scholarly journals Reduction of Human Interaction with Wireless Power Transfer System Using Shielded Loop Coil

Electronics ◽  
2020 ◽  
Vol 9 (6) ◽  
pp. 953
Author(s):  
Akihiko Kumazawa ◽  
Yinliang Diao ◽  
Akimasa Hirata ◽  
Hiroshi Hirayama
Keyword(s):  
Equivalent Circuit ◽  
Human Body ◽  
Impedance Matching ◽  
Wireless Power Transfer ◽  
Transmission Efficiency ◽  
Human Interaction ◽  
Power Transfer ◽  
Wireless Power ◽  
Equivalent Circuit Analysis ◽  
Loop Coil

The impedance variation of wireless power transfer (WPT) coils owing to the presence of the human body may result in mismatches, resulting in a decrease of the transmission efficiency. In addition, one of the decisive factors of the permissible transfer power in WPT systems is a compliance assessment with the guidelines/standards for human protection from electromagnetic fields. In our previous study, we reported that a shielded loop coil can potentially reduce human interaction with WPT coils. In this study, first, the rationale for this reduction is investigated with equivalent circuit models for a WPT system using a shielded loop coil operated in close proximity to the human body. We then conducted an equivalent circuit analysis considering the capacitance between the inner and outer conductors of the shielded loop coil, suggesting the stability of the impedance matching. From computational results, the mitigation capability of the shielded loop coil on impedance matching and transmission efficiency owing to the presence of the human body was verified for 6.78 MHz wireless power transfer. Additionally, the reduction of the specific absorption rate (SAR) with coils comprised of the shielded loop structure was confirmed in the presence of anatomically realistic human body models. The maximum transferable power was increased from 1.5 kW to 2.1 kW for the restrictions of the local SAR limit prescribed in the international safety guidelines/standard.

Network Analysis and Impedance Matching Methods for Wireless Power Transfer via Coupled Magnetic Resonances

2013 ◽  
Vol 437 ◽  
pp. 301-305 ◽  
Author(s):  
Yan Ting Luo ◽  
Yong Min Yang ◽  
Zhong Sheng Chen
Keyword(s):  
Network Analysis ◽  
Power Transmission ◽  
Impedance Matching ◽  
Wireless Power Transfer ◽  
Transmission Efficiency ◽  
Power Transfer ◽  
Wireless Power ◽  
Matching Method ◽  
Transmission Distance ◽  
Magnetic Resonances

Wireless power transfer (WPT) via coupled magnetic resonances has received much attention owing to its high power transmission efficiency at mid-range distance in recent years. In this paper, a novel network method is used to analyze the WPT system. A two-port network model of the system is built and the ABCD parameters of the model are innovatively used to characterize the system. Then the power transmission efficiency is analyzed at different transmission distance. To improve the power transmission efficiency, an impedance matching method is proposed based on the network analysis of the system. In the end, its feasibility is testified by a case study. The results demonstrate that the maximum power transmission efficiency can be achieved by using the impedance matching method proposed in this paper.

scholarly journals Wireless Power Transfer between Two Self-Resonant Coils over Medium Distance Supporting Optimal Impedance Matching Using Ferrite Core Transformers

Energies ◽  
2021 ◽  
Vol 14 (24) ◽  
pp. 8540
Author(s):  
Jinwook Kim ◽  
Do-Hyeon Kim ◽  
Jieun Kim ◽  
Young-Jin Park
Keyword(s):  
Equivalent Circuit ◽  
Impedance Matching ◽  
Wireless Power Transfer ◽  
Transfer Efficiency ◽  
Q Factor ◽  
Power Transfer ◽  
Wireless Power ◽  
Ferrite Core ◽  
Matching Conditions ◽  
Power Transfer Efficiency

An efficient wireless power transfer (WPT) system is proposed using two self-resonant coils with a high-quality factor (Q-factor) over medium distance via an adaptive impedance matching network using ferrite core transformers. An equivalent circuit of the proposed WPT system is presented, and the system is analyzed based on circuit theory. The design and characterization methods for the transformer are also provided. Using the equivalent circuit, the appropriate relation between turn ratio and optimal impedance matching conditions for maximum power transfer efficiency is derived. The optimal impedance matching conditions for maximum power transfer efficiency according to distance are satisfied simply by changing the turn ratio of the transformers. The proposed WPT system maintains effective power transfer efficiency with little Q-factor degradation because of the ferrite core transformer. The proposed system is verified through experiments at 257 kHz. Two WPT systems with coupling efficiencies higher than 50% at 1 m are made. One uses transformers at both Tx and Rx; the other uses a transformer at Tx only while a low-loss coupling coil is applied at Rx. Using the system with transformers at both Tx and Rx, a wireless power transfer of 100 watts (100-watt light bulb) is achieved.

scholarly journals Impedance matching approach of L-section circuit with ohmic loss in reactive components

2018 ◽  
Vol 5 (1) ◽  
pp. 64-74
Author(s):  
Satoshi Suzuki ◽  
Qiaowei Yuan ◽  
Qiang Chen
Keyword(s):  
Wireless Communication ◽  
Impedance Matching ◽  
Wireless Power Transfer ◽  
Transmission Efficiency ◽  
Ohmic Loss ◽  
Reactive Elements ◽  
Power Transfer ◽  
Wireless Power ◽  
Exact Approach ◽  
Selection Of

Impedance matching is very important to improve transmission efficiency not only for wireless communication but also for wireless power transfer. Lumped reactive elements are usually used in the impedance matching circuit. These reactive components such as inductors and capacitors have ohmic loss. An exact approach to design the lumped matching circuit at the presence of the ohmic loss is derived in this paper. Moreover, the condition for selection of impedance matching topology is deduced not only for lossless case but also for lossy case. Finally, the effect of the ohmic loss in the impedance matching circuit on the transmission efficiency is demonstrated quantitatively.

scholarly journals Dual-Band RF Wireless Power Transfer System with a Shared-Aperture Dual-Band Tx Array Antenna

Energies ◽  
2021 ◽  
Vol 14 (13) ◽  
pp. 3803
Author(s):  
Chan-Mi Song ◽  
Hong-Jun Lim ◽  
Son Trinh-Van ◽  
Kang-Yoon Lee ◽  
Youngoo Yang ◽  
...  
Keyword(s):  
Wireless Power Transfer ◽  
Transmission Efficiency ◽  
Array Antenna ◽  
Dual Band ◽  
Single Frequency ◽  
Power Transfer ◽  
Wireless Power ◽  
Beam Focusing ◽  
Received Power ◽  
Rf Wireless

In this paper, a dual-band RF wireless power transfer (WPT) system with a shared-aperture dual-band Tx array antenna for 2.4 and 5.8 GHz is proposed. The final configuration of the Tx array, which is made up of 2.4 GHz right-handed circular polarization (RHCP) patches and 5.8 GHz RHCP patches, is derived from the optimization of 2.4 and 5.8 GHz thinned arrays, ultimately to achieve high transmission efficiency for various WPT scenarios. The dual-band RF WPT Tx system including the Tx array antenna and a Tx module is implemented, and Rx antennas with a 2.4 GHz patch, a 5.8 GHz patch, and a dual-band (2.4 and 5.8 GHz) patch are developed. To validate the proposed dual-band RF WPT system, WPT experiments using a single band and dual bands were conducted. When transmitting RF wireless power on a single frequency (either 2.482 GHz or 5.73 GHz), the received power according to the distance between the Tx and Rx and the position of the Rx was measured. When the distance was varied from 1 m to 3.9 m and the transmitted power was 40 dBm, the received power value at 2.482 GHz and 5.73 GHz were measured and found to be 24.75–13.5 dBm (WPT efficiency = 2.985–0.224%) and 19.25–6.8 dBm (WPT efficiency = 0.841–0.050%), respectively. The measured results were in good agreement with the calculated results, and it is revealed that the transmission efficiency when wireless power is transmitted via beam-focusing increases more than that with conventional beam-forming. Furthermore, the dual-band WPT experiment proves that 2.482 GHz beam and 5.73 GHz beams can be formed individually and that their wireless power can be transmitted to a dual-band Rx or two different Rx.

scholarly journals Novel Resonance-Based Wireless Power Transfer Using Mixed Coupling

Sensors ◽  
2020 ◽  
Vol 20 (24) ◽  
pp. 7277
Author(s):  
SangWook Park ◽  
Seungyoung Ahn
Keyword(s):  
Equivalent Circuit ◽  
Equivalent Circuit Model ◽  
Wireless Power Transfer ◽  
Decomposition Technique ◽  
Power Transfer ◽  
Wireless Power ◽  
Simple Circuit ◽  
Mode Decomposition ◽  
Frequency Split ◽  
Magnetic Couplings

This study presents an equivalent circuit model for the analysis of wireless power transfer (WPT) through both electric and magnetic couplings using merely a resonant coupler. Moreover, the frequency split phenomenon, which occurs when transmitting couplers are near receiving couplers, is explained. This phenomenon was analyzed using simple circuit models derived via a mode decomposition technique. To verify the proposed method, a resonant coupler using mixed coupling was designed and its efficiency was compared with the result obtained using a commercial electromagnetic solver. The results of this study are expected to aid in designing various WPT couplers or sensor antennas by selecting electric, magnetic, or mixed couplings. Furthermore, the results of this study are expected to be applied to technologies that sense objects, or simultaneously transmit and receive information and power wirelessly.

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