JP7403073B2 - Power cutoff device - Google Patents

Description

The present disclosure relates to a power cutoff device used in various electrical devices.

A conventional power cutoff device will be described below. Conventional power cutoff devices detect and compare the voltage across a switch installed between a power source and a load when the switch is instructed to open. , and was conducting judgments regarding fusion failures.

Note that, as prior art document information related to the invention of this application, for example, Patent Document 1 is known.

Japanese Patent Application Publication No. 2006-216516

However, since conventional power cutoff devices detect the voltage across the switch, it is necessary to perform voltage detection at two locations in one switch, and when the power supply voltage is high, In this case, the circuit that performs voltage detection needs to have high insulation performance.

As a result, the circuit configuration of the power cutoff device becomes complicated or the power cutoff device becomes larger.

Therefore, an object of the present disclosure is to easily perform failure detection in a power cutoff device with a small circuit configuration.

In order to achieve this object, the present disclosure provides a positive potential first end, a positive potential second end connected to the positive potential first end by a positive potential transmission path, a negative potential first end, and a positive potential second end connected to the positive potential first end. a negative potential second end connected to the negative potential first end by a negative potential transmission path; a positive potential switch provided on the positive potential transmission path; and a negative potential switch provided on the negative potential transmission path. , connected to a positive potential connection point where the positive potential switch and the positive potential second terminal are connected, and a negative potential connection point where the negative potential switch and the negative potential second terminal are connected. a failure detection circuit; a control circuit that controls opening and closing of the positive potential switch; opening and closing of the negative potential switch; and an operation of the failure detection circuit; a high potential resistor provided with a second end; and a high potential resistor connected to a third end and a fourth end via a DC resistor to supply power from a reference potential end to the third end and the fourth end. and a low potential resistor provided with a fifth end and a sixth end, the first end is connected to the positive potential connection point, and the second end is connected to the reference potential supply circuit. The fifth end is connected to the fourth end, the negative potential connection point is connected to the sixth end, and the control circuit connects the positive potential switch and the negative potential switch. and an instruction to cause the reference potential supply circuit to supply power from the reference potential terminal to the third terminal and the fourth terminal, and to control the potential of the third terminal and the fourth terminal. is detected, and when the potentials of the third end and the fourth end are the same potential as the reference potential, the positive potential switch and the negative potential switch respond to an instruction from the control unit to open the switch. When it is determined that it is possible to react normally to the third end and the fourth end and the potentials at the third end and the fourth end are different from the reference potential, the values of the potentials at the third end and the fourth end The present invention is characterized by having a determination mode in which it is determined that the positive potential switch or the negative potential switch is in a failure state depending on the condition.

According to the present disclosure, the states of the positive potential switch and the negative potential switch can be determined based on the output voltages from the failure detection circuits connected to the positive potential switch and the negative potential switch. The failure detection circuit does not need to detect the potential difference between the positive potential switch and the negative potential switch, but only needs to be able to detect one potential in the positive potential switch and the negative potential switch. Therefore, the control circuit can easily detect whether the positive potential switch and the negative potential switch react normally or are in a failure state with a small number of detection points and a small circuit configuration. It is possible to easily determine with a simple circuit configuration whether the positive potential switch and the negative potential switch can normally respond to an instruction from the control unit to open the switch. be.

A circuit block diagram showing the configuration of a power cutoff device in an embodiment of the present disclosure Vehicle circuit block diagram showing the configuration of a vehicle equipped with a power cutoff device according to an embodiment of the present disclosure Normality determination connection diagram of a positive potential switch of a power cutoff device in an embodiment of the present disclosure Normality determination connection diagram of a negative potential switch of a power cutoff device in an embodiment of the present disclosure Abnormality determination connection diagram of a positive potential switch of a power cutoff device in an embodiment of the present disclosure Abnormality determination connection diagram of a negative potential switch of a power cutoff device in an embodiment of the present disclosure Preliminary judgment connection diagram of a negative potential switch of a power cutoff device in an embodiment of the present disclosure

Embodiments of the present disclosure will be described below with reference to the drawings.

(Embodiment)
FIG. 1 is a circuit block diagram showing the configuration of a power cutoff device in an embodiment of the present disclosure. The power cutoff device 1 includes a positive potential first end 2, a positive potential transmission path 3, a positive potential second end 4, a negative potential first end 5, a negative potential transmission path 6, a negative potential second end 7, and a positive potential switch. 8, a negative potential switch 9, a failure detection circuit 10, and a control circuit 11.

The positive potential second end 4 is connected to the positive potential first end 2 via the positive potential transmission line 3 . The negative potential second end 7 is connected to the negative potential first end 5 by a negative potential transmission path 6 . The positive potential switch 8 is provided on the positive potential transmission line 3. The negative potential switch 9 is provided in the negative potential transmission line 6. The failure detection circuit 10 is connected to a positive potential connection point 12 and a negative potential connection point 13. The positive potential connection point 12 connects the positive potential switch 8 and the positive potential second end 4 . Negative potential connection point 13 connects negative potential switch 9 and negative potential second end 7 . The control circuit 11 controls the opening and closing of the positive potential switch 8, the opening and closing of the negative potential switch 9, and the operation of the failure detection circuit 10.

The failure detection circuit 10 includes a high potential resistor 14, a DC resistor 15, a reference potential terminal 16, a reference potential supply circuit 17, and a low potential resistor 18. High potential resistor 14 has a first end 14A and a second end 14B. The reference potential supply circuit 17 is connected to the third end 19 via a DC resistor 15. Further, the reference potential supply circuit 17 is connected to the fourth terminal 20 via a DC resistor 15. Furthermore, the reference potential supply circuit 17 is capable of supplying a reference potential from the reference potential end 16 to the third end 19 or the fourth end 20. The low potential resistor 18 has a fifth end 18A and a sixth end 18B.

The first end 14A is connected to the positive potential connection point 12, the third end 19 is connected to the second end 14B, the fifth end 18A is connected to the fourth end 20, and the sixth end 18B is connected to the negative potential. Point 13 is connected.

The control circuit 11 is capable of executing the following determination mode for determining whether or not the positive potential switch 8 and the negative potential switch 9 are in a failure state.

When the control circuit 11 makes a determination regarding the positive potential switch 8 and the negative potential switch 9, the control circuit 11 issues an instruction to open the positive potential switch 8 and the negative potential switch 9, and a reference potential supply circuit. 17 to supply power from the reference potential terminal 16 to the third terminal 19 and the fourth terminal 20. The control circuit 11 then detects the potentials at the third end 19 and the fourth end 20. At this time, if the potential detected at the third terminal 19 and the fourth terminal 20 is the same potential as the reference potential supplied from the reference potential terminal 16, the positive potential switch 8 and the negative potential switch 9 are connected to the control circuit. The control circuit 11 determines that it is possible to normally respond to the open state instruction from the control circuit 11.

On the other hand, when the potentials detected at the third terminal 19 and the fourth terminal 20 are not the same potential as the reference potential supplied from the reference potential terminal 16, the potentials at the third terminal 19 and the fourth terminal 20 are The control circuit 11 determines that the positive potential switch 8 or the negative potential switch 9 is in a failure state in which it cannot normally respond to the open state instruction from the control circuit 11. In other words, when the positive potential switch 8 or the negative potential switch 9 cannot respond normally to an open state instruction and is in the connected state, the potential detected at the third terminal 19 and the fourth terminal 20 is high. It differs depending on the voltage division state of the potential resistance 14, the DC resistance 15, and the reference potential end 16. Therefore, it can be determined that either the positive potential switch 8 or the negative potential switch 9 is in a failure state.

With the above configuration and operation, in the power interrupting device 1, the control circuit 11 detects a failure connected to the positive potential switch 8 and the negative potential switch 9, regarding the states of the positive potential switch 8 and the negative potential switch 9. This can be determined by the output voltage from the circuit 10. The failure detection circuit 10 does not need to detect the potential difference between the positive potential switch 8 and the negative potential switch 9, and only needs to be able to detect the potential of one of the positive potential switch 8 and the negative potential switch 9. Therefore, the control circuit 11 uses a small number of detection points to determine whether the positive potential switch 8 and the negative potential switch 9 respond normally to instructions from the control circuit 11 or are in a failure state. configuration can be easily detected.

The configuration and operation of the power cutoff device 1 will be explained in detail below using the vehicle circuit block diagram shown in FIG. 2 showing the configuration of a vehicle equipped with the power cutoff device according to the embodiment of the present disclosure. In particular, an example will be described in which the power cutoff device 1 is used in a vehicle body 23 of a vehicle 22 that is propelled and driven by electric power stored in a storage battery 21.

The power cutoff device 1 is arranged on a vehicle body 23 and connected to a storage battery 21 and a load 24. As mentioned above, the storage battery 21 is disposed in the vehicle body 23 and is mainly used for propelling the vehicle 22. A positive electrode 21P of the storage battery 21 is connected to the positive potential first end 2. The positive potential first terminal 2 may be used as a positive potential input terminal. A negative electrode 21N of the storage battery 21 is connected to the negative potential first end 5. The negative potential first terminal 5 may be used as a negative potential input terminal.

The load 24 is a device disposed in the vehicle 22 for driving and propulsion of the vehicle 22, and the load 24 includes a motor (not shown) and an inverter circuit (not shown) for driving the motor (not shown). Contains such as. End portion 24P and end portion 24N of load 24 are connected to positive potential second end 4 and negative potential second end 7. The positive potential second terminal 4 may be used as a positive potential output terminal. Further, the negative potential second terminal 7 may be used as a negative potential output terminal.

The positive potential second end 4 is connected to the positive potential first end 2 via the positive potential transmission path 3 . The negative potential second end 7 is connected to the negative potential first end 5 by a negative potential transmission line 6 . The positive potential switch 8 is provided on the positive potential transmission line 3. The negative potential switch 9 is provided in the negative potential transmission line 6. The failure detection circuit 10 is connected to a positive potential connection point 12 and a negative potential connection point 13. The positive potential connection point 12 connects the positive potential switch 8 and the positive potential second end 4 . Negative potential connection point 13 connects negative potential switch 9 and negative potential second end 7 . The control circuit 11 controls the opening and closing of the positive potential switch 8, the opening and closing of the negative potential switch 9, and the operation of the failure detection circuit 10.

The failure detection circuit 10 includes a high potential resistor 14, a first DC resistor 15A, a second DC resistor 15B, a reference potential end 16, a reference potential supply circuit 17, and a low potential resistor 18. High potential resistor 14 has a first end 14A and a second end 14B. The reference potential supply circuit 17 is connected to the third end 19 via a first DC resistor 15A. Further, the reference potential supply circuit 17 is connected to the fourth terminal 20 via a second DC resistor 15B. Further, the reference potential supply circuit 17 is capable of supplying power from the reference potential end 16 to the third end 19 or the fourth end 20, and more precisely, from the reference potential end 16 to the third end 19 or the fourth end 20. Switch the power supply route. The low potential resistor 18 has a fifth end 18A and a sixth end 18B.

The first end 14A is connected to the positive potential connection point 12, the third end 19 is connected to the second end 14B, the fifth end 18A is connected to the fourth end 20, and the sixth end 18B is connected to the negative potential. Point 13 is connected.

In other words, both ends of the series body of the first DC resistor 15A and the second DC resistor 15B are connected to the third end 19 on the first DC resistor 15A side and to the fourth end 20 on the second DC resistor 15B side. ing. In other words, the positive potential connection point 12 is connected to the negative potential connection point 13 via a series body composed of a high potential resistance 14, a first DC resistance 15A, a second DC resistance 15B, and a low potential resistance 18 in this order. has been done. A first connection point 16A between the first DC resistor 15A and the second DC resistor 15B is connected to the reference potential supply circuit 17.

The reference potential supply circuit 17 includes a third DC resistor 17A, a diode 17B, and a switch element 17C connected in parallel between the reference potential end 16 and the first connection point 16A. A reference power supply 25 is connected to the reference potential end 16, and a reference potential Vref is applied to the reference potential end 16.

Here, a P-channel MOSFET (metal oxide film field effect diode) may be used instead of the diode 17B and the switch element 17C. The diode 17B corresponds to a parasitic diode of a P-channel MOSFET. Further, a source terminal of a P-channel MOSFET is connected to the reference potential terminal 16. A drain terminal of a P-channel MOSFET is connected to the first connection point 16A. A control circuit 11 controls the gate terminal of the P-channel MOSFET to be connected or disconnected.

The control circuit 11 is capable of executing a determination mode for determining whether or not the positive potential switch 8 and the negative potential switch 9 are in a failure state. When the control circuit 11 makes individual determinations for the positive potential switch 8 or the negative potential switch 9, the switch element 17C enters a cutoff state at the gate terminal of the switch element 17C in which a P-channel MOSFET is used. Apply a voltage equal to or higher than a predetermined value. On the other hand, when the control circuit 11 does not individually judge the positive potential switch 8 or the negative potential switch 9, the voltage is set so that the switch element 17C is connected to the gate terminal of the switch element 17C. is not applied.

The procedure of determination in the determination mode by the control circuit 11 is shown below. It is preferable to determine whether or not the positive potential switch 8 and the negative potential switch 9 are in a failure state before the propulsion drive of the vehicle 22 starts or after the drive is stopped. In other words, it is preferable to carry out the process immediately after the starting switch 26 of the vehicle 22 is turned from off to on by the passenger and before the propulsion of the vehicle 22 starts. Alternatively, it may be carried out after the starting switch 26 of the vehicle 22 is turned from on to off. The control circuit 11 detects that the starting switch 26 is switched from off to on or from on to off.

In the determination mode for failure of the positive potential switch 8 and the negative potential switch 9, the control circuit 11 first instructs the positive potential switch 8 and the negative potential switch 9 to open. Furthermore, the control circuit 11 instructs to supply power from the reference potential terminal 16 to the first connection point via the third DC resistor 17A. In other words, the instruction for the control circuit 11 to supply power from the reference potential end 16 to the first connection point via the third DC resistor 17A is an instruction for the control circuit 11 to turn off the switch element 17C.

The control circuit 11 then detects the potentials at the third end 19 and the fourth end 20. At this time, if the potentials of the third terminal 19 and the fourth terminal 20 are the same value as the reference potential Vref applied from the reference power source 25, the positive potential switch 8 and the negative potential switch 9 are controlled by the control circuit 11. The control circuit 11 determines that the opening can be achieved by operating normally in response to the executed instruction.

At this time, the normality determination connection diagram of the positive potential switch of the power cutoff device in the embodiment of the present disclosure is shown in FIG. 3, and the normality determination connection diagram of the negative potential switch of the power cutoff device in the embodiment of the present disclosure is shown in FIG. As shown in the figure, the positive potential switch 8 and the negative potential switch 9 are in a disconnected state, and there is no closed circuit connected to the positive electrode 21P or the negative electrode 21N of the storage battery 21. Therefore, the reference potential Vref supplied from the reference power source 25 is detected as it is at the third end 19 via the reference potential end 16, the third DC resistor 17A, the first connection point 16A, and the first DC resistor 15A. be done. Similarly, the reference potential Vref supplied from the reference power supply 25 is detected as it is at the fourth terminal 20 via the reference potential terminal 16, the third DC resistor 17A, the first connection point 16A, and the second DC resistor 15B. be done.

Here, as an example, the reference potential Vref is set to 3V. Therefore, in the above determination, 3V is detected at the third end 19 and the fourth end 20. Here, it is sufficient that the reference potential Vref, the third end 19, and the fourth end 20 are substantially the same. Therefore, the values detected at the third end 19 and the fourth end 20 may be within a range where predetermined threshold values are provided above and below 3V. The control circuit 11 may simultaneously detect and compare the values of the reference potential end 16, the third end 19, and the fourth end 20. Alternatively, the control circuit 11 may store the value of the reference potential end 16 detected in advance, and then detect and compare the values at the third end 19 and the fourth end 20.

Further, here, an example is shown in which the control circuit 11 detects the values of both the third end 19 and the fourth end 20. However, when both the positive potential switch 8 and the negative potential switch 9 open normally, the third end 19 and the fourth end 20 are at the same potential. Therefore, the control circuit 11 detects the potential of either the third end 19 or the fourth end 20, and then compares the potential of the reference potential end 16 with the potential of the reference potential end 16. If the potential of either one of the fourth terminal 20 and the fourth end 20 is the same, it may be determined that both the positive potential switch 8 and the negative potential switch 9 open normally. Alternatively, the control circuit 11 determines that both the positive potential switch 8 and the negative potential switch 9 open normally when the potentials of the third terminal 19 and the fourth terminal 20 are the same. Good too.

Here, a case will be described in which the positive potential switch 8 or the negative potential switch 9 does not open normally. As shown in the abnormality determination connection diagram of the positive potential switch of the power cutoff device according to the embodiment of the present disclosure in FIG. First, when the closed state continues, the potential detected at the third end 19 has a value different from the reference potential Vref. A state in which the positive potential switch 8 continues to be closed even though it is instructed to open by the control circuit 11 means that the positive potential switch 8 has a contact (not shown) that can normally be disconnected. ) remain electrically connected due to fusion, etc.

At this time, from the positive electrode 21P of the storage battery 21, the positive potential first end 2, the short-circuited positive potential switch 8, the high potential resistor 14, the first DC resistor 15A, the first connection point 16A, the diode 17B, the reference potential end 16, it becomes a closed circuit up to the reference power source 25. Here, the voltage of the storage battery 21 is 150V, the resistance value of the high potential resistor 14 is 6.9MΩ, the resistance value of the first DC resistor 15A is 25.5KΩ, the forward voltage of the diode 17B is 0.4V, and the reference potential Vref is When set to 3V, the divided potential is outputted to the third terminal 19 as a first predetermined value of 3.94V, and is detected by the control circuit 11 as a value different from the reference potential Vref. Therefore, if the voltage detected at the third end 19 is 3.94V, or if thresholds are provided above and below 3.94V and the voltage is within the range of the voltage threshold detected at the third end 19, It may be determined that the positive potential switch 8 is in a fused state or a short-circuited state. Since the above constants are just examples, each constant may be set as appropriate.

Here, even if the positive potential switch 8 has a certain resistance value in an unstable fused state or a short circuit state, the high potential resistor 14 has a very large resistance value, so the third There is no significant difference in the voltage detected at end 19. Furthermore, when power is supplied from the storage battery 21 to the load 24, current also flows through the high potential resistor 14, the first DC resistor 15A, the first connection point 16A, the second DC resistor 15B, and the low potential resistor 18. Become. However, since the high potential resistor 14 and the low potential resistor 18, which will be described later, have very large resistance values, the flowing current can be ignored.

Further, as shown in the abnormality determination connection diagram of the negative potential switch of the power cutoff device according to the embodiment of the present disclosure in FIG. Nevertheless, if the closed state continues, the potential detected at the fourth end 20 will have a value different from the reference potential Vref. A state in which the negative potential switch 9 continues to be closed despite being instructed to open by the control circuit 11 is a state in which the negative potential switch 9 is connected to a contact (not shown) that can normally be disconnected. ) remain electrically connected due to fusion, etc.

At this time, a closed circuit is formed from the reference power source 25 to the third DC resistor 17A, the first connection point 16A, the second DC resistor 15B, the low potential resistor 18, and the negative electrode 21P of the storage battery 21. Here, the potential of the negative electrode 21N of the storage battery 21 is 0 V, the resistance value of the low potential resistor 18 is 6.9 MΩ, the resistance value of the second DC resistor 15B is 25.5 KΩ, the resistance value of the third DC resistor 17A is 10 MΩ, and the reference When the potential Vref is set to 3V, the divided potential is outputted to the fourth terminal 20 as a second predetermined value of 1.23V, and is detected by the control circuit 11 as a value different from the reference potential Vref. . Therefore, if the voltage detected at the fourth terminal 20 is 1.23V, or if thresholds are provided above and below 1.23V and the voltage is within the range of the voltage threshold detected at the fourth terminal 20, It may be determined that the negative potential switch 9 is in a fused state or a short-circuited state. As in the case described above, the above constants are just examples, so each constant may be set as appropriate.

Here, even if the negative potential switch 9 has a certain resistance value in a fused state or a short-circuited state, the low potential resistor 18 has a very large resistance value, so it is detected by the fourth terminal 20. The resulting voltage does not appear as a large difference from the above value.

As a result, in the power cutoff device 1, the control circuit 11 determines the status of the positive potential switch 8 and the negative potential switch 9, and the failure detection circuit 10 connected to the positive potential switch 8 and the negative potential switch 9. This can be easily determined based on the potential detected at two points, the third end 19 or the fourth end 20. The failure detection circuit 10 does not need to detect the potential difference between the positive potential switch 8 and the negative potential switch 9, and only needs to be able to detect the potential of one of the positive potential switch 8 and the negative potential switch 9. Therefore, the control circuit 11 uses a small number of detection points to determine whether the positive potential switch 8 and the negative potential switch 9 respond normally to instructions from the control circuit 11 or are in a failure state. configuration can be easily detected.

Further, the reference potential Vref, the potential at the third terminal 19 or the fourth terminal 20, which is detected and compared by the control circuit 11, is determined by the high potential resistor 14, which is a resistor used for voltage division, the first DC resistor 15A, and the first DC resistor 15A. By setting the constants of the two DC resistors 15B and the low potential resistor 18, they can be set to values that facilitate detection and comparison by the control circuit 11, and the accuracy of detection and comparison by the control circuit 11 can be improved.

Further, in order to improve detection accuracy, the determination mode is executed immediately after the start switch 26 of the vehicle 22 is turned from off to on by the passenger and before the propulsion drive of the vehicle 22 starts. Preliminary determination mode may be implemented before Alternatively, the preliminary determination mode may be implemented after the activation switch 26 of the vehicle 22 is turned from on to off and before the determination mode is implemented.

In the preliminary determination mode, as shown in the preliminary determination connection diagram of the negative potential switch of the power cutoff device according to the embodiment of the present disclosure in FIG. The instruction is given so that it is in the open state. Further, the control circuit 11 instructs to supply power directly from the reference potential terminal 16 to the first connection point 16A. In other words, the control circuit 11 instructs the switch element 17C to be in the connected state. The control circuit 11 then detects the potentials at the third end 19 and the fourth end 20.

At this time, when the positive potential switch 8 and the negative potential switch 9 open normally according to instructions from the control circuit 11, the reference potential Vref is output as is to the third terminal 19 and the fourth terminal 20. . In particular, at this time, the potential detected at the third terminal 19 and the fourth terminal 20 is less affected by the leakage current of the diode 17B because the switching element 17C is in the connected state, and the reference potential Vref is accurately reflected. It will be done. Therefore, the control circuit 11 may temporarily store the reference potential Vref detected in the preliminary determination mode, and use the reference potential Vref detected in the preliminary determination mode as a comparison standard during operation in the determination mode.

On the other hand, the positive potential switch 8 and the negative potential switch 9 cannot open normally as instructed by the control circuit 11, and both the positive potential switch 8 and the negative potential switch 9 are melted. When the terminal is in a closed state or a short-circuited state, the potential applied by the reference potential Vref and the storage battery 21 is divided, and a third predetermined value of 75 V is detected at the fourth end 20. Here again, the third predetermined value may be a value that has an upper and lower range. Thereby, when both the positive potential switch 8 and the negative potential switch 9 are in a fused state or a short-circuited state, a failure state can be easily detected. When both the positive potential switch 8 and the negative potential switch 9 are in a fused state or a short-circuited state, the control circuit 11 does not execute the determination mode. In addition, since the preliminary judgment mode is executed before the judgment mode, both the positive potential switch 8 and the negative potential switch 9 are not in a fused state or a short-circuit state in the judgment mode, and the judgment is made. The accuracy of determination in the mode can be improved.

In the above description, the control circuit 11 is illustrated and explained as a single circuit. However, the functional part for voltage detection, the functional part for controlling the switch, the functional part for opening and closing the switch, and the functional part for calculating and storing data may be arranged in a distributed manner. These may be collectively referred to as the control circuit 11.

INDUSTRIAL APPLICATION The power interruption device of this invention has the effect that failure detection can be easily implemented with a small circuit configuration, and is useful in various electrical devices.

1 Power interruption device 2 Positive potential first end 3 Positive potential transmission path 4 Positive potential second end 5 Negative potential first end 6 Negative potential transmission path 7 Negative potential second end 8 Positive potential switch 9 Negative potential switch 10 Failure Detection circuit 11 Control circuit 12 Positive potential connection point 13 Negative potential connection point 14 High potential resistance 14A First end 14B Second end 15 DC resistance 15A First DC resistance 15B Second DC resistance 16 Reference potential end 17 Reference potential supply circuit 17A Third DC resistance 18 Low potential resistance 18A 5th terminal 18B 6th terminal 19 3rd terminal 20 4th terminal 21 Storage battery 22 Vehicle 23 Vehicle body 24 Load 25 Reference power source 26 Starting switch

Claims (4)

a positive potential first end;
a positive potential second end connected to the positive potential first end by a positive potential transmission line;
a negative potential first end;
a negative potential second end connected to the negative potential first end by a negative potential transmission line;
a positive potential switch provided on the positive potential transmission path;
a negative potential switch provided in the negative potential transmission path;
A fault connected to a positive potential connection point where the positive potential switch and the positive potential second terminal are connected, and a negative potential connection point where the negative potential switch and the negative potential second terminal are connected. a detection circuit;
a control circuit that controls opening and closing of the positive potential switch, opening and closing of the negative potential switch, and operation of the failure detection circuit;
Equipped with
The failure detection circuit includes:
a high potential resistor provided with a first end and a second end, and a high potential resistor connected to a third end and a fourth end via a DC resistor and having a reference potential with respect to the third end and the fourth end. A reference potential supply circuit capable of supplying power from a reference potential end, and a low potential resistor provided with a fifth end and a sixth end,
The first end is connected to the positive potential connection point, the third end is connected to the second end, the fifth end is connected to the fourth end, and the negative potential connection point is connected to the sixth end. is connected,
The control circuit includes:
Instructing the positive potential switch and the negative potential switch to open, and instructing the reference potential supply circuit to supply power from the reference potential terminal to the third terminal and the fourth terminal, detecting potentials at the third end and the fourth end;
When the potentials of the third terminal and the fourth terminal are the same as the reference potential, the positive potential switch and the negative potential switch normally respond to an instruction from the control circuit to open the switch. It is determined that it is possible to react,
When the potentials at the third end and the fourth end are different from the reference potential, the positive potential switch or the negative potential switch is activated depending on the potential values at the third end and the fourth end. Determine that it is in a failure state,
Has a judgment mode,
Power cutoff device. The reference potential supply circuit is
a series body in which a first DC resistor and a second DC resistor are connected in series, connecting a third end and a fourth end;
A parallel body in which a third DC resistor, a rectifying element, and a switching element are connected in parallel, connecting a first connection point that is a connection point between the first DC resistance and the second DC resistance, and a reference potential terminal. and,
has
The rectifying element has a cathode connected to the reference potential terminal, and an anode connected to a connection point between the first DC resistor and the second DC resistor,
The control circuit includes:
Instructing to open both the positive potential switch and the negative potential switch, and instructing to supply power from the reference potential terminal to the first connection point via the third DC resistor, and detecting the potential between the third end and the fourth end;
When the potentials of the third terminal and the fourth terminal are the same as the reference potential, the positive potential switch and the negative potential switch are in a normal state in response to an instruction from the control circuit to open the switch. It is determined that it is possible to react to
When the potential at the third end is a first predetermined value, determining that the positive potential switch has a short circuit failure;
determining that the negative potential switch has a short circuit failure when the potential at the fourth end is a second predetermined value;
Has a judgment mode,
The power cutoff device according to claim 1. A preliminary determination mode is executed prior to the determination mode,
In the preliminary determination mode, the control circuit is capable of detecting that both the positive potential switch and the negative potential switch are in a failure state,
When the control circuit determines that both the positive potential switch and the negative potential switch are in a failure state, the control circuit does not execute the determination mode.
The power cutoff device according to claim 2. In the preliminary determination mode, the control circuit:
an instruction to cause the positive potential switch and the negative potential switch to open;
instructing the switch element to be in a connected state;
When the potential at the fourth end is a third predetermined value, determining that both the positive potential switch and the negative potential switch are in a failure state;
The power cutoff device according to claim 3.

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