Display device and electronic apparatus

• US 7,324,123 B2
• Filed: 05/19/2006
• Issued: 01/29/2008
• Est. Priority Date: 05/20/2005
• Status: Expired due to Fees

• Current Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Original Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Inventors: Kimura, Hajime, Osame, Mitsuaki, Fukumoto, Ryota, Tanada, Yoshifumi, Koyama, Jun, Yamazaki, Shunpei, Shishido, Hideaki, Yanai, Hiromi
• Primary Examiner(s): LAO, LUN YI
• Application Number:
  US11/419,345
• Publication Number:
  US 20060262054A1
• Time in Patent Office: 620 Days
• Field of Search: 345 60- 83, 345/204, 345/690, 345/207, 345/205, 315/169.3, 315/169.4, 713/300, 713/322
• US Class Current: 345/690
• CPC Class Codes: G09G 2300/0861 with additional control of the display period without amending the charge stored in a pixel memory, e.g. by means of additional select electrodes
• CPC Class Codes: G09G 2310/0267 Details of drivers for scan electrodes, other than drivers for liquid crystal, plasma or OLED displays
• CPC Class Codes: G09G 2310/0275 Details of drivers for data electrodes, other than drivers for liquid crystal, plasma or OLED displays, not related to handling digital grey scale data or to communication of data to the pixels by means of a current
• CPC Class Codes: G09G 2330/021 Power management, e.g. power saving
• CPC Class Codes: G09G 2340/0428 Gradation resolution change
• CPC Class Codes: G09G 2360/141 the light conveying information used for selecting or modulating the light emitting or modulating element
• CPC Class Codes: G09G 2360/144 the light being ambient light
• CPC Class Codes: G09G 3/20 for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters
• CPC Class Codes: G09G 3/2022 using sub-frames
• CPC Class Codes: G09G 3/3225 using an active matrix

Abstract

Outside light is received using a light sensor, and in accordance with the outside light intensity, each of a first display mode which expresses multiple gray scales and a second display-y mode which expresses a gray scale smaller in number than that in the first display mode is switched and used. The switching is controlled by a display controller based on data of the outside light intensity. Accordingly, the visibility can be ensured in a wide range of situations, from under a fluorescent lamp in a dark place or inside, to under sunlight outside. In the second display mode, frequencies of a start pulse and a clock pulse to be inputted to a source signal line driver circuit are reduced and a driving voltage is decreased by the display controller; accordingly, a frame period can be longer than that in the first display mode and power consumption can be reduced.

Claims

1. A display device comprising:

a display;

a display controller; and

a light sensor,

wherein the display device has a first display mode and a second display mode,

wherein in the first display mode, one frame period is divided into a plurality of subframe periods, each of the plurality of subframe periods is either a lighting period or a non-lighting period, and an n-bit (where n is a natural number equal to or more than

     2) gray scale is expressed by the sum total of a lighting time within the one frame period,

wherein in the second display mode, the display is operated by a lower clock frequency and a lower driving voltage than in the first display mode, one frame period is either a lighting period or a non-lighting period, and a one-bit gray scale is expressed by the sum total of a lighting time within the one frame period,

wherein outside light is received by the light sensor, and the first display mode and the second display mode are controlled by the display controller in accordance with intensity of the outside light, and

wherein a plurality of gate signal lines are selected within one gate selection period by dividing one gate selection period into a plurality of sub-gate selection periods and selecting a gate signal line of one row within the sub-gate selection period.

2. The display device according to claim 1, wherein the intensity of outside light when the first display mode is selected is higher than the intensity of outside light when the second display mode is selected.

3. The display device according to claim 1, wherein the display device further comprises a frame memory, n-bit data (where n is a natural number equal to or more than 2) is written into the frame memory, the n-bit data is read from the frame memory to perform display in the first display mode, one-bit data is written into the frame memory, and the one-bit data is read from the frame memory to perform display in the second display mode.

4. The display device according to claim 1, wherein the display includes a light-emitting element in each pixel, and a current applied to the light-emitting element in the first display mode is larger than a current applied to the light-emitting element in the second display mode.

5. The display device according to claim 1, wherein the one frame period has a period for writing to a pixel, a display period, and an erasing period in the first display mode.

6. The display device according to claim 1, wherein when the second display mode is selected, a power supply controlling circuit for a driver circuit in the display controller outputs a voltage lower than that in the first display mode.

7. The display device according to claim 1, wherein the display device is incorporated in to an electronic apparatus selected from the group consisting of a portable information terminal, a personal computer, a video camera, and an image reproducing device.

8. A display device comprising:

a display;

a display controller; and

a light sensor,

wherein the display device has a first display mode and a second display mode,

wherein in the first display mode, one frame period is divided into a plurality of subframe periods, each of the plurality of subframe periods is either a lighting period or a non-lighting period, and an n-bit (where n is a natural number equal to or more than

     2) gray scale is expressed by the sum total of a lighting time within the one frame period,

wherein in the second display mode, the display is operated by a lower clock frequency and a lower driving voltage than in the first display mode, one frame period longer than one frame period in the first display mode is either a lighting period or a non-lighting period, and a one-bit gray scale is expressed by a lighting time within the one frame period are included,

wherein outside light is received by the light sensor, and the first display mode and the second display mode are controlled by the display controller in accordance with intensity of the outside light, and

wherein a plurality of gate signal lines are selected within one gate selection period by dividing one gate selection period into a plurality of sub-gate selection periods and selecting a gate signal line of one row within the sub-gate selection period.

9. The display device according to claim 8, wherein the intensity of outside light when the first display mode is selected is higher than the intensity of outside light when the second display mode is selected.

10. The display device according to claim 8, wherein the display device further comprises a frame memory, n-bit data (where n is a natural number equal to or more than 2) is written into the frame memory, the n-bit data is read from the frame memory to perform display in the first display mode, one-bit data is written into the frame memory, and the one-bit data is read from the frame memory to perform display in the second display mode.

11. The display device according to claim 8, wherein the display includes a light-emitting element in each pixel, and a current applied to the light-emitting element in the first display mode is larger than a current applied to the light-emitting element in the second display mode.

12. The display device according to claim 8, wherein the one frame period has a period for writing to a pixel, a display period, and an erasing period in the first display mode.

13. The display device according to claim 8, wherein when the second display mode is used, a power supply controlling circuit for a driver circuit in the display controller outputs a voltage lower than that in the first display mode.

14. The display device according to claim 8, wherein the display device is incorporated in to an electronic apparatus selected from the group consisting of a portable information terminal, a personal computer, a video camera, and an image reproducing device.

15. A display device comprising:

a display;

a display controller; and

a light sensor,

wherein the display device has a first display mode and a second display mode,

wherein in the first display mode, one frame period is divided into a plurality of subframe periods, each of the plurality of subframe periods is either a lighting period or a non-lighting period, and an n-bit (where n is a natural number equal to or more than

     2) gray scale is expressed by the sum total of a lighting time within the one frame period,

wherein in the second display mode, the display is operated by a lower clock frequency and a lower driving voltage than in the first display mode, one frame period is divided into a plurality of subframe periods, each of the plurality of subframe periods is either a lighting period or a non-lighting period, and an m-bit (where m is a natural number less than n) gray scale is expressed by the sum total of a lighting time within the one frame period are included,

wherein outside light is received by the light sensor, and the first display mode and the second display mode are controlled by the display controller in accordance with intensity of the outside light; and

wherein a plurality of gate signal lines are selected within one gate selection period by dividing one gate selection period into a plurality of sub-gate selection periods and selecting a gate signal line of one row within the sub-gate selection period.

16. The display device according to claim 15, wherein the intensity of outside light when the first display mode is selected is higher than the intensity of outside light when the second display mode is selected.

17. The display device according to claim 15, wherein the display device further comprises a frame memory, n-bit data (where n is a natural number equal to or more than 2) is written into the frame memory, the n-bit data is read from the frame memory to perform display in the first display mode, m-bit data (where m is a natural number less than n) is written into the frame memory, and the m-bit data is read from the frame memory to perform display in the second display mode.

18. The display device according to claim 15, wherein the display includes a light-emitting element in each pixel, and a voltage applied to the light-emitting element in the first display mode is higher than a voltage applied to the light-emitting element in the second display mode.

19. The display device according to claim 15, wherein the one frame period has a period for writing to a pixel, a display period, and an erasing period in the first display mode.

20. The display device according to claim 15, wherein when using the second display mode, a power supply controlling circuit for a driver circuit in the display controller outputs a voltage which is lower than that in the first display mode.

21. The display device according to claim 15, wherein the display device is incorporated in to an electronic apparatus selected from the group consisting of a portable information terminal, a personal computer, a video camera, and an image reproducing device.

22. A driving method of a display device comprising a display and a light sensor, the method comprising:

selecting a display mode between a first display mode and a second display mode in accordance with intensity of an outside light received by the light sensor;

in the selected display mode, selecting a plurality of gate signal lines within one gate selection period by dividing one gate selection period into a plurality of sub-gate selection periods and selecting a gate signal line of one row within the sub-gate selection period,

wherein in the first display mode, one frame period is divided into a plurality of subframe periods, each of the plurality of subframe periods is either a lighting period or a non-lighting period, and an n-bit (where n is a natural number equal to or more than

     2) gray scale is expressed by the sum total of a lighting time within the one frame period, and

wherein in the second display mode, the display is operated by a lower clock frequency and a lower driving voltage than in the first display mode, one frame period is either a lighting period or a non-lighting period, and a one-bit gray scale is expressed by a lighting time within the one frame period.

23. The method according to claim 22, wherein the intensity of outside light when the first display mode is selected is higher than the intensity of outside light when the second display mode is selected.

24. The method according to claim 22, wherein the display device further comprises a frame memory, n-bit data (where n is a natural number equal to or more than 2) is written into the frame memory, the n-bit data is read from the frame memory to perform display in the first display mode, m-bit data (where m is a natural number less than n) is written into the frame memory, and the m-bit data is read from the frame memory to perform display in the second display mode.

25. The method according to claim 22, wherein the display includes a light-emitting element in each pixel, and a voltage applied to the light-emitting element in the first display mode is higher than a voltage applied to the light-emitting element in the second display mode.

26. The method according to claim 22, wherein the one frame period has a period for writing to a pixel, a display period, and an erasing period in the first display mode.

27. The method according to claim 22, wherein the display device is incorporated in to an electronic apparatus selected from the group consisting of a portable information terminal, a personal computer, a video camera, and an image reproducing device.