Display device and a method for driving the same

1. A display device, comprising:

a display panel including a plurality of pixels configured to be driven in a normal mode or an always on display mode;

an illuminance sensor configured to detect illuminance of ambient light;

a direct current (DC)-DC converter configured to supply a power supply voltage having a first voltage level to the pixels through a power supply line when the illuminance is greater than a predetermined reference value in the always on display mode; and

a display panel driver configured to supply a power supply voltage having a second voltage level to the pixels through the power supply line when the illuminance is less than or equal to the predetermined reference value in the always on display mode,

wherein the display panel driver generates an enable signal based on the illuminance of ambient light to enable the DC-DC converter in the always on display mode, and

wherein the DC-DC converter is enabled to supply the power supply voltage having the first voltage level in response to the enable signal provided from the display panel driver.

2. The display device of claim 1 , wherein the DC-DC converter is disabled when the illuminance is less than or equal to the predetermined reference value in the always on display mode.

3. The display device of claim 2 , wherein the display panel driver is electrically disconnected from the power supply line when the illuminance is greater than the predetermined reference value in the always on display mode.

4. The display device of claim 1 , wherein a maximum luminance of the display panel when the DC-DC converter supplies the power supply voltage is higher than a maximum luminance of the display panel when the display panel driver supplies the power supply voltage.

5. The display device of claim 1 , wherein the second voltage level is less than the first voltage level.

6. The display device of claim 1 , wherein the DC-DC converter supplies the power supply voltage to the power supply line in the normal mode, and

wherein the display panel driver is electrically disconnected from the power supply line in the normal mode.

7. The display device of claim 1 , wherein the display panel driver comprises:

a scan driver configured to supply a scan signal to the pixels through a plurality of scan lines;

a data driver configured to supply a data signal to the pixels through a plurality of data lines; and

a controller configured to control the scan driver and the data driver.

8. The display device of claim 7 , wherein the power supply voltage supplied from the display panel driver is generated from a gate high voltage of the scan signal.

9. The display device of claim 7 , wherein the power supply voltage supplied from the display panel driver is generated from a DC voltage provided to the data driver.

10. The display device of claim 1 , wherein the display panel driver changes a magnitude of the power supply voltage according to an illuminance change when the illuminance is less than or equal to the predetermined reference value in the always on display mode.

11. The display device of claim 10 , wherein the power supply voltage is reduced as the illuminance is reduced, when the illuminance is less than or equal to the predetermined reference value in the always on display mode.

12. The display device of claim 10 , wherein a maximum luminance is reduced as the illuminance is reduced, in the always on display mode.

13. The display device of claim 1 , wherein the DC-DC converter controls a magnitude of the power supply voltage according to the illuminance.

14. The display device of claim 13 , wherein the power supply voltage output from the DC-DC converter is reduced as the illuminance is reduced, in the normal mode.

15. A method for driving a display device, comprising:

selecting one of a normal mode and an always on display mode;

detecting an illuminance of ambient light in the always on display mode; and

supplying a power supply voltage to a plurality of pixels by using one of a direct current (DC)-DC converter and a display panel driver in response to the selected mode and the detected illuminance, wherein the DC-DC converter is enabled to supply the power supply voltage in the always on display mode by the display panel driver.

16. The method of claim 15 , wherein when supplying the power supply voltage to the pixels, the DC-DC converter supplies the power supply voltage having a first voltage level to the pixels through a power supply line when the illuminance is greater than a predetermined reference value in the always on display mode.

17. The method of claim 16 , wherein when supplying the power supply voltage to the pixels, the display panel driver supplies the power supply voltage having a second voltage level to the pixels through the power supply line when the illuminance is less than or equal to the predetermined reference value in the always on display mode.

18. The method of claim 17 , wherein a maximum luminance of the display panel when the DC-DC converter supplies the power supply voltage is higher than a maximum luminance of the display panel when the display panel driver supplies the power supply voltage.

19. The method of claim 18 , wherein the second voltage level is less than the first voltage level, and the power supply voltage is transmitted to a driving transistor of each of the pixels.

20. The method of claim 15 , wherein when supplying the power supply voltage to the pixels, the DC-DC converter supplies the power supply voltage to a power supply line in the normal mode and the display panel driver is electrically disconnected from the power supply line in the normal mode.