• Proceedings of the Korea Contents Association Conference
• /
• 2008.05a
• /
• pp.602-606
• /
• 2008

LCD is supplied light by BLU(Back Light Unit) and the light represents color by each color filter. Also LCD adjusts the amount of light by controlling liquid crystal between the glass of upper plate and one of lower. However, it is impossible to completely exclude light due to the structural and physical characteristic of liquid crystal. Therefore, on transfering light through optical sheet and liquid crystal, many problems are generated. They are related with energy efficiency and get effective for the contrast of LCD to have lower contrast ratio than other display devices. To solve the problems, many techniques have been studied and developed but don't exist keys to solution for them. Among methods, local dimming is one example to be applied to LCD. In this paper we propose image processing algorithm for local dimming of BLU of LED used as light source. The proposed algorithm extracts maximum luminance signal and lights using each extracted signal on segmented region of BLU. Also the proposed algorithm generates image signal in corresponding to luminance of the segmented region and supplies them with LCD panel to represent image with improving luminance ratio.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.22 no.11
• /
• pp.788-797
• /
• 2010

This study examines the influence of fluctuating daylight illuminance on daylight dimming control systems. Field measurements were performed for a full-scale mocked-up model under various daylight conditions in winter. Fluctuating ranges for a partially-shielded photosensor were great when the variation of sky ratio was great. When solar altitude was lower the illuminance and fluctuating range of illuminance were great due to the influence of direct components of daylight and the interrefelction between surfaces in rear area of space. It implies that daylight dimming system would not function effectively, unless the desktop illuminance by daylight is enough. Fluctuation ranges of photosensor illuminance were lower than 50 lx under clear sky conditions, but they were greater than 100 lx under partly-cloudy sky conditions. It means that the fluctuation range of electric light output of lighting fixture would greater under the partly-cloudy conditions and cause potential visual annoyance to occupants. Outdoor vertical illuminance reaching the windows would be an effective factor that can be used to predict the fluctuation of photosensor signals for effective controls of daylight dimming system.

• Proceedings of the KIPE Conference
• /
• 2008.06a
• /
• pp.335-337
• /
• 2008

In this paper, an X-Y channel dimming light emitting diode (LED) backlight with temperature compensation for in LCD TVs is proposed. It shows local dimming effects such as reduced power consumption and high dynamic contrast ratio even with much less number of LED drivers than that of the conventional two-dimensional local dimming method. Moreover, the image distortion caused by temperature variation of LED block can be effectively compensated. The validity of the proposed dimming method is verified by simulation and experimental results based on a RGB-LED backlight of a 32-inch LCD TV.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.19 no.9
• /
• pp.843-848
• /
• 2006

This paper explains the design and fabrication of an inverter for LCD backlight using a multilayer piezoelectric transformer. That inverter is operated by the burst dimming method whose dimming signal is controlled by the duty ratio of rectangular switching signal to a PWM controller. The brightness of CCFL's are investigated according to the various dimming signals, and when those CCFL's are turned on, the temperature distributions on the piezoelectric transformer and circuit components of the inverter are also investigated by a thermo-camera.

• Proceedings of the International Microelectronics And Packaging Society Conference
• /
• 2001.11a
• /
• pp.200-204
• /
• 2001

The high efficiency and high power inverter for driving LCD backlight was designed and fabricated. The operating frequency was variable and dimming capability was also included. High dimming ratio could be achieved by PWM dimming. The optimum driving condition for LCD backlight could be obtained by using the excited type inverter.

• Journal of Information Display
• /
• v.11 no.4
• /
• pp.173-181
• /
• 2010

In this paper, light-emitting-diode (LED) backlight driving circuits and dimming method for medium-sized and large liquid crystal displays (LCDs) are proposed. The double loop control method, the intelligent-phase-shifted PWM dimming method, the fast-switching current regulator, and the current matching techniques are proposed to improve not only the current regulation characteristics and the power efficiency but also the current matching characteristics and the transient response of the LED current. The brightness of the backlight using the proposed local dimming method was determined from the histogram of the local block to reduce the power consumption of the backlight without image distortion. The measured maximum power efficiency of the LED backlight driving circuit for medium-sized LCDs was 90%, and the simulation results showed an 88% maximum power efficiency of the LED backlight driving circuit for large LCDs. The maximum backlight power-saving ratio of the proposed dimming method was 41.7% in the simulation with a high-contrast image. The experiment and simulation results showed that the performance of LEDs as LCD backlight units (BLUs) improved with the proposed circuits and method.

• Proceedings of the IEEK Conference
• /
• 2006.06a
• /
• pp.971-972
• /
• 2006

We have demonstrated Carbon Nanotube Back Light Unit (CNT-BLU) which has a triode structure. Local dimming scheme was introduced to the BLU driving system. With this driving method, contrast ratio enhanced 20 times higher than that of conventional Cold Cathode Fluorescent Lamp (CCFL) BLU.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
• /
• 2005.05a
• /
• pp.123-128
• /
• 2005

This study purposes to increase the energy-saving effects by reducing excessive intensity of radiation of artificial lighting through analyzing daylight incident A photosensor sends amounts of detected luminous flux to digital control unit(DCU) as a signal and then, it can decide dimming ratios, received a proper dimming signal from DCU. Generally it Is effective to control artificial lighting with the different control ratio of each row by setting a photosensor as same numbers and rows as artificial lighting. However, it is ineffective to do in initial costs of systems aspect in offices. As a result of grasping the distribution of daylight previously, we can dim different dimming ratios to each row of artificial lighting by a single photosensor.

• 한국정보디스플레이학회:학술대회논문집
• /
• 2008.10a
• /
• pp.143-146
• /
• 2008

Dynamic range of LCD panel can be dramatically improved by adaptive dimming technique. Adaptive control of LED backlight by input signal can reduce the light leakage of LCD panel and achieve high contrast ratio. An algorithm is proposed to distinguish the input signal and get proper luminance level. For lower cost of LCD panel, white light LED is used to accomplish 2D dimming and get better image performance of LCD.

• Proceedings of the KIEE Conference
• /
• 2006.07b
• /
• pp.1055-1056
• /
• 2006

This paper presents a remote dimming control method for the electrodeless lamps using 2.4 GHz RF communication. Since the proposed dimming method are implemented with a simplest open loop control using ISM band HF modem and low cost MCUs, and the remote controller has just several functions such as On/Off and duty ratio increasing/decreasing. It can be made with low cost. In this paper, the detailed digital logics of the proposed remote dimming control are described and the experimental results are presented.