JP2601125B2 - LCD panel drive - 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 panel driving apparatus for driving a liquid crystal panel used in, for example, a liquid crystal television.

[0002]

2. Description of the Related Art A conventional liquid crystal television is generally constructed as shown in FIG. In FIG. 1, reference numeral 1 denotes a television antenna, and a television broadcast wave received by the antenna 1 is input to a tuner 2. The tuner 2 selects a radio wave of a specified channel from the received radio waves, converts the radio wave into an intermediate frequency signal, and outputs the signal to the television linear circuit 3. The TV linear circuit 3 extracts a video signal, a vertical synchronizing signal, and a horizontal synchronizing signal from the intermediate frequency signal from the tuner 2, and outputs the video signal to the A / D conversion circuit 4 and the synchronizing signal to the synchronization control circuit 5, respectively. . This synchronization control circuit 5
Generates various timing signals from the vertical synchronization signal and the horizontal synchronization signal, and outputs the signals to the A / D conversion circuit 4, the segment electrode drive circuit 6, and the common electrode drive circuit 7.

The A / D conversion circuit 4 includes a synchronization control circuit 5
The video signal is converted into digital data of several bits in synchronism with the sampling clock from, and is output to the segment electrode drive circuit 6. This segment electrode drive circuit 6
A gradation signal is generated in accordance with the data from the A / D conversion circuit 4, and a segment electrode drive signal is generated based on the gradation signal to display and drive the segment electrodes of the matrix type liquid crystal panel 8. Further, the common electrode drive circuit 7 generates a common electrode drive signal in accordance with the timing signal from the synchronization control circuit 5, and selectively drives the common electrodes of the liquid crystal panel 8 sequentially.

[0004]

The liquid crystal panel 8 is driven based on the video signal received as described above. Since the liquid crystal panel 8 operates by the cumulative response effect as shown in FIG. The response speed is slow.

FIG. 5 shows the relationship between the liquid crystal driving voltage composite waveform and the light transmittance of the liquid crystal panel 8 when the gradation is "7" or "0". On the other hand, in the above-described conventional liquid crystal panel driving method, the liquid crystal panel 8 is simply driven by generating a gradation signal corresponding to a video signal as shown in FIG. There was a problem that the response characteristics could not be improved, and it was not possible to cope with a fast-moving image. The present invention has been made in view of the above circumstances, and has as its object to provide a liquid crystal panel driving device capable of improving the response speed of gradation change of a liquid crystal panel.

[0006]

According to the present invention, there is provided a liquid crystal panel driving apparatus for displaying an image using a liquid crystal panel which responds cumulatively, comprising an image memory for storing one frame of digital image data, And a comparison circuit for comparing the level of the image data read from the image memory with a delay of one frame. If the current image data and the image data of the previous frame are the same, the current image data is output as it is. If the image data is larger than the image data of the previous frame, the maximum value is output as the image data. If the current image data is smaller than the image data of the previous frame, the minimum value is output as the image data. The panel is driven for display.

[0007]

With the above arrangement, when the image data changes, the liquid crystal panel is driven at the maximum gradation value or the minimum gradation value, and the light transmittance rises or falls rapidly. . As a result, the response speed of the liquid crystal panel can be increased, and it is possible to quickly follow a rapidly changing image.

[0008] The "frame" in the specification of the present application indicates that all picture elements forming one screen are scanned. For example, a picture element forming one screen per one field of a TV signal is used. In a display device that performs display by scanning all of them in one way, one field of a TV signal and one frame referred to in the present application are regarded as being equal, and a "frame" generally used in a TV signal is not necessarily coincident. .

[0009]

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows an example in which the present invention is applied to a liquid crystal television. The same parts as those in FIG. 4 are denoted by the same reference numerals, and detailed description is omitted.

In the present invention, an image memory 11 and a comparison circuit 12 are provided on the output side of the A / D conversion circuit 4 as shown in FIG. The image memory 11 is a dual port memory capable of storing one frame of image data, operates in accordance with a memory address and a read / write command given from the synchronization control circuit 5, and receives, for example, 3 data sent from the A / D conversion circuit 4. The bit image data is sequentially stored and output to the input terminal B of the comparison circuit 12 after one frame.

Image data output from the A / D conversion circuit 4 is input to an input terminal A of the comparison circuit 12. The comparison circuit 12 stores the image data from the A / D conversion circuit 4 applied to the input terminals A and B and the image memory 1
The level is compared with the image data delayed by one frame read out from 1 and the image data D1 to D3 are output from the output terminal P according to the following rules. A> B → P = 7 A = B → P = A A <B → P = 0 The image data D1 to D3 output from the output terminal P of the comparison circuit 12 are sent to the segment electrode drive circuit 6. .

Next, the operation of the above embodiment will be described with reference to the timing charts of FIGS. The 3-bit image data output from the A / D conversion circuit 4 is
2 and input to the image memory 11. The image memory 11 sequentially stores the image data sent from the A / D conversion circuit 4 under the control of the synchronization control circuit 5, and outputs it to the input terminal B of the comparison circuit 12 one frame later. The comparison circuit 12 compares the level of the image data output from the A / D conversion circuit 4 with the level of image data read out from the image memory 11 one frame later, and compares the current image data with the image data of the previous frame. Is high, the maximum value "7", that is, "111" is output as the image data D1 to D3. If the level of the image data of one frame before and the current image data is the same, A / D The image data sent from the conversion circuit 4 is output as it is as the image data D1 to D3, and if the current image data has a lower level than the image data of one frame before, the minimum is set as the image data D1 to D3. The value “0”, that is, “000” is output.

The image data D1 to D3 output from the comparison circuit 12 are sent to the segment electrode drive circuit 6. The segment electrode driving circuit 6 is provided with the comparison circuit 1
A segment electrode drive signal is generated on the basis of the image data D1 to D3 from the LCD 2 to drive the segment electrodes of the liquid crystal panel 8. FIG. 2 and FIG. 3 show the combined waveform of the common electrode drive signal and the segment electrode drive signal for the liquid crystal panel 8 and the relationship between the light transmittance of the liquid crystal panel and the combined waveform. This is the case where the number changes from “7” to “4”.

When the image data output from the A / D conversion circuit 4 changes, the driving voltage composite waveform for the liquid crystal panel 8 changes according to the image data. now,
Assuming that the gradation of the image data output from the A / D conversion circuit 4 changes from, for example, “0” to “4”, the driving voltage composite waveform of the liquid crystal panel 8 in the conventional circuit shown in FIG.
As shown in (a), it corresponds to gradation "4",
The light transmittance of the liquid crystal panel 8 changes stepwise as shown by the solid line A1 in FIG. 2B due to the cumulative response effect of the liquid crystal, and reaches a value corresponding to the gradation "4" after several frames.

The dashed line A2 in FIG. 2B shows, for reference, a change in the light transmittance of the liquid crystal panel when the gradation changes from "0" to "7". on the other hand,
In this embodiment, when the gradation of the image data output from the A / D conversion circuit 4 changes from “0” to “4”,
The comparison circuit 12 outputs the maximum value "7" as the image data D1 to D3. As a result, in the first frame in which the gradation of the image data has changed, the driving voltage composite waveform of the liquid crystal panel 8 corresponds to the gradation “7” as shown in FIG. As shown by the solid line A3 in FIG. 2 (d), the transmittance has a large rising width in the first step.

In the next frame, the image memory 11
Of the data read out from the comparator circuit 12 becomes “4” and the levels of the data input to the input terminals A and B of the comparison circuit 12 become the same, so that the output terminal P of the comparison circuit 12 Is output, that is, the data of the gradation “4”. Accordingly, thereafter, the driving voltage composite waveform of the liquid crystal panel 8 corresponds to the original gradation "4" as shown in FIG. 2C, and the light transmittance of the liquid crystal panel 8 changes accordingly. , And is constant at a value corresponding to the gradation “4”.

When the gradation of the data output from the A / D conversion circuit 4 is increased as described above, the liquid crystal panel 8 is driven at the gradation "7" only in the first frame, so that the light transmittance rises. The width increases, and the time required to reach the light transmittance corresponding to the video data is reduced.

On the other hand, if the gradation output from the A / D conversion circuit 4 decreases, for example, if the gradation changes from "7" to "4", the conventional circuit shown in FIG. In FIG. 3, the driving voltage composite waveform of the liquid crystal panel 8 corresponds to the gradation change as shown in FIG. 3 (a), and the light transmittance of the liquid crystal panel 8 is shown by the solid line B1 in FIG. As shown by, it decreases stepwise, and reaches a value corresponding to the gradation “4” after several frames. The broken line B2 in FIG. 3B shows, for reference, a change in the light transmittance of the liquid crystal panel when the gradation changes from "7" to "0".

On the other hand, in this embodiment, when the gradation of the image data output from the A / D conversion circuit 4 changes from "7" to "4", the comparison circuit 12 outputs the image data as D1 to D3. The minimum value "0" is output. As a result, in the first frame in which the gradation of the image data has changed,
The driving voltage composite waveform of the liquid crystal panel 8 corresponds to the gradation "0" as shown in FIG. 3C, and the light transmittance of the liquid crystal panel 8 becomes 1 as shown by the solid line B3 in FIG. The fall width of the step increases.

In the next frame, the image memory 11
Of the data read out from the comparator circuit 12 becomes “4” and the levels of the data input to the input terminals A and B of the comparison circuit 12 become the same, so that the output terminal P of the comparison circuit 12 Is output, that is, the data of the gradation “4”. Therefore, after that, the driving voltage composite waveform of the liquid crystal panel 8 corresponds to the original gradation "4" as shown in FIG. 3C, and the light transmittance of the liquid crystal panel 8 sequentially decreases accordingly. However, it is constant at a value corresponding to the gradation “4”.

As described above, when the gradation of the data output from the A / D conversion circuit 4 is lowered, the liquid crystal panel 8 is driven at the gradation "0" only in the first frame, so that the light transmittance rises. The downstream width increases, and the time required to reach the light transmittance corresponding to the video data is reduced.

[0022]

As described above in detail, according to the present invention, in a liquid crystal panel driving apparatus for displaying an image using a liquid crystal panel which responds cumulatively, when the gradation of image data changes,
Even if the gray level is halftone, the liquid crystal display panel is driven at the maximum gray level when the gray level increases, and at the minimum gray level when the gray level decreases. Since the liquid crystal display panel is driven at the gradation, the rise and fall of the liquid crystal panel that responds cumulatively can be made sharp and the response speed can be increased, so that a rapidly moving image can be quickly followed. be able to.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a circuit configuration of a liquid crystal panel driving device according to one embodiment of the present invention.

FIG. 2 is a diagram showing a driving voltage composite waveform and a light transmittance for describing an operation when a data gradation changes from “0” to “4” in the embodiment.

FIG. 3 is a diagram showing a driving voltage composite waveform and a light transmittance of the liquid crystal panel when the data gradation changes from “7” to “4” in the embodiment.

FIG. 4 is a block diagram showing a configuration of a conventional liquid crystal television.

FIG. 5 is a diagram showing a relationship between a liquid crystal driving voltage composite waveform and light transmittance of a liquid crystal panel for explaining the operation of FIG. 4;

[Explanation of symbols]

 2 Tuner 3 TV linear circuit 4 A / D conversion circuit 5 Synchronization control circuit 6 Segment electrode drive circuit 7 Common electrode drive circuit 8 Liquid crystal panel 11 Image memory 12 Comparison circuit

Claims (1)

(57) [Claims] 1. A liquid crystal panel driving apparatus for displaying an image using a liquid crystal panel which responds cumulatively, an image memory for storing one frame of digital image data for display, one frame delay from the digital image data and the image memory. The level of the current image data is compared with the level of the read image data. If the current image data is the same as the previous frame, the current image data is output as it is, and the current image data is larger than the previous frame image data. In this case, the comparison circuit outputs the maximum value as the image data, and outputs the minimum value as the image data when the current image data is smaller than the image data of one frame before. And a driving means for driving the display of the liquid crystal panel based on the liquid crystal panel.