Current control device and vehicle system

Abstract

This current control device (1) comprises: a control circuit (10) that outputs a first signal for controlling a current applied to a load (3) from a vehicle power source (2); a photo-MOS relay (30) in which a first input unit causes a first output unit in the path of the current to be conductive or non-conductive in response to the first signal; a resistor (41) in which the voltage between both terminals is at least a specified voltage when an overcurrent flows; a transistor (43) that is driven when the voltage between both terminals of the resistor (41) is at least the specified voltage; and a photocoupler (60) that outputs a second signal, indicating that an overcurrent has flowed through the path, from a second output unit to the control circuit (10) by driving a second input unit with power from the vehicle power source (2) when the transistor (43) connected in series with the second input unit is driven. The power from the vehicle power source (2) is applied to a series circuit including the second input unit and the transistor (43), and the control circuit (10) controls the output of the first signal on the basis of the second signal.

Description

Current control device and vehicle system

[0001] The present disclosure relates to a current control device mounted on a vehicle and a vehicle system.

[0002] Conventionally, there are devices that receive as input a signal indicating the status of a device or the like, and output the status information of the device or the like while being electrically isolated from the input signal. For example, Patent Document 1 discloses a technology for a point display input circuit that outputs an output signal corresponding to an input signal indicating the switching status of an input point. The point display input circuit described in Patent Document 1 isolates the input side from the output side by using a photocoupler consisting of a photodiode and a phototransistor.

[0003] JP 2013-95288 A

[0004] While the above-described conventional technology uses an input signal that indicates normal operation as the device's status, circuits configured as described above are considered applicable when the input signal indicates abnormal operation as the device's status. For example, a digital output (DO) circuit that controls power supplied to a load is required to detect overcurrent abnormalities caused by load short circuits, etc. However, such an overcurrent abnormality detection circuit must constantly monitor whether an overcurrent is flowing while power is being supplied to the load and immediately notify the load when an overcurrent is detected. This necessitates a constant supply of power to the photodiode of the photocoupler. However, providing a dedicated power supply to the photodiode of the photocoupler increases the circuit configuration and increases the circuit size.

[0005] The present disclosure has been made in view of the above, and has an object to provide a current control device that can detect an overcurrent with a simple configuration while controlling the current supplied to a load.

[0006] To solve the above-mentioned problems and achieve the object, the current control device of the present disclosure includes a control circuit that outputs a first signal to control the current applied to a load from a vehicle power supply; a first non-contact relay having a first input and a first output, the first input configured to make a first output in a path of the current conductive or non-conductive in response to the first signal; a resistor disposed in the path, the voltage across which reaches or exceeds a specified voltage when an overcurrent flows in the path; a transistor that is activated when the voltage across the resistor reaches or exceeds the specified voltage; and a second non-contact relay having a second input and a second output, the second input being driven by power from the vehicle power supply when a transistor connected in series with the second input is activated, thereby outputting a second signal from the second output to the control circuit, the second signal indicating that an overcurrent is flowing in the path. Power from the vehicle power supply is applied to the series circuit including the second input and the transistor. The control circuit controls the output of the first signal based on the second signal.

[0007] The current control device of the present disclosure has an advantage that it is possible to detect an overcurrent with a simple configuration while controlling the current supplied to a load.

[0008] FIG. 1 shows an example of the configuration of a current control device according to embodiment 1. FIG. 1 shows an example of the case where an overcurrent occurs due to a load short circuit occurring in a path where the current control device according to embodiment 1 controls the flow of current. FIG. 1 shows an example of the configuration of a current control device according to embodiment 2. FIG. 1 shows an example of the configuration of a current control device according to embodiment 3. FIG. 1 shows an example of the configuration of a current control device according to embodiment 4. FIG. 1 shows an example of the configuration of a current control device according to embodiment 5. FIG. 1 shows an example of the configuration of a current control device according to embodiment 6. FIG. 1 shows an example of the configuration of a vehicle system according to embodiment 7.

[0009] A current control device and a vehicle system according to an embodiment of the present disclosure will be described in detail below with reference to the drawings.

[0010] First Embodiment Fig. 1 is a diagram showing an example configuration of a current control device 1 according to a first embodiment. The current control device 1 is a DO circuit used in a train (not shown) or the like. The current control device 1 is connected to a vehicle power supply 2 and a load 3. The current control device 1 controls the current applied from the vehicle power supply 2 to the load 3 under the control of a control circuit 10, thereby controlling the operation of the load 3. The current control device 1 includes the control circuit 10, resistors 21 and 22, a transistor 23, a control power supply 24, a resistor 25, a photoMOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor) relay (hereinafter referred to as a photoMOS relay) 30, resistors 41 and 42, a transistor 43, a resistor 44, a connection unit 50, a photocoupler 60, a control power supply 71, a resistor 72, and a Schmitt IC (Integrated Circuit) 73. In the following description, the photo MOS relay 30 may be referred to as a first non-contact relay, and the photo coupler 60 may be referred to as a second non-contact relay.

[0011] The current control device 1 is connected to the positive electrode of the vehicle power supply 2 at one end of a connection unit 50, and is connected to the negative electrode of the vehicle power supply 2 at the other end of the connection unit 50 via a load 3. The other end of the connection unit 50 is an OUTPUT terminal. The load 3 is an external component having one end connected to the other end of the connection unit 50 of the current control device 1 and the other end connected to the negative electrode of the vehicle power supply 2. The load 3 is, for example, an on-board device mounted on a train (not shown), for example.

[0012] The control circuit 10 outputs a first signal that controls the current applied from the vehicle power supply 2 to the load 3. The control circuit 10 controls the base current of the transistor 23 using the first signal, thereby controlling the on / off of the transistor 23. By turning the transistor 23 on and off, the control circuit 10 can ultimately control the current applied to the load 3, i.e., the operation of the load 3. The control circuit 10 includes an overcurrent determination circuit 11, a command unit 12, and a combination circuit 13.

[0013] The overcurrent determination circuit 11 receives a second signal, which will be described later, from the Schmitt IC 73. When the overcurrent determination circuit 11 receives the second signal indicating that an overcurrent has flowed in the path of the current applied from the vehicle power supply 2 to the load 3, the overcurrent determination circuit 11 outputs a signal indicating that an overcurrent has flowed in the current path to the combination circuit 13.

[0014] The command unit 12 outputs a command signal to the combination circuit 13 to control the current applied from the vehicle power supply 2 to the load 3. The command unit 12 may be located outside the current control device 1 as long as it is located inside the vehicle in which the current control device 1 is installed.

[0015] Combination circuit 13 controls the output of the first signal based on the signal obtained from overcurrent determination circuit 11 and the command signal obtained from command unit 12. For example, when no overcurrent is flowing in the current path, overcurrent determination circuit 11 outputs a high (H) signal to combination circuit 13, and when current is to be applied from vehicle power supply 2 to load 3, command unit 12 outputs a high (H) command signal to combination circuit 13. At this time, combination circuit 13 performs a logical product operation like an AND circuit to output a high (H) signal as the first signal for applying current from vehicle power supply 2 to load 3. On the other hand, when the combination circuit 13 receives from the overcurrent judgment circuit 11 a low (L) signal indicating that an overcurrent is flowing in the current path, or when it receives from the command unit 12 a low (L) command signal that is output when current is not to be applied from the vehicle power supply 2 to the load 3, the combination circuit 13 outputs a low (L) signal as a first signal that does not allow current to be applied from the vehicle power supply 2 to the load 3, if at least one of the following conditions applies:

[0016] The control circuit 10 can control the output of the first signal by the above-described operations of the overcurrent determination circuit 11, the command unit 12, and the combination circuit 13. Note that the above-described operations are merely examples, and the relationship between the high (H) and low (L) states of each signal and the content of the logical operation in the combination circuit 13 are not limited to the above example.

[0017] The resistor 21 is connected to the base-emitter voltage V of the transistor 23, which is generated by the first signal output from the control circuit 10. ＢＥThe resistor 22 is a resistor for adjusting the magnitude of the base current of the transistor 23 in response to a first signal output from the control circuit 10. The transistor 23 is controlled to be turned on and off by the first signal output from the control circuit 10. When the transistor 23 is turned on under the control of the control circuit 10, power from the control power supply 24 is conducted to the light-emitting diode 31 of the photoMOS relay 30, causing the light-emitting diode 31 to emit light. The control power supply 24 is a power supply that supplies power to the light-emitting diode 31. The resistor 25 is a resistor for adjusting the magnitude of the power supplied from the control power supply 24 to the light-emitting diode 31.

[0018] The photo MOS relay 30 is a first non-contact relay having a light emitting diode 31 as a first input and a light receiving element 32 as a first output. As shown in Fig. 1, the light emitting diode 31 is supplied with power from the control power supply 24 via a resistor 25, and the light receiving element 32 is supplied with power from the vehicle power supply 2 and is connected to an external load 3 via a resistor 41.

[0019] In this embodiment, as described above, the control circuit 10 controls the on / off of the transistor 23, thereby controlling the conduction of power from the control power supply 24 to the light-emitting diode 31 of the photoMOS relay 30. The control circuit 10 conducts power from the control power supply 24 to the light-emitting diode 31 of the photoMOS relay 30, causing the light-emitting diode 31 of the photoMOS relay 30 to emit light, thereby conducting power from the vehicle power supply 2 to the light-receiving element 32 of the photoMOS relay 30. Because the transistor 23 is turned on and off by the first signal from the control circuit 10, it can also be said that the photoMOS relay 30 allows the light-emitting diode 31 to make the light-receiving element 32 in the current path of the vehicle power supply 2 conductive or non-conductive in response to the first signal.

[0020] Resistor 41 is disposed in the path of the current applied from vehicle power supply 2 to load 3, and is a resistor whose voltage across both ends becomes equal to or exceeds a specified voltage when an overcurrent flows in the current path. Resistor 41 also functions to reduce the base-emitter voltage V of transistor 43 due to the current applied from vehicle power supply 2 to load 3.ＢＥ Resistor 42 is a resistor for adjusting the magnitude of the base current of transistor 43 due to the current applied from vehicle power supply 2. Transistor 43 is controlled to be on or off by the voltage across resistor 41 due to the current applied from vehicle power supply 2 to load 3. Transistor 43 is driven when the voltage across resistor 41 is equal to or higher than a specified voltage, i.e., when an overcurrent flows in the current path. Transistor 43 turns on when the voltage across resistor 41 is equal to or higher than a specified voltage, thereby conducting power from vehicle power supply 2 to light-emitting diode 61 of photocoupler 60 and causing light-emitting diode 61 to emit light. Resistor 44 is a resistor for adjusting the magnitude of the power supplied from vehicle power supply 2 to light-emitting diode 61 and transistor 43.

[0021] 2 is a diagram showing an example in which an overcurrent occurs due to a load short circuit occurring in a path in which the current flow is controlled by the current control device 1 according to embodiment 1. In the example of FIG. 2, a case in which the cause of the overcurrent is a load short circuit is shown, but the cause of the overcurrent occurring in the path of the current applied from the vehicle power supply 2 to the load 3 is not limited to a load short circuit.

[0022] The photocoupler 60 is a second non-contact relay having a light-emitting diode 61 as a second input and a light-receiving element 62 as a second output. As shown in Fig. 1, the light-emitting diode 61 is supplied with power from the vehicle power supply 2 via a resistor 44, and the light-receiving element 62 is supplied with power from a control power supply 71 via a resistor 72.

[0023] In this embodiment, since the transistor 43 and the light-emitting diode 61 of the photocoupler 60 are connected in series, when an overcurrent flows in the current path, the current control device 1 drives the transistor 43 to conduct power from the vehicle power supply 2 to the light-emitting diode 61 of the photocoupler 60, causing the light-emitting diode 61 of the photocoupler 60 to emit light, thereby conducting power from the control power supply 71 to the light-receiving element 62 of the photocoupler 60. By conducting power to the light-receiving element 62 of the photocoupler 60, the light-receiving element 62 of the photocoupler 60 can output a second signal corresponding to the potential of the connection point between the resistor 72 and the light-receiving element 62 to the Schmitt IC 73.

[0024] Here, the second signal takes one of two values, low (L) or high (H). When an overcurrent flows through the current path, the light-emitting diode 61 of the photocoupler 60 emits light and the light-receiving element 62 of the photocoupler 60 becomes conductive, resulting in a voltage drop at the connection point between the resistor 72 and the light-receiving element 62. On the other hand, when no overcurrent flows through the current path, the light-emitting diode 61 of the photocoupler 60 does not emit light and the light-receiving element 62 of the photocoupler 60 does not become conductive, resulting in no voltage drop at the connection point between the resistor 72 and the light-receiving element 62. In other words, the light-receiving element 62 of the photocoupler 60 outputs a second signal with a high (H) value when no overcurrent flows through the current path, and outputs a second signal with a low (L) value when an overcurrent flows through the current path.

[0025] In this way, when the transistor 43 connected in series with the light-emitting diode 61 is driven, the light-emitting diode 61 is driven by power from the vehicle power supply 2, and the photocoupler 60 can output a second signal indicating that an overcurrent has flowed in the current path from the light-receiving element 62 to the control circuit 10 via the Schmitt IC 73.

[0026] The control power supply 71 is a power supply that supplies power to the light-receiving element 62. The resistor 72 is a resistor that adjusts the magnitude of the power supplied from the control power supply 71 to the light-receiving element 62. The Schmitt IC 73 is a circuit that changes the input second signal with hysteresis and outputs it. This allows the Schmitt IC 73 to reduce changes in the value of the output second signal, i.e., the value of the second signal input to the control circuit 10, even if the value of the second signal changes in a short period of time due to the influence of noise or the like.

[0027] (1) The control circuit 10 controls the output of the first signal based on the second signal. For example, in the control circuit 10, the overcurrent determination circuit 11 may determine that an overcurrent is flowing in the current path when the value of the second signal is a predetermined value a predetermined number of times consecutively at a predetermined cycle. For example, the overcurrent determination circuit 11 may determine that an overcurrent is flowing in the current path when the value of the second signal is detected at a 100 μs cycle and reaches a value indicating an overcurrent five times consecutively. In this case, the combination circuit 13 controls the output of the first signal to make the light-receiving element 32 of the photoMOS relay 30 non-conductive. The determination conditions in the overcurrent determination circuit 11 may be set by the command unit 12 or externally from the current control device 1, taking into account noise detected by the overcurrent determination circuit 11, etc.

[0028] (2) Alternatively, in the control circuit 10, the overcurrent determination circuit 11 may determine that an overcurrent is flowing in the current path when the number of times the value of the second signal has reached a specified value within a specified cycle is equal to or greater than a threshold value. For example, when the value of the second signal is detected at a 100 μs cycle, the overcurrent determination circuit 11 determines that an overcurrent is flowing in the current path if the number of times the value indicates an overcurrent is eight or more out of the last ten times the value of the second signal has reached a value indicating an overcurrent. In this case, the combination circuit 13 controls the output of the first signal to render the light-receiving element 32 of the photoMOS relay 30 non-conductive. The determination conditions for the overcurrent determination circuit 11 may be set by the command unit 12 or externally from the current control device 1, taking into account noise detected by the overcurrent determination circuit 11, etc.

[0029] (3) In the control circuit 10, the overcurrent determination circuit 11 may determine whether an overcurrent is flowing in the current path when a command signal for controlling the application of current to the load 3 instructs the application of current to the load 3. In this case, although not shown, the overcurrent determination circuit 11 acquires a command signal from the command unit 12. This is because, in general, if the control command from the command unit 12 does not instruct the application of current to the load 3, no current from the vehicle power supply 2 is applied to the load 3, and therefore it is considered that no overcurrent will flow in the load 3.

[0030] (4) In the event of a failure of the current control device 1, the overcurrent determination circuit 11 in the control circuit 10 may determine that an overcurrent is flowing in the current path or that the current control device 1 is faulty based on the second signal and a command signal for controlling the application of current to the load 3. The overcurrent determination circuit 11 in the control circuit 10 can determine that an overcurrent is flowing in the current path using the method described above. Furthermore, for example, if the overcurrent determination circuit 11 in the control circuit 10 determines from the second signal that an overcurrent is flowing in the current path even though the first signal is not being controlled to apply current from the vehicle power supply 2 to the load 3, it can determine that some abnormality has occurred in the current control device 1 and that the current control device 1 is faulty. If the overcurrent determination circuit 11 determines that an overcurrent is flowing in the current path or that the current control device 1 is faulty, the combination circuit 13 controls the output of the first signal to make the light-receiving element 32 of the photoMOS relay 30 non-conductive. In the above description, when an overcurrent flows in the current path or the current control device 1 is faulty, this includes cases where only one of these occurs, as well as cases where both occur.

[0031] When the control circuit 10 determines that an overcurrent is flowing in the current path or that the current control device 1 is malfunctioning in the description of (4), the control circuit 10 may notify a higher-level device (not shown) mounted on the train that an overcurrent is flowing in the current path or that the current control device 1 is malfunctioning. In the control circuit 10, it is assumed that the overcurrent determination circuit 11 notifies the higher-level device, but the combination circuit 13 may also notify the higher-level device (not shown) that an overcurrent is flowing in the current path when the control circuit 10 determines that an overcurrent is flowing in the current path in the descriptions of (1) to (3). In this case, the control circuit 10 may also notify the higher-level device that it is controlling so as not to apply current to the load 3. The higher-level device may be, but is not limited to, a train control and management system (TCMS) that manages and controls the operating state of the train or the on-board equipment that is the load 3.

[0032] In the present embodiment, the current control device 1 uses a photoMOS relay 30 as the first non-contact relay and a photocoupler 60 as the second non-contact relay, but this is not limiting. The current control device 1 may use a photocoupler as the first non-contact relay and a photoMOS relay as the second non-contact relay. Furthermore, the current control device 1 may use photocouplers or photoMOS relays for both the first and second non-contact relays. Furthermore, the current control device 1 may also use mechanical relays for the first and second non-contact relays. In this way, the current control device 1 may use a photocoupler, a photoMOS relay, or a mechanical relay for the first and second non-contact relays.

[0033] As described above, according to the present embodiment, in current control device 1, power from vehicle power supply 2 is applied to a series circuit including light-emitting diode 61 of photocoupler 60 and transistor 43. Current control device 1 uses vehicle power supply 2 as a power source for driving light-emitting diode 61 of photocoupler 60, thereby eliminating the need for a dedicated control power supply for driving light-emitting diode 61 of photocoupler 60. Furthermore, current control device 1 can appropriately set the overcurrent determination conditions in overcurrent determination circuit 11, taking into account noise detected by overcurrent determination circuit 11, etc. In this way, current control device 1 can detect overcurrent with a simple configuration while controlling the current supplied to load 3.

[0034] Second Embodiment In a second embodiment, a case will be described in which a current control device is protected when an overcurrent occurs in the path of a current applied from a vehicle power supply 2 to a load 3.

[0035] Fig. 3 is a diagram showing an example of the configuration of a current control device 1a according to embodiment 2. The current control device 1a is obtained by adding a varistor 45 to the current control device 1 of embodiment 1 shown in Fig. 1. The varistor 45 is connected in parallel to a series circuit including the light-receiving element 32 of the photoMOS relay 30 and the light-emitting diode 61 and transistor 43 of the photocoupler 60. The varistor 45 is arranged closer to the load 3 than the series circuit including the light-receiving element 32 of the photoMOS relay 30 and the light-emitting diode 61 and transistor 43 of the photocoupler 60.

[0036] By providing the varistor 45 at the position shown in FIG. 3, the current control device 1a can protect the light receiving element 32 of the photoMOS relay 30, as well as the series circuit including the light emitting diode 61 of the photocoupler 60 and the transistor 43.

[0037] Third Embodiment In a third embodiment, a configuration of a current control device different from that of the second embodiment will be described for protecting the current control device when an overcurrent occurs in the path of a current applied from the vehicle power supply 2 to the load 3.

[0038] Fig. 4 is a diagram showing an example of the configuration of a current control device 1b according to embodiment 3. The current control device 1b is configured by adding a backflow prevention diode 46 to the current control device 1a of embodiment 2 shown in Fig. 3. The backflow prevention diode 46 is arranged closer to the light receiving element 32 of the photoMOS relay 30 and the series circuit including the light emitting diode 61 of the photocoupler 60 and the transistor 43 than the varistor 45.

[0039] 4, the current control device 1b is provided with a varistor 45 and a backflow prevention diode 46, thereby protecting the light receiving element 32 of the photoMOS relay 30 and also protecting the series circuit including the light emitting diode 61 of the photocoupler 60 and the transistor 43. Furthermore, the current control device 1b can protect the backflow prevention diode 46 by the varistor 45.

[0040] Fourth Embodiment In a fourth embodiment, a configuration of a current control device that differs from those of the second and third embodiments will be described for protecting the current control device when an overcurrent occurs in the path of a current applied from a vehicle power supply 2 to a load 3.

[0041] 5 is a diagram showing a configuration example of a current control device 1c according to embodiment 4. The current control device 1c is configured by adding a backflow prevention diode 47 to the current control device 1a according to embodiment 2 shown in FIG. 3. The backflow prevention diode 47 is disposed between the base and emitter of the transistor 43 together with the resistor 41.

[0042] The current control device 1c is provided with a backflow prevention diode 47 at the position shown in Fig. 5, and the transistor 43 is connected in a Darlington configuration. By arranging the backflow prevention diode 47 at the position shown in Fig. 5, the current control device 1c reduces the apparent base-emitter voltage V ＢＥ The rise in the forward voltage V of the reverse current prevention diode 47 ＦFurthermore, the current control device 1c can protect the light receiving element 32 of the photoMOS relay 30, the series circuit including the light emitting diode 61 of the photocoupler 60 and the transistor 43, and the backflow prevention diode 47 by using the varistor 45.

[0043] Fifth Embodiment In a fifth embodiment, a specific circuit configuration of a control circuit provided in a current control device will be described. Although the fifth embodiment is applicable to any of the current control devices of the first to fourth embodiments, the circuit configuration of the current control device 1c of the fourth embodiment will be described as an example.

[0044] FIG. 6 is a diagram showing a configuration example of a current control device 1d according to a fifth embodiment. The current control device 1d shown in FIG. 6 is obtained by replacing the control circuit 10 of the current control device 1c of the fourth embodiment shown in FIG. 5 with a control circuit 10d. The control circuit 10d includes an overcurrent determination circuit 11d, a command unit 12, and a combination circuit 13. The overcurrent determination circuit 11d includes a noise elimination unit 14 and a latch circuit 15. The noise elimination unit 14 removes noise from the second signal obtained from the Schmitt IC 73. The noise elimination unit 14 removes noise that could not be removed by the Schmitt IC 73 using a filter or the like. The latch circuit 15 holds the value of the second signal obtained from the noise elimination unit 14 for a specified period.

[0045] In the fifth embodiment, the operation of the command unit 12 and the combination circuit 13 included in the control circuit 10d is the same as the operation of the command unit 12 and the combination circuit 13 included in the control circuit 10 of the first embodiment.

[0046] The control circuit 10d can perform operations such as (1) and (2) described in embodiment 1 by providing the overcurrent determination circuit 11d with the above-described configuration. Furthermore, although not shown in FIG. 6, the control circuit 10d can perform operations such as (3) described in embodiment 1 by having the overcurrent determination circuit 11d acquire a command signal from the command unit 12.

[0047] Sixth Embodiment In a sixth embodiment, a specific circuit configuration of a control circuit provided in a current control device will be described. Although the sixth embodiment is applicable to any of the current control devices of the first to fourth embodiments, the circuit configuration of the current control device 1c of the fourth embodiment will be described as an example.

[0048] Fig. 7 is a diagram showing an example of the configuration of a current control device 1e according to a sixth embodiment. The current control device 1e shown in Fig. 7 is obtained by replacing the control circuit 10 of the current control device 1c of the fourth embodiment shown in Fig. 5 with a control circuit 10e. The control circuit 10e includes an overcurrent determination circuit 11e, a command unit 12, and a combination circuit 13. The overcurrent determination circuit 11e includes a noise removal unit 14, a fault detection unit 16, a determination unit 17, and a latch circuit 15.

[0049] The fault detection unit 16 receives the second signal from the noise removal unit 14 and the command signal from the command unit 12. The fault detection unit 16 determines whether or not the current control device 1e has a fault based on the second signal and the command signal. For example, if the command signal instructs the load 3 to apply current from the vehicle power supply 2 and the second signal indicates that an overcurrent is flowing in the current path or the second signal indicates that no overcurrent is flowing in the current path, the fault detection unit 16 determines that the current control device 1e is normal. Furthermore, if the command signal instructs the load 3 not to apply current from the vehicle power supply 2 and the second signal indicates that no overcurrent is flowing in the current path, the fault detection unit 16 determines that the current control device 1e is normal. On the other hand, if the command signal instructs the load 3 not to apply current from the vehicle power supply 2 and the second signal indicates that an overcurrent is flowing in the current path, the fault detection unit 16 determines that the current control device 1e has a fault.

[0050] The determination unit 17 receives the second signal from the noise removal unit 14 and receives the determination result of the failure determination from the failure detection unit 16. If the determination unit 17 determines, based on the second signal and the determination result from the failure detection unit 16, that an overcurrent is flowing in the current path or that the current control device 1e is faulty, the determination unit 17 outputs a signal instructing the combination circuit 13 to output a first signal to make the light-receiving element 32 of the photoMOS relay 30 non-conductive. If the determination unit 17 determines, based on the second signal and the determination result from the failure detection unit 16, that no overcurrent is flowing in the current path and that the current control device 1e is not faulty, the determination unit 17 outputs a signal indicating these determination results. Note that in the above description, the cases where an overcurrent is flowing in the current path or the current control device 1e is faulty include cases where only one of these conditions applies, as well as cases where both conditions apply.

[0051] When the combination circuit 13 receives from the determination unit 17 via the latch circuit 15 a signal instructing it to output a first signal that will make the light-receiving element 32 of the photoMOS relay 30 non-conductive, it outputs a signal instructing it to output a first signal that will make the light-receiving element 32 of the photoMOS relay 30 non-conductive, regardless of the content of the command signal from the command unit 12. When the combination circuit 13 receives from the determination unit 17 via the latch circuit 15 a determination result that no overcurrent is flowing in the current path and that the current control device 1e is not malfunctioning, it outputs a first signal that corresponds to the content of the command signal from the command unit 12.

[0052] In the above example, the control circuit 10e performs the same control when an overcurrent flows in the current path and when the current control device 1e has failed, but this is not limiting. The control circuit 10e may perform different controls when an overcurrent flows in the current path and when the current control device 1e has failed. For example, the control circuit 10e may perform control to stop the operation of the entire current control device 1e when the current control device 1e has failed.

[0053] The control circuit 10e can perform the operation (4) described in the first embodiment and the like by providing the overcurrent determination circuit 11e with the above-described configuration.

[0054] Seventh Embodiment In a seventh embodiment, a vehicle system in which a current control device is connected to a higher-level device will be described. Although the seventh embodiment can be applied to any of the current control devices of the first to fourth embodiments, the circuit configuration of the current control device 1c of the fourth embodiment will be described as an example.

[0055] FIG. 8 is a diagram showing an example configuration of a vehicle system 5 according to a seventh embodiment. The vehicle system 5 includes a current control device 1f and a higher-level device 4. The current control device 1f shown in FIG. 8 is obtained by replacing the control circuit 10 of the current control device 1c according to the fourth embodiment shown in FIG. 5 with a control circuit 10f. The overcurrent determination circuit 11f includes a noise removal unit 14 and a latch circuit 15. The higher-level device 4 is, as described above, a TCMS or the like, but is not limited to this. The higher-level device 4 includes a command unit 12 and a fault detection unit 16.

[0056] In the seventh embodiment, the operations of the noise elimination unit 14, the latch circuit 15, and the failure detection unit 16 are the same as those of the noise elimination unit 14, the latch circuit 15, and the failure detection unit 16 in the sixth embodiment. In the seventh embodiment, the failure detection unit 16 outputs the determination result between the latch circuit 15 and the combination circuit 13, but it is also possible to configure the overcurrent determination circuit 11f to include the determination unit 17, as in the sixth embodiment.

[0057] In the first embodiment, the control circuit 10 notifies the higher-level device even when the current control device 1 is faulty, but in the example of FIG. 8, the higher-level device 4 includes a fault detection unit 16. Therefore, in the seventh embodiment, the control circuit 10f may notify the higher-level device 4 only when it determines that an overcurrent is flowing in the current path. In the vehicle system 5, the higher-level device 4 may include only the command unit 12, and the current control device 1f may include the other components. Note that the higher-level device 4 shown in FIG. 8 may be the higher-level device to which the current control devices 1 to 1e described in the first to sixth embodiments send notifications.

[0058] Thus, in the seventh embodiment, the current control device 1f notifies the higher-level device 4 that an overcurrent has flowed in the current path when it determines that an overcurrent has flowed in the current path through which current is applied from the vehicle power supply 2 to the load 3. The higher-level device 4 controls the output of a command signal for controlling the application of current to the load 3, and when it receives a notification from the current control device 1f that an overcurrent has flowed in the current path, it stops outputting a command signal instructing that a current be applied to the load 3.

[0059] The configurations shown in the above embodiments are merely examples, and may be combined with other known technologies, or different embodiments may be combined with each other. It is also possible to omit or modify parts of the configurations as long as they do not deviate from the gist of the invention.

[0060] 1, 1a, 1b, 1c, 1d, 1e, 1f Current control device, 2 Vehicle power supply, 3 Load, 4 Upper device, 5 Vehicle system, 10, 10d, 10e, 10f Control circuit, 11, 11d, 11e, 11f Overcurrent judgment circuit, 12 Command unit, 13 Combination circuit, 14 Noise removal unit, 15 Latch circuit, 16 Fault detection unit, 17 Judgment unit, 21, 22, 25, 41, 42, 44, 72 Resistor, 23, 43 Transistor, 24, 71 Control power supply, 30 PhotoMOS relay, 31, 61 Light-emitting diode, 32, 62 Light-receiving element, 45 Varistor, 46, 47 Backflow prevention diode, 50 Connection unit, 60 Photocoupler, 73 Schmitt IC.

Claims

1. A current control device comprising: a control circuit that outputs a first signal that controls the current applied to a load from a vehicle power supply; a first non-contact relay having a first input section and a first output section, the first input section making the first output section in a path of the current conductive or non-conductive in response to the first signal; a resistor that is arranged in the path and whose voltage across it reaches a specified voltage or higher when an overcurrent flows in the path; a transistor that is driven when the voltage across the resistor reaches the specified voltage or higher; and a second non-contact relay having a second input section and a second output section, the second input section being driven by power from the vehicle power supply when the transistor connected in series with the second input section is driven, thereby outputting a second signal from the second output section to the control circuit that indicates that an overcurrent has flowed in the path; wherein the power from the vehicle power supply is applied to a series circuit including the second input section and the transistor, and the control circuit controls the output of the first signal based on the second signal.

2. The current control device according to claim 1, characterized in that the control circuit determines that an overcurrent is flowing in the path when the value of the second signal is a specified value a specified number of times in a specified cycle, and controls the output of the first signal to make the first output section non-conductive.

3. The current control device according to claim 1, characterized in that the control circuit determines that an overcurrent is flowing in the path when the number of times that the value of the second signal has become a specified value among the most recent specified number of times in a specified period is equal to or greater than a threshold, and controls the output of the first signal to make the first output section non-conductive.

4. A current control device as described in any one of claims 1 to 3, characterized in that the control circuit determines whether or not an overcurrent is flowing in the path when a command signal for controlling the application of the current to the load instructs the application of the current to the load.

5. A current control device according to any one of claims 1 to 3, characterized in that when the control circuit determines, based on the second signal and a command signal for controlling the application of the current to the load, that an overcurrent is flowing in the load or that the current control device is malfunctioning, it controls the output of the first signal to make the first output section non-conductive.

6. A current control device according to any one of claims 1 to 5, further comprising a varistor connected in parallel with the first output section and the series circuit and arranged closer to the load than the first output section and the series circuit.

7. The current control device according to claim 6, further comprising a backflow prevention diode arranged on the side of said first output section and said series circuit relative to said varistor.

8. The current control device according to claim 6, further comprising a reverse current prevention diode disposed together with said resistor between the base and emitter of said transistor.

9. A vehicle system comprising: a current control device according to any one of claims 1 to 8, which notifies a higher-level device that an overcurrent has flowed in a current path through which a current is applied from a vehicle power source to a load when it is determined that an overcurrent has flowed in the current path; and the higher-level device which controls the output of a command signal for controlling the application of the current to the load, and which, when notified by the current control device that an overcurrent has flowed in the current path, stops the output of the command signal instructing that the current be applied to the load.