• The Transactions of the Korean Institute of Power Electronics
• /
• v.24 no.2
• /
• pp.78-83
• /
• 2019

In this study, we analyze the structure of the transceiver coil in the inductive power transfer (IPT) system. In the IPT system, the transceiver coil design needs to have the highest magnetic coupling possible because of the relatively low magnetic coupling due to the large gap of distance without the core. The transmitting coil may be formed as a multi-layer type according to the distance between the transmitting and receiving coils if the receiving coil is configured as a multi-layer type on the inner structure of the receiving apparatus, thereby improving the magnetic coupling and system efficiency. We compare and analyze the coil magnetic coupling, and system efficiency according to the layer structure of the transmitting and receiving coils and verify the analysis by JMAG simulation. Experimental results show that the layer structure of the transceiver should be considered according to the inner space of the receiving device and the spacing distance.

• The Transactions of the Korean Institute of Power Electronics
• /
• v.26 no.6
• /
• pp.437-445
• /
• 2021

This paper proposes an operating frequency design method that limits the voltage applied to aload-side converter during the initial operation of a loosely coupled resonant dual-active bridge (LCR-DAB) converter and an initial operating strategy that applies it. The LCR-DAB converter uses two wireless power transfer coils instead of the high-frequency transformer of the general DAB converter. The wireless power coil has a physical distance of several tens of millimeter or more between the two coils; thus, the LCR-DAB converter is a bidirectional isolated power conversion system that can easily achieve high insulation performance. However, for the initial operation of the LCR-DAB, if the power-side converter is operated at the resonance frequency while the load-side converter is not operating, then a very high voltage due to resonance is applied to the load-side converter, thereby causing damage to the converter. Therefore, a method that can stably charge the DC link voltage of the secondary-side converter during the initial operation is needed. This paper proposes a method to initially charge the secondary-side DC link by operating the primary-side converter at a frequency with limited voltage gain rather than at a steady-state operating frequency. The validity of the proposed frequency design method and initial operating sequence is verified through simulation and experimentation of the 1 KW LCR-DAB converter.

• Journal of Advanced Navigation Technology
• /
• v.21 no.6
• /
• pp.614-619
• /
• 2017

In this paper, we optimize the wireless power transmission (WPT) coil, and then compare the EM simulation and measurement using magnetic coupling at 6.78 MHz. As transmission efficiency is affected by various factors such as the shape of the system, the size of the coils, the coil structure is proposed to consist of a helical resonant for transmission and a spiral resonant for reception. The size of the coil and the distance between the coils are determined to minimize the volume problem, and the shape of the coil are confirmed by EM simulation. A WPT system is designed with 860mm diameter top plate and cylindrical structure of column spaced 600mm apart, and the characteristics are simulated and measured. The simulation shows that ${\mid}S_{21}{\mid}$ is -0.53 dB with the efficiency of 88%, and the measurement result is that ${\mid}S_{21}{\mid}$ is -0.71 dB with the efficiency of 85%.

• Proceedings of the KIEE Conference
• /
• 2011.07a
• /
• pp.11-12
• /
• 2011

In electromagnetic coupled resonance(ECR) WPT system, the main key for wireless power transmission is the design method of the ECR coils. The ECR coils is classified to the helical coil(3D) type and the spiral coil(2D) type as a coil structure. The pattern of the spiral coil type has been studied in favor of commercialization. In this paper, the design characteristics of the helical coil and the spiral coil is considered using a Vector Network Analyzer. It is analyzed according to the distance of coupling coefficient between the ECR coils. Also, It is analyzed for the relationships such as the maximum transmission efficiency and the resonant frequency depending on the distance between the coils.

• The Transactions of The Korean Institute of Electrical Engineers
• /
• v.66 no.2
• /
• pp.383-386
• /
• 2017

In this study, we introduce a triple-band flexible implantable antenna that is tuned by using a ground slot in three specific bands, namely Medical Implanted Communication Service (MICS: 402-405 MHz) for telemetry, the midfield band (lower gigahertz: 1.45-1.6 GHz) for Wireless Power Transfer (WPT), and the Industrial, Scientific and Medical band (ISM: 2.4-2.45 GHz) for power conservation. This antenna is wrapped inside a printed 3D capsule prototype to show its applicability in different implantable or ingestible devices. The telemetry performance of the proposed antenna was simulated and measured by using a porcine heart. From the simulation and measurement, we found that use of a ground slot in the implantable antenna can improve the antenna performance and can also reduce the Specific Absorption Rate (SAR).

• Electronics and Telecommunications Trends
• /
• v.34 no.3
• /
• pp.86-92
• /
• 2019

New products and services, such as 5G and wireless power transmission equipment, have recently brought about changes in the field of electromagnetic technology. There is a need for the evaluation and measurement of the health effects of such technology. To address this need, the development of international standards related to human exposure to electromagnetic waves of these new technologies are currently being discussed. This article briefly introduces the International Standard Organization standards for human exposure to electromagnetic waves, and focuses on the major standard trends for SAR measurement techniques that employ vector probes, wireless power transfer, and 5G base station measurement.

• Progress in Superconductivity and Cryogenics
• /
• v.18 no.1
• /
• pp.41-45
• /
• 2016

The technology of supplying the electric power by wireless power transfer (WPT) is expected for the next generation power feeding system since it can supply the power to portable devices without any connectors through large air gap. As such a technology based on strongly coupled electromagnetic resonators is possible to deliver the large power and recharge them seamlessly; it has been considered as a noble option to wireless power charging system in the various power applications. Recently, various HTS wires have now been manufactured for demonstrations of transmission cables, motors, MAGLEV, and other electrical power components. However, since the HTS magnets have a lower index n value intrinsically, they are required to be charged from external power system through leads or internal power system. The portable area is limited as well as the cryogen system is bulkier. Thus, we proposed a novel design of wireless power charging system for superconducting HTS magnet (WPC4SM) based on resonance coupling method. As the novel system makes possible a wireless power charging using copper resonance coupled coils, it enables to portable charging conveniently in the superconducting applications. This paper presented the conceptual design and operating characteristics of WPC4SM using different shapes' copper resonance coil. The proposed system consists of four components; RF generator of 370 kHz, copper resonance coupling coils, impedance matching (IM) subsystem and HTS magnet including rectifier system.

• The Transactions of the Korean Institute of Power Electronics
• /
• v.22 no.5
• /
• pp.423-430
• /
• 2017

This paper proposes a control methodology for a high efficiency operation of an inductive power transfer (IPT) converter by combining full bridge (FB) and half bridge (HB) controls. To apply the proposed control to the IPT converter, the characteristics of each control method are analyzed. By examining the output voltages of the IPT converter and a theoretical loss analysis, the control shifting points between FB and HB controls are evaluated in accordance with the coupling coefficients and the load. Based on the control shifting points, the FB-HB control algorithm is implemented. By applying FB-HB control, high efficiency operation at the light load condition can be achieved.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.26 no.3
• /
• pp.300-304
• /
• 2015

This paper presents an omnidirectionally beam-steerable orthogonal loop resonator for wireless power transfer. The resonator is composed of two orthogonal loops. These connections of two loops and the current direction on the loops are determined by the control of switch. The magnetic field direction is determined by the vector sum of each loop current. The beam is steerable to eight directions by four switch modes. Using the suitable switch mode, the simulation and measurement efficiencies in the whole azimuthal direction are 56.3~60.0 %(deviation 3.7 %) and 41.2~48.7 %(deviation 7.5 %), respectively. The results show a little variation of transmission efficiency in the azimuthal direction.

• Journal of the Institute of Electronics and Information Engineers
• /
• v.51 no.9
• /
• pp.41-45
• /
• 2014

In this paper, a high-efficiency power amplifier is implemented by using a drain bias control circuit operated at low input power for WPT(Wireless Power Transfer). Adaptive bias control circuit was added to high-efficiency class-E amplifier. It was possible to obtain the overall improvement in efficiency by adjusting the drain bias at low input power. The proposed adaptive class-E amplifier is implemented by using the input and output matching network and serial resonant circuit for improvement in efficiency. Drain bias control circuit consists of a directional coupler, power detector, and operational amplifier for adjusting the drain bias according to the input power. The measured results show that output powers of 41.83 dBm were obtained at 13.56 MHz. At this frequency, we have obtained the power added efficiency(PAE) of 85.67 %. It was confirmed increase of PAE of an average of 8 % than the fixed bias from the low input power level of 0 dBm ~ 6 dBm.