• KIEAE Journal
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• 제14권6호
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• pp.81-86
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• 2014

In recent years, many researchers have considered the building energy consumption reduction accordingly to deal with abnormal climate changes and greenhouse gas reduction. However, the lighting energy use ratio has increased in spite of the development of the high efficiency lighting device. Therefore, the study aims to produce the LED lighting applications for the effective lighting heat removal by using the heat characteristics of LED lighting and analyzing the heat removal effect. In order to increase radiant heat efficiency, the heat pipe and heat sink was attached on PCB as LED lighting applications. Experiment was conducted to verify the temperature and air velocity of inside duct: thermocouples, anemometer. The heat removal effect of LED lighting applications was measured by observing the temperature of the lighting applications and the change of air velocity in duct. The experiment shows that the temperature change in the duct according to air velocity was $0.9{\sim}5.8^{\circ}C$. It is also concluded that heat removal was calculated from 33 to 81W.

• 기술사
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• 제42권5호
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• pp.41-45
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• 2009

The last century of lighting has been dominated by incandescent, fluorescent and high-intensity discharge(HID)light sources. In the late 1970's, after green LEDs were invented, Dr. Ching Tang at Eastman Kodak discovered that sending an electrical impulse through carbon compound caused such material glow. Present day LED commercial packages have reached 100 lm/W, comparable to the efficacies of fluorescent and certain HID lamps. LED products available today are market as "Green-Industry" but actually low light output compared to typical light sources. The combination of high price and low light output make them a poor replacement for current technology. It is very important to compare new LED products to the most efficient conventional technology that could be used for any specific application. As LED technology advances, costs decrease, and efficiency improves, LEDs will build market share in the general illumination market.

• 청정기술
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• 제20권2호
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• pp.97-102
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• 2014

현재 고효율 백색 발광다이오드(light emitting diode, LED) 구현을 위한 고점도 형광체 토출에 대한 많은 연구가 진행 중이다. 백색 발광다이오드에서 제품성능에 영향을 미칠 수 있어 고점도 형광체의 정량토출은 중요하다. 그러나 기존 연구에서 고점도 형광체 정량토출의 어려움이 있었다. 고점도 형광체의 정량토출을 위해서 본 연구에서는 다양한 점도에서 미세토출이 가능한 정전기력 프린팅 기술을 적용하였다. 전압 변화에 따른 요구 적출형(drop on demand, DOD) 토출 실험을 진행하여 토출 시 노즐의 메니스커스 각도와 토출 도트 직경 사이의 상관관계를 도출하였다. 토출 전압이 증가함에 따라, 토출 메니스커스 각도는 증가하고 토출 도트 직경은 감소하였다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2009년도 춘계학술대회 논문집
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• pp.39-40
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• 2009

This paper presents a white-LED driver IC for a mobile application. It uses a high efficiency current mode boost converter method for a low voltage application. For a LED drive, it provides a PWM(Pulse Width Modulation) and analog dimming function. The device was designed and fabricated using 0.35um BCD process. The evaluated waveforms for an implemented IC show promising results.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1996년도 추계학술대회 논문집
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• pp.274-277
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• 1996

This paper describes the realization of the full-color to the degree of nearest white light by compounding high brightness Red, Green and Blue LEDs with appropriate proportional index. Once these three colors; red, green and blue are mixed, they are genearlly additive mixing and produce white light color contrasted to negative mixing. The luminous efficiency is defined as the product of the efficiency(lm/w), which indicates the degree of perceptual response by the human eye to unit energy(W) of light emitted by an active display devises and as the conversion efficiency of the device from electric power consumed to optical energy produced. We will deduce the each number of LEDs theoretically and design several shapes of LED displays for the full-color. Finally theoretical predictions will be compared with the measured data with different type of display designs.

• Journal of Information Display
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• 제13권2호
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• pp.73-82
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• 2012

In this paper, a light-emitting diode (LED) backlight driver integrated circuit (IC) for medium-sized liquid crystal displays (LCDs) is proposed. In the proposed IC, a linear current regulator with matched internal resistors and an adaptive phase-shifted pulse-width modulation (PWM) dimming controller are also proposed to improve LED current uniformity and reliability. The double feedback loop control boost converter is used to achieve high power efficiency, fast transient characteristic, and high dimming frequency and resolution. The proposed IC was fabricated using the 0.35 ${\mu}m$ bipolar-CMOS-DMOS (BCD) process. The LED current uniformity and LED fault immunity of the proposed IC were verified through experiments. The measured power efficiency was 90%; the measured LED current uniformity, 97%; and the measured rising and falling times of the LED current, 86 and 7 ns, respectively. Due to the fast rising and falling characteristics, the proposed IC operates up to 39 kHz PWM dimming frequency, with an 8-bit dimming resolution. It was verified that the phase difference between the PWM dimming signals is changed adaptively when LED fault occurs. The experiment results showed that the proposed IC meets the requirements for the LED backlight driver IC for medium-sized LCDs.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2010년도 하계학술대회 논문집
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• pp.159-159
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• 2010

We conducted bum-in test by current stress to evaluate acceleration reliability characteristics about p-resistivity influence of GaN-based light-emitting diodes. The LEDs used in this study are the polarization field-induced LED(PF-LED) having low p-resistivity and the highly resistive LED(HR-LED) having high p-resistivity. The result of high stress experiment shows that current crowding phenomenon is occurred from the center of between p-bonding pad and n-bonding pad to either electrodes. In addition, series resistance and optical power decrease dramatically. These results means that the resistance of between p-bonding pad and p-GaN affect reliability. That's why we need to consider the ohmic contact of p-bonding pad when design the high efficiency and high reliability LEDs.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2006년도 춘계학술대회 논문집
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• pp.443-444
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• 2006

The influence of the heat sources on LED junction temperature are Engine room air, Back plate, Electric power device, and so on. LED lamp cooling system is considered to be an important subject fur high light efficiency. Because LED Chip will be problem When LED junction temperature be over $135^{\circ}C$, In this Study, The Looped Heat Pipe System is considered to prevent LED Chip fall. The LHPS is consist of evaporator part, condenser part, heat pipe part. The working fluid of LHPS is HCFC-123. In this study, to prevent LED Chipfall, we study thermal characteristics for Looped Heat Pipe System with LED lamp.

• 반도체디스플레이기술학회지
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• 제18권4호
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• pp.105-109
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• 2019

LED lighting is used as artificial lighting for plant growth because it has high light efficiency and can radiate light of various wavelengths. In this paper, we have developed new structure LED lighting module to improve the performance of LED lighting for plant growth and proposed a lighting control system that can be controlled wirelessly. The proposed LED lighting module was fabricated using optical lens applied to tunnel light and simulated using Relux program. Results of simulation, we confirmed that the light distribution and average illuminance of the proposed lighting were improved. LED lighting control system was developed to wirelessly control R, G, B, W LED lighting according to plant type and growing season. Therefore, it is expected to provide the optimal lighting environment for plant growth and contribute to the improvement of farm productivity and convenience.

• 한국생활과학회지
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• 제19권6호
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• pp.1053-1062
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• 2010

To assist the further development of hight-visibility clothing this study compared the visibility and subjective wear sensation of commercial protective vests with retro-reflecting materials or LEDs. Nine subjects compared high-visibility vests to evaluate how easy they were to see when exposed to the headlight of a car at night, and the subjects assessed the wear sensation of the vests also. The intensity and visibility of five different colored LEDs assembled on the five substrates separately were also evaluated to select the suitable LED color for night protective clothing. The intensity of illumination was measured by an illuminometer, and the visibility was evaluated by 11 participants both in a dark room and in front of a car outdoors at night. Results showed, the most effective LEDs were high intensity LEDs which shift blinking red and white were most effective. However, excessively high intensity of illumination could decrease the working efficiency. In subjective wear evaluation, the most favorable vest had a front opening, were adjustable at the sides, and had an electric power switch on the front of the vest.