the physical structure of four-coil MRC-WPT,the equivalent circuit impedance model is obtained,and the operating principle of the circuit is described.At the same time,the optimal operating frequency,frequency splitting and the mathematical expression of the input impedance are analyzed,and the design difficulties of the RFPA are explained.Secondly.the relationship between the quality factor of spiral coil and the system performance in four-coil MRC-WPT is analyzed.According to the geometric structure,the mathematical model of plane spiral coil is obtained,the mathematical relationship between the quality factor of plane spiral coil and its geometric parameters is discussed,and the design method of plane spiral coil with high quality factor is studied.Then,according to the circuit equivalent model of the four-coil MRC-WPT and the characteristics of the class-DE RFPA,the LCL optimal matching network is designed.The optimal matching network is connected between the RFPA and the four-coil structure,and the input impedance of the four-coil MRC-WPT circuit is rotated clockwise for half a circle on its Smith impedance diagram.The transformed input impedance is equivalent to series resonance at the optimal operating frequency,so that the input impedance increases with the deviation of operating frequency,which is conducive to the class-DE RFPA excitation of four-coil MRC-WPT.The influence of the component error in the optimal matching network on the resonance frequency of the system is analyzed,and the circuit power loss introduced by the network is calculated.According to the input impedance characteristics of four-coil MRC-WPT,the design method of the class-DE RFPA circuit is described.Finally,according to the designed coil structure and circuit parameters,a simulation model is established by MATLAB/simulink and a four-coil MRC-WPT experimental prototype excited by class-DE RFPA is built for the experimental verification.The results verify the correctness of the theoretical analysis and the feasibility of the designed circuit.