LIQUID CRYSTAL DISPLAY
A liquid crystal display capable of preventing a residual image phenomenon from occurring after power is cut off. The liquid crystal display includes: a voltage generating unit outputting a gate-on voltage to a first output node, outputting a gate-off voltage to a second output node, and pulling up the voltage level of the second output node to a level of a positive discharge voltage after a power supply voltage is cut off; a gate driving unit sequentially supplying the gate-on voltage and the gate-off voltage; a data driving unit supplying an image data voltage; and a liquid crystal panel including a plurality of pixels that are turned on or off according to the gate-on voltage or the gate-off voltage, so as to display an image corresponding to the image data voltage.
1 . A liquid crystal display comprising:
a voltage generating unit outputting a gate-on voltage to a first output node, outputting a gate-off voltage to a second output node, and pulling up a voltage level of the second output node to a level of a positive discharge voltage after a power supply voltage is cut off;
a gate driving unit sequentially supplying the gate-on voltage and the gate-off voltage;
a data driving unit supplying an image data voltage; and
a liquid crystal panel comprising a plurality of pixels that are turned on or off according to the gate-on voltage or the gate-off voltage so as to display an image corresponding to the image data voltage.
2 . The liquid crystal display of claim 1 , wherein after the power supply voltage is cut off, each of the plurality of pixels discharges the image data voltage.
3 . The liquid crystal display of claim 2 , wherein
each of the plurality of pixels comprises a switching element that is turned on or off according to the gate-on voltage or the gate-off voltage, and
after the power supply voltage is cut off, the switching element is supplied with the discharge voltage so as to be turned on.
4 . The liquid crystal display of claim 1 , wherein
the voltage generating unit comprises:
a gate-off voltage generating unit generating the gate-off voltage; and
a pull-up unit pulling the voltage level of the second node up to the level of the positive discharge voltage after the power supply voltage is cut off.
5 . The liquid crystal display of claim 4 , wherein
the pull-up unit comprises:
a charge unit being charged with the positive discharge voltage; and
a switching unit enabled so as to pull up the voltage level of the second output node to the level of the discharge voltage, when the power supply voltage is cut off.
6 . The liquid crystal display of claim 5 , wherein the switching unit comprises a PMOS transistor.
7 . The liquid crystal display of claim 5 , wherein the switching unit comprises a PNP-type bipolar junction transistor.
8 . The liquid crystal display of claim 5 , wherein the pull-up unit further comprises a cut-off unit that supplies the discharge voltage to the charge unit and electrically cuts off the discharge voltage from the charge unit when the power supply voltage is cut off.
9 . The liquid crystal display of claim 8 , wherein the cut-off unit comprises a diode having an anode to which the discharge voltage is applied and a cathode connected to the charge unit.
10 . The liquid crystal display of claim 4 , wherein the voltage generating unit further comprises a cut-off unit that electrically disconnects the second output node and the gate-off voltage generating unit when the power supply voltage is cut off.
11 . The liquid crystal display of claim 10 , wherein the cut-off unit comprises an NMOS transistor.
12 . The liquid crystal display of claim 10 , wherein: the cut-off unit comprises an NPN-type bipolar junction transistor.
13 . A liquid crystal display comprising:
a voltage generating unit including a gate-on voltage generating unit outputting a gate-on voltage to a first output node, a gate-off voltage generating unit outputting a gate-off voltage to a second output node, a pull-up unit pulling up the voltage level of the second output node to a level of the gate-on voltage when a power supply voltage is cut off, and a first cut-off unit electrically disconnecting the second output node and the gate-off voltage generating unit when the power supply voltage is cut off;
a gate driving unit sequentially supplying the gate-on voltage and the gate-off voltage;
a data driving unit supplying an image data voltage; and
a liquid crystal panel including a plurality of pixels that are turned on or off according to the gate-on voltage or the gate-off voltage so as to display an image corresponding to the image data voltage, each pixel being supplied with the gate-on voltage so as to discharge the image data voltage when the power supply voltage is cut off.
14 . The liquid crystal display of claim 13 , wherein
the pull-up unit comprises:
a charge unit being charged with the gate-on voltage;
a switching unit enabled when the power supply is cut off so as to pull up the voltage level of the second output node to the level of the gate-on voltage; and
a second cut-off unit connected to the first output node to supply the gate-on voltage to the charge unit and electrically disconnect the first output node from the charge unit when the power supply voltage is cut off.
15 . The liquid crystal display of claim 14 , wherein the second cut-off unit comprises a diode having an anode connected to the first output node and a cathode connected to the charge unit.
16 . The liquid crystal display of claim 14 , wherein: the switching unit comprises a PMOS transistor or a PNP-type bipolar junction transistor.
17 . The liquid crystal display of claim 13 , wherein
the gate-on voltage generating unit comprises
a charge pumping unit outputting to the first output node the gate-on voltage to which the power supply voltage is shifted by a voltage level of a pulse signal, and
a charge unit connected between the first output node and ground and charged with the gate-on voltage so as to prevent ripple of the gate-on voltage, and
the pull-up unit including a switching unit that is enabled to supply the gate-on voltage charged in the charge unit to the second output node when the power supply voltage is cut off.
18 . The liquid crystal display of claim 17 , wherein the switching unit comprises a PMOS transistor or a PNP-type bipolar junction transistor.
19 . The liquid crystal display of claim 17 , wherein the first cut-off unit comprises an NMOS transistor or an NPN-type bipolar junction transistor.