Display device and method of controlling an on-bias stress (OBS) period

1. A display device comprising:

a display panel including a plurality of subpixels, each of the subpixels including a light-emitting element;

a data driver configured to supply a data voltage and an on-bias stress (OBS) voltage to each of the subpixels;

a scan driver configured to output an emission signal for controlling a non-emission period and an emission period of the light-emitting element and an OBS signal for controlling an OBS period; and

a controller,

wherein the controller controls the data driver to supply the data voltage to each of the subpixels in the emission period to emit light and to supply the OBS voltage to each of the subpixels in the non-emission period during a first frame period,

the controller controls the data driver to supply the OBS voltage to each of the subpixels in the non-emission period and maintains the data voltage supplied in the first frame period in the emission period to emit light during a second frame period, and

the controller controls the scan driver to set an OBS period performed in the non-emission period of the second frame period to be twice or more longer than an OBS period performed nearest to the last emission period of the first frame period,

wherein a sum of the OBS period performed nearest to the last emission period of the first frame period and the OBS period performed in the non-emission period of the second frame period is constant, and

wherein, as a difference between a luminance in the first frame period and a luminance in the second frame period increases, a proportion of the OBS period performed nearest to the last emission period of the first frame period decreases, and the OBS period performed in the non-emission period of the second frame period increases.

2. The display device according to claim 1 , wherein the controller controls the scan driver to:

set the OBS period performed nearest to the last emission period of the first frame period to be less than about 30% of a total non-emission period of the first frame period; and

set the OBS period performed in the non-emission period of the second frame period to be equal to or greater than about 60% of a total non-emission period of the second frame period.

3. The display device according to claim 1 , wherein each of the subpixels comprises:

the light-emitting element;

a driving thin film transistor (TFT) configured to apply a driving current to the light-emitting element;

an emission control TFT configured to receive the emission signal to connect the light-emitting element and the driving TFT to each other; and

a switching TFT configured to receive the OBS signal to apply the OBS voltage to a drain of the driving TFT.

4. The display device according to claim 1 , wherein each of the subpixels comprises:

a driving thin film transistor (TFT) including a first electrode connected to a first node, a gate electrode connected to a second node, and a second electrode connected to a third node;

the light-emitting element including an anode connected to a fourth node and a cathode connected to a low-potential voltage;

a first emission control TFT and a second emission control TFT, the first emission control TFT including a gate electrode to which the emission signal is input to supply a high-potential voltage to the first node according to the emission signal, and the second emission control TFT connecting the second node and the fourth node to each other;

a first switching TFT turned on by a first scan signal to connect the second node and the third node to each other, thereby diode-connecting the driving TFT;

a second switching TFT turned on by a second scan signal to apply a data voltage signal to the first node; and

a third switching TFT turned on by a third scan signal to apply an initialization voltage at a low voltage level or an OBS voltage at a high voltage level to the third node.

5. The display device according to claim 4 , wherein the first switching TFT includes an n-type TFT having an oxide semiconductor active layer.

6. The display device according to claim 4 , further comprising a fourth switching TFT turned on by a third scan signal in a subsequent stage to apply a reset voltage to the fourth node.

7. A method of driving a display device including a display panel including a plurality of subpixels, each subpixel including a light-emitting element, the method comprising:

supplying a data voltage to each of the subpixels in an emission period to emit light and to supply an on-bias stress (OBS) voltage to each of the subpixels in a non-emission period during a first frame period; and

supplying an OBS voltage to each of the subpixels in a non-emission period and maintaining the data voltage supplied in the first frame period to emit light in an emission period during a second frame period,

wherein an OBS period performed in the non-emission period of the second frame period is set to be twice or more longer than an OBS period performed nearest to the last emission period of the first frame period,

wherein a sum of the OBS period performed nearest to the last emission period of the first frame period and the OBS period performed in the non-emission period of the second frame period is constant, and

wherein, as a difference between a luminance in the first frame period and a luminance in the second frame period increases, a proportion of the OBS period performed nearest to the last emission period of the first frame period decreases, and the OBS period performed in the non-emission period of the second frame period increases.

8. The method according to claim 7 , wherein:

the OBS period performed nearest to the last emission period of the first frame period is set to be less than about 30% of a total non-emission period of the first frame period, and

the OBS period performed in the non-emission period of the second frame period is set to be equal to or greater than about 60% of a total non-emission period of the second frame period.

9. A display device comprising:

a display panel including a plurality of subpixels, each of the subpixels including a light-emitting element;

a data driver configured to supply a data voltage and an on-bias stress (OBS) voltage to each of the subpixels;

a scan driver configured to output an emission signal for controlling a non-emission period and an emission period of the light-emitting element and an OBS signal for controlling an OBS period; and

a controller,

wherein the controller controls the data driver to supply the data voltage to each of the subpixels in the emission period to emit light and to supply the OBS voltage to each of the subpixels in the non-emission period during a first frame period,

the controller controls the data driver to supply the OBS voltage to each of the subpixels in the non-emission period and maintains the data voltage supplied in the first frame period in the emission period to emit light during a second frame period,

the controller controls the scan driver to set an OBS period performed nearest to the last emission period of the first frame period to be less than about 30% of a total non-emission period of the first frame period, and

the controller controls the scan driver to set an OBS period performed in the non-emission period of the second frame period to be equal to or greater than about 60% of a total non-emission period of the second frame period,

wherein a sum of the OBS period performed nearest to the last emission period of the first frame period and the OBS period performed in the non-emission period of the second frame period is constant, and

wherein, as a difference between a luminance in the first frame period and a luminance in the second frame period increases, a proportion of the OBS period performed nearest to the last emission period of the first frame period decreases, and the OBS period performed in the non-emission period of the second frame period increases.

10. The display device according to claim 9 , wherein the controller controls the scan driver to set the OBS period performed in the non-emission period of the second frame period to be twice or more longer than the OBS period performed nearest to the last emission period of the first frame period.