LIQUID CRYSTAL DISPLAY AND METHOD OF DRIVING THE SAME

• US 20110141002A1
• Filed: 05/11/2010
• Published: 06/16/2011
• Est. Priority Date: 12/15/2009
• Status: Active Grant

• Current Assignee: LG Display Co., Ltd.
• Original Assignee: LG Display Co., Ltd.
• Inventors: KIM, Jonghoon
• Granted Patent: US 9,202,419 B2
• Time in Patent Office: Days
• US Class Current: 345/102
• CPC Class Codes: G09G 2310/0237 Switching ON and OFF the backlight within one frame
• CPC Class Codes: G09G 2310/024 Scrolling of light from the illumination source over the display in combination with the scanning of the display screen
• CPC Class Codes: G09G 2320/0261 in the context of movement of objects on the screen or movement of the observer relative to the screen
• CPC Class Codes: G09G 2320/0271 Adjustment of the gradation levels within the range of the gradation scale, e.g. by redistribution or clipping
• CPC Class Codes: G09G 2320/064 by time modulation of the brightness of the illumination source
• CPC Class Codes: G09G 2320/0646 Modulation of illumination source brightness and image signal correlated to each other
• CPC Class Codes: G09G 2360/16 Calculation or use of calculated indices related to luminance levels in display data
• CPC Class Codes: G09G 3/3406 Control of illumination source illumination devices structurally associated with liquid crystal cells G02F1/1336
• CPC Class Codes: G09G 3/342 using several illumination sources separately controlled corresponding to different display panel areas, e.g. along one dimension such as lines
• CPC Class Codes: G09G 3/3426 the different display panel areas being distributed in two dimensions, e.g. matrix

Abstract

A liquid crystal display includes a liquid crystal display panel, a backlight unit including a plurality of light sources, the backlight unit configured to provide light to the liquid crystal display panel, a light source driving unit configured to drive the light sources of the backlight unit using a backlight control signal, and a backlight controller configured to select a backlight dimming value depending on an input image and vary an off-start time of the backlight control signal based on the backlight dimming value.

Claims

1. A liquid crystal display comprising:

a liquid crystal display panel;

a backlight unit including a plurality of light sources, the backlight unit configured to provide light to the liquid crystal display panel;

a light source driving unit configured to drive the light sources of the backlight unit using a backlight control signal; and

a backlight controller configured to select a backlight dimming value depending on an input image and vary an off-start time of the backlight control signal based on the backlight dimming value.

2. The liquid crystal display of claim 1, wherein the backlight controller advances the off-start time of the backlight control signal as the backlight dimming value decreases.

3. The liquid crystal display of claim 1, wherein the backlight controller includes an input image analysis unit configured to calculate a frame representative value using a mean value, a mode value, or a maximum value of a frame.

4. The liquid crystal display of claim 3, wherein the backlight controller includes a data modulation unit configured to modulate the input image based on the frame representative value.

5. The liquid crystal display of claim 3, wherein the backlight controller includes a diming calculation unit configured to produce the backlight dimming value based on the frame representative value.

6. The liquid crystal display of claim 5, wherein the backlight controller includes a scan time determination unit configured to produce an off-start time data based on the backlight dimming value.

7. The liquid crystal display of claim 6, wherein the backlight controller includes a diming controller configured to produce a duty ratio of the backlight control signal based on the backlight dimming value.

8. The liquid crystal display of claim 7, wherein the duty ratio of the backlight control signal increases as the backlight dimming value increases.

9. The liquid crystal display of claim 7, wherein the diming controller advances or retards a phase of the backlight control signal based on the off-start time data.

10. The liquid crystal display of claim 9, wherein the diming controller retards the phase of the backlight control signal when the off-start time data value increases.

11. The liquid crystal display of claim 6, wherein the scan time determination unit is configured to decrease the off-start time data as the backlight dimming value decreases.

12. The liquid crystal display of claim 1, wherein the backlight controller is configured to advance the off-start time when an off-duty ratio of the backlight control signal increases.

13. The liquid crystal display of claim 1, wherein the backlight controller is configured to increase the backlight dimming value when the duty ratio of the backlight control signal increases.

14. The liquid crystal display of claim 1, wherein the backlight controller is configured to control the light sources based on a local backlight dimming value.

15. The liquid crystal display of claim 1, wherein the backlight control signal is at least one of a pulse width modulation (PWM) signal, pulse amplitude modulation (PAM) signal, and pulse frequency modulation (PFM) signal.

16. A liquid crystal display comprising:

a liquid crystal display panel;

a backlight unit including a plurality of light sources, the backlight unit configured to provide light to the liquid crystal display panel;

a light source driving unit configured to drive the light sources of the backlight unit using a backlight control signal; and

a backlight controller configured to detect a change in a backlight dimming value of consecutive input images and vary an off-start time of the backlight control signal based on the detected change in the backlight dimming value.

17. A backlight controller, comprising:

an input image analysis unit configured to select a frame representative value of an input image corresponding to one frame period;

a dimming calculation unit configured to select a backlight dimming value based on the frame representative value;

a scanning time determination unit configured to generate an off-start time data based on the backlight dimming value and vary the off-start time data depending on changes in the backlight dimming value; and

a dimming controller configured to select a duty ratio of a backlight control signal based on the backlight dimming value and control a falling edge time of the backlight control signal.

18. A method of driving a liquid crystal display, comprising:

providing light to the liquid crystal display panel;

driving light sources of a backlight unit using a backlight control signal;

selecting a backlight dimming value depending on an input image; and

varying an off-start time of the backlight control signal based on the backlight dimming value using a backlight controller.

19. The method of claim 18, wherein the backlight control signal is at least one of a pulse width modulation (PWM) signal, pulse amplitude modulation (PAM) signal, and pulse frequency modulation (PFM) signal.

20. The method of claim 18, wherein the backlight controller controls the light sources based on a local backlight dimming value.

21. The method of claim 18, wherein a duty ratio of the backlight control signal increases as the backlight dimming value increases.

22. The method of claim 18, wherein the backlight controller retards a phase of the backlight control signal when the off-start time data value increases.

23. The method of claim 18, wherein the backlight controller decreases the off-start time data as the backlight dimming value decreases.

24. The method of claim 18, wherein the backlight controller advances the off-start time when an off-duty ratio of the backlight control signal increases.

25. A method of driving a liquid crystal display, comprising:

providing light to the liquid crystal display panel;

driving light sources of a backlight unit using a backlight control signal;

selecting a backlight dimming value depending on an input image; and

varying an off-start time of the backlight control signal based on a change in the backlight dimming value of consecutive input images using a backlight controller.