JP2006340545A - Protection circuit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a simple protection circuit capable of protecting a secondary battery from overcharge and overcurrent. <P>SOLUTION: When the voltage of a secondary battery 6 exceeds a predetermined reference voltage (overcharge protection voltage) Ref1, an overcharge protecting section 51 outputs a signal of the high level. It thereby turns on a transistor Q1, energizes a heater, and turns off a bimetal switch SW1 to protect the secondary battery 6 from overcharge. When the voltage between connecting terminals T1, T2 exceeds the reference voltage (overcharge protection voltage) Ref2, a chattering eliminating section 52 outputs a signal of the high level. It thereby turns on the transistor Q1, energizes the heater, and turns off the bimetal switch SW1 to eliminate chattering of the bimetal switch SW1. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a protection circuit that protects a secondary battery from excessive charging and overcurrent.

  FIG. 14 is a circuit diagram showing a configuration of a battery pack according to the background art. A battery pack 1001 illustrated in FIG. 14 includes a protection circuit 1002 and a secondary battery 1003. The secondary battery 1003 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. Therefore, the battery pack 1001 includes a protection circuit 1002 that protects the secondary battery 1003 from excessive charging (overcharge) and excessive discharge current (overcurrent) (see, for example, Patent Document 1).

  The protection circuit 1002 includes external connection terminals 1004 and 1005, FETs (Field Effect Transistors) 1006 and 1007, reference voltage sources 1008 and 1009, comparators 1010 and 1011, a resistor 1012, and a logic circuit 1013. .

  The external connection terminals 1004 and 1005 are connected to a charging device for charging the secondary battery 1003, or are mobile devices such as mobile phones and digital cameras driven by the discharge current from the secondary battery 1003, electric tools, robots This is a connection terminal for connecting a driving power source such as an electric bicycle. The external connection terminal 1004, the secondary battery 1003, the FET 1006, the FET 1007, and the external connection terminal 1005 are connected in series.

  The FET 1006 has a direction in which the anode of the parasitic diode is on the secondary battery 1003 side, and the FET 1007 has a direction in which the anode of the parasitic diode is on the external connection terminal 1005 side. The FET 1006 is used as an overcurrent protection switch that cuts off the discharge current when an overcurrent flows in the secondary battery 1003. The FET 1007 supplies a charging current when the secondary battery 1003 is overcharged. Used as an overcharge protection switch to shut off.

  Further, the positive terminal of the secondary battery 1003 is applied to the + terminal of the comparator 1010, the reference voltage VRef1 output from the reference voltage source 1008 is applied to the-terminal of the comparator 1010, and the output terminal of the comparator 1010 is applied to the logic circuit 1013. It is connected. As the reference voltage VRef1, a voltage for detecting overcharge of the secondary battery 1003 is set. The comparator 1010 detects overcharge when the secondary battery 1003 is charged by a charging device (not shown) connected to the external connection terminals 1004 and 1005 and the terminal voltage of the secondary battery 1003 exceeds the reference voltage VRef1. The signal is output to the logic circuit 1013.

  The connection point between the FET 1006 and the FET 1007 is connected to the − terminal of the comparator 1011 through the resistor 1012, and the reference voltage VRef 2 output from the reference voltage source 1009 is applied to the + terminal of the comparator 1011. As a result, the discharge current from the secondary battery 1003 flows through the FET 1006, and the voltage drop caused by the on-resistance of the FET 1006 is applied to the − terminal of the comparator 1011 through the resistor 1012. For example, the reference voltage VRef2 is set to a voltage corresponding to a voltage drop caused by the on-resistance of the FET 1006 when the maximum discharge current in a range that does not cause deterioration of the characteristics of the secondary battery 1003 flows through the FET 1006.

  The comparator 1011 is short-circuited, for example, when the external connection terminals 1004 and 1005 come into contact with a metal piece, or when a load device connected to the external connection terminals 1004 and 1005 breaks down. When an overcurrent flows, an increase in voltage drop in the FET 1006 is detected, and a detection signal indicating the overcurrent is output to the logic circuit 1013.

  When the detection signal indicating overcharge is output from the comparator 1010, the logic circuit 1013 turns off the FET 1007 to stop charging the secondary battery 1003, and when the detection signal indicating overcurrent is output from the comparator 1011, The FET 1006 is turned off to stop the discharge of the secondary battery 1003. Thereby, the protection circuit 1002 protects the secondary battery 1003 from overcharge and overcurrent.

  Further, as a protection circuit for protecting the secondary battery from overcharging and overcurrent in this way, a secondary battery 1022 and a bimetal switch 1023 are connected in series as in the battery pack 1021 shown in FIG. When the charging device connected to the external connection terminals 1024 and 1025 fails, the bimetal switch 1023 is heated by overcharging and the secondary battery 1022 generates heat or the bimetal switch 1023 self-heats. In this case, a battery in which the bimetal switch 1023 is turned off to interrupt the charging current and protect the secondary battery 1022 is known.

Further, a secondary battery 1033 and a PTC element 1032 are used using a PTC element 1032 which is a PTC (Positive Temperature Coefficient) element which is a thermistor which is turned off when a predetermined temperature is exceeded as in the battery pack 1031 shown in FIG. Are connected in series, for example, when the charging device 1036 connected to the external connection terminals 1034 and 1035 fails, the secondary battery 1033 generates heat or the PTC element 1032 self-heats due to excessive charging. Thus, it is known that when the PTC element 1032 is heated, the PTC element 1032 is turned off to interrupt the charging current and protect the secondary battery 1033.
JP-A-4-75430

  However, since the protection circuit 1002 shown in FIG. 14 has a parasitic diode in the FET, the discharge current and the charging current in different directions of current cannot be cut off by one FET, and the discharge current is cut off. It was necessary to provide the FET 1006 and the FET 1007 that cuts off the charging current. Further, a reference voltage source 1008 and a comparator 1010 are required to detect overcharge, a reference voltage source 1009, a comparator 1011 and a resistor 1012 are required to detect overcurrent, and output signals from the comparators 1010 and 1011 Therefore, since the logic circuit 1013 for turning on and off the two FETs 1006 and 1007 is required, there is a disadvantage that the circuit scale of the protection circuit 1002 increases.

  Furthermore, as shown in FIG. 15 and FIG. 16, in the configuration in which the secondary battery is protected from overcharging by connecting the temperature switch that operates according to the temperature of the bimetal switch or the PTC element in series with the secondary battery, Because the detection accuracy is low, the secondary battery can be charged with a charging current that does not cause the temperature to rise suddenly, such as when the battery pack is charged by a poor charging device with low charging voltage control accuracy. If the operation is continued, 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 overcharging and overcurrent with a simple circuit.

  According to the present invention, the protection circuit includes a charging device for charging a secondary battery and / or first and second connection terminals for connecting a load device driven by a discharge current from the secondary battery, and a secondary battery. The third and fourth connection terminals connected to both electrodes of the first and the third connection terminals are connected between the first and third connection terminals and are turned off when a predetermined operating temperature is exceeded due to self-heating by the flowing current, Between the third and fourth connection terminals, a thermal switch that is turned off when the operating temperature is exceeded by being externally heated, a heater that heats the thermal switch, a switching means that controls energization of the heater, and The first overcharge protection means for energizing the heater to the switching means when the voltage exceeds a predetermined overcharge protection voltage, and the voltage between the first and second connection terminals exceeds the overcharge protection voltage. Characterized in that it comprises a second overcharge protection means for energizing said heater to said switching means when.

  Further, in the above configuration, the first overcharge protection means includes a first comparator that detects whether or not a voltage between the third and fourth connection terminals exceeds the overcharge protection voltage, The second overcharge protection means includes a second comparator that outputs a high level signal when a voltage between the first and second connection terminals exceeds the overcharge protection voltage, and the switching means Preferably, the heater is energized when at least one of the first and second comparators outputs a high level signal.

  Further, in the above configuration, the switching means includes an OR gate having an input terminal connected to the output terminals of the first and second comparators, a gate connected to the output terminal of the OR gate, and a drain connected to the heater. Preferably, the n-channel field effect transistor is connected, and the source is connected to the second and fourth connection terminals.

  In the above configuration, when the voltage between the third and fourth connection terminals exceeds the voltage obtained by adding a predetermined short-circuit protection voltage to the voltage between the first and second connection terminals, the switching means It is preferable to further comprise short-circuit protection means for energizing the heater.

  Further, in the above configuration, the first overcharge protection means includes a first comparator that detects whether or not a voltage between the third and fourth connection terminals exceeds the overcharge protection voltage, The second overcharge protection means includes a second comparator that outputs a high level signal when a voltage between the first and second connection terminals exceeds the overcharge protection voltage, and the short circuit protection means. Is a third signal that outputs a high level signal when the voltage between the third and fourth connection terminals exceeds the voltage between the first and second connection terminals plus the short-circuit protection voltage. The switching means preferably energizes the heater when at least one of the first to third comparators outputs a high level signal. .

  In the above configuration, the switching means includes an OR gate having an input terminal connected to the output terminals of the first to third comparators, a gate connected to the output terminal of the OR gate, and a drain connected to the heater. And an n-channel field effect transistor having a source connected to the second and fourth connection terminals.

  Further, in the above configuration, it is preferable to further include a temperature control means for causing the switching means to stop energization to the heater when the temperature of the heater reaches a predetermined upper limit temperature higher than the operating temperature of the thermal switch. (Claim 7).

  Further, in the above configuration, the first overcharge protection means includes a first comparator that outputs a high level signal when a voltage between the third and fourth connection terminals exceeds the overcharge protection voltage. The second overcharge protection means includes a second comparator that outputs a high level signal when the voltage between the first and second connection terminals exceeds the overcharge protection voltage, and the short circuit. The protection means outputs a high level signal when the voltage between the third and fourth connection terminals exceeds the voltage obtained by adding the short-circuit protection voltage to the voltage between the first and second connection terminals. A temperature sensor that detects a temperature of the heater; and a fourth signal that outputs a low level signal when the temperature detected by the temperature sensor reaches the upper limit temperature. Compa The switching means includes an OR gate having an input terminal connected to an output terminal of the first to third comparators, an input terminal having an output terminal of the OR gate, and an output terminal of the fourth comparator. An n-channel field effect transistor having a gate connected to the output terminal of the AND gate, a drain connected to the heater, and a source connected to the second and fourth connection terminals. (Claim 8).

  The protection circuit according to the present invention includes a charging device for charging a secondary battery and / or first and second connection terminals for connecting a load device driven by a discharge current from the secondary battery, and a secondary battery. The third and fourth connection terminals connected to both electrodes of the first and the third connection terminals are connected between the first and third connection terminals and are turned off when a predetermined operating temperature is exceeded due to self-heating by the flowing current, Between the third and fourth connection terminals, a thermal switch that is turned off when the operating temperature is exceeded by being externally heated, a heater that heats the thermal switch, a switching means that controls energization of the heater, and First overcharge protection means for energizing the switching means when the voltage exceeds a predetermined overcharge protection voltage, and a predetermined temperature higher than the operating temperature of the thermal switch. If it becomes limited temperature, characterized in that it comprises a temperature control means for stopping the energization of the heater to the switching means.

  Further, in the above configuration, the first overcharge protection unit includes a first comparator that outputs a high level signal when a voltage between the third and fourth connection terminals exceeds the overcharge protection voltage. The temperature control means includes a temperature sensor for detecting the temperature of the heater, and a fourth comparator for outputting a low level signal when the temperature detected by the temperature sensor reaches the upper limit temperature, The switching means energizes the heater when both the first and fourth comparators output a high level signal, and at least one of the comparators outputs a low level signal. In this case, it is preferable to stop the energization of the heater to the switching means.

  In the above configuration, the switching means includes an AND gate having an input terminal connected to the output terminals of the first and fourth comparators, a gate connected to the output terminal of the AND gate, and a drain connected to the heater. And an n-channel field effect transistor having a source connected to the second and fourth connection terminals.

  Moreover, in the said structure, it further has the thermal fuse connected between the said thermal switch and the said 3rd connection terminal, and the voltage between the said 3rd and 4th connection terminals is higher than the said overcharge protection voltage. It is preferable to further include upper limit temperature changing means for changing the upper limit temperature to a temperature higher than the fusing temperature of the thermal fuse when the second overcharge protection voltage is exceeded.

  The protection circuit according to the present invention includes a charging device for charging a secondary battery and / or first and second connection terminals for connecting a load device driven by a discharge current from the secondary battery, and a secondary battery. The third and fourth connection terminals connected to both electrodes of the first and the third connection terminals are connected between the first and third connection terminals and are turned off when a predetermined operating temperature is exceeded due to self-heating by the flowing current, Between the third and fourth connection terminals, a thermal switch that is turned off when the operating temperature is exceeded by being externally heated, a heater that heats the thermal switch, a switching means that controls energization of the heater, and When the voltage exceeds a predetermined overcharge protection voltage, the first overcharge protection means for energizing the heater to the switching means, and the voltage between the third and fourth connection terminals are the first and Second If it exceeds a voltage obtained by adding a predetermined short-circuit protection voltage to the voltage between the connecting terminals, characterized in that it comprises a short circuit protection means for energizing said heater to said switching means.

  Further, in the above configuration, the first overcharge protection means includes a first comparator that detects whether or not a voltage between the third and fourth connection terminals exceeds the overcharge protection voltage, The short circuit protection means outputs a high level signal when the voltage between the third and fourth connection terminals exceeds a voltage obtained by adding a predetermined short circuit protection voltage to the voltage between the first and second connection terminals. It is preferable that a third comparator for outputting is provided, and the switching means energizes the heater when at least one of the first and third comparators outputs a high level signal. Item 14).

  In the above configuration, the switching means includes an OR gate having an input terminal connected to the output terminals of the first and third comparators, a gate connected to the output terminal of the OR gate, and a drain connected to the heater. And an n-channel field effect transistor having a source connected to the second and fourth connection terminals.

  In the above configuration, it is preferable that a resistor is connected in parallel to the thermal switch.

  Further, in the above configuration, when the voltage between the third and fourth connection terminals becomes equal to or lower than a predetermined overdischarge voltage, power supply control means for stopping power supply from the secondary battery to the protection circuit is further provided. It is preferable to provide (Claim 17).

  According to the first aspect of the present invention, the first overcharge protection means, when the voltage between the third and fourth connection terminals (the voltage of the secondary battery) exceeds a preset overcharge protection voltage, Since the heater is energized to the switching means and the thermal switch is heated by the heater to be turned off and the charging current is cut off, the secondary battery can be protected from overcharging.

  Further, when the discharge current from the secondary battery exceeds a predetermined current value, the thermal switch is turned off by self-heating to cut off the discharge current, so that the secondary battery can be protected from overcurrent. Therefore, the FET 1006 for preventing overcurrent, the reference voltage source 1009, and the comparator 1011 for detecting overcurrent as shown in FIG. 14 are not required, and the circuit can be simplified.

  Furthermore, since the discharge current and the charge current can be interrupted by the thermal switch, the circuit can be simplified.

  Here, consider a case where the second overcharge protection means is not present. When the power of the secondary battery is consumed by the heater in the overcharge protection state, the voltage of the secondary battery decreases, the energization of the heater is stopped by the switching means, and the heating of the thermal switch is stopped. When the thermal switch is naturally cooled and becomes below the operating temperature, it is turned on again, a charging current is supplied from the charging device, and the secondary battery is charged again. When charging of the secondary battery is continued, the voltage of the secondary battery exceeds the overcharge protection voltage, and the thermal switch is turned off again. Thus, chattering occurs when the charging device continues to be connected between the first and second connection terminals in the overcharge protection state.

  However, the present invention includes the second overcharge protection means. Therefore, in the overcharge protection state, if the charging device is connected between the first and second connection terminals and charging is continued, and the voltage between the first and second connection terminals exceeds the overcharge protection voltage. To prevent the chattering of the thermal switch that occurs in the overcharge protection state as a result of the thermal switch being turned on continuously even if the voltage of the secondary battery is equal to or lower than the overcharge protection voltage in order to energize the switching means with the heater Can do. Thereby, deterioration of a thermal switch can be prevented.

  According to the invention of claim 2, since the voltage between the third and fourth connection terminals (voltage of the secondary battery) and the voltage between the first and second connection terminals are detected by the comparator, Such detection can be performed with high accuracy.

  According to the invention described in claim 3, since the switching means is constituted by the OR gate and the n-channel field effect transistor, the voltage between the third and fourth connection terminals (the voltage of the secondary battery) is the overcharge protection voltage. Or when the voltage between the first and second connection terminals exceeds the overcharge protection voltage, the heater can be heated more reliably and the thermal switch can be turned off more reliably.

  According to invention of Claim 4, a short circuit protection means is a case where the voltage obtained by subtracting the voltage between the first and second connection terminals from the voltage of the secondary battery exceeds the short circuit protection voltage in the overcurrent protection state. It is determined that the first and second connection terminals are short-circuited or have a low resistance that causes overcurrent, and the heater is heated and the thermal switch is continuously turned off. Chattering of the thermal switch in the current protection state can be prevented. As a result, in the overcharge protection state, it is possible to prevent an overcurrent that flows when chattering is turned on when a load that causes an overcurrent is continuously connected to the first and second connection terminals.

  According to the fifth aspect of the present invention, the first comparator detects whether or not the voltage between the third and fourth connection terminals (the voltage of the secondary battery) exceeds the overcharge protection voltage. And whether the voltage between the second connection terminals exceeds the overcharge protection voltage or not is detected by the second comparator, and the voltage of the secondary battery is reduced to the voltage between the first and second connection terminals. Since the third comparator detects whether or not the voltage to which is added is exceeded, these detections can be performed with high accuracy.

  According to the sixth aspect of the present invention, since the switching means is composed of the OR gate and the n-channel field effect transistor, the voltage between the third and fourth connection terminals (the voltage of the secondary battery) is the overcharge protection voltage. Is exceeded, the voltage between the first and second connection terminals exceeds the overcharge protection voltage, or the voltage obtained by subtracting the voltage between the first and second connection terminals from the voltage of the secondary battery is short-circuited. When the protection voltage is exceeded, the heater can be heated more reliably and the thermal switch can be turned off more reliably.

  According to the seventh aspect of the invention, the temperature control means stops the energization of the heater when the temperature of the heater reaches the upper limit temperature higher than the operating temperature of the thermal switch. It is possible to prevent the thermal switch from being heated to the upper limit temperature or more, and to prevent the thermal switch from being welded.

  According to the invention described in claim 8, the first overcharge protection means, the second overcharge protection means, the short circuit protection means, and the temperature control means are constituted by the first to fourth comparators, and the switching means is ORed. Since the gate, the AND gate, and the n-channel field effect transistor are used, the secondary battery can be more reliably protected from overcharge and overcurrent.

  According to the ninth aspect of the invention, as in the first aspect of the invention, the secondary battery can be protected from overcharge and the circuit can be simplified. When the upper limit temperature higher than the operating temperature of the thermal switch is reached, the energization of the heater is stopped, so overheating protection is achieved and the thermal switch is prevented from being heated above the upper limit temperature. Can be prevented.

  According to the invention described in claim 10, whether or not the voltage between the third and fourth connection terminals (the voltage of the secondary battery) exceeds the overcharge protection voltage is detected by the first comparator, Since the temperature is detected by the temperature sensor and whether or not the temperature of the heater exceeds the upper limit temperature is detected by the fourth comparator, these detections can be performed with high accuracy.

  According to the eleventh aspect of the present invention, since the switching means is composed of an AND gate and an n-channel field effect transistor, the voltage between the third and fourth connection terminals (the voltage of the secondary battery) is the overcharge protection voltage. When it exceeds, the heater can be turned on with high accuracy, and when the temperature of the heater exceeds the upper limit temperature, heating of the heater can be stopped with high accuracy.

  According to the invention of claim 12, when charging is continued in the overcharge protection state, the temperature of the heater further rises and eventually reaches the upper limit temperature, but when the thermal switch is welded, the heater Even if the temperature reaches the upper limit temperature, the charging is continued. Then, when charging is continued and the voltage between the third and fourth connection terminals (the voltage of the secondary battery) exceeds the second overcharge protection voltage, the upper limit temperature becomes higher than the fusing temperature of the thermal fuse. Be changed. Therefore, the thermal fuse can be surely blown, and even if the thermal switch is welded, the secondary battery can be protected from overcharging.

  According to the invention of claim 13, as in the invention of claim 1, the secondary battery can be protected from overcharging, the circuit can be simplified, and the invention of claim 4 can be achieved. Chattering of the thermal switch in the overcurrent protection state can be prevented.

  According to the invention of claim 14, since the voltage between the third and fourth connection terminals (the voltage of the secondary battery) and the voltage between the first and second connection terminals are detected by the comparator, Such detection can be performed with high accuracy.

  According to the fifteenth aspect of the invention, since the switching means is composed of the OR gate and the n-channel field effect transistor, the voltage between the third and fourth connection terminals (the voltage of the secondary battery) is the overcharge protection voltage. Or when the voltage obtained by subtracting the voltage between the first and second connection terminals from the voltage of the secondary battery exceeds the short-circuit protection voltage, the heater can be heated more reliably. It can be turned off more reliably.

  According to the invention of claim 16, in the overcurrent protection state, when the load causing the overcurrent is removed from the first and second connection terminals, the current from the secondary battery is connected to the resistor connected in parallel to the thermal switch. The voltage between the third and fourth connection terminals (the voltage of the secondary battery) and the voltage between the first and second connection terminals are substantially equal, and the voltage of the secondary battery is the first and second voltages. Since it becomes below the voltage which added the short circuit protection voltage to the voltage between connection terminals, the heating of a heater is stopped and a thermal switch is turned on. Thereby, in the overcurrent protection state, when the load is removed and the short circuit or the low resistance state is released, the protection circuit can be quickly returned from the overcurrent protection state to the normal state.

  According to the invention of claim 17, when the voltage between the third and fourth connection terminals (the voltage of the secondary battery) becomes the overdischarge voltage or less, the power supply from the secondary battery to the protection circuit is stopped. Therefore, power consumption of the secondary battery can be prevented, and the secondary battery can be protected from overdischarge in a state where the first and second connection terminals are open.

  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.

(Embodiment 1)
FIG. 1 is an exploded perspective view showing an example of a battery pack according to Embodiment 1 of the present invention. A battery pack 1 shown in FIG. 1 includes a bottomed cylindrical container 2, an external terminal connection unit 3, and a plate-like spacer 4 inserted between the container 2 and the external terminal connection unit 3. . The container 2 accommodates a secondary battery 6 and is sealed by caulking, and a positive electrode terminal 6 a provided in a convex shape on the secondary battery 6 projects from the opening 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 terminal connection unit 3 includes, for example, a resin-molded case 31, and connection terminals T <b> 1 and T <b> 2 for connecting a charging device and a load device are exposed on the surface of the case 31. Further, a connection terminal T4 made of, for example, a plate-like metal connected to the connection terminal T2 is provided so as to protrude in the direction in which the container 2 is connected.

  FIG. 2 shows a circuit diagram of the battery pack 1 shown in FIG. The battery pack 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 circuit that protects the secondary battery 6 from overcharging and overcurrent.

  The protection circuit 5 is disposed inside the external terminal connection unit 3, and includes connection terminals T1 to T4 (first to fourth connection terminals), a bimetal switch (thermal switch) SW1, and an overcharge protection unit (first Overcharge protection means) 51, a chattering prevention unit (second overcharge protection means) 52, a heater R1, a transistor (switching means) Q1, and an OR gate (switching means) G1. The connection terminal T <b> 1 and the connection terminal T <b> 2 are connection terminals for connecting a charging device (not shown) that charges the secondary battery 6 and / or a load device that is 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 connection terminal T3 is connected to the positive electrode of the secondary battery 6, and the connection terminal T4 is connected to the negative electrode of the secondary battery 6. The bimetal switch SW1 is connected between the connection terminals T1 and T3. The heater R1 has one end connected to the connection terminal T3 and the other end connected to the drain of the transistor Q1. The transistor Q1 has a gate connected to the output terminal of the OR gate G1, and a source connected to the connection terminals T2 and T4.

  The overcharge protection unit 51 includes a comparator A1 and a reference voltage source E1, and the chattering prevention unit 52 includes a comparator A2 and a reference voltage source E2. The comparator A1 has a negative terminal connected to the positive electrode of the reference voltage source E1, a positive terminal connected to the connection terminal T3, an output terminal connected to the input terminal of the OR gate G1, a power supply terminal connected to the connection terminal T3, The ground terminal is connected to the connection terminals T2 and T4. The negative electrode of the reference voltage source E1 is connected to the connection terminals T2 and T4.

  The comparator A2 has a positive terminal connected to the connection terminal T1, a negative terminal connected to the positive terminal of the reference voltage source E2, an output terminal connected to the input terminal of the OR gate G1, and a power supply terminal connected to the connection terminal T3. The ground terminal is connected to the connection terminals T2 and T4. The negative electrode of the reference voltage source E2 is connected to the connection terminals T2 and T4.

  The bimetal switch SW1 is a thermal switch that is turned off when a predetermined operating temperature Tsw1 that is set in advance is exceeded. 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. Yes.

  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. In addition, as a thermal switch, instead of a bimetal switch, a switch using a shape memory alloy (for example, one described in Japanese Utility Model Publication Nos. 7-4770 and 11-224579), or a switch using a shape memory resin, It can be used similarly.

  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 to the restored shape can be changed by appropriately selecting the shape memory alloy composition or changing the heat treatment process.

  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 R1, for example, a positive temperature characteristic, that is, a PTC (Positive Temperature Coefficient) thermistor whose resistance value increases or decreases according to an increase or decrease in temperature is used. As a result, when a voltage is applied to the heater R1, the resistance value of the heater R1 increases due to self-heating of the heater R1, and the current flowing through the heater R1 decreases. As a result, the temperature of the heater R1 is finally constant at the final temperature. It becomes. The final temperature 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. Thereby, it can suppress that the secondary battery 6 and the protection circuit 5 are damaged by the heat_generation | fever of heater R1.

  The overcharge protection unit 51 detects overcharge of the secondary battery 6, interrupts the charging current to the secondary battery 6, and puts the secondary battery 6 into an overcharge protection state. The chattering prevention unit 52 prevents chattering of the bimetal switch SW1 that occurs in the overcharge protection state.

  The reference voltage source E <b> 1 is a voltage generation circuit that outputs a reference voltage (overcharge protection voltage) Ref <b> 1 that serves as a determination reference for detecting overcharge of the secondary battery 6. The reference voltage source E2 is a voltage generation circuit that outputs a reference voltage (overcharge protection voltage) Ref2 for preventing chattering of the bimetal switch SW1.

  In the present embodiment, the reference voltage Ref1 and the reference voltage Ref2 are substantially equal, specifically, reference voltage Ref1 = reference voltage Ref2 = 4.3V.

  When the reference voltage Ref1 is applied to the negative terminal and the voltage between the connection terminals T3 and T4, that is, the voltage Vb of the secondary battery 6 exceeds the reference voltage Ref1, the comparator A1 outputs a high level signal, and the voltage Vb When is lower than the reference voltage Ref1, a low level signal is output.

  When the reference voltage Ref2 is applied to the negative terminal of the comparator A2, the voltage between the connection terminals T1 and T2, that is, the voltage Va of the charging device or load device connected to the connection terminals T1 and T2 exceeds the reference voltage Ref2. When the voltage Va is equal to or lower than the reference voltage Ref2, a low level signal is output.

  In the present embodiment, comparators having hysteresis in the input voltage are employed as the comparators A1 and A2 in order to reduce the influence of noise.

  When a high level signal is output from one of the comparators A1 and A2, the OR gate G1 outputs a high level signal to the gate of the transistor Q1, and a low level signal is output from both comparators. In this case, a low level is output to the gate of the transistor Q1.

  The transistor Q1 employs an n-channel FET (field effect transistor), and when a high level signal is output from the OR gate G1, it turns on and energizes the heater R1, heats the heater R1, and turns on the bimetal switch SW1. When the low level signal is output from the OR gate G1, the heater R1 is turned off to stop energization of the heater R1, the heating of the heater R1 is stopped, and the bimetal switch SW1 is turned on.

  Next, the operation of the protection circuit 5 will be described. First, the overcharge protection operation by the protection circuit 5 will be described. When a charging device (not shown) is connected to the connection terminals T1 and T2, and a voltage Va is applied between the connection terminals T1 and T2 from the charging device, the voltages Va and Vb are both in the normal state below the reference voltages Ref1 and Ref2. The bimetal switch SW1 is turned on and the secondary battery 6 is charged. Here, the voltage Va is, for example, a maximum of 4.2 V when normal.

  For example, when voltage control cannot be performed due to a failure of a not-illustrated charging device, the voltage Vb exceeds the reference voltage Ref1. Then, a high level signal is output from the comparator A1, a high level signal is output from the OR gate G1, the transistor Q1 is turned on, a current flows from the connection terminal T3 to the heater R1, 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 overcharge protection state is set. Thereby, the secondary battery 6 is protected from overcharge.

  When the power of the secondary battery 6 is consumed by the heater R1 in the overcharge protection state, the voltage Vb decreases and the output of the comparator A1 becomes low level. Here, consider a case where the chattering prevention unit 52 does not exist. Then, the transistor Q1 is turned off, no current flows through the heater R1, and heating of the bimetal switch SW1 is stopped. When the bimetal switch SW1 is naturally cooled and becomes equal to or lower than the operating temperature Tsw1, the bimetal switch SW1 is turned on again, a charging current is supplied from the charging device, and the secondary battery 6 is charged again. If the secondary battery 6 is continuously charged, the voltage Vb exceeds the reference voltage Ref1, and the bimetal switch SW1 is turned off again. In this way, chattering occurs when the charging device continues to be connected between the connection terminals T1 and T2 in the overcharge protection state.

  However, the protection circuit 5 of this embodiment includes a chattering prevention unit 52. Thus, in the overcharge protection state, the charging device continues to be connected between the connection terminals T1 and T2, and even when the voltage Va exceeds the reference voltage Ref2, a high level signal is output from the comparator A2, and the OR A high level signal is output from the gate G1, the transistor Q1 is turned on, a current flows from the connection terminal T3 to the heater R1, the bimetal switch SW1 is continuously heated, and the bimetal switch SW1 continues to be turned off. As a result, chattering of the bimetal switch SW1 that occurs when the charging device is continuously connected in the overcharge protection state is prevented.

  Next, overcurrent protection by the protection circuit 5 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 T1 and T2, or a load device such as a mobile phone (not shown) connected to the connection terminals T1 and T2 breaks down. Thus, when the connection terminals T1 and T2 are short-circuited or the resistance value between the connection terminals T1 and T2 becomes low resistance, an overcurrent flows from the secondary battery 6 through the bimetal switch SW1. When an overcurrent flows, the bimetal switch SW1 is heated by the contact resistance.

  When the temperature reaches the operating temperature Tsw1, the bimetal switch SW1 is turned off to cut off the discharge current of the secondary battery 6, the protection circuit 5 enters the overcurrent protection state, and the secondary battery 6 is protected from the overcurrent. The When the overcurrent protection state continues, the outputs of the comparators A1 and A2 are both at a low level, and the heating of the heater R1 is stopped, so that the bimetal switch SW1 is naturally cooled. Then, when the bimetal switch SW1 becomes equal to or lower than the operating temperature Tsw1, the bimetal switch SW1 is turned on again, and the protection circuit 5 returns from the overcurrent protection state to the normal state.

  As described above, according to the protection circuit 5 according to the first embodiment, the secondary battery 6 can be protected from overcharge and overcurrent by using the bimetal switch SW1 that is a thermal switch. Like a protection circuit 1002 according to the technology, an FET 1006 that cuts off a discharging current, an FET 1007 that cuts off a charging current, a reference voltage source 1009 for detecting an overcurrent, a comparator 1011, a resistor 1012, and two FETs 1006, The logic circuit 1013 for controlling on / off of 1007 is not required, the circuit of the protection circuit 5 can be simplified, and the protection circuit 5 can be easily downsized.

  Further, since overcharge is detected by the comparator A1 and the bimetal switch SW1 is turned off by heating the bimetal switch SW1 by the heater R1, for example, it is connected in series with the secondary battery 1022 as shown in FIG. 15 and FIG. The overcharge detection accuracy can be improved as compared with the case where the overcharge protection is performed only by the bimetal switch 1023 or the PTC element 1032, and the secondary battery 6 is overcharged without performing the overcharge protection operation. The possibility that the characteristics of the secondary battery 6 deteriorate or the secondary battery 6 expands or deforms can be reduced.

  Further, since the chattering prevention unit 52 is provided, the charging device continues to be connected in the overcharge protection state, and when the voltage Va between the connection terminals T1 and T2 exceeds the reference voltage Ref2, the voltage Vb becomes equal to or lower than the reference voltage Ref1. However, since the transistor Q1 is continuously turned on, the heating of the bimetal switch SW1 is continued, and as a result of the bimetal switch SW1 being kept off, chattering of the bimetal switch SW1 can be prevented, and the bimetal switch SW1 is deteriorated. Can be prevented.

  In this embodiment, the heater R1 is used. However, the present invention is not limited to this. The overcharge protection unit 51, the chattering prevention unit 52, the OR gate G1, and the transistor Q1 are integrated circuits, and the transistor Q1 is mainly turned on. The bimetal switch SW1 may be heated using the heat of the integrated circuit generated in this way. In this case, the heater R1 is unnecessary and the number of parts can be reduced.

(Embodiment 2)
Next, the protection circuit 5a of Embodiment 2 will be described. FIG. 3 shows a circuit diagram of the protection circuit 5a of the second embodiment. The protection circuit 5a according to the second embodiment is characterized in that, in the protection circuit 5 according to the first embodiment, the chattering prevention unit 52 is omitted, and a short circuit protection unit (short circuit protection means) 53 and a resistor R2 are provided. In the second embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and description thereof is omitted.

  The short-circuit protection unit 53 includes a comparator A3 and a reference voltage source E3. The comparator A3 has a negative terminal connected to the connection terminal T1, a positive terminal connected to the reference voltage source E3, an output terminal connected to the input terminal of the OR gate G1, a power supply terminal connected to the connection terminal T3, and a ground. The terminals are connected to the connection terminals T2 and T4.

  The reference voltage source E3 has a positive electrode connected to the connection terminal T3 and a negative electrode connected to the + terminal of the comparator A3. The resistor R2 is connected in parallel with the bimetal switch SW1.

  The comparator A3 detects whether or not the voltage Vb of the secondary battery 6 exceeds the voltage obtained by adding the voltage Va between the connection terminals T1 and T2 and the reference voltage Ref3, and the voltage Vb is the reference voltage (overcurrent protection voltage). If the voltage exceeds the sum of Ref3 and voltage Va (Vb> Ref3 + Va), it is determined that a load that causes an overcurrent is connected or short-circuited to the connection terminals T1 and T2 in the overcurrent protection state. , Output a high level signal. The comparator A3 is a comparator having hysteresis in the input voltage, like the comparators A1 and A2. In the present embodiment, 1V is adopted as the reference voltage Ref3. That is, when the voltage obtained by subtracting the voltage Va from the voltage Vb exceeds 1 V, it is determined that a load that causes an overcurrent is connected or short-circuited to the connection terminals T1 and T2 in the overcurrent protection state. To do.

  Next, the short circuit protection operation in the overcurrent protection state by the protection circuit 5a will be described. Since the process up to the overcurrent protection state is the same as that of the protection circuit 5 of the first embodiment, the description thereof is omitted. Consider a case where there is no short-circuit protection unit 53 in the overcurrent protection state. In this case, since the current does not flow and the heating by the heater R2 is also stopped, the bimetal switch SW1 is naturally cooled, and is eventually turned on at the operating temperature Tsw1 or lower. Here, if the connection terminals T1 and T2 are continuously short-circuited, an overcurrent from the secondary battery 6 flows through the bimetal switch SW1 and is turned off again. When the bimetal switch SW1 is turned off, it is turned on again by natural cooling.

  As described above, in the overcurrent protection state, when the connection terminals T1 and T2 are continuously short-circuited, the bimetal switch SW1 repeatedly chatters on and off.

  However, the protection circuit 5 a according to the present embodiment includes the short-circuit protection unit 53. Therefore, if the connection terminals T1 and T2 are continuously short-circuited in the overcurrent protection state, the voltage Vb exceeds the sum of the voltage Va and the reference voltage Ref3 in the overcurrent protection state. A signal is output, the transistor Q1 is turned on, the resistor R1 continues to generate heat, and the bimetal switch SW1 is continuously heated to continue the off state. Thereby, in the overcurrent protection state, chattering of the bimetal switch SW1 caused by continuing the short circuit of the connection terminals T1 and T2 can be prevented, and an overcurrent flows when the bimetal switch SW1 is turned on by chattering. This can be prevented.

  When the short circuit between the connection terminals T1 and T2 is released, a minute current flows from the secondary battery 6 to the connection terminal T1 via the resistor R2. At this time, since no load is connected between the connection terminals T1 and T2, the voltage Va and the voltage Vb are substantially the same value, and the difference between the voltage Vb and the voltage Va is equal to or less than the reference voltage Ref3. Outputs a low level signal. At this time, since the comparator A1 also outputs a low-level signal, the transistor Q1 is turned off, the bimetal switch SW1 is turned on when heating is stopped and the operating temperature Tsw1 or lower is caused by natural cooling, and the protection circuit 5 is excessive. Quickly returns from the current protection state to the normal state. Note that the overcharge protection by the overcharge protection unit 51 is the same as that in the first embodiment, and thus the description thereof is omitted.

  As described above, according to the protection circuit 5a according to the second embodiment, in addition to being able to protect the secondary battery 6 from overcharge and overcurrent, similarly to the protection circuit 5 of the first embodiment, the short circuit protection unit 53 is provided, chattering that occurs in the overcurrent protection state can be prevented. Therefore, deterioration of the bimetal switch SW1 can be prevented.

  In the second embodiment, the heater R1 is used, but the present invention is not limited to this. The overcharge protection unit 51, the short circuit protection unit 53, the OR gate G1, the transistor Q1, and the resistor R2 are integrated circuits, and the transistor Q1 is mainly used. The bimetal switch SW1 may be heated by utilizing the heat of the integrated circuit caused by turning on. In this case, the heater R1 is unnecessary and the number of parts can be reduced.

(Embodiment 3)
Next, the protection circuit 5b of Embodiment 3 will be described. FIG. 4 shows a circuit diagram of the protection circuit 5b according to the third embodiment. The protection circuit 5b of the third embodiment is characterized in that a short-circuit protection unit 53 is further provided to the protection circuit 5 of the first embodiment, that is, the chattering prevention unit 52 and the short-circuit protection unit 53 are provided. Yes. In addition, the same code | symbol is attached | subjected to the same thing as Embodiment 1, 2, and description is abbreviate | omitted.

  Since the comparators A1 to A3 are connected to the OR gate G1, when a high level signal is output from any of the comparators A1 to A3, the transistor Q1 is turned on, the heater R1 generates heat, The bimetal switch SW1 is turned off.

  As described above, according to the protection circuit 5b according to the third embodiment, since the overcharge protection unit 51 and the chattering prevention unit 52 are provided, the same effects as those of the first embodiment can be obtained, and the short-circuit protection unit 53 is provided. Thus, the same effects as those of the second embodiment can be obtained.

  Although the heater R1 is used in the third embodiment, the present invention is not limited to this, and the overcharge protection unit 51, chattering prevention unit 52, short circuit protection unit 53, OR gate G1, transistor Q1, and resistor R2 are integrated circuits. Alternatively, the bimetal switch SW1 may be heated mainly using the heat of the integrated circuit caused by the transistor Q1 being turned on. In this case, the heater R1 is unnecessary and the number of parts can be reduced.

(Embodiment 4)
Next, the protection circuit 5c according to the fourth embodiment will be described. FIG. 5 shows a circuit diagram of a protection circuit 5c according to the fourth embodiment. The protection circuit 5c according to the fourth embodiment is characterized in that a temperature control unit (temperature control means) 54 and an AND gate G2 are further provided to the protection circuit 5b according to the third embodiment. The temperature control unit 54 includes a temperature sensor S1, a comparator A4, a resistor R3, and a reference voltage source E4. In addition, the same thing as Embodiment 1-3 is attached | subjected the same code | symbol, and abbreviate | omits description.

  The comparator A4 has a negative terminal connected to the connection terminal T3 via the temperature sensor S1, a positive terminal connected to the positive terminal of the reference voltage source E4, an output terminal connected to the input terminal of the AND gate G2, and a power supply terminal. Connected to the connection terminal T3, the ground terminal is connected to the connection terminals T2 and T4. One end of the resistor R3 is connected to the connection terminals T2 and T4, and the other end is connected to the negative terminal of the comparator A4. The reference voltage source E4 has a negative electrode connected to the connection terminals T2 and T4. The output terminal of the OR gate G1 is connected to the AND gate G2.

  The temperature sensor S1 employs a thermistor having a negative characteristic, and the resistance decreases as the temperature of the heater R1 rises. The reference voltage source E4 is a voltage generation circuit that outputs a reference voltage Ref4 for detecting a predetermined upper limit temperature of the heater R1. This upper limit temperature is higher than the operating temperature Tsw1 of the bimetal switch SW1. Here, the reference voltage Ref4 is set such that when the temperature of the heater R1 exceeds the upper limit temperature, the voltage at the positive terminal of the comparator A4 is equal to or lower than the voltage at the negative terminal.

  When the bimetal switch SW1 exceeds the upper limit temperature and the voltage at the − terminal becomes higher than the voltage at the + terminal, the comparator A4 outputs a low level signal and turns off the transistor Q1. The comparator A4 employs a comparator having hysteresis like the comparators A1 to A3.

  Next, the temperature protection operation of the protection circuit 5c will be described. For example, when voltage control cannot be performed due to failure of a not-illustrated charging device, the voltage Vb exceeds the reference voltage Ref1. Then, a high level signal is output from the comparator A1, and a high level signal is output from the OR gate G1. At this time, since the temperature of the bimetal switch SW1 has not reached the upper limit temperature, a high level signal is output from the comparator A4.

  Therefore, a high level signal is output from the AND gate G2, the transistor Q1 is turned on, a current flows from the connection terminal T3 to the heater R1, 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 cut off, and an overcharge protection state is established.

  When the overcharge protection state continues, the temperature of the heater R1 further increases, and the resistance of the temperature sensor S1 decreases accordingly. When the heater R1 reaches the upper limit temperature, the comparator A4 outputs a low level signal, the transistor Q1 is turned off, and the heater R1 stops generating heat. As a result, the bimetal switch SW1 is prevented from being heated to a temperature higher than the upper limit temperature, and contact welding is prevented.

  As described above, according to the protection circuit 5c according to the fourth embodiment, in addition to the effects of the protection circuit 5b according to the third embodiment, welding of the contacts of the bimetal switch SW1 can be prevented.

  In the fourth embodiment, the heater R1 is used, but the present invention is not limited to this. The overcharge protection unit 51, the chattering prevention unit 52, the short circuit protection unit 53, the temperature control unit 54, the OR gate G1, the AND gate G2, and the transistor Q1, the resistor R2, and the temperature sensor S1 may be integrated circuits, and the bimetal switch SW1 may be heated mainly using the heat of the integrated circuit that is generated due to the transistor Q1 being turned on. In this case, the heater R1 is unnecessary and the number of parts can be reduced.

(Embodiment 5)
Next, the protection circuit 5d according to Embodiment 5 will be described. FIG. 6 shows a circuit diagram of a protection circuit 5d according to the fifth embodiment. The protection circuit 5d omits the chattering prevention unit 52 from the protection circuit 5 of the first embodiment, adopts an AND gate G2 instead of the OR gate G1, and includes a temperature fuse F1, a temperature control unit (temperature control means) 54d, And an upper limit temperature changing section (temperature changing means) 55.

  The temperature control unit 54d includes two resistors R4 and R5 connected in series instead of the resistor R3 with respect to the temperature control unit 54 of the fourth embodiment. When the heater R1 reaches the upper limit temperature, the heater R1 is energized. Stop. The upper limit temperature changing unit 55 includes a comparator A5, a reference voltage source E5, and a transistor Q2, and changes the upper limit temperature of the heater R1. The resistors R4 and R5 are set so that the added value of the resistance values is equal to the resistance value of the resistor R3 of the protection circuit 5c.

  The comparator A5 has a positive terminal and a power supply terminal connected to the connection terminal T3 via the temperature fuse F1, a negative terminal connected to the positive electrode of the reference voltage source E5, an output terminal connected to the gate of the transistor Q2, and a ground terminal. Are connected to the connection terminals T2 and T4. The negative electrode of the reference voltage source E5 is connected to the connection terminals T2 and T4. The transistor Q2 is an n-channel FET and is connected in parallel with the resistor R5.

  The reference voltage source E5 applies a reference voltage (second overcharge protection voltage) Ref5 to the negative terminal of the comparator A5. In the present embodiment, the reference voltage Ref5 is set to a value larger than the reference voltage Ref1. As the comparator A5, a comparator having hysteresis is employed as in the comparators A1 to A4.

The thermal fuse F1 is disposed close to or in close contact with the secondary battery 6, and when the secondary battery 6 generates heat due to overcharge or excessive discharge, it is blown by the heat. It is. 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 upper limit temperature Th of the heater R1, 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. 7 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. 7, 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. 7, 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 operation 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 measuring the data shown in FIG. 7, EYP2ML098 manufactured by Panasonic Electronic Device Co., Ltd. was used as the thermal fuse F1.

  Next, the operation of the protection circuit 5d will be described. First, it is assumed that the protection circuit 5d is in the overcharge protection state in the same manner as the protection circuit 5c. When the overcharge protection state continues, the temperature of the heater R1 further rises, and accordingly, the resistance of the temperature sensor S1 decreases and eventually reaches the upper limit temperature Th of the bimetal switch SW1. Then, the comparator A4 outputs a low level signal, the transistor Q1 is turned off, and the heater R1 stops generating heat. As a result, heating to the upper limit temperature Th or higher is prevented, and welding of the contacts is prevented.

  Next, the temperature protection operation by the protection circuit 5d when the contacts of the bimetal switch SW1 are welded will be described. Even if the overcharge protection state is continued and the upper limit temperature Th of the heater R1 is reached, the contact point of the bimetal switch SW1 is welded, so that the secondary battery 6 is continuously charged without being turned off. When the voltage Vb exceeds the reference voltage Ref5 (> Ref1), the comparator A5 outputs a high level signal and the transistor Q2 is turned on. As a result, the resistor R5 is short-circuited, the voltage at the negative terminal of the comparator A4 becomes equal to or lower than the reference voltage Ref4, and the comparator A4 outputs a high level signal. At this time, since the voltage Vb exceeds the reference voltage Ref1, the comparator A1 outputs a high level signal. As a result, the transistor Q1 is turned on, the resistor R1 generates heat, and the bimetal switch SW1 is heated again. As a result, the upper limit temperature of the heater R1 becomes higher than the operating temperature Tfuse1 of the thermal fuse F1. When the temperature of the thermal fuse F1 rises and exceeds the operating temperature Tfuse1, the thermal fuse F1 is melted and stops charging the secondary battery 6.

  As described above, according to the protection circuit 5d according to the fifth embodiment, since the temperature control unit 54d is provided, the temperature range in which the heater R1 heats the bimetal switch SW1 is greater than the operating temperature Tsw1 and less than the operating temperature Tfuse1. Therefore, the welding of the contact point of the bimetal switch SW1 can be prevented. Further, since the upper limit temperature changing unit 55 is provided, when the contact point of the bimetal switch SW1 is welded, the overcharge of the secondary battery 6 is continued, and the voltage Vb exceeds the reference voltage Ref5, the transistor Q2 is turned on, and the heater The upper limit temperature of R1 becomes higher than the operating temperature Tfuse1. As a result, the temperature of the heater R1 further rises, reaches the operating temperature Tfuse1, and the thermal fuse F1 is blown, so that the secondary battery 6 is overcharged even when the contacts of the bimetal switch SW1 are welded. Can be protected from.

  In the fifth embodiment, the heater R1 is used. However, the present invention is not limited to this. The overcharge protection unit 51, the temperature control unit 54d, the AND gate G2, the transistor Q1, and the temperature sensor S1 are integrated circuits. The bimetal switch SW1 may be heated using the heat of the integrated circuit caused by Q1 being turned on. In this case, the heater R1 is unnecessary and the number of parts can be reduced. In this case, the battery pack 1 is preferably configured as shown in FIGS.

  FIGS. 10 to 15 show an exploded configuration diagram of the battery pack 1 when the protection circuit 5d of the fifth embodiment is an integrated circuit, where (a) shows a top view and (b) shows a side view. . As shown in FIG. 10B, the battery pack 1 includes a frame body 110 integrally formed of an insulating material such as a synthetic resin and ceramics, a first wiring conductor 120 formed of a thin metal plate, a thin metal plate, and the like. The formed second wiring conductor 130, a bimetal switch 140 (SW 1), a cover body 150 that covers the bimetal switch 140, and a wiring board 160 are provided.

  The frame body 110 connects the first support member 111, the second support member 112 disposed to face the first support member 111 at a predetermined interval, and the first support member 111 and the second support member 112. And a connecting member 113. A space is provided between the wiring board 160 and the connecting member 113, and the integrated circuit IC is disposed in this space portion.

  The first wiring conductor 120 is disposed on the first support member 111. The second wiring conductor 130 is disposed on the second support member 112. Note that the second wiring conductor 130 is extended to the surface of the connecting member 113.

  The bimetal switch 140 includes a movable contact member 141, a bimetal element 142, and a protrusion 143. The movable contact member 141 has a long shape disposed between the first wiring conductor 120 and the second wiring conductor 130, and a contact 141a protruding upward is provided at the left end, and the right end is the first end. It is fixed on the two wiring conductors 130. The bimetal element 142 has a long shape with a central portion curved toward the movable contact member 141, and is curved toward the movable contact member 141 when heated. The protrusion 143 prevents the bimetal element 142 from being deformed by an external force.

  The contact 141 a is separated from the first wiring conductor 120 when the movable contact member 141 receives a downward force from the bimetal element 142. As a result, the bimetal switch 140 is turned off. On the other hand, the contact 141a contacts the first wiring conductor 120 when the movable contact member 141 does not receive a downward force from the bimetal element 142. As a result, the bimetal switch 140 is turned on.

  Connection terminals T <b> 1 and T <b> 2 are disposed on the upper surface of the wiring board 160. A thermal fuse F <b> 1 is disposed on the left side of the first wiring conductor 120. The thermal fuse F1 and the positive terminal 6a of the secondary battery 6 are electrically connected by a connection wiring L1. A connection wiring L2 for grounding the connection terminal T2 is attached to the right end of the wiring board 160.

  Instead of the battery pack 1 shown in FIG. 10, the battery pack 1 shown in FIG. 11 may be adopted. The battery pack 1 shown in FIG. 11 is characterized in that the space between the wiring board 160 and the secondary battery 6 is filled with a resin 170. Moreover, it may replace with the battery pack 1 shown in FIG. 11, and may employ | adopt the battery pack 1 shown in FIG. The battery pack 1 shown in FIG. 12 is characterized in that the secondary battery 6 and the wiring board 160 are screwed with two screws 131 and 132 in the battery pack of FIG.

  Furthermore, instead of the battery pack 1 shown in FIG. 12, the battery pack 1 shown in FIG. 13 may be adopted. In the battery pack 1 shown in FIG. 13, the wiring board 160 is disposed with the front surface to which the bimetal 140 and the like are attached facing upward and the rear surface facing the secondary battery 6 side, and the connector C1 is provided as the connection terminals T1 and T2. It is characterized by having adopted. In this case, the charging device or the load device includes a connector corresponding to the connector C1, and is electrically connected to the secondary battery 6 by fitting the corresponding connector into the connector C1.

(Embodiment 6)
Next, the protection circuit 60 according to the sixth embodiment will be described. FIG. 8 shows a circuit diagram of the protection circuit 60 of the sixth embodiment. The protection circuit 60 includes an integrated circuit IC and a bimetal switch SW1. The integrated circuit IC includes a transistor (switching means) Q1, a transistor (resistance) Q2, an AND gate (switching means) G2, an OR gate (switching means) G2, a voltage reduction control section (power supply control means) 61, and a power supply control section (power supply). Control means) 62, an overcharge control section (first overcharge protection means and second overcharge protection means) 63, a short circuit protection section (short circuit protection means) 64, and a temperature control section (temperature control means) 65. ing. The transistor Q1 is an n-channel FET, the gate is connected to the output terminal of the AND gate G2, the drain is connected to the connection terminal T3, and the source is connected to the connection terminals T2 and T4. The transistor Q2 is a p-channel FET, the gate is connected to the voltage reduction control unit 61 and the power supply control unit 62, the drain is connected to the connection terminal T3, and the source is connected to the connection terminal T1.

  When the voltage Vb is equal to or lower than a predetermined overdischarge prevention voltage, the reduced voltage control unit 61 turns off the power supply control unit 62 and the transistor Q2 to prevent the secondary battery 6 from being overdischarged.

  The power supply control unit 62 supplies power to the overcharge control unit 63, the short circuit protection unit 64, and the temperature control unit 65. When the bimetal switch SW1 is turned off in the overcharge protection state, the overcharge control unit 63 detects whether the overcharge is continued by connecting a charging device to the connection terminals T1 and T2.

  The short-circuit protection unit 64 detects whether or not a load that causes an overcurrent is connected or short-circuited to the connection terminals T1 and T2 in the overcurrent protection state in which the bimetal switch SW1 is off.

  The temperature control unit 65 detects the temperature of the integrated circuit IC caused by the heat generation of the transistor Q1 serving as both a heater element and a switch element, and turns off the transistor Q1 when this temperature exceeds a predetermined set temperature.

  FIG. 9 is a circuit diagram showing a detailed configuration of the protection circuit 60. The voltage reduction control unit 61 includes a comparator A6 and a reference voltage source E6. The reference voltage source E6 includes a voltage generation circuit, and applies the overdischarge prevention voltage Ref6 to the + terminal of the comparator A6. When the voltage Vb exceeds the overdischarge prevention voltage Ref6, the comparator A6 outputs a low level signal to turn on the transistor Q2 and the power supply control unit 62. Here, the overdischarge prevention voltage Ref6 is smaller than the reference voltages Ref1, Ref3, Ref4.

  The power control unit 62 is connected to the power supply terminals of the comparators A1, A2, A3, and A4, and supplies power to these comparators. In FIG. 9, the connection between the comparator A2 and the power supply control unit 62 is omitted.

  The overcharge control unit 63 includes comparators A1 and A2 and a reference voltage source E1. The comparator A1 and the reference voltage source E1 correspond to the overcharge protection unit 51 shown in the protection circuit 5 according to the first embodiment, and the comparator A2 and the reference voltage source E1 correspond to the chattering prevention unit 52 shown in the protection circuit 5, The overcharge of the secondary battery 6 is detected to protect the secondary battery 6 from overcharge, and chattering that occurs in the bimetal switch SW1 is prevented in the overcharge protection state.

  The short-circuit protection unit 64 includes a comparator A3 and a reference voltage source E3. The comparator A3 has an output terminal connected to the input terminal of the OR gate G1, a positive terminal connected to the negative terminal of the reference voltage source E3, a negative terminal connected to the connection terminal T1, and a power supply terminal connected to the power control unit 62. The ground terminal is connected to the connection terminals T2 and T4.

  When the voltage Vb of the secondary battery 6 exceeds the voltage obtained by adding the reference voltage Ref3 and the voltage Va (Vb> Va + Ref3), the comparator A3 continues to connect the load to the connection terminals T1 and T2 in the overcurrent protection state. Output a high level signal. Thereby, chattering that occurs in the bimetal switch SW1 in the overcurrent protection state can be prevented.

  The temperature control unit 65 includes a comparator A4, a reference voltage source E4, a resistor R3, a temperature sensor S1, and a reference voltage source E7, and corresponds to the temperature control unit 54 shown in the protection circuit 5c according to the fourth embodiment.

  The comparator A4 has an output terminal connected to the input terminal of the AND gate G2, a negative terminal connected to the connection terminals T2 and T4 via the resistor R3, and a positive terminal connected to the connection terminals T2 and T4 via the reference voltage source E4. The ground terminal is connected to the connection terminals T2 and T4. The reference voltage source E7 has a negative electrode connected to the connection terminals T2 and T4, and a positive electrode connected to the negative terminal of the comparator A4 via the temperature sensor S1.

  Next, the operation of the protection circuit 60 according to the sixth embodiment will be described. First, the overdischarge protection operation by the protection circuit 60 will be described. When the discharge of the secondary battery 6 proceeds and the voltage Vb becomes equal to or lower than the overdischarge prevention voltage Ref6, the comparator A6 outputs a high level signal to turn off the transistor Q2 and the power supply control unit 62. Accordingly, the power of the secondary battery 6 is prevented from being supplied to the comparators A1 to A4, and the secondary battery 6 can be protected from overdischarge that occurs when no load is connected between the connection terminals T1 and T2. it can.

  Next, the short circuit protection operation in the overcurrent protection state by the protection circuit 60 will be described. Since the process up to the overcurrent protection state and the process up to preventing chattering of the bimetal switch SW1 in the overcurrent protection state are the same as those of the protection circuit 5a of the second embodiment, description thereof is omitted.

  When the short circuit between the connection terminals T1 and T2 is released in the overcurrent protection state, a minute current flows from the secondary battery 6 to the connection terminal T1 via the transistor Q2. At this time, since no load is connected between the connection terminals T1 and T2, the voltage Va and the voltage Vb are substantially the same value, and the difference between the voltage Vb and the voltage Va is equal to or less than the reference voltage Ref3. Outputs a low level signal. At this time, since the comparator A1 also outputs a low-level signal, the transistor Q1 is turned off, the bimetal switch SW1 is turned on when heating is stopped and the operating temperature Tsw1 or lower is caused by natural cooling, and the protection circuit 5 is turned on. Returns from the overcurrent protection state to the normal state.

  The overcharge protection operation by the overcharge control unit 63 and the chattering prevention operation in the overcharge protection state are the same as those of the protection circuit 5 according to the first embodiment, and the temperature protection operation by the temperature control unit 65 is the same as that of the implementation. Since it is the same as the protection circuit 5c of the form 4, the description is omitted.

  As described above, according to the protection circuit 60 according to the sixth embodiment, the same operation and effect as the protection circuits 5 to 5d according to the first to fifth embodiments can be obtained, and the voltage reduction control unit 61 and the transistor Q2 can be obtained. Therefore, the secondary battery 6 can be protected from overdischarge.

  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 Embodiment 1 of this invention. The circuit diagram of the battery pack shown in FIG. 1 is shown. FIG. 4 is a circuit diagram of a protection circuit according to a second embodiment. FIG. 6 shows a circuit diagram of a protection circuit according to a third embodiment. FIG. 6 shows a circuit diagram of a protection circuit according to a fourth embodiment. FIG. 10 shows a circuit diagram of a protection circuit according to a fifth embodiment. It is a graph which shows an example of the electric current value and operation time of a bimetal switch and a thermal fuse. FIG. 10 shows a circuit diagram of a protection circuit according to a sixth embodiment. FIG. 10 is a circuit diagram showing a detailed configuration of a protection circuit according to a sixth embodiment. It is drawing which shows the structure of a battery back. It is drawing which shows the structure of a battery back. It is drawing which shows the structure of a battery back. It is drawing which shows the structure of a battery back. It is drawing which shows the protection circuit which concerns on background art. It is drawing which shows the protection circuit which concerns on background art. It is drawing which shows the protection circuit which concerns on background art.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Battery pack 2 Container 3 External terminal connection unit 4 Spacer 5 5a-5d, 60 Protection circuit 6 Secondary battery 6a Positive electrode terminal 31 Case 51 Overcharge protection part 52 Chattering prevention part 53 Short-circuit protection part 54 54d Temperature control part 55 Maximum temperature Change unit 61 Voltage reduction control unit 62 Power supply control unit 63 Overcharge control unit 64 Short circuit protection unit 65 Temperature control unit A1 to A6 Comparator E1 to E6 Reference voltage source F1 Thermal fuse Q1 Q2 Transistor R1 Heater R1 to R5 Resistance S1 Temperature sensor SW1 Bimetal switch T1-T4 connection terminal

Claims (17)

A first and second connection terminals for connecting a charging device for charging a secondary battery and / or a load device driven by a discharge current from the secondary battery;
Third and fourth connection terminals connected to both electrodes of the secondary battery;
It is connected between the first and third connection terminals, and is turned off when it exceeds a predetermined operating temperature due to self-heating due to the flowing current, and it is turned off when the operating temperature is exceeded by external heating. A thermal switch,
A heater for heating the thermal switch;
Switching means for controlling energization of the heater;
First overcharge protection means for energizing the switching means with a heater when the voltage between the third and fourth connection terminals exceeds a predetermined overcharge protection voltage;
A protection circuit comprising: second overcharge protection means for energizing the heater in the switching means when the voltage between the first and second connection terminals exceeds the overcharge protection voltage. The first overcharge protection means includes a first comparator that detects whether a voltage between the third and fourth connection terminals exceeds the overcharge protection voltage,
The second overcharge protection means includes a second comparator that outputs a high level signal when a voltage between the first and second connection terminals exceeds the overcharge protection voltage,
2. The protection circuit according to claim 1, wherein the switching means energizes the heater when at least one of the first and second comparators outputs a high level signal. The switching means includes
An OR gate having an input terminal connected to an output terminal of the first and second comparators;
An n-channel field effect transistor comprising: a gate connected to an output terminal of the OR gate; a drain connected to the heater; and a source connected to the second and fourth connection terminals. Item 3. The protection circuit according to Item 2.   When the voltage between the third and fourth connection terminals exceeds a voltage obtained by adding a predetermined short-circuit protection voltage to the voltage between the first and second connection terminals, a short circuit that causes the heater to energize the switching means. The protection circuit according to claim 1, further comprising protection means. The first overcharge protection means includes a first comparator that detects whether a voltage between the third and fourth connection terminals exceeds the overcharge protection voltage,
The second overcharge protection means includes a second comparator that outputs a high level signal when a voltage between the first and second connection terminals exceeds the overcharge protection voltage,
The short-circuit protection means outputs a high level signal when the voltage between the third and fourth connection terminals exceeds the voltage obtained by adding the short-circuit protection voltage to the voltage between the first and second connection terminals. A third comparator for outputting,
5. The protection circuit according to claim 4, wherein the switching means energizes the heater when at least one of the first to third comparators outputs a high level signal. The switching means includes
An OR gate having an input terminal connected to an output terminal of the first to third comparators;
An n-channel field effect transistor comprising: a gate connected to an output terminal of the OR gate; a drain connected to the heater; and a source connected to the second and fourth connection terminals. Item 6. The protection circuit according to Item 5.   The temperature control means which makes the said switching means stop energization to the said heater when the temperature of the said heater becomes the predetermined upper limit temperature higher than the operating temperature of the said thermal switch, The temperature control means is further provided. Protection circuit. The first overcharge protection means includes a first comparator that outputs a high level signal when the voltage between the third and fourth connection terminals exceeds the overcharge protection voltage,
The second overcharge protection means includes a second comparator that outputs a high level signal when a voltage between the first and second connection terminals exceeds the overcharge protection voltage,
The short circuit protection means outputs a high level signal when the voltage between the third and fourth connection terminals exceeds the voltage obtained by adding the short circuit protection voltage to the voltage between the first and second connection terminals. A third comparator for outputting,
The temperature control means includes
A temperature sensor for detecting the temperature of the heater;
A fourth comparator that outputs a low level signal when the temperature detected by the temperature sensor is the upper limit temperature;
The switching means includes
An OR gate having an input terminal connected to an output terminal of the first to third comparators;
An AND gate having an input terminal connected to an output terminal of the OR gate and an output terminal of the fourth comparator;
An n-channel field effect transistor having a gate connected to an output terminal of the AND gate, a drain connected to the heater, and a source connected to the second and fourth connection terminals. Item 8. The protection circuit according to Item 7. A first and second connection terminals for connecting a charging device for charging a secondary battery and / or a load device driven by a discharge current from the secondary battery;
Third and fourth connection terminals connected to both electrodes of the secondary battery;
It is connected between the first and third connection terminals, and is turned off when it exceeds a predetermined operating temperature due to self-heating due to the flowing current, and it is turned off when the operating temperature is exceeded by external heating. A thermal switch,
A heater for heating the thermal switch;
Switching means for controlling energization of the heater;
First overcharge protection means for energizing the switching means with a heater when the voltage between the third and fourth connection terminals exceeds a predetermined overcharge protection voltage;
A protection circuit comprising temperature control means for causing the switching means to stop energization of the heater when the temperature of the heater reaches a predetermined upper limit temperature higher than the operating temperature of the thermal switch. The first overcharge protection means includes a first comparator that outputs a high level signal when the voltage between the third and fourth connection terminals exceeds the overcharge protection voltage.
The temperature control means includes
A temperature sensor for detecting the temperature of the heater;
A fourth comparator that outputs a low level signal when the temperature detected by the temperature sensor reaches the upper limit temperature;
The switching means energizes the heater when both the first and fourth comparators output a high level signal, and at least one of the comparators outputs a low level signal. The protection circuit according to claim 9, wherein energization of the heater is stopped. The switching means includes
An AND gate having an input terminal connected to an output terminal of the first and fourth comparators;
An n-channel field effect transistor comprising: a gate connected to an output terminal of the AND gate; a drain connected to the heater; and a source connected to the second and fourth connection terminals. Item 11. The protection circuit according to Item 10. A thermal fuse connected between the thermal switch and the third connection terminal;
When the voltage between the third and fourth connection terminals exceeds a second overcharge protection voltage that is higher than the overcharge protection voltage, the upper limit temperature is changed to a temperature higher than the fusing temperature of the thermal fuse. The protection circuit according to claim 7, further comprising upper limit temperature changing means. A first and second connection terminals for connecting a charging device for charging a secondary battery and / or a load device driven by a discharge current from the secondary battery;
Third and fourth connection terminals connected to both electrodes of the secondary battery;
It is connected between the first and third connection terminals, and is turned off when it exceeds a predetermined operating temperature due to self-heating due to the flowing current, and it is turned off when the operating temperature is exceeded by external heating. A thermal switch,
A heater for heating the thermal switch;
Switching means for controlling energization of the heater;
First overcharge protection means for energizing the heater to the switching means when the voltage between the third and fourth connection terminals exceeds a predetermined overcharge protection voltage;
When the voltage between the third and fourth connection terminals exceeds a voltage obtained by adding a predetermined short-circuit protection voltage to the voltage between the first and second connection terminals, the switching means is energized with the heater. A protection circuit comprising a short-circuit protection means. The first overcharge protection means includes a first comparator that detects whether a voltage between the third and fourth connection terminals exceeds the overcharge protection voltage,
When the voltage between the third and fourth connection terminals exceeds the voltage obtained by adding a predetermined short-circuit protection voltage to the voltage between the first and second connection terminals, the short-circuit protection means is a high-level signal. A third comparator that outputs
14. The protection circuit according to claim 13, wherein the switching means energizes the heater when at least one of the first and third comparators outputs a high level signal. The switching means includes
An OR gate having input terminals connected to output terminals of the first and third comparators;
An n-channel field effect transistor comprising: a gate connected to an output terminal of the OR gate; a drain connected to the heater; and a source connected to the second and fourth connection terminals. Item 15. The protection circuit according to Item 14.   16. The protection circuit according to claim 4, wherein a resistor is connected in parallel to the thermal switch.   When the voltage between the third and fourth connection terminals becomes equal to or lower than a predetermined overdischarge voltage, it further comprises power supply control means for stopping power supply from the secondary battery to the protection circuit. The protection circuit according to claim 1.

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