WO2015133615A1 - Driving device for led, control method, and portable terminal - Google Patents

Driving device for led, control method, and portable terminal Download PDF

Info

Publication number
WO2015133615A1
WO2015133615A1 PCT/JP2015/056693 JP2015056693W WO2015133615A1 WO 2015133615 A1 WO2015133615 A1 WO 2015133615A1 JP 2015056693 W JP2015056693 W JP 2015056693W WO 2015133615 A1 WO2015133615 A1 WO 2015133615A1
Authority
WO
WIPO (PCT)
Prior art keywords
voltage value
current
voltage
led
value range
Prior art date
Application number
PCT/JP2015/056693
Other languages
French (fr)
Japanese (ja)
Inventor
清水　直
Original Assignee
京セラ株式会社
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by 京セラ株式会社 filed Critical 京セラ株式会社
Publication of WO2015133615A1 publication Critical patent/WO2015133615A1/en

Links

Images

Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04M—TELEPHONIC COMMUNICATION
    • H04M1/00—Substation equipment, e.g. for use by subscribers
    • H04M1/02—Constructional features of telephone sets
    • H04M1/22—Illumination; Arrangements for improving the visibility of characters on dials

Definitions

  • This disclosure relates to a technique for driving and controlling an LED that emits light as a backlight on a display unit of a mobile terminal.
  • Liquid crystal display devices (Liquid Crystal Display, LCD) are widely used in portable terminals and the like.
  • a backlight is disposed on the back surface of the liquid crystal display device to increase the luminance of the liquid crystal display device.
  • a white LED Light Emitting Diode
  • a white LED is generally used as a light source for the backlight.
  • the LED used for the backlight is generally a high-luminance type and requires a forward voltage (Vf) of about 3.3 V or more.
  • Vf forward voltage
  • a battery mounted on a portable terminal has a characteristic that its voltage decreases with use. For this reason, a voltage is not directly supplied from the battery to the LED, and a booster circuit that boosts the battery voltage is used.
  • One aspect of the present disclosure is an LED driving device that emits light as a backlight to a display unit of a mobile terminal, the battery voltage value range in a no-load state of the mobile terminal, and the forward voltage forward current of the LED
  • a storage unit that stores a current value smaller than a characteristic current value corresponding to the voltage value range
  • an acquisition unit that acquires a voltage value of the battery after a voltage drop due to a load at the present time, is acquired
  • a determination unit that determines whether or not the voltage value is within the voltage value range; and, if the voltage value is within the voltage value range, reads the current value corresponding to the voltage value range from the storage unit;
  • a supply control unit configured to control the LED to supply a constant current indicated by the read current value; and a constant current unit configured to supply the LED with a constant current indicated by the current value.
  • a mobile terminal which includes a battery, a display unit, an LED that emits light as a backlight to the display unit, a voltage value range in an unloaded state of the battery, In the forward voltage forward current characteristics of the LED, a storage unit storing a current value smaller than a characteristic current value corresponding to the voltage value range, and a voltage value of the battery after a voltage drop due to a current load is obtained.
  • An acquisition unit that performs determination, a determination unit that determines whether or not the acquired voltage value is within the voltage value range, and if the voltage value is within the voltage value range, corresponds to the voltage value range from the storage unit
  • a supply control unit that controls to read the current value and supply a constant current indicated by the read current value to the LED, and a constant current unit that supplies a constant current indicated by the current value to the LED.
  • the battery voltage fluctuates depending on the use conditions, and this fluctuation causes fluctuations in the current flowing in the LED, so that the LED The intensity of light may fluctuate.
  • Vf-If forward voltage-forward current
  • the battery voltage decreases by 300 mV due to a change in the usage conditions of the mobile terminal, for example, due to a change in the wireless environment or a change in the application being used, the battery voltage becomes 3.1 V (305).
  • the current that may flow through the LED is 10 mA from the Vf-If characteristic (306, 307). Only the current of 10 mA can be passed instead of the set current of 20 mA. When a current of 10 mA is passed, the luminous intensity of the LED is reduced as compared with the case of 20 mA.
  • the current that may be passed through the LED is 27 mA (303, 304).
  • the luminous intensity of the LED returns to the original state.
  • the display part of the mobile terminal may flicker to the user.
  • Embodiment A mobile terminal 100 according to an embodiment of the present disclosure will be described.
  • the mobile terminal 100 is configured to be able to make a call, send / receive an e-mail, or send / receive data to / from another mobile terminal or mobile phone via a wireless base station and a mobile phone network.
  • the portable terminal 100 can fulfill the functions of the application program by executing various application programs. Examples of the application program include a web browser, a music playback program, and a camera shooting program.
  • a liquid crystal panel unit 110 is arranged so that the display surface is exposed.
  • the liquid crystal panel unit 110 includes a backlight 114, and the backlight 114 irradiates light on the back surface of the display surface of the liquid crystal panel unit 110.
  • the mobile terminal 100 includes an antenna 101, a wireless communication unit 102, a control unit 103, an input control unit 104, a key input unit 105, an audio processing unit 106, a speaker 107, a microphone 108, and an input / output control unit 109.
  • the LED drive circuit 113 includes constant current circuits 133, 134, 135, and 136.
  • the control unit 103 includes an acquisition unit 137, a determination unit 138, and a supply control unit 139.
  • the liquid crystal panel unit 110 includes a touch pad unit 110a, a liquid crystal display unit 110b, and a backlight 114.
  • the backlight 114 includes LEDs 141, 142, 143, and 144.
  • the power supply unit 112 includes a voltage detection unit 121.
  • the portable terminal 100 is specifically a computer system including a microprocessor, a digital signal processor, a ROM, a RAM, and the like. A computer program is stored in the RAM. Each processor operates according to the computer program, whereby the portable terminal 100 achieves its functions.
  • Storage unit 115 The memory
  • storage part 115 is comprised from the non-volatile semiconductor memory as an example.
  • the storage unit 115 stores a control table 151, other data, and computer programs such as application programs.
  • the control table 151 is used to set the value of current flowing through the LEDs 141, 142, 143, and 144.
  • the control table 151 includes a plurality of control data as shown in FIG. Each control data includes an identification number, a voltage value range, and a current value in association with each other.
  • the identification number is identification information for uniquely identifying the corresponding control data.
  • the voltage value range indicates a voltage value range of the battery 111.
  • the unit is V (volt).
  • the current value indicates the value of the current passed through the LEDs 141, 142, 143 and 144.
  • the unit is mA (milliampere).
  • control table 151 stores a plurality of control data 161, 171, 181 and 191 as an example.
  • the control data 161 includes an identification number 162 “1”, a voltage value range 163 “3.768 or more”, and a current value 164 “20”.
  • the identification number 162 “1” uniquely identifies the control data 161.
  • the voltage value range 163 “3.768 or more” indicates that the voltage value range is 3.768 V or more.
  • the current value 164 “20” indicates that the current flowing through the LEDs 141, 142, 143, and 144 is 20 mA.
  • the control data 161 when the voltage value of the battery 111 (the voltage value after the voltage drop due to the current load) is 3.768V or more, the current value of 20 mA is the current value that flows through the LEDs 141, 142, 143, and 144. Is set.
  • control data 171 includes an identification number 172 “2”, a voltage value range 173 “3.707 to 3.767”, and a current value 174 “15”.
  • the identification number 172 “2” uniquely identifies the control data 171.
  • the voltage value range 173 “3.707 to 3.767” indicates that the voltage value range is 3.707V or more and 3.767V or less.
  • the current value 174 “15” indicates that the current flowing through the LEDs 141, 142, 143, and 144 is 15 mA.
  • the current value of 15mA is the LED 141, 142, 143 and 144. It is set as a current value to be passed through.
  • the control data 181 includes an identification number 182 “3”, a voltage value range 183 “3.656 to 3.706”, and a current value 184 “13”.
  • the identification number 182 “3” uniquely identifies the control data 181.
  • the voltage value range 183 “3.656 to 3.706” indicates that the voltage value range is 3.656V or more and 3.706V or less.
  • the current value 184 “13” indicates that the current passed through the LEDs 141, 142, 143, and 144 is 13 mA.
  • the current value of 13 mA is the LED 141, 142, 143 and 144. It is set as a current value to be passed through.
  • the control data 191 includes an identification number 192 “4”, a voltage value range 193 “3.655-3.400”, and a current value 194 “10”.
  • the identification number 192 “4” uniquely identifies the control data 191.
  • the voltage value range 193 “3.655 to 3.400” indicates that the voltage value range is 3.655V or more and 3.400V or less.
  • a current value 194 “10” indicates that the current flowing through the LEDs 141, 142, 143, and 144 is 10 mA.
  • the control data 191 when the voltage value of the battery 111 (the voltage value after the voltage drop due to the load at the present time) is 3.655V or more and 3.400V or less, the current value of 10mA is the LED 141, 142, 143 and 144. It is set as a current value to be passed through.
  • the data table 201 includes seven rows of data columns 211, 212,. Each data in the data column 211 in the first row indicates the remaining battery level as a percentage.
  • Each data in the data column 212 in the second row is an actual measurement value, corresponding to the remaining battery level in the data column 211 in the first row, and indicating the battery voltage in a state where there is no load that consumes power.
  • the unit is mV (millivolt).
  • Each data in the data row 213 in the third row is an actual measurement value, corresponding to the remaining battery level in the data row 211 in the first row, and the battery voltage when a load that consumes the maximum power is applied to the mobile terminal 100 Indicates.
  • the unit is mV (millivolt).
  • an example of the load is a call, transmission / reception of e-mail, transmission / reception of data, web browser, music playback, camera shooting, and the like.
  • the load that consumes the maximum power is the power consumption that is the largest among the combinations of loads that can be used simultaneously in the mobile terminal 100.
  • Each data in the data column 214 in the fourth row has the same value as the corresponding data in the data column in the third row.
  • Each data in the data column 214 in the fourth row is shown as a forward voltage of the LED.
  • Each data in the data column 215 in the fifth row indicates the LED forward current based on the LED forward voltage-forward current characteristics.
  • Each forward current in the data column 215 in the fifth row corresponds to a corresponding forward voltage in the data column 214 in the fourth row.
  • Each data in the data column 216 in the sixth row indicates a current value set for the LED.
  • the difference between the data in the data column 215 in the fifth row and the data in the corresponding data column 216 in the sixth row is smaller than the threshold value.
  • the threshold is 5.0 as an example.
  • Each data in the data column 217 of the seventh row indicates an identification number of the control table 151 in FIG.
  • the battery voltage in the no load state is 3768 mV
  • the battery voltage in the state where the load that consumes the maximum power is applied is 3562 mV.
  • the forward current is 20.2 mA for the battery voltage (3562 mV) under a load that consumes the maximum power. Therefore, 20.0 mA smaller than 20.2 mA is set as the set current value of the LED.
  • the difference between 20.2 mA and 20.0 mA is smaller than the threshold value.
  • the battery voltage in the no load state is 3756 mV
  • the battery voltage in the state where the load that consumes the maximum power is applied is 3546 mV.
  • the forward current with respect to the battery voltage (3546 mV) in a state of applying a load that consumes the maximum power is 19.8 mA. Therefore, 15.0 mA, which is smaller than 19.8 mA, is set as the set current value of the LED. The difference between 19.8 mA and 15.0 mA is smaller than the threshold value.
  • the battery voltage in the no load state is 3673 mV
  • the battery voltage in the state where the load that consumes the maximum power is applied is 3474 mV.
  • the forward current is 15.4 mA for the battery voltage (3474 mV) under a load that consumes the maximum power. Therefore, 13.0 mA, which is smaller than 15.4 mA, is set as the set current value of the LED. The difference between 15.4 mA and 13.0 mA is smaller than the threshold value.
  • 13.0 mA is set as the set current value of the LED in the same manner as described above.
  • the battery voltage without load is 3400 mV
  • the battery voltage with a load that consumes the maximum power is 3300 mV.
  • the forward current with respect to the battery voltage (3300 mV) under a load that consumes the maximum power is 10.2 mA. Therefore, 10.0 mA, which is smaller than 10.2 mA, is set as the set current value of the LED. The difference between 10.2 mA and 10.0 mA is smaller than the threshold value.
  • a set current value is determined for each voltage value range, and a control table 151 that stores a current value for each voltage value range shown in FIG. 3 is generated.
  • the antenna 101 transmits and receives radio signals to and from the radio base station via a radio line.
  • the wireless communication unit 102 performs frequency selection, frequency conversion, and the like of a wireless signal transmitted and received by the antenna 101.
  • Speaker 107 outputs sound such as voice.
  • the microphone 108 inputs sound such as voice.
  • the audio processing unit 106 demodulates the audio signal received by the wireless communication unit 102 and outputs it to the speaker 107 as an acoustic signal.
  • the audio signal converted into an electrical signal corresponding to the acoustic signal input from the microphone 108 is modulated and transmitted by the wireless communication unit 102.
  • the key input unit 105 includes a power key as a power switch for turning the mobile terminal 100 ON or OFF, a numeric keypad, and other keys and buttons. When these keys and buttons are operated, the key input unit 105 generates operation information corresponding to the operated keys and buttons. Next, the key input unit 105 outputs the generated operation information to the control unit 103 via the input control unit 104.
  • the input control unit 104 relays operation information between the key input unit 105 and the control unit 103.
  • the timer 116 measures the passage of time.
  • the liquid crystal panel unit 110 includes a touch pad unit 110a, a liquid crystal display unit 110b, and a backlight 114.
  • the liquid crystal display unit 110b has a rectangular display surface, and a touch pad unit 110a is attached to the display surface.
  • the liquid crystal display unit 110b displays a screen including icons and other objects received from the control unit 103 via the input / output control unit 109.
  • the touch pad unit 110a detects the contact position of the operating body with respect to the display surface of the liquid crystal panel unit 110, and outputs the detected contact position to the input / output control unit 109 as an input signal.
  • the backlight 114 is installed on the back surface of the liquid crystal display unit 110b.
  • the backlight 114 includes four LEDs 141, 142, 143, and 144 so that light is emitted toward the back surface of the liquid crystal display unit 110b.
  • the LEDs 141, 142, 143, and 144 are supplied with constant forward current from the corresponding constant current circuits 133, 134, 135, and 136, respectively, and emit light by the supplied forward current.
  • the input / output control unit 109 relays input / output of information between the liquid crystal panel unit 110 and the control unit 103.
  • the LED drive circuit 113 is composed of constant current circuits 133, 134, 135 and 136. Each of the constant current circuits 133, 134, 135, and 136 is supplied with power from the power supply unit 112.
  • the constant current circuits 133, 134, 135, and 136 receive the designation of the current value from the supply control unit 139, generate a constant current indicated by the received current value, and generate the generated constant currents as the LEDs 141, 142, 143, respectively. And 144.
  • the battery 111 is a rechargeable secondary battery.
  • the power supply unit 112 supplies the power output from the battery 111 to each component of the mobile terminal 100.
  • the power supply unit 112 includes a voltage detection unit 121 that detects a voltage of the battery 111 after a voltage drop due to a load at the present time.
  • the voltage detection unit 121 outputs the detected voltage value to the control unit 103.
  • Control unit 103 controls the wireless communication unit 102, the input control unit 104, the voice processing unit 106, and the input / output control unit 109 that are components of the mobile terminal 100.
  • the control unit 103 includes an acquisition unit 137, a determination unit 138, and a supply control unit 139.
  • the acquisition unit 137 acquires the voltage value of the battery 111 after the voltage drop due to the current load from the voltage detection unit 121 of the power supply unit 112.
  • the acquisition unit 137 outputs the acquired voltage value to the determination unit 138.
  • the determining unit 138 determines whether or not the acquired voltage value is in any voltage value range of the control table 151 stored in the storage unit 115.
  • the supply control unit 139 When the determination unit 138 determines that the acquired voltage value exists in any voltage value range, the supply control unit 139 reads a current value corresponding to the voltage value range from the storage unit 115. The supply control unit 139 controls the constant current circuits 133, 134, 135, and 136 so as to supply a constant current indicated by the read current value to the LEDs 141, 142, 143, and 144.
  • the supply control unit 139 sets the constant current supplied to the LEDs 141, 142, 143, and 144 as an initial value to a current value (20 mA) corresponding to the identification number “1” of the control table 151.
  • the supply control unit 139 instructs the constant current circuits 133, 134, 135, and 136 to supply a constant current of 20 mA.
  • the constant current circuits 133, 134, 135, and 136 supply a constant current of 20 mA to the LEDs 141, 142, 143, and 144, respectively.
  • the LEDs 141, 142, 143, and 144 each emit light with a constant current of 20 mA (step S101).
  • the control unit 103 uses the timer 116 to count 20 seconds (step S102). If 20 seconds have not elapsed ("NO” in step S102), the process returns to step S102 and the process is repeated. When 20 seconds have elapsed (“YES” in step S102), the acquisition unit 137 acquires the voltage value of the battery 111 after the voltage drop due to the current load from the voltage detection unit 121 and reads it (step S103). .
  • the determining unit 138 searches the control table 151 stored in the storage unit 115 for a voltage value range including the read voltage value (step S104).
  • the supply control unit 139 reads the current value corresponding to the voltage value range from the control table 151 (step S105).
  • the supply control unit 139 sets the constant current supplied to the LEDs 141, 142, 143, and 144 to the read current value.
  • the supply control unit 139 instructs the constant current circuits 133, 134, 135, and 136 to supply a constant current indicated by the read current value.
  • the constant current circuits 133, 134, 135, and 136 supply constant currents indicated by the read current values to the LEDs 141, 142, 143, and 144, respectively.
  • Each of the LEDs 141, 142, 143, and 144 emits light with a constant current indicated by the read current value (step S106). Next, it returns to step S102 and repeats a process.
  • the current value is constant and does not fluctuate if the fluctuation of the voltage value excluding the voltage drop due to the current load of the battery 111 is within the selected voltage value range.
  • the luminous intensity of each LED does not change, and the liquid crystal display unit 110b does not flicker.
  • the voltage value of the battery 111 is acquired at regular intervals, for example, every 20 seconds. Based on the acquired voltage value, the control table 151 is used to determine the value of the current flowing through the LED.
  • the method is not limited.
  • the voltage value after the voltage drop due to the current load of the battery 111 is acquired three times every 20 seconds.
  • the current value to be passed through the LED may be determined based on the current value corresponding to the voltage value range of the control table 151.
  • the identification number X, the identification number Y, and the identification number Z are provided in the storage unit 115 as three variables.
  • the identification number X, the identification number Y, and the identification number Z are used to store the current identification number, the previous identification number, and the previous identification number, respectively.
  • the supply control unit 139 sets the constant current supplied to the LEDs 141, 142, 143, and 144 as an initial value to the current value (20 mA) indicated by the identification number “1” of the control table 151.
  • the supply control unit 139 instructs the constant current circuits 133, 134, 135, and 136 to supply a constant current of 20 mA.
  • the constant current circuits 133, 134, 135, and 136 supply a constant current of 20 mA to the LEDs 141, 142, 143, and 144, respectively.
  • the LEDs 141, 142, 143, and 144 each emit light with a constant current of 20 mA (step S121).
  • the supply control unit 139 sets “7”, “8”, and “9” in the identification number X, the identification number Y, and the identification number Z, respectively, as initial values. “7”, “8”, and “9” are values that do not exist in the control table 151 and cannot be taken as identification numbers. “7”, “8”, and “9” are different values, and different values are set for the identification number X, the identification number Y, and the identification number Z, respectively (step S122).
  • the control unit 103 counts 20 seconds by the timer 116 (step S123). If 20 seconds have not elapsed ("NO” in step S123), the process returns to step S123 and the process is repeated. When 20 seconds have elapsed (“YES” in step S123), the acquisition unit 137 acquires the voltage value of the battery 111 from the voltage detection unit 121 and reads it (step S124).
  • the determination unit 138 searches the control table 151 stored in the storage unit 115 for a voltage value range including the acquired voltage value (step S125).
  • the supply control unit 139 overwrites the identification number Z with the value stored in the identification number Y (step S126).
  • the value stored in the identification number X is overwritten on the identification number Y (step S127).
  • the supply control unit 139 reads the identification number corresponding to the voltage value range from the control table 151 (step S128). The read identification number is overwritten on the identification number X (step S129). The supply control unit 139 determines whether the identification number X, the identification number Y, and the identification number Z are the same (step S130).
  • step S130 If they are not identical (“NO” in step S130), the process returns to step S123 and the process is repeated.
  • the supply control unit 139 reads the current value corresponding to the voltage value range from the control table 151 (step S131). .
  • the supply control unit 139 sets the constant current supplied to the LEDs 141, 142, 143, and 144 to the read current value.
  • the supply control unit 139 instructs the constant current circuits 133, 134, 135, and 136 to supply a constant current indicated by the read current value.
  • the constant current circuits 133, 134, 135, and 136 supply constant currents indicated by the read current values to the LEDs 141, 142, 143, and 144, respectively.
  • Each of the LEDs 141, 142, 143, and 144 emits light with a constant current indicated by the read current value (step S132). Returning to step S123, the processing is repeated.
  • the current value corresponding to the voltage value range of the control table 151 is set as the current value flowing through the LED. Has been decided.
  • the LED current value By the method described above, it is possible to prevent the LED current value from being changed when the battery voltage fluctuates temporarily.
  • the temporary battery voltage fluctuation occurs, for example, due to temporary use of a web browser.
  • the LED current value is changed. In this way, it is possible to prevent the luminance of the liquid crystal display unit 110b from switching over and over.
  • the voltage value of the battery 111 may be acquired twice, four times, or five times continuously. In this case, when all the voltage values are within the same voltage value range, the current value corresponding to the voltage value range of the control table 151 may be determined as the current value flowing through the LED.
  • the voltage value of the battery 111 is acquired every 20 seconds. However, this is not a limitation. The voltage value of the battery 111 may be acquired every 10 seconds, every 30 seconds, or every minute.
  • control table 151 has four sets of voltage value ranges and current values. However, it is not limited to this.
  • the control table 151 may have a larger number of sets of voltage value ranges and current values.
  • the LEDs 141, 142, 143, and 144 are arranged in parallel as viewed from the LED drive circuit 113.
  • the LEDs 141, 142, 143, and 144 are not connected in series. For example, when four LEDs are connected in series, if each LED requires a voltage of 3.3 V, a total voltage of 13.2 V (3.3 V ⁇ 4) is required. This exceeds the voltage that the battery 111 can output.
  • the voltage detection unit 121 may detect the voltage value of the battery 111 before the voltage drop due to the current load.
  • the determination unit 138 adds the voltage difference value due to the load according to the current usage state to the voltage value detected by the voltage detection unit 121 to calculate the voltage value. Thereby, the voltage value after the voltage drop by the load at the present time is calculated.
  • the determination unit 138 searches the control table 151 stored in the storage unit 115 for a voltage value range including the calculated voltage value.
  • the backlight 114 is installed on the back surface of the liquid crystal display unit 110b.
  • the arrangement is not limited.
  • a light guide plate, a light guide housing, a light guide tube, and the like may be disposed on the back surface of the liquid crystal display unit 110b.
  • the backlight 114 irradiates light to the back surface of the liquid crystal display unit 110b through a light guide plate, a light guide housing, a light guide tube, and the like.
  • the portable terminal of the present invention is a computer system including a microprocessor and a memory.
  • the memory stores a computer program, and the microprocessor operates according to the computer program.
  • the computer program is configured by combining a plurality of instruction codes indicating instructions to the computer in order to achieve a predetermined function.
  • the computer program is recorded on a computer-readable recording medium such as a flexible disk, hard disk, CD-ROM, MO, DVD, DVD-ROM, DVD-RAM, Blu-ray disk, semiconductor memory, etc. Also good.
  • the computer program may be transmitted via an electric communication line, a wireless or wired communication line, a network represented by the Internet, a data broadcast, or the like.
  • the computer program may be recorded on the recording medium and transferred.
  • the computer program may be transferred via a network or the like.
  • the computer program is executed by another independent computer system.
  • the LED driving device can prevent the display unit from flickering without providing a booster circuit. For this reason, it is useful as a technique for driving and controlling an LED that emits light as a backlight to the display unit of the portable terminal.
  • 100 mobile terminal 101 antenna, 102 wireless communication unit, 103 control unit, 104 input control unit, 105 key input unit, 106 audio processing unit, 107 speaker, 108 microphone, 109 input / output control unit, 110 liquid crystal panel unit, 110a touch Pad unit, 110b Liquid crystal display unit, 111 battery, 112 power supply unit, 113 LED drive circuit, 114 backlight, 115 storage unit, 116 timer, 121 voltage detection unit, 133, 134, 135, 136 constant current circuit, 137 acquisition unit 138 Judgment part 139 Supply control part 141, 142, 143, 144 LED

Landscapes

  • Engineering & Computer Science (AREA)
  • Signal Processing (AREA)
  • Telephone Function (AREA)
  • Led Devices (AREA)

Abstract

A portable terminal is provided with: a backlight including an LED; a battery; a storage unit which stores the voltage value range of the battery in unloaded condition, and a current value smaller than a characteristic current value corresponding to the voltage value range in the forward voltage - forward current characteristic of the LED; an acquisition unit which acquires the voltage value after a voltage drop due to a load at the present point in time of the battery; a determination unit which determines whether or not the acquired voltage value is present within the voltage value range; a supply control unit which, when the voltage value is present within the voltage value range, performs control such that a constant current indicated by the current value corresponding to the voltage value range is supplied to the LED; and a constant current circuit which supplies the constant current to the LED.

Description

ＬＥＤの駆動装置、制御方法及び携帯端末LED driving device, control method, and portable terminal
　本開示は、携帯端末の表示部にバックライトとして光を照射するＬＥＤを駆動制御する技術に関する。 This disclosure relates to a technique for driving and controlling an LED that emits light as a backlight on a display unit of a mobile terminal.
　携帯端末などにおいて、液晶表示装置（Liquid　Crystal　Display、ＬＣＤ）が広く用いられている。液晶表示装置の背面には、バックライトが配置され、液晶表示装置の輝度をより高くしている。バックライトの光源としては、一般的に白色ＬＥＤ（Light　Emitting　Diode）が用いられる。 Liquid crystal display devices (Liquid Crystal Display, LCD) are widely used in portable terminals and the like. A backlight is disposed on the back surface of the liquid crystal display device to increase the luminance of the liquid crystal display device. A white LED (Light Emitting Diode) is generally used as a light source for the backlight.
　バックライトに用いられるＬＥＤは、一般的に高輝度タイプであり、順方向電圧（Ｖｆ）として、３．３Ｖ程度以上、必要である。一方、携帯端末に搭載される電池は、その電圧が使用とともに低下するという特性を有している。このため、電池から直接ＬＥＤに電圧を供給することは行われず、電池電圧を昇圧する昇圧回路が用いられる。 The LED used for the backlight is generally a high-luminance type and requires a forward voltage (Vf) of about 3.3 V or more. On the other hand, a battery mounted on a portable terminal has a characteristic that its voltage decreases with use. For this reason, a voltage is not directly supplied from the battery to the LED, and a booster circuit that boosts the battery voltage is used.
　本開示の一態様は、携帯端末の表示部にバックライトとして光を照射するＬＥＤの駆動装置であって、前記携帯端末の無負荷状態における電池の電圧値範囲と、前記ＬＥＤの順電圧順電流特性において、当該電圧値範囲に対応する特性電流値より小さい電流値とを記憶している記憶部と、前記電池の、現時点における負荷による電圧降下後の電圧値を取得する取得部と、取得された前記電圧値が前記電圧値範囲内に存在するか否かを判断する判断部と、前記電圧値範囲内に存在する場合、前記記憶部から当該電圧値範囲に対応する前記電流値を読み出し、読み出した前記電流値により示される定電流を前記ＬＥＤに供給するよう制御する供給制御部と、前記電流値により示される定電流を前記ＬＥＤに供給する定電流部とを備える。 One aspect of the present disclosure is an LED driving device that emits light as a backlight to a display unit of a mobile terminal, the battery voltage value range in a no-load state of the mobile terminal, and the forward voltage forward current of the LED In the characteristics, a storage unit that stores a current value smaller than a characteristic current value corresponding to the voltage value range, an acquisition unit that acquires a voltage value of the battery after a voltage drop due to a load at the present time, is acquired A determination unit that determines whether or not the voltage value is within the voltage value range; and, if the voltage value is within the voltage value range, reads the current value corresponding to the voltage value range from the storage unit; A supply control unit configured to control the LED to supply a constant current indicated by the read current value; and a constant current unit configured to supply the LED with a constant current indicated by the current value.
　また、本開示の別の一態様は、携帯端末であって、電池と、表示部と、前記表示部にバックライトとして光を照射するＬＥＤと、前記電池の無負荷状態における電圧値範囲と、前記ＬＥＤの順電圧順電流特性において、当該電圧値範囲に対応する特性電流値より小さい電流値とを記憶している記憶部と、前記電池の、現時点における負荷による電圧降下後の電圧値を取得する取得部と、取得された前記電圧値が前記電圧値範囲内に存在するか否かを判断する判断部と、前記電圧値範囲内に存在する場合、前記記憶部から当該電圧値範囲に対応する前記電流値を読み出し、読み出した前記電流値により示される定電流を前記ＬＥＤに供給するよう制御する供給制御部と、前記電流値により示される定電流を前記ＬＥＤに供給する定電流部とを備える。 Another aspect of the present disclosure is a mobile terminal, which includes a battery, a display unit, an LED that emits light as a backlight to the display unit, a voltage value range in an unloaded state of the battery, In the forward voltage forward current characteristics of the LED, a storage unit storing a current value smaller than a characteristic current value corresponding to the voltage value range, and a voltage value of the battery after a voltage drop due to a current load is obtained. An acquisition unit that performs determination, a determination unit that determines whether or not the acquired voltage value is within the voltage value range, and if the voltage value is within the voltage value range, corresponds to the voltage value range from the storage unit A supply control unit that controls to read the current value and supply a constant current indicated by the read current value to the LED, and a constant current unit that supplies a constant current indicated by the current value to the LED. Obtain.
本開示の実施の形態としての携帯端末の外観図である。It is an external view of a portable terminal as an embodiment of this indication. 携帯端末の構成を示すブロック図である。It is a block diagram which shows the structure of a portable terminal. 制御テーブルのデータ構造の一例を示す。An example of the data structure of a control table is shown. 制御テーブルを説明するためのデータテーブルである。It is a data table for demonstrating a control table. 携帯端末の動作を示すフローチャートである。It is a flowchart which shows operation | movement of a portable terminal. 変形例としての携帯端末の動作を示すフローチャートである。It is a flowchart which shows operation | movement of the portable terminal as a modification. 白色ＬＥＤのＶｆ－Ｉｆ特性の一例を示す。An example of the Vf-If characteristic of a white LED is shown.
　携帯端末などにおいて電池電圧を昇圧する昇圧回路を設けない場合には、以下に示すように、電池電圧は、その使用条件により変動し、この変動がＬＥＤに流れる電流の変動を引き起こすことで、ＬＥＤの光度が変動する可能性がある。 When a booster circuit for boosting the battery voltage is not provided in a portable terminal or the like, as shown below, the battery voltage fluctuates depending on the use conditions, and this fluctuation causes fluctuations in the current flowing in the LED, so that the LED The intensity of light may fluctuate.
　ＬＥＤのＶｆ－Ｉｆ（順電圧－順電流）特性が図７に示す通りであるとする。ＬＥＤに流す電流を２０ｍＡとし、電池残量の低下により、電池電圧が３．４Ｖとなったとする（３０２）。この場合、図７のＶｆ－Ｉｆ特性によると、ＬＥＤに流してよい電流は、２７ｍＡである（３０３、３０４）。 Suppose that the Vf-If (forward voltage-forward current) characteristics of the LED are as shown in FIG. It is assumed that the current flowing through the LED is 20 mA, and the battery voltage becomes 3.4 V due to a decrease in the remaining battery level (302). In this case, according to the Vf-If characteristic of FIG. 7, the current that can be passed through the LED is 27 mA (303, 304).
　携帯端末の使用条件の変化により、例えば、無線環境の変化や使用しているアプリケーションの変化により、電池電圧が３００ｍＶだけ低下したなら、電池電圧は、３．１Ｖとなる（３０５）。このとき、ＬＥＤに流してよい電流は、Ｖｆ－Ｉｆ特性から、１０ｍＡである（３０６、３０７）。設定した２０ｍＡの電流ではなく、１０ｍＡの電流しか流せなくなる。１０ｍＡの電流を流すと、２０ｍＡの場合と比較して、ＬＥＤの光度が低下する。 If the battery voltage decreases by 300 mV due to a change in the usage conditions of the mobile terminal, for example, due to a change in the wireless environment or a change in the application being used, the battery voltage becomes 3.1 V (305). At this time, the current that may flow through the LED is 10 mA from the Vf-If characteristic (306, 307). Only the current of 10 mA can be passed instead of the set current of 20 mA. When a current of 10 mA is passed, the luminous intensity of the LED is reduced as compared with the case of 20 mA.
　次に、電池電圧が元の状態（３．４Ｖ）に戻ったとき（３０２）、ＬＥＤに流してよい電流は、２７ｍＡである（３０３、３０４）。このとき、２０ｍＡの電流をＬＥＤに流すと、ＬＥＤの光度が元の状態に戻る。利用者には、携帯端末の表示部がちらついて見えるおそれがある。 Next, when the battery voltage returns to the original state (3.4 V) (302), the current that may be passed through the LED is 27 mA (303, 304). At this time, when a current of 20 mA is supplied to the LED, the luminous intensity of the LED returns to the original state. There is a possibility that the display part of the mobile terminal may flicker to the user.
　１．実施の形態
　本開示に係る一の実施の形態としての携帯端末１００について説明する。 1. Embodiment A mobile terminal 100 according to an embodiment of the present disclosure will be described.
　携帯端末１００は、無線基地局及び携帯電話網を介して、他の携帯端末や携帯電話機との間で、通話、電子メールの送受信又はデータの送受信が可能となるように構成されている。また、携帯端末１００は、各種のアプリケーションプログラムを実行させることにより、そのアプリケーションプログラムが有する機能を果たすことができる。アプリケーションプログラムの例は、ウェブブラウザ、音楽の再生プログラム、カメラによる撮影プログラムなどである。 The mobile terminal 100 is configured to be able to make a call, send / receive an e-mail, or send / receive data to / from another mobile terminal or mobile phone via a wireless base station and a mobile phone network. Moreover, the portable terminal 100 can fulfill the functions of the application program by executing various application programs. Examples of the application program include a web browser, a music playback program, and a camera shooting program.
　図１に示すように、携帯端末１００において、表示面が露出するように、液晶パネル部１１０が配置されている。液晶パネル部１１０は、バックライト１１４を備え、バックライト１１４は、液晶パネル部１１０の表示面の背面に光を照射する。 As shown in FIG. 1, in the portable terminal 100, a liquid crystal panel unit 110 is arranged so that the display surface is exposed. The liquid crystal panel unit 110 includes a backlight 114, and the backlight 114 irradiates light on the back surface of the display surface of the liquid crystal panel unit 110.
　１．１　携帯端末１００
　携帯端末１００は、図２に示すように、アンテナ１０１、無線通信部１０２、制御部１０３、入力制御部１０４、キー入力部１０５、音声処理部１０６、スピーカ１０７、マイク１０８、入出力制御部１０９、液晶パネル部１１０、バッテリ１１１、電源部１１２、ＬＥＤ駆動回路１１３、記憶部１１５及びタイマ１１６から構成されている。ＬＥＤ駆動回路１１３は、定電流回路１３３、１３４、１３５及び１３６を含む。制御部１０３は、取得部１３７、判断部１３８及び供給制御部１３９を含む。液晶パネル部１１０は、タッチパッド部１１０ａ、液晶表示部１１０ｂ及びバックライト１１４を含む。バックライト１１４は、ＬＥＤ１４１、１４２、１４３及び１４４を含む。電源部１１２は、電圧検出部１２１を含む。 1.1 Mobile terminal 100
As shown in FIG. 2, the mobile terminal 100 includes an antenna 101, a wireless communication unit 102, a control unit 103, an input control unit 104, a key input unit 105, an audio processing unit 106, a speaker 107, a microphone 108, and an input / output control unit 109. , A liquid crystal panel unit 110, a battery 111, a power source unit 112, an LED drive circuit 113, a storage unit 115, and a timer 116. The LED drive circuit 113 includes constant current circuits 133, 134, 135, and 136. The control unit 103 includes an acquisition unit 137, a determination unit 138, and a supply control unit 139. The liquid crystal panel unit 110 includes a touch pad unit 110a, a liquid crystal display unit 110b, and a backlight 114. The backlight 114 includes LEDs 141, 142, 143, and 144. The power supply unit 112 includes a voltage detection unit 121.
　携帯端末１００は、具体的には、マイクロプロセッサ、デジタル信号プロセッサ、ＲＯＭ、ＲＡＭなどを含むコンピュータシステムである。前記ＲＡＭには、コンピュータプログラムが記憶されている。各プロセッサが、前記コンピュータプログラムに従って動作することにより、携帯端末１００は、その機能を達成する。 The portable terminal 100 is specifically a computer system including a microprocessor, a digital signal processor, a ROM, a RAM, and the like. A computer program is stored in the RAM. Each processor operates according to the computer program, whereby the portable terminal 100 achieves its functions.
　（１）記憶部１１５
　記憶部１１５は、一例として、不揮発性の半導体メモリから構成されている。記憶部１１５は、制御テーブル１５１、その他のデータ、及び、アプリケーションプログラム等のコンピュータプログラムを記憶している。 (1) Storage unit 115
The memory | storage part 115 is comprised from the non-volatile semiconductor memory as an example. The storage unit 115 stores a control table 151, other data, and computer programs such as application programs.
　制御テーブル１５１は、ＬＥＤ１４１、１４２、１４３及び１４４に流す電流値を設定するために用いられる。制御テーブル１５１は、一例として、図３に示すように、複数の制御データを含んでいる。各制御データは、識別番号、電圧値範囲及び電流値を対応付けて含む。 The control table 151 is used to set the value of current flowing through the LEDs 141, 142, 143, and 144. As an example, the control table 151 includes a plurality of control data as shown in FIG. Each control data includes an identification number, a voltage value range, and a current value in association with each other.
　識別番号は、対応する制御データを一意に識別するための識別情報である。電圧値範囲は、バッテリ１１１の電圧値の範囲を示す。単位は、Ｖ（ボルト）である。電流値は、ＬＥＤ１４１、１４２、１４３及び１４４に流す電流の値を示す。単位は、ｍＡ（ミリアンペア）である。バッテリ１１１の電圧値（現時点における負荷による電圧降下後の電圧値）が、制御テーブル１５１のいずれかの電圧値範囲内に存在する場合、その電圧値範囲に対応する電流値がＬＥＤ１４１、１４２、１４３及び１４４に流す電流の値として設定される。 The identification number is identification information for uniquely identifying the corresponding control data. The voltage value range indicates a voltage value range of the battery 111. The unit is V (volt). The current value indicates the value of the current passed through the LEDs 141, 142, 143 and 144. The unit is mA (milliampere). When the voltage value of the battery 111 (the voltage value after the voltage drop due to the load at the present time) exists in any voltage value range of the control table 151, the current values corresponding to the voltage value range are the LEDs 141, 142, 143. And 144 are set as the values of the currents to be passed through.
　制御テーブル１５１は、図３に示すように、一例として、複数の制御データ１６１、１７１、１８１及び１９１を記憶している。 As shown in FIG. 3, the control table 151 stores a plurality of control data 161, 171, 181 and 191 as an example.
　制御データ１６１は、識別番号１６２「１」、電圧値範囲１６３「３．７６８以上」及び電流値１６４「２０」を含む。識別番号１６２「１」は、制御データ１６１を一意に識別する。電圧値範囲１６３「３．７６８以上」は、電圧値の範囲が３．７６８Ｖ以上であることを示す。電流値１６４「２０」は、ＬＥＤ１４１、１４２、１４３及び１４４に流す電流が２０ｍＡであることを示す。制御データ１６１によると、バッテリ１１１の電圧値（現時点における負荷による電圧降下後の電圧値）が、３．７６８Ｖ以上である場合、２０ｍＡの電流値がＬＥＤ１４１、１４２、１４３及び１４４に流す電流値として設定される。 The control data 161 includes an identification number 162 “1”, a voltage value range 163 “3.768 or more”, and a current value 164 “20”. The identification number 162 “1” uniquely identifies the control data 161. The voltage value range 163 “3.768 or more” indicates that the voltage value range is 3.768 V or more. The current value 164 “20” indicates that the current flowing through the LEDs 141, 142, 143, and 144 is 20 mA. According to the control data 161, when the voltage value of the battery 111 (the voltage value after the voltage drop due to the current load) is 3.768V or more, the current value of 20 mA is the current value that flows through the LEDs 141, 142, 143, and 144. Is set.
　また、制御データ１７１は、識別番号１７２「２」、電圧値範囲１７３「３．７０７～３．７６７」及び電流値１７４「１５」を含む。識別番号１７２「２」は、制御データ１７１を一意に識別する。電圧値範囲１７３「３．７０７～３．７６７」は、電圧値の範囲が３．７０７Ｖ以上、３．７６７Ｖ以下であることを示す。電流値１７４「１５」は、ＬＥＤ１４１、１４２、１４３及び１４４に流す電流が１５ｍＡであることを示す。制御データ１７１によると、バッテリ１１１の電圧値（現時点における負荷による電圧降下後の電圧値）が、３．７０７Ｖ以上、３．７６７Ｖ以下である場合、１５ｍＡの電流値がＬＥＤ１４１、１４２、１４３及び１４４に流す電流値として設定される。 Also, the control data 171 includes an identification number 172 “2”, a voltage value range 173 “3.707 to 3.767”, and a current value 174 “15”. The identification number 172 “2” uniquely identifies the control data 171. The voltage value range 173 “3.707 to 3.767” indicates that the voltage value range is 3.707V or more and 3.767V or less. The current value 174 “15” indicates that the current flowing through the LEDs 141, 142, 143, and 144 is 15 mA. According to the control data 171, when the voltage value of the battery 111 (the voltage value after the voltage drop due to the current load) is 3.707V or more and 3.767V or less, the current value of 15mA is the LED 141, 142, 143 and 144. It is set as a current value to be passed through.
　また、制御データ１８１は、識別番号１８２「３」、電圧値範囲１８３「３．６５６～３．７０６」及び電流値１８４「１３」を含む。識別番号１８２「３」は、制御データ１８１を一意に識別する。電圧値範囲１８３「３．６５６～３．７０６」は、電圧値の範囲が３．６５６Ｖ以上、３．７０６Ｖ以下であることを示す。電流値１８４「１３」は、ＬＥＤ１４１、１４２、１４３及び１４４に流す電流が１３ｍＡであることを示す。制御データ１８１によると、バッテリ１１１の電圧値（現時点における負荷による電圧降下後の電圧値）が、３．６５６Ｖ以上、３．７０６Ｖ以下である場合、１３ｍＡの電流値がＬＥＤ１４１、１４２、１４３及び１４４に流す電流値として設定される。 The control data 181 includes an identification number 182 “3”, a voltage value range 183 “3.656 to 3.706”, and a current value 184 “13”. The identification number 182 “3” uniquely identifies the control data 181. The voltage value range 183 “3.656 to 3.706” indicates that the voltage value range is 3.656V or more and 3.706V or less. The current value 184 “13” indicates that the current passed through the LEDs 141, 142, 143, and 144 is 13 mA. According to the control data 181, when the voltage value of the battery 111 (the voltage value after the voltage drop due to the current load) is 3.656 V or more and 3.706 V or less, the current value of 13 mA is the LED 141, 142, 143 and 144. It is set as a current value to be passed through.
　また、制御データ１９１は、識別番号１９２「４」、電圧値範囲１９３「３．６５５～３．４００」及び電流値１９４「１０」を含む。識別番号１９２「４」は、制御データ１９１を一意に識別する。電圧値範囲１９３「３．６５５～３．４００」は、電圧値の範囲が３．６５５Ｖ以上、３．４００Ｖ以下であることを示す。電流値１９４「１０」は、ＬＥＤ１４１、１４２、１４３及び１４４に流す電流が１０ｍＡであることを示す。制御データ１９１によると、バッテリ１１１の電圧値（現時点における負荷による電圧降下後の電圧値）が、３．６５５Ｖ以上、３．４００Ｖ以下である場合、１０ｍＡの電流値がＬＥＤ１４１、１４２、１４３及び１４４に流す電流値として設定される。 The control data 191 includes an identification number 192 “4”, a voltage value range 193 “3.655-3.400”, and a current value 194 “10”. The identification number 192 “4” uniquely identifies the control data 191. The voltage value range 193 “3.655 to 3.400” indicates that the voltage value range is 3.655V or more and 3.400V or less. A current value 194 “10” indicates that the current flowing through the LEDs 141, 142, 143, and 144 is 10 mA. According to the control data 191, when the voltage value of the battery 111 (the voltage value after the voltage drop due to the load at the present time) is 3.655V or more and 3.400V or less, the current value of 10mA is the LED 141, 142, 143 and 144. It is set as a current value to be passed through.
　次に、制御テーブル１５１に示すように、電圧値範囲及び電流値を設定する理由について、図４に示すデータテーブル２０１を用いて説明する。 Next, the reason why the voltage value range and the current value are set as shown in the control table 151 will be described with reference to the data table 201 shown in FIG.
　データテーブル２０１は、７行のデータ列２１１、２１２、・・・、２１７を含んでいる。第１行のデータ列２１１の各データは、電池残量をパーセントで示す。 The data table 201 includes seven rows of data columns 211, 212,. Each data in the data column 211 in the first row indicates the remaining battery level as a percentage.
　第２行のデータ列２１２の各データは、実測値であり、第１行のデータ列２１１の電池残量に対応し、電力消費をする負荷がない状態における電池電圧を示す。単位は、ｍＶ（ミリボルト）である。 Each data in the data column 212 in the second row is an actual measurement value, corresponding to the remaining battery level in the data column 211 in the first row, and indicating the battery voltage in a state where there is no load that consumes power. The unit is mV (millivolt).
　第３行のデータ列２１３の各データは、実測値であり、第１行のデータ列２１１の電池残量に対応し、携帯端末１００に最大の電力消費をする負荷をかけた場合における電池電圧を示す。単位は、ｍＶ（ミリボルト）である。ここで、負荷の一例は、通話、電子メールの送受信、データの送受信、ウェブブラウザ、音楽の再生、カメラによる撮影などである。また、最大の電力消費をする負荷は、携帯端末１００において、同時に使用できる負荷の組合せのうち、電力消費が最大となるものである。 Each data in the data row 213 in the third row is an actual measurement value, corresponding to the remaining battery level in the data row 211 in the first row, and the battery voltage when a load that consumes the maximum power is applied to the mobile terminal 100 Indicates. The unit is mV (millivolt). Here, an example of the load is a call, transmission / reception of e-mail, transmission / reception of data, web browser, music playback, camera shooting, and the like. The load that consumes the maximum power is the power consumption that is the largest among the combinations of loads that can be used simultaneously in the mobile terminal 100.
　第４行のデータ列２１４の各データは、第３行のデータ列の対応するデータと同じ値である。第４行のデータ列２１４の各データは、ＬＥＤの順電圧として示している。 Each data in the data column 214 in the fourth row has the same value as the corresponding data in the data column in the third row. Each data in the data column 214 in the fourth row is shown as a forward voltage of the LED.
　第５行のデータ列２１５の各データは、ＬＥＤの順電圧－順電流特性に基づくＬＥＤの順電流を示す。第５行のデータ列２１５の各順電流は、第４行のデータ列２１４の対応する順電圧に対応している。 Each data in the data column 215 in the fifth row indicates the LED forward current based on the LED forward voltage-forward current characteristics. Each forward current in the data column 215 in the fifth row corresponds to a corresponding forward voltage in the data column 214 in the fourth row.
　第６行のデータ列２１６の各データは、ＬＥＤに対して設定する電流値を示す。ここで、第５行のデータ列２１５の各データと、対応する第６行のデータ列２１６のデータとの差は、閾値より、小さい。また、閾値は、一例として、５．０である。 Each data in the data column 216 in the sixth row indicates a current value set for the LED. Here, the difference between the data in the data column 215 in the fifth row and the data in the corresponding data column 216 in the sixth row is smaller than the threshold value. The threshold is 5.0 as an example.
　第７行のデータ列２１７の各データは、図３の制御テーブル１５１の識別番号を示す。
　図４に示すように、電池残量が３０パーセントである場合、負荷無しの状態の電池電圧は、３７６８ｍＶであり、最大の電力消費をする負荷をかけた状態の電池電圧は、３５６２ｍＶである。ＬＥＤの順電圧－順電流特性に基づいて、最大の電力消費をする負荷をかけた状態の電池電圧（３５６２ｍＶ）に対する順電流は、２０．２ｍＡである。そこで、２０．２ｍＡより小さい２０．０ｍＡをＬＥＤの設定電流値とする。ここで、２０．２ｍＡと２０．０ｍＡとの差は、閾値より、小さい。 Each data in the data column 217 of the seventh row indicates an identification number of the control table 151 in FIG.
As shown in FIG. 4, when the remaining battery level is 30%, the battery voltage in the no load state is 3768 mV, and the battery voltage in the state where the load that consumes the maximum power is applied is 3562 mV. Based on the forward voltage-forward current characteristics of the LED, the forward current is 20.2 mA for the battery voltage (3562 mV) under a load that consumes the maximum power. Therefore, 20.0 mA smaller than 20.2 mA is set as the set current value of the LED. Here, the difference between 20.2 mA and 20.0 mA is smaller than the threshold value.
　電池残量が２５パーセントである場合、負荷無しの状態の電池電圧は、３７５６ｍＶであり、最大の電力消費をする負荷をかけた状態の電池電圧は、３５４６ｍＶである。ＬＥＤの順電圧－順電流特性に基づいて、最大の電力消費をする負荷をかけた状態の電池電圧（３５４６ｍＶ）に対する順電流は、１９．８ｍＡである。そこで、１９．８ｍＡより小さい１５．０ｍＡをＬＥＤの設定電流値とする。１９．８ｍＡと１５．０ｍＡとの差は、閾値より、小さい。 When the remaining battery level is 25%, the battery voltage in the no load state is 3756 mV, and the battery voltage in the state where the load that consumes the maximum power is applied is 3546 mV. Based on the forward voltage-forward current characteristics of the LED, the forward current with respect to the battery voltage (3546 mV) in a state of applying a load that consumes the maximum power is 19.8 mA. Therefore, 15.0 mA, which is smaller than 19.8 mA, is set as the set current value of the LED. The difference between 19.8 mA and 15.0 mA is smaller than the threshold value.
　電池残量が２０パーセント、及び、１５パーセントである場合、上記と同様にして、それぞれ、１５．０ｍＡをＬＥＤの設定電流値とする。 When the remaining battery level is 20% and 15%, 15.0 mA is set as the set current value of the LED in the same manner as described above.
　電池残量が１０パーセントである場合、負荷無しの状態の電池電圧は、３６７４ｍＶであり、最大の電力消費をする負荷をかけた状態の電池電圧は、３４７４ｍＶである。ＬＥＤの順電圧－順電流特性に基づいて、最大の電力消費をする負荷をかけた状態の電池電圧（３４７４ｍＶ）に対する順電流は、１５．４ｍＡである。そこで、１５．４ｍＡより小さい１３．０ｍＡをＬＥＤの設定電流値とする。１５．４ｍＡと１３．０ｍＡとの差は、閾値より、小さい。 When the battery remaining amount is 10%, the battery voltage in the no load state is 3673 mV, and the battery voltage in the state where the load that consumes the maximum power is applied is 3474 mV. Based on the forward voltage-forward current characteristics of the LED, the forward current is 15.4 mA for the battery voltage (3474 mV) under a load that consumes the maximum power. Therefore, 13.0 mA, which is smaller than 15.4 mA, is set as the set current value of the LED. The difference between 15.4 mA and 13.0 mA is smaller than the threshold value.
　電池残量が５パーセントである場合、上記と同様にして、１３．０ｍＡをＬＥＤの設定電流値とする。 When the remaining battery level is 5%, 13.0 mA is set as the set current value of the LED in the same manner as described above.
　電池残量が０パーセントである場合、負荷無しの状態の電池電圧は、３４００ｍＶであり、最大の電力消費をする負荷をかけた状態の電池電圧は、３３００ｍＶである。ＬＥＤの順電圧－順電流特性に基づいて、最大の電力消費をする負荷をかけた状態の電池電圧（３３００ｍＶ）に対する順電流は、１０．２ｍＡである。そこで、１０．２ｍＡより小さい１０．０ｍＡをＬＥＤの設定電流値とする。１０．２ｍＡと１０．０ｍＡとの差は、閾値より、小さい。 When the remaining battery level is 0%, the battery voltage without load is 3400 mV, and the battery voltage with a load that consumes the maximum power is 3300 mV. Based on the forward voltage-forward current characteristics of the LED, the forward current with respect to the battery voltage (3300 mV) under a load that consumes the maximum power is 10.2 mA. Therefore, 10.0 mA, which is smaller than 10.2 mA, is set as the set current value of the LED. The difference between 10.2 mA and 10.0 mA is smaller than the threshold value.
　以上説明したように、各電圧値範囲について、最も小さい電流値を決定することにより、各電圧値範囲内において、電圧の変動があった場合に、ＬＥＤの光度を最も低くし、その結果、液晶表示部１１０ｂがちらついて見えることを防ぐことができる。各電圧値範囲について、設定電流値を決定し、図３に示す電圧値範囲毎に電流値を記憶する制御テーブル１５１を生成する。 As described above, by determining the smallest current value for each voltage value range, when there is a voltage variation within each voltage value range, the luminous intensity of the LED is minimized, and as a result, the liquid crystal It is possible to prevent the display unit 110b from flickering. A set current value is determined for each voltage value range, and a control table 151 that stores a current value for each voltage value range shown in FIG. 3 is generated.
　（２）アンテナ１０１及び無線通信部１０２
　アンテナ１０１は、無線基地局との間で無線回線を介して無線信号を送受信する。無線通信部１０２は、アンテナ１０１により送受信される無線信号の周波数選択や周波数変換等を行う。 (2) Antenna 101 and wireless communication unit 102
The antenna 101 transmits and receives radio signals to and from the radio base station via a radio line. The wireless communication unit 102 performs frequency selection, frequency conversion, and the like of a wireless signal transmitted and received by the antenna 101.
　（３）スピーカ１０７、マイク１０８、音声処理部１０６、キー入力部１０５、入力制御部１０４及びタイマ１１６
　スピーカ１０７は、音声等の音響を出力する。マイク１０８は、音声等の音響を入力する。 (3) Speaker 107, microphone 108, voice processing unit 106, key input unit 105, input control unit 104, and timer 116
The speaker 107 outputs sound such as voice. The microphone 108 inputs sound such as voice.
　音声処理部１０６は、無線通信部１０２により受信された音声信号を復調してスピーカ１０７に対して音響信号として出力する。マイク１０８より入力された音響信号に対応して電気信号に変換された音声信号を変調し、無線通信部１０２により送信させる。 The audio processing unit 106 demodulates the audio signal received by the wireless communication unit 102 and outputs it to the speaker 107 as an acoustic signal. The audio signal converted into an electrical signal corresponding to the acoustic signal input from the microphone 108 is modulated and transmitted by the wireless communication unit 102.
　キー入力部１０５は、携帯端末１００をＯＮ又はＯＦＦとするための電源スイッチとしての電源キー、テンキー、その他のキーやボタンを含む。キー入力部１０５は、これらのキーやボタンが操作されると、操作されたキーやボタンに対応する操作情報を生成する。次に、キー入力部１０５は、入力制御部１０４を介して、生成した操作情報を制御部１０３に対して出力する。 The key input unit 105 includes a power key as a power switch for turning the mobile terminal 100 ON or OFF, a numeric keypad, and other keys and buttons. When these keys and buttons are operated, the key input unit 105 generates operation information corresponding to the operated keys and buttons. Next, the key input unit 105 outputs the generated operation information to the control unit 103 via the input control unit 104.
　入力制御部１０４は、キー入力部１０５と制御部１０３との間で、操作情報を中継する。タイマ１１６は、時間の経過を計測する。 The input control unit 104 relays operation information between the key input unit 105 and the control unit 103. The timer 116 measures the passage of time.
　（４）液晶パネル部１１０及び入出力制御部１０９
　（液晶パネル部１１０）
　液晶パネル部１１０は、タッチパッド部１１０ａ、液晶表示部１１０ｂ及びバックライト１１４から構成されている。液晶表示部１１０ｂは、矩形の表示面を有し、表示面には、タッチパッド部１１０ａが取り付けられている。液晶表示部１１０ｂは、制御部１０３から、入出力制御部１０９を介して受信したアイコン等やその他のオブジェクトを含む画面を表示する。タッチパッド部１１０ａは、液晶パネル部１１０の表示面に対する操作体の接触位置を検出し、検出した接触位置を、入力信号として、入出力制御部１０９に対して出力する。 (4) Liquid crystal panel unit 110 and input / output control unit 109
(LCD panel 110)
The liquid crystal panel unit 110 includes a touch pad unit 110a, a liquid crystal display unit 110b, and a backlight 114. The liquid crystal display unit 110b has a rectangular display surface, and a touch pad unit 110a is attached to the display surface. The liquid crystal display unit 110b displays a screen including icons and other objects received from the control unit 103 via the input / output control unit 109. The touch pad unit 110a detects the contact position of the operating body with respect to the display surface of the liquid crystal panel unit 110, and outputs the detected contact position to the input / output control unit 109 as an input signal.
　バックライト１１４は、液晶表示部１１０ｂの背面に設置されている。バックライト１１４は、液晶表示部１１０ｂの背面に向けて光を照射するように、４個のＬＥＤ１４１、１４２、１４３及び１４４を備えている。ＬＥＤ１４１、１４２、１４３及び１４４は、それぞれ、対応する定電流回路１３３、１３４、１３５及び１３６から定電流の順電流を供給され、供給された順電流により発光する。 The backlight 114 is installed on the back surface of the liquid crystal display unit 110b. The backlight 114 includes four LEDs 141, 142, 143, and 144 so that light is emitted toward the back surface of the liquid crystal display unit 110b. The LEDs 141, 142, 143, and 144 are supplied with constant forward current from the corresponding constant current circuits 133, 134, 135, and 136, respectively, and emit light by the supplied forward current.
　（入出力制御部１０９）
　入出力制御部１０９は、液晶パネル部１１０と制御部１０３との間で、情報の入出力を中継する。 (Input / output control unit 109)
The input / output control unit 109 relays input / output of information between the liquid crystal panel unit 110 and the control unit 103.
　（５）ＬＥＤ駆動回路１１３
　ＬＥＤ駆動回路１１３は、定電流回路１３３、１３４、１３５及び１３６から構成されている。定電流回路１３３、１３４、１３５及び１３６は、それぞれ、電源部１１２から電力の供給を受ける。定電流回路１３３、１３４、１３５及び１３６は、供給制御部１３９から電流値の指定を受け取り、受け取った電流値により示される定電流を生成し、生成した定電流を、それぞれ、ＬＥＤ１４１、１４２、１４３及び１４４に供給する。 (5) LED drive circuit 113
The LED drive circuit 113 is composed of constant current circuits 133, 134, 135 and 136. Each of the constant current circuits 133, 134, 135, and 136 is supplied with power from the power supply unit 112. The constant current circuits 133, 134, 135, and 136 receive the designation of the current value from the supply control unit 139, generate a constant current indicated by the received current value, and generate the generated constant currents as the LEDs 141, 142, 143, respectively. And 144.
　（６）バッテリ１１１及び電源部１１２
　バッテリ１１１は、充電可能な二次電池である。電源部１１２は、バッテリ１１１から出力される電力を、携帯端末１００の各構成要素に供給する。電源部１１２は、バッテリ１１１の、現時点における負荷による電圧降下後の電圧を検出する電圧検出部１２１を備えている。電圧検出部１２１は、検出された電圧値を制御部１０３に対して出力する。 (6) Battery 111 and power supply unit 112
The battery 111 is a rechargeable secondary battery. The power supply unit 112 supplies the power output from the battery 111 to each component of the mobile terminal 100. The power supply unit 112 includes a voltage detection unit 121 that detects a voltage of the battery 111 after a voltage drop due to a load at the present time. The voltage detection unit 121 outputs the detected voltage value to the control unit 103.
　（７）制御部１０３
　制御部１０３は、携帯端末１００の構成要素である無線通信部１０２、入力制御部１０４、音声処理部１０６及び入出力制御部１０９を制御する。制御部１０３は、取得部１３７、判断部１３８及び供給制御部１３９を含んでいる。 (7) Control unit 103
The control unit 103 controls the wireless communication unit 102, the input control unit 104, the voice processing unit 106, and the input / output control unit 109 that are components of the mobile terminal 100. The control unit 103 includes an acquisition unit 137, a determination unit 138, and a supply control unit 139.
　取得部１３７は、電源部１１２の電圧検出部１２１から、バッテリ１１１の、現時点における負荷による電圧降下後の電圧値を取得する。取得部１３７は、取得した電圧値を判断部１３８に対して出力する。 The acquisition unit 137 acquires the voltage value of the battery 111 after the voltage drop due to the current load from the voltage detection unit 121 of the power supply unit 112. The acquisition unit 137 outputs the acquired voltage value to the determination unit 138.
　判断部１３８は、取得された前記電圧値が、記憶部１１５に記憶されている制御テーブル１５１のいずれかの電圧値範囲内に存在するか否かを判断する。 The determining unit 138 determines whether or not the acquired voltage value is in any voltage value range of the control table 151 stored in the storage unit 115.
　供給制御部１３９は、判断部１３８により、取得された電圧値がいずれかの電圧値範囲内に存在すると判断される場合、記憶部１１５から当該電圧値範囲に対応する電流値を読み出す。供給制御部１３９は、読み出した前記電流値により示される定電流を、ＬＥＤ１４１、１４２、１４３及び１４４に供給するよう、定電流回路１３３、１３４、１３５及び１３６を制御する。 When the determination unit 138 determines that the acquired voltage value exists in any voltage value range, the supply control unit 139 reads a current value corresponding to the voltage value range from the storage unit 115. The supply control unit 139 controls the constant current circuits 133, 134, 135, and 136 so as to supply a constant current indicated by the read current value to the LEDs 141, 142, 143, and 144.
　１．２　携帯端末１００の動作
　ＬＥＤ１４１、１４２、１４３及び１４４に対して、定電流を供給する場合における携帯端末１００の動作について、図５に示すフローチャートを用いて説明する。 1.2 Operation of Mobile Terminal 100 The operation of the mobile terminal 100 when a constant current is supplied to the LEDs 141, 142, 143, and 144 will be described with reference to the flowchart shown in FIG.
　供給制御部１３９は、初期値として、ＬＥＤ１４１、１４２、１４３及び１４４に対して供給する定電流を、制御テーブル１５１の識別番号「１」に対応する電流値（２０ｍＡ）に設定する。次に、供給制御部１３９は、２０ｍＡの定電流を供給するように、定電流回路１３３、１３４、１３５及び１３６に対して、指示する。定電流回路１３３、１３４、１３５及び１３６は、それぞれ、ＬＥＤ１４１、１４２、１４３及び１４４に対して、２０ｍＡの定電流を供給する。ＬＥＤ１４１、１４２、１４３及び１４４は、それぞれ、２０ｍＡの定電流により発光する（ステップＳ１０１）。 The supply control unit 139 sets the constant current supplied to the LEDs 141, 142, 143, and 144 as an initial value to a current value (20 mA) corresponding to the identification number “1” of the control table 151. Next, the supply control unit 139 instructs the constant current circuits 133, 134, 135, and 136 to supply a constant current of 20 mA. The constant current circuits 133, 134, 135, and 136 supply a constant current of 20 mA to the LEDs 141, 142, 143, and 144, respectively. The LEDs 141, 142, 143, and 144 each emit light with a constant current of 20 mA (step S101).
　制御部１０３は、タイマ１１６により、２０秒の経過をカウントする（ステップＳ１０２）。２０秒が経過していない場合（ステップＳ１０２で「ＮＯ」）、ステップＳ１０２に戻って、処理を繰り返す。２０秒が経過した場合（ステップＳ１０２で「ＹＥＳ」）、取得部１３７は、電圧検出部１２１からバッテリ１１１の、現時点における負荷による電圧降下後の電圧値を取得することにより、読み出す（ステップＳ１０３）。 The control unit 103 uses the timer 116 to count 20 seconds (step S102). If 20 seconds have not elapsed ("NO" in step S102), the process returns to step S102 and the process is repeated. When 20 seconds have elapsed (“YES” in step S102), the acquisition unit 137 acquires the voltage value of the battery 111 after the voltage drop due to the current load from the voltage detection unit 121 and reads it (step S103). .
　判断部１３８は、記憶部１１５に記憶されている制御テーブル１５１から、読み出した電圧値を含む電圧値範囲を検索する（ステップＳ１０４）。 The determining unit 138 searches the control table 151 stored in the storage unit 115 for a voltage value range including the read voltage value (step S104).
　供給制御部１３９は、電圧値を含む電圧値範囲が存在する場合、当該電圧値範囲に対応する電流値を制御テーブル１５１から読み出す（ステップＳ１０５）。供給制御部１３９は、ＬＥＤ１４１、１４２、１４３及び１４４に対して供給する定電流を、読み出された電流値に設定する。 When the voltage value range including the voltage value exists, the supply control unit 139 reads the current value corresponding to the voltage value range from the control table 151 (step S105). The supply control unit 139 sets the constant current supplied to the LEDs 141, 142, 143, and 144 to the read current value.
　供給制御部１３９は、読み出された電流値により示される定電流を供給するように、定電流回路１３３、１３４、１３５及び１３６に対して、指示する。定電流回路１３３、１３４、１３５及び１３６は、それぞれ、ＬＥＤ１４１、１４２、１４３及び１４４に対して、読み出された電流値により示される定電流を供給する。ＬＥＤ１４１、１４２、１４３及び１４４は、それぞれ、読み出された電流値により示される定電流により発光する（ステップＳ１０６）。次に、ステップＳ１０２に戻って、処理を繰り返す。 The supply control unit 139 instructs the constant current circuits 133, 134, 135, and 136 to supply a constant current indicated by the read current value. The constant current circuits 133, 134, 135, and 136 supply constant currents indicated by the read current values to the LEDs 141, 142, 143, and 144, respectively. Each of the LEDs 141, 142, 143, and 144 emits light with a constant current indicated by the read current value (step S106). Next, it returns to step S102 and repeats a process.
　１．３　まとめ
　以上説明したように、バッテリ１１１の現時点の負荷による電圧低下を除いた電圧値の変動が選択された電圧値範囲内であれば、電流値は、一定で変動しない。各ＬＥＤの光度は、変化することなく、液晶表示部１１０ｂが、ちらつくことはない。 1.3 Summary As described above, the current value is constant and does not fluctuate if the fluctuation of the voltage value excluding the voltage drop due to the current load of the battery 111 is within the selected voltage value range. The luminous intensity of each LED does not change, and the liquid crystal display unit 110b does not flicker.
　２．その他の変形例
　本開示について、上記の実施の形態に基づいて説明しているが、上記の実施の形態には限定されない。以下に示すようにしてもよい。 2. Other Modifications The present disclosure has been described based on the above embodiment, but is not limited to the above embodiment. You may make it show below.
　（１）上記実施の形態の変形例について説明する。
　上記の実施の形態においては、一定の間隔をおいて、例えば、２０秒ごとに、バッテリ１１１の電圧値を取得する。取得した電圧値に基づいて、制御テーブル１５１を用いて、ＬＥＤに流す電流値を決定している。しかし、このような方法には、限定されない。 (1) A modification of the above embodiment will be described.
In the above embodiment, the voltage value of the battery 111 is acquired at regular intervals, for example, every 20 seconds. Based on the acquired voltage value, the control table 151 is used to determine the value of the current flowing through the LED. However, the method is not limited.
　例えば、２０秒ごとに３回連続してバッテリ１１１の、現時点における負荷による電圧降下後の電圧値を取得する。取得された３個の電圧値が同じ電圧値範囲内に存在する場合に、制御テーブル１５１の電圧値範囲に対応する電流値により、ＬＥＤに流す電流値を決定してもよい。以下において、ＬＥＤ１４１、１４２、１４３及び１４４に対して、定電流を供給する場合における携帯端末１００の動作について、図６に示すフローチャートを用いて説明する。 For example, the voltage value after the voltage drop due to the current load of the battery 111 is acquired three times every 20 seconds. When the three acquired voltage values are within the same voltage value range, the current value to be passed through the LED may be determined based on the current value corresponding to the voltage value range of the control table 151. Hereinafter, the operation of the mobile terminal 100 when a constant current is supplied to the LEDs 141, 142, 143, and 144 will be described with reference to the flowchart shown in FIG.
　３個の変数として、識別番号Ｘ、識別番号Ｙ及び識別番号Ｚを、記憶部１１５に設ける。識別番号Ｘ、識別番号Ｙ及び識別番号Ｚは、それぞれ、今回の識別番号、前回の識別番号及び前々回の識別番号を記憶するために用いられる。 The identification number X, the identification number Y, and the identification number Z are provided in the storage unit 115 as three variables. The identification number X, the identification number Y, and the identification number Z are used to store the current identification number, the previous identification number, and the previous identification number, respectively.
　供給制御部１３９は、初期値として、ＬＥＤ１４１、１４２、１４３及び１４４に対して供給する定電流を、制御テーブル１５１の識別番号「１」により示される電流値（２０ｍＡ）に設定する。次に、供給制御部１３９は、２０ｍＡの定電流を供給するように、定電流回路１３３、１３４、１３５及び１３６に対して、指示する。定電流回路１３３、１３４、１３５及び１３６は、それぞれ、ＬＥＤ１４１、１４２、１４３及び１４４に対して、２０ｍＡの定電流を供給する。ＬＥＤ１４１、１４２、１４３及び１４４は、それぞれ、２０ｍＡの定電流により発光する（ステップＳ１２１）。 The supply control unit 139 sets the constant current supplied to the LEDs 141, 142, 143, and 144 as an initial value to the current value (20 mA) indicated by the identification number “1” of the control table 151. Next, the supply control unit 139 instructs the constant current circuits 133, 134, 135, and 136 to supply a constant current of 20 mA. The constant current circuits 133, 134, 135, and 136 supply a constant current of 20 mA to the LEDs 141, 142, 143, and 144, respectively. The LEDs 141, 142, 143, and 144 each emit light with a constant current of 20 mA (step S121).
　供給制御部１３９は、初期値として、識別番号Ｘ、識別番号Ｙ及び識別番号Ｚに、それぞれ、「７」、「８」及び「９」を設定する。「７」、「８」及び「９」は、識別番号として、制御テーブル１５１に存在せず、取り得ない値である。「７」、「８」及び「９」は、異なる値であり、識別番号Ｘ、識別番号Ｙ及び識別番号Ｚに、それぞれ、異なる値が設定される（ステップＳ１２２）。 The supply control unit 139 sets “7”, “8”, and “9” in the identification number X, the identification number Y, and the identification number Z, respectively, as initial values. “7”, “8”, and “9” are values that do not exist in the control table 151 and cannot be taken as identification numbers. “7”, “8”, and “9” are different values, and different values are set for the identification number X, the identification number Y, and the identification number Z, respectively (step S122).
　制御部１０３は、タイマ１１６により、２０秒の経過をカウントする（ステップＳ１２３）。２０秒が経過していない場合（ステップＳ１２３で「ＮＯ」）、ステップＳ１２３に戻って、処理を繰り返す。２０秒が経過した場合（ステップＳ１２３で「ＹＥＳ」）、取得部１３７は、電圧検出部１２１からバッテリ１１１の電圧値を取得することにより、読み出す（ステップＳ１２４）。 The control unit 103 counts 20 seconds by the timer 116 (step S123). If 20 seconds have not elapsed ("NO" in step S123), the process returns to step S123 and the process is repeated. When 20 seconds have elapsed (“YES” in step S123), the acquisition unit 137 acquires the voltage value of the battery 111 from the voltage detection unit 121 and reads it (step S124).
　判断部１３８は、記憶部１１５に記憶されている制御テーブル１５１から、取得された電圧値を含む電圧値範囲を検索する（ステップＳ１２５）。供給制御部１３９は、識別番号Ｙに記憶されている値を識別番号Ｚに上書きする（ステップＳ１２６）。また、識別番号Ｘに記憶されている値を識別番号Ｙに上書きする（ステップＳ１２７）。 The determination unit 138 searches the control table 151 stored in the storage unit 115 for a voltage value range including the acquired voltage value (step S125). The supply control unit 139 overwrites the identification number Z with the value stored in the identification number Y (step S126). In addition, the value stored in the identification number X is overwritten on the identification number Y (step S127).
　供給制御部１３９は、電圧値を含む電圧値範囲が存在する場合、当該電圧値範囲に対応する識別番号を制御テーブル１５１から読み出す（ステップＳ１２８）。読み出した識別番号を識別番号Ｘに上書きする（ステップＳ１２９）。供給制御部１３９は、識別番号Ｘ、識別番号Ｙ及び識別番号Ｚが同一であるか否かを判断する（ステップＳ１３０）。 When the voltage value range including the voltage value exists, the supply control unit 139 reads the identification number corresponding to the voltage value range from the control table 151 (step S128). The read identification number is overwritten on the identification number X (step S129). The supply control unit 139 determines whether the identification number X, the identification number Y, and the identification number Z are the same (step S130).
　同一でない場合（ステップＳ１３０で「ＮＯ」）、ステップＳ１２３へ戻って、処理を繰り返す。識別番号Ｘ、識別番号Ｙ及び識別番号Ｚが同一である場合（ステップＳ１３０で「ＹＥＳ」）、供給制御部１３９は、当該電圧値範囲に対応する電流値を制御テーブル１５１から読み出す（ステップＳ１３１）。 If they are not identical (“NO” in step S130), the process returns to step S123 and the process is repeated. When the identification number X, the identification number Y, and the identification number Z are the same (“YES” in step S130), the supply control unit 139 reads the current value corresponding to the voltage value range from the control table 151 (step S131). .
　供給制御部１３９は、ＬＥＤ１４１、１４２、１４３及び１４４に対して供給する定電流を、読み出された電流値に設定する。供給制御部１３９は、読み出された電流値により示される定電流を供給するように、定電流回路１３３、１３４、１３５及び１３６に対して、指示する。定電流回路１３３、１３４、１３５及び１３６は、それぞれ、ＬＥＤ１４１、１４２、１４３及び１４４に対して、読み出された電流値により示される定電流を供給する。ＬＥＤ１４１、１４２、１４３及び１４４は、それぞれ、読み出された電流値により示される定電流により発光する（ステップＳ１３２）。ステップＳ１２３に戻って、処理を繰り返す。 The supply control unit 139 sets the constant current supplied to the LEDs 141, 142, 143, and 144 to the read current value. The supply control unit 139 instructs the constant current circuits 133, 134, 135, and 136 to supply a constant current indicated by the read current value. The constant current circuits 133, 134, 135, and 136 supply constant currents indicated by the read current values to the LEDs 141, 142, 143, and 144, respectively. Each of the LEDs 141, 142, 143, and 144 emits light with a constant current indicated by the read current value (step S132). Returning to step S123, the processing is repeated.
　以上説明したように、３回連続して取得したバッテリ１１１の電圧値が同じ電圧値範囲内に存在する場合に、制御テーブル１５１の電圧値範囲に対応する電流値をＬＥＤに流す電流値として、決定している。 As described above, when the voltage value of the battery 111 obtained three times in succession is within the same voltage value range, the current value corresponding to the voltage value range of the control table 151 is set as the current value flowing through the LED. Has been decided.
　以上説明した方法により、一時的に電池電圧が変動した場合には、ＬＥＤの電流値を変更しないようにできる。一時的な電池電圧の変動は、例えば、ウェブブラウザの一時的な使用により発生する。一方、継続して電池電圧が低下した場合に、ＬＥＤの電流値を変更する。こうして、液晶表示部１１０ｂの輝度が何度も切り替わることを防ぐことができる。 By the method described above, it is possible to prevent the LED current value from being changed when the battery voltage fluctuates temporarily. The temporary battery voltage fluctuation occurs, for example, due to temporary use of a web browser. On the other hand, when the battery voltage continuously decreases, the LED current value is changed. In this way, it is possible to prevent the luminance of the liquid crystal display unit 110b from switching over and over.
　なお、上記のように、３回連続して電圧値を取得することには、限定されない。２回、４回又は５回連続してバッテリ１１１の電圧値を取得してもよい。この場合、全ての電圧値が同じ電圧値範囲内に存在するとき、制御テーブル１５１の電圧値範囲に対応する電流値をＬＥＤに流す電流値として、決定してもよい。 Note that, as described above, it is not limited to acquiring the voltage value three times in succession. The voltage value of the battery 111 may be acquired twice, four times, or five times continuously. In this case, when all the voltage values are within the same voltage value range, the current value corresponding to the voltage value range of the control table 151 may be determined as the current value flowing through the LED.
　（２）上記の実施の形態では、２０秒毎に、バッテリ１１１の電圧値を取得している。しかし、これには、限定されない。１０秒毎に、３０秒毎に、又は、１分毎に、バッテリ１１１の電圧値を取得してもよい。 (2) In the above embodiment, the voltage value of the battery 111 is acquired every 20 seconds. However, this is not a limitation. The voltage value of the battery 111 may be acquired every 10 seconds, every 30 seconds, or every minute.
　（３）上記の実施の形態では、制御テーブル１５１は、４組の電圧値範囲及び電流値を有している。しかし、これには限定されない。制御テーブル１５１は、さらに多くの組の電圧値範囲及び電流値を有するとしてもよい。 (3) In the above embodiment, the control table 151 has four sets of voltage value ranges and current values. However, it is not limited to this. The control table 151 may have a larger number of sets of voltage value ranges and current values.
　（４）上記の実施の形態では、図２に示すように、ＬＥＤ１４１、１４２、１４３及び１４４は、ＬＥＤ駆動回路１１３から見て、並列に配置されている。 (4) In the above embodiment, as shown in FIG. 2, the LEDs 141, 142, 143, and 144 are arranged in parallel as viewed from the LED drive circuit 113.
　なお、携帯端末１００においては、ＬＥＤ１４１、１４２、１４３及び１４４を直列に接続することはない。例えば、４個のＬＥＤを直列に接続すると、各ＬＥＤが３．３Ｖの電圧を必要とするなら、全体で、１３．２Ｖ（３．３Ｖ×４）の電圧を要する。これは、バッテリ１１１が出力できる電圧を超えている。 In the portable terminal 100, the LEDs 141, 142, 143, and 144 are not connected in series. For example, when four LEDs are connected in series, if each LED requires a voltage of 3.3 V, a total voltage of 13.2 V (3.3 V × 4) is required. This exceeds the voltage that the battery 111 can output.
　（５）電圧検出部１２１は、バッテリ１１１の、現時点における負荷による電圧降下前の電圧値を検出してもよい。この場合、判断部１３８は、電圧検出部１２１により検出された電圧値に、現時点の使用状況に応じた負荷による電圧差分値を加算して、電圧値を算出する。これにより、現時点における負荷による電圧降下後の電圧値が算出される。判断部１３８は、記憶部１１５に記憶されている制御テーブル１５１から、算出された電圧値を含む電圧値範囲を検索する。 (5) The voltage detection unit 121 may detect the voltage value of the battery 111 before the voltage drop due to the current load. In this case, the determination unit 138 adds the voltage difference value due to the load according to the current usage state to the voltage value detected by the voltage detection unit 121 to calculate the voltage value. Thereby, the voltage value after the voltage drop by the load at the present time is calculated. The determination unit 138 searches the control table 151 stored in the storage unit 115 for a voltage value range including the calculated voltage value.
　（６）上記の実施の形態では、バックライト１１４は、液晶表示部１１０ｂの背面に設置されている。しかし、このような配置には、限定されない。導光板、導光筺体、導光管等が液晶表示部１１０ｂの背面に配置されてもよい。バックライト１１４は、導光板、導光筺体、導光管等を介して、液晶表示部１１０ｂの背面に光を照射する。 (6) In the above embodiment, the backlight 114 is installed on the back surface of the liquid crystal display unit 110b. However, the arrangement is not limited. A light guide plate, a light guide housing, a light guide tube, and the like may be disposed on the back surface of the liquid crystal display unit 110b. The backlight 114 irradiates light to the back surface of the liquid crystal display unit 110b through a light guide plate, a light guide housing, a light guide tube, and the like.
　（７）上述したように、本発明の携帯端末は、マイクロプロセッサとメモリとを備えたコンピュータシステムである。前記メモリは、コンピュータプログラムを記憶しており、前記マイクロプロセッサは、前記コンピュータプログラムに従って動作する。 (7) As described above, the portable terminal of the present invention is a computer system including a microprocessor and a memory. The memory stores a computer program, and the microprocessor operates according to the computer program.
　ここで、コンピュータプログラムは、所定の機能を達成するために、コンピュータに対する指令を示す命令コードが複数個組み合わされて構成されたものである。また、前記コンピュータプログラムは、コンピュータ読み取り可能な記録媒体、例えば、フレキシブルディスク、ハードディスク、ＣＤ―ＲＯＭ、ＭＯ、ＤＶＤ、ＤＶＤ－ＲＯＭ、ＤＶＤ－ＲＡＭ、ブルーレィディスク、半導体メモリなどに記録されている、としてもよい。また、前記コンピュータプログラムを、電気通信回線、無線又は有線通信回線、インターネットを代表とするネットワーク、データ放送等を経由して伝送するとしてもよい。 Here, the computer program is configured by combining a plurality of instruction codes indicating instructions to the computer in order to achieve a predetermined function. The computer program is recorded on a computer-readable recording medium such as a flexible disk, hard disk, CD-ROM, MO, DVD, DVD-ROM, DVD-RAM, Blu-ray disk, semiconductor memory, etc. Also good. The computer program may be transmitted via an electric communication line, a wireless or wired communication line, a network represented by the Internet, a data broadcast, or the like.
　また、前記コンピュータプログラムを前記記録媒体に記録して移送してもよい。又は、前記コンピュータプログラムを、ネットワーク等を経由して、移送してもよい。こうして、前記コンピュータプログラムを、独立した他のコンピュータシステムにより実行する。 Further, the computer program may be recorded on the recording medium and transferred. Alternatively, the computer program may be transferred via a network or the like. Thus, the computer program is executed by another independent computer system.
　（８）上記実施の形態及び上記変形例をそれぞれ組み合わせる、としてもよい。
　今回開示された実施の形態はすべての点で例示であって制限的なものではないと考えられるべきである。本開示の範囲は上記した説明ではなくて請求の範囲によって示され、請求の範囲と均等の意味および範囲内でのすべての変更が含まれることが意図される。 (8) The above embodiment and the above modifications may be combined.
The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present disclosure is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.
　本開示にかかるＬＥＤの駆動装置は、昇圧回路を設けることなく、表示部のちらつきを防止することができる。このため、携帯端末の表示部にバックライトとして光を照射するＬＥＤを駆動制御する技術として有用である。 The LED driving device according to the present disclosure can prevent the display unit from flickering without providing a booster circuit. For this reason, it is useful as a technique for driving and controlling an LED that emits light as a backlight to the display unit of the portable terminal.
　１００　携帯端末、１０１　アンテナ、１０２　無線通信部、１０３　制御部、１０４　入力制御部、１０５　キー入力部、１０６　音声処理部、１０７　スピーカ、１０８　マイク、１０９　入出力制御部、１１０　液晶パネル部、１１０ａ　タッチパッド部、１１０ｂ　液晶表示部、１１１　バッテリ、１１２　電源部、１１３　ＬＥＤ駆動回路、１１４　バックライト、１１５　記憶部、１１６　タイマ、１２１　電圧検出部、１３３，１３４，１３５，１３６　定電流回路、１３７　取得部、１３８　判断部、１３９　供給制御部、１４１，１４２，１４３，１４４　ＬＥＤ 100 mobile terminal, 101 antenna, 102 wireless communication unit, 103 control unit, 104 input control unit, 105 key input unit, 106 audio processing unit, 107 speaker, 108 microphone, 109 input / output control unit, 110 liquid crystal panel unit, 110a touch Pad unit, 110b Liquid crystal display unit, 111 battery, 112 power supply unit, 113 LED drive circuit, 114 backlight, 115 storage unit, 116 timer, 121 voltage detection unit, 133, 134, 135, 136 constant current circuit, 137 acquisition unit 138 Judgment part 139 Supply control part 141, 142, 143, 144 LED

Claims (6)

  1. 　携帯端末の表示部にバックライトとして光を照射するＬＥＤの駆動装置であって、
    　前記携帯端末の無負荷状態における電池の電圧値範囲と、前記ＬＥＤの順電圧順電流特性において、当該電圧値範囲に対応する特性電流値より小さい電流値とを記憶するように構成された記憶部と、
    　前記電池の、現時点における負荷による電圧降下後の電圧値を取得するように構成された取得部と、
    　取得された前記電圧値が前記電圧値範囲内に存在するか否かを判断するように構成された判断部と、
    　前記電圧値範囲内に存在する場合、前記記憶部から当該電圧値範囲に対応する前記電流値を読み出し、読み出した前記電流値により示される定電流を前記ＬＥＤに供給するよう制御するように構成された供給制御部と、
    　前記電流値により示される定電流を前記ＬＥＤに供給するように構成された定電流部とを備える、ＬＥＤの駆動装置。     An LED driving device that emits light as a backlight on a display unit of a portable terminal,
    A storage unit configured to store a voltage value range of the battery in a no-load state of the portable terminal and a current value smaller than a characteristic current value corresponding to the voltage value range in the forward voltage forward current characteristic of the LED. When,
    An acquisition unit configured to acquire a voltage value of the battery after a voltage drop due to a load at a current time;
    A determination unit configured to determine whether or not the acquired voltage value is within the voltage value range;
    When the voltage value is within the voltage value range, the current value corresponding to the voltage value range is read from the storage unit, and a constant current indicated by the read current value is supplied to the LED. Supply control unit,
    An LED driving device comprising: a constant current unit configured to supply a constant current indicated by the current value to the LED.
  2. 　前記記憶部に記憶されている前記電流値は、前記電池の電圧値範囲の下限値から前記携帯端末に負荷をかけた場合に生じる電圧降下の最大値を除いた電圧値に対応する特性電流値より小さい電流値である、請求項１に記載のＬＥＤの駆動装置。 The current value stored in the storage unit is a characteristic current value corresponding to a voltage value excluding a maximum value of a voltage drop generated when a load is applied to the mobile terminal from a lower limit value of a voltage value range of the battery. The LED drive device according to claim 1, wherein the LED has a smaller current value.
  3. 　前記取得部は、定期的に前記電圧値を取得し、
    　前記判断部は、前記電圧値の取得の都度、前記判断を行う、請求項２に記載のＬＥＤの駆動装置。     The acquisition unit periodically acquires the voltage value,
    The LED driving device according to claim 2, wherein the determination unit performs the determination each time the voltage value is acquired.
  4. 　前記取得部は、連続して複数の電圧値を取得し、
    　前記判断部は、取得された前記複数の電圧値が前記電圧値範囲内に存在するか否かを判断し、
    　前記供給制御部は、前記複数の電圧値が、前記電圧値範囲内に存在する場合、前記電流値により示される定電流を前記ＬＥＤに供給するよう制御する、請求項２に記載のＬＥＤの駆動装置。     The acquisition unit continuously acquires a plurality of voltage values,
    The determination unit determines whether or not the plurality of acquired voltage values are within the voltage value range;
    The LED drive according to claim 2, wherein the supply control unit controls the LED to supply a constant current indicated by the current value when the plurality of voltage values are within the voltage value range. apparatus.
  5. 　携帯端末の表示部にバックライトとして光を照射するＬＥＤの駆動装置において用いられる制御方法であって、
    　前記駆動装置は、
    　前記携帯端末の無負荷状態における電池の電圧値範囲と、前記ＬＥＤの順電圧順電流特性において、当該電圧値範囲に対応する特性電流値より小さい電流値とを記憶するように構成された記憶部、及び、前記電流値により示される定電流を前記ＬＥＤに供給するように構成された定電流部を含み、
    　前記制御方法は、
    　前記電池の、現時点における負荷による電圧降下後の電圧値を取得するステップと、
    　取得された前記電圧値が前記電圧値範囲内に存在するか否かを判断するステップと、
    　前記電圧値範囲内に存在する場合、前記記憶部から当該電圧値範囲に対応する前記電流値を読み出し、読み出した前記電流値により示される定電流を前記ＬＥＤに供給するよう制御するステップとを備える、制御方法。     A control method used in an LED driving device that irradiates light as a backlight to a display unit of a portable terminal,
    The driving device includes:
    A storage unit configured to store a voltage value range of the battery in a no-load state of the portable terminal and a current value smaller than a characteristic current value corresponding to the voltage value range in the forward voltage forward current characteristic of the LED. And a constant current unit configured to supply a constant current indicated by the current value to the LED,
    The control method is:
    Obtaining a voltage value of the battery after a voltage drop due to a current load;
    Determining whether the acquired voltage value is within the voltage value range; and
    A step of reading the current value corresponding to the voltage value range from the storage unit when the voltage value is within the voltage value range and controlling the LED to supply a constant current indicated by the read current value. , Control method.
  6. 　電池と、
    　表示部と、
    　前記表示部にバックライトとして光を照射するように構成されたＬＥＤと、
    　前記電池の無負荷状態における電圧値範囲と、前記ＬＥＤの順電圧順電流特性において、当該電圧値範囲に対応する特性電流値より小さい電流値とを記憶するように構成された記憶部と、
    　前記電池の、現時点における負荷による電圧降下後の電圧値を取得するように構成された取得部と、
    　取得された前記電圧値が前記電圧値範囲内に存在するか否かを判断するように構成された判断部と、
    　前記電圧値範囲内に存在する場合、前記記憶部から当該電圧値範囲に対応する前記電流値を読み出し、読み出した前記電流値により示される定電流を前記ＬＥＤに供給するよう制御するするように構成された供給制御部と、
    　前記電流値により示される定電流を前記ＬＥＤに供給するように構成された定電流部とを備える、携帯端末。     Battery,
    A display unit;
    An LED configured to irradiate the display unit with light as a backlight; and
    A storage unit configured to store a voltage value range in a no-load state of the battery and a current value smaller than a characteristic current value corresponding to the voltage value range in the forward voltage forward current characteristics of the LED;
    An acquisition unit configured to acquire a voltage value of the battery after a voltage drop due to a load at a current time;
    A determination unit configured to determine whether or not the acquired voltage value is within the voltage value range;
    When present within the voltage value range, the current value corresponding to the voltage value range is read from the storage unit, and a constant current indicated by the read current value is controlled to be supplied to the LED A supply control unit,
    A portable terminal comprising: a constant current unit configured to supply a constant current indicated by the current value to the LED.
PCT/JP2015/056693 2014-03-07 2015-03-06 Driving device for led, control method, and portable terminal WO2015133615A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
JP2014-045703 2014-03-07
JP2014045703A JP6291290B2 (en) 2014-03-07 2014-03-07 LED driving device, control method, and portable terminal

Publications (1)

Publication Number Publication Date
WO2015133615A1 true WO2015133615A1 (en) 2015-09-11

Family

ID=54055415

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/JP2015/056693 WO2015133615A1 (en) 2014-03-07 2015-03-06 Driving device for led, control method, and portable terminal

Country Status (2)

Country Link
JP (1) JP6291290B2 (en)
WO (1) WO2015133615A1 (en)

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2002359090A (en) * 2000-05-12 2002-12-13 Rohm Co Ltd Illumination led element driving circuit for display device in portable apparatus
JP2003332623A (en) * 2002-05-07 2003-11-21 Rohm Co Ltd Light emitting element drive device and electronic apparatus having light emitting element
JP2007059205A (en) * 2005-08-24 2007-03-08 Sharp Corp Power supply circuit and electronic equipment provided with the same

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP4749216B2 (en) * 2006-04-27 2011-08-17 京セラ株式会社 Method and apparatus for controlling power of wireless communication terminal

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2002359090A (en) * 2000-05-12 2002-12-13 Rohm Co Ltd Illumination led element driving circuit for display device in portable apparatus
JP2003332623A (en) * 2002-05-07 2003-11-21 Rohm Co Ltd Light emitting element drive device and electronic apparatus having light emitting element
JP2007059205A (en) * 2005-08-24 2007-03-08 Sharp Corp Power supply circuit and electronic equipment provided with the same

Also Published As

Publication number Publication date
JP2015171047A (en) 2015-09-28
JP6291290B2 (en) 2018-03-14

Similar Documents

Publication Publication Date Title
TW200615733A (en) Power source device and portable machine
WO2013136671A1 (en) Lighting apparatus, and lighting adjustment method
US8710771B2 (en) Duty cycle adjustment of remote illumination source to maintain illumination output
JP2013243910A (en) State-of-charge indicator for battery pack
JP2005523623A (en) Remote control with low voltage status display
KR100608790B1 (en) A method and a apparatus of indication battery capacity for mobile phone
US20100328065A1 (en) Warning circuit and electronic device
US11486936B2 (en) Power supply on-off detection circuit, method, and storage medium
JP6291290B2 (en) LED driving device, control method, and portable terminal
US20070052535A1 (en) Object locator system
US20160192094A1 (en) Device for playing music and control method thereof
US9344545B2 (en) Wireless ear phone and sound broadcasting method thereof
US7411372B2 (en) Digital device with rechargeable battery and recharging method thereof
JP2002190327A (en) Battery pack
JP2006217346A (en) Mobile terminal, charging device, communication system unit, report control method, report control program, and recording medium
JP2007040938A (en) Battery residual quantity display device and portable device using the same
US20110148308A1 (en) Handheld device having lateral illumination for keypad
JP2014530590A (en) Battery charging with dynamic current limit
JP2007142617A (en) Transmitter
JP5741176B2 (en) Electronics
KR20150049359A (en) Apparatus and method for detecting battery life-time and remote controller having the same
US8094032B2 (en) Voltage detecting circuit
JP5509955B2 (en) Semiconductor device and electronic apparatus using the same
TWI417760B (en) Remote controller and electric charge reminding system
US20230419928A1 (en) Indicator device, electronic musical instrument, light emission control method and storage medium

Legal Events

Date Code Title Description
121 Ep: the epo has been informed by wipo that ep was designated in this application

Ref document number: 15757842

Country of ref document: EP

Kind code of ref document: A1

NENP Non-entry into the national phase

Ref country code: DE

122 Ep: pct application non-entry in european phase

Ref document number: 15757842

Country of ref document: EP

Kind code of ref document: A1