JP2007305451A - Secondary battery pack with overcharge protection function - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a secondary battery pack with an overcharge protection function with a simpler protection function control part than a prior art, without the need of inserting a charge/discharge switching element causing heat radiation or damage to a power line where a current flows during a normal use, and capable of protecting itself from overcharging. <P>SOLUTION: The secondary battery pack provided with a secondary battery block 2 comprising one or a plurality of secondary batteries 1 and external output terminals 10, 11 comprises a constant voltage control element 6 connected in parallel with each secondary battery 1, a bypass circuit comprising a switching device 13 and a resistor 12 connected in parallel between the external output terminals 10, 11, and a control means 5 monitoring voltage of the secondary battery block and controlling the switching element 13. The constant voltage control element 6 controls the secondary batteries 1 so that each voltage of theirs shall not exceed a regulated voltage for them 1, and the control means 5 turns the switching element 13 in a conductive state when a voltage of the secondary battery block 2 exceeds the regulated voltage, and lets it bypass a charging current. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a secondary battery pack including a secondary battery block including one to a plurality of secondary batteries and a protection circuit, and more particularly, a secondary battery with an overcharge protection function provided with a function of protecting a secondary battery from an overcharged state. It relates to a battery pack.

  In a secondary battery such as a lithium ion battery, if the battery voltage becomes too high during charging, the battery performance may be deteriorated or the safety thereof may be impaired. Conventionally, as disclosed in Patent Document 1, for the prevention, a protection function control unit having a voltage monitoring function for monitoring a terminal voltage of a secondary battery or a battery block and a charge / discharge switch operated by the control are included. A protection circuit is provided, the terminal voltage of the secondary battery is monitored by the voltage monitoring function, and when the terminal voltage per secondary battery reaches a predetermined voltage value, the charging operation is stopped by the charge / discharge switch. Therefore, the battery voltage (terminal voltage) is kept below a predetermined voltage.

  FIG. 3 is a diagram showing a configuration example of a circuit of a conventional secondary battery pack with a protection circuit composed of a secondary battery block in which a large number of secondary batteries are connected in series, where 1 is a secondary battery and 2 is a secondary battery pack. The secondary battery block, 34 is a protection function control unit, 33 is a current fuse, SW1 at 31 is a discharge control switch, and SW2 at 32 is a charge control switch.

  In FIG. 3, the protection function control unit 34 monitors each terminal voltage of the secondary battery 1, and when the overcharge is detected, turns off the charge control switch 32 and shuts off the charging circuit. The current fuse 33 has a function of cutting off the current by fusing if a charging current or discharging current exceeding a specified value continues to flow for a certain period of time.

JP 2002-152982 A

  In the above conventional battery pack, when a charger that may be applied with a voltage outside the recommended range of the secondary battery block 2 is connected, the protection function control unit 34 sets each terminal voltage of the secondary battery 1. The battery was protected from overcharging by turning off the charging control switch 32 when a voltage exceeding a specified value was monitored. However, in recent years, since the demand for battery packs that can handle high loads has increased, the number of secondary batteries that have to be increased in series has increased, and the terminal voltage of the secondary battery 1 has been monitored as the series number has increased. The protection function control unit 34 to be complicated becomes complicated. Further, since current increases due to an increase in load, heat is generated in the discharge control switch 31 and the charge control switch 32 inserted in the power line between the secondary battery block 2 and the external output terminal 10 connected to the external circuit. In order to suppress such a problem, it is necessary to select an element having a large current capacity and a high breakdown voltage in order to suppress this. Therefore, the battery pack having the conventional protection circuit has a problem that the circuit scale becomes large in the above case, the number of mounting parts increases, and the manufacturing cost increases because a special element is used.

  Therefore, the problem of the present invention is that the protection function control unit becomes simpler than before, there is no need to insert a charge / discharge switch element that generates heat or loss in the power line through which current flows during normal use, and from overcharging. An object of the present invention is to provide a secondary battery pack with an overcharge protection function that can be protected.

  In order to solve the above problems, a secondary battery pack with an overcharge protection function according to the present invention includes a secondary battery block including one to a plurality of secondary batteries and a pair of external output terminals connected to an external circuit. In the pack, a constant voltage control element connected in parallel to each of the secondary batteries, a bypass circuit composed of a switch element and a resistor connected in parallel between the external output terminals, and a voltage of the secondary battery block And control means for controlling the switch element, and the constant voltage control element is controlled so that individual voltages of the secondary battery do not exceed a prescribed voltage for the secondary battery, and the control means When the voltage of the secondary battery block exceeds a specified voltage for the secondary battery block, the switch element is in a conductive state and is controlled to bypass the charging current. Switching elements for controlling charge and discharge of the secondary battery block is not inserted between the terminal and the external output terminal of the secondary battery block.

  Further, in the present invention, a temperature detection element for detecting the temperature of the secondary battery block, temperature determination means for determining a temperature abnormality based on an output from the temperature detection element, and a switch connected in parallel between the external output terminals An emergency bypass circuit comprising an element or a switch element and a resistor is installed, a current fuse is inserted between the terminal of the secondary battery block and the external output terminal, and the temperature of the secondary battery block is controlled by the temperature determination means. When it is determined that an abnormality has occurred, the switch element of the emergency bypass circuit may be in a conductive state, and the current fuse may be blown by passing an overcurrent through the current fuse.

  That is, according to the present invention, it is possible to avoid heat generation and loss due to these switch elements during normal operation by removing the charge / discharge switch that has been conventionally inserted in series with the power line of the secondary battery. is there.

  In addition, for overcharge protection, instead of the conventional charge / discharge switch, a bypass circuit comprising a switch element and a resistor is installed in parallel between the external output terminals of the secondary battery block, and the switch element controls the overcharge circuit. Protect from charging. In addition, by installing a temperature detection element for detecting the temperature of the secondary battery block and a current fuse, it is possible to cope with abnormal heating of the secondary battery block due to overcharging.

  According to the present invention, the controller for protecting against an abnormality is simpler than before, and it is not necessary to insert a charge / discharge switch element that generates heat or loss in a power line through which current flows during normal use, and overcharge. A secondary battery pack with an overcharge protection function can be obtained.

  Hereinafter, embodiments of the present invention will be described based on examples with reference to the drawings.

  FIG. 1 is a circuit diagram showing a first embodiment of a secondary battery pack with an overcharge protection function according to the present invention. In FIG. 1, the secondary battery pack with an overcharge protection function of this embodiment includes a secondary battery block 2 composed of a plurality of secondary batteries 1 and external output terminals 10 and 11 connected to an external circuit. , A constant voltage control element 6 connected in parallel to each of the secondary batteries 1, a bypass circuit including a switch element 13 and a resistor 12 connected in parallel between the external output terminals 10 and 11, and a secondary circuit It comprises control means 5 that monitors the voltage of the battery block 2 and controls the switch element 13. The constant voltage control element 6 controls each voltage of the secondary battery 1 so as not to exceed a prescribed voltage for the secondary battery 1, and the control means 5 regulates the voltage of the secondary battery block 2 to the secondary battery block 2. When the voltage exceeds the voltage, the switch element 13 is turned on and controlled to bypass the charging current. Further, no switching element for controlling charging / discharging of the secondary battery block is inserted between the terminals 3 and 4 of the secondary battery block 2 and the external output terminals 10 and 11.

  Next, the overcharge protection operation of the secondary battery pack with an overcharge protection function of this embodiment will be described. In FIG. 1, first, when a charger is connected to the external output terminals 10 and 11 and charging is started, each terminal voltage of the secondary battery 1 gradually rises. When the terminal voltage of the secondary battery 1 exceeds the specified voltage due to the voltage imbalance, the constant voltage control element 6 bypasses the charging current and avoids the secondary battery 1 being overcharged. Adjust the voltage balance. The overcharge avoidance of the secondary battery 1 by the constant voltage control element 6 and the voltage balance adjustment function between the secondary batteries 1 continue to operate until charging is completed. The constant voltage control element 6 can be constituted by an element having a limiter function such as a Zener diode.

  Further, when the charging operation by the charger proceeds and a charging voltage exceeding the recommended range of the secondary battery pack is applied to the secondary battery block 2, the control means 5 detects the overcharged state of the secondary battery block 2 and switches the switch element. By turning on 13, all of the charging current output from the charger and the discharging current from the secondary battery block 2 are bypassed by the bypass circuit, and the overcharged state of the secondary battery block 2 is avoided.

  FIG. 2 is a circuit diagram showing a second embodiment of the secondary battery pack with an overcharge protection function according to the present invention. In FIG. 2, the battery pack with an overcharge protection function of the present embodiment is a secondary battery pack including a secondary battery block 2 composed of a plurality of secondary batteries 1 and external output terminals 10 and 11 connected to an external circuit. A constant voltage control element 6 connected in parallel to each of the secondary batteries 1, a bypass circuit comprising a switch element 13 and a resistor 12 connected in parallel between the external output terminals 10 and 11, and a secondary battery block 2 is the same as that of the embodiment of FIG. 1, and the operation thereof is also the same.

  However, in this embodiment, the temperature detection element 8 for detecting the temperature of the secondary battery block 2, the temperature determination means 7 for determining the temperature abnormality based on the output from the temperature detection element 8, the external output terminal 10, 11 and an emergency bypass circuit composed of a switch element 14 connected in parallel, and a current fuse 33 is inserted between the terminal 3 of the secondary battery block 2 and the external output terminal 10.

  The operation of the present embodiment is the same as that of the battery pack of the first embodiment with respect to the operation within the normal temperature range, but the temperature of the secondary battery block 2 rises due to abnormal charging or discharging and causes abnormal heat generation. In this case, based on the temperature information obtained from the temperature detection element 8, the temperature determination means 7 determines a temperature abnormality, turns on the switch element 14, and allows an excessive discharge current from the secondary battery block 2 to flow to the emergency bypass circuit. As a result, an excessive current flows through the current fuse 33, so that the current fuse 33 is melted and the charge / discharge path is interrupted.

  In this embodiment, the switch element 13 of the bypass circuit is turned on by the control means 5 during overcharging, but the switch element 14 is also turned on when a temperature abnormality occurs.

  As described above, in the secondary battery pack having the overcharge protection function according to the present invention, even when a charger that performs voltage control exceeding the recommended range of the secondary battery 1 and the secondary battery block 2 is connected, the constant voltage The control element 6, the control means 5 and the temperature determination means 7 are connected in series to the power line from the secondary battery in order to adjust the balance of the secondary battery voltage, bypass the excessive charging current, and interrupt the current path when the temperature is abnormal. It is possible to eliminate the charge / discharge elements inserted in the battery and to avoid heat generation and loss due to these elements during normal operation.

  In addition, this invention is not limited to the said embodiment, A various deformation | transformation is possible. For example, in the above-described embodiment, the functions of the control unit 5 and the temperature determination unit 7 have been described as operating independently. However, the switch element 13 and the switch are connected based on both the charge state and the temperature state. It goes without saying that more appropriate control and prevention of malfunction can be performed by operating the element 14.

The circuit diagram which shows the 1st Example of the secondary battery pack with an overcharge protection function by this invention. The circuit diagram which shows the 2nd Example of the secondary battery pack with an overcharge protection function by this invention. The figure which shows the structural example of the circuit of the conventional battery pack with a protection circuit which consists of a secondary battery block which connected many secondary batteries in series.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Secondary battery 2 Secondary battery block 3, 4 Terminal 5 Control means 6 Constant voltage control element 7 Temperature determination means 8 Temperature detection element 10,11 External output terminal 12 Resistance 13,14 Switch element 31 Discharge control switch 32 Charge control switch 33 Current fuse 34 Protection function controller

Claims (3)

  In a secondary battery pack comprising a secondary battery block composed of one to a plurality of secondary batteries and an external output terminal pair connected to an external circuit, a constant voltage control element connected in parallel to each of the secondary batteries; A bypass circuit composed of a switch element and a resistor connected in parallel between the external output terminals, and a control means for monitoring the voltage of the secondary battery block and controlling the switch element, the constant voltage control element When each voltage of the secondary battery is controlled so as not to exceed a specified voltage for the secondary battery, and when the voltage of the secondary battery block exceeds a specified voltage for the secondary battery block by the control means The switch element is in a conductive state and is controlled to bypass the charging current, and the secondary battery block is interposed between the terminal of the secondary battery block and the external output terminal. Tsu switching element for controlling charging and discharging of the click is characterized by not inserted overcharge protection function rechargeable battery pack.   A temperature detection element for detecting the temperature of the secondary battery block; temperature determination means for determining a temperature abnormality based on an output from the temperature detection element; and a switch element or a switch element connected in parallel between the external output terminals; An emergency bypass circuit composed of a resistor is installed, a current fuse is inserted between the terminal of the secondary battery block and the external output terminal, and the temperature determination means determines that the temperature of the secondary battery block has become abnormal 2. The switch with overcharge protection function according to claim 1, wherein when the switching element of the emergency bypass circuit is turned on, the current fuse is blown by flowing an overcurrent through the current fuse. Next battery pack.   3. The secondary with overcharge protection function according to claim 2, wherein the switch element of the emergency bypass circuit is controlled to be in a conductive state only when the switch element of the bypass circuit is in a conductive state. Battery pack.

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