TW202042426A - Battery pack and protective circuit - Google Patents

Abstract

The present invention provides a battery pack using a protection element capable of blocking a current path without malfunctioning even when exposed to a high-temperature environment. This battery pack comprises a battery cell 15a, a protection element 11 connected in series with the battery cell 15a, and a heat sensitive element 12 that controls the operation of the protection element 11. The protection element 11 is provided with an insulating substrate 26, a first terminal part 22 and a second terminal part 23 that are provided away from the insulating substrate 26 and connected to a charging/discharging path of the battery cell 15a, a fuse element 20 provided to extend from the first terminal part 22 to the second terminal part 23, and a heating resistor 24 connected in series with the heat sensitive element 12, and when the heat sensitive element 12 is heated to a temperature higher than or equal to a predetermined temperature, is energized such that the heating resistor 24 generates heat to a temperature at which the fuse element 20 is blown.

Description

Battery pack, protection circuit

The present invention relates to a battery pack and a protection circuit provided with a protection element for fusing a fuse element arranged on a charging and discharging current path to block the charging and discharging current path.

In recent years, lithium ion secondary batteries have been used in many applications ranging from home appliances such as mobile phones and notebook personal computers to electric tools and electric vehicles. Although the lithium ion secondary battery is a battery with a high energy density and is suitable for high output, in the case of an excessive current output, the battery itself generates heat due to the internal resistance of the battery itself, which may cause smoke and fire. Therefore, in order to ensure the safety of users and electronic equipment, generally speaking, by building a number of protection circuits such as overcharge protection and overdischarge protection in the battery pack, or the PTC (Positive Temperature Coefficient, positive temperature coefficient) element It is connected in series to the charging and discharging current path, and has the function of blocking the input and output of the battery pack under certain circumstances.

However, since the element resistance of the PTC increases according to temperature and the current is limited by the resistance, the DC resistance of the circuit increases due to the connection of the PTC, which is not suitable for the purpose of energizing large currents. In addition, since the protection method using the protection circuit mainly uses the FET to control the energization current, the DC resistance value can be suppressed to be low, but the semiconductor may cause malfunction due to the high temperature environment.

In addition, the industry has proposed a method of connecting a fuse element to the charging and discharging circuit of the battery cell in a battery system such as a lithium-ion secondary battery, and breaking the charging and discharging circuit by blowing the fuse with the heat of a heating resistor body . For example, the protection circuit 100 shown in FIG. 8 includes: FET 102, which switches the energization to the heating resistor 101; battery stack 103, which has battery cells connected in series and/or parallel; and a control IC 104, which monitors the battery stack 103 When the battery stack 103 is abnormal, it outputs a control signal to the FET 102; and a fuse 105, which is connected to the charge and discharge path of the battery stack 103.

The protection circuit 100 regulates the energization to the heating resistor 101 by the FET 102 when there is no abnormality in the battery stack 103. In addition, the protection circuit 100 energizes the heating resistor 101 through the FET 102 when the control IC 104 detects abnormalities such as overcharge or overdischarge of the battery stack 103. Thereby, the protection circuit 100 blows the fuse 105 by heating the heating resistor 101, thereby blocking the charging and discharging path of the battery stack 103. [Prior Technical Literature] [Patent Literature]

[Patent Document 1] JP 2006-109596 A

[The problem to be solved by the invention]

However, in the protection circuit 100, in order to control the energization of the heating resistor 101, it is necessary to control the control IC 104 of the FET 102 and the FET 102, which leads to an increase in the number of parts and an increase in assembly man-hours, and if exposed to a high temperature environment If the situation causes the control IC 104 to malfunction, the fuse 105 may not be blown.

The present invention was proposed in view of the previous actual situation, and its purpose is to provide a battery pack and a protection circuit using a protection element that can interrupt the current path without malfunction even when exposed to a high temperature environment. [Technical means to solve the problem]

In order to solve the above-mentioned problems, the battery pack of the present invention has: a battery cell; a protection element connected in series with the battery cell; and a thermosensitive element that controls the operation of the protection element; and the protection element includes: an insulating substrate; 1 terminal portion and second terminal portion, which are separately provided on the insulating substrate and connected to the charging and discharging path of the battery cell; a fuse element, which is provided between the first terminal portion and the second terminal portion ; And a heating resistor, which is connected in series with the thermal element, and the energization is controlled; and if the thermal element is heated to a temperature higher than a specific temperature, the heating resistor generates heat to the fuse element The way of temperature is energized.

In addition, the protection circuit of the present invention has: first and second electrodes, which are connected to an external circuit; a fuse, which extends between the first and second electrodes and is connected in series on the current path; and a heating resistor, which borrows The fuse is blown by energization; and a thermal element, which controls the energization of the heating resistor; and if the thermal element is heated to a temperature above a specific temperature, the heating resistor will generate heat until the fuse is blown The way of temperature is energized. [Effects of Invention]

According to the present invention, the protection element is activated by the thermal element, thereby reliably blocking the charging and discharging current path of the battery cell even when exposed to a high temperature environment without the risk of malfunction.

Hereinafter, the battery pack and the protection circuit to which the present invention is applied will be described in detail with reference to the drawings. In addition, the present invention is not limited to the following embodiments, and it goes without saying that various modifications can be made without departing from the gist of the present invention. In addition, the drawings are schematic drawings, and the ratio of each size may be different from the actual size ratio. The specific dimensions should be judged by referring to the following description. Moreover, there is no doubt that there are also parts with different dimensions or ratios between the schemas.

[Battery] The battery pack to which the present invention is applied can be configured as a battery pack 1 of, for example, a lithium ion secondary battery as shown in FIG. 1. The battery pack 10 shown in FIG. 1 has, for example, a battery stack 15 that includes a plurality of battery cells 15a of lithium ion secondary batteries; a protection element 11 that is connected in series with the battery stack 15; and a thermal element 12 that controls and protects Movement of element 11.

The protection element 11 blocks the charging and discharging path of the battery stack 15 when the battery pack 10 is abnormal. Electrical characteristics such as conduction, turn-off, resistance value, and output voltage of the thermal element 12 vary according to heat. If it is heated to a temperature above a specific temperature, the protection element 11 is activated. That is, the battery pack 10 controls the operation of the protection element 11 in accordance with the change in the electrical characteristics of the thermal element 1.

The battery stack 15 is formed by connecting battery cells 15a in series and/or parallel that need to be used for protection from overvoltage or overcurrent, etc., and is detachable via the positive terminal 10a and the negative terminal 10b of the battery pack 10 The ground is connected to the charging device 13 and the charging voltage from the charging device 13 is applied. The battery pack 10 charged by the charging device 13 can be operated by connecting the positive terminal 10a and the negative terminal 10b to an electronic device operated by a battery.

In addition, the battery pack 10 has a charge and discharge control circuit 16 that controls the charge and discharge of the battery stack 15. The charge and discharge control circuit 16 includes: two current control elements 17, 18 connected in series to the current path flowing from the battery stack 15 to the charging device 13; and a control unit 19 that controls one of the current control elements 17, 18 action. The current control elements 17 and 18 are composed of, for example, field-effect transistors (hereinafter referred to as FETs). By using the control unit 19 to control the gate voltage, the current path of the battery stack 15 is controlled to conduct in the charging direction and/or the discharging direction. Occlude. The control unit 19 receives the power supply from the charging device 13 and operates, and in accordance with the detection result of the detection circuit not shown in the figure that detects the voltage of each battery cell 15a, it interrupts the current when the battery stack 15 is overdischarged or overcharged The way of the path controls the action of the current control elements 17, 18.

[Protection component] The protection element 11 is, for example, connected to the charge and discharge current path between the battery stack 15 and the charge and discharge control circuit 16, and its action is controlled by the thermal element 12. Specifically, the protection element 11 as shown in FIG. 2(A)(B) includes an insulating substrate 26; first and second electrodes 22, 23, etc. formed on the insulating substrate 26; and a heating resistor 24, which Formed on the surface of the insulating substrate 26; the insulating layer 27 covering the heating resistor 24; the heating body lead electrode 21, which is laminated on the insulating layer 27 and connected to the heating resistor 24; and the fuse element 20, which extends over the first electrode 22. The heating element extraction electrode 21 and the second electrode 23 are mounted via the solder 28 for connection.

The first and second electrodes 22, 23 are connected to the first and second terminal portions on the charging and discharging path of the battery cell 15a, and the first and second external connection electrodes 22a, 23a are respectively formed on the back surface of the insulating substrate 26 through The fort shape is connected. In addition, the heating resistor 24 is connected to the heating body feeding electrode 25 and is connected to the thermosensitive element 12 via the heating body feeding electrode 25. In addition, the heating resistor 24 is electrically connected to the fuse element 20 through the heating element lead electrode 21, and is connected to the fuse element 20 and the charging and discharging path of the battery stack 15.

[Insulating substrate] The insulating substrate 26 is made of, for example, an insulating member such as alumina, glass ceramics, mullite, or zirconia, and is formed in, for example, a substantially rectangular shape. In addition to the insulating substrate 26, materials used for printed wiring substrates such as glass epoxy substrates and phenol substrates can also be used.

The first and second electrodes 22 and 23 are formed at opposite ends of the insulating substrate 26. The first and second electrodes 22 and 23 are respectively formed of conductive patterns such as Ag or Cu. In addition, the first and second electrodes 22 and 23 are connected to the first and second external connection electrodes 22a and 23a formed on the back surface 26b from the surface 26a of the insulating substrate 26 via semicircular holes. The protection element 11 integrates the fuse element 20 by connecting the first and second external connection electrodes 22a, 23a formed on the back side 26b of the insulating substrate 26 to the connection electrodes of the external circuit board on which the protection element 11 is mounted. A part of the current path formed on the circuit board.

[Heating resistor] The heating resistor 24 is a conductive member that has a relatively high resistance value and generates heat when energized, and is made of, for example, nickel, W, Mo, Ru, etc. or materials containing them. The heating resistor 24 can be formed into a paste by mixing the alloy, composition, powder of the compound with a resin binder, etc., and then patterning the paste on the insulating substrate 26 using screen printing technology and firing it And so on.

The heating resistor 24 is thermally connected by overlapping the fuse element 20, and melts the fuse element 20 when it generates heat due to energization. The heating resistor 24 is connected to the thermosensitive element 12 through one end, and current and heating are always regulated. In addition, the heating resistor 24 increases the current due to the energization caused by the thermistor 12 and the decrease in resistance value, and the heat generation increases, so that the fuse element 20 can be blown. In addition, as described later, the heating resistor 24 and the fuse element 20 are also electrically connected.

[Fuse element] The protective element 11 is connected to the fuse element 20 from the first electrode 22 to the second electrode 23 by the solder 28 for connection. The fuse element 20 conducts between the first and second electrodes 22 and 23 during normal use, and constitutes a part of the current path of the external circuit in which the protection element 11 is incorporated. Moreover, the fuse element 20 is fused by self-heating (Joule heat) due to the current exceeding the rated value, or is fused by the heat of the heating resistor 24, thereby shielding the gap between the first and second electrodes 22, 23 Off.

The fuse element 20 has a specific rated current value, and is quickly fused by self-heating when the heating resistor 24 heats or the current exceeds the rated current value. The fuse element 20 preferably contains any one selected from nickel, tin, and lead as a main component. In addition, in this specification, the main component refers to a component that is 50 wt% or more based on the total mass of the material.

In addition, the fuse element 20 may have a laminated structure in which a low melting point metal layer 41 and a high melting point metal layer 42 are laminated. As the low melting point metal, it is preferable to use a solder without Pb solder or the like, and as the high melting point metal, it is preferable to use Ag, Cu, or an alloy containing these as main components. By containing high melting point metal and low melting point metal, in the case of reflow installation of the protection element 11, even if the reflow temperature exceeds the melting temperature of the low melting point metal layer, the low melting point metal will melt, and the fuse element 20 will not be fused.

As shown in FIG. 3, the fuse element 20 may use a low melting point metal for the inner layer and a high melting point metal for the outer layer. By using the outer layer of high melting point metal layer 42 to cover the entire surface of the low melting point metal layer 41 of the inner layer of the soluble conductor, and in the case of using a low melting point metal whose melting point is lower than the reflow temperature, during reflow installation At this time, the low melting point metal in the inner layer can be prevented from flowing out to the outside. In addition, the same is true during fusing. The low-melting-point metal in the inner layer melts, and the high-melting-point metal in the outer layer can be eroded (eroded by the solder) and quickly melted.

[Cover member] In addition, the protective element 11 has a cover member 34 that protects the inside and prevents scattering of the molten fuse element 20 on the surface 26 a of the insulating substrate 26 on which the fuse element 20 is provided. The cover member 34 can be formed of various engineering plastics, ceramics, and other insulating members. The cover member 34 is connected to the surface 26 a of the insulating substrate 26 with an insulating adhesive or the like, thereby covering the fuse element 20.

[Thermal element] The thermal element 12 can be used as an electronic component whose electrical characteristics are temperature-dependent. For example, as shown in FIG. 4, a thermostat that opens and closes the circuit according to the surrounding temperature change can be used. The thermal element 3 is thermally connected by being arranged close to or in contact with the battery stack 15, and becomes hot due to abnormal heat generation of the battery stack 15. As a result, electrical characteristics such as the resistance value and output voltage of the thermal element 12 change.

Taking the case of using a thermostat 12a as the thermal element 12 as an example for description, the thermostat 12a is mounted on an insulating substrate not shown, and as shown in FIG. 4(A), one end is connected to the open end of the battery stack 15 , The other end is connected to the heating resistor 24 of the protection element 11. The thermostat 12a always opens the energization path from the battery stack 15 to the heating resistor 24.

In addition, when the battery pack 10 is heated due to abnormal heat generation of the battery stack 15 and the like, the thermostat 12a is displaced so that the energization path from the battery stack 15 to the heating resistor 24 is a closed circuit. The electric power of the battery stack 15 which is sufficient to melt the fuse element 20 is energized to the heating resistor 24.

As the thermal element 12, in addition to the thermostat 12a, as shown in FIG. 5, a negative characteristic thermal resistor 12b (NTC thermal resistor, CTR thermal resistor) whose resistance value decreases as the surrounding temperature rises can be used. In addition, as the thermal element 12, a diode 12c whose voltage changes when the temperature exceeds the threshold value as shown in FIG. 6 can be used. In addition, as the thermosensitive element 12, a Peltier element, a thermocouple, a bimetal, a temperature sensor, and the like can be cited.

In addition, the thermosensitive element 12 is thermally connected by being arranged close to or in contact with the exterior of the battery cell 15a. Or, the thermal element 12 may be arranged in contact with the exterior of the battery pack 10. In addition, a sheet-like or paste-like heat-conducting material can be interposed between the thermal element 12 and the exterior of the battery cell 15a or the exterior of the battery pack 10. In addition, the battery pack 10 may be provided with one heat-sensitive element 12 for the battery stack 15, or may be provided with a heat-sensitive element 12 for each battery cell 15a. Alternatively, one thermal element 12 may be provided for a plurality of battery cells 15a.

[protect the circuit] The protection element 11 has a circuit configuration as shown in FIGS. 1 and 4(A). That is, the protection element 11 includes a circuit configuration of the following parts: the fuse element 20, which is connected in series across the first and second electrodes 22, 23; and the heating resistor 24, which is connected by the fuse element 20 The point is energized and generates heat, and the fuse element 20 is blown. In addition, the protection element 11 forms an energization path to the heat-sensitive element 12 (thermostat 12a), the heating element feeding electrode 25, the heating resistor 24, and the fuse element 20 to the heating resistor 24, and the heat-sensitive element 12 to control the energization of the heating resistor.

In addition, in the protection element 11 shown in FIG. 1, the first electrode 22 is connected to one open end side of the battery stack 15 via the first external connection electrode 22a, and the second electrode 23 is connected to the battery pack 10 via the second external connection electrode 23a. By this, the fuse element 20 is connected in series to the charging and discharging current path of the battery pack 10 via the first and second external connection electrodes 22a, 23a.

The heating element feeding electrode 25 of the protection element 11 is connected to an open end of the battery stack 15 for energizing the heating resistor 24, and the energization to the heating resistor 24 is regulated by the thermistor 12 (thermostat 12a). Therefore, the fuse element 20 will not be fused due to the heat of the heating resistor 24, and the charge and discharge current path of the battery pack 10 can be energized.

Moreover, when the battery pack 10 needs to interrupt the current path of the battery pack 10 due to abnormal heating caused by the overvoltage of the battery cell 15a or abnormal overheating of the surrounding temperature caused by fire, etc., the thermal element 12 (constant temperature The device 12a) will be heated, and when it exceeds a certain threshold, the energizing path to the heating resistor 24 will be closed. Thereby, electricity is supplied to the heating resistor 24 from the battery stack 15. Therefore, the heating resistor 24 of the protection element 11 heats up to a high temperature, and the fuse element 20 integrated into the current path of the battery pack 10 is melted. When the molten conductor of the fuse element 20 draws the electrode 21 and the first and second electrodes 22 and 23 toward the heating element with high wettability, the fuse element 20 is blown. Therefore, the battery pack 10 melts between the first electrode 22-the heating element extraction electrode 21-the second electrode 23 (FIG. 4(B) ), and the current path of the battery stack 15 can be blocked.

The battery pack 10 can block the charge and discharge current path of the battery stack 15 by using the thermal element 12 to activate the protection element. Therefore, without relying on the switching action of the current control elements 17 and 18 and the control IC for controlling the protection element, the charging and discharging current path of the battery stack 15 can be blocked without the risk of malfunction even when exposed to a high temperature environment.

The protection element 11 is connected to the heating resistor 24 by the fuse element 20 to form a part of the energization path to the heating resistor 24. Therefore, when the protection element 11 melts the fuse element 20, the connection with the external circuit is interrupted, and the energization path to the heating resistor 24 is also interrupted, so that heat generation can be stopped.

[Switch circuit] In addition, as shown in FIG. 7, in addition to the thermal element 12, the battery pack 10 can also be configured to detect the overall voltage of the battery stack 15 and/or the abnormal voltage of each battery cell 15a, and activate the protection element 11 by switching operations. The switch circuit 50. The switch circuit 50 has a protection IC 51 that monitors the voltage of the entire battery stack 15 and/or the voltage of each battery cell 15 a, and a switch S 52 that is operated by the protection IC 51.

The switch S 52 is, for example, an FET, which is connected to the thermal element 12 (the thermal resistor 12b in FIG. 7) by being connected to an open end of the battery stack 15 or the battery cell 15a and connected to the heating resistor 24 of the protection element 11 )in parallel. In addition, the switch S 52 is switched and controlled to the on state and the off state by the protection IC 51.

The protection IC 51 is connected to, for example, the two open ends of the battery stack 15 or each battery cell 15a, and constantly monitors the voltage of the entire battery stack 15 and/or the voltage of each battery cell 15a, and switches the switch S 52 to conduct when the voltage is abnormal. The heating resistor 24 is energized. Specifically, the protection IC 51 detects whether it is an overvoltage based on the voltage across the battery stack 15 and/or the battery cell 15a. For example, the protection IC 51 detects that the voltage of the battery stack 15 or the battery cell 15a is an overvoltage when the battery cell voltage exceeds a preset specific threshold during charging. When the protection IC 51 detects an overvoltage, it controls the switch S 52 to set the self-conduction state to the off state. Thereby, the fuse element 20 is blown by the action of the protection element 11, and the charging and discharging current path of the battery stack 15 can be blocked.

[other] In addition, although in the above-mentioned protection circuit, the thermosensitive element 12 is arranged in parallel with the charging and discharging path of the battery stack 15, it is feasible that the thermosensitive element 12 is arranged on a path that is electrically independent of the charging and discharging path of the battery stack 15. , Power is supplied from a separately set power source. In addition, the battery pack of the present invention is not limited to the case of the battery pack 10 used for lithium ion secondary batteries, and it is undoubtedly applicable to various applications that require blocking of current paths when abnormal overheating occurs.

10: battery pack 10a: Positive terminal 10b: negative terminal 11: Protection element 12: Thermal element 12a: Thermostat 12b: Negative characteristic thermal resistor / thermal resistor 12c: Diode 13: Charging device 15: battery stacking 15a: battery unit 16: charge and discharge control circuit 17: Current control element 18: Current control element 19: Control Department 20: Fuse element 21: The heating element leads the electrode 22: 1st terminal part / 1st electrode 22a: The first external connection electrode 23: 2nd terminal part / 2nd electrode 23a: 2nd external connection electrode 24: Heating resistor 25: Heating body feed electrode 26: Insulating substrate 26a: surface 26b: back 27: Insulation layer 28: Solder for connection 34: cover member 41: low melting point metal layer 42: high melting point metal layer 50: switch circuit 51: Protection IC 52: Switch S 100: Protection circuit 101: resistor body 102: FET 103: battery stack 104: Control IC 105: Fuse

Fig. 1 is a circuit diagram showing a configuration example of a battery pack to which the present invention is applied. Fig. 2 is a diagram showing the protection element; (A) is a plan view showing the cover member omitted; (B) is a cross-sectional view of X-X'. Fig. 3 is a perspective view showing an example of the fuse element. Figure 4 is a circuit diagram of a battery pack using a thermostat as a heat-sensitive element; (A) shows the thermostat before being heated; (B) shows the state where the thermostat is heated and the fuse element is blown. Figure 5 is a circuit diagram of a battery pack using a thermal resistor as a thermal element. Figure 6 is a circuit diagram of a battery pack that uses a diode as a thermal element. Figure 7 is a circuit diagram of a battery pack equipped with a protection IC and a switch to detect abnormal voltages of the battery stack or battery cells in addition to the thermal element. Figure 8 is a diagram showing the circuit configuration of the previous battery pack.

10: battery pack

10a: Positive terminal

10b: negative terminal

11: Protection element

12: Thermal element

12a: Thermostat

13: Charging device

15: battery stacking

16: charge and discharge control circuit

17: Current control element

18: Current control element

19: Control Department

20: Fuse element

21: The heating element leads the electrode

22: 1st terminal part / 1st electrode

23: 2nd terminal part / 2nd electrode

24: Heating resistor

25: Heating body feed electrode

Claims (8)

A battery pack, which includes: Battery unit A protection element, which is connected in series with the above-mentioned battery cell; and Thermal element, which controls the action of the above-mentioned protective element; and The above protection components include: Insulating substrate The first terminal portion and the second terminal portion are separately provided on the insulating substrate and connected to the charging and discharging path of the battery cell; A fuse element, which is provided across the space between the first terminal portion and the second terminal portion; A heating resistor, which is connected in series with the above-mentioned thermal element, and the energization is controlled; and If the heat-sensitive element is heated to a temperature higher than a specific temperature, the heating resistor body will be energized in such a way that it generates heat to a temperature at which the fuse element is melted. Such as the battery pack of claim 1, wherein the thermal element is any one of a thermostat, a thermal resistor, or a diode. The battery pack of claim 1 or 2, wherein the thermal element is arranged close to or in contact with the battery cell, and is thermally connected to the battery cell. The battery pack according to any one of claims 1 to 3, wherein the heating resistor and the thermal element are connected in parallel with the charging and discharging path of the battery unit. A protection circuit, which includes: The first and second electrodes, which are connected to an external circuit; A fuse, which spans between the above-mentioned first and second electrodes and is arranged in series on the current path; A heating resistor, which blows the above-mentioned fuse by energizing; and Thermistor, which controls the energization of the heating resistor; and If the heat-sensitive element is heated to a temperature higher than a specific temperature, the heating resistor body will be energized in such a way that it generates heat to the temperature at which the fuse is blown. Such as the protection circuit of claim 5, wherein the thermal element is connected to the open end of the external circuit. Such as the protection circuit of claim 5 or 6, wherein the thermal element is any one of a thermostat, a thermal resistor, or a diode. The protection circuit according to any one of claims 5 to 7, wherein the heating resistor and the thermal element are connected in parallel with the charging and discharging path of the battery unit.

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