Drive unit

Abstract

A drive unit (1) comprises: a resistor (R1) that is disposed in a current path (P1); a voltage detection circuit (10) that detects the voltage across both ends of a resistor (R1); and a drive circuit (20) that is connected to the resistor (R1) in parallel. When the voltage across both ends of the resistor (R1) is not less than a voltage threshold, the voltage detection circuit (10) outputs a drive signal to the drive circuit (20). Upon receiving input of the drive signal, the drive circuit (20) divides the electric current flowing through the current path (P1) and causes a part of the electric current to flow to an internal resistance (R2) of a pyro fuse (100), so as to cause the pyro fuse (100) to interrupt the current path (P1).

Description

Drive unit

[0001] The present disclosure relates to a drive unit for driving a pyrofuse.

[0002] Patent Document 1 discloses a technique for driving a pyro-fuse by utilizing the arc voltage generated when a blow fuse is blown.

[0003] International Publication No. 2017 / 042321

[0004] In the technology disclosed in Patent Document 1, the current value at which a blow fuse melts, i.e., the current threshold for activating a pyro-fuse, is not fixed because it depends on the melting characteristics of the blow fuse. For example, the melting characteristics of a blow fuse are such that it melts in 20 ms when a current of 5 kA flows, and melts in 1 ms when a current of 10 kA flows, and the current value at which a blow fuse melts is not fixed. Due to these characteristics of blow fuses, it is difficult to activate a pyro-fuse with high accuracy when using the arc voltage generated when the blow fuse melts.

[0005] Therefore, the present disclosure provides a drive unit that can drive a pyrofuse with high precision.

[0006] The drive unit according to the present disclosure is a drive unit for driving a pyro-fuse that has an internal resistance and cuts off a current path by detonating in response to a current flowing through the internal resistance, and comprises a resistor arranged in the current path, a voltage detection circuit that detects the voltage across the resistor, and a drive circuit connected in parallel with the resistor, wherein the voltage detection circuit outputs a drive signal to the drive circuit when the voltage across the resistor is equal to or greater than a voltage threshold, and when the drive signal is input, the drive circuit diverts a portion of the current flowing through the current path and causes the current to flow through the internal resistance, thereby causing the pyro-fuse to cut off the current path.

[0007] 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.

[0008] According to the drive unit according to one aspect of the present disclosure, it is possible to drive the pyrofuse with high precision.

[0009] FIG. 1 is a circuit configuration diagram showing an example of a drive unit according to an embodiment. FIG. 2 is a diagram for explaining interruption of a current path by a pyrofuse. FIG. 3 is a circuit configuration diagram showing an example of a drive unit according to an embodiment. FIG. 4 is a circuit configuration diagram showing an example of a voltage detection circuit according to an embodiment. FIG. 5 is a circuit configuration diagram showing an example of a voltage detection circuit according to an embodiment. FIG. 6 is a circuit configuration diagram showing an example of a plurality of voltage detection circuits according to an embodiment. FIG. 7 is a circuit configuration diagram showing an example of a drive unit according to a first modified example of an embodiment. FIG. 8 is a diagram for explaining an example of operation of a drive unit according to a first modified example of an embodiment. FIG. 9 is a circuit configuration diagram showing an example of a drive unit according to a second modified example of an embodiment. FIG. 10 is a circuit configuration diagram showing an example of a drive unit according to a third modified example of an embodiment. FIG. 11 is a diagram showing an example of an arrangement of resistors and pyrofuses. FIG. 12 is a diagram showing an example of an arrangement of resistors and pyrofuses.

[0010] Hereinafter, the embodiments will be specifically described with reference to the drawings.

[0011] 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.

[0012] (Embodiment) A drive unit according to an embodiment will be described below.

[0013] Fig. 1 is a circuit diagram showing an example of a drive unit 1 according to an embodiment. The drive unit 1 is used in a transport device or the like that includes a battery 200 and a load 300. In addition to the drive unit 1, Fig. 1 also shows a pyrofuse 100, the battery 200, and the load 300 that are provided in the transport device or the like. The drive unit 1 is used in an electric vehicle such as a battery electric vehicle (BEV), a hybrid electric vehicle (HEV), or a fuel cell vehicle (FCV), for example.

[0014] The battery 200 is a battery that can apply a high voltage of, for example, several hundred volts to the load 300. For example, the battery 200 is a main battery (for example, a lithium ion battery) in an electric vehicle.

[0015] The load 300 is, for example, a motor and an inverter of an electric vehicle. The electric vehicle is propelled by power supplied from the battery 200 to the load 300. In the event of an accident or the like, a large current due to a short circuit may flow in the current path P1 connecting the battery 200 and the load 300, which may cause the battery 200 to emit smoke or catch fire. Therefore, the drive unit 1 is used in transportation equipment.

[0016] Pyro fuse 100 is a fuse for cutting off current path P1 connecting battery 200 and load 300 when a large current due to a short circuit flows through current path P1. Pyro fuse 100 contains an explosive (not shown) and ignites the explosive based on an ignition signal from outside pyro fuse 100, irreversibly cutting off current path P1 with the explosive ignition and the resulting explosive force. Specifically, pyro fuse 100 has an internal resistance R2 and a cutting blade. When a relatively large current (e.g., a current of several amperes) flows through internal resistance R2, heat generated in internal resistance R2 ignites the explosive. The explosive force generated by the explosive ignition pushes down the cutting blade at high speed, cutting a bus bar that is part of current path P1, thereby cutting off current path P1. Pyro fuse 100 cuts off current path P1 in response to an ignition signal from drive unit 1. The pyrofuse 100 is also called a pyroswitch, a pyrotechnic switch, or a pyroelectric switch. For example, the pyrofuse 100 is disposed between the negative terminal of the battery 200 and the negative terminal of the load 300.

[0017] The drive unit 1 is a unit that drives a pyrofuse 100 that interrupts a current path P1 connecting a battery 200 and a load 300. The drive unit 1 includes a resistor R1, a voltage detection circuit 10, a drive circuit 20, and the pyrofuse 100.

[0018] Resistor R1 is disposed in current path P1. Resistor R1 is a shunt resistor. For example, resistor R1 may be built into pyrofuse 100, or resistor R1 may be formed by a bus bar of pyrofuse 100. For example, resistor R1 is disposed between the negative terminal of battery 200 and the negative terminal of load 300.

[0019] The voltage across resistor R1 may also be output to a control circuit (not shown), and the reference potential of this control circuit is often set to the potential of the negative terminal of battery 200, and resistor R1 is placed between the negative terminal of battery 200 and the negative terminal of load 300. This is because if resistor R1 is placed between the positive terminal of battery 200 and the positive terminal of load 300, a high voltage will be applied between the reference potential of the control circuit and resistor R1.

[0020] The voltage detection circuit 10 detects the voltage across resistor R1. By detecting the voltage across resistor R1, the voltage detection circuit 10 can detect whether an overcurrent is flowing through current path P1. If the voltage across resistor R1 is equal to or greater than a voltage threshold, the voltage detection circuit 10 determines that an overcurrent that should activate pyrofuse 100 has been detected, and outputs a drive signal to drive circuit 20 to activate pyrofuse 100. If the resistance value of resistor R1 is R, the current value of the current flowing through current path P1 is Is, and the voltage across resistor R1 is V, then V = Is × R, and Is = V / R. Therefore, by using resistor R1 with a known value of R and calculating the above equation using V as the voltage threshold of voltage detection circuit 10, Is can be calculated as the current threshold for activating pyrofuse 100. In this way, the current threshold for activating pyrofuse 100 can be determined arbitrarily by adjusting the resistance value of resistor R1 and the voltage threshold of voltage detection circuit 10.

[0021] Drive circuit 20 is connected in parallel to resistor R1. When a drive signal is input from voltage detection circuit 10, drive circuit 20 shunts a certain amount of current from the overcurrent flowing through current path P1 and causes the current to flow through internal resistor R2 of pyrofuse 100, thereby driving pyrofuse 100 and interrupting current path P1. Because drive circuit 20 is connected in parallel to resistor R1, that is, because drive circuit 20 is provided on the shunt path of current path P1, drive circuit 20 can use a portion of the current flowing through current path P1.

[0022] For example, the drive circuit 20 includes a switch unit 21 and a constant current circuit 22. When a drive signal is input, the switch unit 21 connects the constant current circuit 22 to the current path P1, and the constant current circuit 22 is connected to the current path P1, thereby shunting a portion of the current flowing through the current path P1 and causing the current to flow through the internal resistance R2 of the pyrofuse 100.

[0023] Here, the flow until the current path P1 is cut off by the pyro-fuse 100 will be described with reference to FIGS.

[0024] FIG. 2 is a diagram for explaining how the pyrofuse 100 cuts off the current path.

[0025] First, assume that an overcurrent Is occurs as shown in FIG. 1 . This generates a voltage V corresponding to the overcurrent Is across resistor R1. If the generated voltage V exceeds the voltage threshold of voltage detection circuit 10, voltage detection circuit 10 outputs a drive signal to drive circuit 20 (switch unit 21), and switch unit 21 connects constant current circuit 22 to current path P1. As shown in FIG. 1 , constant current circuit 22 generates a current Ip that is more limited than the overcurrent Is and passes it through internal resistor R2. Then, as shown in FIG. 2 , pyrofuse 100 is activated, and the bus bar is cut by the cutting blade, interrupting current path P1.

[0026] An example of the circuit of the drive unit 1 will now be described with reference to FIG.

[0027] FIG. 3 is a circuit diagram showing an example of the drive unit 1 according to the embodiment.

[0028] As shown in FIG. 3, the voltage detection circuit 10, the switch section 21, and the constant current circuit 22 are connected in parallel with the resistor R1, and the voltage generated in the resistor R1 is applied to the voltage detection circuit 10, the switch section 21, and the constant current circuit 22.

[0029] 3, the voltage detection circuit 10 includes, for example, a voltage dividing resistor, a reset IC, and a pull-up resistor. The voltage across resistor R1 is divided by the voltage dividing resistor and input to the terminal VDD of the reset IC. For example, the reset IC is an IC with an open-drain output. When the voltage input to the terminal VDD exceeds a voltage corresponding to a voltage threshold, the terminal VDD of the reset IC becomes high-level potential due to the pull-up resistor.

[0030] 3, the switch unit 21 includes, for example, an N-channel MOSFET and a P-channel MOSFET. A gate-source resistor is connected between the gate and source of the P-channel MOSFET. When the terminal VDD of the reset IC goes high, that is, when a drive signal indicating a high level is input from the voltage detection circuit 10 to the switch unit 21, the N-channel MOSFET turns on, and the P-channel MOSFET also turns on. This establishes electrical continuity between the current path P1 and the constant current circuit 22.

[0031] As shown in FIG. 3 , the constant current circuit 22 includes, for example, a PNP transistor, a base-emitter resistor, a P-channel MOSFET, and a gate resistor. The resistance value of the base-emitter resistor is determined according to the target output current Ip of the constant current circuit 22. When the current path P1 and the constant current circuit 22 are electrically connected, a current flows through the base-emitter resistor, generating a voltage across the base-emitter resistor. This turns on the PNP transistor, causing a current to flow through the gate resistor, generating a voltage across the gate resistor. When the current flowing through the base-emitter resistor is greater than the target output current Ip, the voltage across the gate resistor increases, and the current flowing through the base-emitter resistor is limited by the P-channel MOSFET and decreases toward the target output current Ip. When the current flowing through the base-emitter resistor is smaller than the target output current Ip, the voltage across the gate resistor decreases, and the current flowing through the base-emitter resistor is less likely to be limited by the P-channel MOSFET, causing the current flowing through the base-emitter resistor to increase toward the target output current Ip. In this way, the constant current circuit 22 can supply a constant current to the internal resistance R2 of the pyrofuse 100.

[0032] In this way, when a drive signal is input to the switch unit 21, that is, when an overcurrent is detected, the switch unit 21 is operated to connect the current path P1 to the constant current circuit 22, and the constant current circuit 22 can drive the pyro-fuse 100 by diverting a portion of the current flowing through the current path P1.

[0033] Next, additional functions of the voltage detection circuit 10 will be described with reference to FIGS.

[0034] 4 and 5 are circuit configuration diagrams showing an example of the voltage detection circuit 10 according to the embodiment.

[0035] 4, the voltage detection circuit 10 may include a detection unit 11 and a low-pass filter 12. The detection unit 11 is a functional unit that detects the voltage across the resistor R1 and outputs a drive signal to the drive circuit 20 when the voltage across the resistor R1 is equal to or greater than a voltage threshold.

[0036] The low-pass filter 12 is a filter that removes noise. If noise is contained in the current flowing through the resistor R1 and the voltage across the resistor R1 also contains noise, there is a risk of erroneous detection of an overcurrent. In response to this, the provision of the low-pass filter 12 can remove noise and suppress erroneous detection of an overcurrent. It can also prevent momentary overcurrents from being detected.

[0037] 5, the voltage detection circuit 10 may include a detection unit 11 and a timer circuit 13. The detection unit 11 outputs a drive signal to the drive circuit 20 when the voltage across the resistor R1 remains equal to or higher than a voltage threshold for a set time period set by the timer circuit 13.

[0038] If the current flowing through resistor R1 contains noise, and if the voltage across resistor R1 also contains noise, there is a risk of falsely detecting an overcurrent. However, because noise generally occurs instantaneously, the provision of timer circuit 13 makes it possible to distinguish between noise and an overcurrent, thereby preventing false detection of an overcurrent. Furthermore, if it is not desired to activate pyrofuse 100 instantly after an overcurrent is detected, the provision of timer circuit 13 makes it possible to activate pyrofuse 100 after a set time has elapsed. Note that timer circuit 13 can be implemented using a reset IC with a delay function, for example.

[0039] The voltage detection circuit 10 may include both the low-pass filter 12 and the timer circuit 13 .

[0040] The drive unit 1 may also include a plurality of voltage detection circuits 10 .

[0041] Fig. 6 is a circuit configuration diagram showing an example of a plurality of voltage detection circuits 10 according to an embodiment. Fig. 6 shows voltage detection circuits 10a, 10b, and 10c as the plurality of voltage detection circuits 10. As shown in Fig. 6, an OR circuit 14 is connected to the voltage detection circuits 10a, 10b, and 10c, and the drive unit 1 may also include the OR circuit 14. When a drive signal is input from any of the voltage detection circuits 10a, 10b, and 10c, the OR circuit 14 outputs the drive signal to the drive circuit 20.

[0042] Each of voltage detection circuits 10a, 10b, and 10c is set with a different set time and a different voltage threshold. For example, voltage detection circuit 10a is set with a voltage threshold of 20 V (e.g., corresponding to a current threshold of 20 kA) and a set time of 1 ms, voltage detection circuit 10b is set with a voltage threshold of 10 V (e.g., corresponding to a current threshold of 10 kA) and a set time of 10 ms, and voltage detection circuit 10c is set with a voltage threshold of 5 V (e.g., corresponding to a current threshold of 5 kA) and a set time of 50 ms. As a result, pyrofuse 100 can be activated after 1 ms when a current of 20 kA or more flows through current path P1, after 10 ms when a current of 10 kA or more but less than 20 kA flows through current path P1, and after 50 ms when a current of 5 kA or more but less than 10 kA flows through current path P1.

[0043] In this way, it is possible to make the pyrofuse 100 behave in the same manner as a blown fuse. Specifically, the larger the current value of the overcurrent, the shorter the time it takes for the pyrofuse 100 to be activated.

[0044] As described above, the voltage generated across resistor R1 arranged in current path P1 when an overcurrent flows through current path P1 serves as a trigger for activating pyrofuse 100, and the current threshold for activating pyrofuse 100 can be determined arbitrarily by adjusting the resistance value of resistor R1 and the voltage threshold of voltage detection circuit 10. Therefore, the current threshold for activating pyrofuse 100 can be set with high precision, and pyrofuse 100 can be activated with high precision.

[0045] Furthermore, with the technology described in Patent Document 1, it takes several milliseconds for the blow fuse to blow, so it takes time for the pyrofuse to be activated after an overcurrent is detected. In contrast, with the technology disclosed herein, the trigger for activating pyrofuse 100 does not use the arc voltage generated when the blow fuse blows, but rather uses the voltage generated across resistor R1 arranged in current path P1. This allows pyrofuse 100 to be activated, for example, within several tens of microseconds after the drive signal is input, that is, after an overcurrent is detected. Furthermore, because pyrofuse 100 can be activated by diverting a portion of the current flowing through current path P1, there is no need to provide a separate power supply and driver circuit for driving pyrofuse 100, which enables the drive unit 1 to be made smaller and less expensive.

[0046] (First Modification of the Embodiment) Next, a drive unit according to a first modification of the embodiment will be described.

[0047] 7 is a circuit diagram showing an example of a drive unit 1a according to a first modification of the embodiment. The drive unit 1a differs from the drive unit 1 according to the embodiment in that it includes a diode bridge circuit, and the drive circuit 20 is connected in parallel to a resistor R1 via the diode bridge circuit. The other points are the same as those in the embodiment, and therefore description thereof will be omitted.

[0048] The drive unit 1a includes, for example, diodes D1, D2, D3, and D4 as a diode bridge circuit. The anode of diode D1 and the cathode of diode D2 are connected to one end of resistor R1 (to the left of resistor R1 in FIG. 7), and the anode of diode D3 and the cathode of diode D4 are connected to the other end of resistor R1 (to the right of resistor R1 in FIG. 7). The cathodes of diode D1 and diode D3 are connected to one end of drive circuit 20 (to the left of drive circuit 20 in FIG. 7), and the anodes of diode D2 and diode D4 are connected to the other end of drive circuit 20 (to the right of drive circuit 20 in FIG. 7).

[0049] As shown in Figure 7, a load 300 is connected to battery 200 and battery 200 discharges to load 300, but there are also cases where a charger 400 is connected to battery 200 and battery 200 is charged from charger 400 (see Figure 9 described below). The direction of the current flowing through current path P1 differs during discharging and charging. Therefore, a diode bridge circuit is provided so that drive unit 1a can drive pyrofuse 100 regardless of the direction of current flow. Here, the operation of drive unit 1a during discharging and charging will be described using Figures 8 and 9.

[0050] 8 and 9 are diagrams for explaining an example of the operation of the drive unit 1a according to the first modified example of the embodiment. The operation during discharging will be explained using Fig. 8, and the operation during charging will be explained using Fig. 9.

[0051] 8, during discharge, a current flows from the positive terminal of battery 200 to the positive terminal of load 300, and from the negative terminal of load 300 to the negative terminal of battery 200. If an overcurrent Is flows through current path P1 during discharge, a current Ip can flow from current path P1 to diode D1, drive circuit 20, internal resistor R2, diode D4, and then to current path P1.

[0052] 9, during charging, current flows from the positive terminal of charger 400 to the positive terminal of battery 200, and from the negative terminal of battery 200 to the negative terminal of charger 400. If an overcurrent Is flows through current path P1 during charging, current Ip can flow from current path P1 to diode D3, drive circuit 20, internal resistor R2, diode D2, and then to current path P1.

[0053] In this way, even if an overcurrent occurs when power is supplied from battery 200 to load 300, or even if an overcurrent occurs when charger 400 is charging battery 200, current can be made to flow in one direction through drive circuit 20, from one end (left side in FIGS. 8 and 9 ) of drive circuit 20 to the other end (right side in FIGS. 8 and 9 ). In other words, it is possible to prevent current from flowing backward through drive circuit 20. Therefore, even if an overcurrent occurs when power is supplied from battery 200 to load 300, or even if an overcurrent occurs when charger 400 is charging battery 200, drive circuit 20 can be operated to drive pyrofuse 100.

[0054] (Second Modification of the Embodiment) Next, a drive unit according to a second modification of the embodiment will be described.

[0055] 10 is a circuit diagram showing an example of a drive unit 1b according to a second modification of the embodiment. The drive unit 1b differs from the drive unit 1 according to the embodiment in that it includes a boost circuit 30 provided between the current path P1 and the voltage detection circuit 10 and the drive circuit 20. The rest of the configuration is the same as in the embodiment, and therefore a description thereof will be omitted. Note that the drive unit 1b may include a diode bridge circuit, as in the drive unit 1a according to the first modification of the embodiment.

[0056] The boost circuit 30 is a circuit such as a DC-DC converter, and operates at a low voltage (e.g., 0.8 V). A certain level of voltage (e.g., 5 V) is required for stable operation of the voltage detection circuit 10 and the drive circuit 20. Increasing the resistance of the resistor R1 disposed in the current path P1 increases the voltage generated across the resistor R1, ensuring stable operation of the voltage detection circuit 10 and the drive circuit 20. However, in this case, heat generation in the resistor R1 and voltage drop across the resistor R1 must be taken into consideration. Therefore, it is desirable to reduce the resistance of the resistor R1. Therefore, by providing the boost circuit 30, even if the voltage generated across the resistor R1 is small, the voltage can be boosted, ensuring stable operation of the voltage detection circuit 10 and the drive circuit 20. In other words, the resistance of the resistor R1 can be reduced, suppressing heat generation and voltage drop.

[0057] (Third Modification of the Embodiment) Next, a drive unit according to a third modification of the embodiment will be described.

[0058] 11 is a circuit diagram showing an example of a drive unit 1c according to a third modification of the embodiment. The drive unit 1c differs from the drive unit 1 according to the embodiment in that it includes a power supply circuit 40 that supplies energy (electric power) to the voltage detection circuit 10 and the drive circuit 20. The rest of the configuration is the same as in the first embodiment, so a description thereof will be omitted. Note that the drive unit 1c may include a diode bridge circuit, like the drive unit 1a according to the first modification of the embodiment.

[0059] The power supply circuit 40 is a circuit such as a DC-DC converter, capable of stepping down the voltage of a lithium-ion battery or lead-acid battery to a voltage at which the voltage detection circuit 10 and the drive circuit 20 can operate. A certain level of voltage (e.g., 5V) is required for stable operation of the voltage detection circuit 10 and the drive circuit 20. Increasing the resistance of resistor R1 disposed in the current path P1 increases the voltage generated across resistor R1, enabling stable operation of the voltage detection circuit 10 and the drive circuit 20. However, in this case, heat generation in resistor R1 and voltage drop across resistor R1 must be taken into consideration. Therefore, it is desirable to reduce the resistance of resistor R1. Therefore, the provision of the power supply circuit 40 allows stable operation of the voltage detection circuit 10 and the drive circuit 20. In other words, the resistance of resistor R1 can be reduced, thereby suppressing heat generation and voltage drop.

[0060] (Layout Examples) Next, layout examples of the resistor R1 and the pyrofuse 100 will be described with reference to FIGS. 12 to 14. FIG.

[0061] 12 to 14 are diagrams showing examples of the arrangement of the resistor R1 and the pyrofuse 100. The examples of the arrangement described below can be applied to the drive units according to the above-described embodiments and their modifications.

[0062] 12, resistor R1 and pyrofuse 100 may be disposed between the positive terminal of battery 200 and the positive terminal of load 300. In this case, resistor R1 may be incorporated into pyrofuse 100.

[0063] 13, resistor R1 and pyrofuse 100 are disposed between the negative terminal of battery 200 and the negative terminal of load 300, and resistor R1 does not have to be built into pyrofuse 100. Furthermore, although not shown, when resistor R1 and pyrofuse 100 are disposed between the positive terminal of battery 200 and the positive terminal of load 300, resistor R1 does not have to be built into pyrofuse 100.

[0064] 14 , resistor R1 may be disposed between the positive terminal of battery 200 and the positive terminal of load 300, and pyrofuse 100 may be disposed between the negative terminal of battery 200 and the negative terminal of load 300. Although not shown, resistor R1 may be disposed between the negative terminal of battery 200 and the negative terminal of load 300, and pyrofuse 100 may be disposed between the positive terminal of battery 200 and the positive terminal of load 300.

[0065] It should be noted that if the resistor R1 is not built into the pyrofuse 100 , the pyrofuse 100 does not have to be a component of the drive unit 1 .

[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] In the above-described embodiment, each component included in the drive unit 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.

[0068] Some or all of the functions of the drive unit according to the above-described embodiments are typically realized as an LSI, which is an integrated circuit. These may be individually integrated into single chips, or may be integrated into a single chip that includes some or all of the functions. Furthermore, the integrated circuit is not limited to an LSI, and may be realized using a dedicated circuit or a general-purpose processor. It is also possible to use 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 an LSI.

[0069] Furthermore, if an integrated circuit technology that can replace LSI emerges due to advances in semiconductor technology or other derivative technologies, it is natural that each component included in the drive unit can be integrated using that technology.

[0070] 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 of the present disclosure.

[0071] (Additional Notes) The above description of the embodiments discloses the following techniques.

[0072] (Technology 1) A drive unit for driving a pyro-fuse that has an internal resistance and cuts off a current path by detonating in response to a current flowing through the internal resistance, the drive unit comprising: a resistor arranged in the current path; a voltage detection circuit that detects a voltage across the resistor; and a drive circuit connected in parallel with the resistor; the voltage detection circuit outputs a drive signal to the drive circuit when the voltage across the resistor is equal to or greater than a voltage threshold; and when the drive signal is input, the drive circuit shunts a portion of the current flowing through the current path and causes the current to flow through the internal resistance, thereby causing the pyro-fuse to cut off the current path.

[0073] According to this, the voltage generated in a resistor placed in the current path when an overcurrent flows through the current path is used as a trigger for activating the pyrofuse, and the current threshold for activating the pyrofuse can be determined arbitrarily by adjusting the resistance value of the resistor and the voltage threshold of the voltage detection circuit. Therefore, the current threshold for activating the pyrofuse can be set with high precision, and the pyrofuse can be activated with high precision.

[0074] Furthermore, with the technology described in Patent Document 1, it takes several milliseconds for the blow fuse to blow, so it takes time for the pyrofuse to be activated after an overcurrent is detected. In contrast, with the technology disclosed herein, the trigger for activating the pyrofuse does not use the arc voltage generated when the blow fuse blows, but rather the voltage generated in a resistor placed in the current path. Therefore, the pyrofuse can be activated, for example, within several tens of microseconds after the drive signal is input, that is, after an overcurrent is detected. Furthermore, because the pyrofuse can be activated by diverting a portion of the current flowing in the current path, there is no need to provide a separate power supply and driver circuit for activating the pyrofuse, which enables the drive unit to be made smaller and less expensive.

[0075] (Technology 2) The drive circuit includes a switch section and a constant current circuit, and when the drive signal is input, the switch section connects the constant current circuit to the current path, and when the constant current circuit is connected to the current path, it diverts a portion of the current flowing through the current path and causes the current to flow through the internal resistance, in a drive unit described in Technology 1.

[0076] In this way, when a drive signal is input to the switch unit, that is, when an overcurrent is detected, the switch unit can be operated to flow a portion of the overcurrent from the current path to the constant current circuit, and the constant current circuit can divert a portion of the current flowing in the current path to drive the pyro-fuse.

[0077] (Technology 3) The drive unit according to Technology 1 or 2, wherein the drive unit further includes a diode bridge circuit, and the drive circuit is connected in parallel with the resistor via the diode bridge circuit.

[0078] This allows the drive circuit to operate and drive the pyro-fuse even if an overcurrent occurs when power is supplied from the battery to the load, or even if an overcurrent occurs when charging the battery from the charger.

[0079] (Technology 4) The drive unit according to any one of technologies 1 to 3, wherein the voltage detection circuit includes a filter that removes noise.

[0080] If the current flowing through the resistor contains noise, and the voltage across the resistor contains noise, there is a risk of falsely detecting an overcurrent. By providing a noise-removing filter, the noise can be removed, preventing false detection of an overcurrent.

[0081] (Technology 5) A drive unit described in any one of Technologies 1 to 4, wherein the voltage detection circuit includes a timer circuit, and the voltage detection circuit outputs the drive signal to the drive circuit when the voltage between both ends remains equal to or greater than the voltage threshold for a set time set by the timer circuit.

[0082] If the current flowing through the resistor contains noise, and the voltage across the resistor also contains noise, there is a risk of falsely detecting an overcurrent. However, because noise generally occurs instantaneously, providing a timer circuit makes it possible to distinguish between noise and an overcurrent, thereby preventing false detection of an overcurrent.

[0083] (Technology 6) The drive unit according to Technology 5, wherein the drive unit includes a plurality of the voltage detection circuits, and a different set time and a different voltage threshold are set for each of the plurality of voltage detection circuits.

[0084] This allows the pyrofuse to behave in the same way as a blown fuse. Specifically, the larger the current value of the overcurrent, the shorter the time it takes for the pyrofuse to activate.

[0085] (Technology 7) The drive unit according to any one of Technologies 1 to 6, further comprising a boost circuit provided between the current path and the voltage detection circuit and the drive circuit.

[0086] A certain level of voltage is required for stable operation of the voltage detection circuit and the drive circuit. Increasing the resistance value of the resistor placed in the current path can increase the voltage generated in the resistor, allowing for stable operation of the voltage detection circuit and the drive circuit. However, in this case, heat generation in the resistor and voltage drop across the resistor must be taken into consideration. For this reason, it is desirable to reduce the resistance value of the resistor. Therefore, by providing a boost circuit, even if the voltage generated across the resistor is small, the voltage can be boosted, allowing for stable operation of the voltage detection circuit and the drive circuit. In other words, the resistance value of the resistor can be reduced, suppressing heat generation and voltage drop.

[0087] (Technology 8) The drive unit according to any one of Technologies 1 to 6, further comprising a power supply circuit that supplies energy to the voltage detection circuit and the drive circuit.

[0088] A certain level of voltage is required for stable operation of the voltage detection circuit and the drive circuit. Increasing the resistance value of the resistor placed in the current path can increase the voltage generated in the resistor, allowing for stable operation of the voltage detection circuit and the drive circuit. However, in this case, heat is generated in the resistor and voltage drop across the resistor must be taken into consideration. For this reason, it is desirable to reduce the resistance value of the resistor. Therefore, providing a power supply circuit allows for stable operation of the voltage detection circuit and the drive circuit. In other words, the resistance value of the resistor can be reduced, suppressing heat generation and voltage drop.

[0089] (Technology 9) A drive unit according to any one of technologies 1 to 8, wherein the drive unit includes the pyro fuse.

[0090] Thus, the drive unit may include a pyrofuse.

[0091] The present disclosure can be applied to a system that cuts off a current path by activating a pyrofuse.

[0092] 1, 1a, 1b, 1c Drive unit 10, 10a, 10b, 10c Voltage detection circuit 11 Detection section 12 Low-pass filter 13 Timer circuit 14 OR circuit 20 Drive circuit 21 Switch section 22 Constant current circuit 30 Boost circuit 40 Power supply circuit 100 Pyro fuse 200 Battery 300 Load 400 Charger D1, D2, D3, D4 Diode P1 Current path R1 Resistor R2 Internal resistance

Claims

1. A drive unit for driving a pyro-fuse that has an internal resistance and cuts off a current path by detonating in response to a current flowing through the internal resistance, the drive unit comprising: a resistor arranged in the current path; a voltage detection circuit that detects a voltage across the resistor; and a drive circuit connected in parallel with the resistor, wherein the voltage detection circuit outputs a drive signal to the drive circuit when the voltage across the resistor is equal to or greater than a voltage threshold, and when the drive signal is input, the drive circuit shunts a portion of the current flowing through the current path and causes the current to flow through the internal resistance, thereby causing the pyro-fuse to cut off the current path.

2. The drive unit according to claim 1, wherein the drive circuit includes a switch section and a constant current circuit, the switch section connects the constant current circuit to the current path when the drive signal is input, and the constant current circuit, when connected to the current path, diverts a portion of the current flowing through the current path and causes the current to flow through the internal resistance.

3. The drive unit according to claim 1 or 2, wherein the drive unit further comprises a diode bridge circuit, and the drive circuit is connected in parallel with the resistor via the diode bridge circuit.

4. The drive unit according to any one of claims 1 to 3, wherein the voltage detection circuit includes a filter that removes noise.

5. A drive unit according to any one of claims 1 to 4, wherein the voltage detection circuit includes a timer circuit, and the voltage detection circuit outputs the drive signal to the drive circuit when the voltage across the terminals remains equal to or greater than the voltage threshold for a set period of time set by the timer circuit.

6. The drive unit according to claim 5, wherein the drive unit includes a plurality of the voltage detection circuits, and a different set time and a different voltage threshold are set for each of the plurality of voltage detection circuits.

7. The drive unit according to any one of claims 1 to 6, further comprising a boost circuit provided between the current path and the voltage detection circuit and drive circuit.

8. The drive unit according to any one of claims 1 to 6, further comprising a power supply circuit that supplies energy to the voltage detection circuit and the drive circuit.

9. A drive unit according to any one of claims 1 to 8, wherein the drive unit includes the pyro fuse.

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