Protective device for vehicle

Abstract

The invention provides a technology capable of protecting a semiconductor circuit breaker. A vehicle protection device (40) is provided with: a semiconductor breaker (51) that is provided between a first conductive path (31) and a second conductive path (32), and that switches between an allowable state in which a current is allowed to flow from the first conductive path (31) to the second conductive path (32) via the semiconductor breaker itself, and a cut-off state in which the current flows from the first conductive path (31) to the second conductive path (32) via the semiconductor breaker itself; the cut-off state is a state in which the flow of current from the first conductive path (31) to the second conductive path (32) via the semiconductor circuit breaker itself is cut off. And a control unit (41) that outputs a control signal for switching the semiconductor circuit breaker (51) from the allowable state to the off state. A fuse (60) that fuses when an overcurrent flows is provided in parallel with the semiconductor breaker (51).

Description

Technical Field

[0001] The present disclosure relates to a protection device for a vehicle. Background Art

[0002] In an energization control system for an electric vehicle, in the event of an abnormality such as when an impact is applied to the vehicle or a load short circuit occurs, a mechanism for cutting off the conduction path between the battery and the load (inverter, DCDC converter, charger, etc.) is used. For example, a structure that uses a physical cutting mechanism such as a contactor or a fuse to cut off the conduction path can be cited.

[0003] In recent years, in consideration of the background of high output and rapid charging of the battery, the battery has been continuously developed to have a lower impedance, and further development of lower impedance has been ongoing. The increase in short-circuit current caused by the low impedance and the increase in the rate of increase of the short-circuit current require a large short-circuit tolerance including the peripheral circuit, resulting in high costs in a structure using a conventional physical cutting mechanism.

[0004] It is considered to use a cutting device that rapidly cuts off the short-circuit current and cuts off the conduction path between the battery and the load through electrical insulation. For example, in the overcurrent protection device disclosed in Patent Document 1, a semiconductor circuit breaker configured as a MOSFET is disconnected by a protection circuit, thereby preventing an overcurrent from flowing through the power supply line.

[0005] Prior Art Documents

[0006] Patent Documents

[0007] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2012-85382 Summary of the Invention

[0008] Problems to be Solved by the Invention

[0009] In a structure that uses a MOSFET as a cutting mechanism as disclosed in Patent Document 1, when a short-circuit breakdown or the like occurs between the drain and source of the MOSFET, conduction may occur after the cutting operation. For example, due to the inductance of the wiring, the surge voltage during the cutting operation of the semiconductor circuit breaker may exceed the avalanche tolerance of the MOSFET or the like.

[0010] The present disclosure has been made based on the above circumstances, and an object thereof is to provide a technology capable of protecting a semiconductor circuit breaker.

[0011] Means for Solving the Problems

[0012] The vehicle protection device of the present disclosure is used for a vehicle power supply system having a first conductive circuit and a second conductive circuit, and includes: a semiconductor circuit breaker disposed between the first conductive circuit and the second conductive circuit, which switches between an allowable state and a cut-off state. The allowable state is a state that allows current to flow from the first conductive circuit to the second conductive circuit through the semiconductor circuit breaker itself, and the cut-off state is a state that cuts off the flow of current from the first conductive circuit to the second conductive circuit through the semiconductor circuit breaker itself; and a control unit that outputs a control signal for switching the semiconductor circuit breaker from the allowable state to the cut-off state. One of an element unit and a fuse is disposed in parallel with the semiconductor circuit breaker. The element unit has at least any one of a resistance component, an inductance component, and a capacitance component, and the fuse melts in the case of overcurrent flow.

[0013] Advantages of the Invention

[0014] The technology related to the present disclosure can protect the semiconductor circuit breaker. Description of the Drawings

[0015] Figure 1 It is a block diagram schematically illustrating a vehicle power supply system including the vehicle protection device of the first embodiment.

[0016] Figure 2 It is a flowchart illustrating the cut-off control process performed by the control unit of the vehicle protection device.

[0017] Figure 3 It is an explanatory diagram illustrating the time change of the current value of the conductive circuit and the time change of the voltage across the semiconductor circuit breaker based on the cut-off control by the control unit.

[0018] Figure 4 It is a block diagram schematically illustrating a vehicle power supply system including the vehicle protection device of the second embodiment.

[0019] Figure 5 It is a flowchart illustrating the cut-off control process performed by the control unit of the vehicle protection device of the second embodiment.

[0020] Figure 6 It is a flowchart illustrating the cut-off control process performed by the control unit of the vehicle protection device of the third embodiment.

[0021] Figure 7 It is an explanatory diagram illustrating the time change of the current value of the conductive circuit, the time change of the voltage across the semiconductor circuit breaker, and the time change of the voltage across the pyrotechnic circuit breaker based on the cut-off control by the control unit of the third embodiment.

[0022] Figure 8It is a block diagram schematically illustrating a vehicle power supply system including a vehicle protection device according to a fourth embodiment.

[0023] Figure 9 It is a block diagram schematically illustrating a vehicle power supply system including a vehicle protection device according to other embodiments.

[0024] Figure 10 It is a block diagram schematically illustrating a vehicle power supply system including a vehicle protection device according to other embodiments.

[0025] Figure 11 It is a block diagram schematically illustrating a vehicle power supply system including a vehicle protection device according to other embodiments. Detailed Embodiment

[0026] 〔1〕A vehicle protection device for a vehicle power supply system having a first conductive circuit and a second conductive circuit, wherein the vehicle protection device has: a semiconductor circuit breaker provided between the first conductive circuit and the second conductive circuit, which switches between a permitted state and a cut-off state, the permitted state being a state in which current is permitted to flow from the first conductive circuit to the second conductive circuit through the semiconductor circuit breaker itself, and the cut-off state being a state in which the flow of the current from the first conductive circuit to the second conductive circuit through the semiconductor circuit breaker itself is cut off; and a control unit that outputs a control signal for switching the semiconductor circuit breaker from the permitted state to the cut-off state. One of an element unit and a fuse is provided in parallel with the semiconductor circuit breaker. The element unit has at least any one of a resistance component, an inductance component, and a capacitance component, and the fuse melts in the case of an overcurrent flowing.

[0027] In the vehicle protection device of the above 〔1〕, based on the switching of the semiconductor circuit breaker from the permitted state to the cut-off state, current can flow through the element unit or the fuse in a state where the time change of the current value is reduced. Therefore, it is possible to suppress the surge voltage generated by the switching of the semiconductor circuit breaker from the permitted state to the cut-off state, and the semiconductor circuit breaker can be protected.

[0028] 〔2〕In the vehicle protection device described in 〔1〕, it has the following characteristics. The fuse is provided in parallel with the semiconductor circuit breaker. The vehicle power supply system includes a power supply unit that supplies power to the first conductive circuit, and the rated current of the fuse is smaller than the current flowing from the first conductive circuit to the second conductive circuit when power is supplied from the power supply unit to the first conductive circuit in the case where the semiconductor circuit breaker is in the permitted state.

[0029] In the vehicle protection device of the above 〔2〕, after the semiconductor circuit breaker changes from the permitted state to the cut-off state, the fuse can be melted and cut off relatively early.

[0030] 〔3〕In the vehicle protection device described in 〔2〕, it has the following characteristics. The impedance of the fuse is greater than the impedance of the semiconductor circuit breaker in the allowable state.

[0031] In the vehicle protection device of 〔3〕 above, it is possible to suppress the current flowing from the power supply unit to the first conduction path via the fuse when the semiconductor circuit breaker is in the allowable state.

[0032] 〔4〕In the vehicle protection device according to any one of 〔1〕 to 〔3〕, it has the following characteristics. The fuse is provided in parallel with the semiconductor circuit breaker, and after the semiconductor circuit breaker switches from the allowable state to the cut-off state based on the control signal from the control unit, the fuse melts after a response time.

[0033] In the vehicle protection device of 〔4〕 above, after the semiconductor circuit breaker switches from the allowable state to the cut-off state, it is possible to reduce the time variation of the current value flowing through the fuse within the response time. Therefore, it is easy to suppress the surge voltage.

[0034] 〔5〕In the vehicle protection device according to any one of 〔1〕 to 〔4〕, it has the following characteristics. The fuse is provided in parallel with the semiconductor circuit breaker, the semiconductor circuit breaker switches from the cut-off state to the allowable state based on a second control signal output from the control unit, the vehicle protection device has a current detection unit that detects the current flowing through one of the first conduction path and the second conduction path, the control unit outputs the control signal when the current detected by the current detection unit becomes an overcurrent state, and outputs the second control signal when the overcurrent state is not detected by the current detection unit before the melting time t. The melting time t is calculated based on the following formula (1): E = I 2 ×t…Formula (1) E: The power value consumed by the fuse required until melting, I: The current value detected by the current detection unit when the overcurrent state occurs, t: The time from when the semiconductor circuit breaker switches from the allowable state to the cut-off state until melting.

[0035] In the vehicle protection device of [5] above, when the control unit does not detect an overcurrent state by the current detection unit before the fusing time t has elapsed, it outputs a second control signal, enabling the semiconductor circuit breaker to be switched from the cut-off state to the allowable state. Therefore, before switching the semiconductor circuit breaker from the cut-off state to the allowable state, it is possible to prevent the fuse from melting. In addition, the fusing time t is determined based on the current value in one of the first conduction path and the second conduction path, so the fusing time t can be determined with high precision.

[0036] 〔6〕In the vehicle protection device according to any one of 〔1〕 to 〔4〕, it has the following characteristics. The fuse is provided in parallel with the semiconductor circuit breaker. The semiconductor circuit breaker is switched from the cut-off state to the allowable state based on the second control signal output from the control unit. The semiconductor circuit breaker has: a storage unit that stores the fusing time t, which is the time from when current starts to flow in the fuse until it melts, and is calculated based on the following formula (2); and a current detection unit that detects the current flowing through one of the first conduction path and the second conduction path. When the current detected by the current detection unit becomes an overcurrent state, the control unit outputs the control signal. When the control unit does not detect the overcurrent state by the current detection unit before the fusing time t stored in the storage unit has elapsed, it outputs the second control signal. The formula (2) is: E = I 2 ×t…Formula (2) E: The power value consumed by the fuse until melting, I: A pre-determined current value, t: The time from when the semiconductor circuit breaker is switched from the allowable state to the cut-off state until melting.

[0037] In the vehicle protection device of [6] above, when the control unit does not detect an overcurrent state by the current detection unit before the fusing time t has elapsed, it outputs a second control signal, enabling the semiconductor circuit breaker to be switched from the cut-off state to the allowable state. Therefore, before switching the semiconductor circuit breaker from the cut-off state to the allowable state, it is possible to prevent the fuse from melting. In addition, by using the pre-determined fusing time t, it is possible to easily perform control during the judgment of the overcurrent state.

[0038] 〔7〕In the vehicle protection device of 〔1〕, it has the following characteristics. The element part having a resistance component is provided in parallel with the semiconductor circuit breaker, and the resistance value of the element part is greater than the on-resistance value of the semiconductor circuit breaker.

[0039] In the vehicle protection device of the above [7], based on the switching of the semiconductor circuit breaker from the allowable state to the cut-off state, current can flow through the element portion having a resistance component in a state where the time change of the current value is reduced, and the short-circuit current can be limited. Therefore, the surge voltage generated due to the switching of the semiconductor circuit breaker from the allowable state to the cut-off state can be suppressed, and the semiconductor circuit breaker can be protected.

[0040] 〔8〕In the vehicle protection device according to any one of [1] to [7], it has the following features. It has a pyrotechnic circuit breaker that breaks based on the explosion of gunpowder by the third control signal output from the control unit, thereby cutting off one of the first conduction path and the second conduction path. The semiconductor circuit breaker and the pyrotechnic circuit breaker are connected in series. When the vehicle power supply system becomes an abnormal state, the control unit outputs the control signal and the third control signal. After the semiconductor circuit breaker switches from the allowable state to the cut-off state based on the control signal from the control unit, based on the third control signal from the control unit, one of the first conduction path and the second conduction path is cut off by the pyrotechnic circuit breaker.

[0041] In the vehicle protection device of the above [8], when the semiconductor circuit breaker is in the cut-off state, one of the first conduction path and the second conduction path can be quickly cut off. In addition, by cutting off one of the first conduction path and the second conduction path by the pyrotechnic circuit breaker, the insulation performance during cutting can be improved.

[0042] <First Embodiment>

[0043] 〔Structure of Vehicle Power Supply System〕

[0044] Figure 1 The vehicle power supply system 100 shown is a power supply system mounted on a vehicle, and includes a power supply unit 10, a load 20, a first conduction path 31, a second conduction path 32, and a vehicle protection device 40. The vehicle power supply system 100 is configured to supply power from the power supply unit 10 to the load 20 via the first conduction path 31 and the second conduction path 32, which are paths for transmitting power between the power supply unit 10 and the load 20.

[0045] The power supply unit 10 is, for example, a DC power supply that generates a DC voltage. The power supply unit 10 supplies power to the first conduction path 31 and the second conduction path 32. As the power supply unit 10, for example, a power supply unit such as a lead storage battery, a lithium-ion storage battery, or an alternator is used. The output voltage of the power supply unit 10 is, for example, the drive voltage of an electric vehicle, such as 400V or 800V. A high-potential side terminal and a low-potential side terminal are provided in the power supply unit 10. The low-potential side terminal is electrically connected to the first conduction path 31, and the high-potential side terminal is electrically connected to a conduction path (not shown in the figure) through which current flows into the load 20, for example. The power supply unit 10 is configured to apply a prescribed output voltage to the conduction path (not shown in the figure) connected to the high-potential side terminal. In addition, in this specification, unless otherwise specified, the voltage is the voltage with respect to the ground as a reference.

[0046] In the present disclosure, "electrically connected" preferably has a structure in which the two connection objects are connected in a mutually conductive state (a state in which current flows) so that the potentials of the two connection objects are equal. However, it is not limited to this structure. For example, "electrically connected" may also be a structure in which an electrical component is interposed between the two connection objects and the two connection objects are connected in a conductive state.

[0047] The load 20 is, for example, an in-vehicle electrical device. The load 20 is, for example, a motor, a compressor, a PTC thermistor, or the like.

[0048] The first conduction path 31 and the second conduction path 32 are provided between the power supply unit 10 and the load 20. The first conduction path 31 and the second conduction path 32 are paths for supplying power from the power supply unit 10. The first conduction path 31 and the second conduction path 32 are paths through which current flows from the load 20 toward the power supply unit 10 when power is supplied from the power supply unit 10 to the load 20. Specifically, current flows from the second conduction path 32 to the first conduction path 31. One end of the first conduction path 31 is electrically connected to the low-potential side terminal of the power supply unit 10. The other end of the first conduction path 31 is electrically connected to the source electrode of a semiconductor circuit breaker 51 described later. One end of the second conduction path 32 is electrically connected to the drain electrode of the semiconductor circuit breaker 51 described later. The other end of the second conduction path 32 is electrically connected to the load 20.

[0049] The vehicle protection device 40 includes a semiconductor circuit breaker 51, a fuse 60, a control unit 41, a drive circuit 42, and a current detection unit 45.

[0050] The semiconductor circuit breaker 51 is disposed between the first conductive circuit 31 and the second conductive circuit 32. The semiconductor circuit breaker 51 is configured as a semiconductor switch that performs on-off operations. The semiconductor circuit breaker 51 is, for example, an n-channel MOSFET (metal oxide semiconductor field effect transistor). The gate of the semiconductor circuit breaker 51 is electrically connected to a drive circuit 42 described later. The source of the semiconductor circuit breaker 51 is electrically connected to the power supply unit 10. The drain of the semiconductor circuit breaker 51 is electrically connected to a load 20 described later.

[0051] Based on a control signal (first control signal) output from a control unit 41 described later, the semiconductor circuit breaker 51 switches from a permitted state (on state) that permits current to flow from the first conductive circuit 31 to the second conductive circuit 32 through the semiconductor circuit breaker 51 itself to a cut-off state (off state) that cuts off between the first conductive circuit 31 and the second conductive circuit 32. Specifically, when a first voltage signal from the drive circuit 42 described later is input to the gate based on the first control signal of the control unit 41, the switch changes from the permitted state to the cut-off state. The first control signal corresponds to the "control signal" of the present disclosure. Based on a control signal (second control signal) output from the control unit 41 described later, the semiconductor circuit breaker 51 switches from the cut-off state to the permitted state. Specifically, when a second voltage signal from the drive circuit 42 is input to the gate based on the second control signal of the control unit 41, the switch changes from the cut-off state to the permitted state.

[0052] The response time of the semiconductor circuit breaker 51 is longer than the response time of the fuse 60. The response time of the semiconductor circuit breaker 51 refers to the time from obtaining a signal (first voltage signal) based on the first control signal until the start of cutting off (until it becomes the cut-off state). The response time of the fuse 60 is the time from the start of overcurrent flowing until the start of melting.

[0053] The fuse 60 is an electrical component that melts when overcurrent flows. The fuse 60 is, for example, a thermal fuse. The fuse 60 is disposed in parallel with the semiconductor circuit breaker 51 between the first conductive circuit 31 and the second conductive circuit 32. One end of the fuse 60 is electrically connected to the source of the semiconductor circuit breaker 51. The other end of the fuse 60 is electrically connected to the drain of the semiconductor circuit breaker 51.

[0054] The rated current of the fuse 60 is less than the current flowing from the first conductive path 31 to the second conductive path 32 when power is supplied from the power supply unit 10 to the first conductive path 31 while the semiconductor circuit breaker 51 is in an allowable state (the current flowing from the power supply unit 10 to the load 20 via the semiconductor circuit breaker 51). The rated current of the fuse 60 is the current value that does not blow when this current is stably applied. In addition, the rated current of the fuse 60 refers to the current value that blows after a specified time when a current larger than this current value flows. For example, when the current value flowing from the power supply unit 10 to the first conductive path 31 is 200 A, 500 A, etc., the rated current of the fuse 60 is 60 A, 100 A, etc. When an overcurrent flows through the fuse 60, the fuse 60 is likely to blow. Thus, after the semiconductor circuit breaker 51 changes from the allowable state to the cut-off state, the fuse 60 can be made to blow and cut off relatively early.

[0055] The cut-off characteristic (fusing characteristic) of the fuse 60 determines at what current value of current flowing for what period of time the fuse will blow. When a current exceeding the rated current flows through the fuse 60, due to the fusing characteristic of the fuse 60, the fuse 60 blows after a specified time.

[0056] The impedance of the fuse 60 is greater than the impedance of the semiconductor circuit breaker 51 in the allowable state. The impedance of the semiconductor circuit breaker 51 in the allowable state includes, for example, the on-resistance of the semiconductor circuit breaker 51. When the semiconductor circuit breaker 51 is in the allowable state, the current flowing through the semiconductor circuit breaker 51 is greater than the current flowing through the fuse 60. It is possible to suppress the current flowing from the power supply unit 10 to the first conductive path 31 from flowing through the fuse 60 when the semiconductor circuit breaker 51 is in the allowable state.

[0057] The control unit 41 controls the operation of supplying power from the power supply unit 10 to the load 20. The control unit 41 is an information processing device having an information processing function, an arithmetic function, a control function, etc. The control unit 41 is constituted mainly by, for example, a microcomputer, and has an arithmetic device 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, etc.

[0058] The control unit 41 controls the on / off operation of the semiconductor circuit breaker 51. The control unit 41 outputs a first control signal to switch the semiconductor circuit breaker 51 from the allowable state to the cut-off state. The control unit 41 outputs a second control signal different from the first control signal to switch the semiconductor circuit breaker 51 from the cut-off state to the allowable state. For example, the first control signal is a low-level signal (e.g., 0V), and the second control signal is a high-level signal (a signal with a voltage higher than the low-level signal).

[0059] The drive circuit 42 is electrically connected to the output terminal of the control unit 41 and the gate of the semiconductor circuit breaker 51. The drive circuit 42 is, for example, a gate drive circuit and can adopt various circuit structures using resistors, diodes, bipolar transistors, etc. The drive circuit 42 is input with a control signal from the control unit 41. The drive circuit 42 is a circuit capable of switching the output of a first voltage signal (e.g., a low-level signal) for making the semiconductor circuit breaker 51 in the off state and the output of a second voltage signal (e.g., a high-level signal) for making the semiconductor circuit breaker 51 in the on state. When the control unit 41 outputs the first control signal, the drive circuit 42 outputs the first voltage signal, and the semiconductor circuit breaker 51 maintains the off state. When the output of the control unit 41 switches from the second control signal to the first control signal, the first voltage signal is output from the drive circuit 42, and the semiconductor circuit breaker 51 switches from the on state to the off state. When the control unit 41 outputs the second control signal, the drive circuit 42 outputs a third voltage signal, and the semiconductor circuit breaker 51 maintains the on state. The second control signal (e.g., a high-level signal) is a voltage signal whose magnitude exceeds the gate threshold voltage of the semiconductor circuit breaker 51.

[0060] The current detection unit 45 detects the current value of the first conductive path 31. The current value detected by the current detection unit 45 is a value capable of determining the current value of the first conductive path 31 (specifically, an analog voltage value). The current detection unit 45 is configured as a current detection circuit, for example. Specifically, the current detection unit 45 is provided between the power supply unit 10 and the semiconductor circuit breaker 51. The current value detected by the current detection unit 45 is output to the control unit 41.

[0061] 〔Operation of the vehicle protection device〕

[0062] Next, with reference to Figure 2 、 Figure 3 etc., an example of the operation of the vehicle protection device 40 will be described. Figure 2The flowchart shown is the control executed by the control unit 41 when the specified start condition is satisfied. When the specified start condition is satisfied, it may be that the start condition for starting the vehicle equipped with the vehicle power supply system 100 is satisfied (for example, the start switch such as the ignition switch is switched from the off state to the on state), or it may be the start of power supply to the vehicle protection device 40 (specifically, the control unit 41), or it may be other conditions. A start signal indicating that the start switch is switched to the on state is provided to the control unit 41 from an external device (for example, an external ECU (Electronic Control Unit)).

[0063] For example, before starting Figure 2 the control shown, the control unit 41 outputs a first control signal (for example, a low-level signal), the drive circuit 42 outputs a first voltage signal, and the semiconductor circuit breaker 51 maintains the open state.

[0064] The control unit 41 first outputs a second control signal (for example, a high-level signal) in step S11. As a result, the second control signal is input to the drive circuit 42, and a second voltage signal (for example, a high-level signal) is output from the drive circuit 42 to the semiconductor circuit breaker 51. And the semiconductor circuit breaker 51 is switched from the cut-off state to the allowable state based on the second voltage signal input by the second control signal. As a result, a state is achieved in which power can be supplied from the power supply unit 10 to the load 20.

[0065] Here, the impedance of the fuse 60 is greater than the impedance of the semiconductor circuit breaker 51 in the allowable state. Therefore, it is possible to suppress the current flowing from the power supply unit 10 to the first conductive path 31 when the semiconductor circuit breaker 51 is in the allowable state from flowing through the fuse 60.

[0066] In the next step S12, the control unit 41 determines whether the first conductive path 31 is in an overcurrent state. The overcurrent state means that the current value of the first conductive path 31 becomes an increasing state. The increasing state of the current value of the first conductive path 31 is, for example, a state in which the current value of the first conductive path 31 exceeds a predetermined threshold, a state in which the increase rate of the current value of the first conductive path 31 exceeds a predetermined threshold, and the like. The overcurrent state of the first conductive path 31 is an example of a predetermined abnormal state.

[0067] The control unit 41 repeatedly performs the process of step S12 until it is determined that the first conduction path 31 is in an overcurrent state. When the control unit 41 determines that the first conduction path 31 is in an overcurrent state (when it is "Yes" in step S12), in step S13, it determines whether a certain period of time has elapsed since the time point when the overcurrent state was detected. When the control unit 41 determines that the overcurrent state has not continued for a certain period of time (the overcurrent state has been eliminated within a certain period of time from the detection time point of the overcurrent state), in step S13, it enters "No" and performs the process of step S12 again.

[0068] On the other hand, when the control unit 41 determines in step S13 that the overcurrent state has continued for a certain period of time (the overcurrent state has not been detected within a certain period of time from the detection time point of the overcurrent state), it enters "Yes" and determines that an abnormal state has been detected (step S14).

[0069] In the next step S15, the control unit 41 outputs a first control signal (for example, a low-level signal). Thereby, the first control signal is input to the drive circuit 42, and a first voltage signal (for example, a low-level signal) is output from the drive circuit 42 to the semiconductor circuit breaker 51. And, the semiconductor circuit breaker 51 switches from the allowable state to the cut-off state according to the first voltage signal input based on the first control signal. Thereby, the first conduction path 31 and the second conduction path 32 can be quickly cut off by the semiconductor circuit breaker 51.

[0070] In the next step S16, the control unit 41 determines whether the overcurrent state of the first conduction path 31 has been eliminated within a specified elapsed time from the time point when the overcurrent state of the first conduction path 31 was detected in step S12. That is, the control unit 41 determines whether the overcurrent state of the first conduction path 31 has not been detected within the specified elapsed time. For example, the case where the overcurrent state of the first conduction path 31 has not been detected means the case where the current value of the first conduction path 31 is lower than a predetermined threshold, the case where the rate of decrease of the current value of the first conduction path 31 exceeds a predetermined threshold, etc.

[0071] Here, the specified elapsed time in step S16 is a time shorter than the fusing time t of the fuse 60. The fusing time t of the fuse 60 is calculated based on the following formula (1). E = I 2 ×t…Formula (1) E: The power value consumed by the fuse 60 required until fusing I: The current value detected by the current detection unit 45 when the first conduction path 31 becomes in an overcurrent state t: The time from when the semiconductor circuit breaker 51 switches from the allowable state to the cut-off state until fusing

[0072] E in the above formula (1) is preset as a fixed value by the control unit 41 in advance. Therefore, when the current value I is detected by the current detection unit 45, using the known power value E, the fusing time t of the fuse 60 is calculated according to the above formula (1).

[0073] When the control unit 41 determines in step S16 that the overcurrent state of the first conduction path 31 has been eliminated within a specified elapsed time, it goes to "Yes" and processes step S11 again. That is, after the semiconductor circuit breaker 51 switches from the allowable state to the cut-off state (after the process of step S15), when the overcurrent state of the first conduction path 31 is not detected by the current detection unit 45 within a specified elapsed time, the control unit 41 outputs a second control signal to switch the semiconductor circuit breaker 51 from the cut-off state to the allowable state (step S11).

[0074] When the control unit 41 goes to "Yes" in step S16, it can output a second control signal before the fusing time t of the fuse 60 elapses and switch the semiconductor circuit breaker 51 from the cut-off state to the allowable state. Therefore, the fuse 60 can be prevented from fusing before the semiconductor circuit breaker 51 is switched from the cut-off state to the allowable state. In addition, since the fusing time t is determined based on the current value of the first conduction path 31, the fusing time t can be determined with high accuracy.

[0075] On the other hand, when the control unit 41 determines in step S16 that the overcurrent state of the first conduction path 31 has not been eliminated within a specified elapsed time, it goes to "No" and ends Figure 2 the control.

[0076] Figure 3 Shows the time variation of the current value of the first conduction path 31 and the time variation of the voltage across the semiconductor circuit breaker 51 (source-drain voltage) after the control unit 41 outputs the first control signal in step S15. As Figure 3 shown, at time t1, the control unit 41 outputs the first control signal. At time t2, after the response time of the semiconductor circuit breaker 51 (the time from obtaining the first voltage signal to the start of cut-off), the semiconductor circuit breaker 51 switches from the allowable state to the cut-off state.

[0077] From time t2 when the semiconductor circuit breaker 51 becomes the cut-off state, current starts to flow through the fuse 60. The period from time t2 to time t3 is the response time of the fuse 60 (the time from the start of current flow to the start of fusing). That is, after the semiconductor circuit breaker 51 switches from the allowable state to the cut-off state based on the control signal from the control unit 41, after the response time elapses, the fuse 60 fuses.

[0078] From time t3, the current value of the first conduction path 31 decreases, and due to the inductance of the first conduction path 31 and the like, the surge voltage and the like cause the voltage across the semiconductor circuit breaker 51 to increase. However, after the semiconductor circuit breaker 51 enters the cut-off state, the current can flow in a state where the time change of the current value (the value obtained by differentiating the current value with respect to time) is reduced within the response time by the fuse 60. That is, the magnitude of the surge voltage is determined by the wiring inductance L (μH) of the first conduction path 31 and the like and the time change of the current value (current slope di / dt). However, the time change of the current value (current slope di / dt) at the time of cut-off by the fuse 60 is smaller than the time change of the current value (current slope di / dt) at the time of cut-off of the semiconductor circuit breaker 51, so that the generation of the surge voltage can be suppressed. Therefore, the surge voltage generated when the semiconductor circuit breaker 51 switches from the allowable state to the cut-off state can be suppressed, and the semiconductor circuit breaker 51 can be protected.

[0079] 〔Effect of the First Embodiment〕

[0080] The following description relates to an example of the effect of the first embodiment.

[0081] In the vehicle protection device 40, a fuse 60 that melts when an overcurrent flows is provided in parallel with the semiconductor circuit breaker 51. Thus, in the vehicle protection device 40, based on the semiconductor circuit breaker 51 switching from the allowable state to the cut-off state, the current can flow in a state where the time change of the current value is reduced via the fuse 60. Therefore, the surge voltage generated when the semiconductor circuit breaker 51 switches from the allowable state to the cut-off state can be suppressed, and the semiconductor circuit breaker 51 can be protected. In addition, in the vehicle protection device 40, since a structure in which a plurality of semiconductor circuit breakers are connected in series or in parallel or a structure using a semiconductor circuit breaker having a withstand voltage higher than the surge voltage is not adopted, the semiconductor circuit breaker 51 can be protected while avoiding enlargement and high cost.

[0082] Moreover, the vehicle power supply system 100 includes a power supply unit 10 that supplies power to the first conduction path 31. The rated current of the fuse 60 is smaller than the current flowing from the first conduction path 31 to the second conduction path 32 when the power supply unit 10 supplies power to the first conduction path 31 in the allowable state of the semiconductor circuit breaker 51. Thus, in the vehicle protection device 40, after the semiconductor circuit breaker 51 changes from the allowable state to the cut-off state, the fuse 60 can be melted and cut off relatively early.

[0083] Furthermore, in the vehicle protection device 40, the impedance of the fuse 60 is greater than the impedance of the semiconductor circuit breaker 51 in the allowable state. Thus, in the vehicle protection device 40, the current flowing from the power supply unit 10 to the first conduction path 31 in the allowable state of the semiconductor circuit breaker 51 can be suppressed from flowing through the fuse 60.

[0084] Further, in the vehicle protection device 40, a fuse 60 is provided in parallel with the semiconductor circuit breaker 51. After the semiconductor circuit breaker 51 is switched from the allowed state to the cut-off state based on the control signal from the control unit 41, the fuse 60 melts after a response time. Thus, in the vehicle protection device 40, after the semiconductor circuit breaker 51 is switched from the allowed state to the cut-off state, the time variation of the current value flowing through the fuse 60 within the response time can be reduced. Therefore, it is easy to suppress the surge voltage.

[0085] Further, in the vehicle protection device 40, the semiconductor circuit breaker 51 is switched from the cut-off state to the allowed state based on the second control signal output from the control unit 41. The vehicle protection device 40 has a current detection unit 45 that detects the current flowing through the first conductive path 31. When the current detected by the current detection unit 45 becomes an overcurrent state, the control unit 41 outputs a first control signal. When the overcurrent state is not detected by the current detection unit 45 before the melting time t elapses, the control unit 41 outputs a second control signal, and the melting time t is calculated based on the following formula (1). E = I 2 ×t…Formula (1) E: The power value consumed by the fuse 60 required until melting I: The current value detected by the current detection unit 45 when an overcurrent state occurs t: The time from when the semiconductor circuit breaker 51 is switched from the allowed state to the cut-off state until melting

[0086] Thus, when the overcurrent state is not detected by the current detection unit 45 before the melting time t elapses, the control unit 41 outputs a second control signal, and the semiconductor circuit breaker 51 can be switched from the cut-off state to the allowed state. Therefore, before the semiconductor circuit breaker 51 is switched from the cut-off state to the allowed state, the fuse 60 can be prevented from melting. In addition, since the melting time t is determined based on the current value of the first conductive path 31, the melting time t can be determined with high accuracy.

[0087] <Second Embodiment>

[0088] The vehicle power supply system 200 of the second embodiment is mainly different from the first embodiment in that the pyrotechnic circuit breaker 252 is provided, and the other aspects are common. In addition, the same reference numerals are assigned to the same structures as those in the first embodiment, and the detailed description is omitted.

[0089] As Figure 4As shown, the vehicle power supply system 200 includes a power supply unit 10, a load 20, a first conductive circuit 31, a second conductive circuit 32, and a vehicle protection device 240. The vehicle protection device 240 has a semiconductor circuit breaker 51, a pyrotechnic circuit breaker 252, a fuse 60, a control unit 41, a first drive circuit 242, a second drive circuit 243, and a current detection unit 45.

[0090] The pyrotechnic circuit breaker 252 is provided in the first conductive circuit 31. The semiconductor circuit breaker 51 is connected in series with the pyrotechnic circuit breaker 252. The pyrotechnic circuit breaker 252 is provided at a position lower in potential (on the side of the power supply unit 10) than the semiconductor circuit breaker 51. The pyrotechnic circuit breaker 252 is a circuit breaker that physically cuts off the first conductive circuit 31 based on a control signal. The pyrotechnic circuit breaker 252 is a pyrotechnic fuse (PYROFUSE (registered trademark)) that breaks by the explosion of gunpowder based on a second control signal output from the control unit 41 described later, thereby cutting off the first conductive circuit 31. Specifically, based on the second control signal output from the control unit 41, when the pyrotechnic circuit breaker 252 is input with a third voltage signal from the second drive circuit 243 described later, it generates an explosion, and by this explosion, the displacement unit moves, thereby physically cutting off the path. One end of the pyrotechnic circuit breaker 252 is electrically connected to the power supply unit 10. The other end of the pyrotechnic circuit breaker 252 is electrically connected to the source electrode of the semiconductor circuit breaker 51.

[0091] The response time of the semiconductor circuit breaker 51 is shorter than the response time of the pyrotechnic circuit breaker 252. The response time of the semiconductor circuit breaker 51 refers to the time from obtaining a signal (first voltage signal) based on the first control signal to the start of cutting off (becoming in a cut-off state). The response time of the pyrotechnic circuit breaker 252 is the time from obtaining a signal (third voltage signal) based on the third control signal to the start of cutting off.

[0092] The control unit 41 controls the cut-off operation of the pyrotechnic circuit breaker 252. The control unit 41 outputs a third control signal to cut off the first conductive circuit 31 through the pyrotechnic circuit breaker 252. The control unit 41 does not perform the cut-off of the first conductive circuit 31 by the pyrotechnic circuit breaker 252 during the period when a fourth control signal different from the third control signal is output. The third control signal may be the same as or different from one of the voltage levels of the first control signal and the second control signal. The third control signal is, for example, a signal (high-level signal) having the same voltage level as the second control signal. The fourth control signal may be the same as or different from one of the voltage levels of the first control signal and the second control signal. The fourth control signal is, for example, a signal (low-level signal) having the same voltage level as the first control signal.

[0093] The first drive circuit 242 has the same structure as the drive circuit 42 of the first embodiment. The second drive circuit 243 is electrically connected to the output terminal of the control unit 41 and the pyrotechnic circuit breaker 252. The second drive circuit 243 can adopt various circuit structures using resistors, diodes, bipolar transistors, etc. The second drive circuit 243 is input with a control signal from the control unit 41. The second drive circuit 243 is a circuit capable of switching from the output of a fourth voltage signal (e.g., a low-level signal) for keeping the pyrotechnic circuit breaker 252 in a non-cut-off state to the output of a third voltage signal (e.g., a high-level signal) for causing the pyrotechnic circuit breaker 252 to perform a cut-off action. In a state where the pyrotechnic circuit breaker 252 does not perform a cut-off action, when the control unit 41 outputs a fourth control signal, the second drive circuit 243 outputs a fourth voltage signal to maintain the state where the pyrotechnic circuit breaker 252 does not perform a cut-off action. When the control unit 41 outputs a third control signal, the second drive circuit 243 outputs a third voltage signal, and the pyrotechnic circuit breaker 252 performs a cut-off action.

[0094] 〔Operation of Vehicle Protection Device〕

[0095] Next, with reference to Figure 5 etc., an example of the operation of the vehicle protection device 240 in the second embodiment will be described. Figure 5 The flowchart shown is the control executed by the control unit 41 when a predetermined start condition is satisfied in the vehicle protection device 240 in the second embodiment. The predetermined start condition is the same condition as the condition described in the first embodiment.

[0096] Figure 5 Steps S11 to S16 of

[0097] are the same as steps S11 to S16 of the first embodiment, and detailed description thereof is omitted. Figure 5 When the control unit 41 determines in step S16 that the overcurrent state of the first conductive circuit 31 has not been eliminated within a predetermined elapsed time, it goes to "No" and performs the process of step S21. The control unit 41 outputs a third control signal (e.g., a high-level signal) in step S21. Thus, when the semiconductor circuit breaker 51 switches from the allowable state to the cut-off state and the overcurrent state of the first conductive circuit 31 is continuously detected by the current detection unit 45 within a predetermined elapsed time, the control unit 41 outputs a third control signal. After the process of step S21, the control unit 41 ends Figure 5 the control.

[0098] The third control signal is input to the second drive circuit 243, and a third voltage signal (e.g., a high-level signal) is output from the second drive circuit 243 to the pyrotechnic circuit breaker 252. Then, the pyrotechnic circuit breaker 252 performs a cutting operation (breaks it to cut off the first conductive circuit 31) according to the third voltage signal input based on the third control signal. Thus, the insulation performance during the cutting of the first conductive circuit 31 can be improved by the pyrotechnic circuit breaker 252. In addition, although the time until the fuse 60 completes the cutting is relatively long, the pyrotechnic circuit breaker 252 can complete the cutting at a higher speed. After the cutting transition of the fuse 60, the cutting is performed by the pyrotechnic circuit breaker 252, so the time change (current slope di / dt) of the current value in the first conductive circuit 31 and the second conductive circuit 32 becomes large, but the surge voltage is generated across the pyrotechnic circuit breaker 252, so the semiconductor circuit breaker 51 can be protected.

[0099] 〔Effects of the Second Embodiment〕

[0100] The following description relates to an example of the effects of the second embodiment.

[0101] In the vehicle protection device 40, there is a pyrotechnic circuit breaker 252 that breaks due to the explosion of gunpowder based on the third control signal output from the control unit 41, thereby cutting off the first conductive circuit 31. The semiconductor circuit breaker 51 and the pyrotechnic circuit breaker 252 are connected in series in the first conductive circuit 31. The control unit 41 outputs the first control signal and the second control signal when the vehicle power supply system 100 becomes an abnormal state. After the semiconductor circuit breaker 51 switches from the allowable state to the cut-off state based on the control signal from the control unit 41, the first conductive circuit 31 is cut off by the pyrotechnic circuit breaker 252 based on the third control signal from the control unit 41. Thus, by setting the semiconductor circuit breaker 51 to the cut-off state, the first conductive circuit 31 can be quickly cut off. In addition, by cutting off the first conductive circuit 31 by the pyrotechnic circuit breaker 252, the insulation performance during cutting can be improved.

[0102] <Third Embodiment>

[0103] The vehicle power supply system of the third embodiment is different from the second embodiment in terms of the operation of the vehicle protection device, and is common in other aspects. In addition, the same reference numerals are used for the same structures as those in the second embodiment, and detailed descriptions are omitted.

[0104] Refer to Figure 6 etc., to describe an example of the operation of the vehicle protection device 240 in the third embodiment. Figure 6The flowchart shown is the control executed by the control unit 41 when a specified start condition is satisfied in the vehicle protection device 240 in the third embodiment. The specified start condition is the same as the condition described in the first embodiment.

[0105] Figure 6 Steps S11 to S14 are the same as steps S11 to S14 in the first embodiment, and thus detailed description thereof is omitted. After the control unit 41 determines in step S14 that an abnormal state has been detected, it outputs a first control signal (for example, a low-level signal) and a third control signal (for example, a high-level signal) in step S31.

[0106] Figure 7 Shows the time variation of the current value of the first conduction path 31, the time variation of the voltage across the semiconductor circuit breaker 51 (source-drain voltage), and the time variation of the voltage across the pyrotechnic circuit breaker 252 after the control unit 41 has output the first control signal and the third control signal in step S31. As Figure 7 shown, at time t11, the control unit 41 outputs the first control signal and the third control signal. At time t12, after the response time of the semiconductor circuit breaker 51 (the time from when the first control signal is obtained until the start of interruption), the semiconductor circuit breaker 51 switches from the allowable state to the interrupted state.

[0107] From time t12 when the semiconductor circuit breaker 51 becomes in the interrupted state, current starts to flow through the fuse 60. The period from time t12 to time t13 is the response time of the fuse 60 (the time from when the current starts to flow until the start of melting).

[0108] From time t13, the current value of the first conduction path 31 decreases, and due to the inductance of the first conduction path 31 and the like, the voltage across the semiconductor circuit breaker 51 increases. However, after the semiconductor circuit breaker 51 becomes in the interrupted state, the current change can be reduced by the fuse 60 and the current can flow. Therefore, the surge voltage can be suppressed to a small value, and the semiconductor circuit breaker 51 can be protected from the influence of the surge voltage.

[0109] At time t14, after the response time of the pyrotechnic circuit breaker 252 (the time from when the second voltage signal is obtained until the start of interruption), the pyrotechnic circuit breaker 252 starts the interruption operation (breaks and interrupts the first conduction path 31).

[0110] Here, in the vehicle protection device 240, it is configured such that after the semiconductor circuit breaker 51 switches from the allowable state to the cut-off state, the pyrotechnic circuit breaker 252 cuts off the first conduction path 31, and the voltage (terminal voltage) applied to the semiconductor circuit breaker 51 does not exceed the absolute maximum rating. After the elapse of time t13, even if the voltage across the semiconductor circuit breaker 51 increases, the pyrotechnic circuit breaker 252 cuts off the first conduction path 31, and the voltage across the semiconductor circuit breaker 51 does not exceed the absolute maximum rating. Therefore, it is possible to suppress the application of a voltage exceeding the absolute maximum rating to the semiconductor circuit breaker 51.

[0111] <Fourth Embodiment>

[0112] The vehicle power supply system 400 according to the fourth embodiment is different from the first embodiment in that a resistor 460 is provided instead of the fuse 60, and is common in other respects. In addition, the same reference numerals are given to the same structures as those in the first embodiment, and detailed descriptions are omitted.

[0113] As Figure 8 shown, the vehicle power supply system 400 includes a power supply unit 10, a load 20, a first conduction path 31, a second conduction path 32, and a vehicle protection device 440. The vehicle protection device 440 has a semiconductor circuit breaker 51, a resistor 460, a control unit 41, a drive circuit 42, and a current detection unit 45.

[0114] The resistor 460 is an element part (resistive element) having a resistive portion. The resistor 460 is provided in parallel with the semiconductor circuit breaker 51 between the first conduction path 31 and the second conduction path 32. One end of the resistor 460 is electrically connected to the source electrode of the semiconductor circuit breaker 51. The other end of the resistor 460 is electrically connected to the drain electrode of the semiconductor circuit breaker 51. In addition, the resistor 460 may be a variable resistor.

[0115] The resistance value of the resistor 460 is 50 mΩ and can be set according to the tolerance of peripheral components. When the output voltage of the power supply unit 10 is 400 V, it is possible to limit the current flowing through the semiconductor circuit breaker 51 to 8000 A or less when the semiconductor circuit breaker 51 is in the cut-off state.

[0116] The impedance of the resistor 460 is greater than the impedance of the semiconductor circuit breaker 51 in the allowable state. The impedance of the semiconductor circuit breaker 51 in the allowable state includes, for example, the on-resistance of the semiconductor circuit breaker 51. That is, the resistance value of the resistor 460 is greater than the resistance value of the on-resistance of the semiconductor circuit breaker 51.

[0117] More specifically, the resistance value of the resistor 460 is much larger than the on-resistance value of the semiconductor circuit breaker 51. Therefore, it is possible to suppress the current flowing from the power supply unit 10 to the first conduction path 31 through the resistor 460 when the semiconductor circuit breaker 51 is in the allowable state. When the semiconductor circuit breaker 51 is in the cut-off state, the current (desired peak current) flowing from the power supply unit 10 to the first conduction path 31 becomes a value obtained by dividing the output voltage of the power supply unit 10 by the resistance value (limiting resistance value) of the resistor 460.

[0118] The vehicle protection device 440 of the fourth embodiment exhibits the same effects as the vehicle protection device 40 of the first embodiment. Based on the switching of the semiconductor circuit breaker 51 from the allowable state to the cut-off state, it is possible to pass a current in a state where the temporal change in the current value is reduced through the resistor 460, and the short-circuit current can be limited. Therefore, it is possible to suppress the surge voltage generated due to the switching of the semiconductor circuit breaker 51 from the allowable state to the cut-off state, and the semiconductor circuit breaker 51 can be protected.

[0119] <Other Embodiments>

[0120] The present disclosure is not limited to the embodiments described above and illustrated in the drawings. For example, the features of the above-described or hereinafter-described embodiments can be combined in all combinations without contradiction. In addition, any feature of the above-described or hereinafter-described embodiments can be omitted if it is not explicitly stated as an essential feature. Also, the above-described embodiments can be modified as follows.

[0121] In the above-described first embodiment, a structure in which the first conduction path 31 is connected to the low-potential side terminal of the power supply unit 10 is illustrated, but it can also be a structure in which the first conduction path 31 is connected to the high-potential side terminal of the power supply unit 10 as in Figure 9 the vehicle power supply system 500 shown. In the Figure 9 structure, the source of the semiconductor circuit breaker 551 is electrically connected to the load 20. The drain of the semiconductor circuit breaker 551 is electrically connected to the power supply unit 10.

[0122] In the above-described second embodiment, a structure in which the first conduction path 31 is connected to the low-potential side terminal of the power supply unit 10 is illustrated, but it can also be a structure in which the first conduction path 31 is connected to the high-potential side terminal of the power supply unit 10 as in Figure 10 the vehicle power supply system 600 shown. In the Figure 10 structure, the source of the semiconductor circuit breaker 651 is electrically connected to the load 20. The drain of the semiconductor circuit breaker 651 is electrically connected to the pyrotechnic circuit breaker 252.

[0123] In the above-described fourth embodiment, a structure in which the first conduction path 31 is connected to the low-potential side terminal of the power supply unit 10 is illustrated, but it can also be a structure in which the first conduction path 31 is connected to the high-potential side terminal of the power supply unit 10 as in Figure 11Like the vehicle power supply system 700 shown, it is a structure in which the first conductive circuit 31 is connected to the high-potential side terminal of the power supply unit 10. In Figure 11 this structure, the source of the semiconductor circuit breaker 751 is electrically connected to the load 20. The drain of the semiconductor circuit breaker 751 is electrically connected to the power supply unit 10.

[0124] In the above first to fourth embodiments, an example is shown in which the melting time t of the fuse 60 is calculated according to the above formula (1) using the current value I detected by the current detection unit 45, but a predetermined time may also be used as the melting time t. For example, the control unit 41 stores the melting time t calculated based on the following formula (2). The control unit 41 corresponds to an example of the "storage unit" of the present disclosure. E = I 2 ×t…Formula (2) E: The power value consumed by the fuse 60 required until melting I: A predetermined current value t: The time from when the semiconductor circuit breaker 51 switches from the allowable state to the cut-off state until melting

[0125] In this way, by using the predetermined melting time t, it is possible to easily perform control during the determination of the overcurrent state.

[0126] In the above first to fourth embodiments, as an example of the predetermined abnormal state (the state determined in step S12), it is shown that the first conductive circuit 31 becomes in an overcurrent state, but it may also be other abnormal states. For example, as the predetermined abnormal state, it may also be a state in which an abnormal state of the vehicle (such as a collision of the vehicle) is detected. For example, a signal indicating that the vehicle is in an abnormal state (such as a collision of the vehicle) is provided to the control unit 41 from an external device (for example, an external ECU (Electronic Control Unit)). The control unit 41 may also determine that it is a predetermined abnormal state when receiving such a signal.

[0127] In the above fourth embodiment, an example is shown in which a resistor 460 is provided in parallel with the semiconductor circuit breaker 51, but an element unit having at least any one of a resistive component, an inductive component, and a capacitive component may also be provided in parallel with the semiconductor circuit breaker 51. The element unit having an inductive component is, for example, a coil. The element unit having a capacitive component is, for example, a capacitor. For example, a structure in which two or more of a resistor, a coil, and a capacitor are connected in series or in parallel may also be provided in parallel with the semiconductor circuit breaker 51.

[0128] In the above first to fourth embodiments, the semiconductor breaker 51 is illustrated as having a structure of an n-channel type MOSFET, but it may also be other semiconductor switches such as an IGBT (Insulated Gate Bipolar Transistor).

[0129] In the above first to fourth embodiments, a charger may be provided to be connected to the first conduction path 31 instead of the load 20.

[0130] In the above first and fourth embodiments, the current detection unit 45 is provided in the first conduction path 31, but it may also be provided in the second conduction path 32. In the above second and third embodiments, the current detection unit 45 is provided between the power supply unit 10 and the pyrotechnic breaker 252 in the first conduction path 31, but it may also be provided between the pyrotechnic breaker 252 and the semiconductor breaker 51 in the first conduction path 31, or between the semiconductor breaker 51 and the load 20 in the second conduction path 32.

[0131] In the above first to third embodiments, a fuse resistor having a resistance larger than that of the fuse may be provided instead of the fuse 60.

[0132] In addition, the embodiments disclosed herein should be considered illustrative in all respects and not restrictive. The scope of the present invention is not limited to the embodiments disclosed herein and is intended to include all modifications within the scope shown in the claims or within the scope equivalent to the claims.

[0133] Reference Numeral Explanation

[0134] 10... Power supply unit

[0135] 20... Load

[0136] 31... First conduction path

[0137] 32... Second conduction path

[0138] 40... Vehicle protection device

[0139] 41... Control unit (storage unit)

[0140] 42... Drive circuit

[0141] 45... Current detection unit

[0142] 51... Semiconductor breaker

[0143] 60... Fuse

[0144] 100... Vehicle power supply system

[0145] 200... Vehicle power supply system

[0146] 240…Protection device for vehicle

[0147] 242…First drive circuit

[0148] 243…Second drive circuit

[0149] 252…Pyrotechnic circuit breaker

[0150] 400…Power supply system for vehicle

[0151] 440…Protection device for vehicle

[0152] 460…Resistor

[0153] 500…Power supply system for vehicle

[0154] 551…Semiconductor circuit breaker

[0155] 600…Power supply system for vehicle

[0156] 651…Semiconductor circuit breaker

[0157] 700…Power supply system for vehicle

[0158] 751…Semiconductor circuit breaker

Claims

1. A protection device for a vehicle, which is used for a vehicle power supply system having a first conductive circuit and a second conductive circuit. Among them, the protection device for the vehicle has: a semiconductor circuit breaker, which is arranged between the first conductive circuit and the second conductive circuit and switches between a permitted state and a cut-off state. The permitted state is a state that permits current to flow from the first conductive circuit to the second conductive circuit through the semiconductor circuit breaker itself, and the cut-off state is a state that cuts off the flow of the current from the first conductive circuit to the second conductive circuit through the semiconductor circuit breaker itself; and a control unit that outputs a control signal for switching the semiconductor circuit breaker from the permitted state to the cut-off state. Either an element part or a fuse is arranged in parallel with the semiconductor circuit breaker. The element part has at least any one of a resistance component, an inductance component, and a capacitance component, and the fuse melts in the case of overcurrent flowing.

2. The protection device for a vehicle according to claim 1, wherein the fuse is arranged in parallel with the semiconductor circuit breaker. the vehicle power supply system has a power supply unit that supplies power to the first conductive circuit. the rated current of the fuse is less than the current that flows from the first conductive circuit to the second conductive circuit when the semiconductor circuit breaker is in the permitted state and power is supplied from the power supply unit to the first conductive circuit.

3. The protection device for a vehicle according to claim 2, wherein the impedance of the fuse is greater than the impedance of the semiconductor circuit breaker in the permitted state.

4. The protection device for a vehicle according to claim 1 or 2, wherein the fuse is arranged in parallel with the semiconductor circuit breaker. after the semiconductor circuit breaker switches from the permitted state to the cut-off state based on the control signal from the control unit, the fuse melts after a response time.

5. The protection device for a vehicle according to claim 1 or 2, wherein the fuse is arranged in parallel with the semiconductor circuit breaker. the semiconductor circuit breaker switches from the cut-off state to the permitted state based on a second control signal output from the control unit. the protection device for the vehicle has a current detection unit that detects the current flowing through either the first conductive circuit or the second conductive circuit. the control unit outputs the control signal when the current detected by the current detection unit becomes an overcurrent state. when the overcurrent state is not detected by the current detection unit before a melting time t has elapsed, the second control signal is output. The melting time t is calculated based on the following formula (1): E = I 2 × t … Equation (1) E: The power value consumed by the fuse required until melting. I: The current value detected by the current detection unit when the overcurrent state occurs. t: The time from when the semiconductor circuit breaker switches from the permitted state to the cut-off state until melting.

6. The protection device for a vehicle according to claim 1 or 2, wherein the fuse is arranged in parallel with the semiconductor circuit breaker. Based on the second control signal output from the control unit, the semiconductor circuit breaker switches from the cut-off state to the allowable state. The semiconductor circuit breaker has: a storage unit that stores a fusing time t, which is the time from when current starts to flow until fusing in the fuse and is calculated based on the following formula (2); and a current detection unit that detects the current flowing through one of the first conduction path and the second conduction path. When the current detected by the current detection unit becomes an overcurrent state, the control unit outputs the control signal. When the overcurrent state is not detected by the current detection unit before the fusing time t stored in the storage unit has elapsed, the control unit outputs the second control signal. The formula (2) is: E = I 2 × t… Equation (2) E: the power value consumed by the fuse until fusing; I: a pre-determined current value; t: the time from when the semiconductor circuit breaker switches from the allowable state to the cut-off state until fusing.

7. The vehicle protection device according to claim 1, wherein the element part having a resistance component is provided in parallel with the semiconductor circuit breaker, and the resistance value of the element part is greater than the on-resistance value of the semiconductor circuit breaker.

8. The vehicle protection device according to claim 1 or 2, wherein the vehicle protection device has a pyrotechnic circuit breaker that breaks by the explosion of gunpowder based on a third control signal output from the control unit, thereby cutting off one of the first conduction path and the second conduction path. The semiconductor circuit breaker and the pyrotechnic circuit breaker are connected in series. When the vehicle power supply system becomes an abnormal state, the control unit outputs the control signal and the third control signal. After the semiconductor circuit breaker switches from the allowable state to the cut-off state based on the control signal from the control unit, one of the first conduction path and the second conduction path is cut off by the pyrotechnic circuit breaker based on the third control signal from the control unit.

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