• 한국전기전자재료학회논문지
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• 제25권1호
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• pp.53-57
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• 2012

In this paper, by designing 20 W class driving circuit for driving high-power LED (Light Emitting Diode), we are going to comparatively carry out the analysis of characteristics for power circuit according to each design method. In this case, 200 V 60 Hz was performed as input data. The electrical characteristics such as voltage, current and ripple are checked for constant current circuit and constant voltage circuit in the LED module. In addition, as the ripple has an influence on illumination of LED light, low temperature working (-20 [$^{\circ}C$]) and high temperature working(80 [$^{\circ}C$]) are measured to make sure the ripple characteristics in accordance with temperature. In low temperature operation -20 [$^{\circ}C$] measurements, both constant current circuit and constant-voltage circuit were less impacted on input fluctuation, whereas in the high temperature operation 80 [$^{\circ}C$], current voltage in constant voltage circuit was surge after 430 [hour]. Voltage current ripple of constant current circuit was much less than constant voltage circuit, therefore we can show that constant current circuit is more stable.

• Journal of Power Electronics
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• 제17권5호
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• pp.1137-1149
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• 2017

In order to reduce the cost, improve the efficiency and simplify the complicated control of existing isolated LED drivers, an improved boundary conduction mode (BCM) Buck ac-dc light emitting diode (LED) driver with extended output voltage and low total harmonic distortion is proposed. With a coupled inductor winding and a stacked output, its output voltage can be elevated to a much higher value when compared to that of the conventional Buck ac-dc converter, without sacrificing the input harmonics and power factor. Therefore, the proposed Buck LED driver can meet the IEC61000-3-2 (Class C) limitation and has a low THD. The operating principle of the topology and the design methodology of the ac-dc LED driver are presented. A 150 W ac-dc prototype was built in the laboratory and it shows that the input current harmonics meet the lighting standard. In addition, the THD is less than 16% at a typical ac input. The peak efficiency is higher than 96.5% at a full load and a normal input.

• 조명전기설비학회논문지
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• 제26권4호
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• pp.6-13
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• 2012

In this paper, we took an indirect reflectance type that irradiates light from an LED module, which reflects light from a reflector onto the road. This LED pedestrian lighting design produces minimal glare from a relatively simple structure. Using LightTools 7.2, we conducted a study on the varying shape and curvature of the reflector. In order to further investigate this data, we researched the ratio of the DLOR and ULOR, the average illuminance, and the uniformity of the illumination. Based on this research, we selected optimum conditions to realize the actual LED pedestrian lighting using RELUX software. We found the average illuminance value to be 22[1x] and the illuminance uniformity ratio to be 0.23, which met the criteria of the proposed standards set in KS C 7658. In addition, it also satisfied the criteria of the standards set in KS A 3701 by having TI (Threshold Increment) at 7[%].

• 한국통신학회논문지
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• 제39C권3호
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• pp.234-238
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• 2014

Multichip packaging was achieved the best solution to significantly reduce thermal resistance at the same time, to increase luminance intensity in LEDs packaging application. For the packaging, thermal spreading resistance is an important parameter to get influence the total thermal performance of LEDs. In this study, silicon-based multichip light emitting diodes (LEDs) packaged module has been examined for thermal characteristics in several parameters. Compared to the general conventional single LED packaged chip module, multichip LED packaged module has many advantages of low cost, low density, small size, and low thermal resistance. This analyzed module is comprised of multichip LED array, which consists of 32 LED packaged chips with supplement power of 0.2 W at every single chip. To realize the extent of thermal distribution, the computer-aided design model of 6.4 W Si-based multichip LED module was designed and was performed by the simulation basis of actual fabrication flow. The impact of thermal distribution is analyzed in alternative ways both optimizing numbers of fins and the thickness of that heatsink. In addition, a thermal resistance model was designed and derived from analytical theory. The optimum simulation results satisfies the expectations of the design goal and the measurement of IR camera results. tart after striking space key 2 times.

• Journal of Electrical Engineering and Technology
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• 제9권5호
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• pp.1643-1653
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• 2014

This paper presents the design and implementation of a wind-solar hybrid power system for LED street lighting and an isolated power system. The proposed system consists of photovoltaic modules, a wind generator, a storage system (battery), LED lighting, and the controller, which can manage the power and system operation. This controller has the functions of maximum power point tracking (MPPT) for the wind and solar power, effective charging/discharging for the storage system, LED dimming control for saving energy, and remote data logging for monitoring the performance and maintenance. The proposed system was analyzed in regard to the operation status of the hybrid input power and the battery voltage using a PSIM simulation. In addition, the characteristics of the proposed system's output were analyzed through experimental verification. A prototype was also developed which uses 300[W] of wind power, 200[W] of solar power, 60[W] LED lighting, and a 24[V]/80[Ah] battery. The control system principles and design scheme of the hardware and software are presented.

• 한국태양에너지학회 논문집
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• 제31권2호
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• pp.31-36
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• 2011

LED is expected as an environmentally friendly next generation light source with its good reliability and long lifetime. The light sources for illumination have a variety of applications in the indoor and outdoor, and the variation of optical power and color rendering of the light source limits their applications. Therefore, it is necessary to research the LED lamp and its luminaire to minimize the variation of dynamic characteristics and to improve the color rendering due to that illuminating environment. Daylight is very good light source to human and can be used as primary or a secondary light source with benefits of energy, productivity and health.This paper presents the design method of LED lighting system to improve poor property in terms of CR(color redering) characteristic to use daylight effectively.

• 전자공학회논문지
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• 제49권11호
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• pp.193-198
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• 2012

LED를 고효율 및 고수명으로 동작시키기 위해 장착되는 LED 컨버터는 정전압 및 정전류 구동을 함으로서 LED에 제공되는 전력을 일정한 전압과 전류 값으로 유지하여 LED를 동작시키게 한다. 하지만 이러한 LED 컨버터는 LED의 과열로 인해 전압이 떨어지거나 전력 선로의 손상으로 인한 과전압 혹은 회로 이상에 따른 과전압 발생 시에도 여전히 일정 전압 및 전류를 계속 LED에 공급하게 된다. 결국 LED에 과도한 전압이나 전류가 유입되어도 LED는 계속적으로 발광하기에 결국 파손되는 문제가 발생하게 된다. 본 논문에서는 LED의 과열이나 전압강하 등의 이유로 과전류가 발생하면 PWM 회로를 정지시키고 일정 전류 이하에서만 PWM 회로가 동작하도록 하며 PWM 회로에서 과전압이 발생되는 경우 회로의 구동을 일시 정지시켜 LED가 과전류와 과전압에 의해 파손되는 것을 방지하는 피드백 회로를 제안한다.

• 전기학회논문지
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• 제61권4호
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• pp.612-616
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• 2012

This paper presents an active current regulator for LED driver IC. The proposed driver circuit is consists of DC-DC converter for supplying constant DC voltage to LED, active current regulator for compensating channel-to-channel current error from LED strings and feedback circuit for controlling duty ratio of the converter. The proposed active current regulator senses current of LED channels by equalizing both $V_{DS}$ and $V_{GS}$ at LED current control transistor. Because the proposed circuit directly measures the LED channel current without a sensing resistor and regulates all channel with same regulation loop, the power consumption and the current error are much small compared with previous works. The measured maximum efficiency of overall LED driver IC is approximately 94% and current error of LED channel-to-channel is under ${\pm}1.3%$. The proposed LED driver IC is fabricated Dongbu 0.35um BCD process.

• 한국전자통신학회논문지
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• 제17권1호
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• pp.71-76
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• 2022

밝기가 동작 전류에 비례하는 LED 조명은 다수의 LED를 직렬 연결하여 정전류원으로 구동하는 방식을 널리 사용하고 있다. 이러한 방식에서는 일부 LED가 고장으로 개방되면 전류 통로가 끊어져 직렬 연결된 모든 LED가 꺼지게 된다. 본 논문에서는 LED 동작 전압보다 약 0.4V 정도 높은 항복전압을 갖는 제너 다이오드를 개별 LED와 병렬로 연결하여 LED 고장 시 전류 우회로를 확보하므로 이러한 문제점을 해결하는 회로를 설계하였다. 시뮬레이션과 실험을 통해 LED 정상 동작 시에는 제너 다이오드로 전류가 거의 흐리지 않고, LED 고장 시에는 제너 다이오드가 안정적으로 전류 우회로로 동작함을 확인하였다.

• 한국정보통신학회:학술대회논문집
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• 한국해양정보통신학회 2010년도 추계학술대회
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• pp.757-758
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• 2010

진료 및 수술 집도 시 조명용 광원으로 할로겐램프와 플라즈마램프가 주로 사용되고 있다. 두 광원은 램프의 수명 및 과도한 발열로 인한 다양한 문제점을 야기할 뿐 아니라 냉각기로 인하여 부피 또한 매우 크다는 단점이 있다. 따라서 본 연구에서는 의료용 신조명 부품으로 주목받고 있는 고휘도 LED를 사용하여 진료실 및 수술실에서 환자의 환부에 대한 국소 무영 촬영이 가능하도록 링라이트를 설계 개발하였다. 개발에 적용한 LED는 환부 근접 무영 촬영시 피사체 고유의 Tone에 대한 섬세한 표현력과 강한 하이라이트, 간결한 쉐도우, 그리고 입체감을 부각시키기 위하여 다양한 색상 구현과 광량 조절이 가능하고 백색광을 얻을 수 있는 FULL COLOR용 고휘도 3색 LED를 사용하였다.