JP2004126199A - Display circuit structure for liquid crystal display - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a display circuit structure for a liquid crystal display of which the power consumption is suppressed. <P>SOLUTION: Each display element is provided with two pixel capacitors 206, 208, two maintenance capacitors 210, 212 and two switching transistors 202, 204. The pixel capacitor 206, the maintenance capacitor 210 and the switching transistor 202 are used for control of a reflection region and the pixel capacitor 208, the maintenance capacitor 212 and the switching transistor 204 are used for control of a transmission region. Breakage inside the reflection region has no effect on an operation in the transmission region and vice versa. The voltage applied to the pixel capacitors 206, 208 is maintained by the maintenance capacitors 210, 212 and it is not necessary to heighten the capacitor value and the charging current is lowered. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a display circuit structure of a liquid crystal display (LCD), and more particularly, to a display circuit structure of a liquid crystal display (LCD) having reflective and transmissive regions.
[0002]
[Prior art]
Liquid crystal displays (LCDs) have long been widely used in electronic products such as digital watches and calculators. In addition, with advances in manufacturing and design techniques, thin film transistor liquid crystal displays (TFT-LCDs) have been used in conventional displays, including the introduction into portable computers, PDAs (Personal Digital Assistants) and color televisions. CRTs were gradually replaced by them. The demand for TFT-LCDs tends to be large.
[0003]
A typical liquid crystal display circuit having both reflective and transmissive regions is shown generally as FIG. 1A. LCD matrix display devices generally consist of an LCD display array 200 that includes a plurality of display elements 50. As shown in an enlarged view in FIG. 1B, the plurality of display elements 50 are arranged in a matrix of rows and columns. Switching devices (not shown) are coupled to the display elements 50 and control the application of video signals to them. As shown in FIG. 1B, each display element 50 functions as one switching device including a pixel capacitor 106 and a maintenance capacitor 108 driven by the switching transistor 104.
[0004]
FIG. 1B is an enlarged view of a circuit of a liquid crystal display having both a reflection region and a transmission region. The switching transistor 104 is usually a thin film transistor (TFT) deposited on a transparent substrate such as glass. The switching transistor 104 is deposited on the same side of the glass as the switching transistor of the display matrix, and its source / drain electrodes are connected to the capacitor electrodes of the pixel capacitor 106 and the maintenance capacitor 108, respectively. The source / drain electrodes of the switching transistor 104 are connected to a column data driver (not shown) via a video data line 100 to which a video signal is applied. The gate electrode of the switching transistor 104 is connected to a row selection driver (not shown) via the scan line 102, and a scan signal for turning on the switching transistor 104 is applied.
[0005]
When the scan line 102 is scanned according to the scan signal, all the switching transistors 104 in the predetermined scan line 102 are turned on. At the same time, the video signal is supplied to the video data line in synchronization with the selected scan line 102. When the switching transistor 104 in a given scan line 102 is selected by the scan signal, the video signal supplied to the switching transistor 104 causes the pixel capacitor 106 and the maintenance capacitor 108 to change the voltage value corresponding to the video signal on the video data line Charge up to. That is, each pixel capacitor 106 with an electrode on the opposite side of the matrix display operates as a capacitor. When the signal on the selected scan line 102 is depleted, the charge in the pixel capacitor 106 is held until the next iteration, that is, until the scan signal again selects that scan line and a new voltage is stored there. You. Thus, a picture is displayed on the matrix display by the electric charge stored in the pixel capacitor 106.
[0006]
However, in the case of a liquid crystal display having both reflective and transmissive regions, the pixel capacitor 106 crosses both regions. If the switching transistor 104 or the pixel capacitor 106 is broken, the display element 50 will not operate thereafter.
[0007]
On the other hand, the main function of the maintenance capacitor 108 is to maintain the continuity of the voltage value applied to the pixel capacitor 106. That is, before the data stored in the pixel capacitor 106 is refreshed, the voltage applied to the pixel capacitor 106 is maintained by the maintenance capacitor 108. However, when referring to a conventional liquid crystal display having both reflective and transmissive regions, the maintenance capacitor 108 simultaneously maintains the voltage applied to the reflective and transmissive regions because the pixel capacitor 106 crosses both regions. Is required. The capacitor value of the maintenance capacitor 108 needs to be increased in order to prevent charge leakage that causes a sharp drop in the applied voltage. As a result, increasing the capacitor value of the maintenance capacitor 108 requires a larger current to perform a data refresh process and allow the refresh process to be completed simultaneously. However, this increases the difficulty of circuit design.
[0008]
[Problems to be solved by the invention]
According to the above description, for a conventional liquid crystal display having both reflective and transmissive regions, each display element 50 has a pixel capacitor 106 and a maintenance capacitor 108, both driven by one switching transistor 104. Thus, if one of them breaks, the entire display element will not work.
[0009]
On the other hand, the pixel capacitor 106 crosses both regions. Therefore, the maintenance capacitor 108 is required to simultaneously maintain the voltages applied to the reflection and transmission regions. The capacitor value of the maintenance capacitor needs to be increased to prevent charge leakage that causes a sharp drop in the applied voltage. Increasing the capacitor value of the maintenance capacitor 108 requires a larger current to perform the data refresh process and allow the refresh process to be completed simultaneously. This increases the difficulty of circuit design. Therefore, the present invention provides a circuit structure that solves these problems.
[0010]
That is, a main object of the present invention is to provide a display circuit structure of a liquid crystal display with reduced power consumption.
Another object of the present invention is to provide a display circuit structure of a liquid crystal display in which a drive current in a refresh process is suppressed.
[0011]
It is yet another object of the present invention when each display element has a plurality of pixel capacitors, a plurality of maintenance capacitors, and a plurality of switching transistors, wherein the capacitors and transistors are separated from each other and one capacitor or transistor is broken Another object of the present invention is to provide a display circuit structure of a liquid crystal display which prevents the entire display element from operating.
[0012]
[Means for Solving the Problems]
The present invention for solving the above-mentioned problems provides a circuit structure of a liquid crystal display having both reflective and transmissive regions. According to the circuit structure of the present invention, each display element includes a plurality of pixel capacitors, a plurality of maintenance capacitors, and a plurality of switching transistors. The reflective and transmissive regions each have a pixel capacitor, a maintenance capacitor, and a switching transistor. As a result, the two regions are separated from each other. That is, damage in the reflective area does not affect the operation of the transmissive area, and vice versa. Furthermore, according to the circuit structure of the present invention, since each maintenance capacitor only needs to maintain the voltage applied to the pixel capacitor in either the reflection or transmission region, it is not necessary to increase the capacitor value. As a result, the charging current can be reduced.
[0013]
Also, according to the circuit structure of the present invention, a scan line is used for controlling the two thin film transistors, and a video data line is used for transmitting a video signal to the pixel capacitor and the maintenance capacitor. When the thin film transistor is selected by the selection signal, the video signal stored therein charges the pixel capacitor and the maintenance capacitor. When there is no select signal, the charge in the pixel capacitor is held until the next iteration, that is, until the select signal next selects the scan line again and a new voltage is stored there. Thus, a picture is displayed on the matrix display by the electric charge stored in the pixel capacitor.
[0014]
BEST MODE FOR CARRYING OUT THE INVENTION
Without limiting the spirit and scope of the present invention, a preferred embodiment of the display circuit structure of a liquid crystal display (LCD) proposed in the present invention is illustrated. By accepting this embodiment, those skilled in the art can apply the circuit design of the present invention to any liquid crystal display and configure the display circuit structure. Not limited.
[0015]
Hereinafter, embodiments of the present invention will be described in detail.
FIG. 2 is a circuit diagram showing a display circuit structure 300 of the liquid crystal display according to the first embodiment of the present invention. The display circuit structure 300 is used for a thin film transistor liquid crystal display (TFT-LCD) having a reflection and transmission region. In this circuit structure, each display element comprises two pixel capacitors 206 and 208, two maintenance capacitors 210 and 212, and two switching transistors 202 and 204. Pixel capacitor 206, maintenance capacitor 210 and switching transistor 202 are used to control the reflective area in the thin film transistor liquid crystal display. Pixel capacitor 208, maintenance capacitor 212 and switching transistor 204 are used to control the transmissive area in the thin film transistor liquid crystal display.
[0016]
The gate electrodes of switching transistors 202 and 204 are both coupled to scan line 302. The scan line 302 is used to control on / off of the switching transistors 202 and 204. The source / drain electrodes of the switching transistor 202 are coupled to a video data line used for transmitting a video signal. Video data line 304 and scan line 302 operate simultaneously to select a display element from a display element array (not shown in this figure). The other source / drain electrode of switching transistor 202 is coupled to the electrodes of pixel capacitor 206 and maintenance capacitor 210, respectively, and further to the source / drain electrode of other switching transistor 204. The other source / drain electrodes of switching transistor 204 are coupled to the electrodes of pixel capacitor 208 and maintenance capacitor 212, respectively.
[0017]
In operation, a select signal is transmitted to scan line 302. That is, a high voltage is applied to the scan line 302 to turn on the switching transistors 202 and 204. At the same time, a video signal is transmitted from the video data line 304 to the source / drain electrodes of the switching transistor 202. Thereafter, the video signal is transmitted to the pixel capacitor 206 and the maintenance capacitor 210 via the channel of the switching transistor 202, and further transmitted to the pixel capacitor 208 and the maintenance capacitor 212 via the channel of the switching transistor 204. The video signal can charge pixel capacitors 206 and 208, and maintenance capacitors 210 and 212, respectively, to the corresponding voltage values applied to the video data lines to drive the liquid crystal in the reflective and transmissive regions.
[0018]
When there is no select signal in scan line 302, switching transistors 202 and 204 are turned off if another select signal has not yet been transmitted to scan line 302. However, charge is retained in pixel capacitors 206 and 208 and maintenance capacitors 210 and 212. Thus, the charge stored in the pixel capacitors 206 and 208 causes a picture to be displayed on the display.
[0019]
According to the above structure, each of the reflection and transmission regions has one pixel capacitor, one maintenance capacitor, and one switching transistor. As a result, the two regions are separated from each other. That is, damage in the reflective area does not affect the operation of the transmissive area, and vice versa. For example, if the pixel capacitor 206 breaks, only the reflective area of the display circuit structure 300 is affected. However, the transmissive area of the display circuit structure 300 operates without any trouble thereafter.
[0020]
Further, according to the circuit structure of the present embodiment, the voltages applied to the pixel capacitors 206 and 208 are maintained by the maintenance capacitors 210 and 212, respectively. Therefore, there is no need to increase the capacitor value. It is also possible to reduce the charging current. In other words, the circuit structure of the present embodiment uses two pixel capacitors and a maintenance capacitor to control the reflection and transmission regions, respectively, and uses only one pixel capacitor and the maintenance capacitor to control the reflection and transmission regions. Is different from the conventional structure. Therefore, the ratio of charge leakage in the structure of the present embodiment for a certain period of time is lower than that of the conventional structure. In other words, since each maintenance capacitor only needs to maintain the voltage applied to the pixel capacitor in either the reflection area or the transmission area, there is no need to increase the capacitor value. As a result, the charging current when the refresh process is performed is reduced.
[0021]
FIG. 3 is a circuit diagram showing a display circuit structure 400 of a liquid crystal display according to a second embodiment of the present invention. This display circuit structure 400 is also used in a thin film transistor liquid crystal display (TFT-LCD) having reflective and transmissive regions. In this circuit structure, each display element comprises two pixel capacitors 406 and 408, two maintenance capacitors 410 and 412, and two switching transistors 402 and 404. Pixel capacitor 406, maintenance capacitor 410, and switching transistor 402 are used to control the reflective area in the thin film transistor liquid crystal display. Pixel capacitor 408, maintenance capacitor 412 and switching transistor 404 are used to control the transmissive area in the thin film transistor liquid crystal display.
[0022]
The gate electrodes of switching transistors 402 and 404 are both coupled to scan line 302. The scan line 302 is used to control on / off of the switching transistors 402 and 404. The source / drain electrodes of the switching transistor 402 are coupled to a video data line used for transmitting a video signal. Video data line 304 and scan line 302 can operate simultaneously to select a display element from a display element array (not shown in this figure). The other source / drain electrode of switching transistor 402 is coupled to the electrodes of pixel capacitor 406 and maintenance capacitor 410, respectively. The source / drain electrodes of switching transistor 404 are coupled to the electrodes of pixel capacitor 408 and maintenance capacitor 412, respectively, and the other source / drain electrode of switching transistor 404 is coupled to video data line 304.
[0023]
During operation, a select signal is transmitted to scan line 302. That is, a high voltage is applied to the scan line 302, and the switching transistors 402 and 404 are turned on. At the same time, a video signal is transmitted from video data line 304 to the source / drain electrodes of switching transistors 402 and 404. Thereafter, the video signal is transmitted to the pixel capacitors 406 and 408 and the maintenance capacitors 410 and 412 via the channels of the switching transistors 402 and 404, respectively. The video signal charges pixel capacitors 406 and 408 and maintenance capacitors 410 and 412, respectively, to the corresponding voltage values applied to the video data lines, thereby driving the liquid crystal in the reflective and transmissive regions.
[0024]
When there is no select signal in scan line 302, switching transistors 402 and 404 are turned off if another select signal has not yet been transmitted to scan line 302. However, charge is retained in pixel capacitors 406 and 408 and maintenance capacitors 410 and 412. Thus, the charge stored in pixel capacitors 406 and 408 causes a picture to be displayed on the display.
[0025]
According to the above structure, each of the reflection and transmission regions has one pixel capacitor, one maintenance capacitor, and one switching transistor. As a result, the two regions are separated from each other. That is, damage in the reflective area does not affect the operation of the transmissive area, and vice versa. For example, if pixel capacitor 406 breaks, only the reflective area of display circuitry 400 is affected. However, the transmissive region of the display circuit structure 400 operates without any abnormalities thereafter.
[0026]
Further, according to the circuit structure of the present embodiment, the voltages applied to the pixel capacitors 406 and 408 are maintained by the maintenance capacitors 410 and 412, respectively. Therefore, there is no need to increase the capacitor value. It is also possible to reduce the charging current. In other words, the circuit structure of the present embodiment uses two pixel capacitors and a maintenance capacitor to control the reflection and transmission regions, respectively, and uses only one pixel capacitor and the maintenance capacitor to control the reflection and transmission regions. Is different from the conventional structure. Therefore, the ratio of charge leakage in the structure of the present embodiment for a certain period of time is lower than that of the conventional structure. In other words, since each maintenance capacitor only needs to maintain the voltage applied to the pixel capacitor in either the reflection area or the transmission area, there is no need to increase the capacitor value. As a result, it is possible to reduce the charging current when the refresh process is performed.
[0027]
As will be appreciated by those skilled in the art, the above preferred embodiments of the present invention are illustrative of the present invention rather than limiting of the present invention. They are intended to protect the appended claims and various modifications and similar arrangements included within the spirit thereof, the scope of which is intended to cover such modifications and similar arrangements. A broad interpretation shall be given.
[0028]
【The invention's effect】
The circuit structure of the present invention avoids the disadvantages of the conventional liquid crystal display circuit structure having a display element consisting of only one pixel capacitor, one maintenance capacitor and one switching transistor. While the conventional circuit structure would render the entire display element inoperative if one of these three devices were broken, the structure of the present invention provides a display element having multiple pixel capacitors, multiple maintenance capacitors and multiple switching transistors. , So that if one device breaks down, the other device can replace it and maintain overall display element operation.
The circuit structure of the present invention also avoids the drawbacks of conventional circuit designs where only one maintenance capacitor with a larger capacitor value is used to maintain the voltage applied to the reflective and transmissive regions.
[Brief description of the drawings]
FIG. 1A is a circuit diagram showing a display circuit structure of a conventional liquid crystal display, and FIG. 1B is an enlarged circuit diagram showing a display element of the display circuit structure of a conventional liquid crystal display.
FIG. 2 is a circuit diagram showing a display circuit structure of the liquid crystal display according to the first embodiment of the present invention.
FIG. 3 is a circuit diagram showing a display circuit structure of a liquid crystal display according to a second embodiment of the present invention.

Claims (16)

In a display circuit structure of a liquid crystal display having a reflection and transmission region,
A first data line and a second data line;
A plurality of transistors connected in series and coupled to the first data line, each having a gate electrode coupled to the second data line;
A plurality of capacitor pairs each having a pixel capacitor and a maintenance capacitor connected in parallel, each being coupled to a source / drain electrode of a corresponding one of the plurality of transistors connected in series;
A display circuit structure comprising: The display circuit structure of claim 1, wherein the second data line is used to control on / off of the plurality of transistors. The display circuit structure according to claim 1, wherein the plurality of capacitor pairs are charged when the plurality of transistors are turned on. In a display circuit structure of a liquid crystal display having a reflection and transmission region,
A first data line;
A second data line intersecting the first data line;
A first transistor having a source / drain electrode coupled to the first data line and a gate electrode coupled to the second data line;
A first pixel capacitor coupled to the first data line via a channel of the first transistor;
A first maintenance capacitor coupled to the first data line through a channel of the first transistor;
A second transistor coupled to the first data line via a channel of the first transistor, and a gate electrode coupled to the second data line;
A second pixel capacitor coupled to the first data line via channels of the first transistor and the second transistor;
A second maintenance capacitor coupled to the first data line via channels of the first transistor and the second transistor;
A display circuit structure comprising: The display circuit structure according to claim 4, wherein the second data line is used to control on / off of the first transistor and the second transistor. The method of claim 4, wherein the first pixel capacitor, the second pixel capacitor, the first maintenance capacitor, and the second maintenance capacitor are charged when the first transistor and the second transistor are turned on. The described display circuit structure. The first transistor, the first pixel capacitor, and the first maintenance capacitor are used to control a reflection area, and the second transistor, the second pixel capacitor, and the second maintenance capacitor are used to control a transmission area. The display circuit structure according to claim 4, wherein the display circuit structure is used for: The first transistor, the first pixel capacitor, and the first maintenance capacitor are used to control a transmission area, and the second transistor, the second pixel capacitor, and the second maintenance capacitor are used to control a reflection area. The display circuit structure according to claim 4, wherein the display circuit structure is used for: In a display circuit structure of a liquid crystal display having a reflection and transmission region,
A first data line and a second data line;
A plurality of transistors each having a source / drain electrode coupled to the first data line and a gate electrode coupled to the second data line;
A plurality of capacitor pairs each having a pixel capacitor and a maintenance capacitor connected in parallel, each being coupled to the first data line via a channel of a corresponding one of the plurality of transistors;
A display circuit structure comprising: The display circuit structure of claim 9, wherein the second data line is used to control on / off of the plurality of transistors. The display circuit structure according to claim 9, wherein the plurality of capacitor pairs are charged when the plurality of transistors are turned on. In a display circuit structure of a liquid crystal display having a reflection and transmission region,
A first data line;
A second data line intersecting the first data line;
A first transistor having a source / drain electrode coupled to the first data line and a gate electrode coupled to the second data line;
A first pixel capacitor coupled to the first data line via a channel of the first transistor;
A first maintenance capacitor coupled to the first data line through a channel of the first transistor;
A second transistor having a source / drain electrode coupled to the first data line and a gate electrode coupled to the second data line;
A second pixel capacitor coupled to the first data line via a channel of the second transistor;
A second maintenance capacitor coupled to the first data line through a channel of the second transistor;
A display circuit structure comprising: The display circuit structure of claim 12, wherein the second data line is used to control on / off of the first transistor and the second transistor. 13. The device of claim 12, wherein the first pixel capacitor, the second pixel capacitor, the first maintenance capacitor, and the second maintenance capacitor are charged when the first transistor and the second transistor are turned on. The described display circuit structure. The first transistor, the first pixel capacitor, and the first maintenance capacitor are used to control a reflection area, and the second transistor, the second pixel capacitor, and the second maintenance capacitor are used to control a transmission area. 13. The display circuit structure according to claim 12, wherein the display circuit structure is used for: The first transistor, the first pixel capacitor, and the first maintenance capacitor are used to control a transmission area, and the second transistor, the second pixel capacitor, and the second maintenance capacitor are used to control a reflection area. 13. The display circuit structure according to claim 12, wherein the display circuit structure is used for:

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