JP2007273221A - Battery protection circuit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a battery protection circuit excellent in safety and capable of having a high impedance, that is, having low power consumption, by protecting the battery protection circuit from outside moisture, an electrolyte leaked from a battery, external noise, and static electricity. <P>SOLUTION: This battery protection circuit is to protect the battery by wrapping a protection circuit body 100 with an aluminum laminated film 200. The aluminum laminated film 200 has an inner layer 206 comprising a resin covering the protection circuit body 100 and having both water resistance and thermal plasticity, an intermediate layer 204 laminated on the inner layer and made of a conductive thin film, and an outer layer 202 laminated on the intermediate layer and made of a heat resistant insulating material. Furthermore, it is equipped with a power line 400 and a voltage measuring line 500 the respective one ends of which are connected to the protection circuit body 100 and the other ends of which are exposed to the outside of the aluminum laminated film 200, and the aluminum laminated film 200 covers a part of the power line 400 and the voltage measuring line 500 and all of the protection circuit body 100, and has a thermal welding part 208 sealed by thermal welding. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a battery protection circuit, and more particularly to a technique for protecting a circuit from static electricity and moisture from the outside by covering a protection circuit body with a package.

  Conventionally, lithium ion battery packs used in portable electronic devices and the like are equipped with some kind of protection circuit. The contents of protection of the protection circuit that is normally performed are mainly three items, that is, stop of charging at the time of overcharge, stop of discharge at the time of overdischarge, and stop of large current discharge such as external short circuit. The reason for installing the protection circuit is that the lithium battery has a risk of heat generation or explosion due to overcharge. In addition, overdischarge can cause deterioration of battery cells that cannot be recovered, resulting in a loss of battery function.

  When the voltage of the lithium ion battery cell is 0.6 V or less, the copper of the copper foil, which is the negative electrode coating substrate, becomes ions and elutes into the electrolyte, and the copper ions become copper during the next charge. To precipitate. The depositing place is not the original base material, but is deposited everywhere inside the cell. In particular, it has an influence on the capacity reduction because it is deposited on the positive electrode and the function of the positive electrode is reduced.

  Also, when copper ions are eluted in the electrolyte, iron is more likely to be ions than copper (the ionization tendency is greater), so copper precipitates as metal and iron becomes ions and dissolves in the electrolyte. There are things to do. This indicates that the iron in the iron can has melted and a hole has opened in the can. That is, when an overdischarge battery is left untreated, a hole is opened in an iron can battery, and the electrolyte solution may come out. When the electrolytic solution is electrically conductive and is charged while attached to the printed board, a charging current flows through the electrolytic solution, and the printed board may generate heat, emit smoke, or ignite.

  Therefore, the role of the protection circuit is very important, and the protection circuit board is usually installed on the side surface of the battery cell or the like.

  However, since the protection circuit is operated while consuming battery power, it is necessary to use a very high impedance circuit. This is because battery power consumption can be suppressed by increasing the impedance of the circuit. For this reason, there is a problem that it is easily affected by external noise and sometimes destroyed by static electricity, and there is a limit to increasing the impedance of the conventional battery protection circuit, that is, reducing the power consumption of the circuit.

  In order to solve this problem, a method of shielding noise with an exterior label has been proposed (see Patent Document 1). 4A and 4B are explanatory views of the battery pack and the exterior label in this embodiment. FIG. 4A is a plan view of the core pack, and FIG. 4B is a plan view of the exterior label. FIG. 5 is a diagram showing the configuration of the protection circuit of the battery pack, FIG. 5 (a) is a diagram showing a state before the exterior label is pasted, and FIG. 5 (b) is a diagram where the exterior label is pasted. It is a figure which shows a back state.

  As shown in FIG. 4A, the core pack used in this battery pack includes a square battery cell 15, a protection element 2, and a protection circuit board 4.

  As shown in FIG.4 (b), the exterior label 6 used for this battery pack is the magnitude | size which can cover both the planes of a core pack, and four side surfaces continuous with them, 0.05- The thickness is about 0.2 mm.

  The conductive pressure-sensitive adhesive 6a to be applied to a portion where the exterior label 6 is bonded to the core pack is formed by mixing a known organic or inorganic conductive compound with a known acrylic pressure-sensitive adhesive or rubber pressure-sensitive adhesive. Therefore, the surface electrical resistance value or the volume electrical resistance value is maintained within a range of 107Ω to 1010Ω depending on the amount of the conductive compound mixed.

 A battery pack is obtained by using the exterior label 6 and the conductive adhesive 6a having such a configuration, applying an adhesive to the adhesion portion of the exterior label, and attaching the adhesive to the core pack of FIG.

  Protection from external noise on the protection circuit board in this battery pack is performed as follows. As shown in FIG. 5A, the protection circuit in the battery pack includes a secondary battery 1 such as a lithium secondary battery, a temperature protection and a current interruption function, and a PTC element that interrupts the current when the temperature rises. , A protective element 2 such as a thermal fuse, a control IC 3 that protects overcurrent and overdischarge, a discharge control switch SW1 that turns on / off a discharge current that is a current in a specific direction, and a charge that turns on / off a charge current And a control switch SW2. The control IC 3 detects the battery cell voltage and the voltage between the control switch elements in order to protect overcharge and overdischarge, and turns on / off the discharge current switch SW1 and the charge control switch SW2 based on the detected voltage. Including a circuit to be controlled. In addition, it becomes such a structure also when a nonelectroconductive adhesive is apply | coated and used for an exterior label.

  When the exterior label is affixed to the core pack, as shown in FIG. 5B, the electric potential of the conductive adhesive on the surface of the battery cell and the exterior label becomes the same. Therefore, in the case of FIG. 5 (a), noise from the outside is caused to enter as indicated by the arrow 20, but in the case of FIG. 5 (b), the conductive adhesive of the exterior label is attached to the surface of the battery cell. , The protection circuit board can be shielded from noise from the outside.

By attaching an exterior label coated with a conductive adhesive in this way to the cell, the entire battery pack is shielded by the surface potential of the battery cell (a positive electrode for aluminum cans and a negative electrode for steel cans). The protection circuit of the battery pack can be protected from external noise and its malfunction can be prevented.
JP 2005-327593 A

  However, even in the case of the battery pack described above, there is a risk that an adverse effect such as a short circuit may be exerted on the protection circuit if the electrolyte solution leaks from the battery. In addition, simply attaching an exterior label may cause a problem that the impedance of the protection circuit is reduced by moisture from the outside.

  Therefore, the present invention protects the battery protection circuit from electrolytes due to external moisture and battery leakage, as well as external noise and static electricity, and is excellent in safety and has high impedance, that is, low power consumption. It is an object of the present invention to provide a possible battery protection circuit.

  In order to solve the above problems, the battery protection circuit according to the present invention is a battery protection circuit that protects a battery by packaging a protection circuit body in a packaging body, and the packaging body includes: An inner layer made of a resin that covers the protective circuit body and has both water resistance and thermoplasticity, an intermediate layer made of a conductive thin film laminated on the inner layer, and a heat-resistant insulator laminated on the intermediate layer And an outer layer.

  The invention according to claim 2 is characterized in that, in claim 1, the packaging body wraps only the protection circuit body, and spatially separates the battery and the protection circuit body.

  According to a third aspect of the present invention, in the first or second aspect, the signal processing device includes a signal line having one end connected to the protection circuit main body and the other end exposed to the outside of the packaging body. A heat welding means for covering a part of the protective circuit body and the whole of the protection circuit main body and sealing them by heat welding.

  According to a fourth aspect of the present invention, in any one of the first to third aspects, the package is an aluminum laminate film.

  The battery protection circuit according to the first invention has a three-layer structure of an outer layer made of a heat-resistant insulator, an intermediate layer made of a conductive thin film, and an inner layer made of a resin having both water resistance and thermoplasticity. Since the protection circuit body is packaged by the package, the protection circuit body can be protected from battery leakage, external moisture, static electricity, and the like.

  Specifically, by using a heat resistant insulator for the outer layer, the thermoplastic resin in the inner layer can be protected from heat. Moreover, since another electronic circuit etc. may be arrange | positioned around a battery protection circuit, a short circuit failure etc. can be prevented by using an insulator for an outer layer.

  By using a conductive thin film for the intermediate layer, static electricity and noise can be prevented from adversely affecting the battery protection circuit. Static electricity is charged in the intermediate layer, which is a conductor having a large area, and then dissipated. It does not affect the inner side of the inner layer.

  Further, by using a resin having both water resistance and thermoplasticity for the inner layer, it is possible to prevent the electrolytic solution due to battery leakage or moisture from penetrating into the protective circuit body. Thermoplasticity is a property that softens when heated and can be deformed or flowed by applying an external force, and becomes hard when the temperature is lowered. Using this property, it is possible to cover the battery protection circuit with a minimum area and no leakage.

  Furthermore, by integrating the function to protect against electrolytes and moisture due to liquid leakage and the function to protect against static electricity and noise into a single package in the form of a three-layer structure, the number of parts can be reduced to a simple structure. it can.

  In this way, by protecting the battery protection circuit from external moisture, battery leakage, and static electricity, the battery protection circuit is excellent in safety and can have high impedance, that is, low power consumption. Can be provided.

  According to the battery protection circuit of the second invention, since only the protection circuit main body is packaged in the packaging body and the battery and the protection circuit main body are spatially separated, even if there is a liquid leak from the battery, By the packaging body that does not pass through, it is possible to prevent the electrolyte from penetrating to the protective circuit body. If the electrolytic solution penetrates to the protection circuit body, it is expected that various problems such as a short circuit will occur. The present invention is to avoid such problems.

  According to the battery protection circuit of the third invention, since the entire protection circuit body is covered with the package and sealed by heat welding, the protection circuit body is more securely protected from the electrolyte due to moisture or battery leakage. can do. Therefore, it is possible to prevent impedance reduction due to moisture, short circuit due to the electrolyte, and the like, and to realize high impedance and low power consumption of the protection circuit.

  According to the battery protection circuit of the fourth invention, since the aluminum laminate film has an ideal three-layer structure, the protection circuit body can be protected from battery leakage, moisture, and static electricity. Specifically, a heat-resistant insulator such as PET (polyethylene terephthalate) or nylon is used for the outer layer of the aluminum laminate film, an aluminum foil that is a conductive thin film is used for the intermediate layer, and water resistance is used for the inner layer. Polyethylene having both properties and thermoplasticity is used. Moreover, since aluminum used for the intermediate layer does not transmit moisture at all, the protective circuit body can be more strongly protected from moisture and liquid leakage.

  Hereinafter, embodiments of the battery protection circuit of the present invention will be described in detail with reference to the drawings.

  1 is a cross-sectional view showing a configuration of a battery protection circuit according to Embodiment 1 of the present invention. The battery protection circuit includes a protection circuit body 100, an aluminum laminate film 200, and a heat welded portion 208. Here, the aluminum laminate film 200 corresponds to the packaging body of the present invention, and the thermal welding portion 208 corresponds to the thermal welding means of the present invention.

  In the first embodiment, the protection circuit body 100 includes the protection circuit board 108 and the circuit element 110, and the aluminum laminate film 200 has a three-layer structure including the outer layer 202, the intermediate layer 204, and the inner layer 206.

  The inner layer 206 covers the protection circuit main body 100 and is made of polyethylene. The material used here is not limited to polyethylene, but may be any resin having both water resistance and thermoplasticity. Examples include PP (polypropylene), HDPE (high density polyethylene), and LDPE (low density polyethylene). Can be mentioned.

  The intermediate layer 204 is laminated on the inner layer 206, and the material is aluminum foil. Here again, the material used is not limited to aluminum foil. Any conductive thin film that does not transmit moisture is ideal. Examples include stainless steel, iron, nickel and the like. Although copper can also be used, it is not practical because copper may be dissolved when a liquid leakage from the lithium ion battery actually occurs.

  The outer layer 202 is laminated on the intermediate layer 204, and the material is PET (polyethylene terephthalate). Here again, the material used is not limited to PET. Any heat-resistant insulator may be used, and ideally it does not transmit moisture. Examples include polystyrene, nylon, polycarbonate, triacetate and the like.

  The heat welding part 208 is, for example, a polyethylene welding tape. The power line 400 and the voltage measurement line 500 correspond to the signal line of the present invention, one end is connected to the protection circuit body 100 and the other end is exposed to the outside of the aluminum laminate film 200. The heat welding part 208 sandwiches the power line 400 and the voltage measurement line 500 and applies heat from the outside, and melts it together with the polyethylene film of the inner layer 206 for heat welding. Therefore, the aluminum laminate film 200 wraps and seals part of the signal lines such as the power line 400 and the voltage measurement line 500 and the entire protection circuit body 100. The relationship between the aluminum laminate film 200 and the protection circuit body 100 is shown in FIG. The battery protection circuit 50 according to the present invention includes a protection circuit body 100 and an aluminum laminate film 200 that wraps and seals the entire protection circuit body 100.

Here, the aluminum laminate film 200 wraps only the protection circuit main body 100 in a package, and spatially separates the battery and the protection circuit main body 100. By doing so, even if there is a liquid leak from the battery, the aluminum laminate film 200 can prevent the electrolytic solution from penetrating to the protection circuit body 100. If the electrolytic solution penetrates into the protection circuit main body 100, various malfunctions such as malfunctions and short circuits are expected to occur. The present invention is for avoiding such problems. Next, protection from external noise, static electricity, moisture, liquid leakage and the like for the protection circuit body in the battery protection circuit of the present invention will be described. FIG. 3 is a circuit configuration diagram when the battery protection circuit according to the first embodiment is used in a lithium ion battery. The protection circuit main body 100 includes a battery measurement circuit 102, a switch control circuit 104, and a switch 106. The power line 400 is connected to the lithium ion battery 300 via the switch 106 inside the protection circuit body 100.

  The voltage measurement circuit 102 measures and monitors the voltage of the lithium ion battery 300 via the voltage measurement line 500. The switch control circuit 104 receives the voltage measurement result of the lithium ion battery 300 from the voltage measurement circuit 102, and performs on / off control of the switch 106 based on the received information. This control prevents an excessive voltage from being applied to the lithium ion battery 300 or a voltage lower than the minimum battery voltage of the lithium ion battery 300.

  The protective circuit body 100 is entirely packaged with the aluminum laminate film 200 as described above, and is thermally welded and sealed with a polyethylene welding tape. Therefore, even if the lithium ion battery 300 leaks, the aluminum foil of the intermediate layer 204 and the polyethylene of the inner layer 206 can prevent the electrolyte from penetrating and prevent the protection circuit body from being short-circuited or reduced in impedance.

  Further, since the aluminum foil of the intermediate layer 204 is a conductor having a large area, noise and static electricity from the outside can be prevented, and malfunction and destruction of the circuit can be prevented.

  As described above, according to the battery protection circuit of Example 1 of the present invention, the outer layer 202 made of PET, which is a heat resistant insulator, the intermediate layer 204 made of aluminum foil, which is a conductive thin film, and the water resistance. The aluminum laminate film 200 having a three-layer structure of an inner layer 206 made of polyethylene, which is a resin having both thermoplasticity and plasticity, wraps only the protective circuit body 100 and is spatially separated from the lithium ion battery 300. It can protect against battery leakage, external moisture, static electricity, etc.

  Specifically, by using PET for the outer layer 202, the polyethylene of the inner layer 206 can be protected from heat. In addition, since another electronic circuit or the like may be disposed around the battery protection circuit, a short circuit failure or the like can be prevented by using PET which is an insulator for the outer layer 202.

  By using an aluminum foil for the intermediate layer 204, static electricity and noise can be prevented from adversely affecting the battery protection circuit. Static electricity is charged to aluminum foil, which is a conductor with a large area, and then dissipated. There is no influence on the inner side of the inner layer 206. Moreover, since aluminum foil does not permeate | transmit a water | moisture content, it also has the role which prevents the electrolyte solution by moisture and a liquid leak osmose | permeate.

  In addition, by using polyethylene for the inner layer 206, it is possible to prevent the electrolytic solution or moisture due to battery leakage from penetrating into the protective circuit body. Moreover, since polyethylene is thermoplastic, it can be coated with a minimum area and no leakage so as to fit the battery protection circuit.

  Furthermore, by integrating the function to protect from electrolyte and moisture due to liquid leakage and the function to protect against static electricity and noise into the aluminum laminate film 200 in the form of a three-layer structure, the number of parts is reduced and the structure is simplified. be able to.

  Further, by using the aluminum laminate film having the above structure, there is an advantage that it is not necessary to develop only for carrying out the present invention, and it can be obtained and used.

  In this way, by protecting the battery protection circuit from external moisture, battery leakage, and static electricity, the battery protection circuit is excellent in safety and can have high impedance, that is, low power consumption. Can be provided.

  In addition, the heat welding portion 208, which is a polyethylene welding tape, covers the entire protection circuit main body 100 with the aluminum laminate film 200 and seals it by heat welding, so that the protection circuit main body is more strongly protected from the electrolyte due to moisture or battery leakage. Can be protected. Therefore, it is possible to prevent impedance reduction due to moisture, short circuit due to the electrolyte, and the like, and to realize high impedance and low power consumption of the protection circuit.

  The present invention can be applied to a protection circuit that protects a secondary battery used in a portable electronic device or the like.

It is sectional drawing which shows the internal structure of the battery protection circuit which concerns on Example 1 of this invention. It is a figure which shows the relationship between the protection circuit main body of the battery protection circuit which concerns on Example 1 of this invention, and an aluminum laminate film. It is a circuit block diagram at the time of using the battery protection circuit which concerns on Example 1 of this invention for a lithium ion battery. It is explanatory drawing of the core pack and exterior label which are used for the conventional battery pack. It is a block diagram of the protection circuit of the conventional battery pack.

Explanation of symbols

1 Secondary battery 2 Protection element 3 Control IC
4 Protection Circuit Board 5a Positive Electrode 5b Negative Electrode 6 Exterior Label 6a (Conductive) Adhesive 10 Core Pack 15 Battery Cell 20, 30 Arrow 50 (Indicates Noise Propagation Direction) Battery Protection Circuit 100 Protection Circuit Body 102 Voltage Measurement Circuit 104 Switch Control Circuit 106 Switch 108 Protection circuit board 110 Circuit element 200 Aluminum laminate film 202 Outer layer 204 Intermediate layer 206 Inner layer 208 Thermal welding part 210 Protection circuit body 300 Lithium ion battery 400 Power line 500 Voltage measurement line

Claims (4)

A battery protection circuit for protecting a battery by wrapping a protection circuit body in a package,
The package includes an inner layer made of a resin that covers the protective circuit body and has both water resistance and thermoplasticity, an intermediate layer made of a conductive thin film laminated on the inner layer, and a heat resistant material laminated on the intermediate layer. A battery protection circuit comprising an outer layer made of an insulating material.   2. The battery protection circuit according to claim 1, wherein the packaging body wraps only the protection circuit main body and spatially separates the battery and the protection circuit main body. One end is connected to the protection circuit body and the other end is provided with a signal line exposed to the outside of the package,
3. The battery protection circuit according to claim 1, wherein the package includes a heat welding means that covers a part of the signal line and the whole of the protection circuit main body and seals by heat welding. 4. . The battery protection circuit according to claim 1, wherein the package is an aluminum laminate film.

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