JP2008250222A - Liquid crystal drive and liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce the circuit scale of a liquid crystal display device including a liquid crystal drive and a liquid crystal panel driven by this drive. <P>SOLUTION: The liquid crystal drive is so configured that a corrected data obtained by correcting current display data with a lookup table 30 is selected by a selection circuit 8 when it is decided that previous display data have a specific grayscale by a comparison circuit 7 and current display data are selected when it is decided that the previous display data do not have the specific grayscale, and the selected data are supplied to a signal line driving circuit for driving the liquid crystal panel. Consequently, the lookup table 30 can be used as a correction table for only the specific grayscale, whereby the circuit scale of the liquid crystal display device including the liquid crystal drive and the liquid crystal panel driven by it can be reduced. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a liquid crystal driving device that makes liquid crystal respond at high speed and a liquid crystal display device including a liquid crystal panel driven by the liquid crystal driving device.

  In a conventional liquid crystal display device, display is performed by applying a voltage so that the transmittance is uniform or has a specific curve (γ characteristic) corresponding to the display gradation in accordance with the voltage-transmittance characteristics of the liquid crystal. It is carried out. In this case, the relationship between display gradation and voltage is unique.

  However, the liquid crystal display device has a drawback that its response speed is not sufficient.

  In recent years, various driving methods have been considered in order to make the liquid crystal respond at high speed, and one of them is overdrive driving. This compares the previous display data (previous display data) with the current (current) display data (current display data), and applies the voltage corrected for the current display data to the liquid crystal according to the increment / decrement. It is to do. Usually, the application pattern is determined by referring to a lookup table (see, for example, Patent Document 1). That is, when the current display data and the previous display data of one frame before are input and the current display data is larger than the previous display data, a voltage corresponding to correction data larger than the current display data is applied to the liquid crystal, When the current display data is smaller than the previous display data, a voltage corresponding to correction data smaller than the current display data is applied to the liquid crystal.

  FIG. 3 is a block diagram showing a circuit configuration of a liquid crystal display device to which the liquid crystal driving device that performs such overdrive driving is applied. In the figure, 1 is an image memory for storing display data to be input, 2 is a synchronization control circuit for receiving display data and outputting display data and a synchronization control signal, and 3 is a synchronization control circuit formed on a ROM. 2 is a look-up table storing correction data corresponding to the input of the current display data output by 2 and the previous display data output from the image memory 1. 4 is a signal line drive circuit that outputs a drive signal to the signal line based on the output of the lookup table 3 and the control signal of the synchronization control circuit 2, and 5 is a scan based on the control signal output from the synchronization control circuit 2. A scanning line driving circuit that outputs a driving signal to a line. Reference numeral 6 denotes a liquid crystal panel that performs display according to display data based on the output of the scanning line driving circuit 5 and the output of the signal line driving circuit 4. Here, an example in the case of 64 gradations (6 bit gradations) is shown.

  Although not shown in particular, the liquid crystal panel 6 includes pixel electrodes arranged in a matrix, a common electrode arranged opposite to the pixel electrodes, and a liquid crystal filled between the pixel electrodes and the common electrode. A liquid crystal capacitor, a thin film transistor (TFT) whose source is connected to the pixel electrode, a row extending in the matrix row direction, a scanning line connected to the gates of the plurality of TFTs, and a column direction in the matrix. And a signal line connected to the drains of the plurality of TFTs, and applying a signal voltage to the pixel electrode selected by the signal line driving circuit 4 and the scanning line driving circuit 5 allows the liquid crystal The arrangement is controlled and predetermined image information is displayed and output. These liquid crystal capacitor and TFT constitute a liquid crystal pixel (display pixel) together with the storage capacitor.

  In such a configuration, the input digital display data is stored in the image memory 1 for one frame, and is determined by two inputs of the input digital display data and the display data read from the image memory 1 with a delay of one frame. The look-up table 3 in which the correction data is stored converts the display data into emphasized correction data, and the liquid crystal panel 6 is driven using this correction data to change the transmittance of the liquid crystal panel 6, that is, the gradation change. The response speed was improved.

In addition, the above-mentioned Patent Document 1 not only performs correction according to display data in this way, but also prepares a plurality of lookup tables, thereby correcting according to the use environment such as the frame rate and ambient temperature. Is also disclosed.
JP 2002-108294 A

In the TFT liquid crystal display device, if each color of R, G, and B is 6-bit data, 2 ⁶ × 2 ⁶ × 2 ⁶ is 256k colors, only G color is 6 bits, and R and B colors are 5 bits. A gradation display of 64k colors is possible with ⁵ × 2 ⁶ × ²⁵ .

Wherein the corresponding in all cases, as shown in FIG. 3, 6 × 2 ⁶ × 2 ⁶ bit required lookup table 3 (6-bit correction data 2 ⁶ × 2 ⁶ pieces for reading) Become. Therefore, the circuit scale was very large.

  SUMMARY An advantage of some aspects of the invention is that it provides a liquid crystal driving device capable of reducing the circuit scale and a liquid crystal display device including a liquid crystal panel driven by the liquid crystal driving device.

The liquid crystal driving device according to claim 1 is provided.
Correction means for correcting the input display data and outputting the correction data;
A discriminating means for discriminating whether or not the display data one frame before has a specific gradation;
When the determination means determines that the specific gradation is selected, correction data obtained by correcting the current display data by the correction means is selected, and when the determination means determines that the specific gradation is not specified, the current display is displayed. A selection means for selecting data;
A drive circuit for driving a liquid crystal panel using the correction data selected by the selection means or the current display data;
Comprising
The correction means has a correction table for only the specific gradation.

The liquid crystal drive device according to claim 2 is the liquid crystal drive device according to claim 1,
The specific gradation includes at least the lowest gradation or the highest gradation.

The liquid crystal drive device according to claim 3 is the liquid crystal drive device according to claim 1 or 2,
The liquid crystal panel includes a vertically aligned liquid crystal.

The liquid crystal drive device according to claim 4 is the liquid crystal drive device according to claim 3,
The specific gradation is a gradation corresponding to a state in which the liquid crystal stands most.

The liquid crystal drive device according to claim 5 is the liquid crystal drive device according to any one of claims 1 to 4,
The correction means receives the current display data and the previous display data of the previous frame,
If the current display data is larger than the previous display data, output correction data larger than the current display data,
When the current display data is smaller than the previous display data, correction data smaller than the current display data is output.

The liquid crystal drive device according to claim 6 is the liquid crystal drive device according to any one of claims 1 to 5,
A plurality of the correction means;
It further comprises switching means for switching and using the plurality of correction means.

The liquid crystal drive device according to claim 7 is the liquid crystal drive device according to claim 6,
The switching means switches according to the color of the pixel of the liquid crystal panel.

The liquid crystal drive device according to claim 8 is the liquid crystal drive device according to claim 6,
The switching means performs switching according to the usage environment of the liquid crystal panel.

A liquid crystal display device according to a ninth aspect includes the liquid crystal driving device according to any one of the first to eighth aspects,
A display panel driven by the liquid crystal driving device;
It is characterized by providing.

  ADVANTAGE OF THE INVENTION According to this invention, the liquid crystal drive device which can make a circuit scale small and the liquid crystal display device containing the liquid crystal panel driven by it can be provided.

  The best mode for carrying out the present invention will be described below with reference to the drawings.

[First Embodiment]
FIG. 1 is a block diagram showing the configuration of the liquid crystal drive device according to the first embodiment of the present invention. In addition, about the structure similar to the liquid crystal drive device which performs the conventional overdrive drive shown in FIG. 3, the same code | symbol is attached | subjected and description is omitted.

(In FIG. 1, the display data and the synchronization signal are separated from the composite video signal and supplied by a separation circuit (not shown), and the synchronization control circuit 2 receives the various control signals by receiving the synchronization signal. Generate and output.)
That is, in the liquid crystal driving device according to the present embodiment, instead of the conventional 6 × 2 ⁶ × 2 ⁶ bit lookup table 3, the 6 × 2 ⁶ bit lookup table 30, the comparison circuit 7 and the selection circuit 8 are used. And. The selection circuit 8 includes two AND gates 81 and 82 and one OR gate 83.

  The lookup table 30 is correction means for outputting 6-bit correction data corresponding to 6-bit current display data (current display data) input from the separation circuit (not shown).

  The comparison circuit 7 is composed of an OR gate that outputs an H (high) level signal only when the 6-bit previous display data one frame before read from the image memory 1 has a specific gradation. In other words, the comparison circuit 7 functions as a determination unit that determines whether or not the display data of the previous frame (previous display data) has a specific gradation. The output signal of the comparison circuit 7 is supplied to the AND gates 81 and 82 of the selection circuit 8 as a control signal. However, one of the AND gates 81 is supplied after being inverted. The one AND gate 81 receives the 6-bit correction data from the look-up table 30 via the OR gate 83 in the subsequent stage only when the control signal from the comparison circuit 7 is at L (low) level. Output to the drive circuit 4. The other AND gate 82 receives the 6-bit current display data input from the separation circuit (not shown) via the OR gate 83 in the subsequent stage only when the control signal from the comparison circuit 7 is at the H level. Output to the signal line drive circuit 4. That is, the selection circuit 8 functions as a selection unit that selects correction data when the previous display data is a specific gradation, and selects current display data when the previous display data is not a specific gradation.

  The liquid crystal disposed on the liquid crystal panel 6 driven by the liquid crystal driving device is a vertical alignment type liquid crystal called VA (Vertical Alignment) liquid crystal.

  FIG. 2 is a diagram showing the relationship between display gradation change and display speed in the vertical alignment type liquid crystal. In the figure, Start Level indicates the gradation of the previous display data, and End Level indicates the gradation of the current display data. The vertical axis represents time (msec).

  As shown in the figure, when the previous display data is 0 gradation (the darkest gradation) which is the lowest gradation, and the current display data is a halftone, the speed is the slowest and the difference between the display data increases. The speed is getting faster. When the previous display data is other than 0 gradation, the speed difference is substantially uniform and is 30 msec or less.

  As described above, the VA liquid crystal is characterized in that the response speed from the state where the liquid crystal stands most (vertical alignment) is slow.

  Therefore, when driving the liquid crystal panel 6 using such vertically aligned liquid crystal, most of the speed-up effect can be obtained if overdrive driving is performed only when the previous display data is 0 gradation.

Therefore, in this embodiment, instead of using the lookup table 3 having a large circuit scale of 6 × 2 ⁶ × 2 ⁶ bits in order to deal with all gradations, only a specific gradation, that is, 0 gradation is dealt with. A lookup table 30 having a small circuit scale of 6 × 2 ⁶ bits is used. Then, the comparison circuit 7 and the selection circuit 8 supply correction data from the lookup table 30 to the signal line driving circuit 4 when the previous display data has 0 gradation, and the previous display data has gradations other than 0 gradation. At this time, the current display data is supplied to the signal line driving circuit 4 as it is.

  The correction means comprising the look-up table 3 receives the current display data and the previous display data one frame before, and if the current display data is larger than the previous display data, the correction means is larger than the previous display data. When the data and the current display data are smaller than the previous display data, correction data smaller than the current display data is output.

  As described above, according to the first embodiment, the overdrive drive is limited to the case where the previous display data is 0 gradation, thereby making the look-up table 30 very small (1/64 of the prior art). As a result, a liquid crystal driving device with a small circuit scale can be configured.

  Although not currently employed, when the polarizing plate is attached in the opposite direction (parallel Nicol) to the normal VA liquid crystal, the state corresponding to the 0th gradation which is the lowest gradation is the highest gradation63. The state corresponds to the gradation.

  Further, the lookup table 30 includes at least the lowest gradation or the highest gradation and has a certain width (for example, in the case of 64 gradations, 0 to 7 gradations or 57 to 63 gradations). However, it goes without saying that a liquid crystal driving device having a small circuit scale can be configured similarly.

[Second Embodiment]
Next, a second embodiment of the present invention will be described.

  If the scale of the lookup table 30 can be reduced as described in the first embodiment, a plurality of lookup tables 30 can be provided.

  For example, when the liquid crystal panel 6 is an RGB color liquid crystal panel having a stripe arrangement, and a liquid crystal having different response speeds for R (red) and B (blue) is arranged, the R pixel (3n-2nd pixel) When it is desired to change the set value between the B pixel and the B pixel (3nth pixel), two or more look-up tables 30 are required. Even if the plurality of lookup tables 30 are switched by switching means (not shown), the circuit scale of the entire liquid crystal driving device does not increase.

  Further, as disclosed in Patent Document 1, a plurality of look-up tables corresponding to the use environment such as the frame rate and the ambient temperature are prepared, and the entire liquid crystal driving device can be used by switching them. Optimal driving can be performed according to the use environment without increasing the circuit scale.

  As described above, according to the second embodiment, since the look-up table is reduced in size, a liquid crystal drive having a small circuit scale can be used even when the setting is switched by providing a plurality of look-up tables. A device can be configured.

  The present invention has been described above based on the embodiments. However, the present invention is not limited to the above-described embodiments, and various modifications and applications are possible within the scope of the gist of the present invention. .

  For example, although the case where each color is 6-bit data has been described as an example, the present invention can be similarly applied to other numbers of bits such as 8-bit data, and the effect of the present invention increases as the number of gradations increases.

1 is a block diagram illustrating a circuit configuration of a liquid crystal driving device according to a first embodiment of the present invention. It is a figure which shows the relationship between the change of the display gradation of VA liquid crystal, and display speed. It is a block diagram which shows the circuit structure of the liquid crystal display device which performs the conventional overdrive drive.

Explanation of symbols

    DESCRIPTION OF SYMBOLS 1 ... Image memory, 2 ... Synchronization control circuit, 3,30 ... Look-up table (correction means), 4 ... Signal line drive circuit, 5 ... Scanning line drive circuit, 6 ... Liquid crystal panel, 7 ... Comparison circuit (discrimination means) 8 ... Selection circuit (selection means), 81, 82 ... AND gate, 83 ... OR gate.

Claims (9)

Correction means for correcting the input display data and outputting the correction data;
A discriminating means for discriminating whether or not the display data one frame before has a specific gradation;
When the determination means determines that the specific gradation is selected, correction data obtained by correcting the current display data by the correction means is selected, and when the determination means determines that the specific gradation is not specified, the current display is displayed. A selection means for selecting data;
A drive circuit for driving a liquid crystal panel using the correction data selected by the selection means or the current display data;
Comprising
The liquid crystal driving apparatus according to claim 1, wherein the correction unit has a correction table for only the specific gradation.   The liquid crystal driving device according to claim 1, wherein the specific gradation includes at least a minimum gradation or a maximum gradation.   The liquid crystal driving device according to claim 1, wherein the liquid crystal panel includes vertically aligned liquid crystal.   The liquid crystal driving device according to claim 3, wherein the specific gradation is a gradation corresponding to a state in which the liquid crystal stands most. The correction means receives the current display data and the previous display data of the previous frame,
If the current display data is larger than the previous display data, output correction data larger than the current display data,
5. The liquid crystal driving device according to claim 1, wherein when the current display data is smaller than the previous display data, correction data smaller than the current display data is output. A plurality of the correction means;
6. The liquid crystal driving device according to claim 1, further comprising switching means for switching and using the plurality of correction means.   The liquid crystal driving device according to claim 6, wherein the switching unit performs switching according to a color of a pixel of the liquid crystal panel.   The liquid crystal driving device according to claim 6, wherein the switching unit performs switching according to a use environment of the liquid crystal panel. A liquid crystal driving device according to any one of claims 1 to 8,
A display panel driven by the liquid crystal driving device;
A liquid crystal display device comprising:

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