• Journal of Electrical Engineering and Technology
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• v.11 no.6
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• pp.1880-1885
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• 2016

This study aims to design a zonal lumen for parking garage LED lightings of a slim appearance and 20 W/2,000 lm capacity and to fabricate a lighting luminaire accordingly. The frame is of a one-dimensional bar type with a reverse V-shaped section, with LED chips arranged along both sides. To maximize the $60^{\circ}$ to $80^{\circ}$ zonal lumen, the geometric structure was designed with the apex of the reverse V-shaped section at $40^{\circ}$ and both sides at $70^{\circ}$. As for the LED light source, focusing lenses with narrower full-width half-maximum (FWHM) in luminous intensity were used. A ray-tracing simulation method was utilized for the zonal lumen simulation of the given structure. An actual hardware of luminaire based on the simulation results was fabricated and characterized. The suggested model is meant to develop LED lightings with a proper level of zonal lumen required in parking garages.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.25 no.12
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• pp.54-59
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• 2011

LED lightings typically do not fail catastrophically during use. However, over time the light output will gradually depreciate. Even if there are same LED lighting, they are so different at all. because of dissimilar the use and environment of each LED lighting. In this paper, we make a description of reliability analysis procedures for the degradation data using collected field data. Reliability analysis procedures are consisted of estimating degradation models and failure time, verification of distribution and parameters of the distribution, and reliability measures estimation. At some point in time, the light emitted from an LED lightings depreciates to a level where it is no longer considered adequate for a specific application.

• Transactions of Materials Processing
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• v.21 no.2
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• pp.131-137
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• 2012

With the advantages of power savings, increased life expectancy and fast response time over traditional incandescent bulb, LEDs are increasingly used for many applications including automotive, aviation, display, and special lighting applications. Since the high heat generation of LED chips can reduce service life, degrade luminous efficiency, and cause variation of color temperature, many studies have been carried out on the optimization of LED packaging and heat sinks. In this study, a fin expansion type cooling device using heat pipe, instead of a solid aluminum heat sink, was designed for LED security lightings based on thermal resistance analysis. Numerical analysis and experimental validation were carried out to evaluate its cooling performance.

• Journal of the Korean Society for Precision Engineering
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• v.29 no.7
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• pp.778-784
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• 2012

In comparison with some other light sources, LED has merits such as increased life expectancy, fast response, pollution free, and high energy efficiency. Lately, due to development of LED with high brightness and capacity, LED has widely used in many industrial fields such as automotive, aviation, display, transportation and special lighting applications. Since the high heat generation of LED chips can cause a reduction in lifetime, degradation of luminous efficiency, and variation of color temperature, studies have been carried out on the optimization of LED packaging and heat sinks. In this study, experiments on measuring the heat generation rate of LED and the cooling performance of a heat sink were carried for analyzing the thermal characteristics of LED lighting system in free convection. From the results, dimensionless correlation on the cooling performance of heat sink in natural convection was proposed with Nusselt number and Rayleigh number as a guideline for designing cooling device of LED lightings.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.25 no.8
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• pp.1-7
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• 2011

Recently, all-electric house technology became one of the green growth technologies and is integrated with various areas such as electricity, machinery, architecture, material, and etc. Fossil fuel energy is used for heating and hot water supply in the conventional houses but electricity is adopted in the new conceptual houses to maximize advantages of electricity such as amenity, safety, cleanness, and so on. In this paper, an economic analysis is carried out when LED lightings are adopted using the California Standard Practice Test which has been used to estimate the effects of existing DSM (Demand Side Management) programs. The results are able to contribute to the diffusion of all-electric houses and the establishment of basic data and planning for DSM policies.

• Science of Emotion and Sensibility
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• v.16 no.3
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• pp.305-310
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• 2013

This user-centered research aims to empirically evaluate color temperature (K) and illuminance (lx) of residential bathroom lightings to determine the most optimal lighting conditions for productive task performance as well as for satisfying users' emotional needs. Using 3 LED lighting fixtures, 4 types of lighting contexts were investigated; main lighting, task lighting, shower lighting, and bath lighting. Two lightings were installed parallel to the vertical edges of the main bathroom mirror to be used as main and task lighting, while another fixture was installed above the bathtub to be used for shower and bathing. For each lighting context, subjects (N＝54) were instructed to perform a few tasks during which time the users were exposed to different lighting conditions with color temperature ranging from 2700 K ~ 6500 K and illuminance ranging from 100 lx ~ 700 lx. Upon completing the given tasks, subjects were asked to evaluate the lighting conditions and their applicability for performing the given tasks. Based on the user evaluations, the most optimal lighting conditions for the different lighting scenarios are as follow: 1) 3500 K ~ 4300 K and 150 lx for main lighting, 2) 3500 K ~ 4300 K and 500 lx ~ 700 lx for task lighting, and 3) 2700 K ~ 3500 K and 100 lx ~ 150 lx for shower/bath lighting. These results can be used to adjust the lighting standards suggested by KS, as well as be utilized by both engineers and designers in designing new types of user-centered bathroom lightings.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.29 no.2
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• pp.8-18
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• 2015

This paper proposes a dimming method and a hybrid LED driving circuit suitable for the ultra high definition (UHD) broadcasting. There are major two problems during the dimming control for traditional LED broadcast lightings; one is a flicker that occurred when camera filming to these lightings, and the other is that linear control is impossible for LED luminous intensity under 10% due to LED electrical characteristics. The proposed dimming method and the driving circuit are designed to solve two problems simultaneously. For high level dimming control region from 10 to 100%, the analog control method was applied to the switching regulator constructed by MOSFET operated in the saturation region. For low level dimming control region under 10%, the fast PWM control method with the linear regulator constructed by MOSFET in the ohmic region was used. We verified experimentally that the dimming method is able to control the luminous intensity linearly from 1 to 100% and the flicker disappears on images taken by the charge coupled device (CCD) and the complementary metal oxide semiconductor (CMOS) cameras. Therefore, the proposed method is suitable for the UHD broadcasting.

• Journal of Advanced Marine Engineering and Technology
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• v.36 no.8
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• pp.1111-1116
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• 2012

At present, indoor optical wireless communications using LED lightings has been widely studied. The combination of this technology to the low voltage powerline grid installed in each home makes an efficient method for fulfilling the premise of broadband access for home networking. In this paper, white LEDs were used for both illumination and remote-control, so that information can be broadcast within a room for control the optical wireless systems. We implemented a model car to evaluate the performance of optical wireless remote-control. The requirement for levels of illumination suitable for communication were investigated and applied to design the test-bed. In spite of limitation of line-of-sight communications, it will open up new applications to the optical wireless remote control system in an electromagnetic interference region.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.27 no.5
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• pp.9-17
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• 2013

Preferred combinations of illuminance and color temperature of lighting depend on daily living activities. We investigated whether the illumination stimuli of LED lighting can enhance attention and relaxation level by controlling color temperature and illuminance level according to activities. Illuminations and color temperatures of LED flat panels are controlled in accordance with activities such as office work and resting. The attention and relaxation level under the task specific lightings are compared with those under normal lighting condition. Single channel EEG signals from the NeuroSky's Mindset are used to estimate attention and relaxation level of human subjects under different lighting conditions. Experiment results show that high color temperature with high illuminance of LED lightings (6600K, 800lx) shows improved attention level compared with conventional lighting conditions (4000K, 500lx).

• Proceedings of the Optical Society of Korea Conference
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• 2009.10a
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• pp.98-98
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• 2009