• 한국전기전자재료학회논문지
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• 제36권5호
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• pp.494-499
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• 2023

In this paper, in order to apply the CF (color filter) type of the micro light emitting device (Micro LED) display method, a study on the manufacturing process of red and green phosphor inks for the inkjet process was conducted. The blue light-emitting KSF and LuAG phosphors were respectively used to control the phosphor particle size to about 1㎛, and a phosphor ink was prepared by synthesizing with a low-viscosity solution (IPA/Eg). A chemical dispersion method was applied to selectively control the dispersion characteristics in the manufacture of phosphor inks, and in particular, phosphor inks with a dispersant applied a dispersant secured stable dispersion characteristic compared to phosphor inks without a dispersion process. Therefore, it seems possible to manufacture CF for Micro LED through an inkjet process capable of controlling the dispersion characteristics of phosphor ink.

• 전력전자학회논문지
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• 제19권4호
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• pp.327-331
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• 2014

LED(Light Emitting Diode) is a semiconductor device utilizing electroluminescent effect is a phenomenon in which a type of P-N junction diode, the light of short wavelength which a voltage is applied in the forward direction is released. LED is advantageous in reducing the energy as environmentally materials that can greatly reduce the carbon emissions, recent it has attracted attention IT(Information Technology) and GT(Green Technology) industry. In addition, there are advantages long life, high efficiency, and excellent response speed, LED have come into the spotlight as the illumination means to replace the existing fluorescent light and incandescent light bulb. When connecting to MR16 electronic transformer for existing LED driver circuit, due to malfunction of the dimmer and the electronic transformer, flicker occurs and linear dimming is not possible. Therefore, in this paper, we suggest an LED drive circuit there is no flicker with the corresponding dimming MR16 electronic transformer. Further, we explain the principles of the LED current control technique and the principle of the drive circuit of the LED, in order to validate the proposed circuit through prototyping and simulation.

• 한국재료학회지
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• 제21권5호
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• pp.273-276
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• 2011

Ultraviolet (UV) light emitting diodes (LEDs) were grown on a patterned n-type GaN substrate (PNS) with 200 nm silicon-di-oxide (SiO2) nano pattern diameter to improve the light output efficiency of the diodes. Wet etched self assembled indium tin oxide (ITO) nano clusters serve as a dry etching mask for converting the SiO2 layer grown on the n-GaN template into SiO2 nano patterns by inductively coupled plasma etching. PNS is obtained by n-GaN regrowth on the SiO2 nano patterns and UV-LEDs were fabricated using PNS as a template. Two UV-LEDs, a reference LED without PNS and a 200 nm PNS UV-LEDs were fabricated. Scanning Electron microscopy (SEM), Transmission Electron Microscopy (TEM), X-Ray Diffraction (XRD), Photoluminescence (PL) and Light output intensity- Input current- Voltage (L-I-V) characteristics were used to evaluate the ITO-$SiO_2$ nanopattern surface morphology, threading dislocation propagation, PNS crystalline property, PNS optical property and UVLED device performance respectively. The light out put intensity was enhanced by 1.6times@100mA for the LED grown on PNS compared to the reference LED with out PNS.

• Journal of Electrical Engineering and Technology
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• 제10권1호
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• pp.436-442
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• 2015

In this paper, we develop an indoor localization device which embeds localization information into indoor light-emitting-diodes (LED) lighting systems. The key idea of our device is the use of the newly proposed "bit stuffing method". Through the use of stuff bits, our device is able to measure signal strengths even in transient states, which prohibits interference between lighting signals. The stuff bits also scatter the parts of the signal where the LED is turned on, thus provides quality indoor lighting. Additionally, for the indoor localization system based on RSSI and TDM to be practical, we propose methods for the control of LED lamps and compensation of received signals. The effectiveness of the proposed scheme is validated through experiments with a low-cost implementation including an indoor navigation task.

• 센서학회지
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• 제32권6호
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• pp.441-446
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• 2023

Electrical and optical characteristics of the GaN-based light-emitting diode (LED) with the improved multi-quantum well (MQW) structure have been studied for light source in bio-sensing systems. Novel GaN/In_0.1GaN/In_0.2GaN/In_0.1GaN/GaN and Al_0.1GaN/GaN/In_0.2GaN/GaN/Al_0.1GaN (MQW) structures were suggested, and their radiative recombination rate, light output power, electroluminescence, and external quantum efficiency were compared with those of the conventional GaN/In_0.2GaN/GaN MQW structure using device simulation. The LED with the GaN/In_0.1GaN/In_0.2GaN/In_0.1GaN/GaN MQW structure showed an excellent recombination rate of 5.57 × 10²⁸ cm^-3·s^-1 that was more than one order improvement over that of the conventional LED. In addition, the efficiency droop was relieved by the suggested stepped MQW structure.

• 산업융합연구
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• 제17권4호
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• pp.125-129
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• 2019

자전거를 이용하는 사람들의 수가 증가함에 따라 자전거 사고의 수도 증가하고 있습니다. LED 조명을 사용하면 자전거를 탈 때 자전거 사고를 최대 11 % ~ 44 %까지 줄일 수 있습니다. 자전거의 헤드라이트는 자전거 라이더의 반대쪽에 노출 효과를, 미등은 후면 자전거 라이더에 노출 효과를 제공하여 안전성을 향상시킵니다. 본 연구에서는 제어 버튼 신호에 응답하여 LED에 의한 방향 전환을 표시 할 수 있는 자전거 안전장치를 구현 하였다. 이 신호는 고정 된 시간 동안 자전거의 페달과 휠에 장착 된 LED 조명을 모듈 유형의 발광 또는 깜박임으로 만듭니다. 야간에 자전거를 타는 사람이 자전거를 타는 경우 LED를 사용하여 안전을 향상시킬 수 있는 페달의 자전거 보조 장치가 본 연구에서 개발되었습니다. 무선 통신 기술을 적용한 자전거 안전장치는 미래에 에너지, 환경 및 안전과 같은 사회적 문제를 해결하기 위한 대체 기술이 될 것으로 예상됩니다.

• Journal of Information Display
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• 제13권1호
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• pp.1-6
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• 2012

Decreasing the thermal resistance is the critical issue for high-brightness light-emitting diodes. In this paper, the effects of some design factors, such as chip size (24 and 35 mil), substrate material (AlN and high-temperature co-fired ceramic), and die-attach material (Ag epoxy and PbSn solder), on the thermal-dissipation characteristics were investigated. Using the thermal transient method, the temperature sensitivity parameter, $R_{th}$ (thermal resistance), and junction temperature were estimated. The 35-mil chip showed better thermal dissipation, leading to lower thermal resistance and lower junction temperature, owing to its smaller heat source density compared with that of the 24-mil chip. By adopting an AlN substrate and a PbSn solder, which have higher thermal conductivity, the thermal resistance of the 24-mil chip can be decreased and can be made the same as that of the 35-mil chip.

• 방송공학회논문지
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• 제15권1호
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• pp.76-88
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• 2010

최근 LED(Light Emitting Diode) 영상표시장치가 방송제작에 사용되고 있으나, 조명과 LED 영상표시장치 간의 상관관계가 정량적으로 분석되지 못해 HD방송의 영상품질 향상을 위해 사용되는 LED 영상표시장치의 효과를 제대로 구현하지 못하고 있다. 따라서 본 논문에서는 조명과 LED 배경화면의 명암비가 피사체에 미치는 명암 및 색채 변화를 실제 방송에서 사용되는 장비들을 이용한 실험을 통해 분석하여, LED 배경화면 명암비와 영상품질의 상관성을 정량적으로 나타냈다. 실험결과 LED 배경화면의 밝기를 6%로 할 경우, 피사체에 20[IRE] 정도의 영향을 미치면서 최적의 영상품질을 구현할 수 있었고, 밝은 LED 배경화면은 영상 명암에 왜곡현상을, 어두운 LED 배경화면은 영상 색에 왜곡현상을 발생시켰다.

• 전자공학회논문지 IE
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• 제48권2호
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• pp.12-18
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• 2011

본 논문은 조명용 LED 모듈과 히트싱크 장치의 방열 특성을 확인하기 위한 수치 시뮬레이션을 하였다. 해석 케이스는 200 W급의 가로등 또는 보안등용 조명장치이며 용도에 따라 장치의 자세가 달라짐을 고려하여 발광면이 정상부를 향하는 경우와 정하부를 향하는 경우로 나누어서 해석이 진행되었고, 또한 발열소자의 체적이 큰 경우와 작은 경우로 나누어 해석하였다. 해석 결과 현재의 히트싱크 형상으로 충분히 LED의 발열량을 외부로 배출시킬 수 있음을 확인하였고, 장치의 자세와 발열소자의 크기에 따라 방열 성능의 차이가 나타남을 조사하였다.

• Medical Lasers
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• 제10권2호
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• pp.96-105
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• 2021

Background and Objectives Skin aging is reportedly associated with regulation in collagen and elastin synthesis. This study investigated the potential of combining light-emitting diode (LED) treatments using a 630-nm and 850-nm LED with simultaneous microcurrent application. Materials and Methods The dorsal skin of female pigs was treated with a home-use device. We examined the treatment effects using photography, thermocamera, microscopic pathology, and histological examination to determine the mechanism of action, efficacy, and safety of the procedure. A histological observation was performed using hematoxylin and eosin, Masson's trichrome, Victoria blue, and immunohistochemical staining. We also used the Sircol soluble collagen and elastin assay kit to measure the amounts of collagen and elastin in the porcine back skin tissue after 2 and 6 weeks. Results Evaluation by visual inspection and devices showed no skin damage or heat-induced injury at the treatment site. Histological staining revealed that accurate treatment of the targeted dermis layer effectively enhanced collagen and elastin deposition. Collagen type I, a protein defined by immunohistochemical staining, was overexpressed in the early stages of weeks 2 and 6. Combined therapy findings showed the superior capability of the 630-nm and 850-nm LED procedures to induce collagen; in contrast, elastin induction was more pronounced after microcurrent treatments. Conclusion The home-use LED device, comprising a combination of 630-nm and 850-nm LEDs and microcurrent, is safe and can be used as an adjunctive treatment for self-administered facial rejuvenation.