Display device and method for driving the same

• US 20030174153A1
• Filed: 03/12/2003
• Published: 09/18/2003
• Est. Priority Date: 03/13/2002
• Status: Active Grant

• Current Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Original Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Inventors: Koyama, Jun
• Granted Patent: US 7,330,169 B2
• Time in Patent Office: Days
• US Class Current: 345/690
• CPC Class Codes: G09G 2300/0809 Several active elements per pixel in active matrix panels
• CPC Class Codes: G09G 2300/0842 forming a memory circuit, e.g. a dynamic memory with one capacitor
• CPC Class Codes: G09G 2310/0251 Precharge or discharge of pixel before applying new pixel voltage
• 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 2320/0626 for control of overall brightness
• CPC Class Codes: G09G 2330/021 Power management, e.g. power saving
• CPC Class Codes: G09G 2360/18 Use of a frame buffer in a display terminal, inclusive of the display panel
• CPC Class Codes: G09G 3/2007 Display of intermediate tones
• CPC Class Codes: G09G 3/2022 using sub-frames
• CPC Class Codes: G09G 3/22 using controlled light sources
• CPC Class Codes: G09G 3/3266 Details of drivers for scan electrodes
• CPC Class Codes: G09G 3/3275 Details of drivers for data electrodes
• CPC Class Codes: G09G 5/18 Timing circuits for raster scan displays specially adapted for television H04N ; synchronisation between the display unit and other display units, videodisc player G09G5/12

Abstract

In a display device using a time gradation method, power consumption at a time when multigradation display is unnecessary is reduced. In a second display mode in which the number of gradations is set to two as compared with a first display mode of multigradation, writing of a digital video signal of a lower order bit into a memory is eliminated by a memory controller of a signal control circuit included in the display device. In addition, readout of the digital video signal of the lower order bit from the memory is eliminated. The amount of information of a digital video signal inputted to a source signal line drive circuit is reduced. In accordance with such operation, a display controller sets a display period for conducting display to be long. When the gradation is reduced, a frame period can be also set to be longer than the first display mode.

Claims

1. A display device comprising:

a display; and

a display controller for dividing a first frame period into a plurality of subframe periods that one of lighting and non-lighting is set to each of the subframe periods and expressing gradation in accordance with a total lighting time during the first frame period, and for setting to one of one-lighting and one-non-lighting during a second frame period.

3. A display device according to claim 1, wherein the display device further comprises a frame memory, n-bits data (n is natural number of two or more) is written and read out so that display is conducted in the first frame period, and 1-bit data is written and read out so that display is conducted. in the second frame period

5. A display device according to claim 1, wherein the display controller is integrally formed on the same substrate as the display.

7. A display device according to claim 1, wherein the display device further comprises a light emitting element for each pixel, a specific voltage is applied to the light emitting element, and a voltage applied to the light emitting element in the first frame period is higher than a voltage applied to the light emitting element in the second frame period.

9. A display device according to claim 1, wherein the display device further comprises a light emitting element for each pixel, a specific current is supplied to the light emitting element, and a current supplied to the light emitting element in the first frame period is larger than a current supplied to the light emitting element in the second frame period.

11. A display device according to claim 1, wherein the first frame period is composed of three periods of a wiring period, a display period, and an erasing period.

23. An electronic appliance using the display device according to claim 1.

2. A display device comprising:

a display; and

a display controller for dividing a first frame period into a plurality of subframe periods that one of lighting and non-lighting is set to each of the subframe periods and expressing gradation in accordance with a total lighting time during the first frame period, and for setting to one of one-lighting and one-non-lighting during a second frame period, wherein the second frame period is longer than the first frame period.

4. A display device according to claim 2, wherein the display device further comprises a frame memory, n-bits data (n is natural number of two or more) is written and read out so that display is conducted in the first frame period, and 1-bit data is written and read out so that display is conducted in the second frame period.

6. A display device according to claim 2, wherein the display controller is integrally formed on the same substrate as the display.

8. A display device according to claim 2, wherein the display device further comprises a light emitting element for each pixel, a specific voltage is applied to the light emitting element, and a voltage applied to the light emitting element in the first frame period is higher than a voltage applied to the light emitting element in the second frame period.

10. A display device according to claim 2, wherein the display device further comprises a light emitting element for each pixel, a specific current is supplied to the light emitting element, and a current supplied to the light emitting element in the first frame period is larger than a current supplied to the light emitting element in the second frame period.

12. A display device according to claim 2, wherein the first frame period is composed of three periods of a wiring period, a display period, and an erasing period.

24. An electronic appliance using the display device according to claim 2.

13. A method of driving a display device including a display and a display controller, comprising:

dividing a first frame period into a plurality of subframe periods that one of lighting and non-lighting is set to each of the subframe periods and expressing gradation in accordance with a total lighting time during the first frame period; and

setting to one of one-lighting and one-non-lighting during a second frame period.

15. A method of driving a display device according to claim 13, wherein the display device further comprises a frame memory, n-bits data (n is natural number of two or more) is written and read out to conduct display in the first frame period, and 1-bit data is written and read out to conduct display in the second frame period.

17. A method of driving a display device according to claim 13, wherein the display device further comprises a light emitting element for each pixel, a specific voltage is applied to the light emitting element, and a voltage applied to the light emitting element in the first frame period is higher than a voltage applied to the light emitting element in the second frame period.

19. A method of driving a display device according to claim 13, wherein the display device further comprises a light emitting element for each pixel, a specific current is supplied to the light emitting element, and a current supplied to the light emitting element in the first frame period is larger than a current supplied to the light emitting element in the second frame period.

21. A method of driving a display device according to claim 13, wherein the first frame period is composed of three periods of a wiring period, a display period, and an erasing period.

25. An electronic appliance using the display device driving method according to claim 13.

14. A method of driving a display device including a display and a display controller, comprising:

dividing a first frame period into a plurality of subframe periods that one of lighting and non-lighting is set to each of the subframe periods and expressing gradation in accordance with a total lighting time during the first frame period; and

setting to one of one-lighting and one-non-lighting during a second frame period,

wherein the second frame period is longer than the first frame period.

16. A method of driving a display device according to claim 14, wherein the display device further comprises a frame memory, n-bits data (n is natural number of two or more) is written and read out to conduct display in the first frame period, and 1-bit data is written and read out to conduct display in the second frame period.

18. A method of driving a display device according to claim 14, wherein the display device further comprises a light emitting element for each pixel, a specific voltage is applied to the light emitting element, and a voltage applied to the light emitting element in the first frame period is higher than a voltage applied to the light emitting element in the second frame period.

20. A method of driving a display device according to claim 14, wherein the display device further comprises a light emitting element for each pixel, a specific current is supplied to the light emitting element, and a current supplied to the light emitting element in the first frame period is larger than a current supplied to the light emitting element in the second frame period.

22. A method of driving a display device according to claim 14, wherein the first frame period is composed of three periods of a wiring period, a display period, and an erasing period.

26. An electronic appliance using the display device driving method according to claim 14.