A Coplanar Wireless Power Transfer Chain Network System For Multiple Loads With Load-Independent Current Output

Among various wireless power transfer(WPT)technologies,magnetic coupled resonant wireless power transfer(MCR-WPT)technology is widely favored by researchers because of it is advantages such as moderate transmission distance,high efficiency,low radiation and high tolerance of coil relative position.In order to solve the problem that the coaxial system is too large,a coplanar MCR-WPT system is proposed in this paper,which makes it easier to install the coils on the desktop,floor,wall and other objects.However,the weak coupling between coplanar coils leads to the low energy transmission efficiency of the system and the very small dynamic range of the driving load.By adding ferrite blocks with low profile,high permeability and low loss at the junction of adjacent coplanar coils,the coupling of adjacent coils is significantly enhanced,while the cross coupling of non-adjacent coils has no obvious effect,thus significantly improving the energy transmission efficiency of the system.This paper mainly studies the multi-output current load-independent coplanar MCRWPT system.The research contents are as follows:(1)Introducing the important parameters,theoretical analysis methods and design criteria of WPT system by taking the series-series basic structure as an example.(2)Finding the reason for the weak coupling of coplanar structure by comparing the coupling strength between coaxial structure and coplanar structure.Scanning the coupling coefficient parameters of planar MCR-WPT system under single-layer and double-layer ferrite structures with different numbers and lengths by Maxwell 3D.Analyzing the influence of different coupling coefficients and quality factors on the power transmission capacity of the system by Mathematica to determine the optimal number and length of ferrite blocks.(3)Based on circuit theory and filter theory,Proving the load-independent current output characteristics of the system by using direct solution and equivalent circuit transformation respectively.However,the loss resistance of devices such as coils and capacitors are inevitable in practical applications.In order to ensure the better constant current output characteristics of the system,a mathematical formula for estimating the dynamic range of the load is proposed and verified by frequency domain circuit simulation using ADS.(4)Building two-load and three-load experiment platforms.Through the analysis of the experimental results,it is proved that the ferrite structure used in the coplanar MCR-WPT system can enhance the coupling between adjacent coils and improve the transmission efficiency of the system.It also proves that the system has better constant current output characteristics independent of no load within the estimated dynamic load range.