Power supply control device, in-vehicle control device, and power supply control method

Abstract

To provide a power supply control device, an in-vehicle control device, and a power supply control method that can detect abnormalities in power supply when a current value is small.SOLUTION: An individual ECU 11a controls the power supply via an electric wire W. A microcomputer 21 of the individual ECU 11a gradually increases the average value of the electric wire current values of the current flowing through the electric wire W. Each time the microcomputer 21 raises the average value of the electric wire current value, the microcomputer determines whether an abnormality has occurred in the power supply via the electric wire W on the basis of the temperature difference between the electric wire temperature of the electric wire W and the environmental temperature around the electric wire W.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present disclosure relates to a power supply control device, an in-vehicle control device, and a power supply control method.

Background Art

[0002] Vehicles are equipped with a power supply control device (see, for example, Patent Document 1) that controls power supply to a load. In the power supply control device described in Patent Document 1, an FET (Field Effect Transistor) is arranged as a switch in the current path of the current flowing through the load. By switching the FET on or off, the power supply to the load is controlled. When the temperature of the FET becomes a temperature equal to or higher than a predetermined temperature while the FET is on, the FET is forcibly switched off. Thereby, it is possible to prevent the FET from reaching an abnormal temperature.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In a conventional power supply control device as described in Patent Document 1, when a cutoff condition for forcibly interrupting the flow of current to a load is satisfied, the FET is forcibly switched off. When starting to supply power to the load after the cutoff condition is satisfied, the FET is switched on again and the on state of the FET is maintained. If the FET is maintained in the on state while the factor that satisfied the cutoff condition has not been eliminated, the cutoff condition is satisfied again, and as a result, the FET is forcibly switched off again.

[0005] A state where the interruption condition is satisfied is a state where the current value of the current flowing through the FET is large, which is not preferable for the components constituting the power supply control device. Therefore, it is necessary to detect an abnormality in power supply in a state where the current value is small.

[0006] The present disclosure has been made in view of such circumstances, and an object thereof is to provide a power supply control device, an in-vehicle control device, and a power supply control method capable of detecting an abnormality in power supply in a state where the current value is small.

Means for Solving the Problems

[0007] A power supply control device according to an aspect of the present disclosure is a power supply control device that controls power supply via an electric wire, and includes a processing unit that executes processing. The processing unit gradually increases an average value of an electric wire current value of a current flowing through the electric wire, and each time the average value of the electric wire current value is increased, based on a temperature difference between an electric wire temperature of the electric wire and an ambient temperature around the electric wire, it is determined whether an abnormality has occurred in the power supply via the electric wire.

[0008] An in-vehicle control device according to an aspect of the present disclosure is an in-vehicle control device that controls the operation of a load, and includes a receiving unit that receives instruction data for instructing the operation or stop of the operation of the load, and a processing unit that executes processing. The processing unit controls the power supply to the load via an electric wire according to the instruction data received by the receiving unit, gradually increases an average value of an electric wire current value of a current flowing through the electric wire, and each time the average value of the electric wire current value is increased, based on a temperature difference between an electric wire temperature of the electric wire and an ambient temperature around the electric wire, it is determined whether an abnormality has occurred in the power supply via the electric wire.

[0009] A power supply control method according to an aspect of the present disclosure is a power supply control method that controls power supply via an electric wire, and includes a step of gradually increasing an average value of an electric wire current value of a current flowing through the electric wire, and a step of determining whether an abnormality has occurred in the power supply via the electric wire based on a temperature difference between an electric wire temperature of the electric wire and an ambient temperature around the electric wire each time the average value of the electric wire current value is increased, which is executed by a computer.

[0010] Note that the present disclosure can be realized not only as a power supply control device including such a characteristic processing unit, but also as a power supply control method having such a characteristic processing as a step, or as a computer program for causing a computer to execute such a step. Further, the present disclosure can be realized as a semiconductor integrated circuit that realizes part or all of the power supply control device, or as a power supply control system including the power supply control device.

Advantages of the Invention

[0011] According to the above aspect, it is possible to detect an abnormality in power supply before a cutoff condition for cutting off the power supply is satisfied.

Brief Description of the Drawings

[0012]

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Figure 12

[0013] [Description of Embodiments of the Present Disclosure] First, embodiments of the present disclosure will be enumerated and described. At least a part of the embodiments described below may be arbitrarily combined.

[0014] (1) A power supply control device according to an aspect of the present disclosure is a power supply control device that controls power supply via an electric wire, and includes a processing unit that executes processing. The processing unit gradually increases an average value of an electric wire current value of a current flowing through the electric wire, and each time the average value of the electric wire current value is increased, based on a temperature difference between an electric wire temperature of the electric wire and an ambient temperature around the electric wire, it is determined whether an abnormality has occurred in the power supply via the electric wire.

[0015] (2) In a power supply control device according to an aspect of the present disclosure, the processing unit acquires the electric wire current value, calculates the temperature difference based on the acquired electric wire current value, and each time the average value of the electric wire current value is increased, based on the calculated temperature difference, it is determined whether the abnormality has occurred.

[0016] (3) A power supply control device according to an aspect of the present disclosure includes a switch disposed in a current path of a current flowing through the electric wire and a switching circuit that switches the switch on or off. The processing unit causes the switching circuit to perform PWM control that alternately switches the switch on and off, and gradually increases the duty of the PWM control to gradually increase the average value of the electric wire current value.

[0017] (4) The power supply control device according to one aspect of the present disclosure includes a storage unit that stores a plurality of upper limit values related to the temperature difference in association with a plurality of duties related to the PWM control. Each time the processing unit increases the average value of the wire current value, the processing unit determines whether the abnormality has occurred based on whether the temperature difference exceeds the upper limit value corresponding to the duty of the PWM control being performed by the switching circuit.

[0018] (5) In the power supply control device according to one aspect of the present disclosure, each time the processing unit increases the average value of the wire current value, the processing unit determines whether the abnormality has occurred based on the rate of increase in the temperature difference that has increased due to the increase in the average value of the wire current value.

[0019] (6) The power supply control device according to one aspect of the present disclosure includes a switch disposed in the current path of the current flowing through the wire and a switching circuit that switches the switch on or off. A signal is input to the switching circuit, and the switching circuit switches the switch on or off according to the input signal. When the wire current value is greater than or equal to a current threshold value, or when the temperature of the switch is greater than or equal to a switch temperature threshold value, the switching circuit switches the switch off regardless of the input signal. After the switching circuit switches the switch off regardless of the input signal, the processing unit gradually increases the average value of the wire current value.

[0020] (7) In the power supply control device according to one aspect of the present disclosure, when the wire temperature is greater than or equal to a wire temperature threshold value, the processing unit cuts off the flow of the current flowing through the wire, and after the wire temperature reaches a temperature greater than or equal to the wire temperature threshold value, the processing unit gradually increases the average value of the wire current value.

[0021] (8) The in-vehicle control device according to one aspect of the present disclosure is an in-vehicle control device that controls the operation of a load, and includes a receiving unit that receives instruction data for instructing the operation or stop of the operation of the load, and a processing unit that executes processing. The processing unit controls power supply to the load via an electric wire according to the instruction data received by the receiving unit, gradually increases the average value of the electric wire current value of the current flowing through the electric wire, and each time the average value of the electric wire current value is increased, based on the temperature difference between the electric wire temperature of the electric wire and the ambient temperature around the electric wire, determines whether an abnormality has occurred in the power supply via the electric wire.

[0022] (9) The power supply control method according to one aspect of the present disclosure is a power supply control method for controlling power supply via an electric wire, and includes a step of gradually increasing the average value of the electric wire current value of the current flowing through the electric wire, and a step of determining whether an abnormality has occurred in the power supply via the electric wire based on the temperature difference between the electric wire temperature of the electric wire and the ambient temperature around the electric wire each time the average value of the electric wire current value is increased, which is executed by a computer.

[0023] In the power supply control device, in-vehicle control device, and power supply control method according to the above aspect, the average value of the electric wire current value over a certain period is gradually increased. Each time the average value of the electric wire current value is increased, it is determined whether an abnormality has occurred in the power supply based on the temperature difference between the electric wire temperature and the ambient temperature. Therefore, it is possible to detect an abnormality in the power supply in a state where the current value is small.

[0024] In the power supply control device according to the above aspect, based on the electric wire current value, the temperature difference between the electric wire temperature and the ambient temperature is calculated. The calculated temperature difference is used to determine whether an abnormality has occurred in the power supply.

[0025] In the power supply control device according to the above aspect, the average value of the electric wire current value is gradually increased by gradually increasing the duty of the PWM control regarding the switch. Therefore, a gradual increase in the average value of the electric wire current value is easily realized.

[0026] In the power supply control device according to the above-described aspect, the determination as to whether or not an abnormality has occurred in the power supply is made based on a comparison between the temperature difference and an upper limit value corresponding to the duty of the PWM control actually performed by the switching circuit.

[0027] In the power supply control device according to the above-described aspect, the determination as to whether or not an abnormality has occurred in the power supply is made based on the rate of increase in the temperature difference that has increased due to an increase in the duty of the PWM control.

[0028] In the power supply control device according to the above-described aspect, the switching circuit forcibly switches off the switch based on the wire current value or the temperature of the switch. After the switching circuit has forcibly switched off the switch, the average value of the wire current value is gradually increased to determine whether or not an abnormality has occurred in the power supply.

[0029] In the power supply control device according to the above-described aspect, when the wire temperature becomes a temperature equal to or higher than the wire temperature threshold value, the flow of current through the wire is forcibly interrupted. After the flow of current has been forcibly interrupted, the average value of the wire current value is gradually increased to determine whether or not an abnormality has occurred in the power supply.

[0030] [Details of Embodiments of the Present Disclosure] A specific example of a control system according to an embodiment of the present disclosure will be described below with reference to the drawings. It should be noted that the present invention is not limited to these examples, and is intended to cover all modifications within the meaning and scope equivalent to the claims, as defined by the claims.

[0031] (Embodiment 1) <Configuration of Control System> FIG. 1 is a block diagram showing the main configuration of the control system 1 in Embodiment 1. The control system 1 is mounted on the vehicle C. The control system 1 includes an integrated ECU 10, an individual ECU 11a, a plurality of individual ECUs 11b, a DC power supply 12, a load 13, an actuator 14, and two sensors 15a and 15b. The DC power supply 12 is, for example, a battery. In FIG. 1, the connection lines for supplying power are shown in thick lines. The connection lines for propagating data or signals are shown in thin lines.

[0032] The integrated ECU 10 is connected to the individual ECU 11a and the plurality of individual ECUs 11b. The individual ECU 11a is connected to the positive electrode of the DC power supply 12 and one end of the electric wire W. The other end of the electric wire W is connected to one end of the load 13. The negative electrode of the DC power supply 12 and the other end of the electric wire W are grounded. Further, a sensor 15a is connected to the individual ECU 11a. Further, the actuator 14 and the sensor 15b are separately connected to the individual ECU 11b.

[0033] The DC power supply 12 supplies power to the load 13 via the individual ECU 11a and the electric wire W. The individual ECU 11a controls the power supply to the load 13 via the electric wire W. The individual ECU 11a functions as a power supply control device. The load 13 is an electrical device such as a lamp or a motor. When power is supplied to the load 13, the load 13 operates. When the power supply to the load 13 stops, the load 13 stops operating. The individual ECU 11a controls the operation of the load 13 by controlling the power supply to the load 13. The individual ECU 11a also functions as an in-vehicle control device.

[0034] The actuator 14 is also an electrical device. The individual ECU 11b outputs a control signal indicating the operation of the actuator 14 to the actuator 14. When the control signal is input, the actuator 14 performs the operation indicated by the input control signal.

[0035] Each of sensors 15a and 15b repeatedly generates vehicle data regarding vehicle C. The vehicle data is data of an image showing the surroundings of vehicle C, data indicating the speed of vehicle C, data indicating whether a switch mounted on vehicle C is on or not, and the like. Each time sensor 15a generates vehicle data, it outputs the generated vehicle data to individual ECU 11a. Similarly, each time sensor 15b generates vehicle data, it outputs the generated vehicle data to individual ECU 11b. Each of individual ECUs 11a and 11b transmits the input vehicle data to integrated ECU 10 each time the vehicle data is input.

[0036] Based on one or more pieces of vehicle data received from at least one of individual ECU 11a and a plurality of individual ECUs 11b, integrated ECU 10 determines the operation of load 13. Here, the determined operation of load 13 is activation or stoppage of the operation. When integrated ECU 10 determines the operation of load 13, it transmits instruction data indicating the determined operation to individual ECU 11a. When individual ECU 11a receives the instruction data from integrated ECU 10, it causes load 13 to perform the operation indicated by the received instruction data.

[0037] Similarly, based on one or more pieces of vehicle data received from at least one of individual ECU 11a and a plurality of individual ECUs 11b, integrated ECU 10 determines the operations of one or more actuators 14. When integrated ECU 10 determines the operations of one or more actuators 14, it transmits instruction data indicating the determined operations to one or more individual ECUs 11b. When an individual ECU 11b receives the instruction data from integrated ECU 10, it outputs a control signal to actuator 14 connected to the individual ECU 11b. The operation indicated by the control signal is the operation indicated by the instruction data received by the individual ECU 11b. As described above, actuator 14 performs the operation indicated by the input control signal.

[0038] <Configuration of Individual ECU 11a> FIG. 2 is a block diagram showing the main configuration of the individual ECU 11a. The individual ECU 11a includes a switch device 20, a microcomputer (hereinafter referred to as a microcontroller) 21, a voltage detection unit 22, and an ambient temperature detection unit 23. The switch device 20 is separately connected to the positive electrode of the DC power supply 12 and one end of the electric wire W. The switch device 20 is further connected to the microcontroller 21. The voltage detection unit 22 is connected to the positive electrode of the DC power supply 12. The voltage detection unit 22 and the ambient temperature detection unit 23 are separately connected to the microcontroller 21. The microcontroller 21 is further connected to the integrated ECU 10 and the sensor 15a.

[0039] The switch device 20 has a switch 30 (see FIG. 3). The switch 30 is arranged in the current path of the current flowing from the positive electrode of the DC power supply 12 to the load 13. When the switch 30 is switched on, the current flows in the order of the positive electrode of the DC power supply 12, the switch 30, the electric wire W, and the load 13. Thereby, power is supplied to the load 13. When the switch 30 is switched off, the flow of the current is interrupted, and the power supply to the load 13 stops.

[0040] The switch device 20 outputs analog current value information indicating the wire current value of the current flowing through the electric wire W to the microcontroller 21. The current value information is a voltage value proportional to the wire current value. The switch device 20 further outputs switch temperature information indicating the temperature of the switch 30 to the microcontroller 21. Hereinafter, the temperature of the switch 30 is referred to as the switch temperature. The switch temperature information is a voltage value that varies according to the switch temperature.

[0041] The microcontroller 21 outputs a PWM (Pulse Width Modulation) signal or an off signal indicating the off state of the switch 30 to the switch device 20. The PWM signal indicates a high-level voltage and a low-level voltage. The off signal indicates a low-level voltage. In the PWM signal, the switching from the low-level voltage to the high-level voltage is periodically performed. The duty of the PWM signal is the ratio that the period during which the voltage indicated by the PWM signal is the high-level voltage occupies in one cycle. The unit of the duty is a percentage. The duty exceeds 0% and is 100% or less. The duty is adjusted by adjusting the timing at which the switching from the high-level voltage to the low-level voltage is performed.

[0042] Note that in the PWM signal, the switching from the high-level voltage to the low-level voltage may be periodically performed. In this case, the duty is adjusted by adjusting the timing at which the switching from the low-level voltage to the high-level voltage is performed.

[0043] Hereinafter, it is assumed that the microcontroller 21 outputs a PWM signal to the switch device 20 in a state where the wire current value is less than a certain current threshold and the switch temperature is less than a certain switch temperature threshold. In this case, when the voltage indicated by the PWM signal switches from the low-level voltage to the high-level voltage, the switch device 20 switches the switch 30 from off to on. In the same case, when the voltage indicated by the PWM signal switches from the high-level voltage to the low-level voltage, the switch device 20 switches the switch 30 from on to off. When the microcontroller 21 outputs a PWM signal, power is supplied to the load 13.

[0044] As described above, the switch device 20 performs PWM control that alternately switches the switch 30 between on and off according to the input PWM signal. The duty of the PWM control is the ratio that the period during which the switch 30 is on occupies in a certain period. The duty of the PWM control matches the duty of the PWM signal. The larger the duty of the PWM signal, the longer the period during which the switch 30 is on. Therefore, the larger the duty of the PWM signal, the larger the average value of the wire current value in a certain period. The certain period is, for example, one cycle of the PWM signal.

[0045] When the microcomputer 21 outputs an off signal, the switch device 20 keeps the switch 30 off. Therefore, when the microcomputer 21 outputs an off signal, the load 13 stops operating.

[0046] When the microcomputer 21 outputs a PWM signal to the switch device 20, when the wire current value is equal to or greater than the current threshold, the switch device 20 forcibly switches the switch 30 off regardless of the PWM signal input to the switch device 20 and maintains the off state of the switch 30. Hereinafter, the forced off of the switch 30 is described as self-cutoff. By forcibly switching the switch 30 off, the flow of current through the wire W is forcibly interrupted.

[0047] When the wire current value of the switch device 20 becomes a current value equal to or greater than the current threshold, the switch device 20 outputs the maximum voltage value that is allowed to be output to the microcomputer 21. Thereby, the execution of self-cutoff is notified to the microcomputer 21. When the execution of self-cutoff is notified, the microcomputer 21 outputs an off signal to the switch device 20. When the microcomputer 21 outputs an off signal to the switch device, the self-cutoff is released.

[0048] When the microcomputer 21 outputs a PWM signal to the switch device 20, if the switch temperature is equal to or higher than the switch temperature threshold value, the switch device 20 performs self-cutoff of the switch 30 regardless of the PWM signal input to the switch device 20. When the switch temperature of the switch device 20 reaches a temperature equal to or higher than the switch temperature threshold value, the switch device 20 outputs the maximum voltage value that is allowed to be output to the microcomputer 21. Thereby, the execution of self-cutoff is notified to the microcomputer 21. When the execution of self-cutoff is notified, the microcomputer 21 outputs an off signal to the switch device 20. When the microcomputer 21 outputs an off signal to the switch device, the self-cutoff is released.

[0049] The voltage detection unit 22 detects the voltage value between both ends of the DC power supply 12. Hereinafter, the voltage value between both ends of the DC power supply 12 is referred to as the power supply voltage value. The voltage detection unit 22 outputs analog power supply voltage value information indicating the detected power supply voltage value to the microcomputer 21. The power supply voltage value information is, for example, a voltage value obtained by dividing the power supply voltage value. The ambient temperature detection unit 23 detects the ambient temperature around the electric wire W. The ambient temperature is the ambient temperature around the electric wire W. The ambient temperature detection unit 23 outputs analog ambient temperature information indicating the detected ambient temperature. The ambient temperature information is, for example, a voltage value that varies according to the ambient temperature. Each time the sensor 15a generates vehicle data, the sensor 15a outputs the generated vehicle data to the microcomputer 21.

[0050] The microcomputer 21 transmits the vehicle data input from the sensor 15a to the integrated ECU 10. The microcomputer 21 receives instruction data for instructing the operation or stop of the operation of the load 13 from the integrated ECU 10. When the microcomputer 21 receives the instruction data for instructing the operation of the load 13, the microcomputer 21 outputs a PWM signal to the switch device 20. When the microcomputer 21 outputs a PWM signal to the switch device 20, the switch device 20 performs PWM control of the switch 30, and power is supplied to the load 13. As a result, the load 13 operates.

[0051] When the microcomputer 21 receives instruction data instructing to stop the operation of the load 13, it outputs an OFF signal to the switch device 20. As a result, the power supply to the load 13 is stopped, so the load 13 stops operating.

[0052] When the microcomputer 21 is outputting a PWM signal to the switch device 20, it adjusts the duty of the PWM signal based on the power supply voltage value indicated by the power supply voltage value information input from the voltage detection unit 22. Further, the microcomputer 21 repeatedly calculates the wire temperature of the wire W based on the wire current value of the wire W indicated by the current value information input from the switch device 20, the environmental temperature indicated by the environmental temperature information input from the environmental temperature detection unit 23, and the duty of the PWM signal output to the switch device 20.

[0053] When the calculated wire temperature of the wire W is equal to or higher than a certain wire temperature threshold value, the microcomputer 21 outputs an OFF signal to the switch device 20. As a result, the switch device 20 switches the switch 30 to OFF. Consequently, the power supply to the load 13 is stopped, so the load 13 stops operating.

[0054] <Configuration of the Switch Device 20> FIG. 3 is a circuit diagram of the switch device 20. The switch device 20 includes, in addition to the switch 30, a drive circuit 31, a current detection circuit 32, and a switch temperature detection circuit 33. The switch 30 is an N-channel type FET. The current detection circuit 32 includes a current output unit 40 and a current detection resistor 41. The switch temperature detection circuit 33 includes an NTC (Negative Temperature Coefficient) type thermistor 50 and a temperature detection resistor 51.

[0055] The drain of the switch 30 is connected to the positive electrode of the DC power supply 12. The source of the switch 30 is connected to one end of the wire W. As described above, the other end of the wire W is connected to one end of the load 13. The gate of the switch 30 is connected to the drive circuit 31. The drive circuit 31 is further connected to the microcomputer 21.

[0056] The drain of switch 30 is further connected to the current output section 40 of the current detection circuit 32. The current output section 40 is further connected to one end of a current detection resistor 41. The other end of the current detection resistor 41 is grounded. The connection node between the current output section 40 and the current detection resistor 41 is connected to the microcomputer 21 and the drive circuit 31.

[0057] In the switch temperature detection circuit 33, a constant voltage is applied to one end of a thermistor 50. The constant voltage is generated, for example, by a regulator (not shown) stepping down the voltage across the DC power supply 12. The reference potential of the constant voltage is the ground potential. The voltage value of the constant voltage is represented by Vc. The other end of the thermistor 50 is connected to one end of a temperature detection resistor 51. The other end of the temperature detection resistor 51 is grounded. The connection node between the thermistor 50 and the temperature detection resistor 51 is connected to the microcomputer 21 and the drive circuit 31.

[0058] In switch 30, when the voltage value of the gate, whose reference potential is the source potential, is equal to or higher than a constant voltage value, switch 30 is on. When switch 30 is on, the resistance value between the drain and the source in switch 30 is sufficiently small. Therefore, current can flow through the drain and the source of switch 30. When switch 30 is on, current flows from the positive electrode of the DC power supply 12, through switch 30, wire W, and load 13 in that order. Therefore, switch 30 is arranged in the current path of the current flowing through wire W.

[0059] In switch 30, when the voltage value of the gate, whose reference potential is the source potential, is less than the constant voltage value, switch 30 is off. When switch 30 is off, the resistance value between the drain and the source in switch 30 is sufficiently large. Therefore, no current flows through the drain and the source of switch 30. When switch 30 is off, no current flows through switch 30 and wire W.

[0060] The microcontroller 21 outputs a PWM signal to the drive circuit 31. Assume that the wire current value is less than the current threshold and the switch temperature is less than the switch temperature threshold. In this case, when the voltage of the PWM signal switches from the low-level voltage to the high-level voltage, the drive circuit 31 raises the voltage value of the gate whose reference potential is the ground potential at the switch 30. As a result, at the switch 30, the voltage value of the gate whose reference potential is the source potential rises to a voltage equal to or higher than a certain voltage value, and the switch 30 switches to the on state.

[0061] In a similar case, when the voltage of the PWM signal switches from the high-level voltage to the low-level voltage, the drive circuit 31 lowers the voltage value of the gate whose reference potential is the ground potential at the switch 30. As a result, at the switch 30, the voltage value of the gate whose reference potential is the source potential rises to a voltage less than a certain voltage value, and the switch 30 switches to the off state.

[0062] As described above, the drive circuit 31 switches the switch 30 on or off by adjusting the voltage value of the gate whose reference potential is the source potential. The drive circuit 31 functions as a switching circuit. Assume that the wire current value is less than the current threshold and the switch temperature is less than the switch temperature threshold. In this case, when the microcontroller 21 outputs a PWM signal to the drive circuit 31, the drive circuit 31 performs PWM control of the switch 30 according to the voltage of the PWM signal. As described above, the duty of the PWM control matches the duty of the PWM signal. When the drive circuit 31 performs PWM control of the switch 30, power is supplied to the load 13.

[0063] The microcontroller 21 outputs an off signal to the drive circuit 31. When the microcontroller 21 outputs an off signal to the drive circuit 31, the drive circuit 31 switches the switch 30 to the off state. While the microcontroller 21 is outputting the off signal, the drive circuit 31 maintains the switch 30 in the off state.

[0064] In the current detection circuit 32, the current output unit 40 draws current from the drain of the switch 30 and outputs the drawn current to the current detection resistor 41. The current value of the current drawn by the current output unit 40 is proportional to the wire current value and is represented by (wire current value) / (predetermined number). The predetermined number is, for example, 1000. The wire current value is the current value of the current flowing through the switch 30 and the wire W.

[0065] In the current detection circuit 32, the voltage value between both ends of the current detection resistor 41 is output as current value information to the microcomputer 21 and the drive circuit 31. The current value information is represented by (wire current value)·(resistance value of the current detection resistor 41) / (predetermined number). "·" represents a product. Since the resistance value of the current detection resistor 41 and the predetermined number are constant values, the wire current value can be calculated based on the current value information. The current value information is larger as the wire current value is larger.

[0066] While the microcomputer 21 outputs a PWM signal to the drive circuit 31, current flows through the switch 30 and the wire W. When the wire current value indicated by the current value information becomes a current value equal to or greater than the wire current threshold value, the drive circuit 31 performs self - interruption of the switch 30 regardless of the input PWM signal.

[0067] When the wire current value indicated by the current value information becomes a current value equal to or greater than the wire current threshold value, the drive circuit 31 applies a voltage between both ends of the current detection resistor 41. The voltage value of this voltage is the maximum voltage value that is allowed to be output to the microcomputer 21. The maximum voltage value is input to the microcomputer 21. Thereby, the microcomputer 21 is notified of the execution of self - interruption of the drive circuit 31. As described above, when the microcomputer 21 is notified of the execution of self - interruption, it outputs an off signal to the drive circuit 31. When the microcomputer 21 outputs an off signal, the self - interruption of the drive circuit 31 is released.

[0068] In the switch temperature detection circuit 33, the thermistor 50 and the temperature detection resistor 51 divide a constant voltage with a voltage value of Vc. The switch temperature detection circuit 33 outputs the divided voltage value obtained by dividing the constant voltage as switch temperature information to the microcomputer 21 and the drive circuit 31. Let the resistance value of the temperature detection resistor 51 be denoted as rd. Let the resistance value of the thermistor 50 be denoted as rt. The switch temperature information, that is, the divided voltage value, is represented by Vc·rd / (rd + rt). Since the voltage value Vc and the resistance value rd are constant, the switch temperature information indicates the resistance value rt of the thermistor 50.

[0069] Since the type of the thermistor 50 is NTC, the resistance value rt becomes smaller as the temperature of the thermistor 50 is higher. The thermistor 50 is arranged near the switch 30. When the switch temperature of the switch 30 rises, the temperature of the thermistor 50 rises. When the switch temperature drops, the temperature of the thermistor 50 drops. Therefore, the resistance value rt of the thermistor 50 becomes smaller as the switch temperature is higher. Thus, the resistance value rt of the thermistor 50 indicates the switch temperature. The switch temperature information, that is, the divided voltage value, is higher as the switch temperature is higher.

[0070] When the switch temperature indicated by the switch temperature information in the drive circuit 31 reaches a temperature equal to or higher than the switch temperature threshold, a voltage is applied across the temperature detection resistor 51. The voltage value of this voltage is the maximum voltage value that is allowed to be output to the microcomputer 21. The maximum voltage value is input to the microcomputer 21. Thereby, the microcomputer 21 is notified of the execution of self-shutdown of the drive circuit 31. As described above, when the microcomputer 21 is notified of the execution of self-shutdown, the microcomputer 21 outputs an off signal to the drive circuit 31. When the microcomputer 21 outputs an off signal, the self-shutdown of the drive circuit 31 is released.

[0071] As described above, when the microcomputer 21 outputs a PWM signal to the drive circuit 31, the drive circuit 31 performs PWM control of the switch 30. As a result, current flows through the switch 30 and the electric wire W, and the switch temperature rises. When the electric wire current value becomes equal to or greater than the electric wire current threshold value, or when the switch temperature becomes equal to or higher than the switch temperature threshold value, the drive circuit 31 performs self-shutdown and notifies the microcomputer 21 of the execution of the self-shutdown. When notified of the execution of the self-shutdown, the microcomputer 21 outputs an off signal to the drive circuit 31. Thereby, the self-shutdown of the drive circuit 31 is released.

[0072] Note that in the switch temperature detection circuit 33, the type of the thermistor 50 is not limited to NTC, and it may be PTC (Positive Temperature Coefficient). In this case, the resistance value of the thermistor 50 increases as the temperature of the thermistor 50, that is, the switch temperature, increases. Therefore, the switch temperature information decreases as the switch temperature increases. Furthermore, the arrangement of the thermistor 50 and the temperature detection resistor 51 may be reversed. In this case, the thermistor 50 is grounded and a constant voltage is applied to the temperature detection resistor 51. When a constant voltage is applied to the temperature detection resistor 51, when the type of the thermistor 50 is NTC, the switch temperature information decreases as the switch temperature increases. In the same case, when the type of the thermistor 50 is PTC, the switch temperature information increases as the switch temperature increases. When a constant voltage is applied to the temperature detection resistor 51 and the drive circuit 31 performs self-shutdown, the drive circuit 31 applies a voltage to the thermistor 50.

[0073] <Main Component Configuration of Microcomputer 21> Figure 4 is a block diagram showing the main configuration of the microcomputer 21. The microcomputer 21 includes A / D conversion units 60, 61, 62, 63, an output unit 64, an input unit 65, a communication unit 66, a storage unit 67, and a control unit 68. These are connected to an internal bus 69. Each of the A / D conversion units 60, 61, 62, 63 is further connected to a voltage detection unit 22, a switch temperature detection circuit 33, a current detection circuit 32, and an environmental temperature detection unit 23. The output unit 64 is further connected to a drive circuit 31. The input unit 65 is further connected to a sensor 15a. The communication unit 66 is further connected to the integrated ECU 10.

[0074] The voltage detection unit 22 outputs analog power supply voltage value information to the A / D conversion unit 60. The A / D conversion unit 60 converts the input analog power supply voltage value information into digital power supply voltage value information. The control unit 68 acquires the digital power supply voltage value information from the A / D conversion unit 60. The output unit 64 is an interface. The output unit 64 outputs a PWM signal and an off signal to the drive circuit 31 according to an instruction from the control unit 68. The duty of the PWM signal output by the output unit 64 is adjusted by the control unit 68.

[0075] The switch temperature detection circuit 33 outputs analog switch temperature information to the A / D conversion unit 61. The A / D conversion unit 61 converts the input analog switch temperature information into digital switch temperature information. The control unit 68 acquires the digital switch temperature information from the A / D conversion unit 61. The current detection circuit 32 outputs analog current value information to the A / D conversion unit 62. The A / D conversion unit 62 converts the input analog current value information into digital current value information. The control unit 68 acquires the digital current value information from the A / D conversion unit 62.

[0076] The environmental temperature detection unit 23 outputs analog environmental temperature information to the A / D conversion unit 63. The A / D conversion unit 63 converts the input analog environmental temperature information into digital environmental temperature information. The control unit 68 acquires the digital environmental temperature information from the A / D conversion unit 63. The input unit 65 is an interface. Each time the sensor 15a generates vehicle data, the generated vehicle data is output to the input unit 65. The control unit 68 acquires the vehicle data input from the sensor 15a from the input unit 65.

[0077] The communication unit 66 transmits the vehicle data to the integrated ECU 10 according to the instruction of the control unit 68. The communication unit 66 receives instruction data for instructing the operation or stop of operation of the load 13 from the integrated ECU 10. The communication unit 66 functions as a receiving unit.

[0078] The storage unit 67 is a non-volatile memory. A computer program P is stored in the storage unit 67. The control unit 68 has a processing element for executing processing, for example, a CPU (Central Processing Unit). The control unit 68 functions as a processing unit. The processing element (computer) of the control unit 68 executes the vehicle data transmission process, the temperature calculation process, the power supply control process, etc. in parallel by executing the computer program P. The vehicle data transmission process is a process of transmitting vehicle data to the integrated ECU 10. The temperature calculation process is a process of calculating the wire temperature of the wire W. The power supply control process is a process of controlling the power supply to the load 13.

[0079] Note that the computer program P may be stored in a non-transitory storage medium A in a readable manner by the processing element of the control unit 68. In this case, the computer program P read from the storage medium A by a reading device (not shown) is written into the storage unit 67. The storage medium A is an optical disk, a flexible disk, a magnetic disk, a magneto-optical disk, a semiconductor memory, or the like. The optical disk is a CD (Compact Disc)-ROM (Read Only Memory), a DVD (Digital Versatile Disc)-ROM, or a BD (Blu-ray (registered trademark) Disc), etc. The magnetic disk is, for example, a hard disk. Also, the computer program P may be downloaded from an external device (not shown) connected to a communication network (not shown), and the downloaded computer program P may be written into the storage unit 67.

[0080] The number of processing elements included in the control unit 68 is not limited to 1, and may be 2 or more. When the number of processing elements included in the control unit 68 is 2 or more, a plurality of processing elements may cooperate to execute vehicle data transmission processing, temperature calculation processing, power supply control processing, and the like.

[0081] The control unit 68 periodically executes temperature calculation processing. In the temperature calculation processing, the control unit 68 calculates the temperature difference between the wire temperature and the ambient temperature, and adds the ambient temperature to the calculated temperature difference. Thereby, the wire temperature is calculated.

[0082] In the calculation of the wire temperature, the control unit 68 calculates the temperature difference ΔTw by substituting the previously calculated leading temperature difference ΔTp, the wire current value Iw of the wire W, the ambient temperature Ta, and the PWM signal, that is, the duty D of the PWM control, into the following mathematical formulas [1] and [2]. ΔTw = ΔTp·exp(-Δt / τr) +Rth·Rw·D·Iw2 ·(1-exp(-Δt / τr)) / 100···[1] Rw = Ro·(1+κ·(Ta+ΔTp-To))···[2]

[0083] The variables and constants used in the mathematical formulas [1] and [2] are explained. In the explanation of the variables and constants, the units of the variables or constants are also shown. ΔTw, ΔTp, Ta, Iw, Rw, Rth, and D are, as described above, the calculated temperature difference (°C), the leading temperature difference (°C), the ambient temperature (°C), the wire current value (A) of the wire W, the wire resistance value (Ω) of the wire W, the wire thermal resistance value (°C / W) of the wire W, and the duty (%) of the PWM signal, respectively. Δt is the period (s) for calculating the temperature difference ΔTw, that is, the period in which the temperature calculation processing is executed. τr is the wire heat dissipation time constant (s) of the wire W.

[0084] To is a predetermined temperature (°C). Ro is the wire resistance value (Ω) at temperature To. κ is the wire resistance temperature coefficient ( / °C) of the wire W. The temperature difference ΔTw, the previous temperature difference ΔTp, the wire current value Iw, and the ambient temperature Ta are variables. The period Δt, the wire heat dissipation time constant τr, the wire thermal resistance value Rth, the wire resistance value Ro, the wire resistance temperature coefficient κ, and the temperature To are constants set in advance.

[0085] Since the value of the first term in Equation [1] decreases as the period Δt becomes longer, the first term in the arithmetic expression [1] represents the heat dissipation of the wire W. Also, since the value of the second term in Equation [1] increases as the period Δt becomes longer, the second term in Equation [1] represents the heat generation of the wire W.

[0086] The storage unit 67 stores the wire temperature and the previous temperature difference of the wire W. Each of the wire temperature and the previous temperature difference stored in the storage unit 67 is changed by the control unit 68.

[0087] Also, in the power supply control process, the control unit 68 gradually increases the duty of the PWM signal. The storage unit 67 stores a temperature difference table Q1. In the temperature difference table Q1, a plurality of upper limit values related to the temperature difference between the wire temperature and the ambient temperature are shown in association with a plurality of duties related to PWM control. Each time the control unit 68 increases the duty of the PWM signal, it determines whether an abnormality has occurred in the power supply to the load 13 via the wire W based on whether the temperature difference is greater than or equal to the upper limit value of the temperature difference corresponding to the duty of the PWM signal output to the drive circuit 31.

[0088] FIG. 5 is a chart showing the content of the temperature difference table Q1. As shown in FIG. 5, in the temperature difference table Q1, the temperature difference between the wire temperature and the ambient temperature is shown in association with each of a plurality of duties. In the example of FIG. 5, a plurality of duties are shown in 10% increments. The upper limit value of the temperature difference corresponding to each duty is shown. The upper limit value is, for example, the temperature difference calculated when the duty of the PWM signal is adjusted to the duty shown in the temperature difference table Q1 when the power supply voltage value of the DC power supply 12 is at the maximum value in the normal state. In the temperature difference table Q1, the larger the duty, the larger the upper limit value.

[0089] As described above, in the power supply control process, the control unit 68 gradually increases the duty of the PWM signal. The storage unit 67 stores a rise width table. In the rise width table Q2, a plurality of rise widths related to the temperature difference between the wire temperature and the ambient temperature are shown in association with the rise of a plurality of duties. Each time the control unit 68 increases the duty of the PWM signal, based on whether the rise width of the temperature difference is equal to or greater than the upper limit value of the rise width corresponding to the actually performed duty increase, it is determined whether an abnormality has occurred in the power supply to the load 13 via the wire W.

[0090] FIG. 6 is a chart showing the content of the rise width table Q2. As shown in FIG. 6, in the rise width table Q2, the upper limit value of the rise width of the temperature difference is shown in association with the rise of a plurality of duties. In the example of FIG. 6, the duty is increased in 10% increments. The upper limit value is, for example, the rise width of the temperature difference calculated when the duty of the PWM signal is increased as shown in the rise width table Q2 when the power supply voltage value of the DC power supply 12 is at the maximum value in the normal state.

[0091] Note that when the ambient temperature is the same, the rise width of the temperature difference corresponds to the rise width of the wire temperature. The wire temperature is represented by the sum of the temperature difference and the ambient temperature. When the ambient temperature is the same, the rise widths of the two wire temperatures are represented by the rise width of the temperature difference.

[0092] <Vehicle data transmission process> In the vehicle data transmission process, the control unit 68 waits until vehicle data is input from the sensor 15a to the input unit 65. When vehicle data is input to the input unit 65, the control unit 68 acquires the vehicle data input to the input unit 65. Next, the control unit 68 instructs the communication unit 66 to transmit the acquired vehicle data to the integrated ECU 10 and ends the vehicle data transmission process. After ending the vehicle data transmission process, the control unit 68 executes the vehicle data transmission process again.

[0093] <Temperature calculation process> FIG. 7 is a flowchart showing the procedure of the temperature calculation process. As described above, the control unit 68 periodically executes the temperature calculation process. In the temperature calculation process, the control unit 68 acquires current value information indicating the wire current value of the wire W from the A / D conversion unit 62 (step S1). When the output unit 64 is outputting the duty of the PWM signal, the control unit 68 acquires the current value information during the period when the PWM signal indicates a high-level voltage. Next, the control unit 68 reads the previous temperature difference from the storage unit 67 (step S2). This previous temperature difference is the temperature difference calculated in the previous temperature calculation process. In the temperature calculation process executed first after the microcomputer 21 is activated, the previous temperature difference is zero degrees. After executing step S2, the control unit 68 acquires environmental temperature information from the A / D conversion unit 63 (step S3).

[0094] The control unit 68 calculates the temperature difference between the wire temperature and the environmental temperature by substituting a plurality of numerical values into formulas [1] and [2] (step S4). The plurality of numerical values are the wire current value indicated by the current value information acquired in step S1, the previous temperature difference read in step S2, the environmental temperature indicated by the environmental temperature information acquired in step S3, and the duty of the PWM signal output by the output unit 64. When the output unit 64 is outputting an off signal, the duty is zero.

[0095] Next, the control unit 68 changes the previous temperature difference stored in the storage unit 67 to the temperature difference calculated in step S4 (step S5). The changed previous temperature difference is used in the next temperature calculation process. The previous temperature difference is the latest temperature difference calculated in the temperature calculation process. After executing step S5, the control unit 68 calculates the wire temperature by adding the temperature difference calculated in step S4 to the ambient temperature indicated by the ambient temperature information acquired in step S3 (step S6).

[0096] Next, the control unit 68 changes the wire temperature stored in the storage unit 67 to the wire temperature calculated in step S6 (step S7). For this reason, the wire temperature stored in the storage unit 67 is the latest wire temperature calculated in the temperature calculation process. After executing step S7, the control unit 68 ends the temperature calculation process. As described above, the storage unit 67 stores the previous temperature difference, which is the latest temperature difference, and the latest wire temperature.

[0097] <Power supply control process> FIG. 8 and FIG. 9 are flowcharts showing the procedure of the power supply control process. In the power supply control process, the control unit 68 adjusts the duty of the PWM signal to a duty at which the related value related to the load 13 becomes a constant target value. The related value is the wire current value, the power supplied to the load 13, or the voltage value of the voltage applied to the load 13. As described above, the wire current value is the current value of the current flowing through the load 13 via the wire W.

[0098] Also, the storage unit 67 stores the value of a flag indicating the state of the individual ECU 11a. The value of the flag is zero, 1, or 2, and is changed by the control unit 68. The fact that the value of the flag is zero means that the power supply to the load 13 is performed normally. The fact that the value of the flag is 1 means that the current through the wire W has been forcibly interrupted. The fact that the value of the flag is 2 means that an abnormality has occurred in the power supply to the load 13.

[0099] The control unit 68 executes power supply control processing while the output unit 64 is outputting an off signal. In the power supply control processing, the control unit 68 first determines whether to operate the load 13 (step S11). In step S11, when the communication unit 66 receives instruction data for instructing the operation of the load 13, the control unit 68 determines to operate the load 13. When the communication unit 66 has not received instruction data for instructing the operation of the load 13, the control unit 68 determines not to operate the load 13. When the control unit 68 determines not to operate the load 13 (S11: NO), it executes step S11 again and waits until the communication unit 66 receives instruction data for instructing the operation of the load 13.

[0100] When the control unit 68 determines to operate the load 13 (S11: YES), it determines whether the value of the flag is zero (step S12). When the control unit 68 determines that the value of the flag is zero (S12: YES), it acquires power supply voltage value information from the A / D conversion unit 60 (step S13). Next, based on the power supply voltage value indicated by the power supply voltage value information acquired in step S13, the control unit 68 calculates the duty of the PWM signal for which the average value of the related value in a certain period becomes a certain target value (step S14). The target value is set in advance. As described above, the certain period is, for example, one cycle of the PWM signal.

[0101] For example, when the load 13 is a lamp having an LED (Light Emitting Diode), the higher the average value of the wire current value in a certain period, the higher the brightness of the load 13. When the load 13 is a lamp having an LED, the related value is the wire current value. The target value is the current value. The wire current value of the current flowing when the switch 30 is on is referred to as the switch current value. The switch current value is calculated based on the power supply voltage value indicated by the power supply voltage value information acquired in step S13. The duty calculated by the control unit 68 in step S14 is represented by 100·(target value) / (switch current value).

[0102] For example, when the load 13 is a headlight having an incandescent bulb, the luminance of the load 13 is higher as the average value of the power supplied to the load 13 within a certain period is larger. When the load 13 is a headlight having an incandescent bulb, the related value is the power supplied to the load 13. The target value is also power. The power supplied to the load 13 when the switch 30 is on is referred to as the load power. The load power is calculated based on the power supply voltage value indicated by the power supply voltage value information acquired in step S13. The duty calculated by the control unit 68 in step S14 is represented by 100· (target value) / (load power).

[0103] For example, when the load 13 is a DC motor, the rotational speed of the load 13 is faster as the average value of the voltage applied to the load 13 within a certain period is higher. When the load 13 is a DC motor, the related value is the voltage value of the voltage applied to the load 13. The target value is also a voltage value. The voltage value of the voltage applied to the load 13 when the switch 30 is on is referred to as the load voltage value. The load voltage value is calculated based on the power supply voltage value indicated by the power supply voltage value information acquired in step S13. The duty calculated by the control unit 68 in step S14 is represented by 100·(target value) / (load voltage value).

[0104] Next, the control unit 68 instructs the output unit 64 to output a PWM signal having the duty calculated in step S14 (step S15). Thereby, the drive circuit 31 performs PWM control of the switch 30 according to the voltage indicated by the PWM signal. The duty of the PWM control performed by the drive circuit 31 is adjusted to the duty calculated in step S14. By the drive circuit 31 performing PWM control of the switch 30, a current flows through the electric wire W, and the average value of the related value is adjusted to the target value. By a current flowing through the electric wire W, power supply to the load via the electric wire W is performed.

[0105] Next, the control unit 68 reads out the latest wire temperature calculated in the temperature calculation process from the storage unit 67 (step S16), and determines whether the read wire temperature is equal to or higher than the wire temperature threshold (step S17). When the control unit 68 determines that the wire temperature is lower than the wire temperature threshold (S17: NO), it determines whether the self-shutdown of the switch 30 has been performed by the drive circuit 31 (step S18). In step S18, the control unit 68 determines that self-shutdown has been performed when the maximum voltage value that can be output to the microcomputer 21 is input to at least one of the A / D conversion units 61 and 62. The control unit 68 determines that self-shutdown has not been performed when the aforementioned maximum voltage value is not input to any of the A / D conversion units 61 and 62.

[0106] When the control unit 68 determines that self-shutdown has not been performed (S18: NO), it determines whether to stop the operation of the load 13 (step S19). In step S19, the control unit 68 determines to stop the operation of the load 13 when the communication unit 66 receives instruction data for instructing the stop of the operation of the load 13. The control unit 68 determines not to stop the operation of the load 13 when the communication unit 66 has not received the instruction data for instructing the stop of the operation of the load 13.

[0107] When the control unit 68 determines not to stop the operation of the load 13 (S19: NO), it acquires power supply voltage value information from the A / D conversion unit 60 (step S20). Next, similar to step S14, the control unit 68 calculates the duty of the PWM signal for which the average value of the related values becomes the target value based on the power supply voltage value indicated by the power supply voltage value information acquired in step S20 (step S21). Next, the control unit 68 changes the duty of the PWM signal output by the output unit 64 to the duty calculated in step S21 (step S22). After executing step S22, the control unit 68 executes step S16 again.

[0108] Assume that the wire temperature is below the wire temperature threshold, self - cut - off has not occurred, and the communication unit 66 has not received instruction data for instructing the stop of the operation of load 13. In this case, the duty is changed according to the power supply voltage value of the DC power supply 12. Specifically, when the power supply voltage value decreases, the control unit 68 increases the duty. When the power supply voltage value increases, the control unit 68 decreases the duty. Thereby, even when the power supply voltage value fluctuates, the related value of load 13 is maintained at the target value. For example, when the positive electrode of the DC power supply 12 is connected to the starter of the vehicle C, when the starter operates, the power supply voltage value decreases. In the same case, when the starter stops operating, the power supply voltage value increases.

[0109] When the control unit 68 determines that the wire temperature is equal to or higher than the wire temperature threshold (S17: YES), or when it determines that self - cut - off has occurred (S18: YES), it changes the value of the flag to 1 (step S23). When the control unit 68 determines to stop the operation of load 13 (S19: YES), or after executing step S23, it instructs the output unit 64 to output an off - signal to the drive circuit 31 (step S24). Thereby, the drive circuit 31 maintains the switch 30 in the off state. As a result, the flow of the current flowing through the wire W is interrupted. Consequently, the power supply to load 13 via the wire W stops. As described above, when the output unit 64 outputs an off - signal while the drive circuit 31 is in the state of self - cut - off, the self - cut - off is released.

[0110] After executing step S24, the control unit 68 ends the power - supply control process. After ending the power - supply control process, the control unit 68 executes the power - supply control process again and waits until the communication unit 66 receives instruction data for instructing the operation of load 13.

[0111] When the control unit 68 determines that the value of the flag is not zero (S12: NO), it determines whether the value of the flag is 1 (step S25). When the control unit 68 determines that the value of the flag is 1 (step S25: YES), it determines whether the latest temperature difference calculated in the temperature calculation process is less than or equal to the reference temperature difference (step S26). The reference temperature difference is a constant value, which is zero degrees or a positive temperature close to zero degrees. The reference temperature difference is set in advance.

[0112] When the control unit 68 determines that the value of the flag is not 1 (S25: NO), or when it determines that the latest temperature difference exceeds the reference temperature difference (S26: NO), it ends the power supply control process without outputting a PWM signal to the output unit 64. After the control unit 68 ends the power supply control process, it executes the power supply control process again. As described above, when the value of the flag is 2, the power supply to the load 13 is not started. Even when the value of the flag is 1, when the latest temperature difference exceeds the reference temperature difference, the control unit 68 does not instruct the output unit 64 to output a PWM signal.

[0113] When the control unit 68 determines that the latest temperature difference is less than or equal to the reference temperature difference (S26: YES), it instructs the output unit 64 to output a PWM signal to the drive circuit 31 (step S27). Thereby, the drive circuit 31 performs PWM control. In step S27, the duty of the PWM signal is adjusted to the smallest duty among the multiple duties indicated by the temperature difference table Q1. In the example of FIG. 5, the duty of the PWM signal is adjusted to 10%. When the control unit 68 executes step S27, a current flows through the load 13 via the electric wire W. Since the duty of the PWM signal is small, the average value of the electric wire current value is small.

[0114] After the control unit 68 executes step S27, it determines whether the latest temperature difference calculated in the temperature calculation process exceeds the upper limit value of the temperature difference corresponding to the duty of the PWM signal output by the output unit 64 in the temperature difference table Q1 (step S28). Note that after the control unit 68 executes step S27, it executes step S28 after a certain period has elapsed. The certain period is equal to or longer than one cycle of the temperature calculation process. Therefore, after step S27 is executed, the temperature difference is calculated at least once.

[0115] When the control unit 68 determines that the latest temperature difference is equal to or less than the upper limit value (S28: NO), it determines whether the increase width of the temperature difference increased by the increase in the duty of the PWM signal exceeds the upper limit value of the increase width corresponding to the actually performed increase in duty in the increase width table Q2 (step S29). In the example of FIG. 6, when the duty increases from 0% to 10% due to the output unit 64 outputting a PWM signal, it is determined whether the increase width exceeds the upper limit value of the increase width corresponding to the increase from 0% to 10%.

[0116] When the control unit 68 determines that the increase width of the temperature difference is equal to or less than the upper limit value (S29: NO), it determines whether the duty of the PWM signal output by the output unit 64 is the reference duty (step S30). The reference duty is a fixed value and is set in advance. The reference duty is the maximum duty shown in the temperature difference table Q1. In the example of FIG. 5, the reference duty is 100%.

[0117] Note that the reference duty is not limited to 100%. The reference duty may be a value less than 100%. For example, when the maximum value of the duty of the PWM signal when adjusting the duty of the PWM signal so that the average value of the related values of the load 13 becomes the target value is 80%, the reference duty may be set to 80%.

[0118] When the control unit 68 determines that the duty of the PWM signal is not the reference duty (S30: NO), it increases the duty of the PWM signal output by the output unit 64 (step S31). The duty of the PWM signal output by the output unit 64 is described as the actual duty. In step S31, the control unit 68 increases the duty of the PWM signal in the temperature difference table Q1 to a duty that is larger than the actual duty and closest to the actual duty. In the example of FIG. 5, when the actual duty is 10%, in step S31, the control unit 68 increases the duty of the PWM signal to 20%.

[0119] After executing step S31, the control unit 68 executes step S28 again. The control unit 68 gradually increases the PWM signal, that is, the duty of the PWM control, until the duty of the PWM signal becomes the reference duty. As a result, the average value of the wire current value over a certain period gradually increases. Each time the control unit 68 increases the duty of the PWM control, it executes steps S28 and S29. When the control unit 68 determines that the duty of the PWM signal is the reference duty (S30: YES), it changes the value of the flag to zero (step S32). After executing step S32, the control unit 68 executes step S20.

[0120] As described above, when the state where the temperature difference is below the upper limit value and the increase width of the temperature difference is below the upper limit value continues until the duty of the PWM signal becomes the reference duty, the individual ECU 11a is considered normal, and the control unit 68 changes the value of the flag to zero. Thereafter, the control unit 68 executes step S20 and adjusts the duty of the PWM signal according to the power supply voltage value of the DC power supply 12.

[0121] When the control unit 68 determines that the temperature difference exceeds the upper limit value (S28: YES), or when it determines that the rate of increase in the temperature difference exceeds the upper limit value (S29: YES), it instructs the output unit 64 to output an off signal to the drive circuit 31 (step S33). As a result, the drive circuit 31 maintains the switch 30 in the off state. After executing step S33, the control unit 68 changes the value of the flag to 2 (step S34) and ends the power supply control process.

[0122] As described above, when the temperature difference exceeds the upper limit value or the rate of increase in the temperature difference exceeds the upper limit value, it is determined that an abnormality has occurred in the power supply to the load 13, and the value of the flag is changed to 2. As described above, when the value of the flag is 2, no power is supplied to the load 13. Each of steps S28 and S29 corresponds to a determination of whether an abnormality has occurred in the power supply to the load 13. Therefore, the determination of whether an abnormality has occurred in the power supply is made based on the comparison between the temperature difference and the upper limit value corresponding to the duty of the PWM control actually performed by the drive circuit 31. Furthermore, the determination of whether an abnormality has occurred in the power supply is made based on the rate of increase in the temperature difference that has increased due to the increase in the duty of the PWM control.

[0123] From the above, the abnormality in the power supply is a phenomenon where the temperature difference becomes a value equal to or greater than the upper limit value, or a phenomenon where the rate of increase in the temperature difference (wire temperature) exceeds the upper limit value. The abnormality in the power supply occurs, for example, when both ends of the load 13 are short-circuited.

[0124] <State transition of power supply> Figure 10 is a state transition diagram of the power supply. When the power supply to the load 13 is performed normally, the value of the flag is zero, and the power supply state is a normal state where the power supply is performed normally. When the calculated wire temperature becomes a temperature equal to or higher than the wire temperature threshold value, the control unit 68 instructs the drive circuit 31 to forcibly switch the switch 30 to the off state. When the wire current value becomes a current value equal to or higher than the current threshold value, or when the switch temperature becomes a temperature equal to or higher than the switch temperature threshold value, the drive circuit 31 forcibly switches the switch 30 to the off state.

[0125] By forcibly switching the switch 30 to the off state, the flow of current through the electric wire W is forcibly interrupted. As a result, the value of the flag is changed to 1, and the power supply state transitions to an interrupted state in which the flow of current through the electric wire W is forcibly interrupted. Even when the power supply state is the normal state, the power supply state may transition to the interrupted state due to, for example, the influence of external disturbance noise.

[0126] When the operation of the load 13 is instructed while the power supply state is the interrupted state, the control unit 68 gradually increases the duty of the PWM signal. FIG. 11 is an explanatory diagram of the gradual increase in the duty of the PWM signal. FIG. 11 shows the waveforms of PWM signals with different duties. As shown in FIG. 11, the control unit 68 gradually increases the duty of the PWM signal. In the example of FIG. 11, the duty of the PWM signal increases in the order of 10%, 50%, 80%, and 100%.

[0127] By gradually increasing the duty of the PWM signal, the electric wire current value gradually increases. Each time the control unit 68 increases the duty, it compares the temperature difference with the upper limit value and compares the increase width of the temperature difference with the upper limit value to determine whether an abnormality has occurred in the power supply to the load 13. If the control unit 68 does not detect an abnormality in the power supply until the duty of the PWM signal reaches the reference duty, it changes the value of the flag to zero and transitions the power supply state to the normal state as shown in FIG. 10.

[0128] If the control unit 68 detects an abnormality in the power supply until the duty of the PWM signal reaches the reference duty, it changes the value of the flag to 2 and transitions the power supply state to an abnormal state in which an abnormality has occurred in the power supply to the load 13. After the power supply state transitions to the abnormal state, the power supply state does not transition, and no power is supplied to the load 13.

[0129] <Effect of the individual ECU 11a> In the individual ECU 11a, the control unit 68 gradually increases the average value of the wire current value over a certain period. Each time the control unit 68 gradually increases the average value of the wire current value, it determines whether an abnormality has occurred in the power supply based on the temperature difference between the wire temperature and the ambient temperature. Therefore, the control unit 68 can detect an abnormality in the power supply when the wire current value is small. The control unit 68 gradually increases the average value of the wire current value by gradually increasing the duty of the PWM signal (PWM control). For this reason, a gradual increase in the average value of the wire current value is easily realized.

[0130] (Embodiment 2) In Embodiment 1, the drive circuit 31 performs PWM control of the switch 30 to realize power supply to the load 13 via the wire W. However, the method of realizing power supply to the load 13 is not limited to the method in which the drive circuit 31 performs PWM control. Hereinafter, the differences between Embodiment 2 and Embodiment 1 will be described. Regarding other configurations except for the configurations described later, they are common to Embodiment 1. For this reason, the same reference numerals as those in Embodiment 1 are assigned to the constituent parts common to Embodiment 1, and the description of those constituent parts is omitted.

[0131] <Configuration of the microcomputer 21> In Embodiment 1, the output unit 64 shown in FIG. 4 outputs a PWM signal and an off signal to the drive circuit 31 according to an instruction from the control unit 68. In Embodiment 2, the output unit 64 further outputs an on signal indicating that the switch 30 is on to the drive circuit 31 according to an instruction from the control unit 68. The on signal indicates a high-level voltage.

[0132] <Configuration of the switch device 20> When the output unit 64 of the microcomputer 21 outputs an on signal to the drive circuit 31, the drive circuit 31 switches the switch 30 to on. While the microcomputer 21 is outputting the on signal, the drive circuit 31 maintains the switch 30 in the on state. As described in the description of Embodiment 1, when the switch 30 is switched to on, current flows from the positive electrode of the DC power supply 12 in the order of the switch 30, the electric wire W, and the load 13. Thereby, since the load 13 is powered, the load 13 operates.

[0133] When the output unit 64 is outputting a PWM signal or an on signal to the drive circuit 31, when the wire current value is equal to or greater than the current threshold value, the drive circuit 31 performs self-cutoff of the switch 30 regardless of the signal input to the drive circuit 31. In the same case, when the switch temperature of the switch 30 is equal to or higher than the switch temperature threshold value, the drive circuit 31 performs self-cutoff of the switch 30 regardless of the signal input to the drive circuit 31. When the drive circuit 31 performs self-cutoff regarding the wire current value or the switch temperature, similar to Embodiment 1, the drive circuit 31 notifies the microcomputer 21 of the execution of the self-cutoff.

[0134] <Temperature calculation process> When the output unit 64 is outputting an on signal, in the calculation of the wire temperature, the control unit 68 uses the mathematical formulas [1] and [2] where the duty D is 100%.

[0135] <Power supply control process> FIG. 12 is a flowchart showing the procedure of the power supply control process in Embodiment 2. A part of the power supply control process in Embodiment 2 is common to a part of the power supply control process in Embodiment 1. In the power supply control process in Embodiment 2, detailed descriptions of steps S11, S12, S16 to S19, and S23 to S34 that are common to the power supply control process in Embodiment 1 are omitted.

[0136] In the power supply control process according to Embodiment 2, when the control unit 68 determines that the value of the flag is zero (S12: YES), it instructs the output unit 64 to output an on signal (step S41). As a result, the drive circuit 31 switches the switch 30 to the on state. The drive circuit 31 maintains the switch 30 in the on state while the output unit 64 is outputting the on signal. As described above, when the switch 30 is on, power is supplied to the load 13, and the load 13 operates. After executing step S41, the control unit 68 executes step S16. As described above, when the value of the flag is zero, power supply to the load 13 is realized by maintaining the switch 30 in the on state.

[0137] When the control unit 68 determines not to stop the operation of the load 13 (S19: NO), it executes step S16 again. Assume that the wire temperature is less than the wire temperature threshold, self-shutdown has not occurred, and the communication unit 66 has not received the instruction data for instructing the stop of the operation of the load 13. In this case, the switch 30 is maintained in the on state.

[0138] After executing step S32, the control unit 68 executes step S41. Therefore, when the value of the flag is changed from 1 to zero, that is, when the power supply state transitions from the cutoff state to the normal state, the switch 30 is maintained in the on state.

[0139] <Effect of the individual ECU 11a> The individual ECU 11a in Embodiment 2 exhibits the same effects as those of the individual ECU 11a in Embodiment 1, excluding the effect obtained by changing the duty of the PWM control according to the power supply voltage value.

[0140] <Modification example> In Embodiments 1 and 2, the timing for performing the abnormality determination as to whether or not an abnormality has occurred in the power supply to the load 13 while gradually increasing the wire current value is not limited to the timing for operating the load 13 when the power supply state is in the cutoff state. The timing for performing the abnormality determination may be, for example, the timing for first operating the load 13 after the ignition switch of the vehicle C is switched from off to on. Further, the switch temperature detection circuit 33 is not limited to a circuit using the thermistor 50, and any circuit capable of detecting the switch temperature of the switch 30 may be used.

[0141] The current value information output by the current detection circuit 32 is not limited to a voltage value corresponding to the wire current value, and may be, for example, digital information. The switch temperature information output by the switch temperature detection circuit 33 is not limited to a voltage value that varies according to the switch temperature, and may be, for example, digital information. Further, the method for notifying the execution of self-cutoff is not limited to the method of applying a voltage, and may be a method of outputting information indicating the execution of self-cutoff to the microcomputer 21.

[0142] The method for adjusting the wire current value is not limited to the method of adjusting the duty of PWM control. When a variable resistor is arranged in the current path, the wire current value may be adjusted by adjusting the resistance value of the variable resistor. The device for calculating the wire temperature is not limited to the individual ECU 11a. For example, the integrated ECU 10 may calculate the wire temperature. The power supply control device for controlling the power supply is not limited to the individual ECU 11a that communicates with the integrated ECU 10.

[0143] The number of sensors connected to each of the individual ECU 11a and the plurality of individual ECU 11b is not limited to 1, and may be 2 or more. The number of actuators 14 connected to each individual ECU 11b is not limited to 1, and may be 2 or more. The switch 30 is not limited to an N-channel type FET, and may be a semiconductor switch different from the N-channel type FET. Examples of semiconductor switches different from the N-channel type FET include a P-channel type FET, an IGBT (Insulated Gate Bipolar Transistor), and a bipolar transistor.

[0144] The disclosed Embodiments 1 and 2 should be considered illustrative in all respects and not restrictive. The scope of the present invention is shown not by the above description but by the claims, and it is intended that all modifications within the meaning and scope equivalent to the claims be included.

Explanation of Reference Numerals

[0145] 1 Control system 10 Integrated ECU 11a Individual ECU (power supply control device, in-vehicle control device) 11b Individual ECU 12 DC power supply 13 Load 14 Actuator 15a, 15b Sensors 20 Switch device 21 Microcomputer 22 Voltage detection unit 23 Ambient temperature detection unit 30 Switch 31 Drive circuit (switching circuit) 32 Current detection circuit 33 Switch temperature detection circuit 40 Current output unit 41 Current detection resistor 50 Thermistor 51 Temperature detection resistor 60, 61, 62, 63 A / D conversion unit 64 Output unit 65 Input unit 66 Communication unit (reception unit) 67 Memory unit 68 Control unit (processing unit) 69 Internal bus A Storage medium C Vehicle P Computer program Q1 Temperature difference table Q2 Rise rate table W Electric wire

Claims

1. A power supply control device for controlling power supply via an electric wire, comprising: a processing unit that executes processing; a switch disposed in a current path of a current flowing through the electric wire; a switching circuit that switches the switch on or off; wherein a signal is input to the switching circuit, the switching circuit switches the switch on or off according to the input signal, the switching circuit switches the switch off regardless of the input signal when the wire current value of the current flowing through the electric wire is equal to or greater than a current threshold value, or when the temperature of the switch is equal to or greater than a switch temperature threshold value, the processing unit stepwise increases an average value of the wire current value of the current flowing through the electric wire, each time the average value of the wire current value is increased, determines whether an abnormality has occurred in the power supply via the electric wire based on a temperature difference between the wire temperature of the electric wire and the ambient temperature around the electric wire, when it is determined that no abnormality has occurred in the power supply, after the switching circuit switches the switch off regardless of the input signal, the switching circuit switches the switch on, thereby stepwise increasing the average value of the wire current value a power supply control device.

2. The processing unit acquires the wire current value, calculates the temperature difference based on the acquired wire current value, and each time the average value of the wire current value is increased, determines whether the abnormality has occurred based on the calculated temperature difference. The power supply control device according to claim 1.

3. a switch disposed in a current path of a current flowing through the electric wire; a switching circuit that switches the switch on or off; wherein the processing unit causes the switching circuit to perform PWM control for alternately switching the switch on and off, and stepwise increases the average value of the wire current value by stepwise increasing the duty of the PWM control. The power supply control device according to claim 1 or claim 2.

4. a storage unit that stores a plurality of upper limit values related to the temperature difference in association with a plurality of duties related to the PWM control; the processing unit determines whether the abnormality has occurred based on whether the temperature difference exceeds an upper limit value corresponding to the duty of the PWM control being performed by the switching circuit each time the average value of the wire current value is increased. The power supply control device according to claim 3.

5. Each time the processing unit increases the average value of the wire current value, it determines whether the abnormality has occurred based on the increase width of the temperature difference that has increased due to the increase in the average value of the wire current value. The power supply control device according to claim 3 or claim 4.

6. The processing unit When the wire temperature is equal to or higher than the wire temperature threshold value, the flow of the current flowing through the wire is interrupted. By restarting the flow of the current flowing through the wire after the wire temperature has reached a temperature equal to or higher than the wire temperature threshold value, the average value of the wire current value is gradually increased. The power supply control device according to any one of claims 1 to 5.

7. An in-vehicle control device that controls the operation of a load, a receiving unit that receives instruction data for instructing the operation or stop of the load, a processing unit that executes processing, a switch disposed in the current path of the current flowing through the wire, and a switching circuit that switches the switch on or off and is provided with a signal is input to the switching circuit, the switching circuit switches the switch on or off according to the input signal, when the wire current value of the current flowing through the wire is equal to or higher than the current threshold value, or when the temperature of the switch is equal to or higher than the switch temperature threshold value, the switching circuit switches the switch off regardless of the input signal, The processing unit controls the power supply to the load via the wire according to the instruction data received by the receiving unit, gradually increases the average value of the wire current value of the current flowing through the wire, each time the average value of the wire current value is increased, it determines whether an abnormality has occurred in the power supply via the wire based on the temperature difference between the wire temperature of the wire and the ambient temperature around the wire, when it is determined that no abnormality has occurred in the power supply, the switching circuit switches the switch off regardless of the input signal and then switches the switch on, thereby gradually increasing the average value of the wire current value. In-vehicle control device.

8. A power supply control method for controlling the power supply via a wire, the step of gradually increasing the average value of the wire current value of the current flowing through the wire, each time the average value of the wire current value is increased, the step of determining whether an abnormality has occurred in the power supply via the wire based on the temperature difference between the wire temperature of the wire and the ambient temperature around the wire. When it is determined that there is no abnormality in power supply, switch the switch arranged in the current path of the current flowing through the electric wire according to the input signal on or off. When the electric wire current value is equal to or greater than the current threshold value, or when the temperature of the switch is equal to or greater than the switch temperature threshold value, a switching circuit that switches the switch off regardless of the input signal switches the switch off regardless of the input signal and then switches the switch on, thereby stepwise increasing the average value of the electric wire current value. A power supply control method executed by a computer.

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