JP3419795B2 - Electro-optical display - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a driving method of an electro-optical display device.

[0002]

2. Description of the Related Art The electro-optical display device to which the present invention is applied includes all liquid crystal devices, EL devices and the like that exhibit capacitance, but the description will be made on the display device using liquid crystal.

FIG. 2 is a connection diagram showing a relationship between a matrix electrode of a simple matrix type liquid crystal display device and its driving circuit. In FIG. 2, X1 to Xm are column electrodes (or column electrodes).
Line), Y1 to Yn are row electrodes (or row electrode lines), 201
The column electrode driving circuit for driving the column electrodes, 202 is the
Row electrode driving circuit for driving the row electrodes, 203 is a control circuit for controlling the column electrode driving circuit 201 and the row electrode driving circuit 202, 204 is the column electrode driving circuit 201, a power supply for driving the row electrode driving circuit 202 Voltage and drive of the column electrode
The column voltage is supplied via the circuit 201 and the row electrode drive circuit 202.
It is a drive power supply circuit that generates a liquid crystal drive voltage applied to the poles and the row electrodes .

Although there are several different methods for the specific example of the configuration shown in FIG. 2, it is complicated to explain all cases, and an example thereof is shown in FIG. 3, and the detailed description is given below. However, the idea of the present application can be effectively implemented in drive circuits of other systems.

In FIG. 5, the column electrode drive circuit 301 is a logic circuit 305 which appropriately processes a signal sent from a control circuit (not shown), and a j-th (j =) based on a command from the logic circuit 305. 1 ... m) to the column electrode Xj of + Vs
Alternatively, the output circuit 302j selectively supplies -Vs. That is, when the transistor 303j is on and the transistor 304j is off, + Vs is applied to the column electrode Xj.
When the transistor 303j is turned off and the transistor 304j is turned on, -Vs is applied to the column electrode Xj. There is no situation where the two transistors 303j and 304j are turned on at the same time. The transistor 303j
And 304j respectively have a positive side power source + Vd and a negative side power source −V applied to the logic circuit 305.
connected to d. (However, | Vd | ≧ | Vs |)

On the other hand, the row electrode drive circuit 306 is a k-th (k = 1 ...) Based on a logic circuit 311 which appropriately processes a signal sent from a control circuit (not shown) and a command from the logic circuit 311. n) output circuit 307 for selectively supplying + Vc or -Vc or 0 to the row electrode line Yk
It consists of k and. That is, when the transistor 308k is on and the transistor 309k and the semiconductor switch 310k are off, + Vc is applied to the row electrode Yk, the transistor 308k and the switch 310k are off, and the transistor 3
When 09k is on, -Vc is applied to the row electrode Yk. When the two transistors 308k and 309k are off and the switch 310k is on, the row electrode Y
A zero potential is applied to k. Transistors 308k, 3
There is no state in which two or more of 09k and switch 310k are turned on at the same time. The bases of the transistors that form the transistors 308k and 309k and the switch 310k are based on the positive power supply + Ve and the negative power supply -Ve (| Ve | ≧ | Vc) applied to the logic circuit 311.
|).

Thus, the column electrode drive voltage VXj (+ is applied to the pixel Pjk formed at the intersection of the column electrode Xj and the row electrode Yk.
Vs, -Vs) and the row electrode drive voltage VYk (+ Vc, 0,
Although a voltage having a difference from −Vc) is applied , there are several ways to select each voltage.

[0008] Figure 4 Ah <br/> Ru a diagram showing an example of an ideal voltage waveforms to be applied to the liquid crystal by using the circuit configuration shown in FIG. In FIG. 4, periods T1 (t1), T2 (t2) ...
Tn (tn) is a period in which the first row electrode Y1, the second row electrode Y2, and the nth row electrode Yn are selectively driven, and the periods T1 to Tn (or the period t).
One vertical scanning period is from 1 to tn). Each pixel has a selection period of 1 / n of one vertical scanning period and 1-1 / n
Driven by the voltage applied during the non-selection period. The In the period T1 the row electrodes Y1 + Vc is applied to the other row electrodes zero potential is applied. In the period T2 , -Vc is applied to the row electrode Y2, and 0 is applied to the other row electrodes.
An electric potential is applied. Such a method of inverting the polarity of the selection drive voltage every time the row to be selectively driven changes is called row-by-row inversion. Further, in the next vertical scanning period t1 ... tn, the polarity of the selection drive voltage applied to each row is further inverted, but this method is called 1-field inversion. Therefore, the method shown in FIG. 4 is the “one-row inversion one-field inversion method”.
Called.

On the other hand, the drive voltage applied to the column electrodes is determined by the data to be displayed. Now, it is assumed that the pixel portion corresponding to the column electrode Xa displays black over the entire period and the pixel portion corresponding to the column electrode Xb displays white during the entire period, and the liquid crystal panel used is a normally black ( As the applied voltage increases, the transparent electrode becomes transparent. Voltages such as VXa and VXb in FIG. 4 are applied to the respective column electrodes. For example, VY1 is applied to the pixel Pa1 at the intersection of the row electrode Y1 and the column electrode Xa. -VXa voltage is applied,
The waveform is as shown by VPa1 in FIG. A voltage such as VPb1 in FIG. 4 is applied to the pixel Pb1 composed of the row electrode Y1 and the column electrode Xb.

Assuming that the liquid crystal responds to the effective value of the applied voltage, the effective value of the voltage applied to the pixel Pa1 (hereinafter referred to as the drive effective voltage) in one scanning period is the mathematical expression 1, and The driving effective voltage applied to the pixel Pb1 is given by the equation 2.

[Equation 1]

[Equation 2]

The difference between the above equations 1 and 2 appears as the difference in the display state (dark and light) of the pixel. Therefore, the larger the difference between Equation 1 and Equation 2, the better the display can be obtained.
Is a condition that the value (Von / Voff) obtained by dividing by is a maximum, and is given by a formula 3. Under this condition, the formula 2 is converted into a formula 1
The value divided by is Equation 4.

[Equation 3]

[Equation 4]

When | Vc | / | Vs | is used as a drive voltage ratio and the drive voltage ratio satisfies the expression 3 , this is called an optimum drive voltage ratio. The Voff and Von are uniquely determined by determining Vc and Vs. A column electrode drive as shown by VXc in FIG.
Driving dynamics between Von and Voff using dynamic voltage waveform
A voltage can be applied to the liquid crystal, and by using such a method, a liquid crystal television that requires gradation display has been realized.

By using the above equation 3, when | Vc | is set to a certain value, | Vs which gives the maximum contrast
The value of | can be obtained, and the contrast decreases with values other than | Vs |. However, the waveform V shown in FIG.
Xa, VXb, VXc, etc. are merely ideal states, and in reality, the liquid crystal drive voltage waveform becomes rounded (including spikes) due to the parasitic resistance parasitic on each part and the capacitance of the liquid crystal. Not in an ideal state. This means that even if the drive voltage is set to obtain the maximum contrast based on Equation 3, the theoretically obtained contrast cannot be obtained. Simply speaking, the greater the rounding of the drive voltage waveform applied to both ends of the liquid crystal, the lower the contrast.

Next, the dullness of the driving waveform causes a decrease in the response of the liquid crystal. That is, the response of the liquid crystal becomes faster as the value of Von / Voff is larger, but if the waveform is blunted, Von / V
The off value becomes small, the response of the liquid crystal is deteriorated, and a so-called afterimage phenomenon becomes prominent when a display with fast movement is performed. Further, the driving waveform rounding is a cause of crosstalk, which has hitherto been pointed out as a big problem in a simple matrix type display device. For example, on an LCD TV,
When the display as shown in (a) is attempted, the actual display is as shown in FIG.
It becomes like (b). In addition, in order to improve the drive duty ratio, the display panel is divided into two parts, that is, the display panel is divided into upper and lower parts, and each of them is driven independently. 5 (d) is displayed, and the display state is different at the top and bottom of the panel.
The cause is also the output resistance of the drive power supply circuit 204, the internal wiring resistance and output resistance of the column electrode drive circuit 201 and the row electrode drive circuit 202, or the connection resistance between both drive circuits and the display panel, the display panel. This is because the voltage waveform applied to the liquid crystal is rounded due to the influence of the resistance of the internal extraction electrode portion and the like, and the ideal state is not obtained.

As described above, the blunting of the voltage waveform applied to both ends of the liquid crystal deteriorates all the characteristics of the liquid crystal display device, and in some cases, the liquid crystal display device is unusable. In order to avoid this phenomenon, the conventional measures have been to first stabilize the voltage externally applied to the drive circuit and then reduce the resistance of each part as much as possible. However, it is difficult to reduce the resistance of each part to zero, and some resistance always remains. Therefore, there have been cases where conventional measures were taken and sufficient effects could not be obtained.

As described above, the rounding of the waveform applied to both ends of the liquid crystal lowers all characteristics of the liquid crystal display.
On the other hand, the present invention has been made to improve the rounding of the waveform by a novel method and realize an ideal driving state in all aspects, but conventionally, as a problem caused by the rounding of the waveform, Since crosstalk has been mainly taken up, in order to clarify the difference from the prior art, the explanation will focus on the crosstalk problem.

A typical description of conventional crosstalk is as shown in FIG. That is, assuming that all the pixels on the column A display only white (or black), the column driving voltage of the column A is inverted every time row scanning is performed,
Since the liquid crystal, which is a capacitive load, is charged / discharged at every inversion, the driving voltage applied across both ends of any one pixel on the column A is in the non-selection period as shown by VA in FIG. Also produces bluntness in the waveform. On the other hand, if the pixels on the column B are in a display state in which black and white are inverted for each row, the column drive voltage of the column B will be kept at a constant value, so that the liquid crystal is not charged / discharged during the non-selection period. The drive voltage applied to both ends of any one pixel on B is as shown by VB in FIG. Comparing the two non-selected periods, the effective value of VA is smaller than the effective value of VB, which is the cause of crosstalk.

As an improvement plan based on the above idea, for example, there is a proposal such as Japanese Patent Publication No. 64-1971 which has a certain effect. However, these conventional techniques do not improve the waveform rounding itself, but focus on equalizing the number of times of charge / discharge that causes the waveform rounding, and the display data is binary (black and white). Since it was made assuming that the above case, it has been said that it is not an effective measure when displaying gradations such as television images.

That is, when the display data is binary, the switching of the driving voltage coincides with the scanning switching timing of the row electrodes. Therefore, by devising the polarity inversion cycle of the row driving voltage, the non-selected charging of each column is completed. It is possible to adjust the number of discharges to be approximately equal and to make the effective value of each column uniform when the column is not selected, regardless of the display pattern. However, in a liquid crystal television with gradation, as shown by VXc in FIG. This is because the switching of the electrode driving voltage does not always coincide with the scanning switching timing of the row electrode, and therefore the number of times of charging and discharging cannot be adjusted even if the polarity of the row driving voltage is reversed.

The inventor has made a detailed examination of the influence of the waveform rounding on the crosstalk, and has found that there are cases where the idea of FIG. 6 cannot be explained. Therefore, in order to analyze this, an attempt was made to model the liquid crystal driving state. It was FIG. 7 shows a conventional model which is the basis of the description of FIG. In FIG. 7, the basis is that a plurality of row electrodes is originally represented by one. That is, of the plurality of row electrodes, only one is selectively applied with a large voltage during a certain period,
Since the rest are all fixed at 0 potential, the influence of the selected row electrode is considered to be sufficiently small overall and eliminated, and an absolute large number of row electrodes in the non-selected state are collectively set to 1
It can be a book. Then, each column electrode can be considered as a set of electrodes each having a capacitance c with respect to one row electrode at 0 potential, and these column electrodes each have a switch S1, S2.・ By + Vs
And -Vs can be considered to be switched.

The only problem with this model is that it focuses only on the column electrodes as resistance components, and also switches (corresponding to the transistors 303j and 304j in FIG. 3).
Only the output resistance of is taken up. Certainly, the output resistance of the integrated liquid crystal drive circuit is in the order of kilo ohms, which is much larger than the resistance added to other circuits. However, there is a resistance (including the output resistance of the power supply) in series in the power supply line although it is small, and it may not be negligible because it involves the total of the currents flowing through the multiple paths.

In particular, the power supply line resistance involved in driving the row electrodes has not been considered at all in the description of FIG.
Considering the appearance of crosstalk in LCD TV images, it can be considered that this is a factor that cannot be ignored. Therefore, when the resistance of each power supply line is added to FIG. 7, it becomes as shown in FIG.
In FIG. 8, a resistor RD is inserted in the + Vs power supply line,
A resistance RS is added to the Vs power supply line. On the other hand, regarding the row electrodes, a resistance RM is added to 0 potential. The resistance R
M also includes the output resistance of the row electrode drive circuit (the output resistance of the semiconductor switch 310k in FIG. 3).

Since crosstalk occurs when the driving waveforms are different between the column electrodes, a plurality of column electrodes can be divided into two groups and considered as a model. FIG. 9 shows a model in which N column electrodes are divided into M and (N−M) lines. In FIG. 9, the equivalent capacity CB of the group grouped into M (hereinafter referred to as B group) is c ·
M, and the equivalent output resistance rB becomes ro / M. On the other hand, the equivalent capacitance CA of the group (hereinafter referred to as A group) grouped into (N−M) lines is c · (N−M), and the equivalent output resistance rA is ro / (N−M). The group B is a switch SB, and the group A is a switch S.
A switches to + Vs and -Vs for connection. Within each group, the display state of each line is the same.

The simulation results in the non-selection period using this model are shown below. In these figures, SWA and SWB are the switches SA and SB of FIG. 9, respectively.
The switch SA is connected to the + Vs side when the SWA is at the H level, and is connected to the -Vs side when the SWA is at the L level. Also VDX, VSX, VM
X, VA, and VB represent potentials or potential differences at the points shown in FIG. Further, in order to make the condition that the influence of the waveform rounding is significant, in FIGS. 10 to 12, (NM) >>
M, the values of ro, c, RD, RS, and RM are selected to be values close to those of an actual display device, and for c,
Although the actual capacitance of the liquid crystal has different values when turned on and off, the value does not change depending on the state in the simulation.

FIG. 10 is a diagram showing simulation results for the case corresponding to FIG. VY in FIG.
1, VY2 and VY3 indicate the row electrode selection timing,
In each of the row electrodes, a hatched portion shows a state in which a selection potential (+ Vc or −Vc) is applied and 0 is applied in other periods. These are just timings and are ignored in the simulation.

Since the group A displays only white or black over all the rows, the state SWA of the switch SA changes to H or L each time the selection period of the row electrode changes, as shown in the figure.
On the other hand, since the B group alternately displays white and black for each row, the state SWB of the switch SB is fixed to, for example, H during one vertical scanning period (fixed to L during the next scanning period).

At this time, the waveforms of VA and VB in FIG. 9 are ideally those shown in VA and VB of FIG. 10, but actually they are like VAX and VBX of FIG. However, the roundness and spikes of the waveform actually show an exponential change, but are represented linearly for simplicity. Also, it is said that spikes of extremely short duration can be ignored when calculating the effective value from the response of the liquid crystal, so they are omitted in the drawings (same below).

Comparing VAX and VBX with FIG.
While AX is in line, VBX is clearly different.
The cause is V due to the existence of the resistors RD, RS and RM in FIG.
This is because DX, VSX, and VMX fluctuate as shown in FIG. Explaining this variation, when the switch state SWA changes from L to H at the time Tp, + Vs in FIG.
Through the resistor RD, the switch SA, the resistor rA, the capacitor cA, and the resistor RM, a spike-shaped current flows toward the 0 potential, and VDX and VMX fluctuate in a spike shape due to the voltage drop due to this current. At this time, no current flows through the resistor RS and VSX does not change. Next, at time Tq, switch state S
When WA changes from H to L, a spike-shaped current flows from 0 potential to −Vs via the resistor RM, the liquid crystal cA, the resistor rA, and the resistor RS, and as a result, VSX and VMX fluctuate. At this time, no current flows through the resistor RD and VDX does not change.

When the value of NM is sufficiently large, r
Since A is sufficiently small, the voltage drop due to the resistor rA is sufficiently smaller than the voltage drop due to the resistors RD and RS. On the other hand, current flows through the capacitor CB as VDX and VMX fluctuate, but M is N- C if sufficiently smaller than M
The value of B is sufficiently smaller than that of cA, and the voltage drop caused by the resistance rB in the current flowing through cB is relatively small, so that the voltage VAX (or VB) applied across the liquid crystal is eventually obtained.
X) is approximately VDX-VMX when the switch state SWA (or SWB) is H, and is approximately VSX-VMX when the switch state SWA (or SWB) is L, as shown in FIG.

In the vicinity of time Tp, the fluctuations of VDX and VDM both act to reduce the effective value for both VAX and VBX, but in the vicinity of time Tq, the fluctuation of VMX is effective value for VBX. It can be seen that it works in the direction of increasing VAX and that both the fluctuations of VMX and VSX work in the direction of lowering the effective value for VAX. Looking at this result, VA
It is considered that the difference between the effective values of X and VBX is more affected by the resistances RD, RS, RM on the row electrode side rather than the column electrode output resistance ro in FIG.

FIG. 11 shows the case where the A group and the B group display black and white opposites over all the rows, and FIG. 12 shows the A group which displays white or black.
It is a figure which shows the simulation result when the said B group displays the gray of the middle, and a symbol, a name, etc. are shown in FIG.
It is similar to the case of 0. SW is different from the case of FIG.
Although there is a point that the current according to the change of B flows in CB of FIG. 9,
Since the value of CB is sufficiently smaller than that of CA as described above, this current component may be ignored.
Therefore, since the same viewpoints as in FIG. 10 may be applied to FIGS. 11 and 12, the individual description will be omitted. However, even if these results are seen, the drive effective voltage applied to the pixels in the A group at the time of non-selection is It is obvious that the driving effective voltage in the non-selected state, which is lowered, is higher than that in the A group. Since the liquid crystal is assumed to be normally black, the display state becomes darker as the drive effective voltage decreases, and the display state becomes brighter as the drive effective voltage increases.
The display state of the pixels in the columns of the group is darker than it should be, and the display state of the pixels in the columns of the B group is relatively brighter than that of the A group (particularly in the case of FIGS. 11 and 12, the original display state is Will be displayed). Comparing the difference between the drive voltages VAX and VBX applied to the pixels of the A group and the B group in the non-selection period in FIGS. 10, 11, and 12, the comparison is made only in the vicinity of time Tq in the case of FIG. 11 and 12 while there is a difference
It can be seen that there is a difference near both times Tp and Tq. In other words, as a matter of course, when the group A column drive voltage changes (at this time, VDX, VMX, VSX change),
A difference occurs in the row in which the display state of the group B is different from the display state of the group A, and the drive effective voltage difference in the entire non-selection period is determined by the number of such rows.

Although the above description relates to the non-selection period, the selection period is complicated but can be considered as follows. For simplicity, ignoring the waveform rounding of the selection voltage (± Vc), for example, in FIG. 10, when the A group is displayed in white, the row electrode drive voltage VY1 should be -Vc at time Tp. Therefore, Y1 of Group A
Since -Vc-VDX is applied to the pixels in the row and the row electrode drive voltage VY2 should be + Vc at the time Tq, + Vc- is applied to the pixels in the Y2 row of the A group. VSX will be applied. In this case VD
It is clear that the direction of the rounding of X and VSX is the direction of decreasing the effective value in the selection period (the direction of darkening white). On the other hand, when the group A displays black, the row electrode drive voltage VY1 should be + Vc at time Tp. Therefore, the pixel in the row Y1 of the group A is + Vc-V.
Since DX is applied and the row electrode drive voltage VY2 should be -Vc at time Tq, -Vc-VSX is applied to the pixels in the Y2 row of the A group. become. In this case, it is clear that the direction in which VDX and VSX are rounded is the direction in which the effective value in the selection period is increased (black is brightened). From the above, it can be said that the dullness of the drive voltage applied to the pixels of the group A during the selection period is effective in decreasing the contrast. Regarding the pixels of the B group, the same voltage as that of the A group is applied to the pixels of the same display as the A group, but regarding the display pixels different from the A group, for example, when the A group is white display, + Vc at time Tq.
Since -VDX is applied, the effective value does not change during the selection period.

Summarizing the above, in the model of FIG.
When NM >> M, the following is obtained. (1) In the non-selected period, the drive effective voltage of the group A decreases regardless of the display state. The amount of decrease depends on the number of times the column electrode drive voltage is switched. (2) In the non-selected period, the driving effective voltage of the B group is higher than that of the A group regardless of the display state. The amount of increase depends on the number of rows in a display state different from that of the A group when the column electrode drive voltage of the A group is switched. (3) In the selection period, when the display changes from black to white, the driving effective voltage of the group A decreases. The drive effective voltage increases when the display changes from white to black. (4) In the selection period, the drive effective voltage of the group B is either increased, decreased, or unchanged depending on the display state.

Since the driving effective voltage actually applied to the liquid crystal has to be calculated over the entire selection period and non-selection period, strictly speaking, extremely complicated calculation must be performed depending on the display state. . However, in any case, it is presumed that the influence of the resistors RD, RS, and RM is large as a cause of crosstalk or contrast reduction, and the conventional way of thinking is insufficient. Therefore, it must be determined that a truly effective countermeasure could not be found. I don't get.

11 to 12 show that the entire column (N lines) of the liquid crystal display device is divided into two column groups (A group and B group), and the number NM of columns of A group is the number of columns of B group. Although the simulation result is set to be sufficiently larger than the number M, FIG. 13 is a diagram showing a simulation result when the number of columns of the A group and the B group is the same, and the timing relationship corresponds to that of FIG. . Figure 11
In Fig. 13, a difference in effective value was clearly recognized between VAX and VBX, but in Fig. 13, no difference in effective value was recognized between VAX and VBX. That is, in this case, crosstalk does not occur, but the important point here is that FIG.
The waveform rounding in each part in Fig. 11 is smaller than that in Fig. 11. As described above, the effective value at the time of selection is affected by the waveform rounding of VDX and VSX. In the case of FIG. 11, since the rounding of VDX and VSX is large, there is a large deviation from the theoretical value of the drive voltage applied to the pixel during the selection period, and the white portion is dark and the black portion is bright. Even if the effective value during the non-selection period is the same, the contrast is lowered, but in the case of FIG. 13, VDX, V
It can be said that the roundness of SX is small and the decrease in contrast is slight. Paradoxically, in order to obtain the maximum contrast, half of the screen should be displayed in white and the other half should be displayed in black. Conversely, when the entire screen is displayed in white or black and the difference between the two is seen. You will get the lowest contrast.

The cause of the difference in waveform rounding between FIGS. 11 and 13 can be understood as follows. FIG. 14A is an equivalent circuit diagram modeling the case of FIG. Let cx be the capacity of the liquid crystal formed in the half of the screen, and let RD, RS, and RM be all rx for simplicity. At this time, current Ix flowing from + Vs
All flow to -Vs, and no current flows toward 0 potential. At this time, the time constant Tx of the circuit is (2 · rx) (cx /
2) = rx · cx, and the roundness of the waveform of the voltage applied across the liquid crystal of the group A is small as shown in FIG. 14 (b).

On the other hand, FIG. 15 (a) is an equivalent circuit corresponding to FIG. 11. If the capacity of the B group is much smaller than that of the A group, this is set to 0 and the capacity of the A group is 2 · (cx). ) Can be used. At this time, all the current flowing from + Vx goes to the 0 potential. At this time, the time constant Tx of the circuit is (2 · rx) (2 · cx) = 4 · rx ·
cx, and the rounding of the waveform of the voltage applied to both ends of the liquid crystal of the group A is four times larger than that of FIG. 14, as shown in FIG. The difference in this time constant is V in FIG.
It means that the waveform rounding of DX and VSX also has a quadruple difference between the maximum and the minimum.

If the RMS values at the time of non-selection are equal, the difference in the display state is determined by the difference between the RMS values at the time of selection, and the RMS value at the time of selection is affected by the waveform rounding of VDX and VSX. Therefore, the difference in the waveform rounding of VDX and VSX means the difference in the effective value at the time of selection, and the portion which should have the same brightness originally depends on the display state. In addition, the difference of 4 times the time constant becomes effective when it is calculated as an effective value.

Very recently, measures against crosstalk have been proposed in consideration of the resistance of the power supply line. "SID 90 DIGE
ST412 21.4: Crosstalk-Fre
eDriving Methods for STN-
In Fig. 3 of "LCDs" (hereinafter referred to as Reference 1), a resistance corresponding to the RM of the present application is drawn, and the voltage drop due to this resistance is one of the causes of crosstalk, and the effect due to this voltage drop is corrected. VM in this application
In addition, a DC bias voltage ΔV is added for each driving period of each row. At this time, the ΔV is calculated from the difference between the number of ON-state pixels on the row electrode in the current selection period and the number of ON-state pixels on the next selected row electrode.

From the conclusion, it can be said that this method is effective as a measure against crosstalk. However, this model does not consider the power source resistances RD and RS as referred to in the present application, and the idea is that the difference in effective voltage during the non-selection period is canceled by the DC bias, so ΔV is relatively small. , The waveform is not rounded. This means that although the effective voltage can be made uniform during the non-selection period, the effect of waveform rounding during the selection period is not greatly improved, and the factor of crosstalk is still left behind. Contrast and responsiveness are also R
There is room for improvement as long as there is an influence of D and RS. Further, this method is effective for so-called frame gradation, as described in Document 1 above. However, it is difficult to apply it to a liquid crystal television that performs gradation display by changing the voltage application time within the selection period.

The ΔV is a DC voltage calculated from the difference between the number of ON-state pixels on the row electrode in the current selection period and the number of ON-state pixels on the next selected row electrode.
However, when performing so-called gradation display,
Even if the number of pixels that change state during the selection period is the same,
The timing of conversion is not always the same. For example all
In some cases, all pixels may be turned on at the same time, or
It may be turned on at the timing of La. Due to the nature of RMS calculation, the RMS values are different in both cases , so simply
Just count the number of pixels that change state and convert to DC voltage
Then correct correction cannot be done .

[0042]

Therefore, an object of the present invention is to make the driving voltage applied to both ends of the liquid crystal as close to the ideal state as possible so that the waveform including the above-mentioned crosstalk problem is displayed in any display mode. There is a solution to the problems caused by blunting.

[0043]

The effect of the resistance of each part (output resistance of a power supply, wiring resistance in a driving integrated circuit circuit, wiring resistance in a panel, etc.) that causes waveform distortion is as follows. It is the effect of the voltage drop caused by the current flowing through the resistor. This current flows in and out of the row electrode drive circuit and the column electrode drive circuit through the liquid crystal that is a capacitive load, and causes a voltage drop when passing through the resistance of each part, and a voltage different from the voltage applied from the outside causes the liquid crystal to flow. Result in being applied to. According to the present invention, the above voltage drops are always present, though they exist to some extent.Focusing on the resistors parasitic on the power supply system, which have a particularly large influence, the currents causing the voltage drops are detected. However, the problem is solved by changing the voltage applied to the drive circuit from the outside according to the current amount.

[0044]

FIG. 16 is an explanatory view for explaining the basic idea of the present invention. When the circuit of FIG. 16A is considered and the voltage waveform applied to the V point and the voltage waveform of the E point corresponding thereto are considered, when the stepwise voltage waveform is applied to V as shown in FIG. 16B. , The waveform rounding at point E is large, but as shown in FIG. 16C, the waveform rounding at point E is reduced by adding an impulse-like correction voltage to the voltage applied to point V. Means adopted by the present invention to solve the problems based on such an idea are "a display device having a row electrode group, a column electrode group, a row electrode drive circuit and a column electrode drive circuit. Then, the amount of current flowing through the display panel is detected. (1) The row electrode drive voltage applied to the row electrode group via the row electrode drive circuit is controlled according to the amount of current. (2) The column electrode drive voltage applied to the column electrode group via the column electrode drive circuit is controlled according to the amount of current. It is a thing.

[0045]

According to the present invention, the voltage drop caused by the current flowing through the display panel is detected and corrected, and as a result, the drive voltage applied to the liquid crystal approaches the ideal state in all states. , The contrast is improved,
Responsiveness is improved and crosstalk is significantly reduced.

[0046]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a first embodiment of the present invention and corresponds to (1) of the above-mentioned "means for solving the problems". In FIG. 1, the correction circuit 100 is configured as follows. The potential EA is applied to the positive input terminal of the first differential amplifier 101, and the output terminal of the first differential amplifier 101 has a resistor R.
The signal is fed back to the negative input terminal of the first differential amplifier 101 via a and the third differential amplifier 103 is supplied via the resistor r.
Connected to the negative input terminal of. The potential EB is applied to the positive input terminal of the second differential amplifier 102, and the second differential amplifier 1
The output terminal of 02 is connected to the second differential amplifier 1 via the resistor Ra.
02 is fed back to the negative input end of the second differential amplifier 103, and is also connected to the negative input end of the third differential amplifier 103 via the resistor r. A potential EA is applied to the positive input terminal of the third differential amplifier 103 via a resistor Rx, and a potential E is applied via a resistor Rx.
B is applied, and the output terminal of the third differential amplifier 103 is fed back to the negative input terminal of the third differential amplifier 103 via the resistor R. The output VH is from the negative input end of the first differential amplifier 101, the output VL is from the negative input end of the second differential amplifier 102, and the output VM is the third differential amplifier 1.
It is taken from the output terminal of 03.

This circuit will be described with reference to FIGS. 17 and 18. The circuit shown in FIG. 17 is a well-known and well-known current detection circuit, and the current flowing from the output V to the load is I
Then, V = E and Vo = E + Ra · I. In the circuit shown in FIG. 18, the output VM is VM = (EA + EB) / 2- (R / r). (EA + e
B). Therefore, in the circuit shown in FIG. 1, the current flowing out from the output VH is IH and the current flowing into the output VL is IL.
When VH = EA, VL = EB, VM = (EA + EB) / 2- (R.Ra / r). (IH
-IL), VM becomes a voltage obtained by subtracting a voltage proportional to IH from the intermediate potential between EA and EB and adding a voltage proportional to IL.

When the correction circuit 100 shown in FIG. 1 is applied to FIG. 9, the configuration shown in FIG. 19 is obtained. In FIG. 19, FIG.
Unlike +, + Vs and -Vs are reference voltages. In Figure 19
Then, the voltage corresponding to + Vs and -Vs in FIG. 9 is
Notated as VH and VL, the voltage corresponding to 0 in FIG. 9 is
It is written as VM. That is, VH and VL are connected via the power line
Drive voltage of a predetermined value that is supplied to the column electrode drive circuit.
VM is supplied to the row electrode drive circuit via the power supply line,
Where the row electrode drive circuit should apply to the row electrodes in the non-selected period
It is a constant drive voltage. As shown in FIG. 1 in FIG.
The correction circuit 100 operates as follows. When EA = + Vs and EB = -Vs, VH = + Vs, VL = -Vs, VM =-(IR.Ra / r). (IH-IL), and when IH flows and VMX tries to rise. Is V
M decreases in proportion to IH, and tends to decrease VMX. When IL flows and VMX is going to drop, VM goes up in proportion to IL and VMX goes up. The proportional constants for multiplying IH and IL are shown in FIG.
Adjustment is made by changing the resistance R.

The proportional constant (hereinafter referred to as "compensation amplification factor")
20 and FIG. 2 show simulation results in the non-selection period in the configuration shown in FIG. 19 when is set to a certain value.
1, shown in FIG. The timing relationships in these figures correspond to those in FIGS. 10, 11 and 12, respectively. Referring to FIG. 20, when the switch state SWA changes from L to H at time Tp, a current of IH flows from VH to VM. This current tries to raise the potential of VMX, but the correction circuit 100 lowers the potential of VM by a voltage proportional to the IH, and consequently VMX does not rise but rather falls. At time Tq
In its, the switch state SWA is switched from H to L, IL becomes a current flows toward the VL from VM, VM
The correction circuit 100 tries to decrease the potential of X.
Causes the potential of VM to rise by a voltage proportional to the IL, and as a result, VMX does not fall but rather rises.

As a result, VAX, V near the time Tp
For both BX, the fluctuation of VDX works to decrease the effective value, while the fluctuation of VMX works to increase the effective value. In the vicinity of time Tq, VAX is V
While the fluctuation of SX acts to lower the effective value, VM
The fluctuation of X acts to increase the effective value, while VMX acts to decrease the effective value with respect to VBX. As these combined action, the effective value of VAX and VBX is rather closer in a direction equal. The point to be noted is that the VMX is originally
To create a steep fluctuation with the opposite polarity to the polarity of the fluctuating fluctuation.
When compensated, the RMS value is corrected very effectively.
It is that. Of course, to make the VMX fluctuations simply 0
Even if the compensation is made, of course, there is no waveform distortion due to the VMX fluctuation.
However, in this case VDX, V
Waveform distortion due to fluctuations in SX still remains.
On the other hand, the polarity opposite to the polarity that originally causes the potential of VMX
If it is changed to the polarity, it may be changed by VDX and VSX.
It is also possible to compensate for the waveform distortion that occurs. That is,
10 and 20, FIG. 11 and FIG. 21, and FIG. 12 and FIG.
It is clear by comparing the potential fluctuation of each VMX
As shown in FIG. 10 and FIG.
1, Fig. 12) where the positive polarity fluctuation originally occurs (Tp)
In the negative polarity, the part (Tq) where the negative polarity originally changes
The effect of compensation is remarkable when the positive polarity fluctuation is given.
Yes. By setting the above-mentioned compensation gain appropriately,
You can get the best compensation effect like.

The important point here is that in the case of the above embodiment, VM
A sharp fluctuation in the opposite direction to the fluctuation that originally occurs in the X potential is generated.
The action that causes it is that positive feedback is used. That is, the current IH flows based on the potential difference between VH and VM, but when IH flows, VM is reduced in proportion to this value, so the value of IH becomes larger and larger. VM is lowered, and as a result, the positive feedback action works, and as a result, IH momentarily becomes a large current. This produces the following effects.

Generally, when considering the charge / discharge characteristics of the capacity, the voltage across the capacity is proportional to the integral value of the charge / discharge current.
In charging / discharging with a small current value, the voltage across the capacity changes slowly, and so-called rounding is large. On the contrary, in charging / discharging with a large current, the voltage across the capacity changes abruptly, and the rounding is small. That is, according to the present embodiment, the positive feedback action described above results in instantaneous charging / discharging of the liquid crystal, which is a capacitive load, and the rounding of the drive voltage waveform applied to both ends of the liquid crystal is significantly improved. It approaches the driving state.
The time td shown in FIG. 20 is drawn larger than the actual simulation result for easy understanding of the effect of the present invention.

Since the same view can be applied to FIGS. 21 and 22, the description thereof will be omitted. Notable is VA
This is the point where the effective values of X and VBX are all considered to be the same over FIGS. 20, 21, and 22. This is shown in FIG. 10 and FIG.
1. It can be seen clearly by comparing with FIG. That is, the effective values of VBX shown in FIG. 11 and VBX shown in FIG. 12 are considered to be equal. However, for these two parties, the VB shown in FIG.
RMS values of X are not considered equal. On the other hand, in FIG. 20, FIG. 21 and FIG.
There is no difference in the effective voltage between X and VAX and V
There is no difference in the effective value between BX.

Although the above is for the non-selection period, the selection period will be described with reference to VDX and VS in FIGS.
There is no difference in X, and as described above, the time td is sufficiently small. According to the liquid crystal theory, it is not necessary to include it in the effective value calculation due to the responsiveness of the liquid crystal when the voltage fluctuation is sufficiently short in time. As described above, from a practical point of view, FIG. In FIG. 22, it can be considered that there is no substantial difference in the driving force of the liquid crystal during the selection period. On the other hand, in the cases of FIGS. 10 to 12, the waveform is blunt and gentle, and it can be said that the driving force of the liquid crystal is affected accordingly.

FIG. 23 shows a second embodiment of the present invention and corresponds to (2) of the above-mentioned "means for solving the problem". In FIG. 23, the correction circuit 230 is configured as follows. The input EA is connected to a point P2 via a resistor r, and the point P2 is connected to the positive input terminal of the second differential amplifier 232. The input EB is connected to the point P3 via the resistor r, and the point P3 is connected to the positive input terminal of the third differential amplifier 233. The point P2 is further connected to a point P1 via a resistor r, and the point P1 is connected to the positive input terminal of the first differential amplifier 231 and also connected to the point P3 via a resistor r. The output terminal P4 of the first differential amplifier 231 has a resistor Ra.
Is fed back to the negative input terminal of the first differential amplifier 231 via
2 is connected to the negative input end of
Is connected to the negative input terminal of the differential amplifier 233. The second
The output terminal of the differential amplifier 232 is fed back to the negative input terminal of the second differential amplifier 232 via the resistor R. The output terminal of the third differential amplifier 233 is fed back to the negative input terminal of the third differential amplifier 233 via the resistor R. The output VH is output from the output terminal of the second differential amplifier 232, the output VL is output from the output terminal of the third differential amplifier 233, and the output VM is output.
Is taken from the negative input of the first differential amplifier 231.

In the configuration of FIG. 23, the potentials at points P1, P2, P3 and P4 are set to VP1, VP2 and VP, respectively.
3, VP4, and IM is the current flowing from the output VM toward the load, VP1 = (EA + EB) / 2, VP2 = (EA + VP
1) / 2, VP3 = (EB + VP1) / 2, VP4 =
It becomes (EA + EB) / 2 + Ra · IM. At this time, the outputs VH, VL, and VM are VH = EA-Ra.IM and VL = EB-Ra.IM VM = (EA + EB) / 2, as is apparent from the function of the differential amplifier. That is, an intermediate potential between EA and EB is output to VM, and potentials obtained by subtracting a variation proportional to the current IM from EA and EB are output to VH and VL, respectively. In the first embodiment described above, VM is corrected according to the current flowing out of VH and VL, whereas in the second embodiment, V is corrected.
VH and VL will be corrected according to the current flowing out of M.

Now, in the correction circuit 230 of FIG.
= + Vs and EB = -Vs, VH = + Vs-Ra.
24. IM, VL = −Vs−Ra · IM, VM = 0, which is replaced by the correction circuit 100 in FIG. The timing relationship in FIG. 24 is the same as that in FIGS. 10 and 20. FIG When the switch state SWA time Tp and have at Figure 24 becomes H from L 2
A current of −IM flows from VH of 3 toward VM, and this current causes VMX to rise in the positive direction. This results in VH
And VL increase by Ra / IM. At this time, VL, IM,
The VM has a positive feedback relationship, and the IM having a large current completes charging and discharging of the liquid crystal of the A group in a short time. Time T
When the switch state SWA changes from H to L for q, V of FIG.
A current IM flows from M to VL, and this current causes VMX to drop in the negative direction. As a result, VH and VL decrease by Ra · IM. At this time, VL, IM, and VM have a positive feedback relationship, and IM completes charging / discharging of the liquid crystal of the group A in a short time. All the operations are completed in an extremely short time, and as a result, the voltages applied to both ends of the liquid crystals of the groups A and B are VAX and VB shown in FIG.
It becomes like X, and the waveform rounding is greatly improved. VA
X, the difference between the effective value between VBX both not observed, it is how Akira et al close to the original ideal waveform. Pay attention here
The following points should be made. Described in paragraph “0050”
As shown in FIG. 1, the row electrode drive voltage VM is
When controlling, the potential VM on the row electrode of the panel
X occurs when there is no control (FIG. 10) as a result of control.
This causes a new fluctuation of the opposite polarity to that of the fluctuation (FIG. 20).
23, that is, the column electrode drive voltage VH,
When controlling VL, the voltage on the column electrodes of the panel is
Occurs when VDX and VSX are not controlled (Fig. 10)
A new fluctuation of the opposite polarity to the fluctuation is occurring (Fig. 24).
And. That is, in these examples, the drive voltage
The control means controls the driving voltage on the electrodes of the display panel.
, Which is the opposite of the voltage fluctuation that would occur without the control.
Control the drive voltage to generate new voltage fluctuation of polarity
To do.

By the way, in the above-mentioned first and second embodiments, when the groups A and B have the same capacitance values and are driven in completely opposite display states, they are substantially There is no effect according to the present invention. That is, under this condition, the values of the currents flowing through the respective groups are equal and do not pass through the resistor RM, as described with reference to FIG. Therefore, in the first embodiment, the absolute values of the currents IH and IL in FIG. 1 are the same and the signs are opposite, so the correction amount is offset and becomes 0, and the VM is not corrected.
Further, in the second embodiment, the current IM in FIG.
Since the value of is 0, VH and VL are not corrected. However, as described above, the amount of waveform blunting when the capacitance values formed by the groups A and B are equal to each other is originally a quarter of the maximum value. Since the influence on the driving force is rapidly reduced, in most cases, sufficient effects can be obtained by implementing the first and second embodiments, a contrast that is substantially close to the theoretical limit is obtained, and responsiveness is also improved. Will be done.

However, when the parasitic resistance is large, or when the display area is large and the formed capacitance is large,
When the values of (rx) and (cx) shown in FIG. 14 become large and the waveform rounding becomes large enough to affect the driving force of the liquid crystal, sufficient effects can be obtained in the first and second embodiments. There are things you can't get.

FIG. 25 shows a third embodiment of the present invention, which makes the driving state of the liquid crystal more ideal in all cases. In the embodiment of FIG. 25, the current flowing in the liquid crystal is detected and the driving voltage applied to the row electrodes and the column electrodes are printed.
Controlling both the drive voltage pressurized simultaneously. FIG. 25 shows FIG.
Also adds a further new component to the first embodiment shown in
Of. Therefore, the reference numerals of the same components as those in FIG. 1 are the same as those in FIG. In FIG. 25, the correction circuit 250 has the following configuration in addition to the configuration of the first embodiment shown in FIG. The positive input terminal of the first differential amplifier 101 is applied with the input EA via the resistor Ri, and is connected to the output terminal of the first differential amplifier 101 via the series circuit of the resistor Rf and the capacitor Cf. It
The positive input terminal of the second differential amplifier 102 is applied with the input EB through the resistor Ri, and is connected to the output terminal of the second differential amplifier 102 through the series circuit of the resistor Rf and the capacitor Cf. It In this configuration, the point of particular interest is the column
Result of current detection performed on the electrode drive voltage side (for example, VH)
The column based on the result (for example, the output of the differential amplifier 101)
It is configured to control the electrode drive voltage.
It In this case, the differential amplifier (eg 101) will detect the current
At the same time as being part of the means, the drive voltage control in the present invention
It is also part of the means. Thus, in the present invention,
Based on the result of current detection performed on one drive voltage side
It may be configured to control the other drive voltage based on
Of the current detection performed on one drive voltage side.
Based on the result, it is configured to control the driving voltage of the one side.
It can also be done. Naturally, the detection on the side of the row electrode drive voltage
Control the row electrode drive voltage based on the result of the output current
You may. Further, in the configuration of FIG. 25, the output of the current detecting means is
It shows that it may be applied to the drive voltage control means via a capacitor.
is doing.

In FIG. 25, the function of the portion added to FIG. 1 is as follows. When the current IH flows, a voltage proportional to this current is generated at the output end of the first differential amplifier 101 as a fluctuation component. The voltage fluctuation is due to the resistance Rf.
And the first differential amplifier 101 via a series circuit of Cf.
Is positively fed back to the positive input terminal of the first differential amplifier 1
The output terminal potential of 01 rises, the potential of the output VH rises, and the output VM falls. Then, the current IH increases, and the output potential of the first differential amplifier further rises due to the positive feedback effect. When the current IL flows, the output VL rapidly drops and the output VM rapidly rises.
These changes are completed in an extremely short time due to the positive feedback action. The role of Rf in this circuit is to adjust the positive feedback amount and suppress oscillation of the circuit.

Special attention should be paid to the embodiment shown in FIG .
When the capacitance Cf is the same as that of the differential amplifiers 101 and 102,
Connected between its output and positive input.
It That is, for example, when the current IH increases, the differential increase increases.
The output potential of the width device 101 rises, but this potential fluctuation
Positive feedback is performed by the amount Cf, and the output voltage of the differential amplifier 101 is increased.
Position rises rapidly, and as a result, the potential of VH is higher than the specified value.
It causes fluctuations in the higher direction. Previous in this configuration
The storage capacitance Cf is a direct current change for direct current change as shown in FIGS.
Instead of making a contact detection and making a determination, it can be detected indirectly through an alternating current
It is used as a means to With the addition of new feedback, the values of the constants in each part of the correction circuit 250 differ from those in the case of FIG.
FIG. 26 shows a result of simulation in which the liquid crystal drive system model shown in FIG. The timing relationship of FIG. 26 corresponds to that of FIGS. 11 and 21, and is extremely significant when the difference between the capacitance values of the groups A and B is 0 and when the difference between the capacitance values is the maximum. An almost perfect ideal drive waveform is obtained except for a short-time spike (not shown).

FIG. 27 is a simplified version of the embodiment of FIG.
This is a more specific example. Although the embodiment of FIG. 1 actually showed a remarkable effect, the following problems were pointed out at the same time. (1) The above-described waveform rounding is a high-speed phenomenon of 1 μS or less in terms of time, and in addition to high speed of several tens to 100 nS, it is necessary to instantaneously output a large amplitude and a relatively large current. is there. (2) Generally, a high-speed amplifier satisfying the above (1) consumes a large amount of current and is difficult to use for a small battery-operated device. (4) Generally, a high-speed amplifier satisfying the above (1) is extremely expensive, and the practice of the invention is limited.

In order to solve the above problems, therefore, the embodiment shown in FIG. 27 is effective, and the effect can be improved with low power consumption and low cost. In FIG. 27, the correction circuit 270 is configured as follows. The negative input terminal of the differential amplifier 271 is connected to the potential EA via the resistor r, connected to the potential EB via the resistor r, and further connected to the output terminal VM of the differential amplifier 271 via the resistor R. To be done. The other output terminal VH is connected to the potential EA via the resistor Ra, and
It is connected to the positive input terminal of the amplifier 271 via x.
The other output terminal VL is connected to the potential EB via the resistor Ra and is connected to the positive input terminal of the amplifier 271 via the resistor Rx.

In this circuit configuration, outputs are VH = EA-Ra.IH, VL = EB + Ra.IL, VM = (EA + EB) / 2- (1/2 + R / r) .Ra.
・ (IH-IL). When the correction circuit 270 shown in FIG. 27 is replaced with the correction circuit 100 shown in FIG.
It has been found that the results substantially similar to those shown in FIGS. 20 to 22 can be obtained by properly selecting the constants such as making the value of Ra sufficiently small. The embodiment shown in FIG. 27 requires a smaller number of differential amplifiers than the embodiment shown in FIG. 1, so that the problems of the embodiment shown in FIG. 1 can be greatly improved.

In the structure shown in FIG. 2, one or both of the column electrode drive circuit 201 and the row electrode drive circuit 202 may be provided in the display panel. For example, in an active type liquid crystal panel, transistors are formed in the panel and driving circuits for these are built in. In a passive type liquid crystal panel, a driving integrated circuit is installed on the panel by a method called COG (chip on glass). In these cases, the drive voltage applied to the liquid crystal is supplied to the drive circuit from the outside of the panel through the wiring inside the panel, but the wiring inside the panel generally has a high specific resistance, and there is a resistance that cannot be ignored. Become.

The applicant of the present invention has disclosed in Japanese Patent Application No. 2-90280 (hereinafter referred to as Reference 1) that (1) it has an extraction electrode for detecting the potential of a specific point in the display panel. Electro-optical display device. (2) A method of driving an electro-optical display device, which detects a potential of a specific point in a display panel and controls the potential of the specific point to have a specific value. Proposed. If this technique is applied to the present invention, more effective results can be obtained.

FIG. 28 is a block diagram showing a case where the technique proposed in Reference 1 is applied to the embodiment shown in FIG. 27 of the present application, in which the column electrode drive circuit 301 and the row electrode drive circuit 306 shown in FIG. A passive liquid crystal panel provided in the display panel 280 by COG is assumed. In FIG. 28, the column electrode drive power supply line of the column electrode drive circuit 301 to which + Vs is supplied is externally connected via a wiring resistance (including a connection resistance for external connection, etc., hereinafter) Rp in the panel. While being drawn out and applied with + Vs, it is drawn out to the outside through a wiring resistance Ro and further connected to the positive input terminal of the differential amplifier 271 through a resistance Rx. Further, the column electrode drive power supply line to which -Vs is supplied is drawn out through the wiring resistance Rp in the panel to apply -Vs, and
It is drawn out to the outside through the wiring resistance Ro, and further the resistance Rx
Is connected to the positive input terminal of the differential amplifier 271 through. The row electrode driving power supply line of the row electrode driving circuit 306, to which 0 potential is supplied, is drawn out through a wiring resistor Rq in the panel, is connected to the output terminal of the differential amplifier 271, and is also a wiring resistor. It is led out to the outside via Rs and further connected to the negative input terminal of the differential amplifier 271 via a resistor R. + Vs is applied to the negative input terminal of the differential amplifier 271 via the resistor r, and -V is applied via the resistor r.
s is applied.

In the embodiment shown in FIG. 28, the panel 28 is used.
The wiring resistance Rp itself within 0 functions as the current detection resistance Ra in FIG. With this configuration, it is not necessary to provide a current detection resistor outside, so + Vs, −
There is no increase in the resistance value of the Vs power supply line, and therefore there is no fear of increasing the waveform rounding of the column electrode drive voltage applied to the liquid crystal through the column electrode drive circuit 301. Further, the resistance Rx in FIG. 27 is replaced with Rx + Ro in FIG. 28, but this resistance should be sufficiently larger than Ra (Rp), and the addition of Ro affects the operation. There is no. Further, the resistance R in FIG.
However, since R is a variable resistance, it can be considered to be within the range of adjustment, and since the detection position of the potential fed back to the negative input terminal of the differential amplifier 271 has changed, the adjustment magnification R / Since r can be made small, it becomes possible to set the resistance r to a relatively large value, and + can be set via the resistance r.
The bleeder current flowing from Vs to -Vs can be reduced.

It is obvious that the technique proposed in the reference 1 can be applied to the embodiments shown in FIGS. 1, 23 and 25 of the present application, but the case applied to FIG. 1 is shown in FIG. The application configuration example of is omitted. FIG. 29 is a configuration diagram showing a configuration when the technique proposed in Reference 1 is applied to the embodiment shown in FIG. 1 of the present application, and the characteristics are further improved. The same symbols as those in FIG. 1 are used for the same portions as those in FIG. 1, and the description of these portions will be omitted. In FIG. 29, the resistance Ra in FIG. 1 is replaced with the wiring resistance Rp in the panel 290. A wiring resistance Rs in the panel 290 is added to the resistance R in FIG. Here, the differential amplifier 10 of FIG.
1 operates so as to keep the potential of VH in FIG. 29 at a constant potential of EA, and the differential amplifier 102 maintains the potential of VL in FIG.
As a result of operating to keep a constant potential of EB,
The current drop of the resistor Rp is corrected, and the same effect as that of RD and RS of the model shown in FIG. 9 becomes extremely small is obtained. Therefore, the waveform rounding of VDX and VSX is greatly reduced, and a more remarkable effect can be obtained.

[0071] Figure 30 is a seventh embodiment of the present invention, electrostatic
It uses an inductor for current detection. Output VH
Is connected to + Vs via inductor L1 and output V
L is connected to the -Vs through Lee Ndakuta L1. The output VM is connected to the output terminal of the differential amplifier 320, and is also connected to the negative input terminal of the differential amplifier 320 via the series circuit of the resistor R and the capacitor CL, and the negative input terminal is connected to the resistor r.
When the + Vs through the inductor L2 coupled with the connected inductor L1 and M comprising coupling coefficient is grounded to a resistor r to further coupled by connected inductor L1 and M comprising coupling coefficient to the -Vs stomach Ndakuta L2
Grounded through . Positive input of the differential amplifier 320 is grounded. This configuration directly changes the current as shown in Figs.
Instead of directly detecting by flow and making judgment, AC coupling
It is more indirectly detected and determined.

[0072] In brief reference to FIG. 30, each in
When the currents IH and IL flowing through the inductor L1 change,
The inductor L2 receives a signal according to the change of the currents IH and IL.
Signal is generated, but the signal detected in this way is a current
It does not show the change values of IH and IL, but I
It shows a value obtained by differentiating the values of H and IL. Therefore
These signals show the fluctuations that occur in VMX
There isn't. However, with the differential amplifier 320 and the capacitance CL,
Set the integration constant appropriately in the configured integration circuit
As a result, the current VM is output to the output VM of the differential amplifier 320.
It is possible to generate a voltage proportional to the difference between H and IL.
That is, in this embodiment, the change in the current flowing through the display panel is
This is not directly detected, but the amount related to the change amount is detected.
The change amount is indirectly obtained by calculation based on the detection result of
It can be said that Therefore, the adjustment circuit of the present invention
In addition to those that have means for directly detecting
Means for indirectly determining the current change amount by detecting the related amount
It also includes those having. Direct or indirect
The means for determining the amount of change in current is defined as the current determination means.
It In this case, in the embodiment of FIG.
The resistor Ra or the amplifier 102 and the resistor Ra are current judging means.
In the embodiment of FIG. 30, a plurality of inductors
And the integration circuit is the current determination means.

FIG. 31 shows an embodiment of the invention relating to the improvement of the differential amplifier used in the present invention. As described above, the differential amplifier used in the present invention is required to have high speed, large amplitude, and relatively large current output, but these performances are required for a short time when a spike-shaped current flows through a capacitive load. Since there is a time between the above and almost no output current is required, a configuration different from that of a normal amplifier is possible.

In FIG. 31, + E1 and -E1 are used as power sources, and the first stage differential amplifier 3 has two input terminals A and B.
The output of 31 is a buffer 332 that uses + E2 and -E2 as power sources.
Applied to. The output of the buffer 332 is applied to the new final stage amplifier 333. The final stage amplifier 333 is configured as follows. The input terminal of the final stage amplifier 333 has a series circuit of a Zener diode 334 and a resistor 335, and a capacitor 336.
It is applied to the base end of the PNP transistor 337 via a parallel circuit with, and the base end of the PNP transistor 337 is connected to the power source + E3 via the resistor 338.
The emitter end of the PNP transistor 337 has a resistor 3
39 through the parallel circuit of the capacitor 39 and the capacitor 340
Connected to. The input terminal of the final stage amplifier 333 further includes an NPN transistor 3 through a series circuit of a Zener diode 341 and a resistor 342 and a parallel circuit of a capacitor 343.
44 applied to the base end of the NPN transistor 3
The base end of 44 is connected to the power supply -E3 via the resistor 345. The emitter terminal of the NPN transistor 344 is connected to the power source -E3 via a parallel circuit of a resistor 346 and a capacitor 347. The PNP transistor 33
7 and the collector end of the NPN transistor 344 are commonly connected to form a final output end, and the output end is a resistor 3
It is connected to the input terminal of the final stage amplifier 333 via 49 and a capacitor 348.

The first stage differential amplifier 331 and the buffer 332
Since it is a well-known configuration and it is considered that it is not necessary to describe it, only the final stage amplifier 333 will be described. However, since the circuit configuration is vertically symmetrical, the upper half will be described. The Zener diode 334 and the resistor 335 will be described. And the resistor 338 determines the static potential of the base end of the PNP transistor 337. Since the resistor 339 inserted in the emitter end of the PNP transistor 337 has a negative feedback function, the static potential at the base end and the resistor 339 are
By properly selecting the value of, the PNP transistor 3
The static current flowing through the collector of 37 can be set to a very small value.

Now, when the input of the final stage amplifier 333 falls, this voltage change is caused by the PNP through the capacitor 336.
It is transmitted to the base end of the transistor 337. The PN
The emitter end of the P-transistor 337 has the capacitance 34
Since it is connected to + E3 by 0, the negative feedback action of the resistor 339 does not work against a sudden change in the base potential, and a large current is generated according to the change in the base potential.
Flows through 0 towards the collector. If the fluctuation of the base potential is short, the PNP transistor 337
If the change in the potential at the emitter end can be made small, and if the change in the potential at the base end is intermittent, then the capacitance 3 via the resistor 339 is changed until the next change in the base potential.
The 40 is recharged and can be returned to its initial static state. When the input of the final stage amplifier 333 rises, the PNP transistor 337 is cut off, and all the current flowing through the resistor 339 is used for recharging the capacitor 340.

The capacitor 348 and the resistor 349 are a negative feedback circuit for preventing self-oscillation and can be omitted in some cases. The capacities 340 and 347 are + E3, −
It may be grounded instead of being connected to E3. The Zener diodes 334 and 341 can be omitted. Further, the capacitors 336 and 343 can be omitted in some cases. The power supplies | E1 |, | E2 |, and | E3 | may have the same voltage or different voltages. In the example, | E2 | was 5 V, and | E1 | and | E3 | were 20 V, which was boosted from 5 V. However, very satisfactory results were obtained in both power consumption and operating speed. Although the bipolar transistor is used as the active element in FIG. 31, a part or all of the bipolar transistor may be formed of a field effect transistor. When the final-stage transistors 337 and 344 of the final-stage amplifier 333 are field-effect transistors, complementary field-effect transistors having a resistance element inserted in the source are used. A normal high-speed differential amplifier may be used as it is for the first-stage differential amplifier 331 or the first-stage differential amplifier 331 and the buffer 332. In this case, the final-stage amplifier 333 is positioned as a high-speed booster. .

[0078]

As is apparent from the above, according to the present invention, by correcting the waveform of the liquid crystal drive voltage to the original ideal shape in all states including gradation display, the non-selection period, close to the theoretical value in effective voltage during the selection period, the contrast reduction due to waveform rounding, it is naturally improving the responsiveness of deterioration and said problem is the Ru also dramatically improved crosstalk. Further, according to the present invention, since the current actually flowing in the liquid crystal is determined and compensated , it is possible to perform stable correction even for a complicated current change in gradation display and for an environmental change. Is obvious. In fact, the display device embodying the present invention provided extremely good display quality. However, at the time of implementation, in order to change the power supply abruptly, study on the potential relation of each part of the circuit such as latch-up,
Measures it is not needless to say that it is necessary to sufficiently perform. When the panel structure is divided into upper and lower parts and the display is different in the upper and lower parts as in the example described in FIGS. 5C and 5D, the present invention needs to be applied to the upper and lower parts respectively. When the same display is performed on both the upper and lower sides, the present invention can be applied to the upper and lower sides in common.

To summarize the effects of the present invention, since the present invention drives the liquid crystal in an ideal state, (1) it is possible to obtain the theoretical maximum contrast. (2) There is no crosstalk. (3) Improved responsiveness. (4) Effective even when there is a gray scale display such as an LCD TV. That is, it is possible to provide an extremely high-quality display device, and the effect is extremely large. In particular, recently, the number of pixels of a display device is increased, the color is increased, the screen is increased, and the load on the driving circuit is increased. For example, a mounting method called a COG (chip on glass) method is adopted. At first, the conditions concerning parasitic resistance tend to be worse,
According to the present invention, a sufficient effect can be exhibited even under such an adverse condition, and it can greatly contribute to the development of the display device. Of course, although the present invention provides an extremely large effect, it is intended to improve the problems to be originally improved from the viewpoint of the driving circuit, and reduces the parasitic resistance of each part which is the true cause of the problem. It goes without saying that efforts should be continued.

A few notes will be added to the present invention. (1) Although the description has been given for the liquid crystal display device, as is clear from the description, it is effective even in the case of an EL display device, for example. Therefore, the applicable range is not limited to the liquid crystal display device. (2) As described above, there are various specific driving methods for the display device. In addition to the driving method used in the description, there is a method for driving the row electrodes and the column electrodes with the driving voltage as shown in FIG. 32, for example. . However, in the driving method of FIG. 32, the row electrode driving voltage Vcom
Considering the potential of 2 as the reference (0), the result is as shown in FIG. 33, and it is obvious that the present invention can be applied. Therefore,
The application of the present invention is not limited to the driving method used in the description. (3) The present invention is not limited to the specific embodiments thereof to the presented examples. (4) For example, in the first embodiment shown in FIG. 1, the method of detecting both the currents flowing in the input voltages EA and EB and controlling the output voltage VM has been described. However, either EA or EB is detected. It has been confirmed that even if the VM is controlled by only one current, it is effective if the control amount is changed. Therefore, it is not limited to detect all the currents flowing in the liquid crystal. (5) Although the detailed description of the present invention has been given for the simple matrix type liquid crystal display device, even in the case of a so-called active type matrix display device, writing is performed all at once when a row is selected, so that the power supply line changes. As a result, the correct charge amount may not be charged / discharged, and the contrast may be lowered or the responsiveness may be lowered, but it is apparent that the present invention can be applied to this case and a great effect can be obtained. Is. Therefore, the present invention is not limited to the simple matrix type display device. (6) Similarly, even in the case of a display configuration that does not form a matrix (for example, what is called a segment type), if there is a decrease in display quality due to a current drop, the display quality can be improved by implementing the present invention. Does not limit the structure of the display device to the matrix type.

[Brief description of drawings]

FIG. 1 is a circuit configuration diagram showing a first embodiment of the present invention.

FIG. 2 is a configuration diagram showing a configuration of a simple matrix type liquid crystal display device.

FIG. 3 is a configuration diagram showing an example of a liquid crystal drive circuit.

FIG. 4 is an operation waveform diagram showing an example of an ideal liquid crystal drive voltage waveform.

FIG. 5 is an explanatory diagram showing the influence of crosstalk.

FIG. 6 is an explanatory view conventionally used to explain crosstalk.

FIG. 7 shows a model of a liquid crystal drive system based on the conventional description.

FIG. 8 is a first model of a newly created liquid crystal drive system according to the present invention.

FIG. 9 is a second model of a newly created liquid crystal drive system according to the present invention.

FIG. 10 is an explanatory diagram for explaining a current problem based on a result of simulating the second model.

FIG. 11 is an explanatory diagram for explaining a current problem based on a result of simulating the second model.

FIG. 12 is an explanatory diagram for explaining current problems based on a result of simulating the second model.

FIG. 13 is an explanatory diagram for explaining a current problem based on a result of simulating the second model.

FIG. 14 is an explanatory diagram for explaining a difference in waveform rounding amount depending on a display state.

FIG. 15 is an explanatory diagram for explaining a difference in waveform rounding amount depending on a display state.

FIG. 16 is an explanatory diagram for explaining the basic idea of the present invention.

FIG. 17 is an explanatory diagram for explaining the first embodiment of the present invention.

FIG. 18 is an explanatory diagram illustrating a first embodiment of the present invention.

FIG. 19 shows the first embodiment of the present invention in the liquid crystal drive system model shown in FIG.
It is a block diagram which shows the case where the Example is applied.

20 is an explanatory diagram for explaining the effect of the present invention based on the result of simulating the configuration of FIG.

21 is an explanatory diagram for explaining the effect of the present invention based on the result of simulating the configuration of FIG.

22 is an explanatory diagram for explaining the effect of the present invention based on the result of simulating the configuration of FIG.

FIG. 23 is a circuit configuration diagram showing a second embodiment of the present invention.

24 is an explanatory diagram based on a result of simulation by applying the second embodiment of the present invention to the liquid crystal drive system model shown in FIG.

FIG. 25 is a circuit configuration diagram showing a third embodiment of the present invention.

FIG. 26 is an explanatory diagram based on a result of simulation by applying the third embodiment of the present invention to the liquid crystal drive system model shown in FIG. 9.

FIG. 27 is a circuit configuration diagram showing a fourth embodiment of the present invention.

FIG. 28 is a circuit configuration diagram showing a fifth embodiment of the present invention.

FIG. 29 is a circuit configuration diagram showing a sixth embodiment of the present invention.

FIG. 30 is a circuit configuration diagram showing a seventh embodiment of the present invention.

FIG. 31 is a circuit configuration diagram showing an embodiment of the invention relating to the improvement of the differential amplifier used in the present invention.

FIG. 32 is a waveform chart showing an example of a liquid crystal drive waveform different from that used in the description of the present invention.

FIG. 33 is an explanatory diagram showing that the present invention can also be applied to the case shown in FIG. 32.

[Explanation of symbols]

100 Correction circuit according to first embodiment of the present invention 201 Column electrode drive circuit 202 row electrode drive circuit 203 control circuit 301 column electrode drive circuit 302j jth output circuit 305 Logic circuit 306 row electrode drive circuit 307k kth output circuit 311 Logic circuit 230 Correction Circuit According to Second Embodiment of the Present Invention 250 Correction Circuit According to Third Embodiment of the Present Invention 270 Correction Circuit According to Fourth Embodiment of the Present Invention 280 LCD display panel 290 LCD display panel 331 First stage differential amplifier 332 shock absorber 333 Final amplifier

Claims (6)

(57) [Claims] 1. An electro-optical display device having a display panel having a row electrode group, a column electrode group, a row electrode drive circuit and a column electrode drive circuit , wherein the row electrode drive circuit performs scanning selection on the row electrode group. Provide signal
The column electrode drive circuit displays data on the column electrode group.
For supplying a signal based on a current determining means for determining the amount of change in the current flowing in the display panel, and a current determining means for supplying to the row electrode driving circuit or the column electrode driving circuit based on the output of the current determining means. A drive voltage control means for controlling a drive voltage to be applied , and the current determination means is the row electrode drive circuit or the column voltage.
It flows through the power supply line that supplies the drive voltage to one side of the pole drive circuit.
Has a configuration for detecting a current, the drive voltage control hand stage, the row electrode driving circuit or the output end
Alternatively, the electro-optical display device has an amplifier connected to the other of the column electrode drive circuit in a direct current manner, and supplies the output of the current determination means to the input side of the amplifier. 2. An electro-optical display device having a display panel having a row electrode group, a column electrode group, a row electrode drive circuit and a column electrode drive circuit , wherein the row electrode drive circuit performs scanning selection on the row electrode group. Provide signal
The column electrode drive circuit displays data on the column electrode group.
For controlling the drive voltage supplied to the column electrode drive circuit based on the output of the current determination means, which determines the amount of change in the current flowing through the display panel. Drive current control means, and the current determination means supplies a drive voltage to the row electrode drive circuit.
An electro-optical display device having a configuration for detecting a current flowing in a power supply line to be supplied . 3. An electro-optical display device having a display panel having a row electrode group, a column electrode group, a row electrode drive circuit and a column electrode drive circuit , wherein the row electrode drive circuit performs scanning selection on the row electrode group. Provide signal
The column electrode drive circuit displays data on the column electrode group.
For controlling the drive voltage supplied to the row electrode drive circuit based on the output of the current determination means, the current determination means determining the amount of change in the current flowing in the display panel. The first drive voltage control means and the second drive voltage control means for controlling the drive voltage supplied to the column electrode drive circuit based on the output of the current determination means are provided, and the first and second drive circuits are provided. For both voltage control means,
An electro-optical display device characterized in that the outputs of the current judging means are commonly supplied . 4. An electro-optical display device having a display panel having a row electrode group, a column electrode group, a row electrode drive circuit and a column electrode drive circuit , wherein the row electrode drive circuit performs scanning selection on the row electrode group. Provide signal
The column electrode drive circuit displays data on the column electrode group.
For controlling the drive voltage supplied to the row electrode drive circuit based on the output of the current determining means, and the current determining means for determining the amount of change in the current flowing through the display panel. A drive voltage control means is provided, and the output of the current determination means is supplied to the drive voltage control means.
On the row electrode in the non-selected state of the display panel ,
The potential fluctuation caused by the current flowing through the panel is
Place it on a new potential change whose direction of change is opposite to that of the potential change.
An electro-optical display device characterized by being supplied so as to be replaced . 5. An electro-optical display device having a display panel having a row electrode group, a column electrode group, a row electrode drive circuit and a column electrode drive circuit , wherein the row electrode drive circuit performs scanning selection on the row electrode group. Provide signal
The column electrode drive circuit displays data on the column electrode group.
In the case of supplying a signal based on, the current judgment for judging the change amount of the current flowing through the display panel.
Determining means and the row electrode based on the output of the current determining means
Drive voltage supplied to the drive circuit or the column electrode drive circuit
And a drive voltage control means for controlling the row electrode drive circuit or the column voltage.
The current flowing through the power supply line that supplies the drive voltage to the pole drive circuit
The drive voltage control means based on the detection result.
Through the power line in which the current determination means has detected the current
Supply to the row electrode drive circuit or the column electrode drive circuit
Drive voltage, the direction in which the change in the detected current increases
In addition, the electro-optical display device is characterized in that it is configured to vary from a predetermined value . Wherein said current determining means according to claim 1 to claim, characterized in that those having a means for detecting a change in current flowing in the display panel by ac coupling 5
The electro-optical display device according to claim 1.