• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.9B
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• pp.1108-1116
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• 2011

The visible light communication system that transmits data by controlling light emission of LED and receives data through photo detecter is considered as one of the strong candidates of the next generation wireless communication systems. The visible light communication provides both lighting and wireless communication wherever the LED lamps are installed. Due to the feature of visible light communication system, the communication is possible within the area that LED light reaches, and the communication quality depends on the light intensity received at the receiver. In this paper, we analyze the effects of LED panel position and lighting angel on communication channel quality in visible light communication systems. Through computer simulations, we prove that position of LED panel and light angle have a great impact on illuminance and SNR of the visible light communication systems.

• Journal of Power Electronics
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• v.16 no.4
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• pp.1268-1276
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• 2016

A triode for alternating current (TRIAC) dimming light emitting diode (LED) driver, which adopts a variable switched capacitor for LED dimming and LED power regulation, is proposed in this paper. The proposed LED driver is power efficient, reliable, and long lasting because of the TRIAC switch that serves as its main switch. Similar to previous TRIAC dimmers for lamps, turn-on timing of a TRIAC switch can be controlled by a volume resistor, which modulates the equivalent capacitance of the proposed variable switched capacitor. Thus, LED power regulation against source voltage variation and LED dimming control can be achieved by the proposed LED driver while meeting the global standards for power factor (PF) and total harmonic distortion (THD). The long life and high power efficiency of the proposed LED driver make it appropriate for industrial lighting applications, such as those for streets, factories, parking garages, and emergency stairs. The detailed analysis of the proposed LED driver and its design procedure are presented in this paper. A prototype of 80 W was fabricated and verified by experiments, which showed that the efficiency, PF, and THD at V_s = 220 V are 93.8%, 0.95, and 22.5%, respectively; 65 W of LED dimming control was achieved with the volume resistor, and the LED power variation was well mitigated below 3.75% for 190 V < V_s < 250 V.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.58 no.3
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• pp.357-361
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• 2009

This study performed analysis on the thermal pattern and current characteristics of an LED ((Light Emitting Diode) street lamp. It did this using a TVS (Thermal Video System) to analyze the LED street lamp's thermal pattern, and measured its characteristics using an oscilloscope. The ambient temperature and humidity during the experiment were maintained at $24{\pm}2[^{\circ}C]$ and 50~60[%]. The capacity of the LED street lamp was 120[W] and nine sets of modules were arranged at uniform intervals. On one module, 24 LED lamps were arranged in a radial pattern. The analysis of the thermal diffusion pattern at the front of the LED lamp showed that the maximum surface temperature was approximately $34[^{\circ}C]$. In addition, there was almost no change in the temperature of the upper cover, and the temperature at the side showed a uniform thermal diffusion pattern. The surface temperature of the converter converting AC to DC increased to approximately $46[^{\circ}C]$. The analysis results of the thermal characteristics of one LED indicated uniform thermal characteristics for an initial eight minutes. However, the temperature at the center of the LED increased to approximately $82[^{\circ}C]$ after 12 minutes had elapsed. It can be seen from this that the temperature at the center of the LED was higher than the allowable temperature, $70[^{\circ}C]$ of the insulating material for general electrical devices. Therefore, it is necessary to design a lamp in such a way that the plastic insulating material does not come into contact with or get close to the LED lamp. The voltage of the LED lamp converted by the AC/DC converter was measured at DC 27[V] and the current was DC 13[A]. Consequently, it can be seen that in order to secure an adequate light source, it is important to supply a stable current that was greater than the current of other light sources. Therefore, appropriate radiation of heat is required to secure the stability and reliability of the system.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.46 no.4
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• pp.503-508
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• 2010

Common LED (Light Emitting Diode) lamp has many advantages to compare with fluorescent lamp, long life and no pollution matter like the mercury. The LED lamp is a good light source especially for shipboard lighting because of its compact structure which prevents explosion and shock. Also, low maintenance cost is expected due to its longer life time in comparison with conventional lamps. The LED lamp, however, need some estimates that change of voltage and frequency, vibration, moisture on board to definite accommodation of the LED lamp to shipboard. The purpose of this study is to compare physical properties of a fluorescent lamp with one of the common LED lamp so as to analyze accommodation of common LED lamp on board. This study was carried out in two stages. First, temperature, humidity of illumination, voltage, electric current, frequency and electric power were measured by using experimental equipments. Second, a comparative analysis of consumption electric power, annual oil charge, annual CO2 emission and lamp life time, etc of the fluorescent lamp and common LED one was made. As a result of the study, the consumption electric power of fluorescent lamp was 50% higher than one of the common LED lamp. As a result of measuring life time, it was found that life time of common LED lamp was more about 3.5 fold than one of the fluorescent lamp. Considering these results, it's thought that common LED lamp is verified that energy saving is possible and using is possible as substitute for fluorescent lamp on board.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2004.05a
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• pp.171-174
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• 2004

Concerning Korean energy consumption, 20% of the total electrical energy (96% is now exported) is consumed in lighting area. Accordingly, it is one of the most important governmental policies to efficiently utilize electricity due to development and application of high-efficiency lighting equipment. In Korea, widely-built traffic signals employ an incandescent and are of 100W/300 mm, and 280,080set/801,932lamps have been installed and operated by 1999. Of them, 58%(161,181set), 25%(69,655set) and 18%(49,244set) correspond to traffic signals, pedestrian signals and other supplementary signals respectively. It was estimated that electrical energy consumed 28MW instantaneously, 245GWH annually. On the other hand, the LED traffic signal is expected to be a future traffic signal since if traffic signals are replaced by LEDs, energy saving effect of 85% and drop of 75% in maintenance fee will be obtained. In this paper, the performance and characteristics of many LED traffic signals made in Korea are summarized in order to reform Korean standard of LED traffic signals.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.30 no.3
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• pp.94-105
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• 2016

The objective of the work was to evaluate the impact of lighting energy to cooling and heating consumption in medium scale office building, when currently installed fluorescent lights were replaced with various LED lighting fixtures. This evaluation comes from an integrated approach combining the proper indoor lighting environment and the thermal aspects of cooling & heating consumption in office building. These simulations were performed by coupling an appropriate luminaire analysis for energy consumption and a dynamic thermal simulation software (TRNSYS). To analyze comparative study of effects on the heating, cooling loads, and energy consumption of an LED lamp application, 2 types of LED lamp with low light power watt(LPW) 24W and high LPW 7.5W and a fluorescent lights(FL) with 37W are used respectively. Integrated building energy consumption decreased up to 3.2% when fluorescent lamps were replaced with LEDs. Thus, the high LPW of LED(7.5W) replaced with the same number of FL shows an effective energy saving and cost- effective luminary.

• Horticultural Science & Technology
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• v.35 no.2
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• pp.178-187
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• 2017

The aim of this study was to investigate the effect of different light sources on the levels of glucosinolates (GSLs) in rocket salad (Eruca sativa L.). The light sources used in the study were: natural light (Control-1 or 2), red light-emitting diodes(LEDs), blue LEDs, mixed red and blue LEDs (R+B LEDs), white LEDs, fluorescent lamps (FL), and fluorescent lamps plus UV-C (FL+UV-C). Two separate experiments were conducted [Experiment I: Control-1, Red LED, Blue LED, Mix (R+B) LED and Experiment II: Control-2, White LED, FL, FL+UV-C] because of the limited number of growth chambers in our laboratory. The rate of increase in the length of rocket salad leaves was the highest under red LEDs and, FL confirming that red LED and, FL affect the growth of rocket salad. We separated and identified seven types of GSLs from the rocket salad:glucoraphanin, diglucothiobeinin, glucoerucin, glucobrassicin, dimeric 4-mercaptobutyl GSL, 4-methoxyglucobrassicin, and gluconasturtiin. The highest total GSL contents in Eexperiment I was found in plants grown under in red LEDs ($4.30{\mu}mol{\cdot}g^{-1}\;dry$ weight, DW), and the lowest under blue LEDs ($0.17{\mu}mol{\cdot}g^{-1}\;DW$). The highest total GSL contents in Experiment II was found in plants grown under FL ($13.45{\mu}mol{\cdot}g^{-1}\;DW$), and the lowest in FL+UV-C ($0.39{\mu}mol{\cdot}g^{-1}\;DW$). Especially in Experiment II, the content of dimeric 4-mercaptobutyl, which has a strong aroma and spicy flavor in rocket salad, was higher under FL and white LEDs than in Control-2, increasing by approximately 14.9 and 3.2-fold respectively. Therefore, light sources such as red LEDs, white LEDs and FL affected the accumulation of GSLs in rocket salad.

• Horticultural Science & Technology
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• v.31 no.1
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• pp.14-23
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• 2013

This study evaluated the influence of light quality and intensity during healing and acclimatization on the $CO_2$ exchange rate, growth, and morphogenesis of grafted pepper (Capsicum annuum L.) transplants, using a system for the continuous measurement of the $CO_2$ exchange rate. C. annuum L. 'Nokkwang' and 'Tantan' were used as scions and rootstocks, respectively. Before grafting, the transplants were grown for four weeks in a growth chamber with artificial light, where the temperature was set at $25/18^{\circ}C$ (light/dark period) and the light period was 14 hours $d^{-1}$. The grafted pepper transplants were then healed and acclimatized under different light quality conditions using fluorescent lamps (control) and red, blue, and red + blue light-emitting diodes (LEDs). All the transplants were irradiated for 12 hours per day, for six days, at a photosynthetic photon flux (PPF) of 50, 100, or 180 ${\mu}mol{\cdot}m^{-2}{\cdot}s^{-1}$. The higher PPF levels increased the $CO_2$ exchange rate during the healing and acclimatization. A smaller increase in the $CO_2$ exchange rates was observed in the transplants under red LEDs. At a PPF of 180 ${\mu}mol{\cdot}m^{-2}{\cdot}s^{-1}$, the $CO_2$ exchange rate of the transplants irradiated with red LEDs was lowest and it was 37% lower than those irradiated with fluorescent lamps. The $CO_2$ exchange rates of transplants irradiated with blue LEDs was the highest and 20% higher than those irradiated under fluorescent lamps. The graft take was not affected by the light quality. The grafted pepper transplants irradiated with red LEDs had a lower SPAD value, leaf dry weight, and dry matter content. The transplants irradiated with blue LEDs had longer shoot length and heavier stem fresh weight than those irradiated with the other treatments. Leaves irradiated with the red LED had the smallest leaf area and showed leaf epinasty. In addition, the palisade and spongy cells of the pepper leaves were dysplastic and exhibited hyperplasia. Grafted pepper transplants treated with red + blue LEDs showed similar growth and morphology to those transplants irradiated with fluorescent lamps. These results suggest that high-quality grafted pepper transplants can be obtained by healing and acclimatization under a combination of blue and red lights at a high PPF level.

• Journal of Korean Society of Forest Science
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• v.95 no.6
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• pp.716-722
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• 2006

Various light sources including LEDs (Light emitting diodes) affecting on shoot growth was examined using in vitro shoots of E. pellita. Generally, it appeared that ventilation treatment was the most important factor affecting on normal shoot growth, irrespective of irradiation sources. Ventilation resulted in better performance of the cultures under 100% blue LED radiation. These include better shoot growth, more number of leaves, more number of internodes, more number of axillary buds, and heavier dry matters. The highest total chlorophyll content was obtained under both cool-white fluorescent lamps and R5B5 (50% red LED + 50% blue LED). The value was $24.5{\mu}g/g$ and $20.1{\mu}g/g$, respectively. In addition, ventilation resulted in higher carotenoid content in all irradiation sources except 100% red LED radiation. In conclusion, shoot growth of E. pellita could be reached maximum by ventilation under R5B5 (50% red LED + 50% blue LED).

• Proceedings of the KIEE Conference
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• 2000.07d
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• pp.3151-3153
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• 2000

현재 국내에서 사용되는 교통신호등용 전구는 전량 해외에서 수입하는 백열전구로써 발열에 의한 낮은 발광 효율과 짧은 수명으로. 전력의 과소비와 과중한 전력요금 부담. 잦은 유지보수로 관리비용의 증가와 교통환경 악화의 원인이 되고 있으며, 국가적으로는 귀중한 에너지의 낭비, 첨두부하 증가에 따른 전력수요관리의 어려움, 발전용 화석연료 사용증가에 따른 환경오염 유발 등의 문제가 발생하고 있다. 그러나 $8{\sim}12$인치의 원형(또는 사각) PCB 기판에 수백개의 고휘도 LED(반도체 발광 다이오드, Light Emitting Diode)와 구동회로로 구성되는 LED 교통신호등은 발열에 의한 열손실이 거의 없고, 특정 파장대의 단색광을 발광하여 착색렌즈 사용에 따른 빛손실이 없어 80% 이상의 대폭적인 에너지 절약이 가능하며. 또한 긴 수명으로 유지보수비용의 절감 및 교통환경개선 효과가 크게 기대되어 미국, 일본 등 고휘도 LEB 기술 선진국을 중심으로 경쟁적으로 LED 신호등 기술개발에 심혈을 기울이고 있으며, 일부 시범 보급중에 있다. 교통신호등은 특성상 국민의 안전과 직결된 사안으로 엄격한 규격으로 제한하고 있다. 그러나 LED 신호등은 발광 원리 및 발광 방식이 기존의 전구식과 달라 현재 규정된 시험방법으로 직접 평가가 불가능하다. 따라서 우리나라의 경우 LED 제조 기술은 세계적인 수준이나 LED 신호등에 대한 기술개발 및 보급은 현실적으로 어려운 실정이다. 본 논문에서는 에너지절약형 우리나라 환경 특성에 적합한 LED 교통 신호등의 규격 제정 및 국내 보급환경 구축을 위해 LED 신호등에 대한 시제품의 특성을 장시간의 옥외 시험을 통해 평가하고자 한다.