Screen saver controller, display device including the same, and method of driving the display device

1. A screen saver controller comprising:

a load calculator configured to generate load data of an image represented by input image data;

a maximum gray level calculator configured to generate maximum gray level data of the image represented by the input image data; and

a screen saver data generator configured to determine a gain of a screen saver mode based on the load data and the maximum gray level data when the screen saver mode is operated and to generate screen saver data based on the input image data and the gain,

wherein:

the load calculator is configured to calculate a sum of all gray levels of N th frame data, where N is a positive integer, and to calculate a load of the N th frame data based on the sum of all the gray levels of the N th frame data;

the maximum gray level calculator is configured to divide a display panel into a plurality of blocks, to calculate gray levels of the blocks, respectively, and to compare the gray levels of the blocks with each other to calculate a maximum gray level of the N th frame data; and

the maximum gray level calculator is configured to compare a number of pixels having a highest gray level with a pre-stored reference number of pixels and to determine the highest gray level as the maximum gray level when the number of the pixels having the highest gray level is greater than or equal to the reference number of the pixels.

2. The screen saver controller of claim 1 , further comprising a still image detector configured to detect a still image from the image represented by the input image data and to count a number of frames of the still image to generate still image data.

3. The screen saver controller of claim 2 , wherein the screen saver mode is operated when the number of the frames of the still image is greater than a reference number of frames.

4. The screen saver controller of claim 1 , wherein the screen saver data generator is configured to determine a gain reduction start time by using a gain reduction start time lookup table in which a relation between the load data and the gain reduction start time and a relation between the maximum gray level and the gain reduction start time are defined.

5. The screen saver controller of claim 4 , wherein the screen saver data generator is configured to generate the screen saver data in which the gain reduction start time is set earlier as the load becomes greater and to generate the screen saver data in which the gain reduction start time is set earlier as the maximum gray level becomes larger.

6. The screen saver controller of claim 1 , wherein the screen saver data generator is configured to determine a gain reduction slope by using a gain reduction slope lookup table in which a relation between the load data and the gain reduction slope and a relation between the maximum gray level and the gain reduction slope are defined.

7. The screen saver controller of claim 6 , wherein the screen saver data generator is configured to generate the screen saver data in which the gain reduction slope of the screen saver mode is set to be larger as the load becomes greater and to generate the screen saver data in which the gain reduction slope is set to be larger as the maximum gray level becomes larger.

8. The screen saver controller of claim 1 , wherein the screen saver data generator is configured to determine a minimum luminance gain by using a minimum luminance gain lookup table in which a relation between the load data and the minimum luminance gain and a relation between the maximum gray level and the minimum luminance gain are defined.

9. The screen saver controller of claim 8 , wherein the screen saver data generator is configured to generate the screen saver data in which the minimum luminance gain is set to be smaller as the load becomes greater and to generate the screen saver data in which the minimum luminance gain is set to be smaller as the maximum gray level becomes larger.

10. A display device comprising:

a display panel including a plurality of pixels;

a data driver configured to provide a data signal to the display panel;

a screen saver controller configured to generate screen saver data for adjusting a luminance of the display panel based on input image data; and

a controller configured to control the data driver, to provide the input image data to the screen saver controller, and to receive the screen saver data from the screen saver controller,

wherein:

the screen saver controller includes:

a load calculator configured to generate load data of an image represented by the input image data;

maximum gray level calculator configured to generate maximum gray level data of the image represented by the input image data; and

a screen saver data generator configured to determine a gain of a screen saver mode based on the load data and the maximum gray level data when the screen saver mode is operated and to generate the screen saver data based on the input image data and the gain;

the load calculator is configured to calculate a sum of all gray levels of N th frame data, where N is a positive integer, and to calculate a load of the N th frame data based on the sum of all the gray levels of the N th frame data;

the maximum gray level calculator is configured to divide the display panel into a plurality of blocks, to calculate gray levels of the blocks, respectively, and to compare the gray levels of the blocks with each other to calculate a maximum gray level of the N th frame data; and

the maximum gray level calculator is configured to compare a number of pixels having a highest gray level with a pre-stored reference number of pixels and to determine the highest gray level as the maximum gray level when the number of the pixels having the highest gray level is greater than or equal to the reference number of the pixels.

11. The display device of claim 10 , wherein the screen saver controller further includes:

a still image detector configured to detect a still image from the image represented by the input image data and to count a number of frames of the still image to generate still image data.

12. The display device of claim 11 , wherein the screen saver mode is operated when the number of the frames of the still image is greater than a reference number of frames.

13. A method of driving a display device, the method comprising:

generating load data based on input image data;

generating maximum gray level data based on the input image data;

generating still image data based on the input image data;

determining whether to operate a screen saver mode based on the still image data;

determining a gain reduction start time of the screen saver mode based on the load data and the maximum gray level data;

determining a gain reduction slope of the screen saver mode based on the load data and the maximum gray level data;

determining a minimum luminance gain of the screen saver mode based on the load data and the maximum gray level data;

generating screen saver data based on the gain reduction start time, the gain reduction slope, and the minimum luminance gain; and

adjusting a luminance of a display panel based on the screen saver data,

wherein:

generating the load data includes:

calculating a sum of all gray levels of N th frame data, where N is a positive integer; and

calculating a load of the N th frame data based on the sum of all the gray levels of the N th frame data; and

generating the maximum gray level data includes:

dividing the display panel into a plurality of blocks;

calculating gray levels of the blocks, respectively;

comparing the gray levels of the blocks with each other to calculate a maximum gray level of the N th frame data;

comparing a number of pixels having a highest gray level with a pre-stored reference number of pixels; and

determining the highest gray level as the maximum gray level when the number of the pixels having the highest gray level is greater than or equal to the reference number of the pixels.