JPH04204593A - Liquid crystal driving system - Google Patents

Abstract

PURPOSE:To improve the response speed of the gradation change with a relatively small memory capacity by providing an image memory storing one frame of the image data allocated with one address to multiple picture elements of a liquid crystal panel. CONSTITUTION:An image memory 11 stores the image data from an A/D converting circuit 4 with one address allocated to four picture elements of a liquid crystal panel 8 according to the memory address and read/write instructions from a synchronization control circuit 5 and outputs the image data to the input terminal B of a comparing circuit 12 after one frame. The image data outputted from the circuit 4 are inputted to the input terminal A of the circuit 12, the image data of the terminals A, B are compared as follows, and image data D1-D3 are outputted. A>B P=7 (maximum gradation), A=B P=A, A<B P=0 (minimum gradation), the image data are fed to a segment driving circuit 6 to drive the liquid crystal panel 8, the leading or trailing width of light permeability is increased, and the time to reach the corresponding light permeability is shortened.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a liquid crystal driving system for driving a liquid crystal panel used in, for example, a liquid crystal television.

[Prior Art] A conventional liquid crystal television is generally configured as shown in FIG. In the figure, reference numeral 1 denotes a television antenna, and television broadcast waves received by this antenna 1 are input to a tuner 2. The tuner 2 selects a designated channel of radio waves from among the received radio waves, converts it into an intermediate frequency signal, and outputs it to the television linear circuit 3. The television linear circuit 3 extracts a video signal, a vertical synchronization signal, and a horizontal synchronization signal from the intermediate frequency signal from the tuner 2, and outputs the video signal to the A/D conversion circuit 4 and the synchronization signal to the synchronization control circuit 5, respectively. . This synchronization control circuit 5 creates various timing signals from the vertical synchronization signal and horizontal synchronization signal, and outputs them to the A/D conversion circuit 4, segment drive circuit 6, and common electrode drive circuit 7.

The A/D conversion circuit 4 converts the video signal into several bits of digital data in synchronization with the sampling clock from the synchronization control circuit 5 and outputs it to the segment drive circuit 6. This segment drive circuit 6 creates a grayscale signal according to the data from the A/D conversion circuit 4, and further creates a segment electrode drive signal based on this grayscale signal,
The common electrodes of the matrix type liquid crystal panel 8 are sequentially and selectively driven.

The liquid crystal panel 8 is driven based on the video signal received as described above, but as shown in FIG. 6, the liquid crystal panel 8 has a characteristic of slow response speed because it operates due to the cumulative response effect. .

FIG. 6 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" and "0". On the other hand, in the conventional liquid crystal panel driving method described above, as shown in FIG. The problem was that the response characteristics of the camera could not be improved, and the system could not handle fast-moving images.

Therefore, a liquid crystal panel driving method with improved response speed can be considered. That is, in addition to the configuration shown in FIG. 5, an image memory for storing one frame of digital image data is provided on the output side of the A/D conversion circuit 4, and the digital image data and the image memory are read out with a one frame delay. A comparison circuit for comparing with image data is provided, and the A/D conversion circuit 4
If the image data input as is is the same as the image data of the previous frame from the image memory, that data is output as is, and the image data from the A/D conversion circuit 4 is the same as the image data of the previous frame from the image memory. If it is larger than the image data, the maximum value is output as the image data, and if the image data from the A/D conversion circuit 4 is smaller than the image data of the previous frame from the image memory, the minimum value is output as the image data. .

With the above configuration, when the image data changes, the liquid crystal panel 8 is driven with the maximum gradation value or the minimum gradation value,
The rise or fall of the light transmittance became steeper, and the response speed of the liquid crystal panel 8 could be increased.

[Problems to be Solved by the Invention] However, in the above-mentioned liquid crystal panel driving method, one address is used for one pixel of the liquid crystal panel in the image memory.
The disadvantage is that the storage capacity of the image memory becomes large.

The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a liquid crystal driving method that can improve the response speed of gradation changes of a liquid crystal panel and reduce the storage capacity of an image memory.

[Means for Solving the Problems] In order to solve the above problems, the present invention provides a liquid crystal drive system that displays images using a liquid crystal panel that responds cumulatively.
An image memory is provided to store one frame of display digital image data in which one address is assigned to a plurality of pixels of a liquid crystal panel, and one address is assigned to a plurality of pixels read out with a one frame delay from the digital image data and the image memory. The comparison circuit compares the levels of the image data for each pixel with the current image data, and if the current image data is the same as the image data of the previous frame in which one address is assigned to multiple pixels, the current image data is output as is, and the current image data is output as is. If the image data is larger than the image data in which one address is assigned to multiple pixels in the previous frame, the maximum value is output as the image data, and the current image data is assigned one address to multiple pixels in the previous frame.
If the address is smaller than the image data to which the address has been assigned, the liquid crystal panel is driven to display based on the image data that outputs the minimum value as the image data.

[Function] By using the above means, the storage capacity of the image memory can be reduced by using one address for multiple pixels of the liquid crystal panel, and when the image data changes, the maximum gradation level can be reduced. By driving the liquid crystal panel at a value or minimum gradation value, the rise or fall of the light transmittance becomes steeper, increasing the response speed of the liquid crystal panel and allowing it to quickly follow rapidly changing images. This made it possible.

[Example] 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, and the same parts as in FIG. 5 are given the same reference numerals and detailed explanations will be omitted. In the present invention, as shown in FIG. 1, an image memory 11 and a comparison circuit 12 are provided on the output side of the A/D conversion circuit 4.

The image memory 11 is a memory capable of storing one frame of display digital image data in which one address is assigned to four pixels of the liquid crystal panel 8, and operates according to the memory address and read/write command given from the synchronization control circuit 5. For example, 3-bit image data sent from the /D conversion circuit 4 is sequentially stored by assigning one address to four pixels of the liquid crystal panel 8, and sequentially outputted to the input terminal B of the comparison circuit 12 after one frame.

That is, as shown in FIG. 2, the image data output from the A/D conversion circuit 4 is transferred to pixels Aa, Ba, . . .
, Ab, Bb, . . . are thinned out every other horizontal stripe and stored in the image memory 11. For example, A of the liquid crystal panel 8
The pixel a is stored at address O in the image memory 11, the pixel Ca is stored at address N in the image memory 11, and the pixel AC is stored at address N in the image memory 11. When reading out from the image memory 11, the same image data as the pixel in which the thinned out pixels are stored is stored in the comparison circuit 11.
Output to 2. In other words, the image data of pixel Aa is compared with the image data stored at address O, and Ba, Ab,
The image data of the Bb pixel is also compared with the image data stored at address 0.

Furthermore, image data output from the A/D conversion circuit 4 is input to the input terminal A of the comparison circuit 12. This comparison circuit 12 has an A/D signal applied to input terminals A and B.
The image data from the conversion circuit 4 is compared in level with the image data read out from the image memory 11 in which one address is assigned to four pixels delayed by one frame, and the image data D1 to D3 are output from the output terminal P according to the following rules. Output.

A>B −+ P-7 (maximum gradation) A-B → P-A A<B −+ P-0 (minimum gradation) And image data D1 output from the output terminal P of the comparison circuit 12 ~D3 is sent to the segment drive circuit 6.

Next, the operation of the above embodiment will be explained with reference to the timing charts of FIGS. 3 and 4. The 3-bit image data output from the A/D conversion circuit 4 is input to the input terminal A of the comparison circuit 12 and the image memory 11. This image memory 11 allocates one address to every other four pixels in the vertical and horizontal directions of the liquid crystal panel 8 according to the control of the synchronization control circuit 5 for the image data sent from the A/D conversion circuit 4. The comparison circuit 12 stores image data output from the A/D conversion circuit 4 and 4 pixels read out from the image memory 11 with a delay of one frame. Compare the levels of the image data in which 1 address is assigned to 4 pixels, and if the level of the current image data is higher than the image data in which 1 address is assigned to 4 pixels in the previous frame, the image data D1 to
If the maximum value r7J, that is, rl 11J, is output as D3, and the level of the current image data is the same as the image data in which 1 address was assigned to 4 pixels in the previous frame,
The image data sent from the A/D conversion circuit 4 is output as is as image data D1 to D3, and furthermore, the current image data has a lower level than the image data in which core addresses are assigned to the four pixels before the previous frame. In this case, the minimum value "0" is set as image data D1 to D3, that is, ro 00J
Output.

Image data D1 to D3 output from the comparison circuit 12
is sent to the segment drive circuit 6.

The segment drive circuit 6 generates segment drive signals based on the image data D1 to D3 from the comparison circuit 12, and drives the segment electrodes of the liquid crystal panel 8. 3 and 4 show the composite waveform of the common drive signal and the segment drive signal for the liquid crystal panel 8, and the relationship between the light transmittance of the liquid crystal panel 8 and this composite waveform, and the gradation ranges from "○" to "4". and r7J −r4J.

Thus, when the image data output from the A/D conversion circuit 4 changes, the drive voltage composite waveform for the liquid crystal panel 8 changes in accordance with the image data.

Now, if the gradation of the image data output from the A/D conversion circuit 4 changes from, for example, "0" to "4", in the conventional circuit shown in FIG. As shown in FIG. 3(a), the light transmittance of the liquid crystal panel 8 corresponds to gradation "4" as shown by the solid line A1 in FIG. 3(b) due to the cumulative response effect of the liquid crystal. and reaches a value corresponding to gradation "4" after several frames have passed. Note that the broken line A2 in FIG. 3(b) is [4
For reference, the change in the light transmittance of the liquid crystal panel 8 when changing to 1 (rOJ - r7J) is shown for reference.On the other hand, in this embodiment, the image data output from the A/D conversion circuit 4 When the gradation changes from "0" to "4", the maximum value "7" is output from the comparison circuit 12 as the image data D1 to D3.As a result, the first frame in which the gradation of the image data changes In this case, the driving voltage composite waveform of the liquid crystal panel 8 corresponds to gradation "7" as shown in FIG. 3(C), and the light transmittance of the liquid crystal panel 8 is as shown in FIG. 3(d).
), the rising width of the first step becomes larger as shown by the solid line A3. Then, in the next frame, one address is assigned to four pixels read from the image memory], and the tone of the image data of one representative pixel becomes "4", which is input to input terminals A and B of the comparison circuit 12. Since the level of the data to be input is the same, the input from output terminal P of comparator circuit 2 is
.

The data applied to terminal A, that is, the data of gradation "4" is output. Therefore, from then on, the drive voltage composite waveform of the liquid crystal panel 8 corresponds to the original gradation "4" as shown in FIG. 3(c), and the light transmittance of the liquid crystal panel 8 changes accordingly. However, the value becomes constant at the value corresponding to gradation "4".

As mentioned above, when the gradation of the image data output from the A/D conversion circuit 4 increases, the liquid crystal panel 8 is driven at gradation "7" only in the first frame, so the rise width of the light transmittance increases. The time required to reach the light transmittance corresponding to the image data is shortened.

On the other hand, if the gradation of the image data output from the A/D conversion circuit 4 decreases, for example, the gradation changes from "7" to "4".
In the conventional circuit shown in FIG. 5, the drive voltage composite waveform of the liquid crystal panel 8 corresponds to the gradation change as shown in FIG. 4(a), and the light transmittance of the liquid crystal panel 8 changes. due to the cumulative response effect of the liquid crystal, decreases stepwise as shown by the solid line B1 in FIG. 4(b), and reaches a value corresponding to gradation "4" after several frames have passed. In addition, Fig. 4(b)
For reference, a broken line B2 in FIG. 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 minimum value rOJ as the image data D1 to D3. is output. As a result, in the first frame in which the gradation of the image data changes, the driving voltage composite waveform of the liquid crystal panel 8 corresponds to gradation "0" as shown in FIG. The light transmittance has a large falling width at the first step, as shown by the solid line B3 in FIG. 4(d). Then, in the next frame, the lv tone of the image data read out from the image memory 11, in which one address is assigned to four pixels, becomes r4J, and the levels of the data input to the input terminals A and B of the comparison circuit 12 become the same. Therefore, the data applied to the input terminal A, that is, the data of gradation "4" is output from the output terminal P of the comparator circuit 12. Therefore, from then on, the driving voltage composite waveform of the liquid crystal panel 8 corresponds to the original gradation "4" as shown in FIG. 4(C), and the light transmittance of the liquid crystal panel 8 also changes accordingly. The value decreases and becomes constant at the value corresponding to gradation "4".

As mentioned above, when the gradation of the image data output from the A/D conversion circuit 4 decreases, only the first frame is driven at the gradation level "0" of the liquid crystal panel 8, so the fall width of the light transmittance becomes larger, and the time required to reach the light transmittance corresponding to the image data is shortened.

In addition, in the above embodiment, four pixels were represented by one pixel, but
The average value of the four pixels may be taken and compared with the new pixel.

Further, in the above embodiment, a case has been described in which four pixels are assigned to one address, but the number of pixels is not limited to four, and a plurality of pixels may be assigned to one address, or an average value of a plurality of pixels may be taken.

[Effects of the Invention] As described above, according to the present invention, in a liquid crystal drive system that displays an image using a liquid crystal panel that responds cumulatively, by using one address for the image memory for multiple pixels of the liquid crystal panel, In addition to reducing the storage capacity of the image memory, when the gradation of image data changes, even if the gradation is an intermediate tone, if the gradation increases, the maximum gradation value is used, and the gradation When the gradation value decreases, the LCD panel is driven at the minimum gradation value, and when there is no gradation change, the LCD panel is driven at that gradation value. The response speed can be increased by making the fall steeper, and even fast-moving images can be quickly followed.

[Brief explanation of the drawing]

Figures 1 to 4 show one embodiment of the present invention.
The figure is a block diagram showing the circuit configuration of the liquid crystal panel drive device.
Figure 2 is an explanatory diagram showing the case where one address of the image memory is assigned to four pixels of the liquid crystal panel, and Figure 3 is an explanatory diagram showing the case where the gradation is "0".
Figure 4 shows the driving voltage composite waveform and light transmittance of the liquid crystal panel when the gradation changes from "7" to "4". Figure 4 shows the driving voltage composite waveform of the liquid crystal panel when the gradation changes from "7" to "4". 5 is a block diagram showing the configuration of a conventional LCD television, and FIG. 6 is a diagram showing the combination of the drive voltage composite waveform of the liquid crystal panel and the light transmittance to explain the operation of FIG. 5. It is a figure showing a relationship. 2...Tuner, 3...TV linear circuit, 4...
A/D conversion circuit, 5... synchronous control circuit, 6... segment drive circuit, 7... common electrode drive circuit, 8... liquid crystal panel, 11... image memory, 12... comparison circuit. Applicant's agent Patent attorney Takehiko Suzue

Claims (1)

[Scope of Claims] In a liquid crystal drive system that displays an image using a liquid crystal panel that responds cumulatively, an image memory that stores one frame of digital image data for display in which one address is assigned to a plurality of pixels of the liquid crystal panel; The levels of the digital image data are compared for each pixel with the image data that is read out from the image memory with one frame delay and one address is assigned to multiple pixels, and one address is assigned to the current image data and multiple pixels one frame before. If the assigned image data is the same, the current image data is output as is, and if the current image data is larger than the image data of the previous frame in which one address was assigned to multiple pixels, the maximum value is output as the image data. , a comparison circuit that outputs the minimum value as image data when the current image data is smaller than the image data of the previous frame in which one address is assigned to multiple pixels; A liquid crystal driving system characterized by comprising a driving means for driving a display panel.