Active-matrix display, active-matrix organic electroluminescent display, and methods of driving them

• US 20030107560A1
• Filed: 09/11/2002
• Published: 06/12/2003
• Est. Priority Date: 01/15/2001
• Status: Active Grant

• Current Assignee: Sony Corporation (Sony Group Corp.)
• Original Assignee: Sony Corporation (Sony Group Corp.)
• Inventors: Asano, Mitsuru, Yumoto, Akira
• Granted Patent: US 7,019,717 B2
• Time in Patent Office: Days
• US Class Current: 345/204
• 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 2300/0804 Sub-multiplexed active matrix panel, i.e. wherein one active driving circuit is used at pixel level for multiple image producing elements
• CPC Class Codes: G09G 2300/0842 forming a memory circuit, e.g. a dynamic memory with one capacitor
• CPC Class Codes: G09G 2310/0262 The addressing of the pixel, in a display other than an active matrix LCD, involving the control of two or more scan electrodes or two or more data electrodes, e.g. pixel voltage dependent on signals of two data electrodes
• CPC Class Codes: G09G 3/30 using electroluminescent panels
• CPC Class Codes: G09G 3/3241 the current through the light-emitting element being set using a data current provided by the data driver, e.g. by using a two-transistor current mirror
• CPC Class Codes: G09G 3/3266 Details of drivers for scan electrodes

Abstract

When a current-writing type pixel circuit is made, it involves a greater number of transistors and TFTs occupy much of the area of the pixel circuit. To alleviate this problem, two pixel circuits (P1, P2) have a first scanning TFT (14), a current-voltage conversion TFT (16), respective second scanning TFTs (15-1, 15-2), capacitors (131,13-2), and drive TFTs (12-1, 12-2) for OLED including organic EL elements (11-2, 11-2) of two pixels, for example, in a row direction. In each of the pixel circuits, the first scanning TFT (14) handling a large amount of current (Iw) as compare with current flowing through the OLED (11-2, 11-2), and the current-voltage conversion TFT (16) are shared between two pixels.

Claims

1. An active matrix type display device including current-writing type pixel circuits arranged in a matrix form for allowing current to pass through said pixel circuits via a data line in accord with luminance to write luminance information thereinto, each pixel circuit having an electro-optical element whose luminance varies with the current passing therethrough, and said pixel circuit comprising:

a conversion part for converting the current provided from the data line into voltage;

a hold part for holding the voltage converted by said conversion part; and

a drive part for converting the voltage held in said hold part into current and passing the converted current through said electro-optical element, wherein said conversion part is shared between at least two separate pixels in a row direction.

2. The active matrix type display device according to claim 1, wherein said pixel circuit has said conversion part shared between pixels in two neighboring rows.

3. The active matrix type display device according to claim 1,

wherein said conversion part has a first field effect transistor (FET) whose drain and gate are short-circuited, said transistor generating voltage across said gate and source when said transistor is supplied with current from said data line;

wherein said hold part has a capacitor for holding said voltage generated across said gate and source of said first FET; and

wherein said drive part has a second FET connected in series with said electro-optical element for driving said electro-optical element in accordance with the voltage held in said capacitor.

4. The active matrix type display device according to claim 3, wherein said first and second FETs have substantially same characteristic and constitute current mirror circuit.

5. The active matrix type display device according to claim 3, wherein said first FET is a single transistor element shared between at least two separate pixels in a row direction.

6. The active matrix type display device according to claim 3, wherein said first FET includes a multiplicity of transistor elements having the drains and gates connected together, said transistor element being shared between at least two separate pixels in a row direction.

7. An active matrix type display device including current-writing type pixel circuits arranged in a matrix form for allowing current to pass through the pixel circuits via a data line in accord with luminance to write luminance information thereinto, each pixel circuit having an electro-optical element whose luminance varies with the current passing therethrough, said pixel circuit comprising:

a first scanning switch for selectively passing the current provided from said data line;

a conversion part for converting the current provided through said first scanning switch into voltage;

a second scanning switch for selectively passing the voltage converted by said conversion part;

a hold part for holding the voltage supplied thereto through said second scanning switch; and

a drive part for converting the voltage held in said hold part into current and passing the converted current through said electro-optical element, wherein said first scanning switch is shared between at least two separate pixels in a row direction.

8. The active matrix type display device according to claim 7, wherein said pixel circuit has said first scanning switch shared between pixels in the two neighboring rows.

9. The active matrix type display device according to claim 7, wherein said pixel circuit has further said conversion part shared between at least two separate pixels in a row direction.

10. The active matrix type display device according to claim 9, wherein said pixel circuit has said first scanning switch and said conversion part both shared between pixels in two neighboring rows.

11. The active matrix type display device according to claim 7,

wherein said first scanning switch includes a first FET having a gate connected to a first scanning line;

wherein said conversion part includes a second FET having a drain and a gate thereof short circuited for generating voltage across the gate and the source thereof when current is supplied from the data line via said first FET;

wherein said second scanning switch includes a third FET having a gate connected to a second scanning line;

wherein said hold part includes a capacitor for holding the voltage generated across said gate and source of said second FET and supplied via said third FET; and

wherein said drive part includes a fourth FET connected in series with said electro-optical element, for driving said electro-optical element in accordance with said voltage held in said capacitor.

12. The active matrix type display device according to claim 11, wherein said second and fourth FETs have substantially same characteristic and together constitute current mirror circuit.

13. The active matrix type display device according to claim 11, wherein said first or second FET is a single transistor element shared between at least two separate pixels in a row direction.

14. The active matrix type display device according to claim 11, wherein said first or second FET includes a multiplicity of transistor elements having their drains and gates connected together, said transistor element being shared between at least two separate pixels in a row direction.

15. A method of driving an active matrix type display device including current-writing type pixel circuits arranged in a matrix form for allowing current to pass through the pixel circuits via a data line in accord with luminance to write luminance information thereinto, each pixel circuit having an electro-optical element whose luminance varies with the current passing therethrough, said pixel circuit comprising a first scanning switch for selectively passing the current provided from said data line, a conversion part for converting the current provided through said first scanning switch into voltage, a second scanning switch for selectively passing the voltage converted by said conversion part, a hold part for holding the voltage supplied thereto through said second scanning switch;

and a drive part for converting the voltage held in said hold part into current and passing the converted current through said electro-optical element, wherein said first scanning switch is shared between at least two separate pixels in a row direction, comprising a step of;

setting second scanning switch to have a sequential selective status by sequentially selecting the preceding row and then the later row while first scanning switch has a selective status when writing to at least two separate pixels in a row direction.

16. An active matrix type organic electroluminescent display device including current-writing type pixel circuits arranged in a matrix form for allowing current to pass through the pixel circuits via a data line in accord with luminance to write luminance information thereinto, each pixel circuit utilizing as a display element organic electroluminescent element having a first electrode, a second electrode and layers of electroluminescent organic material, the layers being placed between the electrodes and including a light-emitting layer, said pixel circuit comprising:

a conversion part for converting the current provided from said data line into voltage;

a hold part for holding the voltage converted by said conversion part; and

a drive part for converting the voltage held in said hold part into current and passing the converted current through the organic electroluminescent element, wherein said conversion part is shared between at least two separate pixels in a row direction.

17. The active matrix type organic electroluminescent display device according to claim 16, wherein said pixel circuit has said conversion part shared between pixels in two neighboring rows.

18. The active matrix type organic electroluminescent display device according to claim 16,

wherein said conversion part has a first field effect transistor (FET) whose drain and gate are short-circuited, said transistor generating voltage across said gate and source when said transistor is supplied with current from said data line;

wherein said hold part has a capacitor for holding said voltage generated across said gate and source of said first FET; and

wherein said drive part has a second FET connected in series with said electro-optical element, for driving said electro-optical element in accordance with the voltage held in said capacitor.

19. The active matrix type organic electroluminescent display device according to claim 18, wherein said first and second FETs have substantially same characteristic and together constitute current mirror circuit.

20. The active matrix type organic electroluminescent display device according to claim 18, wherein said first FET is a single transistor element shared between at least two separate pixels in a row direction.

21. The active matrix type organic electroluminescent display device according to claim 18, wherein said first FET includes a multiplicity of transistor elements having the drains and gates connected together, said transistor element being shared by at least two separate pixels in a row direction.

22. An active matrix type organic electroluminescent display device including current-writing type pixel circuits arranged in a matrix form for allowing current to pass through the pixel circuits via a data line in accord with luminance to write luminance information thereinto, each pixel circuit utilizing as a display element organic electroluminescent element having a first electrode, a second electrode and layers of electroluminescent organic material, said layers being placed between the electrodes and including a light-emitting layer, said pixel circuit comprising:

a first scanning switch for selectively passing the current provided from said data line;

a conversion part for converting the current provided through said first scanning switch into voltage;

a second scanning switch for selectively passing the voltage converted by said conversion part;

a hold part for holding the voltage supplied thereto through said second scanning switch; and

a drive part for converting the voltage held in said hold part into current and passing the converted current through said electro-optical element, wherein said first scanning switch is shared between at least two separate pixels in a row direction.

23. The active matrix type organic electroluminescent display device according to claim 22, wherein said pixel circuit has said first scanning switch shared between pixels in the two neighboring rows.

24. The active matrix type organic electroluminescent display device according to claim 22, wherein said pixel circuit has further said conversion part shared between at least two separate pixels in a row direction.

25. The active matrix type organic electroluminescent display device according to claim 24, wherein said pixel circuit has said first scanning switch and said conversion part both shared between pixels in two neighboring rows.

26. The active matrix type organic electroluminescent display device according to claim 22,

wherein said first scanning switch includes a first FET having a gate connected to a first scanning line;

wherein said conversion part includes a second FET having a drain and a gate thereof short circuited, for generating voltage across the gate and the source thereof when current is supplied from said data line via said first FET;

wherein said second scanning switch includes a third FET having a gate connected to a second scanning line;

wherein said hold part includes a capacitor for holding the voltage generated across said gate and source of said second FET and supplied via said third FET; and

wherein said drive part includes a fourth FET connected in series with said electro-optical element, for driving said electro-optical element in accordance with said voltage held in said capacitor.

27. The active matrix type organic electroluminescent display device according to claim 26, wherein said second and fourth FETs have substantially same characteristic and together constitute current mirror circuit.

28. The active matrix type organic electroluminescent display device according to claim 26, wherein said first or second FET is a single transistor element shared between at least two separate pixels in a row direction.

29. The active matrix type organic electroluminescent display device according to claim 26, wherein said first or second FET includes a multiplicity of transistor elements having their drains and gates connected together, said transistor element being shared between at least two separate pixels in a row direction.

30. A method of driving an active matrix type organic electroluminescent display device including current-writing type pixel circuits arranged in a matrix form for allowing current to pass through the pixel circuits via a data line in accord with luminance to write luminance information thereinto, each pixel circuit having an electro-optical element whose luminance varies with the current passing therethrough, said pixel circuit comprising a first scanning switch for selectively passing the current provided from said data line, a conversion part for converting the current provided through said first scanning switch into voltage, a second scanning switch for selectively passing the voltage converted by said conversion part, a hold part for holding the voltage supplied thereto through said second scanning switch, and a drive part for converting the voltage held in said hold part into current and passing the converted current through said electro-optical element, wherein said first scanning switch is shared between at least two separate pixels in a row direction, comprising a step of:

setting second scanning switch to have a sequential selective status by sequentially selecting the preceding row and then the later row while first scanning switch has a selective status when writing to at least two separate pixels in a row direction.