• The Transactions of the Korean Institute of Power Electronics
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• v.15 no.1
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• pp.52-59
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• 2010

The conventional CCFL (Cold Cathode Fluorescent Lamp) inverter used in the backlight unit for LCD-TV, composed of the three power stage, can degrade the whole power conversion efficiency. In this paper, a novel scheme to drive the CCFL, composed only of the two power stage without using a dc/dc power stage, is proposed to enhance the whole power conversion efficiency. By adopting the proposed "4-in-1 Transformer", the current balance and the simultaneous ignition among the four CCFL lamp are assured with the one inverter circuit. The proposed scheme features the simple circuit structure, which can save the volume and the cost in the LCD backlight unit. Design considerations are discussed and design procedures are derived. Experimental results of the proposed scheme for 40" LCD-TV are presented to confirm the theoretical analysis.

• Korean Journal of Optics and Photonics
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• v.21 no.2
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• pp.53-60
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• 2010

An integrated light guide plate (LGP) was designed for liquid crystal displays (LCD) without using prism and diffuser sheets. The integrated LGP is textured with micro-patterns on both the top and bottom surfaces. The textures effectively substitute for a single prism-sheet and a diffuser sheet in LCD displays without decreasing the brightness and uniformity. A LCD display with our integrated light guide is simulated to give average luminance of 4560 cd/$m^2$, luminance uniformity of 83% horizontal viewing angle $60^{\circ}$ and vertical viewing angle $56^{\circ}$. Therefore an ultra thin (slim) back light unit can be constructed with fewer optical sheets, which reduces the manufacturing cost and so improves price competitiveness.

• 전자공학회논문지 IE
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• v.46 no.4
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• pp.57-65
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• 2009

This paper presents the image contrast enhancement technique suitable for local dimming backlight of small-sized mobile display while achieving the reduction of the power consumption. In addition to the large-sized TFT-LCD, small-sized one has adopted LED for backlight. Since, conventionally, LED was mounted on the side edge of a display panel, global dimming method has been widely used. However, recently, new advanced method of local dimming by placing the LED to the backside of the display panel and it raised the necessity of sub-blocked processing after partitioning the target image. When the sub-blocked image has low brightness, the supply current of a backlight LED is reduced, which gives both enhancement of contrast ratio and power consumption reduction. In this paper, we propose simple and improved image enhancement algorithm suitable for the small-sized mobile display. After partitioning the input image by equal sized blocks and analyzing the pixel information in each block, we realize the primary contrast enhancement by independently processing the sub-blocks using the information such as histogram, mean, and standard deviation values of luminance(Y) component. And then resulting information is transferred to each backlight control unit for local dimming to realize the secondary contrast enhancement as well as reduction of power consumption.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.11a
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• pp.624-627
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• 2004

본 논문은 LCD Backlight로 사용되고 있는 CCFL의 문제점을 해결하기 위해 간단한 구조를 가지는 mercury-free, Xe 평판형 형광램프에 대한 연구를 하였다. 일반적으로, 수은을 포함한 형광램프는 낮은 온도에서의 휘도문제와 상대적으로 긴 점등시간, 수명과 특히, 환경 문제가 있다. 본 논문에는 화학적으로 안정한 불활성 가스인 Xe을 사용함으로써 기존의 백라이트가 가지고 있는 문제점을 해결하였다. 제작된 8인치$(200{\times}156{\times}10mm)$ 램프는 AC 펄스 전압에 의해 높은 균일도, 안정한 방전, 우수한 전기적 및 광학적 특성을 가진다. 또한 본 연구에서, 무수은 Xe 평판형 형광램프의 전극폭에 대한 전기적 및 광학적 실험을 통하여 90[%]의 균일도에서 $7,000[cd/m^2]$의 휘도와 30[lm/W]의 효율을 얻었다.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.11 no.1
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• pp.61-65
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• 2011

Recently, LCD (liquid crystal display) industry is needed to goods of high reliability and wide range temperature condition and it is interested in products for extremely cold condition without failure of light-up. In this experiment, we made the LED backlight unit for Automotive-navigation under the extremely cold condition. And for making this backlight unit, we used to eight side emitting type white LEDs with 3W high power LED. We could know that this backlight unit releases to 18,000 nit in 24W power consumption and start up voltage time is under the 1ms in the ambient temperature at -40.

• Proceedings of the KIPE Conference
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• 2000.07a
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• pp.509-512
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• 2000

LCD displays for flat monitors the backlit using Cold Cathode Flourescent Lamps(CCFLs) In this paper a low-cost series resonant half-bridge inverter for LCD backlight is proposed as a CCFL ballast. It is regulated by asymmetric control for its fixed frequency soft switching model. The attractiveness of this topology is primarily its low cost because of using BJT switches and reduction of anti-parallel diode. Design procedure and experimental verification from 5W 15"LCD backlight are presented.

• Journal of Korea Society of Industrial Information Systems
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• v.12 no.3
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• pp.116-123
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• 2007

Despite the number of backlight manufacturer is increased as the market of flat panel display equipments and related development devices is enlarged, the inspection based on the human eye is still used in many backlight production lines. The defects such as particle, spot and scratch on the light emitting surface of the backlight prevent the LCD device from displaying the colors correctly. From that manual inspection it is difficult to maintain the quality of backlight consistently because the accuracy and the speed of the inspection may change with the physical condition of the operater. In this paper we studied on the development of automatic backlight surface defect inspection system. For this, we made up of the computer vision system and we developed the main program with various user interfaces to operate the inspection system effectively. And we developed the image processing module to extract the defect information. Furthermore, we presented the labeling process to reconstruct defect regions using the labeling table and the defect index. From the experimental results, we found that our system can detect all defect regions identified from human eye and it is sufficient to substitute for the conventional surface inspection.

• Proceedings of the KAIS Fall Conference
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• 2010.05a
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• pp.349-352
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• 2010

본 논문은 LCD LED 백라이트의 정전류 구동 전원공급 장치를 제안한다. 백라이트로 이용되는 LED의 밝기는 LED로 흐르는 전류에 거의 선형적으로 비례하기 때문에 일정한 밝기를 얻기 위해서는 LED에 정전류가 공급되어야 한다. 제안된 전원공급 장치는 구현이 용이하며 간단한 LED 전류제어 방식을 이용하였으며, 200V의 직류 최대 출력전압과 20W의 최대출력전력을 가진다. 그리고 제안된 회로는 컴퓨터 시뮬레이션을 통하여 회로 동작의 정확함을 보인다.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.06a
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• pp.459-460
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• 2006

RGB 3색 LED를 이용 백라이트에서는 백색 광원을 구현을 위해서는 혼색을 위한 충분한 공간 또는 광학계를 필요로 하고 있다. 본 연구에서는 RGB 3색 LED의 컬러 혼색을 위해 광학 설계를 진행을 하였고, 이 광학계는 광경로 변경을 통해 BLU 내부 공간에서 각각의 3색 LED가 충분한 혼색 구간을 확보하여 백색을 구현하게 된다. 최근 적용하고 있는 Side emitting 방식 LED가 아닌 Top view type의 power LED를 이용하여 32인치급 TV LCD 백라이트를 제작하여 최적화를 진행하였다.

• Proceedings of the Optical Society of Korea Conference
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• 2009.02a
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• pp.549-550
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• 2009