protective device

Abstract

The present invention protects a circuit from a surge voltage while miniaturizing the circuit.　A protection device (50) is used in an interruption system (30) comprising: a first circuit (31) which includes a first power path (31A) and a second power path (31B) that are paths through which power is transmitted; an interrupter (33) which includes an interrupting portion (33A) provided so as to be able to interrupt the second power path (31B), and a metal housing (33B) in which at least a part of the interrupting portion (33A) is housed; and a second circuit (32) which provides the interrupting portion (33A) with an interrupt signal (B). The protection device (50) comprises a conduction portion (33G) forming a conduction path between the metal housing (33B) and a portion (20) of interest including a ground portion (G).

Description

[Technical Field]

[0001] The present disclosure relates to a protection device. [Background technology]

[0002] Patent Document 1 discloses a drive circuit that drives a power MOSFET via a pulse transformer. This circuit is configured such that the power MOSFET side is separated from the drive side, to which a PWM signal that controls the power MOSFET is input, by the pulse transformer. With this configuration, for example, even if a surge voltage occurs on the power MOSFET side, the pulse transformer can prevent the surge voltage from entering the drive side. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 62-021322 Summary of the Invention [Problem to be solved by the invention]

[0004] The device disclosed in Patent Document 1 uses a pulse transformer, making it difficult to miniaturize the circuit. For this reason, there is a demand for a technology that prevents surge voltage from entering the drive side while miniaturizing the circuit.

[0005] The present disclosure has been made in light of the above-mentioned circumstances, and aims to provide a protection device that protects a circuit from a surge voltage while miniaturizing the circuit. [Means for solving the problem]

[0006] The protection device of the present disclosure comprises: a first circuit having a power path that is a path along which power is transmitted; a circuit breaker having a circuit breaker unit that is capable of interrupting the power path and a metal housing that accommodates at least a portion of the circuit breaker unit; a second circuit that provides a cutoff signal to the cutoff unit; A protection device for use in a shutdown system comprising: The protection path portion includes a conductive portion that forms a conductive path between the target portion, which includes either the first circuit or the ground portion, and the metal housing, or a parasitic capacitance portion that generates a parasitic capacitance larger than the parasitic capacitance between the metal housing and the second circuit. [Effects of the Invention]

[0007] According to the present disclosure, it is possible to protect a circuit from a surge voltage while miniaturizing the circuit. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a block diagram illustrating an in-vehicle system according to the first embodiment. [Figure 2] FIG. 2 is a block diagram illustrating the details of the circuit breaker according to the first embodiment. [Figure 3] FIG. 3 is a block diagram illustrating details of the circuit breaker according to the second embodiment. [Figure 4] FIG. 4 is a block diagram illustrating details of the circuit breaker according to the third embodiment. [Figure 5] FIG. 5 is a block diagram illustrating details of the circuit breaker according to the fourth embodiment. [Figure 6] FIG. 6 is a block diagram illustrating details of a circuit breaker according to another embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] [Description of the embodiments of the present disclosure] First, embodiments of the present disclosure will be listed and described.

[0010] [1] The protective device disclosed herein is used in an interruption system including a first circuit, a circuit breaker, and a second circuit. The first circuit has a power path, which is a path through which power is transmitted. The circuit breaker has a circuit breaker configured to be able to interrupt the power path, and a metal housing that houses at least a portion of the circuit breaker. The second circuit provides an interruption signal to the circuit breaker. The protective device has a protection path portion that includes a conductive portion that forms a conductive path between a target portion, which includes either the first circuit or a ground portion, and the metal housing, or a parasitic capacitance portion that generates a parasitic capacitance larger than the parasitic capacitance between the metal housing and the second circuit.

[0011] In the protection device of [1] above, even if a surge voltage generated in the first circuit causes an imbalance in the distribution of electric charges within the metal casing, the protection path section can quickly release the imbalance in the distribution of electric charges within the metal casing to the target section, thereby eliminating the imbalance. As a result, the circuit can be made smaller, and the surge voltage generated in the first circuit can be prevented from affecting the second circuit via the metal casing.

[0012] [2] In the protection device of [1] above, the protection path portion has a conductive portion, and the conductive portion can short-circuit the metal housing and the target portion.

[0013] The protective device of the above [2] allows electric charges to move between the metal housing and the target part by the conductive part, so that uneven distribution of electric charges inside the metal housing can be easily released to the target part.

[0014] [3] In the protection device of [2] above, the target portion may include a ground portion, and the protection path portion may form a conductive path between the metal housing and the ground portion.

[0015] The protective device of the above [3] can easily stabilize the potential of the metal housing.

[0016] [4] In any of the above [1] to [3], the power path may include a high-potential conductive path provided on the high-potential side of the circuit breaker and a low-potential conductive path provided on the low-potential side of the circuit breaker. The circuit breaker is provided to be able to cut off between the high-potential conductive path and the low-potential conductive path, and the target part may include the low-potential conductive path.

[0017] The protection device of [4] above can eliminate the uneven distribution of charge between the metal housing and the low-potential conductive path by completing the process within the first circuit, even if the uneven distribution of charge occurs within the metal housing due to a surge voltage generated based on the inductance component of the high-potential conductive path, thereby suppressing the effects of the surge voltage on the second circuit.

[0018] [5] In any of the above [1] to [3], the power path may include a high-potential conductive path provided on the high-potential side of the circuit breaker and a low-potential conductive path provided on the low-potential side of the circuit breaker. The circuit breaker is provided to be able to cut off between the high-potential conductive path and the low-potential conductive path, and the target part may include the high-potential conductive path.

[0019] The protection device of [5] above can eliminate the uneven distribution of charge between the metal housing and the high-potential conductive path in a manner that is completed within the first circuit, even if the uneven distribution of charge occurs within the metal housing due to a surge voltage generated based on the inductance component of the low-potential conductive path, thereby suppressing the effects of the surge voltage on the second circuit.

[0020] [6] In the above [1], the second circuit may include a reference conductive path that is a ground section and a second conductive path that is a conductive path different from the reference conductive path. The target section may include the reference conductive path. The second parasitic capacitance that is a parasitic capacitance between the metal housing and the reference conductive path may be larger than the first parasitic capacitance that is a parasitic capacitance between the metal housing and the second conductive path.

[0021] In the protection device of the above [6], when a surge voltage generated in the first circuit causes a bias in the distribution of electric charges within the metal housing, the second parasitic capacitance, which has a larger capacitance than the first parasitic capacitance, can more easily offset the bias in the distribution of electric charges. Therefore, the surge voltage generated in the first circuit is less likely to affect the second circuit via the metal housing.

[0022] [7] In the protection device of any of [1] to [6] above, the interrupting unit may have an ignition unit that performs an explosive action in response to an interruption signal, a cutoff unit that is provided in the power path and cuts off the power path when the cutoff unit itself is cut, and a displacement unit that is displaced by the force generated by the explosive action. The interrupting unit may be a fuse device that cuts off the cutoff unit by displacement of the displacement unit in response to the explosive action.

[0023] The protective device [7] above can cut off the power line in an extremely short time because the displacement part is rapidly displaced by the force generated by the explosive action of the ignition part. [Details of the embodiments of the present disclosure]

[0024] <Embodiment 1> [Outline of the shutdown system] 1 is a system mounted on a vehicle. The vehicle system 100 includes a power supply unit 90, a load 91, and an interruption system 30. The power supply unit 90 may be, for example, a lead battery or a lithium ion battery. The load 91 is an electronic device provided in the vehicle.

[0025] The interruption system 30 includes a first circuit 31, a second circuit 32, a circuit breaker 33, and a protection device 50. The first circuit 31 includes a first power path 31A electrically connected to a high-potential terminal of a power supply unit 90 and a second power path 31B electrically connected to a low-potential terminal of the power supply unit 90. The first power path 31A and the second power path 31B are paths through which power is transmitted. A contactor 35 is interposed between the first power path 31A and the second power path 31B. Each contactor 35 has the function of switching the first power path 31A and the second power path 31B between a conductive state and a non-conductive state. Each of the first power path 31A and the second power path 31B has an inductance component L. The inductance component L is a parasitic component of each of the first power path 31A and the second power path 31B.

[0026] In each of the first power path 31A and the second power path 31B, a capacitor 36 is electrically connected to the load 91 side of the contactor 35. Each of the first power path 31A and the second power path 31B is electrically connected to a ground part G via the capacitor 36 and a reference conductive path 32C described later. The ground part G is, for example, a chassis that constitutes the vehicle body. The ground part G is included in the configuration of the target part 20.

[0027] In the present disclosure, "electrically connected" preferably means a configuration in which the connection objects are connected in a mutually conductive state (a state in which a current can flow) so that the potentials of both connection objects are equal. However, this configuration is not limited to this. For example, "electrically connected" may also mean a configuration in which the connection objects are connected in a state in which the two connection objects can be electrically connected with an electrical component interposed between them.

[0028] A current detection unit 38 is provided in the second power path 31B, closer to the power supply unit 90 than the contactor 35. The current detection unit 38 has, for example, a resistor and a differential amplifier, and is configured to output a value indicating the current flowing through the second power path 31B (specifically, an analog voltage corresponding to the value of the current flowing through the second power path 31B) as a current value A. The current detection unit 38 detects the state of the current flowing through the second power path 31B.

[0029] The second circuit 32 includes a tripping control unit 32A, a low-voltage power supply unit 32B, and a reference conductive path 32C. The tripping control unit 32A is primarily configured, for example, with a microcomputer and includes an arithmetic unit such as a CPU (Central Processing Unit), a memory such as a ROM (Read Only Memory) or a RAM (Random Access Memory), an A / D converter, and the like. The tripping control unit 32A is configured to receive a current value A output from a current detection unit 38. The tripping control unit 32A is also configured to receive a signal S (e.g., SOC (State of Charge)) indicating the state of the power supply unit 90 from an external device such as a battery management system (BMS) (not shown). The tripping control unit 32A of the second circuit 32 is configured to provide a tripping signal B to an ignition unit 33C of a tripping unit 33A of a circuit breaker 33 (described later) based on the current value A and signal S input from the current detection unit 38 or the external device.

[0030] The low-voltage power supply unit 32B may be, for example, a lead battery or a lithium-ion battery. The voltage generated between the high-potential terminal and the low-potential terminal of the low-voltage power supply unit 32B is lower than that of the power supply unit 90. The low-voltage power supply unit 32B is configured to be able to supply power to the cutoff control unit 32A.

[0031] The reference conductive path 32C is a conductive path maintained at a constant low voltage in the second circuit 32, and in the first embodiment, is electrically connected to the ground section G. The reference conductive path 32C is electrically connected to a low-potential side terminal of the low-voltage power supply section 32B and the cutoff control section 32A. The reference conductive path 32C is also the ground section G.

[0032] For example, a pyrofuse (PYROFUSE (registered trademark)) is used for the circuit breaker 33. As shown in Fig. 2, the circuit breaker 33 has a circuit breaker section 33A and a metal housing 33B. The circuit breaker section 33A has an ignition section 33C, explosives 33F, a displacement section 33D, and a cut section 33E.

[0033] Ignition unit 33C is configured to generate heat when shutoff signal B is given from shutoff control unit 32A. Explosives 33F are provided adjacent to ignition unit 33C. Explosives 33F explode when exposed to heat generated in ignition unit 33C, generating explosive force. In other words, ignition unit 33C performs an explosion operation to ignite explosives 33F in response to shutoff signal B. .strange The displacement portion 33D is provided adjacent to the explosive 33F. The displacement portion 33D is suddenly displaced when subjected to the explosive force generated by the exploded explosive 33F.

[0034] The cut portion 33E is formed, for example, from a strip-shaped conductive metal. The cut portion 33E is provided interposed between the second power path 31B. In other words, the cut portion 33E is provided in the power path. The cut portion 33E is disposed on the opposite side of the displacement portion 33D from the explosive 33F. The cut portion 33E is physically cut in an extremely short time by the displacement portion 33D, which is rapidly displaced by the explosive force generated by the explosive action. As a result, when the cut portion 33E is cut, it interrupts the second power path 31B, which is the power path. In this way, the interrupter 33A interrupts the second power path 31B, which is the power path. In other words, the interrupter 33A is provided so as to be able to interrupt the second power path 31B. The cut portion 33E will not be reconnected. In other words, the second power path 31B, which is interrupted by the interrupter 33A, will not switch to a conductive state that allows current to flow. That is, the interrupter 33A is a fuse device that cuts the cut part 33E by the displacement of the displacement part 33D in response to the explosion action.

[0035] Metal housing 33B is formed into a box shape by, for example, pressing a metal plate. Metal housing 33B houses interrupter 33A. For example, both ends of cut-off portion 33E are configured to protrude outward from metal housing 33B. In other words, metal housing 33B houses a part of interrupter 33A.

[0036] The protection device 50 is used in the interruption system 30. The protection device 50 has a protection path portion 21. The protection path portion 21 has a conductive portion 33G. The conductive portion 33G is formed of a conductive metal. One end of the conductive portion 33G is electrically connected to the metal housing 33B. The other end of the conductive portion 33G is electrically connected to the reference conductive path 32C. The conductive portion 33G is interposed between the metal housing 33B and the ground portion G. In other words, the metal housing 33B is electrically connected to the ground portion G via the conductive portion 33G and the reference conductive path 32C. The conductive portion 33G conducts electricity between the metal housing 33B and the ground portion G, thereby shorting them out. In other words, the conductive portion 33G of the protection path portion 21 forms a conductive path between the ground portion G of the target portion 20 and the metal housing 33B. The protective path portion 21 functions to release the electric charge to the ground portion G via itself when a surge voltage is applied to the metal housing 33B.

[0037] [About the operation of the shutdown system] Based on signals input from current detection unit 38 or an external device, shutdown control unit 32A outputs shutdown signal B to ignition unit 33C of shutdown unit 33A of circuit breaker 33. This heats up ignition unit 33C of shutdown unit 33A, causing explosive 33F to explode. The explosion of explosive 33F then causes displacement unit 33D to suddenly displace, cutting off portion 33E. This causes the current flowing through second power path 31B to suddenly stop flowing. This change in current flow generates a surge voltage on one end or the other end of portion 33E, based on inductance component L of first circuit 31.

[0038] The distribution of electric charge inside the metal housing 33B becomes uneven due to induction by the surge voltage. Metal housing 33B is electrically connected to the ground section G via the conductive section 33G. Therefore, even if the distribution of electric charge becomes uneven inside the metal housing 33B, electric charge is immediately transferred to and from the ground section G, so that the surge voltage is prevented from affecting the cutoff control section 32A of the second circuit 32 via the metal housing 33B.

[0039] Next, the effects of this configuration will be illustrated. The protection device 50 is used in an interruption system 30 including a first circuit 31, a circuit breaker 33, and a second circuit 32. The first circuit 31 includes a first power path 31A and a second power path 31B, which are paths through which power is transmitted. The circuit breaker 33 includes a circuit breaker 33A that is capable of interrupting the second power path 31B, and a metal housing 33B that houses at least a portion of the circuit breaker 33A. The second circuit 32 provides an interruption signal B to the circuit breaker 33A. The protection device 50 includes a protection path portion 21 that includes a conductive portion 33G that forms a conduction path between the target portion 20, which includes a ground portion G, and the metal housing 33B. With this configuration, even if a surge voltage generated in the first circuit 31 causes an imbalance in the distribution of electric charge within the metal housing 33B, the conductive portion 33G of the protection path portion 21 can quickly diffuse the imbalance in the distribution of electric charge within the metal housing 33B to the ground portion G of the target portion 20, thereby eliminating the imbalance. Therefore, it is possible to reduce the size of the circuit and prevent a surge voltage generated in the first circuit 31 from affecting the second circuit 32 via the metal casing 33B.

[0040] In the protection device 50, the protection path portion 21 has a conductive portion 33G, which short-circuits the metal housing 33B and the ground portion G of the target portion 20. With this configuration, the conductive portion 33G allows charge to move between the metal housing 33B and the ground portion G of the target portion 20, making it easy to release bias in the distribution of charge within the metal housing 33B to the ground portion G of the target portion 20.

[0041] In the protection device 50, the target portion 20 includes the ground portion G, and the conductive portion 33G of the protection path portion 21 forms a conductive path between the metal housing 33B and the ground portion G. This configuration makes it easy to stabilize the potential of the metal housing 33B.

[0042] The interrupter 33A includes an ignition unit 33C that explodes in response to the interruption signal B, a cutoff unit 33E that is provided on the power path and that cuts off the second power path 31B when the ignition unit 33C is cut, and a displacement unit 33D that is displaced by the force generated by the explosion. The interrupter 33A is a fuse device that cuts off the cutoff unit 33E by the displacement of the displacement unit 33D in response to the explosion. With this configuration, the displacement unit 33D is rapidly displaced by the force generated by the explosion of the ignition unit 33C, so that the second power path 31B can be cut off in an extremely short time.

[0043] <Embodiment 2> Next, a protection device 150 according to a second embodiment will be described with reference to Fig. 3. The second embodiment differs from the first embodiment in the configuration of the first circuit 31 and in that the metal housing 33B is electrically connected to the low-potential conductive path CL via the conductive portion 133G. The same components as those in the first embodiment are denoted by the same reference numerals, and the same functions and effects as those in the first embodiment will not be described.

[0044] 3, the first power path 31A has an inductance component L. The inductance component L is a parasitic component of the first power path 31A. The inductance component of the second power path 31B is extremely small compared to the first power path 31A, and is negligible.

[0045] The portion of the second power path 31B closer to the load 91 than the circuit breaker 33 is a high-potential conductive path CH that is provided on the high-potential side of the circuit breaker 33. The portion of the second power path 31B closer to the current detection unit 38 than the circuit breaker 33 is a low-potential conductive path CL that is provided on the low-potential side of the circuit breaker 33. In other words, the circuit breaker 33 is provided so as to be able to disconnect between the high-potential conductive path CH and the low-potential conductive path CL.

[0046] The protection device 150 has a protection path portion 121. The protection path portion 121 has a conductive portion 133G. The conductive portion 133G is formed of a conductive metal. One end of the conductive portion 133G is electrically connected to the metal housing 33B. The other end of the conductive portion 133G is electrically connected to the low-potential conductive path CL. In other words, the low-potential conductive path CL is included in the configuration of the target portion 120. The conductive portion 133G is interposed between the metal housing 33B and the low-potential conductive path CL of the second power path 31B, and short-circuits the metal housing 33B and the low-potential conductive path CL of the second power path 31B. In other words, the metal housing 33B is electrically connected to the low-potential conductive path CL of the second power path 31B via the conductive portion 133G. The conductive portion 133G is a conductive path that connects the metal casing 33B and the second power path 31B (first circuit 31).

[0047] [About the operation of the shutdown system] The explosive 33F of the circuit breaker 33 explodes, causing the displacement portion 33D to be suddenly displaced and cutting the cut portion 33E. As a result, a surge voltage is generated at one end of the cut portion 33E based on the inductance component L of the first power path 31A.

[0048] The distribution of electric charge within metal casing 33B becomes uneven due to the surge voltage. Metal casing 33B is electrically connected to low-potential conductive path CL of second power path 31B via conductive portion 133G. Therefore, even if the distribution of electric charge becomes uneven within metal casing 33B, electric charge is immediately transferred to and from low-potential conductive path CL, so that the surge voltage is prevented from affecting cutoff control unit 32A of second circuit 32 via metal casing 33B.

[0049] The power path includes a high-potential conductive path CH provided on the high-potential side of the circuit breaker 33 and a low-potential conductive path CL provided on the low-potential side of the circuit breaker 33. The circuit breaker 33 is provided to be able to disconnect between the high-potential conductive path CH and the low-potential conductive path CL, and the target unit 120 includes the low-potential conductive path CL. With this configuration, even if a surge voltage generated based on the inductance component L of the first power path 31A causes an imbalance in the distribution of charge within the metal casing 33B, the imbalance in the distribution of charge can be eliminated between the metal casing 33B and the low-potential conductive path CL in a manner that is completed within the first circuit 31. Therefore, the influence of the surge voltage on the second circuit 32 can be suppressed.

[0050] <Embodiment 3> Next, a protection device 250 according to a third embodiment will be described with reference to Fig. 4. The third embodiment differs from the second embodiment in that the second power path 31B has an inductance component L, the inductance component of the first power path 31A is much smaller than that of the second power path 31B and can be ignored, and the metal casing 33B is electrically connected to the high-potential conductive path CH via the conductive portion 233G. The same components as those in the second embodiment are denoted by the same reference numerals, and the same functions and effects as those in the second embodiment will not be described.

[0051] As shown in Fig. 4, the second power path 31B has an inductance component L. The inductance component L is a parasitic component of the second power path 31B. The inductance component of the first power path 31A is extremely small compared to the second power path 31B, and is negligible. The circuit breaker 33 is provided to be able to disconnect the high-potential conductive path CH and the low-potential conductive path CL.

[0052] The protection device 250 has a protection path portion 221. The protection path portion 221 has a conductive portion 233G. One end of the conductive portion 233G is electrically connected to the metal casing 33B. The other end of the conductive portion 233G is electrically connected to the high-potential conductive path CH. In other words, the high-potential conductive path CH is included in the configuration of the target portion 220. The conductive portion 233G is interposed between the metal casing 33B and the high-potential conductive path CH of the second power path 31B, and short-circuits the metal casing 33B and the high-potential conductive path CH of the second power path 31B. In other words, the metal casing 33B is electrically connected to the high-potential conductive path CH of the second power path 31B via the conductive portion 233G. The conductive portion 233G is a conductive path that electrically connects the metal casing 33B and the second power path 31B (first circuit 31).

[0053] [About the operation of the shutdown system] The explosive 33F of the circuit breaker 33 explodes, causing the displacement portion 33D to be suddenly displaced and cutting the cut portion 33E. As a result, a surge voltage is generated on the other end side of the cut portion 33E based on the inductance component L of the second power path 31B.

[0054] The distribution of electric charge within the metal casing 33B becomes uneven due to the surge voltage. The metal casing 33B is electrically connected to the high-potential conductive path CH of the second power path 31B via the conductive portion 233G. Therefore, even if the distribution of electric charge becomes uneven within the metal casing 33B, electric charge is immediately exchanged with the high-potential conductive path CH, so that the surge voltage is prevented from affecting the cutoff control portion 32A of the second circuit 32 via the metal casing 33B.

[0055] The power path includes a high-potential conductive path CH provided on the high-potential side of the circuit breaker 33 and a low-potential conductive path CL provided on the low-potential side of the circuit breaker 33. The circuit breaker 33 is provided to be able to disconnect between the high-potential conductive path CH and the low-potential conductive path CL, and the target unit 220 includes the high-potential conductive path CH. With this configuration, even if a surge voltage generated based on the inductance component L of the second power path 31B causes an imbalance in the distribution of charge within the metal casing 33B, the imbalance in the distribution of charge can be eliminated between the metal casing 33B and the high-potential conductive path CH in a manner that is completed within the first circuit 31. This makes it possible to suppress the effects of the surge voltage on the second circuit 32.

[0056] <Embodiment 4> Next, a protection device 350 according to a fourth embodiment will be described with reference to Fig. 5. The fourth embodiment differs from the first to third embodiments in that the protection path portion 321 of the protection device 350 includes a parasitic capacitance portion 23, a first parasitic capacitance C1 is interposed between the metal casing 33B and the second circuit 32, and a second parasitic capacitance C2 having a capacitance larger than the first parasitic capacitance C1 is interposed between the metal casing 33B and the reference conduction path 32C. The same components as those of the first to third embodiments are denoted by the same reference numerals, and the same operations and effects as those of the first to third embodiments will not be described.

[0057] The protection device 350 has a protection path portion 321. The protection path portion 321 includes a parasitic capacitance portion 23. The parasitic capacitance portion 23 is disposed between the metal housing 33B and the reference conductive path 32C. The parasitic capacitance portion 23 may be, for example, an insulating material such as synthetic resin or a space containing air. Both of these may be present as the parasitic capacitance portion 23. The parasitic capacitance portion 23 generates a second parasitic capacitance C2 as a parasitic capacitance between the metal housing 33B and the reference conductive path 32C. The parasitic capacitance portion 23 may have any structure that insulates the metal housing 33B from the reference conductive path 32C. The magnitude of the second parasitic capacitance C2 can be adjusted to a desired magnitude by changing the material or size of the parasitic capacitance portion 23 or by changing the distance between the metal housing 33B and the reference conductive path 32C.

[0058] The second circuit 32 includes a reference conductive path 32C, which is a ground portion G, and a signal line T, which is a second conductive path different from the reference conductive path 32C. The reference conductive path 32C is included in the configuration of the target portion 320. The signal line T has a function of outputting a cutoff signal B from the cutoff control unit 32A to the ignition unit 33C. The metal casing 33B and the signal line T (the second circuit 32) are close to each other, which causes a first parasitic capacitance C1 to be interposed between the metal casing 33B and the signal line T. The signal line T is provided on the high potential side relative to the ignition unit 33C. When the cutoff signal B is output from the cutoff control unit 32A, a current flows from the signal line T to the reference conductive path 32C via the ignition unit 33C. The cutoff signal B output by the cutoff control unit 32A is a current signal that enables the ignition unit 33C to ignite the explosive 33F, and specifically, is a current equal to or greater than a predetermined value. The reference conductive path 32C is provided on the low potential side of the ignition part 33C and is electrically connected to the ground part G. The magnitude of the first parasitic capacitance C1 can be adjusted to a desired magnitude by changing the distance between the metal housing 33B and the signal line T or by inserting a dielectric therebetween.

[0059] The second parasitic capacitance C2 is larger than the first parasitic capacitance C1. That is, the parasitic capacitance unit 23 generates the second parasitic capacitance C2 between the metal casing 33B and the second circuit 32, the second parasitic capacitance C2 being larger than the first parasitic capacitance C1.

[0060] [About the operation of the shutdown system] When the explosive 33F of the circuit breaker 33 explodes, the displacement portion 33D is suddenly displaced and the cut portion 33E is cut, and a surge voltage is generated on one end side or the other end side of the cut portion 33E due to the inductance component L of the first circuit 31.

[0061] The charge distribution in the metal casing 33B becomes biased due to a surge voltage generated in the first circuit 31. The second parasitic capacitance C2 has a larger capacitance than the first parasitic capacitance C1, and therefore the charge in the parasitic capacitance unit 23 and the reference conduction path 32C moves so as to cancel the bias in the charge distribution in the metal casing 33B more quickly than the first parasitic capacitance C1. This makes it difficult for the surge voltage generated in the first circuit 31 to affect the second circuit 32 via the metal casing 33B. In other words, even if the charge distribution becomes biased in the metal casing 33B, the second parasitic capacitance C2 can prevent the surge voltage from affecting the cutoff control unit 32A of the second circuit 32. The parasitic capacitance unit 23 does not directly transfer the charge in the metal casing 33B to the reference conduction path 32C (target unit 320). The charge in the parasitic capacitance unit 23 moves in accordance with the bias in the charge distribution in the metal housing 33B, and it can be considered that the charge moves from the metal housing 33B to the reference conduction path 32C. In other words, the parasitic capacitance unit 23 is an apparent conduction path that moves the charge from the metal housing 33B to the reference conduction path 32C.

[0062] <Other embodiments> The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. The scope of the present invention is not limited to the embodiments disclosed herein, but is defined by the claims, and is intended to include all modifications within the meaning and scope of the claims.

[0063] Unlike the fourth embodiment, a protection device 450 may be configured with a protection path portion 421 as shown in FIG. 6. Specifically, a parasitic capacitance portion 423 included in the protection path portion 421 may be disposed between the metal housing 33B and the second power path 31B, thereby generating a second parasitic capacitance C3 between the metal housing 33B and the second power path 31B, the second parasitic capacitance C3 being larger than the first parasitic capacitance C1. Note that the first power path 31A in the configuration shown in FIG. 6 has an inductance component L, which is a parasitic component. The inductance component in the second power path 31B is extremely small compared to the first power path 31A, and is negligible.

[0064] A comparator may be used as the current detector. In this case, a predetermined high-level signal is output when the current value in the power path is equal to or greater than a predetermined threshold, and a predetermined low-level signal is output when the current value is less than the predetermined threshold. Alternatively, a current transformer or the like may be used.

[0065] Unlike the first embodiment, the entire interrupter may be housed in a metal housing.

[0066] The conductive portion may be configured to short-circuit the target portion and the metal housing, or may be configured to transfer charge via one or more of a resistance component, a capacitance component, and an inductance component.

[0067] The protection path portion may have a configuration in which both a conductive portion and a parasitic capacitance portion exist. [Explanation of symbols]

[0068] 20, 120, 220, 320...Target section 21, 121, 221, 321, 421...Protection path section 23,423...parasitic capacitance section 30...Shut-off system 31…1st circuit 31A…1st power path (power path) 31B…Second power path (power path) 32…Second circuit 32A...Shutoff control section 32B...Low voltage power supply section 32C…Reference conductive path 33...Circuit breaker 33A...breaker 33B...Metal case 33C…Ignition part 33D...Displacement section 33E…Part to be cut 33F... Gunpowder 33G,133G,233G…Conducting part 35...Contactor 36...Capacitor 38...Current detection unit 50,150,250,350,450...protective device 90...Power supply section 91...Load 100...In-vehicle systems A...Current value B...Block signal C1...first parasitic capacitance C2, C3…Second parasitic capacitance CH…High potential conductive path (power path) CL…Low potential conductive path (power path) G...Ground L: Inductance component S…Signal T...Signal line (second conductive path)

Claims

1. a first circuit having a power path that is a path through which power is transmitted; a circuit breaker having a circuit breaker unit that is capable of interrupting the power path and a metal housing that accommodates at least a portion of the circuit breaker unit; a second circuit that provides a cutoff signal to the cutoff unit; A protection device for use in a shutdown system comprising: A protection device having a protection path portion including a conductive portion that forms a conductive path between a target portion including either the first circuit or a ground portion and the metal housing, or a parasitic capacitance portion that generates a parasitic capacitance larger than the parasitic capacitance between the metal housing and the second circuit.

2. the protection path portion includes the conductive portion, The protection device according to claim 1 , wherein the conductive part short-circuits the metal housing and the target part.

3. the target portion includes the ground portion, The protection device according to claim 2 , wherein the protection path portion constitutes the conduction path between the metal housing and the ground portion.

4. the power path includes a high-potential conductive path provided on a high-potential side of the circuit breaker and a low-potential conductive path provided on a low-potential side of the circuit breaker, the circuit breaker is provided to be able to cut off between the high potential conductive path and the low potential conductive path, The protection device according to claim 1 , wherein the target portion includes the low-potential conductive path.

5. the power path includes a high-potential conductive path provided on a high-potential side of the circuit breaker and a low-potential conductive path provided on a low-potential side of the circuit breaker, the circuit breaker is provided to be able to cut off between the high potential conductive path and the low potential conductive path, The protection device according to claim 1 , wherein the target portion includes the high-potential conductive path.

6. the second circuit includes a reference conductive path that is the ground portion and a second conductive path that is a conductive path different from the reference conductive path, the target portion includes the reference conductive path, The protection device according to claim 1 , wherein a second parasitic capacitance, which is a parasitic capacitance between the metal housing and the reference conductive path, is larger than a first parasitic capacitance, which is a parasitic capacitance between the metal housing and the second conductive path.

7. The protection device according to any one of claims 1 to 6, wherein the interrupting unit is a fuse device having an ignition unit that performs an explosive action in response to the interrupting signal, a cutoff unit that is provided in the power path and cuts off the power path when the cutoff unit is cut, and a displacement unit that is displaced by the force generated by the explosive action, and cuts off the cutoff unit by displacement of the displacement unit in response to the explosive action.

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