DISPLAY DEVICE AND METHOD OF DRIVING THE SAME

• US 20100073357A1
• Filed: 03/11/2009
• Published: 03/25/2010
• 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: Industry-University Cooperation Foundation Hanyang University, Samsung Electronics Co. Ltd.
• Inventors: Kwon, Oh-Kyong, MIN, Ung-Gyu
• Granted Patent: US 8,289,247 B2
• Time in Patent Office: Days
• US Class Current: 345/214
• CPC Class Codes: G09G 2300/0814 used for selection purposes, e.g. logical AND for partial update
• 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 2300/0861 with additional control of the display period without amending the charge stored in a pixel memory, e.g. by means of additional select electrodes
• 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 2320/0233 Improving the luminance or brightness uniformity across the screen
• 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 2330/08 Fault-tolerant or redundant circuits, or circuits in which repair of defects is prepared
• CPC Class Codes: G09G 3/3233 with pixel circuitry controlling the current through the light-emitting element
• CPC Class Codes: G09G 3/3258 with pixel circuitry controlling the voltage across 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

A display device and a method of driving the same are provided. The display device includes a plurality of display pixels, a plurality of data lines that are connected to the display pixels, and a plurality of sensing lines that are connected to the display pixels. Each display pixel includes: a driving transistor that has a control terminal, an input terminal, and an output terminal; a capacitor that is connected to the control terminal of the driving transistor; a first switching transistor that is connected to the data line and the control terminal of the driving transistor; a light-emitting element that receives a driving current from the driving transistor to emit light; a second switching transistor that is connected between the sensing line and the light-emitting element; and a third switching transistor that is connected between the output terminal of the driving transistor and the light-emitting element.

Claims

1. A display device, comprising:

a plurality of display pixels;

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

a plurality of sensing lines that are 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 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 to emit light;

a second switching transistor connected between the sensing line and the light-emitting element; and

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

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

a signal controller to correct an input image signal based on a threshold voltage of the driving transistor and to output an output image signal; and

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

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

the sensing data signal comprises a first sensing data signal.

4. The display device of claim 3, wherein the signal controller comprises a first calculating unit to calculate the threshold voltage of the driving transistor from the first sensing data signal.

5. The display device of claim 4, wherein the signal controller corrects the input image signal based on an electric field effect mobility of the driving transistor and outputs the output image signal.

6. The display device of claim 5, wherein the sensing data signal further comprises a second sensing data signal, and

the signal controller further comprises a second calculation unit to calculate the electric field effect mobility of the driving transistor from the second sensing data signal.

7. The display device of claim 6, further comprising a read-only memory (ROM) to receive and store the threshold voltage of the driving transistor and the electric field effect mobility of the driving transistor.

8. The display device of claim 6, wherein sensing of the first sensing data signal and the second sensing data signal is performed before production of the display device is completed.

9. The display device of claim 5, wherein the signal controller corrects the input image signal based on a sequential change of a threshold voltage of the light-emitting element and outputs the output image signal.

10. The display device of claim 9, further comprising a plurality of dummy pixels that do not perform a display operation,

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

11. The display device of claim 10, wherein the signal controller further comprises an image signal correction unit to correct the input image signal based on the threshold voltage of the light-emitting element of the display pixel, the threshold voltage of the light-emitting element of the dummy pixel, the threshold voltage of the driving transistor, and the electric field effect mobility of the driving transistor.

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

13. The display device of claim 12, wherein the basic circuit portion comprises:

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

an analog-to-digital converter to receive the sensing data signal from the display pixel and to convert the received sensing data signal.

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

a first switch that switches the second switching transistor and a ground voltage;

a second switch that switches the second switching transistor and a reference current source;

a third switch that switches the data line and the sensing line;

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

a fifth switch that switches the sensing line and a precharging voltage; and

a sixth switch that switches the sensing line and the analog-to-digital converter.

15. The display device of claim 2, wherein the signal controller corrects the input image signal based on a sequential transition of a threshold voltage the light-emitting element and outputs the output image signal.

16. The display device of claim 1, wherein the driving transistor is a p-channel electric field effect transistor.

17. The display device of claim 16, wherein the first switching transistor, the second switching transistor, and the third switching transistor are each a p-channel electric field effect transistor.

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

connecting the control terminal and the output terminal;

connecting the control terminal and the output terminal to a ground voltage and then disconnecting the control terminal and the output terminal from the ground voltage;

sensing a first voltage of the control terminal through the sensing line; and

calculating a threshold voltage of the driving transistor based on the first voltage.

19. The method of claim 18, further comprising:

connecting a reference current source to the control terminal and the output terminal;

sensing a second voltage of the control terminal through the sensing line; and

calculating an electric field effect mobility of the driving transistor based on the second voltage.

20. The method of claim 19, wherein the driving transistor is a p-channel electric field effect transistor.

21. The method of claim 19, further comprising storing the threshold voltage of the driving transistor and the electric field effect mobility of the driving transistor in a read only memory (ROM).

22. The method of claim 21, wherein the storing of the threshold voltage of the driving transistor and the electric field effect mobility of the driving transistor in the ROM is performed before production of the display device is completed.

23. The method of claim 21, further comprising:

connecting a data voltage to the control terminal; and

connecting a reference voltage to the sensing line.

24. The method of claim 23, further comprising:

disconnecting the control terminal from the data voltage and connecting the light-emitting element to the output terminal; and

disconnecting the sensing line from the reference voltage and connecting the sensing line to an anode terminal of the light-emitting element.

25. The method of claim 24, further comprising:

disconnecting the light-emitting element from the output terminal;

sensing an anode voltage of the light-emitting element through the sensing line when the light-emitting element is disconnected from the output terminal; and

calculating a transition degree of a threshold voltage of the light-emitting element by comparing the anode voltage of the light-emitting element with a reference voltage.

26. The method of claim 25, wherein the reference voltage is an anode voltage of a light-emitting element disposed in a dummy pixel that does not perform a display operation.

27. The method of claim 25, further comprising correcting an input image signal based on the threshold voltage of the driving transistor, the electric field effect mobility of the driving transistor, and the transition degree of the threshold voltage of the light-emitting element.

28. The method of claim 25, wherein sensing the anode voltage of the light-emitting element is performed in more than one frame of the display device.

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

connecting a data voltage to the control terminal;

connecting a reference voltage to the sensing line;

disconnecting the control terminal from the data voltage and connecting the light-emitting element to the output terminal;

disconnecting the sensing line from the reference voltage and connecting the sensing line to an anode terminal of the light-emitting element;

disconnecting the light-emitting element and the output terminal;

sensing an anode voltage of the light-emitting element through the sensing line when the light-emitting element is disconnected from the output terminal; and

calculating a transition degree of a threshold voltage of the light-emitting element by comparing the anode voltage of the light-emitting element with a reference voltage.

30. The method of claim 29, wherein the reference voltage is an anode voltage of a light-emitting element disposed in a dummy pixel that does not perform a display operation.

31. The method of claim 29, further comprising correcting an input image signal based on a transition degree of the threshold voltage of the light-emitting element.

32. The method of claim 29, wherein sensing the anode voltage of the light-emitting element is performed in more than one frame of the display device.