Current interrupt device

Abstract

A current interrupt device (1) comprises: a positive-side main relay (11) provided on a positive-side path connecting a positive-side terminal of a battery (100) and a positive-side terminal of a capacitor (200); a DC / DC converter (20) connected in parallel with the positive-side main relay (11) and having a semiconductor switch (21) and a coil (22); a current measurement circuit (30) that measures a current flowing through the capacitor (200); and a control unit (60) that charges the capacitor (200) with a constant current by controlling the semiconductor switch (21) on the basis of the current measured by the current measurement circuit (30).

Description

Current interrupter

[0001] The present disclosure relates to a current interruption device for interrupting a current.

[0002] Patent Document 1 discloses a technology for suppressing inrush current when the main relay is turned on by connecting a precharge resistor and a precharge relay in parallel with the main relay and turning on the precharge relay before turning on the main relay.

[0003] International Publication No. 2022 / 224857

[0004] In the technology disclosed in Patent Document 1, when the battery voltage increases and the load capacity increases, the inrush current increases when the main relay is turned on. Therefore, in order to suppress the inrush current, it is necessary to connect many pre-charge resistors in series and in parallel, which increases the size of the device.

[0005] The current interruption device according to the present disclosure includes a positive-side main relay provided on a positive-side path connecting the positive terminal of a battery and the positive terminal of a capacitor, a DC / DC converter connected in parallel with the positive-side main relay and having a semiconductor switch and a coil, a current measurement circuit that measures the current flowing through the capacitor, and a control unit that charges the capacitor with a constant current by controlling the semiconductor switch based on the current measured by the current measurement circuit.

[0006] These comprehensive or specific aspects may be realized as a system, a method, an integrated circuit, a computer program, or a computer-readable recording medium such as a CD-ROM, or may be realized as any combination of a system, a method, an integrated circuit, a computer program, and a recording medium.

[0007] According to the current interruption device according to one aspect of the present disclosure, it is possible to suppress an inrush current that occurs when the main relay is turned on, while suppressing an increase in the size of the device.

[0008] Fig. 1 is a block diagram showing an example of a current interruption device according to embodiment 1. Fig. 2 is a flowchart showing an example of an operation of a control unit according to embodiment 1 before turning on a positive side main relay. Fig. 3 is a diagram for explaining an operation of charging a capacitor with a constant current. Fig. 4 is a diagram showing an example of time waveforms of a charging current and a voltage of a capacitor when a main relay is turned on in a comparative example. Fig. 5 is a diagram showing an example of time waveforms of a charging current and a voltage of a capacitor when a main relay is turned on in embodiment 1. Fig. 6 is a block diagram showing an example of a current interruption device according to embodiment 2.

[0009] Hereinafter, the embodiments will be specifically described with reference to the drawings.

[0010] The embodiments described below are all comprehensive or specific examples, and the numerical values, shapes, materials, components, arrangement and connection of the components, steps, and order of steps shown in the following embodiments are merely examples and are not intended to limit the present disclosure.

[0011] (First embodiment) A current interruption device according to a first embodiment will be described below.

[0012] FIG. 1 is a block diagram showing an example of a current interruption device 1 according to the first embodiment.

[0013] The current interruption device 1 is used in transportation equipment or the like that includes a battery 100 and a capacitor 200 connected to a load. In addition to the current interruption device 1, Fig. 1 also shows the battery 100 and the capacitor 200 that are provided in the transportation equipment or the like. The current interruption device 1 is used in transportation equipment, for example, an electric vehicle such as a BEV (Battery Electric Vehicle) or an HEV (Hybrid Electric Vehicle), or a fuel cell vehicle such as an FCV (Fuel Cell Vehicle).

[0014] The battery 100 is a battery capable of applying a high voltage of, for example, several hundred volts to a load. For example, the battery 100 is a main battery (for example, a lithium-ion battery) in an electric vehicle.

[0015] The capacitor 200 is, for example, a capacitor for an inverter of an electric vehicle. The capacitor 200 is, for example, a film capacitor. Power is supplied from the battery 100 to the capacitor 200 to drive the electric vehicle. In the event of an accident or the like, a large current may flow due to a short circuit in the current path connecting the battery 100 and the capacitor 200, which could cause the battery 100 to smoke or catch fire, and therefore the current interruption device 1 is used in transportation equipment.

[0016] The current interruption device 1 is a device for interrupting a current path connecting the battery 100 and the capacitor 200 in the event of an abnormality, and is provided between the battery 100 and the capacitor 200. The current path connecting the battery 100 and the capacitor 200 includes a positive path connecting the positive terminal of the battery 100 and the positive terminal of the capacitor 200, and a negative path connecting the negative terminal of the battery 100 and the negative terminal of the capacitor 200. The current interruption device 1 interrupts the positive path in the event of an abnormality. Note that the current interruption device 1 may also interrupt both the positive path and the negative path in the event of an abnormality.

[0017] The current interruption device 1 includes a positive side main relay 11, a negative side main relay 12, a DC / DC converter 20, a current measurement circuit 30, voltage measurement circuits 41 and 42, an active fuse 50 that is interrupted by an external signal, and a control unit 60. The active fuse 50 is, for example, a pyrotechnic circuit breaker or a pyroelectric switch.

[0018] Positive side main relay 11 is a relay provided on the positive side path, and is controlled by, for example, control unit 60 to switch between conduction and non-conduction between the positive side terminal of battery 100 and the positive side terminal of capacitor 200 via the positive side path. In Fig. 1, the signal line from control unit 60 to positive side main relay 11 is omitted from illustration.

[0019] Negative main relay 12 is a relay provided on the negative path, and is controlled by, for example, control unit 60 to switch between conduction and non-conduction between the negative terminal of battery 100 and the negative terminal of capacitor 200 via the negative path. In Fig. 1, the signal line from control unit 60 to negative main relay 12 is omitted from illustration.

[0020] The active fuse 50 is provided on the positive or negative path and is a fuse for interrupting the positive or negative path. For example, the active fuse 50 is provided on the positive path. The active fuse 50 interrupts the positive path when a large current flows through the current path connecting the battery 100 and the capacitor 200 due to a short circuit. A pyro-fuse used as the active fuse 50 contains an explosive and ignites the explosive based on an interruption command signal from outside the pyro-fuse. The explosive ignition irreversibly interrupts the positive path, thereby interrupting the positive path. The active fuse 50 interrupts the positive path, for example, upon receiving an interruption command signal from the control unit 60. A signal line from the control unit 60 to the active fuse 50 is not shown in FIG. 1 .

[0021] The current measurement circuit 30 is a circuit that detects the current flowing through the capacitor 200. For example, the current measurement circuit 30 is a sensor such as a shunt sensor (e.g., a shunt resistor) or a Hall element. The current measurement circuit 30 outputs the measurement result (current value) to the control unit 60.

[0022] The current measurement circuit 30 is provided in the positive path or the negative path. Specifically, the current measurement circuit 30 is provided on the positive path closer to the capacitor 200 than a connection node with the coil 22 (described later), or on the negative path closer to the capacitor 200 than a connection node with the rectifier 23 (described later). For example, the current measurement circuit 30 is provided in the negative path, and specifically, as shown in FIG. 1 , the current measurement circuit 30 is provided on the negative path closer to the capacitor 200 than a connection node with the rectifier 23.

[0023] If the current measurement circuit 30 is a shunt-type sensor and is provided in the positive path, a high voltage may be applied between the current measurement circuit 30 and the reference potential of the control unit 60, to which the measurement results of the current measurement circuit 30 are output. This is because the reference potential of the control unit 60 is often set to the potential of the negative terminal of the battery 100. In other words, a high voltage may be applied to the current measurement circuit 30, which may affect the control unit 60 connected to the current measurement circuit 30. Therefore, by providing the current measurement circuit 30 in the negative path, it is possible to prevent a high voltage from being applied to the control unit 60.

[0024] However, if the current measurement circuit 30 is a non-contact type sensor such as a Hall element, providing the current measurement circuit 30 in the positive path is unlikely to pose a problem because a high voltage is not applied to the current measurement circuit 30 itself and the control unit 60 is not affected. For this reason, if the current measurement circuit 30 is a non-contact type sensor such as a Hall element, the current measurement circuit 30 may be provided in the positive path.

[0025] Voltage measurement circuit 41 is a circuit that measures the voltage of battery 100 and is connected in parallel to battery 100. Voltage measurement circuit 42 is a circuit that measures the voltage of capacitor 200 and is connected in parallel to capacitor 200. For example, voltage measurement circuits 41 and 42 can be realized by voltage dividing resistors or the like. Voltage measurement circuits 41 and 42 output measurement results (voltage values) to control unit 60. Signal lines from voltage measurement circuits 41 and 42 to control unit 60 are not shown in FIG. 1 .

[0026] The DC / DC converter 20 is a DC / DC converter connected in parallel with the positive-side main relay 11. For example, the DC / DC converter 20 is a non-insulated DC / DC converter. For example, the DC / DC converter 20 is a buck converter. The DC / DC converter 20 includes a semiconductor switch 21, a coil 22, and a rectifier 23.

[0027] One end of the semiconductor switch 21 is connected to the battery-side terminal 11A of the positive-side main relay 11, and the other end of the semiconductor switch 21 is connected to one end of the coil 22 and one end of the rectifier 23. The semiconductor switch 21 is, for example, an N-channel metal oxide semiconductor field effect transistor (MOSFET). One end of the semiconductor switch 21 is a drain, and the other end of the semiconductor switch 21 is a source.

[0028] The other end of the coil 22 is connected to the capacitor side terminal 11B of the positive side main relay 11 .

[0029] One end of the rectifier 23 is connected to the other end of the semiconductor switch 21 and one end of the coil 22, and the other end of the rectifier 23 is connected to the negative path. The rectifier 23 is, for example, a diode. One end of the rectifier 23 is a cathode, and the other end of the rectifier 23 is an anode.

[0030] The control unit 60 controls the positive side main relay 11, the negative side main relay 12, the semiconductor switch 21, and the active fuse 50. For example, the control unit 60 controls the on and off of the semiconductor switch 21 by outputting a gate signal to the gate of the semiconductor switch 21. The control unit 60 is a computer including a processor (microprocessor), a memory, etc. The memory is a read-only memory (ROM) and a random access memory (RAM), etc., and can store programs executed by the processor.

[0031] Note that, although an example will be described below in which the positive side main relay 11, the negative side main relay 12, the semiconductor switch 21, and the active fuse 50 are controlled by one control unit 60, the positive side main relay 11, the negative side main relay 12, the semiconductor switch 21, and the active fuse 50 may each be controlled by a different control unit. For example, the positive side main relay 11 and the negative side main relay 12 may be controlled by an ECU (Electronic Control Unit) or the like, the active fuse 50 may be controlled by a drive circuit for the active fuse 50, and the semiconductor switch 21 may be controlled by the control unit 60.

[0032] The control unit 60 charges the capacitor 200 with a constant current by controlling the semiconductor switch 21 based on the current measured by the current measurement circuit 30. Specifically, the control unit 60 charges the capacitor 200 with a constant current before turning on the main relay (positive side main relay 11) of the current interruption device 1. If the positive side main relay 11 is turned on while the capacitor 200 is not charged, a large inrush current may flow through the positive side main relay 11, causing a malfunction of the positive side main relay 11 (for example, welding of the contacts of the positive side main relay 11). Here, the operation of the control unit 60 before turning on the positive side main relay 11 will be described with reference to FIGS. 2 and 3 .

[0033] FIG. 2 is a flowchart showing an example of an operation of the control unit 60 according to the first embodiment before turning on the positive side main relay 11.

[0034] FIG. 3 is a diagram for explaining the operation of charging the capacitor 200 with a constant current.

[0035] First, the control unit 60 turns off the positive side main relay 11 and turns on the negative side main relay 12 (step S11).

[0036] Next, the control unit 60 turns on the Gate signal (step S12). This turns on the semiconductor switch 21, and as shown in Fig. 3, current begins to flow to the capacitor 200, charging the capacitor 200. At this time, current flows while energy is stored in the coil 22.

[0037] Next, the control unit 60 measures the current flowing through the capacitor 200 (step S13). Specifically, the control unit 60 measures the current flowing through the capacitor 200 by acquiring the measurement result from the current measurement circuit 30. As shown in Fig. 3, the amount of change in the current that flows when the Gate signal is on increases in the early stage of charging when the voltage difference between the voltage of the battery 100 and the voltage of the capacitor 200 is large. Specifically, if the amount of change in current is di / dt, the voltage difference is ΔV, and the inductance of the coil 22 is L, then di / dt = ΔV / L, and it can be seen that the amount of change in current increases as the voltage difference increases.

[0038] Next, the control unit 60 determines whether the measured current value is greater than a set current value (step S14). The set current value is a target constant current, which is a current that is determined in advance.

[0039] If the control unit 60 determines that the measured current value is greater than the set current value (Yes in step S14), it turns off the Gate signal (step S15), turning off the semiconductor switch 21. As shown in FIG. 3 , even after the semiconductor switch 21 is turned off, the current continues to flow through the capacitor 200 due to the energy stored in the coil 22.

[0040] If the control unit 60 determines that the measured current value is equal to or less than the set current value (No in step S14), the process in step S15 is skipped. That is, the gate signal is kept ON until the measured current value becomes greater than the set current value.

[0041] Next, the control unit 60 determines whether the time since the Gate signal was turned on (referred to as the ON time) has reached one switching cycle of the semiconductor switch 21 (step S16). For example, one cycle is a predetermined period. For example, the control unit 60 has a timer and can make the above determination by using the timer.

[0042] If the control unit 60 determines that the ON time has not reached one cycle (No in step S16), it repeats the process from step S13. The process from step S13 to step S16 is repeated until the ON time reaches one cycle. By repeating the process from step S13 to step S16, as shown in FIG. 3 , when the Gate signal is ON, the measured current value gradually increases, and after the measured current value becomes larger than the set current value, the Gate signal is turned OFF and the measured current value gradually decreases.

[0043] When the control unit 60 determines that the on-time has reached one cycle (Yes in step S16), it determines whether the voltage of the capacitor 200 has been charged up to the voltage of the battery 100 (step S17). For example, the control unit 60 can make this determination by obtaining and comparing the measurement results from the voltage measurement circuits 41 and 42.

[0044] If the control unit 60 determines that the voltage of the capacitor 200 has not yet reached the voltage of the battery 100 (No in step S17), the process from step S12 is repeated. That is, the charging of the capacitor 200 continues in the next cycle. By repeating the processes from step S12 to step S17, the voltage of the capacitor 200 increases. That is, the voltage difference between the voltage of the battery 100 and the voltage of the capacitor 200 decreases. As a result, as shown on the right side of FIG. 3 , the amount of change in current decreases and the duty of the Gate signal increases. In this way, the capacitor 200 is charged with a constant current by the DC / DC converter 20.

[0045] The control unit 60 may detect the amount of voltage rise of the capacitor 200 when the capacitor 200 is charged with a constant current, and if the amount of rise is equal to or less than a predetermined value, detect a short circuit in the load connected to the capacitor 200. For example, if the load is short-circuited, the voltage of the capacitor 200 is unlikely to rise even if an attempt is made to charge the capacitor 200 with a constant current. Therefore, by monitoring the amount of rise in the voltage of the capacitor 200, a short circuit in the load can be detected.

[0046] When the control unit 60 determines that the voltage of the capacitor 200 has been charged to the voltage of the battery 100 (Yes in step S17), it turns on the positive side main relay 11 and keeps on the negative side main relay 12 (step S18). At this time, the voltage difference between the voltage of the capacitor 200 and the voltage of the battery 100 is zero, so that the inrush current can be suppressed.

[0047] Thereafter, the control unit 60 drives the active fuse 50 based on the current measured by the current measurement circuit 30. Specifically, when a large current is measured, the active fuse 50 cuts off the positive side path to prevent the battery 100 from emitting smoke or catching fire.

[0048] The current measurement circuit 30 used to drive the active fuse 50 can be used as a circuit for measuring the current required to charge the capacitor 200 at a constant current. In other words, there is no need to separately prepare a current measurement circuit used to charge the capacitor 200 at a constant current, which can prevent the device from becoming larger.

[0049] Here, the effect of charging capacitor 200 with a constant current before turning on positive side main relay 11 will be described with reference to FIGS. 4A and 4B.

[0050] FIG. 4A is a diagram showing an example of the time waveforms of the charging current and the capacitor voltage when the main relay is turned on in the comparative example.

[0051] FIG. 4B is a diagram showing an example of the time waveforms of the charging current and the voltage of capacitor 200 when positive side main relay 11 is turned on in the first embodiment.

[0052] For example, in a comparative example, as in the technology described in Patent Document 1, a precharge relay and a precharge resistor are connected to the main relay, and the precharge relay is turned on before the main relay is turned on. When the capacitor is charged using the precharge resistor, as shown in FIG. 4A, the charging current momentarily increases and then gradually decreases. Therefore, the capacitor voltage increases according to the time constant of the CR, and it takes a long time to charge the capacitor voltage to the battery voltage. For this reason, the main relay is turned on before the capacitor voltage is fully charged to the battery voltage, that is, when there is a voltage difference between the battery voltage and the capacitor voltage. Therefore, when the capacitor is charged using the precharge resistor as in the comparative example, the inrush current cannot be sufficiently suppressed, making it difficult to suppress stress on the main relay.

[0053] On the other hand, when DC / DC converter 20 charges capacitor 200 with a constant current, as shown in Fig. 4B , the voltage of capacitor 200 increases in proportion to time with a coefficient that depends on the constant current, so that the voltage of capacitor 200 can be charged to the voltage of battery 100 in a short time. Therefore, after capacitor 200 is completely charged to the voltage of battery 100, that is, when there is no voltage difference between the voltage of battery 100 and the voltage of capacitor 200, positive side main relay 11 can be turned on. Therefore, when DC / DC converter 20 charges capacitor 200 with a constant current, inrush current can be sufficiently suppressed, and stress on positive side main relay 11 can be suppressed.

[0054] As described above, because the DC / DC converter 20 can charge the capacitor 200 with a constant current, the voltage difference between the voltage of the battery 100 and the voltage of the capacitor 200 can be reduced before the positive-side main relay 11 is turned on, thereby suppressing the inrush current. Furthermore, if a pre-charge resistor is used to suppress the inrush current, when the voltage of the battery 100 increases and the capacitance of the capacitor 200 increases, many pre-charge resistors must be connected in series and in parallel, resulting in an increase in the size of the device. In contrast, in the present disclosure, a pre-charge resistor is not used to suppress the inrush current, so the device can be prevented from becoming large even when the voltage of the battery 100 increases and the capacitance of the capacitor 200 increases. Therefore, the inrush current generated when the main relay is turned on can be suppressed while suppressing an increase in the size of the device.

[0055] Second Embodiment In the first embodiment, an example has been described in which a non-insulated DC / DC converter 20 is used to charge the capacitor 200 with a constant current, but this is not limiting. For example, an insulating DC / DC converter may be used to charge the capacitor 200 with a constant current.

[0056] FIG. 5 is a block diagram showing an example of a current interruption device 1a according to the second embodiment.

[0057] The current interruption device 1a according to the second embodiment differs from the current interruption device 1 according to the first embodiment in that a DC / DC converter 20a is provided instead of the DC / DC converter 20. Since the other points are the same as those in the first embodiment, the following description will focus on the points that are different.

[0058] The DC / DC converter 20a is a DC / DC converter connected in parallel with the positive-side main relay 11. For example, the DC / DC converter 20a is an isolated DC / DC converter. For example, the DC / DC converter 20a is a flyback converter. The DC / DC converter 20a includes a semiconductor switch 21a, a transformer 22a, and a rectifier 23a. The transformer 22a is an example of a coil. The transformer 22a is an isolated transformer and includes a primary winding and a secondary winding.

[0059] One end of the semiconductor switch 21a is connected to the battery-side terminal 11A of the positive-side main relay 11, and the other end of the semiconductor switch 21a is connected to one end of the primary winding of the transformer 22a. The semiconductor switch 21a is, for example, an N-channel MOSFET. One end of the semiconductor switch 21a is a drain, and the other end of the semiconductor switch 21a is a source.

[0060] One end of the rectifier 23a is connected to the capacitor-side terminal 11B of the positive-side main relay 11, and the other end of the rectifier 23a is connected to one end of the secondary winding of the transformer 22a. The rectifier 23a is, for example, a diode. One end of the rectifier 23a is a cathode, and the other end of the rectifier 23a is an anode.

[0061] The other end of the primary winding of the transformer 22a is connected to the negative path. For example, the other end of the primary winding of the transformer 22a is connected to the battery side terminal 11A of the negative side main relay 12. The other end of the secondary winding of the transformer 22a is connected to the negative path. For example, the other end of the secondary winding of the transformer 22a is connected to the capacitor side terminal 11B of the negative side main relay 12.

[0062] The current measurement circuit 30 is provided in the positive path or the negative path. Specifically, the current measurement circuit 30 is provided on the positive path closer to the capacitor 200 than the connection node with the rectifier 23a, or on the negative path closer to the capacitor 200 than the connection node with the secondary winding of the transformer 22a. For example, the current measurement circuit 30 is provided in the negative path, and specifically, as shown in FIG. 5 , the current measurement circuit 30 is provided on the negative path closer to the capacitor 200 than the connection node with the secondary winding of the transformer 22a.

[0063] The control unit 60 controls the positive side main relay 11, the negative side main relay 12, the semiconductor switch 21a, and the active fuse 50. For example, the control unit 60 controls the on and off of the semiconductor switch 21a by outputting a gate signal to the gate of the semiconductor switch 21a. The operation of the control unit 60 to charge the capacitor 200 with a constant current is the same as in the first embodiment, and therefore will not be described again.

[0064] The isolated DC / DC converter 20a having such a circuit configuration can also charge the capacitor 200 with a constant current, as in the first embodiment.

[0065] Also in the DC / DC converter 20a, the control unit 60 may detect the amount of voltage rise of the capacitor 200 when the capacitor 200 is charged with a constant current, and if the amount of rise is equal to or less than a predetermined value, detect a short circuit in the load connected to the capacitor 200. For example, if the load is short-circuited, the voltage of the capacitor 200 is unlikely to rise even if an attempt is made to charge the capacitor 200 with a constant current. Therefore, by monitoring the amount of rise in the voltage of the capacitor 200, a short circuit in the load can be detected.

[0066] (Other Embodiments) As described above, the embodiments have been described as examples of the technology according to the present disclosure. However, the technology according to the present disclosure is not limited to these, and can be applied to embodiments in which modifications, substitutions, additions, omissions, etc. are made as appropriate. For example, the following modifications are also included in one embodiment of the present disclosure.

[0067] For example, in the above embodiment, an example has been described in which the current interruption device includes the negative side main relay 12 , but the current interruption device does not necessarily have to include the negative side main relay 12 .

[0068] For example, in the above embodiment, an example has been described in which the current interruption device includes the active fuse 50 , but the current interruption device does not necessarily have to include the active fuse 50 .

[0069] In the above-described embodiment, each component included in the current interruption device may be configured with dedicated hardware, or may be realized by executing a software program suitable for each component. Each component may be realized by a program execution unit such as a CPU or processor reading and executing a software program recorded on a recording medium such as a hard disk or semiconductor memory.

[0070] Some or all of the functions of the current interruption devices according to the above embodiments are typically realized as an LSI, which is an integrated circuit. These may be individually integrated into a single chip, or some or all of them may be integrated into a single chip. Furthermore, the integrated circuit is not limited to an LSI, and may be realized using a dedicated circuit or a general-purpose processor. An FPGA (Field Programmable Gate Array), which can be programmed after LSI manufacturing, or a reconfigurable processor, which can reconfigure the connections and settings of circuit cells within the LSI, may also be used.

[0071] Furthermore, if an integrated circuit technology that can replace LSI emerges due to advances in semiconductor technology or other derivative technologies, that technology may naturally be used to integrate the components included in the current interruption device.

[0072] In addition, this disclosure also includes forms obtained by making various modifications to the embodiments that a person skilled in the art would think of, and forms realized by arbitrarily combining the components and functions in each embodiment within the scope that does not deviate from the intent of this disclosure.

[0073] (Additional Notes) The above description of the embodiments discloses the following techniques.

[0074] (Technology 1) A current interruption device comprising: a positive-side main relay provided on a positive-side path connecting a positive terminal of a battery and a positive terminal of a capacitor; a DC / DC converter connected in parallel with the positive-side main relay and having a semiconductor switch and a coil; a current measurement circuit that measures the current flowing through the capacitor; and a control unit that charges the capacitor with a constant current by controlling the semiconductor switch based on the current measured by the current measurement circuit, wherein the path connecting the negative terminal of the battery and the negative terminal of the capacitor is used as the negative path.

[0075] According to this, the DC / DC converter can charge the capacitor with a constant current, thereby reducing the voltage difference between the battery voltage and the capacitor voltage before turning on the positive-side main relay, thereby suppressing inrush current. Furthermore, if a pre-charge resistor is used to suppress inrush current, when the battery voltage increases and the capacitor capacity increases, many pre-charge resistors must be connected in series and parallel, resulting in an increase in the device size. In contrast, the present disclosure does not use a pre-charge resistor to suppress inrush current, so the device size can be suppressed even when the battery voltage increases and the capacitor capacity increases. Therefore, the inrush current when the main relay is turned on can be suppressed while suppressing the device size.

[0076] Furthermore, when the capacitor is charged using a pre-charge resistor, the capacitor voltage increases according to the time constant of the CR, so it takes a long time to charge the capacitor voltage to the battery voltage. Therefore, the main relay is turned on before the capacitor voltage is fully charged to the battery voltage, i.e., when there is a voltage difference between the battery voltage and the capacitor voltage. Therefore, when the capacitor is charged using a pre-charge resistor, the inrush current cannot be sufficiently suppressed, making it difficult to suppress stress on the main relay. On the other hand, when the capacitor is charged with a constant current using a DC / DC converter, the capacitor voltage increases at a constant rate according to the constant current, so the capacitor voltage can be charged to the battery voltage in a short time. Therefore, the main relay can be turned on after the capacitor voltage is fully charged to the battery voltage, i.e., when there is no voltage difference between the battery voltage and the capacitor voltage. Therefore, when the capacitor is charged with a constant current using a DC / DC converter, the inrush current can be sufficiently suppressed, and stress on the main relay can be suppressed.

[0077] (Technology 2) The current interruption device according to Technology 1, wherein the DC / DC converter is a non-isolated DC / DC converter.

[0078] In this way, the capacitor can be charged with a constant current by using a non-isolated DC / DC converter.

[0079] (Technology 3) The positive-side main relay has a battery-side terminal connected to a positive terminal of the battery and a capacitor-side terminal connected to the capacitor, the DC / DC converter further has a rectifier, one end of the semiconductor switch is connected to the battery-side terminal of the positive-side main relay, the other end of the semiconductor switch is connected to one end of the coil, the other end of the coil is connected to the capacitor-side terminal of the positive-side main relay, one end of the rectifier is connected to the other end of the semiconductor switch and the one end of the coil, and the other end of the rectifier is connected to the negative path connecting the negative terminal of the battery and the negative terminal of the capacitor.

[0080] A non-isolated DC / DC converter having such a circuit configuration can charge a capacitor with a constant current.

[0081] (Technology 4) The current interruption device according to Technology 1, wherein the DC / DC converter is an isolated DC / DC converter, and the coil is a transformer.

[0082] In this way, the capacitor can be charged with a constant current by the isolated DC / DC converter.

[0083] (Technology 5) The DC / DC converter further includes a rectifier unit, one end of the semiconductor switch is connected to the battery side terminal of the positive side main relay, the other end of the semiconductor switch is connected to one end of a primary winding of the transformer, the other end of the primary winding of the transformer is connected to the negative side path connecting the negative side terminal of the battery and the negative side terminal of the capacitor, one end of the rectifier unit is connected to the capacitor side terminal of the positive side main relay, the other end of the rectifier unit is connected to one end of a secondary winding of the transformer, and the other end of the secondary winding of the transformer is connected to the negative side path.

[0084] An isolated DC / DC converter having such a circuit configuration can charge a capacitor with a constant current.

[0085] (Technology 6) A current interruption device according to any one of technologies 1 to 5, wherein the control unit detects the amount of voltage increase of the capacitor when the capacitor is charged with a constant current, and if the amount of increase is equal to or less than a predetermined value, detects a short circuit in a load connected to the capacitor.

[0086] For example, if the load is short-circuited, the capacitor voltage will not increase easily even if you try to charge the capacitor with a constant current. Therefore, by monitoring the increase in the capacitor voltage, it is possible to detect a short-circuited load.

[0087] (Technology 7) A current interruption device according to any one of technologies 1 to 6, wherein the current measurement circuit is provided on the negative path connecting the negative terminal of the battery and the negative terminal of the capacitor.

[0088] For example, if the current measurement circuit is a shunt-type sensor and is installed in the positive path, a high voltage may be applied between the current measurement circuit and the reference potential of the control unit, which is the output destination of the current measurement circuit's measurement results. This is because the reference potential of the control unit is often set to the potential of the negative terminal of the battery. In other words, a high voltage is applied to the current measurement circuit, which also affects the control unit connected to the current measurement circuit. Therefore, by installing the current measurement circuit in the negative path, it is possible to prevent a high voltage from being applied to the control unit.

[0089] (Technology 8) The current interruption device according to any one of Technologies 1 to 7, further comprising a negative main relay provided on the negative path connecting the negative terminal of the battery and the negative terminal of the capacitor.

[0090] In this way, a main relay may be provided not only in the positive side path but also in the negative side path.

[0091] (Technology 9) The current interruption device according to any one of Technologies 1 to 8, further comprising an active fuse provided on the positive path or the negative path, and the control unit drives the active fuse based on the current measured by the current measurement circuit.

[0092] This allows the current measurement circuit used to drive the active fuse to be used as the circuit that measures the current required to charge the capacitor with a constant current, which means that there is no need to prepare a separate current measurement circuit used to charge the capacitor with a constant current, thereby preventing the device from becoming larger.

[0093] (Technology 10) The current interruption device according to Technology 9, wherein the active fuse is a pyro fuse.

[0094] Thus, the active fuse is preferably a pyro fuse.

[0095] The present disclosure can be applied to a system that uses an active fuse to interrupt a current path.

[0096] REFERENCE SIGNS LIST 1, 1a Current interruption device 11 Positive side main relay 11A Battery side terminal 11B Capacitor side terminal 12 Negative side main relay 20, 20a DC / DC converter 21, 21a Semiconductor switch 22 Coil 22a Transformer 23, 23a Rectifier unit 30 Current measurement circuit 41, 42 Voltage measurement circuit 50 Active fuse 60 Control unit 100 Battery 200 Capacitor

Claims

1. A current interruption device comprising: a positive-side main relay provided on a positive-side path connecting the positive terminal of a battery and the positive terminal of a capacitor; a DC / DC converter connected in parallel with the positive-side main relay and having a semiconductor switch and a coil; a current measurement circuit that measures the current flowing through the capacitor; and a control unit that charges the capacitor with a constant current by controlling the semiconductor switch based on the current measured by the current measurement circuit, wherein the path connecting the negative terminal of the battery and the negative terminal of the capacitor is the negative path.

2. The current interruption device according to claim 1, wherein the DC / DC converter is a non-isolated DC / DC converter.

3. The current interruption device according to claim 2, wherein the positive side main relay has a battery side terminal connected to the positive side terminal of the battery and a capacitor side terminal connected to the capacitor, the DC / DC converter further has a rectifier, one end of the semiconductor switch is connected to the battery side terminal of the positive side main relay, the other end of the semiconductor switch is connected to one end of the coil, the other end of the coil is connected to the capacitor side terminal of the positive side main relay, one end of the rectifier is connected to the other end of the semiconductor switch and the one end of the coil, and the other end of the rectifier is connected to the negative side path connecting the negative side terminal of the battery and the negative side terminal of the capacitor.

4. The current interruption device according to claim 1, wherein the DC / DC converter is an isolated DC / DC converter, and the coil is a transformer.

5. The current interruption device according to claim 4, wherein the DC / DC converter further has a rectifier unit, one end of the semiconductor switch is connected to the battery side terminal of the positive side main relay, the other end of the semiconductor switch is connected to one end of the primary winding of the transformer, the other end of the primary winding of the transformer is connected to the negative side path connecting the negative side terminal of the battery and the negative side terminal of the capacitor, one end of the rectifier unit is connected to the capacitor side terminal of the positive side main relay, the other end of the rectifier unit is connected to one end of the secondary winding of the transformer, and the other end of the secondary winding of the transformer is connected to the negative side path.

6. A current interruption device according to any one of claims 1 to 5, wherein the control unit detects the amount of voltage rise of the capacitor when the capacitor is charged with a constant current, and if the amount of rise is equal to or less than a predetermined value, detects a short circuit in the load connected to the capacitor.

7. The current interruption device according to any one of claims 1 to 6, wherein the current measurement circuit is provided on the negative path connecting the negative terminal of the battery and the negative terminal of the capacitor.

8. The current interruption device according to any one of claims 1 to 7, further comprising a negative main relay provided on the negative path connecting the negative terminal of the battery and the negative terminal of the capacitor.

9. The current interruption device according to any one of claims 1 to 8, further comprising an active fuse provided on the positive path or the negative path, and the control unit drives the active fuse based on the current measured by the current measurement circuit.

10. The current interruption device according to claim 9, wherein the active fuse is a pyro-fuse.

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