• The Transactions of the Korean Institute of Power Electronics
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• v.17 no.2
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• pp.142-149
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• 2012

The independently regulated dual-output LLC resonant converter using only one power stage and one control IC is proposed in this paper. The conventional dual-output LLC resonant converter requires the extra non-isolated DC/DC converter to obtain the tightly regulated slave output voltage, which results in the low power conversion efficiency and high production costs. On the other hand, since the proposed converter controls the master and slave output voltages by pulse width modulation(PWM) and pulse frequency modulation(PFM), it can achieve tightly regulated dual output voltages without the additional non-isolated DC/DC converter. Therefore, it features a high efficiency and low cost. To confirm the validity of the proposed converter, theoretical analysis and experimental results from a 40W LED driver prototype are presented.

• The Journal of the Korea institute of electronic communication sciences
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• v.10 no.5
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• pp.615-622
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• 2015

As the development of high efficiency and high flux density LEDs, the trend of illumination lamp industry transfers from conventional-lamps to the LED-lamps. For energy efficiencies, LED lamps are superior to the conventional lamps, but they have heat problems. Especially, the heat problems are severe for the high luminance lamps. They degrade the soldering point of the metal PCB, and shorten the life cycle of LEDs. So, the solution of the heat sinking is very important to develop high luminance LED lamps. This study suggested a new method to solve the heat problems for high luminance LED lamps, and developed a LED lamp which has 1200W power. In this study, a water jacket is installed to the LED lamp, and the cooing water is circulated by a water pump.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.11
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• pp.7256-7261
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• 2015

This paper devised a plant growing system As LED light source, three monochromatic lights (red, blue, white) and three mixed lights (red1+blue1, red2+blue1, red1+blue2) were made. According to the optical properties of those LED light sources and change in the amount of light, this author analyzed the characteristics of luminance and PPFD and also plant growth. According to the light efficiency of those LED light sources, it was high in white light as 125 lm/W and was low in red1+blue2 light as 9.9 lm/W. This result shows that monochromatic light has higher light efficiency than mixed light. The PPFD ($25{\mu}mol$, $50{\mu}mol$, $100{\mu}mol$) luminance in different wavelengths of LEDs was high in white LEDs and was low in blue LEDs. therefore, it is possible to devise an efficient LED lighting system appropriate for growing plants by variety monochromatic lights and mixed light wave length combination of LED light source.

• Korean Journal of Optics and Photonics
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• v.14 no.2
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• pp.122-129
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• 2003

In the case of a AIGalnP/GaP system rectangular parallelepiped high brightness LED which has side walls etched to be slanted off the vertical direction, we have studied the effects of lossy electrodes and material absorption and etching depth and angle of side walls on its light extraction efficiency. If LEDs have no electrodes, in order to obtain an 80％ light extraction efficiency of a TIP (truncated inverted pyramid) LED, the side-etched LEDs should have an etching angle of 22$^{\circ}$~45$^{\circ}$ and an etching depth of 8~17% of a dice height and an absorption coefficient less than 1 $cm^{-1}$ / In case of etching depth of 16~39% of a dice height, we can obtain a 90% light extraction efficiency of a TIP LED. But when LEDs have two electrodes and no absorption loss, in order to obtain an 80％ light extraction efficiency of a TIP LEBs, the side-etched LEDs should have an etching angle of 25$^{\circ}$-45$^{\circ}$ and an etching depth of 30～36% of a dice height. In case of etching depth of 57~71％ of a dice height, we can obtain a 90％ light extraction efficiency of a TIP LED.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.29 no.4
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• pp.1-10
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• 2015

The light emitting diodes(LED) package of new structure is proposed to promote the reliability and lifespan by maximize heat dissipation occurred on the chip. We designed and fabricated the LED packages mixing the advantages of chip on board(COB) based on conventional metal printed circuit board(PCB) and the merits of Si sub-mount using base as a substrate. The proposed LED package samples were selected for the superior efficiency of the material through the sealant properties, chip characteristics, and phosphor properties evaluations. Reliability test was conducted the thermal shock test and flux rate according to the usage time at room temperature, high-temperature operation, high-temperature operation, high-temperature storage, low-temperature storage, high-temperature and high-humidity storage. Reliability test result, the average flux rate was maintained at 97.04% for each items. Thus, the Si sub-mount based LED package is expected to be applicable to high power down-light type LED light sources.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.14 no.6
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• pp.129-135
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• 2015

This paper shows significant methods that improve the lifespan of LED modules as well as efficiently using an aluminum heat-sink for LED module in high power. It proposes a method that raises stability and lifespan to protect LED modules and the power unit when the LED module has been used for a long hours at high temperatures. During the research, we applied a method of pulse-width modulation (PWM) in order to prevent the phenomenon that the entire power of a system is turned off and the lifespan is reduced when the LED nodule reacts to the high temperatures. To protect the LED module and SMPS based on high efficiency, a temperature sensor is attached underneath the circuit board and the sensor measures the temperature of circuit board when the LED module is powered on. The electrical power connected to SMPS is controlled by PWM when the temperature of the LED module reaches a particular temperature.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.26 no.12
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• pp.1-8
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• 2012

The performance and lighting characteristics of the LED depend on cooling condition because the power LED generates lots of heat. In this paper, the effect of the generated heat from power LED module on lighting characteristics and performance is measured and evaluated. For experiments, the transient temperature of a power LED module with cooling condition is measured. In addition, the temperature and lighting characteristics of the LED module are measured during the steady state. As a result, the cooling condition is less effective on the lighting characteristics of the LED module at rated current but the cooling condition extremely affects those of the LED module over the rated current. Because high temperature of the power LED module causes the low phosphor conversion, luminance efficiency becomes low and color temperature becomes high. When power LED module are driven over the rated condition, higher temperature is directly related to lighting characteristics and performance of the LED module rather than higher current.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.60 no.4
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• pp.253-256
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• 2011

LEDs have small size, long lifespan, high reliability, low power consumption and high color efficiency. Using such a characteristics, LED Back Light Unit has been studying actively. This paper proposes LED driver to minimize power consumption due to LED forward voltage($V_F$) difference and temperature rising. Compared to conventional LED driver, the proposed driver have excellent stability, brief structure and linear output voltage of DC-DC boost converter. Proposed LED Driver circuit was designed using 0.35um CMOS technology. And its operation was verified through simulation.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.56 no.7
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• pp.1261-1267
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• 2007

Although LEDs have been used in various applications with improving the brightness and luminous efficacy, the electrical and optical characteristics of high power LED varies at different temperature and starting time. In this paper, optimal heat sink and apparatus design were conducted using IR camera and ICEPAK on the LED bulb consisting with fourteen LED array. The temperatures of heat sink and LED device of the designed LED bulb without cooling pan were $74^{\circ}C\;and\;96.8^{\circ}C$, respectively, showing in good themal characteristics. For high efficiency driving circuit of LED array adopted optimal heat sink design, driving circuits of constant voltage and current circuits were suggested and fabricated. As a result the efficacy of all driving circuits showed more than 20 lm/W. Also, the constant current circuits are suitable for signal lamp, hallway lamp, and flash lamp having short operating time(about 30 min). On the other hand, a reading light and indoor lamp having long operating time can be controlled by constant voltage circuit.

• 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.