Active matrix display with variable duty cycle

• US 20060012708A1
• Filed: 08/08/2003
• Published: 01/19/2006
• Est. Priority Date: 09/16/2002
• Status: Active Grant

• Current Assignee: InnoLux Corporation
• Original Assignee: Koninklijke Philips Electronics N.V. (Koninklijke Philips N.V.)
• Inventors: Rosmalen, Gerard Eduard
• Granted Patent: US 7,456,827 B2
• Time in Patent Office: Days
• US Class Current: 348/503
• CPC Class Codes: G09G 2320/043 Preventing or counteracting the effects of ageing
• CPC Class Codes: G09G 2330/021 Power management, e.g. power saving
• CPC Class Codes: G09G 3/2014 by modulation of the duration of a single pulse during which the logic level remains constant
• CPC Class Codes: G09G 3/2022 using sub-frames
• CPC Class Codes: G09G 3/3208 organic, e.g. using organic light-emitting diodes [OLED]
• CPC Class Codes: G09G 3/3648 using an active matrix G09G3/367 - G09G3/3696 take precedence

Abstract

The invention relates to an active matrix display device (10) having a plurality of pixels (110). The pixels are grouped into pixel groups (R′, G′, B′). Each pixel group (R′, G′, B′) is assigned a specific duty cycle, such that at least two pixel groups are assigned different duty cycles. The device furthermore comprises circuitry (54) for driving each pixel group (R′, G′, B′) at its assigned duty cycle. The invention also relates to the driving of such display devices.

Claims

1. An active matrix display device (10) having a plurality of pixels (110), wherein the pixels (110) are grouped into pixel groups (R′

, G′

, B′

), and circuitry is present to drive each pixel group R′

, G′

, B′

) at a specific duty cycle (62;

73;

82), wherein at least two pixel groups (R′

, G′

, B′

) are assigned different duty cycles.

2. An active matrix display device (10) according to claim 1, wherein the display device (10) is an organic electroluminescent display device.

3. An active matrix display device (10) according to claim 1, wherein the pixels (110) are grouped into pixel groups (R′

, G′

, B′

) according to a dominant degradation mechanism common to the pixels in each pixel group.

4. An active matrix display device (10) according to claim 1, wherein the pixels (110) are grouped into pixel groups (R′

, G′

, B′

) according to the color they can emit during operation.

5. An active matrix display device (10) according to claim 1, wherein the specific duty cycle (62;

73;

82) assigned to each pixel group (R′

, G′

, B′

) depends on the temperature of the pixels (110) in the corresponding pixel group (R′

, G′

, B′

).

6. An active matrix display device (10) according to claim 1, wherein the specific duty cycle (62;

73;

82) assigned to each pixel group (R′

, G′

, B′

) depends on the history of operation of the corresponding pixel group (R′

, G′

, B′

).

7. An active matrix display device (10) according to claim 1, wherein the pixels (110) are operative to emit a first, a second and a third color, and are grouped into a first, a second, and a third pixel group (R′

, G′

, B′

) accordingly.

8. An active matrix display device (10) according to claim 7, wherein each pixel group (R′

, G′

, B′

) is connected to its own power circuit (51, 52, 53), which is arranged to generate and control the duty cycle (61) of the pixels in the corresponding pixel group (R′

, G′

, B′

).

9. An active matrix display device (10) according to claim 7, wherein each pixel group (R′

, G′

, B′

) is provided with a separate cathode, which is arranged to control the duty cycles (62;

73;

82) of the corresponding pixel group (110).

10. An active matrix display device (10) according to claim 1, arranged to address (71, 72;

81) a pixel group (R′

, G′

, B′

) more than one time in each picture frame.

11. An active matrix display device (10) according to claim 10, arranged to address a pixel group (R′

, G′

, B′

) in separate addressing rows (351, 352, 353).

12. A method for driving pixels (110) in an active matrix display device (10) comprising the steps of:

grouping the pixels into pixel groups (R′

, G′

, B′

);

assigning a specific duty cycle (62;

73;

82) to each pixel group (R′

, G′

, B′

); and

driving each pixel (110) at the specific duty cycle (62;

73;

82) that is assigned to its pixel group (R′

, G′

, B′

).

13. A method according to claim 12, wherein the specific duty cycles (62;

73;

82) are adjusted so as to reduce the degradation of the pixel/pixels (110) in the corresponding pixel group (R′

, G′

, B′

).

14. A method according to claim 12, wherein the grouping of pixels into pixel groups (R′

, B′

, G′

) is such that pixels (110) having operatively similar dominant degradation mechanisms are grouped into a same pixel group (R′

, G′

, B′

).

15. A method according to claim 12, wherein the assignment of a duty cycle (62;

73;

82) to each pixel group (R′

, G′

, B′

) is a static assignment, whereby the duty cycle (62;

73;

82) is the same for the entire lifetime of the display device (10).

16. A method according to claim 12, wherein the assignment of a duty cycle (62;

73;

82) to each pixel group is a dynamic assignment, whereby the duty cycle (62;

73;

82) changes during the lifetime of the display device (10).