Pixel circuit, display apparatus and electronic apparatus equipped with current driving type light-emitting device

• US 20030063081A1
• Filed: 12/09/2002
• Published: 04/03/2003
• Est. Priority Date: 03/12/1997
• Status: Active Grant

• Current Assignee: Seiko Epson Corporation (Seiko Group)
• Original Assignee: Seiko Epson Corporation (Seiko Group)
• Inventors: Kimura, Mutsumi, Kiguchi, Hiroshi, Shimoda, Tatsuya
• Granted Patent: US 7,362,322 B2
• Time in Patent Office: Days
• US Class Current: 345/211
• CPC Class Codes: G09G 2300/0417 Special arrangements specific to the use of low carrier mobility technology
• CPC Class Codes: G09G 2300/0819 used for counteracting undesired variations, e.g. feedback or autozeroing
• CPC Class Codes: G09G 2300/0842 forming a memory circuit, e.g. a dynamic memory with one capacitor
• CPC Class Codes: G09G 2300/088 using a non-linear two-terminal element
• CPC Class Codes: G09G 2320/0285 using tables for spatial correction of display data
• 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 2320/045 Compensation of drifts in the characteristics of light emitting or modulating elements
• CPC Class Codes: G09G 2330/02 Details of power systems and of start or stop of display operation
• CPC Class Codes: G09G 2330/028 Generation of voltages supplied to electrode drivers in a matrix display other than LCD
• CPC Class Codes: G09G 2360/145 the light originating from the display screen
• CPC Class Codes: G09G 2360/148 the light being detected by light detection means within each pixel
• CPC Class Codes: G09G 3/32 semiconductive, e.g. using light-emitting diodes [LED]
• CPC Class Codes: G09G 3/3233 with pixel circuitry controlling the current through the light-emitting element
• CPC Class Codes: H05B 44/00 Circuit arrangements for operating electroluminescent light sources for operating light emitting diodes H05B45/00
• CPC Class Codes: H05B 45/00 Circuit arrangements for operating light-emitting diodes [LED]
• CPC Class Codes: H10K 59/1213 the pixel elements being TFTs
• CPC Class Codes: H10K 59/13 comprising photosensors that control luminance

Abstract

A display apparatus is provided with a current driving type light-emitting device and a driving device for controlling a driving current flowing through the light-emitting device for each pixel of the display apparatus. The display apparatus consists of power source units for supplying power for causing a driving current to flow via the driving device to the light-emitting device via a power source wire, and signal wire driving units for supplying a data signal to the driving device via signal wires. In addition, voltage adjusting units adjust a voltage for the power source units or a data signal from the signal wire driving units so that a quantity of a driving current flowing through the light-emitting device when a data signal of a predetermined voltage is supplied to the driving device via signal wires or a quantity of emitted light emitted from the light-emitting device comes close to a predetermined reference value.

Claims

1. A display apparatus, comprising:

a current driving type light-emitting device provided for each pixel;

a driving device provided for each of said pixels, for controlling a driving current flowing to said light-emitting device according to a voltage of a data signal;

a power source unit for supplying power source through a power wire to cause said driving current to flow to said light-emitting device via said driving device;

a signal wire driving unit for supplying said data signal to said driving device through a signal wire; and

a voltage adjusting unit for adjusting at least one of said power source of said power source unit and said data signal at said signal wire driving unit, in such a manner that, when a data signal of a predetermined voltage is supplied to said driving device through said signal wire, at least one of a quantity of driving current flowing and a quantity of light emitted by said light-emitting device comes close to a predetermined reference value.

2. The display apparatus according to claim 1,

wherein said driving device comprises a thin film transistor having a gate to which said data signal is supplied, and a source and a drain between which said driving current flows, a conductance between said source and said drain being controlled by a gate voltage.

3. The display apparatus according to claim 1,

wherein said voltage adjusting unit comprises:

a current measuring unit for measuring a quantity of driving current when a data signal of said predetermined voltage is supplied to said driving device; and

a voltage control unit for adjusting at least one of said voltages such that said measured current approaches a predetermined reference current.

4. The display apparatus according to claim 1,

wherein said voltage adjusting unit comprises:

a light-emitting measuring unit for measuring the quantity of said emitted light at the time when a data signal of said predetermined voltage is supplied to said drive device; and

a voltage control unit for adjusting at least one of said voltages such that said measured quantity of emitted light approaches said reference quantity of emitted light.

5. The display apparatus according to claim 1, further comprising a controller for controlling said voltage adjusting unit so as to adjust at least one of said voltages at a non-display period preceding a display period.

53. An electronic apparatus comprising a display apparatus according to claim 1.

6. A display apparatus, comprising:

a current driving type display light-emitting device provided for each pixel of a display region;

a driving device provided for each said pixel, for controlling a driving current flowing to said display light-emitting device according to a voltage of a data signal;

a power source unit for supplying power source through a power wire to cause said driving current to flow to said display light-emitting device via said driving device;

a signal wire driving unit for supplying said data signal to said driving device through a signal wire;

a current driving type monitoring light-emitting device provided in a monitoring region and driven by current in the same manner as said display light-emitting device; and

a voltage adjusting unit for adjusting at least one of said power source of said power source unit and said data signal at said signal wire driving unit, in such a manner that at least one of a quantity of driving current flowing and a quantity of light emitted by said monitoring light-emitting device comes close to a predetermined reference value.

7. The display apparatus according to claim 6,

wherein said driving device comprises a thin film transistor having a gate to which said data signal is supplied, and a source and a drain between which said driving current flows, a conductance between said source and said drain being controlled by a gate voltage.

8. The display apparatus according to claim 6,

wherein said voltage adjusting unit comprises:

a current measuring unit for measuring a quantity of current in said monitoring light-emitting device; and

a voltage control unit for adjusting at least one of said voltages such that said measured current approaches a predetermined reference current.

9. The display apparatus according to claim 6, wherein said voltage adjusting unit comprises:

a light-emitting measuring unit for measuring a quantity of light emitted from said monitoring light-emitting device; and

a voltage control unit for adjusting at least one of said voltages such that said measured quantity of emitted light approaches said reference quantity of emitted light.

10. The display apparatus according to claim 6, further comprising a controller for controlling said voltage adjusting unit so as to adjust at least one of said voltages at a non-display period preceding a display period.

11. The display apparatus according to claim 6,

wherein said display light-emitting device and said monitoring light-emitting device are formed on a common substrate.

12. The display apparatus according to claim 6,

wherein said display light-emitting device and said monitoring light-emitting device are formed in an identical step of a process.

13. The display apparatus according to claim 6,

wherein said power source unit provides a power source which supplies said driving current during a display period both to said display light-emitting device and said monitoring light-emitting device.

54. An electronic apparatus comprising a display apparatus according to claim 6.

14. A pixel circuit provided for each of a plurality of matrix pixels constituting a display region of a display apparatus having, at least, a signal wire to be supplied with a data signal and first and second feeder lines for supplying power source to flow a driving current, said pixel circuit comprising:

a current driving type light-emitting device connected between said first and second feeder lines;

a first thin film transistor controlling said driving current flowing through said light-emitting device via a source and a drain connected between said first and second feeder lines in series to said light-emitting device in accordance with a voltage of said data signal supplied to a gate; and

a driving current compensation device for increasing said driving current according to at least one of a decrease in a quantity of driving current and a decrease in a quantity of light emitted from said light-emitting device.

15. The pixel circuit according to claim 14,

wherein said signal wire includes a signal line to be supplied with said data signal and a scanning line to be supplied with a scanning signal,

said pixel circuit further comprising a second thin film transistor connected in such a manner that said data signal is supplied to a gate of said first thin film transistor via a drain and a source when said scanning signal is supplied to a gate.

16. The pixel circuit according to claim 14,

wherein said driving current compensation device controls a resistance between said first feeder line and said second feeder line depending upon a relation between a voltage across said light-emitting device and a quantity of said driving current.

17. The pixel circuit according to claim 16,

wherein an electric potential of said first feeder line is set to be higher than that of said second feeder line, and

said driving current compensation device includes a first correction thin film transistor of n-channel type having a gate connected to an electrode on said first feeder line side of said light-emitting device and a source and a drain connected between said light-emitting device and said second feeder line in series to said light-emitting device.

18. The pixel circuit according to claim 16,

wherein an electric potential of said first feeder line is set to be lower than that of said second feeder line, and

said driving current compensation device includes a first correction thin film transistor of p-channel type having a gate connected to an electrode on said first feeder line side of said light-emitting device and a source and a drain connected between said light-emitting device and said second feeder line in series to said light-emitting device.

19. The pixel circuit according to claim 16,

wherein an electric potential of said first feeder line is set to be higher than that of said second feeder line, and

said driving current compensation device includes a second correction thin film transistor of p-channel type having a gate connected to an electrode on said second feeder line side of said light-emitting device and a source and a drain connected between said light-emitting device and said first feeder line in series to said light-emitting device.

20. The pixel circuit according to claim 16,

wherein an electric potential of said first feeder line is set to be lower than that of said second feeder line, and

said driving current compensation device includes a second correction thin film transistor of n-channel type having a gate connected to an electrode on said second feeder line side of said light-emitting device and a source and a drain connected between said light-emitting device and said first feeder line in series to said light-emitting device.

21. The pixel circuit according to claim 14, further comprising a retention capacitor connected to a gate of said first thin film transistor, for retaining a gate voltage of said first thin film transistor.

22. The pixel circuit according to claim 21,

wherein said driving current compensation device controls a resistance between either of said first or second feeder lines and said retention capacitor, depending on a relationship between a voltage across said light-emitting device and a quantity of said driving current.

23. The pixel circuit according to claim 22,

wherein an electric potential of said first feeder line is set to be higher than that of said second feeder line, and

said driving current compensation device includes a third correction thin film transistor of the same channel type n or p as said first thin film transistor, having a gate connected to an electrode on said first feeder line side of said light-emitting device and a source and a drain connected between said retention capacitor and said first feeder line.

24. The pixel circuit according to claim 22,

wherein an electric potential of said first feeder line is set to be lower than that of said second feeder line, and

said driving current compensation device includes a third correction thin film transistor of the same channel type n or p as said first thin film transistor, having a gate connected to an electrode on said first feeder line side of said light-emitting device and a source and a drain connected between said retention capacitor and said first feeder line.

25. The pixel circuit according to claim 22,

wherein an electric potential of said first feeder line is set to be higher than that of said second feeder line, and

said driving current compensation device includes a fourth correction thin film transistor of the opposite channel type n or p to that of said first thin film transistor, having a gate connected to an electrode on said first feeder line side of said light-emitting device and a source and a drain connected between said retention capacitor and said second feeder line.

26. The pixel circuit according to claim 22,

wherein an electric potential of said first feeder line is set to be lower than that of said second feeder line, and

said driving current compensation device includes a fourth correction thin film transistor of the opposite channel type n or p to that of said first thin film transistor, having a gate connected to an electrode on said first feeder line side of said light-emitting device and a source and a drain connected between said retention capacitor and said second feeder line.

27. The pixel circuit according to claim 14,

wherein said driving current compensation device controls a resistance between said first feeder line and said second feeder line, depending on a relationship between a voltage across said light-emitting device and a quantity of said emitted light.

28. The pixel circuit according to claim 21,

wherein said driving current compensation device controls a resistance between either of said first or second feeder lines and said retention capacitor, depending on a relationship between a voltage across said light-emitting device and a quantity of said emitted light.

29. The pixel circuit according to claim 28,

wherein an electric potential of said first feeder line is set to be higher than that of said second feeder line,

said first thin film transistor is of p channel type, and

said driving current compensation device includes a first correction thin film photo-diode connected between said retention capacitor and said first feeder line.

30. The pixel circuit according to claim 28,

wherein an electric potential of said first feeder line is set to be higher than that of said second feeder line,

said first thin film transistor is of p channel type, and

said driving current compensation device includes a fifth correction thin film transistor having a source and a drain connected between said retention capacitor and said first feeder line.

31. The pixel circuit according to claim 28,

wherein an electric potential of said first feeder line is set to be lower than that of said second feeder line,

said first thin film transistor is of n channel type, and

said driving current compensation device includes a first correction thin film photo-diode connected between said retention capacitor and said first feeder line.

32. The pixel circuit according to claim 28,

wherein an electric potential of said first feeder line is set to be lower than that of said second feeder line,

said first thin film transistor is of n channel type, and

said driving current compensation device includes a fifth correction thin film transistor having a source and a drain connected between said retention capacitor and said first feeder line.

33. The pixel circuit according to claim 28,

wherein an electric potential of said first feeder line is set to be higher than that of said second feeder line,

said first thin film transistor is of n channel type, and

said driving current compensation device includes a second correction thin film photo-diode connected between said retention capacitor and said second feeder line.

34. The pixel circuit according to claim 28,

wherein an electric potential of said first feeder line is set to be higher than that of said second feeder line,

said first thin film transistor is of n channel type, and

said driving current compensation device includes a sixth correction thin film transistor having a source and a drain connected between said retention capacitor and said second feeder line.

35. The pixel circuit according to claim 28,

wherein an electric potential of said first feeder line is set to be lower than that of said second feeder line, said first thin film transistor is of p channel type, and said driving current compensation device includes a second correction thin film photo-diode connected between said retention capacitor and said second feeder line.

36. The pixel circuit according to claim 28,

wherein an electric potential of said first feeder line is set to be lower than that of said second feeder line, said first thin film transistor is of p channel type, and said driving current compensation device includes a sixth correction thin film transistor having a source and a drain connected between said retention capacitor and said second feeder line.

37. The pixel circuit according to claim 14,

wherein said driving current compensation device includes a thin film transistor which is formed in the same step of a process as said first thin film transistor.

52. A display apparatus comprising a pixel circuit set forth in claim 14 is provided for each pixel.

38. A display apparatus comprising:

a current driving type light-emitting device provided for each pixel;

a driving device provided for each said pixel, for controlling a driving current flowing to said light-emitting device according to a voltage of a data signal;

a power source unit for supplying power source through a power wire to cause said driving current to flow to said light-emitting device via said driving device;

a signal line driving circuit for supplying, through a signal line, a data signal having a voltage corresponding to an image signal input from an image signal source to said driving device;

a measuring unit for measuring at least one of a quantity of driving current flowing through said light-emitting device and a quantity of light emitted from said light-emitting device at the time when a data signal of a predetermined voltage is supplied to said driving device via said signal line; and

a correction circuit provided between said image signal source and said signal line driving circuit, for inputting said image signal to said signal line driving circuit after correcting said image signal in such a manner that at least one of said measured quantity of driving current and said measured quantity of emitted light comes close to a predetermined reference value.

39. The display apparatus according to claim 38,

wherein said driving device comprises a thin film transistor having a gate to be supplied with said data signal, and a source and a drain between which said driving current flows, a conductance between said source and said drain being controlled in accordance with the gate voltage.

40. The display apparatus according to claim 38, further comprising a memory device for storing at least one of the measured quantity of driving current and the measured quantity of emitted light,

wherein said correction circuit corrects said image signal in accordance with at least one of said stored quantity of driving current and the stored quantity of emitted light.

41. The display apparatus according to claim 38, said power source wire is provided for each pixel column, and

said measuring unit measures a quantity of said driving current A

said display apparatus further comprising a common line driving circuit which includes:

a changeover switch for switching said power source wire to said power source unit side at a display period, and to said measuring unit side at a non-display period;

a shift register for sequentially outputting sequential pulses in accordance with each said power source wire; and

a transmission switch for sequentially controlling conduction between each said power source wire and said measuring unit in response to said sequential pulses at said non-display period.

42. The display apparatus according to claim 38,

wherein said measuring unit measures a quantity of emitted light, and further comprising:

a light detecting line, provided for each said pixel column, for transmitting an electrical signal indicative of said quantity of emitted light to said measuring unit; and

a light detecting line driving circuit which includes a shift register for sequentially outputting sequential pulses in accordance with each said light detecting lines, and a transmission switch for sequentially controlling conduction between each said light detecting line and said measuring unit in response to said sequential pulses at a non-display period.

43. The display apparatus according to claim 38,

wherein said measuring unit measures said quantity of emitted light through measurement of a photo-excited current of a semiconductor device.

44. The display apparatus according to claim 43,

wherein said semiconductor device comprises a PIN diode.

45. The display apparatus according to claim 43,

wherein said semiconductor device comprises a field effect transistor.

46. The display apparatus according to claim 43,

wherein said driving device comprises a thin film transistor which is formed in the same step of a process as said semiconductor device.

47. The display apparatus according to claim 38,

wherein said driving device comprises a polycrystalline thin film transistor formed through a low-temperature process of 600°

C. or less.

48. The display apparatus according to claim 38,

wherein said light-emitting device comprises an organic electroluminescent device formed through an ink-jet process.

49. The display apparatus according to claim 38,

wherein said measuring unit measures at least one of said driving current and said quantity of emitted light for each pixel, and

said correcting circuit corrects said image signal for said each pixel.

50. The display apparatus according to claim 38,

wherein said measuring unit measures at least one of said driving current and said quantity of emitted light for each predetermined block having a number of pixels, and

said correcting circuit corrects said image signal for each said predetermined block.

51. The display apparatus according to claim 38,

wherein said correcting circuit corrects said image signal by converting a signal level of said image signal from a specified signal level to another specified signal level.

55. An electronic apparatus comprising a display apparatus according to claim 38.