Organic light emitting display device and display panel thereof

1. An organic light emitting display device, comprising:

a display panel including a data line and first and second gate lines;

a gate driving circuit, the first and second gate lines electrically connected to the gate driving circuit; a pixel defined at an intersection of the data line and the first and second gate lines,

wherein the pixel includes a driving transistor and an organic light emitting diode, the driving transistor configured to supply current to the organic light emitting diode, and the driving transistor having a threshold voltage;

wherein a range of compensation for the threshold voltage of the driving transistor has at least one of an upper voltage limit and a lower voltage limit,

wherein the display device is configured to

sense the threshold voltage of the driving transistor; and,

apply a first voltage to a first node of the driving transistor and apply a second voltage to a second node of the driving transistor, when the threshold voltage of the driving transistor is outside of the range of compensation, and

regulate the first and second voltages so that the threshold voltage of the driving transistor is within the range of compensation,

wherein the first node electrically connects to a gate of the driving transistor, and the second node electrically connects to the organic light emitting diode,

wherein the display device is configured to regulate the first and second voltages so that the threshold voltage of the driving transistor is within the range of compensation when the display device is to be powered off; and the display device is configured to apply a ground voltage to all nodes of the driving transistor after regulating the first and second voltages.

2. The organic light emitting display device of claim 1 , wherein

when the threshold voltage of the driving transistor is above the upper voltage limit, the first voltage is lower than the second voltage.

3. The organic light emitting display device of claim 1 , wherein

when the threshold voltage of the driving transistor is below the lower voltage limit, the first voltage is greater than the second voltage.

4. The organic light emitting display device of claim 1 , further comprising:

a reference voltage line,

the first node of the pixel electrically connected to the data line through a first transistor, a gate of the first transistor electrically connected to the first gate line, and the gate driving circuit configured to control the first transistor through application of a scan signal to the first gate line; and

the second node of the pixel electrically connected to the reference voltage line through a second transistor, a gate of the second transistor electrically connected to the second gate line,

the gate driving circuit configured to control the second transistor through application of a sense signal to the second gate line.

5. The organic light emitting display device of claim 4 , further comprising:

a driving voltage line configured to supply a driving voltage;

a storage capacitor electrically connected between the first and second nodes; and

a third node electrically connected to the driving voltage line,

wherein the display device is configured to

apply the scan signal to the first transistor, a data voltage to the first node via the first transistor, the sense signal to the second transistor, and a reference voltage to the second node via the second transistor, a desired voltage thereby occurring between the first and second nodes,

subsequently, to remove application of the reference voltage to the second node, thereby floating the second node, and

after floating the second node, measure the voltage of the second node, and determine the threshold voltage of the driving transistor to be the data voltage subtracted by the measured voltage of the second node.

6. The organic light emitting display device of claim 5 , wherein the first node is electrically connected between the gate of the driving transistor and one of a source or a drain of the first transistor, the second node is electrically connected between an anode of the organic light emitting diode and one of a source or a drain of the driving transistor, and the third node is electrically connected between the other of the source or the drain of the driving transistor and the driving voltage line.

7. The organic light emitting display device of claim 1 , wherein the range of compensation for the threshold voltage of the driving transistor has both the upper voltage limit and the lower voltage limit.

8. The organic light emitting display device of claim 1 , the display device further comprising:

a plurality of the pixels;

the display device configured to further configured to

determine that a threshold voltage shift of one or more of the plurality of the pixels is greater than an upper limit of the range of compensation;

apply negative stress to the corresponding driving transistors of the one or more of the pixels whose threshold voltage shift is greater than the upper limit of the range of compensation;

determine that a threshold voltage shift of one or more others of the plurality of pixels is lower than the lower limit of the range of compensation; and

apply positive stress to the corresponding driving transistors of the one or more others of the pixels whose threshold voltage shift is lower than the lower limit of the range of compensation.

9. A method of compensating for a threshold voltage of a driving transistor, the driving transistor included in a specific pixel of a plurality of pixels of an organic light emitting display device, the method comprising:

determining that the threshold voltage is deviated from a predetermined range of compensation of the threshold voltage;

when the display device is to be powered off, performing recovery driving of the threshold voltage to be within the range of compensation; and

after performing the recovery driving, applying a ground voltage to all nodes of the driving transistor.

10. The method of claim 9 , further comprising:

determining that a threshold voltage shift of one or more of a plurality of the specific pixels is greater than an upper limit of the range of compensation;

applying negative stress to the corresponding driving transistors of the one or more of the specific pixels whose threshold voltage shift is greater than the upper limit of the range of compensation;

determining that a threshold voltage shift of one or more others of the plurality of specific pixels is lower than a lower limit of the range of compensation; and

applying positive stress to the corresponding driving transistors of the one or more others of the specific pixels whose threshold voltage shift is lower than the lower limit of the range of compensation.

11. The method of claim 10 , wherein the applying positive stress includes applying voltages to nodes of the corresponding driving transistors to enable the threshold voltages of the corresponding driving transistors to increase; and

wherein the applying negative stress includes applying voltages to nodes of the corresponding driving transistors to enable the threshold voltages of the corresponding driving transistors to decrease.

12. The method of claim 9 , wherein

the display device simultaneously performs the determining that the threshold voltage shift of the one or more of the specific pixels is greater than the upper limit of the range of compensation, and the determining that the threshold voltage shift of the one or more others of the specific pixels is lower than the lower limit of the range of compensation; and

the display device simultaneously performs the applying negative stress to the corresponding driving transistors of the one or more of the specific pixels whose threshold voltage shift is greater than the upper limit of the range of compensation, and the applying positive stress to the corresponding driving transistors of the one or more others of the specific pixels whose threshold voltage shift is lower than the lower limit of the range of compensation.

13. The method of claim 9 , wherein

the display device sequentially performs, in any sequence, (a) the determining that the threshold voltage shift of the one or more of the specific pixels is greater than the upper limit of the range of compensation, (b) the applying negative stress to the corresponding driving transistors of the one or more of the specific pixels whose threshold voltage shift is greater than the upper limit of the range of compensation, (c) the determining that the threshold voltage shift of the one or more others of the specific pixels is lower than the lower limit of the range of compensation, and (d) the applying positive stress to the corresponding driving transistors of the one or more others of the specific pixels whose threshold voltage shift is lower than the lower limit of the range of compensation.

14. The method of claim 13 , wherein (a) is performed before (b), (b) is performed before (c), and (c) is performed before (d).