Liquid crystal display device
The present invention relates to a liquid crystal display device with a source driver in which a significant signal delay is not generated, and which has a fast response speed. The present invention also provides a liquid crystal display device comprising a scan driver including a D/A converter for outputting analog signals corresponding to gradation data input, a triangular wave generator for outputting triangular wave signals, and a comparator for applying data voltage to each pixel which include OCB liquid crystal cells by comparing the analog signals with the triangular wave signals. The data voltage is a PWM pulse with a varied voltage width.
1. A liquid crystal display device comprising:
a liquid crystal display panel comprising a plurality of pixels which are located at a region where a plurality of scan lines and a plurality of data lines cross each other, each pixel comprising a common electrode, a pixel electrode and OCB liquid crystals;
a scan driver for applying scan signals for selecting the plurality of pixels through the plurality of scan lines;
a source driver for applying data voltages to the plurality of pixels through the plurality of data lines;
a backlight part for applying a light source to the liquid crystal display panel;
a backlight controller for applying a backlight voltage to the backlight part; and
a timing controller for applying control signals for controlling operation of the scan driver, the source driver and the backlight controller,
wherein the source driver comprises a D/A converter for outputting an analog signal corresponding to gradation data input, a triangular wave generator for outputting triangular wave signals, and a comparator for generating the data voltages to be applied to the plurality of pixels without using an amplifier by comparing the analog signal with the triangular wave signals.
2. The liquid crystal display device according to claim 1 , wherein the comparator outputs a driving voltage of the comparator if the triangular wave signals are greater than the analog signal.
3. The liquid crystal display device according to claim 2 , wherein the comparator outputs a reference voltage of the comparator if the triangular wave signals are less than the analog signal.
4. The liquid crystal display device according to claim 1 , wherein the data voltages have a width that is varied according to a level of the analog signal.
5. The liquid crystal display device according to claim 1 , wherein the data voltages have a width varied according to a level of the triangular wave signals.
6. The liquid crystal display device according to claim 1 , wherein the triangular wave generator comprises a function generator.
7. The liquid crystal display device according to claim 1 , wherein the triangular wave generator comprises a square wave generator for producing square waves, and an integrator for integrating the square waves.
8. The liquid crystal display device according to claim 1 , further comprising a DC-DC converter for applying a voltage for bend transition of the OCB liquid crystals to the common electrode.
9. The liquid crystal display device according to claim 1 , wherein the backlight part comprises a red LED, a green LED and a blue LED for sequentially emitting red, green and blue lights.
10. The liquid crystal display device according to claim 1 , wherein the backlight part is a white LED or cold cathode fluorescence lamp (CCFL) for emitting white light.
11. The liquid crystal display device according to claim 10 , wherein the liquid crystal display further comprises red, green and blue color filters for filtering light emitted from the backlight part.
12. A liquid crystal display device comprising:
a liquid crystal display panel comprising a plurality of pixels which are located at a region where a plurality of scan lines and a plurality of data lines cross each other, each pixel comprising a common electrode, a pixel electrode and OCB liquid crystals;
a scan driver for applying scan signals for selecting the plurality of pixels through the plurality of scan lines;
a source driver for applying data voltages to the plurality of pixels through the plurality of data lines;
a backlight part for applying a light source to the liquid crystal display panel;
a backlight controller for applying a backlight voltage to the backlight part; and
a timing controller for applying control signals for controlling operation of the scan driver, the source driver and the backlight controller,
wherein the source driver comprises a D/A converter for outputting an analog signal corresponding to gradation data input, a triangular wave generator for outputting triangular wave signals, and a comparator for generating the data voltages to be applied to the plurality of pixels without using an amplifier by comparing the analog signal with the triangular wave signals, and
wherein each of the plurality of pixels further comprises a switching transistor for transmitting a corresponding one of the data voltages transmitted through the data lines to the pixel electrode in response to a corresponding one of the scan signals; and a storage capacitor for storing an electric charge corresponding to a voltage difference between the corresponding one of the data voltages and a common voltage of the common electrodes.