Liquid crystal display and driving method thereof
View Patent ↗An LCD and a driving method thereof include: data writing for applying a common voltage and a data voltage to a plurality of pixels; and sustaining for applying a shifted common voltage shifted by a predetermined level from the common voltage to the plurality of pixels for a sustain period during which the plurality of pixels emit light, corresponding to the data voltage. The shifted common voltage is shifted to an opposite polarity of a polarity of a gate-off voltage applied to the plurality of pixels to float the plurality of pixels. During a sustain period, a gate-source voltage of the switching transistor can be increased, and accordingly an influence due to the leakage current can be minimized, thereby preventing image deterioration. Further, since capacitance of the sustain capacitor can be reduced so that power consumption of the LCD can be reduced.
1. A driving method of a liquid crystal display device having a plurality of pixels arranged in a matrix format, said method comprising the steps of:
during a data writing period, sequentially turning on switching transistors of all of the pixels, and data writing for applying corresponding data voltages to all of the pixels while applying a single common voltage simultaneously to all of the pixels during a data writing period; and
during a sustain period which immediately follows the data writing period, turning off the switching transistors of all the pixels, sustaining for applying a single shifted common voltage shifted by a predetermined level from the common voltage simultaneously to all of the pixels, and emitting light by all of the pixels corresponding to the data voltages;
wherein the shifted common voltage is shifted to an opposite polarity relative to a polarity of gate-off voltages applied to the plurality of pixels to float the plurality of pixels.
2. The driving method of claim 1 , wherein during the data writing period,
turning on the switching transistor respectively connected to each of the plurality of pixels by sequentially applying a gate-on voltage to a plurality of scan lines respectively connected to the plurality of pixels; and
applying a data voltage corresponding to each of the plurality of pixels through the turned-on switching transistor.
3. The driving method of claim 2 , further comprising the step of turning off the switching transistors connected to the respective scan lines by applying the gate-off voltage to the scan lines during the data writing period.
4. The driving method of claim 3 , wherein a voltage difference between a gate terminal and a source terminal of the turned-off switching transistors is increased by applying the shifted common voltage.
5. The driving method of claim 3 , wherein the switching transistors are n-channel field effect transistors.
6. The driving method of claim 5 , wherein the gate-on voltage is a logic high level voltage and the gate-off voltage is a logic low level voltage.
7. The driving method of claim 6 , wherein the shifted common voltage is a voltage increased by a predetermined level from the common voltage.
8. The driving method of claim 3 , wherein the switching transistors are p-channel field effect transistors.
9. The driving method of claim 8 , wherein the gate-on voltage is a logic low level voltage and the gate-off voltage is a logic high level voltage.
10. The driving method of claim 9 , wherein the shifted common voltage is decreased by a predetermined level from the common voltage.
11. A liquid crystal display device, comprising:
a liquid crystal panel including a plurality of pixels arranged in a matrix format;
a scan driver connected to each of a plurality of scan lines connected to the plurality of pixels, each of the pixels including a switching transistor connected to corresponding ones of the scan lines, the scan driver turning on the switching transistors by sequentially applying a gate-on voltage to the plurality of scan lines during a data writing period during which the switching transistors of all of the pixels are sequentially turned on by the scan driver;
a data driver applying data voltages corresponding to all of the plurality of pixels through the turned-on switching transistors during the data writing period; and
a power supply applying a single common voltage simultaneously to all of the plurality of pixels during the data writing period;
wherein the scan driver sequentially applies a gate-off voltage to each of the scan lines to turn off the switching transistors of each of the scan lines after the data voltages are applied to the plurality of pixels connected to the corresponding scan lines, and,
during a sustain period, which immediately follows the data writing period, in which the switching transistors of all the pixels are turned off by the scan driver and all of the plurality of pixels emit light, the power supply applies a single shifted common voltage simultaneously to all of the plurality of pixels, and the shifted common voltage is shifted to an opposite polarity relative to a polarity of the gate-off voltage to float the plurality of pixels.
12. The liquid crystal display of claim 11 , wherein the switching transistors are n-channel field effect transistors.
13. The liquid crystal display of claim 12 , wherein the gate-on voltage is a logic high level voltage and the gate-off voltage is a logic low level voltage.
14. The liquid crystal display of claim 13 , wherein the shifted common voltage is a voltage increased by a predetermined level from the common voltage.
15. The liquid crystal display of claim 11 , wherein the switching transistors are p-channel field effect transistors.
16. The liquid crystal display of claim 15 , wherein the gate-on voltage is a logic low level voltage and the gate-off voltage is a logic high level voltage.
17. The liquid crystal display of claim 16 , wherein the shifted common voltage is a voltage decreased by a predetermined level from the common voltage.
18. A liquid crystal display device, comprising:
a liquid crystal panel including a plurality of pixels, each of the pixels comprising:
a switching transistor receiving a gate-on voltage from a scan driver via a corresponding scan line during a data writing period for all of the pixels;
the switching transistor receiving a data voltage from a data driver, and receiving a gate-off voltage that turns off the switching transistor after the data voltage is applied to the pixel during the data writing period;
a liquid crystal capacitor connected in parallel with a sustain capacitor, and commonly connected to the switching transistor; and
a power supply applying a common voltage to the liquid crystal capacitor and the sustain capacitor during the data writing period, and applying a shifted common voltage to the liquid crystal capacitor and the sustain capacitor during a sustain period immediately following the data writing period, the shifted common voltage being shifted to an opposite polarity relative to a polarity of the gate-off voltage,
each of the pixels connected to receive the same common voltage, and to receive simultaneously the same shifted common voltage,
during the data writing period, the switching transistors of all of the pixels being sequentially turned on, and
during the sustain period, the switching transistors of all the pixels being turned off.