JPH08340505A - Liquid crystal drive method and liquid crystal display device - Google Patents

Abstract

PURPOSE: To allow a liquid crystal display device to quickly follow even an rapidly changing image by quickening the response of the liquid crystal. CONSTITUTION: The liquid crystal display device displaying an image by using a liquid crystal display panel whose picture elements response to each signal accumulatingly is provided with an image memory 11 storing digital image data equivalent to one frame A/D-converted by an A/D converter circuit 4 and with a comparator circuit 12 comparing a level of the digital image data from the A/D converter circuit 4 with a level of image data read from the image memory 11 by one frame. When image data this time and the image data of one preceding frame are the same, the comparator circuit 12 provides an output of the image data this time without any modification and when the level of the image data this time is higher than the level of the image data of one preceding frame, the comparator circuit 12 provides an output of a maximum level as the image data, and when the level of the image data this time is smaller than the level of the image data of one preceding frame, the comparator circuit 12 provides an output of a minimum level as the image data to drive a liquid crystal display panel 8.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal driving method and a liquid crystal display device 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 is a television antenna, and television broadcast radio waves received by the antenna 1 are 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 television 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 is
A gradation signal is created in accordance with the data from the A / D conversion circuit 4, and liquid crystal drive voltages V1 and V3 are further selected based on this gradation signal to create segment electrode drive signals, and the matrix type liquid crystal panel 8 is formed. The segment electrodes of are driven for display. In addition, the common electrode drive circuit 7 follows the liquid crystal drive voltage V0 according to the timing signal from the synchronization control circuit 5.
, V2, and V4 are selected to generate a common electrode drive signal, and the common electrodes of the liquid crystal panel 8 are selectively driven sequentially. The liquid crystal driving voltages V0 and V4 are selection voltages, and V2 is a non-selection voltage.

[0004]

The liquid crystal panel 8 is driven based on the video signal received as described above. However, since the liquid crystal panel 8 operates by the cumulative response effect as shown in FIG. It has a slow response speed.

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" or "0". On the other hand, in the conventional liquid crystal panel driving method, as shown in FIG. 6, the liquid crystal panel 8 is simply driven by generating a gradation signal corresponding to the video signal. 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 a liquid crystal driving method and a liquid crystal display device capable of speeding up the response of the liquid crystal and promptly following an abruptly changing image. The purpose is to provide.

[0007]

SUMMARY OF THE INVENTION The present invention provides a liquid crystal drive for supplying a liquid crystal drive signal according to the size of image data to a liquid crystal panel to drive the liquid crystal panel with a gradation according to the size of image data. In the method, the current image data and the image data of the previous screen are compared, and if they are equal, a liquid crystal drive signal corresponding to the current image data is supplied to the liquid crystal panel, and if they are different, the image data different from the current image data is dealt with. The liquid crystal drive signal is supplied to the liquid crystal panel.

Further, according to the present invention, in a liquid crystal display device in which a liquid crystal panel is scanned N times (N is an integer of 2 or more) during one field period of a video signal, the current image data and 1
When the comparison result of the image data before the screen is equal to the comparison result of this device, the liquid crystal drive signal corresponding to the current image data is supplied to the pixel of the liquid crystal panel, and the current image data is the image of the previous screen. When it is larger than the data, the liquid crystal drive signal corresponding to the image data larger than the current image data is supplied to the pixel of the liquid crystal panel, and when the current image data is smaller than the image data of the previous screen, the current image data is supplied. Gradation control means for supplying a liquid crystal drive signal corresponding to image data smaller than the image data to the pixel of the liquid crystal panel.

(Operation) With the above configuration, when the image data is changed, the driving for emphasizing the change of the display is performed, so that the responsiveness of the liquid crystal can be speeded up rapidly. It is possible to quickly follow a changing image.

The term "frame" as used in the specification of the present application means that all picture elements that form one screen are scanned. For example, one picture element that forms one screen for each field of a TV signal. In a display device that scans and displays all in one way, one field of a TV signal and one frame referred to in the present application are considered to be equal to each other, and the "frame" generally used in a TV signal does not necessarily match. .

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION 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. 5 are denoted by the same reference numerals, and detailed description is 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 dual port memory capable of storing image data for one frame, operates according to a memory address and a read / write command given from the synchronization control circuit 5, and is sent from the A / D conversion circuit 4, for example, 3 The bit image data is sequentially stored, and after one frame, is sequentially output to the input terminal B of the comparison circuit 12. Also,
The input terminal A of the comparison circuit 12 has an A / D conversion circuit 4
The image data output from is input. The comparison circuit 12 includes an A / D conversion circuit 4 provided to input terminals A and B.
Of the image data from the image memory 11 and the image data read from the image memory 11 by one frame are compared in level, and the image data D1 to D3 are output from the output terminals P and Q according to the following rules.
And a gradation change signal E are output.

A> B.fwdarw.P = 7, Q = 1 A = B.fwdarw.P = A, Q = 0 A <B.fwdarw.P = 0, Q = 1 Then, it is output from the output terminal P of the comparison circuit 12. The image data D1 to D3 and the gradation change signal E output from the output terminal Q are sent to the segment electrode drive circuit 6 '. This segment electrode drive circuit 6'is configured as shown in FIG.

In FIG. 2, reference numeral 21 is a data latch clock generation circuit, which is a data latch start signal STI synchronized with the horizontal synchronization signal from the synchronization control circuit 5 and a clock pulse /
φ1 (inverted signal of φ1) and / φ2 (inverted signal of φ2) are input. This data latch clock generation circuit 21
Clocks data latch start signal STI
It is read by 1 / φ2 and sequentially shifted, and a data latch clock is generated at each shift.

The data latch clock generation circuit 21 outputs m data latch clocks corresponding to the number of segment electrodes of one horizontal line of the liquid crystal panel 8 in one horizontal period and sends them to the data latch circuits 22 of m stages. To be The data latch circuit 22 has a significantly 4-bit configuration, and the 3-bit image data D1 ...
D3 and the 1-bit gradation change signal E are latched in synchronization with the data latch clock.

The data latched by the data latch circuit 22 is read out by a timing signal / φn (an inverted signal of φn) provided for each horizontal cycle and sent to the gradation signal generation circuit 23. This gradation signal generation circuit 2
3 is a timing signal / φn, a gradation signal generating clock / φc (inversion signal of φc), a frame signal / φF (φF
), The 3-bit image data D1 to D3 from the data latch circuit 22 is converted into a gradation signal having a pulse width, and output to the analog multiplexer 24 together with the gradation change signal E. The analog multiplexer 24 has liquid crystal driving voltages V1, V1 ', V2, V3, V
3'is provided via the blanking control circuit 25.

Liquid crystal drive voltages V1, V1 ', V2, V3,
V3 'is V1 at constant level intervals around V2.
(High level side) and V3 (Low level side) are set, and V1 'is set to a level higher than V1 and V3' is set to a level lower than V3. The operation of the blanking control circuit 25 is controlled by a blanking control signal EC. The blanking control circuit 25 outputs the liquid crystal driving voltages V1, V1 ', V3, and V3' as they are to the analog multiplexer 24 during periods other than the vertical blanking period. Is the liquid crystal drive voltage V1, V1 ', V3, V3'
The level is output to the analog multiplexer 24.
The analog multiplexer 24 selects one of the liquid crystal drive voltages V1, V1 ', V3, and V3' in accordance with the grayscale signal and the grayscale change signal from the grayscale signal generation circuit 23 to drive the segment electrode drive signal. Output to the liquid crystal panel 8 as Y1 to Ym.

FIG. 3 shows the analog multiplexer 24.
3 shows details of a circuit portion for generating a segment signal of one electrode in FIG. The liquid crystal driving voltages V1, V1 ', V3, V provided through the blanking control circuit 25
3 'is input to the analog switches 31 to 34. The voltage selected by the analog switches 31 and 32 is sent to the output terminal 37 via the analog switch 35, and the voltage selected by the analog switches 33 and 34 is sent to the output terminal 37 via the analog switch 36.

The gradation change signal sent from the gradation signal generating circuit 23 is input to the control terminals of the analog switches 31 and 34 and also to the control terminals of the analog switches 32 and 33 via the inverter 38. To be done. Further, the grayscale signal sent from the grayscale signal generation circuit 23 is input to the control terminal of the analog switch 36 and also to the control terminal of the analog switch 35 via the inverter 39.

The analog multiplexer 24 configured as described above turns off the analog switches 31 and 34 when the gradation change signal is "0",
8 becomes “1” and the analog switches 32 and 33
Is turned on, whereby the liquid crystal driving voltages V1 and V3 are selected and input to the analog switches 35 and 36. The analog switches 35 and 36 are on / off controlled by a gray scale signal given from the gray scale signal generation circuit 23, so that the liquid crystal driving voltage V1 or V3 is selected according to the gray scale signal, and the segment is output from the output terminal 37. Electrode drive signal Y
To the liquid crystal panel 8.

When the gradation change signal is "1", the analog switches 31 and 34 are turned on, and the output of the inverter 38 becomes "0" so that the analog switches 32 and 34 are turned on.
33 is turned off, which causes liquid crystal drive voltages V1 'and V3'.
Is selected and input to the analog switches 35 and 36. Therefore, the liquid crystal driving voltage V1 'or V3' is selected according to the gradation signal, and is sent from the output terminal 37 to the liquid crystal panel 8 as the segment electrode driving signal Y. In the vertical blanking period, the liquid crystal drive voltage applied from the blanking control circuit 25 is all at the V2 level, so the V2 voltage is used as the segment electrode drive signal Y regardless of the gradation change signal and the gradation signal. Sent to 8.

Next, the operation of the above embodiment will be described with reference to the timing chart of FIG. 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. 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
It outputs to the input terminal B of the comparison circuit 12 after a frame.

The comparison circuit 12 compares the level of the image data output from the A / D conversion circuit 4 with the level of the image data read out from the image memory 11 one frame later. When the level of the data is higher, the maximum value "7", that is, "111" is output as the image data D1 to D3, and "1" is output as the gradation change signal.

When the level of the image data of one frame before and the current image data are the same, the comparison circuit 12
The image data sent from the / D conversion circuit 4 is output as it is as image data D1 to D3, and "0" is output as a gradation change signal. Further, when the level of the current image data is lower than that of the image data of one frame before, the comparison circuit 12 outputs the minimum value “0”, that is, “000” as the image data D1 to D3, "1" is output as a change signal.

The image data D1 to D3 and the gradation change signal E output from the comparison circuit 12 are sent to the segment electrode drive circuit 6 '. The segment electrode driving circuit 6 'is adapted to output the image data D1 to D3 from the comparison circuit 12.
Then, segment electrode drive signals Y1 to Ym are generated based on the gradation change signal E, and the segment electrodes of the liquid crystal panel 8 are driven.

FIG. 4 is a graph showing the relationship between the common electrode drive signal and the segment electrode drive signal for the liquid crystal panel 8, the composite waveform of the common electrode drive signal and the segment electrode drive signal, and the relationship between the light transmittance of the liquid crystal and the composite waveform. Is "0"
The figure shows a case where the change is made from "7" to "4".

However, as shown in FIG.
Assuming that the gradation of the image data output from the conversion circuit 4 has changed from "0" to "7", the comparison circuit 12 outputs a maximum value "7" as data D1 to D3 and a gradation change signal. “1” is output as E. The gradation change signal E is supplied to the segment electrode driving circuit 6 'together with the gradation signal.
After being latched by the data latch circuit 22, it is sent to the analog multiplexer 24 via the data latch circuit 22 and the gradation signal generation circuit 23.

The analog multiplexer 24 shown in detail in FIG. 3, when "1" is given as the gradation change signal E,
As described above, the analog switches 31 and 34 are turned on, the analog switches 32 and 33 are turned off, and the analog switches 35 and 36 are alternately turned on / off according to the gradation signal.
The liquid crystal drive voltage V1 ',
V3 'is selected and sent to the liquid crystal panel 8 as the segment electrode drive signal Y.

That is, in the first frame when the gradation of the image data changes from "0" to "7", the liquid crystal drive voltages V1 'and V3' are selected according to the gradation signal, and the segment signal Y is As shown by the broken line A1 in FIG. 4 (b), the phase is opposite to that of the common signal and has a larger amplitude than in the normal case. As a result, the composite waveform of the drive signal applied between the common and segment electrodes has an amplitude value "V0 + V1" larger than the normal levels "V0 + V1" and "V4 + V3", as indicated by the hatched line A2 in FIG. 4 (c). "", "V4 + V3 '". In this way, the amplitude of the segment electrode drive signal is large, that is, the voltage is high, so that the liquid crystal panel 8
The light transmittance of the solid line B as shown by the broken line A3 in FIG.
Rise is faster than in the conventional case shown in 1.

When the gradation "7" continues after the next frame, the comparison circuit 12 outputs the input terminal A.
The data given to the above are directly output as the image data D1 to D3, and "0" is output as the gradation change signal E. When the gradation change signal E is “0”, the analog multiplexer 24 shown in FIG.
2 and 33 are turned on, and the liquid crystal driving voltages V1 and V3 are alternately selected according to the gradation signal, and the segment electrode driving signal Y
To the liquid crystal panel 8.

When the same gradation continues as described above, the normal liquid crystal driving voltages V1 and V3 are selected in the second and subsequent frames. Further, as the same gradation level continues, the light transmittance of the liquid crystal panel 8 sequentially increases due to the cumulative response effect as shown by the broken line A3 in FIG. 4D, and is constant at the level corresponding to the gradation "7". Becomes

Thereafter, assuming that the image data is reduced from gradation "7" to gradation "4" as shown in FIG. 4, the comparison circuit 12 sets the minimum value "0" as the image data D1 to D3. And outputs “1” as the gradation change signal E.
Is output. When "1" is given as the gradation change signal E, the analog multiplexer 24 alternately selects the liquid crystal driving voltages V1 'and V3' according to the gradation signal as described above, and outputs the liquid crystal panel as the segment electrode driving signal. 8 is output. In this case, since the gradation signal signal is "0", the segment signal Y has the same phase as the common electrode drive signal waveform as shown by the broken line A4 in FIG. 4B.

Accordingly, the composite voltage waveform of the drive signal applied between the common-segment electrodes has a value "V0 + V1 '" obtained by cutting the portion indicated by the oblique line A5 from the normal drive signal waveform as shown in FIG. "And" V4 + V3 '".
That is, when the gradation changes to the lower side, the liquid crystal drive voltage becomes lower than the normal value in the first frame, and the light transmittance of the liquid crystal panel 8 is as shown by the broken line A6 in FIG. 4 (c). The rising speed is faster than in the conventional case shown by the solid line B2.

When the gradation "4" continues after the next frame, the input terminal A
The data given to the above are directly output as the image data D1 to D3, and "0" is output as the gradation change signal E. When the gradation change signal E is "0", the analog multiplexer 24 alternately selects the liquid crystal drive voltages V1 and V3 according to the gradation signal, and outputs the segment electrode drive signal Y to the liquid crystal panel 8. When the same gradation continues in this way, the normal liquid crystal drive voltages V1 and V3 are selected in the second and subsequent frames. Further, since the same gradation level continues, the light transmittance of the liquid crystal panel 8 is reduced as shown in FIG.
As shown by the dashed line A6 in FIG. 6D, the level gradually increases due to the cumulative response effect, and becomes constant at the level corresponding to the gradation "4".

In the above embodiment, the comparison circuit 12 compares the image data of this time sent from the A / D conversion circuit 4 with the image data of one frame before read from the image memory 11 and compares the image data D1. .About.D3 and the gradation change signal E are outputted, a sufficient effect can be obtained even if only the gradation change signal is generated and outputted to the segment electrode drive circuit 6 '. In this case, the image data D1 to D input to the segment electrode drive circuit 6 '
As 3, the output of the A / D conversion circuit 4 may be used as it is.

[0036]

As described above in detail, according to the present invention,
In a liquid crystal driving method and a liquid crystal display device, in which a liquid crystal driving signal corresponding to the size of image data is supplied to the liquid crystal panel to display and drive the liquid crystal panel with a gradation corresponding to the size of the image data, when the image data changes, Since the driving is performed so as to emphasize the change of the display, the responsiveness of the liquid crystal can be sped up, and it is possible to quickly follow a rapidly changing image.

[Brief description of drawings]

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

FIG. 2 is a block diagram showing details of a segment electrode drive circuit in the same embodiment.

FIG. 3 is a block diagram showing a configuration of one stage of the analog multiplexer in FIG.

FIG. 4 is a timing chart for explaining the operation of the present invention.

FIG. 5 is a block diagram showing a configuration of a conventional liquid crystal television.

FIG. 6 is a diagram showing a relationship between a liquid crystal driving voltage composite waveform and light transmittance of liquid crystal for explaining the operation of FIG. 5;

[Explanation of symbols]

 2 Tuner 3 Television linear circuit 4 A / D conversion circuit 5 Synchronization control circuit 6, 6 'segment electrode drive circuit 7 Common electrode drive circuit 8 Liquid crystal panel 11 Image memory 12 Comparison circuit 21 Data latch clock generation comparison circuit 22 Data latch circuit 23 Gradation signal generation circuit 24 Analog multiplexer 25 Blanking control circuit 31-36 Analog switch

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[Procedure amendment]

[Submission date] August 9, 1996

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be amended] Claims

[Correction method] Change

[Correction content]

[Claims]

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0007

[Correction method] Change

[Correction content]

[0007]

The present invention provides image data
LCD drive that converts to LCD drive signal and supplies to LCD panel
In this method, the image supplied this time to the pixel of the liquid crystal panel
The brightness of the data and the image data previously supplied to the pixel
Compare the brightness, the brightness of the image data supplied this time is better
If it is higher than the brightness of the image data supplied last time,
Liquid that corresponds to higher brightness of the supplied image data
This is converted into a crystal drive signal and supplied to the pixels of the liquid crystal panel.
When the supplied brightness is lower than the previously supplied brightness
Sets the brightness of the image data supplied this time to a lower brightness.
It is adapted to be converted into a corresponding liquid crystal drive signal and supplied to the pixels of the liquid crystal panel .

[Procedure 3]

[Document name to be amended] Statement

[Correction target item name] 0008

[Correction method] Change

[Correction content]

Further, the present invention compares the image data of the frame received this time by the receiving means for receiving the image data composed of frame units with the image data of the frame received last time. A liquid crystal driving means for generating a liquid crystal driving signal for emphasizing a change in the brightness of the received image data, and a liquid crystal panel driven by the liquid crystal driving signal generated by the liquid crystal driving means. It is a liquid crystal display device.

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 0036

[Correction method] Change

[Correction content]

[0036]

As described above in detail, according to the present invention,
Convert image data to liquid crystal drive signal and supply to liquid crystal panel
In the liquid crystal driving method and the liquid crystal display device, the driving for emphasizing the change of the display is performed when the image data changes, so that the response of the liquid crystal can be speeded up and the image that changes rapidly can be displayed. However, it can be quickly followed.

Claims (4)

[Claims] 1. A liquid crystal drive method for supplying a liquid crystal drive signal according to the size of image data to a liquid crystal panel to drive the liquid crystal panel for display with a gradation according to the size of image data. Compare the image data in front of the screen. If they are the same, supply the liquid crystal drive signal corresponding to the current image data to the liquid crystal panel, and if they are different, supply the liquid crystal drive signal corresponding to the image data different from the current image data to the liquid crystal panel. A method of driving a liquid crystal, comprising: 2. The liquid crystal drive according to claim 1, wherein the liquid crystal drive signal corresponding to the image data different from the current image data is a liquid crystal drive signal corresponding to the maximum value or the minimum value of the image data. Method. 3. N times (N times) during one field period of the video signal.
Is an integer greater than or equal to 2) In a liquid crystal display device in which a liquid crystal panel is scanned, a means for comparing the current image data with the image data of the previous screen for each pixel, and if the comparison result of this means is equal, A corresponding liquid crystal drive signal is supplied to the pixel of the liquid crystal panel, and when the current image data is larger than the image data of the previous screen, the liquid crystal drive signal corresponding to the image data larger than the current image data is supplied to the liquid crystal panel. And the current image data is smaller than the image data of the previous screen, the gradation for supplying the liquid crystal drive signal corresponding to the image data smaller than the current image data to the pixel of the liquid crystal panel. Control means,
A liquid crystal display device comprising: 4. The liquid crystal display device according to claim 3, wherein the gradation control means supplies the same liquid crystal drive signal N times for each pixel for one field period.