• 한국공작기계학회논문집
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• 제16권3호
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• pp.50-55
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• 2007

The purpose of this research is to enhance the luminance of the LED and to improve the implementation of color by mounting an array lens on the LED without special technology in process. The workmanship of key components considering the economical efficiency and the injection molding technology for high quality of the product are essential to achieve it. In this paper, the mold was computer-aided was designed and manufactured by CAM software (NX4) and high speed machining center. the applied final machining conditions were 3,000-5,000mm/min feed speed, 15,000-25,000rpm and ${\Phi}0.3mm$ ball end-mill. And the Flow analysis was performed using the mold flow software(MPI) in order to get uniformity of resin. Injection conditions acquired by the flow analysis and the injection experiment are as follows. The cylinder temperature is $220-260^{\circ}C$, the mold temperature is $70-80^{\circ}C$, the injection time is about 1.2sec, the injection pressure and velocity is each 7.8-14.7Mpa, and the injection velocity is 0.8-1.2m/sec.

• 한국전기전자재료학회논문지
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• 제21권1호
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• pp.68-72
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• 2008

AlGaInP high-brightness LEDs(HB-LEDs) have gained importance a variety of application operating in the red, orange, yellow and yellow-green wavelength. The light generated from inside LED chips should be emitted to the air through the surfaces of the chips. However, because of the differences between the semiconductor and air or epoxy's refractive index, some of the light was blocked so that caused lowering external quantum efficiency. In this study, nano-scale roughness on the top-GaP layer of AlGaInP epitaxial wafer was fabricated to improve' the brightness of AlGaInP LEDs. Nano-scale roughness was made by ICP dry etcher. Our AlGaInP LEDs with nano-scale roughness has higher brightness (about 28.5 %) than standard AlGaInP LEDs.

• Journal of Electrical Engineering and Technology
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• 제11권3호
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• pp.644-652
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• 2016

This paper presents an improved single-stage ac-dc LED-drive flyback converter using the transformer-coupled lossless (TCL) snubber. The proposed converter is derived from the integration of a full-bridge diode rectifier and a conventional flyback converter with a simple TCL snubber. The TCL snubber circuit is composed of only two diodes, a capacitor, and a transformer-coupled auxiliary winding. The TCL snubber limits the surge voltage of the switch and regenerates the energy stored in the leakage inductance of the transformer. Also, the switch of the proposed converter is turned on at a minimum voltage using a formed resonant circuit. Thus, the proposed converter achieves high efficiency. The proposed converter utilizes only one general power factor correction (PFC) control IC as its controller and performs both PFC and output power regulation, simultaneously. Therefore, the proposed converter provides a simple structure and an economic implementation and achieves a high power factor without the need for any separate PFC circuit. In this paper, the operational principle of the proposed converter is explained in detail and the design guideline of the proposed converter is briefly shown. Experimental results for a 40-W prototype are shown to validate the performance of the proposed converter.

• 전기의세계
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• 제21권3호
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• pp.41-47
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• 1972

The requirements of a successful design for single phase induction motors with a high efficiency have, in recent years, led to the use of non-quadrature stator windings motors in which a high starting torque is a prime requisite. The capacitor motor is one of above machines in which various possible forms of asymmetry can be occur. These forms of asymmetry in the stator phase windings, encountered in machine designs, are 1) an asymmetrical disposition in space of their magnetic axes, 2) a difference in their effective number of turns, 3) a difference in the distribution of their coil groups per pole and 4) amounts of capacitance of an auxiary winding. In order to apply the effective performance prediction of these form to motors, mading of lower quality-domestic magnetic materials, the analysis and the experimental investigations of its sample motors are described in this paper. The utility of such a motor is demonstrated and it is shown that the effects- a good efficiency, good power factor and high starting torque-of the motor mechanism with non-quadrature stator phase windings can development disadvantages by using the lower quality-domestis magnetic materials.

• 한국산학기술학회논문지
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• 제21권4호
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• pp.518-524
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• 2020

본 연구에서는 수학영역, 언어영역 및 창의영역에서 학습효과 증진을 위한 교육용 조명체험실의 조명설계를 위한 기초연구를 진행하였다. 조명환경을 직접 체험할 수 있는 공간 내부는 실험자가 자연스럽게 공부할 수 있는 환경으로 설계하였고, 실험 진행 중 설정조명 외의 다른 색의 영향을 최대한 받지 않도록 외부의 빛은 완벽히 차단하였다. LED조명의 색온도와 조도를 변화시키면서 동일한 방식으로 조명변화에 따른 뇌파의 변화를 분석하였다. 이때 사용되어진 뇌파 분석기는 EMOTIV사(社)를 활용하였다. 가변 RGB LED조명에서 색을 변화시키며 상황별에 따른 실험자의 뇌파를 측정하고, 가변 색온도 LED조명에서는 색온도(3000[K], 4500[K]. 6000[K])와 빛의 세기(50%-250[lux], 70%-350[lux], 100%-500[lux])의 값을 변화시키며 상황별에 따른 실험자의 뇌파를 측정하였다. 그결과, 수리영역의 경우 색온도가 높은 경우가 집중도가 좋은 결과를 보였고 6000[K]의 색온도와 350[lux]의 조도인 조명환경에서 집중도가 가장 높은 결과를 얻었다. 언어영역의 경우 4500[K]의 색온도와 500[lux]조도일때 최적조건이고 창의영역의 경우 3000[K]의 색온도와 500[lux]의 조도일 때 최적 조명환경 조건을 얻었다. 감성조명이 가능한 LED조명원을 활용하는 경우 얻어진 색온도와 조도를 기준하여 조명 환경을 설계한다면 언어, 수리, 창의학습시 집중도가 높아짐을 알았다.

• 한국재료학회지
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• 제15권10호
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• pp.626-631
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• 2005

GaN-related compound semiconductors were grown on the corrugated interface substrate using a metalorganic chemical vapor deposition system to increase the optical power of white LEDs. The patterning of substrate for enhancing the extraction efficiency was processed using an inductively coupled plasma reactive ion etching system and the surface morphology of the etched sapphire wafer and that of the non-etched surface were investigated using an atomic force microscope. The structural and optical properties of GaN grown on the corrugated interface substrate were characterized by a high-resolution x-ray diffraction, transmission electron microscopy, atomic force microscope and photoluminescence. The roughness of the etched sapphire wafer was higher than that of the non-etched one. The surface of III-nitride films grown on the hemispherically patterned wafer showed the nano-sized pin-holes that were not grown partially. In this case, the leakage current of the LED chip at the reverse bias was abruptly increased. The reason is that the hemispherically patterned region doesn't have (0001) plane that is favor for GaN growth. The lateral growth of the GaN layer grown on (0001) plane located in between the patterns was enhanced by raising the growth temperature ana lowering the reactor pressure resulting in the smooth surface over the patterned region. The crystal quality of GaN on the patterned substrate was also similar with that of GaN on the conventional substrate and no defect was detected in the interface. The optical power of the LED on the patterned substrate was $14\%$ higher than that on the conventional substrate due to the increased extraction efficiency.

• 한국전기전자재료학회논문지
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• 제26권10호
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• pp.771-777
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• 2013

This paper dealt with the development of a LED floodlight for naval vessels to replace the conventional floodlight using an incandescent and a halogen lamp. We found a technical solution for current problems of conventional lights and also improved optical characteristics by developing a LED floodlight which has a typical long-lived light source with high efficiency. To satisfy the requirements specified in Korea Standard Vessels (KS V), the optical structure was designed with selected LED package and lens. A LED module was composed of 10 LEDs in series for stable luminous output, and an aluminium heat sink was adopted for effective heat-radiation design. The LED floodlight was fabricated as a module type so that it can easily replace the conventional light source. The power consumption of the prototype floodlight was only a tenth of a conventional one with the same optical performance. Also, a test showed the floodlight satisfied the electrical, optical and environmental requirements of the standards.

• 조명전기설비학회논문지
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• 제22권12호
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• pp.1-9
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• 2008

이 논문에서는 100[W]급 Discrete LED 투광기 조명 제품 개발에 관한 것으로, 3[W] RGBA LED를 이용하여 광색 및 색온도 제어가 가능하도록 광학/방열/회로/시스템 설계를 통한 시제품을 제작하였다. 그 결과, 색온도 $2,000{\sim}10,000[K]$ 범위에서 흑체궤적에 정확히 일치하면서 연색지수가 $71{\sim}91$까지 고연색성을 실현하였으며, 동작전압 $90{\sim}250[Vac]$, 효율 87[%], 역률 93이상의 양호한 전기적 특성을 나타냈다. 또한 투광기의 협각/중각/광자 배광을 만족하기 위하여 LED 렌즈를 설계하였으며, 신뢰성 확보 및 주위온도에 따른 광출력 변화를 최소화할 수 있는 방열설계를 실시하였다.

• 한국세라믹학회지
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• 제40권12호
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• pp.1170-1176
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• 2003

진화최적방법을 이용하여 alkali earth borosilicate 계열(Eu, Mg, Ca, Sr, Ba)$_{x}$ $B_{y}$S $i_{z}$ $O_{d}$에 E $u^{3+}$ 를 도핑 하여 고효율 적색 형광체를 합성하였다. 본 연구는 삼원색 백색 LED로의 적용을 목적으로 한다. 진화최적방법은 유전알고리즘과 조합화학을 연계하여, LED형광체 개발을 위해 개발하였다. 유전알고리즘을 조합화학에 접목함으로써 시간과 자원의 낭비 없이 매우 효율적인 형광체 탐색을 꾀할 수 있었다. 실질적인 실험에 앞서 다양한 목적함수를 이용하여 시뮬레이션을 실시하여 본 연구의 타당성을 증명하고 실제 합성한 결과 삼원색 백색 LED용 적색형광체(E $u_{0.14}$M $g_{0.18}$C $a_{0.07}$B $a_{0.12}$ $B_{0.17}$S $i_{0.32}$ $O_{{\delta}}$)를 얻었다.얻었다.다.얻었다.얻었다.다.

• 한국세라믹학회지
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• 제51권6호
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• pp.533-538
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• 2014

Today, silicon and epoxy resin are used as materials of conversion lenses for white LEDs on the basis of their good bonding and transparency in LED packages. But these materials give rise to long-term performance problems such as reaction with water, yellowing transition, and shrinkage by heat. These problems are major factors underlying performance deterioration of LEDs. In this study, in order to address these problems, we fabricated a conversion lenses using glass, which has good chemical durability and is stable to heat. The fabricated conversion lenses were applied to a remote phosphor type. In this experiment, the conversion lens for white LED was coated on a glass substrate by a screen printing method using paste. The thickness of the coated conversion lens was controlled during 2 or 3 iterations of coating. The conversion lens fabricated under high heat treatment temperature and with a thin coating showed higher luminance efficiency and CCT closer to white light than fabricated lenses under low heat treatment temperature or a thick coating. The conversion lens with $32{\mu}m$ coating thickness showed the best optical properties: the measured values of the CCT, CRI, and luminance efficiency were 4468 K, 68, and 142.22 lm/w in 20 wt% glass frit, 80 wt% phosphor with sintering at $800^{\circ}C$.