JP2002150918A - Protection element - Google Patents

Abstract

(57) [Problem] To provide a protection element capable of reliably protecting with a simple configuration. SOLUTION: Flat connection terminals 13 and 14 are mounted on both sides of the PTC chip 12 so as to sandwich the PTC chip 12 therebetween. At least one of the external connection terminals 13 and 14 has a fuse function. By setting the melting point of the fuse function to 150 ° C. or higher, the PT
The fuse function is prevented from being blown in an atmosphere at or below 120 ° C., which is the temperature at which C appears. For a voltage that exceeds the withstand voltage of the PTC chip 12 and enters the short mode, the fuse is backed up and the current is cut off.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a protection element having a reset element and a fuse.

[0002]

2. Description of the Related Art In recent years, secondary batteries have become widespread as energy sources for personal electronic devices, and among secondary batteries, lithium ion secondary batteries capable of obtaining high output have become widespread.

On the other hand, since a lithium ion secondary battery uses an organic solvent in which a lithium salt is dissolved as an electrolyte, if a large current flows due to a short circuit or misuse,
The battery temperature may rise sharply, causing flammable liquids or decomposed gases to erupt or ignite. For this reason, a protection circuit equipped with a MOS type field effect transistor (FET) is generally provided as an overcharge switch or an overdischarge switch in a battery pack containing a lithium ion secondary battery, and a current interruption performance is provided. PTC (Positive Tem)
It is necessary to at least reduce the flow by incorporating a return type element such as a perture coefficient element.

[0004] Such a resetting element such as a field effect transistor or a PTC element is effective for personal use because it can return to a normal use state by removing a cause of a failure. It is easy to deal with transient accidents such as erroneous short circuit of the pack.

However, when considering the actual use environment,
Consideration must also be given to the fact that a reset type element used as a switch may be damaged due to the application of a voltage exceeding the rating. As described above, when a voltage higher than the rated voltage is applied and the resetting element is damaged with the short-circuit mode, there is a possibility that a fire may occur.

Therefore, in order to protect such a reset type element even in the short-circuit mode, a current fuse or a temperature fuse may be used as a backup for the reset type element.

However, since the current fuse and the thermal fuse do not return even after the cause of the failure is removed, it is possible to prevent the battery pack itself from being used in a damaged state, for example, in a state where the return element is damaged.

On the other hand, the safety of the lithium ion secondary battery is protected by the two stages of the non-return type elements such as the reset type elements and the current fuse or the temperature fuse for backing up these return type elements as described above. Secured by a protection circuit. It should be noted that such a protection circuit may be incorporated in the battery pack or in the device body to which the battery pack is attached, although there is a choice as to whether the protection circuit can be incorporated into the battery pack or the device itself. The transition to cheaper is progressing.

Here, the circuit of the lithium ion secondary battery B equipped with such a protection circuit 1 will be described with reference to FIG.

As shown in FIG. 16, a protection circuit 1 is connected to a terminal of a lithium ion secondary battery B.
Are reset-type field effect transistors Q1 and Q2
Are connected in series, and a control IC 2 for controlling these field-effect transistors Q1 and Q2 is connected in series with the field-effect transistors Q1 and Q2. The fuse 3 is connected. The fuse 3 composed of the field effect transistors Q1 and Q2 and the current fuse is mounted on a board (not shown), electrically connected to the lithium ion secondary battery B, and housed in a battery pack (not shown). To be incorporated.

In the case of the configuration shown in FIG. 16, the field effect transistors Q1 and Q2 are controlled by the control IC 2, so that the operation of the control IC 2 can be set to cope with a custom use. Although large, the number of parts is large, and there are also restrictions such as the need for a protective circuit board for mounting.

On the other hand, depending on the purpose and environment of use, such as high safety of the lithium ion secondary battery B, sufficient protection can be achieved with a simple circuit. For example, as shown in FIG. 17, the protection circuit 1 is a PTC element as a reset type element.
A series circuit of R1 and a fuse 3 such as a temperature fuse or a current fuse is connected in series to the lithium ion secondary battery B.

In the case of the configuration shown in FIG. 17, the number of parts is small, and it can be inexpensively handled.

Here, the fuse 3 composed of the field effect transistors Q1 and Q2 and the current fuse is mounted on a substrate (not shown) and is electrically connected to the lithium ion secondary battery B so as to be mounted in a battery pack (not shown). However, it is difficult to mount the fuse 3 such as the PTC element R1 and the thermal fuse on the substrate.

First, as for the PTC element R1, a small and low impedance specification suitable for protecting the lithium ion secondary battery B cannot be realized. In addition, the influence of the characteristic that the impedance greatly changes due to the thermal stress of soldering applied at the time of mounting the board cannot be ignored.

If a thermal fuse is used as the fuse 3, soldering is impossible because the element of the thermal fuse melts at the temperature at the time of soldering. Further, since the temperature fuse functions by sensing the temperature, it needs to be closely attached to the temperature sensing point of the lithium ion secondary battery B itself. Therefore, as shown in FIG. 18, an electrode is formed on the lithium ion secondary battery B, and a PTC element is formed.
An external connection terminal is formed on R1 and the fuse 3 of the thermal fuse, and the PTC element R1 is connected to the electrode of the lithium ion secondary battery B.
Alternatively, the external connection terminals formed on the fuse 3 of the thermal fuse are spot-welded, and the external connection terminals between the PTC element R1 and the fuse 3 of the thermal fuse are also spot-welded.

[0017]

However, in the configuration shown in FIG. 18 described above, the PTC element R1 and the fuse 3 of the thermal fuse require external connection terminals for spot welding, and the respective configurations are complicated. And an external connection terminal formed on the electrode of the lithium ion secondary battery B and the PTC element R1 or the fuse 3 of the thermal fuse, and the PTC element R1 and the fuse 3 of the thermal fuse.
Spot welding must be performed at two points between the external connection terminals and the manufacturing process.

When a thermal fuse is used for the fuse 3, the fuse 3 is placed before the PTC element R1 in a practical atmosphere.
Has a risk of being melted first.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to provide a protection element which can be reliably protected with a simple configuration.

[0020]

According to a first aspect of the present invention, there is provided a protection element including a resetting element for reducing a circuit current at least when a current value increases by a predetermined value or more, and a melting point sandwiching at least one of the resetting elements. Is provided with a pair of external connection terminals having a fuse function of 150 ° C. or higher. Since the external connection terminal sandwiching the reset type element has a fuse function, the reset type element is externally connected. Since the external connection terminal is required, the resetting element has a fuse function to cut off the current in addition to the function to cut off the current or reduce the current value without complicating the configuration. The fuse function is prevented from operating earlier than the resetting element in a practical atmosphere by setting the melting point of the To.

According to a second aspect of the present invention, there is provided a protection element, wherein a reset type element for reducing a circuit current at least when a current value increases by a predetermined value or more, and a solid phase point of 150 ° C. or more in at least one of the reset type elements. And a pair of external connection terminals having a fuse function. The external connection terminal sandwiching the reset type element has a fuse function, so the reset type element has an external connection terminal connected to the outside. It is necessary to provide a fuse function to interrupt the current in addition to the function of interrupting the current or reducing the current value at least by the resetting element without complicating the configuration without complicating the configuration. Is set to 150 ° C. or more, the fuse function is prevented from operating earlier than the resetting element in a practical atmosphere.

According to a third aspect of the present invention, there is provided the protection element according to the first or second aspect, wherein the rated voltage of the resetting element is a maximum voltage at which the resetting element can be turned on and off without damage. The rated voltage of the fuse is a voltage that can interrupt the current without damaging the fuse function of the external connection terminal.The rated voltage of the fuse is higher than the rated voltage of the resettable element, which may damage the resettable element. Therefore, the fuse functions even if the reset type element is damaged and enters the short mode.

According to a fourth aspect of the present invention, there is provided the protection element according to any one of the first to third aspects, wherein the fuse is slower than the reset type element in an atmosphere at -20 ° C. to 120 ° C. The resetting element operates in an atmosphere of 20 ° C. to 120 ° C., and the fuse has not lost its function even after the operation is restored. Therefore, the fuse can be restarted by returning the resetting element.

According to a fifth aspect of the present invention, there is provided the protection element according to any one of the first to fourth aspects, wherein the external connection terminal has a fuse function by mounting a chip type fuse on a flexible printed circuit board. The terminal for external connection can have a fuse function with a simple configuration.

According to a sixth aspect of the present invention, in the protection element of the first aspect, the external connection terminal has a fuse function by forming a fuse pattern on a part of the flexible printed circuit board. Thus, the external connection terminal can have a fuse function with a simple configuration.

[0026]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the protection element of the present invention will be described below with reference to FIGS.

As shown in FIG. 1 and FIG.
Has a rectangular flat plate-like PTC chip 12 as a return-type element having a PTC function, and flat plate-like external connection terminals 13 and 14 are mounted on both surfaces of the PTC chip 12 so as to sandwich the PTC chip 12 therebetween. .

The external connection terminal 13 is a PTC chip.
The external connection terminal 14 projects from one end of the PTC chip 12 opposite to the one end of the PTC chip 12 from which the external connection terminal 13 protrudes.
Spot welding is performed on the surface of the C chip 12 opposite to the external connection terminal 13. Note that the external connection terminals 13 and 14 are
The connection to the chip 12 is not limited to spot welding, and may be connected by other methods.

As the external connection terminals 13 and 14, the conventional general one uses a metal plate.
At least one of 14 has a fuse function having a melting point of 150 ° C. or more instead of a metal plate. The external connection terminals 13 and 14 have a solid point of 150 instead of the melting point.
The same effect can be obtained even if a fuse function at a temperature of not less than ° C is provided.

Then, the external connection terminals 13 and 14 are connected between the lithium ion secondary battery and the load.

Here, the coordination with the characteristics of the function of the fuse provided in the PTC chip 12 and at least one of the external connection terminals 13 and 14 will be described.

As a basic operation, an overcurrent exceeding a predetermined current value occurs in a normal temperature region in an atmosphere of -20 ° C. to 120 ° C. or lower, for example, at a temperature lower than the PTC onset temperature at which the resistance value of the PTC chip 12 sharply rises. In this case, the PTC chip 12 has a main protection function by interrupting the current or at least decreasing the current value by reducing the current value, and the PTC chip 12 interrupts the current. When the PTC chip 12 is damaged and enters the short mode, the fuse is blown to cut off the current. As described above, since it is necessary to provide the fuse with the backup function, it is necessary to delay the fuse function provided in at least one of the external connection terminals 13 and 14 as compared with the operation of the PTC chip 12.

For this reason, as shown in FIG. 3, the PTC chip 12 is compared with the current value with respect to the operation time of the fuse function.
It is required that the current value with respect to the operation time is always small.

For example, as shown in FIG. 4, when the current value with respect to the operation time of the PTC chip 12 is larger than the current value with respect to the operation time of the fuse function during the earlier operation time, the characteristic crosses with the current Ic1. , Ic1 or more, the fuse function operates first and blows, thereby interrupting the current in a non-recovery state.
The function of resetting is no longer used.

On the contrary, as shown in FIG. 5, the current value with respect to the operation time of the PTC chip 12 is smaller than the current value with respect to the operation time of the fuse function during the early operation time, and the characteristics cross with the current Ic2. If the current is less than Ic2, the fuse operates first, resulting in the same problem as that shown in FIG.

On the other hand, the charging circuit of the lithium ion secondary battery breaks down and, for example, D corresponds to the input voltage of the charging circuit.
When a voltage of about C24V is applied, a PTC chip
This is because there is a possibility that the PTC chip 12 may be damaged with a short mode when the withstand voltage exceeds 12. However, in this case, after the short mode occurs in the PTC chip 12, the fuse operates.

Also, the PTC chip 12 which is the maximum voltage that can be turned on and off without damaging the PTC chip 12
The rated voltage of the fuse function, which is a voltage that can interrupt the current without damaging the fuse functions of the external connection terminals 13 and 14, is higher than the rated voltage of the external connection terminals 13 and 14 so that the PTC chip 12 can be reliably backed up by the fuse function. .

Further, since the operating temperature of the fuse is 150 ° C. and the PTC onset temperature of the PTC chip 12 is 120 ° C., the operating temperature is 150 ° C. in the practical temperature range because the PTC chip 12 operates first. External connection terminals 13,
The fuse function provided to at least one of the external connection terminals 13 and 14 is provided even if the temperature of the lithium ion secondary battery rises because the fuse function provided to at least one of the terminals 14 operates as a backup. Does not cause an operation such as fusing.

Further, even if the temperature fuse is left in the dashboard of the car, it is possible to prevent the thermal fuse as a fuse function provided at one of the external connection terminals 13 and 14 from being blown. Note that the temperature at which the shutdown function of the separator material in the lithium ion secondary battery operates is PT
Considering that the temperature is equal to or higher than the PTC onset temperature of the C chip 12, it is considered that the PTC function of the PTC chip 12 is sufficient for the temperature safety function. Therefore,
In the case of this embodiment, it is necessary that the melting point of the fuse is 150 ° C. or higher, which is higher than 120 ° C. or higher, which is the PTC onset temperature of the PTC chip 12.

Further, the protection element 11 is for electrically disconnecting the lithium ion secondary battery from the outside in any system. Even if the 12 PTCs appear, the fuses of the external connection terminals 13 and 14 are blown, but the protection function is not sufficient. For this reason, the function of the protection circuit 11 is based on current, and it is necessary to focus on the fact that reliable insulation is maintained when fusing, rather than using the temperature fuse function normally used as backup by temperature. .

As described above, by providing at least one of the external connection terminals 13 and 14 with a fuse function, the size of the protection element 11 can be reduced. In addition, by setting the melting point of the fuse function provided to at least one of the external connection terminals 13 and 14 to 150 ° C. or higher, it is possible to prevent the thermal fuse of the fuse function from being blown out more than necessary, and to improve the fuse function. Can be a backup.

[0042]

Next, a first specific example of the protection element 11 will be described with reference to FIGS.

The basic structure of the protection element 11 shown in FIGS. 6 to 8 is the same as that of the protection element 11 shown in FIGS.

The external connection terminal 13 is made of a flexible substrate material (product name: Etcherflex, manufactured by Mitsui Chemicals, Inc.).
The copper on both sides of the flexible substrate material 21 is etched to form a pair of lands 22 and 22 facing each other, and a chip fuse as a chip component (manufactured by Daito Tsushinki Co., Ltd .: Number KMZ80) 23, 23 for 2
This is implemented by using a reflow layer in parallel.

Thus, the external connection terminal 13 has a fuse function.

A second embodiment of the protection element 11 will be described with reference to FIGS.

The basic structure of the protection element 11 shown in FIGS. 9 to 11 is the same as that of the protection element 11 shown in FIGS.

The external connection terminal 13 is made of a flexible substrate (made by Mitsui Chemicals, product name: Etcherflex).
The copper on both sides of the flexible substrate material 21 is etched to form a base 26 for the fuse pattern, and tin (Sn) is plated to a desired thickness to form a fuse element.
27 was formed so that the fuse characteristics in the region of 10 ms or less were the same as those in the first embodiment.

Further, a protective film 28 was formed by coating the fuse element 27 with a silicon resin.

The results of comparing the operating characteristics of the first and second embodiments at a temperature of -20.degree. C., 25.degree. C., 90.degree. C. and 130.degree. C. will be described with reference to FIGS.

First, at −20 ° C. shown in FIG. 12 lower than 120 ° C. at which PTC expression occurs, at 25 ° C. shown in FIG.
At 90 ° C. shown in FIG. 4, the PTC chip 12 operates first, and at 130 ° C. shown in FIG. 15, the PTC element remains in a high resistance state.

The result of applying a DC voltage of 50 V which is higher than the rated voltage of the PTC chip 12 will be described.

Using the first and second embodiments, a test was conducted at a specified short-circuit current of 40 A. As a result, the PTC chip 12 was damaged and the short-circuit mode was reached, but the chip fuse 23 or the fuse element 27 was blown and the circuit was broken. It was opened and it was confirmed that the backup function was performed.

[0054]

According to the protection element of the first aspect, the melting point of the external connection terminal sandwiching the resetting element is 150 ° C.
With the above fuse function, the reset type element requires an external connection terminal to connect to the outside, so at least current reduction to cut off the current or reduce the current value by the reset type element without complicating the configuration In addition to the fuse function, the fuse function for interrupting the current can be provided, and the fuse function can be prevented from operating earlier than the resetting element in a practical atmosphere by setting the melting point of the fuse function to 150 ° C. or higher.

According to the second aspect of the present invention, the solid state point of the external connection terminal sandwiching the reset type element is 150 ° C.
With the above fuse function, the reset type element requires an external connection terminal to connect to the outside, so at least current reduction to cut off the current or reduce the current value by the reset type element without complicating the configuration In addition to the fuse function, a fuse function for interrupting the current can be provided, and the fuse function can be prevented from operating earlier than the resetting element in a practical atmosphere by setting the solid point of the fuse function to 150 ° C. or higher.

According to the protection element of the third aspect, in addition to the protection element of the first or second aspect, the rated voltage of the fuse is higher than the rated voltage of the resetting element that may damage the resetting element. The fuse functions even if the reset type element is damaged, and can reliably protect against overcurrent.

According to the protection element of the fourth aspect, in addition to the protection element of the first aspect, the resetting element operates in an atmosphere of -20 ° C to 120 ° C, and the fuse is operated even after the operation is restored. Since the function is not damaged, it can be restarted by returning the resetting element.

According to the protection element of the fifth aspect, in addition to the protection element of any one of the first to fourth aspects, the external connection terminal has a fuse function by mounting a chip type fuse on a flexible printed circuit board. The external connection terminal can have a fuse function with a simple configuration.

According to the protection element of the sixth aspect, in addition to the protection element of the first to fourth aspects, the external connection terminal has a fuse function by forming a fuse pattern on a part of the flexible printed circuit board. This allows the external connection terminal to have a fuse function with a simple configuration.

[Brief description of the drawings]

FIG. 1 is a plan view showing a protection element according to an embodiment of the present invention.

FIG. 2 is a side view of the same.

FIG. 3 is a graph showing an operation relationship between the PTC and the fuse.

FIG. 4 is a graph showing an operation relationship between the PTC and the fuse.

FIG. 5 is a graph showing an operation relationship between the PTC and the fuse.

FIG. 6 is a plan view showing the protection element of the first embodiment.

FIG. 7 is a side view of the same.

FIG. 8 is a plan view showing the external connection terminal according to the first embodiment;

FIG. 9 is a plan view showing the protection element of the second embodiment.

FIG. 10 is a side view of the same.

FIG. 11 is a plan view showing the external connection terminal according to the third embodiment;

FIG. 12 is a graph showing an operation of an experimental result at a temperature of -20 ° C.

FIG. 13 is a graph showing an operation of an experimental result at the same temperature of 25 ° C.

FIG. 14 is a graph showing an operation of an experimental result at the same temperature of 90 ° C.

FIG. 15 is a graph showing an operation of an experimental result at the same temperature of 130 ° C.

FIG. 16 is a circuit diagram showing a state in which a protection circuit is connected to a conventional lithium ion secondary battery.

FIG. 17 is a circuit diagram showing a state in which a protection circuit is connected to another conventional lithium ion secondary battery.

FIG. 18 is an explanatory diagram illustrating a state in which a PTC and a fuse are connected to a conventional lithium secondary battery.

[Explanation of symbols]

 11 Protection element 12 PTC chip as return type element 13, 14 External connection terminal

 ────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Fukuichi Takamatsu 484 Harigaya-cho, Utsunomiya-shi, Tochigi NFC Mobile Energy Co., Ltd. F-term (reference) 5E034 AA10 DA02 DB01 DC01 DD03 5G502 AA01 BA08 BB13 EE04 EE10 5H022 AA09 CC09 KK01 5H029 AJ12 BJ27 DJ05 HJ14 HJ17 HJ18

Claims (6)

[Claims] 1. A reset type element that at least reduces a circuit current when a current value increases by a predetermined value or more, and a pair having at least one of them having a fuse function with a melting point of 150 ° C. or more, sandwiching the reset type element. And a terminal for external connection. 2. A resetting element for reducing a circuit current at least when a current value increases by a predetermined value or more, and a fuse function having a solidus point of 150 ° C. or more is provided in at least one of the resetting elements sandwiching the resetting element. A protection element comprising: a pair of external connection terminals. 3. A voltage at which a current can be cut off without damaging a fuse function of an external connection terminal from a rated voltage of a resettable element which is a maximum voltage at which the resettable element can be turned on and off without being damaged. 3. The protection element according to claim 1, wherein a certain fuse has a high rated voltage. 4. The protection element according to claim 1, wherein the fuse is slower than the resettable element in an atmosphere at −20 ° C. to 120 ° C. 5. The protection element according to claim 1, wherein the external connection terminal is provided with a fuse function by mounting a chip type fuse on a flexible printed circuit board. 6. The protection element according to claim 1, wherein the external connection terminal has a fuse function by forming a fuse pattern on a part of the flexible printed circuit board.