JP2009104821A - Battery pack - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a battery pack preventing failure or performance degradation, or further, damage or the like of a unit connected by breaking an input and an output in the case leakage current is generated due to adherence, dew condensation or the like of electrolyte solution, moisture or the like on an electric circuit board, and after dissolution of a leakage state, capable of again achieving a function of charging and discharging in a simple circuit structure, without needing any additional components. <P>SOLUTION: The battery pack is provided with a secondary battery 2 and a protective circuit 4, which latter 4 is equipped with a charge controlling FET 7 operating as a charging switch, a discharge controlling FET 8 operating as a discharging switch, and a voltage monitoring circuit 9 controlling these switches, as well as a leakage current detecting electrode 12 structured of two electrodes opposed to each other on a circuit board same as the protective circuit 4, one of which 10 is connected to a gate of the charge controlling FET 7, and the other 11 is connected to a source of the charge controlling FET 7. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention provides a highly reliable battery that stops charging / discharging when leakage current is generated on the protection circuit board due to leakage of electrolyte from the battery cell, submersion of the battery pack, condensation, etc., and eliminates the failure due to leakage. Regarding the pack.

  Secondary batteries with high charge / discharge capacity density, such as lithium ion batteries, are generally used as battery packs that are housed in synthetic resin enclosures, etc. together with internal components such as battery protection circuit boards. The battery protection circuit board protects the battery by turning off the current when an excessive current flows, such as when the battery terminal is short-circuited, or when the battery is overcharged or overdischarged. A protection circuit is provided.

  The secondary battery used in the battery pack has sufficient measures to prevent the battery electrolyte from leaking out of the battery outer can or the sealing portion of the flexible outer packaging material. In some rare cases, the electrolyte solution leaks from the battery outer can due to a rise in battery temperature, a defect in the battery sealing portion, or the like.

  In addition, since lithium ion batteries and the like are used as a power source for portable devices such as mobile phones, the mobile phone may be submerged in the battery pack by accidental immersion in water in daily life, or Condensation may occur inside the battery pack. In such a case, the water and the electrolyte attached to the electric circuit board in the battery pack have sufficient electric conductivity for energization, so that the voltage in the battery pack is applied between the portions where the voltage is applied. An energization circuit may be formed to generate a leakage current, or an abnormal energization circuit may be formed inside the device, resulting in an electric circuit failure or the like.

  Therefore, in order to solve such problems, Patent Documents 1 to 4 listed below disclose means for detecting the above leakage current and stopping charging and discharging.

Japanese Patent No. 3402933 JP 2003-132862 A JP 2006-120353 A JP 2000-030759 A

  Patent Document 1 discloses an organic electrolyte leakage detection device in which a leakage detection electrode for an organic electrolyte is provided on a circuit board, and the leakage is detected by the output of leakage current detection means connected to the leakage detection electrode. Although proposed, a current-carrying-off means is provided separately from the conventional protection circuit, and additional members such as a leakage current detecting means, its output means, and a current-carrying means are required.

  In Patent Document 2, a leakage current detection semiconductor switch is connected to a current leakage detection electrode to detect a leakage current, and the semiconductor switch control circuit for charging and the semiconductor switch control circuit for discharging are controlled and protected by the output. A battery pack for operating a charging switch and a discharging switch of a circuit has been proposed. In addition to a leakage current detecting semiconductor switch for detecting a leakage, a charging semiconductor switch control circuit, a discharging semiconductor switch control circuit, etc. It was necessary to provide it separately from the protection circuit.

  Further, Patent Document 3 has a leakage detection circuit that outputs a leakage detection signal when the leakage current detection electrode and the output terminal are electrically connected, and the output of the voltage monitoring circuit of the protection circuit is short-circuited by the output. There has been proposed a leak detection device that shuts off a discharge switch by setting the monitoring circuit input to a predetermined voltage or less or by short-circuiting the input of the discharge switch. However, this interrupts the discharge, and it is necessary to provide a separate detection circuit for the leakage current during charging.

  Further, Patent Document 4 proposes a battery pack having a function of interrupting charging by connecting an output of a latch circuit to the input side of a charging switch together with a liquid detection electrode. In addition, an additional member such as a latch circuit is required.

  As described above, in order to obtain protection against leakage current in the conventional battery pack, the number of parts to be added to the normal protection circuit is increased, and the circuit configuration becomes complicated. The point was not enough.

  Therefore, the object of the present invention is to provide input / output when a battery pack having a secondary battery such as a lithium ion battery causes leakage current due to adhesion of electrolytic solution, moisture, condensation, etc. to the electric circuit board. By shutting down, it prevents the occurrence of failure, performance degradation, and damage to the equipment connected to it, and the function that enables charging / discharging again after the leakage state is resolved. It is an object of the present invention to provide a battery pack that does not require many additional parts and can be realized with a simple circuit configuration.

  In order to solve the above problems, a battery pack according to the present invention includes a secondary battery, a battery protection circuit board including a charge control FET that operates as a charge switch and a discharge control FET that operates as a discharge switch. In the battery pack, a leakage current detection electrode composed of two electrodes facing each other is provided between the gate and the source of the charge control FET on the battery protection circuit board, and the charging current is detected when the leakage current detection electrode becomes conductive. Charging / discharging is stopped by shutting off the switch.

  The battery protection circuit board includes a positive electrode side and a negative electrode side external connection terminal for connection to an external device and a charging device, and one electrode constituting the leakage current detection electrode is the negative electrode side external connection terminal. Also good.

  In the present invention, the leakage current detection electrode is provided between the gate and the source of the charge control FET, and when the leakage current detection electrode is short-circuited by an electrolyte or moisture, the charging switch is turned off, and the battery cell is charged. Can cut off the energy supply. During discharging, the charging switch is turned off, so that discharging is performed via a parasitic diode in the charging control FET. However, due to instantaneous overcurrent protection, the discharging switch is turned off. Therefore, protection is achieved by stopping the discharge.

  The present invention provides another leakage current detection electrode by providing only a leakage current detection electrode and connecting it to an optimum position on the protection circuit board to detect and control the leakage current as in the conventional leakage detection control circuit. This is based on the finding that a battery pack capable of stable operation can be obtained without adding additional circuit components.

  That is, in the battery pack of the present invention, since the additional circuit such as the charge / discharge control means is not provided as in the prior art, and the leakage current detection electrode is simply provided on the circuit board, the circuit configuration is simple. A function equivalent to that of a conventional battery pack is realized without increasing the number of parts. Further, in the battery pack of the present invention, when the infiltrated moisture or condensed moisture evaporates and the conductivity in the leakage current detection electrode is lowered, the battery pack can be used again. .

  As described above, since the battery pack of the present invention has a configuration in which the leakage current detection electrode is simply provided on the circuit board, a leakage current is generated due to adhesion of electrolytic solution, moisture, etc. to the electric circuit board, condensation, etc. In this case, it is possible to prevent the occurrence of failure, performance deterioration, and damage to the equipment connected to the device by blocking the input / output. A battery pack capable of realizing the enabling function with a simple circuit configuration without requiring many additional parts is obtained.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 is a circuit configuration diagram of Embodiment 1 of a battery pack according to the present invention. In FIG. 1, the battery pack 1 of the present embodiment includes a secondary battery 2 and a protection circuit 4, and the PTC element 3 that cuts off current when the temperature of the secondary battery 2 becomes high is the secondary battery 2. Is inserted in series. The output through the PTC element 3 of the secondary battery 2 is connected to the battery connection terminals 5 a and 5 b of the protection circuit 4. The protection circuit 4 has external connection terminals 6a and 6b for supplying current to an external device and connecting to a charging device.

  The protection circuit 4 includes a charge control FET 7 that cuts off the charging current and operates as a charging switch to prevent the secondary battery 2 from being overcharged, and prevents the battery from being overdischarged. For this purpose, a discharge control FET 8 that cuts off discharge and operates as a discharge switch, and a voltage monitoring circuit 9 that controls these switches are provided, and control signal input terminals of the charge control FET 7 and the discharge control FET 8 are respectively It is connected to the output of the voltage monitoring circuit 9.

  Furthermore, in the present embodiment, a leakage current detection electrode 12 composed of two electrodes facing each other is installed on the same circuit board as the protection circuit 4, and one of the electrodes 10 is the gate of the charge control FET 7. The other electrode 11 is connected to the source of the charge control FET 7.

  The input of the voltage monitoring circuit 9 is connected to the battery connection terminals 5a and 5b and the positive external connection terminal 6a. If the battery voltage exceeds a predetermined level, it is determined that the battery is overcharged. A charge cutoff signal is output to the charge control FET 7 to stop charging and prevent an overcharge state. Further, when the battery voltage becomes a predetermined level or less, it is determined that the battery is in an overdischarge state, and a discharge cutoff signal is output to the discharge control FET 8 to stop the discharge and enter an overdischarge state. It is preventing. In addition, when the discharge current exceeds a predetermined magnitude, the voltage between the battery connection terminal 5b and the external connection terminal 6b becomes larger than a predetermined value, so that the voltage monitoring circuit 9 is in an overcurrent or short-circuit state. It is judged and a discharge interruption signal is output to the discharge control FET 8 to prevent an overcurrent state.

  In the present embodiment, when the electrodes 10 and 11 of the leakage current detection electrode 12 become conductive due to leakage or the like, the gate and the source of the charge control FET 7 are short-circuited, and the charge control FET 7 performs a cutoff operation to charge the battery. Stop.

  In addition, when the electrodes 10 and 11 of the leakage current detection electrode 12 are conductive, the discharging current is passed through a parasitic diode inside the charging control FET 7 because the charging control FET 7 is in a cutoff operation during discharging. When the forward voltage of the internal diode is generated, the voltage between the battery connection terminal 5b and the external connection terminal 6b becomes larger than a predetermined value, so that the voltage monitoring circuit 9 determines that it is in an overcurrent or short-circuit state. Thus, a discharge cut-off signal is output to the discharge control FET 8 instantaneously to prevent discharge.

  On the other hand, if the cause of dew condensation or moisture intrusion is eliminated, the moisture between the two electrodes 10 and 11 of the leakage current detection electrode 12 evaporates, and the conductivity of the leakage current detection electrode 12 decreases, the charge control The blocking operation of the FET 7 is finished, and charging / discharging is possible again.

  FIG. 2 is a circuit configuration diagram of Embodiment 2 of the battery pack according to the present invention. In FIG. 2, the battery pack 21 of the present embodiment has a secondary battery 2, a protection circuit 4, and a PTC element 3 in the same manner as the battery pack 1 of the first embodiment, and the protection circuit 4 includes a battery connection terminal 5a. 5b and external connection terminals 6a and 6b. The operations of the charge control FET 7, the discharge control FET 8 and the voltage monitoring circuit 9 of the protection circuit 4 are the same as those in the first embodiment.

  Also in the present embodiment, the leakage current detection electrode 22 composed of two electrodes facing each other is installed on the same circuit board as the protection circuit 4, and one of the electrodes 20 serves as the gate of the charge control FET 7. Although connected, the negative electrode side external connection terminal 6b is used as the other electrode. That is, since the external connection terminal 6b on the negative electrode side is connected to the source of the charge control FET 7, if the electrode 20 and the external connection terminal 6b on the negative electrode side become conductive due to moisture or the like, the gate and the source of the charge control FET 7 are short-circuited. Then, the charge control FET 7 shuts off and stops charging the battery.

  As described above, in the present invention, when a current flows between the leakage current detection electrodes due to the ingress of moisture into the battery pack, the charging is stopped by the operation of the charge control FET, and the charge control FET Discharging through the parasitic diode increases the voltage at the overcurrent monitoring input terminal of the voltage monitoring circuit, and the voltage monitoring circuit stops the discharge by lowering the input terminal voltage of the discharge control FET to a predetermined value or less. Thus, charging / discharging can be stopped. Thereby, a battery pack with a high reliability can be obtained with a simple circuit configuration with a small number of parts.

The circuit block diagram of Embodiment 1 of the battery pack by this invention. The circuit block diagram of Embodiment 2 of the battery pack by this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,21 Battery pack 2 Secondary battery 3 PTC element 4 Protection circuit 5a, 5b Battery connection terminal 6a, 6b External connection terminal 7 Charge control FET
8 Discharge control FET
9 Voltage monitoring circuit 10, 11, 20 Electrode 12, 22 Leakage current detection electrode

Claims (2)

  A battery pack having a secondary battery, a battery protection circuit board including a charge control FET that operates as a charge switch and a discharge control FET that operates as a discharge switch, and includes two opposed electrodes Leakage current detection electrode is provided between the gate and source of the charge control FET on the battery protection circuit board, and charging / discharging is stopped by shutting off the charging switch when the leakage current detection electrode is conducted. A battery pack characterized by   The battery protection circuit board includes a positive electrode side and a negative electrode side external connection terminal for connection to an external device and a charging device, and one electrode constituting the leakage current detection electrode is the negative electrode side external connection terminal. The battery pack according to claim 1.

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