Display device and driving method thereof

1. A display device, comprising:

a controller to process an input image signal and an input control signal and to output a digital image signal and a control signal;

a gray voltage generator to provide a plurality of first gray reference voltages when a selection signal is in a first state and to provide a single second gray reference voltage corresponding to an insertion gray when the selection signal is in a second state different from the first state; and

a data driver to generate gray voltages based on the plurality of first gray reference voltages or the single second gray reference voltage provided from the gray voltage generator, to receive the digital image signal, to select a gray voltage corresponding to the digital image signal as a data voltage when the gray voltage generator provides the plurality of first gray reference voltages, and to generate an insertion data voltage corresponding to the insertion gray when the gray voltage generator provides the single second gray reference voltage,

wherein the selection signal is periodically changed between the first state and the second state during one frame for the digital image signal.

2. The display device of claim 1 , wherein:

the gray voltage generator comprises a first register to store first gray reference data, which is information for the plurality of first gray reference voltages, and a second register to store a second gray reference data, which is information for the single second gray reference voltage; and

the first register or the second register is selected according to the selection signal.

3. The display device of claim 2 , further comprising:

a data line to transmit the data voltage; and

a pixel to receive the data voltage through the data line,

wherein the pixel comprises a first subpixel and a second subpixel representing different luminances from each other for the same input image signal, and

wherein the first register comprises a third register to store information for a gray reference voltage corresponding to a gamma curve for the first subpixel and a fourth register to store information of a gray reference voltage corresponding to a gamma curve for the second subpixel.

4. The display device of claim 3 , wherein the insertion gray comprises a black-tone of gray or a middle-tone of gray.

5. The display device of claim 1 , further comprising:

a transform circuit coupled to the gray voltage generator and being controlled according to a transform signal included in the control signal,

wherein the gray voltage generator comprises a register to store first gray reference data which is information for the plurality of first gray reference voltages, and

wherein the transform circuit is activated or deactivated according to a level of the transform signal, thereby changing the gray reference voltage generated by the gray voltage generator.

6. The display device of claim 5 , further comprising:

a resistor column coupled between a driving voltage and a ground voltage, the resistor column to provide a reference voltage to the gray voltage generator to generate the gray reference voltage,

wherein the transform circuit is activated according to the transform signal to change a voltage of a node between a plurality of resistors included in the resistor column, thereby changing the reference voltage.

7. The display device of claim 6 , wherein the transform circuit is configured to change the driving voltage, the ground voltage, or both of the driving voltage and the ground voltage provided to the gray voltage generator.

8. The display device of claim 5 , wherein the transform circuit is configured to change a driving voltage, a ground voltage, or both of the driving voltage and the ground voltage provided to the gray voltage generator.

9. The display device of claim 5 , wherein the insertion gray comprises a black-tone gray or a middle-tone gray.

10. The display device of claim 1 , wherein the insertion gray comprises a black-tone gray or a middle-tone gray.

11. A method for driving a display device comprising a controller to process an input image signal and an input control signal to control output of a digital image signal, a gray voltage generator to generate gray reference voltages, and a data driver to generate gray voltages based on the gray reference voltages, the method comprising:

generating a plurality of first gray reference voltages corresponding to the input image signal when a selection signal is in a first state and generating a single second gray reference voltage corresponding to an insertion gray when the selection signal is in a second state different from the first state;

sequentially receiving the plurality of first gray reference voltages and the single second gray reference voltage;

generating gray voltages based on the plurality of first gray reference voltages or the single second gray reference voltage; and

selecting a gray voltage corresponding to the digital image signal as a data voltage when the plurality of first gray reference voltages are input, and generating an insertion data voltage corresponding to the insertion gray when the single second gray reference voltage is input,

wherein the selection signal is periodically changed between the first state and the second state during one frame for the digital image signal.

12. The method of claim 11 , wherein the gray voltage generator comprises:

a first register to store first gray reference data which is information for the plurality of first gray reference voltages; and

a second register to store second gray reference data which is information for the single second gray reference voltage,

the method further comprising:

selecting one of the first register and the second register according to the selection signal.

13. The method of claim 12 , further comprising:

transmitting the data voltage and a pixel to receive the data voltage through the data line,

the pixel comprising a first subpixel and a second subpixel representing different luminances to the input image signal, and

storing information with respect to a gray reference voltage corresponding to a gamma curve with respect to the first subpixel and storing information of a gray reference voltage corresponding to a gamma curve with respect to the second subpixel.

14. The method of claim 11 , further comprising:

controlling a transform circuit according to a transform signal comprising the control signal, and

wherein the gray voltage generator comprises a register to store first gray reference data which is information for the plurality of first gray reference voltages,

the method further comprising:

activating or deactivating the transform circuit according to a level of the transform signal, thereby changing the gray reference voltage generated by the gray voltage generator.

15. The method of claim 14 , further comprising:

providing a reference voltage to the gray voltage generator, and

activating the transform circuit according to the transform signal to change a voltage of a node generated between a plurality of resistors comprised in the resistor column, thereby changing the reference voltage.

16. The method of claim 15 , further comprising:

changing the driving voltage, the ground voltage, or both of the driving voltage and the ground voltage provided to the gray voltage generator in the transform circuit.

17. The method of claim 14 , further comprising:

changing a driving voltage, a ground voltage, or both of the driving voltage and the ground voltage provided to the gray voltage generator in the transform circuit.

18. The method of claim 11 , wherein the insertion gray comprises a black-tone gray or a middle-tone gray.

19. The display device of claim 1 , wherein the insertion gray is determined based on display characteristics separate from those of the input image signal.

20. The method of claim 11 , wherein the insertion gray is determined based on display characteristics separate from those of the input image signal.