Method of driving display panel and display apparatus using the same

1. A method of driving a display panel, the method comprising:

applying a first driving voltage to a gate electrode of a transistor provided in a pixel of the display panel to display an image;

counting an operating time of the display panel to measure a count value;

comparing the count value with a preset reference value;

outputting a comparison signal when the count value matches the preset reference value;

generating a second driving voltage based on the comparison signal;

applying the second driving voltage to the gate electrode of a transistor in the pixel of the display panel to display the image,

wherein the second driving voltage is applied to the gate electrode of the transistor after a predetermined operating time period and a shift in a threshold voltage of the transistor is compensated by the second driving voltage.

2. The method of claim 1 , wherein the second driving voltage is reduced by a preset reference voltage when the count value matches the preset reference value.

3. The method of claim 2 , wherein the second driving voltage comprise a turn-on voltage to turn on the transistor and a turn-off voltage to turn off the transistor, and the turn-on voltage and the turn-off voltage are reduced by the preset reference voltage when the count value matches the reference value.

4. The method of claim 3 , wherein the counting an operating time of the display panel to measure the count value comprises,

counting a signal that notifies the operating time of the liquid crystal display based on the reference clock.

5. The method of claim 4 , wherein an amount of the reduced voltage of the turn-on voltage and the turn-off voltage is same.

6. The method of claim 3 , wherein an amount of the reduced voltage of the turn-on voltage and the turn-off voltage is same.

7. The method of claim 1 , wherein the transistor comprises an oxide semiconductor.

8. The method of claim 7 , wherein the oxide semiconductor comprises Indium Gallium Zinc Oxide (In—Ga—Zn—O) based materials.

9. The method of claim 1 , wherein the measuring an operating time of the display panel to measure the count value comprises,

counting a signal that notifies the operating time of the liquid crystal display based on the reference clock.

10. The method of claim 1 , further comprising updating the reference value when the count value matches the reference value.

11. A display apparatus comprising:

a display panel having a plurality of pixels each provided with at least one transistor to display an image in response to a gate voltage and a data voltage;

a gate driver providing a gate-voltage to a gate electrode of the transistor;

a data driver providing the data voltage to a source electrode of the transistor; and

a compensation circuit configured to compensate for a threshold voltage shift of the transistor by changing the gate voltage of the transistor to display the image,

wherein the compensation circuit comprises,

a counter counting an operating time of the display panel, and

a comparator comparing a count value provided from the counter with a preset reference value and outputting a comparison signal when the count value matches the reference value.

12. The display apparatus of claim 11 , further comprising a DC/DC converter of generating the gate voltage based on the comparison signal.

13. The display apparatus of claim 12 , wherein the DC/DC converter reduces the gate voltage by a preset reference voltage when the count value matches the reference value.

14. The display apparatus of claim 11 , wherein the transistor comprises an oxide semiconductor.

15. The display apparatus of claim 14 , wherein the oxide semiconductor comprises Indium Gallium Zinc Oxide (In—Ga—Zn—O) based materials.