Display device and driving method thereof

• US 7,969,390 B2
• Filed: 09/11/2006
• Issued: 06/28/2011
• Est. Priority Date: 09/15/2005
• Status: Active Grant

• Current Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Original Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Inventors: Yoshida, Yasunori
• Primary Examiner(s): Eisen; Alexander
• Assistant Examiner(s): YEUNG, MATTHEW M
• Application Number:
  US11/530,771
• Publication Number:
  US 20070063935A1
• Time in Patent Office: 1,751 Days
• Field of Search: None
• US Class Current: 345/76
• CPC Class Codes: G09G 2300/0417 Special arrangements specific to the use of low carrier mobility technology
• CPC Class Codes: G09G 2300/0465 Improved aperture ratio, e.g. by size reduction of the pixel circuit, e.g. for improving the pixel density or the maximum displayable luminance or brightness
• CPC Class Codes: G09G 2300/0809 Several active elements per pixel in active matrix panels
• CPC Class Codes: G09G 2300/0852 being a dynamic memory with more than one capacitor
• CPC Class Codes: G09G 2300/0866 by means of changes in the pixel supply voltage
• CPC Class Codes: G09G 2310/0256 with the purpose of reversing the voltage across a light emitting or modulating element within a pixel
• CPC Class Codes: G09G 2320/0223 Compensation for problems related to R-C delay and attenuation in electrodes of matrix panels, e.g. in gate electrodes or on-substrate video signal electrodes
• CPC Class Codes: G09G 2320/043 Preventing or counteracting the effects of ageing
• CPC Class Codes: G09G 2330/08 Fault-tolerant or redundant circuits, or circuits in which repair of defects is prepared
• CPC Class Codes: G09G 3/325 the data current flowing through the driving transistor during a setting phase, e.g. by using a switch for connecting the driving transistor to the data driver
• CPC Class Codes: H10K 2102/3031 Two-side emission, e.g. transparent OLEDs [TOLED]
• CPC Class Codes: H10K 59/12 Active-matrix OLED [AMOLED] displays
• CPC Class Codes: H10K 59/35 comprising red-green-blue [RGB] subpixels
• CPC Class Codes: H10K 71/166 using selective deposition, e.g. using a mask

Abstract

To solve the lack of program time, which is a problem of a display device including an EL element, and to provide a display device including a pixel circuit with a high aperture ratio and a driving method thereof. In a circuit including a driving transistor, a capacitor, a display element which can be used as a capacitor, a first power supply line and a second power supply line, potentials of the first power supply line and the second power supply line are set to be almost the same, thereby a threshold voltage of the driving transistor is held in the display element, and after that, a charge is divided into the display element and the capacitor.

Claims

1. A display device comprising:

a plurality of data lines for supplying a data current;

a plurality of scan lines for transmitting a selection signal; and

a pixel portion comprising a plurality of pixel circuits connected to the plurality of data lines and the plurality of scan lines, each of the plurality of pixel circuits comprising;

a display element configured to emit light at luminance corresponding to the data current;

a transistor having a source electrode, a drain electrode, and a gate electrode, the transistor configured to supply the data current to the display element and;

a first power supply line connected to the source electrode of the transistor;

a second power supply line connected to the display element;

a first capacitor configured to hold a voltage between the source electrode of the transistor and the gate electrode of the transistor;

a first switch element configured to select a connection between the drain electrode of the transistor and the gate electrode of the transistor;

a second switch element configured to select a connection between one of the plurality of data lines and the display element;

a third switch element configured to select a connection between the transistor and the display element; and

a fourth switch element configured to select a connection between the first capacitor and the display element,

wherein the second switch element is directly electrically connected to both the transistor and a current source.

2. The display device according to claim 1, further comprising:

a data line driver circuit connected to the plurality of data lines; and

a scan line driver circuit connected to the plurality of scan lines.

3. The display device according to claim 1, wherein potential of the first power supply line is the same potential as an anode of the display element.

4. The display device according to claim 1, wherein potential of the second power supply line is the same potential as a cathode of the display element.

5. The display device according to claim 1, wherein either potential of the first power supply line or potential of the second power supply line is changed.

6. The display device according to claim 1, wherein the transistor is a p-channel transistor.

7. The display device according to claim 1, wherein the transistor is an n-channel transistor.

8. The display device according to claim 1, wherein the transistor is a driving transistor.

9. The display device according to claim 1, wherein the display element is an EL element.

10. An electronic apparatus having the display device according to claim 1, the electronic apparatus is one selected from the group consisting of a television apparatus, a camera such as a digital camera, a digital video camera, a mobile phone, a portable information terminal such as a PDA, a portable game machine, a monitor, a computer, an audio reproducing device such as a car audio, and an image reproducing device provided with a recording medium such as a home-use game machine.

11. A display device comprising:

a plurality of data lines for supplying a data current;

a plurality of scan lines for transmitting a selection signal; and

a pixel portion comprising a plurality of pixel circuits connected to the plurality of data lines and the plurality of scan lines, each of the plurality of pixel circuits comprising;

a display element which emits light at luminance corresponding to the data current;

a first transistor having a source electrode, a drain electrode, and a gate electrode, the first transistor configured to supply the data current to the display element;

a first power supply line connected to the first transistor;

a second power supply line connected to the display element;

a first capacitor configured to hold a voltage between the source electrode of the first transistor and the gate electrode of the first transistor;

a second transistor configured to select a connection between the drain electrode of the first transistor and the gate electrode of the first transistor;

a third transistor configured to select a connection between one of the plurality of data lines and the display element;

a fourth transistor configured to select a connection between the first transistor and the display element; and

a fifth transistor configured to select a connection between the first capacitor and the display element,

wherein the third transistor is directly electrically connected to both the first transistor and a current source.

12. The display device according to claim 11, further comprising:

a data line driver circuit connected to the plurality of data lines; and

a scan line driver circuit connected to the plurality of scan lines.

13. The display device according to claim 11, wherein potential of the first power supply line is the same potential as an anode of the display element.

14. The display device according to claim 11, wherein potential of the second power supply line is the same potential as a cathode of the display element.

15. The display device according to claim 11, wherein either potential of the first power supply line or potential of the second power supply line is changed.

16. The display device according to claim 11, wherein the first transistor is a p-channel transistor.

17. The display device according to claim 11, wherein the first transistor is an n-channel transistor.

18. The display device according to claim 11, wherein the first transistor is a driving transistor.

19. The display device according to claim 11, wherein the display element is an EL element.

20. An electronic apparatus having the display device according to claim 11, the electronic apparatus is one selected from the group consisting of a television apparatus, a camera such as a digital camera, a digital video camera, a mobile phone, a portable information terminal such as a PDA, a portable game machine, a monitor, a computer, an audio reproducing device such as a car audio, and an image reproducing device provided with a recording medium such as a home-use game machine.

21. The display device according to claim 11, wherein the first to fifth transistors have the same polarity.

22. A display device comprising:

first and second wires;

a capacitor having a first electrode and a second electrode;

a display element having a first electrode and a second electrode;

a transistor having a gate electrode, a first electrode, and a second electrode; and

first to fourth switch elements, each having a first terminal and a second terminal,

wherein the gate electrode of the transistor is connected to the second electrode of the capacitor and the first terminal of the first switch element,

wherein the first electrode of the transistor is connected to the first wire,

wherein the second electrode of the transistor is connected to the second terminal of the first switch element, the second terminal of the second switch element, and the first terminal of the third switch element,

wherein the second switch element is provided between the transistor and a current source, and

wherein the first electrode of the display element is directly electrically connected to the second terminal of the third switch element and the second terminal of the fourth switch element.

23. The display device according to claim 22, wherein the display element functions as a capacitor.

24. The display device according to claim 22, wherein the transistor is a p-channel transistor.

25. The display device according to claim 22, wherein the transistor is an n-channel transistor.

26. The display device according to claim 22, wherein the transistor is a driving transistor.

27. The display device according to claim 22, wherein the display element is an EL element.

28. An electronic apparatus having the display device according to claim 22, the electronic apparatus is one selected from the group consisting of a television apparatus, a camera such as a digital camera, a digital video camera, a mobile phone, a portable information terminal such as a PDA, a portable game machine, a monitor, a computer, an audio reproducing device such as a car audio, and an image reproducing device provided with a recording medium such as a home-use game machine.

29. The display device according to claim 22, wherein the first wire is a power supply line.

30. The display device according to claim 22, wherein the second wire is a data line.

31. A display device comprising:

first and second wires;

a capacitor having a first electrode and a second electrode;

a display element having a first electrode and a second electrode; and

first to fifth transistors, each having a gate electrode, a first electrode, and a second electrode,

wherein the gate electrode of the first transistor is connected to the second electrode of the capacitor and the first electrode of the second transistor,

wherein the first electrode of the first transistor is connected to the first wire,

wherein the second electrode of the first transistor is connected to the second electrode of the second transistor and the first electrode of the fourth transistor,

wherein the third transistor is provided between the first transistor and a current source,

wherein the first electrode of the fifth transistor is connected to the first electrode of the second transistor and the second electrode of the capacitor, and

wherein the first electrode of the display element is directly electrically connected to the second electrode of the fourth transistor and the second electrode of the fifth transistor.

32. The display device according to claim 31, wherein the display element functions as a capacitor.

33. The display device according to claim 31, wherein the first transistor is a p-channel transistor.

34. The display device according to claim 31, wherein the first transistor is an n-channel transistor.

35. The display device according to claim 31, wherein the first transistor is a driving transistor.

36. The display device according to claim 31, wherein the display element is an EL element.

37. An electronic apparatus having the display device according to claim 31, the electronic apparatus is one selected from the group consisting of a television apparatus, a camera such as a digital camera, a digital video camera, a mobile phone, a portable information terminal such as a PDA, a portable game machine, a monitor, a computer, an audio reproducing device such as a car audio, and an image reproducing device provided with a recording medium such as a home-use game machine.

38. The display device according to claim 31, wherein the first wire is a power supply line.

39. The display device according to claim 31, wherein the second wire is a data line.

40. The display device according to claim 31, wherein the first to fifth transistors have the same polarity.

41. A driving method of a display device comprising:

storing a charge in a display element in a threshold writing period by turning a first transistor on, turning a second transistor on, turning a third transistor off, turning a fourth transistor off, and turning a fifth transistor on; and

emitting light from the display element in a light emitting period by turning the second transistor off, turning the third transistor off, turning the fourth transistor on, and turning the fifth transistor off, after the threshold writing period,

wherein the second transistor is connected to the first transistor,

wherein the third transistor is provided between the first transistor and a current source, and

wherein the fourth transistor and the fifth transistor are provided between the display element and the first transistor.

42. The driving method of a display device according to claim 41,

wherein in the threshold writing period, a potential of a power supply line on a cathode side of the display element is the same or almost the same as a potential of a power supply line on an anode side of the display element, and

wherein in the light emitting period, the potential of the power supply line on the cathode side of the display element is lower than the potential of the power supply line on the anode side of the display element.

43. The driving method of a display device according to claim 41, wherein the display element functions as a capacitor.

44. The driving method of a display device according to claim 41, wherein the first transistor is a p-channel transistor.

45. The driving method of a display device according to claim 41, wherein the first transistor is an n-channel transistor.

46. The driving method of a display device according to claim 41, wherein the first transistor is a driving transistor.

47. The driving method of a display device according to claim 41, wherein the display element is an EL element.

48. The driving method of a display device according to claim 41, wherein the first to fifth transistors have the same polarity.

49. A driving method of a display device comprising:

dividing a charge into a display element and a capacitor in a Cs rewriting period by turning a second transistor off, turning a third transistor off, turning a fourth transistor off, and turning a fifth transistor on; and

emitting light from the display element in a light emitting period by turning a first transistor on, turning the second transistor off, turning the third transistor off, turning the fourth transistor on, and turning the fifth transistor off, after the Cs rewriting period,

wherein the second transistor is connected to the first transistor,

wherein the third transistor is provided between the first transistor and a current source, and

wherein the fourth transistor and the fifth transistor are provided between the display element and the first transistor.

50. The driving method of a display device according to claim 49,

wherein in the Cs rewriting period, a potential of a power supply line on a cathode side of the display element is the same or almost the same as a potential of a power supply line on an anode side of the display element, and

wherein in the light emitting period, the potential of the power supply line on the cathode side of the display element is lower than the potential of the power supply line on the anode side of the display element.

51. The driving method of a display device according to claim 49, wherein the display element functions as a capacitor.

52. The driving method of a display device according to claim 49, wherein the first transistor is a p-channel transistor.

53. The driving method of a display device according to claim 49, wherein the first transistor is an n-channel transistor.

54. The driving method of a display device according to claim 49, wherein the first transistor is a driving transistor.

55. The driving method of a display device according to claim 49, wherein the display element is an EL element.

56. The driving method of a display device according to claim 49, wherein the first to fifth transistors have the same polarity.

57. A driving method of a display device comprising:

storing a first charge in a display element;

storing a second charge in a capacitor;

dividing the stored first charge and the stored second charge into the display element and the capacitor by electrically connecting the display element and the capacitor each other through a first switch element; and

emitting light from the display element by turning a transistor and a second switch element on,

wherein a gate electrode of the transistor is electrically connected to the capacitor and the first switch element,

wherein one of a source electrode and a drain electrode of the transistor is electrically connected to the capacitor,

wherein the other of the source electrode and the drain electrode of the transistor is directly electrically connected to the second switch element, and

wherein the second switch element is directly electrically connected to the display element.

58. The driving method of a display device according to claim 57, wherein the display element functions as a capacitor.

59. The driving method of a display device according to claim 57, wherein the transistor is a p-channel transistor.

60. The driving method of a display device according to claim 57, wherein the transistor is an n-channel transistor.

61. The driving method of a display device according to claim 57, wherein the transistor is a driving transistor.

62. The driving method of a display device according to claim 57, wherein the display element is an EL element.