Apparatus and method for luminance control of liquid crystal display device

• US 20060007100A1
• Filed: 05/25/2005
• Published: 01/12/2006
• 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
• Granted Patent: US 7,768,495 B2
• Time in Patent Office: Days
• 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;

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

an arithmetic unit configured to calculate an average peak value of the pixels within each designated area; and

a lamp driver for each of the plurality of lamp units, each lamp driver configured to control the lamp unit providing light to a designated area based on the calculated average peak value for the designated area.

2. The luminance control apparatus according to claim 1, wherein the arithmetic unit is further configured to extract a peak value of a sub-pixel having a maximum gray level among a red sub-pixel, a green sub-pixel and a blue sub-pixel for each of the pixels included in the designated area.

3. The luminance control apparatus according to claim 2, wherein the arithmetic unit comprises:

a scan part configured to detect values of sub-pixels for each image pixel in the designated area of the liquid crystal display panel; and

a calculating part configured to calculate the average peak value.

4. The luminance control apparatus according to claim 1, further comprising:

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

5. 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 it to the lamp units; and

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

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

7. A method for controlling luminance in a liquid crystal display device, the liquid crystal display device comprising a plurality of lamp units each, 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 within the designated areas of the liquid crystal display panel; and

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

8. The luminance control method according to claim 7, 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;

determining a peak value for each pixel within a designated area; and

calculating an average value of the peak values for the pixels within each designated area.

9. The luminance control method according to claim 7, 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.