Data driver and control method thereof
The present disclosure relates to a data driver and a control method thereof, wherein a position of pixels to which pixel data is written and the amount of change in grayscale of the pixel data are judged, and a bias current to an output buffer from which a data voltage corresponding to the pixel data is output is varied according to the position of pixels and the amount of change in grayscale of the pixel data.
1 . A data driver comprising:
an output buffer configured to output a data voltage corresponding to pixel data; and
a bias current coordinator configured to coordinate a bias current applied to the output buffer according to a final bias current value obtained by multiplying a default current value by a position-based bias current value and a grayscale difference-based bias current value, wherein the default current value is applied to all pixels at the same value, the position-based bias current value is varied with a distance between the data driver and a position of pixels, and the grayscale difference-based bias current value is varied with a grayscale difference of the pixel data, and wherein the position of the pixels is based on counting timing signals or counting grayscale difference data input.
2 . The data driver of claim 1 , further comprising:
a data comparator configured to compare the grayscale difference of the pixel data that is varied with time,
wherein the bias current coordinator is configured to vary the bias current based on the grayscale difference data input from the data comparator.
3 . The data driver of claim 2 , wherein the bias current becomes smaller when the pixel data has a small change in a grayscale value than when the pixel data has a large change in the grayscale value.
4 . The data driver of claim 2 , wherein the bias current coordinator is configured to gradually or stepwise increase the bias current as time elapses during one frame period.
5 . The data driver of claim 1 , further comprising:
a logic controller configured to set the bias current in a unit of a frame period in response to option data received from outside the data driver.
6 . A data driver comprising:
a first latch array configured to latch pixel data;
a second latch array configured to latch pixel data output from the first latch array;
a digital-to-analog converter configured to convert the pixel data output from the second latch array to a data voltage;
an output buffer configured to output the data voltage from the digital-to-analog converter;
a data comparator connected to the first latch array and the second latch array and configured to compare first pixel data stored in the first latch array and second pixel data stored in the second latch array; and
a bias current coordinator connected between the data comparator and the output buffer and configured to vary a bias current applied to the output buffer according to a final bias current value obtained by multiplying a default current value by a position-based bias current value and a grayscale difference-based bias current value, wherein the default current value is applied to all pixels at the same value, the position-based bias current value is varied with a distance between the data driver and a position of pixels, and the grayscale difference-based bias current value is varied with a grayscale difference of the pixel data, and wherein the position of the pixels is based on counting timing signals or counting grayscale difference data input.
7 . The data driver of claim 6 , wherein:
the first pixel data is the pixel data to be written to pixels of an (N+1)th pixel line (N is a natural number), and the second pixel data is the pixel data to be written to pixels of an (N)th pixel line, and
the data comparator is configured to compare two most significant bits of the first pixel data with two most significant bits of the second pixel data to output grayscale difference data indicating an amount of change in grayscale between the first pixel data and the second pixel data.
8 . The data driver of claim 7 , wherein the bias current coordinator is configured to vary the bias current in response to the grayscale difference data.
9 . The data driver of claim 7 , wherein the bias current coordinator is configured to vary the bias current based on the grayscale difference of the pixel data.
10 . The data driver of claim 6 , further comprising:
a logic controller; and
a shift register configured to output pixel data input from the logic controller to latches in the first latch array.
11 . The data driver of claim 10 , wherein the logic controller is configured to set the bias current in a unit of a frame period in response to option data received from outside the data driver.
12 . The data driver of claim 7 , wherein the bias current coordinator includes:
a decoder configured to receive the grayscale difference data to output current control data;
a reference current generator configured to generate a reference current; and
a current coordinator connected to the reference current generator to form a current mirror circuit.
13 . The data driver of claim 12 , wherein the reference current generator includes:
a constant current source disposed between a VDD node to which a driving voltage is applied and a gate node and configured to generate the reference current; and
a reference transistor including a first electrode connected to a GND node to which a ground voltage is applied, and a gate electrode and a second electrode connected to the gate node, and
wherein the current coordinator includes:
a plurality of transistors configured to output the bias current having different current values derived from the reference current.
14 . The data driver of claim 13 , wherein the current coordinator includes:
a plurality of first transistors having gate electrodes connected to the gate node; and
a plurality of second transistors connected between the plurality of first transistors and the output buffer, and configured to coordinate the bias current in response to output data from the decoder.
15 . The data driver of claim 12 , wherein a value of output data from the decoder is determined according to the grayscale difference between the first pixel data and the second pixel data, and wherein the bias current is varied by selecting current values according to the output data.
16 . The data driver of claim 15 , wherein:
as the bias current becomes lower, a slew rate of data voltage output through the output buffer becomes lower, and
as the bias current becomes higher, the slew rate of the data voltage output through the output buffer becomes higher.
17 . A control method of a data driver comprising:
judging a position-based bias current value configured to be varied with a distance between a data driver and a position of pixels to which pixel data is written;
judging a grayscale difference-based bias current value configured to be varied with a grayscale difference of the pixel data;
determining a final bias current value by multiplying a default current value by the position-based bias current value and the grayscale difference-based bias current value; and
varying a bias current to an output buffer from which a data voltage corresponding to the pixel data is output according to the final bias current value, wherein the position of the pixels is based on counting timing signals or counting grayscale difference data input.
18 . The control method of claim 17 , further comprising:
determining the position-based bias current value according to the position of pixels, regardless of a grayscale difference of the pixel data; and
determining the grayscale difference-based bias current value based on the grayscale difference of the pixel data indicative of an amount of change in grayscale of the pixel data.
19 . The control method of claim 18 , further comprising:
receiving control data including option information, wherein the default current value is determined according to the option information.