Resonant Coupling Wireless Power Transfer Research Articles

A Planar Magnetically Coupled Resonant Wireless Power Transfer System Using Printed Spiral Coils

A fully planar wireless power transfer (WPT) system via strongly coupled magnetic resonances is presented. In it, both the transmitter and the receiver are planarized with the use of coplanar printed spiral coils (PSCs) and a printed loop. An equivalent circuit model of the proposed planar WPT system is derived to facilitate the design, and a flowchart is provided for the optimization of the system with given size constraints. To realize high peak power transfer efficiency, the quality factor of individual loop or resonator, the mutual coupling between resonators, and the frequency splitting phenomenon of the system are analyzed in addition to the effect of the input impedance of the system on the transmission efficiency. Furthermore, parallel current paths are created by applying auxiliary strips to the backside of the substrates and connecting to the prime resonators using vias to decrease the resistance and to increase the quality factor of the PSC resonators, and this in turn further improves the transfer efficiency of the proposed planar WPT system. The measured results show that the proposed WPT system is able to provide a stable wireless power transfer with up to 81.68% efficiency at a distance of 10 cm. The planar structure and the high transfer efficiency make the proposed design a suitable candidate for wireless power transfer of small portable electronic devices.

Modeling and Analysis of Magnetic Resonance Coupled Wireless Power Transfer Systems

Magnetic resonance coupling (MRC) is a practical high efficient method for midrange wireless power transfer (WPT). In a MRC-WPT system, when the gap between transmitter (Tx) and receiver (Rx) is shorter than the critical coupling distance, the strong coupling will result in two natural resonance frequencies (frequency splitting). When increasing the gap between Tx and Rx, the coupling becomes weaker, and the split resonance frequencies become closer to each other and eventually merge into a single natural resonance frequency. As long as frequency splitting exists, a near to constant maximum power transmission efficiency can be maintained. In this paper, commonly used four-loop and two-loop WPT system configurations are analyzed and compared based on the simplified circuit model. An example symmetrical system simulation shows that with the same Tx, Rx, source and load, the four-loop system has longer transmission distance with relatively lower efficiency compare to the two-loop system. A 3-D physical model of 5-turn, 400mm outer diameter spiral shape four-loop WPT system is designed and simulated by using ANSYS® HFSS®. Operation distance of 550mm with nearly constant maximum transmission efficiency of 92.3% is achieved.

A Novel Optimization Means of Transfer Efficiency for Resonance Coupled Wireless Power Transfer

When the transmitting and receiving coils are equivalent with or not significantly smaller than their separation distance between the two coils, the results of numerical simulations for transfer efficiency of system show that the maximum coupling of two coils or maximum transfer efficiency occur with a certain tilt angle between two coils, which means the two coils with parallel on the same axis is not able to obtain the maximum transmission efficiency. In view of this feature of the wireless power transfer system, we propose a novel means to optimize the transfer efficiency by designing rotatable transmitting coils to achieve the appropriate tile angle. The experimental results show that the presented means is efficient and greatly improves the transfer efficiency. DOI: http://dx.doi.org/10.11591/telkomnika.v11i5.2512 Full Text: PDF

An Investigation on Self-Resonant and Capacitor-Loaded Helical Antennas for Coupled-Resonant Wireless Power Transfer

An Investigation on Self-Resonant and Capacitor-Loaded Helical Antennas for Coupled-Resonant Wireless Power Transfer

Simple efficient resonant coupling wireless power transfer system operating at varying distances between antennas

We found the optimal conditions for an efficient wireless power transfer system (WPTS).In addition, we found that a class-D power amplifier (PA) has an advantage as a source when the input resistance changes with the position of the receiving antenna. Finally, the proposed WPTS was verified through the experimental results. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 54:, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27062

Frequency Splitting and Distance Boundary Condition in Magnetic Resonance Coupled Wireless Power Transfer System

In this paper, a magnetic resonance coupled wireless power transfer system(MRCWPTS) with series capacitor compensation is studied in order to investigate resonance frequency, and then the system transfer model is presented. Research results show that system resonance frequency is likely to occur splitting and maybe appear two or three resonance frequencies(odd /even mode resonance frequency and nature resonance frequency) in close distance under small load, which increases the system instable, and makes the system difficult to control in resonance frequency. By analyzing of the system, the distance boundary condition when resonance frequency splitting is given, under this boundary the system avoid resonance frequency splitting well, then simulation and experiment results verify the theoretical analysis.

Numerical Analysis on Transmission Efficiency of Evanescent Resonant Coupling Wireless Power Transfer System

A practical wireless power transmission system consisting of a large rectangular wire loop and a small square wire loop with a parasitic square helical coil is proposed for use as an efficient evanescent resonant coupling wireless power transmission system in an indoor environment. In addition, a full wave-based numerical analysis on the resonant frequency of and the power transmission efficiency of wireless power transmission system are performed in this paper. The effects of the following on power transmission efficiency and the resonant frequency are numerically investigated: The load of the receiving element and the presence of non-resonant objects such as a conducting box or human body. The numerical results show that a power transmission efficiency of nearly 50% can be achieved when the proposed system is used to charge only one user with the optimized load. The results also show that power transmission efficiency is reduced significantly when a human body is in very close proximity to the receiving element. This reduction in efficiency can be alleviated significantly, however, if the relative distance between the receiving element and the human body is greater than 0.5 m or 0.03? at a resonant frequency of 19.22 MHz.