Display device and driving method thereof

1. A display device comprising:

a scale factor providing unit which calculates a first scale factor based on input grayscales received during a first frame period;

a grayscale converter which calculates first output grayscales by applying the first scale factor to first input grayscales received during a second frame period, wherein the second frame period is a frame period immediately next to the first frame period;

pixels connected to power branch lines commonly connected to a power base line, wherein at least a part of the pixels is configured to display an image based on the first output grayscales;

a power source which supplies a power voltage to the power base line; and

a current limiting unit which provides a first current limiting signal to the power source and provides a second current limiting signal to the scale factor providing unit when a current of the power base line exceeds a reference value.

2. The display device of claim 1 , wherein the power source reduces a magnitude of the power voltage when receiving the first current limiting signal.

3. The display device of claim 1 , wherein the scale factor providing unit provides a second scale factor smaller than the first scale factor when receiving the second current limiting signal.

4. The display device of claim 3 , wherein the grayscale converter calculates second output grayscales by applying the second scale factor to second input grayscales received during the second frame period, and

wherein another part of the pixels is configured to display an image based on the second output grayscales.

5. The display device of claim 4 , wherein the pixels start to display the image based on the first output grayscales and the second output grayscales during the second frame period and end displaying the image during a third frame period after the second frame period.

6. The display device of claim 1 , wherein the scale factor providing unit calculates the first scale factor after receiving all of the input grayscales of the first frame period and before starting to receive the first input grayscales of the second frame period.

7. The display device of claim 6 , wherein the scale factor providing unit calculates the first scale factor smaller, as a load value of the input grayscales of the first frame period increases.

8. The display device of claim 7 , wherein the load value is a sum of gamma conversion values of the input grayscales.

9. The display device of claim 1 , wherein the power source includes feedback resistors, and

wherein the current limiting unit provides the first current limiting signal to a node between the feedback resistors.

10. The display device of claim 9 , wherein the current limiting unit includes:

a comparator having input terminals connected to the power base line;

an integrator having an input terminal connected to an output terminal of the comparator; and

a buffer having an input terminal connected to the integrator and an output terminal connected to the node between the feedback resistors.

11. The display device of claim 10 , wherein the current limiting unit further includes a trigger connected between the output terminal of the comparator and the input terminal of the integrator.

12. The display device of claim 11 , wherein the current limiting unit further includes:

a switch connected between an output terminal of the integrator and the input terminal of the buffer; and

a reset switch having a first electrode connected to the output terminal of the integrator.

13. A driving method of a display device including a power source which supplies a power voltage to a power base line, and pixels connected to power branch lines commonly connected to the power base line, comprising:

calculating a first scale factor based on input grayscales received during a first frame period;

calculating first output grayscales by applying the first scale factor to first input grayscales received during a second frame period, wherein the second frame period is a frame period immediately next to the first frame period;

displaying an image by at least a part of the pixels based on the first output grayscales; and

providing a first current limiting signal to the power source and calculating a second scale factor smaller than the first scale factor when a current of the power base line exceeds a reference value.

14. The driving method of claim 13 , further comprising:

reducing a magnitude of the power voltage by the power source when receiving the first current limiting signal.

15. The driving method of claim 13 , further comprising:

calculating second output grayscales by applying the second scale factor to second input grayscales received during the second frame period; and

displaying an image by another part of the pixels based on the second output grayscales.

16. The driving method of claim 15 , wherein the pixels start to display the image based on the first output grayscales and the second output grayscales during the second frame period and end displaying the image during a third frame period after the second frame period.

17. The driving method of claim 13 , wherein in the calculating of the first scale factor, the first scale factor is calculated after receiving all of the input grayscales of the first frame period and before starting to receive the first input grayscales of the second frame period.

18. The driving method of claim 17 , wherein in the calculating of the first scale factor, the first scale factor is calculated smaller, as a load value of the input grayscales in the first frame period increases.

19. The driving method of claim 18 , wherein the load value is a sum of gamma conversion values of the input grayscales.

20. The driving method of claim 13 , wherein the power source includes feedback resistors, and

wherein the power source receives the first current limiting signal through a node between the feedback resistors.