JP3504512B2 - Liquid crystal display - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device, and more particularly to a liquid crystal display device which applies a reference voltage having a predetermined polarity inversion period to display pixels to display a desired display pattern on a liquid crystal panel.

[0002]

2. Description of the Related Art In recent years, liquid crystal display devices have rapidly become popular as displays for various devices such as digital video cameras and telephones as well as office automation devices such as notebook computers. Liquid crystal display devices have a large screen and display quality (image quality),
Although it is still inferior to the display means such as CRT in terms of price,
Excellent features such as low power consumption, light weight, and space saving are attracting attention.

A conventional liquid crystal display device will be described with reference to FIGS. 9 and 10. As shown in FIG. 9, a conventional liquid crystal display device includes a liquid crystal panel 1 having liquid crystal pixels (display pixels) arranged in a matrix at intersections of a plurality of data lines 2a and gate lines 3a, and a liquid crystal panel. 1 is provided in the vertical (vertical) direction and is provided in the horizontal (horizontal) direction of the liquid crystal panel 1 with the data driver 2 that supplies image display data in pixel units to the data line 2a connected to each display pixel. A gate driver 3 for sequentially turning on / off each display pixel in synchronization with a horizontal synchronizing signal to a gate line 3a connected to the display pixel, and a display control information source 4 such as a personal computer.
The input control unit 5'for controlling the display of desired image data on the liquid crystal panel 1 by the data driver 2 and the gate driver 3 by fetching the image data, the synchronizing signal, the operation clock, etc. And a reference power source 6 ′ for supplying the reference voltage to be applied to the data driver 2.

Further, as shown in FIG. 10, the above-mentioned input control section 5'receives display control information (image data, horizontal synchronizing signal, operation control signal, etc.) from a personal computer or the like, and an input data latch section in the subsequent stage. 12, an input interface (I / F) unit 11 for transmitting a predetermined signal to the data output circuit 13, etc., an input data latch circuit 12 for temporarily holding each image data (R, G, B), and an image data And a data output circuit 13 that performs timing adjustment, waveform shaping, and the like, and outputs the data to the data driver 2.

In such a configuration, the input I / F unit 1
The image data taken in through 1 is output to the data driver 2 at a predetermined timing via the input data latch circuit 12 and the data output circuit 13, and the reference voltage supplied to the data driver 2 by the reference power source is inverted. A driving method is adopted in which the polarity of the data voltage applied to the display pixel is inverted at a constant cycle based on the cycle.

Here, the inversion period of the reference voltage means that the reference voltage applied between the pixel electrode and the counter electrode of the liquid crystal panel alternately repeats positive and negative voltage states with respect to the common voltage. The inversion period, which is usually set to a constant inversion period.

[0007]

In the above-described liquid crystal display device, a driving method for displaying image data by inverting the polarity of the reference voltage (data voltage) with respect to the common electrode voltage at a preset predetermined cycle. Has been adopted. Known methods of inverting the polarity of the data voltage include a method of inverting each frame, a method of inverting each horizontal line or a vertical line, and a method of inverting each display pixel. It is known that, regardless of which inversion method is used, when a pattern having a specific relationship with the inversion cycle of the data voltage is displayed, flicker on the display screen becomes remarkable or power consumption increases. .

Specifically, it occurs when the inversion period of the reference voltage and the change of the display pattern match (synchronize). For example, a checkerboard pattern or a specific horizontal line is formed on a green background. This is especially noticeable in the displayed pattern. The flicker of the screen and the increase of the power consumption in such a specific display pattern are unavoidable problems in the driving method using the reference voltage having the fixed polarity inversion cycle.

As described above, the problems such as the deterioration of the image quality due to the occurrence of the flicker peculiar to the liquid crystal display device, the fatigue of the operator, and the increase of stress are solved, and the power consumption is reduced regardless of the display pattern from the viewpoint of portability. Realization of a liquid crystal display device aiming at this is desired. The present invention provides a liquid crystal display device which solves the above-mentioned problems, prevents flicker that occurs when displaying a specific pattern, prevents deterioration of image quality, and can reduce power consumption regardless of the display pattern. The purpose is to do.

[0010]

In order to achieve the above object, the invention according to claim 1 has a liquid crystal panel having display pixels arranged in a matrix at each intersection of a plurality of data lines and gate lines. A data driver that supplies image data in units of the display pixels to the data lines, a gate driver that sequentially activates each display pixel via the gate lines in synchronization with a horizontal synchronization signal, and at least the image data And an input control unit that supplies a display control signal including the horizontal synchronization signal to the data driver and the gate driver to control image data displayed on the liquid crystal panel, and the liquid crystal panel based on the image data. A liquid crystal display device having a reference power supply generation unit that generates a reference voltage to be applied to the display pixel having a predetermined polarity, the input control unit includes: The correlation between the change cycle of the data display pattern and the polarity inversion cycle of the reference voltage is monitored, and when the state in which the change cycle and the polarity inversion cycle are synchronized is determined, the polarity inversion cycle is arbitrarily switched and set. It is characterized by doing.

According to a second aspect of the present invention, in the liquid crystal display device according to the first aspect, the input control section includes image data extracting means for sequentially extracting the image data, and a change in the extracted image data. The inversion cycle control includes: pattern determination means for counting the amount and comparing it with a predetermined specified value to determine a specific display pattern; and inversion cycle control means for generating reference voltages having different polarity inversion cycles. Means, based on the determination result by the pattern determination means,
The polarity inversion cycle is arbitrarily switched and set, and the reference power supply generation unit generates a reference voltage having the switched polarity inversion cycle and supplies the reference voltage to the data driver.

According to a third aspect of the present invention, in the liquid crystal display device according to the first or second aspect, the input control unit is
The image data extracting unit has an input data latching unit having a plurality of stages of flip-flops for temporarily holding the image data, and the image data extracting unit outputs a predetermined logic with the input and output data of the flip-flop of the input data latching unit as inputs. However, it is characterized by having a logic gate for extracting a change state between adjacent pixel data.

Further, the invention according to claim 4 is the liquid crystal display device according to claim 1, 2 or 3, wherein the reference power source generating section normally selects a predetermined polarity inversion cycle, and the specific display pattern. Alternatively, when it is determined that the cycles are synchronized, the inversion cycle is randomly selected from other inversion cycle groups prepared in advance. The invention according to claim 5 is the liquid crystal display device according to claim 1, 2, 3 or 4, wherein the inversion period control means is:
As a polarity inversion method of the reference voltage applied to the display pixel, there is at least a dot inversion method, a data line and a gate line inversion method, and the specific display pattern or the cycle is synchronized. When the determination is made, the polarity reversal method is arbitrarily switched and set.

That is, according to the present invention, the image data extracting means and the pattern determining means sequentially extract and monitor the image data displayed adjacently, and determine a specific display pattern which causes flicker or an increase in power consumption. Then, the inversion period control means supplies the reference voltage at different polarity inversion periods prepared in advance. Therefore, according to the liquid crystal display device of the present invention, when the polarity inversion of the data voltage applied to the display pixel is performed based on the polarity inversion period set as the initial state, the display screen flickers or consumes. When the image data that displays a specific pattern that causes an increase in power is input, it is possible to switch to different polarity inversion periods, so that the inversion period of the data voltage and the display pattern are avoided, and the liquid crystal It is possible to suppress flicker peculiar to the display device or increase in power consumption.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION (Basic Structure) First, the basic structure of a liquid crystal display device according to the present invention will be described with reference to FIGS. The same components as those of the above-described conventional liquid crystal display device will be described with the same reference numerals.

As shown in FIG. 1, a liquid crystal display device according to the present invention includes a liquid crystal panel 1 having display pixels arranged in a matrix at intersections of a plurality of data lines and gate lines, and a pixel unit. A data driver 2 that supplies image data to the data line group 2a, a gate driver 3 that sequentially activates each pixel via the gate line group 3a in synchronization with a horizontal synchronizing signal, and a display control information source 4 such as a personal computer. Image data, horizontal synchronizing signals, operation control signals, and the like from the input device, which controls the display of a desired pattern on the liquid crystal panel 1 via the data driver 2 and the gate driver 3, and the display pixels of the liquid crystal panel 1. A reference power supply generation unit 6 for supplying a reference voltage to be applied to the data driver 2; When the synchronization between the two is detected, and it is determined that the display pattern is a preset specific display pattern, a polarity inversion cycle different from the original reference voltage is output to the reference power generation unit 6. , And the reference voltage is supplied to the data driver 2 at an arbitrary inversion cycle.

Here, as shown in FIG. 2, the input control section 5 has an input I / F section 11, an input data latch section 12, and a data output circuit 13, as well as the conventional configuration, and also has an input I The output timing of the image data output to the data driver 2 is set based on the synchronization signal and the operation clock CLK input via the / F unit 11 and the image data extraction signal extracted by the input data latch circuit 12. Operation clock CLK2 of the data output circuit 13
And the operation clock of the data driver 2, the data start pulse and the latch pulse, the operation clock of the gate driver 3, the gate start pulse and the output enable signal, and the polarity inversion of the reference voltage supplied from the reference power supply generation unit 6. The timing control circuit 14 outputs a polarity inversion signal for controlling the cycle.

Further, the main structure of the timing control circuit 14 will be described with reference to FIG. As shown in FIG. 3, the timing control circuit 14 includes an image data extraction unit 12a that constitutes image data extraction means, a display pattern determination unit 14a that constitutes pattern determination means, and an inversion period circuit that constitutes inversion period control means. The group 14b and the switch means 14c are included.

The image data extraction unit 12a is attached to a part of the input data latch circuit 12 and sequentially extracts image data that are adjacent to each other. The display pattern determination unit 14a
The change between the extracted adjacent image data, for example, the change amount from white to black and the number of changes are counted to determine a specific display pattern. Here, the specific display pattern is a pattern in which the display flicker or the increase in power consumption becomes remarkable with respect to the polarity inversion cycle of the reference voltage in the initial state, and horizontal lines are arranged on a checkerboard pattern or a green background. It means a pattern such as displaying.

Inversion periodic circuit group 14b and switch means 1
Reference numeral 4c is for switching the polarity inversion signal (polarity inversion cycle) output to the reference power source generation unit 6 when a specific display pattern is detected based on the determination result from the display pattern determination unit 14a. As shown in FIG. 3, for example, an inversion period circuit (A) (B) having two different polarity inversion periods is provided, and normally one inversion period circuit (A) is provided.
When the display operation is performed based on the polarity inversion cycle of 1) and a specific display pattern is detected, the switching means 14c is controlled to switch, and the other inversion cycle circuit (B) is selected to change the polarity inversion cycle. Perform display operation.

Then, the reference power supply generator 6 supplies the reference voltage to the data driver 2 based on the inversion cycle of the polarity inversion signal. As the configuration of the inversion cycle control means, a pair of switch means SW1-SW1 is selected so as to select one of the plurality of inversion cycle circuits (A) and (B) based on the determination result by the display pattern determination unit 14a.
′ And SW2-SW2 ′ are controlled by switching, but the present invention is not limited to this as long as the polarity inversion cycle can be arbitrarily changed and output to the reference power supply generation unit 6. Absent.

(Basic Operation) Next, the inversion cycle control operation of the above timing control circuit will be described with reference to the flowchart of FIG. Here, in the timing control circuit shown in FIG.
The switch means 14c for selecting 4b includes SW1 and SW1.
It is assumed that both ′ are in the ON state and the polarity inversion cycle of the inversion cycle circuit (A) is output to the reference power supply generation unit 6.

First, the input data extraction unit 12a uses the input I
Input to the input data latch circuit 12 via the / F unit 11,
The held image data is constantly monitored, and image data that are adjacent to each other are continuously extracted for each R, G, and B data (S
1). Next, the display pattern determination unit 14a counts the amount of change and the number of times of change in the image data extracted by the input data extraction unit 12a, with respect to the polarity inversion cycle of the inversion cycle circuit (A) set as the initial state. Then, a display pattern that causes flicker on the display screen or causes increase in power consumption is detected and determined (S2).

Then, when a specific display pattern is detected, the switch means SW1 is selected so as to select the other inversion cycle circuit (B) having an inversion cycle different from the currently selected inversion cycle circuit (A). And the combination of SW1 'are turned off, and the combination of SW2 and SW2' is turned on (S3). Then, the polarity inversion cycle of the newly selected inversion cycle circuit (B) is output as the polarity inversion signal to the reference power supply generation unit 6, and the reference voltage is generated in the polarity inversion cycle different from the initial state. 2 is supplied (S4, S5).

On the other hand, when the image data extracted by the input data extraction unit 12a is no longer determined to be a specific display pattern preset in the display pattern determination unit 14a, and the inversion periodic circuit (B) is switched. When a display pattern that causes flickering of the display screen or a display pattern that causes an increase in power consumption is detected with respect to the polarity inversion cycle of the above, the inversion cycle circuit (A) selected in the initial state is switched. The switch means 14c is controlled.

According to such a switching method of the inversion period, a display in which only the display pixels of the positive polarity or the negative polarity of the display pixels of the liquid crystal panel are turned on (ON). When the pattern image data is input, the arrangement of the positive and negative display pixels can be changed by changing the polarity inversion cycle of the reference voltage applied to the display pixels. Here, it is desirable that half of all the display pixels in the changed arrangement of the display pixels are in the ON state even if they have the same display pattern.

Specifically, as shown in FIG. 5, in the normal operation state, the inversion period circuit (A) is set as the initial state.
Is selected, and [RGBRGB.
The data voltage of positive polarity “+” and negative polarity “−” is alternately applied to the arrangement of pixels of [·] like [+ − + − + −...]. In such a state, as shown in FIG. 5B, in the case of a display pattern in which only one polarity pixel, for example, a pixel of positive polarity “+” is turned on (ON), the polarity inversion cycle and the display pattern are changed. Flicker occurs when changes are synchronized.

As described above, the pattern displayed on the display screen is constantly monitored by the input data extraction unit 12a and the display pattern determination unit 14a, and when the display pattern in which the flicker becomes remarkable is detected, the display pattern determination unit. 14
The switch means 14c is controlled so as to switch the inversion periodic circuit group 14b based on the determination result from a. As a result, the other inversion cycle circuit (B) is selected and, for example, a cycle in which polarity inversion is randomly performed in horizontal line units as shown in FIG. 5C or one horizontal line as shown in FIG. 5D. The cycle in which the polarity is alternately inverted for each line is output to the reference power supply generation unit 6 as a polarity inversion signal.

Therefore, when a series of image data having a display pattern that causes a flicker on the display screen and an increase in power consumption is input, the polarity inversion cycle of the reference voltage applied to the display pixel can be immediately switched. Therefore, display quality can be improved and power consumption can be reduced. (Embodiment) An embodiment of the input data extraction unit 12a applied to the liquid crystal display device according to the present invention will be described with reference to FIGS.

As shown in FIGS. 6 and 7, the input data extraction unit 12a includes a plurality of stages of flip-flops (F / F) FRa, FGa, FBa and FR for each R, G and B data.
In the input data latch circuit provided with b, FGb, and FBb, the flip-flops FRb, FGb, and F of the subsequent stage are provided.
Input pattern data and output data of Bb are input, and a predetermined logic output is set as extraction data, and the display pattern determination unit 14a
It has a logic gate for outputting to.

Here, in the case of extracting a checkerboard-like display pattern in which display flicker remarkably occurs, the logic gate, as shown in FIG. 6, performs exclusive NOR () for R data and B data. An ENOR) gate is provided, and an exclusive OR (EOR) gate is provided for G data. In this way, the input data latch circuit 12
By the predetermined logic output that receives the input data and the output data of the flip-flops FRb, FGb, FBb of
The state of change between the image data that are continuously adjacent to each other is R,
It is possible to constantly extract each of the G and B data.

Further, when a display pattern in which the power consumption of the liquid crystal display device is increased, for example, a checkerboard-like black-and-white color is replaced, as shown in FIG. 7, flip-flops for all R, G, and B data are used. FRb, FG
By providing an exclusive OR (EOR) gate that receives input data and output data of b and FBb,
It is possible to always extract the state in which all the G and B image data fluctuate in the synchronized inversion cycle.

Next, an embodiment of the display pattern determining section applied to the liquid crystal display device according to the present invention will be described with reference to FIG. As shown in FIG. 8, the display pattern determination unit 14a has a logical product (AN) to which the R, G, and B logic outputs extracted by the input data extraction unit 12a are input.
D) A gate 15a, a counter 15b which receives the logic output as an input, and outputs a count value as a bit, and a counter 15
Bit output from b and preset specified value (reference value)
A comparison circuit 15c for comparing
It is composed of a plurality of inversion cycle circuit groups 14b which are switched and set by switch means (not shown) and have mutually different polarity inversion cycles.

Here, the inversion cycle circuit group 14b outputs a predetermined polarity inversion signal to the reference power supply generator 6 in the subsequent stage. For example, in the initial state, the inversion cycle circuit (A) is selected, When a specific display pattern that causes a flicker on the display screen is detected, it may be set to another inversion period circuit (B) or (C) by switching, and at least 2 as shown in FIG. It suffices to have one inversion periodic circuit.

Further, as shown in FIG. 8, in the configuration provided with three or more inversion period circuits, the different polarity inversion states shown in FIGS. 5B to 5C are applied to the inversion period circuit (A). By presetting each of (B) and (C), the inversion period circuit (A) is normally selected, and when a specific display pattern is detected, another inversion period circuit (B) is selected.
By randomly selecting one inversion period circuit from among (C), it is possible to avoid synchronization between the polarity inversion period of the reference voltage applied to the display pixel and the change in the display pattern.

In this way, the input data extraction unit 12a and the display pattern determination unit 14a extract consecutively adjacent image data, count the amount of change and the number of times of change, and compare the predetermined specified values. With this, it is possible to monitor and determine a specific display pattern, and avoid flicker consumption of the screen by avoiding synchronization between the cycle of the display pattern displayed on the liquid crystal panel 1 and the polarity inversion cycle of the reference voltage applied to the display pixel. It is possible to suppress an increase in electric power.

Further, according to such a drive control method,
Even if the polarity reversal method of the reference voltage applied to the display pixel is, for example, one dot unit, two dot unit or horizontal line, vertical line unit inversion method, the synchronization state with the cycle of the display pattern is avoided. The polarity inversion cycle can be set appropriately.

[0038]

As described above, according to the liquid crystal display device of the present invention, the image data extracting means and the pattern determining means sequentially extract and monitor the image data displayed adjacently, and flicker or consume. When a specific display pattern that causes an increase in power is determined, the inversion cycle control means switches the inversion cycle so that the data voltage is applied at different polarity inversion cycles prepared in advance, so that the inversion cycle of the data voltage is changed. Flicker peculiar to the liquid crystal display device is avoided by avoiding a state in which the display and the change of the display pattern are synchronized.
Alternatively, an increase in power consumption can be suppressed.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a liquid crystal display device according to the present invention.

FIG. 2 is a schematic configuration diagram of an input control unit applied to the present invention.

FIG. 3 is a main part configuration diagram of a timing control circuit applied to the present invention.

FIG. 4 is a flowchart showing an inversion cycle control operation.

FIG. 5 is a diagram showing a relationship between an operating state of a display pixel and a polarity inversion cycle.

FIG. 6 is an example of an input data extraction unit applied to the present invention.

FIG. 7 is another embodiment of the input data extraction unit applied to the present invention.

FIG. 8 is an example of a display pattern determination unit applied to the present invention.

FIG. 9 is a schematic configuration diagram of a conventional liquid crystal display device.

FIG. 10 is a configuration diagram of a main part of a conventional input control unit.

[Explanation of symbols]

1 LCD panel 2 Data driver 2a Data line group 3 gate driver 3a Gate line group 4 Display control information source 5 Input control section 6 Reference power generation unit 11 Input I / F section 12 Input data latch circuit 12a Input data extraction unit 13 Data output circuit 14 Timing control circuit 14a Display pattern determination unit 14b Inversion periodic circuit group 14c switch means 15a AND gate 15B counter 15c Comparison circuit

Claims (5)

(57) [Claims] 1. A liquid crystal panel having display pixels arranged in a matrix at intersections of a plurality of data lines and gate lines; a data driver for supplying image data in units of the display pixels to the data lines; A gate driver that sequentially activates each display pixel via the gate line in synchronization with a synchronization signal, and a display control signal including at least the image data and the horizontal synchronization signal is supplied to the data driver and the gate driver. Then, an input control unit that controls the image data displayed on the liquid crystal panel, and a reference power supply generation unit that generates a reference voltage to be applied to display pixels of a predetermined polarity of the liquid crystal panel based on the image data. In the liquid crystal display device having the input control unit, the change cycle of the display pattern of the image data and the polarity inversion cycle of the reference voltage. Correlation monitoring of, when the change period and the polarity inversion cycle is determined a state of synchronization, a liquid crystal display device, characterized in that optionally switchable set the polarity inversion period. 2. The input control unit counts the amount of change in the extracted image data and an image data extraction unit that sequentially extracts the image data, and compares the amount of change with a predetermined specified value to display a specific display pattern. Pattern determination means for determining, and inversion cycle control means for generating reference voltages having different polarity inversion cycles, the inversion cycle control means, based on the determination result by the pattern determination means, the polarity inversion cycle 2. The liquid crystal display device according to claim 1, wherein the reference power supply generation unit generates a reference voltage having the polarity inversion cycle that is switched and set, and supplies the reference voltage to the data driver. 3. The input control unit has input data latch means having a plurality of stages of flip-flops for temporarily holding the image data, and the image data extraction means has input to the flip-flops of the input data latch means. 3. The liquid crystal display device according to claim 1, further comprising a logic gate that outputs predetermined logic with the output data as an input and extracts a change state between adjacent pixel data. 4. The reference power source generator normally selects a predetermined polarity reversal cycle, and when it determines the specific display pattern or the state in which the cycles are synchronized, the reference power generation section selects another reversal cycle group prepared in advance. 4. The liquid crystal display device according to claim 1, wherein the inversion period is randomly selected from the inside. 5. The inversion cycle control means has at least a dot inversion method and a data line and gate line inversion method as a polarity inversion method of a reference voltage applied to the display pixel. 3. The polarity inversion method is arbitrarily switched and set when a specific display pattern or a state in which the cycles are synchronized is determined.
3. The liquid crystal display device according to 3 or 4.