• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.32 no.1
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• pp.47-52
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• 2019

Micro-LEDs show lower efficiencies compared to general LEDs having large areas. Simulations were carried out using ray-tracing software to investigate the change in light extraction efficiency and light distribution according to chip-size of blue flip-chip micro-LEDs (FC ${\mu}-LEDs$). After fixing the height of the square FC ${\mu}-LED$ chip at $158{\mu}m$, the length of one side was varied, with dimensions of 2, 5, 10, 30, 50, 100, 300, and $500{\mu}m$. The highest light-extraction efficiency was obtained at $10{\mu}m$, beyond which the efficiency decreased as the chip-size increased. The chip size-dependence of the FC ${\mu}-LEDs$ both without the patterned sapphire substrate, as well as vertical FC ${\mu}-LEDs$, were analyzed.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.29 no.3
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• pp.131-134
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• 2016

This research was analyzed thermal characteristics that was appointed disadvantage when smart LED driver ICs was packaged and we applied extracted thermal characteristics for optimal layout design. We confirmed reliability of smart LED driver ICs package without additional heat sink. If the package is not heat sink, we are possible to minimize package. For extracting thermal loss due to overshoot current, we increased driver current by two and three times. As a result of experiment, we obtained 22 mW and 49.5 mW thermal loss. And we obtained optimal data of 350 mA driver current. It is important to distance between power MOSFET and driver ICs. If thhe distance was increased, the temperature of package was decreased. And so we obtained optimal data of 3.7 mm distance between power MOSFET and driver ICs. Finally, we fabricated real package and we analyzed the electrical characteristics. We obtained constant 35 V output voltage and 80% efficiency.

• Proceedings of the IEEK Conference
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• 2004.08c
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• pp.836-841
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• 2004

This paper describes ASIC design for brightness revision control, A LED Pixel Matrix (LPM) design and LPM in natural color LED vision. A designed chip has 256 levels of gradation correspond to each Red, Green, Blue LED pixel respectively, which have received 8bit image data. In order to maintain color uniformity by reducing the original rank error of LED, we adjusted the specific character value 'a' and brightness revision value 'b' to pixel unit, module unit and LED vision respectively by brightness characteristic function with 'Y=aX+b'. In this paper, if designed custom chip and brightness revision control method are applied to manufacturing of natural color LED vision, we can obtain good quality of image. Furthermore, it may decrease the cost for manufacturing LED vision or installing the plants.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2006.05a
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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.

• Korean Journal of Optics and Photonics
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• v.18 no.2
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• pp.111-116
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• 2007

A high power LED which is being used in many illumination applications as a new light source was simulated for its physical structure and then its optical properties were analyzed. To obtain accurate results from the designed LED model, properties of the die chip and reflector cup were varied. As a result, a high power LED model which has a radiation pattern of a Lambertian with its viewing angle of approximately $140^{\circ}$ and total included angle of $160^{\circ}$ was designed.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.23 no.6
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• pp.609-617
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• 2014

We have studied a chip-on-board LED lighting optical system for various luminous-intensity-distribution angles of the LED. An optical system that can accept different LEDs was made to reduce the systems's weight and size as we selected the chip-on-board LED, which is easy to apply to optical systems, unlike existing package-on-board LEDs. The luminous-intensity-distribution angles were $45^{\circ}$, $60^{\circ}$, $90^{\circ}$, and $120^{\circ}$. We researched these four types of optical systems. The $45^{\circ}$ and $60^{\circ}$ units were developed into reflectors, and the $90^{\circ}$ and $120^{\circ}$ units, into lenses. We checked the performance of the designed optical system through simulation and made a mock-up. Then we made a prototype of the chip-on-board LED high bay for use with the mock-up. After measuring its performance, we tested the luminous-intensity-distribution angles and compared them with simulation data. The resulting prototype was developed considering brightness, light uniformity, age, and economics which are suitable for a factory environment.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.20 no.3
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• pp.361-367
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• 2011

In this paper, it was attempted to analyze the optimal design of light emitting diode (LED), a source of back light unit (BLU). LED is beginning with commercialized red LED which is made by GaAsP compound semiconductor, and has been developed focusing on liquid crystal panel. In order to get the optimal design, optical simulation was made by analyzing luminosity shape, reflector angle, chip depth, and chip position of LED lighting. Final results show that the proposed LED characteristics were useful to increase light efficiency and it has been proven by distribution chart for actual exposed light on the light guide panel (LGP).

• Journal of the Korean Society of Safety
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• v.27 no.6
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• pp.26-30
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• 2012

It is difficult to determine the junction temperature because LED lightings are manufactured using several chips with low power. This paper reports on the finite element method of the determination of junction temperature in the GaN-based LEDs. The calculated junction temperature of the LED chip using FEM was compared with the experimentally measured data. As the results of this study, the junction temperature of LED chips with via holes is lower than that of LED chips without via hole. Therefore, the research of via hole is necessary to decrease junction temperature of LED chips.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2009.05a
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• pp.164-167
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• 2009

It is difficult to measure junction temperature in the LED Module. According to the arrangement control unit and heat sink, temperature distribution is changed in the LED Module. A method of forecasting LED Module thermal resistance is suggested with measuring LED and PCB board temperature.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.08a
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• pp.279-279
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• 2011

본 연구는 LED 등기구에서 방열코팅소재에 따른 방열 효과를 연구하여 LED 등기구를 안정적으로 유지 제어 할 수 있는 방법을 찾고자 한다. 그에 따라 동일한 기구물에서 방열코팅만 변화하여 LED chip 온도의 Steady State 온도를 비교 측정하였다. 방열코팅은 동일한 알루미늄 Heat Sink에 일반분체코팅, Anodizing 처리, 알루미나 방열도료, Graphene이 섞인 알루미나도료, Graphene 잉크 등의 방열코팅소재를 아무 처리를 하지 않은 알루미늄 Heat Sink 와 비교 하였다. 온도는 LED chip, LED base plate, 코팅이 된 표면, 코팅 내부 2 mm 부분의 온도를 각각 Steady State가 될 때까지 측정하였다. 또한 LED의 power를 7 watt에서 13 watt 변화하면서 방열 원리를 분석하였다. 본 연구를 통하여 각 코팅소재에 따른 방열효과와 그 방열 원리를 연구 분석하였다.