JPH02272490A - Liquid crystal display device and power source unit for liquid crystal display device - Google Patents

Abstract

PURPOSE:To prevent charge from being accumulated in a liquid crystal cell by means of turning on/off a power source by supplying a selected potential to a corresponding gate bus in a liquid crystal panel for a prescribed time by means of all analog switches in a vertical scanning circuit when a detecting circuit detects the turned on/off state of the power source. CONSTITUTION:When a detecting circuit 4 detects the turned on/off state of the power source, the selected potential is supplied by the respective analog switches in a vertical scanning circuit 2, and respective picture element transistors (TR) 13 connected to respective gate buses are all turned on. By inputting the potential equivalent to the potential of a facing common electrode instead of a video signal to a horizontal scanning circuit 3, the potential is supplied through respective drain buses D1 and D2 and the respective TRs 13 to the respective liquid crystal driving electrodes, and as a result, a voltage is not impressed to the respective liquid crystal cell 14. Thus by preventing the charge in the liquid crystal display panel from being accumulated at the time of turning on/off the power source, a baking phenomenon and a display deterioration such as a flicker are not generated even when the turning on/off operations of the power source are repeated.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an active matrix type liquid crystal display device such as a liquid crystal television and a power supply device for the liquid crystal display device.

[Conventional technology]

Conventionally, liquid crystal televisions using active matrix type liquid crystal display panels were manufactured using TV technology # June 1988 issue PP50-
64, and its voltage modification is described in the Journal of the Television Society v01.42.
mlO (1988) PP27-33.

[Problem to be solved by the invention]

In the above-mentioned conventional technology, there is no control over when the four power sources of the liquid crystal display device are turned on and off, and due to repeated power on and off,
Liquid j! There was a possibility that the load would accumulate in the i+ display panel, resulting in deterioration of display quality such as burn-in phenomenon and fujifu.

An object of the present invention is to prevent display quality deterioration due to repeated power on/off cycles of a liquid crystal display device.

[Means to solve the problem]

In order to achieve the above object, the present invention provides Il! used in a liquid crystal display device. A detection circuit for detecting whether the power source is on or off is provided, and when the detection circuit detects the on or off state of the power source, each of the analog switches in the vertical scanning circuit applies a selected potential to the liquid crystal for a predetermined period. In addition, a potential equal to the potential of the opposing common electrode of the liquid crystal display panel is input to the horizontal scanning circuit in place of the video signal.

[Effect]

When the detection circuit detects whether the dL source is turned on or off, each analog switch in the vertical scanning circuit supplies a selected potential to each gate bus for a predetermined period, so that the dL source is connected to each gate bus. All pixel transistors are turned on. Then, by inputting a potential equal to the potential of the opposing common electrode to the horizontal scanning circuit instead of the video signal, that potential is supplied to each liquid crystal drive electrode via each drain bus and each pixel transistor, and as a result, , depending on the state in which a voltage is to be applied to each liquid crystal cell.

In this way, the charge accumulation inside the liquid crystal display panel is prevented when the four power sources are turned on or off, and even if the power is turned on and off repeatedly, there is no charge accumulation inside the liquid crystal display panel, so the liquid crystal element is completely removed. It can be driven by alternating current and does not cause display deterioration such as burn-in or flicker.

〔Example〕

A first embodiment of the present invention will be described below with reference to FIG.

Figure 1 shows a liquid crystal display 'A' as a first embodiment of the present invention.
It is a block diagram showing st.

In FIG. 1, reference numeral 1 denotes an active matrix 9x liquid crystal display panel, and gate buses G1 . G2
．． ...and drain buses DI and D wired vertically.
2. An active matrix substrate (not shown) in which the pixel transistor 13 and pixel drive electrodes 81, G2, . . . are formed at the intersections of . A liquid crystal (not shown) is sealed between the two, and a liquid crystal cell 14 is formed at each of the intersection points.

2 is a vertical scanning circuit, which is composed of a shift register 21 and a switch 22. 3 is a horizontal scanning circuit, 4 is a power on/off detection circuit, 41 is an OR circuit, and 42 is a switch.

FIG. 2 is a waveform diagram showing an example of operation waveforms of each part in the embodiment of FIG. 1.

Furthermore, FIG. 3 is a block diagram showing a conventional liquid crystal display device that does not have an OR circuit 41 or switch 42 controlled by a power on/off circuit, and FIG. FIG. 7 is a slant-shaped diagram showing an example of a modified operation.

Hereinafter, the embodiment shown in FIG. 1 and the conventional example shown in FIG. 3 will be compared and explained with reference to the rectangular diagrams shown in FIGS. 2 and 4.

First, in the embodiment shown in FIG. 1, the output of the power on/off detection circuit 4 is 'L' in the normal display state.
As the output waveform STY' of the OR circuit 41, a vertical scanning start signal STY is obtained which is applied to the terminal 203 and is input to the shift register 21. In addition, the switch 42 is connected to the terminal 3
01 is selected and applied to the horizontal scanning circuit 5.

The shift register 21 is a gate that sequentially forms a selection signal using the input data waveform ST'7' and the vertical scanning clock signal applied to the terminal 204, controls the switch 22, and turns on the pixel transistor 13 applied to the terminal 201. - Sequentially outputs the on/off potential iH and the gate off potential VGL that turns off the pixel transistor 15, which is applied to the terminal 202, and connects the gate bus G1. G2. . . ., the sequentially selected waveforms G1°G2 . ···give.

This sequential selection waveform G1. G2. ..., signals obtained by sampling the video signal applied to the terminal 301 according to the position of the pixel to be driven are sequentially sent from the horizontal scanning circuit 5 to the drain bus DI = D2 *...-. When the signal is sent out, the pixel transistor 15 repeatedly turns on and off as appropriate, and the waveform shown in the waveform example shown in FIG. 2 is applied to the pixel electrodes S, S, . . . .

On the other hand, in the normal display state, even in the conventional example shown in FIG.
The operation is the same as that of the embodiment shown in FIG. 1, except that the video signal is input to the terminal 301 and the video signal applied to the terminal 301 is directly input to the horizontal scanning circuit 3.

Next, the operation when the power is turned off will be explained.

First, in the case of the conventional example shown in FIG. 5 without the power on/off detection circuit 4, when the power is turned off, the vertical scanning circuit 2 and the horizontal scanning circuit 3 stop operating. The nine voltages applied to St, S, . . . are held by the capacity of each liquid crystal cell 14, and the liquid crystal cell 1
There was a risk that DC voltage would be applied to 4. If a DC voltage continues to be applied to the liquid crystal cell 14, a load will accumulate on the alignment film, etc. that make up the liquid crystal cell 14, and when the power is turned on again, flickering and burn-in (even if the displayed image is changed) will occur. This may cause problems such as a phenomenon in which the previous display contents remain.

In particular, if the power is turned on and off repeatedly, there is a risk that the above-mentioned accumulated anticipation will be accumulated.

On the other hand, in the embodiment shown in FIG. 1, the tt source off is detected by the four source on/off detection circuit 3, and the
After setting it to H''', for at least one field or more,
Normal operation button for the LCD panel 1 part Co-precipitation occurs when the required minimum power supply voltage is secured, and during that period, the output 8 of the OR circuit 41
TV' is set to 1H', and the potential "ICOM" of the opposing common electrode CO is inputted to the horizontal scanning circuit 3 by the switch 42 instead of the video signal.

Since the data input to the shift register 21 is at 'H', depending on the vertical clock input to the terminal 204,
The output of the shift register 21 becomes ``H'' sequentially, and the entire output becomes 1H'' within one field period.

Therefore, while the minimum power supply voltage is secured, all the switches 22 are connected to the terminal 201 side IC, and the gate electrodes Gj, G2 . Gate on'
The potential VGH is applied to each pixel transistor 13 to turn on all the pixel transistors 13.

On the other hand, since the horizontal scanning circuit 3 is given the potential VOOM of the opposing common electrode CO instead of the video signal, all the drain buses J, D2, @e* have the potential vQ.
OM is being output. Therefore, all pixel electrodes 81
゜s2. ... are supplied with the same potential as the potential VOOM applied to the opposing common electrode CO through the pixel transistor 15, and no voltage is applied to the liquid crystal cell 14.

After achieving this state, if the power is completely turned off, no voltage is applied to the liquid crystal cell 14, so there is no need to worry about charge accumulation within the liquid crystal cell 14.

That is, even if the power is repeatedly turned on and off, abnormal phenomena such as flicker and burn-in can be prevented.

The operation above has been explained using the case of turning off the power as an example, but even when turning on the power, the video signal may be abnormal immediately after the power is turned on, so it is assumed that a normal video signal will be provided. until the gate on potential vG
In some cases, it may be better to apply H to all gate buses and apply the potential vQ ov of the opposing common electrode CO to all drain buses.

Next, FIG. 5 is a block diagram showing a second embodiment of the present invention, and FIG. 6 is a temporary diagram showing an example of the operation of each part in the embodiment of FIG.

In the embodiment of FIG. 5, block 9 having substantially the same function as in the embodiment of FIG. 1 has the same symbol.

The embodiment shown in FIG. 5 differs from the embodiment shown in FIG. The point is that a vertical scanning circuit 5 using a shift register 51 with a set function that outputs "" is used.

According to the embodiment shown in FIG. 5, when the four-source on/off detection circuit 4 detects that one source is off, all the outputs of the shift register with set function 51 become 1H'', so that the gate buses G1, G2... ... are all gate on potentials VGH
becomes.

On the other hand, after the input of the horizontal scanning circuit 60 is switched from the video 18 signal to the potential VCOM of the opposing common pole Co, drain buses DI, D2. It takes one horizontal scanning period to output the potential vOOM to the pixel electrodes s1, . . . through the pixel transistor. s2. Approximately one horizontal scanning period is required until the potential vooM is applied to .

Therefore, in the embodiment shown in FIG.'ig5, the minimum power supply voltage required for normal operation of the liquid crystal display panel 1 needs to be maintained at about 2 horizontal scanning periods or more after detecting power-off, and compared to the embodiment shown in FIG. This has the advantage that the period during which the minimum power supply voltage must be ensured can be shortened.

FIG. 7 is a block diagram showing a third embodiment of the present invention.

The embodiment shown in FIG. 7 differs from the embodiment shown in FIG. 1 in that a switch 43 controlled by a four-source on/off detection circuit 4 is provided in place of the OR circuit 41.

The switch 45 closes the terminal 201 at 1H'' of the detection signal DOF.
Outputs the gate-on potential VGL applied to the terminal 202 at the gate-on potential VGH, 'L″' applied to the terminal 202;
It is applied to the vertical scanning circuit 2. Therefore, when turning off the power
At the same time as the E source on/off detection circuit 4 detects and the detection signal DOF becomes 'L', the switch 2H7C is no longer input with the gate on' potential '/GH (, gate buses Gl, G2, . . . are all gate-on' potentials VG
H, it's true.

In other words, while using the same vertical scanning circuit 2 as in the embodiment of FIG. 1, it is possible to shorten the period during which the minimum '1 source voltage must be ensured, as in the embodiment of i@5. It has the advantage of saying.

FIG. 8 is a block diagram showing a fourth embodiment of the present invention.

The embodiment of FIG. 8 differs from the embodiment of FIG. 61105 or the like is used as the vertical scanning circuit 20.

The vertical scanning circuit 20 connects the output of the shift register 21 and -j
The switch 23 is controlled by the switch control surface % 24 according to the combination of the damage signals, and one of the potentials applied to the four signal lines that are input to the switch 23 is applied to the vertical scanning circuit 2.
The output is 0. Therefore, when the power on/off detection signal DOF is used as the control signal M, and the control signal M (that is, the detection signal DOF) and the output of the shift register 21 are both 'L', the gate-off potential applied to the terminal 202 By connecting VGL so as to selectively output the gate-on range VGH applied to the terminal 201 in the case of other combinations, the liquid crystal display bars J and 11r can be connected in the same manner as in the embodiment shown in FIG. It can be driven to

Further, in the embodiment shown in FIG. 8, as the vertical scanning circuit 20,
As mentioned above, since general commercially available machine C can be used, special
The advantage is that there is no need to develop C.

Now, in each of the embodiments described above,
Although a single source on/off detection circuit 4 is used, its configuration was not described in detail.

Therefore, next, the configuration and operation of the single source on/off detection circuit 4 will be explained.

FIG. 9 is a block diagram showing a specific example of the ItH on/off detection circuit used in the present invention.

In the specific example of FIG. 9, the one-source on/off circuit 4 includes a comparator 421, a Zener diode 422, and a resistor 423.
．． 424.425, -x nf'nf 450 kara w
I will be treated.

The terminal 401 is a switch (not shown) that can be turned on and off.
It is connected to a power supply (not shown) through the 411-T, and the power supply voltage is supplied to the entire liquid I#&S display device through the 411T-. Further, the terminal 412 is a '-power on/off detection terminal for outputting it#, an on/off detection pulse.

10,000, a resistor 423 is connected to the + side input of the comparator 421.
and Zener diode 4221c reference potential Vref
is applied, and a potential V obtained by dividing the source potential by '1' is applied to the ~ inputs by resistors 424 and 425.

When a switch (not shown) connected to the terminal 401 is on, the terminal 401 is connected to a power source (not shown), and a predetermined potential is supplied, V1! Vre
t, the terminal 412 has 'L'.
"rebel" is obtained. Then, when the switch (not shown) is turned off and the terminal 401 is disconnected from the source,
In order to ensure that the potential at the terminal 401 decreases and s'g <vrat, an "H" level is obtained at the terminal 412, and it is possible to detect the power off. - The same applies to Suion.

In addition, even after the 4 source is turned off, due to the condenser f450,
The potential supplied to the entire liquid crystal display device can be maintained within a voltage range in which the liquid crystal display device operates normally for a while.

FIG. 10 is a block diagram showing another specific example of the power on/off detection circuit used in the present invention.

In the specific example shown in FIG. 8g10, the power on/off circuit 4 includes a resistor 426, a bushing switch 427, a monostable multivibrator 42B, a D-type flip-flop 429, an OR circuit 430, and a switch 431.

FIG. 11 is a waveform diagram showing an example of the configuration of each part in the specific example of FIG.

First, the operation when the power is turned on will be explained.

When the bush switch 427 is pressed, the input waveform IN of the monostable multivibrator 428 becomes 1L'', a trigger is applied, and the output shaping DO7 of the monostable multivibrator 428 is determined by the inherent delay time of the monostable multivibrator 428. The period 'r of τ is obtained.

This pulse becomes the power-on detection pulse. At the same time, this pulse is input to the D-type flipflock 429, the state is reversed, and the output signal Q becomes 1H''.O-1 circuit 43
0, the combined sum VON of the waveform Q and the waveform DOF is formed, the switch 451 is closed, and the power supply potential is supplied to the entire liquid crystal display device via the terminal 411.

When the power is turned off, the button switch 427 is pressed as when it is turned on.
By pressing , the corrugator) i K #L''' is input, and the monostable multi-byte circuit 428 causes a time 1 error.
pulses occur in the waveform DOF. This pulse becomes the one-source off detection pulse. In response to this pulse, the output waveform q of the D-type flip-flop 429 is inverted and becomes "L" level, but since the signal VON that controls the switch 431 is the logical sum of the shaped Q and the waveform DOF by the OR circuit 430, , '1 Until the source-off detection pulse disappears (becomes -Lm level), the switch 431 is closed and the power supply potential can be supplied to the entire liquid crystal display device.

If a plurality of power supply potentials are required, the control circuit 440 connected to any one power supply potential may be used to control opening and closing of switches prepared as many as the number of power supply potentials.

Now, next, FIG. 12 is a block diagram showing a fifth embodiment of the present invention.

In FIG. 12, 8 is a liquid crystal display device excluding a power supply section, 9 is a power supply control section, and 94 is a multiple voltage generation circuit. Here, the power supply control section 9 is composed of a power off/off detection circuit 4, a switch 92 using a transistor or the like, and a resistor 93, for example.

On the other hand, vl is a potential applied to the terminal 201, which is equal to the gate-on potential VGH, v2 is a power supply potential that supplies current to the control circuit 6, etc., and Vs and v4 are the video signal processing circuit 7 and the horizontal scanning circuit. The it power supply potential Vs that supplies the t current necessary for analog signal processing such as the video signal of No. 5 is a potential applied to the terminal 202.

In the embodiment shown in FIG. 12, in the normal display state, the switch 92 is off, and the current flowing through the signal line giving the potential Vs is very small, and the voltage drop across the resistor 95 can be almost ignored. Vs is the gate off potential VG
It becomes equal to L. When the tm on/off detection circuit 4 detects that the power is off, the switch 92 is turned on and the potential v5
is approximately equal to the potential v1, that is, the gate-on potential VGH. In this case, at the same time as detecting power off, the potential V5 applied to the terminal 202 is set to the gate on potential VGH.
[By bringing them closer together, it is possible to achieve almost the same operation and effect as the embodiment shown in FIG. Note that the resistor 93 can be omitted by replacing it with the internal impedance of the multiple voltage generating circuit 94.

FIG. 13 is a block diagram showing a sixth embodiment of the present invention.

The difference between the embodiment shown in FIG. 15 and the embodiment shown in FIG. 12 is as follows.
Power supply control section 9tl - simplified, Zener diode 9
1, and uses a power supply control section 90 in which signal lines for supplying d positions V+, V2, and vi, respectively, are short-circuited.

``JE position V+ l V2 * Vs to L Te, for example +5V, 1 potential V4, for example -155V, potential 5V, for example -20V.

The embodiment of FIG. 15 will be described assuming that the Zener voltage of the Zener diode 91 is, for example, 6V.

In the normal display state, the Zener diode 91 is off. 41! When [ is turned off and the output voltage of the cover voltage generation circuit 94 begins to decrease, the current required for the signal line that supplies the potential v4, which is connected to the analog processing circuit in the liquid crystal display device 8, reaches the potential v5. Assuming that the number of currents is greater than the one current required for the signal line to be supplied, the potential V4 rises faster than the potential V5 (that is, it approaches Ov earlier ()).
When the potential difference between the potential v4 and the potential Vs becomes 6V, the Zener diode 91 is turned on. That is, the Zener diode 91 operates as the power on/off detection circuit 4 in the embodiment of FIG.

When the potential v4 further increases (approaches gv), the Zener diode 91 is turned on, so the potential V5 also increases at the same speed as the potential v4. Therefore, the Zener diode 91 is the switch 9 of the embodiment of FIG.
It will function in the same way as 2.

The embodiment shown in FIG. 13 is different from the embodiment shown in FIG.
Since it is not possible to completely prevent the accumulation of charges in the liquid crystal cell, the Zener diode 9
1 has the effect of reducing the amount of charge accumulated in the liquid crystal cell compared to the case where the Zener diode 91 is not used, and therefore flicker and burn-in can be reduced.

〔Effect of the invention〕

As described above, according to the present invention, the power is turned on or off. Since it is possible to prevent or reduce the accumulation of '1' in the liquid crystal cell, it is possible to obtain a good image without flickering or burn-in on the liquid crystal display panel even if the power of the liquid crystal display device is repeatedly turned on and off. It has some effect.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing a first embodiment of the present invention;
The figure is a waveform diagram showing an example of the operation waveform of each part in the embodiment of Fig. 1, Fig. 3 is a block diagram showing a conventional liquid crystal display device, and Fig. 4 is a waveform diagram showing an example of the operation of each part in the conventional example of Fig. 3. 5 is a block diagram showing the second embodiment of the present invention, FIG. 6 is a molding diagram showing an example of the operation of each part in the embodiment of FIG. 5, and FIG. 7 is a block diagram showing the second embodiment of the present invention. FIG. 8 is a block diagram showing a fourth embodiment of the present invention,
FIG. 9 is a block diagram showing a specific example of the power on/off detection circuit used in the present invention, FIG. 10 is a block diagram showing a specific example of the power on/off detection circuit used in the present invention, and FIG. FIG. 11 is a waveform diagram showing a modified example of the operation of each part in the specific example of FIG. 10, FIG. 12 is a block diagram showing a fifth embodiment of the present invention, and FIG. 16 is a $6 embodiment of the present invention. FIG. 1...Liquid crystal display panel, 5...Horizontal scanning circuit, 2゜5, 0...Vertical scanning circuit, 4...'\jL source on/
OFF detection circuit, 6...control circuit, 7...video signal processing circuit, 8...liquid crystal display device excluding power supply section, ? . . . Power control unit, 21 . . . Shift register, 5
1...Shift register with set function, 22.42
．． 45.92...Switch, CO...Opposing common electrode, 13...IIfi elementary transistor, 14...Liquid crystal cell.躬 2 口S8qco)-'( S^ 連 η 1------vcoM すえつ郎高国

Claims (1)

[Claims] 1. A liquid crystal is sealed between a pair of substrates, and at least one of the substrates has a plurality of gate buses extending substantially horizontally on its surface, and a plurality of gate buses extending substantially vertically on its surface. a liquid crystal display means comprising a plurality of drain buses extending in the direction, pixel transistors and liquid crystal drive electrodes respectively arranged at intersections of the gate bus and the drain bus, and a scanning start signal indicating a selected state and a non-selected state. Enter
a shift register that sequentially delays the scanning start signal and sequentially outputs it from a plurality of outputs; and a shift register that is arranged correspondingly to each output of the shift register and the plurality of gate buses, and has a selection potential and a non-selection potential, respectively. When the input signal and the output signal from the output of the corresponding shift register indicate a selected state, the input selection potential is inputted, and when the output signal from the output of the corresponding shift register indicates a non-selection state, the input non-selection potential is used. An active matrix type liquid crystal display comprising: a vertical scanning circuit including a plurality of analog switches that supply signals to corresponding gate buses; and a horizontal scanning circuit that samples input video signals and supplies the sampled video signals to the respective drain buses. In the apparatus, a detection circuit that detects whether a power source used in the liquid crystal display device is turned on or off; and when the detection circuit detects whether the power source is turned on or off, the scanning start signal is input to the shift register; A liquid crystal display device comprising means for generating a signal indicating a selected state for a predetermined period. 2. In the liquid crystal display device according to claim 1, of the substrates of the liquid crystal display means, the other substrate not provided with an image transistor etc. is provided with a counter common electrode on its surface, and a counter common electrode of the counter common electrode. A liquid crystal display device characterized in that a switch is provided for switching a potential equal to the potential to the video signal and inputting the same to the horizontal scanning circuit. 3. The liquid crystal display device according to claim 1 or 2,
After the detection circuit detects that the power supply is turned off, a power supply voltage necessary for normal operation of the liquid crystal display device is secured at least until all gate buses are supplied with the selection potential. Characteristic liquid crystal display device. 4. A liquid crystal is sealed between a pair of substrates, and at least one of the substrates has, on its surface, a plurality of gate buses extending substantially horizontally and a plurality of drains extending substantially vertically. a liquid crystal display means comprising a bus, a pixel transistor and a liquid crystal drive electrode respectively arranged at the intersection of the gate bus and the drain bus, and inputting a scan start signal indicating a selected state and a non-selected state;
a shift register that sequentially delays the scanning start signal and sequentially outputs it from a plurality of outputs; and a shift register that is arranged correspondingly to each output of the shift register and the plurality of gate buses, and has a selection potential and a non-selection potential, respectively. When the input signal and the output signal from the output of the corresponding shift register indicate a selected state, the input selection potential is input, and when the output signal indicates a non-selection state, the input non-selection voltage. An active matrix type liquid crystal display comprising: a vertical scanning circuit including a plurality of analog switches that supply signals to corresponding gate buses; and a horizontal scanning circuit that samples input video signals and supplies the sampled video signals to the respective drain buses. The device is provided with a detection circuit that detects whether the power source used in the liquid crystal display device is turned on or off, and when the side output circuit detects that the power source is turned on or off, all the analog switches immediately switch to a predetermined state. A liquid crystal display device characterized in that the input selection potential is supplied to a corresponding gate bus for a period. 5. The liquid crystal display device according to claim 4, wherein the shift register has an output signal outputted from each output thereof.
A liquid crystal display device comprising a set type shift resist that indicates all selection states when the detection circuit detects whether the power source is turned on or off. 6. The liquid crystal display device according to claim 4, further comprising means for switching the non-selection potential input to each analog switch to a potential equal to the selection potential when the detection circuit detects on or off of the power supply. A liquid crystal display device comprising: 7. The liquid crystal display device according to claim 5 or 6,
Among the substrates of the liquid crystal display means, the other substrate not provided with pixel transistors etc. is provided with a common electrode on its surface, and a potential equal to the potential of the common electrode is switched to the video signal to generate the horizontal signal. A liquid crystal display device characterized by being provided with a switch for inputting to a scanning circuit. 8. A liquid crystal is sealed between a pair of substrates, and at least one of the substrates has on its surface a plurality of gate buses extending substantially horizontally and a plurality of drains extending substantially vertically. a liquid crystal display means comprising a bus, a pixel transistor and a liquid crystal drive electrode respectively arranged at the intersection of the gate bus and the drain bus, and inputting a scan start signal indicating a selected state and a non-selected state;
a shift register that sequentially delays the scanning start signal and sequentially outputs it from a plurality of outputs; and a shift register that is arranged correspondingly to each output of the shift register and the plurality of gate buses, and has a selection potential and a non-selection potential, respectively. When the input signal and the output signal from the output of the corresponding shift register indicate a selected state, the input selection potential is input, and when the output signal indicates a non-selection state, the input non-selection voltage. An active matrix type liquid crystal display comprising: a vertical scanning circuit including a plurality of analog switches that supply signals to corresponding gate buses; and a horizontal scanning circuit that samples input video signals and supplies the sampled video signals to the respective drain buses. In the device, a detection circuit for detecting power off used in the liquid crystal display device, and when the detection circuit detects power off, a non-selection potential input to each analog switch is equal to the selection potential. A liquid crystal display device characterized in that it is provided with means for approaching a potential. 9. A liquid crystal is sealed between a pair of substrates, and at least one of the substrates has a plurality of gate buses extending substantially horizontally and a plurality of drains extending substantially vertically on its surface. a liquid crystal display means comprising a bus, a pixel transistor and a liquid crystal drive electrode respectively arranged at the intersection of the gate bus and the drain bus, and inputting a scan start signal indicating a selected state and a non-selected state;
a shift register that sequentially delays the scanning start signal and sequentially outputs it from a plurality of outputs; and a shift register that is arranged correspondingly to each output of the shift register and the plurality of gate buses, and has a selection potential and a non-selection potential, respectively. When the input signal and the output signal from the output of the corresponding shift register indicate a selected state, the input selection potential is inputted, and when the output signal from the output of the corresponding shift register indicates a non-selection state, the input non-selection potential is used. An active matrix liquid crystal display comprising: a vertical scanning circuit including a plurality of analog switches that supply the corresponding gate buses; and a horizontal scanning circuit that samples input video signals and supplies the sampled video signals to the respective drain buses. A power supply device for a liquid crystal display device that supplies power supply voltages such as the selection potential and non-selection potential necessary for operating the liquid crystal display device from a power source, comprising: a detection circuit that detects when the power source is turned off; A power supply device for a liquid crystal display device, comprising means for bringing the non-selection potential supplied to the liquid crystal display device close to a potential equal to the selection potential when a detection circuit detects that the power supply is turned off.