DISPLAY DEVICE AND DRIVING METHOD THEREOF

• US 20070164938A1
• Filed: 01/16/2007
• Published: 07/19/2007
• Est. Priority Date: 01/16/2006
• Status: Active Grant

• Current Assignee: Samsung Display Company Limited (Samsung Electronics Co. Ltd.)
• Original Assignee: Samsung Electronics Co. Ltd.
• Inventors: PARK, Cheol-Woo, CHAI, Chong-Chul, SHIN, Kyoung-Ju
• Granted Patent: US 8,564,509 B2
• Time in Patent Office: Days
• US Class Current: 345/76
• CPC Class Codes: G09G 2300/0819 used for counteracting undesired variations, e.g. feedback or autozeroing
• CPC Class Codes: G09G 2300/0852 being a dynamic memory with more than one capacitor
• CPC Class Codes: G09G 2300/0866 by means of changes in the pixel supply voltage
• CPC Class Codes: G09G 2310/0254 Control of polarity reversal in general, other than for liquid crystal displays
• 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 2320/0214 with crosstalk due to leakage current of pixel switch in active matrix panels
• CPC Class Codes: G09G 2320/043 Preventing or counteracting the effects of ageing
• CPC Class Codes: G09G 2330/028 Generation of voltages supplied to electrode drivers in a matrix display other than LCD
• 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

A display device includes a light emitting element, a first driving transistor coupled to the light emitting element and supplied with a first driving voltage, and a second driving transistor coupled to the light emitting element and the first driving transistor and supplied with a second driving voltage having a magnitude different from the first driving voltage at least for a time. A method of driving the display device is also provided.

Claims

1. A display device comprising:

a light emitting element;

a first driving transistor coupled to the light emitting element and supplied with a first driving voltage; and

a second driving transistor coupled to the light emitting element and the first driving transistor and supplied with a second driving voltage having a magnitude different from the first driving voltage at least for a time.

2. The display device of claim 1, wherein the first driving voltage and the second driving voltage are periodical signals having time-varying magnitudes.

3. The display device of claim 2, wherein the first driving voltage and the second driving voltage have a reference value during a first time period and have different values during a second time period.

4. The display device of claim 3, wherein the first driving voltage has a first value during the second time period different from the reference value and different from a second value of the second driving voltage during the second time period.

5. The display device of claim 3, wherein the first driving voltage and the second driving voltage have opposite values with respect to the reference value during the second time period.

6. The display device of claim 5, wherein the first time period and the second time period alternate, the first driving voltage maintains a uniform value during the second time period, and the second driving voltage maintains a uniform value during the second time period.

7. The display device of claim 5, wherein the first time period and the second time period alternate, and a value of each of the first driving voltage and the second driving voltage varies in an opposite manner with respect to the reference value during the second time period.

8. The display device of claim 7, wherein the first driving voltage includes a lower value and a higher value than the reference value during the second time period, and the second driving voltage includes a higher value and a lower value than the reference value during the second time period.

9. The display device of claim 3, wherein the light emitting element stops light emission during the second time period.

10. The display device of claim 9, wherein the light emitting element is supplied with a common voltage, and the common voltage has different values between the first time period and the second time period.

11. The display device of claim 10, wherein the common voltage is increased during the second time period.

12. The display device of claim 3, wherein the first time period includes a third time period and a fourth time period, and the light emitting element emits light in the third time period and stops light emission in the fourth time period.

13. The display device of claim 12, wherein the first and second driving transistors are supplied with a reverse bias voltage during the fourth time period to turn off the first and second driving transistors during the fourth time period.

14. The display device of claim 3, wherein the first driving transistor has a control terminal, an input terminal supplied with the first driving voltage, and an output terminal coupled to the light emitting element,

wherein the second driving transistor has a control terminal, an input terminal supplied with the second driving voltage, and an output terminal coupled to the light emitting element, and

wherein the control terminals of the first and the second driving transistors are supplied with a data voltage during the first time period and are floating during the second time period.

15. The display device of claim 14, wherein the first and second driving transistors are supplied with a reverse bias voltage to turn off the first and second driving transistors for a portion of the first time period.

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

a first switching transistor coupled to the first driving transistor and applying a data voltage to a control terminal of the first driving transistor according to a scanning signal; and

a second switching transistor coupled to the second driving transistor and applying a data voltage to a control terminal of the second driving transistor according to the scanning signal.

17. The display device of claim 16, wherein a control terminal of the first switching transistor and a control terminal of the second switching transistor are connected to a same scanning line.

18. The display device of claim 3, further comprising a switching transistor coupled to the first and the second driving transistors and applying a data voltage to control terminals of the first and the second driving transistors according to a scanning signal.

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

a first capacitor connected between a control terminal and an input terminal of the first driving transistor; and

a second capacitor connected between a control terminal and an input terminal of the second driving transistor.

20. The display device of claim 2, wherein the light emitting element emits light when the first driving voltage and the second driving voltage have different values.

21. The display device of claim 1, further comprising a plurality of first driving transistors, a plurality of second driving transistors, and a plurality of pixels, wherein each pixel includes one of the first driving transistors and one of the second driving transistors.

22. The display device of claim 1, further comprising a voltage generator supplying the first driving voltage, the second driving voltage, and a common voltage to the first driving transistor, the second driving transistor, and the light emitting element, respectively.

23. A display device comprising:

a light emitting element; and

at least one driving transistor supplying a current to the light emitting element,

wherein a direction of a current flowing in the at least one driving transistor changes at least for a time.

24. The display device of claim 23, wherein the direction of the current flowing in the at least one driving transistor is opposite between a first time period and a second time period shorter than the first time period, and the light emitting element stops light emission in the second time period.

25. A display device comprising:

a light emitting element;

a first driving transistor supplying a current to the light emitting element; and

a second driving transistor supplying a current to the light emitting element,

wherein a current flowing in the first driving transistor points opposite a current flowing in the second driving transistor at least for a time.

26. The display device of claim 25, wherein the current flowing in the first driving transistor points in a same direction as the current flowing in the second driving transistor during a light emission display period of the light emitting element, and the current flowing in the first driving transistor points opposite the current flowing in the second driving transistor during a refresh period preventing degradation of the first and second driving transistors.

27. A method of driving a display device, the method comprising:

applying a data voltage to control terminals of the first and the second driving transistors having output terminals coupled to a light emitting element;

applying a first driving voltage to an input terminal of the first driving transistor;

applying a second driving voltage to an input terminal of the second driving transistor the second driving voltage; and

differentiating values of the first driving voltage and the second driving voltage.

28. The method of claim 27, wherein differentiating values of the first driving voltage and the second driving voltage includes providing opposite values with respect to a reference value during a refresh period to prevent degradation of the first and second driving transistors.

29. The method of claim 27, further comprising:

equalizing values of the first driving voltage and the second driving voltage,

wherein differentiating values of the first driving voltage and the second driving voltage and equalizing values of the first driving voltage and the second driving voltage are alternately performed.

30. The method of claim 29, wherein equalizing the first driving voltage and the second driving voltage comprises:

emitting the light emitting element, and

wherein differentiating the first driving voltage and the second driving voltage comprises;

stopping emission of the light emitting element.

31. The method of claim 30, wherein stopping emission of the light emitting element comprises:

changing a value of a common voltage applied to the light emitting element.

32. The method of claim 29, wherein the equalizing the first driving voltage and the second driving voltage comprises:

emitting the light emitting element; and

stopping emission of the light emitting element.

33. The method of claim 32, wherein stopping emission of the light emitting element comprises:

applying a negative bias voltage to the control terminals of the first and the second driving transistors.