JP3146686B2 - Backlight dimmer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a display device such as a personal computer, a word processor and a portable device equipped with a display device, and more particularly to a control device for a display backlight which consumes less power.

[0002]

2. Description of the Related Art In general, it is important to reduce power consumption in electronic equipment. Particularly, in a battery-driven system, malfunction or data loss occurs when the battery capacity is reduced or lost during operation. I do. For this reason, the current consumption is conventionally reduced in a battery-driven device. Even in a display device including a backlight which consumes a large amount of power, the backlight is turned off or dimmed at a certain timing.

For example, Japanese Patent Laying-Open No. 216514/1990 discloses means for reducing the brightness of the backlight when the battery becomes low. Also, Japanese Patent Application Laid-Open No. 1-112914
Japanese Patent Laid-Open Publication No. Hei 1-223710 discloses a function of turning off the backlight if there is no key input for a certain period of time. Epson's PC-386 NOTE
The "W" (registered trademark) product has a dimming function that reduces the backlight to about half brightness if there is no key input for a certain period of time, and a light-off function that turns off the backlight.

[0004]

However, in the above-mentioned conventional example, the timing of lowering the luminance of the backlight (hereinafter referred to as dimming) is described, but the method of lowering the luminance is not much described. In other words, Japanese Patent Application Laid-Open No. 2-216514 merely describes a "terminal for forcibly reducing the luminance to 1/2". Epson's "PC-386 NOTE W" (registered trademark) product reduces the brightness of the sidelight by about half (about 30%).
%).

[0005] The luminance of the backlight is closely related to the power consumption, and it is better to reduce the luminance as much as possible to reduce the power consumption. However, when the brightness is reduced by a certain value or more due to the characteristics of the backlight, the brightness is suddenly turned off. The location where the element is turned off is not constant because it has a relationship with the individual variation of the element and the temperature. For this reason, when lowering the luminance, the luminance is not lowered to the lower limit, and the luminance is fixedly set to a lit position. This will be described with reference to FIG. 10 showing the correlation between luminance and power consumption.

In FIG. 10, the horizontal axis represents luminance and the vertical axis represents power consumption. It can be reduced to the lower limit d of the previous stage of the value c that is turned off when the brightness is gradually reduced. However, since the value of d is not clear for each device for the above-described reason, a value larger than the value d with a margin in the case of dimming. f is set. Therefore, extra power is consumed by fd. An object of the present invention is to avoid such useless power consumption by reducing the brightness to a lower limit required at the time of dimming.

[0007]

In order to achieve the above object, the present invention provides a brightness control means for controlling the brightness of a backlight in multiple stages, a power monitoring means for measuring and monitoring the power supplied to the backlight, A state monitoring means for generating an instruction signal for changing the brightness of the backlight; and a power control means for measuring and monitoring the supplied power for each stage when the brightness is changed by the brightness control means. Backlight control means for detecting the set value of the luminance, and the luminance is controlled to the set value detected by the backlight control means when the luminance is changed by an instruction from the state monitoring means.

[0008]

According to the present invention, since the brightness is controlled in multiple stages and the brightness is controlled so as to be the lowest stage that can be turned on at the time of dimming, wasteful power consumption can be avoided.

[0009]

1 to 9 are diagrams for explaining an embodiment of the present invention. FIG. 1 is a block diagram of a backlight dimming device according to the present invention. The present invention relates to a state monitoring unit 21 for generating an instruction to lower the backlight luminance, a backlight control unit 22 for controlling the setting of the backlight luminance in accordance with an instruction from the state monitoring unit 21, and a backlight control unit 22. Brightness control means 23 for controlling the brightness by the setting of, and a brightness control signal from the brightness control means 23,
Backlight power supply 25 that supplies power to the backlight
A backlight 26 receiving power from a backlight power supply 25; and a power monitoring means 24 for monitoring power consumed by the backlight power supply 25.
4 supplies the information of the power to the backlight control means 22.

Next, the operation of the backlight control means 22 will be described with reference to FIGS. FIG. 2 shows the relationship between the power consumed by the backlight and the luminance. The number of the luminance (horizontal axis) indicates a stepwise luminance performed by the luminance control unit 23. The power decreases in proportion to the decrease in luminance toward the bottom. When the brightness falls below a certain level, the backlight cannot be turned on and is turned off. This is the value in FIG.
Conversely, when the backlight is turned on, the backlight is not turned on even if it is turned back on, and is turned on from a place having a certain luminance or higher. This corresponds to FIG. In FIG. 2, the value is a set value when the luminance is reduced.

FIG. 3 is a flowchart showing the operation of the backlight dimming device of the present invention shown in FIG. In step 41, a dimming instruction is issued from the state monitoring means 21. In step 42, the backlight control means 22 instructs the luminance control means 23 to lower the luminance by one step.
In FIG. 2, for example, the operation is performed from the beginning. Step 43
In the backlight control means 22, the backlight power supply 2
The power value is received from the power monitoring means 24 monitoring the power of No. 5 and it is determined whether or not the power value is 0. Here, if the power value is not 0 (that is, N), the process returns to step 42 and the luminance is reduced by one step again. This corresponds to, for example, emptying in FIG.

If it is determined in step 43 that the power value is 0, the value is set to the minimum value n in step 44. This corresponds to FIG. Thereafter, at step 45, the backlight control means 2
2 to the brightness control means 23. This corresponds to being empty in FIG. At step 46, the backlight control means 22 receives the power value from the power monitoring means 24 in order to confirm whether it is turned on. When the power value is 0 at step 46 (ie, N), the process returns to step 45, and the brightness is again adjusted. Raise one step. If it is determined in step 46 that the power value is not 0, the process proceeds to step 47, where the luminance is set to the original set value n + 1 to be dropped. The value of n + 1 corresponds to in FIG. In step 48, the dimming operation ends.

As described above, according to the present invention, since the luminance can be reduced to the minimum, unnecessary power consumption can be avoided. In the present invention, a mechanism for generating a dimming instruction by the state monitoring unit 21 is not described in detail.
For example, as a method, it is conceivable to monitor the presence or absence of a key input and generate it when there is no key input, or, in the case of a battery driven type, to monitor the remaining amount of the battery and generate it when the battery runs out.

In the embodiment of the present invention described above, since the set value n + 1 is detected every time the dimming operation is performed, the dimming operation takes a long time. An embodiment in which this is improved is shown in FIG. The configuration shown in FIG. 4 is obtained by adding a memory 51 to the backlight dimming device of FIG. 1, and there is no change in the configuration other than the addition of the memory. In FIG. 4, when the set value n + 1 is detected once, the value is stored in the memory 51, and when the next dimming operation is performed, the set value n + 1 is called from the memory 51 and used. Speed up.

FIG. 5 shows an embodiment in which the brightness at the time of dimming can be set to a fixed value. In FIG. 5, a brightness selection unit 61 stores a fixed value therein, and selects whether to fix the brightness at the time of dimming or set the brightness to a set value n + 1 obtained by the backlight control unit 22. The flowchart of FIG. 6 explains the operation of the backlight dimming device of FIG. After the dimming instruction is generated in step 71, a luminance value is selected in step 72. This is because when the dimming instruction is issued from the state monitoring unit 21 to the luminance selection unit 61, whether the luminance selection unit 61 uses an internal fixed value or the set value n + 1 obtained from the backlight control unit 22 is used. Is determined. When a fixed value is selected in step 72, the process proceeds to step 73, where the luminance value is set to a fixed value N, and the process ends (step 80). When the set value n + 1 is selected in step 72, an instruction for dimming is issued from the luminance selection unit 61 to the backlight control unit 22. The subsequent operations from step 74 to step 79 are shown in FIG.
Steps 42 to 47 are the same.

The value of the fixed value in the brightness selecting means 61 can be made programmable by connecting the brightness selecting means 61 to a central processing unit (CPU) or the like.
In this way, the user can freely set a fixed value.

The brightness of the backlight is affected by the ambient temperature. Therefore, it is necessary to change the set value n + 1 according to the ambient temperature. FIG. 7 shows a block diagram of a backlight dimming device having a means for measuring the ambient temperature. In FIG. 7, the ambient temperature is measured by the temperature measuring means 81 and the information is supplied to the backlight control means 22. In the backlight control unit 22, the set value is stored in the temperature measurement unit 8.
The information is stored in the memory 82 in association with the temperature information from No. 1. As a result, a set value that changes depending on the ambient temperature is obtained, so that wasteful power consumption and non-lighting that can occur when only a certain set point temperature is stored in the memory and used is avoided.

The brightness of the backlight is also affected by the surrounding illuminance. When the surroundings are dark, lowering the brightness makes it difficult to see, but when the surroundings are brighter, lowering the brightness does not significantly affect the visibility. FIG. 8 shows a block diagram of a backlight dimming device having an illuminance measuring unit 91 for measuring the illuminance of the surroundings. 8, the illuminance measuring device 91 measures the illuminance of the surroundings and supplies the information to the backlight control means 22. The backlight control unit 22 determines a set value in association with the illuminance information from the illuminance measurement unit 91. That is, in FIG. 2, when the surroundings are dark, the set value is changed (see FIG. 3).
In step 47, the setting value is set to (n + 2), and when the surroundings are bright, the set value is set to (n + 1) in step 47 in FIG.

If the setting value for lowering the luminance of the backlight is detected when an instruction to lower the luminance is received, the backlight is turned on and off during use. In addition, it takes time to detect the set value, and the luminance cannot be quickly reduced. FIG. 9 shows a block diagram of a backlight dimming device in which a setting value for lowering the luminance is detected when the backlight is initialized. In FIG. 9, a backlight initialization unit 11 is a unit for instructing initialization of the backlight, for example, when the backlight is turned on when the system is powered on. The backlight initialization means 11 instructs the backlight power supply 25 to initialize (light) the backlight, but also issues an instruction to the backlight control means 22 at the same time. This eliminates ON and OFF during use, improving ease of use and quickly lowering luminance.

[0020]

According to the structure of the present invention, when the luminance is reduced, the luminance can be reduced to the lowest possible value, so that the power consumption of the backlight can be reduced to the maximum. According to the second aspect, since the value for lowering the luminance is stored in the memory, the operation for lowering the luminance can be performed quickly, so that the power consumption can be reduced more quickly. According to the third aspect, since a fixed value can be adopted as the value for lowering the luminance, the luminance can be rapidly reduced. According to the fourth aspect, since a fixed value can be instructed from the central processing unit (programmable), the user can freely set the luminance value when the luminance is lowered, and the usability is improved. According to the fifth aspect, since the value for lowering the luminance changes depending on the ambient temperature, it is possible to eliminate wasteful power consumption and non-lighting of the backlight. According to the sixth aspect, since the value for lowering the luminance changes depending on the surrounding illuminance, the visibility when the luminance is lowered is improved, and unnecessary power consumption can be eliminated. According to claim 7, since there is no ON / OFF during use, the usability is improved. In addition, since the setting value that reduces the brightness at the time of system initialization is detected,
Since the brightness can be quickly reduced at the time of dimming, power consumption can be reduced quickly.

[Brief description of the drawings]

FIG. 1 is a block diagram of a backlight dimming device according to the present invention.

FIG. 2 is a diagram showing a relationship between power consumed by a backlight and multi-step luminance used in the present invention.

FIG. 3 is a flowchart of the operation of the backlight dimming device of the present invention shown in FIG. 1;

FIG. 4 is another embodiment of the backlight dimming device of the present invention.

FIG. 5 is another embodiment of the backlight dimming device of the present invention.

FIG. 6 is a flowchart of the operation of the backlight dimming device of FIG. 5;

FIG. 7 is another embodiment of the backlight dimming device of the present invention.

FIG. 8 is another embodiment of the backlight dimming device of the present invention.

FIG. 9 is another embodiment of the backlight dimming device of the present invention.

FIG. 10 is a diagram illustrating a general relationship between power consumed by a backlight and luminance.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Backlight initialization means 21 State monitoring means 22 Backlight control means 23 Brightness control means 24 Power monitoring means 25 Backlight power supply 26 Backlights 51 and 82 Memory 61 Brightness selection means 81 Temperature measurement means 91 Illuminance measurement means

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G02F 1/133 580 G09G 3/18 H04N 5/66 102 H05B 41/30-43/02 H05B 41/14- 41/16 340 H05B 41/18-41/234

Claims (7)

(57) [Claims] 1. A display device having a backlight, a brightness control means for controlling the brightness of the backlight in multiple stages, a power monitoring means for measuring and monitoring the power supplied to the backlight, and changing the brightness of the backlight. A state monitoring means for generating an instruction signal, and when the luminance is changed by the luminance control means, the power monitoring means measures and monitors the supply power for each stage to thereby set a minimum luminance setting value at which the backlight can be turned on. A backlight dimming device, comprising: backlight control means for detecting, wherein when the luminance is changed by an instruction from the state monitoring means, the luminance is controlled to the set value detected by the backlight control means. 2. The backlight dimming device according to claim 1, wherein a set value detected by said backlight control means is held in a memory. 3. The apparatus according to claim 1, further comprising a luminance selection unit for selecting whether a luminance value when changing the luminance is set to a fixed value or a set value detected by the backlight control unit. The backlight dimming device as described in the above. 4. The backlight dimming device according to claim 3, wherein the fixed value can be designated from a central processing unit (CPU). 5. The backlight according to claim 2, further comprising a temperature measuring means for measuring an ambient temperature, wherein the set value detected by the backlight control means is held in a memory in association with the ambient temperature. Dimming device. 6. The backlight according to claim 1, further comprising illuminance measuring means for measuring ambient illuminance, wherein the set value detected by the backlight control means is changed by the illuminance measured by the illuminance measuring means. Light dimmer. 7. The backlight dimming device according to claim 1, wherein the setting value is detected and held by the backlight control means when the backlight is initialized.