JP2546210B2 - LCD drive system - Google Patents

Description

TECHNICAL FIELD The present invention relates to a liquid crystal drive system for driving a dot matrix liquid crystal display panel.

[Prior Art] Conventionally, a bit matrix liquid crystal display panel is generally used for a portable small television receiver, a display unit of a small electronic computer, and the like. Therefore, when driving the liquid crystal display panel for display, a method of time-division driving as shown in FIG. 4 can be considered. This figure is a timing chart showing a simple time division drive, in which the scanning electrodes X1 to X6 are sequentially selected, and in synchronization with this, signals indicating gradations Y1,1 to Y1,6 are given to the signal electrode Y1. This is a state in which it is set. Therefore, the pixels at the intersections of the scanning electrodes X1 to X6 and the signal electrode Y1 are displayed at the gradation levels Y1,1 to Y1,6.

The above-mentioned driving method causes no problem in a relatively small liquid crystal display panel having a small number of common electrodes, but in a liquid crystal display panel having a large number of scanning electrodes, the duty ratio decreases and the contrast decreases. Currently used duty ratio is up to about 1/100. By the way, in the case of a liquid crystal display panel used in a small television receiver, the number of scanning electrodes is generally around 240 which is the number of effective scanning lines corresponding to one field. If this is simply driven in time division as described above, the duty ratio will be 1/240.
Therefore, the contrast is remarkably lowered and it is not practical.

Several methods have been proposed as measures against the above problem, but as a typical method, there is a method of simultaneously selecting a plurality of scan electrodes adjacent to a scan electrode to be originally selected. FIG. 5 shows the driving method of the scanning electrode X1.
4 to X6, four adjacent ones are sequentially selected at the same time, and the grayscale signals Y1,2 to Y1,6 are applied to the signal electrode Y1 in synchronization therewith. For example, while the scan electrode X4 is selected, "Y1,1" and "Y
When the gradation signals "1,2", "Y1,3" and "Y1,4" are given,
In the pixel at the intersection of the scan electrode X4 and the signal electrode Y1, the average value of the display gradations of the four preceding and following pixels is shown in FIG. 4 as the gradation is (Y1,1 + Y1,2 + Y1,3 + Y1,4) / 4. It will be displayed with a time width of four times. Therefore, compared to the method shown in FIG. 4, for example, in a liquid crystal display panel for a small television device having 240 scanning lines, its duty ratio is 1/60 (4/240), which is four times higher, and the contrast is sufficient. It will be of a practical level.

[Problems to be Solved by the Invention] However, in the driving method shown in FIG. 5, the contrast is improved, but as described above, one pixel is equal to the average value of the gradation values of three adjacent pixels. It will be displayed with gradation. This is because the amount of transmitted light of the liquid crystal cell depends on the effective voltage, so that the display content of the pixel includes a gradation degree other than the gradation that should be originally displayed, and the resolution is lowered. There's a problem.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a liquid crystal drive system for driving a liquid crystal display panel capable of high-resolution display without lowering contrast.

[Means and Actions for Solving the Problem] The present invention is to apply a gradation signal from which the influence of the gradation signal of the adjacent pixel is removed to the signal electrode.

[Embodiment] An embodiment of the present invention will be described below with reference to the drawings.

First, the principle of the embodiment will be described. Here, the number of scan electrodes to be simultaneously selected is, for example, “4”. Therefore, one scan electrode is continuously selected for a time of "4H" if one horizontal scan time is "1H".
If the gradation signal given to the pixel at the intersection of the scan electrode Xn and the signal electrode Ym is Zm, n, Zm, n = (Ym, n-3 + Ym, n-2 + Ym, n-1 + Ym, n) in the conventional method. /Four ···
(1) can be expressed as That is, the gradation signal Ym, n to be originally displayed is added to the three gradation signals Ym, n-3 before that.
The average value of the sum of Ym, n-2 and Ym, n-1 is given to the signal electrode as an actual gradation signal and displayed by the pixel. Here, when the above formula (1) is modified, Ym, n = 4Zm, n-Ym, n-1-Ym, n-2-Ym, n-3 (2) is obtained, and the signal electrode is actually used. The averaged gradation signal “Zm, n” that is given is multiplied by 4 and then 1H, 2
H, 3H before the gradation signal "Ym, n-1""Ym, n-
By subtracting the total sum of 2 "[Ym, n-3", theoretically only the original grayscale signal "Ym, n" is given to the signal electrode. The circuit using the above logic is the circuit shown in FIG.

FIG. 1 shows one of the gradation signal processing circuits provided for each signal electrode, and the number on the signal line in the drawing indicates the number of bits. 3-bit gradation signal "Ym, n" is a multiplier
It is multiplied by 4 at 11. This multiplier 11 is actually composed of a mere bit shifter, and after being made into a 5-bit signal, it is made into a 6-bit signal via a subtractor 12,
Sent to 13. The limiter 13 outputs the signal sent to the signal electrode Ym as a 3-bit signal “Y′m, n”, which is the same as the original gradation signal, and outputs it to the shift register.
Also output to 14. The shift register 14 holds the input gradation signal “Y′m, n” for the horizontal scanning time “1H” of the liquid crystal panel, and then outputs it to the shift register 15 and the adder 16. The shift register 15 is similar to the shift register 14, and holds the input gradation signal for "1H" and then outputs it to the shift register 17 and the adder 16. Shift register 17
Similarly, after holding the input gradation signal for "1H",
Output to the adder 18. That is, the shift registers 14, 15,
Both 17 are used as a delay circuit, and as a timing, the gradation signal “Y′m,
In contrast to “n”, the gradation signal output from the shift register 14 is “1.
"Y'm, n-1" delayed by "H", and the gradation signal output from the shift register 15 is delayed by "2H" by "Y'm, n-".
2 ", the gradation signal output from the shift register 17 becomes"Y'm, n-3 "delayed by" 3H ". The adder 16 performs addition operation on the gradation signals "Y'm, n-1" and "Y'm, n-2",
The sum "Y'm, n-1 + Y'm, n-2" is output to the adder 18 as a 4-bit signal. The adder 18 receives the signal "Y'm, n-1 + Y'm, n-2" from the adder 16 and the shift register.
The gradation signal "Y'm, n-3" from 17 is added and calculated, and the sum "Y'm, n-1 + Y'm, n-2 + Y'm, n-3" is 5
The bit signal is sent to the minus side input terminal of the subtracter 12. Therefore, in the subtractor 12, from the gradation signal "4Ym, n" from the multiplier 11, "Y'm, n-1 + Y'm, n-2 + Y'm, n"
-3 "is subtracted and the difference is sent to the limiter 13. The limiter 13 sets “7” if the transmitted signal is a numerical value of 4 bits or more, that is, “8” or more, and “0” if it is a negative number, and inputs the input 6-bit gradation signal. Like the signal, it has a 3-bit numerical value and outputs it to the signal electrode Ym. This means that if the value of the signal is "8" or more, the output data exceeds the number of bits of the input data, and if the value of the signal is negative, the liquid crystal display panel cannot be driven for display. This is to prevent this, and other types may be used as long as they are output with 3 bits. In this way, the grayscale signal "Y'm, n" from which the elements of the grayscale signal "Y'm, n-1 + Y'm, n-2 + Y'm, n-3" output from the limiter 13 in terms of timing are removed. Will be applied to the signal electrode Ym.

Next, the operation of the above embodiment will be described with reference to FIGS. 2 and 3.

FIG. 2 shows a subtracter when concrete grayscale data Y is input.
FIG. 3 shows a part of the correspondence between the output 12 and the output Y ′ of the limiter 13 and the gradation Z when actually displayed, and the display gradation z according to the conventional method. FIG. It was done. As shown in FIG. 1, in most cases, the display gradation Z according to the method of the present application is close to or exactly equal to the input data Y, as compared with the display gradation z according to the conventional method. . This is sufficiently clear from the graph of FIG. 3, and for the gradation signal Y which is the input data shown by the solid line, the display gradation Z of the present application is shown by a broken line, and the conventional display gradation Z is shown by a dashed line. Where the display gradation Z is exactly equal to the input data Y, for example, the data serial number (S No.) is "8" to "10", "14" ...
In the part such as “17”, the illustration of the input data Y side is omitted in order to prevent the lines from overlapping.

[Effects of the Invention] As described in detail above, according to the present invention, since the grayscale signal from which the influence of the grayscale signal of the adjacent pixel is removed is applied to the signal electrode, the resolution of the resolution can be reduced without lowering the contrast. A liquid crystal driving method for driving a liquid crystal display panel capable of high display can be provided.

[Brief description of drawings]

1 to 3 show an embodiment of the present invention.
FIG. 1 is a block diagram showing a circuit configuration, and FIG. 2 is a diagram showing a part of correspondence between a processing state of gradation data of each part and an actual display gradation degree in comparison with a display gradation degree of a conventional example. 3 is the second
Characteristic diagrams showing the correspondence between the input gradation data corresponding to the drawing and the actual display gradation and the display gradation of the conventional example, FIGS. 4 and 5.
The figures are both timing charts showing selection signals of the conventional liquid crystal driving type scan electrodes. 11 …… Multiplier, 12 …… Subtractor, 13 …… Limiter, 14,15,
17 …… Shift register, 16,18 …… Adder.

Claims (1)

(57) [Claims] 1. In a liquid crystal drive system in which a plurality of k scanning electrodes adjacent to each other are selected and scanned at the same time, as a gradation signal to be given at a timing of n for each signal electrode, , N, the liquid crystal driving method is characterized in that a grayscale signal obtained by subtracting the influence of each of the k−1 grayscale signals given to the signal electrode is given to the signal electrode.