Method for removing noise, switching circuit for performing the same and display device having the switching circuit

This application claims priority under 35 U.S.C. §119 to Korean Patent Application No. 10-200745296, filed in the Korean Intellectual Property Office on May 10, 2007, and Korean Patent Application No. 10-2007-78419, filed on Aug. 6, 2007 in the Korean Intellectual Property Office (KIPO), the contents of which are herein incorporated by reference in their entireties.

1. Field of the Invention

The present invention relates to a method for removing noise, a switching circuit for performing the method, and a display device having the switching circuit. More particularly, the present invention relates to method for removing noise from a gate signal, a switching circuit for performing the method, and a display device having the switching circuit.

2. Description of the Related Art

In order to decrease the size of a liquid crystal display (LCD) and to increase productivity of manufacturing an LCD, a gate driving circuit is integrated directly on a peripheral area of a display substrate during the manufacturing process of a thin-film transistor (TFT) on the display substrate. Such a gate driving circuit is called an amorphous silicon gate (ASG) driving circuit.

The ASG circuit selects a clock signal having a phase that is continuously changed to output a gate-on signal. Thus, the ASG circuit generates noise caused by the clock signal having the phase that is continuously changed in a gate-off period. In order to decrease the noise, prior art ASG circuits have used various holding sections.

However, when the prior art ASG circuit is operated at a high temperature resulting from being driven for a long time, noise may be generated in the form of an abnormal gate-on signal during the gate-off period. Accordingly, prior art ASG circuits may not effectively control the noise. The noise of the abnormal gate-on signal causes display defects on the LCD.

Some embodiments of the present invention provide a method capable of removing noise at a high temperature.

The present invention also provides a switching circuit for performing the above-mentioned method.

The present invention also provides a display device having the above-mentioned switching circuit.

In some embodiments of the present invention, a method for removing noise of a gate signal that is outputted from a gate driving circuit including a plurality of stages includes electrically connecting two terminals of adjacent two stages that have noise components opposite in phase to each other during a first period, and electrically disconnecting the two terminals of the adjacent two stages that have the noise components opposite in phase to each other during a second period.

The second period may include a period for a corresponding stage to output the gate signal and a following period for a following stage of the corresponding stage to output a following gate signal.

In accordance with some preferable embodiments of the present invention, the second period includes a period for a corresponding stage to output the gate signal, the following period for the following stage of the corresponding stage to output the following gate signal, and a previous period for a previous stage of the corresponding stage to output a previous gate signal.

In some embodiments of the present invention, a switching circuit includes: a first switching circuit outputting an output signal of a turn-off level through an output terminal; a second switching circuit including a plurality of second switching elements, each of the second switching elements having an input terminal receiving an input signal of the turn-off level, an output terminal connected to the output terminal of the first switching circuit, and a control terminal receiving a control signal; and a third switching circuit including a control terminal connected to the output terminals of the first and second switching circuits, and switching between a first terminal and a second terminal using the control terminal of the third switching circuit, wherein the second switching elements are connected parallel with each other, and are turned on based on the control signals sequentially received through the control terminals of the second switching elements.

In some embodiments of the present invention, a display device includes: a display panel including a display area displaying an image and a peripheral area surrounding the display area, a plurality of pixel areas being formed in the display area, gate lines and data lines crossing the gate lines; a source driving circuit outputting data signals to the data lines; and a gate driving circuit directly integrated in the peripheral area, and outputting gate signals to the gate lines, wherein the gate driving circuit includes: an m-th stage (wherein ‘m’ is a natural number) including a pull-up section pulling up a first clock signal to a high level to output an m-th gate signal; an (m+1)-th stage connected to the m-th stage, including a pull-up section pulling up a second clock signal opposite in phase to the first clock signal to a high level to output the (m+1)-th gate signal; and a noise removing circuit electrically connecting a control terminal of the pull-up section of the m-th stage and a control terminal of the pull-up section of the (m+1)-th stage, to cancel noise of the control terminal of the pull-up section of the m-th stage and noise of the control terminal of the pull-up section of the (m+1)-th stage.

According to the method for removing the noise, the switching circuit and the display device of the present invention, noise of the gate signal may be decreased. Particularly, the noise of the gate signal at a high temperature may be removed.

The above and other features and advantages of the present invention will become more apparent in light of the following detailed example embodiments thereof with reference to the accompanying drawings, in which:

FIG. 1 is a plan view illustrating a display device according to an embodiment of the present invention;

FIG. 2 is a block diagram of a gate driving circuit according to a first embodiment of the present invention;

FIG. 3 is a schematic circuit diagram illustrating a stage of the gate driving circuit shown in FIG. 2 ;

FIG. 4 is a schematic circuit diagram illustrating a switching circuit used in the driving circuit of FIG. 2 ;

FIG. 5 is a timing diagram of signals of the gate driving circuit in FIG. 2 ;

FIG. 6 is a block diagram of a gate driving circuit according to a second embodiment of the present invention;

FIG. 7 is a schematic circuit diagram illustrating a switching circuit used in the gate driving circuit shown in FIG. 6 ;

FIG. 8 is a timing diagram of signals of the gate driving circuit in FIG. 6 ;

FIG. 9A is a timing diagram of signals applied to a first node of FIG. 2 ; and

FIG. 9B is an enlarged timing diagram of a portion “A” of FIG. 9A .

The invention is described more fully hereinafter with reference to the accompanying drawings, in which embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. In the drawings, the size and relative sizes of layers and regions may be exaggerated for clarity.

It will be understood that when an element or layer is referred to as being “on,” “connected to” or “coupled to” another element or layer, it can be directly on, connected or coupled to the other element or layer or intervening elements or layers may be present. In contrast, when an element is referred to as being “directly on,” “directly connected to” or “directly coupled to” another element or layer, there are no intervening elements or layers present. Like numbers refer to like elements throughout. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items.

It will be understood that, although the terms first, second, third etc. may be used herein to describe various elements, components, regions, layers and/or sections, these elements, components, regions, layers and/or sections should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer or section from another region, layer or section. Thus, a first element, component, region, layer or section discussed below could be termed a second element, component, region, layer or section without departing from the teachings of the present invention.

Spatially relative terms, such as “beneath,” “below,” “lower,” “above,” “upper” and the like, may be used herein for ease of description to describe one element or feature's relationship to another element(s) or feature(s) as illustrated in the figures. It will be understood that the spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, elements described as “below” or “beneath” other elements or features would then be oriented “above” the other elements or features. Thus, the exemplary term “below” can encompass both an orientation of above and below. The device may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms “a,” “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” and/or “comprising,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.

Embodiments of the invention are described herein with reference to cross-section illustrations that are schematic illustrations of idealized embodiments (and intermediate structures) of the invention. As such, variations from the shapes of the illustrations as a result, for example, of manufacturing techniques and/or tolerances, are to be expected. Thus, embodiments of the invention should not be construed as limited to the particular shapes of regions illustrated herein but are to include deviations in shapes that result, for example, from manufacturing. For example, an implanted region illustrated as a rectangle will, typically, have rounded or curved features and/or a gradient of implant concentration at its edges rather than a binary change from implanted to non-implanted region. Likewise, a buried region formed by implantation may result in some implantation in the region between the buried region and the surface through which the implantation takes place. Thus, the regions illustrated in the figures are schematic in nature and their shapes are not intended to illustrate the actual shape of a region of a device and are not intended to limit the scope of the invention.

Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.

Hereinafter, the present invention is explained in detail with reference to the accompanying drawings.

FIG. 1 is a plan view illustrating a display device according to an example embodiment of the present invention.

Referring to FIG. 1 , a display device includes a display panel 100 , a gate driving circuit 200 , a source driving circuit 500 , and a printed circuit board (PCB) 600 .

The display panel 100 includes a display area DA and a peripheral area PA surrounding the display area DA. The display area DA includes gate lines GL extended in a first direction, data lines DL extended in a second direction crossing the first direction, and a plurality of pixels for displaying an image. Each of the pixels includes a thin-film transistor (TFT) connected to one of the gate lines GL and one of the data lines DL, a liquid crystal capacitor CLC electrically connected to the TFT, and a storage capacitor CST connected parallel to the liquid crystal capacitor CLC.

The gate driving circuit 200 includes a shift register having a plurality of stages sequentially providing gate signals to the gate lines GL and a plurality of switching circuits NRCk for removing noise of the gate signals, wherein ‘k’ is a natural number. The shift register includes a plurality of stages SRCm and SRCm+1, wherein ‘m’ is a natural number. A k-th switching circuit NRCk removes noise of an m-th gate signal and an (m+1)-th gate signal that are output signals of an m-th stage SRCm and an (m+1)-th stage SRCm+1. For example, the gate driving circuit 200 may be integrated in the peripheral area PA corresponding to an end of the gate lines GL.

The source driving circuit 500 includes a source driving chip 510 outputting data signals to the data lines DL and a flexible PCB 530 electrically connected to the PCB 600 . The source driving chip 410 is mounted on the flexible PCB 530 . The source driving chip 410 may be directly mounted on the display panel 100 and directly integrated on the display panel 100 .

FIG. 2 is a block diagram of a gate driving circuit 200 a according to a first embodiment of the present invention.

Referring to FIG. 2 , the gate driving circuit 200 a includes a shift register SRC having first to (n+1)-th stages SRC 1 to SRCn+1 cascade-connected to each other, and first to (n/2)-th switching circuits connected adjacent to the stages.

The shift register SRC includes the first to n-th stages SRC 1 to SRCn outputting n gate signals, and the (n+1)-th stage SRCn+1 outputting a reset signal for resetting the first to n-th stages SRC 1 to SRCn. The gate driving circuit 200 a includes one dummy stage SRCn+1 for outputting the reset signal. Alternatively, the gate driving circuit 200 a may include at least two dummy stages for decreasing a ripple of an n-th gate signal. Each of the first to (n+1)-th stages SRC 1 to SRCn+1 includes a first clock terminal CK 1 , a second clock terminal CK 2 , a first input terminal IN 1 , a second input terminal IN 2 , a voltage terminal VSS, a reset terminal RE, a carry terminal CR, an output terminal OUT and a node terminal ND.

The first clock terminal CK 1 of each of the stages SRC (i.e., each of the stages SRC 1 to SRCn+1) receives a clock signal opposite in phase to a clock signal at the stage's second clock terminal CK 2 . For example, odd-numbered stages SRC 1 , SRC 3 , etc., may receive a first clock signal CK at their first clock terminals CK 1 , and receive a second clock signal CKB opposite in phase to the first clock signal CK at their second clock terminals CK 2 . Even-numbered stages SRC 2 , SRC 4 , etc., receive the second clock signal CKB at their first clock terminals CK 1 , and receive the first clock signal CK opposite in phase to the second clock signal CKB at their second clock terminals CK 2 .

The first input terminal IN 1 of each stage SRC receives either a vertical start signal STV or a carry signal CR of the previous stage. For example, the first input terminal IN 1 of the first stage SRC 1 may receive the vertical start signal, and the first input terminal IN 1 of each of the stages SRC 2 to SRC n+1 receives the carry signal of the respective previous stage of the stages SRC 1 to SRCn.

The second input terminal IN 2 of each stage SRC receives either the gate signal of the following stage or the vertical start signal STV. For example, the second input terminals IN 2 of the first to n-th stages SRC 1 to SRCn may receive the gate signals of the respective following stages SRC 2 to SRCn+1, and the second input terminal IN 2 of the final stage SRCn+1 receives the vertical start signal STV.

The voltage terminal VSS of each of the stages receives an off voltage VOFF, and the reset terminal of each of the stages receives the carry signal of the final stage SRCn+1.

The output terminal OUT outputs the gate signal to the gate line electrically connected to the output terminal OUT. When the first clock signal CK is high, the high level of the first clock signal CK is applied to the output terminal OUT of one of the odd-numbered stages SRC 1 , SRC 3 , . . . , with the consecutive odd-numbered stages providing the high level of the first clock signal CK in consecutive periods of the first clock signal CK. When the second clock signal CKB is high, the high level of the second clock signal CKB is applied to the output terminal OUT of one of the even-numbered stages SRC 2 , SRC 4 , . . . , with the consecutive even-numbered stages providing the high level of the second clock signal CKB in consecutive periods of the second clock signal CKB. In this way, the first to (n+1)-th stages SRC 1 to SRCn+1 sequentially output the gate signals of the gate-on voltage level.

The node terminal ND is electrically connected to a first node N 1 of each of the stages SRC 1 to SRCn+1, and outputs a signal of the first node N 1 . Each of the first to (n/2)-th switching circuits NRC 1 to NRCn/2 receives the signal of the first node N 1 outputted from the stages SRC 1 to SRCn+1.

The first to (n/2)-th switching circuits NRC 1 to NRCn/2 are disposed between the odd-numbered stages SRC 1 , SRC 3 , . . . , and the even-numbered stages SRC 2 , SRC 4 , . . . . For example, a first switching circuit NRC 1 may be disposed between the first stage SRC 1 and the second stage SRC 2 . In the same method, a second switching circuit NRC 2 is disposed between the third stage SRC 3 and the fourth stage SRC 4 .

Each of the first to (n/2)-th switching circuits NRC 1 to NRCn/2 includes a first clock terminal CK 1 , a second clock terminal CK 2 , a first input terminal IN 1 , a second input terminal IN 2 , a third input terminal IN 3 , a fourth input terminal IN 4 and a voltage terminal VSS.

The first clock terminal CK 1 receives the first clock signal CK, and the second clock terminal CK 2 receives the second clock signal CKB. The first input terminal IN 1 is connected to the output terminal OUT of each of the odd-numbered stages SRC 1 , SRC 3 , . . . , to receive each of the odd-numbered gate signals. The second input terminal IN 2 is connected to the output terminal OUT of each of the even-numbered stages SRC 2 , SRC 4 , . . . , to receive each of the even-numbered gate signals.

The third input terminal IN 3 is connected to the node terminal ND of each of the odd-numbered stages SRC 1 , SRC 3 , . . . , to receive the signal of the first node N 1 of each of the odd-numbered stages SRC 1 , SRC 3 , . . . .

The fourth input terminal IN 4 is connected to the node terminal ND of each of the even-numbered stages SRC 2 , SRC 4 , . . . , to receive the signal of the first node N 1 of each of the even-numbered stages SRC 2 , SRC 4 , . . . .

The voltage terminal VSS receives the off voltage VOFF.

FIG. 3 is a schematic circuit diagram illustrating a stage of the gate driving circuit 200 a shown in FIG. 2 . FIG. 4 is a schematic circuit diagram illustrating a switching circuit used in gate driving circuit 200 a shown in FIG. 2 . FIG. 5 is a timing diagram of signals of the gate driving circuit in FIG. 2 .

Referring to FIGS. 3 and 5 , an m-th stage SRCm includes a pull-up section 210 and the pull-down section 220 . The pull-up section 210 pulls up the m-th gate signal Gm to the high level of the first clock signal CK in response to the carry signal of the (m−1)-th stage SRCm−1. The pull-down section 220 pulls down the pulled up m-th gate signal Gm to the off voltage VOFF in response to the (m+1)-th gate signal Gm+1 of the (m+1)-th stage SRCm+1.

The pull-up section 210 includes a fifth transistor T 5 having a gate electrode connected to the first node N 1 , a drain electrode connected to the first clock terminal CK 1 , and a source electrode connected to the output terminal OUT.

The pull-down section 220 includes a sixth transistor T 6 having a gate electrode connected to the second input terminal IN 2 , a drain electrode connected to the output terminal OUT, and a source electrode connected to the voltage terminal VSS.

The m-th stage SRCm further includes a pull-up driving section (not shown) turning on the pull-up section 210 in response to the carry signal of the (m−1)-th stage SRCm−1, and turning off the pull-up section 210 in response to the (m+1)-th gate signal of the (m+1)-th stage SRCm+1. The pull-up driving section may include a buffer section 280 , a charging section 270 and a discharging section 230 .

The buffer section 280 includes a thirteenth transistor T 13 having a gate electrode connected to the first input terminal IN 1 , a drain electrode connected to the first input terminal IN 1 , and a source electrode connected to the first node N 1 . The charging section 270 includes a third capacitor C 3 having a first electrode connected to the first node N 1 and a second electrode connected to the output terminal OUT. The discharging section 230 includes a seventh transistor T 7 having a gate electrode connected to the second input terminal IN 2 , a drain electrode connected to the first node N 1 , and a source electrode connected to the voltage terminal VSS. The off voltage VOFF is applied to the source electrode of the seventh transistor T 7 .

When the thirteenth transistor T 13 is turned on in response to the carry signal of the (m−1)-th stage, the carry signal of the (m−1)-th stage SRCm−1 is applied to the first node N 1 to change the first node N 1 to a high level, and the carry signal of the (m−1)-th stage SRCm−1 charges the third capacitor C 3 at substantially the same time.

When the third capacitor C 3 is charged by a voltage greater than the threshold voltage of the fifth transistor T 5 and the first clock terminal CK 1 becomes the high level, the fifth transistor T 5 is bootstrapped to output the high level of the first clock signal CK through the output terminal OUT. That is, the output signal of the m-th stage SRCm is the m-th gate signal Gm.

When the seventh transistor T 7 is turned on in response to the (m+1)-th gate signal Gm+1, the third capacitor C 3 is discharged to the off voltage VOFF of the voltage terminal VSS, so that the fifth transistor T 5 is turned off.

The m-th stage SRCm may further include a first holding section 242 stably maintaining the first node N 1 at the off voltage VOFF during a disable period. The first holding section 242 may stably maintain the off voltage VOFF of first node N 1 discharged by the discharging section 230 independent from the ripple of the first and second clock signals CK and CKB to before an enable period of the next frame.

For example, the first clock signal CK may swing between the high level and the low level during the disable period, so that the ripple may be generated at the first node N 1 by a coupling capacitance between the drain electrode of the fourth transistor T 4 and the gate electrode of the fourteenth T 14 . In order to control the ripple, the first holding section 242 includes an eighth transistor T 18 having a gate electrode connected to the first clock terminal CK 1 , a drain electrode connected to the first node N 1 and a source electrode connected to the output terminal OUT.

When the first clock signal CK has the high level, the eighth transistor T 8 is turned on, and the first node N 1 is connected to the third node N 3 having the off voltage VOFF to stably maintain the level of the off voltage VOFF at the first node N 1 . When the first clock signal CK has the low level, the ripple of the first node N 1 by the coupling capacitance is negligible, so that controlling the level of the voltage applied to the first node N 1 is not required.

In an enable period of the m-th stage SRCm, that is, when the first node N 1 has the high level, the first clock signal CK has the low level. The eighth transistor T 8 is turned off and the first node N 1 becomes the high level due to the high level of the carry signal received from the first input terminal IN 1 .

When the eighth transistor T 8 is turned on in response to the first clock signal CK of the high level, the third node N 3 becomes the high level. Thus, the first node N 1 maintains the high level. The third node N 3 is described hereafter.

After the second holding section 244 discharges the carry signal of the (m−1)-th stage SRCm−1 having the high level and the first input terminal IN 1 of the m-th stage SRCm to the off voltage VOFF, the second holding section 244 may stably maintain the off voltage VOFF during the disable period of the m-th stage SRCm. The carry terminal CR of the (m−1)-th stage SRCm−1 that is the previous stage and the first input terminal IN 1 of the m-th stage SRCm output the signal having the high level. When a ninth transistor T 9 is turned on in response to the second clock signal CKB of the high level, the carry terminal CR of the (m−1)-th stage SRCm−1 and the first input terminal IN 1 of the m-th stage SRCm connected to the first node N 1 are discharged to the off voltage VOFF.

In the disable period, when the second clock signal CKB becomes the high level, the carry terminal CR of the (m−1)-th stage SRCm−1 and the first input terminal IN 1 of the m-th stage SRCm connected to the first node N 1 may stably maintain the off voltage VOFF.

Therefore, each of the first and second holding sections 242 and 244 are sequentially turned on in response to the signals at the respective first and second clock terminals CK 1 and CK 2 , so that the first node N 1 , the carry terminal CR of the (m−1)-th stage SRCm−1 and the first input terminal IN 1 of the m-th stage SRCm may stably maintain the off voltage VOFF.

The m-th stage SRCm may further include a third holding section 246 , a fourth holding section 248 , and a switching section 250 . The third and fourth holding sections 246 and 248 maintain the m-th gate signal Gm at the off voltage VOFF independent from the ripple of the first and second clock signals CK and CKB after the third node N 3 becomes the off voltage VOFF by the pull-down section 220 and before the gate signal of the next frame is outputted. The switching section 250 controls on/off switching of the fourth holding section 248 .

The third holding section 246 includes a tenth transistor T 10 having a gate electrode connected to the second clock terminal CK 2 , a drain electrode connected to the output terminal OUT, and a source electrode connected to the voltage terminal V. The source electrode of the tenth transistor T 10 receives the off voltage VOFF. The fourth holding section 248 includes an eleventh transistor T 11 having a gate electrode connected to the second node N 2 of the switching section 250 , a drain electrode connected to the output terminal OUT, and a source electrode connected to the voltage terminal VSS. The source electrode of the eleventh transistor T 11 receives the off voltage VOFF.

The switching section 250 includes first, second, third and fourth transistors T 1 , T 2 , T 3 and T 4 , respectively, and first and second capacitors C 1 and C 2 .

The first transistor T 1 has a gate electrode connected to the first clock terminal CK 1 , a drain electrode connected to the first clock terminal CK 1 , and a source electrode connected to a drain electrode of the second transistor T 2 . The gate and drain electrodes receive the signal at the first clock terminal CK 1 . The second transistor T 2 has a gate electrode connected to the output terminal OUT, and a source electrode connected to the voltage terminal VSS to receive the off voltage VOFF. The third transistor T 3 has a drain electrode connected to the first clock terminal CK 1 , a gate electrode connected to the first clock terminal CK 1 through the capacitor C 1 , and a source electrode connected to the second node N 2 .

Therefore, the drain and gate electrodes of the third transistor T 3 receive the signal at the first clock terminal CK 1 . The second capacitor C 2 is connected between the gate and source electrodes of the third transistor T 3 . The fourth transistor T 4 has a gate electrode connected to the output terminal OUT, a drain electrode connected to the second node N 2 , and a source electrode connected to the voltage terminal V to receive the off voltage VOFF.

When the m-th stage SRCm outputs the m-th gate signal Gm using the high level of the first clock signal CK through the output terminal OUT, the second and fourth transistors T 2 and T 4 are turned on. Thus the second node N 2 is applied to the off voltage VOFF.

The first and third transistors T 1 and T 3 are turned on in response to the first clock signal having the high level, and a gate electrode of the eleventh transistor T 11 is applied to a divided voltage that is a voltage between a voltage of first clock signal CK and the off voltage VOFF. The divided voltage is proportional to a resistance ratio of the third and fourth transistors T 3 and T 4

When the divided voltage is lower than the threshold voltage of the eleventh transistor T 11 , the eleventh transistor T 11 maintains a turn-off state. Thus, third node N 3 may maintain the high level.

When the second input terminal IN 2 receives the (m+1)-th gate signal Gm+1 of the high level after 1 H (H: horizontal period) has passed, the sixth transistor T 6 is turned on. Thus, the third node N 3 is discharged to the off voltage VOFF and the second and the fourth transistors T 2 and T 4 are turned off. At substantially the same time, the tenth transistor T 10 is turned on in response to the second clock signal CKB having the high level, and the third node N 3 is quickly pulled down to the off voltage VOFF.

The third and fourth holding sections 246 and 248 are sequentially turned on in response to the first and second clock signals CK and CKB to maintain the third node N 3 at the off voltage VOFF during one frame except for a period for outputting the m-th and (m+1)-th gate signals Gm and Gm+1.

The m-th stage of the gate driving circuit 200 may further include a reset section 260 and a carry section 290 .

The reset section 260 includes a twelfth transistor T 12 having a gate electrode connected to the reset terminal RE, a drain electrode connected to the first node N 1 , and a source electrode connected to the voltage terminal V to receive the off voltage VOFF.

The reset terminal RE of the reset section 260 receives the carry signal of the final stage SRCn+1, and resets the first node N 1 at the off voltage VOFF. The third node N 3 of the (n+1)-th stage SRCn+1 is not reset before a vertical start signal STV of the next frame is applied to the second input terminal IN 2 of the stage SRCn+1. Thus, during a blanking period of one frame, the first node N 1 is stabilized at the off voltage VOFF.

The carry section 290 includes a fourteenth transistor T 14 having a gate electrode connected to the first node N 1 , a drain electrode connected to the first clock terminal CK 1 (to receive the first clock signal CK for example), and a source electrode connected to the carry terminal CR. The carry section 290 outputs the first clock signal CK of the high level to the carry terminal CR when the voltage of the first node N 1 becomes high.

Hereinafter, the carry signal outputted from the carry section 290 is applied to the first input terminal IN 1 of the next stage to control a driving timing of the next stage. However, the carry section 290 may be omitted, and the gate signal outputted from the output terminal OUT may be applied to the first input terminal IN 1 of the next stage.

A load on a gate line of a high-resolution panel of XGA or higher resolution or a large-screen panel is greater than that on a low-resolution or a small-screen panel. Thus, when the gate signal is used as the carry signal, the lower end of the panel may be not driven by the delay of the carry signal. In the example embodiment of the present invention, the stage circuit of a high-resolution panel of XGA or higher resolution or a large-screen panel includes the carry section 290 .

After the carry section 290 outputs the carry signal having the high level through the carry terminal CR, the carry terminal CR of the high level is discharged to the off voltage VOFF, and the carry terminal CR is maintained to be the off voltage VOFF during the disable period of the m-th stage SRCm.

As mentioned above, the m-th stage SRCm includes the holding section 242 for removing the noise of the first node N 1 , but the entirety of the noise may not be completely removed. For example, when the transistor is driven at a high temperature, a leakage current of the transistor may be increased, and thus the noise may not be completely removed.

Hereafter, a switching circuit for removing the noise will be explained.

Referring to FIGS. 4 and 5 , a k-th noise removing circuit 300 includes a first switching circuit 310 , a second switching circuit 330 , and a third switching circuit 350 .

The first switching circuit 310 outputs an output signal of the high level through an output terminal. For example, the first switching circuit 310 may include a first switching element TR 1 outputting a high level of the first clock signal CK in response to the high level of the first clock signal CK, and a second switching element TR 2 outputting a high level of the second clock signal CKB in response to the high level of the second clock signal CKB.

For example, the first switching element TR 1 may include a gate electrode connected to first clock terminal CK 1 , a source electrode connected to the first clock terminal CK 1 and a drain electrode connected to a fourth node N 4 . The second switching element TR 2 includes a gate electrode connected to a second clock terminal CK 2 , a source electrode connected to a second clock terminal CK 2 and a drain electrode connected to a fourth node N 4 .

The second switching circuit 330 includes an input terminal that receives an input signal of a low level, an output terminal N 4 connected to an output terminal O 1 of the first switching circuit 310 , and a plurality of control terminals sequentially receiving a plurality of control signals. The control terminals are connected to first input terminal IN 1 and to a second input terminal IN 2 .

For example, the second switching circuit 330 may include a third switching element TR 3 and a fourth switching element TR 4 . The third switching element TR 3 discharges the first clock signal CK of the high level to the off voltage VOFF in response to the high level of the m-th gate signal Gm that is outputted from the m-th stage SRCm. The fourth switching element TR 4 discharges the second clock signal CKB of the high level to the off voltage VOFF in response to the high level of the (m+1)-th gate signal Gm+1 that is outputted from the (m+1)-th stage SRCm+1.

For example, the third switching element TR 3 may include a gate electrode connected to the first input terminal IN 1 , a source electrode connected to the fourth node N 4 , and a drain electrode connected to a voltage terminal VSS. The fourth switching element TR 4 includes a gate electrode connected to the second input terminal IN 2 , a source electrode connected to the fourth node N 4 and a drain electrode connected to the voltage terminal VSS.

The third switching circuit 350 switches between a first terminal and a second terminal based on a signal received from a control terminal connected to the output terminals of the first and the second switching circuits 310 and 330 . The first terminal is connected to the control terminal of the pull-up section of the m-th stage SRCm. The second terminal is connected to the control terminal of the pull-up section of the (m+1)-th stage SRCm+1.

For example, the third switching circuit 350 may include a fifth switching element TR 5 . When the third or fourth switching element TR 3 or TR 4 is turned on, the fifth switching element TR 5 electrically connects between the control terminal of the pull-up section of the m-th stage SRCm and the control terminal of the pull-up section of the (m+1)-th stage SRCm+1 in response to the off voltage VOFF. When the third or fourth switching element TR 3 or TR 4 is turned off, the fifth switching element TR 5 electrically disconnects between the control terminal of the pull-up section of the m-th stage SRCm and the control terminal of the pull-up section of the (m+1)-th stage SRCm+1 in response to the first or second clock signal CK or CKB having the high level.

Referring to FIG. 3 , the control terminal of the pull-up section of the m-th stage SRCm is the first node N 1 of the m-th stage SRCm, and the control terminal of the pull-up section of the (m+1)-th stage SRCm+1 is the first node N 1 of the (m+1)-th stage SRCm+1.

For example, the fifth switching element TR 5 may include a gate electrode connected to the fourth node N 4 , a source electrode connected to a third input terminal IN 3 received a signal of the first node N 1 of the m-th stage SRCm, and a drain electrode connected to a fourth input terminal IN 4 received a signal of the first node N 1 of the (m+1)-th stage SRCm+1. That is, the fifth switching element TR 5 electrically connects or disconnects between the first node N 1 of the m-th stage SRCm and the first node N 1 of the (m+1)-th stage SRCm+1.

A method of driving the k-th noise removing circuit 300 is as follows.

When the first input terminal IN 1 receives the m-th gate signal Gm, the third switching element TR 3 is turned on. Thus, the off voltage VOFF received from the voltage terminal VSS is applied to the fourth node N 4 . When the fourth node N 4 has the off voltage VOFF, the fifth switching element TR 5 is turned off. Thus, the first node N 1 of the m-th stage SRCm and the first node N 1 of the (m+1)-th stage SRCm+1 are electrically disconnected from each other.

When the second input terminal IN 2 receives the (m+1)-th gate signal Gm+1, the fourth switching element TR 4 is turned on. Thus, the off voltage VOFF received from the voltage terminal VSS is applied to the fourth node N 4 . When the fourth node N 4 has the off voltage VOFF, the fifth switching element TR 5 is turned off. Thus, the first node N 1 of the m-th stage SRCm and the first node N 1 of the (m+1)-th stage SRCm+1 are electrically disconnected from each other.

That is, while the first and second input terminals IN 1 and IN 2 receive the m-th gate signal Gm and the (m+1)-th gate signal Gm+1, the first node N 1 of the m-th stage SRCm and the first node N 1 of the (m+1)-th stage SRCm+1 are electrically disconnected from each other.

In addition, while the first and second input terminals IN 1 and IN 2 do not receive the m-th gate signal Gm and the (m+1)-th gate signal Gm+1, the first and 10 second clock terminals CK 1 and CK 2 alternately receive the first and second clock signals CK and CKB.

When the first clock terminal CK 1 receives the first clock signal CK of the high level, the first switching element TR 1 is turned on. Thus, the fourth node N 4 has the high level of the first clock signal CK, so that the fifth switching element TR 5 is turned on. Thus, the first node N 1 of the m-th stage SRCm and the first node N 1 of the (m+1)-th stage SRCm+1 are electrically connected with each other.

In addition, when the first terminal CK 1 receives the first clock of the low level and the second clock terminal CK 2 receives the second clock signal CKB of the high level, the second switching element TR 2 is turned on. Thus, the fourth node N 4 has the high level of the first clock signal CK, so that the fifth switching element TR 5 is turned on. Thus, the first node N 1 of the m-th stage SRCm and the first node N 1 of the (m+1)-th stage SRCm+1 are electrically connected with each other.

While the first and second input terminals IN 1 and IN 2 receive the m-th gate signal Gm and the (m+1)-th gate signal Gm+1, the first and second clock terminals CK 1 and CK 2 also receive the first and second clock signals CK and CKB. Though the first and second switching elements TR 1 and TR 2 are turned on in response to the first and second clock signals CK and CKB, the third and fourth switching elements TR 3 and TR 4 are turned on. The fourth node N 4 has the off voltage VOFF, so that the first node N 1 of the m-th stage SRCm and the first node N 1 of the (m+1)-th stage SRCm+1 are electrically disconnected from each other.

In addition, while the first and second input terminals IN 1 and IN 2 receive the low level of the m-th gate signal Gm and the (m+1)-th gate signal Gm+1, the first node N 1 of the m-th stage SRCm and the first node N 1 of the (m+1)-th stage SRCm+1 are electrically connected by the high level of the first and second clock signals CK and CKB.

Accordingly, during one frame when the m-th and the (m+1)-th stages SRCm and SRCm+1 output the low level of the m-th and (m+1)-th gate signals Gm and Gm+1, the first node N 1 of the m-th stage SRCm and the first node N 1 of the (m+1)-th stage SRCm+1 are electrically connected. Thus, the noise components generated at the first node N 1 of the m-th stage SRCm and the first node N 1 of the (m+1)-th stage SRCm+1 may interfere with and cancel out each other.

FIG. 6 is a block diagram of a gate driving circuit according to a second example embodiment of the present invention. FIG. 7 is a schematic circuit diagram illustrating a switching circuit in FIG. 6 . FIG. 8 is a timing diagram of signals of the gate driving circuit in FIG. 6 .

Referring to FIG. 6 , the gate driving circuit 200 b includes a shift register SRC having first to (n+1)-th stages SRC 1 to SRCn+1 cascade-connected together, and first to (n/2)-th switching circuits connected adjacent to the stages.

The shift register SRC is substantially the same as the gate driving circuit 200 a described in FIG. 2 , and any repetitive explanation concerning the above elements will be omitted.

Each of the first to (n/2)-th switching circuits NRC 1 to NRCn/2 includes a first clock terminal CK 1 , a second clock terminal CK 2 , a first input terminal IN 1 , a second input terminal IN 2 , a third input terminal IN 3 , a fourth input terminal IN 4 , a fifth input terminal IN 5 , and a voltage terminal VSS.

The first clock terminal CK 1 receives the first clock signal CK, and the second clock terminal CK 2 receives the second clock signal CKB. The first input terminal IN 1 is connected to the output terminal OUT of the stage adjacent to the switching circuit among the odd-numbered stages SRC 1 , SRC 3 , . . . , to receive the gate signal outputted from a corresponding stage among the odd-numbered stages SRC 1 , SRC 3 , . . . . The second input terminal IN 2 is connected to the output terminal OUT of the stage adjacent to the switching circuit among the even-numbered stages SRC 2 , SRC 4 , . . . , to receive the gate signal outputted from a corresponding stage among the even-numbered stages SRC 2 , SRC 4 , . . . .

The third input terminal IN 3 is connected to the node terminal ND of the stage adjacent to the switching circuit among the odd-numbered stages SRC 1 , SRC 3 , . . . , to receive the signal of the first node N 1 of a corresponding stage among the odd-numbered stages SRC 1 , SRC 3 , . . . . The fourth input terminal IN 4 is connected to the node terminal ND of the stage adjacent to the switching circuit among the even-numbered stages SRC 2 , SRC 4 , . . . , to receive the signal of the first node N 1 of a corresponding stage among the even-numbered stages SRC 2 , SRC 4 , . . . . The fifth input terminal IN 5 is connected to a previous stage that is disposed in front of the odd-numbered stage outputting the signal applied to the first input stage IN 1 , to receive the output signal of the previous stage. The previous stage is one among the even-numbered stages SRC 2 , SRC 4 , . . . , and the fifth input terminal IN 5 of the first switching circuit NRC 1 receives the vertical start signal STV.

The voltage terminal VSS receives the off voltage VOFF.

Referring to FIGS. 7 and 8 , a k-th noise removing circuit 400 includes a first switching circuit 410 , a second switching circuit 430 , and a third switching circuit 450 .

The first switching circuit 410 includes a first switching element TR 1 outputting a high level of the first clock signal CK in response to the high level of the first clock signal CK, and a second switching element TR 2 outputting a high level of the second clock signal CKB in response to the high level of the second clock signal CKB.

For example, the first switching element TR 1 may include a gate electrode connected to first clock terminal CK 1 , a source electrode connected to the first clock terminal CK 1 and a drain electrode connected to a fourth node N 4 . The second switching element TR 2 may include a gate electrode connected to a second clock terminal CK 2 , a source electrode connected to a second clock terminal CK 2 and a drain electrode connected to a fourth node N 4 .

The second switching circuit 430 includes a third switching element TR 3 , a fourth switching element TR 4 and a fifth switching element TR 5 . The third switching element TR 3 applies the off voltage VOFF to the fourth node N 4 in response to the high level of the m-th gate signal Gm that is outputted from the m-th stage SRCm. The fourth switching element TR 4 applies the off voltage VOFF to the fourth node N 4 in response to the high level of the (m+1)-th gate signal Gm+1 that is outputted from the (m+1)-th stage SRCm+1. The fifth switching element TR 5 applies the off voltage VOFF to the fourth node N 4 in response to the high level of the (m−1)-th gate signal Gm−1 that is outputted from the (m−1)-th stage SRCm−1.

For example, the third switching element TR 3 may include a gate electrode connected to the first input terminal IN 1 , a source electrode connected to the fourth node N 4 , and a drain electrode connected to a voltage terminal VSS. The fourth switching element TR 4 may include a gate electrode connected to the second input terminal IN 2 , a source electrode connected to the fourth node N 4 and a drain electrode connected to the voltage terminal VSS. The fifth switching element TR 5 may include a gate electrode connected to the fifth input terminal IN 5 , a source electrode connected to the fourth node N 4 and a drain electrode connected to the voltage terminal VSS.

The third switching circuit 450 includes a sixth switching element TR 6 . When the third, fourth or fifth switching element TR 3 , TR 4 or TR 5 is turned on, the gate electrode of the sixth switching element TR 6 is applied to the off voltage VOFF. Thus, the sixth switching element TR 6 electrically disconnects between the control terminal of the pull-up section of the m-th stage SRCm and the control terminal of the pull-up section of the (m+1)-th stage SRCm+1 in response to the off voltage VOFF.

When the third, fourth or fifth switching element TR 3 , TR 4 or TR 4 is turned off, the gate electrode of the sixth switching element TR 6 is applied to the first or second clock signal CK or CKB having the high level. Thus, the sixth switching element TR 6 electrically connects between the control terminal of the pull-up section of the m-th stage SRCm and the control terminal of the pull-up section of the (m+1)-th stage SRCm+1 in response to the first or second clock signal CK or CKB having the high level. The control terminal of the pull-up section of the m-th stage SRCm is the first node N 1 of the m-th stage SRCm, and the control terminal of the pull-up section of the (m+1)-th stage SRCm+1 is the first node N 1 of the (m+1)-th stage SRCm+1.

For example, the sixth switching element TR 6 includes a gate electrode connected to the fourth node N 4 , a source electrode connected to a third input terminal IN 3 received a signal of the first node N 1 of the m-th stage SRCm, and a drain electrode connected to a fourth input terminal IN 4 received a signal of the first node N 1 of the (m+1)-th stage SRCm+1. That is, the sixth switching element TR 6 electrically disconnects or connects between the first node N 1 of the m-th stage SRCm and the first node N 1 of the (m+1)-th stage SRCm+1.

A method of driving the k-th noise removing circuit 400 is as follows.

When the fifth input terminal IN 5 receives the (m−1)-th gate signal Gm−1, the fifth switching element TR 5 is turned on. Thus, the fourth node N 4 is applied to a divided voltage that is a voltage between the first and second clock signals CK and CKB having the high level applied to the first or second clock terminal CK 1 or CK 2 , and the off voltage VOFF. When the divided voltage is lower than the threshold voltage of the sixth switching element TR 6 , the sixth switching element TR 6 is turned off. The first node N 1 of the m-th stage SRCm and the first node N 1 of the (m+1)-th stage SRCm+1 are electrically disconnected from each other.

When the first input terminal IN 1 or the second input terminal IN 2 receives the high level of the m-th gate signal Gm or the (m+1)-th gate signal Gm+1, the sixth switching element TR 6 is turned off. The first node N 1 of the m-th stage SRCm and the first node N 1 of the (m+1)-th stage SRCm+1 are electrically disconnected from each other.

That is, while the first, second and fifth input terminals IN 1 , IN 2 and IN 5 receive the high level of the m-th, (m+1)-th and (m−1)-th gate signals Gm, Gm+1 and Gm−1, the first node N 1 of the m-th stage SRCm and the first node N 1 of the (m+1)-th stage SRCm+1 are electrically disconnected from each other.

However, while the first, second and fifth input terminals IN 1 , IN 2 and IN 5 receive the low level of the m-th, (m+1)-th and (m−1)-th gate signals Gm, Gm+1 and Gm−1, the sixth switching element TR 6 is turned on in response to the high level of the first and second clock signals CK and CKB. The high level of the first and second clock signals CK and CKB are alternately input into the first and second clock terminals CK 1 and CK 2 . Thus, the first node N 1 of the m-th stage SRCm and the first node N 1 of the (m+1)-th stage SRCm+1 are electrically connected to each other.

As a result, when the first node N 1 of the m-th stage SRCm has the high level, the first node N 1 of the m-th stage SRCm and the first node N 1 of the (m+1)-th stage SRCm+1 are electrically disconnected from each other. Thus, the m-th stage SRCm outputs the m-th gate signal Gm having the high level. When the first node N 1 of the m-th stage SRCm has the low level that is the off voltage VOFF, the first node N 1 of the m-th stage SRCm and the first node N 1 of the (m+1)-th stage SRCm+1 are electrically connected. Thus, the noise components that are opposite in phase generated at the first node N 1 of the m-th stage SRCm and the first node N 1 of the (m+1)-th stage SRCm+1 may interfere with and cancel out each other.

A time for raising the signal of the first node N 1 from low level to the high level is quicker by about ½ H than a time for outputting the m-th gate signal from the m-th stage SRCm. The voltage of the fourth node N 4 falls to a voltage lower than the threshold voltage of the sixth switching element TR 6 in response to the (m−1)-th gate signal Gm−1 having the high level. Thus, the first node N 1 is stabilized at the off voltage VOFF.

FIG. 9A is a timing diagram of signals applied to a first node N 1 of FIG. 2 . FIG. 9B is an enlarged timing diagram of a portion “A” of FIG. 9A .

Referring to FIG. 9A , each of signals a, b, c and d detected from four sequential stages are illustrated. For example, at the first node N 1 of the first and third stages that generated a gate signal in response to the first clock signal CK, the first signal a and the third signal c were detected. At the first node N 1 of the second and fourth stages that generated a gate signal in response to the second clock signal CKB opposite in phase to the first clock signal CK, the second signal b and the fourth signal d were detected.

Referring to FIG. 9B , a phase difference between noise a′ and c′ including the first and the third signals a and c generated in response to the first clock signal CK, and noise b′ and d′ including the second and the fourth signals b and d generated in response to the second clock signal CKB was 180°.

According to the switching circuit of the present invention, the first noise a′ interferes with the second noise b′ having the phase difference of 180° in relation to the first noise a′, so that the first and second noise components a′ and b′ may be removed. Also, the third noise c′ interferes with the fourth noise d′ having the phase difference of 180° in relation to the third noise a′, so that the third and fourth noise components c′ and d′ may be removed.

As mentioned above, according to an example embodiment of the present invention, a control terminal of a pull-up section of an odd-numbered stage and a control terminal of a pull-up section of an even-numbered stage are electrically disconnected during a period when the first node of the odd-numbered stage and the even-numbered stage is changed to a high level, and connected during a period when the first node of the odd-numbered stage and the even-numbered stage maintains a low level.

Therefore, noise of the control terminal of the pull-up section may be removed, particularly, at a high temperature. The noise of the control terminal of the pull-up section may be decreased, so that noise of a gate signal may be removed. Thus, display quality may be enhanced.

Having described the example embodiments of the present invention and its advantage, it is noted that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the invention as defined by appended claims.