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Do-Hyun Won

Bio: Do-Hyun Won is an academic researcher from Kookmin University. The author has contributed to research in topics: Impedance matching & Wireless power transfer. The author has an hindex of 3, co-authored 4 publications receiving 34 citations.

Papers
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Proceedings ArticleDOI
04 Jul 2010
TL;DR: In this article, the authors proposed a simple design method of a wireless power transfer system using 13.56MHz loop antennas, where the measurements of coupling coefficients and the equations for equivalent circuit model about loop antennas without the complicated electromagnetic analysis.
Abstract: In this paper, we propose a simple design method of a wireless power transfer system using 13.56MHz loop antennas. This method can simple design a wireless power transfer system by only using the measurements of coupling coefficients and the equations for equivalent circuit model about loop antennas without the complicated electromagnetic analysis. Using the proposed design method, a wireless power transfer system with a pair of loop antennas operating at the frequency of 13.56MHz, which have a dimension of 50×50 cm2, is designed and implemented. The input return loss, coupling coefficient, efficiency, and input impedance variation with respect to the distance between loop antennas were measured. The proposed design method provides good agreements between measured and predicted results. Also, the wireless power transfer system with impedance matching circuits designed by the proposed design method shows two times higher efficiency characteristics than the case with the general 50 Ω impedance matching circuits. Therefore, we verified that our design method could be an effective tool to design a wireless power transfer system.

21 citations

Journal ArticleDOI
TL;DR: In this article, the authors proposed a 13.56 MHz WPT system using loop antennas with tunable impedance matching circuits using varactor diodes, which can compensate the effect of this impedance mismatch.
Abstract: In this paper, we proposed a 13.56 MHz wireless power transfer system using loop antennas with tunable impedance matching circuits. In general, a wireless power transfer system shows an impedance mismatching due to a reflected impedance, because a coupling coefficient is varied with respect to separation distance between two resonating antennas. The proposed system can compensate the effect of this impedance mismatch owing to tunable impedance matching circuits using varactor diodes. Therefore, transmission efficiency is enhanced, moreover, the center frequency of the system is not changed, regardless of separation distance between two antennas. In order to demonstrate the performance of the proposed system, a wireless power transfer system with tunable impedance matching circuits is designed and implemented, which has a pair of loop antennas with a dimension of cm. The input return loss, coupling coefficient, efficiency, and input impedance variation with respect to a distance between loop antennas were measured. From measured results, the proposed system shows enhanced performances than the case of the general fixed impedance matching circuits. Therefore, we verified that the proposed wireless power transfer system using the proposed impedance matching scheme will be able to ensure robust operation even when the separation distance of antennas is varied.

9 citations

Journal ArticleDOI
TL;DR: In this article, a wireless power transfer system with a pair of loop antennas operating at the frequency of 13.56 MHz, which has a dimension of, is designed and implemented.
Abstract: In this paper, we propose a new design method to design a wireless power transfer system using loop antennas for consumer electronics. This method can simply design a wireless power transfer system only using measurements of coupling coefficients and simple equations of equivalent circuit model about loop antennas without complicated electromagnetic analysis. Using the proposed design method, a wireless power transfer system with a pair of loop antennas operating at the frequency of 13.56 MHz, which have a dimension of , is designed and implemented. The input return loss, coupling coefficient, efficiency, and input impedance variation with respect to a distance between loop antennas were measured. The proposed design method provides good agreements between measured and predicted results. Also, the wireless power transfer system with impedance matching circuits designed by the proposed design method shows two times higher efficiency characteristics than the case with the general impedance matching circuits. Therefore, we verified that our design method could be an effective tool to design a wireless power transfer system.

5 citations

Journal ArticleDOI
TL;DR: In this article, the authors proposed an adaptive frequency control circuit for power transfer in the short range of the HF-band with a pair of loop antennas with a dimension of 3030.
Abstract: In this paper, we proposed an HF-band wireless power transfer system with adaptive frequency control circuit for efficiency enhancement in a short range. In general, a wireless power transfer system shows an impedance mismatching due to a reflected impedance, because a coupling coefficient is varied with respect to separation distance between two resonating loop antennas. The proposed method can compensate this impedance mismatching by varying input frequency of a voltage-controlled oscillator adaptively with respect to separation distance. Therefore, transmission efficiency is enhanced in a short distance, where large impedance mismatch occurs. The adaptive frequency circuit consists of a directional coupler, a detector, and a loop filter. In order to demonstrate the performance of the proposed system, a wireless power transfer system with adaptive frequency control circuits is designed and implemented, which has a pair of loop antennas with a dimension of 3030 . From measured results, the proposed system shows enhanced efficiency performance than the case without adaptive frequency control.

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Journal ArticleDOI
TL;DR: A new design approach that uses antiparallel resonant loops for CET systems is presented, which achieves frequency variation that is one-sixth that of conventional unidirectional loops, thus improving the power efficiency to a maximum of 87%.
Abstract: Due to the convenience of using electronic devices, contactless energy transfer (CET) systems have garnered interest in various fields of industry. In this paper, a new design approach that uses antiparallel resonant loops for CET systems is presented. Forward and reverse loops forming an antiparallel resonant structure stabilize the transfer efficiency and therefore prevent it from dramatic distance-related changes, a phenomenon that can occur in CET systems with nonradiative methods (or resonant methods). This paper proposes frequency-insensitive antiparallel resonant loops and the optimal design of these loops for uniform transfer efficiency according to the distance. The proposed technique achieves frequency variation that is one-sixth that of conventional unidirectional loops, thus improving the power efficiency to a maximum of 87%. The improved performance of data transmissions for near-field communication is also verified.

133 citations

Journal ArticleDOI
TL;DR: In this paper, the efiect of impedance mismatch of a HF- band wireless power transfer system is carefully investigated and two compensation methods are suggested to overcome this within a short range, where frequent impedance mismatch can occur.
Abstract: High-frequency (HF) band wireless power transfer systems ofier the promise of cutting the last cord, allowing users to seamlessly recharge mobile devices as easily as wireless communication. Yet there are still many technical issues that need to be overcome. Among them, one of the most di-cult problems is maintaining impedance match over a short range, where the distance between a transmitter and receiver could vary. In this paper, the efiect of impedance mismatch of a HF- band wireless power transfer system is carefully investigated and two compensation methods are suggested to overcome this within a short range, where frequent impedance mismatch can occur. Each method has pros and cons. In order to verify the feasibility of the proposed methods, HF-band wireless power transfer systems, with a pair of rectangular loop resonators, were designed. The e-ciency and input impedance variation were simulated and measured. From these results, proposed methods show enhanced e-ciency performance than a typical wireless power transfer system without any compensation circuits.

59 citations

Proceedings ArticleDOI
10 May 2012
TL;DR: Loosely-coupled (LC) wireless power transfer (WPT) offers unique, next-generation improvements in user experience, and product design and innovation towards the vision of ubiquitous power, and infinite stand-by time for a wide range of consumer electronic devices as mentioned in this paper.
Abstract: Loosely-coupled (LC) wireless power transfer (WPT) offers unique, next-generation improvements in user experience, and product design and innovation towards the vision of ubiquitous power, and infinite stand-by time for a wide range of consumer electronic devices. We outline the vision as it relates to today's mobile, battery-powered, hand-held, consumer electronics devices, and consider the unique capabilities of loosely-coupled (LC) WPT. We then describe the physics of the magnetically coupled resonant coil subsystem, which lies at the heart of LC WPT, discuss approaches and challenges in implementing WPT electronic circuits, and review industry progress towards timely, high-quality WPT technical standards.

49 citations

Journal ArticleDOI
TL;DR: In this paper, the superconducting coil was used to improve the transmission efficiency of the magnetic resonance wireless power transfer (WPT) system, and the analysis of the parameters between the superconductor and normal conductor coils was carried out.
Abstract: After Prof. Marin Soljacic of Massachusetts Institute of Technology proposed the magnetic resonance wireless power transfer (WPT) in 2007, magnetic-resonance-type WPT has been tried to be applied to various charging equipment. The need for research of magnetic resonance WPT technology is increasing owing to the expectation on its application to electric vehicle and electric railway. In this paper, we used the superconducting coil in order to improve the transmission efficiency of the magnetic resonance WPT system. We found that the superconducting coil indicated higher transmission efficiency and $Q$ -factor bigger than that of the normal conductor coil through the analysis of the $S$ -parameters between the superconductor and normal conductor coils. If this research will be continued, it is expected to be applicable to high-power transmission systems.

27 citations

Proceedings ArticleDOI
19 May 2014
TL;DR: The paper discuses an important construction aspects of resonant wireless power transfer (WPT) system for small portable devices and its proper construction shape and theoretical presumptions are verified by detailed measurement.
Abstract: The paper discuses an important construction aspects of resonant wireless power transfer (WPT) system for small portable devices. It focuses mainly on key electrical parameters of the systems resonant linkage and its proper construction shape. All presented theoretical presumptions are consequently verified by detailed measurement.

25 citations