• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.24 no.9
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• pp.883-891
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• 2013

In wireless smart phone charging scenario, the transmitter pad is larger than the size of the receiver pad. Thus, it is important to supply a constant power to the receiver regardless of its location. In this paper, we propose a new method to regulate the receiver's power by adjusting a drain bias of class E power amplifier. The proposed LF-band wireless power transfer system is as follows: a buck converter power supply which is controlled by a pulse width modulation(PWM) IC TL494, a class E amplifier using a low cost IRF510 power MOSFET, a transmitter coil whose dimension is $16cm{\times}18cm$, a receiver coil whose dimension is $6cm{\times}8cm$, and a full bridge rectifier using Schottky diodes. A measured performance show a maximum output power of 4 W and system efficiency of 67 % if we fix the bias voltage. If we adjust the bias voltage, the received power can be maintained at a constant power of 2 W regardless of receiver pad location.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.47 no.4
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• pp.31-37
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• 2010

In this paper, highly efficient dual-band class-F power amplifiers(PAs) for cellular and WLAN bands are suggested and implemented. For the first step, single-band class-F amplifiers at 840MHz, 2.4GHz are designed using commercial E-pHEMT FETs. The performance of two single band PAs are as much as 81.2% of efficiency with the output power of 24.4dBm with 840MHz PA and 93.5% of efficiency with 22.4dBm from the 2.4GHz. For the dual-band class-F PA, the harmonic controlling circuit with ideal SPDT switch was suggested. The length of transmission line is variable by a SPDT switch. As a results, the operation in 840MHz showed the peak efficiency of 60.5% with 23.5dBm, while in 2.4GHz mode the efficiency was 50.9% with the output power of 19.62dBm. Besides, it is shown that the harmonic controller of class-F above 2Ghz could be implemented on the low cost FR-4 substrate.

• Journal of Biomedical Engineering Research
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• v.16 no.4
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• pp.447-456
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• 1995

As a part of electro-mechanical totally implantable artificial heart (TIAH) program, a transcut- aneous energy transmission system has been developed. By mutual magnetic induction between the first coil on the skin and the subcutaneously implanted second coil, the system transfers elctrical power through the skin. This research aimed at minimizing the size of the implanted part as well as maximizing the transfer efficiency. Using class I amplifier, we achieved above 75% power transfer efficiency at average 40W power transfer level which is required for normal TIAH operation. In vivo performance of the developed system and bio-compatibility of the material used in Implanted parts were evaluated through animal experiments.

• Proceedings of the KSME Conference
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• 2008.11a
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• pp.1613-1616
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• 2008

A Transcutaneous Energy Transmission System (TET) has been developed for the wireless energy transmission with two magnetically coupled coils. A resonance circuit is used to raise the induced voltage and current of the secondary coil. Its resonance frequency depends on the internal resistance of circuit and the transferred energy. Because the transferred energy usually changes in wide range, the output voltage is unstable and the energy transferring efficiency decrease. A push-pull class E amplifier is usedto generate high frequency AC voltage. To maintain proper resonance frequency, the voltage output of the amplifier was continuously monitored and adjusted to the optimized resonance frequency. Because of its high frequency (370 kHz), a phase lockedloop circuit and a comparator are used to monitor the output waveform. The results of experimentaldata show that the PLL circuit can increase the transmission efficiency and stabilize the output voltage of TET.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.26 no.10B
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• pp.1475-1481
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• 2001

무선 통신을 위한 전력 증폭기를 0.25$\mu\textrm{m}$ CMOS 공정으로 구현하였다. 전력 효율을 증가시키기 위하여 class-E 구조를 사용하여 soft-switching 특성을 활용하였다. Class-E 부하 회로의 DC-feed 인덕터는 유한한 값을 갖도록 하여 RF-choke을 사용하는 경우에 비해 동일한 전력과 공급 전압에 대해 필요로 하는 부하 저항의 크기를 증가시킴으로써 전력 효율을 더욱 증가시킬 수 있었다. 또한 common-gate switching 방법을 사용하여 기존의 switching 방법에 비해 허용되는 공급 전압의 크기를 두배 정도 증가시킬 수 있도록 하였다. 이러한 기법을 사용함으로써 900MHz의 주파수에서 공급 전압이 1.8V일 때 트랜지스터에 아무런 전압 stress를 가하지 않고 0.9W의 전력을 41%의 효율(power added efficiency, PAE)을 가지면서 50Ω 부하에 전달함을 확인하였다.

• Proceedings of the KIPE Conference
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• 2019.07a
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• pp.142-144
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• 2019

Nowadays, multi-MHz wireless power transfer (WPT) system has received a great concern of study due to its desirable characteristics such as user convenience, system compact and better safety as compared to the conventional DC-DC with cord. This paper presents a solution for WPT Lithium Batteries charger with Constant Current (CC) and Constant Voltage (CV) charging process. The proposed system consists of a high frequency class D power amplifier, a pair of PCB coil, transformable high-order resonant network and a full-bridge rectifier. The charger can be implemented CC /CV charging profile thanks to automatic reconfigurable resonant compensator. Therefore, the battery can be fully charged without the help of an additional DC/DC converter. The simulation and 50W-6.78-MHz hardware experimental results are presented to verify the feasibility of the proposed method and to evaluate the performance of the proposed wireless battery charger.

• Proceedings of the KIEE Conference
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• 1995.11a
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• pp.499-501
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• 1995

In this paper, the generation of the intensive ultrasonic waves depend mainly on the energy convention efficiency depending on high frequency oscillation of the generator and the control performance of stable output depending on iode variation. As a result, the ultrasonic generator obtained of 95% differency with 28khz.

• Proceedings of the KIPE Conference
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• 2013.07a
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• pp.173-174
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• 2013

전기장만으로 에너지를 전송하는 전계결합형 비접촉 충전기술은 송수신부를 매개하는 AC링크를 구성하는 전극쌍의 정전용량확보에 한계가 있으므로, 이를 잘 활용하기 위한 송수신회로가 요구된다. 따라서 본 논문에서는 이를 감안하여 전계결합형 에너지전송에 적합한 매칭변압기를 사용한 E급 송수신회로 구조를 제안한다. 제안된 구조에서 AC-링크 캐패시터의 낮은 정전용량을 감안한 최적 설계방식을 제안하고 회로설계에 따른 성능을 모의실험을 통해 예측한다.

• The Journal of the Korea institute of electronic communication sciences
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• v.11 no.10
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• pp.935-940
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• 2016

Recently, wireless power transmission system is gradually extended to technology in various fields such as lighting field, electric vehicles and smartphones wireless charging system. The largest of the two elements for high transmission efficiency of the wireless power transmission system are resonant coils and power amplifiers. In this paper, in order to build a high efficient wireless power transmission system, we introduce the resonance coil manufacturing method and high efficiency power amplifier design method that operates at 6.78MHz.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.26 no.5
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• pp.521-524
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• 2015

This letter presents a selective wireless power transfer architecture using a reconfigurable multi-port amplifier. The proposed wireless power transfer architecture is composed of a phase shifter part controlled by FPGA, two class-E power amplifiers, a four-port power combiner and two coil loads. Depending on the phase control of FPGA, the power ratio of outputs at the two coil loads becomes 1:1, 2:0 and 0:2. The manufactured system has delivered 1W DC power to loads at 125 kHz. The total DC-to-DC conversion efficiency shows more than 40 % including PA efficiency of 79 %.