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 technology]

[0002] A vehicle is 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, a FET (Field Effect Transistor) is arranged as a switch in the current path of the current that flows through the load. When the FET is turned on, The power supply to the load is controlled by switching the FET on or off. If the FET temperature exceeds a predetermined temperature while the FET is on, the FET is forcibly switched off. This prevents the FET from reaching an abnormal temperature. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2000-16200 Summary of the Invention [Problem to be solved by the invention]

[0004] In a conventional power supply control device such as that described in Patent Document 1, when a cutoff condition for forcibly cutting off the flow of current to a load is satisfied, the FET is forcibly switched off. When power supply to the load is started after the cutoff condition is satisfied, the FET is switched on again and maintained on. If the FET is maintained on while the cause of the cutoff condition being satisfied is not resolved, the cutoff condition will be satisfied again, and as a result, the FET is forcibly switched off again.

[0005] When the cutoff condition is met, the current flowing through the FET is large, which is undesirable for the components that make up the power supply control device. For this reason, it is necessary to detect power supply abnormalities when the current value is small.

[0006] The present disclosure has been made in consideration of the above circumstances, and its purpose is to provide a power supply control device, an on-board control device, and a power supply control method that can detect a power supply abnormality when the current value is small. [Means for solving the problem]

[0007] A power supply control device according to one 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 the average value of the electric wire current value of the current flowing through the electric wire, and each time the processing unit increases the average value of the electric wire current value, determines whether or not an abnormality has occurred in the power supply via the electric wire based on the temperature difference between the electric wire temperature and the environmental temperature around the electric wire.

[0008] An on-board control device according to one embodiment of the present disclosure is an on-board control device that controls the operation of a load, and includes a receiving unit that receives instruction data instructing the load to start or stop operation, and a processing unit that executes processing. The processing unit controls the power supply to the load via an electric wire in accordance with 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, determines 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 environmental temperature around the electric wire.

[0009] A 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, in which a computer executes the steps of gradually increasing an average value of the electric wire current value of a current flowing through the electric wire, and determining, each time the average value of the electric wire current value is increased, whether or not an abnormality has occurred in the power supply via the electric wire based on the temperature difference between the electric wire temperature and the environmental temperature around the electric wire.

[0010] The present disclosure can be realized not only as a power supply control device having such a characteristic processing unit, but also as a power supply control method having such characteristic processing steps, or as a computer program for causing a computer to execute such steps. Furthermore, 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. [Effects of the Invention]

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

[0012] [Figure 1] 1 is a block diagram showing the configuration of a main part of a control system 1 according to a first embodiment. [Figure 2] FIG. 2 is a block diagram showing the configuration of a main part of an individual ECU. [Figure 3] FIG. 2 is a circuit diagram of a switch device. [Figure 4] FIG. 2 is a block diagram showing the main configuration of a microcomputer; [Figure 5] 10 is a diagram showing the contents of a temperature difference table. [Figure 6] 10 is a diagram showing the contents of an increase width table. [Figure 7] 10 is a flowchart showing a procedure for a temperature calculation process. [Figure 8] 10 is a flowchart showing the procedure of a power supply control process. [Figure 9] 10 is a flowchart showing the procedure of a power supply control process. [Figure 10] FIG. 10 is a state transition diagram of power supply. [Figure 11] FIG. 10 is an explanatory diagram of a stepwise increase in the duty of a PWM signal. [Figure 12]10 is a flowchart showing the procedure of a power supply control process in the second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0013] [Description of the embodiments of the present disclosure] First, embodiments of the present disclosure will be listed and described. At least some of the embodiments described below may be combined in any combination.

[0014] (1) A power supply control device according to one aspect of the present disclosure is a power supply control device that controls power supply through an electric wire, and includes a processing unit that executes processing. The processing unit gradually increases an average value of the electric wire current value of the current flowing through the electric wire, and each time the processing unit increases the average value of the electric wire current value, determines whether or not an abnormality has occurred in the power supply through the electric wire based on the temperature difference between the electric wire temperature and the environmental temperature around the electric wire.

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

[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 configured to switch the switch on or off. The processing unit controls the switching circuit to perform PWM control that alternately switches the switch on and off, and gradually increases a duty of the PWM control to thereby The average value of the electric wire current is increased in stages.

[0017] (4) A power supply control device according to one embodiment of the present disclosure includes a memory unit in which a plurality of upper limit values ​​for the temperature difference are stored in association with a plurality of duties for the PWM control, and 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 performed by the switching circuit each time the average value of the electric wire current value is increased.

[0018] (5) In a power supply control device according to one embodiment of the present disclosure, the processing unit determines whether or not the abnormality has occurred each time the average value of the electric wire current value is increased based on the increase in the temperature difference caused by the increase in the average value of the electric wire current value.

[0019] (6) A power supply control device according to one 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 configured to switch the switch on or off, wherein a signal is input to the switching circuit, and the switching circuit switches the switch on or off in accordance with the input signal, and the switching circuit switches the switch off regardless of the input signal when the electric wire current value is equal to or greater than a current threshold or when the temperature of the switch is equal to or greater than a switch temperature threshold, and the processing unit gradually increases the average value of the electric wire current value after the switching circuit switches the switch off regardless of the input signal.

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

[0021] (8) An on-board control device according to one embodiment of the present disclosure is an on-board control device that controls the operation of a load, and includes a receiving unit that receives instruction data instructing the load to operate or stop operating, and a processing unit that executes processing. The processing unit controls the power supply to the load via an electric wire in accordance with 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, determines 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 environmental temperature around the electric wire.

[0022] (9) A power supply control method according to one aspect of the present disclosure is a power supply control method for controlling power supply through an electric wire, in which a computer executes the steps of gradually increasing an average value of a wire current value of a current flowing through the electric wire, and determining, each time the average value of the wire current value is increased, whether or not an abnormality has occurred in the power supply through the electric wire based on a temperature difference between the wire temperature of the electric wire and an environmental temperature around the electric wire.

[0023] In the power supply control device, the on-board control device, and the power supply control method according to the above-described aspect, the average value of the electric wire current value over a certain period is increased in stages. Each time the average value of the electric wire current value is increased, it is determined whether or not an abnormality in the power supply has occurred 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 even when the current value is small.

[0024] In the power supply control device according to the above aspect, the temperature difference between the electric wire temperature and the ambient temperature is calculated based on the electric wire current value, and 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 duty of the PWM control for the switch is increased in stages, thereby increasing the average value of the electric wire current in stages. Therefore, a stepwise increase in the average value of the electric wire current can be easily realized.

[0026] In the power supply control device according to the above embodiment, the determination of whether 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 aspect, the determination as to whether or not an abnormality has occurred in the power supply is made based on the increase in the temperature difference caused by an increase in the duty of the PWM control.

[0028] In the power supply control device according to the above aspect, the switching circuit forcibly switches the switch to OFF based on the wire current value or the switch temperature. After the switching circuit forcibly switches the switch to OFF, the average wire current value is increased stepwise to determine whether an abnormality has occurred in the power supply.

[0029] In the power supply control device according to the above aspect, when the electric wire temperature reaches or exceeds the electric wire temperature threshold, the flow of current through the electric wire is forcibly interrupted. After the flow of current is forcibly interrupted, the average value of the electric wire current value is increased stepwise, and it is determined whether or not an abnormality has occurred in the power supply.

[0030] [Details of the embodiments of the present disclosure] Specific examples of control systems according to embodiments of the present disclosure will be described below with reference to the drawings. Note that the present invention is not limited to these examples, but is defined by the claims, and is intended to include all modifications within the meaning and scope of the claims.

[0031] (Embodiment 1) <Control system configuration> FIG. 1 is a block diagram showing the configuration of a main part of a control system 1 in a first embodiment. The control system 1 is mounted on a 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, connection lines for supplying power are indicated by thick lines. Connection lines for transmitting data or signals are indicated by thin lines.

[0032] The integrated ECU 10 is connected to an individual ECU 11a and a plurality of individual ECUs 11b. The individual ECU 11a is connected to the positive terminal of a DC power supply 12 and one end of an electric wire W. The other end of the electric wire W is connected to one end of a load 13. The negative terminal of the DC power supply 12 and the other end of the electric wire W are grounded. A sensor 15a is also connected to the individual ECU 11a. An actuator 14 and a sensor 15b are also 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 electric 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 is stopped, 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 on-board 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. The actuator 14 receives the control signal. When input, the operation indicated by the input control signal is performed.

[0035] Each of the sensors 15a and 15b repeatedly generates vehicle data related to the vehicle C. The vehicle data may be image data showing the periphery of the vehicle C, data indicating the speed of the vehicle C, or data indicating whether a switch mounted on the vehicle C is on. Each time the sensor 15a generates vehicle data, it outputs the generated vehicle data to the individual ECU 11a. Similarly, each time the sensor 15b generates vehicle data, it outputs the generated vehicle data to the individual ECU 11b. Each time the vehicle data is input, each of the individual ECUs 11a and 11b transmits the input vehicle data to the integrated ECU 10.

[0036] The integrated ECU 10 determines the operation of the load 13 based on one or more vehicle data received from the individual ECU 11a and at least one of the multiple individual ECUs 11b. Here, the determined operation of the load 13 is to operate or stop the operation. When the integrated ECU 10 determines the operation of the load 13, it transmits instruction data instructing the determined operation to the individual ECU 11a. When the individual ECU 11a receives the instruction data from the integrated ECU 10, it causes the load 13 to perform the operation instructed by the received instruction data.

[0037] Similarly, the integrated ECU 10 determines the operation of one or more actuators 14 based on one or more vehicle data received from the individual ECU 11a and at least one of the multiple individual ECUs 11b. When the integrated ECU 10 determines the operation of one or more actuators 14, it transmits instruction data instructing the determined operation to one or more individual ECUs 11b. When the individual ECU 11b receives the instruction data from the integrated ECU 10, it outputs a control signal to the 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, the actuator 14 performs the operation indicated by the input control signal.

[0038] <Configuration of individual ECU 11a> 2 is a block diagram showing the configuration of the main parts of the individual ECU 11a. The individual ECU 11a has a switch device 20, a microcomputer (hereinafter referred to as "microcomputer") 21, a voltage detection unit 22, and an ambient temperature detection unit 23. The switch device 20 is 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 microcomputer 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 each connected to the microcomputer 21. The microcomputer 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 disposed in a current path of a 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 from the positive electrode of the DC power supply 12 through the switch 30, the electric wire W, and the load 13 in this order. This allows power to be supplied to the load 13. When the switch 30 is switched off, the flow of current is interrupted, and 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 wire W to the microcomputer 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 microcomputer 21. Hereinafter, the temperature of the switch 30 will be referred to as the switch temperature. The switch temperature information is a voltage value that varies depending on the switch temperature.

[0041] The microcomputer 21 outputs a PWM (Pulse Width Modulation) signal or an OFF signal indicating that the switch 30 is OFF 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 PWM signal periodically switches from low to high voltage. The duty of the PWM signal is the proportion of the time during one cycle that the voltage indicated by the PWM signal is high. The duty is expressed in percentages. The duty is greater than 0% and less than or equal to 100%. The duty is adjusted by adjusting the timing at which the voltage is switched from high to low.

[0042] The PWM signal may be periodically switched from a high level voltage to a low level voltage, in which case the duty is adjusted by adjusting the timing at which the low level voltage is switched to a high level voltage.

[0043] In the following, it is assumed that the microcomputer 21 outputs a PWM signal to the switch device 20 when the wire current value is below a certain current threshold and the switch temperature is below a certain switch temperature threshold. In this case, when the voltage indicated by the PWM signal switches from a low level voltage to a high level voltage, the switch device 20 switches the switch 30 from off to on. In a similar case, when the voltage indicated by the PWM signal switches from a high level voltage to a low level voltage, the switch device 20 switches the switch 30 from on to off. When the microcomputer 21 is outputting the PWM signal, power is supplied to the load 13.

[0044] As described above, the switch device 20 performs PWM control by alternately switching the switch 30 on and off in accordance with the input PWM signal. The duty of the PWM control is the proportion of the period during which the switch 30 is on in a certain period. The duty of the PWM control matches the duty of the PWM signal. The greater the duty of the PWM signal, the longer the period during which the switch 30 is on. Therefore, the greater the duty of the PWM signal, the greater the average value of the electric wire current in the certain period. The certain period is, for example, one cycle of the PWM signal.

[0045] When the microcomputer 21 outputs the OFF signal, the switch device 20 maintains the switch 30 in the OFF state. Therefore, when the microcomputer 21 outputs the OFF signal, the load 13 stops operating.

[0046] When the microcomputer 21 is outputting a PWM signal to the switch device 20 and the wire current value is equal to or greater than the current threshold, the switch device 20 forcibly switches the switch 30 to OFF and maintains the switch 30 OFF, regardless of the PWM signal input to the switch device 20. Hereinafter, the forcible switching off of the switch 30 will be referred to as self-shutdown. By forcibly switching the switch 30 OFF, the flow of current through the wire W is forcibly shut off.

[0047] When the wire current value reaches a current value equal to or greater than the current threshold, the switch device 20 outputs the maximum voltage value that is permitted to be output to the microcomputer 21. This notifies the microcomputer 21 that self-shutdown will be performed. When notified that self-shutdown will be performed, the microcomputer 21 outputs an OFF signal to the switch device 20. When the microcomputer 21 outputs the OFF signal to the switch device, self-shutdown is canceled.

[0048] When the microcomputer 21 is outputting a PWM signal to the switch device 20, if the switch temperature is equal to or higher than the switch temperature threshold, the switch device 20 performs self-shutdown of the switch 30 regardless of the PWM signal input to the switch device 20. When the switch temperature is equal to or higher than the switch temperature threshold, the switch device 20 outputs the maximum voltage value that is permitted to be output to the microcomputer 21. This notifies the microcomputer 21 that self-shutdown will be performed. When notified that self-shutdown will be performed, the microcomputer 21 outputs an OFF signal to the switch device 20. When the microcomputer 21 outputs an OFF signal to the switch device, self-shutdown is It will be 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 will be 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 environmental temperature detection unit 23 detects the environmental temperature around the electric wire W. The environmental temperature is the temperature around the electric wire W. The environmental temperature detection unit 23 outputs analog environmental temperature information indicating the detected environmental temperature. The environmental temperature information is, for example, a voltage value that varies depending on the environmental temperature. The sensor 15a outputs the generated vehicle data to the microcomputer 21 every time the sensor 15a generates the vehicle data.

[0050] The microcomputer 21 transmits vehicle data input from the sensor 15a to the integrated ECU 10. The microcomputer 21 receives instruction data from the integrated ECU 10 instructing the load 13 to operate or stop operating. When the microcomputer 21 receives instruction data instructing the load 13 to operate, it outputs a PWM signal to the switch device 20. When the microcomputer 21 outputs the 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 the load 13 to stop operating, it outputs an OFF signal to the switch device 20. This stops the power supply to the load 13, and the load 13 stops operating.

[0052] When the microcomputer 21 outputs 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. Furthermore, 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, the microcomputer 21 outputs an OFF signal to the switch device 20. This causes the switch device 20 to switch the switch 30 OFF. As a result, power supply to the load 13 is stopped, and the load 13 stops operating.

[0054] <Configuration of Switch Device 20> 3 is a circuit diagram of the switch device 20. In addition to a switch 30, the switch device 20 has a drive circuit 31, a current detection circuit 32, and a switch temperature detection circuit 33. The switch 30 is an N-channel FET. The current detection circuit 32 has a current output unit 40 and a current detection resistor 41. The switch temperature detection circuit 33 has an NTC (Negative Temperature Coefficient) 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 electric wire W. As described above, the other end of the electric 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 the switch 30 is further connected to a 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 It 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 the 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 the switch 30, when the voltage value of the gate, whose reference potential is the potential of the source, is equal to or greater than a certain voltage value, the switch 30 is on. When the switch 30 is on, the resistance between the drain and source of the switch 30 is sufficiently small. Therefore, a current can flow through the drain and source of the switch 30. When the switch 30 is on, a current flows from the positive electrode of the DC power supply 12 through the switch 30, the wire W, and the load 13 in this order. Therefore, the switch 30 is disposed in the current path of the current flowing through the wire W.

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

[0060] The microcomputer 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 low to high, the drive circuit 31 increases the gate voltage value of the switch 30, whose reference potential is the ground potential. As a result, the gate voltage value of the switch 30, whose reference potential is the source potential, increases to a voltage equal to or greater than a certain voltage value, and the switch 30 is turned on.

[0061] In a similar case, when the voltage of the PWM signal switches from a high level voltage to a low level voltage, the drive circuit 31 reduces the gate voltage value, the reference potential of which is the ground potential, of the switch 30. As a result, the gate voltage value, the reference potential of which is the source potential of the switch 30, rises to a voltage below a certain voltage value, and the switch 30 is switched off.

[0062] As described above, the drive circuit 31 switches the switch 30 on or off by adjusting the gate voltage value, the reference potential of which 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 microcomputer 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 microcomputer 21 outputs an OFF signal to the drive circuit 31. When the microcomputer 21 outputs the OFF signal to the drive circuit 31, the drive circuit 31 switches OFF the switch 30. While the microcomputer 21 is outputting the OFF signal, the drive circuit 31 keeps the switch 30 OFF.

[0064] In the current detection circuit 32, the current output section 40 draws a current from the drain of the switch 30 and outputs the drawn current to the current detection resistor 41. The current drawn by the current output section 40 The current value is proportional to the wire current value and is expressed as (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 expressed as (wire current value)·(resistance value of the current detection resistor 41) / (predetermined number), where "·" represents the product. Because 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 increases as the wire current value increases.

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

[0067] When the wire current value indicated by the current value information becomes equal to or greater than the wire current threshold, the drive circuit 31 applies a voltage across the current detection resistor 41. This voltage value is the maximum voltage value that is permitted to be output to the microcomputer 21. The maximum voltage value is input to the microcomputer 21. This notifies the microcomputer 21 that the drive circuit 31 will perform self-shutdown. As described above, when the microcomputer 21 is notified that self-shutdown will be performed, it outputs an OFF signal to the drive circuit 31. When the microcomputer 21 outputs the OFF signal, the self-shutdown of the drive circuit 31 is released.

[0068] In the switch temperature detection circuit 33, the thermistor 50 and temperature detection resistor 51 divide a constant voltage having a voltage value of Vc. The switch temperature detection circuit 33 outputs the divided voltage value obtained by dividing the constant voltage to the microcomputer 21 and the drive circuit 31 as switch temperature information. The resistance value of the temperature detection resistor 51 is denoted as rd. The resistance value of the thermistor 50 is denoted as rt. The switch temperature information, i.e., the divided voltage value, is expressed as Vc·rd / (rd+rt). Because 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 thermistor 50 is an NTC type, the resistance value rt decreases as the temperature of the thermistor 50 increases. The thermistor 50 is disposed near the switch 30. When the switch temperature of the switch 30 increases, the temperature of the thermistor 50 increases. When the switch temperature decreases, the temperature of the thermistor 50 decreases. Therefore, the resistance value rt of the thermistor 50 decreases as the switch temperature increases. Therefore, the resistance value rt of the thermistor 50 indicates the switch temperature. The switch temperature information, i.e., the divided voltage value, increases as the switch temperature increases.

[0070] When the switch temperature indicated by the switch temperature information reaches or exceeds the switch temperature threshold, the drive circuit 31 applies a voltage across the temperature detection resistor 51. The voltage value of this voltage is the maximum voltage value that is permitted to be output to the microcomputer 21. The maximum voltage value is input to the microcomputer 21. This notifies the microcomputer 21 that the drive circuit 31 will execute self-shutdown. As described above, when the microcomputer 21 is notified that self-shutdown will be executed, it outputs an OFF signal to the drive circuit 31. When the microcomputer 21 outputs the 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, a current flows through the switch 30 and the wire W, causing the switch temperature to rise. When the wire current value reaches a current value equal to or greater than the wire current threshold, or when the switch temperature reaches a temperature equal to or greater than the switch temperature threshold, the drive circuit 31 performs a self-shutdown. The microcomputer 21 shuts down the drive circuit 31 and notifies the microcomputer 21 that self-shutdown will be executed. When the microcomputer 21 is notified that self-shutdown will be executed, it outputs an OFF signal to the drive circuit 31. This releases the self-shutdown of the drive circuit 31.

[0072] In the switch temperature detection circuit 33, the thermistor 50 is not limited to an NTC type but may be a PTC (Positive Temperature Coefficient) type. In this case, the resistance value of the thermistor 50 increases as the temperature of the thermistor 50, i.e., 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, if the thermistor 50 is an NTC type, the switch temperature information decreases as the switch temperature increases. Similarly, if the thermistor 50 is a PTC type, the switch temperature information increases as the switch temperature increases. When a constant voltage is applied to the temperature detection resistor 51, the drive circuit 31 applies a voltage to the thermistor 50 when the drive circuit 31 performs self-shutdown.

[0073] <Main components of Microcomputer 21> 4 is a block diagram showing the main configuration of the microcomputer 21. The microcomputer 21 has A / D conversion units 60, 61, 62, and 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. The A / D conversion units 60, 61, 62, and 63 are further connected to the voltage detection unit 22, the switch temperature detection circuit 33, the current detection circuit 32, and the ambient temperature detection unit 23, respectively. The output unit 64 is further connected to the drive circuit 31. The input unit 65 is further connected to the 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 in accordance with instructions 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. Every time the sensor 15a generates vehicle data, the sensor 15a outputs the generated vehicle data to the input unit 65. The control unit 68 acquires, from the input unit 65, the vehicle data input from the sensor 15a.

[0077] The communication unit 66 transmits vehicle data to the integrated ECU 10 in accordance with instructions from the control unit 68. The communication unit 66 receives instruction data instructing the integrated ECU 10 to operate or stop the 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. The storage unit 67 stores a computer program P. 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 integrated ECU 10 executes a computer program P to concurrently perform a vehicle data transmission process, a temperature calculation process, a power supply control process, and the like. The vehicle data transmission process is a process for transmitting vehicle data to the integrated ECU 10. The temperature calculation process is a process for calculating the wire temperature of the wire W. The power supply control process is a process for controlling the power supply to the load 13.

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

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

[0081] The control unit 68 periodically executes a temperature calculation process. In the temperature calculation process, the control unit 68 calculates the temperature difference between the electric wire temperature and the ambient temperature, and adds the ambient temperature to the calculated temperature difference. In this way, the electric wire temperature is calculated.

[0082] In calculating the wire temperature, the control unit 68 calculates the temperature difference ΔTw by substituting the previously calculated preceding temperature difference ΔTp, the wire current value Iw of the wire W, the ambient temperature Ta, and the PWM signal, i.e., the duty D of the PWM control, into the following 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 equations [1] and [2] are explained below. The units of the variables and constants are also shown. As mentioned above, ΔTw, ΔTp, Ta, Iw, Rw, Rth, and D are the calculated temperature difference (°C), the preceding temperature difference (°C), the ambient temperature (°C), the wire current value of wire W (A), the wire resistance value of wire W (Ω), the wire thermal resistance value of wire W (°C / W), and the duty cycle (%) of the PWM signal. Δt is the period (s) for calculating the temperature difference ΔTw, i.e., the period for executing the temperature calculation process. τr is the wire heat dissipation time constant (s) of wire W.

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

[0085] The value of the first term in formula [1] decreases as the period Δt increases, so the first term in formula [1] represents the heat dissipation of the wire W. Also, the value of the second term in formula [1] increases as the period Δt increases. Therefore, the second term in equation [1] represents the heat generated by the wire W.

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

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

[0088] FIG. 5 is a diagram showing the contents of temperature difference table Q1. As shown in FIG. 5, temperature difference table Q1 shows the temperature difference between the wire temperature and the ambient temperature, corresponding to each of a plurality of duties. In the example of FIG. 5, a plurality of duties are shown in 10% increments. An 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 temperature difference table Q1 when the power supply voltage value of DC power supply 12 is at its maximum value in a normal state. In temperature difference table Q1, the higher the duty, the higher 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. An increase amount table is stored in the storage unit 67. The increase amount table Q2 indicates multiple increase amounts for the temperature difference between the electric wire temperature and the ambient temperature, corresponding to multiple increases in the duty. Each time the control unit 68 increases the duty of the PWM signal, the control unit 68 determines whether an abnormality has occurred in the power supply to the load 13 via the electric wire W based on whether the increase amount for the temperature difference is equal to or greater than the upper limit of the increase amount corresponding to the actual increase in the duty.

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

[0091] When the ambient temperature is the same, the increase in the temperature difference corresponds to the increase in the temperature of the wire. The wire temperature is expressed as the sum of the temperature difference and the ambient temperature. When the ambient temperature is the same, the increase in the temperature of the two wires is expressed as the increase in the temperature difference.

[0092] <Vehicle data transmission processing> 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 the 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> 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 periodically executes the temperature calculation process. 2 (step S1). When the output unit 64 is outputting the duty of a 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 out the preceding temperature difference from the storage unit 67 (step S2). This preceding temperature difference is the temperature difference calculated in the previous temperature calculation process. In the temperature calculation process that is executed first after the microcomputer 21 is started up, the preceding 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 electric wire temperature and the ambient temperature by substituting a plurality of numerical values ​​into formulas [1] and [2] (step S4). The numerical values ​​are the electric wire current value indicated by the current value information acquired in step S1, the preceding temperature difference read in step S2, the ambient temperature indicated by the ambient temperature information acquired in step S3, and the duty of the PWM signal output by the output unit 64. When the output unit 64 outputs an off signal, the duty is zero.

[0095] Next, the control unit 68 changes the preceding temperature difference stored in the memory unit 67 to the temperature difference calculated in step S4 (step S5). The changed preceding temperature difference is used in the next temperature calculation process. The preceding 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 environmental temperature indicated by the environmental temperature information acquired in step S3 (step S6).

[0096] Next, the control unit 68 changes the wire temperature stored in the memory unit 67 to the wire temperature calculated in step S6 (step S7). Therefore, the wire temperature stored in the memory 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 leading temperature difference, which is the latest temperature difference, and the latest wire temperature.

[0097] <Power supply control processing> 8 and 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 a 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 to the load 13 via the wire W.

[0098] The memory unit 67 also stores a flag value indicating the state of the individual ECU 11a. The flag value is zero, one, or two, and is changed by the control unit 68. A flag value of zero means that power is being supplied to the load 13 normally. A flag value of one means that the current through the electric wire W has been forcibly interrupted. A flag value of two means that an abnormality has occurred in the power supply to the load 13.

[0099] The control unit 68 executes the power supply control process while the output unit 64 is outputting an OFF signal. In the power supply control process, the control unit 68 first determines whether or not to operate the load 13 (step S11). In step S11, if the communication unit 66 receives instruction data instructing the operation of the load 13, the control unit 68 determines that the load 13 should be operated. If the communication unit 66 does not receive instruction data instructing the operation of the load 13, the control unit 68 determines that the load 13 should not be operated. If the control unit 68 determines that the load 13 should not be operated (S11: NO), it executes step S11 again and waits until the communication unit 66 receives instruction data instructing the operation of the load 13.

[0100] When the control unit 68 determines that the load 13 should be operated (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 such that the average value of related values ​​over a certain period of time becomes a certain target value (step S14). The target value is set in advance. As described above, the certain period of time is, for example, one cycle of the PWM signal.

[0101] For example, if the load 13 is a lamp having an LED (Light Emitting Diode), the brightness of the load 13 increases as the average value of the wire current over a certain period of time increases. If the load 13 is a lamp having an LED, the relevant value is the wire current value. The target value is a current value. The wire current value of the current that flows 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 expressed as 100·(target value) / (switch current value).

[0102] For example, if the load 13 is a headlight equipped with an incandescent bulb, the luminance of the load 13 increases as the average value of the power supplied to the load 13 within a certain period increases. If the load 13 is a headlight equipped with an incandescent bulb, the relevant 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 expressed as 100·(target value) / (load power).

[0103] For example, if the load 13 is a DC motor, the rotation speed of the load 13 increases as the average value of the voltage applied to the load 13 within a certain period of time increases. If 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 expressed as 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). As a result, the drive circuit 31 performs PWM control of the switch 30 in accordance with 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. As the drive circuit 31 performs 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 a target value. As a result of the current flowing through the electric wire W, power is supplied to the load via the electric wire W.

[0105] Next, the control unit 68 reads 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 greater than the wire temperature threshold value (step S17). If the control unit 68 determines that the wire temperature is less than the wire temperature threshold value (S17: NO), the control unit 68 determines whether the drive circuit 31 has caused the switch 30 to self-shut down (step S18). In step S18, the control unit 68 determines that self-shut down has occurred if the maximum voltage value that is allowed to be output to the microcomputer 21 is input to at least one of the A / D conversion units 61 and 62. If the maximum voltage value is not input to either of the A / D conversion units 61 and 62, the control unit 68 determines that self-shut down has not occurred.

[0106] When the control unit 68 determines that self-shutdown has not occurred (S18: NO), it determines whether or not to stop the operation of the load 13 (step S19). In step S19, the control unit 68 determines that the operation of the load 13 is to be stopped if the communication unit 66 has received instruction data instructing the load 13 to stop its operation. When the communication unit 66 has not received instruction data instructing the load 13 to stop its operation, the control unit 68 determines that the operation of the load 13 is not to be stopped.

[0107] When the control unit 68 determines not to stop the operation of the load 13 (S19: NO), the control unit 68 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 whose target value is the average value of the related values ​​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-shutdown has not occurred, and the communication unit 66 has not received instruction data instructing the load 13 to stop operating. In this case, the duty is changed according to the power supply voltage value of the DC power supply 12. Specifically, if the power supply voltage value decreases, the control unit 68 increases the duty. If the power supply voltage value increases, the control unit 68 decreases the duty. As a result, even if the power supply voltage value fluctuates, the related value of the load 13 is maintained at the target value. For example, if the positive electrode of the DC power supply 12 is connected to a starter of the vehicle C, when the starter operates, the power supply voltage value decreases. In a similar case, if the starter stops operating, the power supply voltage value increases.

[0109] If the control unit 68 determines that the wire temperature is equal to or higher than the wire temperature threshold value (S17: YES) or if it determines that self-shutdown has occurred (S18: YES), it changes the value of the flag to 1 (step S23). If the control unit 68 determines that the operation of the load 13 should be stopped (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). This causes the drive circuit 31 to maintain the switch 30 OFF. This cuts off the flow of current through the wire W. As a result, power supply to the load 13 through the wire W is stopped. As described above, if the output unit 64 outputs an OFF signal while the drive circuit 31 is performing self-shutdown, the self-shutdown is canceled.

[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 instructing the load 13 to operate.

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

[0112] If the control unit 68 determines that the value of the flag is not 1 (S25: NO), or if it determines that the latest temperature difference exceeds the reference temperature difference (S26: NO), it ends the power supply control process without causing the output unit 64 to output a PWM signal. After ending the power supply control process, the control unit 68 executes the power supply control process again. As described above, when the flag value is 2, power supply to the load 13 is not started. Even when the flag value is 1, if 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 equal to or smaller than the reference temperature difference (S26: YES), it instructs the output unit 64 to output a PWM signal to the drive circuit 31 (step S27). This causes the drive circuit 31 to perform 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. Because the duty of the PWM signal is small, the average value of the electric wire current is small.

[0114] After executing step S27, the control unit 68 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 the control unit 68 executes step S28 after a certain period of time has elapsed since executing step S27. The certain period of time is equal to or longer than one cycle of the temperature calculation process. Therefore, the temperature difference is calculated at least once after executing step S27.

[0115] If the control unit 68 determines that the latest temperature difference is equal to or less than the upper limit (S28: NO), it determines whether the increase in the temperature difference due to the increase in the duty of the PWM signal exceeds the upper limit of the increase in the increase in the increase in the increase in the duty that was actually performed in the increase ...

[0116] If the control unit 68 determines that the increase in the temperature difference is equal to or less than the upper limit (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 constant value that is set in advance. The reference duty is the maximum duty indicated in the temperature difference table Q1. In the example of FIG. 5, the reference duty is 100%.

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

[0118] If 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 referred to as the actual duty. In step S31, the control unit 68 increases the duty of the PWM signal to a duty that is greater than the actual duty and closest to the actual duty in the temperature difference table Q1. In the example of FIG. 5, if 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, i.e., 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 electric wire current value over a certain period of time increases gradually. The control unit 68 executes steps S28 and S29 each time the duty of the PWM control is increased. If 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, if the temperature difference remains equal to or smaller than the upper limit and the increase in the temperature difference remains equal to or smaller than the upper limit until the duty of the PWM signal reaches the reference duty, the individual ECU 11a is determined to be normal, and the control unit 68 changes the value of the flag to 0. Thereafter, the control unit 68 executes step S20 to adjust the duty of the PWM signal in accordance with the power supply voltage value of the DC power supply 12.

[0121] If the control unit 68 determines that the temperature difference exceeds the upper limit (S28: YES) or that the increase in the temperature difference exceeds the upper limit (S29: YES), it instructs the output unit 64 to output an OFF signal to the drive circuit 31 (step S33). This causes the drive circuit 31 to maintain the switch 30 OFF. 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, if the temperature difference exceeds the upper limit or the increase in the temperature difference exceeds the upper limit, it is determined that an abnormality has occurred in the power supply to the load 13, and the flag value is changed to 2. As described above, if the flag value is 2, no power is supplied to the load 13. Steps S28 and S29 each correspond to a determination as to whether an abnormality has occurred in the power supply to the load 13. Therefore, the determination as to whether 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 drive circuit 31. Furthermore, the determination as to whether an abnormality has occurred in the power supply is made based on the increase in the temperature difference caused by an increase in the duty of the PWM control.

[0123] From the above, a power supply abnormality is a phenomenon in which the temperature difference exceeds the upper limit, or the temperature difference (electric wire temperature) increases beyond the upper limit. A power supply abnormality occurs, for example, when both ends of the load 13 are short-circuited.

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

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

[0126] When the power supply state is interrupted and an instruction to operate the load 13 is given, the control unit 68 increases the duty of the PWM signal in stages. FIG. 11 is an explanatory diagram of the stepwise increase in the duty of the PWM signal. FIG. 11 shows waveforms of PWM signals with different duties. As shown in FIG. 11, the control unit 68 increases the duty of the PWM signal in stages. 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 wire current value increases gradually. Each time the duty is increased, the control unit 68 compares the temperature difference with the upper limit and the increase in the temperature difference with the upper limit, thereby determining whether an abnormality has occurred in the power supply to the load 13. If the control unit 68 does not detect any abnormality in the power supply until the duty of the PWM signal reaches the reference duty, the control unit 68 changes the value of the flag to zero, and transitions the power supply state to the normal state as shown in FIG.

[0128] If the control unit 68 detects a power supply abnormality before the duty of the PWM signal becomes 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 is not transitioned and power is not supplied to the load 13.

[0129] <Effects of individual ECU11a> In the individual ECU 11a, the control unit 68 increases the average value of the electric wire current value in a certain period in a stepwise manner. Each time the control unit 68 increases the average value of the electric wire current value in a stepwise manner, it determines whether or not an abnormality has occurred in the power supply based on the temperature difference between the electric wire temperature and the ambient temperature. Therefore, the control unit 68 can detect an abnormality in the power supply even when the electric wire current value is small. The control unit 68 increases the duty of the PWM signal (PWM control) in a stepwise manner, thereby increasing the average value of the electric wire current in a stepwise manner. Therefore, the stepwise increase in the average value of the electric wire current value can be easily achieved.

[0130] (Embodiment 2) In the first embodiment, the drive circuit 31 performs PWM control of the switch 30 to supply power to the load 13 via the electric wire W. However, the method for supplying power to the load 13 is not limited to the method in which the drive circuit 31 performs PWM control. The following describes the differences between embodiment 2 and embodiment 1. Except for the configurations described below, the configurations are the same as those of embodiment 1. Therefore, the components that are the same as those of embodiment 1 are given the same reference numerals as those of embodiment 1, and descriptions of those components will be omitted.

[0131] <Configuration of Microcomputer 21> 4 outputs a PWM signal and an OFF signal to the drive circuit 31 in accordance with instructions from the control unit 68. In the second embodiment, the output unit 64 further outputs an ON signal indicating that the switch 30 is ON to the drive circuit 31 in accordance with instructions from the control unit 68. The ON signal indicates a high-level voltage.

[0132] <Configuration of 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 ON. While the microcomputer 21 is outputting the ON signal, the drive circuit 31 keeps the switch 30 ON. As described in the description of the first embodiment, when the switch 30 is switched ON, a current flows from the positive electrode of the DC power supply 12 through the switch 30, the electric wire W, and the load 13 in this order. As a result, the load 13 is supplied with power and operates.

[0133] When the output unit 64 is outputting a PWM signal or an ON signal to the drive circuit 31, if the wire current value is equal to or greater than the current threshold, the drive circuit 31 performs self-shutdown of the switch 30 regardless of the signal input to the drive circuit 31. In a similar case, if the switch temperature of the switch 30 is equal to or greater than the switch temperature threshold, the drive circuit 31 performs self-shutdown of the switch 30 regardless of the signal input to the drive circuit 31. When self-shutdown related to the wire current value or switch temperature is performed, the drive circuit 31 notifies the microcomputer 21 of the execution of self-shutdown, as in the first embodiment.

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

[0135] <Power supply control processing> 12 is a flowchart showing the procedure of the power supply control process in embodiment 2. Part of the power supply control process in embodiment 2 is common to part of the power supply control process in embodiment 1. In the power supply control process in embodiment 2, detailed explanations of steps S11, S12, S16 to S19, and S23 to S34 that are common to the power supply control process in embodiment 1 will be omitted.

[0136] In the power supply control process in the second embodiment, 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). This causes the drive circuit 31 to switch on the switch 30. The drive circuit 31 keeps the switch 30 on 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 is supplied to the load 13 by keeping the switch 30 on.

[0137] If the control unit 68 determines not to stop the operation of the load 13 (S19: NO), it executes step S16 again. It is assumed that the wire temperature is below the wire temperature threshold, self-shutdown has not occurred, and the communication unit 66 has not received instruction data instructing the operation of the load 13 to be stopped. In this case, the switch 30 is maintained on.

[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 interrupted state to the normal state, the control unit 68 keeps the switch 30 on.

[0139] <Effects of individual ECU11a> The individual ECU 11a in the second embodiment achieves the same effects as the individual ECU 11a in the first embodiment, except for the effect obtained by changing the duty of PWM control in accordance with the power supply voltage value.

[0140] <Modification> In the first and second embodiments, the timing for determining whether an abnormality has occurred in the power supply to the load 13 while the electric wire current value is increased stepwise is not limited to the timing for operating the load 13 when the power supply state is interrupted. The timing for determining the abnormality may be, for example, the timing for operating the load 13 for the first time after the ignition switch of the vehicle C is switched from off to on. In addition, the switch temperature detection circuit 33 is not limited to a circuit using the thermistor 50, and may be any circuit that can detect the switch temperature of the switch 30.

[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. Furthermore, the method of notifying the execution of self-shutdown is not limited to applying a voltage, and may be a method of outputting information indicating the execution of self-shutdown to the microcomputer 21.

[0142] The method for adjusting the wire current value is not limited to the method for adjusting the duty of PWM control. If 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. Power supply control for controlling power supply The device is not limited to the individual ECU 11 a 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 ECUs 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 FET, and may be a semiconductor switch other than an N-channel FET. Examples of semiconductor switches other than an N-channel FET include a P-channel FET, an IGBT (Insulated Gate Bipolar Transistor), and a bipolar transistor. Polar transistors are examples.

[0144] The disclosed embodiments 1 and 2 are illustrative in all respects and should not be considered limiting. The scope of the present invention is defined by the claims, not by the above meaning, and is intended to include all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0145] 1. Control System 10 Integrated ECU 11a Individual ECU (power supply control device, on-board control device) 11b Individual ECU 12 DC power supply 13 Load 14 Actuators 15a, 15b Sensor 20 Switching device 21 Microcomputer 22 Voltage detection section 23 Environmental temperature detection unit 30 Switch 31 Drive circuit (switching circuit) 32 Current detection circuit 33 Switch temperature detection circuit 40 Current output section 41 Current detection resistor 50 Thermistor 51 Temperature detection resistor 60, 61, 62, 63 A / D conversion section 64 Output section 65 Input section 66 Communication unit (receiving unit) 67 Memory section 68 Control section (processing section) 69 Internal Bus A storage medium C vehicle P Computer Program Q1 Temperature difference table Q2 Increase Table W electric wire

Claims

1. A power supply control device that controls power supply via an electric wire, a processing unit for executing processing, The processing unit increasing the average value of the electric wire current value of the electric current flowing through the electric wire in a stepwise manner; Each time the average value of the electric wire current value is increased, it is determined whether or not an abnormality has occurred in the power supply through the electric wire based on the temperature difference between the electric wire temperature and the environmental temperature around the electric wire. Power supply control device.

2. The processing unit The electric wire current value is acquired, Calculating the temperature difference based on the obtained electric wire current value; Each time the average value of the electric wire current value is increased, it is determined whether or not 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 the current flowing through the electric wire; a switching circuit for switching the switch on or off; Equipped with The processing unit causing the switching circuit to perform PWM control to alternately turn on and off the switch; The duty of the PWM control is increased in stages, thereby increasing the average value of the electric wire current in stages. The power supply control device according to claim 1 or 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 performed by the switching circuit every time the average value of the electric wire current value is increased. The power supply control device according to claim 3 .

5. The processing unit determines whether or not the abnormality has occurred based on an increase in the temperature difference caused by the increase in the average value of the electric wire current each time the processing unit increases the average value of the electric wire current. The power supply control device according to claim 3 or 4.

6. a switch disposed in a current path of the current flowing through the electric wire; a switching circuit for switching the switch on or off; Equipped with A signal is input to the switching circuit, the switching circuit switches the switch on or off in accordance with an input signal; the switching circuit switches off the switch regardless of an input signal when the wire current value is equal to or greater than a current threshold or when the temperature of the switch is equal to or greater than a switch temperature threshold; The processing unit increases the average value of the electric wire current value stepwise after the switching circuit turns off the switch regardless of the input signal. The power supply control device according to any one of claims 1 to 5.

7. The processing unit When the electric wire temperature is equal to or higher than an electric wire temperature threshold, the electric current flowing through the electric wire is interrupted; After the electric wire temperature reaches a temperature equal to or higher than the electric wire temperature threshold, the average value of the electric wire current is increased in stages. The power supply control device according to any one of claims 1 to 6.

8. An on-vehicle control device that controls the operation of a load, a receiving unit that receives instruction data instructing the load to operate or stop operating; a processing unit for executing processing; Equipped with The processing unit Controlling power supply to the load via the electric wire in accordance with the instruction data received by the receiving unit; increasing the average value of the electric wire current value of the electric current flowing through the electric wire in a stepwise manner; Each time the average value of the electric wire current value is increased, it is determined whether or not an abnormality has occurred in the power supply through the electric wire based on the temperature difference between the electric wire temperature and the environmental temperature around the electric wire. In-vehicle control device.

9. A power supply control method for controlling power supply via a power line, comprising: increasing in a stepwise manner an average value of a wire current value of a current flowing through the wire; a step of determining whether or not an abnormality has occurred in power supply via the electric wire based on a temperature difference between the electric wire temperature and an environmental temperature around the electric wire each time the average value of the electric wire current value is increased; The computer executes the power supply control method.

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