JP2006304486A - Protection circuit of secondary battery and battery pack - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a protection circuit for protecting a secondary battery against overcharge or an excessive large discharge current by a simple circuit. <P>SOLUTION: The protection circuit of a secondary battery comprises connection terminals T1 and T2 for connecting a secondary battery 6, connection terminals T3 and T4 for connecting a charger charging the secondary battery 6 and/or a load apparatus driven with a discharge current from the secondary battery 6, a bimetal switch SW1 provided between the connection terminals T1 and T3 to be turned off when a preset temperature is exceeded, a heater R2 connected in parallel with the bimetal switch SW1 and heating the bimetal switch SW1, and an integrated circuit IC1 for turning the bimetal switch SW1 by heating the heater R2 when the voltage of the connection terminal T1 exceeds a preset reference voltage. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a protection circuit that protects a secondary battery from excessive charging and excessive discharge current, and a battery pack including the protection circuit.

  FIG. 19 is a block diagram showing a configuration of a battery pack according to the background art. A battery pack 101 illustrated in FIG. 19 includes a protection circuit 102 and a secondary battery 103. The secondary battery 103 is a rechargeable secondary battery such as a lithium ion secondary battery, a lithium polymer secondary battery, a nickel hydride secondary battery, or a nickel cadmium secondary battery. If such a secondary battery is excessively charged or the discharge current becomes excessive, characteristics such as cycle life may be deteriorated, or the battery may be expanded or deformed. Accordingly, the battery pack 101 includes a protection circuit 102 that protects the secondary battery 103 from excessive charging and excessive discharge current (see, for example, Patent Document 1).

  The protection circuit 102 includes external connection terminals 104 and 105, FETs (Field Effect Transistors) 106 and 107, reference voltage sources 108 and 109, comparators 110 and 111, a resistor 112, and a logic circuit 113. .

  The external connection terminals 104 and 105 connect a charging device for charging the secondary battery 103, mobile devices such as mobile phones and digital cameras driven by the discharge current from the secondary battery 103, electric tools, It is a connection terminal for connecting a driving power source for a robot, an electric bicycle or the like. The external connection terminal 104, the secondary battery 103, the FET 106, the FET 107, and the external connection terminal 105 are connected in series.

  The FET 106 has a direction in which the anode of the parasitic diode is on the secondary battery 103 side, and the FET 107 has a direction in which the anode of the parasitic diode is on the external connection terminal 105 side. The FET 106 is used as an overdischarge protection switch that cuts off the discharge current when the discharge current of the secondary battery 103 becomes excessive, and the FET 107 is charged when the secondary battery 103 is overcharged. Used as an overcharge protection switch that cuts off current.

  Further, the positive terminal of the secondary battery 103 is applied to the + terminal of the comparator 110, the reference voltage Vref 1 output from the reference voltage source 108 is applied to the − terminal of the comparator 110, and the output terminal of the comparator 110 is connected to the logic circuit 113. It is connected. As the reference voltage Vref1, a voltage for detecting overcharge of the secondary battery 103 is set. The comparator 110 detects overcharge when the secondary battery 103 is charged by a charging device (not shown) connected to the external connection terminals 104 and 105 and the terminal voltage of the secondary battery 103 exceeds the reference voltage Vref1. A signal is output to the logic circuit 113.

  The connection point between the FET 106 and the FET 107 is connected to the negative terminal of the comparator 111 via the resistor 112, and the reference voltage Vref 2 output from the reference voltage source 109 is applied to the positive terminal of the comparator 111. As a result, the discharge current from the secondary battery 103 flows through the FET 106, and a voltage drop caused by the on-resistance of the FET 106 is applied to the negative terminal of the comparator 111 via the resistor 112. The reference voltage Vref2 is set to a voltage corresponding to a voltage drop caused by the on-resistance of the FET 106 when the maximum discharge current in the range that does not cause deterioration of the characteristics of the secondary battery 103 flows through the FET 106, for example.

  The comparator 111 is short-circuited, for example, when the external connection terminals 104 and 105 come into contact with a metal piece, or when a load device connected to the external connection terminals 104 and 105 breaks down. When an excessive discharge current flows, an increase in the voltage drop in the FET 106 is detected, and a detection signal indicating an overcurrent discharge is output to the logic circuit 113.

  When the detection signal indicating overcharge is output from the comparator 110, the logic circuit 113 turns off the FET 107 to stop the charging of the secondary battery 103, and the detection signal indicating discharge of the overcurrent is output from the comparator 111. Then, the FET 106 is turned off to stop the discharge of the secondary battery 103. Thereby, the protection circuit 102 protects the secondary battery 103 from excessive charging or overcurrent discharging.

  Further, as a protection circuit for protecting the secondary battery from excessive charging and overcurrent discharge in this way, a secondary battery 122 and a bimetal switch 123 are connected in series as in the battery pack 121 shown in FIG. For example, when the charging device 126 connected to the external connection terminals 124 and 125 fails, the secondary battery 122 generates heat or the bimetal switch 123 self-heats due to excessive charging, whereby the bimetal switch It is known that when the 123 is heated, the bimetal switch 123 is turned off to cut off the charging current and protect the secondary battery 122.

Further, like a battery pack 131 shown in FIG. 21, a secondary battery 133 and a PTC thermistor 132 are connected in series using a PTC (Positive Temperature Coefficient) thermistor 132 that is a temperature switch that is turned off when a predetermined temperature is exceeded. When, for example, the charging device 136 connected to the external connection terminals 134 and 135 fails, the secondary battery 133 generates heat due to excessive charging or the PTC thermistor 132 self-heats. It is known that when the PTC thermistor 132 is heated, the PTC thermistor 132 is turned off to interrupt the charging current and protect the secondary battery 133.
JP-A-4-75430

  However, since the FET has a parasitic diode, the protection circuit 102 shown in FIG. 19 cannot cut off the discharge current and the charge current in different directions of current flow with one FET, and cut off the discharge current. It is necessary to provide the FET 106 and the FET 107 that cuts off the charging current. Further, the reference voltage source 108 and the comparator 110 are required to detect overcharge, the reference voltage source 109, the comparator 111, and the resistor 112 are required to detect excessive discharge current, and the comparators 110 and 111 Since the logic circuit 113 for turning on and off the two FETs 106 and 107 based on the output signal is required, the circuit scale of the protection circuit 102 is increased.

  Further, as shown in FIGS. 20 and 21, in a configuration in which a secondary battery is protected from overcharging by connecting a temperature switch that operates according to temperature, such as a bimetal switch or a PTC thermistor, in series with the secondary battery, The secondary battery is charged with a charging current that does not increase rapidly, such as when the battery pack is charged by a poor charger with low charging voltage control accuracy. If the operation continues, the secondary battery is overcharged without operating the temperature switch, and there is a problem that the characteristics of the secondary battery may be deteriorated or the battery may be expanded or deformed.

  The present invention has been made in view of such problems, and an object of the present invention is to provide a protection circuit capable of protecting a secondary battery from excessive charging and excessive discharge current with a simple circuit. . And it aims at providing the battery pack provided with such a protection circuit.

  In order to achieve the above-described object, a protection circuit for a secondary battery according to the present invention charges first and second connection terminals for connection to both electrodes of the secondary battery, and the secondary battery. Provided between the third and fourth connection terminals for connecting a charging device and / or a load device driven by a discharge current from the secondary battery, and the first and third connection terminals, and set in advance A thermal switch that is turned off when a predetermined temperature is exceeded, a first heater that is connected in parallel to the thermal switch and that heats the thermal switch, and a physical quantity related to the characteristics of the secondary battery. A detection unit for detecting, and a protection control unit for causing the first heater to generate heat and turning off the thermal switch when a physical quantity detected by the detection unit exceeds a preset physical quantity value, Thermal switch It is characterized in that a bimetal switch, the switch using shape memory alloys, and one kind selected from the switch using a shape memory resin.

  In the secondary battery protection circuit, the physical quantity related to the characteristics of the secondary battery is the voltage of the first connection terminal, and the detection unit detects the voltage of the first connection terminal. The protection control unit heats the first heater and turns off the thermal switch when the voltage detected by the detection unit exceeds a preset reference voltage. Yes.

  In the secondary battery protection circuit, the physical quantity related to the characteristics of the secondary battery is the temperature of the secondary battery, and the detection unit detects the temperature of the secondary battery, The protection control unit is characterized in that when the temperature of the secondary battery detected by the detection unit exceeds a preset temperature, the first heater generates heat and the thermal switch is turned off. .

  In the above-described secondary battery protection circuit, the first rectifier element in the direction in which the discharge current of the secondary battery connected to the first connection terminal flows and in the forward direction include the first heater and the first battery. The protection control unit opens and closes a connection between the connection point between the first heater and the first rectifying element and the fourth connection terminal. A switch unit is provided, and the switch unit is turned on when a physical quantity detected by the detection unit exceeds a preset physical quantity value.

  Moreover, in the above-described secondary battery protection circuit, the first heater includes a series circuit of second and third heaters, and the protection control unit includes the second heater and the third heater. And a switch unit that opens and closes the connection between the connection point and the fourth connection terminal, and the physical quantity detected by the detection unit exceeds a preset physical quantity value. It is characterized by turning on the part.

  The secondary battery protection circuit may further include a fourth heater having one end connected to the third connection terminal and heating the thermal switch, wherein the protection control unit includes the fourth battery. A switch unit that opens and closes the connection between the other end of the heater and the fourth connection terminal, and the switch when the physical quantity detected by the detection unit exceeds a preset physical quantity value It is characterized by turning on the part.

  Further, in the above-described secondary battery protection circuit, the first and fourth heaters are caused by the discharge current from the secondary battery connected to the first connection terminal when the thermal switch is turned off. A resistance value to equalize the heat value of the first heater and the heat value of the fourth heater due to the output current from the charging device connected to the third connection terminal when the switch unit is turned on. Is set.

  Further, in the above-described secondary battery protection circuit, a second rectifier element in the direction in which the discharge current of the secondary battery connected to the first connection terminal flows and in the forward direction are connected to the first connection terminal and the first connection terminal. It is further provided between the first heater and the first heater.

  In the above-described secondary battery protection circuit, the second and third heaters are PTC thermistors whose resistance values increase or decrease in accordance with an increase or decrease in temperature, and the PTC thermistors have a substantially plate shape. And at least one surface is divided into a plurality of regions, and a part of the plurality of regions on one surface of the PTC thermistor is used as the first electrode and the first electrode. At least a part of the region excluding one electrode is used as a second electrode, the other surface of the PTC thermistor is used as a third electrode, and the first and third electrodes are used in the second heater. It is used as connection terminals at both ends, and the third and second electrodes are used as connection terminals at both ends in the third heater.

  In the above-described secondary battery protection circuit, the first and fourth heaters are PTC thermistors whose resistance values increase or decrease in accordance with the increase or decrease in temperature, and the PTC thermistors have a substantially plate shape. And at least one surface is divided into a plurality of regions, and a part of the plurality of regions on one surface of the PTC thermistor is used as the first electrode and the first electrode. At least a part of the region excluding one electrode is used as a second electrode, the other surface of the PTC thermistor is used as a third electrode, and the first and third electrodes are used in the first heater. It is used as connection terminals at both ends, and the third and second electrodes are used as connection terminals at both ends in the fourth heater.

  In the protection circuit for a secondary battery described above, the groove divides the one surface of the PTC thermistor into two regions, and the one region divided by the groove serves as a first electrode. And the other region is used as the second electrode.

  In the protection circuit for a secondary battery described above, the groove is a substantially cross-shaped groove that divides the one surface of the PTC thermistor into four regions, and two regions adjacent to each other in the four regions. Is used as the first electrode, and the other regions other than the two regions used as the first electrode among the four regions are used as the second electrode.

  Further, in the above-described secondary battery protection circuit, the PTC thermistor has a shape in which the vertical and horizontal directions can be physically determined. For example, the PTC thermistor has a rectangular shape such as a square or a rectangle, an ellipse, or a rhombus. , A circle with a chip or a protrusion on a part thereof.

  The battery pack according to the present invention includes a secondary battery protection circuit according to any one of the above, and a secondary battery in which both electrodes are connected to the first and second connection terminals of the secondary battery protection circuit. It is characterized by comprising a battery, a bottomed container for accommodating the secondary battery, and an external connection terminal unit for accommodating the protection circuit.

  A protection circuit for a secondary battery having such a structure is a switch using a bimetal switch and a shape memory alloy when a current discharged from the first connection terminal to the third connection terminal exceeds a predetermined current value. Since the thermal switch, which is one type selected from the switches using the shape memory resin, is turned off by self-heating to interrupt the discharge current, the secondary battery can be protected from an excessive discharge current.

  When the thermal switch is turned off, a discharge current flows through the first heater connected in parallel with the thermal switch, the first heater generates heat, and the thermal switch is heated to maintain the thermal switch in the off state. The In this case, for example, if the first heater is not connected in parallel with the thermal switch, the thermal switch is turned off by self-heating, and then the thermal switch is turned on by natural cooling, so that the discharge current of the secondary battery flows, and again There is a possibility that chattering in which the thermal switch repeatedly turns on and off such that the switch is turned off by self-heating and cuts off the discharge current. According to the present invention, the first heater connected in parallel with the thermal switch Thus, even after the thermal switch is turned off by self-heating, the off state of the thermal switch is maintained, so that occurrence of chattering can be suppressed.

  Further, when the physical quantity related to the characteristics of the secondary battery exceeds a preset physical quantity value, the first heater is heated by the protection control unit, and the thermal switch is heated by the first heater. Since the switch is turned off to cut off the charge / discharge current, it is possible to reduce the deterioration of the characteristics of the secondary battery. Further, since the discharge current and the charge current can be cut off by one thermal switch, the circuit can be simplified.

  Further, according to the secondary battery protection circuit described above, when the secondary battery is connected to the first and second connection terminals, the voltage of the secondary battery pole, which is a physical quantity related to the characteristics of the secondary battery, is increased. Applied to the first connection terminal. When the voltage of the first connection terminal exceeds a preset reference voltage, the first heater is heated by the protection control unit, and the thermal switch is heated by the first heater, whereby the thermal switch is Since the charging current is cut off, the secondary battery can be protected from excessive charging. Further, since the discharge current and the charge current can be cut off by one thermal switch, the circuit can be simplified.

  Further, according to the above-described secondary battery protection circuit, the temperature of the secondary battery, which is a physical quantity related to the characteristics of the secondary battery, is detected by the detection unit. When the temperature detected by the detection unit exceeds a preset temperature, the first heater is heated by the protection control unit, and the thermal switch is heated by the first heater, so that the thermal switch is turned off. Since the charge / discharge current is cut off, the secondary battery can be protected from excessive heat generation. Further, since the discharge current and the charge current can be cut off by one thermal switch, the circuit can be simplified.

  Moreover, according to the protection circuit for the secondary battery described above, when the thermal switch is turned off to cut off the discharge current from the first connection terminal to the third connection terminal, the secondary connected to the first connection terminal. The first rectifier element that is forwardly directed to flow the battery discharge current causes the discharge current to flow to the first heater connected in parallel with the thermal switch, so that the first heater generates heat and the thermal switch. Can be heated to maintain the thermal switch in the OFF state. When the physical quantity detected by the detection unit exceeds a preset physical quantity value, the protection control unit turns on the switch unit, and the thermal switch, the first heater, and the switch unit are switched from the third connection terminal. Since a current path to the fourth connection terminal is formed through the first heater, the first heater generates heat and the thermal switch is heated, so that the thermal switch can be turned off.

  Further, according to the protection circuit for the secondary battery described above, when the thermal switch is turned off to cut off the discharge current from the first connection terminal to the third connection terminal, the second and second switches connected in parallel with the thermal switch. Since a discharge current flows through the series circuit of the third heater, the second and third heaters generate heat, the thermal switch is heated, and the thermal switch can be kept in the OFF state. When the physical quantity detected by the detection unit exceeds a preset physical quantity value, the protection control unit turns on the switch unit, and from the third connection terminal through the third heater and the switch unit. A current path to the fourth connection terminal is formed, the third heater generates heat, and the thermal switch is heated, so that the thermal switch can be turned off.

  Further, according to the protection circuit for the secondary battery described above, when the thermal switch is turned off to cut off the discharge current from the first connection terminal to the third connection terminal, the first battery connected in parallel with the thermal switch. Since the discharge current flows through the heater, the first heater generates heat, the thermal switch is heated, and the thermal switch can be kept in the OFF state. Then, when the physical quantity detected by the detection unit exceeds a preset physical quantity value, the protection control unit turns on the switch unit, and from the third connection terminal through the fourth heater and the switch unit A current path to the fourth connection terminal is formed, the fourth heater generates heat, and the thermal switch is heated, so that the thermal switch can be turned off.

  Further, according to the protection circuit for the secondary battery described above, the first and fourth heaters are the first by the discharge current from the secondary battery connected to the first connection terminal when the thermal switch is turned off. Since the heating value of the heater is set equal to the heating value of the fourth heater due to the output current from the charging device connected to the third connection terminal when the switch is turned on, the resistance value is set. If the thermal switch is turned off to protect the secondary battery from excessive discharge current, and the thermal switch is turned off to protect the secondary battery from overcharging, the amount of heat generated to heat the thermal switch is equal. can do.

  Moreover, according to the protection circuit for the secondary battery described above, when the thermal switch is turned off to cut off the discharge current from the first connection terminal to the third connection terminal, the secondary connected to the first connection terminal. Since the discharge current flows to the first heater connected in parallel with the thermal switch by the second rectifying element which is in the forward direction with the direction in which the discharge current of the battery flows, the first heater generates heat and the thermal switch Can be heated to maintain the thermal switch in the OFF state. Then, when the thermal switch is turned off to cut off the charging current to the secondary battery connected to the first connection terminal, the charging current to the secondary battery is passed through the first heater by the second rectifying element. Flow is suppressed.

  In addition, according to the above-described secondary battery protection circuit, since one PTC thermistor can be used as the second and third heaters, it is easy to reduce the size of the protection circuit.

  In addition, according to the above-described secondary battery protection circuit, one PTC thermistor can be used as the first and fourth heaters, so that the protection circuit can be easily downsized.

  Further, according to the above-described secondary battery protection circuit, one surface of the PTC thermistor is divided into two regions, one region is used as the first electrode, and the other region is used as the second electrode. Therefore, one PTC thermistor can be used as two heaters.

  Further, according to the protection circuit for the secondary battery described above, one surface of the PTC thermistor is divided into four regions by the substantially cross-shaped groove, and two regions adjacent to each other in the four regions serve as the first electrode. Of the four regions, the other region excluding the two regions used as the first electrode is used as the second electrode, so that the wiring pattern provided to connect to the first and second electrodes On the other hand, the PTC thermistor can be connected by rotating by 90 °, and the assemblability can be improved. Further, both sides have the same shape by substantially cross-shaped grooves, one side is connected as the first and second electrodes as described above, and the remaining one side is connected to the front side as the third electrode. The target heater can be configured regardless of whether it is turned upside down or rotated 90 ° in any direction, and the assemblability can be further improved.

  Further, according to the protection circuit for the secondary battery described above, since the shape can be physically determined in the vertical and horizontal directions, the PTC with respect to the wiring pattern provided to connect to the first and second electrodes is used. When attaching the thermistor, it becomes easy to match the orientation of the PTC thermistor.

  In the battery pack having such a configuration, the secondary battery protection circuit is housed in the external connection terminal unit, so that the secondary battery housed in the bottomed container is excessively charged by the protection circuit. And protection from excessive discharge current.

  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.

(First embodiment)
FIG. 1 is an exploded perspective view showing an example of a battery pack according to an embodiment of the present invention. The battery pack 1 shown in FIG. 1 includes a bottomed container 2, an external connection terminal unit 3, and a plate-like spacer 4 inserted between the container 2 and the external connection terminal unit 3. A secondary battery 6 is accommodated in the container 2 and is sealed by caulking, and a positive electrode terminal 61 provided in a convex shape on the secondary battery 6 is projected from the open end of the container 2. The container 2 is made of a steel plate with nickel plating on the surface, and the negative electrode of the secondary battery 6 is connected to the container 2 inside the container 2.

  The external connection terminal unit 3 includes, for example, a resin-molded case 31, and connection terminals T 3 and T 4 for connecting a charging device and a load device are exposed on the surface of the case 31. In addition, a connection terminal T <b> 2 made of, for example, a plate-like metal connected to the connection terminal T <b> 4 is provided so as to protrude in a direction to be connected to the container 2.

  FIG. 2 is a circuit diagram showing an example of the electrical configuration of the battery pack 1 shown in FIG. A battery pack 1 shown in FIG. 1 includes a protection circuit 5 and a secondary battery 6. The secondary battery 6 is a rechargeable secondary battery such as a lithium ion secondary battery, a lithium polymer secondary battery, a nickel hydride secondary battery, or a nickel cadmium secondary battery. The protection circuit 5 is a protection circuit that protects the secondary battery 6 from excessive charging and excessive discharge current.

  The protection circuit 5 is disposed inside the external connection terminal unit 3, and includes a connection terminal T1 (first connection terminal), a connection terminal T2 (second connection terminal), and a connection terminal T3 (third connection terminal). Connection terminal), connection terminal T4 (fourth connection terminal), bimetal switch SW1, thermal fuse F1, comparator CMP1 (detection unit), reference voltage source E1, resistor R1, and transistor Q1 (switch unit) ), A heater R2 (first heater), and a diode D1 (first rectifying element). The connection terminal T <b> 1 and the connection terminal T <b> 2 are connection terminals that are respectively connected to both electrodes of the secondary battery 6.

  The connection terminal T3 and the connection terminal T4 are connection terminals for connecting a charging device (not shown) for charging the secondary battery 6 and / or a load device driven by a discharge current from the secondary battery 6. The load device is various electric devices driven by a battery such as a mobile phone, a digital camera, a video camera, a portable personal computer, and an electric tool.

  The bimetal switch SW1 is turned off when the preset operating temperature Tsw1 is exceeded, and is turned off by self-heating when the charging / discharging current of the secondary battery 6 exceeds the preset cutoff current value Isw1. The operating temperature Tsw1 is set to a maximum temperature in a temperature range that does not deteriorate the characteristics of the secondary battery 6, for example, and the cutoff current value Isw1 is within a range that does not cause the characteristics of the secondary battery 6 to deteriorate. The maximum discharge current value is set. The bimetal switch SW1 is a return-type thermal switch that turns on again when the temperature drops after the temperature rises and turns off. As the thermal switch, a switch using a shape memory alloy or a switch using a shape memory resin can be used in the same manner instead of the bimetal switch instead of the bimetal switch.

  The shape memory alloy may be a shape memory alloy having a restoring force based on thermoelastic martensitic transformation and reverse transformation such as nickel-titanium alloy, copper-zinc-aluminum alloy, and these alloys are deformed. The shape change temperature range in which the shape is restored from the restored shape can be changed by changing the heat treatment process appropriately selecting the shape memory alloy composition.

  As the shape memory resin, resins such as polyester, polyurethane, styrene / butadiene, and transpolyisoprene in which a cross-linked or partially crystallized stationary phase and a reversible phase are mixed can be used.

  As the heater R2, for example, a positive temperature characteristic, that is, a PTC thermistor whose resistance value increases or decreases in accordance with an increase or decrease in temperature is used. As a result, when a voltage is applied to the heater R2, the resistance value of the heater R2 increases due to the self-heating of the heater R2, and the current flowing through the heater R2 decreases. As a result, the temperature of the heater R2 finally reaches the final temperature Th. It becomes constant. The final temperature Th is a temperature that exceeds the operating temperature Tsw1 of the bimetal switch SW1, and is set to a temperature that does not damage the secondary battery 6 and the protection circuit 5. As a result, it is possible to suppress the temperature of the heater R2 from excessively rising and the thermal fuse F1 from being blown, or the secondary battery 6 and the protection circuit 5 being damaged by the heat generated by the heater R2.

  The thermal fuse F1 is disposed in close proximity to the secondary battery 6 or in close contact with an insulator, and when the secondary battery 6 generates heat due to overcharge or excessive discharge, a temperature at which the heat fuse F1 is blown. It is a fuse. The operating temperature Tfuse1 at which the thermal fuse F1 blows is set to a temperature higher than the operating temperature Tsw1 of the bimetal switch SW1. Further, the fusing characteristics are set so that the operating speed of the thermal fuse F1 is slower than that of the bimetal switch SW1. The thermal fuse F1 is a non-returnable thermal switch that does not return to a conductive state once it is blown. In this case, the operating temperature Tsw1 of the bimetal switch SW1, the final temperature Th of the heater R2, and the operating temperature Tfuse1 of the thermal fuse F1 have a relationship represented by the following formula (1).

Tsw1 <Th <Tfuse1 (1)
In addition, the setting of the operating temperature and operating speed of the bimetal switch SW1 and the thermal fuse F1 sets the characteristics of the components of the bimetal switch SW1 and the thermal fuse F1 itself, and operates the bimetal switch SW1 before the thermal fuse F1. Therefore, for example, the bimetal switch SW1 and the secondary battery 6 are placed close to each other so that the thermal resistance between the bimetal switch SW1 and the secondary battery 6 is smaller than the thermal resistance between the thermal fuse F1 and the secondary battery 6. For example, the contact resistance of the bimetal switch SW1 or the resistance at the movable piece is increased to increase the amount of self-heating, or the thermal resistance to the surroundings when the bimetal switch SW1 dissipates heat is increased. Reduce the heat capacity by reducing the size of the bimetal switch SW1. The bimetal switch SW1 may be a temperature rise easily formed by self-heating by benefit.

  Further, in order to delay the operation of the thermal fuse F1 from the bimetal switch SW1, for example, the thermal resistance to the surroundings when the thermal fuse F1 radiates heat is reduced, or the thermal fuse F1 is brought into contact with a material having good thermal conductivity, for example. The temperature fuse F1 may be configured not to easily rise in temperature by increasing the apparent heat capacity of the temperature fuse F1 without increasing the size of the temperature fuse F1 by a method.

  FIG. 3 is a graph showing an example of the current value and the operating time when the operating temperature and operating speed of the bimetal switch SW1 and the thermal fuse F1 are set so as to satisfy the above formula (1). In the graph shown in FIG. 3, the vertical axis represents the current value flowing through the bimetal switch SW1 and the thermal fuse F1, and the horizontal axis represents the time from when the vertical current flows until the bimetal switch SW1 and the thermal fuse F1 operate. .

  In FIG. 3, graphs G <b> 1 to G <b> 3 are graphs showing an example of the relationship between the current value flowing through the bimetal switch SW <b> 1 and the operating time in a state where the battery pack 1 is assembled. Graph G1 shows a case where the ambient temperature is −30 ° C., Graph G2 shows a case where the ambient temperature is 0 ° C., Graph G3 shows a case where the ambient temperature is 25 ° C., and Graph G4 shows a case where the ambient temperature is 70 ° C. Graphs G <b> 5 to G <b> 10 are graphs showing an example of the relationship between the current value flowing through the thermal fuse F <b> 1 and the operating time in a state where the battery pack 1 is assembled. Graph G5 is a minimum value when the ambient temperature is 65 ° C., Graph G6 is an average value when the ambient temperature is 65 ° C., Graph G7 is a maximum value when the ambient temperature is 65 ° C., and Graph G8 is an ambient temperature of 25 ° C. In this case, the minimum value, graph G9 shows the average value when the ambient temperature is 25 ° C., and graph G10 shows the maximum value when the ambient temperature is 25 ° C. A graph G11 shows the characteristics of the bimetal switch SW1 as a single component. In the measurement of the data shown in FIG. 3, EYP2ML098 manufactured by Panasonic Electronic Device Co., Ltd. was used as the thermal fuse F1.

  Returning to FIG. 2, the connection terminal T3 is connected to the positive electrode of the secondary battery 6 via the bimetal switch SW1, the thermal fuse F1, and the connection terminal T1, and the negative electrode of the secondary battery 6 is connected via the connection terminal T2. It is connected to the terminal T4. Further, the connection terminal T1 is connected to the power supply terminal of the comparator CMP1, and the connection terminal T2 is connected to the ground terminal of the comparator CMP1, so that the operation power supply voltage of the comparator CMP1 is supplied from the secondary battery 6. Yes.

  A series circuit of the heater R2 and the diode D1 is connected in parallel with the bimetal switch SW1. The diode D1 is provided between the heater R2 and the connection terminal T3, and is forward in the direction in which the discharge current of the secondary battery 6 flows, that is, the direction from the heater R2 toward the connection terminal T3. A transistor Q1 that opens and closes the connection between the connection point between the heater R2 and the diode D1 and the connection terminal T4 is provided.

  The connection terminal T1 is connected to the positive terminal of the comparator CMP1 via the resistor R1, the connection terminal T2 is connected to the negative terminal of the reference voltage source E1, the positive terminal of the reference voltage source E1 is connected to the negative terminal of the comparator CMP1, and the comparator CMP1. Is connected to the gate terminal of the transistor Q1.

  The reference voltage source E <b> 1 is a voltage generation circuit that outputs a reference voltage Vref <b> 1 that serves as a determination reference for detecting overcharge of the secondary battery 6. Thereby, the reference voltage Vref1 is applied to the negative terminal of the comparator CMP1, and when the terminal voltage between the connection terminals T1 and T2, that is, the charging voltage Vc of the secondary battery 6 exceeds the reference voltage Vref1, the comparator CMP1 causes the gate voltage of the transistor Q1. Is set to the high level, the transistor Q1 is turned on, and the heater generates heat.

  Further, as the comparator CMP1, a comparator having a hysteresis in the input voltage is used in order to reduce the influence of noise when the charging voltage Vc is near the reference voltage Vref1. The comparator CMP1, the resistor R1, and the reference voltage source E1 are, for example, integrated and configured as an integrated circuit IC1. In this case, the integrated circuit IC1 and the transistor Q1 correspond to an example of a protection control unit.

  FIG. 4 is an explanatory diagram for explaining the mechanical configuration of the protection circuit 5 shown in FIG. FIG. 4A is a diagram showing a wiring pattern for attaching each component of the protection circuit 5, and FIG. 4B is a cross-sectional view showing an example of a mechanical configuration of the protection circuit 5. Further, in FIG. 4, the mounting positions of the components are indicated by broken lines. FIG. 5A is a top view of the protection circuit 5 shown in FIG. For comparison, FIG. 5B shows the same cross-sectional view as FIG. 4B.

  The wiring pattern shown in FIG. 4A is opposite to the inner surface of the case 31 in the external connection terminal unit 3, that is, the secondary battery 6 accommodated in the container 2 when the external connection terminal unit 3 and the container 2 are combined. For example, a paste-like conductive wiring material composed of metal fine particles is printed on the surface to be printed, and without using a printed wiring board, the wiring pattern is printed directly on the inner surface of the case 31. The integrated circuit IC1, transistor Q1, heater R2, and diode D1 are fixed.

  Thereby, since the protection circuit 5 can be comprised without using a printed wiring board, the protection circuit 5 can be reduced in size by the thickness of a printed wiring board.

  Further, as shown in FIG. 4B, support members 32 and 33 that are formed in a convex shape by integral molding with the case 31, for example, are provided inside the case 31 in the external connection terminal unit 3. The wiring pattern P4 drawn from the top of the support member 32 is connected to a connection terminal T3 provided on the outer surface of the case 31 by, for example, a cylindrical metal member 34 that penetrates the case 31. Furthermore, one end of the movable piece 35 constituting the bimetal switch SW1 is connected and fixed to the wiring pattern P4, for example, by spot welding, on the top of the support member 32. A contact 36 is provided at the other end of the movable piece 35, and the contact 36 is in contact with the wiring pattern P <b> 5 formed on the top of the support member 33.

  In addition, a bimetal 37 is provided below the movable piece 35 so as to be bridged between the support member 32 and the support member 33. When the operating temperature Tsw1 is reached, the bimetal 37 is warped in the opposite direction as shown in FIG. 6 to jump up the movable piece 35 and separate the contact 36 from the wiring pattern P5. The support members 32 and 33, the movable piece 35, the bimetal 37, and the wiring patterns P4 and P5 constitute a bimetal switch SW1. Further, a switch cover 38 for dust prevention and insulation is fixed so as to cover the bimetal switch SW1 and the diode D1 thus configured. In addition, a substantially rectangular plate-shaped heater R2 is disposed below the bimetal 37. When the heater R2 generates heat, the bimetal 37 is heated.

  Thereby, since bimetal switch SW1 can be comprised using the support members 32 and 33 integrally molded with case 31, it is easy to reduce cost rather than the case where bimetal switch SW1 comprised as an individual component is used. It becomes. Further, since the bottom portion of the case when the bimetal switch SW1 is configured as an individual component is not necessary, the bimetal switch SW1 can be reduced in size.

  The conductor leads P6 and P7 constituting the connection terminal of the thermal fuse F1 are, for example, wide plates, and the conductor leads P6 and P7 are bent and integrated with the thermal fuse F1 and the conductor leads P6 and P7. A thermal fuse F1 is attached so as to cover the circuit IC1 and the transistor Q1. The wiring patterns P5 and P8 provided on both sides of the integrated circuit IC1 and the transistor Q1 are connected via the conductor lead P6, the thermal fuse F1, and the conductor lead P7 across the integrated circuit IC1 and the transistor Q1. ing.

  The outer surface of the thermal fuse F1, the conductor leads P6 and P7, and both side surfaces of the conductor leads P6 and P7 are covered with a sheet member 39 for the purpose of insulation and dust prevention, for example.

  Thereby, the thermal fuse F1, the conductor leads P6 and P7, and the sheet member 39 function as a cover that covers the integrated circuit IC1 and the transistor Q1, and in addition to the thermal fuse F1 and the conductor leads P6 and P7, a separate cover is provided. As compared with the above, the mounting area of the thermal fuse F1 on the surface of the case 31 can be reduced, and the protection circuit 5 can be easily downsized.

  Further, the thermal fuse F1, the conductor leads P6 and P7, and the sheet member 39 are used as jumper wirings for passing a current across the integrated circuit IC1 and the transistor Q1 between the wiring pattern P5 and the wiring pattern P8. The area occupied by the wiring pattern on the surface of the protective circuit 5 is reduced, and the protection circuit 5 can be easily downsized.

  Further, the connection terminal T1 is attached to the conductor lead P7 by spot welding, for example. Thereby, since the mounting area of the connection terminal T1 is not occupied on the surface of the case 31, the external connection terminal unit 3 can be easily downsized.

  Furthermore, the external connection terminal unit 3 is heated to conduct the conductive wiring in a state where other components except the thermal fuse F1 and the conductor leads P6 and P7 are mounted on the wiring pattern printed using the conductive wiring material. If the thermal fuse F1 and the conductor leads P6 and P7 are attached after the material is cured, the thermal fuse F1 is not manufactured at the time of manufacture even if the curing temperature of the conductive wiring material is higher than the operating temperature Tfuse1 of the thermal fuse F1. There is no fusing.

  FIG. 7 is an explanatory diagram for explaining a state in which the container 2 and the external connection terminal unit 3 are combined. As shown in FIG. 7, the bimetal switch SW1 and the thermal fuse F1 are close to a position facing the secondary battery 6 accommodated in the container 2 in a state where the container 2 and the external connection terminal unit 3 are combined. It is arranged.

  Next, the operation of the protection circuit 5 configured as described above will be described. First, the overcharge protection operation by the protection circuit 5 will be described. First, when a charging device (not shown) is connected to the connection terminals T3 and T4 in a state where the bimetal switch SW1 is on, and the charging voltage Vc is applied between the connection terminals T3 and T4 from the charging device, the bimetal switch SW1, The secondary battery 6 is charged with the charging voltage Vc via the thermal fuse F1 and the connection terminal T1.

  The charging voltage Vc is, for example, a maximum of 4.2 V when normal. The reference voltage source E1 is set to output, for example, 4.3 V as the reference voltage Vref1 to the comparator CMP1.

  For example, when a charging device (not shown) fails or the output voltage accuracy of the charging device is low and the charging voltage Vc exceeds 4.3 V, the transistor CMP1 is turned on by the comparator CMP1, and the bimetal switch SW1 is connected from the connection terminal T3. A current flows through the heater R2 through this, and the bimetal switch SW1 is heated. When the temperature of the bimetal switch SW1 reaches the operating temperature Tsw1, the bimetal switch SW1 is turned off, the charging current is interrupted, and the secondary battery 6 is protected from overcharging.

  Next, when the voltage of the connection terminal T1 becomes equal to or lower than the reference voltage Vref1 by turning off the bimetal switch SW1 and the charging current is cut off, the transistor Q1 is turned off by the comparator CMP1, and the current flowing through the heater R2 is made zero. The When the temperature of the bimetal switch SW1 falls below the return temperature due to natural cooling, the bimetal switch SW1 is turned on to return from the overcharge protection state to the normal state.

  In this case, the overcharge is detected by the comparator CMP1, and the bimetal switch SW1 is turned off by heating the bimetal switch SW1 by the heater R2. Therefore, for example, as shown in FIGS. 20 and 21, the secondary battery is connected in series. The accuracy of detecting overcharge can be improved as compared with the case where overcharge protection is performed only by the temperature switch, and the secondary battery 6 is overcharged without performing the overcharge protection operation. It is possible to reduce the risk that the battery will deteriorate or the secondary battery 6 will expand or deform.

  Next, the protection operation by the protection circuit 5 when the discharge current from the secondary battery 6 becomes excessive will be described. First, in a state where the bimetal switch SW1 is turned on, for example, a metal piece comes into contact with the connection terminals T3 and T4, or a load device such as a mobile phone (not shown) connected to the connection terminals T3 and T4 breaks down. As a result, when the connection terminals T3 and T4 are short-circuited or the resistance value between the connection terminals T3 and T4 becomes low, the current discharged from the secondary battery 6 via the temperature fuse F1 and the bimetal switch SW1 increases. The bimetal switch SW1 is heated by the contact resistance of the bimetal switch SW1.

  When the temperature of the bimetal switch SW1 reaches the operating temperature Tsw1, the bimetal switch SW1 is turned off, the discharge current of the secondary battery 6 is cut off, and the secondary battery 6 is protected from an excessive discharge current. When the bimetal switch SW1 is turned off, the discharge current of the secondary battery 6 is connected to the connection terminals T3 and T4 from the connection terminal T1 through the temperature fuse F1, the heater R2, the diode D1, and the connection terminal T3. The heater R2 generates heat and heats the bimetal switch SW1 through the load device (or the short-circuit failure portion).

  In this case, the operating condition of the bimetal switch SW1 is set to be turned off before the temperature fuse F1, and the bimetal switch SW1 is a reset-type heat-sensitive switch without fusing the temperature fuse F1, which is a non-reset-type heat-sensitive switch. Since the secondary battery 6 can be protected from excessive charging and excessive discharge current by the switch SW1, for example, the battery pack 1 is removed from the charging device and the load device to eliminate the cause of excessive charging and excessive discharging current. After that, the battery pack 1 can be used repeatedly without replacing the thermal fuse F1, and convenience can be improved.

  Further, for example, when the contact point of the bimetal switch SW1 is welded to cause a short circuit failure, or when any of the integrated circuit IC1, the transistor Q1, and the heater R2 fails and the bimetal switch SW1 cannot be turned off during overcharge. Even in such a case, when the secondary battery 6 generates heat due to overcharge or excessive discharge current, the thermal fuse F1 is melted and the secondary battery 6 can be protected, so that the reliability of the protection circuit 5 can be improved. it can.

  Furthermore, even if the bimetal switch SW1 is turned off and self-heating is eliminated, the heater R2 generates heat due to the current flowing through the load device (not shown), and the bimetal switch SW1 is heated by the heater R2. The bimetal switch SW <b> 1 can be kept off until the factor that causes the discharge current to be excessive due to removal of the load device or the like is removed.

  Thereby, for example, since the bimetal switch SW1 is turned off and self-heating is not generated, the bimetal switch SW1 is turned on by natural cooling, and an excessive discharge current of the secondary battery 6 flows again through the bimetal switch SW1 to turn off the bimetal switch SW1. Thus, the occurrence of chattering operation in which the bimetal switch SW1 is repeatedly turned on and off can be suppressed.

  In addition, since the secondary battery 6 can be protected from excessive charging and excessive discharging current by using the bimetal switch SW1 that is a thermal switch, the discharging current as in the protection circuit 102 according to the background art shown in FIG. FET 106 that cuts off the charge current, FET 107 that cuts off the charging current, reference voltage source 109 for detecting excessive discharge current, comparator 111, resistor 112, and logic circuit for controlling on / off of the two FETs 106 and 107 113, the circuit of the protection circuit 5 can be simplified, and the protection circuit 5 can be easily downsized.

  Then, as shown in FIG. 7, the bimetal switch SW1 and the thermal fuse F1 are close to the position facing the secondary battery 6 accommodated in the container 2 in a state where the container 2 and the external connection terminal unit 3 are combined. Since the thermal coupling between the bimetal switch SW1 and the thermal fuse F1 and the secondary battery 6 is reinforced, when the secondary battery 6 generates excessive heat, the bimetal switch SW1 and the thermal fuse F1 The charging / discharging current of the secondary battery 6 can be cut off.

  Thus, even if the heater R2 cannot be heated when the secondary battery 6 is overcharged due to, for example, a failure of the integrated circuit IC1, transistor Q1, heater R2, etc., the secondary battery 6 generates heat due to overcharge. Then, the bimetal switch SW1 and the thermal fuse F1 are heated. When the temperature of the bimetal switch SW1 reaches the operating temperature Tsw1, the bimetal switch SW1 is turned off and the charging current is interrupted. Therefore, even if the integrated circuit IC1, the transistor Q1, the heater R2, etc. fail, The secondary battery 6 can be protected from overcharging.

  Further, for example, when the contact point of the bimetal switch SW1 is welded to cause a short circuit failure, the bimetal switch SW1 does not turn off even if the temperature of the bimetal switch SW1 reaches the operating temperature Tsw1, but the temperature fuse F1 is further generated by the heat generation of the secondary battery 6. Is heated and the temperature of the thermal fuse F1 reaches the operating temperature Tfuse1, the thermal fuse F1 is blown and the charging current is cut off. Therefore, even if the bimetal switch SW1 fails, the secondary battery 6 is overcharged. Can be protected from.

  Further, since the thermal fuse F1 is disposed in close proximity to the integrated circuit IC1 and the transistor Q1, when the integrated circuit IC1 or the transistor Q1 generates excessive heat, the thermal fuse F1 cuts off the charging / discharging current of the secondary battery 6. Easy to do.

  In addition, although the wiring pattern which comprises the protection circuit 5 showed the example printed on the surface of the side which opposes the secondary battery 6 accommodated in the container 2 in the external connection terminal unit 3, the protection circuit 5 was shown. The wiring pattern to be formed is formed on the printed wiring board instead of being printed on the surface of the sealing portion. On the printed wiring board, an integrated circuit IC1, a transistor Q1, a bimetal switch SW1, and a protective circuit 5 are formed. The diode D1 may be arranged, and in this case, the support members 32 and 33 support the movable piece 35 and the bimetal 37 on the printed wiring board through the through-hole formed in the printed wiring board. It is good.

  Further, the support members 32 and 33 are not limited to an example in which the support members 32 and 33 are integrally formed with the case 31, and may be configured by embedding a cylindrical metal member in the case 31, for example. Moreover, it is good also as a structure which is not provided with the temperature fuse F1, but the conductor lead P6 and the conductor lead P7 were short-circuited. Alternatively, the switch cover 38 and the sheet member 39 may be integrally formed as a single part.

  Moreover, although the protection circuit 5 showed the example comprised by incorporating in the battery pack 1, it is not restricted to the example incorporated in the battery pack 1, For example, it is incorporated in the load apparatus and the secondary built in the load apparatus. It may be used as a battery protection circuit.

  In addition, secondary batteries such as lithium ion secondary batteries, lithium polymer secondary batteries, nickel metal hydride secondary batteries, or nickel cadmium secondary batteries are used after discharge proceeds and the output voltage drops below a predetermined end-of-discharge voltage. If the discharge continues further, the secondary battery may be in an overdischarged state and battery characteristics such as cycle life may be deteriorated. Therefore, in a load device such as a mobile phone connected to the connection terminals T3 and T4, the output voltage between the connection terminals T3 and T4 is detected, and the output voltage between the connection terminals T3 and T4 falls below a predetermined end-of-discharge voltage. In this case, it is desirable to cut off the output current from the connection terminals T3 and T4. Thereby, generation | occurrence | production of the characteristic deterioration by the overdischarge of the secondary battery 6 can be suppressed.

(Second Embodiment)
Next, a battery pack provided with a protection circuit according to the second embodiment of the present invention will be described. The appearance of the battery pack 1a according to the second embodiment of the present invention is the same as that of the battery pack 1 shown in FIG. FIG. 8 is a circuit diagram showing an example of the electrical configuration of the battery pack 1a according to the second embodiment of the present invention. The battery pack 1a shown in FIG. 8 differs from the battery pack 1 shown in FIG. 2 in the configuration of the protection circuit 5a. That is, the protection circuit 5a shown in FIG. 8 includes a series circuit of a heater R3 (second heater) and a heater R4 (third heater) instead of the series circuit of the heater R2 and the diode D1, and the bimetal switch SW1. Connected in parallel. A connection point between the heater R3 and the heater R4 is connected to the connection terminal T4 via the transistor Q1.

  Since the other configuration is the same as that of the battery pack 1 shown in FIG. 2, the description thereof will be omitted, and the characteristic points of the present embodiment will be described below. FIG. 9 is an explanatory diagram showing an example of a configuration of a series circuit of the heater R3 and the heater R4 used in the protection circuit 5a shown in FIG. The series circuit of the heater R3 and the heater R4 shown in FIG. 9 is configured using one thermistor 7.

  The thermistor 7 is, for example, a positive temperature characteristic, that is, a PTC thermistor whose resistance value increases or decreases in accordance with an increase or decrease in temperature, and the shape thereof is a square, a rectangle, or the like that can physically determine the vertical and horizontal directions. It is made into a plate-like shape such as a substantially rectangular shape, an ellipse, a rhombus, or a circle having a chipped portion or a protrusion. A groove 71 is formed on one surface of the thermistor 7 so as to divide the one surface of the thermistor 7 into two regions.

  One region divided by the groove 71 is used as the first electrode 72 (first electrode) and the other region is used as the second electrode 73 (second electrode), and the other surface of the thermistor 7 is used. Is used as the third electrode 74 (third electrode). In this case, the first electrode 72 and the third electrode 74 are used as connection terminals at both ends of the heater R3, and a portion sandwiched between the first electrode 72 and the third electrode 74 functions as the heater R3. Further, the third electrode 74 and the second electrode 73 are used as connecting terminals at both ends of the heater R4, and a portion sandwiched between the third electrode 74 and the second electrode 73 functions as the heater R4.

  As a result, the heater R3 and the heater R4 can be configured by using one thermistor 7, so that the protection circuit 5a can be downsized as compared with the case where the heater R3 and the heater R4 are each configured by one thermistor. Thus, cost reduction can be achieved.

  10 and 11 are explanatory diagrams for explaining the mechanical configuration of the protection circuit 5a shown in FIG. FIG. 10A is a diagram showing a wiring pattern for attaching each component of the protection circuit 5a, and FIG. 10B is a cross-sectional view showing an example of the mechanical configuration of the protection circuit 5a. In FIG. 10, component mounting positions are indicated by broken lines. FIG. 11A is a top view of the protection circuit 5 shown in FIG. For comparison, FIG. 11 (b) shows the same cross-sectional view as FIG. 10 (b). The protection circuit 5a shown in FIGS. 10 and 11 differs from the protection circuit 5 shown in FIGS. 4 and 5 in the method of attaching the thermistor 7 to the case 31 on which the wiring pattern is formed.

  In the thermistor 7, the second electrode 73 is connected to the wiring pattern P4 connected to the connection terminal T3, and the first electrode 72 is connected to the wiring pattern P5 connecting the bimetal switch SW1 and the thermal fuse F1. Yes. In this case, it is necessary to attach the thermistor 7 to the case 31 so that the interval between the wiring pattern P4 and the wiring pattern P5 and the groove 71 in the thermistor 7 coincide with each other. Since the thermistor 7 has a square shape, it becomes easy to make the direction of the groove 71 coincide with the direction of the space between the wiring pattern P4 and the wiring pattern P5, and the workability in the assembly process of the protection circuit 5a is improved. Can be made.

  In addition, as shown in FIG. 12, you may form the groove | channel 71a in the substantially cross shape which divides | segments one surface of the thermistor 7a into four area | regions. Then, as shown in FIG. 13, two adjacent regions in the four regions divided by the groove 71a are used as the first electrode 72 by connecting to the wiring pattern P5, and the two regions used as the first electrode 72 are used. Other areas except for one area may be used as the second electrode 73.

  Thus, when the thermistor 7a provided with the groove 71a is connected to the wiring pattern P4 and the wiring pattern P5, the thermistor 7a is normally attached to the heaters R3 and R3 even if the thermistor 7a is rotated by 90.degree. Since it functions as R4, the restriction | limiting of the attachment direction of the thermistor 7a is reduced, and the workability | operativity in the assembly process of the protection circuit 5a can be improved.

  Further, the third electrode 74 in the thermistor 7 (7a) and the wiring pattern P9 connected to the drain of the transistor Q1 are connected in the air using a jumper line 75, for example, as shown in FIG. Yes.

  Since the other configuration is the same as that of the protection circuit 5 shown in FIGS. 4 and 5, the description thereof will be omitted, and the operation of the protection circuit 5a shown in FIG. 8 will be described. First, the overcharge protection operation by the protection circuit 5a will be described. First, when a charging device (not shown) is connected to the connection terminals T3 and T4 in a state where the bimetal switch SW1 is on, and the charging voltage Vc is applied between the connection terminals T3 and T4 from the charging device, the bimetal switch SW1, The secondary battery 6 is charged with the charging voltage Vc via the thermal fuse F1 and the connection terminal T1.

  The charging voltage Vc is, for example, a maximum of 4.2 V when normal. The reference voltage source E1 is set to output, for example, 4.3 V as the reference voltage Vref1 to the comparator CMP1.

  For example, when a charging device (not shown) fails or the output voltage accuracy of the charging device is low, and the charging voltage Vc exceeds 4.3 V, the transistor CMP1 is turned on by the comparator CMP1, and a current flows from the connection terminal T3 to the heater R4. Current flows from the secondary battery 6 to the heater R3 via the connection terminal T1 and the thermal fuse F1, the heaters R3 and R4 generate heat, and the bimetal switch SW1 is heated. When the temperature of the bimetal switch SW1 reaches the operating temperature Tsw1, the bimetal switch SW1 is turned off, the charging current is interrupted, and the secondary battery 6 is protected from overcharging.

  In this case, even if the bimetal switch SW1 is turned off, the current supply to the heaters R3 and R4 is continued, and the heating of the bimetal switch SW1 by the heaters R3 and R4 is continued, so the bimetal switch SW1 is maintained off and overcharged. The protection operation continues. Further, for example, the position of the groove 71 in the thermistor 7 is adjusted so that the resistance value of the heater R3 is larger than the resistance value of the heater R4, or the resistance of the heater R3 is used by using the thermistors one by one as the heaters R3 and R4. By making the value larger than the resistance value of the heater R4, the discharge current of the secondary battery 6 when the transistor Q1 is turned on is reduced, and the charging device (not shown) mainly connected to the connection terminals T3 and T4 The heater R4 can generate heat by the current supplied from the power supply, and the off-state of the bimetal switch SW1 can be maintained.

  Further, when the current continues to flow from the secondary battery 6 to the heater R3 via the connection terminal T1 and the thermal fuse F1, and the output voltage of the secondary battery 6 drops below the reference voltage Vref1 due to the discharge of the secondary battery 6, the comparator CMP1. This turns off the transistor Q1. Then, since the output voltage of the charging device connected to the connection terminals T3, T4 is higher than the output voltage of the secondary battery 6, the heater R4, the heater R3, the thermal fuse F1, and the connection terminal T1 are connected from the connection terminal T3. A small charging current flows to the secondary battery 6 through the heater R4, the heat generation of the heaters R4 and R3 continues, the bimetal switch SW1 is maintained in the OFF state, and the overcharge protection operation is continued.

  When the secondary battery 6 is charged with the charging current passing through the heaters R4 and R3 and the terminal voltage of the connection terminal T1 again exceeds 4.3 V, the transistor CMP1 is turned on by the comparator CMP1, and the heater R4 is connected from the connection terminal T3. Current flows from the secondary battery 6 to the heater R3 via the connection terminal T1 and the thermal fuse F1, the heaters R3 and R4 generate heat, the bimetal switch SW1 is heated, and the bimetal switch SW1 is turned off. The overcharge protection operation is continued.

  Thus, with the charging / discharging operation of the secondary battery 6, the on / off operation of the transistor Q1 is repeated and the bimetal switch SW1 is maintained in the off state, and the overcharge protection operation of the secondary battery 6 is continued. For example, when the bimetal switch SW1 is turned off in association with the overcharge protection operation, the secondary battery 6 is discharged, the output voltage of the secondary battery 6 is lowered, and the transistor Q1 is turned off by the comparator CMP1. However, since the current does not flow to the heater and the bimetal switch SW1 is prevented from being turned on, the chattering operation in which the bimetal switch SW1 is repeatedly turned on and off with the charge / discharge operation of the secondary battery 6 can be suppressed. .

  Next, the protection operation by the protection circuit 5a when the discharge current from the secondary battery 6 becomes excessive will be described. First, in a state where the bimetal switch SW1 is turned on, for example, a metal piece comes into contact with the connection terminals T3 and T4, or a load device such as a mobile phone (not shown) connected to the connection terminals T3 and T4 breaks down. As a result, when the connection terminals T3 and T4 are short-circuited or the resistance value between the connection terminals T3 and T4 becomes low, the current discharged from the secondary battery 6 via the temperature fuse F1 and the bimetal switch SW1 increases. The bimetal switch SW1 is heated by the contact resistance of the bimetal switch SW1.

  When the temperature of the bimetal switch SW1 reaches the operating temperature Tsw1, the bimetal switch SW1 is turned off, the discharge current of the secondary battery 6 is cut off, and the secondary battery 6 is protected from an excessive discharge current. When the bimetal switch SW1 is turned off, the discharge current of the secondary battery 6 is connected to the connection terminals T3 and T4 from the connection terminal T1 through the temperature fuse F1, the heater R3, the heater R4, and the connection terminal T3. It flows to the load device (or the short-circuit failure part), and the heaters R3 and R4 generate heat to heat the bimetal switch SW1.

  In this case, even if the bimetal switch SW1 is turned off and self-heating is eliminated, the heaters R3 and R4 generate heat due to the current flowing through the load device (not shown), and the bimetal switch SW1 is heated by the heaters R3 and R4. The bimetal switch SW1 can be kept in an off state until the load device or the like that has caused the short-circuit failure is removed and the cause of excessive discharge current is removed.

(Third embodiment)
Next, a battery pack provided with a protection circuit according to the third embodiment of the present invention will be described. The appearance of the battery pack 1b according to the third embodiment of the present invention is the same as that of the battery pack 1 shown in FIG. FIG. 14 is a circuit diagram showing an example of the electrical configuration of the battery pack 1b according to the third embodiment of the present invention. The battery pack 1b shown in FIG. 14 differs from the battery pack 1a shown in FIG. 8 in the configuration of the protection circuit 5b. That is, in the protection circuit 5b shown in FIG. 14, the heater R3 (first heater) is connected in parallel with the bimetal switch SW1. The connection point between the heater R3 and the heater R4 is connected to the connection terminal T3, and the other end is connected to the connection terminal T4 via the transistor Q1. In this case, the heater R4 corresponds to a fourth heater having one end connected to the connection terminal T3 and heating the bimetal switch SW1.

  15 and 16 are explanatory diagrams for explaining the mechanical configuration of the protection circuit 5b shown in FIG. FIG. 15A is a diagram showing a wiring pattern for attaching each component of the protection circuit 5b, and FIG. 15B is a cross-sectional view showing an example of the mechanical configuration of the protection circuit 5a. In FIG. 15, the mounting positions of the components are indicated by broken lines. FIG. 16A is a top view of the protection circuit 5 shown in FIG. For comparison, FIG. 16B shows the same cross-sectional view as FIG. 15B. The protection circuit 5b shown in FIGS. 15 and 16 differs from the protection circuit 5a shown in FIGS. 10 and 11 in the method of attaching the thermistor 7a to the case 31 on which the wiring pattern is formed.

  In the thermistor 7a, two regions adjacent to each other in the four regions divided by the groove 71a are connected to the wiring pattern P5 that connects the bimetal switch SW1 and the thermal fuse F1 as the first electrode 72, and the first electrode 72 The other region excluding the two used regions is connected to the wiring pattern P9 connected to the drain of the transistor Q1 as the second electrode 73. Further, the third electrode 74 in the thermistor 7a and the wiring pattern P4 connected to the connection terminal T3 are connected in the air using a jumper wire 76 as shown in FIG. 16A, for example.

  Since the other configuration is the same as that of the protection circuit 5a shown in FIGS. 8, 10, and 11, description thereof will be omitted, and the operation of the protection circuit 5b shown in FIG. 14 will be described. First, the overcharge protection operation by the protection circuit 5b will be described. First, when a charging device (not shown) is connected to the connection terminals T3 and T4 in a state where the bimetal switch SW1 is on, and the charging voltage Vc is applied between the connection terminals T3 and T4 from the charging device, the bimetal switch SW1, The secondary battery 6 is charged with the charging voltage Vc via the thermal fuse F1 and the connection terminal T1.

  The charging voltage Vc is, for example, a maximum of 4.2 V when normal. The reference voltage source E1 is set to output, for example, 4.3 V as the reference voltage Vref1 to the comparator CMP1.

  For example, when a charging device (not shown) fails or the output voltage accuracy of the charging device is low, and the charging voltage Vc exceeds 4.3 V, the transistor CMP1 is turned on by the comparator CMP1, and a current flows from the connection terminal T3 to the heater R4. Flows, the heater R4 generates heat, and the bimetal switch SW1 is heated. When the temperature of the bimetal switch SW1 reaches the operating temperature Tsw1, the bimetal switch SW1 is turned off, the charging current is interrupted, and the secondary battery 6 is protected from overcharging.

  In this case, even if the bimetal switch SW1 is turned off, the current supply from the charging device (not shown) connected to the connection terminal T3 to the heater R4 is continued, and the heating of the bimetal switch SW1 by the heater R4 is continued. Is kept off and the overcharge protection operation continues.

  Further, since the output voltage of the unillustrated charging device connected to the connection terminal T3 is higher than the output voltage of the secondary battery 6, even if the transistor Q1 is turned on, a current flows from the secondary battery 6 to the heater R3. Since the secondary battery 6 is not discharged, for example, the bimetal switch SW1 is turned off in accordance with the overcharge protection operation, and the secondary battery 6 is discharged, so that the output voltage of the secondary battery 6 is reduced, and the comparator CMP1 When the transistor Q1 is turned off, the current stops flowing through the heater, the bimetal switch SW1 is turned on and the secondary battery 6 is charged again. The bimetal switch SW1 is charged along with the charge / discharge operation of the secondary battery 6. It is possible to suppress the occurrence of chattering operations that repeatedly turn on and off.

  Next, the protection operation by the protection circuit 5a when the discharge current from the secondary battery 6 becomes excessive will be described. First, in a state where the bimetal switch SW1 is turned on, for example, a metal piece comes into contact with the connection terminals T3 and T4, or a load device such as a mobile phone (not shown) connected to the connection terminals T3 and T4 breaks down. As a result, when the connection terminals T3 and T4 are short-circuited or the resistance value between the connection terminals T3 and T4 becomes low, the current discharged from the secondary battery 6 via the temperature fuse F1 and the bimetal switch SW1 increases. The bimetal switch SW1 is heated by the contact resistance of the bimetal switch SW1.

  When the temperature of the bimetal switch SW1 reaches the operating temperature Tsw1, the bimetal switch SW1 is turned off, the discharge current of the secondary battery 6 is cut off, and the secondary battery 6 is protected from an excessive discharge current. When the bimetal switch SW1 is turned off, the discharge current of the secondary battery 6 is supplied from the connection terminal T1 to the connection terminals T3 and T4 via the temperature fuse F1, the heater R3, and the connection terminal T3 (not shown). Alternatively, the heater R3 generates heat and heats the bimetal switch SW1.

  In this case, even if the bimetal switch SW1 is turned off and self-heat generation disappears, the heater R3 generates heat due to the current flowing through the load device (not shown) and the bimetal switch SW1 is heated by the heater R3. The off-state of the bimetal switch SW1 can be maintained until the cause of the excessive discharge current is removed by removing the load device or the like.

  As described above, the protection circuit 5b shown in FIG. 14 protects the secondary battery 6 from overcharging by using a current supplied from a charging device (not shown) connected to the connection terminals T3 and T4. When R4 is heated and the secondary battery 6 is protected from an excessive discharge current, the heater R3 is heated by the current supplied from the secondary battery 6. In this case, since the operating temperature Tsw1 at which the bimetal switch SW1 operates is constant, the heat generation amount of the heater R4 at the time of overcharge protection is equal to the heat generation amount of the heater R3 at the time of protection operation from an excessive discharge current. It is desirable that

Therefore, Vcmax the maximum output voltage of the charging device, the output voltage of the secondary battery 6 VB, the resistance value _{R 3} of the heater R3, and the resistance value of the heater R4 and _{R 4, R 3} and _{R 4,} below It is desirable to set so as to satisfy Equation (2).

Vcmax × Vcmax ÷ R ₄ = VB × VB ÷ R ₃ (2)
As a result, the amount of heat generated by the heater R4 during overcharge protection can be made equal to the amount of heat generated by the heater R3 during protection operation from an excessive discharge current. In this case, for example, the heater R3 and the heater R4 may be configured by individual thermistors, and the resistance value of the heater R3 and the resistance value of the heater R4 may be set so as to satisfy the above equation (2). By adjusting the position of the groove 71 using the thermistor 7 shown in FIG. 9, the resistance value of the heater R3 and the resistance value of the heater R4 may be set so as to satisfy the above formula (2).

  As in the protection circuit 5c shown in FIG. 17, a diode D2 (second rectification element) that is a rectification element may be provided between the thermal fuse F1 and the heater R3 in the protection circuit 5b shown in FIG. The anode of the diode D2 is connected to the connection terminal T1 via the temperature fuse F1, and the cathode of the diode D2 is connected to the connection terminal T3 via the heater R3, that is, a secondary battery connected to the connection terminal T1. 6 are connected in the forward direction in the direction in which the discharge current 6 flows.

  As a result, in the protection circuit 5c shown in FIG. 17, after the bimetal switch SW1 is turned off to protect the secondary battery 6 from overcharging by a charging device (not shown) connected to the connection terminals T3 and T4, the diode D2 Since it is possible to prevent the charging voltage from being applied to the secondary battery 6 from the connection terminal T3 via the heater R3, the protection effect against overcharging of the secondary battery 6 can be improved.

(Fourth embodiment)
Next, a battery pack provided with the protection circuit according to the embodiment of the present invention will be described. The appearance of the battery pack 1d according to the fourth embodiment of the present invention is the same as that of the battery pack 1 shown in FIG. FIG. 18 is a circuit diagram showing an example of an electrical configuration of a battery pack 1d according to the fourth embodiment of the present invention. The battery pack 1d shown in FIG. 18 differs from the battery pack 1b shown in FIG. 14 in the configuration of the protection circuit 5d. That is, the protection circuit 5d shown in FIG. 18 is different in that it further includes a thermistor R5 (detection unit), a resistor R10, and a reference voltage source E2, and an integrated circuit IC1a instead of the integrated circuit IC1.

  The thermistor R5 is, for example, a thermistor whose resistance value decreases as the temperature rises, and is used as a temperature sensor. The thermistor R5 is disposed so as to be close to or in contact with the secondary battery 6 via an insulator, and generates a resistance value corresponding to the temperature of the secondary battery 6. A series circuit of the thermistor R5 and the resistor R10 is connected between both electrodes of the reference voltage source 2, and a connection point between the thermistor R5 and the resistor R10 is connected to the + terminal of the comparator CMP1.

  The reference voltage source E2 is a constant voltage source that outputs a reference voltage for acquiring the resistance value of the thermistor R5 as a voltage. Thereby, the resistance value of the thermistor R5, that is, the temperature of the secondary battery 6 is input to the + terminal of the comparator CMP1. The output voltage of the reference voltage source E2 is generated at the connection point between the thermistor R5 and the resistor R10, for example, when the temperature of the secondary battery 6 reaches a temperature that adversely affects the characteristics of the secondary battery 6. A voltage value is set in advance such that the voltage exceeds the reference voltage Vref1. For example, the comparator CMP1, the reference voltage sources E1 and E2, and the resistor R10 are integrated into an integrated circuit 1a.

  Next, the operation of the protection circuit 5d configured as described above will be described. First, when the bimetal switch SW1 is turned on and a charging device (not shown) is connected to the connection terminals T3 and T4 and the secondary battery 6 is overcharged, the temperature of the secondary battery 6 rises.

  When the temperature of the secondary battery 6 increases, the resistance value of the thermistor R5 decreases, and the voltage at the connection point between the thermistor R5 and the resistor R10 increases. Further, when the voltage at the connection point between the thermistor R5 and the resistor R10 rises and exceeds the reference voltage Vref1, that is, when the temperature of the secondary battery 6 reaches a temperature that adversely affects the characteristics of the secondary battery 6, for example, the comparator CMP1. As a result, the transistor Q1 is turned on, a current flows from the connection terminal T3 to the heater R4, and the bimetal switch SW1 is heated.

  When the temperature of the bimetal switch SW1 reaches the operating temperature Tsw1, the bimetal switch SW1 is turned off to interrupt the charging current, and the secondary battery 6 is protected from heat generation due to overcharging.

  In addition, when an excessive discharge current flows due to an electrical device serving as a power load being connected to the connection terminals T3 and T4 or a short-circuit failure occurring while the bimetal switch SW1 is on, the secondary battery The temperature of 6 rises. Then, as described above, the temperature of the secondary battery 6 rises and the temperature of the secondary battery 6 adversely affects, for example, the characteristics of the secondary battery 6 before the bimetal switch SW1 is turned off by self-heating. Then, the voltage at the connection point between the thermistor R5 and the resistor R10 rises and exceeds the reference voltage Vref1, the transistor CMP1 is turned on by the comparator CMP1, and the heater R3 is connected from the secondary battery 6 through the connection terminal T1 and the temperature fuse F1. A current flows through R4, and the bimetal switch SW1 is heated.

  When the temperature of the bimetal switch SW1 reaches the operating temperature Tsw1, the bimetal switch SW1 is turned off to interrupt the discharge current, and the secondary battery 6 is protected from heat generation due to an excessive discharge current.

  Further, even after the bimetal switch SW1 is turned off, a current flows from the secondary battery 6 to the heaters R3 and R4 via the connection terminal T1 and the temperature fuse F1, and the bimetal switch SW1 is heated and the off state of the bimetal switch SW1 is maintained. Is done.

  As a result, when the secondary battery 6 generates excessive heat, the discharge current and the charging current can be cut off by one bimetal switch SW1, so that the secondary battery 6 can be overcharged using a simple circuit. It can protect from excessive heat generation by an excessive discharge current.

  Further, for example, since the bimetal switch SW1 is turned off and self-heat is not generated, the bimetal switch SW1 is turned on by natural cooling, and the charge / discharge current flows again to the secondary battery 6 through the bimetal switch SW1 to turn off the bimetal switch SW1. As described above, the chattering operation in which the bimetal switch SW1 is repeatedly turned on and off can be suppressed.

  Other configurations and operations are the same as those of the battery pack 1b shown in FIG. Note that the thermistor R5 and the integrated circuit IC1a shown in FIG. 18 may be provided in place of the integrated circuit 1 in the battery packs 1, 1a, and 1c.

  In the battery pack 1 shown in FIG. 1, the secondary battery 6 is accommodated in a bottomed container 2 made of a steel plate with nickel plating on the surface, and the opening of the container 2 and the sealing plate are An example is shown in which the positive terminal 61 provided in a convex shape protrudes from the open end of the container 2 and the negative electrode of the secondary battery 6 is connected to the container 2 inside the container 2. A secondary battery is housed in a bottomed container 2 made of an aluminum alloy, an opening of the container 2 and a sealing plate are sealed by a laser sealing, and a negative electrode provided in a convex shape on the sealing plate When the terminal protrudes from the open end of the container 2 and the positive electrode of the secondary battery 6 is insulated from the negative electrode terminal and is connected to the sealing plate, it is easily implemented by reversing the connection with the protective circuit. can do.

  The protection circuit and the battery pack of the present invention can realize a protection circuit and a battery pack that can protect the secondary battery from excessive charging and excessive discharge current with a simple circuit, and can be used for mobile devices and driving power supplies. Useful as.

It is a disassembled perspective view which shows an example of the battery pack which concerns on one Embodiment of this invention. It is a circuit diagram which shows an example of the electrical constitution of the battery pack shown in FIG. It is a graph which shows an example of the electric current value which flows into a bimetal switch and a thermal fuse, and operation time. It is explanatory drawing for demonstrating an example of a structure of the protection circuit which concerns on the 1st Embodiment of this invention. FIG. 4A is a diagram showing a wiring pattern for attaching each component of the protection circuit, and FIG. 4B is a cross-sectional view showing an example of the mechanical configuration of the protection circuit. FIG. 5A is a diagram illustrating an example of the mechanical configuration of the protection circuit illustrated in FIG. 4. FIG. 5A is a top view illustrating an example of the mechanical configuration of the protection circuit, and FIG. 5B is a diagram illustrating the mechanical configuration of the protection circuit. It is sectional drawing which shows an example. It is explanatory drawing for demonstrating operation | movement of a movable piece. It is explanatory drawing for demonstrating the state with which the container and the sealing part were combined. It is a circuit diagram which shows an example of the electrical constitution of the battery pack which concerns on the 2nd Embodiment of this invention. It is explanatory drawing which shows an example of a structure of the thermistor used as a heater shown in FIG. It is explanatory drawing for demonstrating the mechanical structure of the protection circuit shown in FIG. FIG. 10A is a diagram illustrating a wiring pattern for attaching each component of the protection circuit, and FIG. 10B is a cross-sectional view illustrating an example of a mechanical configuration of the protection circuit. It is explanatory drawing for demonstrating the mechanical structure of the protection circuit shown in FIG. FIG. 11A is a top view of the protection circuit 5 shown in FIG. 10B, and FIG. 11B is a cross-sectional view showing an example of the mechanical configuration of the protection circuit. It is explanatory drawing which shows an example of a structure of the thermistor used as a heater shown in FIG. It is explanatory drawing for demonstrating the mechanical structure of the protection circuit using the thermistor shown in FIG. It is a circuit diagram which shows an example of the electrical constitution of the battery pack which concerns on the 3rd Embodiment of this invention. It is explanatory drawing for demonstrating the mechanical structure of the protection circuit shown in FIG. FIG. 15A is a diagram illustrating a wiring pattern for attaching each component of the protection circuit, and FIG. 15B is a cross-sectional view illustrating an example of a mechanical configuration of the protection circuit. It is explanatory drawing for demonstrating the mechanical structure of the protection circuit shown in FIG. FIG. 16A is a top view of the protection circuit 5 shown in FIG. 16B, and FIG. 16B is a cross-sectional view showing an example of the mechanical configuration of the protection circuit. FIG. 15 is a circuit diagram showing a modification of the electrical configuration of the battery pack shown in FIG. 14. It is a circuit diagram which shows an example of the electrical constitution of the battery pack which concerns on the 4th Embodiment of this invention. It is a block diagram which shows the structure of the battery pack which concerns on background art. It is a block diagram which shows the structure of the battery pack which concerns on background art. It is a block diagram which shows the structure of the battery pack which concerns on background art.

Explanation of symbols

1, 1a, 1b, 1c, 1d Battery pack 2 Container 3 External terminal connection unit 5, 5a, 5b, 5c, 5d Protection circuit 6 Secondary battery 7, 7a Thermistor 37 Bimetal 71, 71a Groove 72 First electrode 73 Second Electrode 74 Third electrode 75, 76 Jumper line CMP1 Comparator D1, D2 Diode E1, E2 Reference voltage source F1 Thermal fuse IC1, IC1a Integrated circuit Q1 Transistor R2, R3, R4 Heater R5 Thermistor SW1 Bimetal switch T1, T2, T3, T4 Connecting terminal

Claims (14)

First and second connection terminals for connecting to both electrodes of the secondary battery,
Third and fourth connection terminals for connecting a charging device for charging the secondary battery and / or a load device driven by a discharge current from the secondary battery;
A thermal switch that is provided between the first and third connection terminals and is turned off when a predetermined temperature is exceeded;
A first heater connected in parallel with the thermal switch and for heating the thermal switch;
A detection unit for detecting a physical quantity related to the characteristics of the secondary battery;
A protection control unit that causes the first heater to generate heat and turn off the thermal switch when the physical quantity detected by the detection unit exceeds a preset physical quantity value;
The protection circuit for a secondary battery, wherein the thermal switch is one selected from a bimetal switch, a switch using a shape memory alloy, and a switch using a shape memory resin. The physical quantity related to the characteristics of the secondary battery is the voltage of the first connection terminal,
The detection unit detects a voltage of the first connection terminal,
The said protection control part makes the said 1st heater generate | occur | produce a heat | fever and turns off the said thermal switch, when the voltage detected by the said detection part exceeds the preset reference voltage. The protection circuit of the secondary battery as described. The physical quantity related to the characteristics of the secondary battery is the temperature of the secondary battery,
The detection unit detects the temperature of the secondary battery,
The protection control unit heats the first heater and turns off the thermal switch when the temperature of the secondary battery detected by the detection unit exceeds a preset temperature. The secondary battery protection circuit according to claim 1. A first rectifying element is further provided between the first heater and the third connection terminal in a forward direction and a direction in which the discharge current of the secondary battery connected to the first connection terminal flows;
The protection control unit includes a switch unit that opens and closes a connection between a connection point between the first heater and the first rectifying element and the fourth connection terminal, and is detected by the detection unit. The protection circuit for a secondary battery according to claim 1, wherein the switch unit is turned on when the physical quantity exceeds a preset physical quantity value. The first heater is composed of a series circuit of second and third heaters,
The protection control unit includes a switch unit that opens and closes a connection between the connection point between the second heater and the third heater and the fourth connection terminal, and is detected by the detection unit. The secondary battery protection circuit according to claim 1, wherein the switch unit is turned on when the physical quantity exceeds a preset physical quantity value. A fourth heater for heating the thermal switch and having one end connected to the third connection terminal;
The protection control unit includes a switch unit that opens and closes a connection between the other end of the fourth heater and the fourth connection terminal, and the physical quantity detected by the detection unit is a preset physical quantity. The secondary battery protection circuit according to any one of claims 1 to 3, wherein the switch unit is turned on when the value of is exceeded. The first and fourth heaters include a heat generation amount of the first heater due to a discharge current from the secondary battery connected to the first connection terminal when the thermal switch is turned off, and the switch unit. The resistance value is set to equalize the amount of heat generated by the fourth heater due to the output current from the charging device connected to the third connection terminal when is turned on. The secondary battery protection circuit according to claim 6. A second rectifying element is further provided between the first connection terminal and the first heater in the forward direction and the direction in which the discharge current of the secondary battery connected to the first connection terminal flows. The secondary battery protection circuit according to claim 6 or 7. The second and third heaters are PTC thermistors whose resistance value increases or decreases with an increase or decrease in temperature,
The PTC thermistor has a substantially plate shape and is formed with a groove that divides at least one surface into a plurality of regions.
Among the plurality of regions on one surface of the PTC thermistor, a part of the region is used as the first electrode and at least a part of the region excluding the first electrode is used as the second electrode,
The other surface of the PTC thermistor is used as a third electrode,
The first and third electrodes are used as connection terminals at both ends of the second heater,
The secondary battery protection circuit according to claim 5, wherein the third and second electrodes are used as connection terminals at both ends of the third heater. The first and fourth heaters are PTC thermistors whose resistance value increases or decreases with an increase or decrease in temperature,
The PTC thermistor has a substantially plate shape and has a groove that divides at least one surface into a plurality of regions.
Among the plurality of regions on one surface of the PTC thermistor, a part of the region is used as the first electrode and at least a part of the region excluding the first electrode is used as the second electrode,
The other surface of the PTC thermistor is used as a third electrode,
The first and third electrodes are used as connection terminals at both ends of the first heater,
The secondary battery protection circuit according to any one of claims 6 to 8, wherein the third and second electrodes are used as connecting terminals at both ends of the fourth heater. The groove divides the one surface of the PTC thermistor into two regions,
11. The secondary battery protection circuit according to claim 9, wherein one region divided by the groove is used as a first electrode and the other region is used as a second electrode. The groove is a substantially cross-shaped groove that divides the one surface of the PTC thermistor into four regions,
Two regions adjacent to each other in the four regions are used as the first electrode,
11. The secondary battery protection circuit according to claim 9, wherein a region other than the two regions used as the first electrode among the four regions is used as the second electrode.   13. The secondary battery protection circuit according to claim 12, wherein the PTC thermistor has a shape in which the vertical and horizontal directions can be physically determined. A protection circuit for a secondary battery according to any one of claims 1 to 13,
A secondary battery in which both electrodes are respectively connected to the first and second connection terminals in the protection circuit of the secondary battery;
A bottomed container for accommodating the secondary battery;
A battery pack comprising: an external connection terminal unit that accommodates the protection circuit.

Images