JP2000332892A - Method and device for controlling back light of portable telephone set - Google Patents

Abstract

PROBLEM TO BE SOLVED: To maximize the battery drive time of a portable telephone set by acquiring the voltage of a battery and controlling the ON time of a back light on the basis of that voltage. SOLUTION: When the initial factor is a back light ON request, a peripheral circuit control LSI 12, which receives the acquisition request of a battery voltage from a back light power source control program 01 through an internal bus 61, requests acquisition of the battery voltage of the portable telephone set at present to a battery voltage acquiring circuit 41. The battery voltage acquiring circuit 41 measures the terminal voltage of a battery 42, converts it to a digital value through A/D conversion and gives it to the peripheral circuit control LSI 12. The peripheral circuit control LSI 12 sends the battery voltage through the internal bus 61 to the back light power source control program 01. The back light power source control program 01 acquires back light ON time and a back light ON current corresponding to the battery voltage from a back light power source control table 02 through the internal bus 61.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a backlight control method and apparatus for a portable telephone.

[0002]

2. Description of the Related Art A mobile phone having an LCD display unit is generally provided with a backlight for illuminating the display with light so that the display can be viewed well in a dark place.
For example, when the power is turned on, when a key is operated,
The backlight is turned on for a certain period of time when there is an incoming call.

Since a portable radio telephone must be small and light because of its portability, a battery as small as possible must be used as its power source. Is required to operate. For this reason, various circuits constituting the portable wireless telephone device have been devised to reduce the power consumption. However, the backlight provided in an LCD (Liquid Crystal Display), an operation unit, or the like has an effective power saving. No countermeasures have been taken, and power consumption has been reduced only by turning off the backlight at best. That is, the power consumed by the backlight of the LCD and the operation unit used in the conventional portable radio telephone device is not reduced at all in the lighting state, and the power required for lighting the backlight is considerably large. Because it is large, if you use the device with the backlight turned on,
The device can be operated only for a short time with a small battery.

A conventional backlight control method and apparatus for a portable telephone will be described in detail with reference to the drawings.

FIG. 4 is a block diagram showing a first conventional example (see, for example, Japanese Patent Application Laid-Open No. 10-084408).
In the figure, 101 is a backlight ON signal input terminal,
Reference numeral 102 denotes a voltage input terminal from a detection unit (an optical sensor in this embodiment) for detecting the brightness around the apparatus, 103 denotes a reference voltage input terminal, 104 denotes a comparator, and 105 denotes an AND.
The circuit 106 is a backlight.

Next, the operation will be described. Input terminal 10
1 at a specific time, for example, when the portable electronic device is a mobile phone, when the power is turned on as described above,
When a key is operated or an incoming call is received, a backlight ON signal (generally, a signal of a logic “H” level; the same applies hereinafter) is input. The configuration of the device for realizing this is the same as that of the conventional device, and a description thereof will be omitted. An optical sensor (not shown) is attached at an appropriate position on the outer periphery of the device, and the brightness of the surroundings is constantly detected, the voltage is input from an input terminal 102, a reference voltage input from an input terminal 103 and a comparator. 104
When the input voltage from the optical sensor becomes lower than the reference voltage, an ON signal is input to the AND circuit 105. Therefore, only when the ambient brightness is equal to or less than a predetermined value set by the reference voltage, the backlight is turned on at a specific time to illuminate the display unit, and unnecessary illumination is not performed. Thus, the battery can be prevented from being consumed.

[0007] However, in the daytime, the device is in a dark place where the display is difficult to see, and even if there is an incoming call or the like at that time, it is possible to immediately move to a bright place.
The backlight can be turned on only at night. on the other hand,
Most portable electronic devices have a built-in clock function,
By judging the time from the clock function, it is possible to detect whether it is daytime or nighttime. Therefore, if a clock function is used at night, an optical sensor or the like is not required and almost the same lighting control of the backlight can be performed.

FIG. 5 is a block diagram showing a second conventional example (see, for example, JP-A-06-120684).
Reference numeral 201 denotes a backlight of the operation unit 9, which is configured by arranging a plurality of light emitting diodes 11. 202 is an LC that displays various information related to communication, mode information of the device, and the like.
D and 203 are batteries that supply power for turning on the backlight 201 or operating various parts of the apparatus, 204 is a current limiting resistor circuit that limits the current flowing to the backlight 201, and 205 is a current limiting resistor circuit. It is a switch circuit for turning on and off, and has transistors 251 and 252 that perform a switching action. 206 is a voltage detecting element for detecting the terminal voltage of the battery 203;
Is a CPU that performs individual control such as backlight on / off control and power saving control, and controls the entire apparatus.
Reference numeral 08 denotes an input / output interface for inputting and outputting various signals to and from the CPU 207. Reference numeral 209 denotes an operation unit including a numeric keypad. The operation unit inputs telephone number information and instructions related to power saving of the backlight. 210 is a CPU 207
Reads and writes data necessary for the operation of
This is a memory in which data related to power saving of the backlight is set.

The user inputs to the CPU 207 from the operation unit 209 whether or not the power saving of the backlight 201 is to be performed, and under what conditions when the power saving is to be performed. The CPU 207 sets the information input by the user in a predetermined area of the memory 210. In this memory 210, condition data for power saving of the backlight 201 is set. Also, since the power is backed up, the stored contents are maintained even when the apparatus is in the off state. For example, it is assumed that the user sets a condition for power saving of the backlight 201 in the CPU 207 from the operation unit 209 when the apparatus is in the standby mode and the remaining power of the battery 203 is low. When such a setting is made, the CPU 207 outputs the terminal voltage of the battery 203 detected by the voltage detecting element 206 to the input / output interface 20.
8, when the read voltage is equal to or higher than a predetermined level, the operation unit 209 turns on both the transistors 251 and 252 of the switch circuit 205 and turns on the backlight 201 in all modes. Light. That is, since the transistor 251 is on at the time of full lighting, the current from the battery 203 is supplied to the transistor 251 via the first, third, and fifth light emitting diodes 211 from the top constituting the backlight 201. Since the light flows toward the collector, these light emitting diodes 211 are turned on. Further, at this time, the transistor 252 is also turned on at the same time.
Since the current flows to the collector side of the transistor 252 via the light emitting diodes 211 of the second and sixth stages, the light emitting diodes 211 are turned on.

When the mode of the apparatus is in the standby state with the backlight 201 turned on as described above,
The CPU 207 measures the terminal voltage of the battery 203 using the voltage detection element 206 as described above, and if the terminal voltage is equal to or higher than a predetermined voltage, the transistors 251 and 252
Are both turned on, the backlight 201
Continues all lighting states of. However, when the apparatus is in the standby state, the CPU 207 notifies the voltage detection element 20 that the terminal voltage of the battery 203 has fallen below the predetermined level.
6 via the input / output interface 208, the CPU 207 turns off the transistor 252, for example, and turns on only the transistor 251 as it is. As a result, the current from the battery 203 is changed to the second, fourth, and sixth stages from the top constituting the backlight 201.
It does not flow to the light emitting diode 211 of the stage,
These light emitting diodes are turned off, and a power saving mode is set in which only the remaining first, third, and fifth light emitting diodes 11 are turned on. In the power saving mode, the power consumption of the battery 203 is reduced, and the
3, the operating time of the device can be extended.

FIG. 6 is a block diagram showing a third conventional example (see, for example, JP-A-07-087007).
In the figure, reference numeral 311 denotes a mobile phone device, which includes a battery pack 312, a power switch 313, a constant voltage generation circuit 314,
The control unit 315 includes a CPU, a keyboard 316 having a backlight, and the like. Further, instead of the battery pack 312, another type of battery pack 317 having a longer life and different physical properties can be mounted by the user's selection.

When the user performs a power-on operation using the keyboard 316, the control unit 315 receives the power-on operation,
A command is issued to turn on the power switch 313. In this case, the keyboard 316 is provided with a backlight so that it can be used even at night, and the backlight is turned on for a few seconds after the power is turned on. The current consumption of this backlight is usually several tens mA, and if there is no additional key input within a certain time (several seconds), the backlight is automatically turned off for battery saving.

When the backlight is turned on and off, it takes several tens of meters.
Since the difference in the current consumption of the battery A occurs, the difference in the terminal voltage of the battery pack in that case depends on the value of the internal impedance of the battery. Therefore, the terminal voltage of the battery when the backlight is turned on and off is monitored. Then, the type of the battery can be specified, and the control unit 15 can perform the remaining amount display and the automatic power-off operation that match the discharge curve of the battery pack.

FIG. 7 shows the flow of the operation program of the portable telephone when the type of the battery is specified by the above-described method, and the display of the remaining amount and the automatic power-off operation are performed accordingly. First, when the power is turned on (step S31), a standby state is entered, and the backlight is turned on for a certain time (step S32). At this time, the terminal voltage is V0, and the current consumption is I0. Next, after a certain period of time, the backlight is turned off (step S33). The terminal voltage at this time is V1,
The current consumption is defined as I1. The control unit 315 determines the internal resistance R of the battery pack 312 from V0 and I0 and V1 and I1, determines the type of battery, and displays the remaining amount according to the discharge curve of the battery pack 312 (step 34). This display of the remaining amount is performed throughout the time of the normal use state (step S35). After the end of the call, the power is automatically turned off and the display of the remaining amount disappears (step 36).

As described above, the difference between the battery terminal voltages due to the backlight on and off accompanying the backlight is detected only by the most common and necessary operation such as the power on and off of the portable telephone device 311. The type can be specified.

[0016]

In the above-described conventional method and apparatus for controlling the backlight of a portable telephone, since the lighting time of the backlight is fixed, the battery voltage of the portable telephone becomes low, that is, the remaining battery power is low. Nevertheless, when a specific operation is performed, the backlight is turned on unconditionally for a certain period of time, and there is a problem that the power consumption of the battery is not reduced.

An object of the present invention is to maximize the battery operating time of a portable telephone.

[0018]

According to a first aspect of the present invention, there is provided a backlight control method for a portable telephone, comprising: a step of obtaining a voltage of a battery; and a step of controlling a lighting time of the backlight based on the obtained voltage. It is comprised including.

According to a second aspect of the present invention, there is provided a method for controlling a backlight of a portable telephone, comprising the steps of: obtaining a battery voltage; controlling a backlight lighting time based on the obtained voltage; And a controlling procedure.

According to a third aspect of the present invention, there is provided a backlight control device for a portable telephone, comprising: a CPU (1) connected to an internal bus (61);
1) a main memory (21) storing a hack light power control program, a ROM (22) storing a backlight power control table, a timer (71), a peripheral circuit control LSI (12), and a battery voltage. A battery voltage acquisition circuit (41) that acquires and supplies the value to the peripheral circuit control LSI (12);
A backlight power supply control circuit (31) for controlling ON / OFF of the backlight power supply based on the control signal from (2), and a current when the backlight is turned on based on a control signal from the peripheral circuit control LSI (12) A backlight current switching circuit (32) for switching a value to a designated value.

According to a fourth aspect of the present invention, in the backlight control device for a cellular phone according to the first aspect, the timer (71) notifies the CPU (11) of a timeout interrupt when the designated time has elapsed.

According to a fifth aspect of the present invention, in the backlight control device for a portable telephone according to the first aspect, the ROM (22) is a flash ram.

A backlight control device for a portable telephone according to a sixth aspect of the present invention includes means for acquiring a voltage of a battery, and means for controlling a lighting time of the backlight based on the acquired voltage.

[0024]

Next, the present invention will be described in detail with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of the present invention. 1 includes a CPU 11 connected to an internal bus 61, a main memory 21 storing a hack light power control program 01, a ROM 22 storing a backlight power control table 02, and a timer 71. And peripheral circuit control LSI1
2 and a battery voltage acquisition circuit 41 which acquires the voltage of the battery 42 and supplies the value to the peripheral circuit control LSI 12
A backlight power control circuit 31 for controlling ON / OFF of the power of the backlight 33 based on a control signal from the peripheral circuit control LSI 12;
And a backlight current switching circuit that switches a current value when the backlight is turned on to a specified value based on a control signal from the backlight.

When the specified time has elapsed, the timer 71
A timeout interrupt notification is sent to U11.

The CPU 11, the peripheral circuit control LSI 12, the main memory 21, the (flash) ROM 22, and the timer 71 are connected by an internal bus 61, and the backlight power control program 01 transmits the peripheral circuit control LSI 12 The backlight power control table 02 and the timer 71 stored in the ROM 22
To access.

Battery voltage acquisition circuit 41, backlight power supply control circuit 31, backlight current switching circuit 32
Are connected to a peripheral circuit control LSI, and control of these circuits is performed by accessing the peripheral circuit control LSI.

The battery voltage acquisition circuit 41 includes a battery 4
2 is a function to measure the terminal voltage and the measured voltage value is D / A
It has the function of converting and notifying as digital information.

The backlight power supply control circuit 31 has a function of controlling ON / OFF of the power supply of the backlight.

The backlight current switching circuit 32 has a function of switching the current value when the backlight is turned on to a specified current value.

The CPU 11 performs a power ON operation of the mobile phone,
It has a function of activating the backlight power control program 01 when a key operation or an incoming call operation is performed.

The backlight power control table stores a backlight lighting time value and a backlight lighting current value corresponding to the voltage value of the battery 42 of the portable telephone.

When the specified time has elapsed, the timer 71
It has a function of notifying the PU 11 of a timeout interrupt.

FIG. 2 is a flowchart for explaining the operation of the present invention.

When the power ON operation, the key operation, and the incoming call operation of the portable telephone are performed, the CPU 11 starts the backlight power control program 01.

The backlight power supply control program 01 started by the CPU 11 controls the peripheral circuit control L through the internal bus 61 when the start-up factor is a backlight lighting request.
It requests the SI 12 to acquire the current battery voltage value of the mobile phone (step A1).

Peripheral circuit control LSI receiving a request for obtaining a battery voltage value from backlight power control program 01
12 requests the battery voltage acquisition circuit 41 to acquire the current battery voltage value of the mobile phone.

The battery voltage acquisition circuit 41 includes a battery 4
2 is measured and converted into a digital value by A / D conversion, and then notified to the peripheral circuit control LSI 12.

The peripheral circuit control LSI notifies the backlight power supply control program 01 of the battery voltage value 03 via the internal bus 61.

The backlight power control program 01 is
Backlight power control table 0 through internal bus 61
A backlight lighting time 04 and a backlight lighting current value 05 corresponding to the battery voltage value 03 are obtained from Step 2 (Step A2).

Next, the backlight power control program 01
Requests the peripheral circuit control LSI 12 through the internal bus 61 to set the backlight lighting current value 05 to the backlight current switching circuit 32 (step A).
3).

The peripheral circuit control LSI 12 that has received the request for setting the backlight lighting current value 05 from the backlight power supply control program 01 sets the backlight lighting current value 05 in the backlight current switching circuit 32.

Next, the backlight power supply control program 01
Requests the peripheral circuit control LSI 12 to turn on the backlight power through the internal bus 61 (step A4 in FIG. 2).

A peripheral circuit control LSI receiving a backlight power ON request from the backlight power control program 01
Reference numeral 12 sets the backlight power supply control circuit 31 to turn on the backlight.

The backlight of the portable telephone is turned on by the above control.

Further, a backlight power control program 01
Sets the backlight lighting time 04 to the timer 71,
The process ends (step A5).

The timer 71 generates a timeout notification interrupt to the CPU 11 when the backlight lighting time elapses.

The CPU 11 that has received the timeout interrupt notification from the timer 71 activates the backlight power control program 01.

The backlight control program 01 started by the CPU 11 transmits the peripheral circuit control LSI 12 through the internal bus 61 when the start-up factor is a time-out notification.
Is requested to turn off the backlight, and the process is terminated (step A6).

Peripheral circuit control LS receiving a backlight power OFF request from the backlight power control program 01
I12 sets the backlight power supply OFF to the backlight power supply control circuit 31.

The backlight of the portable telephone is turned off by the above control.

Next, the operation of the present invention will be specifically described with reference to FIG.

(1) A case where the digital value of the battery voltage of the portable telephone is 250 will be described.

When the power ON operation, key operation, and incoming call operation of the mobile phone are performed, the CPU 11 starts the backlight power control program 01.

The backlight power control program 01 started by the CPU 11 controls the peripheral circuit control L through the internal bus 61 when the start factor is a backlight lighting request.
It requests SI 12 to obtain the current battery voltage value of the mobile phone.

Peripheral circuit control LSI that receives a request to acquire a battery voltage value from backlight power control program 01
12 requests the battery voltage acquisition circuit 41 to acquire the current battery voltage value of the mobile phone.

The battery voltage acquisition circuit 41
2 is measured, and a digital value is obtained by A / D conversion.
250, and notifies the peripheral circuit control LSI 12.

The peripheral circuit control LSI notifies the backlight power supply control program 01 of the battery voltage value = 250 through the internal bus 61.

The backlight power control program 01 is as follows:
Backlight power control table 0 through internal bus 61
2, the backlight lighting time corresponding to the battery voltage value = 250 = 30 seconds and the backlight lighting current value = 120 m
Get A.

Next, the backlight power supply control program 01
Requests the peripheral circuit control LSI 12 through the internal bus 61 to set the backlight lighting current value = 120 mA to the backlight current switching circuit 32.

The peripheral circuit control LSI 12 that has received the request for setting the backlight lighting current value 05 from the backlight power supply control program 01 sets the backlight lighting current value = 120 mA in the backlight current switching circuit 32.

Next, the backlight power supply control program 01
Requests the peripheral circuit control LSI 12 to turn on the backlight power through the internal bus 61.

A peripheral circuit control LSI receiving a backlight power ON request from the backlight power control program 01
Reference numeral 12 sets the backlight power supply control circuit 31 to turn on the backlight.

The backlight of the portable telephone is turned on by the above control.

Further, the backlight power supply control program 01
Sets the backlight lighting time = 30 seconds in the timer 71 and ends the processing.

The timer 71 calculates the backlight lighting time =
When 30 seconds have elapsed, a timeout notification interrupt is generated for the CPU 11.

The CPU 11 that has received the timeout interrupt notification from the timer 71 activates the backlight power control program 01.

The backlight control program 01 started by the CPU 11 sends the peripheral circuit control LSI 12
Is requested to turn off the backlight, and the process ends.

Peripheral circuit control LS receiving a backlight power OFF request from backlight power control program 01
I12 sets the backlight power supply OFF to the backlight power supply control circuit 31.

The backlight of the portable telephone is turned off by the above control.

(2) A case where the digital value of the battery voltage of the portable telephone is 150 will be described.

When the power ON operation, key operation, and incoming call operation of the portable telephone are performed, the CPU 11 starts the backlight power control program 01.

The backlight power control program 01 started by the CPU 11 controls the peripheral circuit control L through the internal bus 61 when the start factor is a backlight lighting request.
It requests SI 12 to obtain the current battery voltage value of the mobile phone.

Peripheral circuit control LSI receiving a request for obtaining a battery voltage value from backlight power control program 01
12 requests the battery voltage acquisition circuit 41 to acquire the current battery voltage value of the mobile phone.

The battery voltage acquisition circuit 41
2 is measured, and a digital value is obtained by A / D conversion.
150 and notifies the peripheral circuit control LSI 12.

The peripheral circuit control LSI notifies the backlight power supply control program 01 of the battery voltage value = 150 through the internal bus 61.

The backlight power control program 01 is
Backlight power control table 0 through internal bus 61
The backlight lighting time corresponding to the battery voltage value = 150 from 2 = 10 seconds and the backlight lighting current value = 60 mA
To get.

Next, the backlight power supply control program 01
Requests the peripheral circuit control LSI 12 through the internal bus 61 to set the backlight lighting current value = 60 mA to the backlight current switching circuit 32.

The peripheral circuit control LSI 12 that has received the request for setting the backlight lighting current value 05 from the backlight power supply control program 01 sets the backlight lighting current value = 60 mA in the backlight current switching circuit 32.

Next, the backlight power supply control program 01
Requests the peripheral circuit control LSI 12 to turn on the backlight power through the internal bus 61.

Peripheral circuit control LSI receiving a backlight power ON request from backlight power control program 01
Reference numeral 12 sets the backlight power supply control circuit 31 to turn on the backlight.

The above control turns on the backlight of the mobile phone.

Further, a backlight power supply control program 01
Sets the backlight lighting time = 10 seconds in the timer 71 and ends the processing.

The timer 71 calculates the backlight lighting time =
When 10 seconds have elapsed, a timeout notification interrupt is generated for the CPU 11.

The CPU 11 that has received the timeout interrupt notification from the timer 71 activates the backlight power control program 01.

The backlight control program 01 started by the CPU 11 sends the peripheral circuit control LSI 12 through the internal bus 61 when the start-up factor is a time-out notification.
Is requested to turn off the backlight, and the process ends.

Peripheral circuit control LS receiving a backlight power OFF request from backlight power control program 01
I12 sets the backlight power supply OFF to the backlight power supply control circuit 31.

The backlight of the portable telephone is turned off by the above control. (3) A case where the digital value of the battery voltage of the mobile phone is 50 will be described.

When the power ON operation, key operation, and incoming call operation of the portable telephone are performed, the CPU 11 starts the backlight power control program 01.

The backlight power supply control program 01 started by the CPU 11 controls the peripheral circuit control L through the internal bus 61 when the start-up factor is a backlight lighting request.
It requests SI 12 to obtain the current battery voltage value of the mobile phone.

Peripheral circuit control LSI receiving a request for obtaining a battery voltage value from backlight power control program 01
12 requests the battery voltage acquisition circuit 41 to acquire the current battery voltage value of the mobile phone.

[0093] The battery voltage acquisition circuit 41
2 is measured, and a digital value is obtained by A / D conversion.
50 and notifies the peripheral circuit control LSI 12.

The peripheral circuit control LSI notifies the backlight power supply control program 01 of the battery voltage value = 50 through the internal bus 61.

The backlight power control program 01 is
Backlight power control table 0 through internal bus 61
From 2, the backlight lighting time = 0 second and the backlight lighting current value = 0 mA corresponding to the battery voltage value = 50 are acquired.

When the backlight lighting time is 0 seconds, the backlight power control program 01 ends the processing without performing the backlight lighting control.

[0097]

The backlight control method and apparatus for a portable telephone according to the present invention provide a portable telephone by providing a function of changing a backlight lighting time and a current value required for lighting of the portable telephone according to a battery voltage of the portable telephone. The goal is to maximize the battery life of the phone.

The reason is that the lighting time of the backlight is shortened when the battery voltage of the portable telephone is reduced by changing the lighting time and current value of the backlight, that is, when the remaining battery power is reduced. This is because the current value can be reduced.

[Brief description of the drawings]

FIG. 1 is a block diagram showing one embodiment of the present invention.

FIG. 2 is a flowchart illustrating the operation of the present invention.

FIG. 3 is a diagram showing an example of the contents of a backlight control table shown in FIG. 1;

FIG. 4 is a block diagram showing a first conventional example.

FIG. 5 is a block diagram showing a second conventional example.

FIG. 6 is a block diagram showing a third conventional example.

FIG. 7 is a flowchart illustrating the operation of FIG. 6;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 CPU 12 Peripheral circuit control LSI 21 Main memory 22 ROM 31 Backlight power control circuit 32 Backlight current switching circuit 33 Backlight 41 Battery voltage acquisition circuit 42 Battery 71 Timer

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference)

Claims (6)

[Claims] 1. A backlight control method for a mobile phone, comprising: a step of obtaining a voltage of a battery; and a step of controlling a lighting time of a backlight based on the obtained voltage. 2. A portable device comprising: a step of acquiring a voltage of a battery; a step of controlling a lighting time of a backlight based on the acquired voltage; and a step of controlling a lighting current of the backlight. A backlight control method for a telephone. 3. A CPU connected to an internal bus (61)
(11) Main memory (21) storing a hack light power control program, ROM (22) storing a backlight power control table, timer (71), peripheral circuit control LSI (12), and battery voltage A battery voltage acquisition circuit (41) for acquiring the value and supplying the value to the peripheral circuit control LSI (12);
A backlight power supply control circuit (31) for controlling ON / OFF of the power supply of the backlight based on a control signal from (12), and a backlight power-on circuit based on a control signal from a peripheral circuit control LSI (12). Backlight current switching circuit (32) for switching a current value to a specified value
And a backlight control device for a mobile phone. 4. The backlight control device for a mobile phone according to claim 3, wherein the timer (71) issues a timeout interrupt notification to the CPU (11) when the designated time has elapsed. 5. The backlight control device according to claim 3, wherein the ROM is a flash ram. 6. A backlight control device for a mobile phone, comprising: means for acquiring a voltage of a battery; and means for controlling a lighting time of a backlight based on the acquired voltage.