Current drive circuit and drive method thereof, and electroluminescent display apparatus using the circuit

• US 20040263437A1
• Filed: 03/11/2004
• Published: 12/30/2004
• Est. Priority Date: 06/27/2002
• Status: Abandoned Application

• Current Assignee: Casio Computer Company Limited, Reiji Hattori
• Original Assignee: Casio Computer Company Limited, Reiji Hattori
• Inventors: Hattori, Reiji
• Application Number:
  US10/801,172
• Publication Number:
  US 20040263437A1
• Time in Patent Office: Days
• US Class Current: 345/76
• CPC Class Codes: G09G 2300/0842 forming a memory circuit, e.g. a dynamic memory with one capacitor
• CPC Class Codes: G09G 2300/0866 by means of changes in the pixel supply voltage
• CPC Class Codes: G09G 2310/0221 with use of split matrices G09G3/3644 and G09G3/3666 take precedence
• CPC Class Codes: G09G 2310/027 Details of drivers for data electrodes, the drivers handling digital grey scale data, e.g. use of D/A converters
• CPC Class Codes: G09G 2310/0294 Details of sampling or holding circuits arranged for use in a driver for data electrodes
• CPC Class Codes: G09G 3/2011 by amplitude modulation
• 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 3/32 semiconductive, e.g. using light-emitting diodes [LED]
• CPC Class Codes: G09G 3/3216 using a passive matrix
• 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: G09G 3/3283 in which the data driver supplies a variable data current for setting the current through, or the voltage across, the light-emitting elements
• CPC Class Codes: G11C 19/00 Digital stores in which the information is moved stepwise, e.g. shift registers
• CPC Class Codes: G11C 27/028 Current mode circuits, e.g. switched current memories
• CPC Class Codes: G11C 5/14 Power supply arrangements , e.g. power down, chip selection or deselection, layout of wirings or power grids, or multiple supply levels

Abstract

A current drive apparatus for an active matrix display operates a plurality of loads, e.g. organic or inorganic EL elements, by applying a current thereto. The apparatus includes a plurality of output terminals to which the loads are respectively connected. A single current generation circuit comprising e.g. a digital to analogue converter and a current mirror, outputs an operating current having a predetermined current value. A plurality of current storage circuits are provided in accordance with the respective output terminals, sequentially sample and hold the operating current and then simultaneously output the drive currents based on the sampled operating currents to the respective output terminals. The operating current has a current value according to an input signal. The current storage circuit includes a voltage component holding section which samples the operating current outputted from the current generation circuit and holds a voltage component for driving a drive control current corresponding to a current value of the operating current for driving a second current mirror.

Claims

1. A current drive apparatus which operates a plurality of loads by applying a current thereto, the current drive apparatus comprising:

a plurality of output terminals to which the loads are respectively connected;

a single current generation circuit which outputs an operating current having a predetermined current value; and

a plurality of current storage circuits which are respectively connected to the output terminals, sequentially fetch and hold the operating current, and simultaneously output a drive current based on the operating current to the output terminals.

2. The current drive apparatus according to claim 1, wherein the operating current has a current value according to an input signal.

3. The current drive apparatus according to claim 2, wherein the current generation circuit comprises:

a control current generation circuit which generates a control current according to the input signal; and

an output current generation circuit which generates and outputs an output current having a predetermined current ratio relative to the control current.

4. The current drive apparatus according to claim 3, wherein the current value of the control current is set larger than a current value of the output current.

5. The current drive apparatus according to claim 3, wherein the input signal is a digital signal having a plurality of bits,

the control current generation circuit comprises a plurality of bit current generation circuits which generate a plurality of bit currents that current values have weightings corresponding to respective bits of the digital signal, and

any of the respective bit currents are selected in accordance with a bit value of the input signal, and the control current is generated by adding the selected bit currents.

6. The current drive apparatus according to claim 3, wherein the output current generation circuit comprises a current mirror circuit having the predetermined current ratio.

7. The current drive apparatus according to claim 1, wherein each of the current storage circuits comprises a voltage component holding section which fetches the operating current outputted from the current generation circuit and holds a voltage component corresponding to a current value of the operating current.

8. The current drive apparatus according to claim 7, wherein the voltage component holding section has a capacitance element in which electric charges corresponding to the operating current are written.

9. The current drive apparatus according to claim 8, wherein the voltage component holding section has a field effect type transistor which causes the operating current to flow between a source and a drain thereof, and

the capacitance element has at least a parasitic capacitance between the source and a gate of the field effect type transistor, and a voltage between the source and the gate corresponding to the operating current is written in the capacitance element.

10. The current drive apparatus according to claim 9, wherein the mobility of the field effect type transistor has a value which is at least approximately 200 cm²/Vs or a larger value.

11. The current drive apparatus according to claim 7, wherein each of the current storage circuits comprises a drive current generation section which generates and outputs the drive current having a predetermined current ratio relative to the operating current based on the voltage component held in the voltage component holding section.

12. The current drive apparatus according to claim 11, wherein the drive current generation section comprises a current mirror circuit having the predetermined current ratio.

13. The current drive apparatus according to claim 1, wherein each of the current storage circuits comprises:

a pair of current storage sections arranged in parallel to each other; and

a control portion which alternately performs an operation to fetch the operating current outputted from the current generation circuit and hold a voltage component corresponding to a current value of the operating current in one current storage section and an operation to output the drive current based on the voltage component held in the other current storage section in parallel.

14. The current drive apparatus according to claim 1, wherein each of the current storage circuits comprises:

current storage sections on a front stage and a rear stage which are arranged in series; and

a control portion which performs an operation to fetch the operating current outputted from the current generation circuit in the current storage section on the front stage, hold a voltage component corresponding to a current value of the operating current and supply a current based on the voltage component to the current storage section on the rear stage and an operation to fetch the current supplied from the current storage section on the front stage, hold a voltage component corresponding to a current value of the current and output the drive current based on the voltage component in parallel.

15. The current drive apparatus according to claim 1, wherein the drive current has the same current value at the output terminals.

16. The current drive apparatus according to claim 15, which further comprises a single input current storage circuit between the current generation circuit and the plurality of the current storage circuits, and wherein

the input current storage circuit fetches the operating current outputted from the current generation circuit, hold a voltage component corresponding to a current value of the operating current and supplies a current based on the voltage component to the plurality of the current storage circuits.

17. The current drive apparatus according to claim 16, wherein the input current storage circuit has a capacitance element in which electric charges corresponding to the operating current are written as the voltage component.

18. The current drive apparatus according to claim 17, wherein the input current storage circuit has a field effect type transistor which causes the operating current to flow between a source and a drain thereof, and

the capacitance element has at least a parasitic capacitance between the source and a gate of the field effect type transistor.

19. The current drive apparatus according to claim 16, wherein the input current storage circuit comprises:

a pair of input current storage sections arranged in parallel to each other; and

a control portion which alternately performs an operation to fetch the operating current outputted from the current generation circuit in one of the input current storage sections and hold a voltage component corresponding to a current value of the operating current in one input current storage section, and an operation to supply a current based on a voltage component held in the other input current storage section to the plurality of the current storage circuits in the other input current storage section in parallel.

20. The current drive apparatus according to claim 15, further comprises a pulse width control circuit which is provided between the plurality of the output terminals and the loads and controls a pulse width of the drive current outputted from the output terminals.

21. The current drive apparatus according to claim 20, wherein the pulse width control circuit controls a pulse width of the drive current in accordance with an input signal.

22. The current drive apparatus according to claim 1, wherein at least the plurality of the current storage circuits and the output terminals are formed on at least one semiconductor chip.

23. The current drive apparatus according to claim 22, wherein the single current generation circuit is formed on a semiconductor chip different from the aforesaid semiconductor chip.

24. The current drive apparatus according to claim 22, wherein the single current generation circuit is formed in the semiconductor chip.

25. A current drive apparatus which operates a plurality of loads by applying a current thereto, the current drive apparatus comprising:

a plurality of output terminals to which the loads are respectively connected;

a single reference current generation circuit which generates and outputs a plurality of reference currents having current values different from each other;

at least one reference current storage circuit which fetches and holds each of the plurality of reference currents and outputs a plurality of gradation reference currents based on the respective reference currents;

at least one gradation current generation circuit which selects any of the respective gradation reference currents in accordance with an input signal and generate gradation currents; and

a plurality of current storage circuits which sequentially fetch and hold the respective gradation currents and simultaneously output drive currents based on the gradation currents to the respective output terminals.

26. The current drive apparatus according to claim 25, wherein the single reference current generation circuit comprises a plurality of reference current generation sections which generate and output the respective reference currents and are arranged in parallel to each other.

27. The current drive apparatus according to claim 26, wherein the input signal is a digital signal having a plurality of bits, and

current values of the respective reference currents outputted from the respective reference current generation sections have weightings corresponding to respective bits of the digital signal.

28. The current drive apparatus according to claim 25, wherein the reference current storage circuit comprises a plurality of reference current storage sections which individually fetch the respective reference currents outputted from the reference current generation circuits, hold voltage components corresponding to the respective reference currents and output the gradation reference currents based on the respective voltage components.

29. The current drive apparatus according to claim 28, each of the reference current storage circuit sections has a capacitance element in which electric charges corresponding to the reference current are written as the voltage component.

30. The current drive apparatus according to claim 29, wherein each of the reference current storage circuit sections has a field effect type transistor which causes the operating current to flow between a source and a drain thereof, and

the capacitance element has at least a parasitic capacitance between the source and a gate of the field effect type transistor.

31. The current drive apparatus according to claim 25, wherein the reference current storage circuit comprises:

a pair of reference current storage circuit portions including a plurality of the reference current storage sections which are arranged in parallel; and

a control portion which alternately performs an operation to fetch the reference current outputted from the reference current generation circuit in one reference current storage circuit portion and hold a voltage component corresponding to a current value of the reference current, and an operation to output the gradation reference current based on a voltage component held in the other reference current storage circuit portion.

32. The current drive apparatus according to claim 25, wherein the input signal is a digital signal having a plurality of bits, and

the gradation current generation circuit selects any of the respective gradation reference currents based on a bit value of the input signal, adds the selected gradation reference currents and generates the gradation current.

33. The current drive apparatus according to claim 25, wherein the current storage circuit comprises a voltage component holding section which fetches the gradation current outputted from the current generation circuit and holds a voltage component corresponding to a current value of the gradation current.

34. The current drive apparatus according to claim 33, wherein the voltage component holding section has a capacitance element in which electric charges corresponding to the gradation current are written as the voltage component.

35. The current drive apparatus according to claim 34, wherein the voltage component holding section has a field effect type transistor which causes the gradation current to flow between a source and a drain thereof, and

the capacitance element has at least a parasitic capacitance between the source and a gate of the field effect type transistor and a voltage between the source and the gate based on the gradation current is written in the capacitance element.

36. The current drive apparatus according to claim 35, wherein the mobility of the field effect type transistor has a value of at least approximately 200 cm²/Vs or a larger value.

37. The current drive apparatus according to claim 25, wherein the reference current storage circuit, the current generation circuits, the current storage circuits and the output terminals are formed on at least one semiconductor chip.

38. The current drive apparatus according to claim 37, wherein the reference current generation circuits are formed on a semiconductor chip different from the aforesaid semiconductor chip.

39. The current drive apparatus according to claim 37, wherein the reference current generation circuit is formed in the semiconductor chip.

40. A drive method of a current drive apparatus which operates a plurality of loads connected to a plurality of output terminals by applying to a current thereto, the drive method comprising the step of:

generating an operating current having a predetermined current value by a single current generation circuit and outputting it to a plurality of current storage circuits;

sequentially fetching and holding the operating current into the respective current storage circuits; and

simultaneously outputting a drive current based on the operating current held in the current storage circuit to the respective output terminals.

41. The drive method of a current drive apparatus according to claim 40, wherein the step of holding the operating-current in the respective current storage circuits and the step of outputting the drive current to the respective output terminals are executed in parallel.

42. The drive method of a current drive apparatus according to claim 40, wherein the step of outputting the operating current to a plurality of the current storage circuits comprises:

a step of fetching and holding a voltage component corresponding to a current value of the operating current outputted from the current generation circuit to a single input current storage circuit; and

a step of supplying a current based on the voltage component held in the input current storage circuit to a plurality of the current storage circuits.

43. A drive method of a current drive apparatus which operates a plurality of loads connected to a plurality of output terminals in a predetermined drive state, the drive method comprising the step of:

generating and supplying a plurality of reference currents set in such a manner that current values have weightings different from each other by a single reference current generation circuit;

fetching and holding the respective reference currents by the reference current storage circuit and outputting a plurality of gradation reference currents based on the respective reference currents;

selecting any of the respective gradation reference currents in accordance with an input signal and generating a gradation current; and

fetching and holding the gradation current and simultaneously outputting a drive current based on the gradation current to the respective output terminals.

44. The drive method of a current drive apparatus according to claim 43, wherein the reference current storage circuit comprises a pair of reference current storage circuit portion arranged in parallel,

the step of outputting the gradation reference current comprises:

a step of fetching the reference current outputted from the reference current generation circuit and holding a voltage component corresponding to a current value of the reference current in one reference current storage circuit portion; and

a step of outputting the gradation reference current based on the voltage component held in the other reference current storage circuit portion in the other reference current storage circuit portion in parallel;

the step of holding the voltage component and the step of outputting the gradation reference current are executed in parallel.

45. A display apparatus which supplies a drive current according to a display signal to each of display pixels of a display panel, and displays image information, the display apparatus comprising:

a display panel having a plurality of scanning lines arranged in a row direction, a plurality of signal lines arranged in a column direction and the plurality of display pixels which is arranged in the vicinity of an intersection of the respective scanning lines and signal lines and has an optical element;

a signal drive circuit comprising;

a single current generation circuit which generates and outputs an operating current having a current value based on the display signal; and

a plurality of current storage circuits which are provided in accordance with the respective signal lines, sequentially fetch the operating current outputted from the current generation circuit and simultaneously output the drive current based on the operating current to a plurality of the signal lines; and

a scanning drive circuit which outputs to each of the plurality of the scanning lines a scanning signal used to sequentially select the display pixel connected to the scanning line.

46. The display apparatus according to claim 45, wherein the current storage circuit comprises a voltage component holding section which fetches the operating current outputted from the current generation circuit and holds a voltage component corresponding to a current value of the operating current.

47. The display apparatus according to claim 46, wherein the voltage component holding section has a capacitance element in which electric charges corresponding to the operating current are written as the voltage component.

48. The display apparatus according to claim 46, wherein the voltage component holding section has a field effect type transistor which causes the operating current to flow between a source and a drain thereof, and

the capacitance element has at least a parasitic capacitance between the source and a gate of the field effect type transistor, and a voltage between the source and the gate based on the operating current is written in the capacitance element.

49. The display apparatus according to claim 48, wherein the mobility of the field effect type transistor has a value of at least approximately 200 cm²/Vs or a larger value.

50. The display apparatus according to claim 45, each of the current storage circuits in the signal drive circuit comprises:

a pair of current storage sections arranged in parallel; and

a control portion which alternately executes an operation to fetch the operating current outputted from the current generation circuit in one of the current storage sections and hold a voltage component corresponding to a current value of the operating current, and an operation to output the drive current based on the voltage component held in the other current storage section in parallel.

51. The display apparatus according to claim 45, wherein each of the current storage circuits in the signal drive circuit comprises:

current storage sections on a front stage and a rear stage arranged in series; and

a control portion which executes an operation to fetch the operating current outputted from the current generation circuit in the current storage section on the front stage, hold a voltage component corresponding to a current value of the operating current and supply a current based on the voltage component to the current storage section on the rear stage, and an operation to fetch the current supplied from the current storage section on the front stage in the current storage section on the rear stage, hold a voltage component according to a current value of the current and output the drive current based on the voltage component in parallel.

52. The display apparatus according to claim 45, wherein the signal drive circuit comprises a single input current storage circuit between the current generation circuit and the plurality of the current storage circuits, and

the input current storage circuit fetches the operating current outputted from the current generation circuit, holds a voltage component corresponding to a current value of the operating current and supplies a current based on the voltage component to the plurality of the current storage circuits.

53. The display apparatus according to claim 52, wherein the input current storage circuit has a capacitance element in which electric charge corresponding to the operating current are written as the voltage component.

54. The display apparatus according to claim 52, wherein the signal drive circuit further comprises a pulse width control circuit which is provided between the plurality of the current storage circuits and the plurality of the signal lines and controls a pulse width of the drive current.

55. The display apparatus according to claim 54, the pulse width control circuit controls a pulse width of the drive current in accordance with an input signal.

56. The display apparatus according to claim 45, wherein at least the plurality of the current storage circuits and the output terminals in the signal drive circuit are formed on at least one semiconductor chip.

57. The display apparatus according to claim 56, wherein the current generation circuit in the signal drive circuit is formed on a semiconductor chip different from the aforesaid semiconductor chip.

58. The display apparatus according to claim 56, wherein the current generation circuit in the signal drive circuit is formed in the semiconductor chip.

59. The display apparatus according to claim 45, wherein the signal drive circuit is configured to include a plurality of semiconductor chips comprising at least the current storage circuits and the output terminals, and

the signal drive circuit has a structure stratified in such a manner the output terminals of the semiconductor chip are sequentially connected to input terminals of a plurality of the semiconductor chips positioned on a next stage.

60. The display apparatus according to claim 45, wherein the optical element in the display pixel includes a light emitting element.

61. The display apparatus according to claim 60, wherein the optical element includes an organic electroluminescent element.

62. A display apparatus which supplies a drive current according to a display signal to each of display pixels of a display panel, and displays image information, the display apparatus comprising:

a display panel comprising;

a plurality of scanning lines arranged in a row direction;

a plurality of signal lines arranged in a column direction; and

the plurality of display pixels which are arranged in the vicinity of intersections of the respective scanning lines and signal lines and have optical elements;

a signal drive circuit comprising;

a single reference current generation circuit which generates and outputs a plurality of reference currents having current values different from each other;

at least one reference current storage circuit which fetches and holds the respective reference currents and outputs a plurality of gradation reference currents based on the respective reference currents;

at least one gradation current generation circuit which selects any of the respective gradation reference currents in accordance with the display signal and generates and outputs gradation currents; and

a plurality of current storage circuits which are provided in accordance with the respective signal lines, sequentially fetch and hold the gradation currents outputted from the gradation current generation circuit and simultaneously output drive currents based on the gradation currents to a plurality of the signal lines; and

a scanning drive circuit which outputs to the respective scanning lines a scanning signal used to sequentially select the display pixels connected to the scanning lines.

63. The display apparatus according to claim 62, wherein the reference current generation circuit comprises a plurality of reference current generation sections which generate and output the respective reference currents and are arranged in parallel.

64. The display apparatus according to claim 63, wherein the display signal is a digital signal having a plurality of bits, and

current values of the respective reference currents outputted from the respective reference current generation section have weightings corresponding to respective bits of the digital signal.

65. The display apparatus according to claim 62, wherein the display signal is a digital signal having a plurality of bits, and

the gradation current generation circuit selects any of the respective gradation reference currents based on a bit value of the display signal, adds the selected gradation reference currents, and generates the gradation currents.

66. The display apparatus according to claim 62, wherein the reference current storage circuit comprises:

a pair of reference current storage circuit portions which are arranged in parallel and each of which includes a plurality of the reference current storage sections; and

a control portion which alternately execute an operation to fetch the reference currents outputted from the reference current generation circuits in one of the reference current storage circuit portions and hold voltage components corresponding to current values of the reference currents and an operation to output the gradation reference currents based on the voltage component held in the other reference current storage circuit portion in parallel.

67. The display apparatus according to claim 62, wherein the current storage circuit comprises a voltage component holding section which fetches the gradation currents outputted from the current generation circuits and holds voltage components corresponding to current values of the gradation currents.

68. The display apparatus according to claim 65, wherein the voltage component holding section has a capacitance element in which electric charges corresponding to the operating current are written.

69. The display apparatus according to claim 68, wherein the voltage component holding section has a field effect type transistor which causes the operating current to flow between a source and a drain thereof, and

the capacitance element has at least a parasitic capacitance between the source and a gate of the electric field type transistor, and a voltage between the source and the gate based on the operating current is written in the capacitance element.

70. The display apparatus according to claim 69, wherein the mobility of the field effect type transistor has a value of at least approximately 200 cm²/Vs or a larger value.

71. The display apparatus according to claim 62, wherein at least the reference current storage circuit, the current generation circuit, the plurality of current storage circuits and the output terminals in the signal drive circuit are formed on at least one semiconductor chip.

72. The display apparatus according to claim 71, wherein the reference current generation circuit in the signal drive circuit is formed on a semiconductor chip different from the aforesaid semiconductor chip.

73. The display apparatus according to claim 72, wherein the reference current generation circuit in the signal drive circuit is formed in the semiconductor chip.

74. The display apparatus according to claim 62, wherein the signal drive circuit is configured to include a plurality of semiconductor chips including at least the current storing means and the output terminals, and

the signal drive circuit has a structure stratified in such a manner that the output terminals of the semiconductor chip are sequentially connected to input terminals of a plurality of the semiconductor chips positioned on a next stage.

75. The display apparatus according to claim 62, wherein the optical element in the display pixel includes a light emitting element.

76. The display apparatus according to claim 75, wherein the optical element includes an organic electroluminescent element.