JPH06324629A - Driving circuit of liquid crystal display device with back light - Google Patents

Abstract

PURPOSE:To shorten the illumination time of a liquid crystal display part as much as possible and to prolong the life of the device by turning off the display of the liquid crystal display part together with the back light unless the display contents of the liquid crystal display part vary continuously for a long time. CONSTITUTION:When it is judged that there is no interruption of input/output (I/O) communication to the liquid crystal display device, it is checked whether or not the timer value of a timer exceeds a user set value set by a user. When it is judged that the timer value exceeds the user set value, an OFF signal, i.e., low-level signal is outputted to the LCD control port P1 and back light control port P2 of the driving circuit of the liquid crystal display device with the back light. Then the driving circuit of the liquid crystal display device 10 with the back light turns OFF both the back light and liquid crystal display part of the liquid crystal display device 10 once the low-level signal is applied to the LCD control port P1 and back light control port P2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a drive circuit for a liquid crystal display device with a backlight, which displays various kinds of information in response to signals from a host device, and particularly when the display content does not change continuously for a preset time. The present invention relates to a drive circuit of a liquid crystal display device with a backlight, which is configured to turn off the display of the liquid crystal display unit when the backlight is turned off.

[0002]

2. Description of the Related Art Conventionally, as a liquid crystal display device, there is known a liquid crystal display device with a backlight which uses a backlight to make the display clear.

This liquid crystal display device with a back light is composed of a liquid crystal display section and a back light for illuminating the liquid crystal display section from the back side.

In such a liquid crystal display device with a backlight, the life of the backlight is, for example, 1
0000 hours, the life of the liquid crystal display unit is, for example, 5000
The life of the backlight is considerably shorter than the life of the liquid crystal display unit, such as 0 hour.

Therefore, conventionally, for example, in a drive circuit of a liquid crystal display device with a backlight for displaying various information by signals from a host device, in order to extend the life of the backlight, the display content by the liquid crystal display unit is changed. A configuration has been proposed in which the backlight is automatically turned off by a signal from the host device unless it continuously changes for a predetermined time set in advance.

[0006]

However, in such a conventional drive circuit for a liquid crystal display device with a backlight, the liquid crystal display section continues to display even if the backlight is turned off. There is an inconvenience that seizure occurs.

Therefore, there has been proposed a structure in which a screen saver is executed together with the turning off of the backlight to prevent burning due to continuous lighting of the liquid crystal display section.

However, in the structure for executing such a screen saver, the liquid crystal display unit is not completely turned off, so that it is possible to prevent the liquid crystal display unit from burning, but the life of the liquid crystal display unit is shortened. The problem arises.

In particular, in the structure in which the backlight of the liquid crystal display device can be replaced, the life of the liquid crystal display portion causes
The life of the liquid crystal display device is determined, and in such a configuration, the life of the liquid crystal display unit is shortened, which is a problem.

Therefore, an object of the present invention is to provide a drive circuit for a liquid crystal display device which is improved so as to prolong the life of the entire device by reducing the lighting time of the liquid crystal display unit as much as possible.

[0011]

To achieve the above object, the present invention comprises a liquid crystal display section and a backlight for illuminating the liquid crystal display section, and a predetermined signal is provided to the liquid crystal display section by a signal from a host device. In a drive circuit of a liquid crystal display device with a backlight for displaying information, it is detected that the display content of the liquid crystal display unit does not continuously change for a predetermined time, and the display of the liquid crystal display unit together with the backlight is displayed. Is characterized by turning off.

[0012]

According to the present invention, when the display content of the liquid crystal display unit does not change continuously for a predetermined time set in advance, the display of the liquid crystal display unit is turned off together with the backlight. As a result, the display time of the liquid crystal display unit is significantly shortened, the life of the liquid crystal display unit is extended, and the life of the entire device can be extended.

Here, the predetermined time may be arbitrarily set by the user.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a drive circuit for a liquid crystal display device with a backlight according to the present invention will be described below in detail with reference to the accompanying drawings.

FIG. 1 shows an embodiment of a drive circuit for a liquid crystal display device with a backlight according to the present invention. In FIG. 1, the drive circuit of the liquid crystal display device with a back light of this embodiment includes a host device (not shown) and an LCD
It is controlled by signals applied to the control port P1 and the backlight control port P2, and when a high level signal for turning on the backlight of the liquid crystal display device with a backlight 10 is applied to the backlight control port P2, this high level signal is output. The level signal is applied to the base of the transistor TR2 via the resistor R3. Transistor TR
2 has its emitter connected to ground of 0V and has a bias resistor R4 connected between its base and emitter, and is turned on when a high level signal is applied to its base. A current flows from the power source to the ground of 0V through the relay coil (RL) 2, the collector of the transistor TR2, and the emitter of the transistor TR2, and the relay coil 2 is excited. here,
The diode D connected in parallel to the relay coil 2 is a diode for protecting the relay coil 2.

When the relay coil 2 is excited, its relay contact 2a is turned on, and 12V power is supplied to the backlight power supply terminal VBL of the liquid crystal display device with a backlight through this relay contact 2a. A backlight (not shown) of the liquid crystal display device 10 with a backlight is turned on.

In this state, when a high level signal for turning on (turning on) a liquid crystal display section (not shown) of the liquid crystal display device 10 with a backlight is applied to the LCD control port P1,
This high level signal is applied to the base of the transistor TR1 via the resistor R1. Transistor TR1
Has its emitter connected to 0V ground and
A bias resistor R2 is connected between the base and the emitter, and becomes active when a high level signal is applied to the base. When the transistor TR1 is activated, the relay contact 2a, the resistance R
5, collector of transistor TR1, transistor TR
A current flows to the ground of 0V through the emitter of 1, and a high level signal is generated from the collector of the transistor TR1. This high level signal is applied to the LCD control terminal CNT of the liquid crystal display device with a backlight 10, Thus, the liquid crystal display unit of the liquid crystal display device with a backlight 10 is turned on.

In order to turn off the backlight of the liquid crystal display device 10 with a backlight, the backlight control port P is used.
When a low level signal is applied to 2, the transistor T
R2 is turned off, which deactivates the relay coil 2 and turns off its relay contact 2a. As a result, the high level signal generated from the collector of TR1 becomes low level, and the liquid crystal display section of the liquid crystal display device with a backlight 10 is also turned off.

FIG. 2 shows the entire structure of a display system constructed by applying the drive circuit of the liquid crystal display device with a backlight. This display system is, for example, an FA.
The display system is configured as a (factory automation) system, and includes a plurality of liquid crystal display devices 10-1, 10-2, and 10-n dispersedly arranged at various places. -2, -10-n
Is connected to the host device 20 via a bus line 30. Then, the plurality of liquid crystal display devices 10-1 and 10
-2 and -10-n are bus lines 3 by the host device 20.
Controlled through 0.

Here, the drive circuit shown in FIG. 1 is housed in each of the liquid crystal display devices 10-1, 10-2, and 10-n, and each of the liquid crystal display devices 10-1, 10-2, 10-2. ~
The host device 2 is connected to the LCD control port P1 and the backlight control port P2 (see FIG. 1) of the 10-n drive circuit.
Drive signals are added from 0, respectively.

FIG. 3 shows a process of generating a drive signal applied to the LCD control port P1 and the backlight control port P2 of each drive circuit in the host device 20 shown in FIG.

The host device 20 shown in FIG. 2 has an input / output (I / O) communication interrupt for displaying predetermined information on each of the liquid crystal display devices 10-1, 10-2, and 10-n. It is monitored whether there is any (step 101). This monitoring is performed for each of the liquid crystal display devices 10-1, 10-2, and 10-n,
In the following description, a plurality of liquid crystal display devices 10-1,
One of the liquid crystal display devices 10-2 to 10-n
Only 1 will be described.

In step 101, the liquid crystal display device 1
If it is determined that there is an input / output (I / O) communication interrupt at 0-1, the process proceeds to step 105 and a timer (not shown) is cleared. While this timer can be configured as an internal timer of the host device 20, step 101
When it is determined that the input / output (I / O) communication is not interrupted by the liquid crystal display device 10-1, it is checked whether or not the timer value of the timer (not shown) exceeds the user set value set by the user. (Step 102). Here, if the timer value does not exceed the user set value, the process proceeds to step 104 and the timer value is added. The addition of the timer value is performed by adding a predetermined clock of the host device 20.

When it is determined in step 102 that the timer value has exceeded the user-set value, the LCD control port P1 and the backlight control port P2 of the drive circuit of the liquid crystal display device with backlight shown in FIG. OF
F, that is, a low level signal is output.

In the drive circuit of the liquid crystal display device with a backlight shown in FIG. 1, when a low level signal is applied to the LCD control port P1 and the backlight control port P2,
Both the backlight and the liquid crystal display section of the liquid crystal display device with a backlight 10 are turned off.

The above description is for a plurality of liquid crystal display devices 1.
Only one liquid crystal display device 10-1 of 0-1, 10-2, and 10-n was used, but the other liquid crystal display device 1 was used.
Similar processing is performed for 0-2 and -10-n.

That is, the host device 20 of FIG. 2 monitors the display state of each of the plurality of liquid crystal display devices 10-1, 10-2, and 10-n, and the user sets the timer value of the timer by the user. When the same display is continuously continued until the value is exceeded, the liquid crystal display devices 10-1 and 10-
A low-level signal is output to the LCD control port P1 and the backlight control port P2 of the driving circuits 2 to 10-n, thereby turning off both the backlight and the liquid crystal display unit of the liquid crystal display device. .

With such a configuration, in each of the liquid crystal display devices 10-1, 10-2, and 10-n, the liquid crystal display unit is turned off and the liquid crystal display unit is turned on each time the backlight is controlled to be turned off. The time can be greatly reduced. The fact that the lighting time of the liquid crystal display unit can be reduced means that each of the liquid crystal display devices 10-1, 10-2, and 10 can be reduced.
It is possible to extend the life of each of the liquid crystal display devices -n, and it is possible to extend the life of each of the liquid crystal display devices 10-1, 10-2, and 10-n.

The user value shown in step 103 of FIG. 3 can be arbitrarily set by the user in the host device 20.

FIG. 4 shows an example of how to set a user value in the host device 20. In FIG. 4, a user value can be set on a save menu displayed on a display device (not shown) of the host device 20, and FIG. 4 shows a display screen of a display device (not shown) of the host device 20. The save menu displayed is shown.

In the save menu shown in FIG. 4, there is an item "backlight off". In this item,
A user value is set for controlling the backlight and the liquid crystal display unit to be turned off.

In this embodiment, three types of user values of "10 minutes", "1 hour", and "none" can be selectively set as the user value. For example, this item can be set by a mouse. By clicking, it is configured so as to circulate and switch as shown in FIG.

[0033]

As described above, according to the present invention,
Since the display of the liquid crystal display unit is turned off together with the backlight when the display content of the liquid crystal display unit does not change continuously for a preset time, the lighting time of the liquid crystal display unit is reduced as much as possible. Therefore, there is an effect that the life of the entire device can be extended.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an embodiment of a drive circuit of a liquid crystal display device with a backlight according to the present invention.

FIG. 2 is a block diagram showing an overall configuration of a display system configured by applying a drive circuit of a liquid crystal display device with a backlight according to the present invention.

FIG. 3 is a flowchart showing a process of generating a drive signal applied to the LCD control port and the backlight control port of each drive circuit in the host device shown in FIG.

FIG. 4 is a diagram showing an example of a method of setting a user value in the host device, showing an example of a save menu displayed on the display screen of the display unit of the host device.

FIG. 5 is a diagram illustrating a method of switching selection of a user value on the save menu shown in FIG.

[Explanation of symbols]

 2 relay coil (RL) 2a relay contact 10 liquid crystal display device with backlight 10-1 to 10-n liquid crystal display device 20 host device 30 bus line

Claims (2)

[Claims] 1. A drive circuit of a liquid crystal display device with a backlight, comprising a liquid crystal display part and a backlight for illuminating the liquid crystal display part, and displaying predetermined information on the liquid crystal display part according to a signal from a host device, Liquid crystal with a backlight, characterized in that it is detected that the display content of the liquid crystal display unit does not continuously change for a preset predetermined time, and the display of the liquid crystal display unit is turned off together with the backlight. Drive circuit of display device. 2. The drive circuit for a liquid crystal display device according to claim 1, wherein the predetermined time can be arbitrarily set by a user.