JPH11202842A - Liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid crystal display device capable of exhibiting power- saving effect without shortening the life of a back light unit. SOLUTION: A synchronizing signal based upon a power-saving mode which is supplied from a personal computer main body 10 is discriminated by a synchronous detecting circuit 26 and a command for reducing working power supplied to the back light unit 32 is sent through a back light control circuit 31. The synchronous detecting circuit 26 sends commands to a synchronous switching circuit 27 and a video switching circuit 23 to reduce the output frequency of a PLL circuit 29 for dot clock qeneration and also supply a black signal to a liquid crystal display unit 24.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a stand-alone liquid crystal display device which is used by connecting it to a desktop personal computer, for example. The present invention relates to a liquid crystal display device capable of reducing driving power.

[0002]

2. Description of the Related Art For example, when the operation of a keyboard or a mouse in a personal computer is suspended for a predetermined time or more, the power consumption of a display is automatically reduced. A display power management system (DPMS) has been established as a protocol to perform such operations.

[0003] In this DPMS, a standby mode, a suspend mode, and an off mode are defined. When the operation of a keyboard or a mouse or the like on the personal computer main body is suspended for, for example, 5 minutes or more, the standby mode is set. For example, when the operation is paused for 10 minutes or more, the suspend mode is set, and when the operation is paused for 30 minutes or more, the suspend mode is set to the off mode.

In any mode, the display function is resumed by operating the keyboard or mouse again.

Here, for example, when a display using a CRT is made to conform to the DPMS, a CR
Since T is a hot cathode ray tube, there is a problem that it takes time to restore the display even if the operation power is turned on. For this reason, CRTs are generally used in any mode.
Is controlled so as not to be turned off, and the display can be instantaneously returned to the display.

However, when a liquid crystal display is used, the power consumption of the backlight is turned off in any of the standby mode, the suspend mode, and the off mode to reduce power consumption. This is because the backlight of a liquid crystal display generally uses a cold cathode ray tube, which has the characteristic that light emission starts at the same time as the operation power is turned on. This is because the function can be restored.

[0007]

By the way, in a liquid crystal display using a cold cathode ray tube as a backlight, if the above-described means for reducing power consumption is adopted, a cold cathode ray tube which functions as a backlight at the moment of switching to a standby mode is adopted. When the power supply to the tube is cut off and the keyboard or the mouse is operated again, the power supply to the cold cathode ray tube is performed, and the off and on operations are repeated every slight pause.

[0008] As is well known, cold cathode ray tubes have a problem that frequent repetition of turning on and off an operating power supply shortens the life thereof, thereby causing a problem of shortening the life of the entire liquid crystal display. I have.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned technical problems of the related art, and it is possible to prevent a life of a backlight function in a liquid crystal display device from being shortened, and to provide a backlight. It is an object of the present invention to provide a liquid crystal display device capable of reducing power consumption in a drive portion of a liquid crystal display excluding functions.

[0010]

According to the present invention, there is provided a liquid crystal display device which is connected to a personal computer main body and displays image information in response to a command signal from the personal computer. When the operation is suspended for a predetermined time or more on the main unit side, the standby mode, the suspend mode, and the off mode are sequentially switched to the non-display state with the elapse of the pause time, and the operation is resumed on the personal computer side. A liquid crystal display device controlled to switch from each mode to a display state, wherein a backlight unit and a liquid crystal display unit in the liquid crystal display device are respectively set to a standby mode and / or a suspend mode. Information, together with the switching to the power save state, the control means for interrupting the operating power in a state that led to off mode is provided.

In this case, preferably, the control means is configured to reduce the brightness of the backlight unit in the power save state.

In some cases, the control means is configured to reduce the frequency of a dot clock for sampling a video signal to be supplied to the liquid crystal display unit in a power saving state.

Further, the control means supplies a black signal as a video signal to the liquid crystal display unit when the liquid crystal display unit is normally black in the power saving state, and supplies a video signal when the liquid crystal display unit is normally white. To supply a white signal to the liquid crystal display unit.

In a preferred embodiment, in the standby mode, the control means reduces the brightness of the backlight unit and the frequency of the dot clock for sampling the video signal to be supplied to the liquid crystal display unit. In the suspend mode, further, when the liquid crystal display unit is in normal black, a black signal is supplied to the liquid crystal display unit as a video signal,
When the liquid crystal display unit is a normal white, a white signal is supplied as a video signal to the liquid crystal display unit.

According to the preferred embodiment of the liquid crystal display device configured as described above, when the operation of the input device such as the keyboard or the mouse on the personal computer main body is suspended for a first predetermined time or more, the standby mode is set. Move to In this case, the operating current is reduced so as to lower the luminance of the backlight unit, and at the same time, control is performed so as to lower the frequency of the dot clock for sampling the video signal supplied to the liquid crystal display unit.

When the operation of an input device such as a keyboard or a mouse is paused for a second predetermined time or more, the mode shifts to a suspend mode. In this case, the operating current is reduced so as to lower the luminance of the backlight unit, and at the same time, control is performed so as to lower the frequency of the dot clock for sampling the video signal supplied to the liquid crystal display unit. In addition, when the liquid crystal display unit is normally black, a black signal is supplied to the liquid crystal display unit as a video signal, and when the liquid crystal display unit is normal white, a white signal is supplied to the liquid crystal display unit as a video signal. Is controlled.

When the operation of an input device such as a keyboard or a mouse is paused for a third predetermined time or more, the mode shifts to the off mode. In this case, the operation current supplied to the backlight unit is cut off, and at the same time, the video signal supplied to the liquid crystal display unit is also cut off.

Therefore, in the standby mode and the suspend mode, the operation current for the backlight unit in the liquid crystal display device is not interrupted, and in such a state, when an input device such as a keyboard or a mouse is operated. Subsequently returns to the display state.

Therefore, the operation current for the backlight unit is not frequently turned off and on, and
Factors that shorten the life of the backlight unit can be eliminated.

In the standby mode and the suspend mode, the frequency of the dot clock applied to the liquid crystal display unit is reduced, and control is performed so as to supply a black signal or a white signal as a video signal.
Power consumption in the liquid crystal display unit can also be reduced.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a liquid crystal display device according to the present invention will be described based on an embodiment shown in the drawings.

FIG. 1 is a block diagram showing a circuit configuration of a liquid crystal display device according to the present invention. The left side part separated by a chain line in the figure shows a personal computer main body 10, to which a keyboard 11 and a mouse 12 as input devices are connected. Then, a liquid crystal display device 20 is connected to the personal computer body 10 as shown on the right side sectioned by a chain line.

The liquid crystal display device 20 is connected to the personal computer 10 by a video signal line 21 and a synchronization signal line 22. The video signal line 2
R, G, and B video signals are supplied to the PC main unit 1 from the PC main unit 10, and the PC main unit 1 is supplied to the synchronization signal line 22.
From 0, synchronization signals of H synchronization (horizontal synchronization) and V synchronization (vertical synchronization) are supplied.

The video signal line 21 is configured so that a video signal is supplied to the liquid crystal display unit 24 via a video switching circuit 23. The switching operation of the video switching circuit 23 causes the video switching circuit 23 to operate. Is supplied to the liquid crystal display unit 24 from a black signal generating circuit 25 connected to the liquid crystal display unit 24.

The synchronization signal line 22 is connected to a synchronization detection circuit 26. The synchronization detection circuit 26 controls the video switching circuit 23 based on the presence or absence of each synchronization signal on the synchronization signal line 22, and controls the video signal. The video signal from the line 21 or the black signal from the black signal generation circuit 25 is alternatively supplied to the liquid crystal display unit 24.

The synchronization detection circuit 26 is provided with a synchronization signal line 2
2 controls the synchronization switching circuit 27 based on the presence or absence of each synchronization signal in the synchronization signal line 22 supplied to the synchronization switching circuit 27.
The synchronizing signal from the synchronizing signal generating circuit 28 connected to the signal generator 7 is selectively output.

The synchronizing signal selectively output by the synchronizing switching circuit 27 supplies the synchronizing signal to the liquid crystal display unit 24 and also supplies the synchronizing signal to a PLL circuit 29 which generates a dot clock for sampling a video signal. The configuration is such that the dot clock generated by the PLL circuit 29 is supplied to the liquid crystal display unit 24.

The control signal from the synchronization detection circuit 26 is supplied to an LCD control circuit 30 to control the display unit 24 by the LCD control circuit 30. The control signal from the synchronization detection circuit 26 Is supplied to the backlight control circuit 31, and the backlight unit 32 connected to the backlight control circuit 31
Is configured to control the operating current with respect to.

In the above configuration, when the operation of the keyboard 11 or the mouse 12 as an input device on the personal computer main body 10 is suspended for a predetermined time or more, the standby mode, the suspend mode, and the off mode are sequentially performed as the pause time elapses. Is set to
Control for switching to the non-display state is performed.

In this case, when the operation of the keyboard 11 or the mouse 12 on the personal computer body 10 is paused for, for example, 5 minutes or more, the standby mode is set. When the operation is paused for 10 minutes or more, for example, When the operation is in the suspend mode and the operation is suspended for, for example, 30 minutes or more, the operation is controlled to be in the off mode.

In any mode, the display function is restarted by operating the keyboard 11 or the mouse 12 again.

In order to set each of the above modes, in the standby mode, only the signal from which the H synchronization is deleted from the synchronization signal supplied to the synchronization signal line 22 from the personal computer body 10, that is, only the V synchronization signal is supplied. In the suspend mode, only the signal from which the V synchronization is deleted, that is, only the H synchronization signal is supplied. Further, in the off mode, a non-synchronous signal from which the H and V synchronizations have been deleted is supplied.

The synchronization detection circuit 26 monitors these states, and determines the display mode in which the H synchronization signal and the V synchronization signal are arriving and the above-described standby, suspend, and off modes by combining the presence or absence of each synchronization signal. Identify from three values.

In the display mode in which the H and V signals are arriving, the synchronization detecting circuit 26 supplies the video switching circuit 23 with R, G, and B video signals from the video signal line 21 to the liquid crystal display unit 24. To control. At the same time, the synchronization detection circuit 26 sends a synchronization signal from the synchronization signal line 22, that is, H synchronization and V synchronization to the synchronization switching circuit 27 to the LCD control circuit 3.
0 to the liquid crystal display unit 24 and a PLL circuit 29 as a dot clock generation circuit.

For this purpose, the PLL circuit 29 obtains H synchronization and V synchronization and generates a dot clock for normal video signal sampling. On the other hand, the synchronization detection circuit 26 controls the backlight control circuit 31 so as to continuously supply a normal operation current to the backlight unit 32 formed of a cold cathode ray tube. As a result, the backlight unit 32 maintains the lighting state, the display unit 24 maintains the image reproduction state, and the display device 2
Numeral 0 displays image information based on a command signal from the personal computer 10.

When the operation of the keyboard 11 or the mouse 12 on the personal computer main body 10 is paused for, for example, 5 minutes or more and the apparatus enters the standby mode, H synchronization is deleted from the synchronization signal line 22 as described above. Only the signal, ie, the V synchronization signal, is supplied. The synchronization detection circuit 26 detects this state and switches the synchronization switching circuit 27 to receive a synchronization signal from the synchronization signal generation circuit 28 side. At this time, normally, the RGB signals in the standby mode, the suspend mode, and the off mode are determined to be black.

The PLL circuit 29 which has received the synchronization signal from the synchronization signal generation circuit 28 lowers the frequency of the generated dot clock for sampling the video signal. On the other hand, the synchronization detection circuit 26 sends a control signal to the backlight control circuit 31, and the operation current supplied from the backlight control circuit 31 to the backlight unit 32 is reduced to a minimum level at which the backlight unit 32 can continue lighting operation. Is controlled so as to be reduced to the operating current.

The power consumption of the display unit 24 controlled to lower the frequency of the dot clock for sampling the video signal is reduced, and the operating current supplied to the backlight unit 32 is also reduced. , Switch to power save mode.

Subsequently, when the operation of the keyboard 11 or the mouse 12 on the personal computer main body 10 is suspended for, for example, 10 minutes or more and the suspend mode is set, the V synchronization is deleted from the synchronization signal line 22 as described above. , Ie, only the H synchronization signal.

The synchronization detection circuit 26 detects this state and controls the synchronization switching circuit 27 in the same manner as in the standby mode. In addition, the synchronization detection circuit 26 sends a control signal to the video switching circuit 23 and controls the black signal generation circuit 25 to supply a black signal as a video signal to the display unit 24. Here, the liquid crystal display unit 24 is of a normal black type. Therefore, by supplying a black signal to such a liquid crystal display unit, power consumption in the liquid crystal display unit 24 is reduced.

When a normal white type liquid crystal display unit 24 is used, the power consumption of the liquid crystal display unit can be similarly reduced by supplying a white signal.

As described above, in the suspend mode, the operating current supplied to the backlight unit 32 is reduced, and the display unit 2
4 is controlled so as to lower the frequency of the dot clock for sampling the video signal, and in addition, a black signal is supplied to the display unit 24 so that the power consumption is further reduced.

Subsequently, when the operation of the keyboard 11 or the mouse 12 on the personal computer body 10 is paused for, for example, 30 minutes or more and the mode is turned off, the H synchronization and the V synchronization on the synchronization signal line 22 are performed as described above.
The synchronizing signal is a deleted non-synchronizing signal. In this case, the synchronization detection circuit 26 sends a control signal to the LCD control circuit 30 to control the operation of the display unit 24 to stop. Further, the synchronization detection circuit 26 gives a command to the backlight control circuit 31 to perform control to cut off (turn off) the operation current to the backlight unit 32.

As a result, the display unit 24 and the backlight unit 32 are turned off.

FIG. 2 is a table showing the power saving function and the control result in the liquid crystal display device according to the embodiment of the present invention described above, and additionally shows the difference from the operation of the conventional liquid crystal display device. It is shown.

As shown in FIG. 2, in the conventional liquid crystal display device, the backlight is turned off in each of the three low power consumption modes.

On the other hand, in the liquid crystal display device according to the embodiment of the present invention, control is performed using a combination of three values of a synchronization signal supplied from the personal computer in accordance with each mode. The backlight is turned on in each of the standby and suspend modes, and is turned off (off) in the off mode.

The frequency of the dot clock for the liquid crystal display unit is lowered in each of the standby mode and the suspend mode to reduce power consumption, and the supply of the dot clock is stopped in the off mode.

Further, the video signal supplied to the liquid crystal display unit is reduced in power consumption by transmitting a black signal in the suspend mode.
The supply is stopped in the off mode.

The above description shows an example of control, and the present invention is not limited to this example, and various changes can be made within the technical scope described in the claims. Of course.

For example, in the embodiment, the switching control is performed in order according to each mode as shown in FIG. 2, but the control mode may be the same between the standby mode and the suspend mode. The power save state may be set only in the standby mode or only in the suspend mode.

[0052]

As is apparent from the above description, according to the liquid crystal display device of the present invention, each of the backlight unit and the liquid crystal display unit is switched to the power save state in the standby mode and / or the suspend mode. In addition, since control means for shutting off the operation power supply in a state where the mode has been turned off is provided, the operation of frequently turning on and off the operation power supply for the backlight unit can be reduced, and therefore, the operation of the liquid crystal display device can be reduced. The service life can be extended.

In addition, by switching the frequency of the dot clock supplied to the display unit and the video signal, the power consumption of the display unit can be reduced.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a liquid crystal display device according to the present invention.

FIG. 2 is a table showing a difference in operation at the time of power saving between the device according to the present invention shown in FIG. 1 and a conventional device.

[Description of Signs] 10 signal source (PC etc.) 11 keyboard 12 mouse 20 liquid crystal display device 21 video signal line 22 synchronization signal line 23 video switching circuit 24 LCD unit 25 black signal generation circuit 26 synchronization detection circuit 27 synchronization switching circuit 28 synchronization Signal generation circuit 29 PLL circuit (dot clock generation circuit) 30 LCD control circuit 31 Backlight control circuit 32 Backlight unit

Claims (5)

[Claims] 1. Image information is displayed by a command signal from a personal computer connected to a personal computer main body.
When the operation is suspended for a predetermined time or more on the personal computer body side, the standby mode, the suspend mode, and the off mode are sequentially switched to the non-display state as the pause time elapses, and the operation is resumed on the personal computer body side. A liquid crystal display device that is controlled to be switched from each of the modes to a display state, wherein each of the backlight unit and the liquid crystal display unit in the liquid crystal display device includes:
A liquid crystal display device comprising a control means for switching to a power saving state in a standby mode and / or a suspend mode, and for shutting off an operation power supply in a state where an off mode is reached. 2. The liquid crystal display device according to claim 1, wherein the control unit is configured to reduce the brightness of the backlight unit in a power save state. 3. The liquid crystal display according to claim 1, wherein the control unit is configured to reduce a frequency of a dot clock for sampling a video signal supplied to the liquid crystal display unit in a power save state. apparatus. 4. The control means supplies a black signal to the liquid crystal display unit as a video signal when the liquid crystal display unit is in a normal black state in a power save state, and outputs an image when the liquid crystal display unit is in a normal white state. The liquid crystal display device according to claim 1, wherein a white signal is supplied to the liquid crystal display unit as a signal. 5. In a standby mode, the control means is configured to lower the luminance of the backlight unit and lower the frequency of a dot clock for sampling a video signal to be supplied to a liquid crystal display unit. In the mode, when the liquid crystal display unit is normally black, a black signal is supplied to the liquid crystal display unit as a video signal, and when the liquid crystal display unit is normal white, a white signal is supplied to the liquid crystal display unit as a video signal. The liquid crystal display device according to claim 1, wherein the liquid crystal display device is configured as follows.