LIQUID CRYSTAL DISPLAY DEVICE AND ELECTRONIC DEVICE

• US 20110199404A1
• Filed: 02/04/2011
• Published: 08/18/2011
• Est. Priority Date: 02/12/2010
• Status: Active Grant

• Current Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Original Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Inventors: MIYAKE, Hiroyuki, UMEZAKI, Atsushi
• Granted Patent: US 8,619,104 B2
• Time in Patent Office: Days
• US Class Current: 345/691
• CPC Class Codes: G02F 1/1368 in which the switching element is a three-electrode device G02F1/136277 takes precedence
• CPC Class Codes: G09G 2300/0426 Layout of electrodes and connections
• CPC Class Codes: G09G 2300/0876 Supplementary capacities in pixels having special driving circuits and electrodes instead of being connected to common electrode or ground; Use of additional capacitively coupled compensation electrodes
• CPC Class Codes: G09G 2310/08 Details of timing specific for flat panels, other than clock recovery
• CPC Class Codes: G09G 2320/0247 Flicker reduction other than flicker reduction circuits used for single beam cathode-ray tubes
• CPC Class Codes: G09G 2330/021 Power management, e.g. power saving
• CPC Class Codes: G09G 2340/0435 Change or adaptation of the frame rate of the video stream
• CPC Class Codes: G09G 3/3648 using an active matrix G09G3/367 - G09G3/3696 take precedence

Abstract

It is an object to suppress deterioration of a displayed still image which is caused when a refresh rate is reduced. A liquid crystal display device includes a display portion controlled by a driver circuit and a timing controller for controlling the driver circuit. An image signal for displaying a still image is supplied to the timing controller. By the timing controller, a refresh rate in displaying an image corresponding to an image signal on the display portion reduced as a gray level number of the image signal is smaller.

Claims

1. A liquid crystal display device comprising:

a driver circuit configured to control a display portion; and

a timing controller configured to control the driver circuit,

wherein an image signal for displaying a still image is supplied to the timing controller, and

wherein the timing controller is configured to reduce a refresh rate to display an image corresponding to the image signal on the display portion as a gray level number of the image signal is smaller.

2. The liquid crystal display device according to claim 1,

wherein the timing controller comprises:

an analyzing portion configured to judge the gray level number of the image signal, and generate a signal;

a lookup table portion configured to store a lookup table for generating the refresh rate in accordance with the signal; and

a panel controller controlled by the lookup table portion, in accordance with the lookup table.

3. The liquid crystal display device according to claim 2,

wherein the analyzing portion comprises:

a counter circuit configured to count by changing a count value in accordance with a bit value of the image signal; and

a determining portion configured to judge whether the count value changes or not, and to output a result to the lookup table portion,

wherein the counter circuit is provided for each bit of the image signal.

4. The liquid crystal display device according to claim 1,

wherein each pixel in the display portion comprises a transistor, and

wherein a semiconductor layer of the transistor includes an oxide semiconductor.

5. The liquid crystal display device according to claim 4, wherein the oxide semiconductor comprises at least one of indium, gallium, tin, and zinc.

6. An electronic device comprising the liquid crystal display device according to claim 1.

7. A liquid crystal display device comprising:

a driver circuit configured to control a display portion;

a timing controller configured to control the driver circuit; and

an image process circuit configured to process an image signal, and to output a processing image signal to the timing controller,

whether the timing controller is configured to reduce a refresh rate to display an image corresponding to the processing image signal on the display portion as a gray level number of the processing image signal is smaller.

8. The liquid crystal display device according to claim 7,

wherein the timing controller comprises:

an analyzing portion configured to judge the gray level number of the processing image signal, and generate a signal;

a lookup table portion configured to store a lookup table for generating the refresh rate in accordance with the signal; and

a panel controller controlled by the lookup table portion, in accordance with the lookup table.

9. The liquid crystal display device according to claim 8,

wherein the analyzing portion comprises:

a counter circuit configured to count by changing a count value in accordance with a bit value of the image signal; and

a determining portion configured to judge whether the count value changes or not, and to output a result to the lookup table portion,

wherein the counter circuit is provided for each bit of the image signal.

10. The liquid crystal display device according to claim 7,

wherein each pixel in the display portion comprises a transistor, and

wherein a semiconductor layer of the transistor includes an oxide semiconductor.

11. The liquid crystal display device according to claim 10, wherein the oxide semiconductor comprises at least one of indium, gallium, tin, and zinc.

12. An electronic device comprising the liquid crystal display device according to claim 7.

13. A liquid crystal display device comprising:

a driver circuit configured to control a display portion; and

a timing controller configured to control the driver circuit,

wherein the timing controller is configured to convert a first refresh rate into a second refresh rate in the display portion,

wherein the first refresh rate corresponds to a first image signal which has a first gray level number, and the second refresh rate corresponds to a second image signal which has a second gray level number, and

wherein the second gray level number is smaller than the first gray level number.

14. The liquid crystal display device according to claim 13,

wherein the timing controller comprises:

an analyzing portion configured to judge the second gray level number, and generate a signal;

a lookup table portion configured to store a lookup table for generating a refresh rate in accordance with the signal; and

a panel controller controlled by the lookup table portion, in accordance with the lookup table.

15. The liquid crystal display device according to claim 14,

wherein the analyzing portion comprises:

a counter circuit configured to count by changing a count value in accordance with a bit value of an image signal; and

a determining portion configured to judge whether the count value changes or not, and to output a result to the lookup table portion,

wherein the counter circuit is provided for each bit of the image signal.

16. The liquid crystal display device according to claim 13,

wherein each pixel in the display portion comprises a transistor, and

wherein a semiconductor layer of the transistor includes an oxide semiconductor.

17. The liquid crystal display device according to claim 16, wherein the oxide semiconductor comprises at least one of indium, gallium, tin, and zinc.

18. An electronic device comprising the liquid crystal display device according to claim 13.

19. A liquid crystal display device comprising:

a driver circuit configured to control a display portion;

a timing controller configured to control the driver circuit; and

an image process circuit configured to process an image signal, and output a processing image signal to the timing controller,

whether the timing controller is configured to convert a first refresh rate into a second refresh rate in accordance with the processing image signal in the display portion,

wherein the first refresh rate corresponds to a first image signal which has a first gray level number, and the second refresh rate corresponds to the processing image signal which has a second gray level number, and

wherein the second gray level number is smaller than the first gray level number.

20. The liquid crystal display device according to claim 19,

wherein the timing controller comprises:

an analyzing portion configured to judge the second gray level number, and generate a signal;

a lookup table portion configured to store a lookup table for generating a refresh rate in accordance with the signal; and

a panel controller controlled by the lookup table portion, in accordance with the lookup table.

21. The liquid crystal display device according to claim 20,

wherein the analyzing portion comprises;

a counter circuit configured to count by changing a count value in accordance with a bit value of the image signal; and

a determining portion configured to judge whether the count value changes or not, and to output a result to the lookup table portion,

wherein the counter circuit is provided for each bit of the image signal.

22. The liquid crystal display device according to claim 19,

wherein each pixel in the display portion comprises a transistor, and

wherein a semiconductor layer of the transistor includes an oxide semiconductor.

23. The liquid crystal display device according to claim 22, wherein the oxide semiconductor comprises at least one of indium, gallium, tin, and zinc.

24. An electronic device comprising the liquid crystal display device according to claim 19.