• Title/Summary/Keyword: High-Power LED

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Effect of the 100Hz PWM Low Power Light Irradiation in Proliferation of NTacSam:SD Bone-marrow Cell (NTacSam:SD 골수 세포의 증식에 100Hz PWM 저출력 광 조사가 미치는 효과)

  • Cheon, Min-Woo;Kim, Seong-Hwan;Lee, Ho-Sic;Park, Yong-Pil
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2008.04b
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    • pp.10-11
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    • 2008
  • We developed the equipment palpating cell proliferation using a high brightness LED. This equipment was fabricated using a micro-controller and a high brightness LED, and designed to enable us to control light irradiation time, intensity, frequency and so on. Especially, to control the light irradiation frequency, FPGA was used, and to control the change of output value, TLC5941 was used. Control stage is divided into 30 levels by program. Consequently, the current value could be controlled by the change of level in Continue Wave(CW) and Pulse Width Modulation(PWM), and the output of a high brightness LED could be controlled stage by stage. And then, each experiment was performed to irradiation group and non-irradiation group for bone marrow cells. MIT assay method was chosen to verify the cell increase of two groups and the effect of irradiation on cell proliferation was examined by measuring 590nm transmittance of ELISA reader. As a result, the cell increase of bone marrow cells was verified in irradiation group as compared to non-irradiation group.

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The Study based on Accelerated Degradation Test of General Lighting 4W LED Lamp using External Converter (조명용 4W 컨버터 외장형 LED램프의 가속열화시험평가)

  • Park, Chang-Kyu;Oh, Geun-Tae
    • Journal of Applied Reliability
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    • v.11 no.3
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    • pp.267-279
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    • 2011
  • LEDs have been used extensively in the mobile device, automobile, and general lighting because they are semi-permanent, long life, less power consumption, reliable and environmentally friendly. In this paper, the accelerated degradation test(ADT) for a general lighting 4W LED Lamp using external converter is considered. The conditions of ADT are high temperature and high humidity. We show that its life time is log-normally distributed with same parameters under both a normal condition and an accelerated condition, and also derive an accelerated factor.

Dimming Control of LED Light Using Pulse Frequency Modulation in Visible Light Communication

  • Lee, Seong-Ho
    • Journal of information and communication convergence engineering
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    • v.19 no.4
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    • pp.269-275
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    • 2021
  • Light-emitting diodes (LEDs) are modulated using a square wave pulse sequence for flicker prevention and dimming control in visible light communication (VLC). In a VLC transmitter, the high and low bits of the non-return-to-zero (NRZ) data are converted to two square waves of different frequencies, which continue for a finite time defined by the fill ratio in an NRZ bit time. As the average optical power was kept constant and independent of data transmission, the LED was flicker-free. Dimming control is carried out by changing the fill ratio of the square wave in the NRZ bit time. In the experiments, the illumination of the LED light was controlled in the range of approximately 19.2% to 96.2% of the continuous square wave modulated LED light. In the VLC receiver, a high-pass filter combined with a latch circuit was used to recover the transmitted signal while preventing noise interference from adjacent lighting lamps.

Modeling of Mixed Phosphors in White Light Emitting Diode (백색 발광다이오드에서의 혼합 형광체 모델링)

  • Kim, Dowoo;Gong, Dayeong;Gong, Myeongkook
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.26 no.7
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    • pp.567-574
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    • 2013
  • An optical model is proposed in the white LED using phosphor and LED chip. In this paper a new model that describes the absorption rate and quantum efficiency with increasing the mixing ratio of phosphor in silicone, and the allotment of the phosphor absorption optical power in the several phosphor mixing in the silicone. Single phosphor in silicone from the optical measurement data before and after molding, the solution to get the blue optical power and the phosphor emission optical power is proposed. By these solution the absorption rate and the quantum efficiency was obtained. The model with single phosphor mixing in the silicone the validity was confirmed.

Low Temperature Co-firing of Camber-free Ceramic-metal Based LED Array Package (세라믹-금속 기반 LED 어레이 패키지의 저온동시소성시 휨발생 억제 연구)

  • Heo, Yu Jin;Kim, Hyo Tae
    • Journal of the Microelectronics and Packaging Society
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    • v.23 no.4
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    • pp.35-41
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    • 2016
  • Ceramic-metal based high power LED array package was developed via thick film LTCC technology using a glass-ceramic insulation layer and a silver conductor patterns directly printed on the aluminum heat sink substrate. The thermal resistance measurement using thermal transient tester revealed that ceramic-metal base LED package exhibited a superior heat dissipation property to compare with the previously known packaging method such as FR-4 based MCPCB. A prototype LED package sub-module with 50 watts power rating was fabricated using a ceramic-metal base chip-on-a board technology with minimized camber deformation during heat treatment by using partially covered glass-ceramic insulation layer design onto the aluminum heat spread substrate. This modified circuit design resulted in a camber-free packaging substrate and an enhanced heat transfer property compared with conventional MCPCB package. In addition, the partially covered design provided a material cost reduction compared with the fully covered one.

A Synthesis Ratio of Light Emitting Diodes and Quantization Noise for Increasing Brightness of Head-up Displays (헤드업 디스플레이 휘도 증가를 위한 LED 합성비율과 영상잡음에 대한 연구)

  • Chi, Yongseok
    • Journal of Broadcast Engineering
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    • v.21 no.5
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    • pp.816-823
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    • 2016
  • This paper studies a light emitting diode(LED) overlapping method of a head-up display that consists of a digital micro device(DMD) panel and a red, green, blue LED in order to increase the brightness of display system and optical output power. This optimization overlapping method removes a quantization noise which occur due to LED overlapping too excessive and stabilizes the junction temperature of LED. In order to reduce junction temperature of LED, the a correlation between a green duty and LED overlapping ratio is studied. Throughout this study, the brightness of head-up display exhibited high increasement ratio of luminance around 33.3 percent at 39 percent overlapping method.

A Study on the Psychological Responses by the change of Illuminance and Color temperature in LED (LED 광원의 색온도와 조도 변화에 따른 심리반응 연구)

  • Yi, Yon-Soo;Ha, Mi-Kyoung
    • Korean Institute of Interior Design Journal
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    • v.21 no.6
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    • pp.129-136
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    • 2012
  • As the importance of eco-friendly and energy saving issues are emphasized in lighting as consciousness about energy saving is elated worldwide, demand for natural resources such as gas increases, supply of LED lighting is spread. Owing to white LED's development and price fall. It is expected to LED High Luminance Emitting Diode. LED's brightness and long life-time that surpass fluorescent light in the latest as well as is used by back light source of thin film LCD, low electric power attrition rate by advantage do and widen the market at the world lighting lamp market that is potential market. Accordingly, study about suitability of LED lighting is activated but space that apply actual LED lighting fixtures yet is less and advanced researches about LED fixtures' applied apaces are slight compared to existing light source up to now because is not many on this. The result of the experiment shows similar tendency with the existing light sources'. Through a psychological reaction experiment in the LED lighting experiencing space that can control of color temperature and lighting level, this study is wished to use to the data for lighting design of space that LED lighting fixtures are applied hereafter.

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Driving Method for Dimming of LED Lamps using Selectively Charged Charge Pump (선택적 충전방식 전하펌프를 사용한 LED 램프 조광구동 기술)

  • Kim, Jaehyun;Yun, Janghee;Ryeom, Jeongduk
    • Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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    • v.27 no.9
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    • pp.15-22
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    • 2013
  • A new LED lamp driving technology with a charge pump instead of a conventional DC-DC converter is proposed. The proposed driving technology is used to control the LED lamp with digital dimming. The power loss in the zener diodes is reduced because the charging process of the capacitors is selectively controlled according to the digital control signal. From the experimental results, when dimming four LED lamps simultaneously, the average driving circuit efficiency of 89% is obtained, regardless of the dimming level. White light with color temperature over a range of 2800~7200K was produced by dimming control of red, green, blue and amber LED lamps with the proposed driving circuit. The characteristics of the driving circuits can be changed depending on the characteristics of the R, G, B, and A LED lamps. The efficiency of the driving circuits up to a maximum 89% can also be obtained depending on the combination of LED lamps. The driving technology with digital dimming control for LED lamps proposed in this paper would be effective for obtaining high efficiency in LED driving circuits and remote control of LED lamps using digital communications.

Consideration of LED Saloon light for rolling stock (철도차량 LED 실내등 적용 검토)

  • Jeong, Hyun-Jeong;Kim, Shin-Gug;Ahn, Hong-Kwan;Kim, Jae-Gi
    • Proceedings of the KSR Conference
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    • 2011.05a
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    • pp.1457-1465
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    • 2011
  • The saloon light is the device that can offer convenience and comfort to the driver and passenger when the train is operated at night or in the tunnel. Generally, The fluorescent type saloon for the rolling stock have been used, but the problems that are short life and the generation of heat have been brought about because the saloon lihgts of rolling stock are supposed to operated continuously long time, and high power consumption. So, the development of new type of saloon lights has been requested in order to solve these problems. And recently the various LED type lights have been developed and LED type saloon lights for rolling stock also has been developed. Therefore, we survey the characteristic, function and needed condition of the LED type saloon lights for rolling stock, and analyze the good and bad point, and then research the complement of weak point. We want to find the direction and develop the design of future LED saloon light type.

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A study on the small Flash Lamp Design using LED (휴대폰용 소형 Flash에 적합한 LED 램프 설계 연구)

  • Jeong, Hak-Geun;Jung, Bong-Man;Han, Su-Bin;Park, Suk-In;Song, Yu-Jin;Lee, Jeong-Hoon
    • Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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    • 2007.11a
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    • pp.107-109
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    • 2007
  • LED is expected as an environmentally friendly light source with its good reliability and long lifetime. A few ten mW white LED can substitute for the indicator light source, and it is required to study several watt multi-chip semiconductor light sources in order to replace the light sources for general illumination such as incandescent lights and fluorescent lamps. Since the optical technology used for several mW white LED light source uses only 30% to 50% of the light, it is required to develop the design technology of optical system and lens to improve the efficiency more than 80% for insuring the high power of white LED. In this paper, we designed and fabricated new structure reflector to increase the efficiency.

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