Display device and method of driving the same

• US 8,294,696 B2
• Filed: 03/18/2009
• Issued: 10/23/2012
• Est. Priority Date: 09/24/2008
• Status: Active Grant

• Current Assignee: Industry-University Cooperation Foundation Hanyang University, Samsung Display Company Limited (Samsung Electronics Co. Ltd.)
• Original Assignee: Iucf-hyu, Samsung Display Company Limited (Samsung Electronics Co. Ltd.)
• Inventors: Kwon, Oh-Kyong, Min, Ung-Gyu
• Primary Examiner(s): Tzeng, Fred
• Application Number:
  US12/406,631
• Publication Number:
  US 20100073335A1
• Time in Patent Office: 1,315 Days
• Field of Search: 345/204, 345/76, 345/81, 345/87, 345/207, 345/211, 345/214, 313/506
• US Class Current: 345/204
• CPC Class Codes: G09G 2300/0413 Details of dummy pixels or dummy lines in flat panels
• CPC Class Codes: G09G 2300/0814 used for selection purposes, e.g. logical AND for partial update
• 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 2310/0262 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 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 2320/0285 using tables for spatial correction of display data
• 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 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 3/3291 in which the data driver supplies a variable data voltage for setting the current through, or the voltage across, the light-emitting elements

Abstract

The present invention provides a display device and a method of driving the same. The display device includes a plurality of display pixels to display an image, a plurality of data lines connected to the display pixel, and a plurality of sensing lines connected to the display pixel. Each display pixel includes: a driving transistor including a control terminal, an input terminal, and an output terminal; a capacitor connected to the control terminal of the driving transistor; a first switching transistor connected to the data line and the control terminal of the driving transistor; a light-emitting element to receive a driving current from the driving transistor, the light-emitting element to emit light; a second switching transistor connected between the sensing line and the output terminal of the driving transistor; and a third switching transistor connected between the output terminal of the driving transistor and the light-emitting element, wherein the driving transistor is a p-channel electric field effect transistor.

Claims

1. A display device, comprising:

a plurality of display pixels configured to display an image;

a plurality of data lines connected to the display pixels; and

a plurality of sensing lines connected to the display pixels,

wherein each display pixel comprises;

a driving transistor comprising a control terminal, an input terminal, and an output terminal;

a capacitor connected to the control terminal of the driving transistor;

a first switching transistor connected between the data line and the control terminal of the driving transistor;

a light-emitting element to receive a driving current from the driving transistor, the light-emitting element to emit light;

a second switching transistor connected between the sensing line and the output terminal of the driving transistor; and

a third switching transistor connected between the output terminal of the driving transistor and the light-emitting element, and

wherein the driving transistor is a p-channel electric field effect transistor.

2. The display device of claim 1, further comprising:

a signal controller configured to correct an input image signal and to output an output image signal in consideration of a threshold voltage of the driving transistor; and

a data driver configured to determine an image data voltage based on the output image signal and to apply the image data voltage to the data line.

3. The display device of claim 2, wherein the sensing line is configured to transfer a sensing signal from the display pixel to the data driver, and

the sensing signal comprises a first sensing signal related to the threshold voltage of the driving transistor.

4. The display device of claim 3, wherein the signal controller comprises a first frame memory configured to store the first sensing signal.

5. The display device of claim 4, wherein the signal controller is configured to correct the input image signal and output the output image signal in consideration of an electric field effect mobility of the driving transistor.

6. The display device of claim 5, wherein the sensing signal further comprises a second sensing signal related to the electric field effect mobility of the driving transistor, and

the signal controller further comprises a second frame memory configured to store the second sensing signal.

7. The display device of claim 6, wherein the signal controller is configured to correct the input image signal and output the output image signal in consideration of a degradation of the light-emitting element.

8. The display device of claim 7, further comprising a plurality of dummy pixels configured to not display an image,

wherein the degradation of the light-emitting element is determined by comparing a threshold voltage of a light-emitting element of the display pixel and a threshold voltage of a light-emitting element of the dummy pixel.

9. The display device of claim 8, wherein the signal controller further comprises:

a lookup table configured to store a degradation factor representing a degradation degree of the light-emitting element; and

a third frame memory configured to receive and to store the degradation factor from the lookup table.

10. The display device of claim 9, wherein the signal controller further comprises an image signal correction unit configured to correct the input image signal based on the first sensing signal, the second sensing signal, and the degradation factor.

11. The display device of claim 2, wherein the data driver comprises a basic circuit portion and a switching circuit portion,

wherein the basic circuit portion comprises:

a digital-to-analog converter configured to convert the output image signal to the image data voltage; and

an analog-to-digital converter configured to receive the first sensing signal, the second sensing signal, a third sensing signal, and a fourth sensing signal from the display pixel, the analog-to-digital converter configured to convert the received sensing signal.

12. The display device of claim 11, wherein the switching circuit portion comprises:

a first switch configured to switch the second switching transistor and a ground voltage;

a second switch configured to switch the second switching transistor and a reference current source;

a third switch configured to switch the data line and the sensing line;

a fourth switch configured to switch the data line and the digital-analog converter;

a fifth switch configured to switch the sensing line and a precharging voltage;

a sixth switch configured to switch the data line and a driving voltage; and

a seventh switch configured to switch the sensing line and the analog-to-digital converter.

13. The display device of claim 1, wherein the first switching transistor, the second switching transistor, and the third switching transistor are each p-channel electric field effect transistors.

14. A method of driving a display device comprising a capacitor, a driving transistor connected to the capacitor, the driving transistor comprising a control terminal, an input terminal, and an output terminal, and a light-emitting element connected to the output terminal, the method comprising:

connecting a data voltage to the control terminal;

emitting light by the light-emitting element; and

sensing a first voltage of the output terminal,

wherein light emission of the light-emitting element is stopped, the control terminal and the output terminal are connected to a ground voltage, the control terminal and the output terminal are disconnected from the ground voltage, and then the first voltage of the output terminal is sensed.

15. The method of claim 14, further comprising sensing a second voltage of the output terminal by connecting a data voltage to the control terminal and emitting light by the light-emitting element, then light emission of the light-emitting element is stopped, a reference current source is connected to the control terminal and the output terminal, and then the second voltage of the output terminal is sensed.

16. The method of claim 15, further comprising sensing a third voltage of the output terminal after connecting a data voltage to the control terminal and the emitting of light by the light-emitting element, wherein when the same voltage is connected to the input terminal and the control terminal, the third voltage is sensed.

17. The method of claim 16, further comprising calculating a degradation factor representing a degradation of the light-emitting element by comparing the third voltage with a reference threshold voltage.

18. The method of claim 17, wherein the reference threshold voltage is an anode voltage of a light-emitting element disposed in a dummy pixel that does not perform a display operation.

19. The method of claim 17, further comprising correcting an input image signal based on the first voltage, the second voltage, and the degradation factor.

20. The method of claim 16, wherein sensing the first voltage, sensing the second voltage, and sensing the third voltage are performed within different frames.

21. A method of driving a display device comprising a capacitor, a driving transistor connected to the capacitor, the driving transistor comprising a control terminal, an input terminal, and an output terminal, and a light-emitting element connected to the output terminal, the method comprising:

connecting a data voltage to the control terminal;

emitting light by the light-emitting element;

sensing a voltage of the output terminal; and

correcting an input image signal based on the sensed voltage,

wherein light emission of the light-emitting element is stopped, a reference current source is connected to the control terminal and the output terminal, and then the voltage of the output terminal is sensed.

22. A method of driving a display device comprising a capacitor, a driving transistor connected to the capacitor, the driving transistor comprising a control terminal, an input terminal, and an output terminal, and a light-emitting element connected to the output terminal, the method comprising:

connecting a data voltage to the control terminal;

emitting light by the light-emitting element; and

sensing a voltage of the output terminal,

wherein after repeating the connecting of a data voltage to the control terminal and the emitting of light by the light-emitting element, when the same voltage is connected to the input terminal and the control terminal, the voltage of the output terminal is sensed.

23. The method of claim 22, further comprising:

calculating a degradation factor representing a degradation of the light-emitting element by comparing the voltage of the output terminal with a reference threshold voltage; and

correcting an input image signal based on the degradation factor.

24. The method of claim 23, wherein the reference threshold voltage is an anode voltage of a light-emitting element disposed in a dummy pixel that does not perform a display operation.