JP2002095154A - Electronic device protecting circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electronic device protecting circuit which can prevent surely an overvoltage from being applied to a secondary battery, a semiconductor element or other electronic devices, and can prevent breakdown, damage, etc., of the protecting circuit itself. SOLUTION: In this electronic device protecting circuit 100, a temperature fuse 7 and a Zener diode 5 are so installed that thermal conduction is mutually enabled. When an overvoltage exceeding a rated voltage is applied to a battery cell 9, a current corresponding to the voltage flows, the Zener diode 5 generates heat, and accelerates fusion of a temperature fuse 7. The current is bypassed to the Zener diode 5 and a positive temperature coefficient resistor 3, and the amount of current flowing in the battery cell 9 is reduced. When a resistance value of the resistor 3 increases, a current flowing in the Zener diode 5 is set to be restrained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is to prevent an excessive voltage exceeding a rated voltage from being applied to an electronic device such as a lithium ion secondary battery or a semiconductor element, thereby deteriorating the performance of the electronic device. The present invention relates to an electronic device protection circuit for protecting from damage and the like.

[0002]

2. Description of the Related Art When an excessive voltage exceeding the rated voltage is applied to an electronic device, performance may be deteriorated or severely damaged. Various protection circuits have been proposed for protection.

[0003] In recent years, with the development of portable electronic devices and portable telephones, lithium ion secondary batteries have been used as thin secondary batteries which are small and can be discharged for a relatively long time. Lithium ion secondary batteries are generally charged at a voltage slightly higher than the rated discharge voltage. At this time, if any abnormalities occur in the charger, or if the user mistakenly connects a non-standard charger, and an excessive charging voltage exceeding the rated voltage is applied to the lithium ion secondary battery, the The internal battery cells may deteriorate due to heat generation, or may be damaged due to an increase in gas pressure. In order to protect the lithium ion secondary battery from such deterioration or damage, a protection circuit for preventing an excessive voltage from being applied to the lithium ion secondary battery is required.

As a technique relating to a protection circuit for a lithium ion secondary battery, for example, there is a technique proposed in Japanese Patent Application Laid-Open No. 2-87935 (Japanese Patent No. 2720988). This is because a Zener diode is connected in parallel to the battery cell inside the secondary battery, and a thermal fuse is connected in series with the battery cell, so that when an excessive voltage is applied, current flows through the Zener diode. Then, the thermal fuse is blown by the heat and the heat generated by the thermal fuse itself, thereby preventing an excessive voltage from being applied to the battery cell.

Further, Japanese Utility Model Laid-Open No. Hei 6-31345 discloses that
The voltage between the positive and negative terminals of the secondary battery is detected by the voltage detection circuit, and when it is detected that the voltage has risen to an excessive voltage exceeding the rated voltage, the heating switching element is turned on. There has been proposed a technique in which an excessive voltage is prevented from being applied to a secondary battery by generating heat and heating the heat-sensitive shut-off element by the heat to be in a cut-off state.

In addition, a charging voltage is applied to a secondary battery through a protection circuit having a complicated circuit configuration using a thermistor, a digital circuit element, or the like, or a bimetal is used instead of a fuse. Various things have been proposed.

[0007]

However, according to the above-mentioned conventional techniques, when an excessively high voltage is applied, the protection circuit itself is broken and becomes inoperable, or heat is generated. There is a problem that the battery cell may be deteriorated.

In the technique proposed in Japanese Patent Application Laid-Open No. 2-87935, for example, when a user erroneously connects a secondary battery to a non-standard charger, a charging voltage significantly larger than a rated voltage is applied to the secondary battery. When the voltage is applied, for example, the thermal fuse generates heat and is blown first, so that application of an excessive voltage to the secondary battery can be avoided. However, when an excessive current that greatly exceeds the rated current continues to flow through the Zener diode due to the application of the excessive voltage, the Zener diode itself is overheated, and the heat deteriorates or damages the battery cell. There is.

Further, before the thermal fuse is blown, the Zener diode is destroyed and opened, and this Zener diode fixedly bypasses the current,
The battery cell may not be charged forever or the positive and negative terminals of the battery cell may be always short-circuited, and may not be used as a secondary battery. Alternatively, the Zener diode may be broken down to an incomplete electrical resistance, and a current may continue to flow through the electrical resistance, and the Zener diode itself may be overheated, and the heat may cause the battery cell to deteriorate or break.

In the technique proposed in Japanese Utility Model Laid-Open Publication No. Hei 6-31345, for example, similarly to the case described above, when a charging voltage significantly larger than the rated voltage is applied to a secondary battery by mistake, for example, At the moment when the excessive charging voltage is applied, the reset-type thermosensitive element is not yet in the cut-off state.At that moment, an excessive current flows and the heat generating switching element is destroyed, and the excessive charging voltage is applied. Nevertheless, it cannot be detected, and the reset type thermosensitive element does not function. As a result, an excessively high charging voltage is continuously applied to the secondary battery, and the secondary battery generates heat and is deteriorated or damaged. Alternatively, if the heat-generating switching element is destroyed due to the application of an excessive charging voltage and is constantly turned on, current continues to flow forever and the heat-generating switching element is overheated, and the heat deteriorates or damages the battery cell. May be.

It is considered effective to increase the setting of the rated current (allowable current amount) of the heat-generating switching element and the Zener diode in order to prevent the damage of the protection circuit itself conventionally proposed as described above. Can be However, if the rated current is increased in such a manner, it becomes difficult to detect the applied voltage exceeding the rated voltage, and to reliably perform cutoff and fusing in response thereto.

Alternatively, in the case of a configuration in which a thermal fuse is simply connected in series to a secondary battery without using a protection circuit, the secondary battery may be overheated until the thermal fuse is blown. Since an excessive current caused by the voltage continues to flow, there is a problem that the secondary battery may deteriorate or generate heat during that time. Similarly, when a bimetal is used in place of a fuse, an excessive current continues to flow through the secondary battery until the bimetal interrupts the current, causing the secondary battery to deteriorate or generate heat. There is a problem that sometimes.

Further, in the case of a protection circuit using a thermistor, a digital circuit element, or the like, there is a problem that the circuit configuration becomes complicated, and it is difficult to reduce the size and cost.

In addition to the charging of the secondary battery, a protection circuit used to prevent an excessive voltage from being applied to, for example, a semiconductor element or a liquid crystal display element is also described.
There are similar problems as described above.

The present invention has been made in view of such a problem, and an object of the present invention is to reliably prevent an excessive voltage from being applied to a secondary battery, a semiconductor element, or another electronic device. It is another object of the present invention to provide an electronic device protection circuit capable of preventing the protection circuit itself from being broken or damaged.

[0016]

SUMMARY OF THE INVENTION An electronic device protection circuit according to the present invention is provided for preventing a voltage exceeding a rated voltage from being applied to positive and negative voltage input terminals of an electronic device. It has the characteristic that the electrical resistance value increases when it increases, and a current flows by applying a voltage exceeding the rated voltage to a posistor whose one end is connected to one of the voltage input terminals of the electronic device. The temperature rises at the temperature and has the characteristic of fusing, the temperature fuse which one end is connected to the other voltage input terminal of the electronic device, and the current increases when the applied voltage exceeds the breakdown voltage set above the rated voltage A zener diode connected to the other end of the posistor and the other end of the thermal fuse, and the thermal fuse and the zener diode conduct heat with each other. When an excessive voltage exceeding the rated voltage is applied to the voltage input terminal of the electronic device, a current corresponding to the voltage flows, and the zener diode generates heat to accelerate the blowing of the thermal fuse. At the same time, the current caused by the excessive voltage is bypassed to the zener diode and the posistor to reduce the amount of current flowing to the electronic device, and when the electric resistance of the posistor increases, the current flowing to the zener diode and the posistor is reduced by the electric resistance. It has a configuration that is set so as to be suppressed below the rated current.

Further, another electronic device protection circuit according to the present invention has a characteristic that the current increases when the applied voltage exceeds a breakdown voltage set to a rated voltage or more. A zener diode having one end connected to one of the voltage input terminals and a characteristic in which a current rises due to the application of a voltage exceeding the rated voltage to cause a temperature rise and fusing, and the other voltage input terminal of the electronic device And the Curie point, which is a temperature at which the electric resistance value increases non-linearly and steeply when the current increases, is higher than the melting temperature of the thermal fuse. A posistor that is set high and is connected to the other end of the zener diode and the other end of the thermal fuse is provided. When an excessive voltage exceeding the rated voltage is applied to the voltage input terminal of the electronic device, a current corresponding to the voltage flows, the Zener diode and the posistor generate heat, and the temperature of the thermal fuse is reduced. In addition to promoting fusing, the excessive current is bypassed to the zener diode and posistor to reduce the amount of current flowing to the electronic device, and when the electric resistance of the posistor increases, the electric resistance causes the current to flow to the zener diode and posistor. It has a configuration that is set so as to suppress the current below their rated current.

In the electronic device protection circuit according to the present invention,
When an excessive voltage exceeding the rated voltage is applied to the voltage input terminal of the electronic device, a current corresponding to that voltage flows and the Zener diode generates heat, promoting the blowing of the thermal fuse, and the thermal fuse being reliably blown Is done. Further, the current caused by the application of the excessive voltage is bypassed to the Zener diode and the posistor to reduce the amount of current flowing to the electronic device. Further, when an excessive current caused by the application of an excessive voltage continues to flow and the electric resistance of the posistor increases, the electric resistance suppresses the current flowing through the zener diode and the posistor to the rated current or less.

In another electronic device protection circuit according to the present invention, when an excessive voltage exceeding a rated voltage is applied to a voltage input terminal of an electronic device, a current corresponding to the voltage flows, so that a posistor and a zener diode are provided. Generates heat, which promotes the blowing of the thermal fuse, and the thermal fuse is reliably blown. In addition, the current caused by the excessive voltage is bypassed to the Zener diode and the posistor to reduce the amount of current flowing to the electronic device. Further, when a current continues to flow through the posistor and its electric resistance increases, the electric resistance suppresses a current flowing through the zener diode and the posistor to a value equal to or lower than their rated current.

A thermal fuse having a higher fusing temperature than the above-mentioned thermal fuse is further interposed between the Zener diode and the posistor. After the thermal fuse has blown, the thermal fuse having a higher fusing temperature is blown. , The current flowing through the Zener diode and the posistor may be cut off.

A thermostat is provided in place of the above-mentioned thermal fuse, and a voltage exceeding the rated voltage is applied to the voltage input terminals of the positive electrode and the negative electrode of the electronic device, and the Zener diode and the posistor generate heat and the temperature exceeds a predetermined temperature. When the current is cut off, the current is cut off. After the cutoff, if the temperature drops due to the elimination of excessive voltage, etc., the circuit will automatically return to the original conductive state and can be used repeatedly. It may be.

Alternatively, a thermostat having a higher cut-off temperature than that of the thermostat is provided in place of the above-mentioned thermal fuse having a high fusing temperature, so that when the excessive voltage is not applied and the temperature drops, the thermostat can be returned to the original conductive state. You may.

The electronic device protection circuit of the present invention is suitable for, for example, a lithium ion secondary battery, a lithium polymer secondary battery, a lithium metal secondary battery, a nickel cadmium secondary battery, and a nickel hydride secondary battery. However, the present invention is not limited to this, and other electronic devices, such as semiconductor devices and display devices, whose performance may be deteriorated or damaged when a voltage exceeding the rated voltage is applied, for example. Needless to say, it can also be suitably used for applications such as protecting

[0024]

Embodiments of the present invention will be described below in detail with reference to the drawings.

[First Embodiment] FIG. 1 is a circuit diagram showing a schematic configuration of an electronic device protection circuit according to a first embodiment. The electronic device protection circuit 100 includes a posistor 3, a zener diode 5, and a thermal fuse 7 in its main part. For example, the electronic device protection circuit 100 is provided in a battery pack of a lithium ion secondary battery, and a battery cell 9 is provided.
To prevent the charging voltage exceeding the rated voltage from being applied to the positive electrode 91 and the negative electrode 93.

More specifically, the posistor 3 has such a characteristic that the electric resistance increases with an increase in current, and the electric resistance increases more rapidly when the detected voltage is exceeded.
One end is connected to the positive electrode of the battery cell 9, and the other end is connected to one end of the Zener diode 5.

The temperature fuse 7 has a characteristic that it generates heat when a large current flows and rises in temperature, and fuses when the temperature exceeds a predetermined temperature. One end is connected to the negative electrode of the battery cell 9 and the other end is connected. Is connected to the negative terminal side external connection terminal and to the other end of the Zener diode 5 which is different from the above-mentioned one end. Therefore, the temperature fuse 7 and the battery cell 9 are connected in series, and a circuit from the positive side external connection terminal 11 to the negative side external connection terminal 13 through the battery cell 9 and the temperature fuse 7 is formed. Is formed.

The Zener diode 5 has a characteristic that the current sharply increases when the applied voltage exceeds a rated voltage (breakdown voltage). One end of the Zener diode 5 is connected to the posistor 3 (the other end described above). The other end is the negative side external connection terminal 13
And the thermal fuse 7 (the other end described above). Therefore, the zener diode 5 and the posistor 3 are connected in series, and a circuit is formed from the positive side external connection terminal 11 to the negative side external connection terminal 13 through the zener diode 5 and the posistor 3. ing. The Zener diode 5 is mounted so that good heat conduction can be performed between the thermal fuse 7 and the posistor 3 (the details will be described later).

In the electronic device protection circuit 100, a circuit passing through the Zener diode 5 and the posistor 3 is connected in parallel with a pair passing through the above-described circuit passing through the thermal fuse 7 and the battery cell 9. Therefore, the current flowing when a voltage is applied to the positive side external connection terminal 11 and the negative side external connection terminal 13 is transmitted to a circuit passing through the battery cell 9 and the temperature fuse 7 and a circuit passing through the zener diode 5 and the posistor 3. , Will be divided. At this time, the ratio of the current flowing through each circuit is basically (theoretical) inversely proportional to the electric resistance of the battery cell 9 and the thermal fuse 7 and the electric resistance of the zener diode 5 and the posistor 3. Is determined. Therefore, if the voltage applied to the positive side external connection terminal 11 and the negative side external connection terminal 13 is equal to or lower than the rated voltage of the Zener diode 5, the Zener diode 5 becomes substantially non-conductive. Flows into the battery cell 9 through the thermal fuse 7, and the battery cell 9 is charged without any trouble. If the applied voltage exceeds the rated voltage of the Zener diode 5, the Zener diode 5 becomes conductive and a current also flows through a circuit in which the Zener diode 5 and the posistor 3 are connected in series. . In this way, when an excessive voltage is applied, all the excessive current caused by the application of the excessive voltage can be bypassed to the Zener diode 5 and the posistor 3 instead of flowing into the battery cell 9. If an excessive current caused by the application of an excessive voltage continues to flow or a higher voltage is applied, the thermal fuse 7 generates heat and the Zener diode 5 generates heat, and the thermal fuse 7 is blown by the heat. ,
The application of excessive voltage to the battery cell 9 itself can be cut off.

Even if the thermal fuse 7 is blown in this way, an excessive voltage is continuously applied to a circuit formed by connecting the Zener diode 5 and the posistor 3 in series. Therefore, in this state, the Zener diode 5 is destroyed due to an excessive current or a rise in temperature. But,
The posistor 3 has an electrical resistance of several Ω to several tens of Ω over a wide temperature range from −30 ° C. to 60 ° C. around normal temperature, and the electrical resistance has a characteristic that increases sharply when the temperature exceeds the detection temperature. is there. Therefore, when an excessive voltage is applied and the Zener diode 5 becomes conductive and a current flows through the posistor 3 connected in series, the electric resistance of the posistor 3 itself increases sharply, and the zener diode 5 and the posistor 3 3 can be prevented from flowing an excessive current, and the destruction of the Zener diode 5 can be avoided.

Here, it is desirable that the breakdown voltage of the Zener diode 5 be set to at least the rated charging voltage of the battery cell 9. For example, when the rated charging voltage of the battery cell 9 is 4.2 V, the breakdown voltage of the Zener diode 5 is set to 6.0 V in consideration of the voltage drop by the posistor 3 and the safety factor. This is Zener diode 5
Is set lower than the rated charging voltage of the battery cell 9, the Zener diode 5 and the posistor 3 are connected in series during charging at the regular rated voltage or during long-term storage of the lithium ion secondary battery. This is because the current is bypassed to the connected circuit, which may cause a decrease in charging efficiency and a remarkable decrease in discharge capacity of the lithium ion secondary battery. For example, when the rated charging voltage of the battery cell 9 is 4.2 V and the breakdown voltage of the Zener diode 5 is set to 4.2 to 4.5 V or lower, a lithium ion secondary battery is used. Even when it is not, a current of about 0.1 mA or more flows through the Zener diode 5 and the posistor 3, and the power stored in the lithium ion secondary battery is dissipated like a dark current, and the lithium ion The discharge capacity of the secondary battery will be significantly reduced. Further, even if the regular rated charging voltage is applied, the charging current caused by the normal charging voltage bypasses the zener diode 5 and the posistor 3 and flows therethrough. Is significantly reduced.
However, by setting the breakdown voltage of the Zener diode 5 higher than the charging rated voltage of the battery cell 9 such as, for example, 6.0 V, the battery cell 9 can be efficiently charged when the rated charging voltage is applied. And the power in the battery cell 9 held after charging can be reliably held without being lost. As an example, the dark current flowing through the Zener diode 5 whose breakdown voltage is set to 6.0 V is extremely small, about 50 μA or less.

It is needless to say that the thermal fuse 7 should be surely blown by the heat of the Zener diode 5 and the thermal of the thermal fuse 7 itself when the rated charging voltage is applied. As the fusing element used for such a thermal fuse 7, one made of a low melting point alloy having a melting point of 90 to 130 ° C. is suitable. Alternatively, when it is necessary to have a lower melting point, cadmium (C
A material to which d) is further added, or a material having a fuse resistance composition material layer including heat-expandable microcapsules may be used. Alternatively, a thermal fuse 7 having a general structure including a fusible body, a spring, and a contact may be used.

Further, as the posistor 3, for example, 0-6
It has an electric resistance of 10 to 200 Ω in a temperature environment of 0 ° C., and has a characteristic that the electric resistance sharply increases when the temperature of the posistor 3 itself becomes 100 to 150 ° C., for example, 20 to 100 mA or more. When a current flows, the temperature rises and the electric resistance sharply increases, and a device that suppresses the current from flowing through the posistor 3 itself,
It can be suitably used. However, it is needless to say that the present invention is not limited to such specifications. As a material of a main part of the posistor 3, a PTC conductive polymer composition comprising a polymer component and carbon black, a BaTiO ³ semiconductor composition, a ceramic composition, or the like is preferable. The temperature (detection temperature) at which the posistor 3 is maintained in the high resistance state is 100 to 150.
C is desirable. In addition, if such a posistor 3 has a positive temperature-sensitive resistance characteristic that an electric resistance increases in response to an increase in temperature, for example, a semiconductor having a temperature-sensitive function is used as a temperature-sensitive resistance material. It may be something. The rate of change of the temperature-sensitive resistance in this case is, for example, 4000 ppm /
C. and the like are preferred.

FIG. 2 schematically shows a state in which an electronic device protection circuit is mounted so as to be connected to a battery cell inside a battery pack of a lithium ion secondary battery.

For example, in a thin box-type battery pack such as a lithium ion secondary battery for a mobile phone, a copper alloy or stainless steel sheet is used to form an outer end of an outer case 15 made of an insulating material such as plastic. The formed positive side external connection terminal 11 and negative side external connection terminal 13 are provided. A battery cell 9 that can be charged and discharged is built in the exterior case 15. When the outer can 95 of the battery cell 9 is a negative electrode, the outer can 95 is connected to the negative external connection terminal 13 via the electronic device protection circuit 100, and the positive electrode 97 of the battery cell 9 is connected to the positive external connection. It is configured to be connected to the terminal 11. Alternatively, when the outer can 95 of the battery cell 9 is a positive electrode, the outer can 95 is connected to the positive side external connection terminal 11 and the negative electrode 97 of the battery cell 9 is connected.
Is connected to the negative electrode side external connection terminal 13 via the electronic device protection circuit 100.

The electronic device protection circuit 100 is provided inside the battery pack, and the thermal fuse 7, the Zener diode 5, and the posistor 3 are electrically connected to each other using, for example, flame-retardant insulating paper, polyester tape, or thermosetting plastic. The battery cell 9 is covered with an electrically insulating casing 103 and mounted on the side surface of the battery cell 9 in a unit shape. The casing 103 desirably has a certain degree of heat retention. This is to ensure that the heat generated from the Zener diode 5 and the posistor 3 when an excessive voltage is applied is not released to the outside and the temperature rise of the thermal fuse 7 can be surely promoted. For this purpose, it is desirable to make the wiring between the Zener diode 5 and the thermal fuse 7 as short and as large as possible, and to make the material of the wiring as good as possible thermal conductivity. Further, it is desirable that the material of the casing 103 itself has high thermal insulation so that heat inside the casing 103 can be prevented from being conducted to the battery cells 9.

FIG. 3 is a sectional view showing an example of a substantial structure for connecting a thermal fuse and a Zener diode. It is. The main part of the thermal fuse 7 includes a fusing element 71, two electrode terminals 73 and 75 made of a metal plate connected to the fusing element 71, and an electrically insulating exterior material 77 that surrounds them. The Zener diode 5 has a structure in which two electrodes 51 and 53 made of a metal plate are arranged to face each other, a semiconductor element 55 is sandwiched between the electrodes, and these are enclosed by an electrically insulating exterior material 57. ing. The portions of the two electrodes 51 and 53 that protrude outward from the exterior material 57 serve as electrode terminals for electrical connection.

One electrode terminal 73 of the thermal fuse 7 is
The other electrode terminal 75 is connected to the outer can 95 of the battery cell 9 and the other electrode terminal 75 of the zener diode 5. The other electrode 5 of the Zener diode 5
3 is connected to one end of the posistor 3 not shown in FIG. The other end of the posistor 3 is connected to the positive electrode 9 of the battery cell 9.
1 and the positive electrode side external connection terminal 11.

Although the illustration of the posistor 3 is omitted in each of FIGS. 3 to 13, the electrode 53 projecting rightward in the figure of the zener diode 5 is actually provided with the posistor 3.
The other end of the posistor 3 is connected to the positive electrode 91 of the battery cell 9. Further, an electrode terminal 75 for connecting the thermal fuse 7 and the Zener diode 5 is provided.
The electrode 51 is connected to the negative-side external connection terminal 13 via a connection wiring or the like not shown in each of FIGS. 3 to 13.

Here, each of the above-mentioned electrode terminals and electrodes is made of a strip-shaped metal plate, and is made of a material having good electrical conductivity such as copper, brass or a nickel-based alloy. Is desirable. In addition, the joining of the metal plates can be performed by, for example, electric resistance welding, soldering, or the like.

In particular, it is desirable that the metal plate connecting the zener diode 5 and the thermal fuse 7 be made thicker and wider so that the cross-sectional area is as large as possible. It is desirable that the length of the wiring be as short as possible. Further, it is desirable that the electrode terminal 75 of the thermal fuse 7 and the electrode 51 of the Zener diode 5 are joined so that the overlap is as wide as possible to further improve their thermal conductivity. In this way, by improving the thermal conductivity between the Zener diode 5 and the thermal fuse 7, the heat generated from the Zener diode 5 is efficiently conducted to the thermal fuse 7. Thus, the thermal fuse 7 can be blown more reliably.

FIG. 4 is a sectional view showing another example of a substantial structure for connecting a thermal fuse and a Zener diode. The thermal fuse 7 and the Zener diode 5 are arranged in a stack. Zener diode 5
Are arranged so as to protrude outward in the same direction, but in order to avoid a short circuit between the electrodes 51 and 53, an insulating film is provided between them. 59 are arranged. Thermal fuse 7
The exterior material 77 and the exterior material 57 of the Zener diode 5 are both made of a material having an electrical insulation property. It is formed as thin as possible without impairing it.

With such a structure, the heat generated from the semiconductor element 55 of the Zener diode 5 is efficiently conducted to the fusing element 71 of the thermal fuse 7 through the thin outer package members 57 and 77, and this is ensured. Can be blown.

FIG. 5 is a sectional view showing still another example of a substantial structure for connecting a thermal fuse and a Zener diode. The thermal fuse 7 and the Zener diode 5 are bonded to one heat conductive plate 17 having high thermal conductivity. For the bonding, an adhesive (not shown) having good thermal conductivity is used. In addition, thermal fuse 7
The thickness of the parts of the exterior members 77 and 57 of the Zener diode 5 that are bonded to the heat conductive plate 17 is formed as thin as possible without impairing the electrical insulation and mechanical strength. As the heat conductive plate 17, it is desirable to use a metal material having high thermal conductivity and good workability, such as copper, brass, aluminum, and nickel.

With such a structure, the heat generated from the Zener diode 5 can be efficiently conducted to the thermal fuse 7 by the thermal conductive plate 17 and the thermal fuse 7 can be reliably blown.

Each of FIGS. 6 to 13 illustrates a substantial structure in which the fusing element of the thermal fuse and the semiconductor element of the Zener diode are enclosed in one package made of an insulating material. It was done.

In the structure shown in FIG. 6, the fusing element 71 of the thermal fuse 7 and the semiconductor element 55 of the Zener diode 5 are arranged on the front and back of one electrode 21 respectively. On the upper surface of the electrode 21 in the figure, a fusing element 71 is arranged so as to be offset to the left, and about half thereof is set to protrude to the left. An electrode terminal 73 is joined to the lower surface of the protruding portion. The electrode terminal 73 protrudes outward from the exterior material 19 to the left in the figure, and is connected to the exterior can 95 of the battery cell 9 or the like. Electrode 2
A semiconductor element 55 is joined to almost the entire lower surface of the semiconductor device 1. An electrode 53 is joined to the lower surface of the semiconductor element 55, and the electrode 53 protrudes outward from the exterior material 19 to the right in the figure and is connected to the positive electrode 91 of the battery cell 9. With such a structure, inside the exterior material 19,
The heat generated from the semiconductor element 55 is efficiently conducted to the fusing element 71 via the electrode 21 while preventing the heat generated from the semiconductor element 55 from escaping to the outside, so that the fusing element 71 can be reliably blown. And the semiconductor element 55 can be further simplified.

Alternatively, for example, as shown in FIG. 7, a structure may be employed in which the semiconductor element 55 is arranged on the upper surface of the electrode 23 together with the fusing element 71.

The structure shown in FIG. 8 is obtained by additionally disposing a heat conducting plate 17 made of a metal such as aluminum having good heat conductivity and an insulating film 61 in addition to the structure shown in FIG. With such a structure, the semiconductor element 55 is interposed between the heat conductive plate 17 and the insulating film 61.
Can be more effectively conducted to the fusing element 71. Further, since the fusing element 71 and the semiconductor element 55 are fixed to one heat conductive plate 17, even if a mechanical impact force or a thermal stress is applied from the outside, the fusing caused by them is performed. Damage to the element 71 and the semiconductor element 55 and breakage of the electrical connection can be prevented by reinforcing the mechanical strength of the heat conductive plate 17. Here, needless to say, the reason why the insulating film 61 is interposed between the heat conductive plate 17 and the fusing element 71 is to prevent an electrical short circuit between them.

In the structure shown in FIG. 9, the semiconductor element 55 and the fusing element 71 are directly laminated, and the electrode 53 is provided on the upper surface of the semiconductor element 55, and the electrode 83 is provided on the lower surface of the fusing element 71.
Are joined together. With such a structure, the heat generated from the semiconductor element 55 is directly conducted to the fusing element 71, so that the most effective heat conduction can be performed.

Alternatively, for example, as shown in FIG.
The electrode 85 may be interposed between the semiconductor element 55 and the fusing element 71 as an electrode.

In the structure shown in FIG. 11, the semiconductor element 55 and the fusing element 71 are both joined to a single electrode 87, and the electrode 87 is used as an electrical connection wiring.
This is used as a member for conducting heat. The electrode 53 is joined to the semiconductor element 55. The electrode 53 is connected to the positive electrode 91 of the battery cell 9. An electrode 83 is joined to the fusing element 71. The electrode 83 is connected to the outer can 95 of the battery cell 9. With such a structure, the fusing element 71 and the semiconductor element 55 are connected in series via one electrode 87, and the fusing element 71 and the semiconductor element 5 are connected via the electrode 87.
5 can perform good heat conduction. Moreover, the structure can be simplified.

Alternatively, for example, as shown in FIG.
By further adhering the heat conductive plate 17 to the surface of the electrode 87, heat conduction between the fusing element 71 and the semiconductor element 55 can be further improved, and
The mechanical strength can be further reinforced.

The structure shown in FIG.
4, 86, the fusing element 71, and the semiconductor element 55 are arranged side by side in a plane, and the end faces adjacent to each other are
For example, they are joined by a welding method or the like.
An electrode terminal 88 is interposed between the fusing element 71 and the semiconductor element 55, and is connected to the negative side external connection terminal 13 via a connection wiring (not shown). With such a structure, the heat generated from the semiconductor element 55 can be directly conducted to the fusing element 71 to make the heat conduction more effective. 55 can be made simplest and thinner.

In each of the structures shown in FIGS. 6 to 13, the thermal fuse 7 and the Zener diode 5 are formed in an integrated structure, and the one exterior material 19 made of an insulating material is formed. Although enclosed inside, the Zener diode 5 and the posistor 3 may be formed in an integrated structure and enclosed in one exterior material. With such a structure, when a large current flows and the Zener diode 5 generates heat, the heat is reliably transmitted to the posistor 3 to increase the electric resistance, thereby suppressing the flow of the excessive current and thereby preventing the Zener diode 5 from flowing. 5 can be reliably prevented.

FIG. 14 is a sectional view showing an example of a substantial structure in which a thermal fuse, a Zener diode, and a posistor are contained in one casing. The Zener diode 5 is disposed on the thermal fuse 7 in an overlapping manner.
Further, the posistor 3 is arranged on the zener diode 5 so as to overlap. The thermal fuse 7 is connected to the fusing element 71.
Is covered with a special exterior material 77. The Zener diode 5 is obtained by covering the semiconductor element 55 with a special package member 57. The posistor 3 is obtained by covering the temperature-sensitive element 31 with a special exterior material 37. Those exterior materials 37,
57 and 77 are both made of an electrically insulating material.

Temperature fuse 7, Zener diode 5,
Electrode terminals 171 and 17 are provided on the side surfaces of the posistor 3, respectively.
3, 151, 153, 131 and 133 are arranged. Electrode terminal 171 on the left side surface of thermal fuse 7 in the figure
Is connected to the negative electrode of the battery cell 9, and the electrode terminal 173 on the right side is joined to the electrode terminal 153 on the right side of the Zener diode 5. Zener diode 5
Is connected to the electrode terminal 131 on the left side surface of the posistor 3. The electrode terminal 133 on the right side surface of the posistor 3 is connected to the positive electrode side external connection terminal 11 and the positive electrode of the battery cell 9. The electrode terminals 173 and 153 connecting the thermal fuse 7 and the Zener diode 5 and the electrode terminals 151 and 131 connecting the Zener diode 5 and the posistor 3 are made of, for example, copper, brass, aluminum alloy, silver, or the like. It is desirable to use a metal plate having good thermal conductivity.

With such a structure, heat can be efficiently conducted from the Zener diode 5 to the thermal fuse 7 so that the thermal fuse 7 can be reliably blown when an excessive voltage is applied. . In addition, heat is efficiently conducted from the Zener diode 5 to the posistor 3, and when an excessive current flows, the temperature of the posistor 3 is surely increased to increase its electric resistance. The destruction of the Zener diode 5 can be prevented. Further, the temperature fuse 7 and the negative electrode 93 of the battery cell 9
The electrode terminal 171 for connecting the positive electrode 91 and the electrode terminal 133 for connecting the posistor 3 to the positive electrode 91 of the battery cell 9 have high electrical conductivity, for example, a nickel-based metal or an iron-based metal.
It is desirable to use a material having relatively low thermal conductivity. By doing so, it is possible to prevent the battery cells 9 from being overheated due to the heat generated from the Zener diode 5.

The structure shown in FIG. 15 is based on the fusing element 71 of the thermal fuse 7 and the semiconductor element 5 of the Zener diode 5.
5 and the temperature-sensitive element 31 of the posistor 3 are connected to the electrodes 172, 1
It is bonded and integrated via the vias 74 and 176, and is contained in one exterior material 181. The electrode 83 joined to the lower surface of the fusing element 71 in the figure is connected to the negative electrode 93 of the battery cell 9. An electrode 83 is connected to the lower surface of the fusing element 71. Electrode 1 arranged on upper surface of fusing element 71
72 and the electrode 17 arranged on the lower surface of the semiconductor element 55
Reference numeral 4 is connected to the negative electrode side external connection terminal 13 via a connection wiring (not shown). An electrode 176 is arranged between the upper surface of the semiconductor element 55 and the lower surface of the temperature sensing element 31. An electrode 53 is joined to the upper surface of the temperature sensing element 31, and the electrode 53 is connected to the positive electrode side external connection terminal 1.
1 connected. With such a structure, by efficiently conducting heat from the semiconductor element 55 to the fusing element 71, the fusing element 71 can be reliably blown when an excessive voltage is applied. In addition, by efficiently conducting heat from the semiconductor element 55 to the temperature-sensitive element 31, it is possible to surely raise the temperature of the temperature-sensitive element 31 and increase its electric resistance when an excessive current flows. As a result, it is possible to prevent the semiconductor element 55 from being destroyed due to an excessive current.

Alternatively, as shown in FIG. 16, the temperature-sensitive element 31 and the semiconductor element 55 may be directly joined without the interposition of the electrode 176 to have a simpler structure.

Next, a more detailed operation of the electronic device protection circuit according to the first embodiment will be described.

At the time of charging or the like, the battery cell 9 is connected to the negative side external connection terminal 13 and the positive side external connection terminal 11.
When an excessive voltage exceeding the rated voltage is applied, the voltage is also applied to a circuit in which the zener diode 5 and the posistor 3 are connected in series. At this time, since the electric resistance of the posistor 3 has not yet increased,
Is small, and an excessive voltage is applied to the Zener diode 5 even if the voltage drop is subtracted. If the applied voltage exceeds the breakdown voltage of the Zener diode 5, a large current flows through the Zener diode 5 to generate heat, and the heat is conducted to the thermal fuse 7 to heat the thermal fuse 7. . Eventually, the thermal fuse 7 is blown and the application of the excessive voltage to the battery cell 9 is completely cut off. Until then, most of the large current due to the excessive voltage is reduced by the Zener diode 5 and the posistor 3.
, And hardly flows into the battery cell 9, so that the battery cell 9 can be protected from damage or deterioration due to application of an excessive voltage even before the thermal fuse 7 is blown.

At this time, the current flowing through the Zener diode 5 and the posistor 3 is changed to the negative side external connection terminal 1.
The value obtained by subtracting the breakdown voltage of the Zener diode 5 from the voltage applied to the positive terminal 3 and the external terminal 11 is divided by the initial resistance of the posistor 3. Accordingly, when the applied voltage is extremely large and the current value corresponding to the applied voltage is larger than the rated current value of the posistor 3, the electric resistance of the posistor 3 increases, and the
The current flowing through itself and the Zener diode 5 is suppressed. Further, even when a large current continues to flow and heat is generated, and the Zener diode 5 is overheated, the heat increases the electric resistance of the posistor 3 and suppresses the current flowing through the posistor 3 and the zener diode 5. I do. This can prevent the Zener diode 5 from being damaged.

FIG. 17 shows the respective transient characteristics of current, voltage and temperature when an excessive voltage is applied to a lithium ion secondary battery incorporating the electronic device protection circuit according to the first embodiment. It is. In the example shown here, the ambient temperature is 20 ° C., the rated charging voltage of the battery cell 9 is 4.2 V, the fusing temperature of the thermal fuse 7 is 90 ° C., the breakdown voltage of the Zener diode 5 is 6 V, and the continuous rated power is 60
0 mW, the maximum instantaneous power is 1200 mW, the rated current of the POSISTOR 3 is 100 mW, the detection temperature is 130 ° C., and the resistance value at 25 ° C. is set to 20Ω, and the rated output is 10 V · 1 A when a charger is connected. 5 shows the transient characteristics of FIG.

When the charger is connected to the lithium ion secondary battery, the applied voltage rises, a voltage exceeding the breakdown voltage of 6 V is applied to the Zener diode 5, and a current starts flowing through the Zener diode 5 and the posistor 3. . Eventually, when the applied voltage becomes 10 V around 3 seconds, the voltage applied to the posistor 3 becomes 4 V. At this time, since the posistor 3 has not yet been overheated and is lower than the detection temperature,
Its electric resistance is about 20Ω, which is the initial value. Therefore,
At this time, the initial value of the current of the posistor 3 is about 200 mA. At this time, the voltage applied to the Zener diode 5 is about 6 V, and the current is about 200 mA, which is the same as that of the posistor 3. Therefore, the power consumed for the heat generation is about 1200 mW, which is the maximum instantaneous power of the Zener diode 5. It is 1200 mW or less.

The current value of the posistor 3 continues to increase until the posistor 3 itself reaches the detection temperature. Due to the increased current, the amount of heat generated by the Zener diode 5 and the posistor 3 also increases. When the temperature of the posistor 3 rises to reach the detection temperature of 130 ° C., the electric resistance of the posistor 3 itself sharply increases to about 40Ω, and the current becomes 200 mA.
To 100 mA. At this time, since the voltage applied to the Zener diode 5 is 6 V due to a voltage drop due to the electric resistance of 40Ω of the posistor 3, the power consumption due to the heat generated by the Zener diode 5 is 600 mW. Of 600 mW or less. When this heat generation continues, the temperature of the Zener diode 5 gradually rises up to about 100 ° C. The heat generated from the Zener diode 5 heats the thermal fuse 7. When the temperature reaches 90 ° C., the thermal fuse 7 is blown, and the application of the excessive voltage to the battery cell 9 is completely cut off. Until the thermal fuse 7 is blown, the current flowing from the charger to the entire lithium ion secondary battery is stable at about 800 to 1000 mA.

When the thermal fuse 7 is blown, the current resulting from the application of the excessive voltage does not flow to the circuit including the battery cell 9 but to the circuit formed by connecting the Zener diode 5 and the posistor 3 in series. However, at this time, since the electric resistance of the posistor 3 has already increased, the current flowing through the zener diode 5 is suppressed to 100 mA, and the applied voltage is 6 V due to the voltage drop due to the electric resistance of the posistor 3. Therefore, destruction and overheating of the Zener diode 5 can be prevented.

FIG. 18 shows an example of the result of an experiment in which an excessive voltage exceeding the charging rated voltage is applied to a thin lithium ion secondary battery incorporating the electronic device protection circuit according to the first embodiment. It is shown.

In this experiment, the structure is such that the thermal fuse 7 and the Zener diode 5 are connected by a short band-shaped metal plate. The ambient temperature at which this experiment was performed is about 30 ° C. The output voltage of the charger as a DC power supply is 10 V, and the maximum current is 2 A. The electrical resistance value of the posistor 3 at 30 ° C. is about 20 A, and the detection temperature is 120 ° C. The breakdown voltage of the Zener diode 5 is about 6 V, and the fusing temperature of the thermal fuse 7 is 90 ° C. In the graph of FIG. 18, the horizontal axis indicates the elapsed time from the start of voltage application, and the left vertical axis indicates the Zener diode 5, the posistor 3, and the battery cell 9
The vertical axis on the right shows the charging current of the battery cell 9 and the current flowing through the Zener diode 5 in amperes (A), and the temperature of the thermal fuse 7 in degrees Celsius (° C.). I have.

First, when the charger is connected, after a rise time (response delay) of about 1 second, the voltage of the battery cell 9 rises to 10 V, and a voltage of 4 V is applied to the posistor 3. A voltage of 6 V is applied to the Zener diode 5. At this time, since a voltage equal to or higher than the breakdown voltage of the Zener diode 5 is applied, the Zener diode 5 enters a state in which a current flows, and about 20 volts are applied to the Zener diode 5 and the posistor 3 connected in series thereto.
A current of 0 mA flows. Therefore, the Zener diode 5
Generates heat by electric power of about 1200 mW (= 6 V × 200 mA), and the heat heats the Zener diode 5, the posistor 3, and the thermal fuse 7 to increase their temperature. Also, the POSISTOR 3 itself is about 80
Heat is generated by electric power of 0 mW (= 4 V × 200 mA), and this heat also contributes to heating of the thermal fuse 7 and the like. At this time, a voltage of 10 V is applied to the battery cell 9, and a charging current of about 1.8 A flows stably.

When such a state of charge is continued for, for example, several minutes, the battery cell 9 may generate heat due to charging with an excessive voltage and may be deteriorated or damaged. When the charging state continues for about 40 seconds, the thermal fuse 7 reaches the fusing temperature of 90 ° C. and blows, so application of an excessive voltage to the battery cell 9 (in other words, inflow of an excessive current) is cut off. When the thermal fuse 7 is blown in this manner, the voltage of the battery cell 9 becomes the rated output voltage of 4.2 V or lower, or a voltage value during charging.

However, even if the thermal fuse 7 is blown, the current of about 200 mA continues to flow through the Zener diode 5 and the posistor 3, so that the heat generation of the Zener diode 5 and the posistor 3 is continued. This heat is conducted to the thermal fuse 7, and the temperature continues to rise even after the blow, and reaches about 100 ° C. 50 seconds after the start of the application of the excessive voltage. This means that the temperature of the Zener diode 5 has reached at least about 100 ° C. or higher. When such a state is further continued, the zener diode 5 and the posistor 3 may be overheated to be deteriorated or damaged. However, the temperature of the posistor 3 is the detected temperature 1
When the temperature reaches 20 ° C. (not shown), the electric resistance of the posistor 3 sharply increases, and the current flowing through the posistor 3 and the zener diode 5 is suppressed to about 100 mA. The calorific value is reduced to less than half. This can prevent the Zener diode 5 and the posistor 3 from being deteriorated or damaged due to overheating.

When the excessive voltage applied to the battery cell 9 is less than twice the breakdown voltage of the Zener diode 5 as in this experiment, the heat generation of the Zener diode 5 is more dominant than that of the posistor 3. By conducting the heat generated from the Zener diode 5 to the thermal fuse 7, the thermal fuse 7 can be reliably blown.

[Second Embodiment] FIG. 19 is a diagram showing a schematic configuration of an electronic device protection circuit according to a second embodiment of the present invention. This electronic device protection circuit 101
In this embodiment, the posistor 3 and the zener diode 5 in the first embodiment as shown in FIG. Further, the structure may be such that the Zener diode 5 in the structure shown in each of FIGS. 3 to 13 in the first embodiment is replaced with a posistor 3, and each of FIGS. What is necessary is just to replace the arrangement of the Zener diode 5 and the posistor 3 in the structure shown.

In this electronic device protection circuit 101, when an excessive voltage is applied to the positive external connection terminal 11 and the negative external connection terminal 13, a voltage exceeding the breakdown voltage is applied to the Zener diode 5 and a current is generated. As a result, the Zener diode 5 generates heat,
The posistor 3 generates heat. The posistor 3 and the zener diode 5 are arranged in a structure that can efficiently conduct heat to the thermal fuse 7.
Therefore, when the posistor 3 and the Zener diode 5 generate heat due to the application of the excessive voltage, the heat surely blows the thermal fuse 7. In addition, thermal fuse 7
After the fuse is blown, the heat generation of the posistor 3 and the zener diode 5 is continued for a while. However, when the temperature rises and reaches the detection temperature of the posistor 3, the electric resistance of the posistor 3 increases sharply. Thereafter, the currents of the posistor 3 and the zener diode 5 are suppressed, so that deterioration or breakage of the zener diode 5 due to overheating can be prevented.

When the posistor 3 is arranged close to the thermal fuse 7 as described above, a voltage of about twice or more of the breakdown voltage of the zener diode 5 is applied by using the posistor 3 having a large heat value. In this case, the posistor 3 generates heat effectively, and the thermal fuse 7 can be reliably blown.

FIG. 20 shows this electronic device protection circuit 10.
1 shows an example of a result of an experiment in which an excessive voltage exceeding a charging rated voltage is actually applied to a thin lithium ion secondary battery incorporating the battery No. 1. In this experiment,
The thermal fuse 7 and the posistor 3 are electrically and thermally connected by a short band-shaped metal plate. The temperature of the atmosphere in which the experiment was performed is about 30 ° C. The output voltage of the charger as a DC power supply is 15 V, and the maximum current is 0.9 A.
The electrical resistance of the posistor 3 at 30 ° C. is about 20Ω, and the detection temperature is 120 ° C. The breakdown voltage of the Zener diode 5 is about 6 V, and the fusing temperature of the thermal fuse 7 is 90 ° C. In the graph of FIG. 20, the horizontal axis indicates the elapsed time from the start of voltage application, the left vertical axis indicates the respective voltages of the Zener diode 5, the posistor 3, and the battery cell 9, and the right vertical axis The axis shows the charging current of the battery cell 9 and the current flowing through the Zener diode 5, and the temperature of the thermal fuse 7 in degrees Celsius.

First, when the charger is connected, after a rise time of about 1 second elapses, the voltage of the battery cell 9 becomes 15V.
, And a voltage of about 9 V is applied to the posistor 3 and a voltage of about 6 V is applied to the Zener diode 5. At this time, since a voltage equal to or higher than the breakdown voltage of the Zener diode 5 is applied, the Zener diode 5 becomes conductive, and a current of about 100 mA flows through the Zener diode 5 and the posistor 3 connected in series thereto. . Therefore, the Zener diode 5 is about 600 m
Heat is generated by electric power of W (= 6 V × 100 mA). The posistor 3 also generates heat by electric power of about 900 mW (= 9 V × 100 mA), and the heat mainly causes the thermal fuse 7.
Heat. At this time, a voltage of 15 V is applied to the battery cell 9, and a charging current of about 0.8 A flows stably.

When such a state continues, the posistor 3
Since the electric resistance is increased by the heat generated by the heat generated by itself and the heat generated by the thermal fuse 7, the current of the posistor 3 and the Zener diode 5 gradually decreases. For example, the current value which was 0.1 A in about 1 second becomes about 20
It has dropped to 0.07A per second. However, the heat generation of the posistor 3 and the Zener diode 5 is continued without stopping, and the heat causes the thermal fuse 7
Will be heated further. For example, in 20 seconds, Posista 3
Has reached about 120 ° C. (not shown). When such heat generation is continued and the temperature of the thermal fuse 7 reaches the fusing temperature of 90 ° C., the thermal fuse 7 is blown and the application of the excessive voltage to the battery cell 9 is cut off.

However, on the other hand, the Zener diode 5
Since a current of about 60 mA continues to flow through the posistor 3 and the zener diode 5 even after the thermal fuse 7 is blown.
Further, the heat generation of the posistors 3 is continued, and the temperatures of the pistors 3 themselves further rise. For this reason, the temperature of the thermal fuse 7 after being blown reaches about 98 ° C. 40 seconds after the start of the application of the excessive voltage. This means that the temperature of the posistor 3 has reached at least about 98 ° C. or higher. If such a state is further continued, the posistor 3 is further overheated and the zener diode 5 is also overheated, which may cause deterioration or damage. However, when the temperature of the posistor 3 reaches its detection temperature of 120 ° C., the electric resistance of the posistor 3 sharply increases, and the current flowing through the posistor 3 and the zener diode 5 is rapidly suppressed. 5 and the heat of the posistor 3 are suppressed. This can prevent the Zener diode 5 and the posistor 3 from being deteriorated or damaged due to overheating.

As confirmed by this experiment, the structure in which the posistor 3 having a large amount of heat is arranged close to the thermal fuse 7 and heat is conducted from the posistor 3 to the thermal fuse 7 is adopted. When the excessive voltage applied to the battery cell 9 is more than twice the breakdown voltage of the zener diode 5, the heat generated by the posistor 3 is more dominant than the heat generated by the zener diode 5, and is generated from the posistor 3. By conducting heat to the thermal fuse 7, the thermal fuse 7 can be reliably blown, and the time required for the posistor 3 to suppress the current after the thermal fuse 7 has blown can be further reduced.

[Third Embodiment] FIG. 21 shows an electronic device protection circuit according to a third embodiment of the present invention. This electronic device protection circuit uses a thermostat 70 instead of the thermal fuse in the protection circuit according to the first embodiment. Here, the thermostat 70 has a function of shutting off current when heated to a temperature exceeding the cutoff threshold, and returning to a state in which current can flow when the temperature returns below the cutoff threshold. Electric circuit element. Therefore, by setting the cut-off threshold temperature of the thermostat 70 to be the same as the fusing temperature of the thermal fuse 7, a function as a protection circuit similar to that of the first embodiment can be realized. In addition to this, the thermostat 70 and the Zener diode 5
When the temperature returns to the normal room temperature, the thermostat 70
Returns to the original conductive state again, so that the thermostat 70 is automatically returned any number of times, and the electronic device protection circuit 1
02 can be used repeatedly.

Here, as the thermostat 70, for example, two kinds of metal plates having different coefficients of thermal expansion are bonded to each other, and an electric contact is arranged at the tip of the thermostat. A bimetal (not shown) set so as to be able to perform the above-described operation with a simple structure is desirable. For example, in the case of the experimental example described in the first embodiment, the cut-off threshold temperature of the thermostat 70 is set to, for example, 70 ° C. to 9 ° C.
What is necessary is just to set to about 0 degreeC.

Even in the case of the circuit configuration and the substantial structure described in the second embodiment in which the posistor 3 is arranged close to the thermal fuse 7, the electronic device protection circuit 103 shown in FIG. Alternatively, a thermostat 70 can be used instead of the thermal fuse 7.

[Fourth Embodiment] FIG. 23 is a diagram showing a schematic configuration of an electronic device protection circuit according to a fourth embodiment of the present invention. This electronic device protection circuit has a first
In the electronic device protection circuit according to the embodiment, a thermal fuse having a higher fusing temperature (hereinafter referred to as a high thermal fuse) is interposed between the posistor and the Zener diode. Other configurations are the same as those of the first embodiment.

In the electronic device protection circuit 104, when an excessive voltage is applied, first, the Zener diode 5
And the posistor 3 generates heat, and the negative side external connection terminal 1
The thermal fuse 7 provided between the battery 3 and the negative electrode of the battery cell 9 is blown. The operation up to this point is the same as in the first embodiment. Even after the thermal fuse 7 is blown in this way, a current equal to or less than the detected current value of the posistor 3 continues to flow through the posistor 3, the zener diode 5, and the high-temperature fuse 79. The current value at that time changes depending on the temperature of the posistor 3 and the amount of heat radiation. For example, under the same conditions as in the first embodiment, about 20 to 10
It is about 0 mA. As described above, since the current continues to flow even after the thermal fuse 7 is blown, the heat generation of the posistor 3 and the Zener diode 5 is continued. However, the heat further heats the high temperature fuse 79 to reach the blowout temperature and blow. You. As described above, when an excessive voltage is applied, the thermal fuse 7 connected to the battery cell 9 is blown first, and thereafter, when the excessive voltage is further applied, the high-temperature fuse 79 is blown. As a result, it is possible to reliably prevent an excessive voltage from being applied to the battery cell 9, and to completely cut off the current flowing through the posistor 3 and the zener diode 5 after the thermal fuse 7 is blown by blowing the high-temperature fuse 79. As a result, deterioration and damage due to overheating of the posistor 3, the Zener diode 5, and the battery cell 9 can be more reliably prevented.

In the case of the circuit configuration and the substantial structure in which the posistor 3 is arranged close to the thermal fuse 7 as described in the second embodiment, the electronic device protection circuit 105 shown in FIG. As described above, the high temperature fuse 79 is inserted between the Zener diode 5 and the posistor 3, and the posistor 3 and the zener diode 5 are similarly connected as described above.
It is possible to completely cut off the current flowing through.

In place of the thermal fuse 7, a thermostat set to the same cut-off threshold temperature is used, and instead of the high temperature fuse 79, a high cut-off temperature set to the same cut-off threshold temperature is used. A temperature thermostat may be used. By doing so, the thermostat or the high-temperature thermostat can be automatically returned and used repeatedly as many times as necessary.

[Fifth Embodiment] FIG. 25 shows a general configuration including a control IC, a field-effect transistor and the like (not shown) together with the electronic device protection circuit described in each of the above embodiments. 3 schematically shows a schematic configuration inside a lithium ion secondary battery when an overvoltage charging prevention circuit is used together. By thus using the overvoltage charging prevention circuit 110 and the electronic device protection circuit 100 together, the lithium ion secondary battery 1
A higher safety factor can be achieved with respect to prevention of breakage and deterioration of the battery cell 9 due to application of an excessive voltage to the battery cell 9. For example, even if the overvoltage charging prevention circuit 110 malfunctions due to accidental failure such as electrostatic breakdown or circuit damage, the electronic device protection circuit 100
Thereby, the battery cell 9 can be reliably protected from application of an excessive voltage.

It is needless to say that the electronic device that can be protected by applying the electronic device protection circuit according to the present invention is not limited to the battery cells described in the above embodiments. . In addition, the present invention can be applied to, for example, preventing an excessive voltage from being applied to an electronic device such as a semiconductor integrated circuit or a liquid crystal display device to which a driving voltage or the like is supplied from a power supply.

[0091]

As described above, claims 1 to 7 are described.
According to the electronic device protection circuit according to any of the above, when an excessive voltage exceeding the rated voltage is applied to the voltage input terminal of the electronic device, a current corresponding to the voltage flows through the zener diode to generate heat, Since the heat promotes the blowing of the thermal fuse, there is an effect that the thermal fuse can be reliably blown when an excessive voltage is applied. Also, at this time, the current caused by the application of the excessive voltage is bypassed to the zener diode and the posistor to reduce the amount of current flowing through the electronic device. Can be prevented from flowing due to excessive current caused by the application of. In addition, if the excessive current continues to flow and the electrical resistance of the posistor increases, the electrical resistance suppresses the current flowing through the zener diode and the posistor to make them less than their rated currents. It is possible to prevent overheating, destruction, damage, and the like of the Zener diode and the posistor due to the application.

According to the electronic device protection circuit of the present invention, a posistor and a thermal fuse are provided close to each other, and an excessive voltage exceeding a rated voltage is applied to a voltage input terminal of the electronic device. When voltage is applied,
Since the Zener diode becomes conductive, a current corresponding to the excessive voltage flows, the Postar and the Zener diode generate heat together, and the heat generated by the Postar is mainly used to promote the blowing of the thermal fuse. When an excessive voltage is applied, the temperature fuse can be blown more reliably. In addition, at this time, the current caused by the application of the excessive voltage is bypassed to the zener diode and the posistor to reduce the amount of current flowing to the electronic device. It is possible to prevent an excessive current from flowing due to the application. In addition, when an excessive current continues to flow, the electric resistance value of the posistor increases sharply due to its own heat generation, and the electric resistance suppresses the current flowing through the zener diode and the posistor to make them less than their rated current. As a result, overheating, destruction, damage, and the like of the Zener diode and the posistor due to the application of the excessive voltage can be more quickly and reliably prevented.

According to the electronic device protection circuit according to any one of claims 8 to 13 or 20 to 24, a thermostat is provided instead of a thermal fuse so that excessive voltage is not applied. If the temperature drops, it can return to the original normal state,
If the excessive voltage is no longer applied and the state returns to the state where the normal voltage is applied, there is an effect that the device can be used repeatedly as many times as necessary without replacing components such as the thermal fuse.

According to the electronic device protection circuit according to any one of claims 5 and 6, or 17 or 18, the fusing temperature is lower than the thermal fuse between the Zener diode and the posistor. A high-temperature fuse was further inserted, and after the above-mentioned thermal fuse was blown, the high-temperature fuse with a high fusing temperature was blown to cut off the current flowing through the Zener diode and the posistor. Overheating, destruction or damage of the Zener diode, posistor or battery cell
The effect that it can prevent more reliably is produced.

According to the electronic device protection circuit according to the twelfth or thirteenth aspect, or the twenty-third or the twenty-third aspect, the shut-off temperature between the Zener diode and the posistor is further lower than that of the thermostat. As we inserted high thermostat more,
The overheating, destruction, damage, etc. of the Zener diode and posistor caused by the application of excessive voltage can be prevented more reliably, and the excess voltage is no longer applied and the normal voltage within the rated voltage range is applied. On return, the thermostat between the zener diode and the posistor automatically returns to its original conducting state without the need for replacement of components such as thermal fuses, allowing it to be used over and over again This has the effect.

[Brief description of the drawings]

FIG. 1 is a circuit diagram illustrating a schematic configuration of an electronic device protection circuit according to a first embodiment of the present invention.

FIG. 2 is a diagram schematically illustrating an electronic device protection circuit mounted so as to be connected to a battery cell inside a battery pack of a lithium ion secondary battery.

FIG. 3 is a sectional view showing an example of a substantial structure for connecting a thermal fuse and a Zener diode.

FIG. 4 is a cross-sectional view showing another example of a substantial structure for connecting a thermal fuse and a Zener diode.

FIG. 5 is a cross-sectional view showing still another example of a substantial structure for connecting a thermal fuse and a Zener diode.

FIG. 6 is a diagram showing an example of a substantial structure in which a fusing element of a thermal fuse and a semiconductor element of a Zener diode are contained in one exterior material.

FIG. 7 is a diagram showing another example of a substantial structure in which a fusing element of a thermal fuse and a semiconductor element of a Zener diode are enclosed in one exterior material.

FIG. 8 is a diagram showing another example of a substantial structure in which a fusing element of a thermal fuse and a semiconductor element of a zener diode are enclosed in one exterior material.

FIG. 9 is a diagram showing another example of a substantial structure in which a fusing element of a thermal fuse and a semiconductor element of a zener diode are contained in one exterior material.

FIG. 10 is a diagram showing another example of a substantial structure in which a fusing element of a thermal fuse and a semiconductor element of a zener diode are enclosed in one exterior material.

FIG. 11 is a diagram showing another example of the substantial structure in which the fusing element of the thermal fuse and the semiconductor element of the Zener diode are enclosed in one exterior material.

FIG. 12 is a diagram showing another example of a substantial structure in which a fusing element of a thermal fuse and a semiconductor element of a zener diode are contained in one exterior material.

FIG. 13 is a diagram showing another example of a substantial structure in which a fusing element of a thermal fuse and a semiconductor element of a Zener diode are enclosed in one exterior material.

FIG. 14 is a cross-sectional view showing an example of a substantial structure in which a thermal fuse, a zener diode, and a posistor are contained in one casing.

FIG. 15 is a cross-sectional view showing an example of a substantial structure in which a fusing element of a thermal fuse, a semiconductor element of a Zener diode, and a thermosensitive element of a posistor are joined and integrated via electrodes. .

FIG. 16 is a cross-section showing another example of a substantial structure in which a fusing element of a thermal fuse, a semiconductor element of a Zener diode, and a thermosensitive element of a posistor are joined together through electrodes to be integrated. FIG.

FIG. 17 is a diagram illustrating transient characteristics of current, voltage, and temperature when an excessive voltage is applied to a lithium ion secondary battery incorporating an electronic device protection circuit.

FIG. 18 is a diagram illustrating an example of a result of an experiment in which an excessive voltage exceeding a charging rated voltage is applied to a thin lithium ion secondary battery incorporating an electronic device protection circuit.

FIG. 19 is a diagram illustrating a schematic configuration of an electronic device protection circuit according to a second embodiment of the present invention.

FIG. 20 shows an example of a result of an experiment in which an excessive voltage exceeding a charging rated voltage is actually applied to a thin lithium ion secondary battery incorporating the electronic device protection circuit according to the second embodiment. FIG.

FIG. 21 is a diagram showing a main part of a circuit configuration using a thermostat instead of a thermal fuse in the electronic device protection circuit.

FIG. 22 is a diagram showing a main part of a circuit configuration using a thermostat instead of a thermal fuse in the circuit shown in FIG. 21;

FIG. 23 illustrates a main part of a circuit configuration in which a high-temperature fuse is interposed between a posistor and a zener diode in the electronic device protection circuit illustrated in FIG.

FIG. 24 illustrates a main part of a circuit configuration in which a high-temperature fuse is interposed between a Zener diode and a posistor in the electronic device protection circuit illustrated in FIG. 2;

FIG. 25 is a schematic diagram showing the schematic internal configuration of a lithium ion secondary battery when a general overvoltage protection circuit including a control IC and a field effect transistor is used together with an electronic device protection circuit. FIG.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Lithium ion secondary battery, 3 ... Posister, 5 ... Zener diode, 7 ... Thermal fuse, 9 ... Battery cell, 7
0: thermostat, 100: electronic device protection circuit

Claims (24)

[Claims] An electronic device protection circuit for preventing a voltage exceeding a rated voltage from being applied to voltage input terminals of a positive electrode and a negative electrode of an electronic device, wherein an electric resistance value increases when a current increases. A posistor having one end connected to one of the voltage input terminals of the voltage input terminals of the electronic device; and a characteristic in which a temperature rises and a fusing is caused by a current flowing by applying a voltage exceeding the rated voltage. A temperature fuse having one end connected to the other voltage input terminal of the electronic device; and a characteristic in which a current increases when an applied voltage exceeds a breakdown voltage set to be equal to or higher than the rated voltage. And a Zener diode connected to the other end of the thermal fuse. The thermal fuse and the Zener diode are provided so as to be able to conduct heat to each other. When an excessive voltage exceeding the rated voltage is applied to the voltage input terminal of the electronic device, a current corresponding to the voltage flows, and the Zener diode generates heat to accelerate the blowing of the thermal fuse. In addition, the current due to the excessive voltage is bypassed to the Zener diode and the posistor to reduce the amount of current flowing to the electronic device, and further, when the electric resistance of the posistor increases, the electric resistance causes
An electronic device protection circuit, wherein a current flowing through the Zener diode and the posistor is set to be equal to or less than their rated current. 2. The thermal fuse, the posistor, and the zener diode are provided so as to be able to conduct heat, and the Curie point at which the electric resistance of the posistor increases non-linearly and steeply is set at the temperature of the thermal fuse. It is set higher than the fusing temperature, and when an excessive voltage exceeding the rated voltage is applied to the voltage input terminal of the electronic device, the posistor and the zener diode generate heat to accelerate the fusing of the thermal fuse. The electronic device protection circuit according to claim 1, wherein 3. The thermal fuse, wherein a length of a conductor electrically connecting the thermal fuse and the Zener diode is shorter than a length of a conductor electrically connecting the thermal fuse and the battery. 2. The electronic device protection circuit according to claim 1, wherein a distance required for heat conduction between the thermal fuse and the Zener diode is shorter than a distance required for heat conduction between the thermal fuse and the battery. . 4. The electronic device protection circuit according to claim 1, wherein said Zener diode and said thermal fuse are thermally coupled by a heat conducting member. 5. The electronic device protection circuit according to claim 1, wherein a thermal fuse having a higher fusing temperature than the thermal fuse is further interposed between the Zener diode and the posistor. 6. The electronic device protection circuit according to claim 5, wherein the thermal fuse having a high fusing temperature, the zener diode, and the posistor are provided so as to be able to conduct heat. 7. The electronic device protection circuit according to claim 1, wherein the electronic device is a lithium ion secondary battery. 8. A thermostat that, in place of the thermal fuse, is provided with a thermostat that cuts off current when a voltage exceeding a rated voltage is applied to voltage input terminals of a positive electrode and a negative electrode of the electronic device and exceeds a predetermined temperature. The electronic device protection circuit according to claim 1, wherein: 9. A thermostat for interrupting a current when a voltage exceeding a rated voltage is applied to a voltage input terminal of a positive electrode and a negative electrode of the electronic device and a temperature exceeds a predetermined temperature is provided instead of the thermal fuse. The electronic device protection circuit according to claim 2, wherein: 10. A thermostat for interrupting a current when a voltage exceeding a rated voltage is applied to a voltage input terminal of a positive electrode and a negative electrode of the electronic device and a temperature exceeds a predetermined temperature, instead of the thermal fuse. The electronic device protection circuit according to claim 3, wherein: 11. A thermostat for interrupting a current when a voltage exceeding a rated voltage is applied to a voltage input terminal of a positive electrode and a negative electrode of the electronic device and a temperature exceeds a predetermined temperature is provided instead of the thermal fuse. The electronic device protection circuit according to claim 4, wherein: 12. The electronic device protection circuit according to claim 8, wherein a thermostat having a higher cut-off temperature than the thermostat is further interposed between the Zener diode and the posistor. 13. The electronic device protection circuit according to claim 12, wherein the thermostat having a high cutoff temperature, the zener diode, and the posistor are provided so as to be able to conduct heat. 14. An electronic device protection circuit for preventing a voltage exceeding a rated voltage from being applied to voltage input terminals of a positive electrode and a negative electrode of an electronic device, wherein the breakdown voltage is set to be equal to or higher than the rated voltage. When the voltage exceeds the voltage, the current increases.The Zener diode having one end connected to one of the voltage input terminals of the electronic device. A temperature fuse having one end connected to the other voltage input terminal of the electronic device, and having a characteristic that the electric resistance increases as the current increases, A Curie point at which the electric resistance value sharply increases nonlinearly is set higher than the fusing temperature of the thermal fuse, and the other end of the Zener diode and the temperature A posistor connected to the other end of the fuse, wherein the temperature fuse, the posistor, and the zener diode are provided so as to be able to conduct heat, and the voltage input terminal of the electronic device exceeds the rated voltage. When an excessive voltage is applied, a current corresponding to the applied voltage flows, and the Zener diode and the posistor generate heat to promote blowing of the thermal fuse. By reducing the amount of current flowing through the electronic device by bypassing the posistor, and further increasing the electric resistance of the posistor, the electric resistance suppresses the current flowing through the zener diode and the posistor below their rated current. Electronic device protection circuit characterized by being set as follows: Road. 15. A length of a conductor that electrically connects the thermal fuse and the posistor is shorter than a length of a conductor that electrically connects the thermal fuse and the battery. 15. The electronic device protection circuit according to claim 14, wherein a distance required for heat conduction with the posistor is shorter than a distance required for heat conduction between the thermal fuse and the battery. 16. The electronic device protection circuit according to claim 14, wherein said posistor and said thermal fuse are thermally coupled by a heat conducting member. 17. A thermal fuse having a higher fusing temperature than the thermal fuse is further interposed between the Zener diode and the posistor.
5. The electronic device protection circuit according to 4. 18. The electronic device protection circuit according to claim 17, wherein the thermal fuse having a high fusing temperature, the zener diode, and the posistor are provided so as to be able to conduct heat. 19. The electronic device protection circuit according to claim 14, wherein the electronic device is a lithium ion secondary battery. 20. A thermostat which, in place of said thermal fuse, cuts off current when a voltage exceeding a rated voltage is applied to voltage input terminals of a positive electrode and a negative electrode of said electronic device and exceeds a predetermined temperature. The electronic device protection circuit according to claim 14, wherein: 21. A thermostat for interrupting a current when a voltage exceeding a rated voltage is applied to a voltage input terminal of a positive electrode and a negative electrode of the electronic device and a temperature exceeds a predetermined temperature, instead of the thermal fuse. The electronic device protection circuit according to claim 15, wherein: 22. A thermostat which, in place of said thermal fuse, cuts off current when a voltage exceeding a rated voltage is applied to voltage input terminals of a positive electrode and a negative electrode of said electronic device and exceeds a predetermined temperature. 17. The electronic device protection circuit according to claim 16, wherein: 23. The electronic device protection circuit according to claim 20, wherein a thermostat having a higher cut-off temperature than the thermostat is further interposed between the zener diode and the posistor. 24. The electronic device protection circuit according to claim 23, wherein the thermostat having a high cutoff temperature, the zener diode, and the posistor are provided so as to be able to conduct heat.