Protection device

Abstract

And the circuit is miniaturized and is protected from being influenced by surge voltage at the same time. A protection device (50) is used in a shut-off system (30) provided with: a first circuit (31) having a first power line (31A) and a second power line (31B), which are lines for transmitting power; a circuit breaker (33) having a cut-off part (33A) provided so as to be able to cut off the second power line (31B), and a metal case (33B) that accommodates at least a part of the cut-off part (33A); and a second circuit (32) that supplies a cutoff signal (B) to the cutoff unit (33A). The protection device (50) is provided with a conduction part (33G), and the conduction part (33G) forms a conduction line between the object part (20) including the grounding part (G) and the metal housing (33B).

Description

Technical Field

[0001] The present disclosure relates to protection devices. Background Art

[0002] Patent Document 1 discloses a drive circuit for driving a power MOSFET via a pulse transformer. The circuit is configured to separate the power MOSFET side from the drive side to which a PWM signal for controlling the power MOSFET is inputted by a pulse transformer. According to this structure, for example, even if a surge voltage is generated on the power MOSFET side, the pulse transformer can prevent the surge voltage from intruding into the drive side.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Laid-Open No. 62-021322 Summary of the invention

[0006] Problems to be solved by the invention

[0007] The circuit of Patent Document 1 uses a pulse transformer, so it is difficult to miniaturize the circuit. Therefore, a technology for preventing surge voltage from invading the drive side while miniaturizing the circuit is desired.

[0008] The present disclosure has been made based on the above circumstances, and an object of the present disclosure is to provide a protection device that can reduce the size of a circuit and protect the circuit from a surge voltage.

[0009] Means for solving problems

[0010] The protection device disclosed in the present invention is used in a cutting system, which comprises: a first circuit having a power line as a line for transmitting power; a circuit breaker having a cutting portion arranged in a manner capable of cutting off the power line and a metal shell that accommodates at least a portion of the cutting portion; and a second circuit that provides a cutting signal to the cutting portion, wherein the protection device has a protection line portion, and the protection line portion includes: a conductive portion that constitutes a conductive line between an object portion and the metal shell, and the object portion includes either the first circuit and the grounding portion; or a parasitic capacitance portion that generates a parasitic capacitance larger than the parasitic capacitance between the metal shell and the second circuit.

[0011] Effects of the Invention

[0012] According to the present disclosure, it is possible to protect a circuit from a surge voltage while miniaturizing the circuit. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] [ Figure 1 ] Figure 1 This is a block diagram illustrating the in-vehicle system according to the first embodiment.

[0014] [ Figure 2 ] Figure 2 This is a block diagram illustrating details of the circuit breaker according to the first embodiment.

[0015] [ Figure 3 ] Figure 3 This is a block diagram illustrating details of the circuit breaker according to the second embodiment.

[0016] [ Figure 4 ] Figure 4 This is a block diagram illustrating details of the circuit breaker according to the third embodiment.

[0017] [ Figure 5 ] Figure 5 This is a block diagram illustrating details of the circuit breaker according to the fourth embodiment.

[0018] [ Figure 6 ] Figure 6 This is a block diagram illustrating details of a circuit breaker according to another embodiment. DETAILED DESCRIPTION

[0019] [Description of Embodiments of the Present Disclosure]

[0020] First, embodiments of the present disclosure will be described below.

[0021] [1] The protection device disclosed in the present invention is used in a disconnection system having a first circuit, a circuit breaker, and a second circuit. The first circuit has a power line as a line for transmitting electric power. The circuit breaker has a disconnection portion arranged in a manner capable of disconnecting the power line and a metal shell that accommodates at least a portion of the disconnection portion. The second circuit provides a disconnection signal to the disconnection portion. The protection device has a protection line portion, which includes: a conductive portion that constitutes a conductive line between an object portion and the metal shell, and the object portion includes either the first circuit or the grounding portion; or a parasitic capacitance portion that generates a parasitic capacitance larger than the parasitic capacitance between the metal shell and the second circuit.

[0022] The protection device of the above-mentioned [1] can quickly release the deviation of the distribution of the charge generated in the metal shell to the target part through the protection line part, even if the distribution of the charge in the metal shell is deviated due to the surge voltage generated in the first circuit, so as to eliminate it. Therefore, the circuit can be miniaturized, and the surge voltage generated in the first circuit can be prevented from affecting the second circuit through the metal shell.

[0023] [2] In the protection device of [1] above, the protection line portion has a conductive portion, and the conductive portion can short-circuit the metal housing and the target portion.

[0024] The protection device of the above-mentioned [2] can transfer electric charge between the metal casing and the target part through the conductive part, so that the deviation of the distribution of electric charge in the metal casing can be easily released to the target part.

[0025] [3] In the protection device of [2] above, the target part includes a ground portion, and the protection line part can form a conductive path between the metal housing and the ground portion.

[0026] The protection device of the above-mentioned [3] can easily stabilize the potential of the metal casing.

[0027] [4] In any one of [1] to [3] above, the power line may include a high potential conductive line provided on the high potential side relative to the circuit breaker and a low potential conductive line provided on the low potential side relative to the circuit breaker. The circuit breaker is provided to be able to cut off the high potential conductive line from the low potential conductive line, and the target part may include the low potential conductive line.

[0028] The protection device of the above-mentioned [4] can eliminate the deviation of the charge distribution between the metal case and the low-potential conductive line in a manner that solves the problem in the first circuit, even if the distribution of the charge in the metal case is deviated due to the surge voltage generated by the inductance component of the high-potential conductive line. Therefore, the influence of the surge voltage in the second circuit can be suppressed.

[0029] [5] In any one of [1] to [3] above, the power line may include a high potential conductive line provided on the high potential side relative to the circuit breaker and a low potential conductive line provided on the low potential side relative to the circuit breaker. The circuit breaker is provided to be able to cut off the high potential conductive line from the low potential conductive line, and the target part may include the high potential conductive line.

[0030] The protection device of the above-mentioned [5] can eliminate the deviation of the charge distribution between the metal case and the high-potential conductive line in a manner that solves the problem in the first circuit, even if the distribution of the charge in the metal case is deviated due to the surge voltage generated by the inductance component of the low-potential conductive line. Therefore, the influence of the surge voltage in the second circuit can be suppressed.

[0031] [6] In the above [1], the second circuit may include a reference conductive line as a ground portion and a second conductive line as a conductive line different from the reference conductive line. The object portion may include the reference conductive line. The parasitic capacitance between the metal housing and the reference conductive line, i.e., the second parasitic capacitance, may be greater than the parasitic capacitance between the metal housing and the second conductive line, i.e., the first parasitic capacitance.

[0032] In the protection device of the above-mentioned [6], when the distribution of charge in the metal casing is deviated due to the surge voltage generated in the first circuit, the second parasitic capacitor having a larger capacitance than the first parasitic capacitor is more likely to offset the deviation in the distribution of charge. Therefore, the influence of the surge voltage generated in the first circuit is less likely to spread to the second circuit via the metal casing.

[0033] [7] In the protection device of any one of [1] to [6] above, the cut-off portion may include: an ignition portion that performs an explosion action in response to a cut-off signal; a cut-off portion that is provided in the power line and cuts off the power line when the cut-off portion is cut off; and a displacement portion that is displaced by a force generated by the explosion action. The cut-off portion may be a fuse device that cuts off the cut-off portion by displacement of the displacement portion corresponding to the explosion action.

[0034] The protection device of the above-mentioned [7] receives the force generated by the explosion action of the ignition part, and the displacement part is rapidly displaced, so that the power line can be cut off in a very short time.

[0035] [Details of the embodiments of the present disclosure]

[0036] <Implementation Method 1>

[0037] [Overview of the cutting system]

[0038] Figure 1 The vehicle-mounted system 100 shown is a system mounted on a vehicle. The vehicle-mounted system 100 includes a power supply unit 90, a load 91, and a disconnection system 30. For example, a lead battery or a lithium ion battery is used for the power supply unit 90. The load 91 is an electronic device installed in the vehicle.

[0039] The cutoff 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 line 31A which is a power line electrically connected to a terminal on a high potential side of the power supply unit 90, and a second power line 31B which is a power line electrically connected to a terminal on a low potential side of the power supply unit 90. The first power line 31A and the second power line 31B are lines for transmitting power. Contactors 35 are respectively provided on the first power line 31A and the second power line 31B. Each contactor 35 has a function of switching the first power line 31A and the second power line 31B to a conducting state and a non-conducting state, respectively. The first power line 31A and the second power line 31B each have an inductance component L. The inductance component L is a parasitic component that each of the first power line 31A and the second power line 31B has.

[0040] In each of the first power line 31A and the second power line 31B, a capacitor 36 is electrically connected on the load 91 side relative to the contactor 35. The first power line 31A and the second power line 31B are electrically connected to the ground portion G via the capacitor 36 and the reference conductive line 32C described later. The ground portion G is, for example, a chassis constituting a vehicle body. The ground portion G is included in the structure of the target part 20.

[0041] In the present disclosure, "electrical connection" is preferably a structure in which the potentials of both connection objects are equal and the connection is in a state of mutual conduction (a state in which current flows). However, it is not limited to this structure. For example, "electrical connection" may also be a structure in which an electrical component is sandwiched between two connection objects and the two connection objects are connected in a state in which conduction is possible.

[0042] In the second power line 31B, a current detection unit 38 is provided on the power supply unit 90 side relative to the contactor 35. The current detection unit 38 is configured to include, for example, a resistor and a differential amplifier, and can output a value indicating a current flowing through the second power line 31B (specifically, an analog voltage corresponding to the value of the current flowing through the second power line 31B) as a current value A. The current detection unit 38 detects the state of the current flowing through the second power line 31B.

[0043] The second circuit 32 includes a cutoff control unit 32A, a low voltage power supply unit 32B, and a reference conductive path 32C. The cutoff control unit 32A is mainly composed of, for example, a microcomputer, and includes a CPU (Central Processing Unit) or other computing devices, a ROM (Read Only Memory) or a RAM (Random Access Memory) or other memories, an A / D converter, and the like. The cutoff control unit 32A is configured to receive the current value A output from the current detection unit 38. In addition, the cutoff control unit 32A is configured to receive a signal S (SOC (State Of Charge) etc.) indicating the state of the power supply unit 90 from an external device such as a battery management system (BMS) not shown. The cutoff control unit 32A of the second circuit 32 is configured to provide a cutoff signal B to an ignition unit 33C of a cutoff unit 33A of a circuit breaker 33 described later, based on the current value A and the signal S input from the current detection unit 38 and the external device.

[0044] The low voltage power supply unit 32B uses, 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 supply power to the cutoff control unit 32A.

[0045] The reference conductive path 32C is a conductive path that is maintained at a constant low voltage in the second circuit 32, and in the first embodiment, is electrically connected to the ground G. The low potential side terminal of the low voltage power supply unit 32B and the cutoff control unit 32A are electrically connected to the reference conductive path 32C. The reference conductive path 32C is also the ground G.

[0046] The circuit breaker 33 uses, for example, a high-temperature fuse (PYROFUSE (registered trademark)). Figure 2 As shown, the circuit breaker 33 includes a cut-off portion 33A and a metal case 33B. The cut-off portion 33A includes an ignition portion 33C, explosive 33F, a displacement portion 33D, and a cut-off portion 33E.

[0047] The ignition part 33C is configured to generate heat when a cutoff signal B is provided from the cutoff control part 32A. The gunpowder 33F is provided adjacent to the ignition part 33C. The gunpowder 33F explodes when receiving the heat generated in the ignition part 33C, generating an explosive force. That is, the ignition part 33C performs an explosive action of igniting the gunpowder 33F according to the cutoff signal B. The displacement part 33D is provided adjacent to the gunpowder 33F. The displacement part 33D is rapidly displaced when receiving the explosive force generated from the exploding gunpowder 33F.

[0048] The cut-off portion 33E is formed of, for example, a conductive strip metal. The cut-off portion 33E is sandwiched in the second power line 31B. That is, the cut-off portion 33E is provided in the power line. The cut-off portion 33E is arranged on the opposite side of the gunpowder 33F across the displacement portion 33D. The cut-off portion 33E is physically cut off in a very short time by the displacement portion 33D that is rapidly displaced by the explosive force generated by the explosion action. Thus, the cut-off portion 33E cuts off the second power line 31B as the power line when it is cut off. In this way, the cut-off portion 33A cuts off the second power line 31B as the power line. That is, the cut-off portion 33A is provided to be able to cut off the second power line 31B. The cut-off portion 33E is not connected again. That is, the second power line 31B cut off by the cut-off portion 33A is not switched to a conductive state that allows current to flow. That is, the cut-off portion 33A is a fuse device that cuts off the cut-off portion 33E by the displacement of the displacement portion 33D corresponding to the explosion action.

[0049] The metal shell 33B is formed into a box shape by, for example, stamping a metal plate. The metal shell 33B accommodates the cut portion 33A. For example, both ends of the cut portion 33E are configured to protrude from the metal shell 33B to the outside. That is, the metal shell 33B accommodates a part of the cut portion 33A.

[0050] The protection device 50 is used to cut off the system 30. The protection device 50 has a protection circuit part 21. The protection circuit part 21 has a conductive part 33G. The conductive part 33G is formed of a conductive metal. One end of the conductive part 33G is electrically connected to the metal shell 33B. The other end of the conductive part 33G is electrically connected to the reference conductive path 32C. The conductive part 33G is interposed between the metal shell 33B and the grounding part G. That is, the metal shell 33B is electrically connected to the grounding part G via the conductive part 33G and the reference conductive path 32C. The conductive part 33G conducts the metal shell 33B and the grounding part G to short-circuit. That is, the conductive part 33G of the protection circuit part 21 constitutes a conductive path between the grounding part G of the target part 20 and the metal shell 33B. The protection circuit part 21 functions in a manner that when a surge voltage is applied to the metal shell 33B, the electric charge is released to the grounding part G via itself.

[0051] [About the action of shutting down the system]

[0052] The cut-off control unit 32A outputs a cut-off signal B to the ignition unit 33C of the cut-off unit 33A of the circuit breaker 33 based on the signal input from the current detection unit 38 or the external device. Then, the ignition unit 33C of the cut-off unit 33A generates heat, and the gunpowder 33F explodes due to the heat. Then, the displacement unit 33D rapidly displaces with the explosion of the gunpowder 33F, thereby cutting off the cut-off unit 33E. As a result, the current flowing in the second power line 31B does not flow rapidly. With the change in the current flow, a surge voltage is generated on one end side or the other end side of the cut-off unit 33E based on the inductance component L of the first circuit 31.

[0053] The distribution of the charge in the metal housing 33B is deviated due to the induction of the surge voltage. The metal housing 33B is connected to the grounding portion G via the conducting portion 33G. Therefore, even if the distribution of the charge in the metal housing 33B is deviated, the charge is immediately exchanged with the grounding portion G, thereby preventing the influence of the surge voltage from spreading to the cutoff control portion 32A of the second circuit 32 via the metal housing 33B.

[0054] Next, the effects of this structure are exemplified.

[0055] The protection device 50 is used for the disconnection system 30 including the first circuit 31, the circuit breaker 33, and the second circuit 32. The first circuit 31 includes a first power line 31A and a second power line 31B as lines for transmitting power. The circuit breaker 33 includes a disconnection portion 33A provided in a manner capable of disconnecting the second power line 31B and a metal housing 33B accommodating at least a part of the disconnection portion 33A. The second circuit 32 provides a disconnection signal B to the disconnection portion 33A. The protection device 50 includes a protection line portion 21 including a conduction portion 33G forming a conduction path between the target part 20 including the ground portion G and the metal housing 33B. According to this structure, even if the distribution of the charge in the metal housing 33B is deviated due to the surge voltage generated in the first circuit 31, the deviation of the distribution of the charge generated in the metal housing 33B can be quickly diffused to the ground portion G of the target part 20 by the conduction portion 33G of the protection line portion 21 and eliminated. Therefore, it is possible to reduce the size of the circuit and prevent the surge voltage generated in the first circuit 31 from affecting the second circuit 32 via the metal case 33B.

[0056] In the protection device 50, the protection circuit portion 21 has a conductive portion 33G that short-circuits the metal shell 33B and the ground portion G of the target portion 20. According to this structure, electric charge can be transferred between the metal shell 33B and the ground portion G of the target portion 20 through the conductive portion 33G, so that the deviation of the charge distribution in the metal shell 33B is easily released to the ground portion G of the target portion 20.

[0057] In the protection device 50 , the target part 20 includes the ground part G, and the conductive part 33G of the protection line part 21 forms a conductive path between the metal casing 33B and the ground part G. According to this structure, the potential of the metal casing 33B can be easily stabilized.

[0058] The cut-off section 33A includes an ignition section 33C that performs an explosion action according to the cut-off signal B; a cut-off section 33E that is provided in the power line and cuts off the second power line 31B when the cut-off section 33E is cut off; and a displacement section 33D that is displaced by the force generated by the explosion action. The cut-off section 33A is a fuse device that cuts off the cut-off section 33E by the displacement of the displacement section 33D corresponding to the explosion action. According to this structure, the displacement section 33D is rapidly displaced by the force generated by the explosion action of the ignition section 33C, so that the second power line 31B can be cut off in a very short time.

[0059] <Implementation Method 2>

[0060] Next, refer to Figure 3The protection device 150 of Embodiment 2 is described. Embodiment 2 is different from Embodiment 1 in that the structure of the first circuit 31 and the metal housing 33B are electrically connected to the low potential conductive line CL via the conductive portion 133G. The same reference numerals are given to the same structures as those in Embodiment 1, and the same functions and effects as those in Embodiment 1 are omitted.

[0061] like Figure 3 As shown, the first power line 31A has an inductance component L. The inductance component L is a parasitic component of the first power line 31A. The inductance component of the second power line 31B is extremely small compared to the first power line 31A and is negligible.

[0062] The portion of the second power line 31B on the load 91 side relative to the circuit breaker 33 is a high potential conductive line CH provided at the high potential side relative to the circuit breaker 33. The portion of the second power line 31B on the current detection unit 38 side relative to the circuit breaker 33 is a low potential conductive line CL provided at the low potential side relative to the circuit breaker 33. That is, the circuit breaker 33 is provided so as to cut off the high potential conductive line CH from the low potential conductive line CL.

[0063] The protection device 150 has a protection circuit portion 121. The protection circuit portion 121 has a conduction portion 133G. The conduction portion 133G is formed of a conductive metal. One end of the conduction portion 133G is electrically connected to the metal shell 33B. The other end of the conduction portion 133G is electrically connected to the low potential conductive line CL. That is, the low potential conductive line CL is included in the structure of the object portion 120. The conduction portion 133G is interposed between the metal shell 33B and the low potential conductive line CL of the second power line 31B, so that the metal shell 33B and the low potential conductive line CL of the second power line 31B are short-circuited. In other words, the metal shell 33B is electrically connected to the low potential conductive line CL of the second power line 31B via the conduction portion 133G. The conduction portion 133G is a conduction line that conducts the metal shell 33B and the second power line 31B (first circuit 31).

[0064] [About the action of shutting down the system]

[0065] As the explosive 33F of the circuit breaker 33 explodes, the displaceable portion 33D is rapidly displaced, and the cut portion 33E is cut off. As a result, a surge voltage is generated on one end of the cut portion 33E due to the inductance component L of the first power line 31A.

[0066] The distribution of the charge in the metal housing 33B is deviated due to the surge voltage. The metal housing 33B is electrically connected to the low potential conductive path CL of the second power line 31B through the conductive portion 133G. Therefore, even if the distribution of the charge in the metal housing 33B is deviated, the charge is immediately exchanged with the low potential conductive path CL, thereby preventing the influence of the surge voltage from spreading to the cutoff control unit 32A of the second circuit 32 via the metal housing 33B.

[0067] The power line includes a high potential conductive line CH provided on the high potential side relative to the circuit breaker 33 and a low potential conductive line CL provided on the low potential side relative to the circuit breaker 33. The circuit breaker 33 is provided so as to be able to cut off the high potential conductive line CH and the low potential conductive line CL, and the target part 120 includes the low potential conductive line CL. According to this structure, even if the distribution of the charge in the metal case 33B is deviated due to the surge voltage generated based on the inductance component L possessed by the first power line 31A, the deviation in the distribution of the charge can be eliminated between the metal case 33B and the low potential conductive line CL in a manner that is completely resolved in the first circuit 31. Therefore, the influence of the surge voltage in the second circuit 32 can be suppressed.

[0068] <Implementation Method 3>

[0069] Next, refer to Figure 4 The protection device 250 of the third embodiment is described. The third embodiment is different from the second embodiment in that the second power line 31B has an inductance component L, the inductance component of the first power line 31A is extremely small and negligible compared to the second power line 31B, and the metal housing 33B is connected to the high potential conductive line CH via the conductive portion 233G. The same reference numerals are attached to the same structures as those in the second embodiment, and the same functions and effects as those in the second embodiment are omitted.

[0070] like Figure 4 As shown, the second power line 31B has an inductance component L. The inductance component L is a parasitic component of the second power line 31B. The inductance component in the first power line 31A is extremely small compared to the second power line 31B and is negligible. The circuit breaker 33 is configured to disconnect the high potential conductive line CH from the low potential conductive line CL.

[0071] The protection device 250 has a protection circuit portion 221. The protection circuit portion 221 has a conduction portion 233G. One end of the conduction portion 233G is electrically connected to the metal shell 33B. The other end of the conduction portion 233G is electrically connected to the high potential conductive line CH. That is, the high potential conductive line CH is included in the structure of the object portion 220. The conduction portion 233G is interposed between the metal shell 33B and the high potential conductive line CH of the second power line 31B, and short-circuits the metal shell 33B and the high potential conductive line CH of the second power line 31B. In other words, the metal shell 33B is electrically connected to the high potential conductive line CH of the second power line 31B via the conduction portion 233G. The conduction portion 233G is a conduction line that conducts the metal shell 33B and the second power line 31B (first circuit 31).

[0072] [About the action of shutting down the system]

[0073] As the explosive 33F of the circuit breaker 33 explodes, the displaceable portion 33D is rapidly displaced, and the cut portion 33E is cut off. In response, a surge voltage is generated on the other end side of the cut portion 33E due to the inductance component L of the second power line 31B.

[0074] The distribution of the charge in the metal housing 33B is deviated due to the surge voltage. The metal housing 33B is electrically connected to the high potential conductive path CH of the second power path 31B through the conductive portion 233G. Therefore, even if the distribution of the charge is deviated in the metal housing 33B, the charge can be immediately exchanged with the high potential conductive path CH, thereby preventing the influence of the surge voltage from spreading to the cutoff control unit 32A of the second circuit 32 via the metal housing 33B.

[0075] The power line includes a high potential conductive line CH provided on the high potential side relative to the circuit breaker 33 and a low potential conductive line CL provided on the low potential side relative to the circuit breaker 33. The circuit breaker 33 is provided so as to be able to cut off the high potential conductive line CH and the low potential conductive line CL, and the target part 220 includes the high potential conductive line CH. According to this structure, even if the distribution of the charge in the metal case 33B is deviated due to the surge voltage generated based on the inductance component L of the second power line 31B, the deviation in the distribution of the charge can be eliminated between the metal case 33B and the high potential conductive line CH in a manner that is completely resolved in the first circuit 31. Therefore, the influence of the surge voltage in the second circuit 32 can be suppressed.

[0076] <Implementation Method 4>

[0077] Next, refer to Figure 5The protection device 350 of the fourth embodiment is described. The fourth embodiment is different from the first to third embodiments in that the protection circuit portion 321 of the protection device 350 includes a parasitic capacitor portion 23, a first parasitic capacitor C1 exists between the metal housing 33B and the second circuit 32, and a second parasitic capacitor C2 having a capacitance greater than the first parasitic capacitor C1 exists between the metal housing 33B and the reference conductive path 32C. The same reference numerals are used for the same structures as those in the first to third embodiments, and the same functions and effects as those in the first to third embodiments are omitted.

[0078] The protection device 350 has a protection circuit portion 321. The protection circuit portion 321 includes a parasitic capacitor portion 23. The parasitic capacitor portion 23 is arranged between the metal shell 33B and the reference conductive path 32C. The parasitic capacitor portion 23 is, for example, an insulating material such as a synthetic resin and a space in which air exists. As the parasitic capacitor portion 23, both of these may exist. The parasitic capacitor portion 23 generates a second parasitic capacitor C2 as a parasitic capacitor between the metal shell 33B and the reference conductive path 32C. The parasitic capacitor portion 23 only needs to have a structure that insulates the metal shell 33B from the reference conductive path 32C. The size of the capacitance of the second parasitic capacitor C2 can be adjusted to a desired size by changing the material, size, etc. of the parasitic capacitor portion 23 or changing the distance between the metal shell 33B and the reference conductive path 32C.

[0079] The second circuit 32 includes a reference conductive line 32C as a ground portion G and a signal line T as a second conductive line different from the reference conductive line 32C. The reference conductive line 32C is included in the structure of the object 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 shell 33B is close to the signal line T (the second circuit 32), and thus, the first parasitic capacitance C1 as a parasitic capacitance is interposed between the metal shell 33B and the signal line T. The signal line T is set on the high potential side relative to the ignition unit 33C. When the cutoff signal B is output from the cutoff control unit 32A, the current flows from the signal line T to the reference conductive line 32C via the ignition unit 33C. The cutoff signal B output by the cutoff control unit 32A is a current signal that can perform an action of igniting the gunpowder 33F through the ignition unit 33C, specifically, a current greater than a specified value. The reference conductive line 32C is set on the low potential side relative to the ignition unit 33C and is electrically connected to the ground portion 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 interposing a dielectric therebetween.

[0080] The capacitance of the second parasitic capacitor C2 is greater than the capacitance of the first parasitic capacitor C1 . That is, the parasitic capacitor portion 23 generates the second parasitic capacitor C2 which is greater than the first parasitic capacitor C1 between the metal housing 33B and the second circuit 32 .

[0081] [About the action of shutting down the system]

[0082] When the displaceable portion 33D is rapidly displaced by the explosion of the explosive 33F of the circuit breaker 33 and the cut-off portion 33E is cut off, a surge voltage is generated on one end or the other end of the cut-off portion 33E due to the inductance component L of the first circuit 31 .

[0083] The distribution of the charge in the metal housing 33B is deviated by the surge voltage generated in the first circuit 31. Moreover, since the capacitance of the second parasitic capacitor C2 is larger than that of the first parasitic capacitor C1, the charge in the parasitic capacitor section 23 and the reference conductive path 32C moves in a manner that cancels the deviation of the distribution of the charge in the metal housing 33B more quickly than the first parasitic capacitor C1. Therefore, it is possible to make it difficult for the influence of the surge voltage generated in the first circuit 31 to affect the second circuit 32 via the metal housing 33B. That is, even if the distribution of the charge is deviated in the metal housing 33B, the influence of the surge voltage can be prevented from affecting the cutoff control section 32A of the second circuit 32 by the second parasitic capacitor C2. The parasitic capacitor section 23 does not allow the charge in the metal housing 33B to move directly to the reference conductive path 32C (the target section 320). The charge in the parasitic capacitor section 23 moves according to the deviation of the distribution of the charge in the metal housing 33B, and thus it can be understood superficially that the charge moves from the metal housing 33B to the reference conductive path 32C. That is, the parasitic capacitance portion 23 is superficially a conductive path that transfers electric charge from the metal casing 33B to the reference conductive path 32C.

[0084] <Other Implementation Methods>

[0085] The embodiments disclosed herein are to be considered in all respects as illustrative and non-restrictive. The scope of the present invention is not limited to the embodiments disclosed herein but is indicated by the claims, and is intended to include all modifications within the meaning and scope equivalent to the claims.

[0086] Different from implementation mode 4, Figure 6 As shown, a protection device 450 having a protection line portion 421 may also be configured. Specifically, a parasitic capacitor portion 423 included in the protection line portion 421 may be arranged between the metal housing 33B and the second power line 31B, thereby generating a second parasitic capacitor C3 larger than the first parasitic capacitor C1 between the metal housing 33B and the second power line 31B. In addition, Figure 6 The first power line 31A in the illustrated configuration has a parasitic inductance component L. The inductance component in the second power line 31B is extremely small compared to the first power line 31A and is negligible.

[0087] A comparator may be used as the current detection unit. In this case, a predetermined high-level signal is output when the current value in the power line indicates a value above a predetermined threshold value, and a predetermined low-level signal is output when the current value indicates a value below the predetermined threshold value. Alternatively, a structure using a current transformer or the like may be used.

[0088] Unlike the first embodiment, the entire cutting portion may be housed in a metal casing.

[0089] The conductive portion may be a structure that short-circuits the target portion and the metal case, or may be a structure that allows charge to be transferred via any one or more of a resistance component, a capacitance component, and an inductance component.

[0090] The protection line portion may have a structure including both a conductive portion and a parasitic capacitance portion.

[0091] Description of Reference Numerals

[0092] 20, 120, 220, 320…Target part

[0093] 21, 121, 221, 321, 421…protection line

[0094] 23, 423… Parasitic capacitance

[0095] 30…Shut off system

[0096] 31…1st Circuit

[0097] 31A…First Power Line (Power Line)

[0098] 31B…Second power line (power line)

[0099] 32…Second Circuit

[0100] 32A... Cut-off control unit

[0101] 32B…Low voltage power supply unit

[0102] 32C…Baseline Conductive Circuit

[0103] 33…Circuit Breaker

[0104] 33A…cutting part

[0105] 33B…Metal housing

[0106] 33C…Ignition

[0107] 33D…Displacement

[0108] 33E…cut off part

[0109] 33F…Gunpowder

[0110] 33G, 133G, 233G...conductivity

[0111] 35…Contactor

[0112] 36…Capacitor

[0113] 38…Current detection unit

[0114] 50, 150, 250, 350, 450…protective devices

[0115] 90…Power supply

[0116] 91…Load

[0117] 100…In-vehicle systems

[0118] A…current value

[0119] B…Cut off signal

[0120] C1…First parasitic capacitance

[0121] C2, C3…Second parasitic capacitance

[0122] CH…High potential conductive line (power line)

[0123] CL…Low potential conductive line (power line)

[0124] G…Ground

[0125] L…Inductance component

[0126] S…Signal

[0127] T…Signal line (second conductive line)

Claims

1. A protection device used in a cutoff system, the cutoff system comprising: a first circuit having a power line as a line for transmitting power; A circuit breaker having a cut-off portion provided in a manner capable of cutting off the power line and a metal housing accommodating at least a portion of the cut-off portion; and a second circuit for providing a cut-off signal to the cut-off portion, wherein: The protection device has a protection circuit portion, which includes: a conductive portion constituting a conductive circuit between an object portion and the metal shell, wherein the object portion includes any one of the first circuit and a grounding portion; or a parasitic capacitance portion generating a parasitic capacitance greater than the parasitic capacitance between the metal shell and the second circuit.

2. The protection device according to claim 1, wherein: The protection circuit portion has the conductive portion. The conductive portion short-circuits the metal housing and the counterpart portion.

3. The protection device according to claim 2, wherein: The object portion includes the ground portion, The protection circuit portion forms the conducting circuit between the metal housing and the ground portion.

4. The protection device according to any one of claims 1 to 3, wherein: The power line includes: a high potential conductive line, which is arranged at a high potential side relative to the circuit breaker; and a low potential conductive line, which is arranged at a low potential side relative to the circuit breaker. The circuit breaker is configured to cut off the connection between the high-potential conductive line and the low-potential conductive line. The object portion includes the low-potential conductive line.

5. The protection device according to any one of claims 1 to 3, wherein: The power line includes: a high potential conductive line, which is arranged at a high potential side relative to the circuit breaker; and a low potential conductive line, which is arranged at a low potential side relative to the circuit breaker. The circuit breaker is configured to cut off the connection between the high-potential conductive line and the low-potential conductive line. The object portion includes the high-potential conductive line.

6. The protection device according to claim 1, wherein: The second circuit includes a reference conductive circuit as the ground portion and a second conductive circuit as a conductive circuit different from the reference conductive circuit. The object portion includes the reference conductive circuit, The parasitic capacitance between the metal housing and the reference conductive path, namely the second parasitic capacitance, is greater than the parasitic capacitance between the metal housing and the second conductive path, namely the first parasitic capacitance.

7. The protection device according to any one of claims 1, 2, 3 and 6, wherein: The cut-off part is a fuse device, and the fuse device comprises: an ignition part, which performs an explosion action according to the cut-off signal; and a cut-off part, which is provided in the power line and cuts off the power line when the fuse device itself is cut off; and a displacement portion that is displaced by the force generated by the explosion, wherein the fuse device cuts off the cut-off portion by the displacement of the displacement portion corresponding to the explosion.

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