# Patent

## Title
Gate driver and liquid crystal display using the same

## Abstract

A gate driver and a liquid crystal display using the same are provided. The gate driver includes a scan signal generating unit and a compensation unit. The scan signal generating unit has a plurality of output channels, and is used for sequentially outputting a scan signal through the output channels according to a basic clock and a start pulse. The compensation unit is coupled to the scan signal generating unit, and used for compensating the total resistance of each of the output channels, and sequentially receiving and transmitting the scan signal to a display panel.

## Background
CROSS-REFERENCE TO RELATED APPLICATION
This is a divisional application of and claims the priority benefit of U.S. application Ser. No. 14/322,929, filed on Jul. 3, 2014, now allowed. The prior U.S. application Ser. No. 14/322,929 is a divisional application of and claims the priority benefit of U.S. application Ser. No. 12/790,994, filed on Jun. 1, 2010, which claims the priority benefit of Taiwan application serial no. 99110754, filed on Apr. 7, 2010. The entirety of each of the above-mentioned patent applications is hereby incorporated by reference herein and made a part of this specification.


BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates generally to a flat panel display technology and more particularly, to a gate driver having a resistance compensation function and a liquid crystal display using the gate driver.
2. Description of Related Art
In recent years, with great advance in the semiconductor technique, portable electronic devices and flat panel displays (FPDs) have been rapidly developed. Among the various types of flat panel displays, liquid crystal displays (LCDs) have become the mainstream among the display products mainly due to their advantages such as low operating voltage, lack of harmful radiation, light weight, and small footprint.
Generally speaking, as shown in FIG. 1, when a conventional gate driver 103 is employed in a high resolution display panel 101, since a wiring distance from each of the output channels OUT of the gate driver 103 to the display panel 101 is different (e.g., a wiring distance to the region A of the display panel 101 is shorter than a wiring distance to the regions B and C), a layout resistance variation between each of the output channels OUT of the gate driver 103 and the display panel 101 is overly large. For example, a smallest layout resistance is approximately 82Ω, whereas a largest layout resistance is approximately 1021 Ω.
Accordingly, based on each of the output channels OUT of the gate driver 103 having a same loading on the display panel 101, and since the layout resistance variation between each of the output channels OUT of the gate driver 103 and the display panel 101 is overly large (e.g., may be a difference of several hundred ohms), therefore a scan signal outputted by each of the output channels OUT of the gate driver 103 may have too large a disparity.
Consequently, in condition of the display panel 101 is a normally black type, when the gate driver 103 outputs scan signals having large variations through all of its output channels OUT to the display panel to turn on all the scan lines (e.g., all the pixels), the display panel 101 does not display an ideal all black image. Rather, a so-called “multi-band phenomenon” may be generated (e.g., the middle region A of the display panel 101 may display the black image, while the regions B and C of the display panel 101 may display a continuous gradient gray image), thereby affecting the quality of images displayed by the display panel 101.
SUMMARY OF THE INVENTION
In view of the foregoing, an aspect of the invention provides a gate driver capable of mitigating the issues set forth in the description of related art.
An aspect of the invention provides a gate driver including a scan signal generating unit and a compensation unit. The scan signal generating unit has a plurality of output channels, and is used for sequentially outputting a scan signal through the output channels according to a basic clock and a start pulse. The compensation unit is coupled to the plurality of output channels, used for compensating a total resistance of each of the output channels, and sequentially receiving and transmitting the scan signal to a display panel.
Another aspect of the invention provides a gate driver including a scan signal generating unit and a compensation unit. The scan signal generating unit has a plurality of output channels, and is used for sequentially outputting a scan signal through the output channels according to a basic clock and a start pulse. The compensation unit is coupled to the plurality of output channels, and the compensation unit includes a switching means and a resistance-supply means. The compensation unit is used for respectively providing a compensation resistance to compensate a total resistance of each of the output channels through the switching means and the resistance-supply means accordance to at least an external configuration signal and/or the scan signal, and sequentially receiving and transmitting the scan signal to a display panel.
Another aspect of the invention provides a liquid crystal display having the aforesaid gate driver.
In summary, by employing the switching means and the resistance-supply means therein, the gate driver according to an embodiment of the invention lowers a layout resistance between each of the output channels of the gate driver and the display panel. Accordingly, a variation of the scan signal outputted by each of the output channels of the gate driver is reduced, and a possibility of the “multi-band phenomenon” occurring on the display panel in the description of the related art is lowered, thereby enhancing the quality of images displayed by the display panel.
It should be noted that the above described general descriptions and following embodiments are only taken as examples and used for illustration, not for limiting the scope of the invention.



BRIEF DESCRIPTION OF THE DRAWINGS
The accompanying drawings are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification. The drawings illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention.
FIG. 1 is a schematic view illustrating a layout resistance between each of the output channels of a conventional gate driver and a display panel.
FIG. 2 is a schematic view of a liquid crystal display in accordance with a first embodiment of the invention.
FIG. 3 is a schematic view of a gate driver in accordance with the first embodiment of the invention.
FIG. 4 is a circuit diagram of a compensation circuit in accordance with the first embodiment of the invention.
FIG. 5 is a schematic diagram illustrating the compensation of a total resistance of each of the output channels of the gate driver according to the first embodiment by a corresponding compensation circuit.
FIG. 6 is a schematic view of a liquid crystal display in accordance with a second embodiment of the invention.
FIG. 7 is a schematic view of a gate driver in accordance with the second embodiment of the invention.
FIGS. 8 and 9 are schematic views respectively illustrating two sub-compensation units in accordance with the second embodiment of the invention.
FIG. 10 is a schematic view of a liquid crystal display in accordance with a third embodiment of the invention.
FIG. 11 is a schematic view of a gate driver in accordance with the third embodiment of the invention.
FIGS. 12 and 13 are schematic views respectively illustrating two sub-compensation units in accordance with the third embodiment of the invention.



DESCRIPTION OF EMBODIMENTS
Descriptions of the invention are given with reference to the exemplary embodiments illustrated with accompanied drawings, wherein same or similar parts are denoted with same reference numerals. In addition, whenever possible, identical or similar reference numbers stand for identical or similar elements in the figures and the embodiments.
The First Embodiment
FIG. 2 is a schematic view of a liquid crystal display 200 in accordance with a first embodiment of the invention. Referring to FIG. 2, the liquid crystal display 200 includes a display panel 201, a gate driver 203, a source driver 205, a timing controller 207, and a backlight module 209. In the first embodiment, the backlight module 209 is used for providing a light source required by the display panel 201. The timing controller 207 is used for controlling the operation of the gate driver 203 and the source driver 205, such that the gate driver 203 and the source driver 205 respectively generates scan signals and data signals to drive the display panel 201, whereby the display panel 201 displays images.
According to the description of the related art, since a wiring distance from each of the output channels of the conventional gate driver to the display panel is different, a layout resistance variation between each of the output channels of the gate driver to the display panel is too large (e.g., may be a difference of several hundred ohms). Consequently, in condition of each of the output channels of the gate driver having a same loading on the display panel, the scan signal outputted by each of the output channels of the gate driver may have too large a disparity and thus causing the “multi-band phenomenon”.
Accordingly, an embodiment of the invention provides a gate driver having a resistance compensation function, such that a variation of the scan signal outputted by each of the output channels of the gate driver is reduced, and a possibility of the “multi-band phenomenon” occurring on the display panel in the description of the related art is lowered, thereby enhancing the quality of images displayed by the display panel.
More specifically, FIG. 3 is a schematic view of the gate driver 203 in accordance with the first embodiment of the invention. Referring to FIGS. 2 and 3 together, the gate driver 203 includes a scan signal generating unit 301 and a compensation unit 303. In the first embodiment, the scan signal generating unit 301 has, for example but not limited to, 900 output channels OUT1-OUT900. Moreover, a number of the output channels may be determined according to a resolution of the display panel 201. For example, assuming the resolution of the display panel 201 is 1024*768, then this represents the scan signal generating unit may have 768 output channels, and likewise for other scenarios. Generally speaking, the scan signal generating unit 301 is used for sequentially outputting a plurality of scan signals S1-S900 through the output channels OUT1-OUT900 according to a basic clock CPV and a start pulse STV provided by the timing controller 207. Moreover, the scan signal generating unit 301 may also achieve a bidirectional scanning function according to a direction signal (not drawn) provided by the timing controller 207.
From another perspective, the compensation unit 303 is coupled to the output channels OUT1-OUT900 of the scan signal generating unit 301. The compensation unit 303 is used for compensating a total resistance of each of the output channels OUT1-OUT900, and sequentially receiving and transmitting the scan signals S1-S900 to the display panel 201, thereby turning on each of the scan lines G1-G900 in the display panel 201 one by one. In the first embodiment, the compensation unit 303 includes a plurality of compensation circuits CC1-CC900 equivalent in quantity to the number of output channels OUT1-OUT900 of the scan signal generating unit 301, and respectively corresponding to the output channels OUT1-OUT900 of the scan signal generating unit 301. In other words, the compensation circuit CC1 corresponds to the output channel OUT1, the compensation circuit CC2 corresponds to the output channel OUT2, and likewise for other compensation circuits.
More specifically, FIG. 4 is a circuit diagram of a compensation circuit CCn (n=1-900) in accordance with the first embodiment of the invention. Referring to FIGS. 2-4 together, the compensation circuit CCn (n=1-900) includes a buffer Buf, resistors R1-R3, and switches SW1-SW3. An input terminal of the buffer Buf is used for receiving a corresponding scan signal Sn (n=1-900). A first terminal of the resistor R1 is coupled to an output terminal of the buffer Buf A first terminal of the resistor R2 is coupled to a second terminal of the resistor R1. A first terminal of the resistor R3 is coupled to a second terminal of the resistor R2, and a second terminal of the resistor R3 is coupled to a corresponding scan line Gn (n=1-900) in the display panel 201.
A first terminal of the switch SW1 is coupled to the first terminal of the resistor R1, a second terminal of the switch SW1 is coupled to the second terminal of the resistor R1, and a control terminal of the switch SW1 is used for receiving an external configuration signal En1 (n=1-900). A first terminal of the switch SW2 is coupled to the first terminal of the resistor R1, a second terminal of the switch SW2 is coupled to the second terminal of the resistor R2, and a control terminal of the switch SW2 is used for receiving an external configuration signal En2 (n=1-900). A first terminal of the switch SW3 is coupled to the first terminal of the resistor R1, a second terminal of the switch SW3 is coupled to the second terminal of the resistor R3, and a control terminal of the switch SW3 is used for receiving an external configuration signal En3 (n=1-900).
In the first embodiment, a resistance of each of the resistors R1-R3 may be set according to an actual design requirement. However, for ease of description, the resistance value of each of the resistors R1-R3 is exemplarily assumed to be 0.55Ω, although the invention should be construed as limited thereto. According to a logic state (see Table 1 below) of the external configuration signals En1-En3, the compensation circuit CCn may provide different resistances to the corresponding output channel OUTn (e.g., compensating the total resistance of the output channel OUTn).












TABLE 1










Compensation



En1
En2
En3
Resistance









0
0
0
1.5 Ω



1
0
0
  1 Ω



0
1
0
0.5 Ω



0
0
1
  0 Ω










According to Table 1 above, the compensation circuit CCn may provide 1.5Ω, 1Ω, 0.5Ω, or 0Ω of compensation resistance to the corresponding output channel OUTn. Consequently, after the total resistance of each of the output channels OUTn has been compensated by the corresponding compensation circuit CCn, the changes generated are presented in Table 2 below.












TABLE 2







Com-






pensation
Compensation
Compensation
Compensation



Resistance =
Resistance =
Resistance =
Resistance =



0 Ω
0.5 Ω
1 Ω
1.5 Ω




















OUT1
1020.01 Ω
1020.01 Ω
1020.01 Ω
1021.01 Ω


OUT2
1017.93 Ω
1018.92 Ω
1019.42 Ω
1019.92 Ω


OUT3
1015.84 Ω
1017.84 Ω
1018.84 Ω
1019.84 Ω


—
—
—
—
—


—
—
—
—
—


OUT255
 489.66 Ω
 743.66 Ω
 870.66 Ω
 997.66 Ω


—
—
—
—
—


—
—
—
—
—


OUT450
 82.59 Ω
 531.59 Ω
 756.09 Ω
 980.59 Ω


OUT451
  82.3 Ω
 531.30 Ω
 755.8 Ω
 980.3 Ω


—
—
—
—
—


OUT675
 550.2 Ω
 775.21 Ω
 887.71 Ω
1000.21 Ω


—
—
—
—
—


OUT898
 1014.9 Ω
1016.90 Ω
1017.90 Ω
1018.90 Ω


OUT899
 1017.3 Ω
1018.30 Ω
1018.80 Ω
1019.30 Ω


OUT900
 1021.2 Ω
1021.20 Ω
1021.20 Ω
1021.20 Ω









As shown in Table 2 above, when the total resistances of the output channels OUTn are not compensated by the corresponding compensation circuits CCn, a largest variation of the total resistances is up to several hundred ohms (e.g., 1021.2Ω−82.59Ω), but once the total resistances of the output channel OUTn are compensated by the corresponding compensation circuits CCn, the variation is gradually reduced as the compensation resistance increases (e.g., 0 Ω→0.5 Ω→1 Ω→1.5Ω, or even higher), it can be clearly seen as illustrated by curves 501-504 in FIG. 5 according to the numerical values in Table 2.
Therefore, before product shipment of the liquid crystal display 200 according to the first embodiment, merely the logic states of the external configuration signals En1-En3 received by each of the compensation circuits CCn need to be set. Accordingly, the layout resistance variation between each of the output channels OUTn of the gate driver 203 and the display panel 201 may be drastically reduced (e.g., may only be tens of ohms left). Consequently, based on each of the output channels OUTn of the gate driver 203 having a same loading on the display panel 201, the scan signal Sn outputted by each of the output channels OUTn of the gate driver 203 is substantially the same or similar.
Accordingly, in condition of the display panel 201 is the normally black/white type, when the gate driver 203 outputs the same or similar scan signals S1-S900 through all the output channels OUT1-OUT900 to the display panel 201 to turn on all the scan lines G1-G900 (e.g., all the pixels), the display panel 201 can display the ideal all black/white image, and the “multi-band phenomenon” depicted in the description of the related arts is not generated. Therefore, the compensation unit 303 according to the first embodiment not only lowers the possibility of the “multi-band phenomenon” from occurring on the display panel 201, but the quality of images displayed by the display panel 201 may also be enhanced.
The Second Embodiment
FIG. 6 is a schematic view of a liquid crystal display 600 in accordance with a second embodiment of the invention. FIG. 7 is a schematic view of a gate driver 603 in accordance with the second embodiment of the invention. Referring to FIGS. 2-3 and 6-7 together, a difference between the liquid crystal displays 200 and 600 is in the dissimilar structures of the compensation units 303 and 703 in the gate drivers 203 and 603, although the gate driver 603 achieves similar technical effects of the gate driver 203.
In the second embodiment, a compensation unit 703 includes two sub-compensation units SCU1 and SCU2. The sub-compensation unit SCU1 is coupled to a portion of the output channels of the scan signal generating unit 301, for example the output channels OUT1-OUT450. The sub-compensation unit SCU2 is coupled to a remaining portion of the output channels of the scan signal generating unit 301, that is the output channels OUT451-OUT900.
More specifically, FIGS. 8 and 9 respectively illustrate schematic views of the sub-compensation units SCU1 and SCU2 in accordance with the second embodiment of the invention. Referring to FIGS. 8 and 9 together, the sub-compensation unit SCU1 includes a line resistance LR1 and a plurality of compensation circuits CC1-CC450 equivalent in quantity to the output channels OUT1-OUT450. The sub-compensation unit SCU2 includes a line resistance LR2 and a plurality of compensation circuits CC451-CC900 equivalent in quantity to the output channels OUT451-OUT900. Moreover, the resistance values of the line resistances LR1 and LR2 are substantially the same, which may be determined according to an actual design need.
In the second embodiment, the compensation circuits CC1-CC450 are respectively corresponding to the output channels OUT1-OUT450 of the scan signal generating unit 301. In other words, the compensation circuit CC1 corresponds to the output channel OUT1, the compensation circuit CC2 corresponds to the output channel OUT2, and likewise for other compensation circuits. Similarly, the compensation circuits CC451-CC900 are respectively corresponding to the output channels OUT451-OUT900 of the scan signal generating unit 301. In other words, the compensation circuit CC451 corresponds to the output channel OUT451, the compensation circuit CC452 corresponds to the output channel OUT452, and likewise for other compensation circuits.
Moreover, in the second embodiment, each of the compensation circuits CCn (n=1-900) includes a buffer Buf, a NOT gate NG, and switches SW1-SW3.
First, exemplarily taking the compensation circuits CCn (n=1-450) of the sub-compensation unit SCU1 as an example, an input terminal of the buffer Buf is used for receiving a corresponding scan signal Sn (n=1-450). An input terminal of the NOT gate NG is coupled to the input terminal of the buffer Buf. A first terminal of the switch SW1 is coupled to an output terminal of the buffer Buf, a second terminal of the switch SW1 is coupled to a corresponding scan line Gn (n=1-450) in the display panel 201, and a control terminal of the switch SW1 is coupled to an output terminal of the NOT gate NG. A first terminal of the switch SW2 is coupled to the output terminal of the buffer Buf, a second terminal of the switch SW2 is coupled to the line resistance LR1, and a control terminal of the switch SW2 is coupled to the input terminal of the NOT gate NG. A first terminal of the switch SW3 is coupled to the second terminal of the switch SW1, a second terminal of the switch SW3 is coupled to the line resistance LR1, and a control terminal of the switch SW3 is coupled to the input terminal of the NOT gate NG.
Furthermore, exemplarily taking the compensation circuits CCn (n=451-900) of the sub-compensation unit SCU2 as an example, the input terminal of the buffer Buf is used for receiving a corresponding scan signal Sn (n=451-900). The input terminal of the NOT gate NG is coupled to the input terminal of the buffer Buf. The first tell signal of the switch SW1 is coupled to the output terminal of the buffer Buf, the second terminal of the switch SW1 is coupled to a corresponding scan line Gn (n=451-900) in the display panel 201, and the control terminal of the switch SW1 is coupled to the output terminal of the NOT gate NG. The first terminal of the switch SW2 is coupled to the output terminal of the buffer Buf, the second terminal of the switch SW2 is coupled to the line resistance LR2, and the control terminal of the switch SW2 is coupled to the input terminal of the NOT gate NG. The first terminal of the switch SW3 is coupled to the second terminal of the switch SW1, the second terminal of the switch SW3 is coupled to the line resistance LR2, and the control terminal of the switch SW3 is coupled to the input terminal of the NOT gate NG.
According to the description disclosed in the first embodiment above, when the total resistances of the output channels OUTn are not compensated by the corresponding compensation circuits CCn, the largest variation of the total resistances is up to several hundred ohms. However, once the total resistances of the output channel OUTn are compensated by the corresponding compensation circuits CCn, the variation is gradually reduced as the compensation resistance increases.
Accordingly, when the scan signal generating unit 301 outputs the scan signal S1 through the output channel OUT′, since the logic state (logic high) of the input terminal of the NOT gate NG of the compensation circuit CC1 is dissimilar to the logic state (logic low) of the output terminal thereof, the switch SW1 is turned off, whereas the switches SW2 and SW3 are turned on. Consequently, the scan signal S1 outputted by the output channel OUT1 is first buffered by the buffer Buf, then subsequently transmitted to the scan line G1 of the display panel 201 through the switch SW2, the line resistance LR1, and the switch SW3, thereby turning on the scan line G1 until the scan signal generating unit 301 outputs the scan signal S2 through the output channel OUT2.
Similarly, when the scan signal generating unit 301 outputs the scan signal S2 through the output channel OUT2, since the logic state (logic high) of the input terminal of the NOT gate NG of the compensation circuit CC2 is dissimilar to the logic state (logic low) of the output terminal thereof, the switch SW1 is turned off, whereas the switches SW2 and SW3 are turned on. Consequently, the scan signal S2 outputted by the output channel OUT2 is first buffered by the buffer Buf, then subsequently transmitted to the scan line G2 of the display panel 201 through the switch SW2, the line resistance LR1, and the switch SW3, thereby turning on the scan line G2 until the scan signal generating unit 301 outputs the scan signal S3 through the output channel OUT3.
Likewise, in a similar way, when the scan signal generating unit 301 outputs the scan signal S450 through the output channel OUT450, since the logic state (logic high) of the input terminal of the NOT gate NG of the compensation circuit CC450 is dissimilar to the logic state (logic low) of the output terminal thereof, the switch SW1 is turned off, whereas the switches SW2 and SW3 are turned on. Consequently, the scan signal S450 outputted by the output channel OUT450 is first buffered by the buffer Buf, then subsequently transmitted to the scan line G450 of the display panel 201 through the switch SW2, the line resistance LR1, and the switch SW3, thereby turning on the scan line G450 until the scan signal generating unit 301 outputs the scan signal S451 through the output channel OUT451.
According to the foregoing description, as a variable n increases in value, a transmission path length on the line resistance LR1 of the scan signal Sn (n=1-450) outputted by the output channel OUTn (n=1-450) increases. Therefore, for the output channels OUTn (n=1-450) ordered from small to large by the value of the variable n, the compensation resistance provided by the corresponding compensation circuit (n=1-450) is also ordered from low to high. Consequently, after the total resistance of each of the output channels OUTn (n=1-450) has been compensated by the corresponding compensation circuit CCn (n=1-450), the changes presented in Table 2 above are also generated.
On the other hand, when the scan signal generating unit 301 outputs the scan signal S451 through the output channel OUT451, since the logic state (logic high) of the input terminal of the NOT gate NG of the compensation circuit CC451 is dissimilar to the logic state (logic low) of the output terminal thereof, the switch SW1 is turned off, whereas the switches SW2 and SW3 are turned on. Consequently, the scan signal S451 outputted by the output channel OUT451 is first buffered by the buffer Buf, then subsequently transmitted to the scan line G451 of the display panel 201 through the switch SW2, the line resistance LR2, and the switch SW3, thereby turning on the scan line G451 until the scan signal generating unit 301 outputs the scan signal S452 through the output channel OUT452.
Similarly, when the scan signal generating unit 301 outputs the scan signal S452 through the output channel OUT452, since the logic state (logic high) of the input terminal of the NOT gate NG of the compensation circuit CC452 is dissimilar to the logic state (logic low) of the output terminal thereof, the switch SW1 is turned off, whereas the switches SW2 and SW3 are turned on. Consequently, the scan signal S452 outputted by the output channel OUT452 is first buffered by the buffer Buf, then subsequently transmitted to the scan line G452 of the display panel 201 through the switch SW2, the line resistance LR2, and the switch SW3, thereby turning on the scan line G452 until the scan signal generating unit 301 outputs the scan signal S453 through the output channel OUT453.
Likewise, in a similar way, when the scan signal generating unit 301 outputs the scan signal S900 through the output channel OUT900, since the logic state (logic high) of the input terminal of the NOT gate NG of the compensation circuit CC450 is dissimilar to the logic state (logic low) of the output terminal thereof, the switch SW1 is turned off, whereas the switches SW2 and SW3 are turned on. Consequently, the scan signal S900 outputted by the output channel OUT900 is first buffered by the buffer Buf, then subsequently transmitted to the scan line G900 of the display panel 201 through the switch SW2, the line resistance LR2, and the switch SW3, thereby turning on the scan line G900 until the scan signal generating unit 301 again outputs the scan signal S1 through the output channel OUT1 (e.g., a next frame period).
According to the foregoing description, as the variable n increases in value, the transmission path length on the line resistance LR2 of the scan signal Sn (n=451-899) outputted by the output channel OUTn (n=451-900) decreases. Therefore, for the output channels OUTn (n=451-900) ordered from small to large by the value (e.g., 451-900) of the variable n, the compensation resistance provided by the corresponding compensation circuit CCn (n=451-900) is conversely ordered from high to low. Consequently, after the total resistance of each of the output channels OUTn (n=451-900) has been compensated by the corresponding compensation circuit CCn (n=451-900), the changes presented in Table 2 above are also generated.
It should be noted that, during a mass production process of the liquid crystal display 600 according to the second embodiment, the liquid crystal display 600 merely needs the resistance values of the line resistances LR1 and LR2 determined according to an actual design requirement. Therefore, similar to the first embodiment, the layout resistance variation between each of the output channels OUTn of the gate driver 603 and the display panel 201 may be drastically reduced (e.g., may only be tens of ohms left). Moreover, compared to the first embodiment, the implementation of the gate driver 603 according to the second embodiment may be easier than the implementation of the gate driver 203 according to the first embodiment.
The Third Embodiment
FIG. 10 is a schematic view of a liquid crystal display 1000 in accordance with a third embodiment of the invention. FIG. 11 is a schematic view of a gate driver 1003 in accordance with the third embodiment of the invention. Referring to FIGS. 6-7 and 10-11 together, a difference between the liquid crystal displays 600 and 1000 is in the dissimilar structures of the compensation units 703 and 1103 in the gate drivers 603 and 1003, although the gate driver 1003 achieves similar technical effects of the gate driver 603.
More specifically, FIGS. 12 and 13 respectively illustrate schematic views of the sub-compensation units SCU1 and SCU2 in accordance with the third embodiment of the invention. Referring to FIGS. 12 and 13 together, the sub-compensation unit SCU1 includes line resistances LR1 and LR2, and a plurality of compensation circuits CC1-CC450 equivalent in quantity to the output channels OUT1-OUT450. The sub-compensation unit SCU2 includes line resistances LR3 and LR4, and a plurality of compensation circuits CC451-CC900 equivalent in quantity to the output channels OUT451-OUT900. The resistance values of the line resistances LR1 and LR2 are substantially different, whereas the resistance values of the line resistances LR1 and LR3 are substantially the same. Moreover, the resistance values of the line resistances LR3 and LR4 are substantially different, whereas the resistance values of the line resistances LR2 and LR4 are substantially the same. Furthermore, the line resistance values of the line resistances LR1-LR4 may be determined according to an actual design need.
In the third embodiment, the compensation circuits CC1-CC450 are respectively corresponding to the output channels OUT1-OUT450 of the scan signal generating unit 301. In other words, the compensation circuit CC1 corresponds to the output channel OUT1, the compensation circuit CC2 corresponds to the output channel OUT2, and likewise for other compensation circuits. Similarly, the compensation circuits CC451-CC900 are respectively corresponding to the output channels OUT451-OUT900 of the scan signal generating unit 301. In other words, the compensation circuit CC451 corresponds to the output channel OUT451, the compensation circuit CC452 corresponds to the output channel OUT452, and likewise for other compensation circuits.
Moreover, in the third embodiment, each of the compensation circuits CCn (n=1-900) includes a buffer Buf, NOT gates NG1 and NG2, tri-state gates TG1 and TG2, and switches SW1-SW5.
First, exemplarily taking the compensation circuits CCn (n=1-450) of the sub-compensation unit SCU1 as an example, an input terminal of the buffer Buf is used for receiving a corresponding scan signal Sn (n=1-450). An input terminal of the NOT gate NG1 is coupled to the input terminal of the buffer Buf. A first terminal of the switch SW1 is coupled to an output terminal of the buffer Buf, a second terminal of the switch SW1 is coupled to a corresponding scan line Gn (n=1-450) in the display panel 201, and a control terminal of the switch SW1 is coupled to an output terminal of the NOT gate NG1. A first terminal of the switch SW2 is coupled to the output terminal of the buffer Buf, and a second terminal of the switch SW2 is coupled to the line resistance LR1. A first terminal of the switch SW3 is coupled to the second terminal of the switch SW1, and a second terminal of the switch SW3 is coupled to the line resistance LR1. A first terminal of the switch SW4 is coupled to the output terminal of the buffer Buf, and a second terminal of the switch SW4 is coupled to the line resistance LR2. A first terminal of the switch SW5 is coupled to the second terminal of the switch SW1, and a second terminal of the switch SW5 is coupled to the line resistance LR2. An input terminal of the NOT gate NG2 is used for receiving an external configuration signal En (n=1-450). An input terminal of the tri-state gate TG1 is coupled to the input terminal of the buffer Buf, an output terminal of the tri-state gate TG1 is coupled to the control terminals of the switches SW2 and SW3, and an enable control terminal of the tri-state gate TG1 is coupled to an output terminal of the NOT gate NG2. An input terminal of the tri-state gate TG2 is coupled to the input terminal of the buffer Buf, an output terminal of the tri-state gate TG2 is coupled to the control terminals of the switches SW4 and SW5, and an enable control terminal of the tri-state gate TG2 is coupled to the input terminal of the NOT gate NG2.
Moreover, exemplarily taking the compensation circuits CCn (n=451-900) of the sub-compensation unit SCU2 as an example, the input terminal of the buffer Buf is used for receiving a corresponding scan signal Sn (n=451-900). The input terminal of the NOT gate NG1 is coupled to the input terminal of the buffer Buf. The first terminal of the switch SW1 is coupled to the output terminal of the buffer Buf, the second terminal of the switch SW1 is coupled to a corresponding scan line Gn (n=451-900) in the display panel 201, and the control terminal of the switch SW1 is coupled to the output terminal of the NOT gate NG1. The first terminal of the switch SW2 is coupled to the output terminal of the buffer Buf, and the second terminal of the switch SW2 is coupled to the line resistance LR3. The first terminal of the switch SW3 is coupled to the second terminal of the switch SW1, and the second terminal of the switch SW3 is coupled to the line resistance LR3. The first terminal of the switch SW4 is coupled to the output terminal of the buffer Buf, and the second terminal of the switch SW4 is coupled to the line resistance LR4. The first terminal of the switch SW5 is coupled to the second terminal of the switch SW1, and the second terminal of the switch SW5 is coupled to the line resistance LR4. The input terminal of the NOT gate NG2 is used for receiving an external configuration signal En (n=451-900). The input terminal of the tri-state gate TG1 is coupled to the input terminal of the buffer Buf, the output terminal of the tri-state gate TG1 is coupled to the control terminals of the switches SW2 and SW3, and the enable control terminal of the tri-state gate TG1 is coupled to the output terminal of the NOT gate NG2. The input terminal of the tri-state gate TG2 is coupled to the input terminal of the buffer Buf, the output terminal of the tri-state gate TG2 is coupled to the control terminals of the switches SW4 and SW5, and the enable control terminal of the tri-state gate TG2 is coupled to the input terminal of the NOT gate NG2.
According to the foregoing description, two line resistances of different resistance values are in each of the sub-compensation units SCU1 and SCU2 according to the third embodiment. In other words, the sub-compensation unit SCU1 has line resistances LR1 and LR2 of two different resistance values inside, whereas the sub-compensation unit SCU2 has line resistances LR3 and LR4 of two different resistance values inside. Accordingly, in the third embodiment, by merely adjusting a logic state of the external configuration signal En (n=1-900), the enabling of the tri-state gates TG1 and TG2 is controlled through the NOT gate NG2, such that a transmission path traveled by the scan signal Sn (n=1-900) can reflect the logic state of the external configuration signal En (n=1-900), and thereby the scan signal Sn (n=1-900) is transmitted to the corresponding scan line Gn (n=1-900) in the display panel 201.
For example, when the logic state of the external configuration signal E1 of the compensation circuit CC1 is logic high, then the tri-state gate TG1 is disabled, whereas the tri-state gate TG2 is enabled. Consequently, when the scan signal generating unit 301 outputs the scan signal S1 through the output channel OUT1, since the logic state (logic high) of the input terminal of the NOT gate NG1 of the compensation circuit CC1 is dissimilar to the logic state (logic low) of the output terminal thereof, the switches SW1-SW3 are turned off, whereas the switches SW4 and SW5 are turned on. Accordingly, the scan signal S1 outputted by the output channel OUT1 is first buffered by the buffer Buf, then subsequently transmitted to the scan line G1 of the display panel 201 through the switch SW4, the line resistance LR2, and the switch SW5, thereby turning on the scan line G1 until the scan signal generating unit 301 outputs the scan signal S2 through the output channel OUT2.
On the other hand, when the logic state of the external configuration signal E1 of the compensation circuit CC1 is logic low, then the tri-state gate TG1 is enabled, whereas the tri-state gate TG2 is disabled. Consequently, when the scan signal generating unit 301 outputs the scan signal S1 through the output channel OUT1, since the logic state (logic high) of the input terminal of the NOT gate NG1 of the compensation circuit CC1 is dissimilar to the logic state (logic low) of the output terminal thereof, the switches SW1, SW4, and SW5 are turned off, whereas the switches SW2 and SW3 are turned on. Therefore, the scan signal S1 outputted by the output channel OUT1 is first buffered by the buffer Buf, then subsequently transmitted to the scan line G1 of the display panel 201 through the switch SW2, the line resistance LR1, and the switch SW3, thereby turning on the scan line G1 until the scan signal generating unit 301 outputs the scan signal S2 through the output channel OUT2. Since the detailed operation of the other compensation circuits CCn (n=2-450) in the sub-compensation unit SCU1 may be derived from the above description, further explanation thereof is omitted hereafter.
Similarly, when the logic state of the external configuration signal E900 of the compensation circuit CC900 is logic high, then the tri-state gate TG1 is disabled, whereas the tri-state gate TG2 is enabled. Consequently, when the scan signal generating unit 301 outputs the scan signal S900 through the output channel OUT900, since the logic state (logic high) of the input terminal of the NOT gate NG1 of the compensation circuit CC900 is dissimilar to the logic state (logic low) of the output terminal thereof, the switches SW1-SW3 are turned off, whereas the switches SW4 and SW5 are turned on. Therefore, the scan signal S900 outputted by the output channel OUT900 is first buffered by the buffer Buf, then subsequently transmitted to the scan line G900 of the display panel 201 through the switch SW4, the line resistance LR4, and the switch SW5, thereby turning on the scan line G900 until the scan signal generating unit 301 again outputs the scan signal S1 through the output channel OUT1 (e.g., a next frame period).
On the other hand, when the logic state of the external configuration signal E900 of the compensation circuit CC900 is logic low, then the tri-state gate TG1 is enabled, whereas the tri-state gate TG2 is disabled. Consequently, when the scan signal generating unit 301 outputs the scan signal S900 through the output channel OUT900, since the logic state (logic high) of the input terminal of the NOT gate NG1 of the compensation circuit CC1 is dissimilar to the logic state (logic low) of the output terminal thereof, the switches SW1, SW4, and SW5 are turned off, whereas the switches SW2 and SW3 are turned on. Therefore, the scan signal S900 outputted by the output channel OUT900 is first buffered by the buffer Buf, then subsequently transmitted to the scan line G900 of the display panel 201 through the switch SW2, the line resistance LR3, and the switch SW3, thereby turning on the scan line G900 until the scan signal generating unit 301 again outputs the scan signal S1 through the output channel OUT) (e.g., a next frame period). Since the detailed operation of the other compensation circuits CCn (n=451-899) in the sub-compensation unit SCU2 may be derived from the above description, further explanation thereof is omitted hereafter.
Accordingly, during a mass production process and before product shipment of the liquid crystal display 1000 according to the third embodiment, the liquid crystal display 1000 merely needs the resistance values of the line resistances LR1-LR4 determined according to an actual design requirement, and the logic state of the external configuration signal En received by each of the compensation circuits set. Therefore, similar to the first and second embodiments, the layout resistance variation between each of the output channels OUTn of the gate driver 1003 and the display panel 201 may be drastically reduced (e.g., may only be tens of ohms left). Moreover, compared to the second embodiment, the gate driver 1003 according to the third embodiment may have more configurable design options than the gate driver 603 according to the second embodiment.
To summarize the foregoing description, each of the switches and the control signals thereof (e.g., at least an external configuration signal and/or the scan signal) in the compensation units 303, 703, and 1103 of the embodiments above may be viewed as a switching means. Moreover, the resistors and line resistances in the compensation units 303, 703, and 1103 of the embodiments above may be viewed as a resistance-supply means. That is to say, as long as similar switching means and resistance-supply means are combined and integrated in a gate driver, such that the total resistance of each of the output channels is compensated, then these mechanisms/means/techniques falls within the scope of the invention.
In light of the foregoing, by employing the switching means and the resistance-supply means therein, the gate driver according to an embodiment of the invention lowers the layout resistance between each of the output channels of the gate driver and the display panel. Accordingly, the variation of the scan signal outputted by each of the output channels of the gate driver is reduced, and the possibility of the “multi-band phenomenon” occurring on the display panel in the description of the related art is lowered, thereby enhancing the quality of images displayed by the display panel.
Although the invention has been described with reference to the above embodiments, it will be apparent to one of the ordinary skill in the art that modifications to the described embodiment may be made without departing from the spirit of the invention. Accordingly, the scope of the invention will be defined by the attached claims not by the above detailed descriptions.

## Claims

1. A gate driver, comprising:
a scan signal generating unit having a plurality of output channels, used for sequentially outputting a scan signal through the output channels according to a basic clock and a start pulse; and
a compensation unit coupled to the output channels, used for compensating a total resistance of each of the outputting channels, and sequentially receiving and transmitting the scan signal to a display panel,
wherein the compensation unit comprises:
a plurality of compensation circuits respectively corresponding to the output channels, each of the compensation circuits comprising:
a buffer having an input terminal used for receiving the corresponding scan signal;
a first resistor having a first terminal coupled to an output terminal of the buffer;
a second resistor having a first terminal coupled to a second terminal of the first resistor;
a third resistor having a first terminal coupled to a second terminal of the second resistor, and a second terminal coupled to the display panel;
a first switch having a first terminal coupled to the first terminal of the first resistor, a second terminal coupled to the second terminal of the first resistor, and a control terminal used for receiving a first external configuration signal;
a second switch having a first terminal coupled to the first terminal of the first resistor, a second terminal coupled to the second terminal of the second resistor, and a control terminal used for receiving a second external configuration signal; and
a third switch having a first terminal coupled to the first terminal of the first resistor, a second terminal coupled to the second terminal of the third resistor, and a control terminal used for receiving a third external configuration signal.

2. The gate driver as claimed in claim 1, wherein a wiring distance from each of the output channels to the display panel is different.

3. The gate driver as claimed in claim 2, wherein a layout resistance between each of the output channels and the display panel is different.

4. A liquid crystal display having the gate driver as claimed in claim 1.

5. A gate driver, comprising:
a scan signal generating unit having a plurality of output channels, used for sequentially outputting a scan signal through the output channels according to a basic clock and a start pulse; and
a compensation unit coupled to the output channels and comprising a switching means and a resistance-supply means, the compensation unit being used for respectively providing a compensation resistance to compensate a total resistance of each of the output channels through the switching means and the resistance-supply means according to at least an external configuration signal and/or the scan signal, and sequentially receiving and transmitting the scan signal to a display panel,
wherein the compensation unit comprises:
a plurality of compensation circuits respectively corresponding to the output channels, each of the compensation circuits comprising:
a buffer having an input terminal used for receiving the corresponding scan signal;
a first resistor having a first terminal coupled to an output terminal of the buffer;
a second resistor having a first terminal coupled to a second terminal of the first resistor;
a third resistor having a first terminal coupled to a second terminal of the second resistor, and a second terminal coupled to the display panel;
a first switch having a first terminal coupled to the first terminal of the first resistor, a second terminal coupled to the second terminal of the first resistor, and a control terminal used for receiving a first external configuration signal;
a second switch having a first terminal coupled to the first terminal of the first resistor, a second terminal coupled to the second terminal of the second resistor, and a control terminal used for receiving a second external configuration signal; and
a third switch having a first terminal coupled to the first terminal of the first resistor, a second terminal coupled to the second terminal of the third resistor, and a control terminal used for receiving a third external configuration signal.