Circuit breaker drive circuit and battery protection circuit

Abstract

In a drive circuit (10) of a circuit breaker (1) that physically and irreversibly breaks a power line, a first switch (SW1) is connected between a first control power supply and one end of an igniter (1a). A second switch (SW2) is connected to the other end of the igniter (1a). A voltage drop element (D1) is connected between the second switch (SW2) and a drive circuit reference ground connection point. A pull-up circuit (12) is connected between a second control power supply and a first connection point (N1), and includes a third switch (SW3) and a pull-up resistor (R1). A control circuit (11) complementarily turns on / off the first switch (SW1) and the second switch (SW2) while monitoring the voltage at the first connection point (N1) and the voltage at a second connection point (N2), to thereby execute failure diagnosis of the conduction path to the igniter (1a).

Description

Circuit breaker drive circuit, battery protection circuit

[0001] The present disclosure relates to a circuit breaker drive circuit and a battery protection circuit that uses an igniter to instantly interrupt high voltage and large current.

[0002] In the event of a battery abnormality in a battery system, it is necessary to reliably disconnect the battery from the load and cut off the current from the battery to the load, thereby transitioning to a safe state. Mechanical relays are widely used as switches to cut off the current from the battery to the load, but in recent years, pyroelectric fuses, which are less expensive than mechanical relays, have also been adopted in battery systems installed in EVs.

[0003] A pyrofuse is an irreversible active fuse that physically cuts off the power line connecting the battery and load by burning an igniter (initiator) when an external current is supplied to it, generating gas that pushes down a piston inside the cylinder, causing the piston to cut the bus bar connecting the battery and load.Unlike passive fuses, pyrofuses can also cut off the power line in response to an external signal when a serious abnormality other than overcurrent occurs (for example, battery overcharging or a vehicle collision).

[0004] Pyrofuses require a drive circuit to supply current to the igniter and activate the pyrofuse in the event of an abnormality. If the pyrofuse drive circuit malfunctions, the pyrofuse will not be able to activate when needed, so a fault diagnosis function is required to check whether the pyrofuse drive circuit is operating normally.

[0005] Patent Document 1 discloses a method for checking the integrity of a pyrofuse drive circuit by passing a weak current through an igniter (load resistor) in a pyrofuse and monitoring the voltage across the load resistor. However, because this method performs a fault diagnosis using a weak current that does not cause the igniter to burn, it is not possible to check whether the drive circuit is capable of generating a large current that is sufficient to burn the igniter.

[0006] Patent Document 2 discloses a method for verifying the integrity of a shunt resistor by providing a dedicated path that passes through the shunt resistor on a power line and measuring the current value of the path. Provided that the shunt resistor is verified to be healthy, a pyroelectric fuse is activated when an overcurrent is detected. The fault diagnosis disclosed in Patent Document 2 is for diagnosing a fault in the shunt resistor used to detect overcurrent, but is not for diagnosing a fault in the pyroelectric fuse drive circuit itself.

[0007] JP 2022-190197 A International Publication No. 2019-084304

[0008] The present disclosure has been made in view of the above circumstances, and its purpose is to provide a technology for performing fault diagnosis of the electrical system and drive circuit of a circuit breaker including an igniter with high accuracy.

[0009] In order to solve the above-mentioned problems, a circuit breaker drive circuit according to one embodiment of the present disclosure includes an igniter that is connected to a drive circuit reference ground via a drive circuit reference ground connection point and that ignites in response to an externally supplied current, and that irreversibly physically interrupts a power line when the igniter is activated, the circuit breaker drive circuit comprising: a first switch connected between a first control power source and one end of the igniter; a second switch connected to the other end of the igniter; a voltage drop element connected between the second switch and the drive circuit reference ground connection point; a second control power source; and a pull-up circuit connected between the other end of the igniter and a first connection point between the second switch and the second switch, the pull-up circuit including a third switch and a pull-up resistor; and a control circuit that activates the circuit breaker by turning on the first switch and the second switch when a predetermined unsafe event occurs. The control circuit performs fault diagnosis of the electrical path to the igniter by complementarily turning on / off the first switch and the second switch while monitoring the voltage at the first connection point and the voltage at the second connection point between the second switch and the voltage drop element.

[0010] According to the present disclosure, fault diagnosis of the electrical system and drive circuit of a circuit breaker including an igniter can be performed with high accuracy.

[0011] Fig. 1 is a diagram showing the overall configuration for explaining a pyrofuse and a drive circuit according to an embodiment; Fig. 2 is a diagram showing a graph summarizing the first-stage sequence of a fault diagnosis of an electric current path to an igniter; Fig. 3 is a diagram showing the overall configuration for explaining a pyrofuse and a drive circuit according to a comparative example;

[0012] FIG. 1 is a diagram illustrating the overall configuration of a pyrofuse 1 and a drive circuit 10 according to an embodiment. Pyrofuse 1 is a circuit breaker that irreversibly physically interrupts a power line through which a main current flows. In this embodiment, an example is assumed in which pyrofuse 1 is connected to a power line between a battery pack 2 of an electric vehicle and a load 3. Battery pack 2 is, for example, a high-voltage drive power supply including a large number of lithium-ion battery cells. Load 3 includes an inverter and a motor. The inverter converts DC power supplied from battery pack 2 into AC power, and the motor (e.g., a three-phase AC motor) converts the AC power supplied from the inverter into rotational energy.

[0013] Pyro fuse 1 includes an igniter 1a, a piston 1b, and a bus bar 1c. One end of bus bar 1c is connected to a power line connected to battery pack 2, and the other end of bus bar 1c is connected to a power line connected to load 3.

[0014] The drive circuit 10 is a circuit for supplying current to the igniter 1a to externally cut off the pyrofuse 1. In this specification, the pyrofuse 1 and the drive circuit 10 are collectively referred to as a battery protection circuit.

[0015] When a current is supplied to the igniter 1a from the drive circuit 10, the igniter 1a burns. The piston 1b in the cylinder is pushed down by the gas pressure generated by the combustion, physically cutting the bus bar 1c. In most typical pyrofuses 1, the electrical resistance of the igniter 1a is around 2 Ω, and the operating current required for ignition is often designed to be 1 A or more. Therefore, even if a weak current is passed through the igniter 1a, the igniter 1a will not ignite.

[0016] The drive circuit 10 includes a first switch SW1, a second switch SW2, a first diode D1, a pull-up circuit 12, a high resistor R2, and a control circuit 11. The first switch SW1, the second switch SW2, and the third switch SW3 can be semiconductor switches such as MOSFETs (Metal Oxide Semiconductor Field Effect Transistors) and bipolar transistors, or small relays.

[0017] The first switch SW1 is connected between the first control power supply Vb and one end of the igniter 1a, and is a switch connected to the high side of the igniter 1a. When the battery protection circuit is used in an electric vehicle, the first control power supply Vb can be an auxiliary battery. Typically, a 12V lead battery is used as the auxiliary battery.

[0018] The second switch SW2 is connected between the other end of the igniter 1a and the anode terminal of the first diode D1, and is connected to the low side of the igniter 1a. The cathode terminal of the first diode D1 is connected to the drive circuit reference potential (hereinafter referred to as ground potential). When the battery protection circuit is used in an electric vehicle, the cathode terminal of the first diode D1 is connected to the vehicle body (chassis earth).

[0019] The pull-up circuit 12 is connected between the second control power supply Vdd and a first connection point N1 between the other end of the igniter 1a and the second switch SW2. The second control power supply Vdd can be, for example, a power supply voltage (3.3 V to 5.0 V) for the control circuit 11 that is generated by stepping down the first control power supply Vb using a linear regulator.

[0020] The pull-up circuit 12 includes a third switch SW3, a pull-up resistor R1, and a second diode D2, which are connected in series. The second diode D2 may be omitted.

[0021] The high resistance R2 is connected as a pull-down circuit between the first connection point N1 and the ground potential connection point. Note that when a transition is made from a state in which the first switch SW1 is on, the second switch SW2 is off, and the third switch SW3 is off to a state in which the first switch SW1 is off, the second switch SW2 is on, and the third switch SW3 is off, if the voltage at the first connection point N1 converges to a value equivalent to 0 V within a specified time, the high resistance R2 may be omitted.

[0022] The control circuit 11 is composed of a microcontroller. When a predetermined unsafe event occurs, the control circuit 11 turns on the first switch SW1 and the second switch SW2 to activate the pyrofuse 1. Examples of predetermined unsafe events include when an overcurrent is detected by a current sensor (not shown), when an overcharging of the battery pack 2 is detected by a voltage sensor (not shown), when an abnormally high temperature of the battery pack 2 is detected by a temperature sensor (not shown), and when abnormal vibration is detected by an acceleration sensor (not shown).

[0023] The control circuit 11 can perform fault diagnosis of the electrical path to the igniter 1a by switching the on / off states of the first switch SW1-third switch SW3 while monitoring the voltage at the first connection point N1 and the voltage at the second connection point N2 between the second switch SW2 and the first diode D1.

[0024] Fig. 2 is a graph summarizing the first-stage sequence of fault diagnosis of the current path to the igniter 1a. Fig. 3 is a graph summarizing the second-stage sequence of fault diagnosis of the current path to the igniter 1a. The first-stage sequence mainly diagnoses faults in the current path from the first switch SW1, the igniter 1a, and the first control power supply Vb to the second switch SW2 (hereinafter referred to as the first-stage current path). The second-stage sequence mainly diagnoses faults in the second switch SW2, the first diode D1, the current path from the second switch SW2 to the ground potential connection point (hereinafter referred to as the second-stage current path), and the pull-up circuit 12.

[0025] 2 and 3, failure modes assumed for the wire harness connecting drive circuit 10 and pyro-fuse 1 are a power short circuit to first control power supply Vb, a ground short circuit, and an open circuit. Failure modes assumed for the first switch SW1-third switch SW3 and the first diode D1-second diode D2 are a short circuit and an open circuit.

[0026] "Vg" in Figures 2 and 3 represents ground potential, and is 0 V when grounded. Note that "Vg," "Vb," and "Vf" in Figures 2 and 3 conceptually represent not only true values ​​but also approximate values ​​that include quantization errors of the A / D converter and other factors in addition to the true values. The voltages corresponding to the ground potential Vg, the voltage corresponding to the voltage of the first control power supply Vb, and the voltage corresponding to the forward voltage Vf of the first diode D1, described below, conceptually represent approximate values ​​that include error components in addition to the true values. The true value for a short circuit is 0 Ω, and the true value for an open circuit is ∞ Ω. However, even in the case of an open circuit fault, some resistance component may be generated, and a minute voltage such as 0.03 V may be detected instead of 0 V.

[0027] First, the control circuit 11 controls the first switch SW1 to be OFF, the second switch SW2 to be OFF, and the third switch SW3 to be OFF. The control circuit 11 monitors the voltage at the first connection point N1, and if a voltage equivalent to the voltage of the first control power source Vb is detected as the voltage at the first connection point N1, it diagnoses that a short circuit fault has occurred in the first switch SW1 or in the preceding stage current path due to a short circuit with the first control power source Vb.

[0028] When the first switch SW1, the second switch SW2, and the third switch SW3 are all off, the voltage at the first connection point N1 should normally be equivalent to 0 V. In contrast, when a short circuit fault occurs in the first switch SW1, a voltage equivalent to the voltage of the first control power supply Vb is detected as the voltage at the first connection point N1.

[0029] Furthermore, even if no short circuit fault has occurred in first switch SW1, if there is a short circuit with first control power supply Vb at any point in the previous stage current path, a voltage equivalent to the voltage of first control power supply Vb will be detected as the voltage at first connection point N1. For example, inside a vehicle, the coatings of the wire harness connecting drive circuit 10 and pyro fuse 1 and the wire harness for supplying first control power supply Vb may peel off, causing the exposed parts to come into contact and causing a short circuit.

[0030] If no fault is detected with the first switch SW1 off, the second switch SW2 off, and the third switch SW3 off, the control circuit 11 turns on the first switch SW1, causing a transition to a state where the first switch SW1 is on, the second switch SW2 is off, and the third switch SW3 is off. The control circuit 11 monitors the voltage at the first connection point N1, and if a voltage equivalent to the voltage of the first control power source Vb is detected as the voltage at the first connection point N1, the control circuit 11 diagnoses that the first switch SW1 and the pre-stage current path are normal. Because the pre-stage current path includes the electrical system of the igniter 1a, the electrical system of the igniter 1a is also diagnosed as normal.

[0031] When the control circuit 11 detects a voltage equivalent to ground potential (near 0 V) ​​as the voltage at the first connection point N1, it diagnoses that an open fault has occurred in the first switch SW1, an open fault has occurred in the previous stage current path, or a short fault has occurred in the previous stage current path with ground potential.

[0032] When the first switch SW1 is on, the second switch SW2 is off, and the third switch SW3 is off, the voltage at the first connection point N1 should normally be a voltage equivalent to the voltage of the first control power supply Vb. In contrast, if an open circuit fault occurs in the first switch SW1, a voltage equivalent to ground potential is detected as the voltage at the first connection point N1. Even if no open circuit fault occurs in the first switch SW1, if an open circuit fault occurs anywhere in the pre-stage current path, a voltage equivalent to ground potential is detected as the voltage at the first connection point N1. For example, possible open circuit faults in the pre-stage current path include a broken wire or a loose connector.

[0033] Furthermore, even if no open fault has occurred in first switch SW1 and no open fault has occurred in the previous-stage current path, if there is a short circuit to ground potential at any point in the previous-stage current path, a voltage equivalent to ground potential will be detected as the voltage at first connection point N1. For example, inside a vehicle, if the coating of the wire harness connecting drive circuit 10 and pyro-fuse 1 peels off and the exposed part comes into contact with the vehicle body, there is a possibility of a short circuit to ground potential.

[0034] If there is a ground short in the stage after the igniter 1a, the pyroelectric fuse will be activated during diagnosis, but if diagnosis is limited to when the vehicle is stopped, it will transition to the safe side and will not cause an unsafe event (such as a sudden stop of the vehicle).However, it is difficult to determine from the voltage at the first connection point N1 whether there is a ground short in the stage before the igniter 1a, a ground short in the stage after the igniter 1a, an open circuit fault in the first switch SW1, or an open circuit fault in the previous stage current path.

[0035] When the control circuit 11 detects a voltage at the first connection point N1 that corresponds to the forward voltage Vf (usually about 0.7 V) of the first diode D1, it diagnoses that a short circuit has occurred in the second switch SW2. When a short circuit has occurred in the second switch SW2, the first control power supply Vb is electrically connected to the ground potential, and the first diode D1 is interposed between the first connection point N1 and the ground potential, so that the voltage at the first connection point N1 becomes the forward voltage Vf.

[0036] If no fault is detected with the first switch SW1 on, the second switch SW2 off, and the third switch SW3 off, the control circuit 11 turns off the first switch SW1 and then turns on the second switch SW2, transitioning the state to the first switch SW1 off, the second switch SW2 on, and the third switch SW3 off. The control circuit 11 monitors the voltage at the second connection point N2, and if a voltage equivalent to ground potential is detected as the voltage at the second connection point N2, it diagnoses that the downstream current path is normal.

[0037] When the control circuit 11 detects a voltage at the second connection point N2 that is equivalent to the forward voltage Vf of the first diode D1, it diagnoses that a short circuit has occurred in the third switch SW3. When the first switch SW1 is off, the second switch SW2 is on, and the third switch SW3 is off, the voltage at the second connection point N2 should be a voltage equivalent to ground potential. In contrast, when a short circuit has occurred in the third switch SW3, conduction occurs between the second control power supply Vdd and ground potential, and the first diode D1 is interposed between the second connection point N2 and ground potential, so the voltage at the second connection point N2 becomes the forward voltage Vf.

[0038] If no fault is detected with the first switch SW1 off, the second switch SW2 on, and the third switch SW3 off, the control circuit 11 turns on the third switch SW3 to transition to a state where the first switch SW1 is off, the second switch SW2 is on, and the third switch SW3 is on. The control circuit 11 monitors the voltage at the second connection point N2, and if a voltage equivalent to the forward voltage Vf of the first diode D1 is detected as the voltage at the second connection point N2, the control circuit 11 diagnoses the pull-up circuit 12 as normal.

[0039] When a voltage equivalent to ground potential is detected as the voltage at the second connection point N2, the control circuit 11 diagnoses that an open fault has occurred in the pull-up circuit 12, the second switch SW2, the first diode D1, or the downstream current path. If an open fault occurs in any of the elements or wiring included in the current path between the second control power supply Vdd and ground potential, the voltage at the second connection point N2 becomes a voltage equivalent to ground potential.

[0040] If any of the failure modes is detected in the above diagnostic sequence, the control circuit 11 does not allow the load system (in this embodiment, the vehicle system) including the battery pack 2 and the load 3 to start up, or starts it up in limp home mode.

[0041] 4 is a diagram illustrating the overall configuration of a pyro-fuse 1 and a drive circuit 10 according to a comparative example. The drive circuit 10 according to the comparative example includes a power storage unit 13, an operating current source 14, a diagnostic current source 15, a control circuit 11, a first switch SW1, and a second switch SW2. The power storage unit 13 is a capacitor or a storage battery that stores power supplied from the auxiliary battery. The operating current source 14 is a current source for supplying the igniter 1a with a current necessary to ignite the igniter 1a. The diagnostic current source 15 is a current source for supplying the igniter 1a with a weak current that will not ignite the igniter 1a in the fault diagnosis sequence.

[0042] In the fault diagnosis sequence, the control circuit 11 first checks whether the voltage of the power storage unit 13 is normal. Next, the control circuit 11 selects the diagnostic current source 15 and turns on the first switch SW1 and the second switch SW2 to pass a weak current through the igniter 1a. The control circuit 11 measures the voltage across the igniter 1a and diagnoses whether it is within a specified value.

[0043] This method can diagnose whether the current path including the diagnostic current source 15 and the igniter 1a is normal. However, in the fault diagnosis sequence, if current is supplied from the actuation current source 14 to the igniter 1a, the igniter 1a will ignite. Therefore, it is not possible to diagnose whether the actuation current source 14 can actually generate the current required to ignite the igniter 1a.

[0044] Furthermore, the drive circuit 10 needs to be provided with an operating current source 14 and a diagnostic current source 15. Furthermore, in order to measure the voltage across the igniter 1a with high accuracy when a weak current is passed through the igniter 1a, an operational amplifier is required to amplify the voltage across the igniter 1a. Therefore, the circuit size and cost of the drive circuit 10 are large in the comparative example.

[0045] In contrast, in the present embodiment, the same voltage as when actually activating pyro-fuse 1 is applied to igniter 1a for diagnosis, rather than the comparative example in which a current is passed through igniter 1a for diagnosis. In this embodiment, the first switch SW1 and the second switch SW2 are turned on one by one in a complementary manner, so if high resistor R2 is not connected, essentially no current flows through igniter 1a. Even when high resistor R2 is connected, the current flowing through igniter 1a is weak due to the high resistor R2.

[0046] In this embodiment, since the operating current source 14 is not used, there is no need to consider failure of the operating current source 14, and therefore it is possible to perform failure diagnosis with higher accuracy than in the comparative example. Furthermore, since the operating current source 14 and the diagnostic current source 15 are not required and there is no need to use an operational amplifier to measure the voltage at the connection points N1 and N2, it is possible to reduce the circuit size and cost compared to the comparative example.

[0047] The present disclosure has been described above based on the embodiments. The embodiments are merely examples, and it will be understood by those skilled in the art that various modifications are possible in the combination of the respective components and processing steps, and that such modifications are also within the scope of the present disclosure.

[0048] In the above-described embodiment, an example has been described in which the output voltage (12 V) of the auxiliary battery is used as the first control power supply, and the power supply voltage (3.3 V to 5.0 V) of the control circuit 11 is used as the second control power supply. In this regard, the output voltage (12 V) of the auxiliary battery may be used as both the first control power supply and the second control power supply. Also, the power supply voltage (3.3 V to 5.0 V) of the control circuit 11 may be used as both the first control power supply and the second control power supply. For example, if the electrical resistance of the igniter 1a is 2 Ω, a current of 1.65 A can be passed through the igniter 1a even if the voltage of the first control power supply is 3.3 V, and the igniter 1a can be ignited.

[0049] In the above-described embodiment, an example has been described in which the first diode D1 is connected as an element for generating a voltage drop between the second switch SW2 and the ground potential. In this regard, an element other than the first diode D1 (for example, a resistive element) may be connected as long as it is an element that can generate a voltage drop between the second switch SW2 and the ground potential.

[0050] In the above-described embodiment, an example is assumed in which pyrofuse 1 is connected to a power line between battery pack 2 and load 3 of an electric vehicle. In this regard, a battery protection circuit including pyrofuse 1 and drive circuit 10 can also be used to interrupt power lines for purposes other than automotive applications. For example, it can be used to interrupt power lines in solar power generation systems and stationary energy storage systems.

[0051] The embodiment may be specified by the following items.

[0052] [Item 1] A drive circuit (10) for a circuit breaker (1) including an igniter (1a) connected to a drive circuit reference ground via a drive circuit reference ground connection point and igniting in response to a current supplied from an external source, the circuit breaker (1) irreversibly physically interrupting a power line when the igniter (1a) is activated, the drive circuit (10) including: a first switch (SW1) connected between a first control power source and one end of the igniter (1a); a second switch (SW2) connected to the other end of the igniter (1a); a voltage drop element (D1) connected between the second switch (SW2) and the drive circuit reference ground connection point; a pull-up circuit (12) connected between the second control power source and a first connection point (N1) between the other end of the igniter (1a) and the second switch (SW2), the pull-up circuit (12) including a third switch (SW3) and a pull-up resistor (R1); and a control circuit (11) that activates the circuit breaker (1) by turning on the first switch (SW1) and the second switch (SW2) when a predetermined unsafe event occurs, wherein the control circuit (11) performs fault diagnosis of the current path to the igniter (1 a) by complementarily turning on / off the first switch (SW1) and the second switch (SW2) while monitoring the voltage of the first connection point (N1) and the voltage of a second connection point (N2) between the second switch (SW2) and the voltage drop element (D1). This allows fault diagnosis of the electrical system of the circuit breaker (1) including the igniter (1 a) and the drive circuit (10) with high accuracy. [Item 2] The drive circuit (10) for the circuit breaker (1) according to Item 1, wherein when a voltage corresponding to the voltage of the first control power supply is detected as the voltage at the first connection point (N1) in a state in which the first switch (SW1), the second switch (SW2), and the third switch (SW3) are off, the control circuit (11) diagnoses that a short circuit fault has occurred in the first switch (SW1) or a short circuit fault between the first control power supply and the current path from the first switch (SW1) to the second switch (SW2). This makes it possible to accurately detect a short circuit fault in the first switch (SW1) or a short circuit fault between the current path to the second switch (SW2) and the first control power supply.[Item 3] The drive circuit (10) for the circuit breaker (1) according to Item 1, wherein when a voltage equivalent to the voltage of the first control power supply is detected as the voltage of the first connection point (N1) in a state in which the first switch (SW1) is on, the second switch (SW2) is off, and the third switch (SW3) is off, the control circuit (11) diagnoses that the first switch (SW1) and the current path from the first control power supply to the second switch (SW2) are normal. This makes it possible to determine with high accuracy whether the current path from the first switch (SW1) to the second switch (SW2) is normal. [Item 4] The drive circuit (10) for the circuit breaker (1) according to Item 1, wherein when a voltage corresponding to the potential of the drive circuit reference ground is detected as the voltage at the first connection point (N1) in a state in which the first switch (SW1) is on, the second switch (SW2) is off, and the third switch (SW3) is off, the control circuit (11) diagnoses that an open fault has occurred in the first switch (SW1), an open fault in the current path from the first control power supply to the second switch (SW2), or a short fault between the current path to the second switch (SW2) and the drive circuit reference ground. This makes it possible to accurately detect an open fault in the first switch (SW1), an open fault in the current path to the second switch (SW2), or a short fault between the current path to the second switch (SW2) and the drive circuit reference ground. [Item 5] The drive circuit (10) for the circuit breaker (1) according to Item 1, wherein the control circuit (11) diagnoses that a short circuit fault has occurred in the second switch (SW2) when a voltage corresponding to the voltage drop amount of the voltage drop element (D1) is detected as the voltage at the first connection point (N1) in a state where the first switch (SW1) is on, the second switch (SW2) is off, and the third switch (SW3) is off. This makes it possible to detect a short circuit fault in the second switch (SW2) with high accuracy.[Item 6] The drive circuit (10) for the circuit breaker (1) according to Item 1, wherein when a voltage corresponding to the potential of the drive circuit reference ground is detected as the voltage at the second connection point (N2) with the first switch (SW1) off, the second switch (SW2) on, and the third switch (SW3) off, the control circuit (11) diagnoses that the second switch (SW2), the voltage drop element (D1), and the current path from the second switch (SW2) to the drive circuit reference ground connection point are normal. This makes it possible to determine with high accuracy whether the current path from the second switch (SW2), the voltage drop element (D1), and the second switch (SW2) is normal. [Item 7] The drive circuit (10) for the circuit breaker (1) according to Item 1, wherein the control circuit (11) diagnoses that a short circuit fault has occurred in the third switch (SW3) when a voltage corresponding to the voltage drop amount of the voltage drop element (D1) is detected as the voltage at the second connection point (N2) with the first switch (SW1) off, the second switch (SW2) on, and the third switch (SW3) off. This enables highly accurate detection of a short circuit fault in the third switch (SW3). [Item 8] The drive circuit (10) for the circuit breaker (1) according to Item 1, wherein the control circuit (11) diagnoses that a current path from the second control power supply to the drive circuit reference ground connection point is normal when a voltage corresponding to the voltage drop amount of the voltage drop element (D1) is detected as the voltage at the second connection point (N2) with the first switch (SW1) off, the second switch (SW2) on, and the third switch (SW3) on. Item 9: The drive circuit (10) for the circuit breaker (1) according to Item 1, wherein, when a voltage equivalent to the potential of the drive circuit reference ground is detected as the voltage of the second connection point (N2) with the first switch (SW1) turned off, the second switch (SW2) turned on, and the third switch (SW3) turned on, the control circuit (11) diagnoses that an open fault has occurred in the pull-up circuit (12) or the voltage drop element (D1).This allows for highly accurate detection of an open circuit fault in the pull-up circuit (12). [Item 10] A drive circuit (10) for a circuit breaker (1) according to any one of Items 1 to 9, further including a high resistance (R2) connected between the first connection point (N1) and the drive circuit reference ground connection point. This prevents a floating state of the electrical path from the first control power supply to the second switch (SW2). [Item 11] A battery protection circuit (1, 10) comprising: a circuit breaker (1) connected via the drive circuit reference ground and the drive circuit reference ground connection point, the circuit breaker (1) including an igniter (1a) that ignites in response to an externally supplied current, and the igniter (1a) irreversibly physically interrupts a power line when activated; and the drive circuit (10) according to any one of Items 1 to 9. This allows for highly accurate fault diagnosis of the electrical system of the battery protection circuit (1, 10).

[0053] The present disclosure can be used to diagnose faults in pyrofuse drive circuits.

[0054] 1 Pyro fuse, 1a Igniter, 1b Piston, 1c Bus bar, 2 Battery pack, 3 Load, 10 Drive circuit, 11 Control circuit, 12 Pull-up circuit, 13 Power storage unit, 14 Operating current source, 15 Diagnostic current source, SW1 First switch, SW2 Second switch, SW3 Third switch, D1 First diode, D2 Second diode, R1 Pull-up resistor, R2 High resistor.

Claims

1. A circuit breaker drive circuit includes an igniter that is connected to a drive circuit reference ground via a drive circuit reference ground connection point and ignites in response to an externally supplied current, and that irreversibly physically interrupts a power line when the igniter is activated, the circuit breaker drive circuit comprising: a first switch connected between a first control power source and one end of the igniter; a second switch connected to the other end of the igniter; a voltage drop element connected between the second switch and the drive circuit reference ground connection point; a pull-up circuit connected between the second control power source and a first connection point between the other end of the igniter and the second switch, the pull-up circuit including a third switch and a pull-up resistor; and a control circuit that turns on the first switch and the second switch when a predetermined unsafe event occurs, thereby activating the circuit breaker; the control circuit monitors the voltage at the first connection point and the voltage at the second connection point between the second switch and the voltage drop element, and performs fault diagnosis of the current path to the igniter by complementarily turning on and off the first switch and the second switch. Circuit breaker drive circuit.

2. The circuit breaker drive circuit according to claim 1, wherein when a voltage equivalent to the voltage of the first control power supply is detected as the voltage at the first connection point while the first switch, the second switch, and the third switch are all off, the control circuit diagnoses that a short circuit fault has occurred in the first switch or a short circuit fault with the first control power supply has occurred in the current path from the first switch to the second switch.

3. The circuit breaker drive circuit according to claim 1, wherein the control circuit diagnoses that the first switch and the current path from the first control power supply to the second switch are normal when a voltage equivalent to the voltage of the first control power supply is detected as the voltage at the first connection point while the first switch is on, the second switch is off, and the third switch is off.

4. The circuit breaker drive circuit according to claim 1, wherein when a voltage equivalent to the potential of the drive circuit reference ground is detected as the voltage at the first connection point while the first switch is on, the second switch is off, and the third switch is off, the control circuit diagnoses that an open fault has occurred in the first switch, an open fault in the current path from the first control power supply to the second switch, or a short fault in the current path with the drive circuit reference ground.

5. The circuit breaker drive circuit according to claim 1, wherein the control circuit diagnoses that a short circuit fault has occurred in the second switch when a voltage corresponding to the voltage drop amount of the voltage drop element is detected as the voltage at the first connection point while the first switch is on, the second switch is off, and the third switch is off.

6. The circuit breaker drive circuit according to claim 1, wherein the control circuit diagnoses that the second switch, the voltage drop element, and the current path from the second switch to the drive circuit reference ground connection point are normal when a voltage equivalent to the potential of the drive circuit reference ground is detected as the voltage at the second connection point while the first switch is off, the second switch is on, and the third switch is off.

7. The circuit breaker drive circuit according to claim 1, wherein the control circuit diagnoses that a short circuit fault has occurred in the third switch when a voltage corresponding to the voltage drop amount of the voltage drop element is detected as the voltage at the second connection point while the first switch is off, the second switch is on, and the third switch is off.

8. The circuit breaker drive circuit according to claim 1, wherein the control circuit diagnoses that the current path from the second control power supply to the drive circuit reference ground connection point is normal when a voltage corresponding to the voltage drop amount of the voltage drop element is detected as the voltage at the second connection point while the first switch is off, the second switch is on, and the third switch is on.

9. The circuit breaker drive circuit according to claim 1, wherein the control circuit diagnoses that an open fault has occurred in the pull-up circuit or the voltage drop element when a voltage equivalent to the potential of the drive circuit reference ground is detected as the voltage at the second connection point while the first switch is off, the second switch is on, and the third switch is on.

10. A circuit breaker drive circuit according to any one of claims 1 to 9, further comprising a high resistance connected between the first connection point and the drive circuit reference ground connection point.

11. A battery protection circuit comprising: an igniter connected to a drive circuit reference ground via a drive circuit reference ground connection point and ignited in response to an externally supplied current, wherein the activation of the igniter irreversibly physically interrupts a power line; and a circuit breaker comprising the drive circuit according to any one of claims 1 to 9.

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