Research On 6.78MHz Magnetic Coupling Resonant Omnidirectional Wireless Power Transmission Device

With the increasing penetration of consumer electronic products such as smart phones and watches over the years,people have increasingly higher requirements for the freedom of charging electronic products.Compared with the traditional wired plug-in charging method,wireless charging is more and more used in consumer electronic products due to its features of convenience,safety and beauty.At present,most of the wireless power transmission(WPT)terminal products are flat structures and use low frequency magnetic induction coupling technology.When charging,users need to aim the device in the designated energy receiving direction and be close to the charging terminal.This approach actually reduces the user’s freedom of operation.In order to improve the degree of freedom of wireless charging,this dissertation adopts 6.78 MHz magnetic coupled resonance technology to design the omnidirectional WPT device.The main contents of this article are as follows:This dissertation first analyzes the working principle of the traditional one-to-one structure WPT system,and obtains the main factors that affect the energy transmission efficiency and power of the system.Then,The omnidirectional WPT coupling mechanism of spatial triorthogonal transmitting coil and planar receiving coil(3TX-1RX)is designed.The resultant magnetic field vector of the excitation current in the triorthogonal transmitting coil and the influence of the relative position of receiving coil on the transmission performance of the system were analyzed.In order to improve the magnetic field distribution of the coupling mechanism,the shaping effect of the ferromagnetic plate and the conductive metal plate on the magnetic field were studied.Considering the shaping effect comprehensively,the aluminum conductive metal plate is selected as the shaping material of the transmitting coil.The 3Tx-1Rx coupling mechanism model was built in the finite element simulation software,and the magnetic field distribution of the transmitting coil was observed and analyzed.Optimize the coil structure based on actual measurement.The physical object of the coupling mechanism was built,and the relevant parameters of the coil were measured by using the impedance analyzer to sweep the frequency.A Class E~2 DC-DC converter composed of Class E power amplifier and Class E rectifier is used to transmit and receive energy and a new wide band gap gallium nitride(Ga N)switching device are used to achieve 6.78 MHz switching operation in order to overcome the disadvantage of high power consumption of traditional hard switching at high frequency.In this dissertation,the working process of Class E rectifier,coupling mechanism and Class E power amplifier is analyzed,and the corresponding circuit parameters are calculated.In the simulation softwares ADS and LTSPICE,the parameters of the Class E~2 DC-DC converter circuit with impedance matching network are simulated and optimized,and the soft switching characteristics are better realized.Finally,an experimental prototype of omnidirectional WPT system is built.The circuit of each part of the system has been debugged.The feasibility of the omnidirectional WPT system was verified by setting multiple positions and angles of the receiving coil.