Electrical equipment and in-vehicle systems

Abstract

To provide an electrical instrument which can prevent inflow of the excessive current via a lead wire and an on-vehicle system having the electrical instrument.SOLUTION: An electrical instrument 10 is mounted on a vehicle C. A ground terminal (first connection part) 31 is connected to a body E of the vehicle C. An instrument connector (second connection part) 32 is connected to a switch device (external device) 11. A connection switch 36 is connected between the ground terminal 31 and the apparatus connector 32. When the connection switch 36 is turned on, the current flows in the instrument connector 32, the connection switch 36 and the ground terminal 31 in this order. A switching circuit 33 switches the connection switch 36 from on to off when the voltage between the ground terminal 31 and the instrument connector 32 becomes equal to or greater than the prescribed voltage.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to electric devices and in-vehicle systems. [Background technology]

[0002] Patent Document 1 discloses an electrical device mounted on a vehicle. One end of a signal line and one end of a ground line are connected to the electrical device. The electrical device has a ground terminal that is grounded. In the electrical device, the ground terminal is connected to one end of the ground line. The electrical device outputs a signal, with the potential of the ground line as a reference potential, via the signal line. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2010-105411 A Summary of the Invention [Problem to be solved by the invention]

[0004] Regarding Patent Document 1, if a short circuit occurs in which the positive electrode of the vehicle battery is connected to the ground line, an overcurrent may flow from the ground line to the electrical device. If an overcurrent flows through the electrical device, components in the electrical device may break down.

[0005] The present disclosure has been made in consideration of the above circumstances, and its purpose is to provide an electrical device that can prevent the inflow of overcurrent through a conductor, and an in-vehicle system equipped with the electrical device. [Means for solving the problem]

[0006] An electrical device according to one embodiment of the present disclosure is an electrical device mounted on a vehicle, and includes a first connection part connected to a body of the vehicle, a second connection part connected to an external device, a switch connected between the first connection part and the second connection part, and a switching circuit that switches the switch on or off, wherein when the switch is on, current flows through the second connection part, the switch, and the first connection part in that order, and when the voltage between the first connection part and the second connection part becomes equal to or higher than a predetermined voltage, the switching circuit switches the switch from on to off.

[0007] An in-vehicle system according to one embodiment of the present disclosure is an in-vehicle system in which an electrical device outputs a voltage to a second electrical device, or the second electrical device outputs a voltage to the electrical device, the electrical device having a first connection part connected to a vehicle body, a second connection part connected to the second electrical device, a switch connected between the first connection part and the second connection part, and a switching circuit that switches the switch on or off, when the switch is on, current flows in the order of the second connection part, the switch, and the first connection part, and the switching circuit switches the switch from on to off when the voltage between the first connection part and the second connection part becomes equal to or higher than a predetermined voltage. Effect of the Invention

[0008] According to the above aspect, it is possible to prevent an overcurrent from flowing through the conductor. [Brief description of the drawings]

[0009] [Figure 1] 1 is a block diagram showing a configuration of a main part of an in-vehicle system according to a first embodiment. [Diagram 2] FIG. 2 is a plan view of an electrical device and a switch device. [Diagram 3] 4 is a timing chart for explaining the operation of a switching circuit. [Figure 4] FIG. 11 is a block diagram showing a configuration of a main part of an in-vehicle system according to a second embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] [Description of the embodiments of the present disclosure] First, the embodiments of the present disclosure will be listed and described. At least a part of the embodiments described below may be arbitrarily combined.

[0011] (1) An electrical device according to one embodiment of the present disclosure is an electrical device mounted on a vehicle, and includes a first connection part connected to a body of the vehicle, a second connection part connected to an external device, a switch connected between the first connection part and the second connection part, and a switching circuit that switches the switch on or off. When the switch is on, current flows through the second connection part, the switch, and the first connection part in that order, and when the voltage between the first connection part and the second connection part becomes equal to or higher than a predetermined voltage, the switching circuit switches the switch from on to off.

[0012] In the above embodiment, when a power short occurs in which the positive electrode of the DC power supply, the negative electrode of which is connected to the body, is connected to the conductor between the second connection part and the external device, the voltage between the first connection part and the second connection part becomes equal to or higher than a predetermined voltage, and the switch is switched from on to off, thereby preventing the inflow of an overcurrent through the conductor.

[0013] (2) An electric device according to an embodiment of the present disclosure includes an electronic component that outputs or detects a voltage with the potential of the first connection portion as a reference potential.

[0014] In the above aspect, the electronic component is, for example, a microcomputer, and outputs or detects a voltage based on the potential of the first connection portion.

[0015] (3) An electrical device according to one aspect of the present disclosure includes a substrate on which the switch and the switching circuit are disposed, the substrate being connected to the external device.

[0016] In the above embodiment, the substrate is connected to the outside by the conductor. device Therefore, there is a high possibility of a short circuit to the power supply via the conductor. There is a high need for a function to prevent overcurrent from flowing through the conductor.

[0017] (4) In an electrical device according to one embodiment of the present disclosure, the switch is switched from on to off when the voltage between the output terminal from which current is output and the control terminal becomes less than a threshold value, the switching circuit has a second switch connected between the output terminal and the control terminal of the switch, and the second switch is switched from off to on when the voltage between the first connection portion and the second connection portion becomes equal to or greater than the predetermined voltage.

[0018] In the above embodiment, when the voltage between the first connection part and the second connection part becomes equal to or higher than a predetermined voltage, the second switch is turned on. This causes the voltage between the output terminal and the control terminal of the switch to drop to 0 V, which is less than the threshold value. As a result, the switch is turned off.

[0019] (5) An in-vehicle system according to one embodiment of the present disclosure is an in-vehicle system in which an electrical device outputs a voltage to a second electrical device or the second electrical device outputs a voltage to the electrical device, the electrical device having a first connection part connected to a body of a vehicle, a second connection part connected to the second electrical device, a switch connected between the first connection part and the second connection part, and a switching circuit that switches the switch on or off, when the switch is on, current flows through the second connection part, the switch, and the first connection part in that order, and the switching circuit switches the switch from on to off when the voltage between the first connection part and the second connection part becomes equal to or higher than a predetermined voltage.

[0020] In the above embodiment, when a power short occurs in which the positive electrode of the DC power supply, the negative electrode of which is connected to the body, is connected to the conductor between the second connection part and the external device, the voltage between the first connection part and the second connection part becomes equal to or higher than a predetermined voltage, and the switch of the electric device is switched from on to off. As a result, an overcurrent is prevented from flowing into the electric device through the conductor.

[0021] (6) In an in-vehicle system according to one embodiment of the present disclosure, the electrical device has a substrate on which the switch and switching circuit are arranged, and the second electrical device has a second substrate, the substrate being connected to the second substrate.

[0022] In the above embodiment, the board is connected to the second board by a conductor. Therefore, there is a high possibility that a short circuit to the power supply will occur in the conductor. As a result, there is a high demand for a function to prevent an overcurrent from flowing in through the conductor in the electric device.

[0023] [Details of the embodiment of the present disclosure] Specific examples of in-vehicle systems according to embodiments of the present disclosure will be described below with reference to the drawings. Note that the present invention is not limited to these examples, but is defined by the claims, and is intended to include all modifications within the meaning and scope of the claims.

[0024] (Embodiment 1) <In-vehicle system configuration> FIG. 1 is a block diagram showing a main configuration of an in-vehicle system 1 in the first embodiment. The in-vehicle system 1 is mounted on a vehicle C. The vehicle C is further mounted with a DC power supply 20, a power switch 21, and a load 22. The in-vehicle system 1 has an electric device 10 and a switch device 11. The DC power supply 20 is, for example, a battery. The power switch 21 is switched on, for example, when an ignition power supply or an accessory power supply is switched on. In this configuration, the power switch 21 is switched off, when the ignition power supply or the accessory power supply is switched off.

[0025] The electrical device 10 has a power supply terminal 30, a ground terminal 31, and a device connector 32. The switch device 11 has an input terminal 40, an output terminal 41, a device connector 42, a power supply switch 43, and a drive circuit 44. The power supply switch 43 is an N-channel type field effect transistor (FET). When the power supply switch 43 is on, the resistance between the drain and the source is sufficiently small. Therefore, a current can flow through the drain and the source. When the power supply switch 43 is off, the resistance between the drain and the source is sufficiently large. Therefore, no current flows through the drain and the source. The drive circuit 44 switches the power supply switch 43 on or off.

[0026] The negative electrode of the DC power supply 20 is connected to the body E of the vehicle C. The body E is a conductor. The connection to the body E realizes grounding. The positive electrode of the DC power supply 20 is connected to one end of the power switch 21. The other end of the power switch 21 is detachably connected to the power terminal 30 of the electric device 10 and is detachably connected to the input terminal 40 of the switch device 11. The ground terminal 31 of the electric device 10 is connected to the body E. The ground terminal 31 functions as a first connection part. One end of the load 22 is detachably connected to the output terminal 41 of the switch device 11. The other end of the load 22 is connected to the body E. The device connector 32 of the electric device 10 is detachably connected to one end of the signal line F and the ground line G. The other ends of the signal line F and the ground line G are detachably connected to the device connector 42 of the switch device 11. The signal line F and the ground line G are conductors. The device connector 32 is connected to the device connector 42 by a signal line F and a ground line G. The switch device 11 functions as an external device and a second electric device. The device connector 32 functions as a second connection portion.

[0027] In the switch device 11, the drain and source of the power supply switch 43 are connected to the input terminal 40 and the output terminal 41, respectively. When the power switch 21 is on, a current flows from the positive electrode of the DC power supply 20 to the power switch 21, the electric device 10, the body E, and the negative electrode of the DC power supply 20 in this order. This supplies power to the electric device 10. While power is being supplied to the electric device 10, the electric device 10 operates. The electric device 10 instructs the drive circuit 44 of the switch device 11 to switch the power supply switch 43 on or off.

[0028] When the power switch 21 and the power supply switch 43 are on, a current flows from the positive electrode of the DC power supply 20 through the power switch 21, the input terminal 40, the power supply switch 43, the output terminal 41, the load 22, the body E, and the negative electrode of the DC power supply 20 in this order. This causes power to be supplied to the load 22. When the power switch 21 or the power supply switch 43 is off, the flow through the power supply switch 43 stops. As a result, power supply from the DC power supply 20 to the load 22 stops.

[0029] The load 22 is, for example, a lamp. While the DC power supply 20 supplies power to the load 22, the load 22 operates. When the power supply from the DC power supply 20 to the load 22 stops, the load 22 stops operating. The electric device 10 and the switch device 11 control the power supply from the DC power supply 20 to the load 22. When the power switch 21 is off, the power supply from the DC power supply 20 to the electric device 10 stops. In this case, the electric device 10 stops operating.

[0030] <Configuration of Electrical Device 10 and Switch Device 11> The electrical device 10 has a power supply terminal 30, a ground terminal 31, and a device connector 32, as well as a switching circuit 33, a regulator 34, a microcomputer (hereinafter referred to as a MCU) 35, and a connection switch 36. The switching circuit 33 has a circuit switch 50, a first circuit resistor 51, and a second circuit resistor 52. The connection switch 36 and the circuit switch 50 are NPN-type bipolar transistors.

[0031] The power supply terminal 30 is connected to one end of a first circuit resistor 51 of the switching circuit 33 and to the regulator 34. In the switching circuit 33, the other end of the first circuit resistor 51 is connected to the collector of a circuit switch 50. The circuit switch 50 functions as a second switch. The base of the circuit switch 50 is connected to one end of a second circuit resistor 52. A connection node between the collector of the circuit switch 50 and the first circuit resistor 51 is connected to the base of a connection switch 36. The emitter and collector of the connection switch 36 are connected to a ground terminal 31 and an equipment connector 32, respectively. The emitter of the circuit switch 50 is connected to a connection node between the emitter of the connection switch 36 and the ground terminal 31. The other end of the second circuit resistor 52 is connected to the ground terminal 31.

[0032] The regulator 34 is further connected to the ground terminal 31 and the microcomputer 35. The microcomputer 35 is further connected to the ground terminal 31 and the device connector 32. The connection node between the device connector 32 and the collector of the connection switch 36 is connected to the connection node between the base of the circuit switch 50 and the second circuit resistor 52.

[0033] In the switch device 11, the gate of the power supply switch 43 is connected to a drive circuit 44. The drive circuit 44 is further connected to a connection node between the input terminal 40 and the power supply switch 43, and to the device connector 42.

[0034] The regulator 34 and the first circuit resistor 51 are connected to the power switch 21 via the power terminal 30. The regulator 34, the microcomputer 35, the emitter of the connection switch 36, the emitter of the circuit switch 50, and the other end of the second circuit resistor 52 are connected to the body E via the ground terminal 31. The microcomputer 35 is connected to the signal line F via the device connector 32. The collector of the connection switch 36, the base of the circuit switch 50, and one end of the second circuit resistor 52 are connected to the ground line G via the device connector 32. The drive circuit 44 is connected to the signal line F and the ground line G, respectively, via the device connector 42. The drain of the power supply switch 43 and the drive circuit 44 are connected to the power switch 21 via the input terminal 40. The source of the power supply switch 43 is connected to the load 22 via the output terminal 41.

[0035] FIG. 2 is a plan view of the electric device 10 and the switch device 11. The electric device 10 and the switch device 11 each have an equipment board Bm and a device board Bs. The equipment board Bm and the device board Bs each have a rectangular plate shape. A regulator 34, a microcomputer 35, a connection switch 36, a circuit switch 50, a first circuit resistor 51, and a second circuit resistor 52 are arranged on the wide surface of the equipment board Bm. The regulator 34 and the microcomputer 35 are each, for example, an integrated circuit element. With respect to the plate, the wide surface is a surface different from the end surface. A power supply switch 43 and a drive circuit 44 are arranged on the wide surface of the device board Bs. The drive circuit 44 is, for example, an integrated circuit element.

[0036] The equipment board Bm and the device board Bs are connected by a signal line F. The equipment board Bm and the device board Bs are further connected by a ground line G. Note that in FIG. 2, the power supply terminal 30, the ground terminal 31, the equipment connector 32, the input terminal 40, the output terminal 41 and the device connector 42 are omitted from the illustration. The power supply terminal 30, the ground terminal 31 and the device connector 32 are disposed on the wide surface of the equipment board Bm. The input terminal 40, the output terminal 41 and the device connector 42 are disposed on the wide surface of the device board Bs. The device board Bs functions as a second board.

[0037] The operation of the electric device 10 and the switch device 11 will be described with reference to FIG. 1. Hereinafter, the voltage of the positive electrode of the DC power supply 20 with the potential of the negative electrode, i.e., the potential of the body E as the reference potential, will be referred to as the power supply voltage. Since the ground terminal 31 is connected to the body E, the power supply voltage is a positive voltage with the potential of the ground terminal 31 as the reference potential. When the power switch 21 is on, a current flows from the positive electrode of the DC power supply 20 through the power switch 21, the power supply terminal 30, the regulator 34, the ground terminal 31, the body E, and the negative electrode of the DC power supply 20 in this order. As a result, the power supply voltage of the DC power supply 20 is applied to the regulator 34, and power is supplied to the regulator 34. The regulator 34 operates while power is being supplied.

[0038] The regulator 34 steps down the power supply voltage to a constant target voltage. The regulator 34 applies the target voltage obtained by stepping down to the microcomputer 35. The target voltage is a voltage with the potential of the ground terminal 31 as a reference potential. The power supply voltage is, for example, 12 V. The target voltage is 3.3 V or 5.5 V. When the regulator 34 applies the target voltage to the microcomputer 35, a current flows from the positive electrode of the DC power supply 20 through the power switch 21, the power supply terminal 30, the regulator 34, the microcomputer 35, the ground terminal 31, the body E, and the negative electrode of the DC power supply 20 in this order, and power is supplied to the microcomputer 35. The microcomputer 35 operates while power is being supplied.

[0039] When the power switch 21 is switched off, the flow of current through the regulator 34 stops. As a result, the power supply from the DC power supply 20 to the regulator 34 stops. When the power supply from the DC power supply 20 to the regulator 34 stops, the regulator 34 stops operating. When the regulator 34 stops operating, the flow of current through the microcomputer 35 stops. As a result, the power supply from the DC power supply 20 to the microcomputer 35 stops. When the power supply from the DC power supply 20 to the microcomputer 35 stops, the microcomputer 35 stops operating.

[0040] While the power supplied to the drive circuit 44 of the switch device 11 is less than a predetermined power, the drive circuit 44 is not in operation. While the power supplied to the drive circuit 44 is equal to or greater than the predetermined power, the drive circuit 44 is in operation.

[0041] When the connection switch 36 and the circuit switch 50 are in the on state, the resistance between the collector and the emitter is sufficiently small. Therefore, current can flow through the collector and the emitter. When the connection switch 36 and the circuit switch 50 are in the off state, the resistance between the collector and the emitter is sufficiently large. Therefore, no current flows through the collector and the emitter. The switching circuit 33 switches the connection switch 36 on or off depending on the voltage of the ground line G with the potential of the ground terminal 31 as the reference potential.

[0042] When the power switch 21 is on and the connection switch 36 is on, a current flows from the positive electrode of the DC power supply 20 through the power switch 21, the input terminal 40, the drive circuit 44, the device connector 42, the ground wire G, the equipment connector 32, the connection switch 36, the ground terminal 31, the body E, and the negative electrode of the DC power supply 20 in this order. This current flow supplies a predetermined amount of power or more to the drive circuit 44. When the connection switch 36 is on, a current flows through the collector and emitter of the connection switch 36 in this order. Therefore, the collector of the connection switch 36 functions as an input end to which a current is input. The emitter of the connection switch 36 functions as an output end to which a current is output.

[0043] When the power switch 21 is on and the connection switch 36 is off, a current flows from the positive electrode of the DC power supply 20 through the power switch 21, the input terminal 40, the drive circuit 44, the device connector 42, the ground wire G, the equipment connector 32, the second circuit resistor 52, the ground terminal 31, the body E, and the negative electrode of the DC power supply 20 in this order. Since the current flows through the second circuit resistor 52, the power supplied to the drive circuit 44 is small. Therefore, as a result, the power supplied to the drive circuit 44 by the current flowing through the drive circuit 44 and the second circuit resistor 52 is less than the predetermined power.

[0044] Regarding the power supply switch 43, when the gate voltage with the source potential as the reference potential is equal to or higher than a certain voltage, the state of the power supply switch 43 is on. When the gate voltage with the source potential as the reference potential is less than the certain voltage, the state of the power supply switch 43 is off. The microcomputer 35 of the electric device 10 outputs a high-level voltage or a low-level voltage to the drive circuit 44 of the switch device 11 via the signal line F. The output voltage of the microcomputer 35 is a voltage with the potential of the ground terminal 31 as the reference potential. The microcomputer 35 functions as an electronic component.

[0045] The microcomputer 35 switches the output voltage to be output to the drive circuit 44 via the signal line F between a low-level voltage or a high-level voltage. The drive circuit 44 detects the voltage of the signal line F with the potential of the ground line G as a reference potential. When the connection switch 36 is on, the potential of the ground line G substantially coincides with the potential of the ground terminal 31, i.e., the ground potential. Therefore, the voltage of the signal line F detected by the drive circuit 44 is the output voltage of the microcomputer 35.

[0046] When the connection switch 36 is on and the microcomputer 35 switches the output voltage from a low-level voltage to a high-level voltage, the drive circuit 44 increases the gate voltage of the power supply switch 43, with the potential of the ground line G as the reference potential. As a result, in the power supply switch 43, the gate voltage, with the potential of the source as the reference potential, increases to a value equal to or higher than a certain voltage, and the power supply switch 43 is switched on.

[0047] In a similar case, when the microcomputer 35 switches the output voltage from a high-level voltage to a low-level voltage, the drive circuit 44 lowers the gate voltage of the power supply switch 43, which has the potential of the ground line G as its reference potential. As a result, the gate voltage of the power supply switch 43, which has the potential of the source as its reference potential, drops to a value less than a certain voltage, and the power supply switch 43 is switched off.

[0048] When the switching circuit 33 switches the connection switch 36 from on to off, the flow of current through the ground line G, the connection switch 36, and the ground terminal 31 stops.

[0049] For the connection switch 36, the state is on when the base voltage with respect to the emitter potential as the reference potential is equal to or greater than a certain threshold. The threshold is a positive value. When the base voltage with respect to the emitter potential as the reference potential is less than the threshold, the state is off. Thus, the connection switch 36 switches from on to off when the base voltage with respect to the emitter potential as the reference potential falls to a value less than the threshold. The base of the connection switch 36 functions as a control end.

[0050] For the circuit switch 50, when the base voltage with the emitter potential as the reference potential is equal to or greater than a certain reference voltage, the state is on. When the base voltage with the emitter potential as the reference potential is less than the reference voltage, the state is off. The reference voltage is a positive value. As described above, the emitter of the circuit switch 50 is connected to the ground terminal 31. The base of the circuit switch 50 is connected to the ground wire G. Therefore, for the circuit switch 50, the base voltage with the emitter potential as the reference potential is the voltage of the ground wire G with the ground terminal 31 potential as the reference potential. Therefore, the circuit switch 50 switches from off to on when the voltage of the ground wire G with the ground terminal 31 potential as the reference potential rises to a value equal to or greater than the reference voltage. The voltage of the ground wire G is equal to the voltage of the portion of the device connector 32 that is conductive to the ground wire G. Therefore, the voltage of the ground wire G corresponds to the voltage of the device connector 32.

[0051] FIG. 3 is a timing chart for explaining the operation of the switching circuit 33. With respect to the connection switch 36, the base voltage with the potential of the ground terminal 31 as the reference potential is described as the base voltage. FIG. 3 shows the transition of the base voltage and the voltage of the ground line G. The reference potential of the voltage of the ground line G is the potential of the ground terminal 31, that is, the potential of the body E. As described above, the voltage of the ground line G corresponds to the voltage of the device connector 32. FIG. 3 shows the transition of the states of the power switch 21, the circuit switch 50, and the connection switch 36. Vb is the power supply voltage of the DC power supply 20. Vth and Vr are the threshold and the reference voltage, respectively. As described above, when the ground terminal 31 is connected to the body E, the power supply voltage is a positive voltage with the potential of the ground terminal 31 as the reference potential.

[0052] As shown in Fig. 2, the ground wire G is disposed between the device board Bm and the equipment board Bs. Therefore, there is a possibility that the ground wire G may come into contact with a conductor connected to the positive electrode of the DC power supply 20. If the ground wire G comes into contact with the conductor, there is a possibility that the ground wire G may be connected to the positive electrode of the DC power supply 20. The phenomenon in which the ground wire G is connected to the positive electrode of the DC power supply 20 is called a power short. If a power short occurs to the ground wire G, the voltage of the ground wire G rises to the power supply voltage Vb.

[0053] When the power switch 21 is off, no current flows through the second circuit resistor 52. Therefore, the voltage of the ground line G is 0V. As shown in FIG. 3, when the voltage of the ground line G is 0V, the voltage of the ground line G is less than the reference voltage Vr. Therefore, while the voltage of the ground line G is 0V, the circuit switch 50 is off. When the power switch 21 and the circuit switch 50 are off, no current flows through the regulator 34 and the first circuit resistor 51. Therefore, the base voltage of the connection switch 36 is 0V, which is less than the threshold value Vth, and the connection switch 36 is off. When the power switch 21 is switched from off to on, the power supply voltage Vb is applied to one end of the first circuit resistor 51 through the power switch 21.

[0054] When the circuit switch 50 is off, almost no current flows through the first circuit resistor 51. Therefore, when the power switch 21 is switched from off to on, the base voltage of the connection switch 36 rises to the power supply voltage Vb. Because the threshold value Vth is equal to or lower than the power supply voltage Vb, when the base voltage of the connection switch 36 rises to the power supply voltage Vb, the connection switch 36 is switched from off to on. As described above, when the connection switch 36 is on, the potential of the ground line G substantially matches the potential of the ground terminal 31, i.e., the ground potential.

[0055] When a short circuit to the ground line G occurs, the voltage of the ground line G rises to the power supply voltage Vb. Since the power supply voltage Vb is equal to or higher than the reference voltage Vr, when the voltage of the ground line G rises to the power supply voltage Vb, the circuit switch 50 switches from off to on. When the circuit switch 50 switches on, the base voltage of the connection switch 36 drops to 0 V, which is less than the threshold value Vth. This causes the connection switch 36 to switch from on to off.

[0056] When the connection switch 36 is off, no current flows through the ground wire G and the connection switch 36. The current flows in the order of the ground wire G, the device connector 32, the second circuit resistor 52, and the ground terminal 31. Since the current flows through the second circuit resistor 52, the current flowing into the electric device 10 through the ground wire G is small. An overcurrent is prevented from flowing into the electric device 10 through the ground wire G. The resistance value of the second circuit resistor 52 is sufficiently larger than the resistance value between the collector and the emitter of the connection switch 36 that is on.

[0057] While the voltage of the ground line G is equal to or higher than the reference voltage Vr, the connection switch 36 is maintained off. When the short-to-power condition of the ground line G is eliminated while the power switch 21 is on, a current flows from the positive electrode of the DC power supply 20 through the power switch 21, the input terminal 40, the drive circuit 44, the device connector 42, the ground line G, the equipment connector 32, the second circuit resistor 52, the ground terminal 31, the body E, and the negative electrode of the DC power supply 20 in this order. This causes the voltage of the ground line G to drop to a voltage lower than the reference voltage Vr. As a result, the circuit switch 50 switches from on to off.

[0058] When the circuit switch 50 is switched off, the base voltage of the connection switch 36 rises to the power supply voltage Vb, and the connection switch 36 is switched from off to on. When the connection switch 36 is switched on, the voltage of the ground wire G drops to 0 V. The resistance value of the second circuit resistor 52 is a value at which the voltage of the ground wire G drops to a voltage less than the reference voltage Vr when a current flows from the positive electrode of the DC power supply 20 through the power switch 21, the input terminal 40, the drive circuit 44, the device connector 42, the ground wire G, the equipment connector 32, the second circuit resistor 52, the ground terminal 31, the body E, and the negative electrode of the DC power supply 20 in this order.

[0059] When the power switch 21 is switched off, no current flows through the regulator 34 and the first circuit resistor 51. Therefore, the base voltage of the connection switch 36 drops to 0 V, which is less than the threshold value Vth, and the connection switch 36 is switched off. When a short-to-power occurs on the ground line G, the voltage of the ground line G is the power supply voltage Vb regardless of the state of the power switch 21. Therefore, while a short-to-power occurs on the ground line G, the circuit switch 50 and the connection switch 36 are maintained on and off, respectively.

[0060] <Effects of 10 Electrical Devices> As described above, the switching circuit 33 switches the connection switch 36 from on to off when the voltage of the ground line G, which has the potential of the ground terminal 31 as a reference potential, rises to a value equal to or higher than the reference voltage. Therefore, when a short circuit to the ground line G occurs, the connection switch 36 switches from on to off, preventing an overcurrent from flowing into the electric device 10 via the ground line G. Since the device board Bm is connected to the device board Bs of the switch device 11 by the ground line G, there is a high possibility that a short circuit to the ground line G will occur. For this reason, there is a high need for a function to prevent an overcurrent from flowing in via the ground line G.

[0061] The switching performed by the switching circuit 33 does not use a processing element that executes processing according to a program. The switching circuit 33 is configured with hardware. For this reason, the period from when the voltage of the ground line G, which has the potential of the ground terminal 31 as the reference potential, rises to a value equal to or higher than the reference voltage until the connection switch 36 switches from on to off is short.

[0062] When the power switch 21 and the circuit switch 50 are on and off, a current flows from the positive electrode of the DC power supply 20 through the power switch 21, the power terminal 30, the first circuit resistor 51, the connection switch 36, the ground terminal 31, the body E, and the negative electrode of the DC power supply 20 in this order. In the connection switch 36, the current flows through the base and the emitter in this order. Since this current is close to 0 A, the current flowing through the circuit switch 50 is substantially 0 A. However, while a voltage is applied to the base of the connection switch 36, power is consumed in the connection switch 36. When the operation of the switch device 11 is stopped, the application of a voltage to the base of the connection switch 36 can be stopped by switching the power switch 21 off.

[0063] <Modification of the first embodiment> In the first embodiment, the load 22 is disposed outside the switch device 11. However, the location where the load 22 is disposed is not limited to the outside of the switch device 11. For example, the switch device 11 may have the load 22. In this case, the load 22 is disposed on, for example, a wide surface of the device substrate Bs of the switch device 11.

[0064] There is no problem with the power supply switch 43 of the switch device 11 as long as it is a switch that can be switched by the drive circuit 44. Therefore, the power supply switch 43 is not limited to an N-channel FET, and may be a P-channel FET, a bipolar transistor, a relay contact, or the like. Furthermore, there is no problem with the device connected to the electric device 10 as long as it is a device that operates in response to the output voltage of the microcomputer 35. Therefore, the device connected to the electric device 10 is not limited to the switch device 11.

[0065] (Embodiment 2) The electric device 10 in the first embodiment outputs a voltage to the switch device 11 via the signal line F. However, the operation performed by the electric device 10 is not limited to outputting a voltage. The following describes the differences between embodiment 2 and embodiment 1. Except for the configuration described below, other configurations are common to embodiment 1. For this reason, components common to embodiment 1 are given the same reference numerals as embodiment 1, and descriptions of those components are omitted.

[0066] <Configuration of in-vehicle system 1> 4 is a block diagram showing a configuration of a main part of the in-vehicle system 1 in the second embodiment. When the second embodiment is compared with the first embodiment, the device connected to the electric device 10 is different. The in-vehicle system 1 in the second embodiment has a temperature detection device 12 instead of the switch device 11. The temperature detection device 12 is mounted on the vehicle C. The temperature detection device 12 has a second device connector 60. In the second embodiment, the temperature detection device 12 functions as an external device and a second electric device.

[0067] As described in the description of the first embodiment, the device connector 32 of the electric device 10 is detachably connected to one end of the signal line F and the ground line G. The device connector 32 is further detachably connected to one end of the voltage line H. The other ends of the voltage line H, the signal line F and the ground line G are detachably connected to the second device connector 60 of the temperature detection device 12. The voltage line H is a conductor.

[0068] The temperature detection device 12 detects the temperature inside the vehicle C, the temperature of a semiconductor switch, etc. The temperature detection device 12 outputs to the electric device 10 a voltage indicating the detected temperature.

[0069] <Configuration of Electrical Device 10 and Temperature Detector 12> In the electric device 10, a connection node between the power supply terminal 30 and the first circuit resistor 51 of the switching circuit 33 is connected to the device connector 32. This connection node is connected to the voltage line H via the device connector 32.

[0070] The temperature detection device 12 has a fixed resistor 61 and a thermistor 62 in addition to the second device connector 60. The resistance value of the fixed resistor 61 is constant regardless of the temperature of the fixed resistor 61. The resistance value of the thermistor 62 varies depending on the temperature of the thermistor 62. If the thermistor 62 is an NTC (Negative Temperature Coefficient) type, the resistance value of the thermistor 62 increases as the temperature of the thermistor 62 increases. If the thermistor 62 is a PTC (Positive Temperature Coefficient) type, the resistance value of the thermistor 62 decreases as the temperature of the thermistor 62 increases.

[0071] The thermistor 62 can be used to detect the environmental temperature around the thermistor 62. Therefore, when detecting the temperature inside the cabin of the vehicle C, the thermistor 62 is disposed inside the cabin of the vehicle C. When detecting the temperature of a semiconductor switch, the thermistor 62 is disposed in the vicinity of the semiconductor switch.

[0072] One end of the fixed resistor 61 is connected to the second device connector 60. The other end of the fixed resistor 61 is connected to one end of the thermistor 62. The other end of the thermistor 62 is connected to the second device connector 60. A connection node between the fixed resistor 61 and thermistor 62 is connected to the second device connector 60.

[0073] One end of the fixed resistor 61 is connected to a voltage line H via the second device connector 60. A connection node between the fixed resistor 61 and the thermistor 62 is connected to a signal line F via the second device connector 60. The other end of the thermistor 62 is connected to a ground line G via the second device connector 60.

[0074] The temperature detection device 12 may have a device board Bs, similar to the switch device 11 of embodiment 1. In this case, the second device connector 60, the fixed resistor 61, and the thermistor 62 are arranged on the wide surface of the device board Bs.

[0075] As described in the description of the first embodiment, when the power switch 21 is on and no short circuit to the ground line G occurs, the switching circuit 33 keeps the connection switch 36 on. When the power switch 21 and the connection switch 36 are on, a current flows from the positive electrode of the DC power supply 20 through the power switch 21, the power terminal 30, the device connector 32, the voltage line H, the second device connector 60, the fixed resistor 61, the thermistor 62, the second device connector 60, the ground line G, the device connector 32, the circuit switch 50, the ground terminal 31, the body E, and the negative electrode of the DC power supply 20 in this order. As a result, the power supply voltage of the DC power supply 20 is applied between one end of the fixed resistor 61 and the other end of the thermistor 62 via the voltage line H and the ground line G.

[0076] When the power supply voltage of the DC power supply 20 is applied between one end of the fixed resistor 61 and the other end of the thermistor 62, the fixed resistor 61 and the thermistor 62 divide the power supply voltage. A divided voltage obtained by the voltage division is output from the temperature detection device 12 to the microcomputer 35 of the electrical device 10 via a signal line F. The divided voltage is a voltage with the potential of the ground line G as a reference potential.

[0077] In the first embodiment, the microcomputer 35 outputs a high-level voltage or a low-level voltage via the signal line F. In the second embodiment, instead of outputting a voltage, the microcomputer 35 detects the voltage of the signal line F with the potential of the ground terminal 31 as a reference potential. When the connection switch 36 is on, the voltage detected by the microcomputer 35 substantially matches the divided voltage.

[0078] The divided voltage is higher as the resistance value of thermistor 62 increases. As described above, the resistance value of thermistor 62 varies depending on the temperature of thermistor 62. Therefore, the divided voltage indicates the temperature at the location where thermistor 62 is located.

[0079] In the second embodiment, when the short circuit to the ground wire G is eliminated while the power switch 21 and the connection switch 36 are on and off, respectively, a current flows from the positive electrode of the DC power supply 20 through the power switch 21, the power terminal 30, the device connector 32, the voltage line H, the second device connector 60, the fixed resistor 61, the thermistor 62, the second device connector 60, the ground wire G, the device connector 32, the second circuit resistor 52, the ground terminal 31, the body E, and the negative electrode of the DC power supply 20 in this order. In this case, the resistance value of the second circuit resistor 52 is adjusted so that the voltage of the ground wire G, with the potential of the ground terminal 31 as the reference potential, drops to a value less than the reference voltage Vr. Therefore, the resistance value of the second circuit resistor 52 is less than the minimum value of the combined resistance value of the fixed resistor 61 and the thermistor 62.

[0080] <Effects of 10 Electrical Devices> The electric device 10 in the second embodiment achieves the same effects as the electric device 10 in the first embodiment.

[0081] <Modification of the second embodiment> In the second embodiment, the connection positions of the fixed resistor 61 and the thermistor 62 may be interchanged. In this case, one end of the fixed resistor 61 is connected to the ground line G. The other end of the thermistor 62 is connected to the voltage line H. When the connection positions of the fixed resistor 61 and thermistor 62 are interchanged, the divided voltage becomes lower as the resistance value of the thermistor 62 becomes larger.

[0082] The voltage applied to the circuit including the fixed resistor 61 and thermistor 62 is not limited to the power supply voltage, and may be, for example, a target voltage generated by the regulator 34. In this case, instead of the connection node between the power supply terminal 30 and the first circuit resistor 51, the connection node between the regulator 34 and the microcomputer 35 is connected to the voltage line H via the device connector 32. The fixed resistor 61 and thermistor 62 divide the target voltage. There is no problem with the device connected to the electric device 10 as long as it is a device that outputs a voltage or a signal to the electric device 10. Therefore, the device connected to the electric device 10 is not limited to the temperature detection device 12.

[0083] <Modifications of the First and Second Embodiments> In the first and second embodiments, the connection switch 36 is not limited to an NPN bipolar transistor, and may be an N-channel FET or an IGBT (Insulated Gate Bipolar Transistor), etc. Similarly, the circuit switch 50 is not limited to an NPN bipolar transistor, and may be an N-channel FET or an IGBT, etc. The power supply terminal 30 of the electric device 10 may be directly connected to the positive electrode of the DC power supply 20.

[0084] The switching circuit 33 may be configured to switch the connection switch 36 on or off depending on the voltage of the ground line G, with the potential of the ground terminal 31 set as the reference potential. For this reason, the switching circuit 33 is not limited to a configuration including the circuit switch 50, the first circuit resistor 51, and the second circuit resistor 52. When the switching circuit 33 is configured differently from the configuration including the circuit switch 50, the first circuit resistor 51, and the second circuit resistor 52, the connection switch 36 may be a relay contact.

[0085] The technical features (constituent elements) described in the first and second embodiments can be combined with each other, and by combining them, new technical features can be formed. The disclosed embodiments 1 and 2 are illustrative in all respects and should not be considered as limiting. The scope of the present invention is defined by the claims, not by the above meaning, and is intended to include all modifications within the scope and meaning equivalent to the claims. [Explanation of symbols]

[0086] 1. In-vehicle systems 10 Electrical Equipment 11 Switch device (external device, second electrical device) 12 Temperature detection device (external device, second electrical device) 20 DC power supply 21 Power switch 22 Load 30 Power terminal 31 Ground terminal (first connection part) 32 Equipment connector (second connection part) 33 Switching Circuit 34 Regulator 35 Microcomputer (electronic component) 36 Connection Switch 40 Input terminal 41 Output terminal 42 Equipment Connector 43 Power supply switch 44 Drive circuit 50 Circuit switch (second switch) 51 1st circuit resistance 52 2nd circuit resistance 60 Secondary Device Connector 61 Fixed resistance 62 Thermistor Bm equipment board Bs Device board (second board) C Vehicle E-Body F signal line G ground wire H voltage line

Claims

1. An electrical device mounted on a vehicle, A first connection portion connected to a body of the vehicle; A second connection portion connected to an external device; a switch connected between the first connection portion and the second connection portion; a switching circuit for switching the switch on or off; Equipped with When the switch is on, a current flows through the second connection, the switch, and the first connection in that order; the switching circuit switches the switch from on to off when a voltage between the first connection portion and the second connection portion becomes equal to or higher than a predetermined voltage; The switch is switched from on to off when a voltage between an output terminal from which a current is output and a control terminal becomes less than a threshold value; the switching circuit includes a second switch connected between the output terminal and a control terminal of the switch; the second switch is switched from off to on when a voltage between the first connection portion and the second connection portion becomes equal to or higher than the predetermined voltage, a control end of the second switch is connected to one end of a second circuit resistor; The other end of the second circuit resistor is connected to the first connection portion. Electrical equipment.

2. An electronic component that outputs or detects a voltage with the potential of the first connection portion as a reference potential. The electrical device according to claim 1 .

3. a substrate on which the switch and switching circuit are disposed; The board is connected to the external device.

3. The electrical device according to claim 1 or 2.

4. An in-vehicle system in which an electric device outputs a voltage to a second electric device, or the second electric device outputs a voltage to the electric device, The electrical device includes: A first connection portion that is connected to a body of a vehicle; A second connection portion connected to the second electrical device; a switch connected between the first connection portion and the second connection portion; a switching circuit for switching the switch on or off; having When the switch is on, a current flows through the second connection, the switch, and the first connection in that order; the switching circuit switches the switch from on to off when a voltage between the first connection portion and the second connection portion becomes equal to or higher than a predetermined voltage; The switch is switched from on to off when a voltage between an output terminal from which a current is output and a control terminal becomes less than a threshold value; the switching circuit includes a second switch connected between the output terminal and a control terminal of the switch; the second switch is switched from off to on when a voltage between the first connection portion and the second connection portion becomes equal to or higher than the predetermined voltage, a control end of the second switch is connected to one end of a second circuit resistor; The other end of the second circuit resistor is connected to the first connection portion. In-vehicle systems.

5. the electrical device includes a substrate on which the switch and a switching circuit are disposed; the second electrical device has a second substrate; The substrate is connected to the second substrate. The in-vehicle system according to claim 4.

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