Display apparatus, and driving circuit for the same

• US 20050168416A1
• Filed: 01/31/2005
• Published: 08/04/2005
• Est. Priority Date: 01/30/2004
• Status: Active Grant

• Current Assignee: Renesas Electronics Corporation
• Original Assignee: NEC Electronics Corporation (Renesas Electronics Corporation)
• Inventors: Hashimoto, Yoshiharu, Yoneyama, Teru
• Granted Patent: US 7,595,776 B2
• 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 2310/0251 Precharge or discharge of pixel before applying new pixel voltage
• 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 2320/0276 for the purpose of adaptation to the characteristics of a display device, i.e. gamma correction
• CPC Class Codes: G09G 3/3233 with pixel circuitry controlling the current through the light-emitting element
• 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: 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

A drive circuit for a display apparatus includes a gradation voltage generation circuit and a D/A conversion circuit. The gradation voltage generation circuit generates a plurality of different first gradation voltages and a plurality of different second gradation voltages. The D/A conversion circuit drives a light emitting element of a pixel through a data line with a gradation voltage based on one of the first gradation voltages as a first specific gradation voltage in a precharge period and drives the light emitting element of the pixel through the data line with a gradation current based on one of the second gradation voltages as a second specific gradation voltage. The D/A conversion circuit includes a voltage driver to drive the light emitting element, and a current driver to drive the light emitting element.

Claims

1. A data line driving circuit comprising:

pixels including light emitting elements and arranged at intersections of a plurality of data lines and a plurality of scanning lines, a brightness of each of said pixels being controlled based on a drive current; and

a gradation voltage generating circuit including a resistance string circuit having a plurality of resistances connected in series and configured to generate a plurality of first gradation voltages corresponding to a current-voltage characteristic of said pixels and a plurality of second gradation voltages corresponding to a gamma characteristic of said light emitting elements.

2. A drive circuit for a display panel, including a gradation voltage generating circuit which comprises:

a first voltage generating circuit whose output is connected with a first wiring line;

a second voltage generating circuit whose output is connected with a second wiring line; and

a first resistance string circuit adaptive for a gamma characteristic, and provided between said first and second wiring lines.

3. The drive circuit according to claim 2, wherein said first voltage generating circuit comprises:

a power supply line;

a first current source;

a first transistor whose current path is connected with said power supply line and said first current source, and whose control gate is connected with said first current source; and

a voltage follower circuit provided between said control gate and said first wiring line.

4. The drive circuit according to claim 3, wherein said first voltage generating circuit further comprises:

a second resistance string circuit provided between said first and second wiring lines;

a selector configured to select a predetermined node of nodes of said second resistance string circuit to output a predetermined voltage; and

a voltage follower provided between an output of said selector and a node of said first resistance string circuit.

5. A drive circuit comprising:

a light emitting element;

a drive transistor configured to drive said light emitting element;

a voltage drive circuit configured to supply a predetermined voltage to said drive transistor;

a current drive circuit configured to supply a predetermined current to said drive transistor;

a first gradation voltage generating circuit configured to generate a plurality of first gradation voltages based on a current-voltage characteristic of said drive transistor; and

a second gradation voltage generating circuit configured to generate a plurality of second gradation voltages based on a current-voltage characteristic of said current drive circuit.

6. A drive circuit for a display apparatus, comprising:

a gradation voltage generation circuit configured to generate a plurality of first gradation voltages different from each other and a plurality of second gradation voltages different from each other; and

a D/A conversion circuit configured to drive a light emitting element of a pixel through a data line with a gradation voltage based on one of said plurality of first gradation voltages as a first specific gradation voltage in a precharge period and to drive said light emitting element of said pixel through said data line with a gradation current based on one of said plurality of said second gradation voltages as a second specific gradation voltage.

7. The drive circuit according to claim 6, wherein said D/A conversion circuit comprises:

a voltage driver configured to drive said light emitting element with said gradation voltage based on said first specific gradation voltage in said first period; and

a current driver configured to drive said light emitting element with said gradation current based on said second specific gradation voltage to in said second period.

8. The drive circuit according to claim 7, wherein said pixel includes a driving transistor to drive said light emitting element,

said current driver includes a current driver transistor, and

a conductive type of said driving transistor is opposite to that of said current driver transistor.

9. The drive circuit according to claim 7, wherein said gradation voltage generating circuit comprises:

a first gradation voltage generating circuit configured to generate said plurality of first gradation voltages adaptive for a current-voltage characteristic of said pixel; and

a second gradation voltage generating circuit configured to generate said second plurality of gradation voltages adaptive for a gamma characteristic of said light emitting element of said pixel.

10. The drive circuit according to claim 9, wherein said gradation voltage generating circuit further comprises:

a multiplexer connected with said first gradation voltage generating circuit and said second gradation voltage generating circuit and configured to select said plurality of first gradation voltages in said first period to output to said D/A conversion circuit, and to select said plurality of second gradation voltages in said second period to output to said D/A conversion circuit.

11. The drive circuit according to claim 9, wherein said first gradation voltage generating circuit generates said plurality of first gradation voltages based on first gradation setting data, and

said second gradation voltage generating circuit generates said second plurality of gradation voltages based on second gradation setting data.

12. The drive circuit according to claim 7, wherein said gradation voltage generating circuit comprises:

a first gradation setting data register configured to hold first gradation setting data;

a second gradation setting data register configured to hold second gradation setting data;

a multiplexer configured to select said first gradation setting data in said first period, and to select said second gradation setting data in said second period; and

a gradation voltage generating circuit configured to generate said plurality of first gradation voltages based on said first gradation setting data in said first period, and to generate said plurality of second gradation voltages based on said second gradation setting data in said second period.

13. The drive circuit according to claim 7, wherein said D/A conversion circuit further comprises:

a first switch interposed between said voltage driver and said data line, such that said first switch connects said voltage driver with said data line in said first period and disconnects said voltage driver from said data line in said second period.

14. The drive circuit according to claim 13, wherein said D/A conversion circuit further comprises:

a decoder configured to decode display data; and

a gradation voltage selecting circuit configured to select said first specific gradation voltage from said plurality of first gradation voltages in said first period based on said display data decoded by said decoder to supply to said voltage driver, and to select said second specific gradation voltage from said plurality of second gradation voltages in said second period based on said display data decoded by said decoder to supply to said current driver, and

said first switch is connected between said first gradation voltage selecting circuit and said data line.

15. The drive circuit according to claim 14, wherein said D/A conversion circuit further comprises:

a second switch interposed between said current driver and said data line, such that said second switch disconnects said current driver from said data line in said first period, and connects said current driver with said data line in said second period.

16. The drive circuit according to claim 14, wherein said D/A conversion circuit further comprises:

a capacitor connected between an input of said voltage driver and a ground potential;

a third switch interposed between said gradation voltage selecting circuit and said voltage driver to connect said gradation voltage selecting circuit with said voltage driver and said capacitor in said first period; and

a fourth switch interposed between said gradation voltage selecting circuit and said current driver to connect said gradation voltage selecting circuit with said current driver in said second period.

17. The drive circuit according to claim 14, wherein said current driver comprises:

a first current driver configured to flow out said gradation current; and

a second current driver configure to suck said gradation current,

said D/A conversion circuit further comprises;

a fifth switch interposed between said first current driver and said data line; and

a sixth switch interposed between said second current driver and said data line, and

one of said fifth switch and said sixth switch is activated based on a conductive type of a drive transistor of said pixel for driving said light emitting element.

18. The drive circuit according to claim 13, wherein said D/A conversion circuit comprises:

a decoder configured to decode display data;

a first gradation voltage selecting circuit configured to select said first specific gradation voltage from said plurality of first gradation voltages in said first period to supply to said voltage driver, wherein said first switch is connected between said first gradation voltage selecting circuit and said data line; and

a second gradation voltage selecting circuit configured to select said second specific gradation voltage from said plurality of second gradation voltages in said second period to supply to said current driver.

19. The drive circuit according to claim 7, wherein said first gradation voltage generating circuit comprises:

a first reference voltage generating circuit configured to generate a plurality of voltages;

a first selector circuit configured to select a first reference voltage and a second reference voltage from said plurality of voltages supplied from said reference voltage generating circuit based on said first setting data; and

a first voltage follower circuit configured to carry out impedance conversion of said first reference voltage and said second reference voltage; and

a first resistance string circuit configured to voltage-divide a voltage difference between said first reference voltage and said second reference voltage after the impedance conversion and to generate said plurality of first gradation voltages.

20. The drive circuit according to claim 7, wherein said first gradation voltage generating circuit comprises:

a first reference voltage generating circuit configured to generate a plurality of voltages;

a first selector circuit configured to select a first reference voltage and a second reference voltage from said plurality of voltages supplied from said reference voltage generating circuit based on said first setting data;

a first voltage follower circuit configured to carry out impedance conversion of said first reference voltage and said second reference voltage;

a second resistance string circuit configured to voltage-divide a voltage difference between said first reference voltage and said second reference voltage after the impedance conversion and to generate a plurality of voltages; and

a correcting circuit configured to correct said plurality of voltages generated by said second resistance string circuit based on first setting data.

21. The drive circuit according to claim 7, wherein said second gradation voltage generating circuit comprises:

a second reference voltage generating circuit configured to generate a plurality of voltages based on first and second voltage;

a first voltage supply circuit configured to supply said first voltage to said reference voltage generating circuit;

a second voltage supply circuit configured to supply said second voltage to said reference voltage generating circuit;

a second selector circuit configured to select a third reference voltage and a fourth reference voltage from said plurality of voltages supplied from said reference voltage generating circuit based on second setting data;

a second voltage follower circuit configured to carry out impedance conversion to said third reference voltage and said fourth reference voltage; and

a third resistance string circuit configured to voltage-divide a voltage difference between said third reference voltage and said fourth reference voltage after the impedance conversion to adapt to a gamma characteristic of said light emitting element to generate said plurality of second gradation voltages.

22. The drive circuit according to claim 21, wherein each of said first voltage supply circuit and said second voltage supply circuit comprises:

a current source;

a reference voltage follower circuit; and

a reference voltage generation transistor, wherein a source of said reference voltage generation transistor is connected with said power supply line, a drain thereof is connected with said current source, and a gate thereof is connected with said drain thereof and is connected with an input of said reference voltage follower circuit.

23. The drive circuit according to claim 21, wherein said second gradation voltage generating circuit further comprises:

a fourth resistance string circuit configured to generate a plurality of voltages by voltage-dividing the voltage difference between said third reference voltage and said fourth reference voltage after the impedance conversion; and

a correcting circuit configured to correct said plurality of second gradation voltages from the plurality of voltages generated by said fourth resistance string circuit based on said second setting data.

24. The drive circuit according to claim 7, wherein a bias current is supplied to said voltage driver in said first period such that said voltage driver is activated and said bias current is blocked off in said second period such that said voltage driver is inactivated.

25. The drive circuit according to claim 7, wherein said current driver comprises a MOS-type transistor, and

a gate voltage of said MOS-type transistor is controlled such that said gradation current is generated.

26. The drive circuit according to claim 7, wherein said voltage driver is configured of a transistor of a same conductive type as transistors of said second gradation voltage selecting circuit.

27. The drive circuit according to claim 18, wherein said first gradation voltage selecting circuit comprises a plurality of first selection switches connected in parallel, and when said display data is n bits, a number of said plurality of first selection switches is less than 2ⁿ, and

said second gradation voltage selecting circuit comprises a plurality of second selection switches connected in parallel, and a number of said plurality of second selection switches is 2ⁿ.

28. The drive circuit according to claim 6, wherein a row of specific connection pads is provided between a row of connection pads for input signals and power supply voltages and a row of pads for output terminals of said D/A conversion circuit, and

a plurality of first power supply voltages are supplied to said voltage drivers through said row of specific connection pads.

29. The drive circuit according to claim 14, wherein said gradation voltage generating circuit and said gradation voltage selecting circuit are separated for each of RGB colors and are arranged in a continuous area.

30. The drive circuit according to claim 6, wherein at least one of said gradation voltage generating circuit and said D/A conversion circuit is formed on a semiconductor chip.

31. The drive circuit according to claim 8, wherein said pixel is formed on a glass substrate, and

said current driver and said second gradation voltage generating circuit are formed on a semiconductor chip.

32. A display apparatus comprising:

a plurality of data lines;

a plurality of scanning lines arranged in a direction orthogonal to said plurality of data lines;

a pixel arranged at each of intersections said plurality of data lines and said plurality of scanning lines, wherein said pixel has a light emitting element which changes a brightness in response to a supplied signal; and

a data line driving circuit configured to drive each of said plurality of data lines when each of said plurality of scanning lines is selected,

wherein said data line drive circuit comprises;

a gradation voltage generation circuit configured to generate a plurality of first gradation voltages different from each other and a plurality of second gradation voltages different from each other; and

a D/A conversion circuit configured to drive a light emitting element of a pixel through a data line with a gradation voltage based on one of said plurality of first gradation voltages as a first specific gradation voltage in a precharge period and to drive said light emitting element of said pixel through said data line with a gradation current based on one of said plurality of said second gradation voltages as a second specific gradation voltage.

33. The display apparatus according to claim 32, wherein said D/A conversion circuit comprises:

a voltage driver configured to drive said light emitting element with said gradation voltage based on said first specific gradation voltage in said first period; and

a current driver configured to drive said light emitting element with said gradation current based on said second specific gradation voltage to in said second period.

34. The display apparatus according to claim 33, wherein said gradation voltage generating circuit comprises:

a first gradation voltage generating circuit configured to generate said plurality of first gradation voltages adaptive for a current-voltage characteristic of said pixel;

a second gradation voltage generating circuit configured to generate said second plurality of gradation voltages adaptive for a gamma characteristic of said light emitting element of said pixel; and

a multiplexer connected with said first gradation voltage generating circuit and said second gradation voltage generating circuit and configured to select said plurality of first gradation voltages in said first period to output to said D/A conversion circuit, and to select said plurality of second gradation voltages in said second period to output to said D/A conversion circuit.

35. The display apparatus according to claim 33, wherein said gradation voltage generating circuit comprises:

a first gradation setting data register configured to hold first gradation setting data;

a second gradation setting data register configured to hold second gradation setting data;

a multiplexer configured to select said first gradation setting data in said first period, and select said second gradation setting data in said second period; and

a gradation voltage generating circuit configured to generate said plurality of first gradation voltages based on said first gradation setting data in said first period, and to generate said plurality of second gradation voltages based on said second gradation setting data in said second period.

36. The display apparatus according to claim 33, wherein said D/A conversion circuit further comprises:

a first switch interposed between said voltage driver and said data line, such that said first switch connects said voltage driver with said data line in said first period and disconnects said voltage driver from said data line in said second period;

a decoder configured to decode display data; and

a gradation voltage selecting circuit configured to select said first specific gradation voltage from said plurality of first gradation voltages in said first period based on said display data decoded by said decoder to supply to said voltage driver, and to select said second specific gradation voltage from said plurality of second gradation voltages in said second period based on said display data decoded by said decoder to supply to said current driver.

37. The display apparatus according to claim 33, wherein said D/A conversion circuit further comprises:

a first switch interposed between said voltage driver and said data line, such that said first switch connects said voltage driver with said data line in said first period and disconnects said voltage driver from said data line in said second period;

a decoder configured to decode display data;

a first gradation voltage selecting circuit configured to select said first specific gradation voltage from said plurality of first gradation voltages in said first period to supply to said voltage driver, wherein said first switch is connected between said first gradation voltage selecting circuit and said data line; and

a second gradation voltage selecting circuit configured to select said second specific gradation voltage from said plurality of second gradation voltages in said second period to supply to said current driver.

38. The display apparatus according to claim 32, wherein a row of specific connection pads is provided between a row of connection pads for input signals and power supply voltages and a row of pads for output terminals of said D/A conversion circuit, and

a plurality of first power supply voltages are supplied to said voltage drivers through said row of specific connection pads.