Organic light emitting diode display and method of driving the same

• US 20090213046A1
• Filed: 10/22/2008
• Published: 08/27/2009
• Est. Priority Date: 02/22/2008
• Status: Active Grant

• Current Assignee: LG Display Co., Ltd.
• Original Assignee: LG Display Co., Ltd.
• Inventors: Nam, Woo Jin
• Granted Patent: US 8,305,303 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 2300/0842 forming a memory circuit, e.g. a dynamic memory with one capacitor
• CPC Class Codes: G09G 2310/0251 Precharge or discharge of pixel before applying new pixel 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 2320/0295 by monitoring each display pixel
• 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

An organic light emitting diode display includes a data line, a gate line that crosses the data line to receive a scan pulse, a high potential driving voltage source to generate a high potential driving voltage, a low potential driving voltage source to generate a low potential driving voltage, a light emitting element to emit light due to a current flowing between the high potential driving voltage source and the low potential driving voltage source, a drive element connected between the high potential driving voltage source and the light emitting element to control a current flowing in the light emitting element depending on a voltage between a gate electrode and a source electrode of the drive element, and a driving current stabilization circuit to apply a first voltage to the gate electrode of the drive element to turn on the drive element and to sink a reference current through the drive element to set a source voltage of the drive element at a sensing voltage and to modify the voltage between the gate and source electrodes of the drive element to scale a current to be applied to the light emitting element from the reference current.

Claims

1. An organic light emitting diode display, comprising:

a data line;

a gate line that crosses the data line to receive a scan pulse;

a high potential driving voltage source to generate a high potential driving voltage;

a low potential driving voltage source to generate a low potential driving voltage;

a light emitting element to emit light due to a current flowing between the high potential driving voltage source and the low potential driving voltage source;

a drive element connected between the high potential driving voltage source and the light emitting element to control a current flowing in the light emitting element depending on a voltage between a gate electrode and a source electrode of the drive element; and

a driving current stabilization circuit to apply a first voltage to the gate electrode of the drive element to turn on the drive element and to sink a reference current through the drive element to set a source voltage of the drive element at a sensing voltage and to modify the voltage between the gate and source electrodes of the drive element to scale a current to be applied to the light emitting element from the reference current.

2. The organic light emitting diode display of claim 1, wherein the first voltage is a reference voltage.

3. The organic light emitting diode display of claim 1, wherein the first voltage is the high potential driving voltage.

4. The organic light emitting diode display of claim 1, wherein the drive current stabilization circuit sets the source voltage of the drive element at a sensing voltage during a first period and then modifies the voltage between the gate and source electrodes of the drive element during a second period, such that the light emitting element is turned off during the first and second periods and turned on during a third period following the second period.

5. The organic light emitting diode display of claim 4, wherein the first period is a first half period of the scan pulse maintained in a high logic voltage state, the second period is a second half period of the scan pulse maintained in a high logic voltage state, and the third period is a period during which the scan pulse is maintained in a low logic voltage state.

6. The organic light emitting diode display of claim 1, wherein the drive current stabilization circuit changes a potential of the gate electrode of the drive element to reduce or increase the voltage between the gate and source electrodes of the drive element to scale the current to be applied to the light emitting element.

7. The organic light emitting diode display of claim 6, wherein a potential of the source electrode of the drive element is fixed at the sensing voltage and the potential of the gate electrode of the drive element falls from the first voltage.

8. The organic light emitting diode display of claim 7 further comprising a sensing line positioned parallel to the data line.

9. The organic light emitting diode display of claim 8, wherein the driving current stabilization circuit includes

a cell drive circuit connected to the drive element and the light emitting element at a crossing of the data line, the sensing line, and the gate line, and

data drive circuit connected to the cell drive circuit through the data line and the sensing line.

10. The organic light emitting diode display of claim 9, wherein the cell drive circuit includes

a storage capacitor including a first electrode connected to the gate electrode of the drive element through a first node and a second electrode connected to the source electrode of the drive element through a second node,

a first switch thin film transistor (TFT) to switch on and off a current path between the data line and the first node in response to the scan pulse, and

a second switch TFT to switch on and off a current path between the sensing line and the second node in response to the scan pulse.

11. The organic light emitting diode display of claim 9, wherein the data drive circuit includes

a first data driver to supply the first voltage to the data line during a first period and to supply a data voltage that is reduced from the first voltage by a data change amount to the data line during a second period, and

a second data driver to sink the reference current through the sensing line to set the sensing voltage during the first period and to keep the set sensing voltage constant during the second period.

12. The organic light emitting diode display of claim 11, wherein the first data driver includes

a data generation unit to alternately generate the first voltage and the data voltage, to extract the data change amount stored in memory based on a deviation amount of a mobility of the drive element depending on driving time, and to subtract or add the data change amount from the first voltage to generate the data voltage, and

a first buffer to stabilize the first voltage and the data voltage generated by the data generation unit to output the stabilized first voltage and the stabilized data voltage to the data line.

13. The organic light emitting diode display of claim 11, wherein the second data driver includes

a reference current source to sink the reference current,

a second buffer to keep the sensing voltage constant,

a first switch to form a current path between the reference current source and an input terminal of the second buffer during the first period and to cut off the current path between the reference current source and the input terminal of the second buffer during the second period, and

a second switch to form a current path between the sensing line and the reference current source during the first period and to form a current path between the sensing line and an output terminal of the second buffer during the second period.

14. The organic light emitting diode display of claim 1, wherein the drive current stabilization circuit changes a potential of the source electrode of the drive element to reduce or increase the voltage between the gate and source electrodes of the drive element to scale the current to be applied to the light emitting element from the reference current.

15. The organic light emitting diode display of claim 14, wherein a potential of the gate electrode of the drive element is fixed at the first voltage and the potential of the source electrode of the drive element rises from the sensing voltage.

16. The organic light emitting diode display of claim 15 further comprising a reference voltage supply line used to supply the first voltage.

17. The organic light emitting diode display 6f claim 16, wherein the driving current stabilization circuit includes

a cell drive circuit connected to the drive element and the light emitting element at a crossing of the data line and the gate line,

a data drive circuit connected to the cell drive circuit through the data line, and

a reference voltage source connected to the reference voltage supply line to supply the first voltage.

18. The organic light emitting diode display of claim 17, wherein the cell drive circuit includes

a storage capacitor including a first electrode connected to the gate electrode of the drive element through a first node and a second electrode connected to the source electrode of the drive element through a second node,

a first switch TFT to switch on and off a current path between the reference voltage supply line and the first node in response to the scan pulse, and

a second switch TFT to switch on and off a current path between the data line and the second node in response to the scan pulse.

19. The organic light emitting diode display of claim 18, wherein the data drive circuit sinks the reference current through the data line during a first period to set the sensing voltage and then supplies the data voltage that increases from the sensing voltage by a data change amount to the data line during the second period while keeping the sensing voltage set by the reference current constant.

20. The organic light emitting diode display of claim 19, wherein the data drive circuit includes

a reference current source to sink the reference current,

a data generation unit to generate the data voltage obtained by adding a data change amount to the sensing voltage, to extract the data change amount stored in memory based on a deviation amount of a mobility of the drive element depending on driving time, and to add the data change amount to the first voltage to generate the data voltage,

a buffer to stabilize the data voltage generated by the data generation unit while keeping the sensing voltage constant to output the stabilized data voltage to the data line,

a first switch to form a current path between the reference current source and an input terminal of the buffer during the first period and to cut off the current path between the reference current source and the input terminal of the buffer during the second period, and

a second switch to form a current path between the data line and the reference current source during the first period and to form a current path between the data line and an output terminal of the buffer during the second period.

21. The organic light emitting diode display of claim 15, wherein the driving current stabilization circuit includes

a cell drive circuit connected to the drive element and the light emitting element at a crossing of the data line and the gate line, and

a data drive circuit connected to the cell drive circuit through the data line.

22. The organic light emitting diode display of claim 21, wherein the cell drive circuit includes

a storage capacitor including a first electrode connected to the gate electrode of the drive element through a first node and a second electrode connected to the source electrode of the drive element through a second node,

a first switch TFT to switch on and off a current path between the high potential driving voltage source and the first node in response to the scan pulse, and

a second switch TFT to switch on and off a current path between the data line and the second node in response to the scan pulse.

23. The organic light emitting diode display of claim 8, wherein the gate line includes first and second gate lines forming a pair,

the drive element including first and second driving elements connected in parallel between the high potential driving voltage source and the light emitting element and are alternately driven, and

the driving current stabilization circuit includes

a first cell driver connected to the first driving element and the light emitting element at a crossing of the data line, the sensing line, and the first gate line,

a second cell driver connected to the second driving element and the light emitting element at a crossing of the data line, the sensing line, and the second gate line, and

a data drive circuit connected to the first and second cell drivers through the data line and the sensing line.

24. The organic light emitting diode display of claim 23, wherein

the first cell driver includes

a first storage capacitor including a first electrode connected to a gate electrode of the first drive element through a first node and a second electrode connected to a source electrode of the first drive element through a second node,

a first switch TFT to switch on and off a current path between the data line and the first node in response to a first scan pulse received from the first gate line, and

a second switch TFT to switch on and off a current path between the sensing line and the second node in response to the first scan pulse, and wherein the second cell driver includes

a second storage capacitor including a first electrode connected to a gate electrode of the second drive element through a third node and a second electrode connected to a source electrode of the second drive element through a fourth node,

a third switch TFT to switch on and off a current path between the data line and the third node in response to a second scan pulse received from the second gate line, and

a fourth switch TFT to switch on and off a current path between the sensing line and the fourth node in response to the second scan pulse,

wherein the first and second scan pulses are alternately generated.

25. The organic light emitting diode display of claim 16, wherein the gate line includes first and second gate lines forming a pair,

the drive element including first and second driving elements connected in parallel between the high potential driving voltage source and the light emitting element and are alternately driven, and

the driving current stabilization circuit includes

a first cell driver connected to the first driving element and the light emitting element at a crossing of the data line and the first gate line,

a second cell driver connected to the second driving element and the light emitting element at a crossing of the data line and the second gate line,

a data drive circuit connected to the first and second cell drivers through the data line, and

a reference voltage source connected to the reference voltage supply line to supply the first voltage.

26. The organic light emitting diode display of claim 25, wherein

the first cell driver includes

a first storage capacitor including a first electrode connected to a gate electrode of the first drive element through a first node and a second electrode connected to a source electrode of the first drive element through a second node,

a first switch TFT to switch on and off a current path between the reference voltage supply line and the first node in response to a first scan pulse received from the first gate line, and

a second switch TFT to switch on and off a current path between the data line and the second node in response to the first scan pulse,

wherein the second cell driver includes

a second storage capacitor including a first electrode connected to a gate electrode of the second drive element through a third node and a second electrode connected to a source electrode of the second drive element through a fourth node,

a third switch TFT to switch on and off a current path between the reference voltage supply line and the third node in response to a second scan pulse received from the second gate line, and

a fourth switch TFT to switch on and off a current path between the data line and the fourth node in response to the second scan pulse,

wherein the first and second scan pulses are alternately generated.

27. The organic light emitting diode display of claim 15, wherein the gate line includes first and second gate lines forming a pair,

the drive element includes first and second driving elements connected in parallel between the high potential driving voltage source and the light emitting element and are alternately, and

the driving current stabilization circuit includes

a first cell driver connected to the first driving element and the light emitting element at a crossing of the data line and the first gate line,

a second cell driver connected to the second driving element and the light emitting element at a crossing of the data line and the second gate line, and

a data drive circuit connected to the first and second cell drivers through the data line.

28. The organic light emitting diode display of claim 27, wherein

the first cell driver includes

a first storage capacitor including a first electrode connected to a gate electrode of the first drive element through a first node and a second electrode connected to a source electrode of the first drive element through a second node,

a first switch TFT to switch on and off a current path between the high potential driving voltage source and the first node in response to a first scan pulse received from the first gate line, and

a second switch TFT to switch on and off a current path between the data line and the second node in response to the first scan pulse,

wherein the second cell driver includes

a second storage capacitor including a first electrode connected to a gate electrode of the second drive element through a third node and a second electrode connected to a source electrode of the second drive element through a fourth node,

a third switch TFT to switch on and off a current path between the high potential driving voltage source and the third node in response to a second scan pulse received from the second gate line, and

a fourth switch TFT to switch on and off a current path between the data line and the fourth node in response to the second scan pulse,

wherein the first and second scan pulses are alternately generated.

29. A method of driving a organic light emitting diode display including a data line, a gate line that crosses the data line to receive a scan pulse, a high potential driving voltage source to generate a high potential driving voltage, a low potential driving voltage source to generate a low potential driving voltage, a light emitting element to emit light due to a current flowing between the high potential driving voltage source and the low potential driving voltage source, and a drive element connected between the high potential driving voltage source and the light emitting element to control a current flowing in the light emitting element depending on a voltage between a gate electrode and a source electrode of the drive element, the method comprising:

applying a first voltage to the gate electrode of the drive element to turn on the drive element;

sinking a reference current through the drive element to set a source voltage of the drive element at a sensing voltage; and

modifying the voltage between the gate and source electrodes to scale a current to be applied to the light emitting element from the reference current.

30. The method of claim 29, wherein the first voltage is a reference voltage.

31. The method of claim 29, wherein the first voltage is the high potential driving voltage.

32. The method of claim 29, wherein the source voltage of the drive element is set at the sensing voltage during a first period, the voltage between the gate and source electrodes of the drive element is modified during a second period, and the light emitting element is driven using the scaled current during a third period, wherein the light emitting element is turned off during the first and second periods and turned on during the third period following the second period.

33. The method of claim 29, wherein the step of modifying includes changing a potential of the gate electrode of the drive element to reduce or increase the voltage between the gate and source electrodes of the drive element to scale the current to be applied to the light emitting element.

34. The method of claim 33, wherein a potential of the source electrode of the drive element is fixed at the sensing voltage and the potential of the gate electrode of the drive element falls from the first voltage.

35. The method of claim 29, wherein the step of modifying includes changing a potential of the source electrode of the drive element to reduce or increase the voltage between the gate and source electrodes of the drive element to scale the current to be applied to the light emitting element.

36. The method of claim 35, wherein a potential of the gate electrode of the drive element is fixed at the first voltage and the potential of the source electrode of the drive element rises from the sensing voltage.

37. A drive stabilization circuit for an organic light emitting diode display comprising:

a high potential driving voltage source to generate a high potential driving voltage to be applied to a drive element for driving a light emitting element;

a low potential driving voltage source to generate a low potential driving voltage; and

a data drive circuit to apply a first voltage to the gate electrode of the drive element to turn on the drive element and to sink a reference current through the drive element to set a source voltage of the drive element at a sensing voltage and to modify the voltage between the gate and source electrodes of the drive element to scale a current to be applied to a light emitting element from the reference current.

38. The drive stabilization circuit of claim 37, wherein the first voltage is a reference voltage.

39. The drive stabilization circuit of claim 37, wherein the first voltage is the high potential driving voltage.