JP3490003B2 - Driving method of liquid crystal display device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of driving a liquid crystal display device used in a video camera or the like,
In particular, the present invention relates to a control method for driving two types of liquid crystal display devices by a set of a chroma control integrated circuit and a controller integrated circuit.

[0002]

2. Description of the Related Art A video movie device is a typical device using a liquid crystal display device. The liquid crystal display device is mounted for the purpose of displaying an image pickup state and a recording / playback state during video shooting. In recent years, two types of liquid crystal have been built in the finder section for the 0.5-inch class electronic viewfinder (hereinafter referred to as EVF) and for the 3-4 inch class monitors installed on the outer periphery of the main body. Display devices tend to be installed.

Normally, a liquid crystal display device for EVF uses a polysilicon type liquid crystal panel (hereinafter referred to as a high temperature polysilicon type liquid crystal panel) manufactured by a high temperature process suitable for ultra-miniaturization, and is used for a monitor. A liquid crystal display device is often used in combination with an amorphous silicon type liquid crystal panel, but recently, a driver IC for a monitor has been recently used.
A polysilicon type liquid crystal panel (hereinafter referred to as a low temperature polysilicon type liquid crystal panel) made by a low temperature process that enables built-in, high definition and low cost has been partially put into practical use.

In order to drive these liquid crystal display devices, a chroma control integrated circuit (hereinafter, referred to as a chroma IC) for controlling an image signal and a controller integrated circuit (hereinafter, a controller for controlling a drive timing signal of the liquid crystal display device). It is necessary to supply a driving voltage such as a video signal from an IC, a logic control signal, a counter signal voltage, etc., but a constant counter driving method (mainly high temperature / low temperature) in which the counter signal voltage is a DC voltage depending on the supply method. It is roughly divided into a polysilicon type liquid crystal panel) and a 1H counter inversion driving method (mainly used for an amorphous silicon type liquid crystal panel) in which a counter signal voltage is inverted every horizontal synchronization period (1H).

FIG. 6 shows a conventional example of driving a liquid crystal display device in a device equipped with two types of liquid crystal display devices. Here, it is assumed that the two types of liquid crystal display devices have different panel specifications and drive systems.

In FIG. 6, 31A and 31B are chroma I.
C, 32A and 32B are controller ICs, and 33 and 34 are liquid crystal panels. The first liquid crystal display device is a chroma IC
It is driven by supplying a dedicated output signal from the 31A and the controller IC 32A to the first liquid crystal panel 33,
Similarly, the second liquid crystal display device is driven by supplying a dedicated output signal from the chroma IC 31B and the controller IC 32B to the second liquid crystal panel 34. Also, the chroma ICs 31A, 31B and the controller ICs 32A,
A common video signal and a common signal are input to 32B.

By adopting such a configuration, each chroma IC 31A, 31B and controller IC 32A, 3
2B is capable of independently driving the first and second liquid crystal display devices to the respective liquid crystal panels 33 and 34, while the chroma IC and controller IC corresponding to each liquid crystal display device.
Must be provided individually, each requiring two sets of ICs.

If a pair of chroma IC and controller I
Parallel display is required to display two types of liquid crystal display devices in C. There is no problem if the drive system and panel specifications (number of pixels, pixel arrangement configuration, etc.) are the same, but in general, EV
The liquid crystal display device for F and the liquid crystal display device for monitor usually have different panel specifications and drive systems. Since the chroma IC and the controller IC are in one set, the output signal thereof can basically be only one that matches one type of liquid crystal display device, so that naturally one of the liquid crystal display devices becomes an irregular signal. Will end up. Especially, in addition to the control timing, the difference in the video signal level has an influence, resulting in an abnormal display state.

For example, when the driving system of the first liquid crystal display device is the constant opposed drive system and the driving system of the second liquid crystal display device is the 1H counter-reversal drive system, the first or second liquid crystal display device is selected. When parallel driving is performed with matched control signals, in a liquid crystal display device in which the control signals do not match, the operation timing of the driver IC that drives the liquid crystal panel is incorrect, and the AC drive balance to the liquid crystal display element is disturbed. The occurrence of vertical stripes or vertical stripes on the display screen, blackening of the entire screen, etc. causes a direct current component on the liquid crystal display element, which causes a strong burn-in after a long time. Therefore, even if the control signal is returned to the normal display mode, burn-in damage appears, which causes a fatal defect in reliability.

[0010]

As described above, in the video movie equipment equipped with the above-mentioned two kinds of liquid crystal display devices, two sets of chroma ICs corresponding to each liquid crystal display device are provided.
Therefore, the controller IC is required, and there is a problem that the mounting area, circuit parts, cost, etc. increase.

In view of the above, the present invention has a set of chroma I
A driving method in which two types of liquid crystal display devices are driven in parallel by the configuration of C and a controller IC, and the liquid crystal display devices are controlled without damaging each other's reliability in terms of reliability, thereby reducing the mounting area of the drive circuit and reducing the cost. The purpose is to provide.

[0012]

SUMMARY OF THE INVENTION The present invention comprises a chroma control integrated circuit for controlling an image signal and a controller integrated circuit for controlling a drive timing signal of a liquid crystal display device as one set. When the second liquid crystal display device is driven in parallel, the control signals from the chroma control integrated circuit and the controller integrated circuit are shared and the first liquid crystal display device is shared.
Of the horizontal display start control signal and the vertical scanning start control signal of the second liquid crystal display device when the first liquid crystal display device is driven. In the system in which the vertical scanning start control signal is stopped and the second liquid crystal display device supplies the counter electrode with a voltage that is inverted every horizontal scanning period, the analog system power supply voltage of the second liquid crystal display device is used. (Vee) and the counter electrode to the analog power supply voltage (VD
D) is supplied with a voltage (Vee ') via a forward diode and a video signal is interleaved with a signal of Vee power supply voltage level within one horizontal scanning period. A liquid crystal display device that does not perform a main display operation, at least the vertical scanning start signal is stopped to stop the operation of capturing the video signal into the liquid crystal panel and the line-sequential scanning operation, and the video signal voltage for the standard display operation. By changing the level and the counter electrode voltage level so that the relationship between the video signal voltage and the counter voltage becomes substantially the same level, the accumulated voltage in the liquid crystal display element can be eliminated, and burn-in damage can be avoided.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION The invention according to claim 1 of the present invention comprises: a scanning signal electrode line and an image signal electrode line which are arranged in a matrix; and the intersections of the scanning signal electrode line and the image signal electrode line. A pixel electrode with a display material interposed therebetween, a switching element connected between the image signal electrode line and the pixel electrode and having a disconnection control terminal connected with a scanning signal electrode line, and the display material interposed. Parallel driving of a first liquid crystal display device and a second liquid crystal display device composed of a corresponding pixel electrode and a counter electrode arranged in a corresponding manner, and a chroma control integrated circuit for controlling an image signal and driving of the liquid crystal display device. A controller integrated circuit for controlling the timing signal is constituted by one set, and the control signals from the chroma control integrated circuit and the controller integrated circuit are sent to the first liquid crystal display device or the second liquid crystal display. A signal which meets the specifications of the device is generated and supplied in parallel to the first liquid crystal display device and the second liquid crystal display device, and the second liquid crystal display device is driven when the display operation of the first liquid crystal display device is driven. Of the horizontal display start control signal and the vertical scan start control signal, at least the vertical scan start control signal is stopped, and the second liquid crystal display device supplies the counter electrode with a voltage that is inverted every horizontal scanning period. In this case, the analog system power supply voltage (Vee) of the second liquid crystal display device is supplied from the analog system power supply voltage (VDD) of the driving device as a voltage (Vee ') through the forward diode, and the counter electrode is also provided. The same voltage (Vee ') is also supplied to the image signal, and the signal of the Vee power supply voltage level is applied to the video signal within one horizontal scanning period.

With this driving method, regarding the liquid crystal display device that does not perform the main display operation, the operation of capturing the video signal into the liquid crystal panel and the line-sequential scanning operation are stopped, and
By setting the relationship between the video signal voltage and the counter voltage at substantially the same level, the voltage accumulated in the liquid crystal display element can be eliminated, and burn-in damage can be avoided.

A second aspect of the present invention relates to parallel driving of the first liquid crystal display device and the second liquid crystal display device, wherein the second liquid crystal is driven when the display operation of the first liquid crystal display device is driven. In a system in which the display device supplies a DC voltage to the counter electrode, the video signal is a DC center voltage of the video signal, and the invention according to claim 3 is
The horizontal display supplied to the second liquid crystal display device according to claim 2, wherein in the system in which the first liquid crystal display device which performs a normal display operation supplies a voltage which is inverted every horizontal scanning period to the counter electrode. At least the vertical scanning start control signal of the start control signal and the vertical scanning start control signal is stopped.

With this driving method, regarding the liquid crystal display device that does not perform the main display operation, the operation of capturing the video signal into the liquid crystal panel and the line-sequential scanning operation are stopped, and
By setting the video signal to the DC center voltage of the video signal, the relationship between the video signal voltage and the counter voltage can be made approximately the same level, eliminating the accumulated voltage in the liquid crystal display element,
Burn-in damage can be avoided.

The invention according to claim 4 of the present invention relates to parallel driving of the first liquid crystal display device and the second liquid crystal display device, wherein the second liquid crystal is driven when the display operation of the first liquid crystal display device is driven. Among the horizontal display start control signal and the vertical scanning start control signal of the display device, at least the horizontal scanning start control signal is stopped. The invention according to claim 5 is the invention according to claim 4, In the system in which the second liquid crystal display device supplies a voltage, which is inverted every horizontal scanning period, to the first liquid crystal display device which operates normally, the voltage supplied to the counter electrode is floated. It is characterized by being in a state.

With this driving method, regarding the liquid crystal display device that does not perform the main display operation, the operation of capturing the video signal into the liquid crystal panel and the line-sequential scanning operation are stopped, and
By setting the supply voltage to the counter electrode in the floating state, the storage voltage to the liquid crystal display elements of all pixels is averaged via the counter electrode, and the accumulated voltage can be made almost zero, thus preventing burn-in damage. It can be avoided.

Embodiments of the present invention will be described below with reference to the drawings. (Embodiment 1) FIG. 1 shows a liquid crystal display device for implementing a method for driving a liquid crystal display device according to the present invention.

As a liquid crystal display device, a first liquid crystal panel 3 is used.
Is a panel corresponding to the constant constant driving method such as high temperature polysilicon or low temperature polysilicon type, and the second liquid crystal panel 4 is a panel corresponding to the 1H counter inversion driving method such as amorphous silicon or low temperature polysilicon type.

In FIG. 1, 1 is a chroma IC for processing a video signal and a sync signal, 2 is a controller IC for controlling the drive timing of a display device, 3 is a first liquid crystal panel, 4 is a second liquid crystal panel, 5,6,7,8,9,10
Is a switch circuit for switching a video output signal and a logic control signal from the chroma IC 1 and the controller IC 2, 11
Is a selection switch circuit of the main display liquid crystal panel, 12 is a buffer circuit that supplies a 1H inversion signal to the counter electrode, 13 is a buffer circuit that supplies a 1H inversion signal to the scanning signal electrode that controls line-sequential scanning, and 14 is Diode, R1, R
2, R3, R4 are pull-down resistors connected between the signal line and the ground, R5, R6 are bias resistors for giving a DC center voltage of the video signal of the first liquid crystal panel 3, and R7, R8 are second liquid crystals. Bias resistors C1 and C for applying the DC center voltage of the video signal of panel 4
Reference numerals 2 and C3 are coupling capacitors, and VR is a counter electrode voltage setting resistor of the first liquid crystal panel 3.

The center voltage level of the video signal of each liquid crystal panel is generally 6 V for the high temperature polysilicon type panel (first liquid crystal panel 3) and 2.5 V for the amorphous silicon type panel (second liquid crystal panel 4). Target.
Therefore, the video output signal from the chroma IC 1 has a constant center voltage level even if the amplitude level can be varied, so it is necessary to match the higher one in order to drive the two types of liquid crystal panels 3 and 4. When driving the silicon type panel (second liquid crystal panel 4), the center voltage level of the video signal must be converted. Here, the direct current component is cut by the coupling capacitance C1 and the level is changed from 6 volt to 2.5 volt by the bias resistors R7 and R8.

Chroma IC1 and controller IC2 are each one
The video output signal and the logic control signal are composed of one set, and if the signal from the liquid crystal panel selection switch circuit 11 is at a high level, a signal matching the first liquid crystal panel 3 is output, and if it is at a low level, the second signal is output. In this configuration, a signal matching the liquid crystal panel 4 is output. These signals are commonly supplied to the first liquid crystal panel 3 and the second liquid crystal panel 4, and basically have a form of parallel drive. At the same time, the switch circuits 5, 6, 7, 8, 9, and 10 are also controlled in conjunction with the output of the liquid crystal panel selection switch circuit 11, and when the signal is high level, it is on the (A) side, and when it is low level, it is on the (B) side. It is designed to switch. A liquid crystal display unit device 40 is configured including these two types of liquid crystal display panels and a chroma IC and a controller IC that drive and control the liquid crystal display panels.

As described in the conventional example, when two types of liquid crystal panels are simply driven in parallel, the liquid crystal panel which does not have the proper video signal level or timing signal loses the AC drive balance and becomes in an abnormal display state. However, a direct current component is applied to the liquid crystal display element, which causes irreversible burn-in damage. Therefore, in the present invention, a driving method that avoids the damage described above is realized by taking measures such as changing the video signal level and stopping the supply of the logic control signal to the liquid crystal panel to which the irregular signal is supplied. It was made.

The specific operation will be described below, focusing on signal measures in order to avoid damage to the liquid crystal panel.
As a signal control measure to avoid damage, Chroma I
In relation to the output signal from C1, the video output signal (Video
o) R, G, B and the switching control of each signal of the COM signal that causes polarity inversion for each horizontal scanning period for the counter inversion drive, and the liquid crystal panel is related to the output signal from the output signal from the controller IC2. ST of the signal for controlling the horizontal display start for each horizontal scanning period when the video signal of
Switching control of the H signal and similarly each signal of the STV signal of the signal for controlling the vertical scanning start for every one vertical scanning period is performed, and the switch circuits 5, 6,
It is controlled by 7, 8, 9, 10. The switch circuit 5 switches the horizontal display start signal (STH), the switch circuit 6 switches the vertical scan start signal (STV), the switch circuit 7 switches the video signal (Video), and the switch circuit 8 switches the second liquid crystal panel 4 To the center bias voltage of the video signal supplied to the second liquid crystal panel 4, the switch circuit 9 controls the opening and closing of the analog power supply voltage of the second liquid crystal panel 4, and the switch circuit 10 switches the counter electrode voltage Vcom of the second liquid crystal panel 4. To do.

When the output of the liquid crystal panel selection switch circuit 11 is set to the high level, the first liquid crystal panel 3 becomes the main display operation, and the switch circuits 5, 6, 7, 8, 9, 10 are switched to the (A) side. . Chroma IC1, controller IC
As for each output signal from 2, the irregular signal is supplied to the second liquid crystal panel 4. In order to avoid damage to the second liquid crystal panel 4 due to this, the controller I
With respect to the signal from C2, the horizontal display start signal (STH) and the vertical scanning start signal (STV) are opened by the switch circuits 5 and 6. Since pull-down resistors R2 and R4 are connected to the ground with respect to the (B) side of the switch circuits 5 and 6, ST of the second liquid crystal panel 4 is connected.
The potentials of the H and STV terminals become zero, and the control signal is stopped. On the other hand, for the signal from the chroma IC 1, the switch circuit 7 causes the video output signal (Video) to be output.
o) is open. Vid to the second liquid crystal panel 4
The eo signal becomes a non-signal state and the switch circuit 8
Then, the bias resistor R7 is short-circuited and pulled up to the DC voltage level of the analog system power supply voltage VDD of the driving device for the second liquid crystal panel 4. On the other hand, Vcom, which is the voltage supplied to the counter electrode, is separated from the buffer circuit 12 by the switch circuit 10 and becomes a DC voltage level from the 1H inversion signal voltage to the analog power supply voltage VDD of the second liquid crystal panel drive device. . Further, the switch circuit 9 provided between the analog power supply voltage Vee of the second liquid crystal panel 4 and the analog power supply voltage VDD of the driving device is opened. At this time, the switch circuit 9 is connected to the diode 14 in parallel.
Is connected in the forward direction, the supply voltage to Vee is approximately VDD-0.7 V (forward voltage drop of one diode).

A mechanism capable of avoiding damage to the second liquid crystal panel 4 due to the 1H counter inversion driving method by such control will be described in detail with reference to FIG. FIG. 2 is an excerpt of a control portion related to avoiding damage to the second liquid crystal panel 4. The schematic structure of the second liquid crystal panel 4 will be briefly described. The display part is a TFT made of amorphous silicon
19 (switching element) and the liquid crystal display element 20 constitute one pixel 21, and the gate G of the TFT 19 (disconnection control terminal)
Is connected to the scanning signal electrode line 18, the source S is connected to the image signal electrode line 16, the drain D is connected to the pixel electrode of the liquid crystal display element 20, and the liquid crystal display element 20 is opposed to the liquid crystal display element 20 with a display material interposed therebetween. The counter signal electrode line 22 is connected to the electrode. A gate driver 17 is connected to the scanning signal electrode line 18, and the gate driver 17 selects the scanning signal electrode line 18 every 1H period to control line-sequential scanning. The image signal electrode line 16 is connected to the source driver 15, and a signal corresponding to the Video signal is sent from the source driver 15. The liquid crystal display element 20 includes a source driver 1
An image display is performed by controlling the amount of light from a backlight or the like by accumulating the potential difference between the image signal voltage from 5 and the counter electrode voltage from the counter signal electrode line 22. The polarity of the image signal voltage is inverted every one vertical scanning period so that the image signal voltage is AC driven. Source driver 15 is Vid
The eo signal is timing-controlled by the analog switch 25 by various control signals including STH, and is sent from the buffer 27 to the image signal electrode 16 as an image signal via the sample pool circuit (S / H) 26. The analog power supply voltage Vee of the source driver 15 is supplied to the sample hold circuit (S / H) 26 and the buffer 27. Further, the video signal terminal is provided with protection diodes 24 and 23 between the ground and the analog power supply voltage line for protection against abnormal voltage input.

If the switch circuits 8, 9 and 10 are on the (B) side where no damage countermeasure is taken, then Vid
The eo signal is supplied with a DC voltage divided by bias resistors R7 and R8 (normally 1/2 of VDD: 2.5 V if VDD = 5 V), and the analog power supply voltage Vee is VDD (VDD = 5). Vee = 5 Volt), but source driver 1
Since the video signal sent at the time of the normal signal is accumulated in the sample and hold circuit 26 of No. 5, since the signal is in the non-normal state in the second liquid crystal panel 4 due to the timing specifications matched with the first liquid crystal panel 3, Even if the horizontal display start signal is stopped, the video signal voltage is output from some of the buffers 27 to the image signal electrode line 16 due to unstable operation. As a result, vertical stripes or vertical strips are displayed, and screen burn-in occurs. Happens. As a method for avoiding this, it suffices to eliminate the accumulated voltage in the liquid crystal display element 20. Therefore, a means for equalizing the voltage of the image signal electrode line 16 and the counter electrode voltage Vcom was implemented.

First, the counter electrode voltage Vcom is made equal to the analog voltage system power source Vee of the second liquid crystal panel 4. Therefore, as the counter electrode voltage Vcom, the switch circuit 10 switches the 1H inversion signal voltage to the analog power supply voltage Vee and supplies the analog system power supply voltage Vee. Next, the image signal electrode wire 1
It is necessary to make the voltage supplied to 6 (the output voltage from the buffer 27) equal to the analog power supply voltage Vee.
To do this, the buffer output voltage must be Vee.
As the means, the output of the sample hold circuit (S / H) 26 may be set to Vee. To this end, by increasing the Video signal with respect to the analog power supply voltage Vee and setting the relationship of Video signal voltage> Vee, the sample and hold operation is not performed and the output is forcibly set to the high level state (Vee). You can First, in the video signal line, the bias resistance R7 is short-circuited by the switch circuit 8 to set the video signal voltage to the VDD voltage which is the analog power supply voltage of the driving device. On the other hand, the voltage to the analog voltage terminal of the liquid crystal display device is supplied to the analog power supply voltage VD by the switch circuit 9.
D is opened and the analog power supply voltage VDD is supplied via the diode 14. As a result, the video signal voltage = VDD, the analog power supply voltage Vee = VDD− (diode forward drop voltage), and the video signal voltage> the analog power supply voltage.

Here, the reason for using the diode 14 is as follows: (1) The protection diode 23 is provided because power is constantly supplied to the analog system power supply voltage line through the protection diode 23 provided at the Video signal terminal. If the reliability is lowered, the risk of destruction is suppressed. (2) Since the temperature characteristic of the forward drop voltage is the same as that of the protection diode 23 when the analog power supply voltage Vee is supplied via the diode 14, the protection diode cancels each other out even when the temperature changes. Suppress the flow of current from the. Is. With respect to the inflow of current from the protection diode 23, in consideration of a margin, a resistor R0 is connected in parallel with the die diode 14 to maintain the relationship of Video signal voltage> analog power supply voltage Vee while maintaining analog power supply. It is better to increase the voltage slightly (several hundred millivolts).

By the control as described above, it is possible to avoid damage to the second liquid crystal panel 4. The video signal voltage at the time of avoiding damage is always the analog power supply voltage VDD of the driving device. However, if a signal at the VDD voltage level is present in a part of one horizontal scanning period, the damage avoiding operation is not performed. There is no particular problem. This is because the sample-hold circuit (S / H) 26 is in a high impedance state and is held at the maximum level in the video signal voltage, so that the analog power supply voltage VD is apparently always maintained.
It is assumed to be equivalent to the state in which D is applied.

Next, the avoidance of damage to the first liquid crystal panel 3 when the second liquid crystal panel 4 performs the main display operation will be described. Liquid crystal panel selection switch circuit 11 in FIG.
Is set to a low level, each switch circuit 5, 6, 7,
8, 9 and 10 are switched to the (B) side. As for each output signal from the chroma IC 1 and the controller IC 2, an irregular signal is supplied to the first liquid crystal panel 3. In order to avoid damage to the first liquid crystal panel 3 due to this,
With respect to the signal from the controller IC2, the horizontal display start signal (STH) and the vertical scanning start signal (STV) are opened by the switch circuits 5 and 6. Since the pull-down resistors R1 and R3 are connected to the ground on the (A) side of the switch circuits 5 and 6, the potentials of the STH and STV terminals of the first liquid crystal panel 3 become zero, and the control signal Will be stopped. On the other hand, for the signal from the chroma IC 1, the switch circuit 7 opens the video output signal (Video). First liquid crystal panel 3
The video signal to (1) becomes a non-signal state, but the video signal center voltage (usually 6 V) is supplied by the divided voltage of the bias resistors R5 and R6. The reason for supplying the DC voltage of the Video signal is that if the horizontal display start signal (STH) and the vertical scanning start signal (STV) are simply stopped, the video signal level may change due to operation with irregular timing specifications. Causes instability of the display operation, and a state in which vertical stripes or the like occur and damage is not completely avoided appears as described above. Therefore, in the first fixed constant driving method of the first liquid crystal panel 3, since the video signal center voltage and the counter electrode voltage are substantially at the same level, the video signal is not applied and the video signal center voltage is used. As a result, the accumulated voltage to the liquid crystal display element can be set to (video signal center voltage)-(opposite electrode voltage) ≈ 0, so that the liquid crystal display element will not be damaged due to the direct current component, and thus avoided. Is possible.

(Second Embodiment) FIG. 3 shows a second embodiment of the present invention. As a liquid crystal display device, the first liquid crystal panel 3 is a high-temperature polysilicon or low-temperature polysilicon type panel corresponding to a fixed constant driving method, and the second liquid crystal panel 4 is an amorphous silicon or low-temperature polysilicon type 1H counter-inverted type. The panel is compatible with the driving method. The difference from the first embodiment is that the second liquid crystal panel 4 has a specification that the center voltage level of the video signal of the liquid crystal panel is about 6 volts, which is equivalent to that of the high temperature polysilicon type panel (first liquid crystal panel 3). In this case, only the avoidance of damage to the second liquid crystal panel 4 will be described below.

When the output of the liquid crystal panel selection switch circuit 11 is set to the high level, the first liquid crystal panel 3 becomes the main display operation, and the switch circuits 5, 6, 7, 8, 9, 10 are switched to the (A) side. . Chroma IC1, controller IC
As for each output signal from 2, the irregular signal is supplied to the second liquid crystal panel 4. In order to avoid damage to the second liquid crystal panel 4 due to this, the controller I
With respect to the signal from C2, the horizontal display start signal (STH) and the vertical scanning start signal (STV) are opened by the switch circuits 5 and 6. Since pull-down resistors R2 and R4 are connected to the ground with respect to the (B) side of the switch circuits 5 and 6, ST of the second liquid crystal panel 4 is connected.
The potentials of the H and STV terminals become zero, and the control signal is stopped. On the other hand, with respect to the signal from the chroma IC 1, the switch circuit 7 controls the opening and closing of the video output signal (Video) only for the first liquid crystal panel 3, and for the second liquid crystal panel 4. First liquid crystal panel 3
The same Video signal as is supplied. This is because the video signal center voltage is almost the same and the video signal amplitude level is also the same. On the other hand, Vcom, which is the voltage supplied to the counter electrode, is separated from the buffer circuit 12 by the switch circuit 10 and becomes the floating voltage level in the open state. As described above, it is assumed that the floating voltage of the counter electrode averages the stored voltages in the liquid crystal display elements 20 of all pixels via the counter electrode, resulting in almost no stored voltage. Even with such a control method, damage can be avoided.

(Embodiment 1) (Embodiment 2)
In the above, the means for stopping both the horizontal scanning start control signal and the vertical scanning start control signal for avoiding damage is shown. However, when two types of liquid crystal display devices are driven in parallel, the horizontal scanning start control signal / vertical scanning start signal is started. FIG. 4 and FIG. 5 show how the damage state becomes in relation to the presence or absence of the control signal and the video signal level.

Here, a high-temperature polysilicon panel for EVF (constant constant drive system), an amorphous silicon TFT panel for monitor (1H counter-reversal drive system) or a low-temperature polysilicon panel (1H counter-reversal drive system or constant constant drive system). Here is an example of using.

As can be seen from the table, the damage avoidance signal control conditions are different depending on the panel type and the driving method of the liquid crystal display device when a different type of signal is supplied so that the entire white screen is not damaged.

For example, in order to avoid damage in a combination of a high temperature polysilicon panel for EVF and an amorphous silicon TFT panel for monitor, in the high temperature polysilicon panel, the Video signal level is the Video signal center voltage (1/2 Vdc = 6 V) and , It is necessary to stop at least the vertical scanning start control signal ([E in FIG.
For VF: High temperature polysilicon panel] (2))).

On the other hand, in the amorphous silicon TFT panel, the Video signal level is set to the analog power supply voltage Ve.
e (+ 5V), and at least the vertical scanning start control signal must be stopped (see [for monitor: amorphous silicon TFT panel] in FIG. 5).

Similarly, in order to avoid damage in a combination of a high temperature polysilicon panel for EVF and a low temperature polysilicon panel for monitor, in the high temperature polysilicon panel, the Video signal level is set to the Video signal center voltage (6V) or low temperature. The video signal for the polysilicon panel can be used as it is ([EVF in FIG. 4
For: High-temperature polysilicon] (1), to)), in the low-temperature polysilicon panel, set the Video signal level to the Video signal center voltage (6V), or at least leave the Video signal for the high-temperature polysilicon panel as it is. It is necessary to stop the horizontal scanning start control signal (refer to [monitoring: low temperature polysilicon panel] of FIG. 5).

As is apparent from the table, depending on the type and driving method of the liquid crystal panel, it may be irrelevant whether the horizontal scanning start control signal or the vertical scanning start control signal is present, but the image signal is supplied to the liquid crystal panel during this period. Since it is considered to be stable operationally if not performed, it is basically preferable to stop both the horizontal scanning start control signal and the vertical scanning start control signal.

In each of the above embodiments, the chroma I
The handling of the 1H inverted signal COM output from C2 was not particularly mentioned, but the Vgl voltage is also supplied from the buffer 13 to the scanning signal electrode 18 via the gate driver. At the time of avoiding damage without performing the main display operation, the capacitance of the panel may affect the voltage of the counter electrode, so basically it is better to stop the COM signal. Switching control was performed for the logic signals STH, STV and Video signals by the external switch circuits 5, 6 and 7, but these switch circuits and pull-down resistors R1 and R were used.
2, R3 and R4 are of course chroma IC1 and controller I
It can also be built in C2. Also, the chroma IC
The IC 1 and the controller IC 2 are generally separate ICs, but if they are integrated into a one-chip IC by the Bi-CMOS semiconductor process technology, the parts can be further downsized.

Further, although not shown here, a signal from the liquid crystal panel selection switch circuit 11 is used to switch the control of the Video signal and the timing control signal from the chroma IC 1 and the controller IC 2 which meet the specifications of each liquid crystal panel. It is also possible to receive and control the chroma IC1 and the controller IC2 by the microcomputer control circuit.

[0044]

As described above, according to the present invention, in the parallel driving of two kinds of liquid crystal display devices by one set of the chroma IC and the controller IC, at least the vertical scanning is performed on the liquid crystal panel which does not perform the main display operation. The start signal is stopped to stop the operation of capturing the video signal to the liquid crystal panel and the line-sequential scanning operation, and the video signal voltage level and the counter electrode voltage level are changed by changing the video signal voltage level and the counter electrode voltage level for the standard display operation. By setting the relationship to be almost at the same level, it is possible to eliminate the accumulated voltage in the liquid crystal display element and avoid burn-in damage. Therefore, it is possible to drive two types of liquid crystal display devices without causing damage even if they are driven in parallel.

As a result, it is possible to provide a reduction in mounting area, power consumption, and cost because it is possible to configure one pair that required two pairs of chroma IC and controller IC in the past. The practical effect is great.

[Brief description of drawings]

FIG. 1 is a drive circuit configuration diagram for avoiding damage in parallel driving of a first liquid crystal panel and a second liquid crystal panel according to (Embodiment 1) of the present invention.

FIG. 2 is a configuration diagram of a main part for avoiding damage to a second liquid crystal panel in the same embodiment.

FIG. 3 is a drive circuit configuration diagram for avoiding damage in parallel driving of a first liquid crystal display panel and a second liquid crystal panel according to (Embodiment 2) of the present invention.

FIG. 4 is a diagram illustrating a damage state depending on the presence or absence of a Video signal level and a horizontal / vertical scan start control signal on the side when a high temperature polysilicon panel (constant constant driving method) is used for EVF in the embodiment of the present invention. Figure

FIG. 5 is a Video signal in an example in which an amorphous silicon panel (1H counter inversion drive method) or a low temperature polysilicon panel (1H counter inversion drive method or constant constant drive method) is used for a monitor in the embodiment of the present invention. Explanatory diagram of damage state depending on level and presence / absence of horizontal / vertical scanning start control signal

FIG. 6 is a configuration diagram for driving two types of conventional liquid crystal display devices.

[Explanation of symbols]

1 Chroma IC 2 Controller IC 3,4 LCD panel 5,6,7,8,9,10 switch circuit 11 Liquid crystal panel selection switch circuit 40 Liquid crystal display unit device

Claims (5)

(57) [Claims] 1. A scanning signal electrode line and an image signal electrode line arranged in a matrix form, and a pixel electrode having a display material interposed between each scanning signal electrode line and the image signal electrode line. A switching element connected between the image signal electrode line and the pixel electrode and having a disconnection control terminal connected to the scanning signal electrode line; and a counter electrode arranged corresponding to the pixel electrode with the display material interposed therebetween. Concerning the parallel driving of the first liquid crystal display device and the second liquid crystal display device configured as described above, a chroma control integrated circuit for controlling an image signal and a controller integrated circuit for controlling a drive timing signal of the liquid crystal display device are configured as one set. Generating control signals from the chroma control integrated circuit and the controller integrated circuit to meet the specifications of the first liquid crystal display device or the second liquid crystal display device, The signals are supplied in parallel to the first liquid crystal display device and the second liquid crystal display device, and when the display operation of the first liquid crystal display device is driven, the horizontal display start control signal and the vertical scanning start signal of the second liquid crystal display device. Among the control signals, at least the vertical scanning start control signal is stopped, and in the system in which the second liquid crystal display device supplies the counter electrode with a voltage that is inverted every horizontal scanning period, the second liquid crystal display The analog system power supply voltage (Vee) of the device is supplied from the analog system power supply voltage (VDD) of the driving device as a voltage (Vee ') via the forward diode, and the same voltage (Vee') is applied to the counter electrode. And a method of driving a liquid crystal display device, wherein a Vee power supply voltage level signal is applied to the video signal within one horizontal scanning period. 2. A scanning signal electrode line and an image signal electrode line arranged in a matrix, and a pixel electrode having a display material interposed between each scanning signal electrode line and each intersection of the image signal electrode lines. A switching element connected between the image signal electrode line and the pixel electrode and having a disconnection control terminal connected to the scanning signal electrode line; and a counter electrode arranged corresponding to the pixel electrode with the display material interposed therebetween. Concerning the parallel driving of the first liquid crystal display device and the second liquid crystal display device configured as described above, a chroma control integrated circuit for controlling an image signal and a controller integrated circuit for controlling a drive timing signal of the liquid crystal display device are configured as one set. Generating control signals from the chroma control integrated circuit and the controller integrated circuit to meet the specifications of the first liquid crystal display device or the second liquid crystal display device, A method in which the first liquid crystal display device and the second liquid crystal display device are supplied in parallel, and the second liquid crystal display device supplies a DC voltage to the counter electrode when the display operation of the first liquid crystal display device is driven. Then, a driving method of a liquid crystal display device in which a video signal is a DC center voltage of the video signal. 3. A horizontal display supplied to a second liquid crystal display device in a system in which a first liquid crystal display device which is in a normal display operation supplies a voltage which is inverted every horizontal scanning period to a counter electrode. The method for driving a liquid crystal display device according to claim 2, wherein at least the vertical scan start control signal is stopped among the start control signal and the vertical scan start control signal. 4. A scanning signal electrode line and an image signal electrode line arranged in a matrix form, and a pixel electrode with a display material interposed between each scanning signal electrode line and each image signal electrode line. A switching element connected between the image signal electrode line and the pixel electrode and having a disconnection control terminal connected to the scanning signal electrode line; and a counter electrode arranged corresponding to the pixel electrode with the display material interposed therebetween. Concerning the parallel driving of the first liquid crystal display device and the second liquid crystal display device configured as described above, a chroma control integrated circuit for controlling an image signal and a controller integrated circuit for controlling a drive timing signal of the liquid crystal display device are configured as one set. Generating control signals from the chroma control integrated circuit and the controller integrated circuit to meet the specifications of the first liquid crystal display device or the second liquid crystal display device, The signals are supplied in parallel to the first liquid crystal display device and the second liquid crystal display device, and when the display operation of the first liquid crystal display device is driven, the horizontal display start control signal and the vertical scanning start signal of the second liquid crystal display device. A method of driving a liquid crystal display device, wherein at least a horizontal scanning start control signal of the control signals is stopped. 5. In a system in which a second liquid crystal display device supplies a voltage that is inverted every horizontal scanning period to the first liquid crystal display device which operates normally, to the counter electrode. The method for driving a liquid crystal display device according to claim 4, wherein the supply voltage of is set to a floating state.