Apparatus and method for luminance control of liquid crystal display device

• US 7,768,495 B2
• Filed: 05/25/2005
• Issued: 08/03/2010
• Est. Priority Date: 05/27/2004
• Status: Active Grant

• Current Assignee: LG Display Co., Ltd.
• Original Assignee: LG Display Co., Ltd.
• Inventors: Kwon, Kyung Joon, Hong, Hee Jung
• Primary Examiner(s): Awad; Amr
• Assistant Examiner(s): Sherman; Stephen G
• Application Number:
  US11/136,666
• Publication Number:
  US 20060007100A1
• Time in Patent Office: 1,896 Days
• Field of Search: 345/102, 345/87, 345/204
• US Class Current: 345/102
• CPC Class Codes: G02F 1/133603 with LEDs
• CPC Class Codes: G02F 1/133604 with lamps
• CPC Class Codes: G02F 1/133613 characterized by the sequence of light sources

Abstract

An apparatus and method for controlling luminance in an liquid crystal display device includes: a liquid crystal display panel having at least two designated areas; at least two lamp units irradiating light the designated areas of the liquid crystal display panel; an arithmetic unit configured to scan image pixels within each of the designated areas of the liquid crystal display panel, to extract a peak value of the gray level of pixels, and to calculate an average peak value for each designated area; and a lamp driver configured to control the lamp units, irradiating light to each designated area, based on the average peak value.

Claims

1. A luminance control apparatus of a liquid crystal display device comprising:

a liquid crystal display panel divided into a plurality of designated areas, each designated area including a plurality of pixels, each pixel including a red sub-pixel, a green sub-pixel and a blue sub-pixel;

a plurality of lamp units, each lamp unit providing light to a designated area of the plurality of designated areas of the liquid crystal display panel;

an arithmetic unit including;

a scan part configured to detect a gray level value of the red sub-pixel, the green sub-pixel and the blue sub-pixel for each pixel within each designated area; and

a calculating part configured to extract a peak value of each pixel by selecting a maximum gray-level value from among the detected gray level values, and to calculate an average peak value of each designated area by averaging the extracted peak values of the pixels within the designated area;

a lamp driver for each of the plurality of lamp units, each lamp driver configured to control the corresponding lamp unit based on the calculated average peak value corresponding to the designated area of the lamp unit; and

a look up table arranged between the arithmetic unit and the lamp driver, the lookup table configured to map the average peak value calculated by the arithmetic unit to a control signal,

wherein each of the plurality of lamp units are divisionally driven in each designated area every image frame.

2. The luminance control apparatus according to claim 1, wherein the lamp driver includes:

an inverter circuit that boosts a voltage supplied from a power source to generate a boosted alternating current signal, and supplies the boosted alternating current signal to the lamp units; and

a pulse width modulator arranged between the inverter circuit and the arithmetic unit to control the signal generated from the inverter circuit in accordance with the average peak value calculated by the arithmetic unit.

3. The luminance control apparatus according to claim 1, wherein the arithmetic unit is integrated within the lamp driver.

4. A method for controlling luminance in a liquid crystal display device divided into a plurality of designated areas each designated area including a plurality of pixels, each pixel including a red sub-pixel, a green sub-pixel and a blue sub-pixel, the liquid crystal display device comprising a plurality of lamp units, each lamp unit providing light to a designated area of the liquid crystal display panel, the method comprising:

calculating an average peak value for pixels for each designated area of the liquid crystal display panel; and

controlling the luminance of each lamp unit based on the calculated average peak value corresponding to the designated area of the lamp unit,

wherein the calculating the average peak value for each designated area of the liquid crystal display panel comprises;

scanning each pixel within each designated area of the liquid crystal display panel to detect a gray level value of the red sub-pixel, the green sub-pixel and the blue sub-pixel for each pixel;

determining a peak value for each pixel by selecting a maximum gray level value from among the detected gray level values; and

calculating an average peak value of each designated area by averaging the determined peak values of the pixels within the designated area,

wherein controlling the luminance of each lamp unit based on the calculated average peak value corresponding to the designated area of the lamp unit comprises;

mapping a look up table and the average peak value; and

divisionally driving each of the plurality of lamp units in each designated area every image frame.

5. The luminance control method according to claim 4, wherein

controlling the luminance of the plurality of lamp units based on the calculated average peak value for a designated area comprises:

converting at least one of a pulse duty ratio and a pulse amplitude of a pulse driving the lamp units based on the average peak value; and

converting a tube current to be supplied the lamp unit in accordance with at least one of the converted pulse duty ratio and pulse amplitude.