JPS5834492A - Liquid crystal element driving circuit - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a driving circuit for liquid crystal display atoms, and particularly to a circuit for driving liquid crystal display atoms in a time-division manner using a voltage averaging method.

Conventionally, a voltage averaging method has been known as a method for time-divisionally driving liquid crystal display elements.

This means that 'yIi,
By applying a constant and uniform bias voltage to the non-lighted segments when EE is applied, the crosstalk voltage that occurs when the liquid crystal display element is time-divisionally driven is made uniform. By doing this, even if crosstalk occurs due to high time division and driving, crosstalk can be avoided, especially in liquid crystal display devices with a structure in which pixels are arranged over the entire screen, such as those used for graphic displays. Since it can be regarded as a uniform background, display quality does not deteriorate much.

FIG. 1 shows an example of a driving circuit for this type of liquid crystal display atom. In the figure, ll (1=1-1n) is a scanning electrode,
2j (j''l~n) is a signal electrode, 3 is a running/non-running side drive circuit,
4 is a signal side drive circuit, 5 is a timing circuit, 6 is a display memo 1c, γ is an AC power supply, and 8 is an electrolytic erosion circuit for generating a voltage level.

In the liquid crystal display element having the above configuration, by applying a scanning voltage x1 and a signal voltage Yj as shown in FIG. Each pixel formed at the intersection of the pole 11 and the signal electrode 2j has a %'1 pressure X1-Y as shown in FIG.
j is applied. In FIG. 2, (a).

(b), (c), (d), (e), (
f) and (g) are respectively XI and X21X8. Y2
1Y8. Y4. Indicates Y9. Also, in Figure 3 (a
), (h) indicate the voltage applied to the unlit pixel, (0), (d) indicate the voltage applied to the pixel in the lit state, and (a) indicates the voltage applied to the pixel in the lit state, respectively.
Yg, (b) is Xa-Ys, (o) is Xa-Yg, (d
) corresponds to Xa-Ye. .

Here, for each of the scanning voltage and the signal voltage waveform, the value indicated by the bias ratio a-i, where N is the number of time divisions is optimal, and the maximum operating margin can be obtained at this time. These pressure levels are generated by a resistive divider circuit as shown in FIG.

In the figure, 11 is a scanner, 12 and 13 are selection switches, 14 is a data latch, 15 is a shift register, and 16 is a transmission gate. Also, S
l indicates a scanning signal, S2 indicates an AC signal, and D indicates data. As is clear from the figure, the above-mentioned six levels of voltages Va to ■f are obtained from the power supply voltage VO by resistance division.

However, from Hiko, when driving a liquid crystal display element with a drive circuit like this [7], in reality, distortion occurs in the drive waveform, especially in high time division driving, and as a result, the crosstalk voltage is not uniform, and the display Unevenness occurs. Is this display unevenness caused by pixels placed all over the screen, such as for graphic displays and TVs? 17 (~) This is particularly noticeable in liquid crystal display elements and significantly deteriorates display quality.

The present invention has been made in view of the above-mentioned circumstances, and its purpose is to process a liquid crystal display element using a pressure averaging method.
An object of the present invention is to provide a drive circuit for a liquid crystal display element that can easily eliminate display unevenness caused by irregular drive waveforms when driving in five divisions.

In order to achieve this purpose, the present invention separates a voltage dividing circuit that divides the power supply voltage to generate each heavy voltage level into a scanning side and a signal side, and outputs two levels of voltage on the scanning side. A variable impedance is provided between the two voltages so that the levels of both voltages can be changed in the same manner and in opposite directions.

That is, as mentioned above, the display unevenness is caused by the fact that the liquid crystal display element appears to have a large capacity, but since the drive circuit has an internal resistance, the pulse waveform of each drive voltage is as shown in Figure 2. This is because the waveform collapses from the ideal rectangular shape shown in FIG. 5 as shown by the solid line in FIG. In this case, as shown in the figure, this waveform distortion is significant on the scanning side, whereas it is almost negligible on the Shin-7 (ull).
: When driving a liquid crystal display element in a time-division manner, it is difficult to increase the time-division secretion 7 easily, so the number of eclipse electrodes that can be eroded is generally kept to a small number. For this reason, the number of scanning electrodes is smaller than that of signal electrodes, and the load applied to each scanning electrode is therefore large, resulting in large waveform distortion.

Due to such waveform distortion of the scanning voltage, the waveform of the electric current is also distorted from the ideal Hiko state shown in FIG. 3 to that shown by the solid line in FIG. In FIG. 6, (a).

As is clear from FIG. 1, the pixels to which the voltage X1-Yg1Xl-Ys shown in FIG. The waveform of Xl-Ys is one' of the waveform of Xs-Yg.
, and the effective value of pressure becomes slightly larger, so that the pixel to which the voltage of XI-Yg is applied becomes slightly darker than the pixel of Xa-Yg, as shown in FIG. As a result, the uniformity of the background is lost, resulting in uneven display.

In this way, the display unevenness caused by the distortion of the drive waveform of the high time division drive liquid crystal display element is caused by the impedance of the drive circuit system. it is obvious. 1- However, the impedance of the drive circuit system is affected by a large number of factors, including the impedance of the power supply, the impedance of the drive TJS, the impedance of the connection between the drive circuit and the liquid crystal display element, and the impedance of the wiring inside the liquid crystal cell. Element 6: L, L The degree of influence of each of these elements on the waveform image has been sufficiently analyzed at present. If all of these impedances are designed to be sufficiently low, the display unevenness may be reduced, but this will increase the cost and cannot be easily adopted.

On the other hand, in the present invention, since the liquid crystal has effective voltage dependence, if the deviation of the effective value due to waveform distortion of the driving voltage is compensated, the problem can be substantially eliminated.1. to exert force equivalently to
By changing the six voltage levels for the bias III FJE configuration, distortion can be eliminated without changing the driving conditions, and the voltage adjustment accuracy is 1. Since the voltage is sufficiently high, the dielectric voltage can be easily adjusted to eliminate display unevenness, etc., so the electrolytic erosion voltage is divided into 1.0 and then connected to a resistor divider circuit that generates each voltage level. A volume is included.An example will be described below.

FIG. 7 shows an embodiment of a driving circuit for a liquid crystal display element according to the present invention, and the same parts as in FIG. 4 are denoted by the same symbols, and detailed explanation thereof will be omitted. In the 7th part 1, a resistance divider circuit that divides the current voltage Vo to obtain a voltage Va=Vf is divided into 4 levels on the scanning side Va=Va + Vh + Ve
+Vf=O circuit and 4 levels Var on the signal side
Separate into circuits that obtain Vo + vd and +We j-1
Moreover, the resistance between the output terminals of the two levels Vb and Ve on the scanning side is set as 〒i]variant resistance Rv=(a-2)R+ΔR. Therefore, the voltage Vc output to Tani Inui 1 child = (1-')V
o, va=-vo, Ve=-Lvo-ΔV, Vf=
0 and a a a, and compared to the circuit of FIG. 4, vb and Ve on the scanning side each increase or decrease by ΔV.

Therefore, the rectangular frost 1 pressure formed by these pressure levels is corrected as shown by the broken line in FIG. As a result, as shown in Fig. 6, when the effective value of
In order to reduce the effective value of t-ya, the effective value of both m′
ii+ and r□ pressures can be made equal. in this case,
As is clear from FIG. 6, no DC component remains in the drive 1b2 pressure, and therefore, DC current and pressure are often applied to the liquid crystal, causing the liquid crystal to work. To make the adjustment, move the liquid crystal display element 7774 times, and while watching the display, adjust the variable resistor Rv to change the drive box 1 pressure so that display unevenness is minimized.

If the variation in waveform distortion is small, a fixed correction voltage may be determined in advance and adjusted.

As explained above, according to the present invention, there is a running electric current.

1. Correct the deviation of the effective value due to the waveform distortion of the scanning voltage (by simultaneously changing the two voltage levels forming the - in opposite directions), and correct the deviation of the effective value due to the waveform distortion of the scanning voltage. Since the value voltage can be ensured, it has an excellent effect of preventing the occurrence of display unevenness due to non-uniform crosstalk voltage.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing the configuration of a drive circuit for a liquid crystal display element;
Figures 2 and 3 are waveform diagrams showing the ideal scanning voltage, signal voltage, and drive voltage based on the pressure averaging method, respectively; Figure 4 is a circuit diagram showing a conventional resistance divider circuit; Figures 5 and 3 are FIG. 6 is a waveform diagram showing the waveform distortion of the actual scanning voltage, signal voltage, and drive box 1 pressure, respectively, and an example of their correction according to the present invention, and FIG. 7 is a circuit diagram showing an embodiment of the present invention. . 1...Scanning electrode, 2...1 signal side pole, 11...
...Scanner, 12.13...Selection switch, 14
...Data latch, 15...Shift register, 16...Transmission gate, Mill 1...
...Scanning signal, s2...AC signal, D...data, vo...'K Xt voltage, Rv...variable resistance.

Claims (1)

[Claims] A drive circuit that includes a voltage divider circuit that divides a power supply voltage to generate each voltage level constituting a scanning voltage and a signal voltage, and drives liquid crystal display atoms in a time-division manner by a voltage averaging method, wherein the voltage divider circuit is Minute N1 for the tanshi side and the signal side. -
A drive circuit for a liquid crystal display element, characterized in that a variable impedance is connected between two output terminals for taking out two voltage levels on the scanning side so that the two voltage levels can be changed simultaneously in opposite directions. .