Digital gamma circuit and source driver including the same
Disclosed are a digital gamma circuit capable of reducing a chip area and adjusting white color coordinates, and a source driver including the same. The digital gamma circuit may include a digital gamma algorithm for setting a gamma curve for each R, G, or B. Through the digital gamma algorithm, values of X-axis points of the gamma curve may be set, values of Y-axis points of the gamma curve corresponding to the values of the X-axis points may be set, and a value of at least one Y-axis point indicative of white among the values of the Y-axis points may be adjusted by adding an offset value thereto.
1. A digital gamma circuit comprising:
a digital gamma algorithm for setting a gamma curve for each R, G, or B,
wherein through the digital gamma algorithm, values of X-axis points of the gamma curve are set, values of Y-axis points of the gamma curve corresponding to the values of the X-axis points are set, and a value of at least one Y-axis point of the gamma curve indicative of white among the values of the Y-axis points is adjusted by adding an offset value thereto,
wherein the digital gamma algorithm receives a gray signal, selects values of two X-axis points adjacent to the gray signal and values of two Y-axis points corresponding to the values of the two X-axis points, and calculates a luminance value by using the selected values of the two X-axis points and the selected values of the two Y-axis points.
2. The digital gamma circuit of claim 1 , wherein the values of the X-axis points are set at intervals of a square of 2.
3. The digital gamma circuit of claim 1 , wherein the digital gamma algorithm adjusts, as another offset value, the values of two or more Y-axis points of the gamma curve indicative of white among the values of the Y-axis points.
4. The digital gamma circuit of claim 1 , wherein, when one of the Y-axis points is set to a white point, the digital gamma algorithm adjusts values of Y-axis points after the white point to a same offset value.
5. The digital gamma circuit of claim 1 , wherein the offset values are differently set with respect to each of various color standards.
6. The digital gamma circuit of claim 5 , wherein when receiving a command signal for adjusting white color coordinates, the digital gamma algorithm adjusts the value of the at least one Y-axis point corresponding to a white, based on an offset value set for a color standard corresponding to the command signal.
7. The digital gamma circuit of claim 1 , wherein the digital gamma algorithm converts the 12-bit gray signal into 10-bit data.
8. The digital gamma circuit of claim 1 , wherein:
the values of the Y-axis points are set as several sets depending on target brightness of a panel, and
when receiving brightness information from an application, the digital gamma algorithm selects a set corresponding to the brightness information or calculates values of Y-axis points between the sets through linear interpolation.
9. The digital gamma circuit of claim 1 , wherein:
the digital gamma circuit comprises an X point generation unit, a Y point set linear interpolation unit, a Y point offset unit, an X-Y point selection unit, a linear interpolation unit and a dithering unit for the digital gamma algorithm,
the X point generation unit receives the values of the X-axis points and generates the values of the X-axis points of the gamma curve at intervals of a square of 2,
the Y point set linear interpolation unit receives brightness information and values of first Y-axis points of a plurality of sets and calculates values of second Y-axis points through linear interpolation for values of first Y-axis points between sets adjacent to the brightness information,
the Y point offset unit adjusts a value of the at least one second Y-axis point corresponding to the white, based on an offset value set for a color standard corresponding to in response to an external command signal,
the X-Y point selection unit receives an external first gray signal and selects values of two X-axis points adjacent to the first gray signal and values of two second Y-axis points corresponding to the values of the two X-axis points, wherein the values of the two X-axis points are selected among the values of the X-axis points provided by the X point generation unit, and the values of the two second Y-axis points are selected among the values of the Y-axis points provided by the Y point offset unit,
the linear interpolation unit receives the first gray signal and outputs a second gray signal having a luminance value calculated using the values of the two X-axis points and the values of the two second Y-axis points selected by the X-Y point selection unit, and
the dithering unit converts the second gray signal having a first bit number into data having a second bit number and indicative of the luminance value through dithering and outputs the data.
10. A source driver comprising:
a digital gamma circuit configured to set a gamma curve for each R, G, or B and convert an inputted gray signal into data indicative of a luminance value by using the gamma curve;
a gamma voltage generator configured to generate and provide gamma voltages; and
a gamma decoder configured to receive the gamma voltages and the data and select and output a gamma voltage corresponding to the data,
wherein the digital gamma circuit sets values of X-axis points of the gamma curve, sets values of Y-axis points of the gamma curve corresponding to the values of the X-axis points, and adjusts a value of at least one Y-axis point of the gamma curve indicative of white among the values of the Y-axis points by adding an offset value thereto,
wherein the digital gamma circuit receives a gray signal, selects values of two X-axis points adjacent to the gray signal and values of two Y-axis points corresponding to the values of the two X-axis points, and calculates a luminance value by using the selected values of the two X-axis points and the selected values of the two Y-axis points.
11. The source driver of claim 10 , wherein the digital gamma circuit sets the values of the X-axis points at intervals of a square of 2.
12. The source driver of claim 10 , wherein the digital gamma circuit adjusts, as another offset value, the values of two or more Y-axis points indicative of white.
13. The source driver of claim 10 , wherein, when one of the Y-axis points is set to a white point, the digital gamma circuit adjusts values of Y-axis points after the white point to a same offset value.
14. The source driver of claim 10 , wherein the offset values are differently set with respect to each of various color standards.
15. The source driver of claim 14 , wherein when receiving a command signal for adjusting white color coordinates, the digital gamma circuit adjusts the value of the at least one Y-axis point corresponding to the white, based on an offset value set for a color standard corresponding to the command signal.
16. The source driver of claim 10 , wherein the digital gamma circuit converts the 12-bit gray signal into 10-bit data.
17. The source driver of claim 10 , wherein:
the values of the Y-axis points are set as several sets depending on target brightness of a panel, and
when receiving brightness information from an application, the digital gamma circuit selects a set corresponding to the brightness information or calculates values of Y-axis points between the sets through linear interpolation.
18. The source driver of claim 10 , wherein:
the digital gamma circuit comprises an X point generation unit, a Y point set linear interpolation unit, a Y point offset unit, an X-Y point selection unit, a linear interpolation unit and a dithering unit,
the X point generation unit receives the values of the X-axis points and generates the values of the X-axis points of the gamma curve at intervals of a square of 2,
the Y point set linear interpolation unit receives brightness information and values of first Y-axis points of a plurality of sets and calculates values of second Y-axis points through linear interpolation for values of first Y-axis points between sets adjacent to the brightness information,
the Y point offset unit adjusts a value of at least one second Y-axis point corresponding to the white, based on an offset value set for a color standard in response to an external command signal,
the X-Y point selection unit receives an external first gray signal and selects values of two X-axis points adjacent to the first gray signal and values of two second Y-axis points corresponding to the values of the two X-axis points, wherein the values of the two X-axis points are selected among the values of the X-axis points provided by the X point generation unit, and the values of the two second Y-axis points are selected among the values of the Y-axis points provided by the Y point offset unit,
the linear interpolation unit receives the first gray signal and outputs a second gray signal having a luminance value calculated using the values of the two X-axis points and the values of the two second Y-axis points selected by the X-Y point selection unit, and
the dithering unit converts the second gray signal having a first bit number into data having a second bit number and indicative of the luminance value through dithering and outputs the data.