JP2017070204A - Secondary-battery protecting integrated circuit, secondary battery protection apparatus, and battery pack - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable recovery from a discharge prevention state even when a diode is present between a control terminal and a negative terminal.SOLUTION: A secondary-battery protecting integrated circuit comprises: a power supply terminal connected to a positive electrode of a secondary battery; a ground terminal connected to a negative electrode of the secondary battery; an input terminal connected to the negative terminal; a control terminal at which a control signal is input; a pull-down resistor connected between the control terminal and the ground terminal; a voltage monitoring circuit configured to monitor a voltage between the control terminal and the ground terminal; a potential comparison circuit configured to compare a potential at the control terminal with a potential at the input terminal; and a control circuit configured to turn off a discharge control transistor included in the switch circuit in response to the voltage monitoring circuit detecting that the voltage between the control terminal and the ground terminal is higher than a prescribed first threshold, and turn on the discharge control transistor in response to the potential comparison circuit detecting that the potential at the control terminal is lower than the potential at the input terminal.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a secondary battery protection integrated circuit, a secondary battery protection device, and a battery pack.

  Conventionally, a circuit for protecting the secondary battery by turning off the discharge FET inserted in the charge / discharge current path between the negative electrode of the secondary battery and the negative terminal connected to the ground of the load is known. (For example, refer to Patent Document 1). This circuit has a terminal to which a control signal is input. When a control signal is input to the terminal, the circuit is powered down and the discharge FET is turned off to reduce power consumption of the secondary battery. It is to suppress.

JP 2012-257407 A

  FIG. 1 is a diagram illustrating an example of a configuration of a secondary battery protection integrated circuit 420 including a control terminal CNT to which a control signal is input. The secondary battery protection integrated circuit 420 is an example of a circuit that protects the secondary battery 500 from an abnormal state such as overdischarge by turning off the discharge control transistor 312 when an abnormal state such as overdischarge is detected. . The discharge control transistor 312 and the charge control transistor 311 are inserted in series in a charge / discharge current path between the negative electrode 502 of the secondary battery 500 and the negative terminal P− connected to the ground of the electronic device 430. The electronic device 430 is an example of a load having a resistance 452. The secondary battery protection integrated circuit 420, the secondary battery 500, the discharge control transistor 312, and the charge control transistor 311 are built in the battery pack 400. The battery pack 400 supplies power to the electronic device 430 connected via the charge / discharge prohibition switch 510.

  A control signal whose voltage value changes depending on whether the charge / discharge prohibition switch 510 is on or off is input to the control terminal CNT. When the charge / discharge inhibition switch 510 is turned on, the voltage at the control terminal CNT increases. When the detection circuit 370 detects that the voltage at the control terminal CNT exceeds a predetermined charge / discharge inhibition mode detection threshold, the control circuit 398 turns off the discharge control transistor 312 and the charge control transistor 311. Thereby, charging / discharging of the secondary battery 500 is prohibited. On the other hand, when the charge / discharge prohibition switch 510 is turned off, the voltage at the control terminal CNT decreases. When the detection circuit 370 detects that the voltage at the control terminal CNT is equal to or lower than a predetermined charge / discharge inhibition mode return threshold, the control circuit 398 turns on the discharge control transistor 312 and the charge control transistor 311. Thereby, charging / discharging of the secondary battery 500 is permitted.

  However, the pull-down resistor 373 is inserted between the control terminal CNT and the ground terminal VSS, and the diode 451 is parasitic between the control terminal CNT and the minus terminal P− or inserted for countermeasures against static electricity. There may be. In this case, even in a state where discharge of the secondary battery 500 is prohibited by the turn-off of the discharge control transistor 312 (discharge prohibited state), the discharge current 437 from the secondary battery 500 includes the positive electrode 501, the resistance 452, The current flows through the path of the diode 451, the control terminal CNT, the pull-down resistor 373, the ground terminal VSS, and the negative electrode 502.

  By increasing the resistance value of the pull-down resistor 373, an increase in the discharge current 437 in the discharge prohibited state can be suppressed. However, when the resistance value of the pull-down resistor 373 is increased, the voltage at the control terminal CNT is raised by the discharge current 437, so that even if the charge / discharge prohibition switch 510 is turned off, the discharge prohibition state may not be recovered. That is, as a result of the increase in the voltage of the control terminal CNT, the detection circuit 370 does not detect that the voltage of the control terminal CNT is equal to or lower than the charging / discharging prohibition mode return threshold value. It may not be possible to switch from the off state to the on state.

  Therefore, an object of the present invention is to enable recovery from the discharge prohibited state even if a diode exists between the control terminal and the minus terminal.

One idea is that
A secondary battery protection integrated circuit for protecting the secondary battery by controlling a switch circuit inserted in series in a charge / discharge current path between the negative electrode of the secondary battery and a negative terminal connected to the ground of the load Because
A power supply terminal connected to the positive electrode of the secondary battery;
A ground terminal connected to the negative electrode of the secondary battery;
An input terminal connected to the negative terminal;
A control terminal to which a control signal is input;
A pull-down resistor connected between the control terminal and the ground terminal;
A voltage monitoring circuit for monitoring a voltage between the control terminal and the ground terminal;
A potential comparison circuit that compares the potential of the control terminal with the potential of the input terminal;
When the voltage monitoring circuit detects that the voltage between the control terminal and the ground terminal is higher than a predetermined first threshold, the discharge control transistor included in the switch circuit is turned off to turn off the second control transistor. Discharging the secondary battery is prohibited, and when the potential comparison circuit detects that the potential of the control terminal is lower than the potential of the input terminal, the secondary battery is discharged by turning on the discharge control transistor. A secondary battery protection integrated circuit is provided comprising a control circuit to permit.

  According to one aspect, even if a diode exists between the control terminal and the minus terminal, it is possible to return from the discharge prohibited state.

It is a figure which shows an example of a structure of a secondary battery protection integrated circuit provided with the control terminal into which a control signal is input. It is a block diagram which shows an example of a battery pack and an electronic device. It is an equivalent circuit diagram in the case where a diode exists in a state where the charge / discharge prohibition switch, the discharge control transistor, and the charge control switch are turned off. It is an example of the state transition diagram of a control circuit. It is a block diagram which shows an example of a battery pack and an electronic device. It is an equivalent circuit diagram in case a diode exists in a short circuit detection state.

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

  FIG. 2 is a configuration diagram illustrating an example of the battery pack 100 and the electronic device 130. The battery pack 100 includes a secondary battery 200 that can supply power to the electronic device 130 connected to the plus terminal 5 and the minus terminal 6 and a secondary battery protection device 110 that protects the secondary battery 200. . The battery pack 100 may be built in the electronic device 130 or may be externally attached. The battery pack 100 supplies the power of the secondary battery 200 to the electronic device 130 connected via the charge / discharge prohibition switch 210.

  The electronic device 130 is an example of a load that uses the secondary battery 200 of the battery pack 100 as a power source. A specific example of the electronic device 130 is a portable terminal device that can be carried. Specific examples of the mobile terminal device include a mobile phone, a smartphone, a tablet computer, a game machine, a TV, a music and video player, and an electronic device such as a camera.

  Specific examples of the secondary battery 200 include a lithium ion battery and a lithium polymer battery.

  The secondary battery protection device 110 is an example of a secondary battery protection device that operates using the secondary battery 200 as a power source and controls the secondary battery 200 from overdischarge by controlling charging and discharging of the secondary battery 200. . The secondary battery protection device 110 includes a charge / discharge control circuit 140, a battery positive electrode connection terminal 3, a battery negative electrode connection terminal 4, a positive terminal 5, a negative terminal 6, and a control input terminal 10.

  The charge / discharge control circuit 140 is an example of a charge / discharge control circuit that protects the secondary battery 200 from overdischarge or the like by controlling charge / discharge of the secondary battery 200. The charge / discharge control circuit 140 includes a switch circuit 13, a secondary battery protection integrated circuit 120, a resistor 1, a capacitor 2, a resistor 9, and a sense resistor 15.

  The battery positive electrode connection terminal 3 is a terminal connected to the positive electrode 201 of the secondary battery 200, and the battery negative electrode connection terminal 4 is a terminal connected to the negative electrode 202 of the secondary battery 200. The plus terminal 5 is an example of a terminal connected to the device plus terminal 131 of the electronic device 130, and is connected to the device power supply path 141 of the electronic device 130 via the device plus terminal 131. The minus terminal 6 is an example of a terminal connected to the device minus terminal 133 of the electronic device 130, and is connected to the device ground 139 of the electronic device 130 via the device minus terminal 133. The control input terminal 10 is an example of a terminal connected to the control output terminal 132 of the electronic device 130, and is connected to the control unit 134 of the electronic device 130 via the control output terminal 132.

  The electronic device 130 is an example of a load having a resistance component 152. The electronic device 130 includes a control unit 134 having a diode 151 and a resistance component 152. The diode 151 is an element that is parasitic between the control output terminal 132 and the device minus terminal 133 or is inserted for countermeasures against static electricity. The anode of the diode 151 is connected to the device minus terminal 133 and is connected to the minus terminal 6 and the input terminal 95 via the device minus terminal 133. The cathode of the diode 151 is connected to the control output terminal 132 and is connected to the control terminal 96 through the control output terminal 132.

  The battery positive electrode connection terminal 3 and the positive terminal 5 are connected by a positive power supply path 8, and the battery negative electrode connection terminal 4 and the negative terminal 6 are connected by a negative power supply path 7. The positive power supply path 8 is an example of a charge / discharge current path between the battery positive electrode connection terminal 3 and the positive terminal 5, and the negative power supply path 7 is a charge between the battery negative electrode connection terminal 4 and the negative terminal 6. It is an example of a discharge current path.

  The secondary battery protection device 110 includes a switch circuit 13. The switch circuit 13 is inserted in series in the negative power supply path 7 between the first negative connection point 7a and the second negative connection point 7b. The switch circuit 13 is, for example, a series circuit in which a charge control transistor 11 and a discharge control transistor 12 are connected in series. When the charge control transistor 11 is turned off, the negative power supply path 7 through which the charging current of the secondary battery 200 flows is interrupted, and the charging current flow of the secondary battery 200 is prohibited. When the discharge control transistor 12 is turned off, the negative power supply path 7 through which the discharge current of the secondary battery 200 flows is interrupted, and the flow of the discharge current of the secondary battery 200 is prohibited.

  Each of the charge control transistor 11 and the discharge control transistor 12 is, for example, a MOSFET (Metal Oxide Semiconductor Field Effect Transistor). The charge control transistor 11 is inserted into the negative power supply path 7 so that the forward direction of the parasitic diode of the charge control transistor 11 matches the direction in which the discharge current of the secondary battery 200 flows. The discharge control transistor 12 is inserted into the negative power supply path 7 so that the forward direction of the parasitic diode of the discharge control transistor 12 coincides with the direction in which the charging current of the secondary battery 200 flows.

  The secondary battery protection device 110 includes a secondary battery protection integrated circuit 120. The secondary battery protection integrated circuit 120 is an example of a secondary battery protection integrated circuit that operates using the secondary battery 200 as a power source and controls the secondary battery 200 from overcurrent by controlling charging and discharging of the secondary battery 200. It is. The secondary battery protection integrated circuit 120 is supplied with power from the secondary battery 200 to protect the secondary battery 200.

  The secondary battery protection integrated circuit 120 includes, for example, a power supply terminal 91, a ground terminal 92, a charge control terminal 93, a discharge control terminal 94, an input terminal 95, a control terminal 96, and a current detection terminal 97. .

  The power supply terminal 91 is a positive power supply terminal connected to the positive electrode 201 of the secondary battery 200 through the positive connection point 8a and the battery positive connection terminal 3, and may be referred to as a VDD terminal. The power supply terminal 91 is connected to, for example, a connection point between the other end of the resistor 1 whose one end is connected to the plus-side power supply path 8 and the other end of the capacitor 2 whose one end is connected to the minus-side power supply path 7. One end of the capacitor 2 is connected to the negative power supply path 7 between the battery negative electrode connection terminal 4 and the discharge control transistor 12 at a first negative connection point 7a.

  The ground terminal 92 is a negative power supply terminal connected to the negative electrode 202 of the secondary battery 200 via the first negative connection point 7a and the battery negative connection terminal 4, and may be referred to as a VSS terminal. The ground terminal 92 is connected to the negative power supply path 7 at the first negative connection point 7 a and is connected to the source of the discharge control transistor 12.

  The charging control terminal 93 is a terminal that outputs a signal for prohibiting charging of the secondary battery 200, and may be referred to as a COUT terminal. The charge control terminal 93 is connected to a control electrode (for example, a gate in the case of a MOSFET) of the charge control transistor 11.

  The discharge control terminal 94 is a terminal that outputs a signal for prohibiting the discharge of the secondary battery 200, and is sometimes referred to as a DOUT terminal. The discharge control terminal 94 is connected to a control electrode (for example, a gate in the case of a MOSFET) of the discharge control transistor 12.

  The input terminal 95 is a terminal connected to the minus terminal 6 connected to the device ground 139 of the electronic device 130 and may be referred to as a V-terminal. The input terminal 95 is connected to the negative power supply path 7 between the negative terminal 6 and the charge control transistor 11 through the resistor 9 at the second negative connection point 7b. The input terminal 95 is connected to the source of the charge control transistor 11 via the resistor 9.

  The control terminal 96 is a terminal to which a control signal having the minus terminal 6 as a reference potential is input via the control input terminal 10, and is sometimes referred to as a CNT terminal. The control input terminal 10 is connected to the control output terminal 132.

  The current detection terminal 97 is an example of a current detection terminal used by the secondary battery protection integrated circuit 120. The current detection terminal 97 is a terminal connected to the negative power supply path 7 at the third negative connection point 7c opposite to the first negative connection point 7a with respect to the sense resistor 15, and the CS terminal Sometimes called. The sense resistor 15 is a current detection resistor inserted in series with the negative power supply path 7. One end of the sense resistor 15 is connected to the negative electrode 202 and the ground terminal 92 of the secondary battery 200 via the first minus side connection point 7a, and the other end of the sense resistor 15 is connected to the third minus side connection point 7c. To the source of the transistor 12 and the current detection terminal 97.

  The secondary battery protection integrated circuit 120 performs a protection operation for the secondary battery 200. The secondary battery protection integrated circuit 120 includes an abnormality detection circuit 21 and a control circuit 98. The abnormality detection circuit 21 is an example of a unit that detects an abnormality in the current or voltage of the secondary battery 200. The control circuit 98 includes a switch control circuit that controls on / off of the transistors 11 and 12 of the switch circuit 13 based on the abnormality detection result by the abnormality detection circuit 21. The control circuit 98 and the switch control circuit are configured by a logic circuit, for example.

  For example, the control circuit 98 performs an operation (overcharge protection operation) for protecting the secondary battery 200 from overcharge. For example, the abnormality detection circuit 21 monitors the battery voltage (cell voltage) of the secondary battery 200 by detecting the voltage between the power supply terminal 91 and the ground terminal 92. The abnormality detection circuit 21 outputs an overcharge detection signal on the assumption that overcharge of the secondary battery 200 is detected by detecting a cell voltage equal to or higher than a predetermined overcharge detection voltage Vdet1.

  The control circuit 98 that has detected the overcharge detection signal waits for the elapse of a predetermined overcharge detection delay time tVdet1 and executes an overcharge protection operation in which a low-level control signal for turning off the transistor 11 is output from the charge control terminal 93. To do. When the transistor 11 is turned off, charging of the secondary battery 200 is prohibited regardless of whether the transistor 12 is on or off, and the secondary battery 200 can be prevented from being overcharged.

  For example, the control circuit 98 performs an operation (overdischarge protection operation) for protecting the secondary battery 200 from overdischarge. For example, the abnormality detection circuit 21 monitors the battery voltage (cell voltage) of the secondary battery 200 by detecting the voltage between the power supply terminal 91 and the ground terminal 92. The abnormality detection circuit 21 outputs an overdischarge detection signal on the assumption that overdischarge of the secondary battery 200 is detected by detecting a cell voltage equal to or lower than a predetermined overdischarge detection voltage Vdet2.

  The control circuit 98 that has detected the overdischarge detection signal waits for the elapse of a predetermined overdischarge detection delay time tVdet2, and executes an overdischarge protection operation in which a low level control signal for turning off the transistor 12 is output from the discharge control terminal 94. To do. When the transistor 12 is turned off, discharge of the secondary battery 200 is prohibited regardless of whether the transistor 11 is on or off, and the secondary battery 200 can be prevented from being overdischarged.

  On the other hand, the abnormality detection circuit 21 detects a cell voltage equal to or higher than a predetermined overdischarge return voltage Vrel2, and outputs an overdischarge return signal indicating that the secondary battery 200 has returned from the overdischarge state to the normal state (“ The output of the overdischarge detection signal may be stopped ”). The overdischarge recovery voltage Vrel2 is higher than the overdischarge detection voltage Vdet2.

  The control circuit 98 that has detected the overdischarge return signal (or the control circuit 98 that has detected the stop of the output of the overdischarge detection signal) outputs a high-level control signal for turning on the transistor 12 from the discharge control terminal 94. The overdischarge protection operation ends when the transistor 12 is turned on.

  For example, the control circuit 98 performs an operation for protecting the secondary battery 200 from discharge overcurrent (discharge overcurrent protection operation). For example, the abnormality detection circuit 21 detects a sense voltage generated between the current detection terminal 97 and the ground terminal 92 by the current flowing through the sense resistor 15. The abnormality detection circuit 21 detects a discharge overcurrent which is an abnormal current flowing in the negative battery path 7 in the discharge direction of the secondary battery 200 by detecting a sense voltage equal to or higher than a predetermined discharge overcurrent detection voltage Vdet3. A discharge overcurrent detection signal indicating that is output.

  The control circuit 98 that has detected the discharge overcurrent detection signal waits for the elapse of a predetermined discharge overcurrent detection delay time tVdet3 and outputs a low level control signal for turning off the transistor 12 from the discharge control terminal 94. Perform the action. When the transistor 12 is turned off, discharge of the secondary battery 200 is prohibited regardless of whether the transistor 11 is on or off, and it is possible to prevent overcurrent from flowing in the direction in which the secondary battery 200 is discharged. it can.

  For example, the control circuit 98 performs an operation for protecting the secondary battery 200 from a charging overcurrent (charging overcurrent protection operation). For example, the abnormality detection circuit 21 detects a sense voltage generated between the current detection terminal 97 and the ground terminal 92 by the current flowing through the sense resistor 15. The abnormality detection circuit 21 detects a sense voltage equal to or lower than a predetermined charge overcurrent detection voltage Vdet4, thereby detecting a charge overcurrent that is an abnormal current flowing in the negative battery path 7 in the charging direction of the secondary battery 200. A charge overcurrent detection signal indicating that is output.

  The control circuit 98 that has detected the charge overcurrent detection signal waits for the elapse of a predetermined charge overcurrent detection delay time tVdet4 and outputs a low level control signal for turning off the transistor 11 from the charge control terminal 93. Perform the action. When the transistor 11 is turned off, charging of the secondary battery 200 is prohibited regardless of whether the transistor 12 is on or off, and overcurrent can be prevented from flowing in the direction in which the secondary battery 200 is charged. it can.

  For example, the control circuit 98 performs an operation (short circuit protection operation) for protecting the secondary battery 200 from a short circuit current by controlling the transistor 12. For example, when the abnormality detection circuit 21 detects a voltage equal to or higher than a predetermined first short circuit detection voltage Vshort1 between the current detection terminal 97 and the ground terminal 92, the abnormality detection circuit between the positive terminal 5 and the negative terminal 6 is detected. A short-circuit detection signal indicating that has been detected is output. Alternatively, for example, when the abnormality detection circuit 21 detects a voltage equal to or higher than a predetermined second short circuit detection voltage Vshort 2 between the input terminal 95 and the ground terminal 92, the short circuit between the positive terminal 5 and the negative terminal 6. A short circuit detection signal indicating that an abnormality has been detected is output. The second short circuit detection voltage Vshort2 is sufficiently larger than the first short circuit detection voltage Vshort1.

  The control circuit 98 that has detected the short-circuit detection signal performs a short-circuit protection operation in which a low-level control signal that turns off the transistor 12 is output from the discharge control terminal 94. When the transistor 12 is turned off, discharge of the secondary battery 200 is prohibited regardless of whether the transistor 11 is on or off, and a short-circuit current can be prevented from flowing in the direction in which the secondary battery 200 is discharged. it can.

  The secondary battery protection integrated circuit 120 includes a pull-down resistor 73, a voltage monitoring circuit 70, and a potential comparison circuit 80. The pull-down resistor 73 is inserted and connected between the control terminal 96 and the ground terminal 92. The voltage monitoring circuit 70 monitors the voltage between the control terminal 96 and the ground terminal 92. The voltage monitoring circuit 70 includes, for example, a threshold voltage generation circuit that generates a threshold voltage 72 and a comparator 71. The potential comparison circuit 80 includes a comparator that compares the potential of the control terminal 96 with the potential of the input terminal 95.

  A control signal whose voltage value changes in accordance with the on / off state of the charge / discharge prohibition switch 210 is input to the control terminal 96. When the charging / discharging prohibition switch 210 is turned on, the voltage between the control terminal 96 and the ground terminal 92 increases. When the comparator 71 of the voltage monitoring circuit 70 detects that the voltage between the control terminal 96 and the ground terminal 92 has exceeded the charge / discharge inhibition mode detection threshold (an example of a predetermined first threshold), the control circuit 98. Turns off the discharge control transistor 12 and the charge control transistor 11. Thereby, charging / discharging of the secondary battery 500 is prohibited. On the other hand, when the charge / discharge inhibition switch 210 is turned off, the voltage between the control terminal 96 and the ground terminal 92 decreases. The comparator 71 of the voltage monitoring circuit 70 confirms that the voltage between the control terminal 96 and the ground terminal 92 is equal to or lower than a predetermined charge / discharge inhibition mode return threshold (an example of a predetermined second threshold equal to or lower than the first threshold). If detected, the control circuit 98 turns on the discharge control transistor 12 and the charge control transistor 11. Thereby, charging / discharging of the secondary battery 500 is permitted.

  The diode 151 of the electronic device 130 is an element that is parasitic between the control output terminal 132 and the device minus terminal 133 or inserted for countermeasures against static electricity. The anode of the diode 151 is connected to the device minus terminal 133 and is connected to the minus terminal 6 and the input terminal 95 via the device minus terminal 133. The cathode of the diode 151 is connected to the control output terminal 132 and is connected to the control terminal 96 through the control output terminal 132.

  When the diode 151 is not present between the control terminal 96 and the negative terminal 6, the control terminal 96 is pulled down to the ground terminal 92 by the pull-down resistor 73, so that the control circuit 98 can recover from the charge / discharge prohibited state. That is, since the control circuit 98 detects that the voltage between the control terminal 96 and the ground terminal 92 is equal to or lower than a predetermined charge / discharge inhibition mode return threshold, the comparator 71 of the voltage monitoring circuit 70 detects the discharge control transistor 12 and The charge control transistor 11 can be turned on.

  On the other hand, when the diode 151 is present between the control terminal 96 and the negative terminal 6, in the state where the discharge control transistor 12 and the charge control transistor 11 are turned off, the discharge from the secondary battery 200 is performed as shown in FIG. A current 137 flows.

  FIG. 3 is an equivalent circuit diagram in the case where the diode 151 is present with the charge / discharge prohibition switch 210, the discharge control transistor 12, and the charge control transistor 11 turned off. The voltage of the control terminal 96 is determined by the discharge current 137 from the secondary battery 200, the resistor 152, and the pull-down resistor 73. Accordingly, when the resistance value of the pull-down resistor 73 is relatively high, the voltage between the control terminal 96 and the ground terminal 92 is excessively raised by the discharge current 137. Therefore, even if the charge / discharge prohibition switch 210 is turned off, the voltage monitoring circuit 70 cannot detect that the voltage between the control terminal 96 and the ground terminal 92 is equal to or lower than the charge / discharge prohibition mode return threshold value. May not return from. However, when the discharge current 137 flows, the potential of the control terminal 96 becomes lower by the forward voltage of the diode 151 than that of the input terminal 95 or the negative terminal 6.

  Therefore, when the potential comparison circuit 80 detects that the potential of the control terminal 96 is lower than the potential of the input terminal 95, the control circuit 98 turns on the discharge control transistor 12 and the charge control transistor 11 to turn on the secondary battery. Allow 200 charging / discharging. Thereby, it is possible to return from the charge / discharge prohibited state.

  FIG. 4 is a state transition diagram of the control circuit 98.

  In the normal state S10, the control circuit 98 turns on the discharge control transistor 12 and the charge control transistor 11 by setting the COUT terminal and the DOUT terminal to a high level. In the normal state S10, the control circuit 98 sets the COUT terminal to the high level and the DOUT terminal to the low level when the abnormality detection circuit 21 detects the cell voltage lower than the predetermined overdischarge detection voltage Vdet2. As a result, the operation state of the control circuit 98 transitions to the overdischarge detection state S20 in which the discharge control transistor 12 is turned off. In the overdischarge detection state S20, the control circuit 98 sets the COUT terminal to the high level and the DOUT terminal to the high level when the abnormality detection circuit 21 detects the cell voltage higher than the predetermined overdischarge return voltage Vrel2. As a result, the operating state of the control circuit 98 transitions to the normal state S10.

  In the normal state S10, when the voltage monitoring circuit 70 detects that the voltage of the control terminal 96 exceeds the charge / discharge inhibition mode detection threshold (CNT = H), the control circuit 98 sets the COUT terminal and the DOUT terminal to the low level. Thus, the discharge control transistor 12 and the charge control transistor 11 are turned off. As a result, the operating state of the control circuit 98 transitions to the charge / discharge inhibition state S30.

  When the voltage monitoring circuit 70 detects that the voltage between the control terminal 96 and the ground terminal 92 is equal to or lower than the charge / discharge inhibition mode return threshold in the charge / discharge inhibition state S30 (CNT = L), or the control terminal When the potential comparison circuit 80 detects that the potential of 96 is lower than the potential of the input terminal 95 (CNT <V−), the control circuit 98 sets the COUT terminal and the DOUT terminal to high level. As a result, the discharge control transistor 12 and the charge control transistor 11 are turned on, and the operation state of the control circuit 98 transitions to the normal state S10.

  In the charge / discharge inhibition state S30, the control circuit 98 sets the COUT terminal to the high level and the DOUT terminal to the low level when the abnormality detection circuit 21 detects the cell voltage lower than the predetermined overdischarge detection voltage Vdet2. As a result, the operating state of the control circuit 98 transitions to the overdischarge detection state S20.

  Therefore, according to the present embodiment, whether the charging / discharging of the secondary battery 200 is permitted or not can be controlled by turning on / off the charging / discharging prohibition switch 210 regardless of the presence / absence of the diode 151 on the electronic device 130 side. In addition, it is possible to return from the discharge prohibited state without changing the configuration on the electronic device 130 side, and the current consumption of the battery pack 100 can also be suppressed.

  Further, as shown in FIG. 5, when the short circuit abnormality 211 between the positive terminal 5 and the negative terminal 6 is detected, as described above, the control circuit 98 turns off the discharge control transistor 12 (discharge prohibited state). ). Even in the discharge prohibited state due to the short circuit abnormality 211, when the diode 151 exists, the voltage between the control terminal 96 and the ground terminal 92 rises. Therefore, the voltage monitoring circuit 70 may detect that the voltage between the control terminal 96 and the ground terminal 92 has exceeded the charge / discharge inhibition mode detection threshold, and may erroneously detect the charge / discharge inhibition mode.

  However, in the discharge prohibited state due to the short circuit abnormality 211, the potential of the control terminal 96 is lower than the potential of the input terminal 95 by the forward voltage of the diode 151 (see FIG. 6). The diode detection function of the potential comparison circuit 80 makes it possible to detect a decrease in the potential of the control terminal 96, thereby eliminating erroneous detection in the charge / discharge inhibition mode.

  As described above, the secondary battery protection integrated circuit has been described by the embodiment, but the present invention is not limited to the above embodiment. Various modifications and improvements such as combinations and substitutions with some or all of the other embodiments are possible within the scope of the present invention.

5 plus terminal 6 minus terminal 7 minus side power supply path 10 control input terminal 13 switch circuit 91 power supply terminal 92 ground terminal 95 input terminal 96 control terminal 98 control circuit 100 battery pack 110 secondary battery protection device 120 secondary battery protection integrated circuit 130 Electronic device 139 Device ground 140 Charge / discharge control circuit 200 Secondary battery

Claims (6)

A secondary battery protection integrated circuit for protecting the secondary battery by controlling a switch circuit inserted in series in a charge / discharge current path between the negative electrode of the secondary battery and a negative terminal connected to the ground of the load Because
A power supply terminal connected to the positive electrode of the secondary battery;
A ground terminal connected to the negative electrode of the secondary battery;
An input terminal connected to the negative terminal;
A control terminal to which a control signal is input;
A pull-down resistor connected between the control terminal and the ground terminal;
A voltage monitoring circuit for monitoring a voltage between the control terminal and the ground terminal;
A potential comparison circuit that compares the potential of the control terminal with the potential of the input terminal;
When the voltage monitoring circuit detects that the voltage between the control terminal and the ground terminal is higher than a predetermined first threshold, the discharge control transistor included in the switch circuit is turned off to turn off the second control transistor. Discharging the secondary battery is prohibited, and when the potential comparison circuit detects that the potential of the control terminal is lower than the potential of the input terminal, the secondary battery is discharged by turning on the discharge control transistor. A secondary battery protection integrated circuit comprising a control circuit to permit.   When the voltage monitoring circuit detects that the voltage between the control terminal and the ground terminal is lower than a predetermined second threshold value not more than the first threshold value, the discharge control transistor The secondary battery protection integrated circuit according to claim 1, wherein discharging of the secondary battery is permitted by turning on.   The control circuit turns off a charge control transistor included in the switch circuit when the voltage monitoring circuit detects that the voltage between the control terminal and the ground terminal is higher than the first threshold value. The secondary battery is prohibited from being charged, and when the potential comparison circuit detects that the potential of the control terminal is lower than the potential of the input terminal, the secondary battery is turned on by turning on the charge control transistor. The secondary battery protection integrated circuit according to claim 1, wherein charging of the battery is permitted.   When the voltage monitoring circuit detects that the voltage between the control terminal and the ground terminal is lower than a predetermined second threshold value not more than the first threshold value, the control circuit causes the switch circuit to The secondary battery protection integrated circuit according to claim 2, wherein charging of the secondary battery is permitted by turning on a charge control transistor included therein.   A secondary battery protection device comprising the secondary battery protection integrated circuit according to claim 1 and the switch circuit.   A battery pack comprising the secondary battery protection device according to claim 5 and the secondary battery.

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