A Low-profile Dynamic Multi-load Constant Voltage Output Wireless Power Transfer

The emergence of wireless power transfer(WPT)technology has made it possible to transfer power between the receiver and transmitter without contact.It has begun to show great potential in people’s lives,work and production fields.This technology has been widely used in portable electronic devices,medical implants and electric vehicles.Most of them use Magnetically-Coupled Resonant Wireless Power Transfer(MCRWPT)technology.Traditional WPT technology generally transmits power from a single transmitter to a single receiver.However,many application scenarios require power supply to multiple loads at the same time while maintaining a stable voltage.Therefore,in this paper,a low-profile dynamic multi-load constant-voltage output wireless power transmission system is proposed.The system can supply power to multiple receivers over long distances.The output voltage at both ends of the receiving coil does not change with the change of the receiver resistance,and it has loadindependent constant voltage output characteristics.When one or more receivers are inserted or removed from the system,it does not affect other receivers and has high degrees of freedom and segmental expansion characteristics.The main research content is as follows:(1)The following is a brief explanation of three common WPT technologies and the principle and model of MCR-WPT technology.Then,formula derivation for maximum transmission efficiency and maximum output power transmission efficiency is carried out.Finally,an analysis is done on how mutual inductance and coupling coefficient affect system transmission efficiency.(2)Using Kirchhoff’s theoretical knowledge,calculate the normalized circuit model of the three-load structure of the system,and use Mathematica calculation software,K change theory knowledge and ADS simulation software to analyze the load-independent constant voltage output characteristics and the removal of the receiving coil Feasibility and feasibility of adding multiple receiving coils above the relay coil for theoretical analysis and simulation verification.Finally,considering the impact of the external environment and the loss between coils on the system,a load dynamic range is proposed.(3)An experimental platform with two and three receivers was built.The measurement results obtained are basically consistent with theoretical analysis,which verifies the dynamic load constant voltage output characteristics of the system.By placing ferrite plates on the upper and lower sides of adjacent coplanar coils,the main coupling coefficient of adjacent coils is much larger than the cross-coupling coefficient of non-adjacent coils,thereby improving the Power Transmission Efficiency(PTE)of the system.the maximum measured PTE of two and three receivers reached 94.1% and90.3% respectively.