JP2002006789A - Backlight control device - Google Patents

Abstract

(57) Abstract: Provided is a backlight control device that realizes switching between a high luminance mode and a low luminance mode at low cost in a display device including a plurality of backlights. Further, the present invention provides a backlight control device for realizing a longer backlight life in a low luminance mode. SOLUTION: Mode switching instructing means for instructing switching between a high brightness mode and a low brightness mode, and when a high brightness mode is instructed by the mode switching instructing means, switches a first backlight and a second backlight. Both are turned on, and when the low-luminance mode is instructed, this is realized by providing a backlight control unit that turns on either one of the first backlight and the second backlight alternately.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a display device having a plurality of backlights, and more particularly, to a display device having a standby mode and a plurality of run modes, and a function of adjusting brightness according to each of the run modes. And a display device having the same.

[0002]

2. Description of the Related Art Conventionally, some display devices having a plurality of pairs of backlights have a power control function for controlling a power mode between a run mode and a standby mode. The run mode is a normal operation state, in which a backlight is turned on and a display is performed. The standby mode is a state in which the system is not operating, and is a state in which power is supplied to only a minimum necessary circuit for suppressing power consumption. The mode can be changed between the run mode and the standby mode depending on the presence or absence of a display control signal to the display device. In the run mode, the brightness of the backlight may be changed by changing the brightness dimming voltage.

FIG. 10 is a system configuration diagram of a display device based on the prior art. The system includes a power supply 80 for supplying power to the entire system, a microcontroller 81 for controlling the operation of the system, a panel 88 for displaying, and a panel 8.
Converter 84, analog RG for controlling
A / D converter 82 for converting B input to digital, A
Video decoder 83 for converting V input to digital, backlight 87 for lighting panel 88, backlight 8
Backlight power supply voltage controller 86 for supplying power to the power supply 7
And a backlight luminance voltage generator 85 for adjusting the luminance of the backlight.

The conventional operation of the present system is as follows. When the power is turned on while the power is not turned on, the microcontroller 8
1 is turned on, and the backlight 87 is turned on by the backlight power supply voltage control unit 86 in accordance with a command from the microcontroller 81. At this time, all the backlights 87 mounted on the system are turned on. In this state, when there is an input to the scan converter 84, the panel 88 is controlled by the scan converter 84.
Is displayed, and the system operates in the run mode. In the run mode, the backlight luminance voltage generator 85 changes the luminance dimming voltage under the control of the microcontroller 81 to adjust the luminance. If there is no input to the scan converter 84, the supply of the voltage to the backlight 87 from the backlight power supply voltage control unit 86 is stopped, the backlight 87 is turned off, and the mode transits to the standby mode.

As described above, all the mounted backlights are turned on in the run mode, and all the backlights are turned off in the standby mode.

Japanese Patent Application Laid-Open No. 9-146073 discloses that
A backlight dimming circuit that adjusts backlight luminance by detecting external light illuminance by a plurality of light sensors and changing a luminance dimming voltage according to an average value of the detection results and a manual dimming set amount is disclosed. Have been.

Japanese Patent Application Laid-Open No. 10-228020 discloses a backlight provided with a plurality of fluorescent lamps,
The fluorescent lamps are sequentially switched by a switching mechanism,
A liquid crystal display device capable of extending the life of a backlight by turning on only a single fluorescent lamp at an arbitrary time is disclosed.

Japanese Patent Application Laid-Open No. H11-352460 discloses a system in which a plurality of lamps are provided, and the lamps are turned on or changed alternately at predetermined times by a timer each time the power is turned on. A liquid crystal backlight circuit capable of extending the life of a lamp is disclosed.

Japanese Patent Application Laid-Open No. 2000-28990 discloses a large fluorescent lamp having a large light amount at the upper end of a light guide plate.
Disclosed is a liquid crystal display device that has a small fluorescent lamp with a small light amount at the lower end and can select a light source with a light amount suitable for the display resolution by lighting only a fluorescent lamp selected according to the size of the display resolution. Have been.

[0010]

However, in the above-mentioned conventional system, all the backlights are turned on in the run mode, and the life of the backlight is shortened. Further, in a display device having a plurality of pairs of backlights, the backlight dimming circuit described in Japanese Patent Application Laid-Open No. 9-146073 increases the number of backlights to be supplied with power, resulting in wasteful power consumption. .

More specifically, when operating in the run mode, regardless of the intended use, even if it is sufficient to use it at a low luminance such as used as a display device of a personal computer, Since all the backlights are turned on, the life of the backlight is shortened and power is wasted.

Further, in the method of adjusting the luminance by changing the voltage as in the backlight dimming circuit described in Japanese Patent Application Laid-Open No. 9-146073, the circuit configuration for the method becomes large-scale and complicated. There has been a problem that the cost is increased.

In the backlight dimming circuit described in Japanese Patent Application Laid-Open No. 9-146073, it is impossible to automatically adjust the luminance of the backlight according to the type of video signal input to the display device. There was a problem.

In the technique described in Japanese Patent Application Laid-Open No. Hei 10-228020, a backlight switching mechanism is required, so that the cost is increased, the durability is increased, the switching must be performed by a user, and the brightness is reduced. There was a problem that switching was not possible.

The technique described in Japanese Patent Application Laid-Open No. 11-352460 has a problem that the luminance cannot be switched.

Further, the technique described in Japanese Patent Application Laid-Open No. 2000-28990 has a problem in that when the display is performed in the low-luminance display mode, it is not possible to extend the life of a small rod-shaped fluorescent lamp having a small light amount. .

The present invention solves the above-mentioned drawbacks, automatically switches the brightness of the backlight according to the purpose of use, and provides a low-cost backlight control device for extending the life of the backlight. It is intended to be realized.

[0018]

According to the present invention, there is provided a backlight control device comprising: a display device having a first backlight and a second backlight;
Mode switching instructing means for instructing switching between a high brightness mode and a low brightness mode, and when the high brightness mode is instructed by the mode switching instructing means, turns on both the first backlight and the second backlight, When a low-luminance mode is instructed, a backlight control means for turning on one of the first backlight and the second backlight is provided.

The backlight control means, when the mode switching instruction means gives an instruction to switch to the low brightness mode, which one of the first backlight and the second backlight was used in the previous low brightness mode. It is characterized in that it is determined whether or not the backlight is lit, and a backlight different from the lit backlight is lit.

The backlight control means may alternately turn on the first backlight and the second backlight at predetermined intervals while the low-luminance mode is instructed by the mode switching instructing means. Features.

Further, the mode switching instructing means issues a mode switching instruction in accordance with the type of an image signal input to the display device.

[0022]

DESCRIPTION OF THE PREFERRED EMBODIMENTS [First Embodiment] An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows a system configuration of a display device according to the present embodiment. The display device includes a backlight on / off control unit 10, a first backlight 11, a second backlight 12, a panel 13, a power supply 14, a microcontroller 1, and the like.
5, scan converter 16, video decoder 17, A
A / D converter 18 and an input switch 19 are provided.

The video decoder 17 inputs a video signal (composite signal) from a video device or the like, and
After the conversion, the data is output to the scan converter 16. The A / D converter 18 receives an analog RGB signal from a personal computer or the like, performs A / D conversion, and outputs the signal to the scan converter 16.

The scan converter 16 outputs the YUV output (or RGB output) converted by the video decoder 17 and the R output converted by the A / D converter 18.
A GB output is input, a control signal to the panel 13 is generated, and display control is performed.

The microcontroller 15 includes a video decoder 17, an A / D converter 18, and an input switch 1.
9, connected to the scan converter 16 and the backlight on / off control unit 10 to determine whether a video signal is input, whether an analog RGB signal is input, and an input switch 19
And controls the scan converter 16 and the backlight on / off control unit 10 according to the state. The backlight ON / OFF control unit 10 is connected to a luminance switching control line 22 and a standby control line 23.

The backlight on / off control unit 10 controls on / off of the first backlight 11 and the second backlight 12 with two output ports. The control of the first backlight 11 is performed by a first backlight control line. 20, the second backlight 12 is controlled by the second backlight control line 2
The control is independently performed by each of the control signals.

The panel 13 performs display by a control signal from the scan converter 16 and by backlight from the first backlight 11 and the second backlight 12.

The power supply 14 is connected to each device so that power can be supplied to each device.

FIG. 2 is a diagram for explaining the arrangement of the backlight. In FIG. 2, the first backlight 11 and the second
The backlight 12 is composed of two fluorescent lamps. Light guide plate 2 installed behind panel 13
2 at the upper edge and the lower edge of each of the two fluorescent lamps (1 at the upper edge of the first backlight 11).
One of the book and the second backlight 12, and one of the first backlight 11 and the second backlight 12 at the lower edge.
Are arranged side by side. It is desirable that the same brightness is provided when only the two fluorescent lamps of the first backlight 11 are turned on and when only the two fluorescent lamps of the second backlight 12 are turned on.

Next, the operation of the display device will be described with reference to FIG. When the user turns on the power supply 14, the microcontroller 15 is first turned on to detect which of the video decoder 17 and the A / D converter 18 has a signal input. Generally, when a video signal is input to the video decoder 17, high brightness is required. Therefore, the microcontroller 15 causes the backlight on / off control unit 10 to perform display with high brightness (first mode). (To turn on the power of the backlight 11 and the second backlight 12). In addition, when an analog RGB signal is input to the A / D converter 18, the brightness may be low, so the microcontroller 15 causes the backlight on / off control unit 10 to perform display with low brightness (the first backlight). 11 or second backlight 1
2).

When there is no input to the video decoder 17 and the A / D converter 18, the standby mode is set, and the first backlight 11 and the second backlight 12 are output so that the power is turned off. When there are both inputs to the video decoder 17 and the A / D converter 18, the video decoder 17 or the A / D converter 18
Which signal input is to be validated is determined, and the above-described output is performed according to the determination result.

FIG. 3 shows ON / OFF waveforms of the first backlight 11 and the second backlight 12. In the standby mode, both the first backlight 11 and the second backlight 12 are off. In the high brightness mode, the first backlight 11 and the second backlight 1
2 are both on. Further, in the low luminance mode, only the first backlight 11 is turned on, and the second backlight 12 is turned off.

In the low brightness mode, it is desirable to alternately switch between the state in which only the first backlight 11 is turned on and the state in which only the second backlight 12 is turned on, in order to extend the life of the display device.

FIG. 4 shows ON / OFF waveforms of the first backlight 11 and the second backlight 12 in that case. First
When transitioning from the low-luminance mode in which the backlight 11 is on to the standby mode, the information that the first backlight 11 was on is stored, the first backlight 11 is turned off, and the mode transits to the standby mode. Thereafter, when transiting to the low-luminance mode again, the information of the backlight that was previously turned on is read from the storage device, and the power of the backlight other than the read backlight, that is, the second backlight 12 is turned on.

FIG. 5 shows a detailed configuration diagram of the backlight on / off control unit 10 for realizing the above-described operation. As shown in FIG. 5, the backlight on / off control unit 1
0 is the storage unit 10a, the delay unit 10b, the first OR circuit 10
c, a second OR circuit 10d, an inverting circuit 10e, a first AND circuit 10f, and a second AND circuit 10g.

An output terminal of the storage unit 10a is connected to an input terminal of the first OR circuit 10c, and a luminance switching control line 22 is connected to the other input terminal. The output of the storage unit 10a is connected to the input terminal of the second OR circuit 10d through the inverting circuit 10e, and the brightness switching control line 22 is connected to the other input terminal.

The input terminal of the first AND circuit 10f is connected to the output of the first OR circuit 10c and the standby control line 23, and the input terminal of the second AND circuit 10g is connected to the input terminal of the second OR circuit 10d. The output and the standby control line 23 are connected. The two outputs from the backlight on / off control unit 10 are the first backlight 11 and the second backlight 1 respectively.
Connected to 2.

When the standby signal input from the standby control line 23 is low, the first backlight 11 and the second backlight 12 are low (OFF) by the operations of the above-described OR circuits and AND circuits. . When the standby signal is High and the luminance switching signal input from the luminance switching control line 22 is High, the first backlight 11 and the second backlight 12 are High (ON).
become.

The storage unit 10a stores the time when the luminance switching signal changes from low to high, that is, the time when the low luminance mode is switched to the high luminance mode (immediately before), and the time when the standby signal changes from high to low, that is, The state of the signal line to the first backlight 11 at the time (just before) when the mode is switched from the run mode to the standby mode is stored (latched).

The delay unit 10b is a delay circuit for surely storing the state immediately before the mode change in the storage unit 10a. The delay unit 10b delays the output change of the second AND circuit 10g by a very short time to the storage unit 10a. To convey. The delay unit 10b can be realized by a simple CR circuit including only a capacitor and a resistor.

Each of the above-mentioned OR circuits, AND circuits and storage units are simple logic circuits and can be realized at low cost.

Next, the backlight on / off control unit 10
Will be described with reference to the time chart of FIG.

In the initial state (at time T0), it is assumed that the standby signal is Low, the luminance switching signal is Low, and the storage content (output) of the storage unit 10a is High. At this time, the first
The backlight 11 and the second backlight 12 are driven low (OF) by the operation of the OR circuit and the AND circuit.
F).

When the standby signal changes from low to high at T1, only the first backlight 11 is driven high by the operation of the OR circuit and the AND circuit.
(ON). The storage content (output) of the storage unit 10a does not change, and the delay unit 10b outputs the state (Low) of the second backlight 12 to the storage unit 10a with a slight delay.

When the standby signal changes from High to Low at T2, the first backlight 11 is driven Low (OF) by the operation of the OR circuit and AND circuit.
F), the storage unit 10a stores and outputs the output (Low) from the delay unit 10b at that time.

At T3, the standby signal again becomes Lo
When the signal changes from w to High, only the second backlight 12 becomes H due to the operation of the OR circuit and AND circuit.
becomes high (ON). The storage content (output) of the storage unit 10a does not change, and the delay unit 10b delays the state (High) of the second backlight 12 with a slight delay.
Output to

At T4, the standby signal becomes Hi again.
When the second backlight 12 changes from gh to Low, the operation of the OR circuit and the AND circuit causes the second backlight 12 to become Low.
(OFF), and the storage unit 10a stores and outputs the output (High) from the delay unit 10b at that time. Since the delay unit 10b outputs the state (Low) of the second backlight 12 to the storage unit 10a with a slight delay, the state (High) immediately before the change of the second backlight 12 is stored in the storage unit 10a. Will be.

Since the state of T5 is the same as the state of T0, the steps from T5 are repeated from T0 to T4.

As described above, when the standby mode and the low brightness mode are repeated, the low brightness mode (T1 to T2) in which only the first backlight 11 is turned on,
Since the low luminance mode (T3 to T4) in which only the second backlight 12 is turned on is alternately repeated, the life of the display device can be extended.

The operation of the backlight on / off control unit 10 will be further described with reference to the time chart of FIG.

In the initial state (at time T0), the standby signal is High, the luminance switching signal is High, and the storage unit 10a
It is assumed that the storage content (output) of is low. At this time, the first backlight 11 and the second backlight 12 operate as High (O) by the operation of the OR circuit and the AND circuit.
N).

When the luminance switching signal changes from High to Low at T1, only the first backlight 11 is driven Low (O) by the operation of the OR circuit and AND circuit.
FF). The storage content (output) of the storage unit 10a does not change, and the delay unit 10b outputs the state (High) of the second backlight 12 to the storage unit 10a with a slight delay.

At T2, the luminance switching signal changes from low to high.
When the first backlight 11 changes to High, the operation of the OR circuit and AND circuit causes the first backlight 11 to switch to High (O
N), the storage unit 10a stores and outputs the output (High) from the delay unit 10b at that time.

At T3, the luminance switching signal again becomes High.
When the state changes from h to Low, only the second backlight 12 becomes Lo due to the operation of the OR circuit and the AND circuit.
w (OFF). Storage contents (output) of storage unit 10a
Does not change, and the delay unit 10 b
The state (Low) of 2 is output to the storage unit 10a with a slight delay.

At T4, the luminance switching signal again becomes Low.
When the second backlight 12 changes from High to High, the operation of the OR circuit and the AND circuit causes the second backlight 12 to change to High.
At the same time as (ON), the storage unit 10a stores and outputs the output (Low) from the delay unit 10b at that time. Since the delay unit 10b outputs the state (High) of the second backlight 12 to the storage unit 10a with a slight delay, the state (Low) immediately before the change of the second backlight 12 is stored in the storage unit 10a. Will be.

Since the state of T5 is the same as the state of T0, the steps from T5 are repeated from T0 to T4.

As described above, when the high luminance mode and the low luminance mode are repeated, the low luminance mode (T1 to T2) in which only the second backlight 12 is turned on and the first luminance
Since the low-luminance mode (T3 to T4) in which only the backlight 11 is turned on is alternately repeated, the life of the display device can be extended.

[Second Embodiment] A display device according to a second embodiment of the present invention will be described with reference to FIGS. Note that the main system configuration of the display device according to the second embodiment is the same as that of the display device according to the first embodiment, and is as shown in FIG.

The display device according to the second embodiment has a long service life of the backlight by alternately turning on / off the first backlight 11 and the second backlight 12 at predetermined time intervals in the low brightness mode. It is trying to make it.

FIG. 8 is a diagram showing a detailed configuration of the backlight on / off control unit 10 in the system configuration shown in FIG. As shown in FIG. 8, the backlight ON / OFF control unit 10 includes a timer 10h, a first OR circuit 10c, a second OR circuit 10d, an inverting circuit 10e, a first AND circuit 10f, and a second AND circuit 10g. Have.

The output of the timer 10h is connected to the input terminal of the first OR circuit 10c, and the brightness switching control line 22 is connected to the other input terminal. The output of the timer 10h is connected to the input terminal of the second OR circuit 10d through the inverting circuit 10e, and the luminance switch control line 22 is connected to the other input terminal.

The input terminal of the first AND circuit 10f is connected to the output of the first OR circuit 10c and the standby control line 23, and the input terminal of the second AND circuit 10g is connected to the input terminal of the second OR circuit 10d. The output and the standby control line 23 are connected. The two outputs from the backlight on / off control unit 10 are the first backlight 11 and the second backlight 1 respectively.
Connected to 2.

When the standby signal input from the standby control line 23 is Low, the first backlight 11 and the second backlight 12 are Low (OFF) by the operations of the respective OR circuits and AND circuits. . When the standby signal is High and the luminance switching signal input from the luminance switching control line 22 is High, the first backlight 11 and the second backlight 12 are High (ON).
become.

The timer 10h sets the standby signal to Hi.
gh, and operates when the luminance switching signal is Low, and repeatedly outputs High and Low at predetermined time intervals. Note that the standby signal is Low or the luminance switching signal is High.
At the time of non-operation for power saving (Lo by pull-down)
w is output).

Although the repetition period of the timer 10h is not particularly defined, it may be set arbitrarily, for example, every 1/60 second, every second, every minute, every hour, every day, etc. .

Each of the above-mentioned OR circuits, AND circuits,
Timers are simple logic circuits and can be implemented at low cost.

Next, the backlight on / off control unit 10
Will be described with reference to the time chart of FIG.

In the initial state (at time T0), it is assumed that the standby signal is Low, the luminance switching signal is Low, and the output of the timer 10h is Low. At this time, the first backlight 11 and the second backlight 12 are Low (OFF) due to the operation of the OR circuit and the AND circuit.

When the standby signal changes from low to high at T1, the timer 10h starts operating and outputs high. Then, only the first backlight 11 becomes High (ON) by the operation of the logical sum circuit and the logical product circuit.

At T2, the output of the timer 10h becomes Hi.
gh to Low, the first backlight 11 is driven Low by the operation of the OR circuit and the AND circuit.
(OFF) and the second backlight 12 becomes Hi.
gh (ON).

At T3, when the output of the timer 10h changes from Low to High again, the first backlight 11 is turned High (ON) and the second backlight 12 is turned on by the operation of the OR circuit and AND circuit.
Becomes Low (OFF).

At T4, when the output of the timer 10h changes from High to Low again, the first backlight 11 is turned Low (OFF) and the second backlight 12 is turned off by the operation of the OR circuit and AND circuit.
Becomes High (ON).

At T5, when the luminance switching signal changes from low to high, both the first backlight 11 and the second backlight 12 become high (ON) by the operation of the OR circuit and the AND circuit. Also,
The timer 10h stops operating and outputs Low.

As described above, in the low-luminance mode, the output of the timer 10h repeats low and high at predetermined time intervals, so that only the first backlight 11 is turned on in the low-luminance mode (T1 to T2, T3 to T3). T4),
Since the low-brightness mode (T2 to T3, T4 to T5) in which only the second backlight 12 is turned on is alternately repeated, the life of the display device can be extended.

The contents of the embodiments described so far are not limited to the contents described above unless the gist of the present invention is changed. For example, the backlight on / off control unit 10 may be realized by software control by a microcomputer.

[0077]

As described above, according to the backlight control device of the present invention, the switching of the brightness of the backlight is performed by controlling whether to turn on or off each of the plurality of backlights, so that the cost and the cost are reduced. This has the effect that the brightness of the backlight can be switched with power consumption.

Further, according to the backlight control device of the present invention, in the low-luminance mode, a plurality of backlights are alternately switched on to emit light, so that the life of the backlight can be extended.

Further, according to the backlight control device of the present invention, since the brightness is automatically switched according to the input image signal, the number of backlights according to the intended use can be reduced without the user's hand. Can be lit,
This has the effect of reducing power consumption and extending the life of the backlight.

[Brief description of the drawings]

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

FIG. 2 is an explanatory diagram showing an arrangement of backlights.

FIG. 3 is a time chart showing an example of a backlight on / off operation.

FIG. 4 is a time chart showing an example of a backlight on / off operation.

FIG. 5 is a block diagram illustrating one detailed configuration of a backlight on / off control unit.

FIG. 6 is a time chart illustrating an example of a backlight on / off control unit and a backlight on / off operation.

FIG. 7 is a time chart illustrating an example of a backlight on / off control unit and a backlight on / off operation.

FIG. 8 is a block diagram illustrating a detailed configuration of a backlight on / off control unit.

FIG. 9 is a time chart illustrating an example of a backlight on / off control unit and a backlight on / off operation.

FIG. 10 is a block diagram illustrating a configuration example of a conventional display device.

[Explanation of symbols]

 Reference Signs List 10 backlight on / off control unit 11 first backlight 12 second backlight 13 panel 14 power supply 15 microcontroller 16 scan converter 17 video decoder 18 A / D converter 19 input switch 20 first backlight control line 21 second backlight Control line 22 Brightness switching control line 23 Standby control line 10a Storage unit 10b Delay unit 10c First OR circuit 10d Second OR circuit 10e Inverting circuit 10f First AND circuit 10g Second AND circuit 10h Timer

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (Reference) G09G 3/20 642 G09G 3/34 Z 3/34 G02F 1/1335 530

Claims (4)

[Claims] 1. A display device comprising a first backlight and a second backlight, wherein: a mode switching instructing unit for instructing switching between a high luminance mode and a low luminance mode; and a high luminance mode by the mode switching instruction unit. Is instructed, the first backlight and the second backlight are both turned on. If the low-luminance mode is instructed, one of the first backlight and the second backlight is turned on. A backlight control device comprising backlight control means for turning on the light. 2. The backlight control unit according to claim 1, wherein when the mode switching instruction unit issues an instruction to switch to a low-luminance mode, the backlight control unit determines which of the first backlight and the second backlight was used in the previous low-luminance mode. A backlight control device characterized in that it is determined whether the backlight is lit, and a backlight different from the lit backlight is lit. 3. The backlight control means controls that the first backlight and the second backlight are alternately turned on at predetermined intervals while a low-luminance mode is instructed by the mode switching instruction means. 3. The backlight control device according to claim 1, wherein: 4. The backlight control according to claim 1, wherein said mode switching instruction means issues a mode switching instruction in accordance with a type of an image signal input to said display device. apparatus.