JP2001325929A - Protector for battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a resistor for current detecting circuit from emitting smoke and enable miniaturizing a battery pack by mounting on a device for breaking circuit, one of the protection circuits for the battery pack, a resistor for current detecting circuit, whose abnormal heating can also fuse and break a fuse element of the device. SOLUTION: On a board I, there are provided a heater element 1 which is conducted with electricity to heat in abnormal circumferences as one of the circuit parts P contained in a battery pack, for a protection circuit against overcharge and over discharge, a resistor for a current detecting circuit as a part of the protection circuit, and fuse elements 31, 32 which are broken by an abnormal heating of either the resistor or the heater element 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a battery protector used as one circuit component of a battery pack.

[0002]

2. Description of the Related Art In a secondary battery, for example, a lithium ion secondary battery, a battery is usually housed in a pack together with a protection circuit for protecting it from overcharge and overdischarge, and ± terminals are pulled out for charging and discharging. Has this terminal connected to a load or charger. As one circuit component of such an overcharge / overdischarge protection circuit, a heat-generating element 1 ′, which is energized and generates heat in the event of an abnormality, indicated by P ′ in FIG.
Fuse elements 31 ', 3 which are blown by the heat generated by the current flowing through them.
2. Description of the Related Art A shutoff circuit device in which 2 'is provided on a substrate and sealed with a resin or the like is known.

FIG. 9 shows an example of an overcharge / overdischarge protection circuit using the above-mentioned device for a cutoff circuit, and shows a switching circuit S '(for example, an overcurrent formed in a direction in which a parasitic diode cuts off a charging current). An N-channel M including an FET for preventing charging, an FET for preventing overdischarge formed in a direction in which a parasitic diode blocks a discharge current, and the like.
OSFET) and a main control circuit C1 'for detecting an abnormality during charging / discharging and operating the switching circuit S'.
A current detection circuit A ′ for detecting a circuit current, a cutoff circuit P ′ including the above device, and a main control circuit C1 ′.
Detects an abnormality and issues an operation command to the switching circuit S ', but an auxiliary control circuit C2 for activating the cutoff circuit P' when the current detection circuit A 'detects the non-operation of the switching circuit S'. And a shut-off circuit device P 'is used as a backup when the switching circuit does not operate at the time of abnormality. FIG.
In E, E 'indicates a secondary battery and B' indicates a battery pack. A charger is connected between the ± terminals when charging the battery, and a load is connected between the ± terminals when using battery discharging.

[0004]

The current detection circuit A '
Is configured to shunt a circuit current to the shunt resistor 2 'and detect the voltage between both ends of the shunt resistor using an operational amplifier or the like. In FIG. 9, if the. +-. Terminal is temporarily short-circuited, the shunt resistor 2 'may emit smoke due to overcurrent. To eliminate this danger, the current fuse is used. Is incorporated. However,
In this configuration, an increase in the size of the battery pack is inevitable.
There is an inconvenience that an impulsive sound is generated when the current fuse is shut off, and the current fuse is unsuitable as a power supply for portable equipment.

SUMMARY OF THE INVENTION It is an object of the present invention to mount a resistor for a current detection circuit on a device for a shut-off circuit, which is a circuit component of a protection circuit for a battery pack, and to blow the fuse element of the device even if the resistor generates abnormal heat. By doing so, it is possible to prevent the current detection circuit resistor from emitting smoke and to reduce the size of the battery pack.

[0006]

A battery protector according to the present invention is a circuit component of an overcharge / overdischarge protection circuit housed in a battery pack, and includes a heat-generating element which is energized and generates heat when an abnormality occurs. A resistor for a current detection circuit as a part of a protection circuit, and a fuse element which is blown by any abnormal heating of the resistor and the heating element. The overcharge / overdischarge protection circuit includes, for example, a switching circuit, a main control circuit for detecting an abnormality during charging / discharging and operating the switching circuit, and a current detection circuit for detecting a circuit current. The switching circuit does not operate even though the resistor, the breaking circuit, and the main control circuit detect an abnormality, and the breaking circuit is operated when the current detection circuit detects the malfunction of the switching circuit. A circuit which includes an auxiliary control circuit, the first circuit component is a assembly of a shut-off circuit and the current detection circuit resistance.

In the above, the heat-generating element and the current detecting circuit resistor are disposed with an insulating film interposed therebetween, or the fuse element is disposed on one side of the insulating substrate. A heater element and a resistor for a current detection circuit are disposed on the other side of the fuse element so as to overlap with the fuse element, and further, immediately after the fuse element is blown, the charging energy of the battery is reduced.
Can be disposed on the substrate, and can be sealed with at least one of a resin and a case.

[0008]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows an example of a circuit in a battery pack incorporating one embodiment of a battery protector according to the present invention. In FIG. 1, E is a secondary battery,
An example is a lithium ion secondary battery. B indicates a battery pack, and a charger is connected between terminals when charging the battery, and a load is connected between terminals when discharging the battery. S is a switching circuit, for example, an overcharge preventing FET formed in a direction in which a parasitic diode blocks a charging current and an overdischarge preventing FET formed in a direction in which a parasitic diode blocks a discharging current. N-channel MOSFE
T can be used. C1 is a main control circuit for detecting the abnormality at the time of abnormality during charging / discharging and operating the switching circuit S. P is the battery protector according to the present invention.
FIG. 1 shows an embodiment of a heating resistor 1 that generates heat by energization.
A shunt resistor 2 for a current detection circuit, fuse elements 31 and 32 which are blown by any abnormal heat generation of the shunt resistor 2 and the heating resistor 1, and a discharge resistor 4 on a common substrate. It is mounted on. A is an operational amplifier for transmitting a voltage between both ends of the shunt resistor 2 to the main control circuit C1, and the operational amplifier A and the shunt resistor 2 constitute a current detection circuit. C2 is an auxiliary control circuit,
Even when the main control circuit C1 detects a charge / discharge abnormality and issues an operation command to the switching circuit S, when the current detection circuit A detects that the circuit is energized, the transistor Tr
Is turned on, and by the conduction of the transistor Tr, the heating resistor 1 is energized and heated by the energy of the battery E, so that the fuse elements 31 and 32 are blown.

The discharge resistor 4 is a battery protector.
When the fuse elements 31 and 32 are blown, the charge energy stored in the secondary battery E is discharged. After the battery protector is activated, the battery pack is quickly lowered. ０0 stored energy state, and safe disposal of the battery pack can be guaranteed.

The resistance value R1 of the heating resistor 1 and the resistance value R4 of the discharging resistor are, for example, R1 = 40Ω and R4 = 100.
As shown in FIG. 2, the discharge resistor 4 is connected in parallel to the half part 31 of the fuse element, and
Can be inserted in series.

In FIG. 1, when a charge / discharge abnormality is detected by the main control circuit C1, a command for operating the switching circuit S is issued, and when the switching circuit S operates normally, the current flowing through the shunt resistor 2 is reduced. Becomes zero, and the voltage across the shunt resistor becomes zero through the operational amplifier A.
Is transmitted to Accordingly, the auxiliary control circuit C2 does not operate, and the battery protector P does not operate. On the other hand, when the switching circuit S does not operate normally and the current flowing through the shunt resistor 2 does not become a predetermined switching current and the voltage across the shunt resistor is transmitted to the main control circuit C1 via the operational amplifier A, the auxiliary control is performed. By the operation of the circuit C2, the transistor Tr is turned on, the heating element 1 of the battery protector P is energized and heated, and the generated heat fuses the fuse elements 31 and 32 to charge the secondary battery E. Completely disconnected from the machine or load. Immediately after the fuse elements 31 and 32 of the battery protector P are blown, the charging energy stored in the secondary battery E is discharged via the discharging resistor 4, and in this case, the battery voltage V Is given by (e ^{−t / cR 4} ) where the capacitance of the battery E is c, and the resistance R4 of the discharging resistor 4 is compared with the resistance R1 of the heating resistor 1. , R1 <R4 (R4 / R1>
1.1, preferably R4 / R1 = 5 to 40, more preferably 10 to 30), the battery can be discharged sufficiently quickly, and the battery pack can be discarded with confidence.

[0012] In FIG 1, if the resistance value of the shunt resistor 2 and R _2, when between ± terminals are short-circuited, Ju shunt resistance of V ² / R ₂ - is generating Le heat, this Ju Since the fuse elements 31 and 32 of the battery protector P are blown sufficiently quickly even by the Joule heat generated by the shunt resistor 2, even if the terminals are short-circuited, the shunt can be performed. The smoke of the resistor 2 can be prevented, and safety can be ensured.

In the above description, a low-melting-point fusible alloy having a melting point of 100.degree. C. to 150.degree. C. is used for the fuse elements 31 and 32. Since the alloy is easily oxidized, a flux is applied to prevent the oxidation. As described later, it is effective to seal the element with a resin, a double-sided adhesive tape, a case, a protective plate, or the like, and to shield the element from external oxygen.

FIG. 3A shows a protector according to the present invention.
FIG. 3B is a cross-sectional view showing one embodiment, and FIG. 3B is a plan view before sealing. In FIG. 3, I is an insulating substrate having heat resistance and good thermal conductivity. Reference numerals 51 to 55 denote membrane electrodes provided on the substrate I, and reference numerals 31 and 32 denote one low-melting-point fusible alloy piece as a fuse element, which is joined to the membrane electrodes 51-52-53 by welding or the like. . Reference numeral 6 denotes a flux applied to the low-melting-point fusible alloy pieces 31 and 32. For example, a flux mainly composed of rosin can be used. 1 is a membrane electrode 5
This is a heat-generating film resistor provided between 2-54. Reference numeral 2 denotes a shunt film resistor for a current detection circuit provided between the film electrodes 53 and 55. a to d are lead conductors joined to the membrane electrodes 51 and 53 to 55 by welding or the like. 4 is a membrane electrode 51-54
This is a discharge film resistor provided between the two. The arrangement pattern of the film resistors 4 and the film resistors 1 and 2 and the fuse elements 31 and 32 is configured according to the connection shown in FIG. In FIG. 3, 61 is a case having a lead wire insertion groove,
The resin 7 is sealed between the case 61 and the substrate 4 and between the case 61 and the lead wires a to c. Reference numeral 8 denotes a protective film (for example, protection for preventing cracking of the film resistor) provided on each of the above-mentioned film resistors 1, 2, 4 and, for example, a glass baking film can be used. This protective film is usually provided before the trimming of the film resistor, but may be provided after the trimming.

The insulating substrate I includes an inorganic substrate such as a ceramic substrate (for example, an alumina substrate or an aluminum nitride substrate) or a glass substrate, a ceramic coated metal plate, a ceramic impregnated glass fiber substrate, an epoxy resin impregnated glass fiber substrate, or paper. A phenol substrate or the like can be used. The membrane electrode can be formed by printing and baking a conductive paste.
As the conductive paste, a material obtained by adding an organic binder (vehicle) to a metal powder, glass, and a metal mixture can be used. For example, a silver-based paste of Ag, Ag-Pd, Ag-Pt, a gold-based paste of Au, and a nickel-based paste of Ni are used as the metal powder.
And copper-based paste of Cu. Instead of printing and printing the conductive paste, it is also possible to use a plating method or an etching method for a metal layer of a metal layer laminate insulating plate. The film resistors 1, 2 and 4 can be formed by printing and baking a resistor paste, and a resistor paste made of a metal oxide powder, a mixture of glass and metal and an organic binder (vehicle) can be used. For example, a ruthenium system using ruthenium oxide as the metal oxide powder can be used. In addition, Ag-P
d, silver-based paste adjusted to a predetermined specific resistance value by adjusting the blending of Ag-Pt, etc., carbon-based paste using carbon as resistance powder, resin-based resin mixed with metal powder, etc. can also be used. .

When a film resistor is used for the heat-generating resistor 1 and the shunt resistor 2, the heat-generating resistor 1 and the current detecting circuit resistor 2 are arranged via an insulating film with the fuse elements 31, 32 interposed therebetween. Thus, the heat transfer resistance from each film resistor to the fuse element can be reduced, and the discharge resistor can be quickly blown by the heat generated by each film resistor.

A chip resistor can be used for the heating resistor 1, the shunt resistor 2, and the discharging resistor 4. As the discharge resistor 4, an appropriate resistor can be used as long as it satisfies the above-mentioned resistance value condition with respect to the heat-generating resistor 1. A high-resistance circuit element, for example, a light emitting diode
It is also possible to use a semiconductor such as a semiconductor.

The lead wires a to d prevent the transmission of heat to the fuse element when soldering the nickel wire and the lead wire, which are easy to weld, to the circuit board, in addition to the copper wire. For example, a low heat conductive wire, such as an iron wire or a copper-plated iron wire, can be used. Also, these leads are used to facilitate soldering.
The lead wire may be plated with a metal such as tin, solder, silver, gold or lead / cadmium free. As the case 61, a resin case, for example, a case made of nylon or phenol, an insulating coated metal case, or the like can be used. It is also possible to use a metal case and insulate the case from the lead wire with an insulator, for example, to apply an epoxy resin paint to the lead wire side. The case 61 may be filled with a sealing agent, for example, an epoxy resin, but it is sufficient that the flux 6 applied to the low melting point fusible alloy pieces 31, 32 can be prevented from coming into contact with the outside. The case 61 and the substrate I may be simply fixed with a resin or a double-sided adhesive tape. A pin is integrally formed on the inner surface of the case, and a pin insertion hole is provided in the substrate.
It is also possible to fix the substrate to the substrate by a pin fitting method. The sealing of one surface of the substrate may be performed as long as the fuse-coated fuse element can be shielded from the outside air and can be mechanically protected. As shown in FIG.
A structure in which a plate 62 is disposed, and the periphery of the protection plate 62 and one surface of the substrate or an electrode on one surface thereof is sealed with a resin 7 (a gap may be left immediately below the protection plate, or (It may be filled with a resin). Further, the protective plate may be covered with the resin, or the protective plate may be sealed with a resin or a double-sided adhesive tape alone. The above protection plate includes:
An inorganic plastic plate such as an engineering plastic sheet, a metal plate (for example, a stainless steel plate), and a ceramic plate can be used. As the resin, a thermosetting resin such as an epoxy resin, an ultraviolet curable resin, or a thermo-plastic resin or the like can be used.

The battery protector according to the present invention is mounted on a circuit board of a predetermined conductor pattern together with the main control circuit, switching circuit, operational amplifier for current detection circuit, auxiliary control circuit and transistor, The circuit plate and the secondary battery are used by being housed in a pack. Any of the lead wires a to d of the battery protector may be provided on the circuit board side, and some of the lead wires may be omitted as in the battery protector shown in FIG.

FIG. 6 shows a battery protector according to the present invention.
As shown in FIG. 7, a chip method can be used. In this case, the electrodes can be exposed on the back surface of the substrate by a through-hole. Although not shown in FIGS. 6 and 7, a pin is integrally formed on the inner surface of the case, a pin insertion hole is provided in the substrate, and the case is fixed to the substrate by a pin fitting method. H indicates a pin insertion hole of the substrate.

FIG. 8A is a drawing showing another embodiment of the chip system. FIG. 8B is a plan view of the same embodiment before sealing, and FIG. Each shows a bottom view of the example. In FIG. 8, I is an insulating substrate having heat resistance and good thermal conductivity. 51 to 55 are membrane electrodes provided on one side of the substrate I, 56 to 60 are membrane electrodes provided on the other side of the substrate I,
Some of the membrane electrodes are formed on both surfaces of the insulating substrate I. 31, 32 are film electrodes 51-52- on one surface of the insulating substrate.
A low-melting-point fusible alloy piece provided over 53, 1 denotes a heat-generating film resistor provided on the other surface of the insulating substrate I, and 4 denotes a shunt film resistor.
The low melting point fusible alloy pieces 31 and 32 and the heat generating film resistor 1
The discharge film resistor 4 and the shunt film resistor 2 are connected in accordance with the wiring pattern shown in FIG. Reference numeral 6 denotes a flux applied to the low melting point fusible alloy pieces 21 and 22. Reference numeral 600 denotes a sealing material for the flux-applied low-melting-point fusible alloy piece, similar to the above, for the case 61 and the resin 7 or the double-sided adhesive tape for sealing between the case 61 and the substrate I; Or a resin that covers the case and the case and seals between the case and the substrate, a protective plate and a resin that seals between the protective plate and the flux-coated fuse element, Alternatively, the protective plate may be made of a resin which covers the protective plate and seals between the protective plate and the flux-coated fuse element, or only a resin or a double-sided adhesive tape. Reference numeral 8 denotes a protective film, for example, a glass baking film, which covers the heat-generating film resistor 1, the shunt film resistor 2, and the discharge film resistor 4 collectively.

[0022]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A battery protector having the structure shown in FIG. A conductive paste is formed by printing and baking, the film resistance is provided by printing and baking of a ruthenium oxide-based resistance paste, the resistance of the heating resistor is trimmed to 40Ω, and the resistance of the shrinking resistor is trimmed. The resistance value of the discharge resistor was adjusted to 1000 Ω by trimming, and a glass-based protective film was formed on each film resistor by printing.
Further, a cross section of 0.5 mm × 0.3 at a solidus temperature of 110 ° C.
mm fuse element, a rosin-based flux is applied dropwise to the fuse element, a tin-plated iron wire is used for a lead wire, and a nylon case is used for sealing. The insulating substrate was bonded with an epoxy adhesive. 6. One of the two battery protectors manufactured in this manner was used.
When a 2V overcharged battery was connected, the fuse element was blown out 20 seconds after the connection. The surface temperature of the battery protector at this time was about 120 ° C., but the discharge was completed in 240 minutes, and the surface temperature of the fuse with the resistor at that time was almost normal temperature. In addition, a short circuit is made between the lead lines (between the lead lines b and d in FIG. 3) of another battery protector, and the other lead line (between the lead line a in FIG. 3). -C
When a 7.2V overcharged battery was connected during the period, the fuse element was blown within one second after the connection.

[0023]

When the battery protector according to the present invention is used as a circuit component in a battery pack used in a portable device, for example, a notebook computer, a short circuit occurs between ± terminals connected to a charger or a load side. Even if an overcurrent flows through the shunt resistor, it is possible to prevent the shunt resistor from emitting smoke by blowing the fuse element of the battery protector, thereby ensuring safety.
Further, since a function for preventing overcurrent smoke from the shunt resistor is incorporated in the battery protector, there is no need to provide a separate current fuse or the like, so that the size of the battery pack can be reduced. In addition, the battery protector fuse
The battery pack that has become unusable due to the operation of the storage element can be removed from the device after quickly discharging the storage energies of the battery from the device, so that the battery pack can be discarded or left safely.

[Brief description of the drawings]

FIG. 1 is a drawing showing a protection circuit incorporating a battery protector according to the present invention.

FIG. 2 is a drawing showing a circuit of another example of the battery protector according to the present invention.

FIG. 3 is a view showing an embodiment of a battery protector according to the present invention.

FIG. 4 is a view showing a main part of another embodiment of the battery protector according to the present invention, which is different from the above.

FIG. 5 is a view showing a main part of another embodiment of the battery protector according to the present invention, which is different from the above.

FIG. 6 is a drawing showing a main part of another embodiment of the battery protector according to the present invention, which is different from the above.

FIG. 7 is a view showing a main part of another embodiment of the battery protector according to the present invention, which is different from the above.

FIG. 8 is a view showing another embodiment of the battery protector according to the present invention.

FIG. 9 is a drawing showing a protection circuit incorporating a conventional battery protector.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Heat generation element 2 Current detection circuit resistance 31 Fuse element 32 Fuse element 4 Discharge resistance I substrate 6 Flux 61 Case 62 Plate 7 Resin

Claims (7)

[Claims] An overcharge / overdischarge protection circuit housed in a battery pack, which is a circuit component, generates heat when a circuit abnormality occurs, and a current detection circuit resistor as a part of the protection circuit. And a fuse element which is blown by any abnormal heat generation of the resistor and the heat-generating element on a substrate. 2. An overcharge / overdischarge protection circuit comprising: a switching circuit; a main control circuit for detecting an abnormality during charging / discharging to activate the switching circuit; and a resistor for a current detection circuit for detecting a circuit current. An interrupting circuit; and an auxiliary control circuit for shutting off the interrupting circuit when the current detecting circuit detects the malfunction of the switching circuit without operating the switching circuit even though the main control circuit detects an abnormality. The protector for a battery according to claim 1, wherein the circuit comprises: a circuit component comprising an assembly of a resistor and a cutoff circuit for a current detection circuit. 3. A heating element and a resistor for a current detection circuit are disposed on both sides of the fuse element with an insulating film interposed therebetween.
Or the battery protector according to 2. 4. A fuse element is provided on one side of an insulating substrate, and a heating element and a current detecting circuit resistor are disposed on the other side of the substrate so as to overlap with the fuse element. The battery protector according to claim 1, wherein the battery protector is provided. 5. The battery protector according to claim 1, wherein a discharge resistor for discharging charging energy of the battery is disposed on the substrate immediately after the fuse element is blown. 6. The battery protector according to claim 1, which is sealed with a sealing material. 7. The battery protector according to claim 6, wherein the sealing material is at least one of a resin, a double-sided adhesive tape, a plate, and a case.