Wire breakage detection circuit for vehicle

Abstract

When the first electrical path (91) is interrupted, current flows to the diode (20). The switch (11) remains open when current does not flow to the diode (20) and switches to the closed state in response to current flowing to the diode (20). When the switch (11) is open, the power supply voltage is input from the first power circuit (12) to the first input terminal (10A). When the switch (11) is closed, the voltage of the second ground connection (15) is input to the first input terminal (10A). When the second electrical path (92) is not interrupted, the second conductive path (18) is short-circuited to the vehicle body (90) via the second ground connection (15), and the voltage of the vehicle body (90) is input to the second input terminal (10B). When the second electrical path (92) is interrupted, the power supply voltage is input from the second power circuit (13) to the second input terminal (10B).

Description

Technical Field

[0001] This disclosure relates to a vehicle-mounted open circuit detection circuit. Background Technology

[0002] Patent Document 1 discloses a wire breakage detection circuit. This circuit includes a control unit, a first external connection terminal, a second external connection terminal, and a transistor. The control unit has a ground connection terminal and an input terminal. The first external connection terminal is connected to a control-side grounding line, which is a conductive path connected to the ground connection terminal, and can be connected to an external ground. The second external connection terminal is connected to a power-side grounding line, which is a conductive path with a current greater than that of the control-side grounding line, and can be connected to an external ground. The transistor restricts the direction of power in a first bypass line connected between the control-side grounding line and the power-side grounding line to one direction, and outputs a detection signal corresponding to the power passing through the first bypass line to the input terminal. With this configuration, when power passes through the first bypass line, a detection signal corresponding to the power is output from the transistor to the input terminal of the control unit. Therefore, the control unit can detect wire breaks, etc., by using the detection signal input from the input terminal.

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 2017-195489 Summary of the Invention

[0006] The problem that the invention aims to solve

[0007] In the configuration of Patent Document 1, it is possible to detect a break in the wire connecting the first external connection terminal to the external ground. In recent years, it has also been desirable to detect a break in the wire connecting the second external connection terminal to the external ground.

[0008] The purpose of this disclosure is to provide a technique capable of detecting a break in either of two electrical paths connected to a vehicle body.

[0009] Methods for solving problems

[0010] The vehicle-mounted open circuit detection circuit disclosed herein includes: The control circuit has a first input terminal, a second input terminal, and a ground connection terminal; The first grounding connection part is electrically connected to the vehicle body; The first conductive path is electrically connected to the first grounding connection part; The reference conductive circuit electrically connects the grounding connection terminal to the first conductive circuit via itself; The second grounding connection is electrically connected to the vehicle body; The second conductive path is electrically connected to the second grounding connection portion; and A diode is disposed between the first conductive path and the second conductive path. The diode allows current to flow from the first conductive path side to the second conductive path side, and prevents current from flowing from the second conductive path side to the first conductive path side. When the first electrical path between the first grounding connection and the vehicle body is not interrupted, current flows from the reference conductive path to the second grounding connection without passing through the diode. When the first electrical path is interrupted, current flows through the diode from the reference conductive path to the second ground connection. The vehicle-mounted open circuit also features: The first power circuit is supplied with a power voltage; and The switch has a first terminal, a second terminal, and a third terminal. The first terminal is electrically connected to the first power circuit and the first input terminal. The second terminal is electrically connected to the second grounding connection via the second conductive path. The third terminal is electrically connected to the first conductive circuit. The switch maintains an open state, preventing current from flowing from the first terminal to the second terminal, when no current flows to the diode. In response to current flowing to the diode, it supplies current to the third terminal, switching to an on state, allowing current to flow from the first terminal to the second terminal. When the switch is in the open state, the power supply voltage is input from the first power circuit to the first input terminal. When the switch is in the ON state, the voltage of the second grounding connection is input to the first input terminal. The vehicle-mounted open circuit also features: The second power circuit is supplied with the power voltage; and The pull-up resistor is electrically connected to the second power circuit. The second conductive path is electrically connected to the second input terminal, short-circuited to the second ground connection, and electrically connected to the second power path via the pull-up resistor. With the second electrical path between the second grounding connection and the vehicle body not interrupted, the second conductive path is short-circuited to the vehicle body via the second grounding connection, and the voltage of the vehicle body is input to the second input terminal. When the second electrical path is disconnected, the power supply voltage is input from the second power path to the second input terminal.

[0011] Invention Effects

[0012] The technology disclosed herein is capable of detecting a break in either of two electrical paths connected to the vehicle body. Attached Figure Description

[0013] Figure 1 This is a circuit diagram of the vehicle-mounted open circuit detection circuit according to the first embodiment.

[0014] Figure 2 This is an explanatory diagram showing the flow of current when the first electrical path is broken.

[0015] Figure 3 This is a conceptual diagram illustrating the situation where the power supply voltage of the second electrical circuit is input to the second input terminal when the second electrical path is disconnected.

[0016] Figure 4 This is an explanatory diagram showing the voltage input to the first and second input terminals in their respective states.

[0017] Figure 5 This is a circuit diagram of the vehicle-mounted open circuit detection circuit according to the second embodiment.

[0018] Figure 6 This is a circuit diagram of the vehicle-mounted open circuit detection circuit according to the third embodiment. Detailed Implementation

[0019] [Description of embodiments of this disclosure]

[0020] The following are examples and illustrations of the embodiments involved in this disclosure.

[0021] [1] A vehicle-mounted open circuit detection circuit, comprising: The control circuit has a first input terminal, a second input terminal, and a ground connection terminal; The first grounding connection part is electrically connected to the vehicle body; The first conductive path is electrically connected to the first grounding connection part; The reference conductive circuit electrically connects the grounding connection terminal to the first conductive circuit via itself; The second grounding connection is electrically connected to the vehicle body; The second conductive path is electrically connected to the second grounding connection portion; and A diode is disposed between the first conductive path and the second conductive path. The diode allows current to flow from the first conductive path side to the second conductive path side, and prevents current from flowing from the second conductive path side to the first conductive path side. When the first electrical path between the first grounding connection and the vehicle body is not interrupted, current flows from the reference conductive path to the second grounding connection without passing through the diode. When the first electrical path is interrupted, current flows through the diode from the reference conductive path to the second ground connection. The vehicle-mounted open circuit also features: The first power circuit is supplied with a power voltage; and The switch has a first terminal, a second terminal, and a third terminal. The first terminal is electrically connected to the first power circuit and the first input terminal. The second terminal is electrically connected to the second grounding connection via the second conductive path. The third terminal is electrically connected to the first conductive circuit. The switch maintains an open state, preventing current from flowing from the first terminal to the second terminal, when no current flows to the diode. In response to current flowing to the diode, it supplies current to the third terminal, switching to an on state, allowing current to flow from the first terminal to the second terminal. When the switch is in the open state, the power supply voltage is input from the first power circuit to the first input terminal. When the switch is in the ON state, the voltage of the second grounding connection is input to the first input terminal. The vehicle-mounted open circuit also features: The second power circuit is supplied with the power voltage; and The pull-up resistor is electrically connected to the second power circuit. The second conductive path is electrically connected to the second input terminal, short-circuited to the second ground connection, and electrically connected to the second power path via the pull-up resistor. With the second electrical path between the second grounding connection and the vehicle body not interrupted, the second conductive path is short-circuited to the vehicle body via the second grounding connection, and the voltage of the vehicle body is input to the second input terminal. When the second electrical path is disconnected, the power supply voltage is input from the second power path to the second input terminal.

[0022] When the first electrical path is cut off, the above-mentioned vehicle-mounted open circuit can discharge the current from the reference conductive path to the vehicle body through the diode and the second grounding connection.

[0023] Furthermore, when the first electrical path is not disconnected, the switch remains open because current does not flow to the diode. Therefore, the power supply voltage is input from the first electrical path to the first input terminal. Additionally, when the second electrical path is not disconnected, the second electrical path is short-circuited to the vehicle body, so the vehicle body voltage (0V) is input to the second input terminal.

[0024] In this state, when the first electrical path is interrupted, current flows to the diode, and the switch is switched to the ON state. As a result, since the voltage of the second ground connection is input to the first input terminal, both the first and second input terminals are input with 0V.

[0025] Conversely, when the second electrical path is disconnected, the power supply voltage is input from the second electrical path to the second input terminal. As a result, the power supply voltage is input to both the first and second input terminals.

[0026] Thus, the combinations of voltages input to the first and second input terminals differ depending on whether the first and second electrical paths are not disconnected, whether only the first electrical path is disconnected, or whether only the second electrical path is disconnected. Therefore, the above-described vehicle-mounted open circuit detection circuit can detect both the disconnection of the first and second electrical paths via the control circuit.

[0027] [2] As described in [1], the vehicle-mounted open circuit detection circuit, wherein, The switch is an NPN bipolar transistor. The first terminal is a collector. The second terminal is the emitter. The third terminal is the base.

[0028] According to this configuration, by allowing a small amount of current to flow into the base, the NPN bipolar transistor switches to the ON state, thus making it easy to detect grounding floating caused by the first electrical path being cut off.

[0029] [3] The vehicle-mounted open circuit detection circuit as described in [1] or [2], wherein, The vehicle-mounted open circuit detection circuit further includes a component section, which is connected in series with respect to the diode between the first conductive path and the second conductive path. The element suppresses the current flowing through the diode, or cuts off the current flowing through the diode in the event of an overcurrent.

[0030] In the aforementioned vehicle-mounted open circuit detection circuit, there is a concern that overcurrent may flow through the diode when the first electrical path is interrupted and current flows to the diode. However, the aforementioned vehicle-mounted open circuit detection circuit can suppress the current flowing through the diode through the component section, or cut off the current flowing through the diode in the event of an overcurrent.

[0031] Therefore, the above-mentioned vehicle-mounted open circuit can suppress overcurrent flow even when the first electrical path is cut off.

[0032] [4] As described in [3], the vehicle-mounted open circuit detection circuit, wherein, The component is configured to include a fuse.

[0033] In the case where the first electrical path is interrupted and overcurrent flows through the diode, the aforementioned vehicle-mounted open circuit can interrupt the current flowing through the diode via a fuse. Furthermore, the fuse can also be implemented using a patterned fuse that intentionally forms a fine wiring pattern and then cuts it off.

[0034] [5] As described in [3], the vehicle-mounted open circuit detection circuit, wherein, The component section is configured to include a second diode.

[0035] Even if the first electrical path is cut off, the above-mentioned vehicle-mounted open circuit can suppress the current flowing through the second diode through the second diode.

[0036] [6] As described in [3], the vehicle-mounted open circuit detection circuit, wherein, The component section is composed of resistors.

[0037] Even if the first electrical path is cut off, the above-mentioned vehicle-mounted open circuit can suppress the current flowing through the diode through the resistor.

[0038] [Details of the embodiments disclosed herein]

[0039] 1. First Implementation Method

[0040] 1-1. Configuration of Vehicle-Mounted Disconnection Detection Circuit 1

[0041] Figure 1The vehicle-mounted open circuit detection circuit 1 of the first embodiment shown is a circuit mounted in a vehicle. The vehicle-mounted open circuit detection circuit 1 includes a control circuit 10, a switch 11, a first power circuit 12, a second power circuit 13, a first ground connection 14, a second ground connection 15, a reference conductive circuit 16, a first conductive circuit 17, a second conductive circuit 18, a pull-up resistor 19, a diode 20, a component section 21, and a substrate 22. The control circuit 10, switch 11, first power circuit 12, second power circuit 13, first ground connection 14, second ground connection 15, reference conductive circuit 16, first conductive circuit 17, second conductive circuit 18, pull-up resistor 19, diode 20, and component section 21 are disposed on the substrate 22.

[0042] The control circuit 10 is configured, for example, to include a microcomputer. The control circuit 10 has a first input terminal 10A, a second input terminal 10B, and a ground connection terminal 10C.

[0043] Switch 11 has a first terminal 11A, a second terminal 11B, and a third terminal 11C. When no current is supplied to the third terminal 11C, switch 11 remains in an open state, preventing current from flowing from the first terminal 11A to the second terminal 11B. When current is supplied to the third terminal 11C, switch 11 switches to an on state, allowing current to flow from the first terminal 11A to the second terminal 11B. Switch 11 is an NPN bipolar transistor. The first terminal 11A is the collector. The second terminal 11B is the emitter. The third terminal 11C is the base.

[0044] Power supply voltage VCC is applied to the first power circuit 12. Power supply voltage VCC is applied to the second power circuit 13. Power supply circuit 12 and power supply circuit 13 may or may not be connected to each other.

[0045] The first grounding connection 14 is electrically connected to the vehicle body 90 via the first electrical path 91. The second grounding connection 15 is electrically connected to the vehicle body 90 via the second electrical path 92.

[0046] The first input terminal 10A, the first power circuit 12, and the first terminal 11A are electrically connected to each other. A first resistor section 31 is provided between the first power circuit 12 and the first input terminal 10A and the first terminal 11A. The first resistor section 31 is composed of a resistor. The first input terminal 10A and the first terminal 11A are short-circuited. In this specification, a short circuit means an electrical connection without a resistor.

[0047] The second input terminal 10B, the second terminal 11B, and the second grounding connection 15 are electrically connected to each other. The second terminal 11B is electrically connected to the second grounding connection 15 via the second conductive path 18.

[0048] The reference conductive path 16 is electrically connected to the ground connection terminal 10C. The reference conductive path 16 connects the ground connection terminal 10C to the first conductive path 17 via itself.

[0049] The first conductive path 17 is electrically connected to the reference conductive path 16, the third terminal 11C, and the first ground connection 14. The first conductive path 17 is short-circuited with the first ground connection 14. The first conductive path 17 is short-circuited to the vehicle body 90 while the first electrical path 91 is not disconnected. A second resistor 32 is provided between the third terminal 11C and the first conductive path 17. The second resistor 32 is composed of a resistor.

[0050] The second conductive path 18 is electrically connected to the second input terminal 10B and the second ground connection 15. The second conductive path 18 is electrically connected to the second input terminal 10B via the third resistor 33. The second conductive path 18 is short-circuited with the second ground connection 15. The second conductive path 18 is short-circuited to the vehicle body 90 while the second electrical path 92 is not disconnected. The third resistor 33 is composed of a resistor. The pull-up resistor 19 is composed of a resistor. The pull-up resistor 19 electrically connects the second conductive path 18 and the second power path 13 via itself.

[0051] Diode 20 is disposed between the first conductive path 17 and the second conductive path 18. Diode 20 allows current to flow from the first conductive path 17 side to the second conductive path 18 side. Diode 20 prevents current from flowing from the second conductive path 18 side to the first conductive path 17 side.

[0052] The component section 21 is connected in series with respect to the diode 20 between the first conductive path 17 and the second conductive path 18. The component section 21 is configured to include a fuse 21A. The fuse 21A interrupts the current flowing through the diode 20 in the event of an overcurrent.

[0053] With the first electrical path 91 not disconnected, current flows from the reference conductive path 16 to the second ground connection 15 without passing through diode 20, and current is not supplied from the reference conductive path 16 to the third terminal 11C via the first conductive path 17. Therefore, switch 11 remains in the open state. When switch 11 is in the open state, the power supply voltage VCC is input from the first power circuit 12 to the first input terminal 10A.

[0054] If the first electrical path 91 is disconnected, a voltage floats due to the reference conductor 16, such as Figure 2 As shown, current flows through diode 20 from reference conductor 16 to second ground connection 15, and current is supplied from reference conductor 16 to third terminal 11C via first conductor 17. As a result, switch 11 is switched to the ON state. When switch 11 is in the ON state, voltage from second ground connection 15 is input to first input terminal 10A.

[0055] With the second electrical path 92 not disconnected, the second conductive path 18 is short-circuited to the vehicle body 90 via the second grounding connection 15. Therefore, the voltage of the vehicle body 90 is input to the second input terminal 10B.

[0056] In the event that the second electrical path 92 is disconnected, such as Figure 3 As shown, the power supply voltage VCC is input from the second power circuit 13 to the second input terminal 10B.

[0057] 1-2. Effects

[0058] As described above, when the first electrical path 91 is cut off, the vehicle-mounted open circuit 1 can discharge the current from the reference conductive path 16 to the vehicle body via the diode 20 and the second ground connection 15.

[0059] Furthermore, when the first electrical path 91 is not disconnected, since current does not flow to diode 20, switch 11 remains open. Therefore, the power supply voltage VCC is input from the first power circuit 12 to the first input terminal 10A. Additionally, when the second electrical path 92 is not disconnected, since the second conductive path 18 is short-circuited with the vehicle body 90, the voltage of the vehicle body 90, i.e., 0V, is input to the second input terminal 10B. In other words, when the first electrical path 91 and the second electrical path 92 are not disconnected, such as... Figure 4 As shown, the first input terminal 10A is supplied with the power supply voltage VCC, and the second input terminal 10B is supplied with 0V.

[0060] In this state, when the first electrical path 91 is disconnected, a voltage float is generated in the reference conductive path 16, current flows to the diode 20, and the switch 11 switches to the ON state. As a result, since the voltage of the second ground connection 15 is input to the first input terminal 10A, therefore... Figure 4 As shown, the first input terminal 10A and the second input terminal 10B are input with 0V.

[0061] Conversely, when the second electrical path 92 is disconnected, the power supply voltage VCC is input from the second power path 13 to the second input terminal 10B. As a result, as... Figure 4 As shown, the first input terminal 10A and the second input terminal 10B are supplied with the power supply voltage VCC.

[0062] Thus, the combinations of voltages input to the first input terminal 10A and the second input terminal 10B differ depending on whether the first electrical path 91 and the second electrical path 92 are not disconnected, whether only the first electrical path 91 is disconnected, or whether only the second electrical path 92 is disconnected. Therefore, the vehicle-mounted open circuit detection circuit 1 can detect both the disconnection of the first electrical path 91 and the disconnection of the second electrical path 92 through the control circuit 10.

[0063] Specifically, when the first input terminal 10 receives a power supply voltage VCC and the second input terminal 10B receives 0V, the control circuit 10 determines that neither the first electrical path 91 nor the second electrical path 92 is disconnected. When both the first input terminal 10A and the second input terminal 10B receive 0V, the control circuit 10 determines that only the first electrical path 91 is disconnected. When both the first input terminal 10A and the second input terminal 10B receive a power supply voltage VCC, the control circuit 10 determines that only the second electrical path 92 is disconnected.

[0064] Furthermore, switch 11 is an NPN bipolar transistor. Terminal 11A is the collector. Terminal 2 is the emitter. Terminal 3 is the base. With this configuration, the NPN bipolar transistor switches to the ON state when a small current flows into the base, thus making it easy to detect grounding faults caused by the first electrical path 91 being cut off.

[0065] Furthermore, in the vehicle-mounted open circuit detection circuit 1, there is a concern that overcurrent may flow through the diode 20 when the first electrical path 91 is interrupted and current flows to the diode 20. However, the vehicle-mounted open circuit detection circuit 1 can interrupt the current flowing through the diode 20 by means of the fuse 21A when the first electrical path 91 is interrupted and overcurrent flows through the diode 20.

[0066] 2. Second Implementation Method

[0067] In the second embodiment, the component section includes a second diode. Furthermore, in the second embodiment, the same reference numerals are used for configurations identical to those in the first embodiment, and detailed descriptions are omitted.

[0068] The vehicle-mounted disconnection detection circuit 201 of the second embodiment is as follows: Figure 5 As shown, a component section 221 is provided instead of a component section 21 in the first embodiment. The vehicle-mounted disconnection detection circuit 201 of the second embodiment is otherwise common to the vehicle-mounted disconnection detection circuit 1 of the first embodiment.

[0069] Component section 221 comprises a fuse 21A and a second diode 21B. The fuse 21A and the second diode 21B are connected in series with respect to diode 20. The second diode 21B allows current to flow from the first conductive path 17 side to the second conductive path 18 side. The second diode 21B prevents current from flowing from the second conductive path 18 side to the first conductive path 17 side. The second diode 21B may have the same or different performance characteristics as diode 20. For example, the forward voltage drop of the second diode 21B may be the same as or different from that of diode 20.

[0070] Even when the first electrical path 91 is interrupted, the on-board open circuit 201 can suppress the current flowing through the diode 20 via the second diode 21B. In other words, the on-board open circuit 201 can suppress the current flowing from the first conductive path 17 side to the second conductive path 18 side via the diode 20 and the second diode 21B. Furthermore, when the first electrical path 91 is interrupted and current flows through the diode 20, the on-board open circuit 201 can interrupt the current flowing through the diode 20 via the fuse 21A.

[0071] 3. Third Implementation Method

[0072] In the third embodiment, a configuration in which the component section includes a resistor is described. Furthermore, in the third embodiment, the same reference numerals are used for configurations identical to those in the first embodiment, and detailed descriptions are omitted.

[0073] The vehicle-mounted disconnection detection circuit 301 of the third embodiment is as follows: Figure 6 As shown, a component section 321 is provided instead of a component section 21 in the first embodiment. The vehicle-mounted disconnection detection circuit 301 of the third embodiment is otherwise common to the vehicle-mounted disconnection detection circuit 1 of the first embodiment.

[0074] The component section 321 is configured to include a resistor 21C. The resistor 21C is connected in series with respect to the diode 20 between the first conductive path 17 and the second conductive path 18.

[0075] The vehicle-mounted open circuit 301 can suppress the current flowing through the diode 20 even if the first electrical path 91 is cut off.

[0076] <Other Implementation Methods>

[0077] This disclosure is not limited to the embodiments described above and illustrated in the accompanying drawings. For example, the features of the embodiments described above or below can be combined in any way without contradiction. Furthermore, any feature of the embodiments described above or below may be omitted unless explicitly stated as essential. In addition, the embodiments described above can be modified as follows.

[0078] In the second embodiment described above, only one second diode 21B is provided. Conversely, a configuration with multiple second diodes 21B can also be used. These multiple second diodes 21B can be connected in series with respect to diode 20 between the first conductive path 17 and the second conductive path 18.

[0079] Furthermore, the embodiments disclosed herein are illustrative in all respects and are not restrictive. The scope of the invention is not limited to the embodiments disclosed herein, but is intended to include all modifications within the scope set forth in the claims or equivalent to the claims.

[0080] Explanation of reference numerals in the attached figures

[0081] 1... Vehicle-mounted open circuit

[0082] 10... Control Circuit

[0083] 10A... Input Terminal 1

[0084] 10B...Second Input Terminal

[0085] 10C...Grounding connection terminal

[0086] 11...Switch

[0087] 11A...Terminal 1

[0088] 11B...Terminal 2

[0089] 11C...Terminal 3

[0090] 12...First Electric Circuit

[0091] 13...Second Electric Circuit

[0092] 14...First grounding connection part

[0093] 15...Second Grounding Connection

[0094] 16...Reference Conductive Circuit

[0095] 17...First conductive path

[0096] 18...Second Conductive Circuit

[0097] 19...Pull-up resistor

[0098] 20... Diode

[0099] 21...Components Department

[0100] 21A...fuse

[0101] 21B...Second Diode

[0102] 21C... resistor

[0103] 22...Substrate

[0104] 31...First Resistor Section

[0105] 32...Second Resistor Section

[0106] 33...3rd Resistor Section

[0107] 90...body

[0108] 91...First Electrical Path

[0109] 92...Second Electrical Path

[0110] 201... Vehicle-mounted open circuit detection circuit

[0111] 221...Components Section

[0112] 301... Vehicle-mounted open circuit detection circuit

[0113] 321...Components Section

[0114] VCC...power supply voltage

Claims

1. A vehicle-mounted open circuit detection circuit, comprising: The control circuit has a first input terminal, a second input terminal, and a ground connection terminal; The first grounding connection part is electrically connected to the vehicle body; The first conductive path is electrically connected to the first grounding connection part; The reference conductive circuit electrically connects the grounding connection terminal to the first conductive circuit via itself; The second grounding connection is electrically connected to the vehicle body; The second conductive path is electrically connected to the second grounding connection portion; and A diode is disposed between the first conductive path and the second conductive path. The diode allows current to flow from the first conductive path side to the second conductive path side, and prevents current from flowing from the second conductive path side to the first conductive path side. When the first electrical path between the first grounding connection and the vehicle body is not interrupted, current flows from the reference conductive path to the second grounding connection without passing through the diode. When the first electrical path is interrupted, current flows through the diode from the reference conductive path to the second ground connection. The vehicle-mounted open circuit also features: The first power circuit is supplied with a power voltage; and The switch has a first terminal, a second terminal, and a third terminal. The first terminal is electrically connected to the first power circuit and the first input terminal. The second terminal is electrically connected to the second grounding connection via the second conductive path. The third terminal is electrically connected to the first conductive circuit. The switch maintains an open state, preventing current from flowing from the first terminal to the second terminal, when no current flows to the diode. In response to current flowing to the diode, it supplies current to the third terminal, switching to an on state, allowing current to flow from the first terminal to the second terminal. When the switch is in the open state, the power supply voltage is input from the first power circuit to the first input terminal. When the switch is in the ON state, the voltage of the second grounding connection is input to the first input terminal. The vehicle-mounted open circuit also features: The second power circuit is supplied with the power voltage; and The pull-up resistor is electrically connected to the second power circuit. The second conductive path is electrically connected to the second input terminal, short-circuited to the second ground connection, and electrically connected to the second power path via the pull-up resistor. With the second electrical path between the second grounding connection and the vehicle body not interrupted, the second conductive path is short-circuited to the vehicle body via the second grounding connection, and the voltage of the vehicle body is input to the second input terminal. When the second electrical path is disconnected, the power supply voltage is input from the second power path to the second input terminal.

2. The vehicle-mounted open circuit detection circuit as described in claim 1, wherein, The switch is an NPN bipolar transistor. The first terminal is a collector. The second terminal is the emitter. The third terminal is the base.

3. The vehicle-mounted open circuit detection circuit as described in claim 1 or 2, wherein, The vehicle-mounted open circuit detection circuit further includes a component section, which is connected in series with respect to the diode between the first conductive path and the second conductive path. The element suppresses the current flowing through the diode, or cuts off the current flowing through the diode in the event of an overcurrent.

4. The vehicle-mounted open circuit detection circuit as described in claim 3, wherein, The component is configured to include a fuse.

5. The vehicle-mounted open circuit detection circuit as described in claim 3, wherein, The component section is configured to include a second diode.

6. The vehicle-mounted open circuit detection circuit as described in claim 3, wherein, The component section is composed of resistors.

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