DISPLAY DEVICE AND METHOD OF DRIVING THE SAME

• US 20100141644A1
• Filed: 04/16/2009
• Published: 06/10/2010
• Est. Priority Date: 12/05/2008
• Status: Active Grant

• Current Assignee: Samsung Display Company Limited (Samsung Electronics Co. Ltd.)
• Original Assignee: Samsung Display Company Limited (Samsung Electronics Co. Ltd.)
• Inventors: Lee, Baek-Woon, Woo, Doo-Hyung, Park, Kyong-Tae, Park, Seong-Il, Eom, Ji-Hye
• Granted Patent: US 8,537,077 B2
• Time in Patent Office: Days
• US Class Current: 345/214
• 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 2320/0223 Compensation for problems related to R-C delay and attenuation in electrodes of matrix panels, e.g. in gate electrodes or on-substrate video signal electrodes
• CPC Class Codes: G09G 2320/0261 in the context of movement of objects on the screen or movement of the observer relative to the screen
• CPC Class Codes: G09G 2320/043 Preventing or counteracting the effects of ageing
• CPC Class Codes: G09G 3/2014 by modulation of the duration of a single pulse during which the logic level remains constant
• CPC Class Codes: G09G 3/3208 organic, e.g. using organic light-emitting diodes [OLED]
• 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

A display device and a method of driving the same in which moving image blurring is prevented and a contrast ratio is enhanced by providing a light-emitting element, switching transistors, and a driving transistor with driving signals that include specific voltages at predetermined times, so that the light-emitting element does not emit light for an entire frame and the light output is not influenced by a threshold voltage of the driving transistor.

Claims

1. A display device comprising:

a light-emitting element;

a first capacitor that is connected between first and second contact points;

a driving transistor that has an output terminal, an input terminal that is connected to a first voltage, and a control terminal that is connected to the second contact point;

a first switching transistor that is controlled by a first scanning signal and that is connected between a data voltage and the first contact point;

a second switching transistor that is controlled by the first scanning signal and that is connected between a second voltage and the first contact point;

a third switching transistor that is controlled by the first scanning signal and that is connected between the second contact point and the output terminal of the driving transistor; and

a fourth switching transistor that is controlled by a second scanning signal and that is connected between the light-emitting element and the output terminal of the driving transistor.

2. The display device of claim 1, wherein the first scanning signal comprises a high voltage and a low voltage, and the second scanning signal comprises the high voltage, the low voltage, and an intermediate voltage that has a value between the high voltage and the low voltage.

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

a first scanning driver that generates the first scanning signal; and

a second scanning driver that generates the second scanning signal.

4. The display device of claim 3, wherein the second scanning driver comprises:

a multiplexer that selects and outputs one of the high voltage and the intermediate voltage according to a first input signal; and

an inverter that outputs one of an output signal of the multiplexer and the low voltage as the second scanning signal according to a second input signal.

5. The display device of claim 4, wherein the first input signal is the same as the first scanning signal.

6. The display device of claim 2, wherein the fourth switching transistor is turned on and the light-emitting element does not emit light when the second control signal has a value of the intermediate voltage.

7. The display device of claim 1, further comprising a scanning driver generating scanning signals, wherein at first to fifth periods of the scanning signals that are sequentially connected,

for the first period, the first, third, and fourth switching transistors are turned off and the second switching transistor is turned on;

for the second period, the first, third, and fourth switching transistors are turned on and the second switching transistor is turned off;

for the third period, the first and third switching transistors are turned on and the second and fourth switching transistors are turned off;

for the fourth period, the first, third, and fourth switching transistors are turned off and the second switching transistor is turned on; and

for the fifth period, the first and third switching transistors are tamed off and the second and fourth switching transistors are turned on.

8. The display device of claim 7, wherein the light-emitting element discontinues light emission for the first, second, third, and fourth periods and emits light for the fifth period.

9. The display device of claim 8, wherein the sum of the first to fifth periods is one frame.

10. The display device of claim 9, wherein the fifth period is a half frame.

11. The display device of claim 1, wherein the first switching transistor, the third switching transistor, and the fourth switching transistor are each an n-channel electric field effect transistor, and the second switching transistor and the driving transistor are each a p-channel electric field effect transistor.

12. The display device of claim 1, further comprising a fifth switching transistor that is connected between the second voltage and the second contact point.

13. The display device of claim 12, wherein the first switching transistor, the third switching transistor, and the fifth switching transistor are each an n-channel electric field effect transistor, and the second switching transistor, the fourth switching transistor, and the driving transistor are each a p-channel electric field effect transistor.

14. The display device of claim 1, further comprising a fifth switching transistor that is connected between a third voltage and the second contact point.

15. The display device of claim 14, wherein the third voltage is a pull-down voltage.

16. The display device of claim 15, wherein the first switching transistor, the third switching transistor, and the fifth switching transistor are each an n-channel electric field effect transistor, and the second switching transistor, the fourth switching transistor, and the driving transistor are each a p-channel electric field effect transistor.

17. A method of driving a display device including a light-emitting element, a capacitor that is connected between first and second contact points, and a driving transistor that has an input terminal, an output terminal and a control terminal that is connected to the second contact point, the method comprising:

disconnecting a connection between the output terminal of the driving transistor and the light-emitting element;

connecting a data voltage to the first contact point, connecting the second contact point to the output terminal of the driving transistor, and connecting the output terminal of the driving transistor to the light-emitting element;

disconnecting a connection between the output terminal of the driving transistor and the light-emitting element, in a state where the data voltage is connected to the first contact point and the second contact point is connected to the output terminal of the driving transistor; and

disconnecting a connection between the first contact point and the data voltage, connecting a sustain voltage to the first contact point and connecting the light-emitting element to the output terminal of the driving transistor.

18. The method of claim 17, wherein at the connecting of a data voltage to the first contact point, the connecting of the second contact point to the output terminal of the driving transistor, and the connecting of the output terminal of the driving transistor to the light-emitting element, the light-emitting element does not emit light so as to emit light.

19. The method of claim 18, wherein the disconnecting of a connection between the first contact point and the data voltage, the connecting of the sustain voltage to the first contact point, and the connecting of the light-emitting element to the output terminal of the driving transistor are performed for a half frame.

20. A display device comprising:

a light-emitting element;

a first capacitor that is connected between first and second contact points;

a driving transistor that has an output terminal, an input terminal that is connected to a first voltage, and a control terminal that is connected to a second contact point;

a first switching transistor that is controlled by a first scanning signal and that is connected between a data voltage and the first contact point;

a second switching transistor that is controlled by the first scanning signal and that is connected between a second voltage and the first contact point;

a third switching transistor that is controlled by a second scanning signal and that is connected between the second contact point and the output terminal of the driving transistor;

a fourth switching transistor that is controlled by a third scanning signal and that is connected between the light-emitting element and the output terminal of the driving transistor; and

a fifth switching transistor that is controlled by a fourth scanning signal and that is connected between the second voltage and the second contact point.

21. The display device of claim 20, wherein the first, second, third, and fourth scanning signals consist of a high voltage and a low voltage, and periods in which each of the second and fourth scanning signals is a high voltage do not overlap.

22. The display device of claim 20, wherein high voltages of each of the second and fourth scanning signals are sustained for more than half a horizontal period.

23. The display device of claim 20, wherein the high voltage of the first scanning signal is sustained for two horizontal periods.

24. The display device of claim 23, wherein a period in which the first scanning signal is a high voltage overlaps with each of periods in which the second and fourth scanning signals are a high voltage.

25. The display device of claim 24, wherein the high voltage of the fourth scanning signal is sustained for two horizontal periods.

26. The display device of claim 20, wherein a period in which the third scanning signal is a high voltage is longer than a period in which the first, second, and fourth scanning signals are a high voltage.

27. The display device of claim 20, wherein the second voltage has a lower value than the first voltage.

28. A method of driving a display device including a light-emitting element a capacitor that is connected between first and second contact points, and a driving transistor that has an input terminal, an output terminal, and a control terminal that is connected to the second contact point, the method comprising:

disconnecting a connection between the output terminal of the driving transistor and the light-emitting element;

connecting a sustain voltage to the first and second contact points;

disconnecting a sustain voltage that is connected to the first and second contact points, connecting a data voltage to the first contact point, and connecting the second contact point to the output terminal of the driving transistor;

disconnecting a connection between the first contact point and the data voltage, disconnecting a connection between the second contact point and the output terminal of the driving transistor, and reconnecting the first contact point and the sustain voltage; and

connecting the light-emitting element to the output terminal of the driving transistor so as to emit light.

29. The method of claim 28, wherein the connecting of the data voltage to the first contact point and the connecting of the second contact point to the output terminal of the driving transistor comprise connecting the second contact point to the output terminal of the driving transistor when a predetermined time period has elapsed after the data voltage is connected to the first contact point.

30. The method of claim 28, wherein the connecting of a sustain voltage to the first and second contact points is performed for more than half a horizontal period.

31. The method of claim 30, wherein the connecting of the second contact point to the output terminal of the driving transistor is performed for more than half a horizontal period.

32. The method of claim 31, wherein the connecting of a data voltage to the first contact point is performed for two horizontal periods.

33. The method of claim 32, wherein the connecting of a sustain voltage to the first and second contact points is performed for two horizontal periods.

34. The method of claim 31, wherein the sustain voltage is lower than the driving voltage.

35. A method of driving a display device including a light-emitting element, a capacitor that is connected between first and second contact points, and a driving transistor that has an input terminal an output terminal, and a control terminal that is connected to the second contact point, the method comprising:

disconnecting a connection between the output terminal of the driving transistor and the light-emitting element;

connecting a pull-down voltage to the second contact point;

disconnecting the pull-down voltage that is connected to the second contact point, connecting a data voltage to the first contact point, and connecting the second contact point to the output terminal of the driving transistor;

disconnecting a connection between the first contact point and the data voltage, disconnecting a connection between the second contact point and the output terminal of the driving transistor, and connecting the first contact point and the sustain voltage; and

connecting the light-emitting element to the output terminal of the driving transistor so as to emit light.

36. The method of claim 35, wherein the connecting of the data voltage to the first contact point and the connecting of the second contact point to the output terminal of the driving transistor comprise connecting the second contact point to the output terminal of the driving transistor when a predetermined time period has elapsed after the data voltage is connected to the first contact point.

37. The method of claim 35, wherein the connecting of the pull-down voltage to the second contact point is performed for more than half a horizontal period.

38. The method of claim 35, wherein the connecting of the second contact point to the output terminal of the driving transistor is performed for more than half a horizontal period.

39. The method of claim 35, wherein the sustain voltage and the pull-down voltage are lower than the driving voltage.