JPH06167947A - Driving method, driving circuit and display device for liquid crystal element or the like - Google Patents

Abstract

PURPOSE:To simplify a driving circuit and to reduce manufacturing cost of a display device by selecting simultaneously plural scanning electrodes and applying voltage by dividing a period of one frame of a selecting period into plural times. CONSTITUTION:Plural scanning electrodes are simultaneously selected, and voltage is applied to them by dividing a period of one frame of a selecting period into plural times. That is, driving waveforms which are applied to scanning electrodes simultaneously selected by X1-X15 are shown, as an example of a driving waveform, when the number of lines of scanning electrodes simultaneously selected are made 15 lines, also a driving waveform which is applied to a signal electrodes when Y1 is display data on a signal electrode Y1 is shown. And the maximum voltage of each driving waveform applied to scanning electrodes and signal electrodes is made approximately a same level. Thereby, withstanding voltage of each electrode driver can be made the same level, and the number of levels of a power supply can be decreased. Further, voltage levels of data signal and signals of a transfer clock or the like inputted to each driver is not required to change.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a driving method for a liquid crystal element or the like, a driving circuit and a display device thereof.

[0002]

2. Description of the Related Art A conventional driving method for a liquid crystal element or the like is known as a method for driving several scanning electrodes simultaneously.
There is a method shown in 143482.

[0003]

For example, when there are 240 lines of scanning electrodes and 4 lines of them are simultaneously selected, the driving waveform applied to the scanning electrodes is compared with the driving waveform applied to the signal electrodes. The voltage of the waveform applied to the scan electrode is about 4 to 5 times higher than that of the waveform.

Therefore, the withstand voltage of the driving voltage of the driver for driving the liquid crystal may be high for the scanning electrodes and low for the signal electrodes.
In this case, as shown in FIG. 7A, the GN of each driver is
Since the D level is different, two logic power supplies are required and the power supply level increases.

Further, the data signals and signals such as transfer clocks to be put into each driver must be level-shifted according to the logic level of each driver, resulting in cost increase.

Further, if the number of lines selected simultaneously is increased, the number of times the display data is read out from the frame memory during one frame period is increased, the reading frequency of the display data is increased, and the access speed of the memory cannot be kept in time. The data cannot be read from the frame memory.

[0007]

A scan electrode driver and a signal electrode driver are arranged such that a plurality of scan electrodes are sequentially selected at the same time and a voltage is applied by dividing the selection period into a plurality of times within one frame period. , The voltage levels of the logic system power supplies are made common, and the number of simultaneously selected lines at which the drive voltage applied to the scan electrode and the drive voltage applied to the signal electrode are almost the same is n, The number of lines that can be adjusted within the withstand voltage range of the driver is + a, -b
As the number of lines to be simultaneously selected from (n−b) to (n
Drive in the range of + a). Further, it is characterized in that the selection periods of m times in one frame period are grouped k by k to make a selection period of one block, and the selection periods of j blocks are made in one frame period.

Further, k indicating the polarity of the display data read from the frame memory and the selection waveform applied to the scan electrodes.
A group of selection pulse data is calculated by an arithmetic circuit to create k kinds of conversion data, which are written in k groups of line memories, and the conversion data sequentially read from this line memory are transferred to the signal electrode driver. Further, the display data read from the frame memory and k sets of selection pulse data indicating the polarities of the selection waveforms to be applied to the scan electrodes are operated by the operation circuit to create k kinds of conversion data, which are transferred to the signal electrode driver, The data holding circuit holds k types of conversion data in the signal electrode driver, sequentially switches k types of conversion data in accordance with each selection pulse, and outputs a signal electrode waveform according to the conversion data. To do.

A display device is provided with the above-described driving method and driving circuit.

[0010]

EXAMPLE In this example, as shown in Japanese Patent Application No. 4-143482, a driving method for simultaneously selecting several lines of scanning electrodes will be described as an example.

(Embodiment 1) In Embodiment 1, a case will be described in which how many of 240 scan electrodes are simultaneously selected. The graph shown in FIG. 6A shows the number of lines to be simultaneously selected and the voltage of the drive waveform applied to the scan electrode and the drive waveform applied to the signal electrode at that time. The scan electrode waveform, and 602, the voltage of the signal electrode waveform. As can be seen from FIG. 6A, the voltages of the drive waveform applied to the scan electrodes and the drive waveform applied to the signal electrodes are substantially the same when approximately 15 lines are simultaneously selected.

Therefore, the number of lines of the scanning electrodes selected at the same time is set to the number of lines within a range of ± several lines centering on 15 lines. The range of the number of lines to be selected at the same time varies somewhat depending on the withstand voltage of the driver, but for example, the withstand voltage of the driver is set to 15 V and the number of lines to be selected is set to about 10 to 20 lines. it can.

FIG. 1 shows an example of drive waveforms when the number of scan electrode lines selected simultaneously is 15, and X is
1 to X15 are examples of drive waveforms applied to the scanning electrodes selected at the same time, and examples of drive waveforms applied to the signal electrodes when Y1 is the display data on the signal electrode Y1 in FIG. 5 are shown. Then, the maximum voltage of each drive waveform applied to the scan electrode and the signal electrode becomes substantially the same.

As described above, when the maximum voltages of the drive voltages applied to the scan electrodes and the signal electrodes are made substantially the same,
The withstand voltage of the scan electrode driver and the signal electrode driver can be made substantially the same, the GND level of each driver can be made the same as shown in FIG. 7B, and the number of power supply levels can be reduced. . Further, it is not necessary to change the voltage level of a signal such as a data signal or a transfer clock input to each driver.

The graph shown in FIG. 6B shows the number of lines selected simultaneously when the number of scan electrodes is 480, the drive waveform applied to the scan electrodes and the drive waveform applied to the signal electrodes at that time. It shows how many volts the voltage becomes, and 603 shows the voltage of the scan electrode waveform and 604 shows the voltage of the signal electrode waveform. As can be seen from FIG. 6 (b), almost 2
When two lines are simultaneously selected, the drive waveform applied to the scan electrodes and the drive waveform applied to the signal electrodes have substantially the same voltage.

Therefore, the number of lines of the scanning electrodes to be selected at the same time is set so that the number of lines is within a range of ± several lines centering on 22 lines. The range of the number of lines to be selected at the same time varies somewhat depending on how many volts the withstand voltage of the driver is set to, but for example, the withstand voltage of the driver is set to 15 volts and the number of lines to be selected is set between about 19 and 25 lines. it can.

(Embodiment 2) FIG. 2 shows an example of driving waveforms when the number of scanning electrodes to be simultaneously selected is 15, and an example of driving waveforms applied to the scanning electrodes to be simultaneously selected by X1 to X15. 5 shows an example of the drive waveform applied to the signal electrode when Y1 is the display data on the signal electrode Y1 in FIG.

In the drive waveform shown in the first embodiment, there are 16 selection periods in one frame period as shown in FIG.
The display data for one screen was read 16 times from the frame memory.

In the second embodiment, the selection periods indicated by t1 to t16 are grouped into several periods, for example, t1 to t4, t5 to t8, t9 to t12, t13 to t16 as shown in FIG. The four periods are collectively set as a selection period of four blocks in one frame period.

FIG. 3 is a block diagram showing an example of the drive circuit in the second embodiment, in which the display data 302 from the personal computer 301 is written in the frame memory 303. The display data for each of the 15 lines selected at the same time is sequentially read from the frame memory 303, and first, the display data for the 15 lines selected first and the controller 30 are read.
The calculation circuit 306 compares and calculates four sets of selection pulse data indicating the polarities of the scan electrode waveforms from 4 from t1 to t4, and writes the resulting four sets of conversion data 307 to the line memory 308. In the line memory 308, the conversion data corresponding to the t1 period is written in 1-A, the conversion data corresponding to the t2 period is written in 2-A, the conversion data corresponding to the t3 period is written in 3-A, and the t4 period is written. The conversion data corresponding to 4 is written into 4-A, and when the writing is completed, the conversion data corresponding to the t1 period is read from 1-A, transferred to the signal electrode driver 310, and simultaneously selected.
When the conversion data for the line is completely transferred, the signal electrode waveform as indicated by Y1 in FIG. 2 is output to each signal electrode. In this way, the signal electrode waveform for the period t1 to t4 is output. During the period in which the signal electrode waveform is output during the period from t1 to t4, 1-B, 2-B, 3-B of the line memory 308,
The conversion data of 15 lines that are selected at the same time next is written in 4-B, and when the period of t1 to t4 is selected, the scanning electrodes of 15 lines that are selected next at the same time are selected.
1-B, 2-B, 3-B, 4-B of line memory 308
Each signal electrode waveform is output according to the conversion data sequentially read from. When all the scanning electrodes have been selected once in this way, the process returns to the original state, and as shown in the period from t5 to t8, the 15 lines to be simultaneously selected are selected first.

In this way, each scanning electrode is divided into four blocks and selected during one frame period F1, and display data may be read from the frame memory four times in one frame period.

Further, the line memory 308 of FIG. 3 is eliminated, and instead, as shown in FIG. 4, the shift registers 1, 2, 3, 408 in the signal electrode driver 401 are shown.
Provide latch circuits 1, 2, 3, and 4 indicated by 4 and 409,
For example, regarding the period from t1 to t4, the arithmetic circuit 306 in FIG. 3 outputs four types of conversion data 307 corresponding to each period from t1 to t4 to the 4 in the signal electrode driver 401 in FIG.
Shift register 1 input to 02-405 and indicated by 408
4 to 4 by the transfer clock 406, and when the conversion data for 15 lines selected at the same time are completely transferred, they are latched in the latch circuits 1 to 4 indicated by 409 by the latch signal 407. When the latching is completed, the shift registers 408 1-4
The conversion data of the next 15 lines to be selected is transferred to. The multiplexer 410 sequentially selects the conversion data corresponding to the period t1 to t4 held in the latch circuits 409, and outputs the conversion data in the order of t1, t2, t3, and t4. The generated signal electrode waveform is output from the signal electrode driver 401. t1 to t4
When the period is selected, the scanning electrodes of 15 lines that are simultaneously selected next are selected, and the signal electrode waveform corresponding thereto is output. When all the scanning electrodes have been selected once in this way, the process returns to the original state, and as shown in the period from t5 to t8, the 15 lines to be simultaneously selected are selected first.

In this way, each scanning electrode is divided into four blocks and selected during one frame period F1, and display data may be read from the frame memory four times in one frame period.

In the second embodiment, the case of selecting 15 lines at the same time has been described, but 3 lines, 4 lines,
7 lines, 8 lines, etc., or more lines, and any number of lines can be used with the same idea. Also, from t1
Although four selection periods of t16 are grouped into one block, one block may be grouped into any number of selection periods.

[0025]

As described above, according to the present invention, since the driving voltage of the signal electrode waveform and the scan electrode waveform can be lowered, the withstand voltage of the signal electrode driver and the scan electrode driver can be lowered and the voltage level of the power source can be reduced. The number can be reduced and the cost of the display device can be reduced by eliminating the level shift circuit for each signal.

Further, even if the number of lines of the scanning electrodes selected at the same time is increased, it is not necessary to increase the reading speed of the data from the frame memory so much, and a normal RAM can be used to read the data at high speed. There is no need to complicate the frame memory circuit, the cost of the display device can be reduced, and the power consumption can be reduced.

[Brief description of drawings]

FIG. 1 is a diagram showing an example of drive waveforms according to a first embodiment of the present invention.

FIG. 2 is a diagram showing an example of drive waveforms according to a second embodiment of the present invention.

FIG. 3 is a block diagram showing an example of a drive circuit according to a second embodiment of the present invention.

FIG. 4 is a block diagram showing an example of a signal electrode driver circuit according to a second embodiment of the present invention.

FIG. 5 is a diagram showing an example of a display pattern.

FIG. 6 is a diagram showing the relationship between the number of lines selected at the same time and the drive voltage.

FIG. 7 is a diagram showing voltage levels of respective power supplies for the scan electrode driver and the signal electrode driver.

[Explanation of symbols]

 301 personal computer 303 frame memory 304 controller 306 arithmetic circuit 308 line memory 310 signal electrode driver 311 scan electrode driver 312 liquid crystal panel 401 signal electrode driver 408 shift register 409 latch circuit 410 multiplexer

Claims (6)

[Claims] 1. A driving method for a liquid crystal element or the like in which a substrate having a scanning electrode and a liquid crystal element having a liquid crystal layer interposed between a substrate having a signal electrode are driven in a multiplex manner. A method of driving a liquid crystal element or the like, characterized in that the voltage is applied by selecting and selecting the selection period in a plurality of times within one frame period. 2. The scan electrode driver and the signal electrode driver are made to have substantially the same withstand voltage, the voltage level of the power supply of the logic system is made common, and the drive voltage of the drive waveform applied to the scan electrode and the drive waveform applied to the signal electrode are set. The number of simultaneously selected lines that are almost the same is n, the number of lines that can be adjusted within the withstand voltage range of the driver is + a, -b, and the number of lines that are simultaneously selected is driven in the range (n-b) to (n + a). The method for driving a liquid crystal element or the like according to claim 1, characterized in that. 3. A selection period which is m times in one frame period is k
2. The method for driving a liquid crystal element or the like according to claim 1, wherein the selection period for one block is collectively j times, and the selection period for the block is j times in one frame period. 4. A display circuit read from a frame memory and k sets of selection pulse data indicating the polarities of selection waveforms to be applied to scan electrodes are operated by an operation circuit to generate k types of conversion data, and k sets of lines are formed. A drive circuit for a liquid crystal element or the like, which writes in a memory and transfers the conversion data sequentially read from the line memory to a signal electrode driver. 5. The display data read out from the frame memory and k sets of selection pulse data indicating the polarities of the selection waveforms applied to the scan electrodes are operated by an operation circuit to create k kinds of conversion data, which are then applied to the signal electrode driver. The data holding circuit holds k types of conversion data in the signal electrode driver, switches the k types of conversion data in sequence according to each selection pulse, and outputs a signal electrode waveform according to the conversion data. A drive circuit for a liquid crystal element or the like. 6. A display device comprising the method for driving a liquid crystal element or the like according to any one of claims 1, 2 and 3 and the drive circuit for the liquid crystal element or the like according to claims 4 and 5.