Organic light emitting display and driving method thereof

• US 20080231562A1
• Filed: 03/21/2008
• Published: 09/25/2008
• Est. Priority Date: 03/22/2007
• Status: Active Grant

• Current Assignee: Samsung Display Company Limited (Samsung Group)
• Original Assignee: Samsung Display Company Limited (Samsung Group)
• Inventors: Kwon, Oh-kyong
• Granted Patent: US 8,373,687 B2
• Time in Patent Office: Days
• US Class Current: 345/77
• CPC Class Codes: G09G 2300/043 Compensation electrodes or other additional electrodes in matrix displays related to distortions or compensation signals, e.g. for modifying TFT threshold voltage in column driver
• 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 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

Abstract

An organic light emitting display capable of displaying images of uniform luminance and a method for driving the display are disclosed. The display senses degradation of the organic light emitting diode and threshold and/or mobility of a drive transistor and modifies the data supplied to the pixel according to the sensed parameters.

Claims

1. An organic light emitting display, comprising:

a plurality of pixels disposed near intersections of data lines, scan lines, and emission control lines;

a scan driver configured to supply a scan signal to the scan lines and to supply an emission control signal to the emission control lines;

a control line driver configured to supply a control signal to control lines;

a data driver configured to generate data signals for the data lines;

a sensing unit configured to sense degradation information of an organic light emitting diode and a and threshold voltage and/or mobility information of a drive transistor included in each of the pixels;

a switch unit configured to connect one of the sensing unit and the data driver to the data lines;

a control block configured to store the sensed degradation information and the sensed threshold voltage and/or mobility information; and

a timing controller configured to generate second data based on first data from another circuit, the sensed degradation information, and the sensed threshold voltage and/or mobility information.

2. The organic light emitting display as claimed in claim 1, wherein the sensing unit includes:

a sensing circuit for each channel;

an analog-digital converter configured to convert the sensed threshold voltage and/or mobility information and the sensed degradation information from the sensing circuit into a first digital value and a second digital value, respectively.

3. The organic light emitting display as claimed in claim 2, wherein the sensing circuit includes:

a current sink unit configured to sink a first electric current from the pixel; and

a current source unit configured to supply a second electric current to the pixel.

4. The organic light emitting display as claimed in claim 3, wherein the switch unit includes three switching elements for each channel, wherein the three switching elements include:

a third switching element disposed between the current sink unit and the data line, the third switching element configured to be turned on when the threshold voltage information is sensed;

a second switching element disposed between the current source unit and the data, the second switching element configured to be turned on when the degradation information is sensed; and

a first switching element disposed between the data driver and the data line, the first switching element configured to be turned on when the data signal is supplied.

5. The organic light emitting display as claimed in claim 4, wherein the control block includes:

a memory configured to store the first digital value and the second digital value; and

a controller configured to transfer the first digital value and the second digital value to the timing controller.

6. The organic light emitting display as claimed in claim 5, wherein the controller of the control block is configured to transfer the first digital value and the second digital value for a certain pixel to the timing controller when the first data for the certain pixel is input to the timing controller.

7. The organic light emitting display as claimed in claim 5, wherein the timing controller generates the second data based at least in part on the first data and the second data has a greater number of bits than the first data.

8. The organic light emitting display as claimed in claim 7, wherein the second data compensates for at least one of degradation of the organic light emitting diode and variation of the threshold voltage and/or mobility of the drive transistor.

9. The organic light emitting display as claimed in claim 5, wherein each of the pixels includes:

the organic light emitting diode;

a first transistor coupled with the scan line and the data line, the first transistor configured to be turned on when a scan signal is supplied to the scan line;

a storage capacitor configured to be charged with a voltage corresponding to the data signal supplied to the data line;

a second transistor configured to supply an electric current corresponding to the voltage stored in the storage capacitor to the organic light emitting diode;

a third transistor between the second transistor and the organic light emitting diode, the third transistor configured to be turned off when an emission control signal is supplied to the emission control line; and

a fourth transistor between an anode electrode of the organic light emitting diode and the data line, the fourth transistor configured to be turned on a control signal is supplied to the control line.

10. The organic light emitting display as claimed in claim 9, wherein the first transistor, the third transistor, and the fourth transistor are turned on when the threshold voltage and/or mobility information is sensed.

11. The organic light emitting display as claimed in claim 10, wherein the first voltage generated when the first current is sunk is converted into the first digital value.

12. The organic light emitting display as claimed in claim 10, wherein sensing of the threshold voltage and/or mobility information is performed at least once prior to the distribution of the organic light emitting display.

13. The organic light emitting display as claimed in claim 10, wherein a cathode voltage of the organic light emitting diode is increased when the threshold voltage and/or mobility information is sensed.

14. The organic light emitting display as claimed in claim 9, wherein the fourth transistor is turned on when the degradation information of the organic light emitting diode is sensed.

15. The organic light emitting display as claimed in claim 14, wherein the second voltage generated when the second electric current is supplied to the organic light emitting diode is converted into the second digital value.

16. The organic light emitting display as claimed in claim 15, wherein the degradation information of the organic light emitting diode is sensed at least once when power is supplied to the organic light emitting display.

17. The organic light emitting display as claimed in claim 15, wherein the degradation information of the organic light emitting diode is sensed before the data signal is supplied to the pixel.

18. The organic light emitting display as claimed in claim 9, wherein the fourth transistor maintains an off state while a data signal is supplied to the storage capacitor and the organic light emitting diode emits light.

19. The organic light emitting display as claimed in claim 5, wherein each of the pixels includes:

the organic light emitting diode;

a first transistor coupled with the scan line and the data line, the first transistor configured to be turned on when a scan signal is supplied to the scan line;

a storage capacitor configured to be charged with a voltage corresponding the data signal supplied to the data line;

a second transistor configured to supply an electric current corresponding to the voltage stored in the storage capacitor to the organic light emitting diode;

a third transistor between the second transistor and the organic light emitting diode, the third transistor configured to be turned off when an emission control signal is supplied to the emission control line; and

a fourth transistor between an anode electrode of the organic light emitting diode and the gate electrode of the drive transistor, the fourth transistor configured to be turned on a control signal is supplied to the control line.

20. The organic light emitting display as claimed in claim 19, wherein the first transistor, the third transistor, and the fourth transistor are turned-on when the threshold voltage and/or mobility information is sensed.

21. The organic light emitting display as claimed in claim 20, wherein a cathode voltage of the organic light emitting diode is increased when the threshold voltage is sensed.

22. The organic light emitting display as claimed in claim 20, wherein the first transistor and fourth transistor are turned on when the degradation information of the organic light emitting diode is sensed.

23. The organic light emitting display as claimed in claim 20, wherein the fourth transistor maintains an off state while a data signal is supplied to the storage capacitor and the organic light emitting diode emits light.

24. The organic light emitting display as claimed in claim 1, wherein each of the pixels includes:

the organic light emitting diode;

a first NMOS transistor coupled with the scan line and the data line, the first NMOS transistor configured to be turned on when a scan signal is supplied to the scan line;

a storage capacitor configured to be charged with a voltage corresponding the data signal supplied to the data line;

a second NMOS transistor configured to control an electric current through the organic light emitting diode, the current corresponding to a voltage stored in the storage capacitor;

a third NMOS transistor located between the second transistor and the organic light emitting diode, the third transistor configured to be turned off when an emission control signal is supplied to the emission control line; and

a fourth NMOS transistor located between an anode electrode of the organic light emitting diode and the data line, the fourth transistor configured to be turned on when a control signal is supplied to the control line.

25. The organic light emitting display as claimed in claim 7, wherein the data driver includes:

a shift register unit configured to sequentially generate a sampling signal;

a sampling latch unit configured to sequentially store the second data according to the sampling signal;

a holding latch unit configured to temporarily store the second data stored in the sampling latch;

a signal generator configured to generate data signals based on the second data stored in the holding latch unit; and

a buffer unit configured to transfer the data signals to the data line when the first switching element is turned on.

26. A method of driving an organic light emitting display, the method comprising:

generating a first voltage while sinking a first electric current through a drive transistor in a selected one of a plurality of pixels;

converting the first voltage into a first digital value;

storing the first digital value in a memory;

generating a second voltage while supplying a second electric current to an organic light emitting diode in the selected pixel;

converting the second voltage into a second digital value;

storing the second digital value in the memory; and

generating second data based on first data received from another circuit, the first digital value and the second digital value, wherein the second data has more bits than the first data value.

27. The method as claimed in claim 26, wherein the second data is generated by adjusting a value of the first data in order to compensate for at least one of a variation in threshold voltage of the drive transistor, a variation in the mobility of the drive transistor, and a degradation of the organic light emitting diode.

28. The method as claimed in claim 26, further comprising:

generating a data signal using the second data; and

supplying the data signal to the pixel to generate light based on the data signal.

29. The method as claimed in claim 26, wherein generating and converting the first voltage are performed at least once prior to selling the display.

30. The method as claimed in claim 26, wherein generating and converting the second voltage are performed at least once when power is supplied to the organic light emitting display.

31. The method as claimed in claim 26, wherein generating and converting the second voltage are performed before a data signal is supplied to the pixel.