JP5064455B2 - Protection circuit, battery pack, and charging system - Google Patents

Description

  The present invention relates to a protection circuit for a secondary battery, and a battery pack and a charging system including the protection circuit.

  Conventionally, a battery pack provided with a secondary battery is known in which a thermal fuse is connected in series with the secondary battery. In such a battery pack, when an abnormality of the secondary battery is detected, the heater is heated by the output voltage of the secondary battery, and the temperature fuse is blown to permanently disable the battery pack. It is like that.

  However, if the battery voltage of the secondary battery is low, even if the battery voltage is applied to the heater, the amount of heat generated by the heater may be insufficient and the temperature fuse may not blow. In such a case, there is a problem that not only the temperature fuse cannot be blown but also the temperature of the battery pack rises because the heater continues to generate heat in the battery pack.

  Therefore, when the battery voltage of the secondary battery is less than the predetermined voltage that can blow the thermal fuse, the secondary battery is charged and waits for the battery voltage to reach the predetermined voltage. There is known a technique that melts and melts (see, for example, Patent Document 1).

JP 2007-215310 A

  By the way, when an abnormality that tries to blow the fuse occurs, it is desirable from the viewpoint of safety that the fuse can be blown out as much as possible without discharging the secondary battery. This is because when the secondary battery is discharged and the fuse is blown with the electric power, the temperature of the secondary battery is further increased by the discharge.

  However, the technique described in Patent Document 1 is preferable from the viewpoint of safety because the secondary battery is discharged and the thermal fuse is blown when an abnormality such as blowing the fuse occurs. There was an inconvenience.

  An object of the present invention is to provide a secondary battery protection circuit capable of reducing the chance of discharging a secondary battery, and a battery pack including the same, as compared with the technique described in Patent Document 1 when a thermal fuse is blown. And providing a charging system.

  The protection circuit according to the present invention includes a connection terminal that receives a voltage for charging a secondary battery, a switching element interposed between the connection terminal and the secondary battery, the connection terminal, and the switching A temperature fuse for interrupting a conductive path between the element, a heater for blowing the temperature fuse, a terminal voltage detection unit for detecting the voltage of the connection terminal, and a recoverable abnormality set in advance A first abnormality detection unit that detects that a first abnormality has occurred; a second abnormality detection unit that detects that a second abnormality preset as an abnormality that should cause the thermal fuse to melt; and When the first abnormality is detected by the abnormality detector, the protection controller that turns off the switching element, the second abnormality is detected by the second abnormality detector, and the terminal voltage detector Therefore, when the detected voltage is equal to or higher than a threshold voltage set as a voltage capable of causing the heater to generate heat and blow the thermal fuse, the voltage applied to the conductive path is supplied to the heater. And a heater control unit that executes a thermal fuse fusing process.

  According to this configuration, when the first abnormality is detected by the first abnormality detection unit, the switching element is turned off, the connection between the connection terminal and the secondary battery is cut off, and the secondary battery is protected. . The second abnormality is detected by the second abnormality detection unit, and the voltage detected by the terminal voltage detection unit is equal to or higher than a threshold voltage set as a voltage capable of causing the heater to generate heat and blow the temperature fuse. At some time, the voltage received by the connection terminal by the heater controller is supplied to the heater via the conductive path, and the temperature fuse is blown by the heat generated by the heater.

  At this time, since voltage is supplied to the heater from the conductive path between the connection terminal and the switching element, even if the switching element is turned off and discharge of the secondary battery is prohibited, power is received by the connection terminal. As a result, the temperature fuse can be blown using the generated voltage. As a result, when the temperature fuse is blown, the chance of discharging the secondary battery can be reduced as compared with the technique described in Patent Document 1.

  On the other hand, even when the second abnormality detecting unit detects the second abnormality that should blow the thermal fuse, the voltage detected by the terminal voltage detecting unit does not reach the threshold voltage, and is therefore received by the connection terminal. When it is considered that the temperature fuse cannot be blown with the heater heat generation based on the voltage, voltage is not supplied from the connection terminal to the heater via the conductive path, and the heater continues to generate heat with a heat generation amount that the temperature fuse cannot be blown. The risk of doing so is reduced.

  The battery control unit further includes a battery voltage detection unit that detects a battery voltage of the secondary battery, and the heater control unit is configured to detect the terminal voltage when the second abnormality is detected by the second abnormality detection unit. When the voltage detected by the unit is less than the threshold voltage and the battery voltage detected by the battery voltage detection unit is equal to or higher than the threshold voltage, the switching element is forcibly turned on and applied to the conductive path. It is preferable to supply the applied voltage to the heater.

  According to this configuration, even if the voltage received by the connection terminal is less than the threshold voltage, and therefore it is considered that the thermal fuse cannot be blown by the amount of heat generated by the heater based on the voltage received by the connection terminal, When the battery voltage detected by the battery voltage detection unit is equal to or higher than the threshold voltage, and thus it is considered that the thermal fuse can be blown by the amount of heat generated by the heater based on the battery voltage, the heater control unit forcibly turns on the switching element. Then, the secondary battery is connected to the conductive path, and the battery voltage of the secondary battery is supplied to the heater via the conductive path. The thermal fuse is blown by the heat generated by the heater. Here, “forcedly on” means that the switching element is turned on by the heater control unit even when the switching element is turned off by the protection control unit.

  In this case, even if the temperature fuse cannot be blown by the voltage received by the connection terminal, the temperature fuse can be blown by the battery voltage, so that the possibility that the temperature fuse cannot be blown can be reduced. Even if the battery voltage is equal to or higher than the threshold voltage, if the voltage at the connection terminal is equal to or higher than the threshold voltage, the thermal fuse can be blown without discharging the secondary battery. The chance of discharging the secondary battery can be reduced as compared with the technique described in Patent Document 1.

  A voltage output requesting unit that requests a voltage output equal to or higher than the threshold voltage when the second abnormality detecting unit detects the second abnormality in the charging unit that outputs a voltage according to the request to the connection terminal; The heater control unit may further include a voltage detected by the terminal voltage detection unit in the thermal fuse blow processing after the voltage output is requested by the charging unit by the voltage output request unit. It is preferable to execute processing for confirming whether or not the above is true.

  According to this configuration, when the second abnormality is detected by the second abnormality detection unit, the voltage output request unit requests the charging unit to output a voltage equal to or higher than the threshold voltage. Then, unless there is a circumstance that the charging unit cannot output the voltage according to the request, for example, the charging unit is not connected to the connection terminal, a voltage equal to or higher than the threshold voltage is output to the connection terminal. After the voltage output request by the voltage output request, it is confirmed whether or not the voltage detected by the terminal voltage detection unit is equal to or higher than the threshold voltage. When the voltage is higher than the threshold voltage, the voltage is applied to the conductive path. The voltage supplied from the charging unit, that is, the voltage supplied from the charging unit can be supplied to the heater, so that the thermal fuse can be blown. Therefore, the chance that the thermal fuse can be blown without discharging the secondary battery can be increased.

  Further, it is preferable that the heater control unit cuts off the voltage supply from the conductive path to the heater when the voltage detected by the terminal voltage detection unit is less than the threshold voltage.

  According to this configuration, when the voltage detected by the terminal voltage detector does not reach the threshold voltage, and therefore it is considered that the thermal fuse cannot be blown with the amount of heat generated by the heater based on the voltage received at the connection terminal, the connection terminal Since the voltage supply to the heater through the conductive path is cut off, the possibility that the heater continues to generate heat with a heat generation amount that cannot blow the thermal fuse is reduced.

  In addition, the heater control unit, when the voltage detected by the terminal voltage detection unit is less than the threshold voltage, and the battery voltage detected by the battery voltage detection unit is less than the threshold voltage, the temperature fuse It is preferable to determine that it is difficult to melt and cut off the voltage supply from the conductive path to the heater.

  According to this configuration, when the voltage detected by the terminal voltage detection unit is less than the threshold voltage and the battery voltage detected by the battery voltage detection unit is less than the threshold voltage, that is, the voltage received at the connection terminal, If it is considered that the thermal fuse cannot be blown even if the heater is heated using either the battery voltage of the secondary battery or the secondary battery, the voltage supply to the heater from the connection terminal and the secondary battery through the conductive path is cut off. Therefore, the possibility that the heater continues to generate heat with a heat generation amount that cannot blow the thermal fuse is reduced.

  In addition, the heater control unit determines that it is difficult to blow the thermal fuse, and when a preset waiting time elapses, if the voltage detected by the terminal voltage detection unit is equal to or higher than the threshold voltage, the heater control unit The voltage applied to the conductive path is supplied to the heater, the voltage detected by the terminal voltage detector is less than the threshold voltage, and the battery voltage detected by the battery voltage detector is not less than the threshold voltage. In this case, it is preferable to supply the voltage applied to the conductive path to the heater.

  Even if the heater control unit determines that the thermal fuse does not melt even if the heater generates heat and shuts off the voltage supply, the voltage after the threshold voltage is received by the connection terminal, etc. If this changes, the thermal fuse may be blown. Therefore, after the waiting time during which such a change in the condition can be expected has elapsed, the heater control unit converts the voltage received by the connection terminal into the conductive path if the voltage detected by the terminal voltage detection unit is equal to or higher than the threshold voltage. When the voltage detected by the terminal voltage detector does not reach the threshold voltage and the battery voltage detected by the battery voltage detector is equal to or higher than the threshold voltage, the battery voltage is passed through the conductive path. By supplying to the heater, the opportunity to blow the thermal fuse can be increased.

  A temperature detection unit that detects a temperature related to the thermal fuse; and a threshold voltage setting unit that sets the threshold voltage so that the threshold voltage decreases as the temperature detected by the temperature detection unit increases. It is preferable.

  According to this configuration, the threshold voltage is set by the threshold voltage setting unit so that the threshold voltage decreases as the temperature related to the temperature fuse detected by the temperature detection unit, for example, the temperature of the temperature fuse or the environmental temperature increases. When the temperature related to the thermal fuse is high and easily melted, the heater control unit blows the thermal fuse even if the voltage at the connection terminal is low. Thereby, the opportunity to blow the thermal fuse can be increased.

  The heater further includes a heater switching element for controlling heat generation of the heater, and the temperature fuse is a series connection of two temperature fuses to be blown by the heater. The path for supplying the voltage at the connection point of the two temperature fuses to the heater is opened and closed, and the heater control unit turns on the voltage applied to the conductive path by turning on the heater switching element. It is preferable to cut off the voltage supply to the heater by supplying the heater and turning off the heater switching element.

  According to this configuration, two temperature fuses are connected in series, and a path for supplying the voltage at the connection point to the heater is opened and closed by turning on and off the heater switching element, thereby controlling the voltage supply to the heater. According to this, when the two thermal fuses are blown by heat generation of the heater, both the voltage supply path from the connection terminal to the heater via the conductive path and the voltage supply path from the secondary battery to the heater via the conductive path are cut off. Then, since the heater stops generating heat, the heater does not continue to generate heat after the thermal fuse is blown.

  The protection control unit further turns off the switching element when the second abnormality detection unit detects the second abnormality.

  According to this configuration, when the second abnormality is detected by the second abnormality detection unit, the connection between the secondary battery and the connection terminal can be quickly cut off regardless of whether or not the thermal fuse is blown. So safety is improved.

  The battery pack according to the present invention includes the above-described protection circuit and the secondary battery.

  According to this configuration, in the battery pack including the secondary battery, the temperature fuse can be blown using the voltage received by the connection terminal. The chance of discharging the secondary battery can be reduced as compared with the technology.

  The charging system according to the present invention includes the above-described protection circuit, the secondary battery, and the charging unit.

  According to this configuration, it is possible to increase the chance that the thermal fuse can be blown without discharging the secondary battery.

  The protection circuit, the battery pack, and the charging system having such a configuration can reduce the chance of discharging the secondary battery when the thermal fuse is blown.

It is a block diagram which shows an example of a structure of a battery pack and the charging system provided with the protection circuit which concerns on one Embodiment of this invention. 3 is a flowchart showing an example of the operation of the protection circuit shown in FIG. 3 is a flowchart showing an example of the operation of the protection circuit shown in FIG.

  Embodiments according to the present invention will be described below with reference to the drawings. In addition, the structure which attached | subjected the same code | symbol in each figure shows that it is the same structure, The description is abbreviate | omitted. FIG. 1 is a block diagram illustrating an example of the configuration of a battery pack 1 and a charging system 100 including a protection circuit 2 according to an embodiment of the present invention.

  The charging system 100 is configured by connecting the battery pack 1 and a charging device 3 (charging unit). Note that the charging device 3 may be incorporated in a battery-equipped device such as an electronic device such as a portable personal computer, a digital camera, or a mobile phone, or a vehicle such as an electric vehicle or a hybrid car. The charging system 100 may be configured as follows.

  The charging device 3 may be, for example, a power supply circuit that generates a charging current for the battery pack 1 from a commercial power supply voltage, such as a power generation device that generates power based on natural energy such as sunlight, wind power, or hydraulic power, an internal combustion engine, or the like A power generation device that generates power by motive power may be used.

  The battery pack 1 includes a protection circuit 2 and a secondary battery 14. Further, the protection circuit 2 includes connection terminals 11, 12, 13, temperature sensors 15, 16, a current detection resistor 17, a battery voltage detection unit 18, a battery temperature detection unit 19, a communication unit 20, a temperature detection unit 21, and a terminal voltage detection. A unit 22, a control unit 201, a discharging switching element SW1, a charging switching element SW2, a heater switching element SW3, temperature fuses F1 and F2, and a heater Rh are provided.

  The protection circuit 2 is not necessarily built in the battery pack. For example, the protection circuit 2 may be configured as an in-vehicle ECU (Electric Control Unit), and is built in the battery-equipped device. May be.

  The charging device 3 includes connection terminals 31, 32, 33, a power supply circuit 35, a communication unit 36, and a control unit 37. The power supply circuit 35 is connected to connection terminals 31 and 32 for power feeding, and the communication unit 36 is connected to the connection terminal 33.

  Further, when the battery pack 1 is attached to the charging device 3, the connection terminals 11, 12, 13 of the battery pack 1 and the connection terminals 31, 32, 33 of the charging device 3 are connected to each other. Yes.

  The communication units 20 and 36 are communication interface circuits configured to be able to transmit / receive data to / from each other via the connection terminals 13 and 33. The power supply circuit 35 is a power supply circuit that supplies current and voltage corresponding to a control signal from the control unit 37 to the battery pack 1 via the connection terminals 31 and 32.

  The control unit 37 is a control circuit configured using, for example, a microcomputer. When the request instruction transmitted from the control unit 201 in the battery pack 1 by the communication unit 20 is received by the communication unit 36, the control unit 37 responds to the request instruction received by the communication unit 36 with the power supply circuit 35. Is controlled to output a current and a voltage corresponding to the request instruction transmitted from the battery pack 1 from the power supply circuit 35 to the connection terminals 11 and 12.

  The connection terminal 11 is connected to the positive electrode of the secondary battery 14 via the temperature fuses F1 and F2, the charging switching element SW2, and the discharging switching element SW1. The thermal fuses F1 and F2 are cut off to cut off the conductive path L1 between the connection terminal 11 and the charging switching element SW2.

  For example, a p-channel FET (Field Effect Transistor) is used as the discharging switching element SW1 and the charging switching element SW2.

  In the discharge switching element SW1, the cathode of the parasitic diode is directed to the secondary battery 14, and when turned off, only the current in the discharge direction of the secondary battery 14 is cut off. Further, the switching element SW2 for charging has the cathode of the parasitic diode in the direction of the connection terminal 11. When turned off, only the current in the charging direction of the secondary battery 14 is cut off.

  The connection terminal 12 is connected to the negative electrode of the secondary battery 14 via the current detection resistor 17, and the temperature fuses F 1 and F 2, the charging switching element SW 2, the discharging switching element SW 1, the secondary battery are connected to the connecting terminal 11. A current path to the connection terminal 12 through the battery 14 and the current detection resistor 17 is configured.

  The connection terminals 11, 12, and 13 may be any terminals that electrically connect the battery pack 1 to the charging device 3 or an external circuit. For example, the connection terminals 11, 12, and 13 may be electrodes, connectors, terminal blocks, etc. Or a wiring pattern such as a pad.

  One end of the heater Rh is connected to one point of the conductive path L1, for example, a connection point between the temperature fuse F1 and the temperature fuse F2, and the other end is connected to the connection terminal 12 via the heater switching element SW3. .

  The temperature fuse F with a heater sealed in one package may be used in a state where the temperature fuses F1 and F2 are connected in series and the heater Rh is connected to the connection point of the temperature fuses F1 and F2. . One thermal fuse may be provided.

  The current detection resistor 17 converts the charging current and discharging current of the secondary battery 14 into voltage values.

  The secondary battery 14 may be, for example, a single battery, for example, an assembled battery in which a plurality of secondary batteries are connected in series, for example, an assembled battery in which a plurality of secondary batteries are connected in parallel. Alternatively, an assembled battery in which series and parallel are combined and connected may be used. As the secondary battery 14, various secondary batteries such as a lithium ion secondary battery and a nickel hydride secondary battery are used.

  The battery voltage detection unit 18, the battery temperature detection unit 19, the temperature detection unit 21, and the terminal voltage detection unit 22 are configured using, for example, an analog-digital conversion circuit.

  The battery voltage detection unit 18 detects the battery voltage Vb of the secondary battery 14 and outputs a signal indicating the voltage value to the control unit 201. The terminal voltage detector 22 detects the terminal voltage Vt between the connection terminals 11 and 12 and outputs a signal indicating the voltage value to the controller 201.

  The temperature sensors 15 and 16 are temperature sensors configured using, for example, a thermistor or a thermocouple.

  The temperature sensor 15 is, for example, in close contact with the secondary battery 14 or disposed in the vicinity of the secondary battery 14, detects the temperature of the secondary battery 14, and outputs a voltage signal indicating the temperature value to the battery temperature detection unit. 19 output. The battery temperature detection unit 19 outputs a signal indicating the temperature of the secondary battery 14 to the control unit 201 based on the voltage signal output from the temperature sensor 15.

  The temperature sensor 16 is disposed in close contact with, for example, the temperature fuses F1 and F2 (or the temperature fuse F with a heater) or in the vicinity of the temperature fuses F1 and F2 (or the temperature fuse F with a heater). The temperature t related to F2 is detected, and a voltage signal indicating the temperature value is output to the temperature detector 21. The temperature detector 21 outputs a signal indicating the temperature t to the controller 201 based on the voltage signal output from the temperature sensor 16.

  The temperature t is not limited to the temperature itself of the temperature fuses F1 and F2, but may be any temperature related to the temperature of the temperature fuses F1 and F2, such as the environmental temperature in the vicinity of the temperature fuses F1 and F2. In the following description, the temperature t is described as the temperature of the thermal fuses F1 and F2.

  The control unit 201 includes, for example, a CPU (Central Processing Unit) that executes predetermined arithmetic processing, a ROM (Read Only Memory) that stores a predetermined control program, and a RAM (Random Access Memory) that temporarily stores data. And an analog-digital conversion circuit, a timer circuit, and peripheral circuits thereof.

  Then, the control unit 201 executes a control program stored in the ROM, whereby a first abnormality detection unit 211, a second abnormality detection unit 212, a threshold voltage setting unit 213, a voltage output request unit 214, and a heater control unit 215. , Function as a protection control unit 216 and a current detection unit 217.

  The current detection unit 217 detects the voltage Vr across the current detection resistor 17 and divides this voltage Vr by the resistance value R of the current detection resistor 17, thereby obtaining the charge / discharge current value Ic flowing through the secondary battery 14. get.

  The first abnormality detection unit 211 detects the occurrence of a first abnormality preset as a recoverable abnormality, and notifies the protection control unit 216 of the first abnormality. Specifically, for example, as the first abnormality, overcharge, overdischarge, or temperature within a range that does not permanently damage the secondary battery 14 is set.

  For example, when the battery voltage Vb detected by the battery voltage detection unit 18 exceeds a first overcharge voltage value set in advance to a value exceeding the full charge voltage, the first abnormality detection unit 211 indicates that the first abnormality is Detect what happened. For example, when the secondary battery 14 is a lithium ion secondary battery, the first overcharge voltage value is 4.228 V with respect to the terminal voltage per cell connected in series in the secondary battery 14. Can be used.

  In addition, for example, when the battery voltage Vb detected by the battery voltage detection unit 18 becomes a voltage lower than an overdischarge voltage value set in advance to prevent overdischarge of the secondary battery 14, the first abnormality is also caused. The detection unit 211 detects that the first abnormality has occurred. For example, when the secondary battery 14 is a lithium ion secondary battery, 2.5 V is used as the overdischarge voltage value with respect to the terminal voltage per cell connected in series in the secondary battery 14. Can do.

  In addition, for example, the temperature of the secondary battery 14 detected by the battery temperature detection unit 19 exceeds a first abnormality determination temperature set in advance as a temperature at which the secondary battery 14 may be deteriorated, for example, 60 ° C. Even when the temperature becomes high, the first abnormality detection unit 211 detects that the first abnormality has occurred.

  The first abnormality determination temperature may be different between charging and discharging, for example, 60 ° C. during charging and 73 ° C. higher than charging during discharging.

  Further, since the first abnormality is a recoverable abnormality, when the first abnormality detection unit 211 detects that the detected first abnormality has been resolved, the protection control unit 216 indicates that the first abnormality has been resolved. Notify

  The second abnormality detection unit 212 detects the occurrence of a second abnormality set in advance as an abnormality that should permanently prohibit charging / discharging of the secondary battery 14 and notifies the protection control unit 216 and the heater control unit 215 of the occurrence. Specifically, as the second abnormality, a level of overcharge, heat generation, or the like that may cause permanent damage to the secondary battery 14 is set.

  For example, the battery voltage Vb detected by the battery voltage detection unit 18 may be a second overvoltage that is preset to a voltage value that exceeds the first overcharge voltage value as a voltage that may permanently damage the secondary battery 14. When the charging voltage is further exceeded, the second abnormality detection unit 212 detects that the second abnormality has occurred. For example, when the secondary battery 14 is a lithium ion secondary battery, the second overcharge voltage value is 4.28 V with respect to the terminal voltage per cell connected in series in the secondary battery 14. Can be used.

  Further, for example, the temperature of the secondary battery 14 detected by the battery temperature detection unit 19 is a second abnormality determination temperature set in advance as a temperature at which the separator inside the secondary battery 14 may be melted, for example, 90 ° C. Even when the value exceeds the value, it is detected that the second abnormality has occurred.

  When the first abnormality is detected by the first abnormality detection unit 211, the protection control unit 216 turns off the discharging switching element SW1 or the charging switching element SW2 to discharge or charge the secondary battery 14. By prohibiting, the secondary battery 14 is protected from deterioration.

  For example, when the battery voltage Vb detected by the battery voltage detection unit 18 exceeds the first overcharge voltage value and becomes the first abnormality, the protection control unit 216 turns off the charging switching element SW2 to perform charging. By prohibiting, overcharge of the secondary battery 14 is prevented.

  For example, when the battery voltage Vb detected by the battery voltage detection unit 18 falls below the overdischarge voltage value and becomes the first abnormality, the protection control unit 216 turns off the discharge switching element SW1 to discharge the battery. By prohibiting, the secondary battery 14 is prevented from being deteriorated due to overdischarge.

  Furthermore, the protection control unit 216 turns off both the discharging switching element SW1 and the charging switching element SW2 when the second abnormality detecting unit 212 detects the second abnormality. When the second abnormality is detected by the second abnormality detection unit 212, the heater control unit 215 blows the thermal fuses F1 and F2, but it takes time to blow the thermal fuses F1 and F2, or the charging device 3 Depending on the voltage supply state from the battery and the terminal voltage of the secondary battery 14, the thermal fuses F1, F2 may not be blown.

  Therefore, when the second abnormality detection unit 212 detects the second abnormality, the protection control unit 216 turns off both the discharging switching element SW1 and the charging switching element SW2. Thereby, even if it takes a long time to blow the thermal fuses F1 and F2 or the thermal fuses F1 and F2 cannot be blown, charging / discharging of the secondary battery 14 can be promptly prohibited. The safety of the battery pack 1 can be improved.

  In addition, it is not restricted to the example provided with switching element SW1 for discharge, and switching element SW2 for charge, It is provided with one switching element which interrupts | blocks the charging / discharging path | route of the secondary battery 14, and the protection control part 216 is 1st abnormality, or The switching element may be turned off when the second abnormality is detected.

  The threshold voltage setting unit 213 determines a threshold voltage Vth for determining whether or not the battery voltage Vb of the secondary battery 14 can blow the temperature fuses F1 and F2 by causing the heater Rh to generate heat. It sets so that it may fall, so that the temperature t detected by the temperature detection part 21 is high.

  Thermal fuses are easily blown when the temperature is high, and are difficult to blow when the temperature is low. In view of this, the minimum battery voltage Vb at which a heat generation amount that can blow the temperature fuses F1 and F2 by the heater Rh according to the temperature t of the temperature fuses F1 and F2 is obtained experimentally in advance and stored in the ROM as a data table, for example. Remember.

  The threshold voltage setting unit 213 refers to this data table, for example, and acquires the minimum battery voltage Vb that can blow the temperature fuses F1 and F2 at the temperature t based on the temperature t detected by the temperature detection unit 21. The threshold voltage Vth may be set. Thus, the thermal fuse is easily blown when the temperature is high, and is difficult to blow when the temperature is low. Therefore, the threshold voltage Vth is set to a lower voltage value as the temperature t is higher.

  The heater control unit 215 is configured to detect the second abnormality detected by the second abnormality detection unit 212 and the threshold voltage set by the threshold voltage setting unit 213 based on the voltage between the connection terminals 11 and 12 detected by the terminal voltage detection unit 22. When the voltage Vth is exceeded, the heater switching element SW3 is turned on, whereby the voltage applied to the conductive path L1 is supplied to the heater Rh, and the heater Rh generates heat.

  Here, when the second abnormality is detected by the second abnormality detection unit 212, the discharge switching element SW1 and the charging switching element SW2 are both turned off by the protection control unit 216. Even if it is turned on, no current is supplied from the secondary battery 14 to the heater Rh. Then, the current supplied from the charging device 3 is supplied to the heater Rh via the conductive path L1 and the heater switching element SW3.

  The protection control unit 216 does not necessarily have to turn off both the discharging switching element SW1 and the charging switching element SW2 when the second abnormality is detected by the second abnormality detecting unit 212.

  In this case, since the determination condition of the second abnormality by the second abnormality detection unit 212 is stricter than the determination condition of the first abnormality by the first abnormality detection unit 211, the second abnormality is detected by the second abnormality detection unit 212. Usually, the first abnormality is detected by the first abnormality detection unit 211 before that, and at least one of the switching element SW1 for discharging and the switching element SW2 for charging is turned off by the protection control unit 216. Will be.

  For example, when the first abnormality is detected due to overdischarge or temperature of the secondary battery 14, the discharge switching element SW1 is turned off. Therefore, even if the heater switching element SW3 is turned on, the secondary switching element SW3 is turned on. No current is supplied from the battery 14 to the heater Rh. Then, the current supplied from the charging device 3 is supplied to the heater Rh via the conductive path L1 and the heater switching element SW3.

  Further, the heater control unit 215 sets the terminal voltage Vt detected by the terminal voltage detection unit 22 by the threshold voltage setting unit 213 even when the second abnormality detection unit 212 detects the second abnormality. When the threshold voltage Vth is not reached, the battery voltage Vb detected by the battery voltage detector 18 is further confirmed. When the battery voltage Vb exceeds the threshold voltage Vth set by the threshold voltage setting unit 213, the discharging switching element SW1. Also, by turning on the heater switching element SW3, the voltage applied to the conductive path L1 is supplied to the heater Rh, and the heater Rh generates heat.

  The heater control unit 215, when the terminal voltage Vt detected by the terminal voltage detection unit 22 is less than the threshold voltage Vth and the battery voltage Vb detected by the battery voltage detection unit 18 is less than the threshold voltage Vth, It is determined that it is difficult to blow the thermal fuses F1 and F2, and the heater Rh is not heated while the heater switching element SW3 is turned off.

  Furthermore, the heater control unit 215 measures the elapsed time Tp after determining that it is difficult to blow the thermal fuses F1 and F2 by a timer circuit (not shown). The elapsed time Tp timed by the timer circuit is a time when the environmental temperature of the battery pack 1 may change or the voltage supply from the charging device 3 may start, for example, about 1 hour. When the preset waiting time Tw is exceeded and the voltage between the connection terminals 11 and 12 detected by the terminal voltage detection unit 22 exceeds the threshold voltage Vth, the heater switching element SW3 is turned on again to turn on the thermal fuse F1. , F2 is blown.

  Next, the operation of the protection circuit 2 configured as described above will be described. 2 and 3 are flowcharts showing an example of the operation of the protection circuit 2 shown in FIG.

  First, the first abnormality detection unit 211 detects whether or not a first abnormality has occurred (step S1). If the first abnormality detection unit 211 does not detect the occurrence of the first abnormality (NO in step S1), the protection control unit 216 turns on the discharge switching element SW1 and the charging switching element SW2 to turn on the second abnormality. The secondary battery 14 can be charged / discharged (step S3), and the process proceeds to step S4.

  On the other hand, when the first abnormality detection unit 211 detects the occurrence of the first abnormality (YES in step S1), the protection control unit 216 determines the discharge switching element SW1 and the charging switching element according to the abnormality content. At least one of SW2 is turned off (step S2), and the process proceeds to step S4. For example, when the first abnormality is overcharge, only the charging switching element SW2 is turned off. When the first abnormality is overdischarge, only the discharge switching element SW1 is turned off, and the first abnormality is abnormally high. In this case, the discharging switching element SW1 and the charging switching element SW2 are turned off.

  Next, in step S4, the second abnormality detection unit 212 detects whether or not a second abnormality has occurred (step S4). If the second abnormality detection unit 212 does not detect the occurrence of the second abnormality (NO in step S4), the process returns to step S1 again and the first abnormality detection unit 211 confirms whether or not the first abnormality has occurred. The

  Here, since the first abnormality is a recoverable abnormality, if the first abnormality is resolved at this time and the first abnormality detection unit 211 does not detect the occurrence of the first abnormality (NO in step S1), step S3 is performed. Then, the protection control unit 216 turns on the discharging switching element SW1 and the charging switching element SW2 to enable the secondary battery 14 to be charged and discharged again.

  On the other hand, when occurrence of the second abnormality is detected by the second abnormality detection unit 212 in step S4 (YES in step S4), the discharge switching element SW1 and the charging switching element SW2 are turned off by the protection control unit 216. In step S5, charging / discharging of the secondary battery 14 is immediately prohibited.

  As a result, in step S2, only one of the discharging switching element SW1 and the charging switching element SW2 is turned off, or the secondary battery 14 has reached the end of its life. Even when both the switching element SW1 for discharging and the switching element SW2 for charging are turned on as in the case where an abnormality that is not the first abnormality occurs, the charging / discharging of the secondary battery 14 can be prohibited immediately. This improves safety.

  Next, the threshold voltage setting unit 213 sets the threshold voltage Vth to a lower voltage value as the temperature t detected by the temperature detection unit 21 is higher (step S6).

  Next, a request signal for requesting the output of the heater voltage Vh set to be equal to or higher than the threshold voltage Vth is transmitted to the charging device 3 by the voltage output requesting unit 214 using the communication unit 20 (step S7). Then, if the charging device 3 is connected to the battery pack 1, this request signal is received by the communication unit 36 and output to the control unit 37. The control unit 37 controls the power supply circuit 35 in response to the request signal, and the heater voltage Vh is applied between the connection terminals 11 and 12.

  As the heater voltage Vh, for example, a voltage value capable of fusing the temperature fuses F1 and F2 regardless of the temperature t may be set in advance, and the threshold voltage Vth set by the threshold voltage setting unit 213 is used as it is. You may make it use as.

  Even if the charging device 3 is connected to the battery pack 1, the charging device 3 does not always output a voltage equal to or higher than the threshold voltage Vth that can blow the thermal fuses F <b> 1 and F <b> 2. Therefore, the voltage output request unit 214 requests the output of the heater voltage Vh by the charging device 3, and causes the charging device 3 to output the heater voltage Vh between the connection terminals 11 and 12. The opportunity to blow the thermal fuses F1, F2 by the voltage can be increased.

  In addition, in the technology described in the background art, when the thermal fuse is to be blown, some abnormality has occurred in the battery pack, so the secondary battery cannot output a voltage at a level that can blow the thermal fuse. Probability is high. In this case, the technique described in Patent Document 1 has a disadvantage that there is a high possibility that the thermal fuse cannot be blown when an abnormality occurs.

  However, according to the protection circuit 2, the thermal fuses F <b> 1 and F <b> 2 are blown by the output voltage of the charging device 3, so that the chances of blowing the thermal fuses F <b> 1 and F <b> 2 can be increased as compared with the background art.

  Next, the heater control unit 215 compares the terminal voltage Vt detected by the terminal voltage detection unit 22 with the threshold voltage Vth set by the threshold voltage setting unit 213 (step S8), and the terminal voltage Vt is the threshold voltage. If it is Vth or higher (YES in step S8), the thermal fuses F1 and F2 can be blown by the terminal voltage Vt, so that the heater switching element SW3 is turned on by the heater control unit 215 (step S9). .

  Then, the heater voltage Vh supplied from the power supply circuit 35 is applied to the heater Rh via the connection terminals 31 and 11 and the temperature fuse F1, the heater Rh generates heat, and the temperature fuses F1 and F2 are blown.

  Thereby, in the situation where the 2nd abnormality has occurred, since the temperature fuses F1 and F2 can be blown out without discharging the secondary battery 14, the opportunity to discharge the secondary battery 14 can be reduced. As a result, safety is improved.

  On the other hand, if the terminal voltage Vt does not reach the threshold voltage Vth (NO in step S8), the temperature fuses F1 and F2 cannot be blown by the terminal voltage Vt. The process proceeds to step S10 to determine whether or not fusing is possible.

  Here, in step S6, the threshold voltage setting unit 213 sets the threshold voltage Vth to a lower voltage value as the temperature t of the current temperature fuses F1 and F2 is higher. For example, the heater Rh under the condition of the temperature t. Is set as the threshold voltage Vth, so that the temperature t is high, for example, unlike the case where the threshold voltage Vth is a fixed value. The temperature fuses F1 and F2 can be blown even when the battery voltage Vb is low, but the battery voltage Vb does not reach the threshold voltage Vth set when the temperature t is low. The risk of losing the opportunity to blow the thermal fuses F1 and F2 without fusing F1 and F2 can be reduced.

  Then, the heater control unit 215 compares the battery voltage Vb detected by the battery voltage detection unit 18 with the threshold voltage Vth set by the threshold voltage setting unit 213 (step S10), and the battery voltage Vb is equal to or higher than the threshold voltage Vth. If so (YES in step S10), since the thermal fuses F1 and F2 can be blown by the battery voltage Vb, the heater switching unit SW1 is turned on by the heater controller 215 (step S11), and further the heater Switching element SW3 is turned on (step S9).

  Then, the battery voltage Vb supplied from the secondary battery 14 is applied to the heater Rh, the heater Rh generates heat, and the thermal fuses F1, F2 are blown.

  Here, since the temperature fuses F1 and F2 are connected in series and the heater Rh is connected to the connection point of the temperature fuses F1 and F2, when the temperature fuses F1 and F2 are blown, the power supply circuit 35 passes through the connection terminal 11. Thus, both the path for supplying voltage to the heater Rh (temperature fuse F1) and the path for supplying voltage from the secondary battery 14 to the heater Rh (temperature fuse F2) are cut off, and the heat generation of the heater Rh stops. The heater Rh does not continue to generate heat after the thermal fuses F1, F2 are blown.

  According to the processes of steps S8, S10, S11, and S9, the secondary battery 14 is discharged in order to blow the thermal fuses F1 and F2. However, if the discharge switching element SW1 and the charging switching element SW2 are simply turned off without the thermal fuses F1 and F2 being blown, the battery voltage Vb of the secondary battery 14 is lowered, and eventually the control unit 201 or The power supply voltage for operation of the discharging switching element SW1 and the charging switching element SW2 cannot be supplied, and it becomes difficult to maintain the discharging switching element SW1 and the charging switching element SW2 in the off state.

  If so, the secondary battery 14 cannot be protected in a state where the second abnormality has occurred, which is not preferable. On the other hand, according to the processing of steps S8, S10, S11, and S9, the secondary battery 14 is temporarily discharged. However, if the thermal fuses F1 and F2 can be blown, the thermal fuses F1 and F2 are blown. This is preferable because the safety is improved rather than being impossible.

  Also, the thermal fuses F1 and F2 are blown by discharging the secondary battery 14, for example, when the charging device 3 is not connected to the battery pack 1, the voltage output requesting unit 214 sends the heater voltage to the charging device 3. This is limited to the case where a voltage equal to or higher than the threshold voltage Vth is not supplied between the connection terminals 11 and 12 in spite of the output request of Vh. Therefore, as in the background art, the secondary battery is always discharged and the temperature fuse Compared with the technique of fusing the battery, the chance of discharging the secondary battery can be reduced.

  On the other hand, if the battery voltage Vb does not satisfy the threshold voltage Vth in step S10 (NO in step S10), the thermal fuses F1 and F2 cannot be blown by any of the terminal voltage Vt and the battery voltage Vb. The unit 215 determines that it is difficult to blow the thermal fuses F1 and F2, and proceeds to step S12 while keeping the heater switching element SW3 off.

  As a result, when the terminal voltage Vt and the battery voltage Vb are low, even if the heater switching element SW3 is turned on, the amount of heat generated by the heater Rh is insufficient and the temperature fuses F1 and F2 cannot be blown. Since the heater Rh does not generate heat, the risk of raising the temperature of the battery pack 1 without melting the thermal fuses F1, F2 can be reduced.

  Next, in step S12, the heater control unit 215 uses an unillustrated timer circuit to measure the elapsed time Tp since it was determined in step S11 that it is difficult to blow the thermal fuses F1 and F2 (step S13). . When the elapsed time Tp becomes equal to or longer than the waiting time Tw (YES in step S13), the heater control unit 215 tries to blow the thermal fuses F1 and F2 by repeating the processes after step S5 again.

  That is, even if it is determined in step S10 that the thermal fuses F1 and F2 are not blown even if the heater Rh is heated, a time equal to or longer than the waiting time Tw elapses thereafter, and the environmental temperature rises during that time. When the temperature t rises or the charging device 3 is connected to the battery pack 1, the thermal fuses F1 and F2 may be blown by repeating the processing after step S5 again. Thereby, the opportunity which can fuse | melt the thermal fuse F1, F2 can be increased.

  The threshold voltage setting unit 213 may not be provided, and a voltage value at a level at which the temperature fuses F1 and F2 can be blown by the amount of heat generated by the heater Rh regardless of the temperature t may be set in advance as the threshold voltage Vth. If the terminal voltage Vt is less than the threshold voltage Vth in step S8 (NO in step S8), the heater control unit 215 determines that it is difficult to blow the thermal fuses F1 and F2 without executing steps S10 and S11. It is good also as a structure which determines and transfers to step S12.

  Further, the voltage output request unit 214 may not be provided and step S7 may not be executed. Further, the protection control unit 216 may not execute step S5.

  Even with such a configuration, the chance of discharging the secondary battery can be reduced as compared with the technique of discharging the secondary battery and blowing the thermal fuse as in the background art.

  A protection circuit for a secondary battery according to the present invention, and a battery pack provided with the protection circuit include electronic devices such as portable personal computers, digital cameras and mobile phones, vehicles such as electric vehicles and hybrid cars, solar cells and power generation devices. Can be suitably used as a protection circuit for a secondary battery used in various battery-mounted devices, such as a power supply system combining a secondary battery and a secondary battery, and a battery pack.

DESCRIPTION OF SYMBOLS 1 Battery pack 2 Protection circuit 3 Charging device 11, 12, 13, 31, 32, 33 Connection terminal 14 Secondary battery 15, 16 Temperature sensor 17 Current detection resistor 18 Battery voltage detection part 19 Battery temperature detection part 20, 36 Communication part DESCRIPTION OF SYMBOLS 21 Temperature detection part 22 Terminal voltage detection part 35 Power supply circuit 100 Charging system 201 Control part 211 1st abnormality detection part 212 2nd abnormality detection part 213 Threshold voltage setting part 214 Voltage output request part 215 Heater control part 216 Protection control part 217 Current Detector F, F1, F2 Thermal fuse L1 Conductive path Rh Heater SW1 Discharging switching element SW2 Charging switching element SW3 Heating switching element Tp Elapsed time Tw Waiting time Vb Battery voltage Vh Heater voltage Vt Terminal voltage Vth Threshold voltage

Claims (11)

A connection terminal for receiving a voltage for charging the secondary battery;
A switching element interposed between the connection terminal and the secondary battery;
A thermal fuse for interrupting a conductive path between the connection terminal and the switching element;
A heater for fusing the thermal fuse;
A terminal voltage detector for detecting the voltage of the connection terminal;
A first abnormality detection unit for detecting that a first abnormality preset as a recoverable abnormality has occurred;
A second abnormality detection unit for detecting that a second abnormality preset as an abnormality to melt the thermal fuse has occurred;
A protection control unit that turns off the switching element when the first abnormality is detected by the first abnormality detection unit;
The threshold value set as a voltage at which the second abnormality is detected by the second abnormality detection unit and the voltage detected by the terminal voltage detection unit is capable of causing the heater to generate heat and blow the thermal fuse. And a heater control unit that performs a thermal fuse blowing process for supplying a voltage applied to the conductive path to the heater when the voltage is equal to or higher than a voltage. A battery voltage detector for detecting a battery voltage of the secondary battery;
The heater control unit
The battery voltage detected by the battery voltage detector when the second abnormality is detected by the second abnormality detector and the voltage detected by the terminal voltage detector does not satisfy the threshold voltage. 2. The protection circuit according to claim 1, wherein when the voltage is equal to or higher than the threshold voltage, the switching element is forcibly turned on to supply the voltage applied to the conductive path to the heater. The charging unit that outputs a voltage according to a request to the connection terminal further includes a voltage output requesting unit that requests a voltage output equal to or higher than the threshold voltage when the second abnormality is detected by the second abnormality detecting unit. ,
The heater control unit
After the voltage output is requested by the charging unit by the voltage output requesting unit, it is confirmed whether or not the voltage detected by the terminal voltage detecting unit in the thermal fuse blowing process is equal to or higher than the threshold voltage. The protection circuit according to claim 1 or 2, wherein the processing is executed. The heater control unit
The protection circuit according to claim 1, wherein when the voltage detected by the terminal voltage detection unit is less than the threshold voltage, voltage supply to the heater from the conductive path is cut off. The heater control unit
When the voltage detected by the terminal voltage detector is less than the threshold voltage and the battery voltage detected by the battery voltage detector is less than the threshold voltage, it is determined that the thermal fuse is difficult to blow, The protection circuit according to claim 2, wherein voltage supply to the heater from the conductive path is cut off. The heater control unit
The voltage applied to the conductive path if the voltage detected by the terminal voltage detector is equal to or higher than the threshold voltage when a preset waiting time has elapsed after determining that the thermal fuse is difficult to blow. Is applied to the conductive path when the voltage detected by the terminal voltage detector is less than the threshold voltage and the battery voltage detected by the battery voltage detector is greater than or equal to the threshold voltage. The protection circuit according to claim 5, wherein a voltage that is applied is supplied to the heater. A temperature detection unit for detecting a temperature related to the thermal fuse;
The threshold voltage setting part which sets the said threshold voltage is further provided so that the said threshold voltage may fall, so that the temperature detected by the said temperature detection part is high, The any one of Claims 1-6 characterized by the above-mentioned. The protection circuit according to. A heater switching element for controlling the heat generation of the heater;
The thermal fuse is
Two thermal fuses to be blown by the heater are connected in series,
The heater switching element is:
Open and close a path for supplying a voltage at a connection point of the two temperature fuses to the heater;
The heater control unit
The voltage applied to the conductive path is supplied to the heater by turning on the heater switching element, and the voltage supply to the heater is cut off by turning off the heater switching element. The protection circuit according to claim 1. The protection control unit further includes:
The protection circuit according to any one of claims 1 to 8, wherein when the second abnormality is detected by the second abnormality detection unit, the switching element is turned off. The protection circuit according to any one of claims 1 to 9,
A battery pack comprising the secondary battery. A protection circuit according to claim 3;
The secondary battery;
A charging system comprising: the charging unit.

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