JP2011249237A - Battery pack and electronic apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress beforehand capacity deterioration caused by long-term storage under a fully charged state, in a battery pack including a battery set.SOLUTION: A battery pack 100 includes a battery set 102 comprised of a plurality of unit batteries 140 connected in series; and a discharge section 110 for reducing the charge amount of the battery set 102 to a set value. The discharge section 110 controls discharge between a positive electrode and a negative electrode in accordance with a voltage between the positive electrode and the negative electrode of the battery set 102. Thus, in the battery pack 100 including the battery set 102, capacity deterioration caused by long-term storage under a fully charged state can be suppressed beforehand.

Description

  The present invention relates to a battery pack and an electronic device.

  Conventionally, for example, Patent Document 1 described below describes a technique that is intended to prevent capacity deterioration of a unit cell in a battery pack including a unit cell and a protection circuit for the unit cell. Conventionally, since this type of battery pack is generally used for portable electric devices whose use time is not specified, many battery packs are prepared for unexpected use while the battery is fully charged.

JP 2001-23588 A

  However, for example, in a battery such as a lithium ion storage battery, when the battery is fully charged and stored for a long time while maintaining a high voltage, there is a problem that the battery undergoes severe capacity deterioration and the charge / discharge performance decreases. In particular, long-term storage in a high temperature environment has a problem of causing more severe capacity deterioration.

  Moreover, although the technique described in Patent Document 1 is provided with discharge means for the unit cell, since the discharge unit is provided at both ends of the unit cell, a discharge unit is required for each unit cell, There is a problem that the configuration becomes complicated and the cost increases.

  Therefore, the present invention has been made in view of the above problems, and an object of the present invention is a novel and capable of suppressing capacity deterioration due to long-term storage in a fully charged state. An object is to provide an improved battery pack and electronic device.

  In order to solve the above problems, according to an aspect of the present invention, an assembled battery composed of a plurality of unit cells connected in series, and a discharge unit that reduces a charge amount of the assembled battery to a set value. The battery pack is provided, wherein the discharge unit controls discharge between the positive electrode and the negative electrode according to a voltage between the positive electrode and the negative electrode of the assembled battery.

  The discharge unit is connected between the Zener diode and the first fixed resistor connected in series between the positive electrode and the negative electrode, and between the positive electrode and the negative electrode, and the first fixed resistor. And a transistor connected in parallel with each other, and the transistor may be turned on / off according to the potential at both ends of the fixed resistor.

  Moreover, a temperature detection unit may be further provided, and the discharge unit may start discharge when the temperature detected by the temperature detection unit is equal to or higher than a predetermined temperature set in advance.

  The discharge unit may be included in a microcomputer, and may increase the self-consumption current of the microcomputer when the voltage between the positive electrode and the negative electrode of the assembled battery is equal to or higher than a predetermined value.

  Moreover, in order to solve the said subject, according to another viewpoint of this invention, the discharge part which reduces the charging amount of the assembled battery comprised from the several unit cell connected in series to the said assembled battery to a setting value And the discharge unit controls the discharge between the positive electrode and the negative electrode according to the voltage between the positive electrode and the negative electrode of the assembled battery, and receives power from the battery pack. An electronic device is provided that includes an electronic circuit to be supplied.

  ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to provide the battery pack and electronic device which can suppress the capacity | capacitance degradation by being preserve | saved for a long time in a full charge state.

It is a schematic diagram which shows the battery pack used as the premise of embodiment of this invention. It is a schematic diagram which shows the circuit block example 1 of the battery pack which concerns on this embodiment. It is a schematic diagram which shows the circuit block example 2 of the battery pack which concerns on this embodiment. It is a schematic diagram which shows the structural example which added the temperature detection part to the structure of FIG. 2 or FIG. It is a schematic diagram which shows the structure of the portable electronic device which concerns on this embodiment. It is a schematic diagram which shows the example which comprised the discharge control part by fixed resistance, while using a Zener diode as a voltage detection part. It is a schematic diagram which shows the example comprised so that it might discharge in a short period from the state of a full charge to about 90% capacity | capacitance. It is a schematic diagram which shows the structure which changed FET of the discharge part shown in FIG. 7 into the transistor. FIG. 4 is a schematic diagram illustrating an example in which a self-consumption current of μCOM is used for a discharge unit in the configuration of FIG. 3. 10 is a flowchart showing a processing procedure in the configuration of FIG. 9.

  Exemplary embodiments of the present invention will be described below in detail with reference to the accompanying drawings. In addition, in this specification and drawing, about the component which has the substantially same function structure, duplication description is abbreviate | omitted by attaching | subjecting the same code | symbol.

The description will be made in the following order.
1. Configuration example of battery pack 2. 2. Configuration example of portable electronic device Specific configuration example of battery pack

1. Configuration Example of Battery Pack FIG. 1 is a schematic diagram showing a battery pack 500 which is a premise of the present embodiment. As shown in FIG. 1, the battery pack 500 includes an assembled battery 102 and a protection / control circuit 104 for the assembled battery. The electric power of the assembled battery 102 is output from the positive electrode 106 and the negative electrode 108 via the protection / control circuit 104. A control electrode 107 is connected to the protection / control circuit 104.

  FIG. 2 is a schematic diagram showing a circuit block example 1 of the battery pack 100 according to the present embodiment. The battery pack 100 includes an assembled battery 102 and a protection / control circuit 104 for the assembled battery 102. The protection / control circuit 104 detects an overcharge, overdischarge, or overcurrent state of the assembled battery 102, and forcibly stops input / output to the battery with a control circuit or a fuse so that the assembled battery 102 or circuit components are Reduce damage.

  Further, the battery pack 100 includes a discharge unit 110 in the protection / control circuit 104. The discharge unit 110 includes a voltage detection unit 120 and a discharge control unit 122. The discharging unit 110 has a function of lowering the charge amount of the assembled battery 102 to a set value. In the drawing, for ease of explanation, the discharge unit 110 is illustrated adjacent to the protection / control circuit 104, but the discharge unit 110 is provided in the protection / control circuit 104. Further, as shown in the figure, the protection / control circuit 104 and the discharge unit 110 can be configured separately.

  FIG. 3 is a schematic diagram showing a circuit block example 2 of the battery pack 100 according to the present embodiment. The battery pack 100 includes an assembled battery 102 and a protection / control circuit 104 for the assembled battery. Further, the battery pack 100 has a discharge part 112. The discharge unit 112 includes a voltage detection unit 120 and a discharge control unit 122, and the voltage detection unit 120 and the discharge control unit 122 are configured as an integral block. Similar to the configuration of FIG. 2, the discharging unit 112 has a function of lowering the charge amount of the assembled battery 102 to a set value.

  2 and 3 are connected between the terminals of the positive electrode 106 and the negative electrode 108 of the battery pack 100, so that even the assembled battery 102 is discharged by only one discharge unit 110, 112. This can be realized, and the charge amount of the assembled battery 102 can be lowered to a set value. As described above, the discharge units 110 and 112 include the voltage detection unit 120 and the discharge control unit 122, and can discharge at a preset current ratio.

  Further, as shown in FIG. 3, the voltage detection unit 120 and the discharge control unit 122 can be integrated to use a microcomputer (μCOM). The discharge controller 122 stops the discharge when the voltage falls below the set voltage.

  FIG. 4 is obtained by adding a temperature detection unit 114 to the configuration of FIG. 2 or 3. By adding the temperature detection unit 114 as shown in FIG. 4, discharge can be started when the set temperature is reached.

2. Configuration Example of Portable Electronic Device FIG. 5 is a schematic diagram illustrating a configuration of a portable electronic device 200 according to the present embodiment. Examples of the portable electronic device 200 include a digital still camera, a digital video camera (Dsc / Videocamera), and a mobile phone device, but are not limited thereto. As shown in FIG. 5, the portable electronic device 200 includes a battery pack 100, and the battery pack 100 is electrically connected to an electronic circuit 202 of the portable electronic device 200.

  As shown in FIG. 5, the battery pack 100 is configured by housing an assembled battery 102 and a protection / control circuit 104 for the assembled battery 102 in a battery case 150, and has a positive electrode 106 with respect to the main body of the portable electronic device 200. The positions of the three types of electrodes, the negative electrode 108 and the control electrode 107, are provided correspondingly. The positive electrode 106, the negative electrode 108, and the control electrode 107 are electrically connected to the three electrodes of the main body of the portable electronic device 200 and configured to supply power from the battery pack 100 to the main body of the portable electronic device 200. Yes.

  The assembled battery 102 is configured by connecting two lithium ion storage batteries 140 in series. As an example, the assembled battery voltage at the time of full charge is 8.4 V and the battery capacity is reduced to 50%. However, it is not limited to this, and can be implemented with appropriate modifications.

3. Specific Configuration Example of Battery Pack Hereinafter, a more detailed configuration example of the battery pack 100 according to the present embodiment will be described. 6 to 9 described below show the configuration of the discharge unit 110 more specifically and in detail.

  The configuration shown in FIG. 6 uses a Zener diode 124 with a threshold value of about 7.5 V as the voltage detection unit 120, and the discharge control unit 122 is configured with a fixed resistor 126 having a relatively high resistance value. 124 and a fixed resistor 126 are connected in series. While the voltage between the positive electrode 106 and the negative electrode 108 exceeds the threshold value, the Zener diode 124 is turned on, and the assembled battery 102 is discharged via the fixed resistor 126.

  For example, by setting the resistance value of the fixed resistor 126 in advance so that it takes about 10 to 20 days for the battery capacity of the assembled battery 102 to decrease from full charge to 50% capacity, the assembled battery 102 is always discharged. However, the amount of current is slightly higher than that during spontaneous discharge, and does not cause a problem for normal use. On the other hand, after the charge amount of the assembled battery 102 is reduced to about 50%, the Zener diode 124 is turned off and the state is maintained.

  FIG. 7 shows an example in which the battery is discharged in a short period from a fully charged state to about 90% capacity. An FET 128 and a fixed resistor 130 are further added to the structure of the discharging unit 110 in FIG. Is. In the vicinity of the fully charged state, a voltage equal to or higher than the threshold voltage (Vth) of the FET 128 is generated at both ends of the fixed resistor 126 using the Zener current Iz of the Zener diode 124, and a discharge current is generated between the drain and source of the FET 128. The amount of charge is reduced in a short time from full charge to about 90%.

  On the other hand, when the charge amount is 90% or less of the battery capacity, the FET 128 does not operate, so the discharge amount is the same as that in FIG. And after the amount of charge decreases to about 50%, the state is maintained. According to the above configuration, the amount of charge can be reduced in a short period from full charge to about 90%, so that deterioration of the battery pack 100 can be more reliably suppressed. In addition, by appropriately setting the threshold voltage (Vth) of the FET 128 and the values of the fixed resistors 126 and 130, the value of the charging capacity (90% of full charge in the above example) to be reduced in a short period is appropriately set. be able to.

  FIG. 8 shows a configuration in which the FET 128 of the discharge unit 110 shown in FIG. In this way, a transistor such as a bipolar transistor can be used instead of the FET 128. Even in this case, the charging capacity can be reduced in a short period of time by appropriately setting the threshold values of the fixed resistor 134, the fixed resistor 130, and the transistor 132 connected to the contact point between the fixed resistor 126 and the Zener diode 124. It can be set to a desired value.

  9, as in FIG. 3, the discharge unit 112 including the voltage detection unit 120 and the discharge control unit 122 and the temperature detection unit 114 are configured by a microcomputer (μCOM) 160, and the self-consumption of the μCOM 160 is performed by the discharge unit 112. An example using current is shown. In this case, the discharge part 112 and the temperature detection part 114 can be comprised by the microcomputer and the software (program) which functions this. During long-term storage, the μCOM 160 maintains a self-current consumption of about several tens of uA in the halt state (Power Save state) to reduce the self-current consumption, but the inter-electrode voltage of the assembled battery 102 is 8.0V. If the ambient temperature exceeds 40 ° C., the active state is entered, and the self-consumption current is increased to about several mA. On the other hand, when the voltage between the electrodes of the assembled battery 102 is 8.0 V or lower or the ambient temperature is 40 ° C. or lower, the battery enters the halt state (power save state) and the charge amount is maintained.

  FIG. 10 is a flowchart showing a processing procedure in the configuration of FIG. The processing in steps S10 to S16 shown in FIG. 10 indicates processing for switching from the active state to the power saving state. Further, the processing in steps S20 and S22 shown in FIG. 10 indicates processing for canceling the power save state.

  First, in step S10, the timer is set to 1 second. In the next step S12, a timer interruption permission is accepted. In the next step S14, it is determined whether or not the voltage of the assembled battery 102 exceeds 8.0V and the ambient temperature exceeds 40 ° C.

  In step S14, when the voltage of the assembled battery 102 exceeds 8.0V and the ambient temperature exceeds 40 ° C., the process waits in step S14. On the other hand, when the voltage between the electrodes of the assembled battery 102 is 8.0 V or lower or the ambient temperature is 40 ° C. or lower, the halt state is set in the next step S16. In the flowchart shown on the left side of FIG. 10, the battery pack 100 is in an active state in the processes of steps S10, S12, and S14.

  In step S16, a timer interruption step S20 is performed at the interval (1 second) set in step S10. When the timer is interrupted, in step S22, the halt state is canceled and the process returns to step S14. In the above example, conditions are set at a voltage of the assembled battery 102 of 8.0 V and an ambient temperature of 40 ° C., but the voltage, temperature, or other condition settings can be arbitrarily changed. Further, the increase in self-consumption current is not limited to the active state, and the method is not limited, for example, only a part of the circuits in the μCOM is operated.

  Furthermore, the voltage detection unit 120 of the assembled battery 102 is not limited to the Zener diode 124 and the μCOM 160, but can adopt various modes such as one using a comparator using an operational amplifier.

  Further, the discharge control unit 122 is not limited to the self-consumption current of the fixed resistor 126 and μCOM 160, but may be configured such that the resistance value is varied according to the voltage drop of the assembled battery 102 to increase or decrease the discharge amount.

  In addition to the above-described configuration, it can be provided not only on the battery pack 100 but also on the portable electronic device 200, and the detection method is not limited.

  As described above, according to the present embodiment, the charge amount of the assembled battery 102 is forcibly decreased, and the battery pack 100 is stored in a state where the voltage of the assembled battery 102 is lower than the set value. In addition, it is possible to prevent capacity deterioration even during long-term storage. Accordingly, the long-term reliability of the battery pack can be greatly improved.

  Moreover, according to this embodiment, it is not necessary to provide a discharge part for every unit cell by providing the discharge means at both ends of the positive electrode and the negative electrode terminal of the battery pack, and an assembled battery can be realized with one discharge means. Therefore, the configuration can be simplified and a significant cost reduction can be achieved.

  The preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings, but the present invention is not limited to such examples. It is obvious that a person having ordinary knowledge in the technical field to which the present invention pertains can come up with various changes or modifications within the scope of the technical idea described in the claims. Of course, it is understood that these also belong to the technical scope of the present invention.

DESCRIPTION OF SYMBOLS 100 Battery pack 102 Assembly battery 106 Positive electrode 108 Negative electrode 110,112 Discharge part 114 Temperature detection part 124 Zener diode 126,130,134 Fixed resistance 128 FET
132 transistor 140 unit cell 160 μCOM
200 Electronic equipment 202 Electronic circuit

Claims (5)

An assembled battery composed of a plurality of unit cells connected in series;
A discharge unit for reducing the charge amount of the assembled battery to a set value,
The discharge unit controls a discharge between the positive electrode and the negative electrode according to a voltage between a positive electrode and a negative electrode of the assembled battery. The discharge part is
A zener diode and a fixed resistor connected in series between the positive electrode and the negative electrode;
A transistor connected between the positive electrode and the negative electrode and connected in parallel to the fixed resistor,
The battery pack according to claim 1, wherein the transistor is turned on / off according to a potential across the fixed resistor.   The battery pack according to claim 1, further comprising a temperature detection unit, wherein the discharge unit starts discharge when the temperature detected by the temperature detection unit is equal to or higher than a predetermined temperature set in advance.   The battery pack according to claim 1, wherein the discharge unit is included in a microcomputer, and increases a self-consumption current of the microcomputer when a voltage between a positive electrode and a negative electrode of the assembled battery is equal to or higher than a predetermined value. An assembled battery composed of a plurality of unit cells connected in series; and a discharge unit that reduces a charge amount of the assembled battery to a set value, wherein the discharge unit includes a positive electrode and a negative electrode of the assembled battery. A battery pack for controlling discharge between the positive electrode and the negative electrode according to a voltage between;
An electronic circuit supplied with power from the battery pack;
Electronic equipment comprising.

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