JP2012156139A - Protection device for secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a protection device for a secondary battery capable of monitoring a voltage of the secondary battery even in a charge stop state or a discharge stop state to enable a safety measure to be taken, and of grasping an operation history and the like of the secondary battery even in an external device to enable a safety measure to be taken.SOLUTION: A secondary battery 1 and a protection device 2 for protecting the secondary battery 1 are mounted. The protection device 2 has: an overcharge protection circuit 3 that stops charging; an overdischarge protection circuit 4 that stops discharging; a voltage monitoring control circuit 5 monitoring a charge voltage and a discharge voltage and operating the overcharge protection circuit 3 and the overdischarge protection circuit 4; a non-volatile memory 6; and a communication circuit 7. The voltage monitoring control circuit 5 has means of detecting a voltage of the secondary battery 1 and recording data of the detected voltage in the non-volatile memory 6 at a predetermined time interval during operation of the overcharge protection circuit 3 or the overdischarge protection circuit 4. The communication circuit 7 has a reading circuit for reading the non-volatile memory 6, and a communication signal terminal for communicating data read by the reading circuit to an external device.

Description

  The present invention relates to a secondary battery, and more particularly to a protection device for a secondary battery that monitors and protects overcharge and overdischarge.

  Secondary batteries with high energy density, such as lithium ion batteries, are mounted as a battery pack that is integrated with a protective device that protects the battery from overcharge and overdischarge in order to prevent battery deterioration or to ensure safety. It is used by being mounted on battery-powered equipment.

  A conventional example of a secondary battery pack provided with the above-described protection device is disclosed in Patent Document 1 and the like, and FIG. 3 shows an example of a typical circuit block diagram thereof. The secondary battery protection device 12 includes a voltage monitoring control circuit 15 for monitoring the voltage of the secondary battery 11 including one or a plurality of secondary batteries, and a switch element inserted in a charge / discharge path controlled thereby. The overcharge protection circuit 13 and the overdischarge protection circuit 14 are configured as follows. The voltage monitoring control circuit 15 monitors the battery voltage of the secondary battery 11, detects overcharge when the battery voltage reaches the first set voltage near the upper limit of the operable voltage, and switches the overcharge protection circuit 13. When the voltage of the secondary battery becomes equal to or lower than the second set voltage near the lower limit of the operable voltage, control is performed to detect overdischarge and turn off the switch of the overdischarge protection circuit 14.

Japanese Patent No. 3622243

  The above-described conventional secondary battery protection device only performs an operation of cutting off the charging path with a switch when overcharge is detected, and blocking the discharge path with a switch when overdischarge is detected. After the protection circuits are switched off, that is, in the charge stop state after overcharge detection and the discharge stop state after overdischarge detection, the circuits are simply left off. That is, there is a problem that the state of the secondary battery is not known after the circuit is shut off until the voltage returns to the operable range and the switch is automatically turned on. In this way, when the state of the secondary battery after shutoff is not monitored, for example, after overcharge is detected, detection when the secondary battery rises abnormally without stopping charging due to malfunction of the switch etc. In addition, there is a drawback that it is impossible to monitor voltage drop due to long-term storage of the secondary battery after overdischarge detection.

  Another problem is that conventional protection devices cannot obtain information even if overcharge or overdischarge tends to occur due to deterioration of the secondary battery. In other words, when a secondary battery is used connected to an external device, the secondary device's voltage status data and data such as overcharge / overdischarge detection operation history are transmitted to the external device, and the external device is also in that state. This is because it is desirable to be able to take safety measures such as circuit disconnection or power supply circuit connection according to the above, and replacement of the secondary battery.

  Therefore, the object of the present invention is to take a safety measure by monitoring the voltage of the secondary battery even in the charge stop state after overcharge detection or the discharge stop state after overdischarge detection, and connecting to the secondary battery. Another object of the present invention is to provide a secondary battery protection device which can take safety measures by grasping the operation history of the secondary battery even in an external device.

  In order to solve the above-described problems, the present invention provides a secondary battery protection device for controlling overcharge and overdischarge of a secondary battery, wherein the overcharge is inserted into the charging path of the secondary battery and stops charging by its operation. A protection circuit; and a voltage monitoring control circuit that monitors a charging voltage and operates the overcharge protection circuit when an overcharge of a predetermined voltage or more occurs. During operation of the overcharge protection circuit, a predetermined time interval And a means for detecting the voltage of the secondary battery and recording data of the detected voltage in a nonvolatile memory.

  Also, an overdischarge protection circuit that is inserted into the discharge path of the secondary battery and stops discharge by its operation, and the discharge voltage is monitored, and the overdischarge protection circuit is operated when an overdischarge below a predetermined voltage occurs. A voltage monitoring control circuit, and a means for detecting the voltage of the secondary battery at predetermined time intervals during operation of the overdischarge protection circuit and recording data of the detected voltage in a nonvolatile memory. .

  An overcharge protection circuit which is inserted into the charging path of the secondary battery and stops charging by the operation; an overdischarge protection circuit which is inserted into the discharge path of the secondary battery and stops discharging by the operation; and a charging voltage A voltage monitoring control circuit that monitors the discharge voltage and operates the overcharge protection circuit when overcharge exceeds a predetermined voltage, and operates the overdischarge protection circuit when overdischarge occurs below a predetermined voltage. And a means for detecting the voltage of the secondary battery at predetermined time intervals during operation of the overcharge protection circuit or overdischarge protection circuit and recording data of the detected voltage in a nonvolatile memory. Good.

  The nonvolatile memory may record at least one of data relating to the operation time or the number of operations of the overcharge protection circuit or the overdischarge protection circuit.

  In addition, it is preferable to include means for transmitting the data recorded in the nonvolatile memory to an external device connected to the secondary battery.

  As described above, in the present invention, even after overcharge detection or overdischarge detection, the voltage of the secondary battery is detected at predetermined time intervals, the data is recorded in the nonvolatile memory, and the data is further stored in an external device. By providing a means to communicate, safety measures can be taken by monitoring the voltage of the secondary battery even in the charge stop state after overcharge detection or the discharge stop state after overdischarge detection, and connected to the secondary battery Even in an external device, a secondary battery protection device capable of grasping the operation history of the secondary battery and taking safety measures can be obtained.

  As a result, it is possible to determine the discharge state of the secondary battery after detecting the overdischarge of the secondary battery. The secondary battery can be used safely. Further, the charging voltage state of the secondary battery after detecting the overcharging of the secondary battery can be determined, and if the overcharged state continues, measures such as stopping the connection to the external device can be taken.

  In addition, by transmitting the voltage state stored in the nonvolatile memory, the operation history of the protection circuit, etc. to the external device, the external device can determine the abnormal state occurrence and the voltage state of the secondary battery after the abnormal state occurs. The external device can determine whether or not recharge is possible after the overcharge state and the charge method after the overdischarge state, and the secondary battery can be used safely.

The circuit block diagram which shows the secondary battery pack which uses the protection apparatus of the secondary battery which is one embodiment of this invention. The flowchart which shows the process in which a voltage monitoring control circuit detects overcharge or overdischarge, and records the voltage of a secondary battery regularly in a non-volatile memory. The figure which shows an example of the conventional typical circuit block diagram of the secondary battery pack which installed the protective device.

  Next, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a circuit block diagram showing a secondary battery pack using a secondary battery protection device according to an embodiment of the present invention. As shown in FIG. 1, a secondary battery 1 as a secondary battery body and a protection device 2 that protects the secondary battery body are mounted inside the secondary battery pack, and the protection device 2 is inserted into the charging path of the secondary battery 1. An overcharge protection circuit 3 that stops charging by the operation, an overdischarge protection circuit 4 that is inserted in the discharge path of the secondary battery 1 and stops discharge by the operation, and monitors the charge voltage and the discharge voltage to a predetermined voltage. The voltage monitoring control circuit 5 operates the overcharge protection circuit 3 when the overcharge occurs as described above, and operates the overdischarge protection circuit 4 when the overdischarge occurs below a predetermined voltage. Furthermore, the protection device according to the present embodiment includes the nonvolatile memory 6 and the communication circuit 7, and the voltage monitoring control circuit 5 is secondary at predetermined time intervals during the operation of the overcharge protection circuit 3 or the overdischarge protection circuit 4. Means are provided for detecting the voltage of the battery 1 and recording data of the detected voltage in the nonvolatile memory 6.

The voltage monitoring control circuit 5 monitors the operations of the overcharge protection circuit 3 and the overdischarge protection circuit 4 and performs the following operations.
(1) When the voltage monitoring control circuit 5 detects overcharge and the overcharge protection circuit 3 operates to cut off the charging path A, the voltage monitoring control circuit 5 starts monitoring the voltage of the secondary battery 1, After a lapse of time, the voltage of the secondary battery 1 is recorded in the nonvolatile memory 6. The voltage is recorded at predetermined time intervals while the overcharge protection circuit 3 is operating. Therefore, the voltage of the secondary battery 1 in the overcharge protection state is periodically recorded in the nonvolatile memory 6.
(2) When the voltage monitoring control circuit 5 detects overdischarge, and the overdischarge protection circuit 4 operates to cut off the discharge path B, the voltage monitoring control circuit 5 starts monitoring the voltage of the secondary battery 1, After a lapse of time, the voltage of the secondary battery 1 is recorded in the nonvolatile memory 6. The voltage is recorded at predetermined time intervals while the overdischarge protection circuit 3 is operating. Therefore, the voltage of the secondary battery 1 in the overdischarge protection state is periodically recorded in the nonvolatile memory 6.
(3) In addition, data relating to the operation time and the number of operations of the overcharge protection circuit 3 or the overdischarge protection circuit 4 is recorded in the nonvolatile memory.

  The communication circuit 7 has a read signal of the nonvolatile memory 6 and a communication signal terminal for transmitting the read data to an external device connected to the secondary battery 1, and is stored in the nonvolatile memory 6. The voltage record of the secondary battery 1 can be read from an external device such as a charger or a communication device main body via the communication signal terminal from the communication circuit 7. The read content is a history of the overdischarge / overcharge state of the secondary battery. When a discharge state close to 0 V, for example, has occurred in the past, the charger uses the indicator to inform the operator of past abnormalities and You can post a message to refrain from charging for safety.

  FIG. 2 is a flowchart showing a process in which the voltage monitoring control circuit 5 detects overcharge or overdischarge and periodically records the voltage of the secondary battery in the nonvolatile memory 6. After the operation of the overcharge protection circuit 3 or the overdischarge protection circuit 4, the detection voltage is periodically recorded at predetermined time intervals by a monitoring timer. When overcharge and overdischarge are released and the operations of the overcharge protection circuit 3 and the overdischarge protection circuit 4 are stopped, recording is also stopped. As the predetermined time interval of the timer, for example, a value of several seconds to several minutes can be set, and is set according to the expected charging time, discharging time and the memory amount of the nonvolatile memory 6. As the nonvolatile memory 6, an EEPROM, an EPROM, a flash memory, or the like can be used.

  As described above, according to the present invention, safety measures can be taken by monitoring the voltage of the secondary battery even in the charge stop state or the discharge stop state, and further, the operation history of the secondary battery can be grasped also in an external device. Therefore, the secondary battery protection device according to the present invention is particularly suitable for lithium ion secondary batteries used in mobile devices such as mobile phones that require various types of safety management. It can be suitably used.

  It goes without saying that the secondary battery protection device of the present invention is not limited to the above-described embodiment. For example, according to the purpose of use, only one of the overcharge protection circuit and the overdischarge protection circuit is provided. It is also applicable when It is also possible to provide means for taking safety measures in the secondary battery pack based on the recorded data.

DESCRIPTION OF SYMBOLS 1,11 Secondary battery 2,12 Protection device 3,13 Overcharge protection circuit 4,14 Overdischarge protection circuit 5,15 Voltage monitoring control circuit 6 Non-volatile memory 7 Communication circuit

Claims (4)

In the secondary battery protection device that controls overcharge and overdischarge of the secondary battery,
An overdischarge protection circuit that is inserted into the discharge path of the secondary battery and stops discharge by its operation;
A voltage monitoring control circuit that monitors the discharge voltage and operates the overdischarge protection circuit when an overdischarge occurs below a predetermined voltage;
An apparatus for protecting a secondary battery, comprising means for detecting a voltage of the secondary battery at predetermined time intervals during operation of the overdischarge protection circuit and recording data of the detected voltage in a nonvolatile memory.   The secondary battery protection device according to claim 1, wherein at least one of data relating to an operation time or the number of operations of the overdischarge protection circuit is recorded in the nonvolatile memory.   The secondary battery protection device according to claim 1, further comprising means for transmitting the data recorded in the nonvolatile memory to an external device connected to the secondary battery. .   4. The voltage monitoring control circuit according to claim 1, wherein the voltage monitoring control circuit starts or stops recording the data of the detection voltage in the nonvolatile memory based on an operation of the overdischarge protection circuit. Secondary battery protection circuit.

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