JP2006296180A - Protection component, protecting device, battery pack and portable electronic device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a protecting device of secondary battery that meets the basic functions of overcharge, overcurrent protections of a secondary battery, and achieves simplified circuits, reduced cost, and reduced size. <P>SOLUTION: A protective device has a switching circuit, connected to a battery charging circuit that feeds electricity to secondary batteries, and the like, connected in parallel relative to the charging circuit, and forces the device into conduction by the voltages that are not smaller than the threshold voltage, a first resistance element connected to the switching circuit in series, and a second resistance element connected to the charging circuit in series, the first resistance element and the second resistance element utilizing a protecting component comprising at least one heating elements. If the first resistive element of the heating element is Rb, the second resistance element of the heating element is Rb, the voltage protection of the secondary battery is X, and the voltage of the charge circuit is Y, the inequality equation Ra/Rb>(Y-X)/X is obtained. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a protective component, a protective device, a battery pack, and a portable electronic device, and more specifically, a secondary battery protective component during charging, a protection circuit, a secondary battery pack including the protective component during charging, and charging. The present invention relates to a portable electronic device having a time protection function.

  A charger is used to supply power to a secondary battery configured to be chargeable / dischargeable. When the secondary battery reaches an overcharged state or an overcurrent flows through the secondary battery, the secondary battery is used. May be deformed or, in the worst case, burst or ignite.

  For example, in a lithium ion battery used for a mobile device such as a mobile phone as a secondary battery, a non-standard voltage / current is applied due to overcharge, charger failure, etc., and the battery is deformed. Alternatively, if the battery terminal portion is contacted by a conductor and the terminals are short-circuited, an accident such as an overcurrent flowing through the battery and the battery deforming occurs.

  For such a problem, a device for protecting a rechargeable element is described in Patent Document 1 below.

Next, a charging device using a conventional protection circuit will be described with reference to FIG.
In the circuit diagram of FIG. 13, the protective element 20A is composed of one PTC material and at least three electrodes provided thereon, and the PTC material functions as two or more PTC elements. In this protection circuit, the terminals A1 and A2 are connected to electrode terminals of a protected device such as a lithium ion battery, and the terminals B1 and B2 are connected to electrode terminals of a charger or the like.

  In this protection circuit, an FET is used as a switching element, and the source terminal S / drain terminal D of the FET and the second PTC element 1b are connected in series, and these, the first PTC element 1a, Are connected in parallel.

On the other hand, the gate terminal G of the FET is connected to an IC that detects the terminal voltage of the protected circuit, and the IC controls the potential of the gate terminal G of the FET according to the detected terminal voltage value of the protected circuit. To do. That is, when the IC does not detect an abnormality, that is, when the terminal voltage of the protected circuit is lower than a predetermined voltage, the IC turns on the FET, and the FET can energize the second PTC element 1b. Accordingly, at this time, a current corresponding to the resistance value is supplied to both the first PTC element 1a and the second PTC element 1b. In addition, when an overcurrent occurs when both the PTC elements 1a and 1b are energized in this way, the current is suppressed by tripping of the respective PTC elements 1a and 1b.

  On the other hand, when the IC detects an abnormality, that is, when an overvoltage in which the terminal voltage of the protected circuit is equal to or higher than a predetermined voltage is detected, the IC turns off the FET, and the FET goes to the second PTC element 1b. Shut off the power of the. As a result, at the time of abnormality, only the first PTC element 1a is energized, and the first PTC element 1a trips quickly due to the energization current.

Thus, according to the protection circuit of the prior art, overcharge protection can be performed by tripping the PTC during overcharge protection.
JP 2001-44003 A

As described above, according to the protection circuit of the prior art, the overcharge protection can be performed by tripping the PTC during overcharge protection. However, in actuality, the overcharge current is limited by increasing the PTC resistance, thereby reducing the current. It ’s just that.
Therefore, the overcharge protection state in the prior art can be said to be a state in which the overcharge state by a minute current is continued. The secondary battery may be deformed, swollen, ruptured, or ignited, which is an incomplete technology as an overcharge protection circuit and its components in a strict sense.

In view of the above, there has been a demand for a protection circuit and components that completely eliminate the charging current for overcharge protection.
Further, as for the protection element, it is required to avoid the use of a fuse made of a low melting point metal for protection of the secondary battery and the electronic device / circuit because of the requirement that repeated use is desirable.

  The present invention relates to a rechargeable secondary battery protection component, a secondary battery protection device, and a secondary battery pack that satisfy the basic functions of overcharge and overcurrent protection of a secondary battery and that can simplify and downsize the circuit. And it aims at providing a portable electronic device.

A first aspect of the protection device of the present invention is a switching circuit that is connected to a charging circuit that supplies power to a secondary battery or the like, is connected in parallel to the charging circuit, and is conducted by a voltage that is equal to or higher than a threshold voltage; A first resistance element connected in series to the switching circuit; and a second resistance element connected in series to the charging circuit, wherein the first resistance element and the second resistance element are at least 1 A protection device using a protection component comprising two heating elements, the resistance Rb of the first resistance element of the heating element, the resistance Ra of the second resistance element of the heating element, and protection of the secondary battery When the voltage is X and the voltage of the charging circuit is Y,
Ra / Rb> (Y-X) / X
This is a protective device.

According to a second aspect of the protection device of the present invention, a switching circuit connected in parallel to a charging circuit for supplying power to the secondary battery and conducted by a voltage equal to or higher than a threshold voltage, and connected in series to the switching circuit, At least one heating element comprising a first resistance element and a second resistance element;
A protection device using a heat-responsive element having a structure that switches the supply of electric power to the heat generating element by the heat generated by the power supply or by the heat from the heat generating element. A resistance Rb included in the resistance element, a resistance Ra included in the second resistance element, a minimum current value I required to switch the supply of power to the heating element by heat from the heating element, and a protection voltage of the secondary battery X, when the charging circuit voltage is Y,
Ra / Rb> (Y-X) / X (1)
Ra + Rb <X / I (2)
Ra> 0 (3)
Rb> 0 (4)
This is a protective device.

  According to a third aspect of the protection device of the present invention, after the thermally responsive element is switched to the heating element, the state of the thermally responsive element is maintained by the heat generation of the heating element itself, and the charging circuit for the secondary battery is provided. It is a protective device characterized in that it can be shut off.

  According to a fourth aspect of the protection device of the present invention, the thermally responsive element is a bimetal switch that switches a current path from the charging circuit to the heating element by heating.

  According to a fifth aspect of the protection device of the present invention, the bimetal switch has a movable conductor piece electrically connected to the secondary battery through a contact, and a concave surface disposed on the heating element. And a bimetal which switches the electrical connection of the movable conductor piece from the secondary battery to the heating element by reversing the direction of the concave surface by heat.

  According to a sixth aspect of the protection device of the present invention, the movable conductor piece and the bimetal are integrally formed.

  According to a seventh aspect of the protection device of the present invention, the heat generating element is a positive temperature coefficient thermistor.

  According to an eighth aspect of the protection device of the present invention, the protection device is characterized in that at least three electrodes are provided on one heating element.

  According to a ninth aspect of the protection device of the present invention, the switching circuit is a Zener diode.

  According to a tenth aspect of the protection device of the present invention, the switching circuit is in a conductive state in a state where a voltage detection circuit that detects the voltage of the secondary battery and an output voltage from the voltage detection circuit is equal to or higher than a threshold voltage. It is comprised from the field effect transistor used as follows.

  According to an eleventh aspect of the protection device of the present invention, a protection device further comprising a comparator for suppressing or preventing leakage current is provided between the voltage detection circuit and the field effect transistor. It is.

  A twelfth aspect of the protection device of the present invention is the protection device characterized in that the thermally responsive element and the heat generating element are thermally connected and housed in one case.

  In a thirteenth aspect of the protection device of the present invention, the thermally responsive element and the heating element are thermally connected, and the thermally responsive element, the heating element, and the switching circuit are housed in one case. This is a protective device.

  In a fourteenth aspect of the protection device of the present invention, a battery side terminal electrically connected to the secondary battery and a charging unit side terminal electrically connected to the charging circuit are provided on the surface of the case. Each of the protective devices is exposed and attached.

  One aspect of the secondary battery pack of the present invention is such that the above-described protection device is electrically connected and integrated with the secondary battery, and a charging side terminal that is electrically connected to an external charging circuit is exposed. It is the secondary battery pack characterized by being attached.

One aspect of the portable electronic device of the present invention is a portable electronic device having the protective device described above.
According to a first aspect of the secondary battery protection component of the present invention, there is provided a movable conductor piece electrically connected via a contact, at least one heating element that generates heat due to a current flowing through the switching circuit, and the heating element. A bimetal that has a concave surface that is thermally connected and reverses its direction by heating, and that switches the electrical connection of the movable conductor piece from the secondary battery to the heat generating element by reversing the concave surface, and supports the heat generating element. A secondary battery protection component comprising: at least two or more support members that electrically connect the heat generating elements and external terminals; and a pressing member that presses the heat generating elements toward the support members. is there.

A second aspect of the secondary battery protection component of the present invention is a secondary battery protection component characterized in that the bimetal and the movable conductor piece are integrally formed.

  A third aspect of the secondary battery protection component of the present invention is a secondary battery protection component characterized in that the pressing member is a protrusion formed on the case.

  The 4th aspect of the secondary battery protection component of this invention is a secondary battery protection component characterized by the said press member being a part of said movable conductor piece.

According to the present invention, in addition to flowing a current to the second resistance element of the heating element during normal operation, a current is passed to the first resistance element of the heating element during overcharging, so that The current to the secondary battery or the like changes from the charging direction to the discharging direction, and overcharge protection becomes possible.
As a result, the secondary battery can be prevented from swelling, bursting, or igniting, and if the power supply is removed, the temperature of the heating element is lowered and the resistance value returns to the initial state, so that it can be used repeatedly. It becomes.
Furthermore, when an overcurrent is generated, the second resistance element of the heat generating element trips, thereby enabling overcurrent protection. Even in this case, when the abnormality is removed, the temperature of the heating element decreases and the resistance value returns to the initial state, so that it can be used repeatedly.

  Furthermore, according to the present invention, a current is passed through the heating element during overcharging to cause the heating element to generate heat, and the heat-responsive element is operated by heat from the heating element to supply power during charging from the secondary battery to the heating element. As a result, the thermo-responsive element can be self-held by heat, the protection circuit can be operated stably, and the secondary battery can be protected by simple, low-cost, small components. Become. Further, when the charger is removed and the temperature falls below a predetermined value, the thermally responsive element returns to its original state and returns to a chargeable state.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
(First embodiment)
FIG. 1A is a circuit diagram showing a state in which a secondary battery and a charger are connected via the secondary battery protection circuit according to the first embodiment of the present invention, and FIG. It is a circuit diagram which shows a part of battery protection circuit.

  In FIG. 1A, the secondary battery 1 is connected to a DC charging circuit 2 via a protection circuit 3 and charged.

  The protection circuit 3 is connected to the charging side positive terminal 4 a connected to the positive terminal of the charging circuit 2, the charging side negative terminal 4 b connected to the negative terminal of the charging circuit 2, and the positive terminal of the secondary battery 1. The battery side positive terminal 5 a and the battery side negative terminal 5 b connected to the negative terminal of the secondary battery 1 are provided. The charging side positive terminal 4 a and the battery side positive terminal 5 a are connected via the first wiring 6, and the charging side negative terminal 4 b and the battery side negative terminal 5 b are connected to the second wiring 8 and the heating element 11. The two resistance elements 12a are connected to each other.

  The heating element 11 has a structure in which at least three electrodes 13a, 13b and 13c are provided in one positive temperature coefficient thermistor (PTC: Positive Temperature Coefficient) 12 as shown in FIG. In the thermistor 12, a resistance element (PTC) is provided between the first electrode 13a and the third electrode 13c and between the second electrode 13b and the third electrode 13c as shown in FIG. 12a and 12b exist. Note that two PTCs 12a and 12b may be connected.

  The first electrode 13a of the PTC 12 is connected to the charging side negative terminal 4b connected to the negative terminal of the charging circuit 2, and the second electrode 13b is connected to the first wiring 6 via the Zener diode 14 which is a switching circuit. In addition, the third electrode 13 c of the PTC 12 is connected to the battery side negative terminal 5 b via the second wiring 8.

The positive temperature coefficient thermistor 12 is generally made of an oxide ceramic mainly composed of barium titanate (BaTiO ₃ ) and a conductive polymer in which a conductive material such as a carbon filler is mixed with a resin. There are polymer PTCs, and any of them may be adopted.

  Here, the heating element 11 may be a combination of a resistance element made of PTC and a fixed resistance, or a combination of a fixed resistance and a fixed resistance.

  Further, the Zener diode 14 is a switching element, and has an anode connected to the second electrode 13 b of the heat generating element 11 and a cathode connected to the first wiring 6, whereby the first diode 14 is connected via the heat generating element 11. The wiring 6 and the second wiring 8 are connected with a reverse bias.

Here, the Zener diode 14 is not necessarily a Zener diode, and may be an element that conducts only when a voltage of a secondary battery or a charging circuit exceeds a predetermined threshold value.
Here, it is possible to determine in which part of the secondary battery or the power supply circuit the voltage detection is performed including other design items.

  Next, charging the secondary battery 1 using the protection circuit 3 and the charging circuit 2 described above will be described.

  First, in a state where the secondary battery 1 is connected to the charging circuit 2 via the protection circuit 3 and charging is performed normally, the charging circuit 2 is connected via the first wiring 6 in FIG. Power is supplied to the secondary battery 1 through the second wiring 8 and the second resistance element 12a of the heating element 11. At this time, the secondary battery voltage or the charging voltage gradually increases as time passes from the start of charging.

  When the charging voltage is overcharged and a voltage higher than the threshold is applied to the Zener diode 14 between the first wiring 6 and the second wiring 8, the first wiring 6 to the second wiring are applied to the Zener diode 14. As a result, a current flows to the first resistance element 12 b of the heating element 11.

At this time, the first resistance element 12b and the second resistance element 12a of the heat generating element 11 generate heat according to the respective applied voltages, and the resistance value fluctuates, but the resistance Rb, second resistance of the first resistance element When the resistance Ra of the resistor element, the voltage X of the secondary battery, and the voltage of the charging circuit 2 are Y,
Ra / Rb> (Y-X) / X
Thus, the relationship between the resistance values of the first resistance element 12b and the second resistance element 12a is always the relationship of the above equation.

As a result, the power at the time of charging can be fed back to the charging circuit 2 via the Zener diode 14 and the heating element 11, and the power of the secondary battery can be fed back via the Zener diode 14 and the first resistance element 12b. It can be returned to the next battery.
That is, the current for charging the secondary battery can be eliminated.

When the overcharged state of the secondary battery 1 is released and the Zener diode 14 is turned OFF, the charging circuit 2 is connected to the second wiring 8 and the second heating element 11 via the first wiring 6. It automatically returns to a normal charging state in which power is supplied to the secondary battery 1 via the resistance element 12a.
Here, since the resistance value of the second resistance element 12a is determined according to the voltage applied to the second resistance element 12a, it automatically returns to the initial low resistance state.

In addition, even if some trouble occurs during charging and overcurrent occurs in the secondary battery, the second resistance element 12a suddenly generates heat, and the resistance value can be increased, and overcurrent protection is performed. It is possible.
When the problem is resolved, the temperature of the second resistance element 12a decreases, and the protection circuit 3 automatically recovers when the resistance value changes to the initial low resistance state.

  Note that the PTC 12 does not become higher than the predetermined temperature due to the Curie temperature, and does not rise to a temperature at which the resin case body 20 and the lid 21 are abnormally deformed or melted.

  In the protective circuit 3 as described above, if the charging circuit 2 is removed and the temperature drops to room temperature or the abnormality of the charging circuit is resolved, the battery automatically returns to a chargeable state and functions again as a protective circuit. Therefore, there is no need for replacement.

(Second Embodiment)
FIG. 2A is a circuit diagram showing a state in which the secondary battery and the charger are connected via the secondary battery protection circuit according to the second embodiment of the present invention, and FIG. It is a circuit diagram which shows a part of battery protection circuit.

  In FIG. 2A, the secondary battery 1 is connected to the DC charging circuit 2 via the protection circuit 3 and charged.

  The protection circuit 3 is connected to the charging side positive terminal 4 a connected to the positive terminal of the charging circuit 2, the charging side negative terminal 4 b connected to the negative terminal of the charging circuit 2, and the positive terminal of the secondary battery 1. The battery side positive terminal 5 a and the battery side negative terminal 5 b connected to the negative terminal of the secondary battery 1 are provided. The charging side positive terminal 4 a and the battery side positive terminal 5 a are connected via the first wiring 6, and the charging side negative terminal 4 b and the battery side negative terminal 5 b are connected via the second wiring 8. Yes.

  In the middle of the second wiring 8, a thermal protector 9 is connected in series. The thermal protector 9 includes a bimetal switch 10 and a heating element 11 that are thermally connected to each other. The bimetal switch 10 is a thermally responsive element that changes a current path by heat.

  The bimetal switch 10 includes a fixed point 10a connected to the battery side negative terminal 5b via the second wiring 8, a first contact 10b connected to the charging side negative terminal 4b via the second wiring 8, It has the 2nd contact 10c connected to the heat generating element 11, and has the structure where the 1st contact 10b and the fixed point 10a are electrically connected by 10 d of movable conductors in a normal charge state. Further, the movable conductor piece 10d has a structure in which the contact is switched by the heat generated in the bimetal switch 10 or the heat from the heating element 11 to electrically connect the fixed point 10a and the second contact 10c. .

  The heating element 11 has a structure in which at least three electrodes 13a, 13b, and 13c are provided in one positive temperature coefficient thermistor (PTC: Positive Temperature Coefficient) 12 as shown in FIG. In the thermistor 12, a resistance element (PTC) is provided between the first electrode 13a and the third electrode 13c and between the second electrode 13b and the third electrode 13c as shown in FIG. 12a and 12b exist equivalently. Note that two PTCs 12a and 12b may be connected.

  The first electrode 13a of the PTC 12 is connected to the first contact 10b of the bimetal switch 10, the second electrode 13b is connected to the first wiring 6 via the Zener diode 14 that is a switching circuit, and the first electrode 13a of the PTC 12 The second contact 10c of the bimetal switch 10 is connected to the third electrode 13c.

The positive temperature coefficient thermistor 12 is generally made of an oxide ceramic mainly composed of barium titanate (BaTiO ₃ ) and a conductive polymer in which a conductive material such as a carbon filler is mixed with a resin. There are polymer PTCs, and any of them may be adopted.

  The Zener diode 14 is a switching element, and has an anode connected to the second electrode 13 b of the heating element 11 and a cathode connected to the first wiring 6, whereby the first wiring 6 is connected via the heating element 11. The second wiring 8 is connected with a reverse bias.

By the way, the heat generating element 11 and the bimetal switch 10 have a structure in which they are placed in one case and thermally connected, as shown in FIGS.

  In FIG. 3, a PTC 12 is attached as a heat generating element 11 at substantially the center of the bottom surface of the case body 20 having a hollow inside. A first electrode 13a and a second electrode 13b are attached to the lower surface of the PTC 12, and a third electrode 13c is attached to the upper surface thereof.

  The first electrode 13a of the PTC 12 is connected to the first lead terminal 22 drawn out through one side of the case body 20, and the second electrode 13b of the PTC 12 is connected to the outside through the other side of the body 21 of the case 20. Is connected to the second lead terminal 23 that is led out.

  On the PTC 12, a bimetal piece 24 having a concave surface whose inversion center is substantially central is disposed. The bimetal piece 24 has a concave surface facing downward at room temperature, and is curved so that the concave surface is inverted upward when the temperature rises to a predetermined temperature. The shape seen from above is substantially rectangular, circular, elliptical, or the like. ing.

  Further, the bimetal piece 24 is placed in a state where the edge thereof can come into contact with the convex portion 25 of the case body 20 around the PTC 12 at room temperature, and when the concave surface is inverted by heat, the bimetal piece 24 is almost The central portion is placed at a position where it comes into contact with the approximate center of the third electrode 13c of the PTC 12. Furthermore, the bimetal piece 24 has such a shape that its concave surface is turned upward so that the edge lifts the movable conductor piece 27 described later.

  The bimetal piece 24 has, for example, a structure in which two materials of Cu—Ni—Mn on the high expansion side and Ni—Fe on the low expansion side are laminated. For example, the temperature rises from room temperature to about 80 ° C. The relationship between temperature and shape has a hysteresis characteristic such that the concave surface is inverted from downward to upward at the time of heating, and further returns to downward when the temperature is lowered and cooled to about 40 ° C. If the heating element 11 is set to a temperature higher than the predetermined temperature, the bimetal piece 24 remains inverted upward and the movable conductor piece 27 is lifted, so that the interruption state of the charging circuit can be maintained. Thereby, the bimetal piece 24 will be in the state which can connect the movable conductor piece 27 and PTC12 thermally and electrically, and comprises the bimetal switch 10 shown to Fig.2 (a) with the movable conductor piece 7. FIG.

  On the other side of the case body 20, a third lead terminal 26 penetrates and is attached at a position away from the second lead terminal 23. In the case body 20, the fixed end of the movable conductor piece 27 is connected to the third lead terminal 26, and the convex movable contact 28 on the lower surface of the free end has the concave surface of the bimetal piece 24 facing downward. In the state, it is in contact with the fixed contact 22 a of the first lead terminal 22. The movable conductor piece 27 and the bimetal piece 24 correspond to the movable conductor piece 10d in FIG. Further, the first lead terminal 22 corresponds to the first contact 10c of the bimetal switch 10 shown in FIG. 2, the third lead terminal 26 corresponds to the fixed ceiling 10a shown in FIG. This corresponds to the second contact 10b of the bimetal switch 10 shown in FIG.

  On the lower surface of the movable conductor piece 27, a convex portion 27a that contacts the bimetal piece 24 whose concave surface is inverted upward may be formed by press molding, and a conductive member may be welded as the convex portion 27a.

As the material of the movable conductor piece 27, a Cu—Be alloy is preferable, but a conductive spring material such as phosphor bronze, Cu—Ti alloy, white, brass, Cu—Ni—Si alloy may be used.
The movable contact 28 of the movable conductor piece 27 and the fixed contact 22a of the first lead terminal 22 in contact with the movable contact 28 are each preferably a nickel-silver alloy, specifically a silver alloy containing about 10 mass% nickel. Although preferable, a copper-silver alloy, a gold-silver alloy, a carbon-Ag alloy, a tungsten-silver alloy, or the like may be used.

  The material constituting the first to third lead terminals 22, 23, 26 is preferably copper, but phosphor bronze, Cu—Ti alloy, Cu—Be alloy, white, brass, Cu—Ni—Si alloy. A conductive material such as, for example, may be used.

  The opened upper surface of the case body 20 is closed by a lid 21. The case body 20 and the lid 21 are made of a resin such as polyphenylene sulfide (PPS), liquid crystal polymer (LCP), or polybutylene terephthalate (PBT) that has excellent heat resistance. The case body 20 and the lid 21 are welded by ultrasonic welding or the like, and thereby the PTC 12, the fixed contact 22 a, the movable contact 28, the movable conductor piece 24, the bimetal 27, etc. are enclosed in the cases 20 and 21.

  The first lead terminal 22 is connected to the negative terminal of the secondary battery 1, the second lead terminal 23 is connected to the Zener diode 14, and the third lead terminal 26 is connected to the negative terminal of the charging circuit 2. Arranged so that.

  Next, charging the secondary battery 1 using the protection circuit 3 and the charging circuit 2 described above will be described.

  First, when the secondary battery 1 is connected to the charging circuit 2 via the protection circuit 3 and charging is performed normally, the bimetal switch 10 in FIG. 2 connects the first contact 10b and the fixed point 10a. Since the second wiring 8 is made conductive, the charging circuit 2 supplies power to the secondary battery 1 via the first wiring 6 and the second wiring 8. The charging voltage gradually increases as time passes from the start of charging.

  This state will be described with reference to FIGS. 3 and 4. The bimetal piece 24 has a concave surface facing downward, and the movable conductor piece 27 (10d) is fixed to the first lead terminal 22 which is the first contact 10b. The third lead terminal 26 which is the contact 10a is made conductive. Here, even if the bimetal piece 24 electrically connects the movable conductor piece 27 and the third electrode 13c of the PTC 12, the PTC 12 has an electric resistance larger than that of the movable conductor piece 27, so that the bimetal piece 24 is reversed. There is no fever.

  When the charging voltage is overcharged and a voltage higher than the threshold is applied to the Zener diode 14 between the first wiring 6 and the second wiring 8, the first wiring 6 to the second wiring are applied to the Zener diode 14. A current flows toward 8, and thus a current also flows through the PTC 12.

  As a result, the PTC 12 generates heat, and when the temperature reaches a predetermined value, for example, 80 ° C., the concave surface of the bimetal piece 24 shown in FIGS. 3 and 4 is reversed and the movable conductor piece 27 is lifted by the barrier metal piece 24. The bimetal piece 24 is separated from the first lead terminal 22 and stops charging the secondary battery 1, and the bimetal piece 24 electrically connects the movable conductor piece 27 (10 d) and the third electrode 13 c of the PTC 12 to form one part of the PTC 12. Current is passed through the part.

  That is, in FIG. 2, when a reverse current flows through the Zener diode 14, current flows through the PTCs 12a and 12b to generate heat, and the movable conductor piece 10d brings the fixed point 10a of the bimetal switch 10 and the second contact 10c into conduction. Then, the middle of the second wiring 8 is electrically disconnected, and further, a current is passed through one PTC 12 a via the second wiring 8 and the bimetal switch 10.

  Therefore, the bimetal switch 10 thermally connected to the first PTC 12a is self-holding. In this case, the power during charging can be fed back to the charging circuit 2 via the Zener diode 14 and the PTC 12.

Even when the overcharged state of the secondary battery 1 is released and the Zener diode 14 is turned off, the current flows through the PTC 12 and the bimetal switch 10 is heated. Can be operated stably because the switch is not switched.
Note that the PTC 12 does not become higher than the predetermined temperature due to the Curie temperature, and does not rise to a temperature at which the resin case body 20 and the lid 21 are abnormally deformed or melted.

  The secondary battery 1 attached to an electronic device, for example, a mobile phone is generally a lithium ion battery, and the charging method of the lithium ion battery is a constant current or constant voltage method. Therefore, when the current flows through the Zener diode 14, the combined resistance of the secondary battery 1 and the PTC 12 is held almost constant.

  By the way, if the charging circuit 2 is broken or the charging side negative terminal 4a and the charging side negative terminal 4b are contacted by a conductor and short-circuited, an overcurrent flows in the protection circuit 3 and an overcurrent flows in the movable conductor piece 27. Flows. In this case, since the movable conductor piece 27 itself generates heat and heats the bimetal piece 24, the movable conductor piece 27 is turned upside down so that the concave surface of the bimetal piece 24 is on the upper side. While the contact of the first lead terminal 22 is cut off and charging of the secondary battery 1 is cut off, a current flows through the third electrode 13c of the PTC 12 through the movable conductor piece 27 and the bimetal piece 24 (10d).

  As a result, the PTC 12 generates heat and holds the state of the movable conductor piece 27 as it is, so that the state in which the concave surface of the bimetal piece 24 faces upward is self-held. In addition, since the PTC 12 has a high resistance, even if a current flows through the PTC 12, an overcurrent is prevented. In addition, when the PTC 12 having a Curie point is used, the PTC 12 itself does not generate heat more than necessary.

  In the protection circuit 3 as described above, when the charging circuit 2 is removed and the temperature becomes a predetermined value or less, for example, room temperature or less, the movable conductor piece 27 (10d) returns to its original state and returns to a chargeable state.

In the present invention, the resistance Rb included in the heating element 12b, the resistance Ra included in the heating element 12a, the minimum current I required to switch the supply of power to the heating element by heat from the heating element, the secondary battery When the protection voltage X and the voltage of the charging circuit 2 are Y,
Ra / Rb> (Y-X) / X (1)
Ra + Rb <X / I (2)
Ra> 0 (3)
Rb> 0 (4)
It stipulates. This is to protect the battery from overcharging and overvoltage. If all of the above formulas (1), (2), (3), and (4) are not satisfied, the charging voltage exceeds the protection voltage X of the secondary battery, the secondary battery becomes high temperature, and the worst expansion, ignition, and rupture Problems occur. For example, in the case of a lithium ion secondary battery, if Y = 30V, X = 4.2V, and I = 0.2A, the formula (1) becomes Ra / Rb> 6.143. In the formula, Ra + Rb <21 (Ω).

(Third embodiment)
FIG. 5 is a sectional view showing a thermal protector constituting a protection circuit according to the second embodiment of the present invention, and FIG. 6 is a perspective view showing a movable conductor piece of the thermal protector shown in FIG. 5 and 6, the same reference numerals as those in FIG. 3 indicate the same elements.

  In FIG. 5, a PTC 12 is attached to substantially the center of the bottom of the case body 21 as in the first embodiment, and the first electrode 13 a on the lower surface of the PTC 12 is connected to the first lead terminal 22. The second electrode 13 b on the lower surface is connected to the second lead terminal 23.

  Above the PTC 12, a movable conductor piece 30 in which the movable conductor piece 24 and the bimetal piece 24 of FIGS. 3 and 4 are integrated is disposed. The movable conductor piece 30 has, for example, Cu—Ni—Mn (Mn content: about 50 mass% to about 75 mass%) and Cu—Zn on the high thermal expansion side, and Ni—Fe (Ni content: 30 mass%) on the low thermal expansion side. And a bimetallic structure in which two materials such as about 50 as% are laminated, and as shown in FIG. 5, the PTC 12 has a planar shape widened to a square, a circle, an ellipse, etc. as shown in FIG. 30a has an inversion center portion that is curved and has a concave surface facing downward at room temperature.

  A movable contact 31 that can be brought into and out of contact with the first lead terminal 22 is attached to the first end of the movable conductor piece 30. Further, the second end of the movable conductor piece 30 is connected to the third lead terminal 26.

  When such a thermal protector 9 is used in the protection circuit 3 as shown in FIG. 2A, in the overcharge state, the voltage becomes higher than the threshold value of the Zener diode 14, a Zener current flows, the PTC 12 generates heat, and the bimetal is heated. The concave surface of the movable conductor piece 30 is inverted upward, the second contact 10c of the bimetal switch 10 shown in FIG. 2A is connected to the fixed point 10a, and a high resistance is connected in series with the second wiring 8. The PTC 12 is connected. As a result, a current flows through the PTC 12 and heat generation continues, and the movable conductor piece 30 (10d) is self-held.

  Further, when an overcurrent flows through the protection circuit 3, the movable conductor piece 30 in the thermal protector 9 generates heat, and the concave surface of the widened portion 30a is inverted by its own heat, so that the bimetal switch 10 shown in FIG. The second contact 10 c and the fixed point 10 a are connected, and a high resistance PTC 12 is connected in series in the middle of the second wiring 8. As a result, current flows through the PTC 12 and heat generation continues, and the movable conductor piece 30 (10d) is self-held.

(Fourth embodiment)
FIG. 7 is a circuit diagram for connecting a charging circuit and a secondary battery via a protection circuit according to a third embodiment of the present invention, and FIG. 8 is a cross-sectional view showing a thermal protector used in the protection circuit. In FIG. 7, the same reference numerals as those in FIG. 2 denote the same elements.

In FIG. 7, the secondary battery 1 is connected to the DC charging circuit 2 via the protection circuit 3 and charged.
Similarly to the first embodiment, the protection circuit 3 includes a charging side plus terminal 4a, a charging side minus terminal 4b, a battery side plus terminal 5a, and a battery side minus terminal 5b. The charging side positive terminal 4 a and the battery side positive terminal 5 a are connected via the first wiring 6, and the charging side negative terminal 4 b and the battery side negative terminal 5 b are connected via the second wiring 8. Yes.

  In the middle of the second wiring 8, a thermal protector 9 is connected in series. The thermal protector 9 includes a bimetal switch 10 and a heating element 11 that are thermally connected to each other.

  The bimetal switch 10 has a fixed point 10a connected to the charging side negative terminal 4b, a first contact 10b connected to the battery side negative terminal 5b, and a second contact 10c connected to the heating element 11. The first contact 10b and the fixed point 10a are electrically connected in a state other than overcurrent and overvoltage, and the second contact 10c and the fixed point 10a are electrically connected in overcurrent and overvoltage. The fixed point 10a and the second contact 10c are electrically connected by heat generated by the bimetal switch 10 or the heat generating element 11, while the fixed point 10a and the first contact 10b are electrically connected at room temperature. ing.

  The heating element 11 has a circuit configuration in which two PTCs 12a and 12b are connected in series. The first electrode 13a is connected to the second contact 10c of the bimetal switch 10, and the second electrode 13b is a Zener. It is connected to the first wiring 6 through the diode 14, and the third electrodes 13c of the two PTCs 12a and 12b are connected to the battery side negative terminal 5b.

  The Zener diode 14 has an anode connected to the second electrode 13 b of the heating element 11 and a cathode connected to the first wiring 6, whereby the first wiring 6 and the second wiring 8 are connected via the heating element 11. It has a structure connected to.

  Incidentally, the first and second PTCs 12a and 12b and the bimetal switch 10 have a structure in which they are placed in one case and thermally connected as shown in FIG.

FIG. 8 is a cross-sectional view showing a thermal protector 9 used in the protection circuit according to the third embodiment of the present invention.
In FIG. 8, the thermal protector 9 has a structure in which the first and second PTCs 12a and 12b, which are heat generating elements, and a bimetal piece 24 are thermally connected in one case.

The first PTC 12a is attached to the bottom of the case body 21 having a hollow inside.
The third electrode 13c attached to the lower surface of the first PTC 12a is connected to a first lead terminal 32 that passes through one side of the case body 21 and is drawn to the outside.

  Also, on the first PTC 12a, as in the first embodiment, a bimetal piece 24 having a reversal center portion provided substantially in the center is disposed, and the bimetal piece 24 has a concave surface facing downward at a normal temperature and is kept at a predetermined temperature. It has a structure in which the concave surface is inverted upward in a heated state, and the shape seen from above is substantially square, circular, elliptical, or the like.

  The edge of the bimetal piece 24 comes into contact with the convex portion 25 inside the case body 21 provided around the first PTC 12a at room temperature. In addition, when the bimetal piece 24 is heated and its concave surface is inverted, the substantially central portion of the bimetal piece 24 comes into contact with the substantially central portion of the first electrode 13a on the upper surface of the first PTC 12a. The material of the bimetal piece 24 is the same as that of the first embodiment, and the relationship between the inversion of the concave surface and the temperature has a hysteresis characteristic.

  Further, a third lead terminal 26 is attached to the other side of the case body 21 so as to penetrate therethrough. Further, a movable conductor piece 33 is disposed on the third lead terminal 26. The fixed end of the movable conductor piece 33 is connected to the third lead terminal 26, and the movable end has a movable contact 34 that can be brought into contact with and separated from the first lead terminal 32.

  The movable conductor piece 33 is connected to the first lead terminal 32 in the case main body 21 when the concave surface of the bimetal piece 24 faces downward, and is pushed up by the bimetal piece 24 when the concave surface is inverted upward to be the first. The lead terminal 32 of the first PTC 12a is electrically connected to the first electrode 13a through a bimetal piece.

  Moreover, although the material of the movable conductor piece 33 is preferably a Cu—Be alloy, a conductive material such as phosphor bronze, Cu—Ti alloy, white, brass, Cu—Ni—Si alloy may be used.

  Further, the movable conductor piece 33 is formed with a press 33 by pressing so as to contact the bimetal piece 24 whose concave surface is inverted upward. A conductive member may be welded as the protrusion 33a.

  Further, a second PTC 12 b placed in the case body 20 is attached to the lid 21 that covers the upper surface of the case body 20. The third terminal 13d formed on the one surface of the second PTC 12b is connected to the first lead terminal 32 via the wiring pattern 35 formed on the lower surface of the lid 21, and formed on the one surface of the second PCT 12b. The formed second electrode 13 b is connected to a second lead terminal 23 attached to the lower surface of the lid 21. The second lead terminal 23 is drawn out of the case body 20.

  The material constituting the first to third lead terminals 32, 23, 26 and the wiring pattern 35 is preferably copper, but phosphor bronze, Cu-Ti alloy, Cu-Be alloy, white, brass, Cu-Ni. A conductive material such as a Si alloy may be used. The fixed contact 32a of the first lead terminal 32 and the movable contact 34 of the movable conductor piece 33 are preferably a nickel-silver alloy, specifically a silver alloy containing 10 mass% nickel, but a copper-silver alloy. Gold-silver alloy, carbon-Ag alloy, tungsten-silver alloy, or the like may be used.

  The material constituting the case body 20 and the lid 21 is the same resin as in the first embodiment. The case body 20 and the lid 21 are welded by ultrasonic welding or the like.

  When used in the protection circuit 3 as described above, when the secondary battery 1 is normally charged, heat generation that reverses the concave surface of the bimetal piece 24 in the thermal protector 9 is the first. The first lead terminal 32 and the third lead terminal 26 are electrically connected via the movable conductor piece 33 because they are not generated from the second PTCs 12a and 12b. That is, in the bimetal switch 10 shown in FIG. 7, the fixed point 10a and the first contact 10b are electrically connected via the movable conductor piece 33 (10d), and the second wiring 8 is made conductive with a low resistance.

  On the other hand, in the overcharge state, the second PTC 12b generates heat due to the flow of the Zener current of the Zener diode 14, and the concave surface of the bimetal piece 24 is inverted upward, whereby the movable contact 34 of the movable conductor piece 33 is The movable conductor piece 33 is electrically connected to the first electrode 13a of the first PTC 12a through the bimetal piece 24 while leaving the fixed contact 32a of the first lead wire 32.

  As a result, the first PTC 12 a having high resistance is connected in series in the middle of the second wiring 8. In addition, since the current flows through the first PTC 12a and the first PTC 12a generates heat and the concave surface of the bimetal piece 24 is held upward, the movable conductor piece 33 is self-held.

  When an overcurrent flows through the protection circuit 3, the movable conductor piece 33 in the thermal protector 9 generates heat, and the heat causes the concave surface of the bimetal piece 24 to be reversed upward to cause the second contact 10 c of the bimetal switch 10. And the fixed point 10a are electrically connected, and the first PTC 12a having a high resistance is connected in series with the second wiring 8. As a result, a current flows through the first PTC 12a to generate heat, and the state where the second contact 10c of the bimetal switch 10 and the fixed point 10a are connected by the movable conductor piece 24 is maintained.

(Fifth embodiment)
FIG. 9 is a cross-sectional view showing a thermal protector constituting a protection circuit according to the fourth embodiment of the present invention. 9, the same reference numerals as those in FIG. 8 denote the same elements.
In FIG. 9, the first PTC 12 a is attached to substantially the center of the bottom of the case body 20, as in the third embodiment, and the third electrode 13 c below the first PTC 12 a is connected to the first lead terminal 32. It is connected to the. At the bottom of the case body 20, a switching circuit 39, for example, a Zener diode 14 connected in series is disposed in the middle of the second lead 23. The structure in which the switching circuit 39 is built in the case body 20 as described above may be applied to the above-described embodiments and the embodiments described later.

  A movable conductor piece 30 having a shape as shown in FIG. 6 is disposed on the first PTC 12a. The movable conductor piece 30 includes a first end portion having a movable contact 28 that can be contacted and separated from the first lead terminal 32 in the case body 20, and a second end portion that is connected and fixed to the second lead terminal 26. Have. This movable conductor piece 30 is made of bimetal and has a planar shape widened to a square, a circle, an ellipse, etc. above the first PTC 12a, and the widened portion 30a has an inversion center portion with the concave surface facing downward at room temperature. Have.

  Similarly to the third embodiment, the second PTC 12b is attached to the lower surface of the lid 21 covering the upper surface of the case body 20, and the third terminal 13d of the second PTC 12b has a wiring pattern 35 on the lower surface of the lid. In addition, the second terminal 13b of the second PTC 12b is connected to a third lead terminal 23 drawn from the lower surface of the lid 21.

  When such a thermal protector 9 is used in the protection circuit 3 as shown in FIG. 7, in the overcharged state, the second PTC 12b generates heat by the flow of the Zener current of the Zener diode 14, and the concave surface of the movable conductor piece 30 made of bimetal. And the second contact 10c of the bimetal switch 10 and the fixed point 10a are connected, and the first electrode 13a and the third lead terminal 26 of the first PTC 12a are electrically connected via the movable conductor piece 30. Connect to.

  As a result, the first PTC 12 a having high resistance is connected in series in the middle of the second wiring 8 shown in FIG. 7, and a current flows through the first PTC 12 a to generate heat, which is caused by the movable conductor piece 30. The connection state between the second contact 10c and the fixed point 12a is self-held. Thereby, the overcharge to the secondary battery 1 is prevented.

  In addition, when an overcurrent flows through the protection circuit 3, the movable conductor piece 30 in the thermal protector 3 generates heat, and the concave surface is reversed by the heat of itself to separate from the first lead terminal 32, and the first The PTC 12 a is connected to the second wiring 8 in series. As a result, a current flows through the first PTC 12a and heat generation continues, so that the separated state of the first contact 10b and the fixed point 10a by the movable conductor piece 30 is self-held. As a result, no overcurrent flows through the secondary battery 1.

(Sixth embodiment)
FIG. 10 is a circuit diagram showing a state in which the secondary battery and the charger are connected via the secondary battery protection circuit according to the first embodiment of the present invention.

  In FIG. 10, the secondary battery 1 is connected to the DC charging circuit 2 via the protection circuit 3 and is charged.

  Similarly to the first embodiment, the protection circuit 3 includes a charging side plus terminal 4a, a charging side minus terminal 4b, a battery side plus terminal 5a, and a battery side minus terminal 5b. The charging side positive terminal 4 a and the battery side positive terminal 5 a are connected via the first wiring 6, and the charging side negative terminal 4 b and the battery side negative terminal 5 b are connected via the second wiring 8. Yes.

  In the middle of the second wiring 8, the thermal protector 9 shown in the first embodiment or the second embodiment is connected in series. The thermal protector 9 includes a bimetal switch 10 and a heating element 11 that are thermally connected to each other, and has, for example, the same structure as that shown in FIGS.

  The bimetal switch 10 has a fixed point 10a connected to the battery side negative terminal 5b, a first contact 10b connected to the charge side negative terminal 4b, and a second contact 10c connected to the heating element 11. The first contact 10b and the fixed point 10a are electrically connected in a state other than overcurrent and overvoltage, and the second contact 10c and the fixed point 10a are electrically connected during overcurrent and overvoltage.

  Due to the heat generated by the bimetal switch 10 or the heat from the heat generating element 11, the movable conductor piece 10d is switched to electrically connect the fixed point 10a and the second contact 10c.

  The heating element 11 has a circuit configuration in which two PTCs 12a and 12b are connected in series. The first electrode 13 a of the heating element 11 is connected to the first contact 10 b of the bimetal switch 10, and the second electrode 13 b is connected to the first wiring 6 via the bypass circuit 40. Further, the connection point between the two PTCs 12 a and 12 b is connected to the second contact 10 c of the bimetal switch 10.

  A voltage detection circuit 41 is connected to the first wiring 6 and the second wiring 8 of the protection circuit 3.

  The voltage detection circuit 41 is configured by connecting at least two high-resistance resistance elements 41a and 41b in series in order to detect the voltage between the terminals of the secondary battery 1, and the resistance ratio of the resistance elements 41a and 41b. Is preliminarily selected to design the voltage applied to each of the resistance elements 41a and 41b. The resistance elements 41 a and 41 b have a resistance value of, for example, about several thousand Ω, and a current hardly flows even when connected in parallel to the charging circuit 2. That is, the resistance value of the voltage detection circuit 41 is designed such that most of the current flows from the charging circuit 2 to the secondary battery 1 during charging. The voltage detection circuit 41 in the present embodiment is configured by connecting first and second resistance elements 41a and 41b in series, and adjusting the resistance ratio thereof, the first and second resistance elements 41a. , 41b are designed.

  The bypass circuit 40 includes, for example, an n-channel field effect transistor (n-FET) 40a as a switching element, the source of the n-FET 40a is connected to the second electrode 13b of the heating element 11, and the drain thereof is a first element. It is connected to the wiring 6. The gate of the n-FET 40a is connected to the connection point of the first resistance element 41a and the second resistance element 41b of the voltage detection circuit 41, and the voltage at the connection point becomes the gate voltage of the n-FET 40a. It is configured as follows. Such a bypass circuit 40 constitutes a switching circuit together with the voltage detector 41.

  Thereby, in the normal charge state of the secondary battery 1, the bypass circuit 40 is cut off, and no current flows through the bypass circuit 40. However, when the secondary battery 1 is overcharged, the voltage of the secondary battery 1 rises, the voltage signal from the voltage detection circuit 41 to the bypass circuit 40 exceeds the threshold voltage, and the bypass circuit 40 enters the energized state. Charging power supplied from the circuit 2 to the secondary battery 1 flows through the bypass circuit 40 to the PTCs 12 a and 12 b that are the heating elements 11 of the thermal protector 9.

  As a result, similarly to the first embodiment, the bimetal switch 10 is switched and the PTC 12a is connected in series to the second wiring 8, and the bimetal switch 10 self-holds due to the heat generated by the PTC 12a. Thereby, the second wiring 8 becomes electrically high resistance and is substantially cut off.

  In addition, when an overcurrent flows through the protection circuit 3, the temperature of the bimetal switch 10 becomes high, and the connection point of the movable conductor 10d of the bimetal switch 10 is changed from the first contact 10b to the first point as in the first embodiment. The PTC 12a is connected in series to the second wiring 8 by switching to the two contacts 10c, and the state in which the bimetal switch 10 is switched by the heat generated by the PTC 12a is self-held. Thereby, the second wiring 8 becomes electrically high resistance and is substantially cut off.

  In addition, you may use the components of the structure shown in FIG. 8, FIG. 9 as the thermal protector 9, and the equivalent circuit becomes like FIG.

(Seventh embodiment)
FIG. 14 is a circuit diagram showing a state where the secondary battery and the charger are connected via the secondary battery protection circuit according to the seventh embodiment of the present invention.

  In FIG. 14, the secondary battery 1 is connected to the DC charging circuit 2 via the protection circuit 3 and charged. The protection circuit 3 is connected via the second wiring 8. In the middle of the second wiring 8, the thermal protector 9 shown in the first embodiment or the second embodiment is connected in series. The operation content of the thermal protector 9 is the same as the content described in the fifth embodiment.

  A voltage detection circuit 41 is connected to the first wiring 6 and the second wiring 8 of the protection circuit 3. The operation content of the voltage detection circuit 41 is the same as the content described in the fifth embodiment.

  A comparator 52 is connected between the connection point of the first and second resistance elements 41a and 41b connected in series by the voltage detection circuit 41 and the gate contact of the switching element, for example, the n-FET 40a.

  The bypass circuit 40 is energized only when the voltage signal from the voltage detection circuit 41 to the bypass circuit 40 exceeds the threshold voltage during overcharging by the comparator 52. When the voltage is equal to or lower than the threshold voltage, the leakage current flowing between the drain and source of the switching element n-FET 40a is suppressed or prevented, and energization of the bypass circuit 40 can be performed more reliably.

  Further, when the secondary battery 1 is connected to a load (not shown) via the protection circuit 3, that is, when discharging to the load, the leakage current flowing to the protection circuit 3 other than being supplied to the load is minimized, or It is desirable to prevent it from affecting the discharge characteristics of the secondary battery 1.

  For example, when the secondary battery is a lithium ion battery with a charging voltage of 4.2 V, the discharge voltage of the secondary battery is set to about 4.5 V if the predetermined threshold voltage of the comparator 52 is about 4.5 V. Since it is 4.2 V or less, the leakage current flowing through the protection circuit 3 during discharge is suppressed, and the influence on the discharge characteristics of the lithium ion battery can be reduced. For example, if the resistance of 41b is on the order of MΩ and the threshold voltage of the comparator 52 is 4.5V, the leakage current of the protection circuit 3 can be suppressed to several μA or less.

  The comparator 52 is provided on the minus side so as to have a reference potential Vref (including zero potential) from an arbitrary place. For example, the minus side of the comparator 52 may be connected to the minus side of the charging circuit 2.

  Further, an arbitrary reference potential Vref may be externally applied using the lead terminal 22, the lead terminal 23, and / or the lead terminal 26. Alternatively, at least one lead terminal L is provided separately from the lead terminal 22, the lead terminal 23, and / or the lead terminal 26, the minus side of the comparator is connected to the lead terminal L, and an arbitrary reference potential Vref can be applied from the outside. You may do it.

(Eighth embodiment)
FIG. 15 is a circuit diagram showing a state where the secondary battery and the charger are connected via the secondary battery protection circuit according to the seventh embodiment of the present invention.

In FIG. 15, the secondary battery 1 is connected to the DC charging circuit 2 via the protection circuit 3 and charged.
In the middle of the first wiring 6, the thermal protector 9 shown in the first embodiment is connected in series. That is, in the first embodiment, the thermal protector 9 connected to the negative electrode side of the secondary battery 1 is different in the present embodiment from being connected to the positive electrode side (in this case, the N-FET 40a may be used for the bypass circuit 40). ).

  FIG. 15 is based on the circuit diagram (FIG. 14) in the seventh embodiment, but the same configuration is used in the second, fourth, sixth, etc. embodiments (FIGS. 2, 7, and 7). 10 and 11).

(Ninth embodiment)
FIG. 16D is a cross-sectional view showing a thermal protector constituting the protection circuit according to the ninth embodiment of the present invention. 16, the same reference numerals as those in FIG. 5 denote the same elements.

  FIGS. 16A, 16B, and 16C show the movable conductor piece 30, the support component 35, and the heating element 12 (11), respectively. By assembling these components, the thermal protector shown in FIG. Indicates that

  In the present embodiment, the heat generating element 12 (11) is mounted on the support members 13a and 13b having a round upper portion. This is to minimize the thermal contact between the heat generating element and the support member and to achieve sufficient electrical contact. The support members 13a and 13b are electrically connected to the external terminals 22 and 23, respectively. The support component 35 is provided to press the heat generating element from above in order to make electrical contact between the heat generating element and the support member.

  The method of preventing overcharging of the secondary battery by reversing the concave portion of the movable conductor piece 30 made of bimetal due to the PTC 12 generating heat in an overcharged state is the same as in the second embodiment described above. is there.

(Tenth embodiment)
FIG. 17E is a cross-sectional view showing a thermal protector constituting the protection circuit according to the tenth embodiment of the present invention. 17, the same reference numerals as those in FIG. 3 denote the same elements.

FIGS. 17A, 17B, 17C, and 17D show a case top lid 21, a movable conductor piece 27, a bimetal 24, and a heating element 12 (11), respectively. 17
It shows that the thermal protector shown in (e) is configured.

  A protrusion shown in FIG. 17A is formed on the upper lid 21 of the case at the center lower portion. The heating element 12 is pressed by the protrusion. In the movable conductor piece 27 and the bimetal 24, holes for allowing the protrusions of the upper lid 21 to pass therethrough are formed as shown in FIGS. 17 (b) and 17 (c).

  The method in which the PTC 12 generates heat in an overcharged state and the bimetal 24 reverses the concave portion upward to push up the movable conductor piece 27 and prevent the secondary battery from being overcharged is the first embodiment described above. Is the same.

(Eleventh embodiment)
FIG. 18E is a cross-sectional view showing a thermal protector constituting the protection circuit according to the eleventh embodiment of the present invention. 18, the same reference numerals as those in FIG. 3 denote the same elements.

  18 (a), (b), (c), and (d) are a perspective view of the movable conductor piece 27, a cross-sectional view of the movable conductor piece 27, the bimetal 24, and the heating element 12 (11), respectively. 18 shows that the thermal protector shown in FIG. 18E is constructed by assembling the parts.

  A cutout portion is provided in the center of the movable conductor piece 27 as shown in FIG. 18A, and the main cutout portion is bent downward as shown in FIG. 18B. The bimetal 24 is pressed by the elastic force of the notch, and the heating element 12 provided therebelow is pressed.

  The method in which the PTC 12 generates heat in an overcharged state and the bimetal 24 reverses the concave portion upward to push up the movable conductor piece 27 and prevent the secondary battery from being overcharged is the first embodiment described above. Is the same.

  In the above-described embodiment, as shown in FIG. 12, the thermal protector 9 or a device to which the above-described switching circuit is added as necessary may be housed in one case to form the secondary battery protection device 51. The secondary battery protection device 51 is connected and fixed to electrodes 53a and 53b at one end of a case 52 in which a secondary battery is accommodated, and is further sealed by a lid 54, thereby forming a secondary battery pack 50. The

  Further, the cover body 54 is provided with through holes 55a and 55b for connecting a charger to the secondary battery via the secondary battery protection device 51. Then, when the secondary battery pack 50 is electrically connected to the charger, charging is started, the secondary battery protection device 51 functions, and the secondary battery pack 50 can prevent overcharge.

  When a switching circuit composed of the Zener diode 14, the FET 41a, etc. is accommodated in the case, the switching circuit functions if it is at least electrically connected. Therefore, it can be provided at an arbitrary position if electric wiring is appropriately performed. Furthermore, when a diode or a transistor is used as the switching circuit, it is preferable to avoid a place where the temperature is higher than necessary. In addition, cooling or temperature control is performed as necessary.

  Further, since the secondary battery protection device is housed and fixed in the secondary battery pack, it is desirable to make the secondary battery protection device small in order to reduce the size of the secondary battery pack.

  The protection device or protection circuit of the present invention may be provided with a switching circuit on the electronic device or charger side, and the secondary battery protection device may be divided and provided as a PTC and a bimetal switch.

  Moreover, although the thermoresponsive element of the present invention has been described as bimetal, a trimetal using three metals may be used. Trimetals include, for example, three layers of high thermal expansion type Cu—Ni—Mn, intermediate layer Cu, and low thermal expansion side Ni—Fe. At this time, the intermediate layer Cu is inserted for adjusting the volume resistivity of the thermal responsive element, and adjusts the amount of heat generated by the current flowing through the thermal responsive element itself (square of electric current × electric resistance). Moreover, Cu-Ni etc. may be used for an intermediate | middle layer.

  In addition, the present invention can be used as a protection circuit, a protection component, a protection device, a battery pack, etc. that protects overdischarge when it is connected to a load after charging and is overdischarged from the secondary battery to the load. It is.

  Note that the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the scope of the invention.

  The lithium ion secondary battery was charged using the circuit described in the second embodiment. The charging conditions were Y = 30V, X = 4.2V, and I = 0.2A. Table 1 shows the value of the resistor Rb included in the heating element 12b, the value of the resistor Ra included in the heating element 12a, and the result of charging.

  As is apparent from Table 1, the inventive examples have excellent characteristics. However, in Comparative Examples 1, 2, and 3, since Ra and Rb do not satisfy the present invention, the surface temperature of the lithium ion secondary battery increased.

FIG. 1 is a circuit diagram showing a state in which a secondary battery and a charging circuit are connected via a secondary battery protection circuit according to the first embodiment of the present invention. FIG. 2 is a circuit diagram showing a state in which the secondary battery and the charging circuit are connected via the secondary battery protection circuit according to the second embodiment of the present invention. FIG. 3 is a cross-sectional view of a thermal protector used in the secondary battery protection circuit according to the second embodiment of the present invention. FIG. 4 is an exploded perspective view of a thermal protector used in the secondary battery protection circuit according to the second embodiment of the present invention. FIG. 5 is a cross-sectional view showing a thermal protector of the secondary battery protection circuit according to the third embodiment of the present invention. FIG. 6 is a perspective view showing the movable conductor piece of the thermal protector of the secondary battery protection circuit according to the third embodiment of the present invention. FIG. 7 is a circuit diagram showing a state in which the secondary battery and the charging circuit are connected via the secondary battery protection circuit according to the fourth embodiment of the present invention. FIG. 8 is a cross-sectional view of a thermal protector used in the secondary battery protection circuit according to the fourth embodiment of the present invention. FIG. 9 is a cross-sectional view of a thermal protector used in the secondary battery protection circuit according to the fifth embodiment of the present invention. FIG. 10 is a circuit diagram showing a state in which the secondary battery and the charging circuit are connected via the secondary battery protection circuit according to the sixth embodiment of the present invention. FIG. 11 is another circuit diagram showing a state in which the secondary battery and the charging circuit are connected via the secondary battery protection circuit according to the sixth embodiment of the present invention. FIG. 12 is an exploded perspective view showing the secondary battery pack according to the embodiment of the present invention. FIG. 13 is a circuit diagram showing a state in which a secondary battery and a charging circuit are connected via a secondary battery protection circuit according to the prior art. FIG. 14 is a circuit diagram showing a state in which the secondary battery and the charging circuit are connected via the secondary battery protection circuit according to the seventh embodiment of the present invention. FIG. 15 is a circuit diagram showing a state where the secondary battery and the charging circuit are connected via the secondary battery protection circuit according to the eighth embodiment of the present invention. FIG. 16 is a cross-sectional view of a thermal protector used in the secondary battery protection circuit according to the ninth embodiment of the present invention. FIG. 17 is a cross-sectional view of a thermal protector used in the secondary battery protection circuit according to the tenth embodiment of the present invention. FIG. 18 is a cross-sectional view of a thermal protector used in the secondary battery protection circuit according to the eleventh embodiment of the present invention.

Explanation of symbols

1: Secondary battery 2: Charging circuit 3: Protection circuit 4a: Charging side plus terminal 4b: Charging side minus terminal 5a: Battery side plus terminal 5b: Battery side minus terminal 6, 8: Wiring 9: Thermal protector 10: Bimetal switch 11: Heating element 12, 12a, 12b: PTC
35: Supporting part 39: Switching circuit 40: Bypass circuit 41: Voltage detection circuit 50: Battery pack 51: Secondary battery protection device 52: Comparator

Claims (20)

A switching circuit that is connected to a charging circuit that supplies power to a secondary battery or the like, is connected in parallel to the charging circuit and is conducted by a voltage equal to or higher than a threshold voltage, and a first resistor connected in series to the switching circuit Protection using a protection component comprising an element and a second resistance element connected in series to the charging circuit, wherein the first resistance element and the second resistance element are at least one heating element A device,
When the resistance Rb of the first resistance element of the heating element, the resistance Ra of the second resistance element of the heating element, the protection voltage of the secondary battery is X, and the voltage of the charging circuit is Y,
Ra / Rb> (Y-X) / X
The protective device characterized by being. A switching circuit that is connected in parallel to a charging circuit that supplies power to the secondary battery and that conducts by a voltage equal to or higher than a threshold voltage; and a first resistance element and a second resistance element that are connected in series to the switching circuit A protection device using at least one heat generating element and a heat responsive element having a structure that switches the power supply to the heat generating element by the heat generated by the power supply or by the heat from the heat generating element. ,
The resistance Rb included in the first resistance element of the heating element, the resistance Ra included in the second resistance element, and the minimum current I required to switch the supply of power to the heating element by heat from the heating element. When the protection voltage X of the secondary battery and the voltage of the charging circuit are Y,
Ra / Rb> (Y-X) / X (1)
Ra + Rb <X / I (2)
Ra> 0 (3)
Rb> 0 (4)
The protective device characterized by being. 3. The charging circuit of the secondary battery can be shut off by maintaining the state of the thermal response element by the heat generation of the heating element itself after the thermal response element is switched to the heating element. The protective device described. The protection device according to any one of claims 1 to 3, wherein the thermally responsive element is a bimetal switch that switches a current path from the charging circuit to the heating element by heating. The bimetal switch has a movable conductor piece electrically connected to the secondary battery via a contact and a concave surface disposed on the heating element, and reverses the direction of the concave surface by heat. The protective device according to claim 4, further comprising: a bimetal that switches electrical connection of the movable conductor piece from the secondary battery to the heating element. The protection device according to claim 5, wherein the movable conductor piece and the bimetal are integrally formed. The protection device according to claim 1, wherein the heating element is a positive temperature coefficient thermistor. The protection device according to claim 1, wherein at least three electrodes are included in one of the heat generating elements. The protection device according to claim 1, wherein the switching circuit is a Zener diode. The switching circuit is composed of a voltage detection circuit that detects the voltage of the secondary battery, and a field effect transistor that becomes conductive when the output voltage from the voltage detection circuit is equal to or higher than a threshold voltage. The protective device according to claim 1, wherein the protective device is characterized in that: The protection device according to claim 10, wherein a comparator that further suppresses or prevents a leakage current is configured between the voltage detection circuit and the field effect transistor. The protection device according to any one of claims 1 to 11, wherein the thermally responsive element and the heat generating element are thermally connected and housed in one case. The heat-responsive element and the heat-generating element are thermally connected, and the heat-responsive element, the heat-generating element, and the switching circuit are housed in one case. The protective device according to claim 1. A battery side terminal electrically connected to the secondary battery and a charging unit side terminal electrically connected to the charging circuit are respectively exposed and attached to the surface of the case. The protection device according to claim 12 or 13. The protection device according to any one of claims 3 to 14, wherein the protection device is electrically connected to and integrated with the secondary battery, and a charging side terminal that is electrically connected to an external charging circuit is exposed. A secondary battery pack characterized by being attached. A portable electronic device comprising the protection device according to claim 3. A movable conductor piece electrically connected via a contact; at least one heating element that generates heat due to a current flowing through the switching circuit; and a concave surface that is thermally connected to the heating element and reverses its direction by heating. And a bimetal for switching the electrical connection of the movable conductor piece from the secondary battery to the heating element by reversing the concave surface, supporting the heating element, and electrically connecting the heating element and an external terminal. A secondary battery protection component comprising: two or more support members; and a pressing member that presses the heat generating element toward the support member. The secondary battery protection component according to claim 17, wherein the bimetal and the movable conductor piece are integrally formed. The secondary battery protection component according to claim 17 or 18, wherein the pressing member is a protrusion formed on the case. The secondary battery protection component according to claim 17, wherein the pressing member is a part of the movable conductor piece.

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