Liquid crystal display device and driving method thereof
A liquid crystal display, comprising a plurality of pixels, a data driver and a sense signal generator, where each of the pixels comprises a switch coupled to a data line and a liquid crystal capacitor. The liquid crystal capacitor is coupled to the switch and its capacitance is varied in response to external touch. The gate driver provides a gate signal to the pixel and the data driver provides data voltage to a data line. The sense signal generator generates a sensing signal by sensing a capacitance of the liquid crystal capacitor.
1 . A liquid crystal display, comprising:
a data line;
a gate line;
a data driver having an output terminal for applying a data voltage to the data line during a display period;
a gate driver for applying a gate voltage to the gate line;
a pixel comprising a liquid crystal capacitor coupled to a switching transistor, wherein the liquid crystal capacitor is charged to a voltage via the switching transistor which is coupled to the gate line and the data line;
a sense signal generator having an input and being adapted to sense a capacitance value of the liquid crystal capacitor and generate a sense signal; and
a first switch operable to selectively couple the sense signal generator to the liquid crystal capacitor.
2 . The liquid crystal display according to claim 1 wherein the sense signal generator comprises a switched capacitor amplifier.
3 . The liquid crystal display according to the claim 2 , wherein the switched capacitor amplifier comprises:
an input node;
an amplifier having a first input terminal, a second input terminal and a an output terminal;
a first capacitor coupled between the first input terminal and the input node;
a second capacitor coupled between the first input terminal and the second node which is an output terminal of the amplifier;
a second switch for selectively connecting the first node to the second input terminal; and
a third switch for selectively connecting the first input terminal to the output terminal.
4 . The liquid crystal display according to the claim 3 , wherein the first switch couples the liquid crystal capacitor to the input node during a sensing period.
5 . The liquid crystal display according to the claim 4 , wherein the first switch is operable to connect the data line to the switching transistor during a time other than during the sensing period.
6 . The liquid crystal display according to the claim 2 , wherein the switched capacitor amplifier amplifies a capacitance variation of the liquid crystal capacitor.
7 . The liquid crystal display according to the claim 1 , wherein the displaying period may comprise a sensing period.
8 . A liquid crystal display, comprising:
a plurality of data lines;
a plurality of gate lines;
a display panel having an upper substrate and a lower substrate for displaying image;
a plurality of pixels arranged in a matrix in a pixel area, in which each pixel group has a plurality of pixels;
a data driver having output terminals for applying data voltages to associated data lines;
a gate driver for applying gate voltages to associated gate lines;
a sense signal generator coupled to the pixel groups and positioned on the lower substrate;
a plurality of first switches operable to selectively couple the sense signal generator to the pixels; and
a comparing circuit coupled to an output of the sense signal generator.
9 . The liquid crystal display according to the claim 8 , wherein the sense signal generator comprises a plurality of sensing circuits.
10 . The liquid crystal display according to the claim 9 , wherein each sense circuit comprises:
an input node;
an amplifier having a first input terminal, a second input terminal and a an output terminal;
a first capacitor coupled between the first input terminal and the input node;
a second capacitor coupled between the first input terminal and the second node which is an output terminal of the amplifier;
a second switch for selectively connecting the first node to the second input terminal; and
a third switch for selectively connecting the first input terminal to the output terminal.
11 . The liquid crystal display according to the claim 10 , wherein the plurality of first switches is commonly coupled to the first node during a sensing period.
12 . The liquid crystal display according to the claim 10 , wherein the plurality of first switches is commonly coupled to the output terminals of the data driver except during a sensing period.
13 . A driving method of liquid crystal display, comprising:
connecting an output terminal of a data driver to a data line by using a first switch;
providing a data voltage from the data driver to a pixel which includes a liquid crystal capacitor;
selectively connecting a sense circuit to the pixels;
sensing a capacitance of the liquid crystal capacitor;
amplifying the data voltage by using the capacitance;
generating a sensing signal in response to the amplified data voltage; and
comparing the sensing signal with the data voltage in a comparing circuit.
14 . A driving method of liquid crystal display according to the claim 13 , wherein sensing the capacitance is performed during a sensing period.
15 . A driving method of liquid crystal display according to the claim 13 , further comprising storing the data voltage to a storage capacitor.
16 . A driving method of liquid crystal display according to the claim 13 , further comprising disconnecting the sense circuit from the pixels after sensing the capacitance.