JPS62141520A - Liquid crystal driving method - Google Patents

Abstract

PURPOSE:To drive liquid crystal at a low voltage by connecting two kinds of scanning electrode driving circuits which differ in reference voltage to scanning electrodes of a liquid crystal panel alternately, putting one on a plus side and the other on a minus side about a specific bias point, and eliminating DC unbalance between driving voltages by utilizing a certain period in one frame. CONSTITUTION:When a shift data signal SR for scanning is outputted from a display control circuit 5 to the 1st scanning electrode driving circuit 2 in synchronism with a vertical synchronizing signal, this shift data signal SR is shifted in a shift register 11 in synchronism with shift clocks -phiN2 and phiN2 having a period 2H and the output of a stage where the shift data signal of this shift register 11 opens a gate 14 to select a voltage VO; when there is a blanking period signal phiB, a gate 16 is closed and a gate 17 is open, so a voltage -VO/a is selected. Further, the 2nd scanning electrode driving circuit 3 selects a voltage -VO with the output of a stage where the shift data signal SR of a shift register 11' is stored, and when there is a blanking period signal phiB, a voltage VO/a is selected.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a liquid crystal driving method.

[Prior art to the invention and complications involved]

The drive waveform shown in FIG. 6 is known as a drive waveform for time-division driving of a Mado IJ type TJM liquid crystal. This method is called the optimal bias driving method, and it is possible to theoretically obtain the maximum operating margin. However, the amplitude of the signal 'f11fi driving waveform becomes ylVOl (
α is the bias ratio) 1 to 2 V (volt), but the maximum amplitude of the scan electrode drive circuit flash is 21V0, which is 30V.
A voltage higher than v is required. Therefore, the scanning circuit needs to have a withstand voltage of 30 V or more, which poses problems in manufacturing.

On the other hand, a drive waveform as shown in FIG. 7 is also known. In this case, the maximum amplitude of both the polar drive waveform and the scanning polar drive waveform of the signal is 1 Vol, and the amplitude is 15V. The scanning electrode drive circuit +1111 can be manufactured with a withstand voltage of about 15V, but the signal electrode magnetic circuit has a very complicated structure, and when used for television display, high-speed operation of 3 MHz or higher is required. , there is a problem in that obtaining a withstand voltage of 15V requires manufacturing work.

Therefore, in the conventional liquid crystal driving method, whether the waveform shown in FIG. 6 or the waveform shown in FIG. 7 is adopted, there is a problem in that a sophisticated manufacturing technology is required.

[Purpose of the invention]

This invention has been made in view of the above circumstances, and in contrast to the conventional liquid crystal driving method, it is possible to perform one scan without increasing the driving voltage of the signal electric IF@drive circuit! It is an object of the present invention to provide a liquid crystal driving method in which the driving voltage of a pole driving circuit is lowered so that both driving circuits can be driven at a low voltage.

[Key points of the invention]

In order to achieve this object, the present invention uses two types of scan electrode drive circuits with different reference voltages, and alternately wires their respective output terminals to the scan electrodes of the liquid crystal panel. + one side based on the bias point
The present invention is characterized in that one side is operated on the other side, and a certain period within one frame is used to prevent DC imbalance of the drive voltage.

[Embodiments of the invention]

Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a circuit block diagram for realizing the liquid crystal driving method of the present invention, in which 1 is a liquid crystal panel with 120 scanning electrodes and 160 signal electrodes, 2 is a first scanning electrode driving circuit,
3 is a second scanning electrode@driving circuit, and 4 is a signal electrode driving circuit. The first scan electrode drive circuit 2 is connected to odd-numbered scan electrodes X1, ×3, ... X2, X4, ... are connected to X120.

On the other hand, the signal electrode drive circuit 4 is connected to each signal electrode Y1, Y2, . . . Y160 of the liquid crystal panel 1.

Further, the first scan electrode drive circuit 2 has an ME source voltage r
Vo, GND (ground), -vo (α bias ratio), fJ/c2 scan electrode drive circuit 3 has -Vo%GND, -TD, and signal electrode drive circuit 4 jc VDn (+11E fA), GN
D, -Vo, --Vof)Sα
α are supplied respectively. Reference numeral 5 denotes a display control circuit which supplies the scanning side control signal A to the scanning electrode drive circuit 2.3 via a level shift +6.7, and supplies the signal side control signal B to the signal electrode drive circuit 4. The scanning side control signal B includes a blanking period signal φl, a display data row 1 shift clock φ-, a latch clock 11, a gradation signal creation lock C frame switching signal φf.

Figure 2 shows the liquid crystal driving waveform, and (1) is the first scanning single-pole driving time! (2) is the drive waveform of Yl of the signal drive circuit 4. The signal type and 1 drive waveform are based on the case where all Yl are selected.
It is arranged so that it is inverted every one common period. (3)
is the waveform of the voltage applied to the Xl-Yl liquid crystal. Also,
Tt is 1 frame T o is the selection period of 1 scanning pole (1
(common period), TC is a DC component correction period. Note that the waveform output from the second scan electrode drive circuit 3 has a potential that is inverted based on the ground level GND, as shown in Figure i3. 1 Now, if the liquid crystal is driven with such a waveform, as is clear from FIG. 2, the amplitude of the scanning electrode drive signal becomes Vo +-!
-Vo, M No. 1111 t N Drive ftH1fr
It is possible to make the signal waveform +14j c: TD 't'α 〆uniform, but below we will consider two various conditions when driving with this waveform.

■ Exchange, □flow, pivot conditions.

Assume that the x-yi-pixel selection period and non-selection period are equal. And the liquid crystal applied voltage VaV is.

Vav =, Vo Tc - Vo TnTN liquid crystal generally cannot be applied with direct current, so Vαν = O ;, 'l'c = a 'l'o
-・= 11) Here, if we consider that the above assumption does not hold, then formula (1) % Formula %: 120 x 160 LCD panel with NTSO system TV 900 million 2 TD = 2 H (horizontal scanning period) TF = 2 65.5 H α = 11.5 (described later), so ±TD is almost negligible. .

Furthermore, considering the period of nTr, it can be considered that the above-mentioned provisional treasure is almost established.

■ Optimum bias ratio condition The effective value of the applied voltage waveform at the selected point is calculated by substituting equation (1), and the effective value of the applied voltage waveform at the non-selected point is (substituting equation 11, the applied voltage ratio between the selected point and non-selected point is (Margin) The larger α is, the higher the contrast is, and the maximum condition for α is α 2α.Therefore, t'pot (1+(α-2α)5) TD t T.

, °, (2z-2)(1+(z +2z),5)=(2
z+2) (1+(cL-2a), 1=,)F Here, if we set 5-β, then β=α2 β〉0, so α=F (β is the reciprocal of the duty ratio)...・(2)
Therefore, the optimum bias ratio condition is met.

■ TD period condition The TC period is a period for correcting DC imbalance, and scanning is not possible. Therefore, if the number of scanning lines is N, then N = U TD Substituting equations (1) and (2) into this equation = β-7 If N = 120 as in the example, 120 = β-Dl, °, β=131.5 α=Fgoi5=11.5 From the above, TD, TC, and 1'F of a 120×160 pixel liquid crystal display using the NTSOe% semi-method are as follows.

TD = 2 H Tc = 22.5 H TF = 262.5H Therefore, Tl? is close to the vertical W m line M of the television, which is convenient as a method of displaying television images.

Next, the authority of the main parts of the first scan electrode active circuit 2, the second scan electrode, and the drive circuit 3 will be explained with reference to FIG. Figure 4 (α) is the first scan! The main part of the taku drive circuit 2, and FIG. 11 is a 119 role shift register,
The scanning data signal SR is shifted by two-phase shift clocks φN2 and φN2 whose phases are opposite to each other. These shift clocks ψN2, ψN2 are signals having a period twice that of the horizontal synchronizing signal.

12 is a multiplexer consisting of an inverter 13, gates 14 and 15, and when the output from the shift register 11 is 1'', the gate 14 is opened and the signal @zl is output as 'O''.
In the case of ', the gate 15 is opened and the signal line lx is selected.

The source voltage vO is connected to the signal @t1, and the source voltage ()ND and -Vo are connected to the signal line t2 at the gate 16.1.
7 through Saka Pass α. The gate 16 opens when the blanking period signal φl is not present, and the output power of the inverter 18 becomes f''1'', and the gate 15 opens when the blanking period signal φl is 11''.
Opens when. The blanking period signal φ is a signal whose period is 1'', which is equal to Tc. The only difference is that there are 120 stages of α shift registers 11' instead of (2), and the rest is the same, so the explanation will be omitted.

In the circuit structure configured as described above, when the scanning shift data signal 8R is output from the display control circuit 5 to the first scanning electrode drive circuit 2 in synchronization with the vertical synchronization signal, this shift data The signal 8R is shifted in the shift register 11 in synchronization with shift clocks φN2 and φN2 with a period of 2H, and the output of the stage in which the shift data signal of the shift register 11 is stored opens the gate 14 and selects the voltage Vo. The outputs of the other stages open the gate 15 and select the voltage GND. Also, when there is a blanking period signal φ,
Since gate 16 is closed and gate 17 is open, voltage -j-Vo
is selected. Therefore, a scanning electrode drive waveform as shown in FIG. 3(1) is obtained. Further, in the second scan electrode drive circuit 3, the shift data signal SR of the shift register 11 is
The output of the stage in which is stored selects the voltage -Vo, the outputs of the other stages select the voltage GND, and furthermore, when the blanking period signal φ1 is present, the voltage -Vo is selected, so fa
A drive waveform as shown in Figure 3 (2) α is obtained.

Therefore, scanning electrode drive signals X *, X x, X 11
9. If X 110 is illustrated as an example, it will look like an IIES diagram.The configuration of the signal electrode drive circuit 4 is almost the same as the conventional drive waveform generating circuit shown in FIG. Omitted.

[Effects of the Invention] As explained above, according to the present invention, two types of scan electrode drive circuits with different reference voltages are used, and their respective output terminals are alternately connected to the scan electrodes of the liquid crystal panel. Since the drive circuit is operated on one side with a certain bias point as a reference and the other side is operated on the one side, and a certain period within one frame is used to prevent DC imbalance of the drive voltage, the scan electrode drive circuit also The signal electrode drive circuit can also be driven with a low voltage, which has the effect of causing no small voltage or DC imbalance.

[Brief explanation of drawings]

Figures 1 to 5 are diagrams for explaining one embodiment of the present invention, Figures 6 and 7 are diagrams showing the prior art, and Figure 1 is a circuit block for realizing the present invention. Figure, @Figure 2, 3rd
Figure, tIA5 figure shows the liquid crystal drive waveform, p44 figure shows the running current! @4 is a diagram showing the configuration of the main parts of the dynamic circuit, Figure 6,!
Figure IK7 is a diagram showing a conventional liquid crystal drive waveform. l...Liquid crystal panel 2...First scan electrode drive circuit 3...Second scan electrode drive circuit 4...Signal electrode drive circuit 5...Display control circuit 6.7...Level shifter 11...Shift register 12...Multiplexer

Claims (1)

[Scope of Claims] Odd-numbered scan electrodes of the liquid crystal panel are driven with a voltage V during the selection period with the drive voltage during the non-selection period as a reference (0), and a voltage −1/αV ( α is the bias ratio), and the even-numbered scanning electrodes are driven with a voltage of 0 during the non-selection period and with a voltage of -V during the selection period, and are driven with a voltage of (1/α)V during the DC component correction period, The signal electrode is driven with a voltage of ±/αV during the selection period and the non-selection period, and with a voltage of 0 during the DC component correction period, and the polarity of the selection period and the non-selection period is reversed every scan electrode selection period T_D. A liquid crystal driving method characterized in that a correction period is approximately a·T_D.