Self-luminous display device and driving method of the same

• US 20090160743A1
• Filed: 12/01/2008
• Published: 06/25/2009
• Est. Priority Date: 12/21/2007
• Status: Active Grant

• Current Assignee: JDI Design and Development GK
• Original Assignee: Sony Corporation (Sony Group Corp.)
• Inventors: Tomida, Masatsugu, Asano, Mitsuru
• Granted Patent: US 7,868,859 B2
• Time in Patent Office: Days
• US Class Current: 345/80
• 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 2300/0866 by means of changes in the pixel supply voltage
• CPC Class Codes: G09G 2310/0256 with the purpose of reversing the voltage across a light emitting or modulating element within a 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 3/3233 with pixel circuitry controlling the current through the light-emitting element
• CPC Class Codes: G09G 3/3266 Details of drivers for scan electrodes
• 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

Disclosed herein is a self-luminous display device including: pixel circuits; and a drive circuit, wherein each of the pixel circuits includes a light-emitting diode, a drive transistor connected to a drive current path of the light-emitting diode, and a holding capacitor coupled to a control node of the drive transistor, during a period in which at least actual threshold voltage and mobility corrections are performed on the drive transistor before the light-emitting diode can emit light, the drive circuit performs a preliminary threshold voltage correction of the drive transistor, i.e., a dummy Vth correction, with the light-emitting diode in a non-light emitting state, the drive circuit next performs a correction preparation for a constant period by reverse-biasing the light-emitting diode and initializing the voltage held by the holding capacitor, and the drive circuit performs the actual threshold voltage correction and mobility correction after the correction preparation.

Claims

1. A self-luminous display device comprising:

pixel circuits; and

a drive circuit, wherein

each of the pixel circuits includes a light-emitting diode, a drive transistor connected to a drive current path of the light-emitting diode, and a holding capacitor coupled to a control node of the drive transistor,

during a period in which at least actual threshold voltage and mobility corrections are performed on the drive transistor before the light-emitting diode can emit light, the drive circuit performs a preliminary threshold voltage correction of the drive transistor, i.e., a dummy Vth correction, with the light-emitting diode in a non-light emitting state,

the drive circuit next performs a correction preparation for a constant period by reverse-biasing the light-emitting diode and initializing the voltage held by the holding capacitor, and

the drive circuit performs the actual threshold voltage correction and mobility correction after the correction preparation.

2. The self-luminous display device of claim 1 comprising:

a pixel array, the pixel array including a plurality of pixel circuits arranged in a matrix form, each of the plurality of pixel circuits including a sampling transistor adapted to sample a data potential and feed the potential to the control node, wherein

the drive circuit sets the light-emitting diode to a reverse bias state, with the sampling transistor turned off, by removing a supply voltage connection from a node opposite to the node to which the light-emitting diode is connected,

the drive circuit next performs the dummy Vth correction, followed by the correction preparation,

after the correction preparation, the drive circuit performs the actual threshold voltage correction and mobility correction, and

in the correction preparation, the period of time during which the supply voltage connection is removed is constant in all screen display periods, each of which is determined for each pixel row of the pixel array.

3. The self-luminous display device of claim 2, wherein the drive circuit changeably controls the end of light emission in an immediately preceding other screen display period by beginning the reverse bias state setting.

4. The self-luminous display device of claim 1, wherein

the drive circuit performs the non-light emitting state setting and the dummy Vth correction adapted to cause the holding capacitor to hold a voltage equivalent to a threshold voltage of the drive transistor, and

the drive circuit performs the correction preparation, actual threshold voltage correction and mobility correction, the mobility correction being adapted to adjust the voltage held by the holding capacitor according to the driving capability of the drive transistor by writing a data potential to the control node, within a constant period with the light-emitting diode reverse-biased, so that the light-emitting diode is forward-biased to emit light according to the data potential.

5. The self-luminous display device of claim 1 comprising:

a pixel array including a plurality of said pixel circuits arranged in a matrix form;

a plurality of video signal lines adapted to commonly connect the plurality of pixel circuits on a column by column basis in the pixel array;

power scan lines adapted to commonly connect the plurality of pixel circuits on a row by row basis in the pixel array and transmit a power drive pulse generated by the drive circuit; and

write scan lines adapted to commonly connect the plurality of pixel circuits on a row by row basis in the pixel array and transmit a write drive pulse generated by the drive circuit, wherein

the drive transistor and organic light-emitting diode are cascaded between the power scan line and a predetermined voltage line,

the holding capacitor is connected between the cathode of the light-emitting diode connected to the drive transistor and the control node of the drive transistor, and

a sampling transistor controlled by the write drive pulse is connected between the control node and video signal line.

6. The self-luminous display device of claim 5, wherein

the drive circuit controls the power scan line to change from a first level of the power drive pulse to a second level adapted to reverse-bias the light-emitting diode, and the drive circuit changes, during a reference potential period in which no pulse of the data potential is superimposed on the video signal line, the level of the write scan line to an active level of the write drive pulse where the sampling transistor turns on so as to set the light-emitting diode to a reverse bias state,

the drive circuit performs the dummy Vth correction by changing the power scan line to the first level during the reference potential period and changing the write drive pulse of the write scan line to an inactive level,

the drive circuit maintains constant, in the correction preparation, the period of time during which the power scan line is maintained at the second level in all screen display periods, each of which is determined for each pixel row of the pixel array so as to control the levels of the power scan line and write scan line in the same setting as is done with the reverse bias state, and

the drive circuit performs the actual threshold voltage correction by controlling the levels of the power scan line and write scan line in the same manner as is done with the dummy Vth correction.

7. A driving method of a self-luminous display device, the self-luminous display device including pixel circuits, each of the pixel circuits including a light-emitting diode, a drive transistor connected to a drive current path of the light-emitting diode, and a holding capacitor coupled to a control node of the drive transistor, the driving method comprising:

a non-light emission setting step of setting the light-emitting diode to a non-light emitting state;

a dummy Vth correction step of performing a preliminary threshold voltage correction of the drive transistor;

a correction preparation step of reverse-biasing the light-emitting diode and initializing the voltage held by the holding capacitor;

an actual threshold voltage correction step of performing a threshold voltage correction of the drive transistor;

a mobility correction step of performing a mobility correction of the drive transistor by writing a data potential to the pixel circuit; and

a light emission setting step of forward-biasing the light-emitting diode to emit light according to the written data potential.

8. The driving method of a self-luminous display device of claim 7, wherein the dummy Vth correction step, correction preparation step, actual threshold voltage correction step, mobility correction step, light emission setting step and non-light emission setting step are performed in this order to fit a row display period determined for each pixel row of the pixel array in which the pixel circuits are arranged in a matrix form.

9. The driving method of a self-luminous display device of claim 7, wherein the correction preparation step, actual threshold voltage correction step, mobility correction step, light emission setting step, dummy Vth correction step and non-light emission setting step are performed in this order to fit a row display period determined for each pixel row of the pixel array in which the pixel circuits are arranged in a matrix form.

10. The driving method of a self-luminous display device of claim 7, wherein, in the correction preparation step, the period of time during which the light-emitting diode is set to a reverse bias state is constant in all the screen display periods.