• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.07b
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• pp.1038-1042
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• 2003

LED(Light Emitting Diodes)를 이용한 LCD 백라이트는 현재까지 모바일용의 $2{\sim}3$ 인치정도의 소형모델에서 상용화되고있다. 현재 동종분야에서 $5{\sim}7$ 인치 이상의 중대형에서는 아직 검토나 개발단계인 것으로 파악되고 있다. LED의 특징인 장수명, 고색순도, Robustness 등의 장점에도 불구하고 광효율이나 경제적측면에서 아직 형광램프 Type 에 비해 개선점이 남아있는 것도 개발지연 이유중의 하나다. 최근에 일부 광원업체에서 소비전력 5W로 높은 출광효율을 갖는 고휘도를 가진 LED가 개발되고있다. 고색재현성을 요구하는 TV등의 민수용 디스플레이시장이 커지는 현 추세에 한 방법으로 3색의 고휘도 LED광원을 사용한 백 라이트를 개발했다. R(Red), G(Green), B(Blue)의 3색 점광원 다수를 이중도광판 구조의 장변에 일정 간격으로 배열하여 최종 출사면에서 백색이 되도록 소정의 구성비로 설계하였다. 점광원간의 간격으로 인해 발생되는 혼색도를 보완하기위해 광원과 출사면까지의 광경로를 점광원이 아닌 튜브형의 형광광원 사용시보다 일정량 길게 설계해야 되는데, 이것으로 인해 출광효율이 형광램프구조에 비해 떨어지는 결과로 나타났다. 본 연구에서는 17인치 모니터구조의 백라이트에서 색재현성 105%와 소비전력 67W에서 표면휘도 $2000cd/m^2$ 정도를 달성하였다.

• The Transactions of the Korean Institute of Power Electronics
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• v.12 no.6
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• pp.441-448
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• 2007

To enhance the competitive edge of the material cost, IP(Integrated Power) Board form of inverter circuit is widely used in large area LCD TV(Greater than or equal to 40 in.). This scheme is Two Stage System and one inverter drives multi-lamp in a parallel circuit. This paper analyzes the conventional IP Board inverter controlled with Pulse Width Modulation (PWM), and its problems such as serious hard switching and excessive circulating energy can be solved by a proposed Pulse Count Modulation (PCM) scheme. To confirm the validity and superiority of the proposed system, theoretical analysis and experimental results are presented.

• Korean Journal of Materials Research
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• v.19 no.1
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• pp.7-12
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• 2009

TFT-LCD is the most popular type of flat display panel in the information technology field. The back light unit is a main part of the structure of a TFT-LCD panel. Occasionally, studies have shown that failures of the CCFL of the BLU occur due to the poor weld characteristics of these materials. The aim of this study was to prepare some technical data and to characterize a microjoined electrode for the CCFL. Microstructure examinations, microhardness measurements, resistance measurements and microtensile tests of the microjoined electrode were carried out. The result indicates that a large amount of grain coarsening exists in the heat-affected zone (HAZ) of the weld between the cup and the pin. This grain coarsening of the HAZ between the cup and pin is caused by the welding cycle, which may have an influence on the lowest microhardness values. Fracturing of the microjoined electrode also occurred at the HAZ close to the cup between the weld holding the cup and the pin. Additionally, no specific changes of the electrical resistance among the cup, pin, and lead wire themselves or in the microjoined electrode were observed.

• Korean Journal of Optics and Photonics
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• v.30 no.3
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• pp.101-105
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• 2019

An LCD backlight unit (BLU) using RGB light sources is designed and simulated, in order to improve its optical energy efficiency. A color-matching BLU is designed with a lenticular lens array (LLA) with elements that image the linear RGB light sources onto the RGB subpixels of the color filter. Type-A and Type-B simulations are performed, according to the location of the light sources. As a result, the luminance increases to 210% in Type-A and 270% in Type-B respectively. The optimum values for the height and the gap of the LLA for maximum efficiency are found to be $25{\mu}m$ and $3{\mu}m$ respectively.

• The Transactions of the Korean Institute of Power Electronics
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• v.9 no.6
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• pp.577-583
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• 2004

Optimal parameters were selected to design an inverter circuit that drives a cold cathode fluorescent lamp for LCD backlight using a piezoelectric transformer and it was verified by an experiment. In this paper, the applied inverter topologies are a push-pull type and a half-bridge type, and the dimming control methods of these drive system were used a analog control method and a burst control method each other. When change a control voltage from 2.5V to 4.5V in the analog control method, the brightness 0-100% was seen in current 1-6 mA. And, the input/output efficiency were obtained 90.3%. Also, the control performance of 1-6 mA was seen in duty ratio 5-50% in the burst control method, and the input/output efficiency of the designed inverter got 82.1%.

• Proceedings of the Korean Vacuum Society Conference
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• 2008.02a
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• pp.195-195
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• 2008

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.26 no.9
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• pp.8-17
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• 2012

This paper proposes high performance control of light emitting diode(LED) drive system for liquid crystal display(LCD) backlight. The CCFL(cold cathode fluorescent lamp)was used to a conventional LCD backlight. Due to improvement on luminous efficiency, long life and wide color gamut, LED has gradually substituted for CCFL as backlight. The backlight using LED is necessary to use many LED. For that reason, the LED backlight is using a lot of LED driving circuits. The many LED driving circuit is generated a current deviation between LED. Eventually, it is caused brightness deviation between LED. Therefore, this paper improves the current deviation using transformer and balancing capacitor to solve this problem. Also, for accurate and uniform brightness control, this paper is applied the artificial intelligent control to a dimming control. This paper is compared with conventional system, and validity of this paper proves through that result.

• Proceedings of the KIPE Conference
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• 2006.06a
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• pp.235-238
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• 2006

As the screen size of LCD TV increases, an external electrode fluorescent lamp (EEFL) has been suggested to be applicable as backlight source for LCD TV. Since the EEFL has non-linear characteristics, which makes the analysis and design complicated. In this paper, the characteristics of the EEFL are investigated and a full-bridge RLC series-resonant inverter is analyzed and designed for EEFL backlight of 32-inch LCD TV. Finally, the experimental results are shown to validate the analysis and design.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.33 no.8
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• pp.720-725
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• 2009

Among many kinds of parts for Liquid Crystal Display (LCD), a Back Light Unit (BLU) that changes the path of the light from light source to screen is the most important part to improve optical performances such as uniformity and average value of brightness. Up to recently, design process of BLU has been carried out by depending on the experience of design engineer. Using this approach, however, is proven that it is hard to effectively deal with difficulties in a process of the LCD development such as frequent design modifications, various design requirements, and short-term development. To cope with this situation, we applied a Process Integration and Design Optimization (PIDO) based design environment. PIDO is a software package to integrate multiple simulation processes and find a better solution using various design techniques. In this research, we found a design solution satisfying all design requirements by using the PIDO.

• Proceedings of the KIPE Conference
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• 2007.07a
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• pp.117-119
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• 2007

본 논문에서는 램프가 한개 이상 개방 시 피드백 제어 회로를 동작하지 않도록 하면서, 램프를 보호할 수 있는 개방전압을 출력하는 LCD 백라이트 구동용 인버터 회로도에 관한 것이다. 램프 개방전압 출력을 위한 회로는 램프 전류 피드백 블록, 개방전압시 이상신호를 감지하는 전압 피드백 블록, 램프 개수에 상관없이 최고치 값을 감지하는 블록으로 되어 있다. 전술한 회로가 내장된 인버터는 램프의 개방 시 램프의 개수 상관없이 CCFL의 보호 스펙인 2500V의 개방전압을 출력한다. 이러한 인버터가 내장된 LCD패널은 향상된 안정화 동작을 구현하게 된다.