JP2007089265A - Portable electronic device and method for charging battery in portable electronic device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a portable electronic device for effectively utilizing a battery capacity without a waste and used for a long time even if the battery capacity of a sub battery is not large, and a method for charging the battery in the portable electronic device. <P>SOLUTION: A control section 105 switches from a main battery 103 to the sub battery 108, operates it in a power saving mode when an output from the main battery 103 is a first preset voltage in the vicinity of a lower limit for operating the portable electronic device or less, boosts the output from the main battery, and charges the sub battery when an output from the sub battery 108 is a second preset voltage for operating the portable electronic device or less. In the power saving mode, the control section reduces its operating clock frequency, restricts a camera function, activates an off-line mode for inhibiting a call, deactivates a back light function, and uses a voltage boosting circuit of a back light as a circuit for boosting the output from the main battery. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a portable electronic device, and more particularly to a portable electronic device provided with a sub-battery charging circuit when switching between a main battery and a sub-battery and a battery charging method for the portable electronic device.

  Currently, lithium-ion batteries are the mainstream power source for portable electronic devices. Generally, lithium-ion batteries used in mobile phones and the like have a battery voltage of about 4.2 V when fully charged, and are discharged. If the battery voltage is too high, the function as a battery will be significantly reduced. Therefore, a mechanism has been considered in which an overdischarge protection circuit is built in and the protection circuit is operated when the battery voltage reaches about 2.3V. When the battery voltage becomes about 3.4 V, the battery voltage drops rapidly due to the load current due to the discharge load characteristics (see FIGS. 2 and 3 to be described later). A mechanism for displaying a battery exhaustion alarm at 4 V and turning the power off is considered. However, in the power source of this portable electronic device, the remaining battery capacity within a certain voltage range (about 3.4 V to 2.3 V) of the lithium ion battery cannot be used for the operation of the electronic device.

On the other hand, regarding a power supply device for an electronic device having a main battery and a rechargeable sub battery, the reduced voltage of the main battery is used for the purpose of effectively using energy remaining in the main battery after switching the power source to the sub battery. There has been proposed a power supply device that uses a booster circuit that boosts the energy of a main battery to a sub battery (see Patent Document 1).
JP 2004-336934 A

  As a method for making available the remaining battery capacity of a battery that is not used for the operation of a portable electronic device, the power supply device described in Patent Document 1 boosts the reduced voltage of the main battery and transfers it to the sub battery. It is. However, in this power supply device, after the main battery is consumed, it is simply switched to the secondary battery, and both the main battery and the secondary battery are treated equally as power sources for electronic devices. After switching to, the operation time of the electronic device could not be secured sufficiently, and eventually the total operation time of the main battery and the sub battery could not be sufficiently extended.

An object of the present invention is to solve the above problems and provide a portable electronic device and a battery charging method for the portable electronic device that can effectively use the battery capacity without waste and can extend the operation time. To do.
An object of the present invention is to provide a portable electronic device that can be used for a long time even if the battery capacity of the sub-battery is not so large, and a battery charging method for the portable electronic device.

  The portable electronic device of the present invention is a portable electronic device having a main battery and a sub-battery, and the first set voltage (for example, a lithium ion battery) near the lower limit at which the output of the main battery can operate the portable electronic device. In this case, when V1 = 3.4V) or less, the main battery is switched to the sub battery and the power saving mode is set to operate, so that the sub battery can operate the portable electronic device (for example, lithium). In the case of an ion battery, it has a control unit that boosts the output of the main battery and charges the sub-battery when V2 = 3.6 V or less, or the main battery and at least two sub-batteries The output of the main battery is equal to or lower than a first set voltage near the lower limit at which the portable electronic device can operate. The main battery is switched to the first sub-battery, and when the output of the first sub-battery falls below the second set voltage at which the portable electronic device can operate, the output of the main battery is boosted. The first sub-battery is charged, and when the output of the first sub-battery becomes equal to or lower than the first set voltage near the lower limit at which the portable electronic device can be operated, Switch to the battery, and when the output of the second sub-battery becomes equal to or lower than the second set voltage at which the portable electronic device can operate, the output of the first sub-battery is boosted and the first sub-battery is charged. A control unit that sequentially performs control is provided, and the control unit operates as a power saving mode when switching to a sub-battery.

  Further, the control unit stops charging the sub-battery when the charging source battery becomes equal to or lower than a third set voltage (for example, V3 = 2.3 V in the case of a lithium ion battery), and the sub-battery is the fourth battery. When the voltage becomes lower than the set voltage (for example, V4 = 3.4V in the case of a lithium ion battery), a battery exhaustion alarm is notified and the power is turned off.

  Further, the control unit reduces the operation clock frequency of the control unit in the power saving mode, and has a camera function, and restricts the camera function in the power saving mode. The portable electronic device is a portable communication terminal, and the power saving mode is an offline mode in which a telephone call is not possible. Further, in the power saving mode, the backlight function is stopped (not used), and a backlight booster circuit is used as a circuit for boosting the output of the main battery.

  A battery charging method for a portable electronic device according to the present invention is a battery charging method for a portable electronic device having a main battery and a sub-battery, and the first output near the lower limit at which the output of the main battery can operate the portable electronic device. When the voltage drops below the set voltage (for example, V1 = 3.4V in the case of a lithium ion battery), the main battery is switched to the sub battery and the power saving mode is activated, and the output of the sub battery operates the portable electronic device. When the voltage becomes lower than a possible second set voltage (for example, V2 = 3.6 V in the case of a lithium ion battery), the output of the main battery is boosted to charge the sub battery, or A battery charging method for a portable electronic device having at least two sub-batteries, wherein the output of the main battery is portable When the voltage drops below the first set voltage near the lower limit at which the slave device can be operated, the main battery is switched to the first sub-battery, and the output of the first sub-battery is the second that can operate the portable electronic device. When the voltage falls below the set voltage, the output of the main battery is boosted, the first sub-battery is charged, and the output of the first sub-battery is below the first set voltage near the lower limit at which the portable electronic device can be operated. The first sub-battery is switched to the second sub-battery, and when the output of the second sub-battery becomes equal to or lower than the second set voltage at which the portable electronic device can operate, the first sub-battery Control is performed in order to boost the output of the battery and charge the first sub-battery, and the power-saving mode is operated when switching to the sub-battery.

  Further, when the charging source battery becomes equal to or lower than a third set voltage (for example, V3 = 2.3 V in the case of a lithium ion battery), charging of the sub-battery is stopped, and the sub-battery stops at a fourth set voltage (for example, In the case of a lithium ion battery, when V4 = V3 = 3.4V) or less, an alarm of battery exhaustion is notified and the power is turned off.

  Further, in the power saving mode, the clock frequency of the control unit operation is lowered to limit the camera function, the portable electronic device is a portable communication terminal, and the power saving mode is set to an offline mode in which a call is impossible. . Further, in the power saving mode, a backlight boosting circuit is used as a circuit for stopping the backlight function and boosting the output of the main battery.

  Further, when the main battery exceeds a first set voltage (for example, V1 = 3.4V in the case of a lithium ion battery) due to recharging of the battery after switching from the main battery to the sub battery, the output of the main battery is changed. When the voltage is boosted to charge the sub-battery and the second set voltage (for example, V2 = 3.6V in the case of a lithium ion battery) is exceeded, the sub-battery is switched to the main battery, and the output of the sub-battery is the desired charge When the voltage has been reached, charging of the sub-battery by boosting the output of the main battery is stopped.

  Further, each set voltage has a relationship of third set voltage <first set voltage <second set voltage, third set voltage <first set voltage = fourth set voltage <second set voltage. Can be set to

  In the present invention, the remaining battery capacity of the main battery is refilled (charged) into the sub battery, and after switching to the sub battery, it is configured to operate in the power saving mode, so that the battery capacity of the main battery is fully used. In addition, since the load current can be continuously supplied for a long time, the usage time of the portable electronic device (terminal) can be extended.

  In addition, the sub battery can be used while being charged with the remaining battery capacity of the main battery, and after switching to the sub battery, it is configured to operate in the power saving mode. Can be used for a long time.

  In addition, when the power saving mode is applied to a mobile phone or the like by turning off the backlight, switching to a lower control clock frequency, or switching the camera function or call function, the voltage of the main battery drops. Even after switching to the sub-battery, the sub-battery enables operations such as checking the address book and phone book and using electronic money. It is possible to continue the operation.

  In particular, by configuring the backlight booster circuit to be diverted to charge the sub-battery, it is not necessary to use an independent booster circuit for charging, and it is preferable to turn off the backlight with high power consumption and switch to the power saving mode. Can be linked to

  Further, the relationship between the main battery and the sub-battery of the present invention can be realized even between a plurality of sub-batteries, and the remaining battery capacity of the sub-battery is refilled (charged) with a smaller sub-battery, thereby providing a battery capacity. It is possible to use the portable electronic device for a longer time by effectively using the.

(Configuration of the first embodiment)
FIG. 1 is a block diagram showing the configuration of the first exemplary embodiment of the present invention. In FIG. 1, the portable electronic device (terminal) of this embodiment includes a charging terminal 101 to which an AC adapter or the like is connected, a charging circuit (1) 102 for charging the main battery 103, and the voltage of the main battery 103. A / D converter (1) 104 for converting to a digital signal, control unit 105 for controlling the entire terminal, boost DC / DC converter 106 for boosting the voltage of the main battery 103 to a voltage that can be charged by the sub battery 108, and the sub battery 108 The charging circuit (2) 107 for charging the battery, the A / D converter (2) 109 for converting the voltage of the sub-battery 108 into a digital signal, and switching the power supply source to the control unit 105 (whether the main battery or the sub-battery Switch 110 to be selected. Here, the control unit 105 stores various setting values such as a setting value that is a threshold value relating to the voltage of the battery, and the voltage of the main battery 103 through the A / D converter (1) 104 and the A / D converter (2). The voltage of the sub battery 108 is monitored by digital processing through 109, and the operation / stop (on / off) of the switch 110 and the step-up DC / DC converter 106 is controlled.

(Operation of the first embodiment)
Hereinafter, specific numerical examples will be described to facilitate understanding of the operation of the embodiment.
FIG. 2 is a diagram showing characteristics of a lithium ion battery used as a main battery, and FIG. 3 is a diagram showing characteristics of a lithium ion battery used as a sub battery. The main battery 103 of this embodiment has a capacity of 500 mAh, and the sub-battery 108 has a capacity of 50 mAh, and each is a lithium ion battery having discharge characteristics as shown in FIGS.

First, the operation at the time of discharging of the battery according to the first embodiment of the present invention will be described.
FIG. 4 is a diagram showing a flowchart of the operation during discharging according to the first embodiment of the present invention.
First, both the main battery 103 and the sub battery 108 are fully charged (for example, 4.2 V), the switch 110 is connected to the main battery 103 side, and power is supplied from the main battery 103 to the control unit 105. And

  When the voltage of the main battery 103 reaches a set value 1 (for example, 3.4 V) with use of the portable electronic device (terminal) (step 401), the control unit 105 switches the switch 110 to Switching to power supply (step 402).

  Here, when switching to power supply from the sub-battery 108, the sub-battery 108 has a small battery capacity, so the control unit 105 is put into a power saving mode by reducing the operation clock frequency of the control unit 105, etc. Reduce current consumption. In addition, as described later, functions that consume a large amount of current, such as camera functions and backlight functions, are restricted, and in the case of a mobile phone, it is possible not to make a call (offline mode) to reduce current consumption. Good. By doing so, it is possible to effectively use the sub-battery 108 having a small battery capacity.

  When the voltage of the sub-battery 108 reaches a set value 2 (eg, 3.6 V) with further use of the terminal (step 403), the control unit 105 operates the step-up DC / DC converter 106 to The voltage of the battery 103 is boosted to a voltage (for example, 5 V) that the sub battery 108 can charge, and the sub battery 108 is charged by the charging circuit (2) 107 (step 404). The sub battery 108 is charged until the voltage of the main battery 103 reaches a set value 3 (for example, 2.3 V). When the voltage of the main battery 103 reaches the set value 3 (for example, 2.3 V) (step 405), Control unit 105 stops step-up DC / DC converter 106 and ends charging of sub battery 108 (step 406).

  Here, from FIGS. 2 and 3, if a load current of 50 mA is supplied when the main battery 103 is 3.4 V, the voltage drops immediately and cannot be used. However, the sub battery 108 cannot be used. It can be seen that if the remaining battery capacity (3.4 V to 2.3 V) is charged and used, a load current of 50 mA can be passed at a more stable voltage. That is, according to the present invention, the battery capacity of the main battery 103 can be fully utilized (from 4.2 V to 2.3 V).

  Thereafter, the terminal operates until the voltage of the sub battery 108 reaches a set value 4 (for example, 3.4 V). When the voltage of the sub battery 108 reaches the set value 4 (for example, 3.4 V) (step 407), control is performed. Unit 105 displays a battery exhaustion alarm and turns off the terminal (step 408).

  The battery capacity and voltage have been described above with specific numerical values. However, these numerical values are merely examples, and can be set to arbitrary values. Further, in order to explain the operation at the time of discharging according to the present invention, an example in which both the main battery and the sub battery are lithium ion batteries has been described. However, with respect to the discharging operation according to the present invention, a primary battery is connected to the main battery. Applicable even if used. That is, the main battery may be any type of battery regardless of whether it is a primary battery or a secondary battery, and the sub battery may be any rechargeable secondary battery. Further, the main battery and the sub-battery may be ones that store electric charges, such as a capacitor such as a super capacitor.

Next, the operation at the time of charging the battery according to the first embodiment of the present invention will be described.
FIG. 5 is a diagram showing a flowchart of the operation at the time of charging according to the first embodiment of the present invention.
First, it is assumed that both the main battery 103 and the sub battery 108 are set to 2.3 V, for example, and the switch 110 is connected to the sub battery 108 side.

  When an AC adapter or the like is connected to the charging terminal 101 (step 501), charging of the main battery 103 is started by the charging circuit (1) 102 and the step-up DC / DC converter 106 is also turned on, and the charging circuit (2) 107 starts charging the sub-battery 108 (step 502). When the voltage of the sub-battery 108 increases and becomes equal to or higher than a set value 5 (for example, 3.6 V) (step 503), the control unit 105 checks the voltage of the main battery 103. Here, if the voltage of the main battery 103 is equal to or higher than a set value 6 (for example, 3.4 V) (step 504), the control unit 105 switches the switch 110 to switch to power supply from the main battery 103 (step 505). .

  Thereafter, when the sub battery 108 is fully charged (for example, 4.2 V) (step 506), the control unit 105 stops the step-up DC / DC converter 106, and the charging circuit (2) 107 charges the sub battery 108. (Step 507), and when the main battery 103 is fully charged (for example, 4.2V) (Step 508), the charging circuit (1) 102 ends the charging of the main battery 103 (Step 509). .

  As described above, the battery capacity, voltage, and the like have been described with specific numerical values. However, these numerical values are merely examples, and can be set to arbitrary values. The charging operation of the present invention may be any secondary battery that can charge the main battery and the sub-battery, and may be one that can store charges, such as a capacitor such as a super capacitor.

(Configuration of Second Embodiment)
FIG. 6 is a block diagram showing the configuration of the second exemplary embodiment of the present invention. In FIG. 6, the portable electronic device (terminal) of the present embodiment uses the charging terminal 601 to which an AC adapter or the like is connected, the charging circuit (1) 602 for charging the main battery 603, and the voltage of the main battery 603. A / D converter (1) 604 for converting to a digital signal, a control unit 605 for controlling the entire terminal, a backlight 612 of an LCD display device, etc., up to a voltage required to turn on the backlight 612, or a sub A step-up DC / DC converter 606 that boosts the voltage of the main battery 603 to a voltage that can be charged by the battery 608, a switch 611 that connects the output of the step-up DC / DC converter 606 to the backlight 612 or the charging circuit (2) 607, and the sub-battery 608 Charging circuit (2) 607 for charging the battery, the voltage of the sub-battery 608 A / D converter (2) 609 for converting the digital signal, switches the power supply source to the control unit 605 (to select whether the main battery or the secondary battery) is configured from the switch 610. Here, the control unit 605 stores various setting values such as a setting value that is a threshold value relating to the voltage of the battery, a user key input setting, or a predetermined backlight setting, and the A / D converter (1) 604. The voltage of the main battery 603 and the voltage of the sub-battery 608 are monitored through the A / D converter (2) 609, and the switches 610 and 611 and the backlight 612 are turned on / off and the step-up DC / DC converter 606 is activated / stopped ( On / off).

(Operation of Second Embodiment)
Hereinafter, a specific numerical example will be described to facilitate understanding of the operation of the second embodiment.
The main battery 603 of this embodiment has a capacity of 500 mAh and is a lithium ion battery having discharge characteristics as shown in FIG. 2, and the sub-battery 608 has a capacity of 50 mAh and has discharge characteristics as shown in FIG. A lithium ion battery is used.

First, the operation at the time of discharging according to the second embodiment of the present invention will be described.
FIG. 7 is a diagram showing a flowchart of the operation at the time of discharging according to the second embodiment of the present invention.
First, both the main battery 603 and the sub-battery 608 are fully charged (for example, to 4.2 V), the switch 610 is connected to the main battery 603 side, and power is supplied from the main battery 603 to the control unit 605. . The switch 611 is on the backlight 612 side, and the controller 605 turns on / off the step-up DC / DC converter 606 so that the backlight 612 can be turned on / off.

  When the voltage of the main battery 603 reaches a set value 1 (for example, 3.4 V) as the terminal is used (step 701), the control unit 605 switches the switch 610 to switch to power supply from the sub battery 608, In addition, the switch 611 is switched to the charging circuit (2) 607 side so that the backlight function is turned off, that is, the backlight 612 cannot be turned on, so that the sub-battery 608 can be charged at any time (step). 702). Here, turning off the backlight function to reduce the current consumption of the terminal is useful for effectively using the sub battery 608 because the sub battery 608 has a small battery capacity.

  When the voltage of the sub-battery 608 reaches a set value 2 (eg, 3.6 V) with further use of the terminal (step 703), the control unit 605 turns on the step-up DC / DC converter 606 to turn on the main battery. The voltage of the battery 603 is boosted to a voltage that can be charged by the sub battery 608, and the sub battery 608 is charged by the charging circuit (2) 607 (step 704). Charging the sub-battery 608 is performed until the voltage of the main battery 603 reaches a set value 3 (for example, 2.3 V), and when the voltage of the main battery 603 reaches the set value 3 (for example, 2.3 V) (step 705). The control unit 605 turns off the step-up DC / DC converter 606 and ends the charging of the sub-battery 608 (step 706).

  Here, due to the discharge characteristics shown in FIG. 2 and FIG. 3, if the main battery 603 tries to pass a load current of 50 mA when the voltage is a set value 1 (for example, 3.4 V), the voltage drops immediately. However, it can be seen that if the remaining capacity (for example, 3.4 V to 2.3 V) of the main battery 603 is charged to the sub battery 608 and used, a load current of 50 mA can be supplied with a more stable voltage. That is, according to the present invention, the battery capacity of the main battery 603 can be fully utilized (for example, from 4.2 V to 2.3 V).

  Thereafter, the terminal operates until the voltage of the sub-battery 608 reaches a set value 4 (for example, 3.4 V), and when the voltage of the sub-battery 608 reaches the set value 4 (for example, 3.4 V) (step 707), control is performed. The unit 605 displays a battery exhaustion alarm and turns off the terminal (step 708).

  As described above, the battery capacity, voltage, and the like have been described with specific numerical values. However, these are merely examples, and of course, any value can be set. Further, in order to explain the operation at the time of discharging according to the present invention, an example in which both the main battery and the sub battery are lithium ion batteries has been described. However, with respect to the discharging operation according to the present invention, a primary battery is connected to the main battery. Applicable even if used. That is, the main battery may be any type of battery regardless of whether it is a primary battery or a secondary battery, and the sub battery may be any rechargeable secondary battery. Further, the main battery and the sub-battery may be ones that store electric charges, such as a capacitor such as a super capacitor.

  Here, the capability of the step-up DC / DC converter is also considered. For example, in a general mobile phone, four white LEDs are used as the backlight for the main LCD, the voltage required for lighting them is about 5 V, and the total current is about 80 mA (in parallel). At least a step-up DC / DC converter capable of supplying this voltage and current is mounted.

  If the sub-battery of the present invention is a 4.2 V, 50 mAh lithium ion battery, the voltage required for charging is about 5 V and the current is considered to be about 50 mA. This means that the sub-battery can be charged sufficiently if the capability of the LCD backlight boost DC / DC converter is satisfied, that is, the backlight DC and DC boost DC / DC converter can be combined. To do.

Next, the operation at the time of charging the battery according to the second embodiment of the present invention will be described.
FIG. 8 is a diagram showing a flowchart at the time of charging according to the second embodiment of the present invention.
First, both the main battery 603 and the sub battery 608 are set to 2.3 V, for example, and the switch 610 is on the sub battery 608 side. The switch 611 is on the charging circuit (2) 607 side, and the sub-battery 608 can be charged by turning on the step-up DC / DC converter 606.

  When an AC adapter or the like is connected to the charging terminal 601 (step 801), charging of the main battery 603 is started by the charging circuit (1) 602, and the step-up DC / DC converter 606 is also turned on, and the charging circuit (2). The charging of the sub battery 608 is also started by 607 (step 802). When the voltage of the sub-battery 608 increases and becomes equal to or higher than a set value 5 (eg, 3.6 V) (step 803), the control unit 605 checks the voltage of the main battery 603. Here, if the voltage of the main battery 603 is equal to or higher than a set value 6 (eg, 3.4 V) (step 804), the control unit 605 switches the switch 610 to switch to the power supply from the main battery 603 (step 805). ).

  Thereafter, the control unit 605 can turn on the backlight 612 (step 806). When the backlight 612 is turned on, the control unit 605 switches the switch 611 to the backlight 612 side to turn on the backlight. When the backlight 612 is turned off (step 807), the switch 611 is switched to the charging circuit (2) 607 side to turn off the backlight 612 and charge the sub battery 608 again (step 807). Step 808).

  When the sub battery 608 is fully charged (for example, 4.2 V) (step 809), the charging circuit (2) 607 ends the charging of the sub battery 608, and the control unit 605 fixes the switch 611 to the backlight 612 side. If the backlight 612 is off, the step-up DC / DC converter 606 is also turned off (step 810). When the main battery 603 is fully charged (for example, 4.2 V) (step 811), the charging circuit (1) 602 ends the charging of the main battery 603 (step 812).

  The battery capacity and voltage have been described above with specific numerical values. However, these are merely examples and can be set to arbitrary values. Regarding the charging operation of the present invention, the main battery and the sub-battery may be any secondary battery that can be charged, and may be an electric charge stored such as a capacitor such as a super capacitor.

  As described above, according to the present invention, the remaining battery capacity of the main battery is refilled (charged) into the sub-battery so that the load current can be flowed, so that the battery capacity of the main battery is fully used. And the usage time of the terminal can be lengthened.

Also, when applied to mobile communication devices such as mobile phones, the main battery voltage drops and can no longer be used, and after switching to the sub-battery, the sub-battery can be used to check the address book and phone book, The use of money is possible, and since the sub battery is used while being charged with the remaining battery capacity of the main battery, even if the battery capacity of the sub battery is not so large, it can be used for a long time.
In particular, in this embodiment, the sub-battery is charged by the booster circuit of the backlight, so that the circuit can be realized compactly.

(Third embodiment)
FIG. 9 is a diagram showing the configuration of the third exemplary embodiment of the present invention. Only the configuration example that enables operation in the power saving mode when using the sub-battery is shown in more detail, and the clock frequency that mainly reduces the power consumption by switching the clock frequency that regulates the operation of the control unit to a lower frequency A control circuit for extending the operation time by the sub-battery by the switching control 105c, the camera function control 105d for switching on / off of the camera photographing function including the flash photographing, the call function control 105e for limiting the call operation by the on / off control, and the like. Each function of the power saving mode can be configured to be selectively set.

  In the present embodiment, when the main battery 103 is used, the comparison unit 105a compares the output of the A / D converter (1) 104 with the first set voltage V1, and the voltage of the main battery 103 is set to the first set voltage V1. When the voltage drops below, a switch signal for switching the switch 110 to the sub-battery 108 side is output. Further, the switch signal is used to switch the clock frequency, switch to camera function restriction (shooting disabled state, etc.), and call function restriction. Switch to (offline). After switching to the sub-battery 108, the comparison unit 105b compares the output of the A / D converter (2) 104 with the second set voltage V2, and the voltage of the main battery 103 is equal to or lower than the first set voltage V2. When the voltage drops, the step-up DC / DC converter 106 is switched to operate, and the sub-battery 108 is charged with the step-up voltage via the charging circuit (2) 107. Thereby, power consumption in the portable electronic device and the control unit 105 can be suppressed, and the operation time of the sub battery 108 can be extended.

  The specific function limitation of the power saving mode of the present embodiment can be set in advance or can be selectively set by user key input, and the function limitation after switching to the sub-battery is preferable. It is configured to enable checking of the address book and telephone book and the use of electronic money.

(Fourth embodiment)
In the above embodiment, an example in which one main battery and one sub battery are used has been described. However, three or more batteries are prepared, and a larger battery (main battery, sub battery) is smaller than a smaller battery. By configuring the battery (sub-battery) to refill (charge) the remaining battery capacity sequentially, the remaining battery capacity can be effectively used even between small batteries (sub-batteries), and the usable time of portable electronic devices can be further extended. Is possible.

  FIG. 10 is a block diagram showing the configuration of the fourth exemplary embodiment of the present invention. This is a configuration example using two first and second sub-batteries 1008a and 1008b as sub-batteries, and a switch 1001 for switching input between the main battery 1010 and the sub-batteries 1008a and 1008b is input to the step-up DC / DC converter 1006. The charging changeover switch 1002 of the sub-batteries 1008a and 1008b that are charged by the output of the charging circuit (2) 1006, and the outputs of the three batteries 1010, 1008a, and 1008b that are output to the A / D converters (1) and (2). Changeover switches 1003a and 1003b, and a changeover switch 1004 for supplying power by three batteries 1010, 1008a and 1008b to the control unit 1005 and the like.

  The control unit 1005 starts the operation with the main battery 1010 from the fully charged state of each battery, and when the output reaches a set value near the lower limit at which the portable electronic device can be operated, the main battery 1010 to the first sub battery 1008a. When the first sub-battery 1008a is operable but falls to a predetermined set value, the output of the main battery 1010 is supplied to the first sub-battery 1008a via the step-up DC / DC converter 1006 and the charging circuit (2) 1006. When the output of the main battery 1010 reaches a lower limit set value that is not used for the operation, switching of the switches 1001 to 1003b is controlled so as to end the charging.

  Furthermore, when the output of the first sub-battery 1008a reaches a set value near the lower limit at which the portable electronic device can operate, the control unit 1005 switches from the first sub-battery 1008a to the second sub-battery 1008a, When the sub-battery 108b of the first sub-battery 108b is lowered to a predetermined settable value, the output of the first sub-battery 1008a charges the second sub-battery 108a via the step-up DC / DC converter 1006 and the charging circuit (2) 1006. When the output of the first sub-battery 1008a reaches a lower limit set value that is not used for the operation, the switching of the switches 1001 to 1003b is controlled so as to end the charging.

  This embodiment uses three or more sub-batteries and sequentially repeats the same operation, thereby further extending the usable time of the portable electronic device by effectively using the remaining battery capacity. It is clear. It goes without saying that the switching to the power saving mode of the second and third embodiments can be applied to the present embodiment.

It is a block diagram which shows the structure of the 1st Embodiment of this invention. It is a figure which shows the characteristic of the lithium ion battery used as a main battery. It is a figure which shows the characteristic of the lithium ion battery used as a subbattery. It is a figure which shows the flowchart of the operation | movement at the time of discharge of the 1st Embodiment of this invention. It is a figure which shows the flowchart of the operation | movement at the time of charge of the 1st Embodiment of this invention. It is a block diagram which shows the structure of the 2nd Embodiment of this invention. It is a figure which shows the flowchart of the operation | movement at the time of discharge of the 2nd Embodiment of this invention. It is a figure which shows the flowchart of the operation | movement at the time of charge of the 2nd Embodiment of this invention. It is a block diagram which shows the structure of the 3rd Embodiment of this invention. It is a block diagram which shows the structure of the 4th Embodiment of this invention.

Explanation of symbols

101, 601 charging terminal 102, 602 charging circuit (1)
103, 603, 1010 Main battery 104, 604 A / D converter (1)
105, 605 Control unit 106, 606, 1006 Step-up DC / DC converter 107, 607, 1007 Charging circuit (2)
108, 108a, 108b, 608 Sub-battery 109, 609 A / D converter (2)
110, 610, 611, 1001, 1002, 1003a, 1003b, 1004 Switch 612 Backlight of display device, etc.

Claims (16)

A portable electronic device having a main battery and a sub battery, wherein the main battery is switched to the sub battery when the output of the main battery becomes equal to or lower than a first set voltage near a lower limit at which the portable electronic device can be operated. And a control unit that operates as a power saving mode and boosts the output of the main battery and charges the sub battery when the output of the sub battery becomes equal to or lower than a second set voltage at which the portable electronic device can operate. A portable electronic device characterized by A portable electronic device having a main battery and at least two sub-batteries, wherein when the output of the main battery falls below a first set voltage near a lower limit at which the portable electronic device can be operated, Switch to one sub-battery, and when the output of the first sub-battery falls below a second set voltage that can operate the portable electronic device, boost the output of the main battery and charge the first sub-battery When the output of the first sub-battery becomes equal to or lower than the first set voltage in the vicinity of the lower limit at which the portable electronic device can operate, the second sub-battery is switched from the first sub-battery to the second sub-battery. Control for sequentially boosting the output of the first sub-battery and charging the first sub-battery when the output of the battery becomes equal to or lower than the second set voltage at which the portable electronic device can operate. Portable electronic device, characterized in that it comprises a. The portable electronic device according to claim 2, wherein the control unit is operated in a power saving mode when switching to the sub-battery. 4. The portable electronic device according to claim 1, wherein in the power saving mode, the operation clock frequency of the control unit is lowered. 5. The portable electronic device according to claim 1, further comprising a camera function, wherein the camera function is limited in the power saving mode. The portable electronic device according to claim 1, 3, 4, or 5, wherein the portable electronic device is a portable communication terminal, and the power saving mode is an offline mode in which a telephone call is impossible. The portable electronic device according to claim 1, wherein the backlight function is stopped in the power saving mode. 8. The portable electronic device according to claim 1, wherein a backlight boosting circuit is used as a circuit for boosting the output of the main battery. A battery charging method for a portable electronic device having a main battery and a sub-battery, wherein when the output of the main battery falls below a first set voltage near a lower limit at which the portable electronic device can be operated, Switching to the battery and operating in the power saving mode, the sub battery is charged by boosting the output of the main battery when the sub battery falls below a second set voltage at which the portable electronic device can operate. A method for charging a battery of a portable electronic device. A battery charging method for a portable electronic device having a main battery and at least two sub-batteries, wherein the output of the main battery is equal to or lower than a first set voltage near a lower limit capable of operating the portable electronic device. When switching from the main battery to the first sub-battery and the output of the first sub-battery falls below the second set voltage at which the portable electronic device can operate, the output of the main battery is boosted and the first sub-battery When the battery is charged and the output of the first sub-battery becomes equal to or lower than the first set voltage near the lower limit at which the portable electronic device can operate, the first sub-battery is switched to the second sub-battery, When the output of the second sub-battery becomes equal to or lower than the second set voltage at which the portable electronic device can be operated, the output of the first sub-battery is boosted and the first sub-battery is charged. Battery charging method for a portable electronic device which is characterized in that the control sequence. 3. The battery charging method for a portable electronic device according to claim 2, wherein the battery is operated in a power saving mode when switching to the sub battery. 12. The battery charging method for a portable electronic device according to claim 9, wherein the clock frequency of the control operation is lowered in the power saving mode. The battery charging method for a portable electronic device according to claim 9, wherein the camera function is provided, and the camera function is limited in the power saving mode. The portable electronic device according to any one of claims 9, 11, 12, and 13 to 13, wherein the portable electronic device is a portable communication terminal, and the power saving mode is an offline mode in which a telephone call is not possible. Battery charging method for electronic devices. 15. The battery charging method for a portable electronic device according to claim 9, 11, 12, 13, or 14, wherein the backlight function is stopped in the power saving mode. 16. The battery charging method for a portable electronic device according to claim 9, wherein a backlight boosting circuit is used as a circuit for boosting the output of the main battery. .

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