TWI653654B - Switching circuit - Google Patents

Abstract

The present invention interrupts a short-circuited current path and opens a short-circuit of a current path in a predetermined sequence, and irreversibly switches the current path. The second heating element 11 is connected to a switching element 26 that passes current to the second heating element 11, and connects the open end of the first heating element 2 and the connection end 16 of the second heating element 11 and the open-side fusible conductor 12 The second heating element 11 is energized and heated by the operation of the switching element 26, and the open-side fusible conductor 12 is fused, thereby blocking the main circuit and the second external circuit 24. 1 The heating element 2 is energized and generates heat, and the short-circuit-side fusible conductor 3 is fused, thereby short-circuiting the switch 4 and energizing the main circuit and the first external circuit 23.

Description

Switching circuit

The invention relates to a switching circuit for switching a current path.

Most rechargeable and reusable secondary batteries are processed into battery packs and provided to users. Especially in lithium ion secondary batteries with high weight and energy density, in order to ensure the safety of users and electronic equipment, generally, several protection circuits such as overcharge protection and overdischarge protection are built into the battery pack. In the case of blocking the output of the battery pack.

Among such protection elements, there are the following: a field-effect transistor (FET) switch built into the battery pack is used to turn on / off the output, thereby performing battery pack Charge protection or over-discharge protection works. However, when the FET switch is short-circuited and broken for some reason, when a large current flows momentarily by applying a lightning surge or the like, or due to the life of the battery cell, the output voltage In the case of an abnormal drop or an abnormally large abnormal voltage, the battery pack or electronic device needs to be protected from accidents such as fire. Therefore, in order to safely block the output of the battery cell under any conceivable abnormal state, a fuse element including a fuse element is used. A protection element having a function of blocking a current path by a signal from the outside.

As a protective element for a protective circuit such as a lithium ion secondary battery, there is a protective element described in Patent Document 1 that is fusible across a first electrode, a heater lead-out electrode, and a second electrode in a current path. The conductor also serves as a part of the current path, and the fusible conductor on the current path is blown by self-heating of the overcurrent or a heating element provided inside the protection element. In such a protection element, a molten liquid-like fusible conductor is concentrated on a conductor layer connected to a heating element, thereby blocking a current path.

[Prior technical literature]

[Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open No. 2010-003665

[Patent Document 2] Japanese Patent Laid-Open No. 2004-185960

[Patent Document 3] Japanese Patent Laid-Open No. 2012-003878

However, even if the charge / discharge current circuit of an abnormal lithium ion secondary battery is blocked, a large amount of energy equivalent to the capacity of the battery is stored in the battery cell. Risk of thermal accident caused by leakage current of the unit. Therefore, it is preferable to discharge the internal battery cells until the battery voltage drops to a safe voltage after stopping using the battery pack.

Thus, for example, in a battery pack of a lithium ion secondary battery, it is required to have the following The element, that is, the current path of the battery cell can be surely switched from the charge / discharge path in the normal state to the discharge path in the abnormal state.

Therefore, an object of the present invention is to provide a switching circuit that blocks a short-circuited current path in a normal order in accordance with a predetermined sequence, short-circuits a current path used in an abnormal state, and irreversibly switches the current path.

In order to solve the problem, the switching circuit of the present invention includes a short-circuit circuit and an open circuit. The short-circuit circuit includes a first heating element that generates heat by passing a current. One end is connected to the first heating element, and the other end is connected to the first heating element. The short-circuit-side fusible conductor connected to the main circuit, and a switch connected to the short-circuit-side fusible conductor at one end and connected to the main circuit, and connected to the first external circuit at the other end, by the first heating element. The short circuit-side fusible conductor is fused by heat, and the switch is short-circuited by the short-circuit-side fusible conductor. The open circuit includes a second heating element that generates heat by passing a current, and the second heating element is connected to the first heating element. 2 The open-side fusible conductor connected to the second heating element and having one end connected to the second external circuit and the other end connected to the main circuit. The open-side fusible conductor is fused by the heat generated by the second heating element. A switch element is connected to one end of the second heating element, and the switching element receives a switching signal to cause a current to be passed from the main circuit to the second heating element, and the current of the first heating element of the short circuit is The discharge end is connected to the connection end of the second heating element of the open circuit and the open-side fusible conductor, and the second heating element of the open circuit is energized and generates heat by operating the switching element. , The open-side fusible conductor is blown, thereby blocking the main circuit and the second external circuit. The fusible conductor on the release side is fused, and the first heating element of the short circuit is energized and generates heat, and the fusible conductor on the short circuit side is melted, thereby short-circuiting the switch, and causing the main circuit to disconnect from the first circuit. 1 The external circuit is energized.

Moreover, the switching circuit of the present invention includes a short circuit and an open circuit, the short circuit includes a first heating element that generates heat by passing a current, one end of which is connected to the first heating element, and the other end of which The short-circuit-side fusible conductor, and a switch connected to the short-circuit-side fusible conductor at one end and connected to the main circuit, and connected to the first external circuit at the other end, cause the heat generated by the first heating element to cause the The short-circuit-side fusible conductor is blown, and the switch is short-circuited by the short-circuit-side fusible conductor. The open circuit includes a second heating element that generates heat by passing a current, and is connected to the second heating element. And one end is connected to the second external circuit and the other end is connected to the open-side fusible conductor, and the open-side fusible conductor is fused by the heat generated by the second heating element, and the first A first switching element is connected to one end of the heating element, and the first switching element receives a switching signal to energize current from the main circuit to the first heating element, and a second terminal is connected to one end of the second heating element. Switching element The second switching element receives a switching signal to energize current from the main circuit to the second heating element, and the second switching element operates while the second heating element of the open circuit is energized. When the heat is generated, the open-side fusible conductor is blown, thereby blocking the main circuit and the second external circuit, and operated by the first switching element, and the first heating element of the short circuit is energized, Heat is generated, and the short-circuit-side fusible conductor is melted, thereby short-circuiting the switch, and energizing the main circuit and the first external circuit.

Furthermore, the switching circuit of the present invention includes a short-circuit portion and an open portion. The short-circuit portion includes a first heating element that generates heat by passing a current, one end of which is connected to the first heating element, and the other end of which is connected to a first external circuit. The connected short-circuit-side fusible conductor, and a switch connected to the short-circuit-side fusible conductor at one end and connected to the first external circuit, and connected to the main circuit at the other end, are caused by heat from the first heating element. The short-circuit-side fusible conductor is blown, and the switch is short-circuited by the short-circuit-side fusible conductor. The open portion includes: a second heating element that generates heat by passing a current, and the second heating element An open-side fusible conductor which is connected to a body and has one end connected to the other end of the switch and the main circuit, and the other end connected to a second external circuit; The fuse conductor is blown, and the first heating element is connected to the first switching element. The first switching element receives a switching signal and causes a current to flow from the main circuit to the first heating element. The second heating element is connected to the first heating element. 2nd switching element connection The second switching element receives a switching signal to energize current from the main circuit to the second heating element. The second switching element operates and the second heating element in the open portion is energized and generates heat. The open-side fusible conductor is blown, thereby blocking the main circuit and the second external circuit, and operated by the first switching element, and the first heating element of the short-circuit portion is energized and generates heat, The short-circuit-side fusible conductor is melted, short-circuiting the switch, and energizing the main circuit and the first external circuit.

According to the present invention, by operating the switching element, the current path from the main circuit to the second external circuit can be blocked, and the electricity reaching the first external circuit can be constructed. Flow path, and the current path of the main circuit can be switched from the second external circuit to the first external circuit. In this case, according to the present invention, it is possible to irreversibly block and short-circuit the current path by melting the first open-side fusible conductor.

1‧‧‧short circuit

2‧‧‧The first heating element

3‧‧‧ Short-circuit side fusible conductor

4‧‧‧ switch

5‧‧‧The first electrode

6‧‧‧Second electrode

7‧‧‧The first heating element electrode

10‧‧‧ open circuit

11‧‧‧The second heating element

12‧‧‧ open side fusible conductor

12a‧‧‧The first open side fusible conductor

12b‧‧‧ 2nd open side fusible conductor

13‧‧‧3rd electrode

14‧‧‧ 4th electrode

15‧‧‧Second heating element electrode

16‧‧‧Connection terminal electrode

21‧‧‧short-circuit element

22‧‧‧ open element

23‧‧‧The first external circuit

24‧‧‧ 2nd external circuit

25‧‧‧Power circuit

26‧‧‧ Switching element

30‧‧‧The first switching circuit

31‧‧‧Protection resistor

32‧‧‧discharge circuit

33‧‧‧Charge and discharge current circuit

40‧‧‧ battery pack

40a‧‧‧Positive terminal

40b‧‧‧ negative terminal

41 ~ 44‧‧‧ battery unit

45‧‧‧ Battery Stack

46‧‧‧Detection circuit

50‧‧‧Charge and discharge control circuit

51, 52‧‧‧Current control element

55‧‧‧Charging circuit

60‧‧‧The second switching circuit

61‧‧‧The first switching element

62‧‧‧The second switching element

70‧‧‧3rd switching circuit

71‧‧‧short circuit

72‧‧‧ Open Department

1 (A) and 1 (B) are circuit diagrams of a short-circuit circuit constituting a switching circuit. FIG. 1 (A) shows a short circuit before, and FIG. 1 (B) shows a short circuit.

2 (A) and 2 (B) are circuit diagrams of an open circuit constituting a switching circuit. FIG. 2 (A) shows before opening, and FIG. 2 (B) shows after opening.

FIG. 3 is a block diagram showing a configuration of a first switching circuit.

4 (A) and 4 (B) are circuit diagrams showing a first switching circuit before switching. FIG. 4 (A) shows an example having two open-side fusible conductors, and FIG. 4 (B) shows having one open circuit. Example of a side fusible conductor.

FIG. 5 is a circuit diagram showing a first switching circuit in which a second heating element is energized by a switching element.

FIG. 6 is a circuit diagram showing a first switching circuit that energizes a first heating element.

FIG. 7 is a circuit diagram showing a first switching circuit after switching.

FIG. 8 is a circuit diagram of a battery pack to which a first switching circuit is applied.

FIG. 9 is a circuit diagram showing a modification of the first switching circuit.

FIG. 10 is a circuit diagram of a battery pack to which a first switching circuit of a modified example is applied.

FIG. 11 is a block diagram showing a configuration of a second switching circuit.

12 (A) and 12 (B) are circuit diagrams showing a second switching circuit, and FIG. 12 (A) shows an example provided with two open-side fusible conductors, and FIG. 12 (B) shows an example provided with one open-side fusible conductor.

FIG. 13 is a circuit diagram of a battery pack to which a second switching circuit is applied.

FIG. 14 is a circuit diagram showing a modification of the second switching circuit.

15 is a circuit diagram of a battery pack to which a second switching circuit of a modified example is applied.

16 (A) and 16 (B) are circuit diagrams showing a third switching circuit. FIG. 16 (A) shows an example having two open-side fusible conductors, and FIG. 16 (B) shows one having an open-side fusible conductor. Examples of conductors.

FIG. 17 is a circuit diagram of a battery pack to which a third switching circuit is applied.

FIG. 18 is a circuit diagram showing a modification of the third switching circuit.

19 is a circuit diagram of a battery pack to which a third switching circuit according to a modification is applied.

Hereinafter, the switching circuit to which the present invention is applied will be described in detail with reference to the drawings. The present invention is not limited to the following embodiments, and various changes can be made without departing from the scope of the present invention. In addition, the drawings are schematic, and the ratios of dimensions and the like may be different from actual situations. Specific dimensions and the like should be determined with reference to the following description. It is a matter of course that the drawings include portions having different dimensional relationships or ratios.

The switching circuit to which the present invention is applied includes a short-circuit circuit or a short-circuit portion that fuses a fusible conductor and connects electrodes that are open to each other through the fused conductor; and an open circuit or an open portion that melts the fusible conductor. The electrodes that are short-circuited by the fusible conductor are blocked. First, for short circuits and open circuits Explains how it works.

As shown in FIG. 1 (A), the short-circuit circuit 1 includes: a first heating element 2; a short-circuit-side fusible conductor 3 connected in series with the first heating element 2 and fused by the heat generated by the first heating element 2; The first electrode 5 and the second electrode 6 are open to each other, and the short-circuit-side fusible conductor 3 is melted to generate a short circuit through the molten conductor and constitute the switch 4. The first electrode 5 is connected to a power source (not shown), and the second electrode 6 is connected to an external circuit connected when the switch 4 is turned on. The first heating element 2 is connected to a switching element such as an FET (not shown) via the first heating element electrode 7 and controls the current supply.

When the short-circuit circuit 1 is operated by a switching element, and the first heating element 2 is supplied with power through the first electrode 5 and the short-circuit-side fusible conductor 3, as shown in FIG. 1 (B), the first heating element 2 generates heat. The short-circuit-side fusible conductor 3 is blown. Therefore, in the short-circuit circuit 1, the molten conductor of the short-side-side fusible conductor 3 condenses across the first electrode 5 and the second electrode 6, and the first electrode 5 and the second electrode 6 are short-circuited. Thereby, the switch 4 of the short circuit 1 is turned on, and the power source and an external circuit are energized.

As shown in FIG. 2 (A), the open circuit 10 includes: a second heating element 11; an open-side fusible conductor 12 that is fused by the heat generated by the second heating element 11; The third electrode 13 and the fourth electrode 14. The third electrode 13 and the fourth electrode 14 are provided on a current path, and the second heating element 11 is connected to a switching element such as a FET (not shown) via the second heating element electrode 15 and controls the current supply.

When the open circuit 10 is operated by a switching element and power is supplied to the second heating element 11 through the third electrode 13 and the open-side fusible conductor 12, as shown in FIG. 2 (B), The open-side fusible conductor 12 is blown by the heat generated by the second heating element 11. Thereby, the open circuit 10 can block the current path.

[First switching circuit]

As shown in FIG. 3, the first switching circuit 30 includes a short-circuiting element 21 constituting the short-circuiting circuit 1 and connected to the power supply circuit 25 serving as the main circuit and the first external circuit 23 which is energized after switching; and the opening element 22 constitutes an opening The circuit 10 is connected to a power supply circuit 25 and a second external circuit 24 that is energized before switching. The first switching circuit 30 supplies power to the second heating element 11 via a switching element 26 that receives a switching signal. As a result, the second heating element 11 generates heat and blocks the space between the third electrode 13 and the fourth electrode 14, the first heating element 2 generates heat, and the first electrode 5 and the second electrode 6 are short-circuited. Thereby, the first switching circuit 30 can switch the current path of the power supply circuit 25 from the second external circuit 24 to the first external circuit 23.

Specifically, the first switching circuit 30 has a circuit configuration shown in FIGS. 4 (A) and 4 (B). The short-circuit circuit 1 includes: a first heating element 2 that generates heat by passing a current; a short-circuit-side fusible conductor 3 having one end connected to the first heating element 2 and the other end connected to the power circuit 25; The side fusible conductor 3 is connected and connected to the power supply circuit 25, and the other end is connected to the first external circuit 23.

The switch 4 is connected to the power supply circuit 25 via the first electrode 5, and is connected to the first external circuit 23 via the second electrode 6. The first heating element 2 is connected to the connection terminal electrode 16 of the open circuit 10 via the first heating element electrode 7.

The open circuit 10 includes a second heating element 11 that generates heat when a current flows, and an open-side fusible conductor 12 connected to the second heating element 11 and One end is connected to the power supply circuit 25 and the other end is connected to the second external circuit 24. In the first switching circuit 30 shown in FIG. 4 (A), the open-side fusible conductor 12 includes a first open-side fusible conductor 12a, one end of which is connected to the power supply circuit 25 via the third electrode 13, and the other end The second heat-generating body 11 is connected to the second open-side fusible conductor 12b. One end is connected to the second external circuit 24 via the fourth electrode 14, and the other end is connected to the second heat-generating body 11.

In addition, as shown in FIG. 4 (B), the open circuit 10 may include only the first open-side fusible conductor 12a. In this case, one end of the first open-side fusible conductor 12a is connected to the power supply circuit 25 via the third electrode 13, the other end is connected to the second heating element 11, and is connected to the second external circuit 24 via the fourth electrode 14. .

In addition, the first switching circuit 30 is connected to a switching element 26 at one end of the second heating element 11 via the second heating element electrode 15. The switching element 26 receives a switching signal and causes a current to flow from the power supply circuit 25 to the second heating element 11. power ups. Further, the first switching circuit 30 connects the first heating element electrode 7 of the short circuit 1 and the connection terminal electrode 16 which is connected to the second heating element 11 and the open-side fusible conductor 12 of the open circuit 10. .

The switching element 26 includes, for example, a field effect transistor (FET), and controls the conduction and blocking of the current path to the second heating element 11 by controlling the gate voltage.

[Operation of the first switching circuit]

In the initial state, as shown in FIGS. 4A and 4B, the first switching circuit 30 having such a configuration is a current path from the power supply circuit 25 to the second external circuit 24 via the open circuit 10. At this time, the first switching circuit 30 uses a switching element 26, the power supply to the second heating element 11 is restricted, and the two ends of the first heating element 2 have substantially the same potential, so that a current hardly flows to the short-circuit circuit 1.

When it is necessary to switch the current path of the power supply circuit 25 from the second external circuit 24 to the first external circuit 23, a switching signal is output to the switching element 26. When the switching element 26 receives the switching signal, it controls the current so as to supply power to the second heating element 11. As a result, as shown in FIG. 5, the first switching circuit 30 causes the second heating element 11 of the open circuit 10 to be energized and generates heat, and the open-side fusible conductor 12 is blown. Therefore, a current path from the power supply circuit 25 to the second external circuit 24 is blocked.

Then, as shown in FIG. 6, the current from the power supply circuit 25 flows into the short-circuit circuit 1 side through the first electrode 5, and flows to the open circuit through the short-circuit-side fusible conductor 3, the first heating element 2, and the first heating element electrode 7. 10 and the switching element 26 side, thereby, in the first switching circuit 30, the first heating element 2 of the short circuit 1 is energized and generates heat. As shown in FIG. 7, the short-circuit-side fusible conductor 3 is fused, and the fused conductor On the other hand, the first electrode 5 and the second electrode 6 are short-circuited, that is, the switch 4 is turned on, thereby constructing a current path from the power supply circuit 25 to the first external circuit 23.

In addition, the second heating element 11 interrupts the power supply path by melting both the open-side fusible conductor 12 and the short-circuit-side fusible conductor 3, so that the heat generation stops. In addition, the first heating element 2 blocks the power supply path when the short-circuit-side fusible conductor 3 is blown, and thus the heat generation stops.

In this way, according to the first switching circuit 30, by operating the switching element 26, the current path to the second external circuit 24 via the third electrode 13 and the fourth electrode 14 can be blocked, and the power source circuit 25 can be constructed through the first Electrode 5, switch 4, second The electrode 6 reaches the current path of the first external circuit 23, and the current path of the power supply circuit 25 is switched from the second external circuit 24 to the first external circuit 23.

In addition, according to the first switching circuit 30, the open-side fusible conductor 12 and the short-circuit fusible conductor 3 are melted to irreversibly block between the third electrode 13 and the fourth electrode 14, and the first electrode 5, Short circuit between the second electrodes 6. Therefore, compared with the case of electronically switching by software or the like, it is possible to improve a switching failure caused by a malfunction, and it is possible to improve a weakness for an unauthorized switching caused by cracking or the like.

[Example of mounting the first switching circuit]

As shown in FIG. 8, such a first switching circuit 30 is used in a circuit incorporated in a battery pack 40 of a lithium ion secondary battery, for example. The battery pack 40 includes, for example, a battery stack 45 including battery cells 41 to 44 of a total of four lithium ion secondary batteries.

The battery pack 40 includes: a battery stack 45; a charge and discharge control circuit 50 that controls the charge and discharge of the battery stack 45; a short-circuit element 21 and an open element 22, which are configured to block charging and cause the The first switching circuit 30 to which the present invention is applied; the detection circuit 46 detects the voltage of each of the battery cells 41 to 44; and the switching element 26 detects the first switching circuit 30 based on the detection result of the detection circuit 46. Control of the operation.

The battery stack 45 is connected in series with a battery cell 41 to a battery cell 44. The battery cell 41 to the battery cell 44 need to be controlled to protect it from being overcharged and overdischarged. The battery stack 45 passes the positive terminal of the battery pack 40 40a, The negative terminal 40b is detachably connected to the charging circuit 55, and a charging voltage from the charging circuit 55 is applied. The battery pack 40 charged by the charging circuit 55 connects the positive terminal 40 a and the negative terminal 40 b to an electronic device that operates using a battery, thereby enabling the electronic device to operate.

The charge / discharge control circuit 50 controls the operation of two current control elements 51 and 52 connected in series to a current path, and the current path runs from the battery stack 45 to the charging circuit 55. The current control element 51 and the current control element 52 include, for example, a field effect transistor (hereinafter referred to as a FET), and the gate voltage is controlled by the charge and discharge control circuit 50, thereby controlling the conduction and blocking of the current path of the battery stack 45 . The charge and discharge control circuit 50 operates by receiving power supply from the charging circuit 55. When the battery stack 45 is overdischarged or overcharged according to the detection result of the detection circuit 46, the current control element 51, The operation of the current control element 52 is controlled.

The short-circuit element 21 is connected in parallel with the battery stack 45 and is connected in series with a protection resistor 31 for discharging the electric energy accumulated in the battery stack 45 to below the upper limit discharge current of the battery cells 41 to 44. Thereby, the first switching circuit 30 constitutes a discharge circuit 32 provided with a short-circuit element 21 and a protection resistor 31.

The open element 22 is connected to the charge / discharge current circuit 33 between the battery stack 45 and the charging circuit 55, and its operation is controlled by the switching element 26.

The detection circuit 46 is connected to each of the battery cells 41 to 44 and detects the voltage value of each of the battery cells 41 to 44 to supply each voltage value. To the charge and discharge control circuit 50. The detection circuit 46 outputs a control signal for controlling the switching element 26 when any one of the battery cells 41 to 44 is at an overcharge voltage.

The switching element 26 includes, for example, a FET. When the voltage value of the battery cells 41 to 44 exceeds a predetermined overcharged voltage based on the detection signal output from the detection circuit 46, the first switching circuit 30 is operated without Depending on the switching operation of the current control element 51 and the current control element 52, the charge / discharge current circuit 33 of the battery stack 45 is blocked and controlled so that the current path of the battery stack 45 is switched from the charge / discharge current circuit 33 via the open element 22 To the discharge circuit 32 via the short-circuit element 21.

Specifically, the battery pack 40 outputs a switching signal to the switching element 26 when an abnormal voltage is detected in any of the battery cells 41 to 44 by the detection circuit 46. The switching element 26 controls the current of the battery stack 45 so that the second heating element 11 of the open element 22 is energized. Thereby, in the first switching circuit 30, the open-side fusible conductor 12 is blown, and the charge / discharge current circuit 33 of the battery stack 45 is blocked. Furthermore, the first switching circuit 30 energizes the first heating element 2 and the short-circuit-side fusible conductor 3 is fused, whereby the first electrode 5 and the second electrode 6 are short-circuited, and the current path of the battery stack 45 is switched to the protection resistor 31 provided. The discharge circuit 32 side.

In this way, the battery pack 40 in which the first switching circuit 30 is incorporated blocks the charge / discharge current circuit 33 of the battery stack 45 in which the abnormality has occurred, and switches the current path of the battery stack 45 storing a large amount of electric power corresponding to the battery capacity. To the discharge circuit 32 provided with the protection resistor 31. Therefore, after the battery pack 40 is stopped, the internal The battery cells 41 to 44 are discharged until they drop to a safe voltage.

[Built-in protection element]

In addition, as shown in FIG. 8, in the first switching circuit 30, in addition to providing a protection resistor 31 on the discharge circuit 32, as shown in FIG. 9, a protection resistor 31 may be built in the short circuit 1. In this case, as shown in FIG. 10, it is not necessary to provide a protection resistor 31 in the discharge circuit 32 of the battery pack 40.

[Second switching circuit]

Next, the second switching circuit 60 will be described. In the following description, the same components as those of the first switching circuit 30 are assigned the same reference numerals, and detailed descriptions thereof are omitted. As shown in FIG. 11, the second switching circuit 60 includes a short-circuiting element 21 constituting the short-circuiting circuit 1 and connected to the power supply circuit 25 and the first external circuit 23 energized after switching; and an open element 22 constituting the open-circuit 10 and It is connected to the power supply circuit 25 and the second external circuit 24 which is energized before switching.

In the second switching circuit 60, the short-circuit element 21 is connected to the first switching element 61, and the open element 22 is connected to the second switching element 62. The short-circuit element 21 supplies power to the first heating element 2 through the first switching element 61 that receives the switching signal. The open element 22 supplies power to the second heating element 11 via the second switching element 62 that has received the switching signal. Therefore, according to the second switching circuit 60, the order of the output of the switching signals to the first switching element 61 and the second switching element 62 can be used to change the order of the short circuit by the short-circuit element 21 and the opening by the open element 22.

Specifically, the second switching circuit 60 has a circuit configuration shown in FIGS. 12 (A) and 12 (B). The short-circuit circuit 1 includes a first heating element 2 and a short-circuit-side fusible conductor. 3 and switch 4, the short-circuit-side fusible conductor 3 is fused by the heat generated by the first heating element 2, and the switch 4 is short-circuited by the fused conductor. In the second switching circuit 60, the short circuit 1 has the same configuration as the first switching circuit 30 except that the first heating element 2 is connected to the first switching element 61 via the first heating element electrode 7.

The open circuit 10 includes a second heating element 11 and an open-side fusible conductor 12, and the open-side fusible conductor 12 is blown by the heat generated by the second heating element 11. In the second switching circuit 60, the open circuit 10 has the same configuration as the first switching circuit 30 except that the second heating element 11 is connected to the second switching element 62 via the second heating element electrode 15.

In the second switching circuit 60 shown in FIG. 12 (A), the open-side fusible conductor 12 includes a first open-side fusible conductor 12a, one end of which is connected to the power supply circuit 25 via the third electrode 13, and another One end is connected to the second heating body 11; the second open-side fusible conductor 12b is connected to the second external circuit 24 through the fourth electrode 14 at one end and is connected to the second heating body 11 at the other end.

Moreover, in the switching circuit 60, as shown in FIG. 12 (B), the open circuit 10 may include only the first open-side fusible conductor 12a. In this case, one end of the first open-side fusible conductor 12a is connected to the power supply circuit 25 via the third electrode 13, and the other end is connected to the second external circuit 24 via the second heating element 11 and the fourth electrode 14.

[Operation of the Second Switching Circuit]

In the initial state, the second switching circuit 60 having such a configuration constitutes a current path from the power supply circuit 25 to the second external circuit 24 through the open circuit 10 as shown in FIGS. 12 (A) and 12 (B). At this time, the short circuit 1 passes the first switching element 61. To limit the power supply to the first heating element 2, the switch 4 is turned off. In the open circuit 10, the power supply to the second heating element 11 is restricted by the second switching element 62.

If it is necessary to switch the current path of the power supply circuit 25 from the second external circuit 24 to the first external circuit 23, first, a switching signal is output to the second switching element 62. When the second switching element 62 receives the switching signal, it controls the current so as to supply power to the second heating element 11. Thereby, in the second switching circuit 60, the second heating element 11 of the open circuit 10 is energized and generates heat, and the open-side fusible conductor 12 is blown. Therefore, a current path from the power supply circuit 25 to the second external circuit 24 is blocked.

Then, the second switching circuit 60 outputs a switching signal to the first switching element 61. When the first switching element 61 receives the switching signal, it controls the current so as to supply power to the first heating element 2. Thereby, in the second switching circuit 60, the first heating element 2 of the short circuit 1 is energized and generates heat, the short-circuit-side fusible conductor 3 is blown, and the first electrode 5 and the second electrode 6 are short-circuited by the molten conductor. That is, the switch 4 is turned on, thereby constructing a current path from the power supply circuit 25 to the first external circuit 23.

When the second switching circuit 60 needs to switch the current path of the power supply circuit 25 from the second external circuit 24 to the first external circuit 23, the second switching circuit 60 may first output a switching signal to the first switching element 61 to construct a route from the power circuit 25. After the current path of the first external circuit 23, a switching signal is output to the second switching element 62 to block the current path to the second external circuit 24. Thereby, the power of the power supply circuit 25 is not interrupted, and the current path can be switched from the second external circuit 24 to the first external circuit 23.

The second heating element 11 is blown by the open-side fusible conductor 12 When the power supply path is blocked, the heat generation stops. In addition, the first heating element 2 blocks the power supply path when the short-circuit-side fusible conductor 3 is blown, and thus the heat generation stops.

In this way, according to the second switching circuit 60, the first switching element 61 and the second switching element 62 are operated to block the current path that reaches the first external circuit 23 through the third electrode 13 and the fourth electrode 14, and constructs The current path from the power supply circuit 25 to the first external circuit 23 via the first electrode 5, the switch 4, and the second electrode 6 can be switched from the second external circuit 24 to the first external circuit 23.

At this time, also in the second switching circuit 60, the short-circuit-side fusible conductor 3 and the open-side fusible conductor 12 are melted, thereby irreversibly blocking between the third electrode 13 and the fourth electrode 14 and the first electrode. 5. Short circuit between the second electrodes 6. Therefore, it is possible to improve a switching failure caused by a malfunction in comparison with a case where the switching is performed electronically by software or the like, and it is possible to improve the vulnerability to an unauthorized switching due to cracking or the like.

In addition, according to the second switching circuit 60, the order of the output of the switching signals to the first switching element 61 and the second switching element 62 can be changed between the short circuit by the short-circuit element 21 and the opening by the open element 22.

[Example of mounting the second switching circuit]

As shown in FIG. 13, such a second switching circuit 60 is used in a circuit incorporated in a battery pack 40 of a lithium ion secondary battery, for example. In this case, the switching signal is sequentially output from the detection circuit 46 to the second switching element 62 and the first switching element 61, thereby firstly blocking the charge / discharge current circuit 33 by the open element 22, and then, by The short-circuit element 21 short-circuits the discharge circuit 32.

That is, when the battery pack 40 detects an abnormal voltage in any of the battery cells 41 to 44 by the detection circuit 46, it first outputs a switching signal to the second switching element 62. The second switching element 62 controls the current of the battery stack 45 so that the second heating element 11 of the open element 22 is energized. Thereby, in the second switching circuit 60, the open-side fusible conductor 12 is blown, and the charge / discharge current circuit 33 of the battery stack 45 is blocked. When the blocking of the charge / discharge current circuit 33 is sensed, the detection circuit 46 then outputs a switching signal to the first switching element 61. The first switching element 61 controls the current of the battery stack 45 so that the first heating element 2 of the short-circuit element 21 is energized. As a result, the first heating element 2 is energized, and the short-circuit-side fusible conductor 3 is fused, whereby the first electrode 5 and the second electrode 6 are short-circuited, and the current path of the battery stack 45 is switched to a discharge circuit provided with a protection resistor 31 32 sides.

In this way, the battery pack 40 in which the second switching circuit 60 is installed blocks the charge / discharge current circuit 33 of the battery stack 45 in which the abnormality has occurred, and the current path of the battery stack 45 storing a large amount of electric power corresponding to the battery capacity, It is switched to the discharge circuit 32 provided with a protection resistor. Therefore, after the battery pack 40 is stopped, the internal battery cells can be discharged until the battery voltage is reduced to a safe voltage.

[Built-in protection element]

In addition, as shown in FIG. 13, in the second switching circuit 60, in addition to providing a protection resistor 31 on the discharge circuit 32, as shown in FIG. 14, a protection resistor 31 may be built in the short-circuit circuit 1. In this case, as shown in FIG. 15, it is not necessary to provide a protection resistor 31 in the discharge circuit 32 of the battery pack 40.

[3rd switching circuit]

Next, the third switching circuit 70 will be described. As shown in FIGS. 16 (A) and 16 (B), the third switching circuit 70 has a short-circuit portion 71 having the same function as the short-circuit circuit 1 and an open portion 72 having the same function as the open-circuit 10. form.

The short-circuit portion 71 includes: a first heating element 2; a short-circuit-side fusible conductor 3, one end of which is connected to the first heating element 2 and the other end of which is connected to the first external circuit 23; and a switch 4, one end of which is connected to the short-circuit side fusible conductor 3. Further, it is connected to the first external circuit 23 and the other end is connected to the power supply circuit 25.

The open portion 72 includes a second heating element 11 and an open-side fusible conductor 12 connected to the second heating element 11 and having one end connected to the other end of the switch 4 and the power supply circuit 25 and the other end connected to the second external circuit 24.

In the short-circuit portion 71, the first heating element 2 is connected to the first switching element 61 via the first heating element electrode 7. In the short-circuit section 71, the switch 4 is connected to the first external circuit 23 via the first electrode 5, and is connected to the power supply circuit 25 via the second electrode 6. The second electrode 6 is also connected to one end side of the open-side fusible conductor 12 provided in the open portion 72.

In the open portion 72, the second heating element 11 is connected to the second switching element 62 via the second heating element electrode 15. In the open portion 72, the open-side fusible conductor 12 is connected to the second external circuit 24 via the fourth electrode 14, and is connected to the power supply circuit 25 via the second electrode 6. In the third switching circuit 70 shown in FIG. 16 (A), the open-side fusible conductor 12 includes a first open-side fusible conductor 12a, one end of which is connected to the second external circuit 24 via the fourth electrode 14, so that The other end and the second heating element 11 connection; and the second open-side fusible conductor 12b, one end of which is connected to the power supply circuit 25 via the second electrode 6, and the other end is connected to the second heating element 11.

In addition, as shown in FIG. 16 (B), the open portion 72 may include only the first open-side fusible conductor 12a. In this case, one end of the first open-side fusible conductor 12 a is connected to the power supply circuit 25 via the second electrode 6, the other end is connected to the second heating element 11, and is connected to the second external circuit 24 via the fourth electrode 14. .

[Operation of the Third Switching Circuit]

In the initial state, as shown in FIGS. 16 (A) and 16 (B), the third switching circuit 70 having such a configuration constitutes a current path from the power supply circuit 25 to the second external circuit 24 via the open portion 72. At this time, the short-circuit section 71 restricts the power supply to the first heating element 2 by the first switching element 61, and the switch 4 is turned off. In addition, the opening portion 72 restricts the power supply to the second heating element 11 by the second switching element 62.

If it is necessary to switch the current path of the power supply circuit 25 from the second external circuit 24 to the first external circuit 23, first, a switching signal is output to the second switching element 62. When the second switching element 62 receives the switching signal, it controls the current so as to supply power to the second heating element 11. Thereby, in the third switching circuit 70, the second heating element 11 of the open portion 72 is energized and generates heat, and the open-side fusible conductor 12 is blown. Therefore, a current path from the power supply circuit 25 to the second external circuit 24 is blocked.

Then, the third switching circuit 70 outputs a switching signal to the first switching element 61. When the first switching element 61 receives the switching signal, it controls the current so as to supply power to the first heating element 2. As a result, in the third switching circuit 70, the first heating element 2 of the short-circuit portion 71 is energized and generates heat, and the short-circuit-side fusible conductor 3 is fused, and by this melting The conductor is short-circuited between the first electrode 5 and the second electrode 6, that is, the switch 4 is turned on, thereby constructing a current path from the power supply circuit 25 to the first external circuit 23.

In addition, when the third switching circuit 70 needs to switch the current path of the power supply circuit 25 from the second external circuit 24 to the first external circuit 23, it may first output a switching signal to the first switching element 61 to construct a route from the power circuit 25 After the current path of the first external circuit 23, a switching signal is output to the second switching element 62 to block the current path to the second external circuit 24. Thereby, the power of the power supply circuit 25 is not interrupted, and the current path can be switched from the second external circuit 24 to the first external circuit 23.

In addition, the second heating element 11 is fused by the open-side fusible conductor 12 to block the power supply path, and the heat generation is stopped. In addition, the first heating element 2 is fused by the short-circuit-side fusible conductor 3 to block the power supply path, and the heat generation stops.

In this way, according to the third switching circuit 70, the first switching element 61 and the second switching element 62 are operated to block the current path to the first external circuit 24 through the second electrode 6 and the fourth electrode 14, and to construct The current path from the power supply circuit 25 to the first external circuit 23 through the second electrode 6, the switch 4, and the first electrode 5, so that the current path of the power supply circuit 25 can be switched from the second external circuit 24 to the first external circuit 23. .

At this time, in the third switching circuit 70, the short-circuit-side fusible conductor 3 and the open-side fusible conductor 12 may be irreversibly blocked between the second electrode 6 and the fourth electrode 14 and the first electrode. 5. Short circuit between the second electrodes 6. Therefore, it is possible to improve the switching caused by a malfunction in comparison with the case where the switching is performed electronically by software. Defective, and it can improve the vulnerability to unauthorized switching caused by cracking or the like.

In addition, according to the third switching circuit 70, the order of the output of the switching signals to the first switching element 61 and the second switching element 62 can be changed between the short circuit by the short-circuit element 21 and the opening by the open element 22.

[Example of mounting the third switching circuit]

As shown in FIG. 17, such a third switching circuit 70 is used in a circuit incorporated in a battery pack 40 of a lithium ion secondary battery, for example. In this case, the first switching element 61 connects the first heating element electrode 7 of the switching circuit 70 and the positive (+) side terminal of the battery stack 45. The second switching element 62 connects the second heating element electrode 15 of the switching circuit 70 and the negative (-) side terminal of the battery stack 45. In the switching circuit 70, the first electrode 5 connected to the -side terminal of the battery stack 45 is set to the -potential, and the second electrode 6 connected to the + side terminal of the battery stack 45 is set to the + potential, and is connected to the first switching element. The first heating element electrode 7 connected to 61 is set to a + potential. In the switching circuit 70, the fourth electrode 14 connected to the charge / discharge current circuit 33 is set to a + potential, and the second heating element electrode 15 connected to the second switching element 62 is set to a-potential.

When the battery pack 40 detects a voltage abnormality in any of the battery cells 41 to 44, it outputs a switching signal to the second switching element 62 and the first switching element 61 in sequence from the detection circuit 46. The charge / discharge current circuit 33 is blocked by the open section 72, and then the discharge circuit 32 is short-circuited by the short-circuit section 71.

That is, when the battery pack 40 detects an abnormal voltage in any one of the battery cells 41 to 44 through the detection circuit 46, it first turns on the second switch. The off element 62 outputs a switching signal. The second switching element 62 controls the current of the battery stack 45 so that the second heating element 11 of the open portion 72 is energized. Thereby, in the third switching circuit 70, the open-side fusible conductor 12 is blown, and the charge / discharge current circuit 33 of the battery stack 45 is blocked. When the blocking of the charge / discharge current circuit 33 is sensed, the detection circuit 46 then outputs a switching signal to the first switching element 61. The first switching element 61 controls the current of the battery stack 45 so that the first heating element 2 of the short-circuit portion 71 is energized. Thereby, the first heating element 2 is energized, and the short-circuit-side fusible conductor 3 is fused, so that the first electrode 5 and the second electrode 6 are short-circuited, and the current path of the battery stack 45 is switched to the discharge circuit 32 side provided with the protection resistor 31 .

In this manner, the battery pack 40 in which the third switching circuit 70 is installed blocks the charge / discharge current circuit 33 of the battery stack 45 in which the abnormality has occurred, and switches the current path of the battery stack 45 storing a large amount of electric power corresponding to the battery capacity. To the discharge circuit 32 provided with a protection resistor. Therefore, after the battery pack 40 is stopped, the internal battery cells can be discharged until the battery voltage is reduced to a safe voltage.

[Built-in protection element]

In addition, as shown in FIG. 17, in the third switching circuit 70, in addition to providing the protection resistor 31 in the discharge circuit 32, as shown in FIG. 18, the protection resistor 31 may be built in the short-circuit portion 71. In this case, as shown in FIG. 19, it is not necessary to provide a protection resistor 31 in the discharge circuit 32 of the battery pack 40.

[Industrial availability]

According to the present invention, by setting the first external circuit 23 as a light-emitting circuit, a sound-producing circuit, a circuit accompanying an electronic signal, etc., it can be applied to the following alarms The functional open circuit, that is, the state of the operation of the open circuit 10 or the open section 72 is notified to the outside as an alarm.

The present invention can also be applied as a circuit for activating various devices or software. For example, the first external circuit 23 is configured as a functional circuit of various devices or software, and the second external circuit 24 is configured as a circuit that restricts a part of the functions. In the initial setting, a second external circuit with a limited function is connected. twenty four. When the user goes through a license agreement procedure and activates the device, the user switches to the first external circuit 23 which is a functional circuit of the device.

Furthermore, the present invention can be applied as an information security circuit for protecting information in a database. For example, the second external circuit 24 is configured as a functional circuit connected to the database, and the first external circuit 23 is configured as a circuit disconnected from the database. In the initial setting, the database can be accessed via the second external circuit 24 For access. When hacking or cracking is sensed, in order to protect the information in the database, it is switched to the first external circuit 23 which is cut off from the database.

In the present invention, the function circuit is switched by fusing the short-side fusible conductor 3 and the open-side fusible conductor 12, so that the function switching can be controlled physically and irreversibly. Therefore, unlike the case where the circuit is electronically switched by software, it is possible to improve a poor switching caused by a malfunction, or to improve the vulnerability to improper switching caused by hacking, cracking, or the like.

Claims (20)

A switching circuit includes a short-circuit circuit including a first heating element that generates heat by passing a current, one end of which is a short-circuit-side fusible conductor connected to the first heating element, and the other end of which is connected to a main circuit. The switch connected to the short-circuit-side fusible conductor and connected to the main circuit, and the other end of which is connected to the first external circuit, fuses the short-circuit-side fusible conductor by the heat generated by the first heating element, and The short-circuit-side fusible conductor short-circuits the switch and opens a circuit including a second heating element that generates heat by passing a current, and a second heating element connected to the second heating element and connected to a second external circuit at one end and the other end The open-side fusible conductor connected to the main circuit fuses the open-side fusible conductor by heat from the second heating element, and a switching element is connected to one end of the second heating element. The switching element receives a switching signal to cause a current to flow from the main circuit to the second heating element, and connects the open end of the first heating element of the short circuit and the second heating element of the open circuit. And said open The connection end of the side fusible conductor is connected, and the second heating element of the open circuit is energized and generates heat by the operation of the switching element, and the open side fusible conductor is blown, thereby blocking the main circuit from all The second external circuit is fused by the open-side fusible conductor, and the first heating element of the short-circuit circuit is energized and generates heat, and the short-circuit fusible conductor is melted to short-circuit the switch. The main circuit and the first external circuit are energized. The switching circuit according to item 1 of the scope of patent application, wherein the main circuit is a power supply circuit with a battery stack, the first external circuit is a discharge circuit that releases electricity from the battery stack, and the second external circuit The circuit is a charge-discharge current circuit of the battery stack. The open circuit is used to block the power supply circuit and the charge-discharge current circuit and stop charging the battery stack. The power supply circuit is short-circuited with the discharge circuit, thereby discharging the electric energy accumulated in the battery stack. The switching circuit according to item 2 of the scope of patent application, wherein a protection resistor is provided at the other end of the switch of the short circuit, and the protection resistor is used to discharge the electric energy stored in the battery stack to the battery The maximum discharge current of the cell is below. The switching circuit according to item 2 of the scope of patent application, wherein in the discharge circuit, a protection resistor is connected to the other end of the switch of the short-circuit circuit, and the protection resistor is used to cause accumulation in the battery stack. The electric energy is discharged below the upper limit discharge current of the battery cell. The switching circuit according to any one of claims 1 to 4, wherein the open-side fusible conductor includes: a first open-side fusible conductor, one end of which is connected to the main circuit and the other end of which is The second heating element is connected; and the second open-side fusible conductor, one end is connected to the second external circuit and the other end is connected to the second heating element. A switching circuit includes a short-circuit circuit including a first heating element that generates heat by passing a current, one end of which is a short-circuit-side fusible conductor connected to the first heating element, and the other end of which is connected to a main circuit. The switch connected to the short-circuit-side fusible conductor and connected to the main circuit, and the other end of which is connected to the first external circuit, fuses the short-circuit-side fusible conductor by the heat generated by the first heating element, and The short-circuit-side fusible conductor short-circuits the switch and opens a circuit including a second heating element that generates heat by passing a current, and a second heating element connected to the second heating element and connected to a second external circuit at one end and the other end The open-side fusible conductor connected to the main circuit fuses the open-side fusible conductor by heat from the second heating element, and a first switching element is connected to one end of the first heating element. The first switching element receives a switching signal to energize current from the main circuit to the first heating element, a second switching element is connected to one end of the second heating element, and the second switching element receives switching Signal The current flows from the main circuit to the second heating element, and operates through the second switching element, and the second heating element of the open circuit is energized and generates heat, and the open-side fusible conductor is blown, As a result, the main circuit and the second external circuit are blocked, and the first switching element operates, and the first heating element of the short circuit is energized and generates heat, and the short-circuit-side fusible conductor is melted. As a result, the switch is short-circuited, and the main circuit and the first external circuit are energized. The switching circuit according to item 6 of the scope of patent application, wherein the main circuit is a power supply circuit with a battery stack, the first external circuit is a discharge circuit that releases electricity from the battery stack, and the second external circuit The circuit is a charge / discharge current circuit of the battery stack, and the second switching element is operated to block the power circuit and the charge / discharge current circuit by the open circuit, and stop the battery stack from being charged. After charging, the first switching element is operated to short-circuit the power circuit and the discharge circuit through the short-circuit circuit, thereby discharging the electric energy stored in the battery stack. The switching circuit according to item 7 of the scope of patent application, wherein a protection resistor is provided at the other end of the switch of the short circuit, and the protection resistor is used to discharge the electric energy stored in the battery stack to the battery The maximum discharge current of the cell is below. The switching circuit according to item 7 of the scope of patent application, wherein in the discharge circuit, a protection resistor is provided between the discharge circuit and the other end of the switch of the short circuit, and the protection resistor is used for accumulating The electric energy in the battery stack is discharged below the upper limit discharge current of the battery cell. The switching circuit according to item 6 of the scope of patent application, wherein the first switching element is operated and the first external circuit is short-circuited by the short-circuiting circuit, and then the second switching element is operated to borrow The second external circuit is blocked by the open circuit. The switching circuit according to item 6 of the scope of patent application, wherein the second switching element is operated and the second external circuit is blocked by the open circuit, and then the first switching element is operated and The first external circuit is short-circuited by the short-circuit circuit. The switching circuit according to any one of claims 6 to 11 in the scope of patent application, wherein the open-side fusible conductor includes: a first open-side fusible conductor, one end of which is connected to the main circuit and the other end of which is The second heating element is connected; and the second open-side fusible conductor, one end is connected to the second external circuit and the other end is connected to the second heating element. A switching circuit includes a short-circuit portion including a first heating element that generates heat by passing a current, a short-circuit-side fusible conductor connected at one end to the first heating element, and connected at the other end to a first external circuit, and one end A switch connected to the short-circuit-side fusible conductor and connected to the first external circuit and the other end of which is connected to a main circuit, the short-circuit-side fusible conductor is fused by heat from the first heating element, and The switch is short-circuited by the short-circuit-side fusible conductor, and the open portion includes a second heating element that generates heat by passing a current, and a second heating element that is connected to the second heating element and has one end connected to the other end of the switch. And the open-side fusible conductor connected to the main circuit and the other end connected to the second external circuit, the open-side fusible conductor is fused by the heat generated by the second heating element, and the first heating element and the A first switching element is connected, and the first switching element receives a switching signal to cause a current to flow from the main circuit to the first heating element, the second heating element is connected to a second switching element, and the second switch The component receives the switching signal and makes A current is energized from the main circuit to the second heating element, and is operated by the second switching element. The second heating element of the open portion is energized and generates heat, and the open-side fusible conductor is blown. Thereby, the main circuit and the second external circuit are blocked, and the first switching element operates, and the first heating element of the short-circuit portion is energized and generates heat, and the short-circuit-side fusible conductor is melted, As a result, the switch is short-circuited, and the main circuit and the first external circuit are energized. The switching circuit according to item 13 of the scope of patent application, wherein the main circuit is a power supply circuit with a battery stack, the first external circuit is a discharge circuit that releases electricity from the battery stack, and the second external circuit The circuit is a charge / discharge current circuit of the battery stack, and the second switching element is operated to block the power supply circuit and the charge / discharge current circuit by the open portion, and stop the battery stack from being charged. After charging, the first switching element is operated, the power supply circuit and the discharge circuit are short-circuited by the short-circuiting section, and the electric energy stored in the battery stack is discharged. The switching circuit according to item 14 of the scope of patent application, wherein a protection resistor is provided at the other end of the switch in the short-circuit portion, and the protection resistor is used to discharge the electric energy stored in the battery stack to the battery The maximum discharge current of the cell is below. The switching circuit according to item 14 of the scope of patent application, wherein in the discharge circuit, a protection resistor is provided between the discharge circuit and the other end of the switch in the short-circuit portion, and the protection resistor is used to accumulate The electric energy in the battery stack is discharged below the upper limit discharge current of the battery cell. The switching circuit according to item 13 of the scope of patent application, wherein the first switching element is operated and the first external circuit is shorted by the short-circuiting section, and then the second switching element is operated to borrow The second external circuit is blocked by the open portion. The switching circuit according to item 13 of the scope of patent application, wherein the second switching element is operated and the second external circuit is blocked by the opening portion, and then the first switching element is operated and The short circuit portion is used to short-circuit the first external circuit. The switching circuit according to any one of claims 13 to 18 in the scope of patent application, wherein the open-side fusible conductor includes: a first open-side fusible conductor, one end of which is connected to the second external circuit and another One end is connected to the second heating element; and a second open-side fusible conductor, one end is connected to the main circuit and the other end is connected to the second heating element. The switching circuit according to any one of the scope of claims 1, 6, or 13, wherein the first external circuit is a light-emitting circuit, a sound-producing circuit, or a circuit accompanying electronic signal generation.