Display device, display module, electronic apparatus and driving method of the display device

• US 7,714,816 B2
• Filed: 03/29/2006
• Issued: 05/11/2010
• Est. Priority Date: 03/31/2005
• Status: Expired due to Fees

• Current Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Original Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Inventors: Umezaki, Atsushi
• Primary Examiner(s): Nguyen; Chanh
• Assistant Examiner(s): Yang; Kwang-Su
• Application Number:
  US11/277,883
• Publication Number:
  US 20060221006A1
• Time in Patent Office: 1,504 Days
• Field of Search: 345/36, 345/45, 345/76, 345/82, 345/204
• US Class Current: 345/82
• CPC Class Codes: G09G 2300/0842 forming a memory circuit, e.g. a dynamic memory with one capacitor
• CPC Class Codes: G09G 2320/029 by monitoring one or more pixels in the display panel, e.g. by monitoring a fixed reference pixel
• 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 3/3233 with pixel circuitry controlling the current through the light-emitting element
• CPC Class Codes: G09G 3/3291 in which the data driver supplies a variable data voltage for setting the current through, or the voltage across, the light-emitting elements

Abstract

To provide a display device which can apply a voltage at which an operating point becomes a saturation region even when a light-emitting element deteriorates without applying a voltage to a driving TFT and the light-emitting element larger than necessary. A monitor pixel has a monitor pixel power supply line, a first light-emitting element, and a first TFT, while a pixel in the display region has a power supply line, a second TFT as a driving TFT, a signal line which gives a signal to a gate of the second TFT, a third TFT, and a second light-emitting element. A potential of the monitor pixel power supply line and a gate potential of the first TFT of the monitor pixel are sampled to be set as a potential of the power supply line of the pixel and a potential of the signal line of the pixel, respectively.

Claims

1. A display device comprising:

a current source;

a monitor pixel region comprising;

a first wiring;

a second wiring;

a first light-emitting element; and

a first transistor;

a display portion including a pixel, a source driver, and a gate driver, the pixel comprising;

a second transistor; and

a second light-emitting element electrically connected to one of a source and a drain of the second transistor; and

a first sampling circuit electrically connected to the first wiring and the other of the source and the drain or the second transistor,

wherein one of a source and a drain of the first transistor is electrically connected to the current source through the first wiring,

wherein the other of the source and the drain of the first transistor is connected to a gate of the first transistor, and

wherein the other of the source and the drain of the first transistor and the gate of the first transistor are electrically connected to the second wiring and one electrode of the first light-emitting element.

2. The display device according to claim 1, wherein the first transistor is a normally off transistor.

3. The display device according to claim 1, wherein the display device is incorporated into an electronic apparatus selected from the group consisting of a video camera, a digital still camera, a goggle type display, a navigation system, an audio reproducing device, a personal computer, a game machine, a mobile computer, a mobile phone, a portable game machine, an electronic book, and an image.

4. The display device according to claim 1, wherein the display device further comprising:

a second sampling circuit electrically connected to the second wiring.

5. The display device according to claim 1, wherein the display device further comprises a digital-analog converter circuit electrically connected to the first and second wiring.

6. The display device according to claim 1, wherein the other of the source and the drain of the first transistor is connected directly to the gate of the first transistor without any intervening elements.

7. A display device comprising:

a current source;

a monitor pixel region comprising;

a first wiring;

a second wiring;

a first light-emitting element; and

a first transistor;

a display portion including a pixel, a source driver, and a gate driver, the pixel comprising;

a third wiring;

a second transistor; and

a second light-emitting element electrically connected to one of a source and a drain of the second transistor;

a first sampling circuit electrically connected to the first wiring and the other of the source and the drain of the second transistor through the third wiring;

a second sampling circuit; and

a digital-analog converter circuit,

wherein one of a source and a drain of the first transistor is electrically connected to the current source through the first wiring, the other of the source and the drain of the first transistor is connected to a gate of the first transistor, and the other of the source and drain of the first transistor and the gate of the first transistor are electrically connected to the second wiring and one electrode of the first light-emitting element,

wherein the first sampling circuit configured to hold a first potential of the first wiring for a certain period and supply a second potential to the third wiring,

wherein the second sampling circuit is configured to hold a third potential of the second wiring for a certain period;

wherein the digital-analog converter circuit is configured to determine a minimum output potential and a maximum output potential by the first potential held in the first sampling circuit and the third potential held in the second sampling circuit, and

wherein the source driver is configured to supply a signal in accordance with an output of the digital-analog converter circuit to a gate of the second transistor.

8. The display device according to claim 7, wherein a fourth potential of the signal is smaller than the first potential of the first wiring.

9. The display device according to claim 7, wherein the first transistor and the second transistor are P-channel transistors.

10. The display device according to claim 7, wherein a channel width and a channel length of the first transistor are the same as a channel width and a channel length of the second transistor.

11. The display device according to claim 7, wherein the first transistor and the second transistor are formed over the same substrate as the second light-emitting element.

12. The display device according to claim 7, wherein an operating point of the first transistor and the first light-emitting element and an operating point of the second transistor and the second light-emitting element are a saturation region of the first transistor and a saturation region of the second transistor respectively.

13. The display device according to claim 7, wherein a structure of first light-emitting element is the same as a structure of the second light-emitting element.

14. The display device according to claim 7, wherein the first transistor is a normally off transistor.

15. The display device according to claim 7, wherein the display device is incorporated into an electronic apparatus selected from the group consisting of a video camera, a digital still camera, a goggle type display, a navigation system, an audio reproducing device, a personal computer, a game machine, a mobile computer, a mobile phone, a portable game machine, an electronic book, and an image reproducing device.

16. The display device according to claim 7, wherein the other of the source and the drain of the first transistor is connected directly to the gate of the first transistor without any intervening elements.

17. A display device comprising:

a current source

a monitor pixel region comprising;

a first wiring;

a second wiring;

a first light-emitting element; and

a first transistor;

a display portion including a pixel, a source driver, and a gate driver, the pixel comprising;

a third wiring;

a fourth wiring;

a fifth wiring;

a second transistor;

a third transistor; and

a second light-emitting element electrically connected to one of a source and a drain of the second transistor;

a first sampling circuit electrically connected to the first wiring and the other of the source and the drain of the second transistor through the third wiring;

a second sampling circuit; and

a digital-analog converter circuit;

wherein one of a source and a drain of the first transistor is electrically connected to the current source through the first wiring, the other of the source and the drain of the first transistor is connected to a gate of the first transistor, and the other of the source and drain of the first transistor and a gate of the first transistor are electrically connected to the second wiring and one electrode of the first light-emitting element,

wherein one of a source and a drain of the third transistor is electrically connected to the fourth wiring, and the other of the source and the drain of the third transistor is electrically connected to a gate of the second transistor, and a gate of the third transistor is electrically connected to the fifth wiring,

wherein the first sampling circuit is configured to hold a first potential of the first wiring for a certain period and supply a second potential to the third wiring,

wherein a second sampling circuit configured to hold a potential of the second wiring for a certain period,

wherein the digital-analog converter circuit is configured to determine a minimum output potential and a maximum output potential by the first potential held in the first sampling circuit and a third potential held in the second sampling circuit,

wherein the source driver is configured to supply a signal in accordance with an output of the digital-analog converter circuit to the fourth wiring, and

wherein the gate driver is configured to supply a selection signal to the fifth wiring.

18. The display device according to claim 17, wherein a fourth potential of the signal is smaller than the first potential of the first wiring.

19. The display device according to claim 17, wherein the first transistor and the second transistor are P-channel transistors.

20. The display device according to claim 17, wherein a channel width and a channel length of the first transistor are the same as a channel width and a channel length of the second transistor.

21. The display device according to claim 17, wherein the first transistor and the second transistor are formed over the same substrate as the second light-emitting element.

22. The display device according to claim 17, wherein an operating point of the first transistor and the first light-emitting element and an operating point of the second transistor and the second light-emitting element are a saturation region of the first transistor and a saturation region of the second transistor respectively.

23. The display device according to claim 17, wherein a structure of first light-emitting element is the same as a structure of the second light-emitting element.

24. The display device according to claim 17, wherein the first transistor is a normally off transistor.

25. The display device according to claim 17, wherein the display device is incorporated into an electronic apparatus selected from the group consisting of a video camera, a digital still camera, a goggle type display, a navigation system, an audio reproducing device, a personal computer, a game machine, a mobile computer, a mobile phone, a portable game machine, an electronic book, and an image reproducing device.

26. The display device according to claim 17, wherein the other of the source and the drain of the first transistor is connected directly to the gate of the first transistor without any intervening elements.

27. A display device comprising:

a current source;

a monitor pixel region comprising;

a first wiring;

a second wiring;

a first light-emitting element; and

a first transistor;

a display portion including a pixel, a source driver, and a gate driver, the pixel comprising;

a third wiring;

a second transistor; and

a second light-emitting element electrically connected to one of a source and a drain of the second transistor;

a first sampling circuit electrically connected to the first wiring and the other of the source and the drain of the second transistor through the third wiring;

a second sampling circuit electrically connected to the second wiring; and

a digital-analog converter circuit electrically connected to the first and second sampling circuits, and

wherein one of a source and a drain of the first transistor is electrically connected to the current source through the first wiring, the other of the source and the drain of the first transistor is connected to a gate of the first transistor, and the other of the source and the drain of the first transistor and the gate of the first transistor are electrically connected to the second wiring and one electrode of the first light-emitting element.

28. The display device according to claim 27, wherein the first transistor and the second transistor are P-channel transistors.

29. The display device according to claim 27, wherein a channel width and a channel length of the first transistor are the same as a channel width and a channel length of the second transistor.

30. The display device according to claim 27, wherein the first transistor and the second transistor are formed over the same substrate as the second light-emitting element.

31. The display device according to claim 27, wherein a structure of first light-emitting element is the same as a structure of the second light-emitting element.

32. The display device according to claim 27, wherein the first transistor is a normally off transistor.

33. The display device according to claim 27, wherein the display device is incorporated into an electronic apparatus selected from the group consisting of a video camera, a digital still camera, a goggle type display, a navigation system, an audio reproducing device, a personal computer, a game machine, a mobile computer, a mobile phone, a portable game machine, an electronic book, and an image reproducing device.

34. The display device according to claim 27, wherein the other of the source and the drain of the first transistor is connected directly to the gate of the first transistor without any intervening elements.