Display device and driving method thereof

• US 20080198103A1
• Filed: 02/12/2008
• Published: 08/21/2008
• Est. Priority Date: 02/20/2007
• Status: Active Grant

• Current Assignee: Sony Corporation (Sony Group Corp.)
• Original Assignee: Sony Corporation (Sony Group Corp.)
• Inventors: Yamamoto, Tetsuro, Uchino, Katsuhide, Toyomura, Naobumi
• Granted Patent: US 8,174,466 B2
• Time in Patent Office: Days
• US Class Current: 345/77
• CPC Class Codes: G09G 2300/0819 used for counteracting undesired variations, e.g. feedback or autozeroing
• 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 2320/0233 Improving the luminance or brightness uniformity across the screen
• CPC Class Codes: G09G 2320/0295 by monitoring each display pixel
• CPC Class Codes: G09G 2320/043 Preventing or counteracting the effects of ageing
• CPC Class Codes: G09G 3/3233 with pixel circuitry controlling the current through the light-emitting element
• 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

Abstract

Disclosed herein is a display device including: a pixel array unit having pixel circuits arranged in a form of a matrix; and a control unit having a writing scanning unit for outputting, to the sampling transistor, a writing scanning pulse. The control unit effects control to supply a control input terminal of the drive transistor with a fixed potential for a threshold value correcting operation for retaining a voltage corresponding to a threshold voltage of the drive transistor in the storage capacitor. When setting a voltage across the storage capacitor to the threshold voltage of the drive transistor by repeating the threshold value correcting operation a plurality of times on a time division basis, the control unit effects control to perform each the threshold value correcting operation and the sampling transistor to a conducting state.

Claims

1. A display device comprising:

a pixel array unit including pixel circuits arranged in a form of a matrix, said pixel circuits each including a drive transistor for generating a driving current, an electrooptic element connected to an output terminal of said drive transistor, a storage capacitor for retaining information corresponding to a signal potential of a video signal, a sampling transistor for writing the information corresponding to said signal potential to said storage capacitor, and a light emission controlling transistor for adjusting an emission period of said electrooptic element, said light emission controlling transistor being disposed between a power supply terminal of said drive transistor and a power supply line, said drive transistor generating the driving current based on the information retained in said storage capacitor and sending the driving current through said electrooptic element, whereby said electrooptic element emits light; and

a control unit including a writing scanning unit for outputting, to said sampling transistor, a writing scanning pulse for performing line-sequential scanning of said pixel circuits by sequentially controlling said sampling transistor and writing information corresponding to a signal potential of a video signal to each of storage capacitors in one row, and a horizontal driving unit for supplying a video signal for one row to a video signal line according to a signal potential writing operation of said sampling transistor;

wherein said control unit effects control to supply a control input terminal of said drive transistor with a fixed potential for a threshold value correcting operation for retaining a voltage corresponding to a threshold voltage of said drive transistor in said storage capacitor, and when setting a voltage across said storage capacitor to the threshold voltage of said drive transistor by repeating said threshold value correcting operation a plurality of times on a time division basis, said control unit effects control to perform each said threshold value correcting operation by changing said light emission controlling transistor and said sampling transistor to a conducting state in such a manner as to be interlocked with each other in periods in which said fixed potential is supplied during a period of a plurality of said threshold value correcting operations.

2. The display device according to claim 1,

wherein said horizontal driving unit outputs the fixed potential for said threshold value correcting operation as said video signal in a part of a horizontal scanning period.

3. The display device according to claim 1,

wherein prior to said threshold value correcting operation, said control unit effects control to perform a preparatory operation for said threshold value correcting operation, said preparatory operation setting the voltage across said storage capacitor to the threshold voltage of said drive transistor or higher.

4. The display device according to claim 3,

wherein said pixel circuit has said storage capacitor disposed between the control input terminal and said output terminal of said drive transistor, and has a switch transistor disposed between a reference potential for setting the voltage across said storage capacitor to the threshold voltage of said drive transistor or higher and said output terminal of said drive transistor, in addition to said drive transistor, said sampling transistor, and said light emission controlling transistor, and

said control unit sets said switch transistor in a conducting state during the preparatory operation for said threshold value correcting operation.

5. The display device according to claim 1,

wherein after said threshold value correcting operation, said control unit effects control to perform mobility correcting operation for adding an amount of correction for mobility of said drive transistor to the information written to said storage capacitor.

6. The display device according to claim 1,

wherein said control unit stops supplying said video signal to said control input terminal of said drive transistor by setting said sampling transistor in a non-conducting state at a point in time at which the information corresponding to said signal potential is written to said storage capacitor, and enables an operation in which potential of said control input terminal of said drive transistor is interlocked with change in potential of said output terminal of said drive transistor.

7. A driving method of a pixel circuit, said pixel circuit including a drive transistor for generating a driving current, an electrooptic element connected to an output terminal of said drive transistor, a storage capacitor for retaining information corresponding to a signal potential of a video signal, a sampling transistor for writing the information corresponding to said signal potential to said storage capacitor, and a light emission controlling transistor for adjusting an emission period of said electrooptic element, said light emission controlling transistor being disposed between a power supply terminal of said drive transistor and a power supply line, said drive transistor generating the driving current based on the information retained in said storage capacitor and sending the driving current through said electrooptic element, whereby said electrooptic element emits light, said driving method comprising:

a control unit effecting control to supply a control input terminal of said drive transistor with a fixed potential for a threshold value correcting operation for retaining a voltage corresponding to a threshold voltage of said drive transistor in said storage capacitor, and when setting a voltage across said storage capacitor to the threshold voltage of said drive transistor by repeating said threshold value correcting operation a plurality of times on a time division basis, said control unit effecting control to perform each said threshold value correcting operation by changing said light emission controlling transistor and said sampling transistor to a conducting state in such a manner as to be interlocked with each other in periods in which said fixed potential is supplied during a period of a plurality of said threshold value correcting operations.

8. A display device comprising:

pixel array means for including pixel circuits arranged in a form of a matrix, said pixel circuits each including a drive transistor for generating a driving current, an electrooptic element connected to an output terminal of said drive transistor, a storage capacitor for retaining information corresponding to a signal potential of a video signal, a sampling transistor for writing the information corresponding to said signal potential to said storage capacitor, and a light emission controlling transistor for adjusting an emission period of said electrooptic element, said light emission controlling transistor being disposed between a power supply terminal of said drive transistor and a power supply line, said drive transistor generating the driving current based on the information retained in said storage capacitor and sending the driving current through said electrooptic element, whereby said electrooptic element emits light; and

control means for including a writing scanning unit for outputting, to said sampling transistor, a writing scanning pulse for performing line-sequential scanning of said pixel circuits by sequentially controlling said sampling transistor and writing information corresponding to a signal potential of a video signal to each of storage capacitors in one row, and a horizontal driving unit for supplying a video signal for one row to a video signal line according to a signal potential writing operation of said sampling transistor;

wherein said control means effects control to supply a control input terminal of said drive transistor with a fixed potential for a threshold value correcting operation for retaining a voltage corresponding to a threshold voltage of said drive transistor in said storage capacitor, and when setting a voltage across said storage capacitor to the threshold voltage of said drive transistor by repeating said threshold value correcting operation a plurality of times on a time division basis, said control means effects control to perform each said threshold value correcting operation by changing said light emission controlling transistor and said sampling transistor to a conducting state in such a manner as to be interlocked with each other in periods in which said fixed potential is supplied during a period of a plurality of said threshold value correcting operations.