Current interruption circuit and current interruption system

Abstract

To provide a current interruption circuit and a current interruption system capable of reducing erroneous disconnection of a fuse.SOLUTION: When the resistor Rp is energized, the ignition type fuse is cut. IPD231 and 232 are provided on both sides of the resistor Rp, and when both are turned on, the resistor Rp is energized. The current sensor 241,242 detects a current of a current path in which the ignition-type fuse is provided. The overcurrent determination circuit 251 determines an overcurrent based on the output of the current sensor 241. The second overcurrent determining circuit 252 determines an overcurrent based on the output of the current sensor 242. IPD231 is turned on based on the determination result of the overcurrent determination circuit 251. IPD232 is turned on based on the determination result of the overcurrent determination circuit 252.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a current interruption circuit and a current interruption system. [Background technology]

[0002] As an example of the above-mentioned current interruption circuit, a power supply system is proposed as shown in Patent Document 1. According to the power supply system of Patent Document 1, a blowout fuse is blown when an overcurrent flows through the main battery, which is the driving source of the vehicle. A blowout fuse takes time to blow after an overcurrent flows. In recent years, with the increase in current in BEVs (Battery Electric Vehicles), there has been a need to immediately interrupt the current when an overcurrent occurs. Therefore, instead of a blowout fuse, an ignition-type fuse has been proposed (Patent Document 2), which receives an output of an overcurrent detection signal and ignites explosives to quickly cut off the current path.

[0003] If an ignition fuse were to blow during normal driving conditions, the vehicle would come to a halt. For this reason, ignition fuses are required to blow reliably when an overcurrent occurs, but not blow under normal conditions. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-103949 [Patent Document 2] Japanese Patent Publication No. 2020-136055 Summary of the Invention [Problem to be solved by the invention]

[0005] The present invention has been made in consideration of the above-mentioned circumstances, and its purpose is to provide a current interruption circuit and current interruption system that can accurately cut off an ignition fuse when an overcurrent occurs, and that can reduce the erroneous cutting of the ignition fuse during normal operation when no overcurrent is occurring. [Means for solving the problem]

[0006] In order to achieve the above object, the current interruption circuit according to the present invention has the following features. a first switch and a second switch that are included in the ignition type fuse and are provided on both sides of a first resistor that burns out due to heat at the time of ignition, and that allow the first resistor to be energized when both switches are turned on; a first current sensor and a second current sensor for detecting a current in a current path in which the ignition-type fuse is provided; a first overcurrent determination circuit that determines an overcurrent based on an output of the first current sensor; a second overcurrent determination circuit that determines an overcurrent based on an output of the second current sensor; the first switch is turned on based on a determination result of the first overcurrent determination circuit; the second switch is turned on based on the determination result of the second overcurrent determination circuit; It must be a current interruption circuit.

[0007] In order to achieve the above-mentioned object, the current interruption system according to the present invention has the following features. a second resistor and a diode connected in series between a first power supply voltage and a connection point of the first resistor and the first switch; a third resistor connected between a second power supply voltage and a connection point of the first resistor and the second switch; a dummy voltage output circuit that outputs a dummy voltage corresponding to an overcurrent; a third switch that switches an input to the first overcurrent determination circuit between the output of the first current sensor and the dummy voltage output by the dummy voltage output circuit; a fourth switch that switches an input to the second overcurrent determination circuit between the output of the second current sensor and the dummy voltage output by the dummy voltage output circuit, The current interruption circuit; a control unit that determines a fault based on a voltage between the second resistor and the first resistor or a voltage between the third resistor and the first resistor when the third switch is switched to the first current sensor side and the fourth switch is switched to the second current sensor side, when the third switch is switched to the dummy voltage output circuit side and the fourth switch is switched to the second current sensor side, and when the third switch is switched to the first current sensor side and the fourth switch is switched to the dummy voltage output circuit side, It must be a current interruption system.

[0008] In order to achieve the above-mentioned object, the current interruption system according to the present invention has the following features. The overcurrent interruption circuit; a control unit that turns off the active signal, The first switch and the second switch are not turned on while the active signal is off. It must be a current interruption system. [Effects of the Invention]

[0009] The current interruption circuit and current interruption system according to the present invention have the effect of reducing the erroneous blowing of fuses.

[0010] The present invention has been briefly described above. The details of the present invention will become clearer by reading the following detailed description of the invention (hereinafter referred to as "embodiments") with reference to the accompanying drawings. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a block diagram showing an embodiment of a current interruption system according to the first embodiment of the present invention. [Figure 2] FIG. 2 is a graph showing the output characteristics of the current sensor 241 shown in FIG. [Figure 3] FIG. 3 is a graph showing the output characteristics of the current sensor 242 shown in FIG. [Figure 4] FIG. 4 is a circuit diagram showing details of the overcurrent determination circuits 251 and 252 shown in FIG. [Figure 5] FIG. 5 is a perspective view showing an example of the current sensors 241 and 242 shown in FIG. [Figure 6] FIG. 6 is a flowchart showing a processing procedure in the failure determination process of the microcomputer shown in FIG. [Figure 7] FIG. 7 is a table showing details of the failure determinations at S4, S7, and S8 shown in FIG. [Figure 8] FIG. 8 is a circuit diagram showing an overcurrent determination circuit according to the second embodiment. [Figure 9] FIG. 9 is a circuit diagram showing details of the + side attachment determination circuit and the − side attachment determination circuit shown in FIG. [Figure 10] FIG. 10 is a circuit diagram showing an overcurrent determination circuit according to the third embodiment. [Figure 11] FIG. 11 is a block diagram showing an embodiment of a current interruption system according to the fourth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0012] Specific embodiments of the present invention will be described below with reference to the accompanying drawings.

[0013] (First embodiment) The current interruption system 1 of the present invention blows an ignition-type fuse provided in a current path through which a discharge current (positive direction) and a charge current (negative direction) flow from a battery that serves as a drive source for a vehicle. The current interruption system 1 includes a current interruption circuit 2 and a microcomputer 3 (hereinafter abbreviated as "microcomputer 3") that controls the current interruption circuit 2. The current interruption circuit 2 includes a power supply circuit 21 that generates 12V and an LDO (Low Dropout) regulator 22 that generates 5V.

[0014] The current interruption circuit 2 includes an IPD 231 (first switch) and an IPD 232 (second switch), a current sensor 241 (first current sensor) and a current sensor 242 (second current sensor), an overcurrent judgment circuit 251 (first overcurrent judgment circuit) and an overcurrent judgment circuit 252 (second overcurrent judgment circuit), AND circuits 273 and 274, and a fault judgment circuit 28.

[0015] The ignition fuse includes a thin plate conductor connected to a current path, an igniter having a resistor Rp (first resistor), and a cutter. When the resistor Rp is energized, its heat ignites the gunpowder in the igniter, causing an explosion. The pressure of this explosion causes the cutter to cut the thin plate conductor. The resistor Rp is burned by the explosion. IPDs (Intelligent Power Devices) 231 and 232 are provided on both sides of the resistor Rp, and when both are turned on, the resistor Rp is energized. IPD 231 is connected between the power supply circuit 21 and one end of the resistor Rp. When turned on, IPD 231 supplies 12 V to one end of the resistor Rp. IPD 232 is connected between the ground and the other end of the resistor Rp. When turned on, IPD 232 supplies 0 V to the other end of the resistor Rp. When IPDs 231 and 232 are turned on, 12 V is applied to both ends of the resistor Rp, causing the resistor Rp to be energized and the ignition fuse to blow.

[0016] The current sensors 241, 242 detect the current flowing in a current path in which an ignition type fuse is provided. The ignition type fuse is provided in the current path through which the discharge current and charge current of the battery flow. The current sensors 241, 242 output analog signals with good response. The current sensors 241, 242 are, for example, composed of a Hall IC type current sensor that measures the magnetic flux density of the current and outputs a voltage, or a shunt type current sensor that measures the voltage generated across a resistor due to the current flowing through a shunt resistor and outputs a voltage. In this embodiment, the current sensors 241, 242 are, for example, composed of a Hall IC type current sensor that can detect currents of +2000 A to -2000 A.

[0017] As shown in FIG. 2, the output of current sensor 241 increases as the current flowing through the current path increases. As shown in FIG. 3, the output of current sensor 242 decreases as the current flowing through the current path increases. Also, as shown in FIG. 2, when a large current flows in the positive direction, the output of current sensor 241 is clamped to a first clamp voltage (e.g., 4.6 V) under normal circumstances, and when a large current flows in the negative direction, the output is clamped to a second clamp voltage (e.g., 0.4 V). As shown in FIG. 3, when a large current flows in the positive direction, the output of current sensor 242 is clamped to a second clamp voltage (0.4 V) under normal circumstances, and when a large current flows in the negative direction, the output is clamped to the first clamp voltage (4.6 V). That is, the outputs of current sensors 241 and 242 normally fluctuate within a range of 0.4 V or more and 4.6 V or less. On the other hand, when a fault such as a short circuit or an open circuit occurs, the outputs of current sensors 241 and 242 stick to the first power supply voltage (5 V) or the second power supply voltage (0 V).

[0018] The overcurrent determination circuit 251 is a circuit that determines an overcurrent based on the output of the current sensor 241. In this embodiment, the overcurrent determination circuit 251 determines, for example, a current of 1300 A or more in both the positive and negative directions as an overcurrent. When the output of the current sensor 241 exceeds a first threshold (e.g., 4.3 V) or falls below a second threshold (e.g., 0.7 V), the overcurrent determination circuit 251 detects an overcurrent and outputs an H-level overcurrent signal S11. When the output of the current sensor 241 is equal to or less than the first threshold (4.3 V) and equal to or greater than the second threshold (0.7 V), the overcurrent determination circuit 251 outputs an L-level overcurrent signal S11 indicating normal operation.

[0019] Overcurrent determination circuit 252 is a circuit that determines an overcurrent based on the output of current sensor 242. Similar to overcurrent determination circuit 251, overcurrent determination circuit 252 detects an overcurrent and outputs an H-level overcurrent signal S12 when the output of current sensor 242 exceeds a first threshold (4.3 V) or falls below a second threshold (0.7 V). When the output of current sensor 242 is equal to or less than the first threshold (4.3 V) and equal to or greater than the second threshold (0.7 V), overcurrent determination circuit 252 outputs an L-level overcurrent signal S12 indicating normal operation.

[0020] Next, the overcurrent determination circuits 251 and 252 will be described in detail. Since the overcurrent determination circuits 251 and 252 have the same circuit configuration, the overcurrent determination circuit 251 will be described as a representative. As shown in FIG. 1, the overcurrent determination circuit 251 includes a discharge-side overcurrent determination circuit 25A, a charge-side overcurrent determination circuit 25B, and an OR circuit 25C. When the output of the current sensor 241 exceeds a first threshold (4.3 V), the discharge-side overcurrent determination circuit 25A determines an overcurrent in the positive direction (discharging direction) and outputs an H-level signal. When the output of the current sensor 241 falls below a second threshold (0.7 V), the charge-side overcurrent determination circuit 25B determines an overcurrent in the negative direction (charging direction) and outputs an H-level signal. When either the discharge-side overcurrent determination circuit 25A or the charge-side overcurrent determination circuit 25B outputs an H-level signal indicating an overcurrent, the OR circuit 25C outputs an H-level overcurrent signal S11.

[0021] Next, an example of the discharge-side overcurrent determination circuit 25A and the charge-side overcurrent determination circuit 25B will be described with reference to Fig. 4. As shown in the figure, the discharge-side overcurrent determination circuit 25A has a first threshold value output circuit 25A-1, a comparator CP11 (first comparator), and low-pass filters 25A-2 to 25A-4. The charge-side overcurrent determination circuit 25B has a second threshold value output circuit 25B-1, a comparator CP12 (first comparator), and low-pass filters 25B-2 to 25B-4.

[0022] The first threshold output circuit 25A-1 outputs a first threshold (4.3 V). The first threshold output circuit 25A-1 has resistors R11 and R12 connected in series between the output of the LDO regulator 22 and ground. The first threshold output circuit 25A-1 outputs a voltage obtained by dividing 5 V by the resistors R11 and R12 as the first threshold (4.3 V).

[0023] The comparator CP11 receives the output of current sensor 241 at its non-inverting input via low-pass filter 25A-3, and receives a first threshold (4.3 V) at its inverting input via low-pass filter 25A-2. Comparator CP11 compares the output of current sensor 241 with the first threshold (4.3 V), and outputs an H-level signal when the output of current sensor 241 is higher than the first threshold (4.3 V). Comparator CP11 outputs an L-level signal when the output of current sensor 241 is equal to or lower than the first threshold (4.3 V).

[0024] The second threshold output circuit 25B-1 outputs a second threshold (0.7 V). The second threshold output circuit 25B-1 has resistors R13 and R14 connected in series between the output of the LDO regulator 22 and ground. The second threshold output circuit 25B-1 outputs a voltage obtained by dividing 5 V by the resistors R13 and R14 as the second threshold (0.7 V).

[0025] The output of current sensor 241 is input to the inverting input of comparator CP12 via low-pass filter 25B-3, and a second threshold (0.7V) is input to the non-inverting input via low-pass filter 25B-2. Comparator CP12 compares the output of current sensor 241 with the second threshold (0.7V), and outputs an H-level signal when the output of current sensor 241 is lower than the second threshold (0.7V). Comparator CP12 outputs an L-level signal when the output of current sensor 241 is equal to or higher than the second threshold (0.7V).

[0026] The low-pass filter 25A-2 (first low-pass filter) is provided between the first threshold output circuit 25A-1 and the input of the comparator CP11. The low-pass filter 25A-2 has a resistor R15 connected between the junction of the resistors R11 and R12 and the inverting input of the comparator CP11, and a capacitor (capacitor) C11 connected between the junction of the resistor R15 and the comparator CP11 and ground. The low-pass filter 25A-2 removes high-frequency noise above its cutoff frequency from the output of the first threshold output circuit 25A-1. The cutoff frequency is determined by the values ​​of the resistor R15 and the capacitor C11 and is set within a range that does not sacrifice response speed.

[0027] Low-pass filter 25A-3 (second low-pass filter) is provided between current sensor 241 and the input of comparator CP11. Low-pass filter 25A-3 has a resistor R16 connected between current sensor 241 and the non-inverting input of comparator CP11, and a capacitor (capacitance) C12 connected between the junction of resistor R16 and comparator CP11 and ground. Low-pass filter 25A-3 removes high-frequency noise above its cutoff frequency from the output of current sensor 241. The cutoff frequency is determined by the values ​​of resistor R16 and capacitor C12, and is therefore set within a range that does not sacrifice response speed.

[0028] In this embodiment, in order to prevent the first threshold (4.3V) from dropping earlier than the output of the current sensor 241 when the power supply to the LDO regulator 22 is turned off, the capacitance of the capacitor C11 is set to be larger than that of the capacitor C12.

[0029] The low-pass filter 25B-2 (third low-pass filter) is provided between the second threshold output circuit 25B-1 and the input of the comparator CP12. The low-pass filter 25B-2 has a resistor R17 connected between the junction of the resistors R13 and R14 and the non-inverting input of the comparator CP11, and a capacitor (capacitor) C13 connected between the junction of the resistor R17 and the comparator CP12 and ground. The low-pass filter 25B-2 removes high-frequency noise above its cutoff frequency from the output of the second threshold output circuit 25B-1. The cutoff frequency is determined by the values ​​of the resistor R17 and the capacitor C13 and is set within a range that does not sacrifice response speed.

[0030] Low-pass filter 25B-3 (fourth low-pass filter) is provided between current sensor 241 and the input of comparator CP12. Low-pass filter 25B-3 has a resistor R18 connected between current sensor 241 and the inverting input of comparator CP12, and a capacitor (capacitor) C14 connected between the junction of resistor R18 and comparator CP12 and ground. Low-pass filter 25B-3 removes high-frequency noise above its cutoff frequency from the output of current sensor 241. The cutoff frequency is determined by the values ​​of resistor R18 and capacitor C14, and is therefore set within a range that does not sacrifice response speed.

[0031] In this embodiment, in order to prevent the output of the current sensor 241 from dropping below the second threshold (0.7 V) before the power supply to the LDO regulator 22 is turned off, the capacitance of the capacitor C14 is set to be larger than that of the capacitor C13.

[0032] The low-pass filter 25A-4 is provided between the output of the comparator CP11 and the input of the OR circuit 25C. The low-pass filter 25A-4 has a resistor R19 connected between the comparator CP11 and the input of the OR circuit 25C, and a capacitor (capacitor) C15 connected between the junction of the resistor R19 and the input of the OR circuit 25C and ground. The low-pass filter 25A-4 removes high-frequency noise above the cutoff frequency from the output of the comparator CP11. The cutoff frequency is determined by the values ​​of the resistor R19 and the capacitor C15, and is set within a range that does not sacrifice response speed.

[0033] The low-pass filter 25B-4 is provided between the output of the comparator CP12 and the OR circuit 25C. The low-pass filter 25B-4 has a resistor R110 connected between the comparator CP12 and the input of the OR circuit 25C, and a capacitor (capacitor) C16 connected between the junction of the resistor R110 and the input of the OR circuit 25C and ground. The low-pass filter 25B-4 removes high-frequency noise above the cutoff frequency from the output of the comparator CP12. The cutoff frequency is determined by the values ​​of the resistor R110 and the capacitor C16, and is therefore set within a range that does not sacrifice response speed.

[0034] The output of comparator CP11 is input to OR circuit 25C via low-pass filter 25A-4, and the output of comparator CP12 is input to OR circuit 25C via low-pass filter 25B-4. Therefore, when the output of current sensor 241 exceeds the first threshold (4.3 V) or falls below the second threshold (0.7 V), OR circuit 25C outputs an H-level overcurrent signal S11. When the output of current sensor 241 is equal to or less than the first threshold (4.3 V) and equal to or greater than the second threshold (0.7 V), OR circuit 25C outputs an L-level overcurrent signal S11.

[0035] The overcurrent determination circuit 252 can be explained by replacing "overcurrent determination circuit 251" with "overcurrent determination circuit 252," "current sensor 241" with "current sensor 242," and "overcurrent signal S11" with "overcurrent signal S12" in the description of the overcurrent determination circuit 251 above.

[0036] 1, the AND circuit 273 receives the above-mentioned overcurrent signal S11 and an active signal from the microcomputer 3. The AND circuit 274 receives the above-mentioned overcurrent signal S12 and an active signal from the microcomputer 3.

[0037] Next, a description will be given of the configuration of the failure determination circuit 28. The above-mentioned failure determination circuit 28 is a circuit that determines failures in the overcurrent determination circuit 251, the IPDs 231 and 232, and the resistor Rp. The failure determination circuit 28 includes a resistor R32, a diode D1, a resistor R33, a discharge-side dummy voltage output circuit 281, a charge-side dummy voltage output circuit 282, a switch SW3 (third switch), a switch SW4 (fourth switch), and a switch SW5.

[0038] Resistor R32 and diode D1 are connected in series between 5 V and the connection point of resistor Rp and IPD231. Diode D1 is connected in the forward direction from 5 V to the connection point of resistor Rp and IPD231. Resistor R33 is connected between ground and the connection point of resistor Rp and IPD232.

[0039] The discharge-side dummy voltage output circuit 281 outputs a dummy voltage (4.5V) equivalent to an overcurrent in the positive direction (discharge direction). The charge-side dummy voltage output circuit 282 outputs a dummy voltage (0.5V) equivalent to an overcurrent in the negative direction (charge direction). The discharge-side dummy voltage output circuit 281 and the charge-side dummy voltage output circuit 282 are composed of voltage-dividing resistors connected in series between the output (5V) of the LDO regulator 22 and ground, and output voltages obtained by dividing 5V by the voltage-dividing resistors as the discharge-side dummy voltage (4.5V) and the charge-side dummy voltage (0.5V), respectively.

[0040] Switch SW5 is a switch for selecting either the dummy voltage (4.5 V) output by discharge-side dummy voltage output circuit 281 or the dummy voltage (0.5 V) output by charge-side dummy voltage output circuit 282. Switch SW3 switches the input to overcurrent determination circuit 251 between the output of current sensor 241 and either the dummy voltage (4.5 V) or the dummy voltage (0.5 V), selected by switch SW5. Switch SW4 switches the input to overcurrent determination circuit 252 between the output of current sensor 242 and either the dummy voltage (4.5 V) or the dummy voltage (0.5 V), selected by switch SW5.

[0041] The voltage at the connection point between the resistor R32 and the diode D1 is input to the microcomputer 3 as a fault detection voltage. The microcomputer 3 outputs an overcurrent switching signal S31 and forced shutoff signals S32 and S33 to the switches SW3 to SW5 to control the switches SW3 to SW5. The microcomputer 3 detects a fault based on the fault detection voltage output while a dummy voltage (4.5V) or a dummy voltage (0.5V) is being input to the overcurrent determination circuits 251 and 252. When the microcomputer 3 detects a fault based on the fault detection voltage, it stops outputting the active signal.

[0042] The current interruption circuit 2 constituting the above-described current interruption system 1 is mounted on a substrate on which current sensors 241, 242 are mounted. More specifically, if the current sensors 241, 242 are Hall IC type, they will be as shown in Figure 5. The current sensors 241, 242 each have a bus bar 243 connected to the current path, a core 244 surrounding the bus bar 243, and a Hall IC 245 located in the gap of the core 244.

[0043] One bus bar 243 and one core 244 are provided (shared) for the two current sensors 241, 242. One Hall IC 245 is provided for each of the two current sensors 241, 242. The IPDs 231, 232, overcurrent determination circuits 251, 252, and fault determination circuit 28 that constitute the current interruption circuit 2 are mounted on a substrate 246 on which the Hall IC 245 is mounted. The microcomputer 3 may be, for example, a microcomputer used to monitor a battery, and is not mounted on the substrate 246.

[0044] According to the above configuration, there is no need to provide separate boards for the current sensors 241 and 242 and for the IPDs 231 and 232, overcurrent determination circuits 251 and 252, and failure determination circuit 28, which allows for a reduction in the number of parts and size.

[0045] Next, we will explain the operation of the current interruption system 1 configured as described above. When the vehicle ignition switch is turned on and power is supplied, the microcomputer 3 sets the active signal to L level (OFF) for a certain period after power supply is supplied until the outputs of the power supply circuit 21 and the LDO regulator 22 stabilize. As a result, the outputs of the AND circuits 273 and 274 become L level, and the IPDs 231 and 232 are not turned on while the active signal is L level.

[0046] If the power supply is unstable, the first threshold (4.3 V) and the second threshold (0.7 V) generated by the overcurrent determination circuits 251 and 252 will be inaccurate. This may cause the overcurrent determination circuits 251 and 252 to make erroneous determinations. In this embodiment, after power is turned on, the active signal is set to L level until the power supply stabilizes, preventing the IPDs 231 and 232 from being turned off during that time. This reduces erroneous determinations by the overcurrent determination circuits 251 and 252 and reduces erroneous blowing of ignition-type fuses.

[0047] Next, we will explain what happens after the active signal becomes H level. When the overcurrent determination circuits 251 and 252 determine an overcurrent and output H-level overcurrent signals S11 and S12, the IPDs 231 and 232 turn on. This makes the resistor Rp conductive, blows the ignition fuse, and cuts off the large current.

[0048] Furthermore, when overcurrent determination circuit 251 outputs an H-level overcurrent signal S11 and overcurrent determination circuit 252 outputs an L-level overcurrent signal S12, IPD 231 is turned on but IPD 232 is not turned on. As a result, resistor Rp is not energized and the ignition fuse is not blown. Conversely, when overcurrent determination circuit 252 outputs an H-level overcurrent signal S12 and overcurrent determination circuit 251 outputs an L-level overcurrent signal S11, IPD 232 is turned on but IPD 231 is not turned on. In this case as well, resistor Rp is not energized and the ignition fuse is not blown.

[0049] If the current interruption circuit 2 is normal and a large current flows through the current path, the two overcurrent detection circuits 251 and 252 output H-level overcurrent signals S11 and S12. As described above, if only one of the overcurrent detection circuits 251 and 252 detects an overcurrent and the other does not, it is highly likely that some abnormality has occurred in the current interruption circuit 2 and that a large current is not flowing through the current path. In this embodiment, the IPD 231 is turned on when the overcurrent detection circuit 2 detects an overcurrent, and the IPD 232 is turned on when the overcurrent detection circuit 252 detects an overcurrent. In other words, by conducting current through the resistor Rp only when both of the two overcurrent detection circuits 251 and 252 detect an overcurrent, the ignition fuse can be accurately blown when an overcurrent occurs and erroneous blowing of the ignition fuse can be reduced during normal operation when no overcurrent is occurring.

[0050] According to the above-described embodiment, the two current sensors 241, 242 have different output changes in response to an increase in current, as shown in Figures 2 and 3. Therefore, even if noise from the same noise source is present in the outputs of the current sensors 241, 242, the noise is present in different ways. Therefore, even if one of the overcurrent determination circuits 251, 252 determines an overcurrent due to noise, the other is more likely not to determine an overcurrent, thereby reducing the risk of erroneous blowing of the ignition fuse.

[0051] Next, the fault determination process using the fault determination circuit 28, which is executed by the microcomputer 3, will be described with reference to FIGS. 6 and 7. This fault determination process is executed at startup, shutdown, or at regular intervals. The active signal is at H level. First, the microcomputer 3 acquires the outputs of the current sensors 241 and 242 (Sp1). Next, the microcomputer 3 determines whether the outputs (digital values) of the current sensors 241 and 242 are within the normal operating range (Sp2). In this embodiment, the normal operating range is set to 0.4 V to 4.8 V. If the outputs of the current sensors 241 and 242 are outside the normal operating range (N in Sp2), the microcomputer 3 determines that the current sensors 241 and 242 are faulty (Sp15), sets the active signal to L level (S20), and then ends the process. If the outputs of the current sensors 241 and 242 are within the normal operating range (Y in Sp2), the microcomputer 3 proceeds to Sp3.

[0052] In Sp3, the microcomputer 3 determines whether the output difference between the current sensors 241 and 242 is within the allowable range. If the output difference between the current sensors 241 and 242 exceeds the allowable range (N in Sp3), the microcomputer 3 determines that the current sensors 241 and 242 are faulty (Sp16), sets the active signal to L level (Sp20), and ends the process. Next, if the output difference between the current sensors 241 and 242 is within the allowable range (Y in Sp3), the microcomputer 3 proceeds to Sp4. In S4, the microcomputer 3 acquires the fault detection voltage and determines whether the acquired fault detection voltage is within the allowable range. At this time, as shown in the top row of FIG. 7, the microcomputer 3 outputs L-level forced shutdown signals S32 and S33, and the outputs of the current sensors 241 and 242 are input to the overcurrent determination circuits 251 and 252.

[0053] In Sp4, if no fault (abnormality) has occurred in the current interruption circuit 2, the IPDs 231 and 232 are turned off, and the fault detection voltage is an intermediate voltage (Mid) of 5V. Furthermore, if an open circuit abnormality in resistor R11 of the overcurrent determination circuit 252, a short circuit abnormality in resistor R12 of the overcurrent determination circuit 252, or a short circuit abnormality in the IPD 232 has occurred, the IPD 232 is turned on, and the fault detection voltage is 0V (Low). Furthermore, if an open circuit abnormality in resistor Rp has occurred, the fault detection voltage is 5V (High) even if the IPDs 231 and 232 are off. Furthermore, if an open circuit abnormality in resistor R11 of the overcurrent determination circuit 251, a short circuit abnormality in resistor R12 of the overcurrent determination circuit 251, or a short circuit abnormality in the IPD 231 has occurred, the IPD 231 is turned on, and the fault detection voltage is 5V (High).

[0054] In Sp4, if the fault detection voltage is within the allowable range that can be considered as Mid, the microcomputer 3 does not determine that there is a fault, but if the fault detection voltage is outside the allowable range, it determines that there is a fault. If the fault detection voltage is outside the allowable range (N in Sp4), the microcomputer 3 determines that there is a circuit fault (Sp17), sets the active signal to L level (Sp20), and then ends the processing.

[0055] If the fault detection voltage is within the allowable range (Y in Sp4), the microcomputer 3 outputs an H-level forced shutdown signal S32 (Sp5). By the operation of Sp5, a discharge-side dummy voltage or a charge-side dummy voltage is supplied to the overcurrent determination circuit 251, and the output of the current sensor 242 is supplied to the overcurrent determination circuit 252. Next, the microcomputer 3 takes in the fault detection voltage and determines whether the taken-in fault detection voltage is within the allowable range (Sp6).

[0056] The fault determination of Sp6 will be described with reference to FIG. 7. At this time, as shown in the second row from the top of FIG. 7, the microcomputer 3 outputs an H-level forced shutdown signal S32 and an L-level forced shutdown signal S33. When no fault (abnormality) occurs in the current interruption circuit 2, if a discharge-side dummy voltage or a charge-side dummy voltage is supplied, the overcurrent determination circuit 251 outputs an H-level overcurrent signal S11, turning on the IPD 231. Since the IPD 232 turns off, the fault detection voltage becomes 5V (High). Furthermore, if an open fault or other abnormality occurs in the IPD 231, the IPD 231 cannot be turned on, and the fault detection voltage becomes an intermediate voltage (Mid) of 5V. Furthermore, for example, if an open fault of the resistor R12 of the overcurrent determination circuit 251 and a short fault of the IPD 232 occur simultaneously, the IPD 231 turns off and the IPD 232 turns on, resulting in a fault detection voltage of 0V (High).

[0057] In S6, if the fault detection voltage is within the allowable range that can be considered high, the microcomputer 3 does not determine that there is a fault, but if the fault detection voltage is outside the allowable range, it determines that there is a fault. If the fault detection voltage is outside the allowable range (N in Sp6), the microcomputer 3 determines that there is a circuit fault (Sp18), sets the active signal to L level (Sp20), and then ends the process.

[0058] If the fault detection voltage is within the allowable range (Y in Sp6), the microcomputer 3 outputs an L-level forced shutdown signal S32 (Sp7) and outputs an H-level forced shutdown signal S33 (Sp8). By the operations of Sp7 and Sp8, a discharge-side dummy voltage or a charge-side dummy voltage is supplied to the overcurrent determination circuit 252, and the output of the current sensor 241 is supplied to the overcurrent determination circuit 251. Next, the microcomputer 3 takes in the fault detection voltage and determines whether the taken-in fault detection voltage is within the allowable range (Sp9).

[0059] The fault determination in S9 will be described with reference to FIG. 7. At this time, as shown in the third row from the top in FIG. 7, the microcomputer 3 outputs an H-level forced shutoff signal S33 and an L-level forced shutoff signal S32. When no fault (abnormality) occurs in the current interruption circuit 2, if a discharge-side dummy voltage or a charge-side dummy voltage is supplied, the overcurrent determination circuit 252 outputs an H-level overcurrent signal S12, and the IPD 232 turns on. Furthermore, since the IPD 231 turns off, the fault detection voltage becomes 0 V (Low). Furthermore, if an open circuit abnormality occurs in the IPD 232, the IPD 232 cannot be turned on, and the fault detection voltage becomes an intermediate voltage (Mid) of 5 V. Furthermore, if an open circuit abnormality occurs in the resistor Rp, the fault detection voltage becomes 5 V (High) even if the IPD 231 and the IPD 232 are off. Furthermore, for example, if an open fault of the resistor R12 of the overcurrent determination circuit 252 and a short fault of the IPD 231 occur simultaneously, the IPD 231 turns on and the IPD 232 turns off, so the fault detection voltage becomes 5V (High).

[0060] In Sp9, if the fault detection voltage is within the allowable range that can be considered low, the microcomputer 3 does not determine that there is a fault, but if the fault detection voltage is outside the allowable range, it determines that there is a fault. If the fault detection voltage is outside the allowable range (N in Sp9), the microcomputer 3 determines that there is a circuit fault (Sp19), sets the active signal to L level (Sp20), and then ends the processing.

[0061] If the fault detection voltage is within the allowable range (Y in Sp9), the microcomputer 3 outputs an L-level forced shutdown signal S33 (Sp10) and determines whether the overcurrent switching signal S31 has been switched (Sp11). If the signal has not been switched (N in Sp11), the microcomputer 3 switches the overcurrent switching signal S31 from H to L or from L to H (S14). As a result, when Sp6 and Sp10 are executed for the first time, one of the discharge-side dummy voltage and the charge-side dummy voltage is input to the overcurrent determination circuits 251 and 252, and when Sp6 and Sp10 are executed after switching, the other of the discharge-side dummy voltage and the charge-side dummy voltage is input to the overcurrent determination circuits 251 and 252.

[0062] If the switching has been completed (Y in Sp11), the microcomputer 3 switches the overcurrent switching signal S31 from H level to L level or from L level to H level (Sp12), and then maintains the active signal at H level (Sp13) to end the process.

[0063] According to the above-described embodiment, the failure determination circuit 28 can determine failures other than those of the current sensors 241 and 242, thereby reducing erroneous determinations by the overcurrent determination circuits 251 and 252 and reducing erroneous blowing of the ignition type fuse.

[0064] (Second embodiment) Next, a second embodiment will be described. The difference between the first and second embodiments is the configuration of overcurrent determination circuits 251B and 252B. As shown in Fig. 8, the overcurrent determination circuits 251 and 252 include a discharge-side overcurrent determination circuit 25A, a charge-side overcurrent determination circuit 25B, a +side attachment determination circuit 261, a -side attachment determination circuit 262, an AND circuit 263, an OR circuit 264, and an AND circuit 265. The discharge-side overcurrent determination circuit 25A and the charge-side overcurrent determination circuit 25B are the same as those in the first embodiment.

[0065] As described above, when a large current flows through the current sensors 241 and 242, they are clamped to the first clamp voltage (4.6 V) and the second clamp voltage (0.4 V). On the other hand, when the current sensors 241 and 242 fail, they are clamped to the first power supply voltage (5 V) and the second power supply voltage (0 V). Therefore, if the output of the current sensors 241 and 242 exceeds a third threshold (e.g., 4.8 V) set between the first clamp voltage (4.6 V) and the first power supply voltage (5 V), the + side stick determination circuit 261 determines that the current sensors 241 and 242 are faulty and outputs an L-level stick signal S21. If the output of the current sensors 241 and 242 is equal to or lower than the third threshold (e.g., 4.8 V), the + side stick determination circuit 261 determines that the current sensors 241 and 242 are not failing and outputs an H-level stick signal S21. Furthermore, if the outputs of the current sensors 241, 242 are lower than a fourth threshold (e.g., 0.2 V) set between the second power supply voltage (0 V) and the second clamp voltage (0.4 V), the negative side sticking determination circuit 261 determines that the current sensors 241, 242 are faulty and outputs an L-level sticking signal S21. If the outputs of the current sensors 241, 242 are equal to or higher than the fourth threshold (e.g., 0.2 V), the negative side sticking determination circuit 261 determines that the current sensors 241, 242 are not faulty and outputs an H-level sticking signal S21.

[0066] The outputs of the + side sticking determination circuit 261 and the - side sticking determination circuit 262 are input to the AND circuit 263. The outputs of the discharge side overcurrent determination circuit 25A and the charge side overcurrent determination circuit 25B are input to the OR circuit 264. The outputs of the OR circuit 264 and the AND circuit 263 are input to the AND circuit 265. The output of the AND circuit 263 is connected to the inputs of the AND circuits 273 and 274 shown in FIG.

[0067] 8, when at least one of the positive side attachment determination circuit 261 and the negative side attachment determination circuit 262 determines a fault and outputs an L-level fault signal S21, the IPDs 231 and 232 are not turned on (turned off) regardless of the determination results of the discharge side overcurrent determination circuit 25A and the charge side overcurrent determination circuit 25B. That is, when at least one of the current sensors 241 and 242 fails, both the IPDs 231 and 232 are not turned on. This reduces the risk of erroneous blowing of the ignition type fuse.

[0068] Next, the + side sticking determination circuit 261 and the - side sticking determination circuit 262 will be described in detail with reference to Fig. 9. As shown in Fig. 9, the + side sticking determination circuit 261 includes a third threshold output circuit 26A, a comparator CP21, a low-pass filter 26C, a low-pass filter 26D, and a low-pass filter 26G. The - side sticking determination circuit 262 includes a fourth threshold output circuit 26B, a comparator CP22, a low-pass filter 26E, a low-pass filter 26F, and a low-pass filter 26H.

[0069] The third threshold output circuit 26A outputs a third threshold (4.8 V). The third threshold output circuit 26A has resistors R21 and R22 connected in series between the output of the LDO regulator 22 and ground. The third threshold output circuit 26A outputs a voltage obtained by dividing 5 V by the resistors R21 and R22 as the third threshold (4.8 V).

[0070] The outputs of current sensors 241 and 242 are input to the inverting input of comparator CP21 via low-pass filter 26D, and a third threshold (4.8V) is input to the non-inverting input via low-pass filter 26C. Comparator CP21 compares the outputs of current sensors 241 and 242 with the third threshold (4.8V), and outputs an H-level signal when the outputs of current sensors 241 and 242 are lower than the third threshold (4.8V). Comparator CP21 outputs an L-level signal when the outputs of current sensors 241 and 242 are equal to or higher than the third threshold (4.8V).

[0071] The fourth threshold output circuit 26B outputs a fourth threshold (0.2 V). The fourth threshold output circuit 26B has resistors R23 and R24 connected in series between the output of the LDO regulator 22 and ground. The fourth threshold output circuit 26B outputs a voltage obtained by dividing 5 V by the resistors R23 and R24 as the fourth threshold (0.2 V).

[0072] The outputs of current sensors 241 and 242 are input to the non-inverting input of comparator CP22 via low-pass filter 26F, and a fourth threshold (0.2V) is input to the inverting input via low-pass filter 26E. Comparator CP22 compares the output of current sensor 241 with the fourth threshold (0.2V), and outputs an H-level signal when the output of current sensor 241 is higher than the fourth threshold (0.2V). Comparator CP22 outputs an L-level signal when the output of current sensor 241 is equal to or lower than the fourth threshold (0.2V).

[0073] The low-pass filter 26C is provided between the third threshold output circuit 26A and the comparator CP21. The low-pass filter 26C has a resistor R25 connected between the junction of resistors R21 and R22 and the inverting input of the comparator CP21, and a capacitor (capacitor) C21 connected between the junction of resistor R25 and comparator CP21 and ground. The low-pass filter 26C removes high-frequency noise above the cutoff frequency from the output of the third threshold output circuit 26A. The cutoff frequency is determined by the values ​​of resistor R25 and capacitor C21, and is set within a range that does not sacrifice response speed.

[0074] Low-pass filter 26D is provided between current sensor 241 and comparator CP21. Low-pass filter 26D has a resistor R26 connected between current sensor 241 and the inverting input of comparator CP21, and a capacitor (capacitance) C22 connected between the junction of resistor R26 and comparator CP21 and ground. Low-pass filter 26D removes high-frequency noise above its cutoff frequency from the outputs of current sensors 241 and 242. The cutoff frequency is determined by the values ​​of resistor R26 and capacitor C22, and is therefore set within a range that does not sacrifice response speed.

[0075] In this embodiment, in order to prevent the third threshold (4.8V) from dropping earlier than the outputs of the current sensors 241 and 242 when the power supply to the LDO regulator 22 is turned off, the capacitance of the capacitor C21 is set to be larger than that of the capacitor C22.

[0076] The low-pass filter 26E is provided between the fourth threshold output circuit 26B and the comparator CP22. The low-pass filter 26E has a resistor R27 connected between the junction of resistors R23 and R24 and the inverting input of the comparator CP22, and a capacitor (capacitor) C23 connected between the junction of resistor R27 and comparator CP22 and ground. The low-pass filter 26E removes high-frequency noise above the cutoff frequency from the output of the fourth threshold output circuit 26B. The cutoff frequency is determined by the values ​​of resistor R27 and capacitor C23, and is set within a range that does not sacrifice response speed.

[0077] The low-pass filter 26F is provided between the current sensors 241, 242 and the comparator CP22. The low-pass filter 26F has a resistor R28 connected between the current sensors 241, 242 and the non-inverting input of the comparator CP22, and a capacitor (capacitance) C24 connected between the connection point of the resistor R28 and the comparator CP22 and ground. The low-pass filter 26F removes high-frequency noise above the cutoff frequency from the outputs of the current sensors 241, 242. The cutoff frequency is determined by the values ​​of the resistor R28 and the capacitor C24, and is therefore set within a range that does not sacrifice response speed.

[0078] In this embodiment, in order to prevent the output of the current sensor 241 from dropping below the fourth threshold (0.2 V) before the power supply to the LDO regulator 22 is turned off, the capacitance of the capacitor C24 is set to be larger than that of the capacitor C23.

[0079] The low-pass filter 26G is provided between the output of the comparator CP21 and the AND circuit 263. The low-pass filter 26G has a resistor R29 connected between the comparator CP21 and the input of the AND circuit 263, and a capacitor (capacitor) C25 connected between the connection point of the resistor R29 and the input of the AND circuit 26I and ground. The low-pass filter 26G removes high-frequency noise above the cutoff frequency from the output of the comparator CP21. The cutoff frequency is determined by the values ​​of the resistor R29 and the capacitor C25, and is therefore set within a range that does not sacrifice response speed.

[0080] The low-pass filter 26H is provided between the output of the comparator CP22 and the AND circuit 263. The low-pass filter 26H has a resistor R210 connected between the comparator CP22 and the input of the AND circuit 263, and a capacitor (capacitor) C26 connected between the connection point of the resistor R210 and the input of the AND circuit 263 and ground. The low-pass filter 26H removes high-frequency noise above the cutoff frequency from the output of the comparator CP22. The cutoff frequency is determined by the values ​​of the resistor R210 and the capacitor C26, and is therefore set within a range that does not sacrifice response speed.

[0081] The AND circuit 263 receives the output of comparator CP21 via low-pass filter 26G and the output of comparator CP22 via low-pass filter 26H. Therefore, when the outputs of current sensors 241 and 242 are higher than the third threshold (4.8 V) or lower than the fourth threshold (0.2 V), AND circuit 263 outputs a L-level pin signal S21. When the output of current sensor 241 is equal to or lower than the third threshold (4.8 V) and equal to or higher than the fourth threshold (0.2 V), AND circuit 263 outputs a H-level pin signal S21.

[0082] (Third embodiment) Next, a third embodiment will be described. The difference between the second and third embodiments is the configuration of overcurrent determination circuits 251C and 252C. As shown in Fig. 10, the overcurrent determination circuits 251C and 252C include a discharge-side overcurrent determination circuit 25A, a charge-side overcurrent determination circuit 25B, a +side attachment determination circuit 261, a -side attachment determination circuit 262, AND circuits 266 and 267, and an OR circuit 25C. The discharge-side overcurrent determination circuit 25A, the charge-side overcurrent determination circuit 25B, the +side attachment determination circuit 261, and the -side attachment determination circuit 262 are the same as those in the first embodiment.

[0083] The outputs of the + side sticking determination circuit 261 and the discharge side overcurrent determination circuit 25A are input to the AND circuit 266. The outputs of the - side sticking determination circuit 262 and the charge side overcurrent determination circuit 25B are input to the AND circuit 267. The outputs of the AND circuits 266 and 267 are input to the OR circuit 25C. In this case as well, the same effect as in the second embodiment can be obtained.

[0084] (Fourth embodiment) Next, a fourth embodiment will be described. A major difference between the first and second embodiments is the provision of a failure determination circuit 29 for two current sensors 241, 242. As shown in FIG. 11 , the failure determination circuit 29 is an analog circuit that determines whether the output difference between the two current sensors 241, 242 is within an acceptable range, a task previously performed by the microcomputer 3. The failure determination circuit 29 can be configured to include a differential amplifier circuit that amplifies the output difference between the current sensors 241, 242, and a comparator that compares the output of the differential amplifier circuit with a threshold value. The output of the failure determination circuit 29 is connected to the inputs of AND circuits 273, 274. This prevents the ignition fuse from being blown when the output difference between the current sensors 241, 242 is large enough to indicate that one of the current sensors is faulty, thereby preventing erroneous blowing of the ignition fuse.

[0085] The present invention is not limited to the above-described embodiments, and can be appropriately modified, improved, etc. Furthermore, the material, shape, size, number, location, etc. of each component in the above-described embodiments are arbitrary and not limited as long as they can achieve the present invention.

[0086] According to the above-described embodiment, the output of current sensor 241 increases as the current increases, and the output of current sensor 242 decreases as the current increases, but this is not limited to this. Current sensors 241 and 242 may have outputs that change in the same way.

[0087] According to the above-described embodiment, the IPDs 231 and 232 are used as the first switch and the second switch, but this is not limiting. Semiconductor switches such as field-effect transistors (MOSFETs) may also be used as the first switch and the second switch.

[0088] In the above-described embodiment, the voltage between the resistor R32 and the diode D1 is supplied to the microcomputer 3 as the fault detection voltage, but this is not limited to this. The voltage between the resistor R33 and the resistor Rp may be supplied to the microcomputer 3 as the fault detection voltage, or the voltage between the diode D1 and the resistor Rp may be supplied to the microcomputer 3 as the fault detection voltage.

[0089] According to the above-described embodiment, the dummy voltage output circuits 281, 282 output both the discharge-side dummy voltage and the charge-side dummy voltage, but this is not limited to this. Only the discharge-side dummy voltage output circuit 281 may be provided so that only the discharge-side dummy voltage output circuit 281 can output the discharge-side dummy voltage. Alternatively, only the charge-side dummy voltage output circuit 282 may be provided so that only the charge-side dummy voltage output circuit 282 can output the charge-side dummy voltage.

[0090] The above-mentioned dummy voltage may be varied under the control of the microcomputer 3.

[0091] Here, the features of the above-described embodiments of the current interruption circuit and current interruption system according to the present invention will be briefly summarized and listed below in [1] to [8].

[0092] [1] a first switch (231) and a second switch (232) that are included in the ignition fuse and are provided on both sides of a first resistor (Rp) that burns out due to heat at the time of ignition, and when both switches are turned on, the first resistor (Rp) is energized; a first current sensor (241) and a second current sensor (242) for detecting a current in a current path in which the ignition-type fuse is provided; a first overcurrent determination circuit (251) that determines an overcurrent based on the output of the first current sensor (241); a second overcurrent determination circuit (252) that determines an overcurrent based on the output of the second current sensor (242); The first switch (231) is turned on based on the determination result of the first overcurrent determination circuit (251), The second switch (232) is turned on based on the determination result of the second overcurrent determination circuit (252). Current interruption circuit (2).

[0093] According to the configuration [1] above, by energizing the first resistor (Rp) only when both the first and second overcurrent determination circuits (251, 252) determine that an overcurrent has occurred, the ignition fuse can be accurately cut off when an overcurrent occurs, and erroneous cutting of the ignition fuse can be reduced during normal operation when no overcurrent is occurring.

[0094] [2] In the current interruption circuit (2) according to [1], a failure determination circuit (29) for determining whether the first current sensor (241) and the second current sensor (242) have a failure based on an output difference between the first current sensor (241) and the second current sensor (242); The first switch (231) and the second switch (232) are not turned on while the failure determination circuit (29) determines a failure. Current interruption circuit (2).

[0095] According to the configuration [2], when at least one of the first and second current sensors (241, 242) fails, both the first and second switches (231, 232) are prevented from being turned on, thereby reducing the risk of erroneous blowing of the ignition fuse.

[0096] [3] In the current interruption circuit (2) according to [1], the first switch (231), the second switch (232), the first overcurrent determination circuit (251), and the second overcurrent determination circuit (252) are mounted on a substrate (246) on which the first current sensor (241) and the second current sensor (242) are mounted; Current interruption circuit (2).

[0097] According to the configuration [3], it is not necessary to provide separate boards for the first and second current sensors (241, 242) and the first and second switches (231, 232) and the first and second overcurrent determination circuits (251, 252), thereby reducing the number of components and achieving miniaturization.

[0098] [4] In the current interruption circuit (2) according to [1], The output of the first current sensor (241) increases in response to an increase in the current flowing through the current path, The output of the second current sensor (242) decreases in response to an increase in the current flowing through the current path. Current interruption circuit (2).

[0099] According to the configuration [4] above, even if noise from the same noise source is superimposed on the outputs of the first and second current sensors (241, 242), the manner in which the noise is superimposed is different. Therefore, even if one of the first and second overcurrent determination circuits (251, 252) determines an overcurrent due to noise, the other is more likely not to determine an overcurrent, thereby reducing erroneous blowing of fuses.

[0100] [5] In the current interruption circuit (2) according to [1], The first overcurrent determination circuit (251) and the second overcurrent determination circuit (252) each include: a first threshold output circuit (25A-1) that outputs a first threshold; a first comparator (CP11) that compares the first threshold value with the output of the first current sensor (241) or the second current sensor (242); a second threshold output circuit (25B-1) that outputs a second threshold that is smaller than the first threshold; a second comparator (CP12) that compares the second threshold value with the output of the first current sensor (241) or the second current sensor (242); a first low-pass filter (25A-2) provided between the first threshold output circuit (25A) and the first comparator (CP11); a second low-pass filter (25A-3) provided between the first current sensor (241) or the second current sensor (242) and the first comparator (CP11); a third low-pass filter (25B-2) provided between the second threshold output circuit (25B-1) and the second comparator (CP12); a fourth low-pass filter (25B-3) provided between the first current sensor (241) or the second current sensor (242) and the second comparator (CP12); The capacitance of the first low-pass filter (25A-2) is set to be larger than the capacitance of the second low-pass filter (25A-3), The capacitance of the fourth low-pass filter (25B-3) is set larger than the capacitance of the third low-pass filter (25B-2). Current interruption circuit (2).

[0101] According to the configuration [5] above, it is possible to reduce erroneous determinations by the first and second overcurrent determination circuits (251, 252) when the power to the first and second threshold output circuits (25A-1, 25B-1) is cut off, thereby reducing erroneous blowing of fuses.

[0102] [6] In the current interruption circuit (2) according to [1], a second resistor (R32) and a diode (D1) connected in series between a first power supply voltage (5V) and a connection point between the first resistor (Rp) and the first switch (231); a third resistor (R33) connected between a second power supply voltage and a connection point between the first resistor (Rp) and the second switch (232); a dummy voltage output circuit (281, 282) that outputs a dummy voltage corresponding to an overcurrent; a third switch (SW3) that switches an input to the first overcurrent determination circuit (251) between the output of the first current sensor (241) and the dummy voltage output by the dummy voltage output circuit (281, 282); a fourth switch (SW4) that switches an input to the first overcurrent determination circuit (251) between the output of the second current sensor (242) and the dummy voltage output from the dummy voltage output circuit (281, 282); Current interruption circuit (2).

[0103] According to the configuration [6] above, a dummy voltage can be input to the first and second overcurrent determination circuits (251, 252), and a fault in the current interruption circuit (2) can be determined based on the voltage between the second resistor (R32) and the first resistor (Rp) or the voltage between the third resistor (R33) and the first resistor (Rp).

[0104] [7] [6] The current interruption circuit (2), a control unit (3) that determines a fault based on a voltage between the second resistor (R32) and the first resistor (Rp) or a voltage between the third resistor (R33) and the first resistor (Rp) for each of the following cases: when the third switch (SW3) is switched to the first current sensor (241) side and the fourth switch (SW4) is switched to the second current sensor (242) side; when the third switch (SW3) is switched to the dummy voltage output circuit (281, 282) side and the fourth switch (SW4) is switched to the second current sensor (242); and when the third switch (SW3) is switched to the first current sensor (241) side and the fourth switch (SW4) is switched to the dummy voltage output circuit (281, 282) side. Current interruption system (1).

[0105] According to the configuration [7] above, the control unit (3) can determine whether the current interruption circuit (2) has a fault.

[0106] [8] [1] The current interruption circuit (2), a control unit (3) that turns on an active signal; The first switch (231) and the second switch (232) are not turned on while the active signal is off. Current interruption system (1).

[0107] According to the configuration [8] above, for example, after power-on, the active signal is kept off for a certain period until the power is stabilized, and the first and second switches (231, 232) are not turned off during that time. This reduces erroneous determinations by the first and second overcurrent determination circuits (251, 252) and reduces erroneous blowing of fuses. [Explanation of symbols]

[0108] 1 Current interruption system 2 Current interruption circuit 3 Microcomputer (control unit) 25A-1 First threshold output circuit 25B-1 Second threshold output circuit 25A-2 Low-pass filter (first low-pass filter) 25A-3 Low-pass filter (second low-pass filter) 25B-2 Low-pass filter (third low-pass filter) 25B-3 Low-pass filter (4th low-pass filter) 29 Failure determination circuit 231 IPD (first switch) 232 IPD (second switch) 241 Current sensor (first current sensor) 242 Current sensor (second current sensor) 246 PCB 251 Overcurrent judgment circuit (first overcurrent judgment circuit) 252 Overcurrent judgment circuit (second overcurrent judgment circuit) 281 Discharge side dummy voltage output circuit (dummy voltage output circuit) 282 Charging side dummy voltage output circuit (dummy voltage output circuit) CP11 Comparator (first comparator) CP12 Comparator (second comparator) D1 Diode R32 Resistor (second resistor) R33 resistor (3rd resistor) Rp resistance (1st resistance) SW3 switch (third switch) SW4 switch (4th switch)

Claims

1. a first switch and a second switch that are included in the ignition type fuse and are provided on both sides of a first resistor that burns out due to heat at the time of ignition, and that allow current to flow through the first resistor when both switches are turned on; a first current sensor and a second current sensor for detecting a current in a current path in which the ignition-type fuse is provided; a first overcurrent determination circuit that determines an overcurrent based on an output of the first current sensor; a second overcurrent determination circuit that determines an overcurrent based on an output of the second current sensor, the first switch is turned on based on a determination result of the first overcurrent determination circuit, the second switch is turned on based on a determination result of the second overcurrent determination circuit; Current interruption circuit.

2. 2. The current interruption circuit according to claim 1, a failure determination circuit that determines a failure of the first current sensor and the second current sensor based on an output difference between the first current sensor and the second current sensor; the first switch and the second switch are not turned on while the failure determination circuit determines a failure; Current interruption circuit.

3. 2. The current interruption circuit according to claim 1, the first switch, the second switch, the first overcurrent determination circuit, and the second overcurrent determination circuit are mounted on a substrate on which the first current sensor and the second current sensor are mounted; Current interruption circuit.

4. 2. The current interruption circuit according to claim 1, an output of the first current sensor increases in response to an increase in the current flowing through the current path; an output of the second current sensor decreases in response to an increase in the current flowing through the current path; Current interruption circuit.

5. 2. The current interruption circuit according to claim 1, The first overcurrent determination circuit and the second overcurrent determination circuit each include: a first threshold output circuit that outputs a first threshold; a first comparator that compares the first threshold value with the output of the first current sensor or the second current sensor; a second threshold output circuit that outputs a second threshold that is smaller than the first threshold; a second comparator that compares the second threshold value with the output of the first current sensor or the second current sensor; a first low-pass filter provided between the first threshold output circuit and the first comparator; a second low-pass filter provided between the first current sensor or the second current sensor and the first comparator; a third low-pass filter provided between the second threshold output circuit and the second comparator; a fourth low-pass filter provided between the first current sensor or the second current sensor and the second comparator, The capacitance of the first low-pass filter is set to be larger than the capacitance of the second low-pass filter, The capacitance of the fourth low-pass filter is set to be larger than the capacitance of the third low-pass filter. Current interruption circuit.

6. 2. The current interruption circuit according to claim 1, a second resistor and a diode connected in series between a first power supply voltage and a connection point of the first resistor and the first switch; a third resistor connected between a second power supply voltage and a connection point of the first resistor and the second switch; a dummy voltage output circuit that outputs a dummy voltage corresponding to an overcurrent; a third switch that switches an input to the first overcurrent determination circuit between the output of the first current sensor and the dummy voltage output by the dummy voltage output circuit; a fourth switch that switches an input to the second overcurrent determination circuit between the output of the second current sensor and the dummy voltage output by the dummy voltage output circuit, Current interruption circuit.

7. The current interruption circuit according to claim 6; a control unit that determines a fault based on a voltage between the second resistor and the first resistor or a voltage between the third resistor and the first resistor when the third switch is switched to the first current sensor side and the fourth switch is switched to the second current sensor side, when the third switch is switched to the dummy voltage output circuit side and the fourth switch is switched to the second current sensor side, and when the third switch is switched to the first current sensor side and the fourth switch is switched to the dummy voltage output circuit side, Current interruption system.

8. The current interruption circuit according to claim 1; a control unit that turns on an active signal, the first switch and the second switch are not turned on while the active signal is off; Current interruption system.

Images