Power supply control device and power supply control method

Abstract

To provide a power feeding control device and power feeding control method that stop power feeding to a load in the event of a short-circuit failure.SOLUTION: In a power supply system of a vehicle, a power feeding control device (ECU) comprises: an upstream switch F1 disposed on the upstream side of a load in a path of current flowing via a load E1; a downstream switch Ga disposed on the downstream side of the load E1 in the current path; and a regulator having a processing unit. The processing unit commands switching to On or Off of the upstream switch and the downstream switch, determines whether current is flowing or not in a state in which switching is commanded, and, when determined that current is flowing, commands switching to Off of the upstream switch and the downstream switch. The current path is a path of the current output from a fuse 11. Power is supplied to the processing unit from a connection node between the fuse and the upstream switch. The processing unit executes transmission processing for transmitting data to the outside. Even when a short-circuit failure occurs in the upstream switch, power continues to be supplied to the processing unit via the fuse.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to a power supply control device and a power supply control method. [Background technology]

[0002] Patent Document 1 discloses a power supply control device for a vehicle that controls power supply from a DC power supply to a load. A switch is arranged in a current path of a current flowing from the DC power supply to the load. The control device controls power supply to the load by instructing the switch to be switched on or off. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2019-41508 Summary of the Invention [Problem to be solved by the invention]

[0004] In the configuration of Patent Document 1, even though the control device has instructed the switch to be turned off, if a short-circuit fault occurs in which current flows through the switch, the DC power supply continues to supply power to the load, which may result in unnecessary consumption of power from the DC power supply.

[0005] The present disclosure has been made in consideration of the above circumstances, and its purpose is to provide a power supply control device and a power supply control method that can stop power supply to a load when a short-circuit fault occurs. [Means for solving the problem]

[0006] A power supply control device according to one embodiment of the present disclosure is a power supply control device that controls power supply to a load, and includes: an upstream switch that is arranged upstream of the load in a current path of a current flowing through the load; a downstream switch that is arranged downstream of the load in the current path; and a processing unit that executes processing, wherein the processing unit instructs a first switch included in the upstream switch and the downstream switch to be switched on or off, determines whether or not a current is flowing through the first switch while instructing to switch the first switch off, and if it determines that a current is flowing through the first switch, instructs a second switch included in the upstream switch and the downstream switch to be switched off, the current path is a path of a current output from a fuse, power is supplied to the processing unit from a connection node between the fuse and the upstream switch, and the processing unit executes a transmission process to transmit data to an external device, and power continues to be supplied to the processing unit via the fuse even if a short-circuit failure occurs in the upstream switch.

[0007] A power supply control method according to one aspect of the present disclosure is a power supply control method for controlling power supply to a load, the method including the steps of: instructing a first switch included in an upstream switch located upstream of the load in a current path of a current flowing through the load, and a downstream switch located downstream of the load in the current path, to be switched on or off; determining whether or not a current is flowing through the first switch while instructing to switch the first switch off; and, if it is determined that a current is flowing through the first switch, instructing a second switch included in the upstream switch and the downstream switch to be switched off; the current path is a path of a current output from a fuse; power is supplied to the computer from a connection node between the fuse and the upstream switch; and the computer executes a transmission process to transmit data to an external device; and power continues to be supplied to the computer via the fuse even if a short-circuit failure occurs in the upstream switch.

[0008] 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]

[0009] According to the above aspect, it is possible to stop the supply of power to the load when a short-circuit fault occurs. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a block diagram showing the configuration of a main part of a power supply system according to a first embodiment. [Figure 2] FIG. 2 is a block diagram showing the configuration of a main part of an ECU. [Figure 3] FIG. 2 is a block diagram showing the main configuration of a microcomputer; [Figure 4] 10 is a flowchart showing the procedure of a write process. [Figure 5] 10 is a flowchart showing a procedure of a transmission process. [Figure 6] 10 is a flowchart illustrating a procedure for downstream switch control processing. [Figure 7] 10 is a flowchart showing the procedure of a power supply control process. [Figure 8] 10 is a timing chart for explaining the effect of the ECU. [Figure 9] FIG. 10 is a block diagram showing the configuration of a main part of an ECU according to a second embodiment. [Figure 10] FIG. 11 is a block diagram showing the configuration of a main part of an ECU according to a third embodiment. [Figure 11] FIG. 10 is a block diagram showing the configuration of a main part of a power supply system according to a fourth embodiment. [Figure 12] FIG. 2 is a block diagram showing the configuration of a main part of an ECU. [Figure 13] FIG. 2 is a block diagram showing the main configuration of a microcomputer; [Figure 14] FIG. 11 is a block diagram showing the configuration of a main part of an ECU according to a fifth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0011] [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.

[0012] (1) A power supply control device according to one embodiment of the present disclosure is a power supply control device that controls power supply to a load, and includes an upstream switch that is arranged upstream of the load in a current path of a current flowing through the load, a downstream switch that is arranged downstream of the load in the current path, and a processing unit that executes processing, wherein the processing unit instructs a first switch included in the upstream switch and the downstream switch to be switched on or off, determines whether or not a current is flowing through the first switch while instructing to switch the first switch off, and if it determines that a current is flowing through the first switch, instructs a second switch included in the upstream switch and the downstream switch to be switched off.

[0013] (2) In a power supply control device according to one aspect of the present disclosure, the current path is a path of current output from a fuse, power is supplied to the processing unit from a connection node between the fuse and an upstream switch, and the processing unit executes a transmission process to transmit data to the outside.

[0014] (3) In a power supply control device according to one aspect of the present disclosure, the processing unit instructs the upstream switch to be switched on or off, determines whether or not current is flowing through the upstream switch while instructing the upstream switch to be switched off, and if it determines that current is flowing through the upstream switch, instructs the downstream switch to be switched off.

[0015] (4) In a power supply control device according to one aspect of the present disclosure, the processing unit acquires a voltage value at one end downstream of the upstream switch while instructing the upstream switch to be switched off, and if the acquired voltage value is equal to or greater than a voltage threshold, determines that current is flowing through the upstream switch.

[0016] (5) In a power supply control device according to one embodiment of the present disclosure, the number of downstream switches is two, each of the two downstream switches is a semiconductor switch, a parasitic diode is connected between both ends of each of the two downstream switches, and the anode of the parasitic diode of one downstream switch is connected to the anode of the parasitic diode of the other downstream switch.

[0017] (6) In a power supply control device according to one embodiment of the present disclosure, the number of downstream switches is two, each of the two downstream switches is a semiconductor switch, a parasitic diode is connected between both ends of each of the two downstream switches, and the cathode of the parasitic diode of one downstream switch is connected to the cathode of the parasitic diode of the other downstream switch.

[0018] (7) In a power supply control device according to one aspect of the present disclosure, a load is arranged in each current path of a plurality of currents, the number of the upstream switches is two or more, an upstream switch is arranged in each current path upstream of the load, the plurality of currents flow through the common downstream switch, and the processing unit instructs each of the plurality of upstream switches to be switched on or off, and when instructing one of the plurality of upstream switches to be switched off, determines whether or not a current is flowing through the upstream switch instructed to be switched off, and if it determines that a current is flowing through the upstream switch instructed to be switched off, instructs the downstream switch to be switched off.

[0019] (8) A power supply control method according to one aspect of the present disclosure is a power supply control method for controlling power supply to a load, the method including the steps of instructing a first switch included in an upstream switch arranged upstream of the load in a current path of a current flowing through the load and a downstream switch arranged downstream of the load in the current path to be switched on or off, determining whether or not a current is flowing through the first switch while instructing to switch the first switch off, and instructing a second switch included in the upstream switch and downstream switch to be switched off when it is determined that a current is flowing through the first switch.

[0020] In the power supply control device and the power supply control method according to the above aspects, when a short-circuit failure occurs in the first switch, an instruction to switch the second switch off is issued. As a result, the second switch is switched off, and power supply to the load is stopped. A short-circuit failure in the first switch is a phenomenon in which current flows through the first switch despite an instruction to switch the first switch off.

[0021] In the power supply control device according to the above aspect, if a short-circuit failure occurs in the first switch, the second switch is switched off. After the second switch is switched off, the current flowing through the fuse is a current for supplying power to the processing unit, and the current value of the current flowing through the fuse is small. As a result, the possibility of the fuse being blown is low. As long as the fuse is not blown, power continues to be supplied to the processing unit. Therefore, even if a short-circuit failure occurs in the first switch, the processing unit can continue to execute the process of transmitting data to the outside.

[0022] In the power supply control device according to the above aspect, the first switch and the second switch are an upstream switch and a downstream switch, respectively.

[0023] In the power supply control device according to the above aspect, current flows, for example, from the positive electrode of the DC power supply through the upstream switch, the load, and the downstream switch in that order, and then returns to the negative electrode of the DC power supply. When the upstream switch is off while the downstream switch is on, the voltage value at one end downstream of the upstream switch is substantially zero volts. When the downstream switch is on and a short-circuit fault occurs in the upstream switch, the voltage value at one end of the downstream switch is relatively high. When the downstream switch is on and the voltage value at one end downstream of the upstream switch is equal to or greater than a voltage threshold, the processing unit detects the occurrence of a short-circuit fault in the upstream switch.

[0024] In the power supply control device according to the above aspect, the anode of the parasitic diode of one downstream switch is connected to the anode of the other downstream switch. Therefore, even if the positive electrode of the DC power supply is mistakenly connected to one end of the downstream side of the series circuit including the two downstream switches, no current will flow through the parasitic diodes of the two downstream switches as long as the two downstream switches are off.

[0025] In the power supply control device according to the above aspect, the cathode of the parasitic diode of one downstream switch is connected to the cathode of the other downstream switch. Therefore, even if the positive electrode of a DC power supply is mistakenly connected to one end of the downstream side of a series circuit including two downstream switches, no current will flow through the parasitic diode of the downstream switch as long as the two downstream switches are off.

[0026] In the power supply control device according to the above aspect, power supply to a plurality of loads can be stopped by switching off the common downstream switch.

[0027] [Details of the embodiments of the present disclosure] Specific examples of power supply 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.

[0028] (Embodiment 1) <Power supply system configuration> FIG. 1 is a block diagram showing the configuration of a main part of a power supply system 1 in a first embodiment. The power supply system 1 is mounted on a vehicle C. The power supply system 1 includes a DC power supply 10, a fuse 11, an ECU 12, a sensor 13, and a load E1. The DC power supply 10 is, for example, a battery. The fuse 11 is a mechanical fuse such as a chip fuse, a blade fuse, a thermal fuse, or a fusible link. ECU is an abbreviation for Electronic Control Unit.

[0029] The negative electrode of the DC power supply 10 is grounded. The grounding is achieved, for example, by connecting it to the body of the vehicle C. The positive electrode of the DC power supply 10 is connected to one end of a fuse 11. The other end of the fuse 11 is connected to an ECU 12. The ECU 12 is grounded. The ECU 12 is further connected to both ends of a load E1. The ECU 12 is further connected to a sensor 13. The ECU 12 is further connected to a communication line Lc. The communication line Lc is further connected to one or more communication devices (not shown) mounted on the vehicle C.

[0030] A current flows from the positive electrode of the DC power supply 10 through the fuse 11 and the ECU 12 in this order, and then returns to the negative electrode of the DC power supply 10. The DC power supply 10 supplies power to the ECU 12. The ECU 12 performs various operations using the power supplied from the DC power supply 10. The ECU 12 controls the power supply to the load E1. The ECU 12 functions as a power supply control device. When power is being supplied to the load E1, a current flows from the positive electrode of the DC power supply 10 through the fuse 11, the ECU 12, the load E1, and the ECU 12 in this order, and then returns to the negative electrode of the DC power supply 10.

[0031] The load E1 is an electrical device. When power is supplied to the load E1, the load E1 operates. When the power supply to the load E1 is stopped, the load E1 stops operating.

[0032] The sensor 13 detects vehicle values ​​related to the vehicle C. As a first example, the vehicle values ​​are the speed or acceleration of the vehicle C, or the brightness around the vehicle C. As a second example, the vehicle values ​​are values ​​indicating a state related to the vehicle C. The state related to the vehicle C is, for example, the state of an operation switch operated by an occupant of the vehicle C. The sensor 13 repeatedly outputs sensor data indicating the detected vehicle values ​​to the ECU 12. Note that the sensor 13 may capture an image instead of detecting the vehicle values. In this case, the sensor data is image data of the captured image.

[0033] The ECU 12 receives communication data from one or more communication devices via the communication line Lc. The ECU 12 determines whether to supply power to the load E1 based on, for example, the received communication data or the sensor data input from the sensor 13. The ECU 12 determines whether to stop power supply to the load E1 based on, for example, the received communication data or the sensor data input from the sensor 13.

[0034] The ECU 12 transmits the sensor data input from the sensor 13 to the communication device via the communication line Lc. The communication device performs various operations based on the sensor data received from the ECU 12.

[0035] When a current flows through the fuse 11, the fuse 11 generates heat. The greater the current value of the current flowing through the fuse 11, the greater the amount of heat generated by the fuse 11. If the amount of heat generated per unit time by the fuse 11 is greater than the amount of heat dissipated per unit time, the temperature of the fuse 11 rises. The greater the difference between the amount of heat generated and the amount of heat dissipated, the faster the rate at which the temperature of the fuse 11 rises. If the amount of heat generated per unit time by the fuse 11 is less than the amount of heat dissipated per unit time, the temperature of the fuse 11 decreases. The greater the difference between the amount of heat generated and the amount of heat dissipated, the faster the rate at which the temperature of the fuse 11 decreases. If the temperature of the fuse 11 rises above a certain temperature threshold, the fuse 11 is blown.

[0036] When a current with a large current value flows through fuse 11, fuse 11 is blown. This prevents an overcurrent from flowing from DC power supply 10.

[0037] <Configuration of ECU12> Figure 2 is a block diagram showing the main part configuration of ECU12. ECU12 includes a regulator 20, a microcomputer 21, an upstream switch F1, a downstream switch Ga, a drive circuit K1, and a voltage detection circuit M1. A microcomputer is an abbreviation for a microcomputer. Each of the upstream switch F1 and the downstream switch Ga is an N-channel type MOSFET (Metal Oxide Semiconductor Field Effect Transistor). Therefore, each of the upstream switch F1 and the downstream switch Ga is a semiconductor switch.

[0038] A parasitic diode H1 is connected between the drain and source of the upstream switch F1. The cathode and anode of the parasitic diode H1 are connected to the drain and source of the upstream switch F1, respectively. A parasitic diode Ja is also connected between the drain and source of the downstream switch Ga. The cathode and anode of the parasitic diode Ja are connected to the drain and source of the downstream switch Ga, respectively.

[0039] One end on the downstream side of fuse 11 is connected to the drain of the upstream switch F1. The source of the upstream switch F1 is connected to one end on the upstream side of load E1. One end on the downstream side of load E1 is connected to the drain of the downstream switch Ga. The source of the downstream switch Ga is grounded.

[0040] The connection node between the fuse 11 and the upstream switch F1 is further connected to a regulator 20. The regulator 20 is further connected to a microcomputer 21. The gate of the upstream switch F1 is connected to a drive circuit K1. The drive circuit K1 is further connected to the microcomputer 21. The source of the upstream switch F1 is further connected to a voltage detection circuit M1. The voltage detection circuit M1 is further connected to the microcomputer 21. The gate of the downstream switch Ga is connected to the microcomputer 21. The microcomputer 21 is grounded. The microcomputer 21 is further connected to the sensor 13 and the communication line Lc.

[0041] For each of the upstream switch F1 and the downstream switch Ga, the higher the gate voltage value, where the reference potential is the source potential, the smaller the resistance value between the drain and source. For each of the upstream switch F1 and the downstream switch Ga, when the gate voltage value, where the reference potential is the source potential, is equal to or greater than a certain voltage value, the state is on. When the state is on, the resistance value between the drain and source is sufficiently small. Therefore, current can flow through the drain and source.

[0042] For each of the upstream switch F1 and the downstream switch Ga, when the gate voltage value is less than a certain voltage value where the reference potential is the source potential, the state is off. When the state is off, the resistance between the drain and source is sufficiently large so that no current flows through the drain and source.

[0043] When the upstream switch F1 and the downstream switch Ga are on, current flows from the positive terminal of the DC power supply 10 to the fuse 11, the upstream switch F1, the load E1, and the downstream switch Ga in this order. At this time, power is supplied to the load E1. When at least one of the upstream switch F1 and the downstream switch Ga is off, no current flows through the load E1.

[0044] As described above, the current output from the fuse 11 flows in the order of the upstream switch F1, the load E1, and the downstream switch Ga. Therefore, the current path of the current flowing through the upstream switch F1, the load E1, and the downstream switch Ga is the path of the current output from the fuse 11. In the current path, the upstream switch F1 is arranged upstream of the load E1. In the current path, the downstream switch Ga is arranged downstream of the load E1.

[0045] The voltage at the connection node between the fuse 11 and the drain of the upstream switch F1 is referred to as the node voltage. The reference potential of the node voltage is ground potential. The regulator 20 steps down the node voltage to a constant target voltage. The reference potential of the target voltage is ground potential. The regulator 20 applies the target voltage generated by stepping down to the microcontroller 21. As a result, current flows from the positive electrode of the DC power supply 10 through the fuse 11, the regulator 20, and the microcontroller 21, and then returns to the negative electrode of the DC power supply 10. The DC power supply 10 supplies power to the microcontroller 21 via the fuse 11 and the regulator 20. The microcontroller 21 performs various operations using the power supplied from the DC power supply 10.

[0046] The microcomputer 21 outputs a high-level voltage or a low-level voltage to the drive circuit K1. The reference potential of the high-level and low-level voltages output by the microcomputer 21 is the ground potential. The microcomputer 21 switches the voltage output to the drive circuit K1 to a high-level voltage or a low-level voltage. When the voltage input from the microcomputer 21 switches from a low-level voltage to a high-level voltage, the drive circuit K1 increases the voltage value of the gate of the upstream switch F1. Hereinafter, the gate voltage value will be referred to as the gate voltage value. The reference potential of the gate voltage value is the ground potential.

[0047] When the driver circuit K1 increases the gate voltage of the upstream switch F1, the gate voltage, whose reference potential is the source potential, increases to a voltage value equal to or greater than a certain voltage value, thereby switching on the upstream switch F1.

[0048] When the voltage input from the microcomputer 21 switches from a high-level voltage to a low-level voltage, the drive circuit K1 lowers the gate voltage of the upstream switch F1. In this case, the gate voltage of the upstream switch F1, whose reference potential is the source potential, drops to a voltage value less than a certain voltage value. This switches the upstream switch F1 off. As described above, the drive circuit K1 switches the upstream switch F1 on or off by adjusting the gate voltage of the upstream switch F1.

[0049] The voltage detection circuit M1 detects the voltage value of the source of the upstream switch F1. Hereinafter, the source voltage value will be referred to as the source voltage value. The reference potential of the source voltage value is the ground potential. The voltage detection circuit M1 outputs analog voltage value information indicating the detected source voltage value to the microcomputer 21. The voltage value information is, for example, a voltage value obtained by dividing the voltage of the source of the upstream switch F1.

[0050] The microcomputer 21 outputs a high-level voltage or a low-level voltage to the gate of the downstream switch Ga. When the microcomputer 21 outputs a high-level voltage to the gate of the downstream switch Ga, the voltage value of the gate, whose reference potential is the source potential, is equal to or greater than a certain voltage value. As a result, the downstream switch Ga is on. When the microcomputer 21 outputs a low-level voltage to the gate of the downstream switch Ga, the voltage of the gate, whose reference potential is the source potential, is less than a certain voltage value. As a result, the downstream switch Ga is off.

[0051] As described above, the microcomputer 21 switches the voltage output to the gate of the downstream switch Ga between a high-level voltage and a low-level voltage, thereby switching the downstream switch Ga on or off. No circuitry for switching the downstream switch Ga on or off is required.

[0052] The microcomputer 21 receives communication data via the communication line Lc. The sensor 13 outputs sensor data to the microcomputer 21. For example, when the ignition switch of the vehicle C is turned on, the microcomputer 21 turns on the downstream switch Ga. The microcomputer 21 determines whether to supply power to the load E1, for example, based on the received communication data or the sensor data input from the sensor 13. If the microcomputer 21 determines to supply power to the load E1, it switches the voltage output to the drive circuit K1 from a low-level voltage to a high-level voltage while keeping the downstream switch Ga on. This causes the drive circuit K1 to turn on the upstream switch F1. As a result, power is supplied to the load E1.

[0053] The microcomputer 21 determines whether to stop power supply to the load E1, for example, based on the received communication data or the sensor data input from the sensor 13. If the microcomputer 21 determines to stop power supply to the load E1, it switches the voltage output to the drive circuit K1 from a high-level voltage to a low-level voltage while keeping the downstream switch Ga on. This causes the drive circuit K1 to switch the upstream switch F1 off. As a result, power supply to the load E1 is stopped. For example, when the ignition switch of the vehicle C is switched off, the microcomputer 21 switches the downstream switch Ga off.

[0054] The microcomputer 21 determines whether a short-circuit fault has occurred in the upstream switch F1 based on the voltage value information input from the voltage detection circuit M1, i.e., the source voltage value of the upstream switch F1 detected by the voltage detection circuit M1. A short-circuit fault in the upstream switch F1 is a phenomenon in which current flows through the drain and source of the upstream switch F1 despite an instruction to turn the upstream switch F1 off. If the microcomputer 21 determines that a short-circuit fault has occurred in the upstream switch F1, it turns off the downstream switch Ga.

[0055] <Configuration of Microcomputer 21> 3 is a block diagram showing the main configuration of the microcomputer 21. The microcomputer 21 has a communication unit 30, an input unit 31, a memory unit 32, a control unit 33, a first output unit T1, a second output unit U, and an A / D conversion unit X1. These are connected to an internal bus 34. The first output unit T1 is further connected to a drive circuit K1. The A / D conversion unit X1 is further connected to a voltage detection circuit M1. The second output unit U is further connected to the gate of the downstream switch Ga. The communication unit 30 is further connected to a communication line Lc. The input unit 31 is further connected to the sensor 13.

[0056] As described above, the DC power supply 10 supplies power to the microcomputer 21 via the fuse 11 and the regulator 20. When power is supplied to the microcomputer 21, power is also supplied to the communication unit 30, the input unit 31, the storage unit 32, the control unit 33, the first output unit T1, and the second output unit U. Therefore, power is supplied to the A / D conversion unit X1, the communication unit 30, the input unit 31, the storage unit 32, the control unit 33, the first output unit T1, the second output unit U, and the A / D conversion unit X1 from the connection node between the fuse 11 and the upstream switch F1.

[0057] The first output unit T1 outputs a high-level voltage or a low-level voltage to the drive circuit K1. The voltage output by the microcomputer 21 to the drive circuit K1 is the voltage output by the first output unit T1 to the drive circuit K1. The control unit 33 instructs the first output unit T1 to switch the upstream switch F1 on or off. When the control unit 33 instructs the first output unit T1 to switch the upstream switch F1 on, the first output unit T1 switches the voltage output to the drive circuit K1 to a high-level voltage. When the control unit 33 instructs the first output unit T1 to switch the upstream switch F1 off, the first output unit T1 switches the voltage output to the drive circuit K1 to a low-level voltage.

[0058] The voltage detection circuit M1 outputs analog voltage value information to the A / D conversion unit X1. The A / D conversion unit X1 converts the analog voltage value information input from the voltage detection circuit M1 into digital voltage value information. The control unit 33 acquires the digital voltage value information converted by the A / D conversion unit X1. As described above, the voltage value information indicates the source voltage value of the upstream switch F1. Acquiring the voltage value information corresponds to acquiring the source voltage value of the upstream switch F1.

[0059] The second output unit U outputs a high-level voltage or a low-level voltage to the gate of the downstream switch Ga. The voltage that the microcomputer 21 outputs to the gate of the downstream switch Ga is the voltage that the second output unit U outputs to the gate of the downstream switch Ga. The control unit 33 instructs the second output unit U to switch the downstream switch Ga on or off.

[0060] When the control unit 33 instructs the second output unit U to switch the downstream switch Ga on, the second output unit U switches the voltage output to the gate of the downstream switch Ga to a high-level voltage. This switches the downstream switch Ga on. When the control unit 33 instructs the second output unit U to switch the downstream switch Ga off, the second output unit U switches the voltage output to the gate of the downstream switch Ga to a low-level voltage. This switches the downstream switch Ga off.

[0061] The communication unit 30 receives communication data transmitted by the communication device via the communication line Lc. The communication unit 30 transmits sensor data to the communication device in accordance with instructions from the control unit 33. The sensor 13 outputs the sensor data to the input unit 31.

[0062] The storage unit 32 is configured with, for example, a volatile memory and a non-volatile memory. A computer program P is stored in the storage unit 32. The control unit 33 has processing elements that execute processing. The control unit 33 functions as a processing unit. The processing elements are, for example, a CPU (Central Processing Unit) and are a computer. The processing elements of the control unit 33 execute the computer program P to concurrently execute write processing, transmission processing, downstream switch control processing, power supply control processing, and the like.

[0063] The write process is a process of writing communication data and sensor data to the memory unit 32. The transmission process is a process of transmitting communication data to a communication device. The downstream switch control process is a process of switching the downstream switch Ga on or off. The power supply control process is a process of controlling the power supply to the load E1.

[0064] The computer program P may be provided to the microcomputer 21 using a non-transitory storage medium A that readably stores the computer program P. The storage medium A is, for example, a portable memory. When the storage medium A is a portable memory, the processing element of the control unit 33 may read the computer program P from the storage medium A using a reading device (not shown). The read computer program P is written to the storage unit 32. Furthermore, the computer program P may be provided to the microcomputer 21 by a communication unit (not shown) of the microcomputer 21 communicating with an external device. In this case, the processing element of the control unit 33 acquires the computer program P through the communication unit. The acquired computer program P is written to the storage unit 32.

[0065] The number of processing elements included in the control unit 33 may be two or more. In this case, the multiple processing elements included in the control unit 33 may cooperate to execute the write process, the transmission process, the downstream switch control process, the power supply control process, and the like.

[0066] <Write process> 4 is a flowchart showing the procedure of the write process. In the write process, the control unit 33 first determines whether the communication unit 30 has received communication data via the communication line Lc (step S1). If the control unit 33 determines that the communication unit 30 has not received communication data (S1: NO), it determines whether sensor data has been input from the sensor 13 to the input unit 31 (step S2). If the control unit 33 determines that sensor data has not been input to the input unit 31 (S2: NO), it executes step S1 again. The control unit 33 waits until the communication unit 30 receives communication data or until sensor data is input to the input unit 31.

[0067] When the control unit 33 determines that the communication unit 30 has received communication data (S1: YES), it writes the communication data received by the communication unit 30 to the storage unit 32 (step S3). When the control unit 33 determines that sensor data has been input to the input unit 31 (S2: YES), it writes the sensor data input to the input unit 31 to the storage unit 32 (step S4). After executing one of steps S3 and S4, the control unit 33 ends the write process. After ending the write process, the control unit 33 executes the write process again.

[0068] <Send process> 5 is a flowchart showing the procedure of the transmission process. In the transmission process, the control unit 33 determines whether sensor data has been input to the input unit 31 from the sensor 13 (step S11). When the control unit 33 determines that sensor data has not been input to the input unit 31 (S11: NO), the control unit 33 executes step S11 again. The control unit 33 waits until sensor data is input to the input unit 31.

[0069] When the control unit 33 determines that the sensor data has been input to the input unit 31 (S11: YES), it instructs the communication unit 30 to transmit the sensor data to the communication device via the communication line Lc (step S12). After executing step S12, the control unit 33 ends the transmission process. After ending the transmission process, the control unit 33 executes the transmission process again. The transmission process is not related to the control of power supply to the load E1. Therefore, the transmission process is different from the process related to the control of power supply to the load E1.

[0070] <Downstream switch control processing> 6 is a flowchart showing the procedure of the downstream switch control process. In the downstream switch control process, the control unit 33 determines whether to switch on the downstream switch Ga (step S21). In step S21, the control unit 33 determines to switch on the downstream switch Ga when, for example, IG on information indicating that the ignition switch of the vehicle C has been switched on is input to an input unit (not shown). If the IG on information is not input, the control unit 33 determines not to switch on the downstream switch Ga.

[0071] When the control unit 33 determines not to switch the downstream switch Ga on (S21: NO), it determines whether to switch the downstream switch Ga off (step S22). In step S22, for example, if IG off information indicating that the ignition switch of the vehicle C has been switched off is input to an input unit (not shown), the control unit 33 determines to switch the downstream switch Ga off. When the IG off information is not input, the control unit 33 determines not to switch the downstream switch Ga off. When the control unit 33 determines not to switch the downstream switch Ga off (S22: NO), it executes step S21 again. The control unit 33 waits until the timing arrives to switch the downstream switch Ga on or off.

[0072] When the control unit 33 determines that the downstream switch Ga should be switched on (S21: YES), it instructs the second output unit U to switch on the downstream switch Ga (step S23). As a result, the second output unit U switches the voltage output to the gate of the downstream switch Ga to a high-level voltage. As a result, the downstream switch Ga is switched on.

[0073] When the control unit 33 determines to switch the downstream switch Ga off (S22: YES), it instructs the second output unit U to switch the downstream switch Ga off (step S24). As a result, the second output unit U switches the voltage output to the gate of the downstream switch Ga to a low-level voltage. As a result, the downstream switch Ga is switched off. After executing one of steps S23 and S24, the control unit 33 ends the downstream switch control process. After ending the downstream switch control process, the control unit 33 executes the downstream switch control process again.

[0074] <Power supply control processing> 7 is a flowchart showing the procedure of the power supply control process. The control unit 33 executes the power supply control process when the downstream switch Ga is on. In the power supply control process, the control unit 33 first determines whether or not to supply power to the load E1 based on, for example, the latest communication data or the latest sensor data stored in the memory unit 32 (step S31). When the control unit 33 determines not to supply power to the load E1 (S31: NO), it executes step S31 again. The control unit 33 waits until the timing to supply power to the load E1 arrives.

[0075] When the control unit 33 determines that power is to be supplied to the load E1 (S31: YES), it instructs the first output unit T1 to switch on the upstream switch F1 (step S32). As a result, the first output unit T1 switches the voltage output to the drive circuit K1 to a high-level voltage. The drive circuit K1 switches on the upstream switch F1. The upstream switch F1 functions as a first switch.

[0076] After executing step S32, the control unit 33 determines whether or not to stop the power supply to the load E1 based on, for example, the latest communication data or the latest sensor data stored in the storage unit 32 (step S33). If the control unit 33 determines not to stop the power supply to the load E1 (S33: NO), it executes step S33 again. The control unit 33 waits until the timing to stop the power supply to the load E1 arrives.

[0077] When the control unit 33 determines that power supply to the load E1 should be stopped (S33: YES), it instructs the first output unit T1 to switch the upstream switch F1 off (step S34). As a result, the first output unit T1 switches the voltage it is outputting to the drive circuit K1 to a low-level voltage. The drive circuit K1 switches the upstream switch F1 off. If one of the first output unit T1, drive circuit K1, and upstream switch F1 does not operate normally, the upstream switch F1 is not switched off.

[0078] After executing step S34, the control unit 33 acquires voltage value information from the A / D conversion unit X1 while instructing to turn off the upstream switch F1 (step S35). The source voltage value of the upstream switch F1 indicated by the voltage value information acquired by the control unit 33 substantially matches the source voltage value of the upstream switch F1 at the time of acquisition. As described above, acquiring the voltage value information corresponds to acquiring the source voltage value of the upstream switch F1.

[0079] Next, the control unit 33 determines whether or not a current is flowing through the upstream switch F1 based on the source voltage value of the upstream switch F1 indicated by the voltage value information acquired in step S35. (Step S36). The control unit 33 executes step S36 while instructing to turn off the upstream switch F1. As described above, a phenomenon in which current flows through the upstream switch F1 despite an instruction to turn off the upstream switch F1 is a short-circuit fault. In step S36, the control unit 33 determines whether a short-circuit fault has occurred.

[0080] A constant positive value near zero V is referred to as the voltage threshold. When no current flows through the upstream switch F1, no current flows through the load E1. Therefore, the source voltage value of the upstream switch F1 is substantially zero V and is below the voltage threshold. When current flows through the upstream switch F1, current flows through the load E1. Therefore, the source voltage value of the upstream switch F1 is relatively high and is equal to or greater than the voltage threshold. When the upstream switch F1 and the downstream switch Ga are on, the source voltage value of the upstream switch F1 substantially matches the voltage value across the DC power supply 10.

[0081] In step S36, if the source voltage value of the upstream switch F1 indicated by the voltage value information acquired in step S35 is less than the voltage threshold, the control unit 33 determines that no current is flowing through the upstream switch F1. In step S36, if the source voltage value of the upstream switch F1 indicated by the voltage value information acquired in step S35 is equal to or greater than the voltage threshold, the control unit 33 determines that a current is flowing through the upstream switch F1. As described above, the control unit 33 detects the occurrence of a short-circuit fault in the upstream switch F1 when the downstream switch Ga is on and the control unit 33 has instructed to switch the upstream switch F1 off and the source voltage value of the upstream switch F1 is equal to or greater than the voltage threshold.

[0082] When the control unit 33 determines that no current is flowing through the upstream switch F1 (S36: NO), the control unit 33 ends the power supply control process. When the downstream switch Ga is on at the time when the power supply control process ends, the control unit 33 executes the power supply control process again.

[0083] When the control unit 33 determines that current is flowing through the upstream switch F1 (S36: YES), it assumes that a short-circuit fault has occurred and instructs the second output unit U to switch the downstream switch Ga off (step S37). As a result, the second output unit U switches the voltage output to the gate of the downstream switch Ga to a low-level voltage. The downstream switch Ga switches off. Consequently, the power supply to the load E1 stops. After executing step S37, the control unit 33 ends the power supply control process. In this case, since the power supply control process ends with the downstream switch Ga off, the control unit 33 does not execute the power supply control process again. The downstream switch Ga functions as the second switch.

[0084] <Effect of the ECU12> Figure 8 is a timing chart for explaining the effect of the ECU12. In Figure 8, the transitions of the instructions performed by the control unit 33, the state of the upstream switch F1, and the state of the downstream switch Ga are shown. In these transitions, time is shown on the horizontal axis. The ON instruction is an instruction to switch the upstream switch F1 on. The OFF instruction is an instruction to switch the upstream switch F1 off. In Figure 8, the switch from the OFF instruction to the ON instruction means the execution of the ON instruction. The switch from the ON instruction to the OFF instruction means the execution of the OFF instruction.

[0085] For example, when the ignition switch of the vehicle C is switched on, the control unit 33 instructs the second output unit U to switch the downstream switch Ga on. As a result, as shown in Figure 8, the downstream switch Ga switches on. The control unit 33 executes the power supply control process with the downstream switch Ga on. When the first output unit T1, the drive circuit K1, and the upstream switch F1 are operating normally, when the control unit 33 issues an ON instruction, the upstream switch F1 switches on. In a similar case, when the control unit 33 issues an OFF instruction, the upstream switch F1 switches off.

[0086] When the upstream switch F1 is switched on, power is supplied to the load E1, and the load E1 operates. When the upstream switch F1 is switched off, power supply to the load E1 is stopped, and the load E1 stops operating.

[0087] If the upstream switch F1 remains on despite the control unit 33 issuing an off command, the source voltage value of the upstream switch F1 substantially matches the voltage value across the DC power supply 10. Therefore, the source voltage value of the upstream switch F1 is equal to or greater than the voltage threshold. The control unit 33 detects the occurrence of a short-circuit failure in the upstream switch F1. When the control unit 33 detects the occurrence of a short-circuit failure in the upstream switch F1, it instructs the second output unit U to switch the downstream switch Ga off. This switches the downstream switch Ga off. As a result, power supply to the load E1 is stopped.

[0088] Therefore, if a short-circuit failure occurs in the upstream switch F1, power supply to the load E1 is stopped. If a short-circuit failure occurs in the upstream switch F1, the downstream switch Ga is switched off. After the downstream switch Ga is switched off, the current flowing through the fuse 11 is a current for supplying power to the microcomputer 21, and the current value of the current flowing through the fuse 11 is small. As a result, the possibility of the fuse 11 being blown is low. Unless the fuse 11 is blown, the DC power supply 10 continues to supply power to the microcomputer 21. Therefore, even if a short-circuit failure occurs in the upstream switch F1, the control unit 33 can continue to execute the write process, the transmission process, and the like.

[0089] When a short - circuit fault occurs in the upstream switch F1 in a configuration where the downstream switch Ga is not provided, the DC power supply 10 continues to supply power to the load E1. When the DC power supply 10 continues to supply power to the load E1 while a generator (not shown) that charges the DC power supply 10 is stopped, the power stored in the DC power supply 10 decreases. When the power supplied to the load E1 is large, so - called battery boost is likely to occur. However, in the ECU12, when a short - circuit fault occurs in the upstream switch F1, the downstream switch Ga switches to the off state. Therefore, after a short - circuit fault occurs in the upstream switch F1, the DC power supply 10 does not continue to supply power to the load E1.

[0090] (Embodiment 2) In Embodiment 1, the number of downstream switches that the ECU12 has is 1. However, the number of downstream switches that the ECU12 has may be 2. Hereinafter, regarding Embodiment 2, the differences from Embodiment 1 will be described. For other configurations except the configurations described later, since they are common to Embodiment 1, the same reference numerals as those in Embodiment 1 are assigned to the common components in Embodiment 1 and their descriptions are omitted.

[0091] <Configuration of ECU12> FIG. 9 is a block diagram showing the main - part configuration of the ECU12 in Embodiment 2. The ECU12 in Embodiment 2 has the same components as those of the ECU12 in Embodiment 1. The ECU12 in Embodiment 2 further has a downstream switch Gb. The downstream switch Gb is an N - channel MOSFET, similar to the downstream switch Ga. Therefore, each of the downstream switches Ga and Gb is a semiconductor switch.

[0092] A parasitic diode Jb is connected between the drain and source of the downstream switch Gb. The cathode and anode of the parasitic diode Jb are connected to the drain and anode of the downstream switch Gb, respectively.

[0093] In the second embodiment, the source of the downstream switch Ga is not grounded. The source of the downstream switch Ga is connected to the source of the downstream switch Gb. The drain of the downstream switch Gb is grounded. Therefore, the anode of the parasitic diode Ja of the downstream switch Ga is connected to the anode of the parasitic diode Jb of the downstream switch Gb.

[0094] As described in the description of the first embodiment, the microcomputer 21 has a second output unit U (see FIG. 3). The output terminals of the second output unit U that output a high-level voltage and a low-level voltage are connected to the gates of the two downstream switches Ga and Gb.

[0095] For the downstream switch Gb, the higher the gate voltage value, where the reference potential is the source potential, the smaller the resistance value between the drain and source. For the downstream switch Gb, when the gate voltage value, where the reference potential is the source potential, is equal to or greater than a certain voltage value, the downstream switch Gb is on. When the downstream switch Gb is on, the resistance value between the drain and source is sufficiently small. Therefore, current can flow through the drain and source of the downstream switch Gb.

[0096] When the gate voltage of the downstream switch Gb is less than a certain voltage value, the reference potential of which is the source voltage, the downstream switch Gb is off. When the downstream switch Gb is off, the resistance between the drain and source of the downstream switch Gb is sufficiently large. Therefore, no current flows through the drain and source of the downstream switch Gb.

[0097] In the following, the connection of the DC power supply 10 when the positive electrode of the DC power supply 10 is connected to one end of the fuse 11 and the negative electrode of the DC power supply 10 is grounded will be referred to as normal connection. The connection of the DC power supply 10 when the positive electrode of the DC power supply 10 is grounded and the negative electrode of the DC power supply 10 is connected to one end of the fuse 11 will be referred to as reverse connection.

[0098] When the DC power supply 10 is connected normally, the second output unit U of the microcomputer 21 outputs a high-level voltage or a low-level voltage to the gates of the two downstream switches Ga and Gb. The voltages output to the gates of the two downstream switches Ga and Gb are the same. When the second output unit U outputs a high-level voltage to the gates of the downstream switches Ga and Gb, the gate voltage value of each of the downstream switches Ga and Gb, whose reference potential is the source potential, is equal to or greater than a certain voltage value. As a result, the two downstream switches Ga and Gb are on.

[0099] When the second output unit U outputs a low-level voltage to the gates of the two downstream switches Ga and Gb, the gate voltages of the downstream switches Ga and Gb, whose reference potential is the source potential, are less than a certain voltage value. As a result, the two downstream switches Ga and Gb are off. No circuitry is required to switch the downstream switches Ga and Gb on or off.

[0100] As described in the description of the first embodiment, the microcomputer 21 has a communication unit 30, an input unit 31, a memory unit 32, a control unit 33, a first output unit T1, a second output unit U, and an A / D conversion unit X1 (see FIG. 3). When the DC power supply 10 is properly connected, power is supplied to the microcomputer 21, and the communication unit 30, the input unit 31, the memory unit 32, the control unit 33, the first output unit T1, the second output unit U, and the A / D conversion unit X1 operate.

[0101] When the DC power supply 10 is normally connected, the control unit 33 instructs the second output unit U to switch the two downstream switches Ga and Gb on or off. When the control unit 33 instructs the second output unit U to switch the two downstream switches Ga and Gb on, the second output unit U switches the voltage output to the gates of the two downstream switches Ga and Gb to a high-level voltage. This switches the two downstream switches Ga and Gb on. When the control unit 33 instructs the second output unit U to switch the two downstream switches Ga and Gb off, the second output unit U switches the voltage output to the gates of the two downstream switches Ga and Gb to a low-level voltage. This switches the two downstream switches Ga and Gb off.

[0102] When the DC power supply 10 is normally connected and the upstream switch F1 and the two downstream switches Ga and Gb are on, a current flows from the positive electrode of the DC power supply 10 to the fuse 11, the upstream switch F1, the load E1, and the downstream switches Ga and Gb in this order. Therefore, in the current path of the current output from the fuse 11, the two downstream switches Ga and Gb are arranged downstream of the load E1.

[0103] When the DC power supply 10 is connected normally and the upstream switch F1 is off, no current flows through the load E1 regardless of the states of the two downstream switches Ga and Gb. When the DC power supply 10 is connected normally and the two downstream switches Ga and Gb are off, no current flows through the load E1 regardless of the state of the upstream switch F1.

[0104] <Configuration of Microcomputer 21> When the DC power supply 10 is properly connected, the control unit 33 of the microcomputer 21 executes the write process, the transmission process, the downstream switch control process, the power supply control process, and the like, similarly to the first embodiment.

[0105] <Downstream switch control processing> In step S21 of the downstream switch control process in embodiment 2, the control unit 33 determines whether to switch on the two downstream switches Ga and Gb. As in embodiment 1, the control unit 33 determines whether to switch on the two downstream switches Ga and Gb based on, for example, whether IG on information has been input to an input unit (not shown).

[0106] In step S22 of the downstream switch control process in embodiment 2, the control unit 33 determines whether to switch off the two downstream switches Ga and Gb. As in embodiment 1, the control unit 33 determines whether to switch off the two downstream switches Ga and Gb based on, for example, whether IG off information has been input to an input unit (not shown).

[0107] If the control unit 33 determines that the two downstream switches Ga, Gb should be switched on (S21: YES), then in step S23 the control unit 33 instructs the second output unit U to switch the two downstream switches Ga, Gb on. As a result, the two downstream switches Ga, Gb are switched on. If the control unit 33 determines that the two downstream switches Ga, Gb should be switched off (S22: YES), then in step S24 the control unit 33 instructs the second output unit U to switch the two downstream switches Ga, Gb off. As a result, the two downstream switches Ga, Gb are switched off.

[0108] <Power supply control processing> In the second embodiment, the control unit 33 executes the power supply control process when the two downstream switches Ga and Gb are on. Regarding step S36, when the upstream switch F1 and the two downstream switches Ga and Gb are on, the source voltage value of the upstream switch F1 substantially matches the voltage value across the DC power supply 10. When the two downstream switches Ga and Gb are on and the control unit 33 has instructed to switch the upstream switch F1 off, the control unit 33 detects the occurrence of a short-circuit fault in the upstream switch F1 when the source voltage value of the upstream switch F1 is equal to or greater than the voltage threshold value.

[0109] <Operation of ECU 12 when DC power supply 10 is reversely connected> When the DC power supply 10 is reversely connected, the regulator 20 does not operate and stops operating. As a result, no power is supplied to the microcomputer 21, and the microcomputer 21 stops operating. When the microcomputer 21 stops operating, the drive circuit K1 maintains the gate voltage value of the upstream switch F1 at zero V. As described in the description of the first embodiment, the reference potential of the gate voltage value is the ground potential.

[0110] When the DC power supply 10 is reversely connected, when the gate voltage of the upstream switch F1 is zero V, the gate voltage of the upstream switch F1, whose reference potential is the source potential, is less than a certain voltage value, and therefore the upstream switch F1 is off.

[0111] When the microcomputer 21 stops operating, the microcomputer 21 maintains the voltage values of the gates of the two downstream switches Ga and Gb at zero volts. When the connection of the DC power supply 10 is reverse-connected, when the gate voltage values of the two downstream switches Ga and Gb are zero volts, for each of the downstream switches Ga and Gb, the voltage value of the gate whose reference potential is the source potential is less than a certain voltage value. Therefore, the two downstream switches Ga and Gb are off.

[0112] As described above, the anode of the parasitic diode Ja of the downstream switch Ga is connected to the anode of the parasitic diode Jb of the downstream switch Gb. Therefore, even when the connection of the DC power supply 10 is reverse-connected, as long as the two downstream switches Ga and Gb are off, no current flows through the parasitic diodes Ja and Jb. The ECU 12 in Embodiment 2 exhibits the same effects as the ECU 12 in Embodiment 1.

[0113] (Embodiment 3) In Embodiment 2, the anode of the parasitic diode Ja of the downstream switch Ga is connected to the anode of the parasitic diode Jb of the downstream switch Gb. This prevents current from flowing through the parasitic diodes Ja and Jb. However, the configuration for preventing current from flowing through the parasitic diodes Ja and Jb is not limited to the configuration of connecting the anode of the parasitic diode Ja to the anode of the parasitic diode Jb. Hereinafter, the differences between Embodiment 3 and Embodiment 2 will be described. For other configurations except the configurations described later, since they are common to Embodiment 2, the same reference numerals as those in Embodiment 2 are assigned to the components common to Embodiment 2 and the description thereof is omitted.

[0114] <Configuration of ECU 12> 10 is a block diagram showing the configuration of the main parts of the ECU 12 in the third embodiment. In the third embodiment, one end on the downstream side of the load E1 is connected to the source of the downstream switch Gb. The drain of the downstream switch Gb is connected to the drain of the downstream switch Ga. Therefore, the cathode of the downstream switch Ga is connected to the cathode of the downstream switch Gb. The source of the downstream switch Ga is grounded.

[0115] As for the second output unit U of the microcomputer 21, the output terminals that output the high-level voltage and the low-level voltage are connected to the gates of the two downstream switches Ga and Gb, similarly to the second embodiment.

[0116] When the DC power supply 10 is normally connected, the second output unit U outputs a high-level voltage or a low-level voltage to the gates of the two downstream switches Ga and Gb, as in the second embodiment. The voltages output to the gates of the two downstream switches Ga and Gb are the same. When the second output unit U outputs a high-level voltage to the gates of the downstream switches Ga and Gb, the gate voltage value of each of the downstream switches Ga and Gb, whose reference potential is the source potential, is equal to or greater than a certain voltage value. As a result, the two downstream switches Ga and Gb are on.

[0117] When the second output unit U outputs a low-level voltage to the gates of the two downstream switches Ga and Gb, the gate voltages of the downstream switches Ga and Gb, whose reference potential is the source potential, are less than a certain voltage value, and as a result, the two downstream switches Ga and Gb are off.

[0118] When the DC power supply 10 is normally connected and the upstream switch F1 and the two downstream switches Ga and Gb are on, a current flows from the positive electrode of the DC power supply 10 to the fuse 11, the upstream switch F1, the load E1, and the downstream switches Gb and Ga in this order. Therefore, in the current path of the current output from the fuse 11, the two downstream switches Ga and Gb are arranged downstream of the load E1.

[0119] When the DC power supply 10 is connected normally and the upstream switch F1 is off, no current flows through the load E1 regardless of the states of the two downstream switches Ga and Gb. When the DC power supply 10 is connected normally and the two downstream switches Ga and Gb are off, no current flows through the load E1 regardless of the state of the upstream switch F1.

[0120] <Operation of ECU 12 when DC power supply 10 is reversely connected> When the microcomputer 21 is stopped, the microcomputer 21 maintains the gate voltage values ​​of the two downstream switches Ga and Gb at zero V. When the DC power supply 10 is reversely connected and the gate voltage values ​​of the two downstream switches Ga and Gb are zero V, the gate voltage values ​​of the downstream switches Ga and Gb, whose reference potential is the source potential, are less than a certain voltage value. Therefore, the two downstream switches Ga and Gb are off.

[0121] As described above, the cathode of the parasitic diode Ja of the downstream switch Ga is connected to the cathode of the parasitic diode Jb of the downstream switch Gb. Therefore, even if the DC power supply 10 is reversely connected, no current flows through the parasitic diodes Ja and Jb as long as the two downstream switches Ga and Gb are off. The ECU 12 in the third embodiment achieves the same effects as the ECU 12 in the second embodiment.

[0122] (Embodiment 4) In the first embodiment, the ECU 12 controls the power supply to one load E1. However, the ECU 12 may control the power supply to a plurality of loads. The following describes the differences between embodiment 4 and embodiment 1. Except for the configurations described below, other configurations are common to embodiment 1, and therefore the same reference numerals as in embodiment 1 are used for the components common to embodiment 1, and the description thereof will be omitted.

[0123] <Configuration of Power Supply System 1> FIG. 11 is a block diagram showing a main configuration of the power supply system 1 in Embodiment 4. The power supply system 1 in Embodiment 4 includes the same components as those included in the power supply system 1 in Embodiment 1. The power supply system 1 in Embodiment 4 further includes (n - 1) loads E2, E3, ···, En. Here, n is an integer of 2 or more. Therefore, the power supply system 1 in Embodiment 4 includes n loads E1, E2, ···, En. Hereinafter, an arbitrary integer that is 2 or more and n or less is represented by i. The integer i may be any of 2, 3, ···, n.

[0124] One ends of the loads E1, E2, ···, En are separately connected to the ECU 12, and the other ends of the loads E1, E2, ···, En are connected to a common one end of the ECU 12. The ECU 12 controls not only power supply to the load E1 but also power supply to the load Ei. The ECU 12 separately controls power supply to the n loads E1, E2, ···, En. When power is supplied to the load Ei, the current flows from the positive electrode of the DC power supply 10 through the fuse 11, the ECU 12, the load Ei, and the ECU 12 in this order and returns to the negative electrode of the DC power supply 10.

[0125] The load Ei is an electrical device similar to the load E1. When power is supplied to the load Ei, the load Ei operates. When power supply to the load Ei is stopped, the load Ei stops operating. The ECU 12 determines whether or not to supply power not only to the load E1 but also to the load Ei.

[0126] <Configuration of ECU 12> FIG. 12 is a block diagram showing the main configuration of the ECU 12. The ECU 12 in the fourth embodiment has the same components as the ECU 12 in the first embodiment. The ECU 12 in the fourth embodiment further has (n-1) upstream switches F2, F3,...,Fn, (n-1) drive circuits K2, K3,...,Kn, and (n-1) voltage detection circuits M2, M3,...,Mn. Therefore, the ECU 12 in the fourth embodiment has n upstream switches F1, F2,...,Fn, n drive circuits K1, K2,...,Kn, and n voltage detection circuits M1, M2,...,Mn. The upstream switch Fi is an N-channel MOSFET, similar to the upstream switch F1. Therefore, the upstream switch Fi is a semiconductor switch.

[0127] A parasitic diode Hi is connected between the drain and source of the upstream switch Fi. The cathode and anode of the parasitic diode Hi are connected to the drain and source of the upstream switch Fi, respectively.

[0128] The drain of the upstream switch Fi is connected to one end on the downstream side of the fuse 11. The source of the upstream switch Fi is connected to one end on the upstream side of the load Ei. One end on the downstream side of the load Ei is connected to the drain of the downstream switch Ga. The source of the downstream switch Ga is grounded. The gate of the upstream switch Fi is connected to a drive circuit Ki. The drive circuit Ki is further connected to the microcomputer 21. The source of the upstream switch Fi is further connected to a voltage detection circuit Mi. The voltage detection circuit Mi is further connected to the microcomputer 21.

[0129] For the upstream switch Fi, the higher the gate voltage value, where the reference potential is the source potential, the smaller the resistance value between the drain and source. For each of the upstream switch F1 and the downstream switch Ga, when the gate voltage value, where the reference potential is the source potential, is equal to or greater than a certain voltage value, the upstream switch Fi is on. When the upstream switch Fi is on, the resistance value between the drain and source of the upstream switch Fi is sufficiently small. Therefore, current can flow through the drain and source of the upstream switch Fi.

[0130] For each upstream switch Fi, when the gate voltage value, whose reference potential is the source voltage, is less than a certain voltage value, the upstream switch Fi is off. When the upstream switch Fi is off, the resistance value between the drain and source of the upstream switch Fi is sufficiently large. Therefore, no current flows through the drain and source of the upstream switch Fi.

[0131] When the upstream switch Fi and the downstream switch Ga are on, current flows from the positive terminal of the DC power supply 10 through the fuse 11, the upstream switch Fi, the load E1, and the downstream switch Ga in this order. Power is supplied to the load Ei. When at least one of the upstream switch Fi and the downstream switch Ga is off, no current flows through the load Ei. Therefore, when the downstream switch Ga is off, no power is supplied to the n loads E1, E2, ..., En.

[0132] When the upstream switches F1, F2, ..., Fn and the downstream switch Ga are on, the current output from the fuse 11 is divided into n currents. As in the first embodiment, one current flows through the upstream switch F1, the load E1, and the downstream switch Ga in that order. Each of the remaining (n-1) currents flows through the upstream switch Fi, the load Ei, and the downstream switch Ga in that order. Therefore, one of the n loads E1, E2, ..., En is arranged in the current path of each of the n currents output from the fuse 11. The load arranged in each current path is different from the loads arranged in the other current paths.

[0133] In the current path of a current flowing through the load E1, the upstream switch F1 is arranged upstream of the load E1. In this current path, the downstream switch Ga is arranged downstream of the load E1. Similarly, in the current path of a current flowing through the load Ei, the upstream switch Fi is arranged upstream of the load Ei. In this current path, the downstream switch Ga is arranged downstream of the load Ei. Therefore, the n currents flow through the common downstream switch Ga.

[0134] The microcomputer 21 outputs a high-level voltage or a low-level voltage to the drive circuit Ki. The microcomputer 21 switches the voltage output to the drive circuit Ki between a high-level voltage and a low-level voltage. Like the drive circuit K1, the drive circuit Ki adjusts the gate voltage value of the upstream switch Fi according to the voltage input from the microcomputer 21. The reference potential of the gate voltage value is the ground potential. Like the drive circuit K1, the drive circuit Ki switches the upstream switch Fi on or off according to the voltage input from the microcomputer 21.

[0135] Similar to the voltage detection circuit M1, the voltage detection circuit Mi detects the source voltage value of the upstream switch Fi. The reference potential of the source voltage value is the ground potential. The voltage detection circuit Mi outputs analog voltage value information indicating the detected source voltage value to the microcomputer 21.

[0136] The microcomputer 21 determines whether or not to supply power to the load Ei based on, for example, the received communication data or the sensor data input from the sensor 13. If the microcomputer 21 determines to supply power to the load Ei, it switches the voltage output to the drive circuit Ki from a low-level voltage to a high-level voltage while keeping the downstream switch Ga on. This causes the drive circuit Ki to switch on the upstream switch Fi. As a result, power is supplied to the load Ei.

[0137] The microcomputer 21 determines whether to stop power supply to the load Ei, for example, based on the received communication data or the sensor data input from the sensor 13. If the microcomputer 21 determines to stop power supply to the load Ei, it switches the voltage output to the drive circuit Ki from a high-level voltage to a low-level voltage while keeping the downstream switch Ga on. This causes the drive circuit Ki to switch the upstream switch F1 off. As a result, power supply to the load Ei is stopped. For example, when the ignition switch of the vehicle C is switched off, the microcomputer 21 switches the downstream switch Ga off.

[0138] The microcomputer 21 determines whether a short-circuit fault has occurred in the upstream switch Fi based on the voltage value information input from the voltage detection circuit Mi, i.e., the source voltage value of the upstream switch Fi detected by the voltage detection circuit Mi. A short-circuit fault in the upstream switch Fi is a phenomenon in which current flows through the drain and source of the upstream switch Fi despite an instruction to turn off the upstream switch Fi. If the microcomputer 21 determines that a short-circuit fault has occurred in the upstream switch Fi, it turns off the downstream switch Ga.

[0139] <Configuration of Microcomputer 21> 13 is a block diagram showing the main configuration of the microcomputer 21. The microcomputer 21 in the fourth embodiment has the same components as the ECU 12 in the first embodiment. The ECU 12 in the fourth embodiment further has (n-1) first output units T1, T2, . . . , Tn and (n-1) A / D conversion units X2, X3, . . . , Xn. The first output unit Ti is further connected to a drive circuit Ki. The A / D conversion unit Xi is further connected to a voltage detection circuit Mi.

[0140] When power is supplied to the microcomputer 21, power is supplied to the first output unit Ti and the A / D conversion unit Xi. Power is supplied to the first output unit Ti and the A / D conversion unit Xi from the connection node between the fuse 11 and the upstream switch Fi.

[0141] The first output unit Ti outputs a high-level voltage or a low-level voltage to the drive circuit Ki. The voltage output by the microcomputer 21 to the drive circuit Ki is the voltage output by the first output unit Ti to the drive circuit Ki. The control unit 33 instructs the first output unit Ti to switch the upstream switch Fi on or off. When the control unit 33 instructs the first output unit Ti to switch the upstream switch Fi on, the first output unit Ti switches the voltage output to the drive circuit Ki to a high-level voltage. When the control unit 33 instructs the first output unit Ti to switch the upstream switch Fi off, the first output unit Ti switches the voltage output to the drive circuit Ki to a low-level voltage.

[0142] The voltage detection circuit Mi outputs analog voltage value information to the A / D conversion unit Xi. The A / D conversion unit Xi converts the analog voltage value information input from the voltage detection circuit Mi into digital voltage value information. The control unit 33 acquires the digital voltage value information converted by the A / D conversion unit Xi. As described above, the voltage value information indicates the source voltage value of the upstream switch Fi. Acquiring the voltage value information converted by the A / D conversion unit Xi corresponds to acquiring the source voltage value of the upstream switch Fi.

[0143] The processing elements of the control unit 33 execute the computer program P to perform write processing, transmission processing, downstream switch control processing, power supply control processing for the load E1, and the like, as in the first embodiment. The processing elements of the control unit 33 execute the computer program P to further perform power supply control processing for the load Ei. The power supply control processing for the load Ei is processing to control the power supply to the load Ei. The control unit 33 executes power supply control processing for each of the n loads E1, E2, ..., En. The transmission processing is different from the processing related to the control of the power supply to the loads E1, E2, ..., En.

[0144] If the number of processing elements possessed by the control unit 33 is two or more, the multiple processing elements possessed by the control unit 33 may cooperate to perform write processing, transmission processing, downstream switch control processing, and power supply control processing for loads E1, E2, ..., En.

[0145] <Power supply control process for load Ei> When the downstream switch Ga is on, the control unit 33 executes the power supply control process for the load Ei in the same manner as the power supply control process for the load E1. In the description of the power supply control process for the load E1, the load E1, the upstream switch F1, the drive circuit K1, the first output unit T1, and the A / D conversion unit X1 are replaced with the load Ei, the upstream switch Fi, the drive circuit Ki, the first output unit Ti, and the A / D conversion unit Xi, respectively. This makes it possible to explain the power supply control process for the load Ei. When the downstream switch Ga is on and the control unit 33 has instructed to switch the upstream switch Fi off, and the source voltage value of the upstream switch Fi is equal to or higher than the voltage threshold, the control unit 33 detects the occurrence of a short-circuit fault in the upstream switch Fi.

[0146] When the control unit 33 executes step S37 during one of the power supply control processes for the loads E1, E2, ···, En, it ends the remaining power supply control processes. In step S37, the control unit 33 instructs the second output unit U to switch the downstream switch Ga to off. The control unit 33 does not execute the power supply control process for the loads E1, E2, ···, En again.

[0147] As described above, the control unit 33 executes the power supply control process for the loads E1, E2, ···, En. Therefore, the control unit 33 instructs each of the n upstream switches F1, F2, ···, Fn to switch to on or off. The control unit 33 determines whether current is flowing through the upstream switch that has been instructed to switch to off while one of the n upstream switches F1, F2, ···, Fn has been instructed to switch to off. When the control unit 33 determines that current is flowing through the upstream switch that has been instructed to switch to off, it instructs the second output unit U to switch the downstream switch Ga to off.

[0148] <Effect of ECU12> In the ECU12 in Embodiment 4, by the second output unit U of the microcomputer 21 switching the downstream switch Ga to off, the power supply to the n loads E1, E2, ···, En can be stopped. The ECU12 in Embodiment 4 exhibits the same effects as the ECU12 in Embodiment 1.

[0149] <Modification Example of Embodiment 4> In the ECU12 in Embodiment 4, similar to Embodiment 2 or Embodiment 3, the downstream switch Gb may be provided on the upstream side or the downstream side of the downstream switch Ga. In this case, even when the connection of the DC power supply 10 is reverse-connected, as long as the two downstream switches Ga and Gb are off, current does not flow through the parasitic diodes Ja and Jb.

[0150] (Embodiment 5) In Embodiment 1, the control unit 33 of the microcomputer 21 uses the source voltage value of the upstream switch F1 to determine whether current is flowing through the upstream switch F1. However, the value used to determine whether current is flowing through the upstream switch F1 is not limited to the source voltage value of the upstream switch F1. Hereinafter, regarding Embodiment 5, the differences from Embodiment 1 will be described. For other configurations except for the configurations described later, since they are common to Embodiment 1, the same reference numerals as those in Embodiment 1 are assigned to the constituent parts common to Embodiment 1, and the description thereof is omitted.

[0151] <Configuration of ECU12> FIG. 14 is a block diagram showing the main configuration of the ECU12 in Embodiment 5. The ECU12 in Embodiment 5 has the same other constituent parts as those of the ECU12 in Embodiment 1, excluding the voltage detection circuit M1. The ECU12 in Embodiment 5 further has a current output circuit Q1 and a resistor R1. The current output circuit Q1 is connected to the drain of the upstream switch F1 and one end of the resistor R1. The other end of the resistor R1 is grounded. The connection node between the current output circuit Q1 and the resistor R1 is connected to the A / D conversion unit X1 of the microcomputer 21.

[0152] The current output circuit Q1 draws current from the drain of the upstream switch F1 and outputs the drawn current to the resistor R1. The current value of the current flowing through the upstream switch F1 is referred to as the switch current value. The current value of the current output by the current output circuit Q1 to the resistor R1 is referred to as the resistor current value. The current output circuit Q1 adjusts the resistor current value to (switch current value) / (predetermined number). The predetermined number is, for example, 1000.

[0153] The voltage value across both ends of the resistor R1 is represented by (switch current value)·(resistance value of resistor R1) / (predetermined number). “·” represents the product. The resistance value of the resistor R1 and the predetermined number are constant values. Therefore, the voltage value across both ends of the resistor R1 is analog current value information indicating the switch current value. The current value information is output to the A / D conversion unit X1 of the microcomputer 21.

[0154] <Configuration of Microcontroller 21> The A / D conversion unit X1 of the microcontroller 21 converts the analog current value information input from the connection node between the current output circuit Q1 and the resistor R1 into digital current value information. The control unit 33 acquires the digital current value information converted by the A / D conversion unit X1. The acquisition of the current value information corresponds to the acquisition of the switch current value.

[0155] <Power Supply Control Process> In step S35 of the power supply control process, the control unit 33 of the microcontroller 21 acquires the current value information from the A / D conversion unit X1. The switch current value indicated by the current value information acquired by the control unit 33 substantially coincides with the switch current value at the acquisition time. In step S36 of the power supply control process, when the switch current value indicated by the current value information acquired in step S35 is 0 A, the control unit 33 determines that no current is flowing through the upstream switch F1. When the switch current value indicated by the current value information acquired in step S35 exceeds 0 A, the control unit 33 determines that current is flowing through the upstream switch F1.

[0156] <Effect of ECU 12> The ECU 12 in Embodiment 5 exhibits the same effects as the ECU 12 in Embodiment 1.

[0157] <Modification Example of Embodiment 5> The configuration for detecting the current value of the current flowing through the upstream switch F1 is not limited to the configuration using the current output circuit Q1, and for example, a configuration using a shunt resistor may be used. In this case, a shunt resistor is arranged between the source of the upstream switch F1 and one end on the upstream side of the load E1. The resistance value of the shunt resistor is a constant value. Therefore, the voltage value between both ends of the shunt resistor is the analog current value information indicating the switch current value. The current value information is input to the A / D conversion unit X1. In the ECU 12 in Embodiment 5, similar to Embodiment 2 or Embodiment 3, the downstream switch Gb may be provided on the upstream side or the downstream side of the downstream switch Ga.

[0158] <Modification Examples of Embodiments 1 to 5> In the second and third embodiments, current value information, rather than voltage value information, may be used to determine whether or not a current is flowing through the upstream switch F1, as in the fifth embodiment. In the fourth embodiment, current value information, rather than voltage value information, may be used to determine whether or not a current is flowing through at least one of the n upstream switches F1, F2, ..., Fn.

[0159] In the first to third and fifth embodiments, two upstream switches may be arranged upstream of the load E1. In this case, the two upstream switches are connected in the same manner as the two downstream switches Ga and Gb in the second or third embodiment. When two upstream switches are used, the downstream switch Gb may not be provided. Similarly, in the fourth embodiment, two upstream switches may be arranged upstream of each load. In this case, the two upstream switches are also connected in the same manner as the two downstream switches Ga and Gb in the second or third embodiment. When two upstream switches are arranged upstream of each load, the downstream switch Gb may not be provided. When two upstream switches are arranged upstream of the load, the gates of the two upstream switches are connected to a common drive circuit. The drive circuit switches both upstream switches on or off.

[0160] In the first embodiment, the control unit 33 of the microcomputer 21 instructs the upstream switch F1 to be switched on or off while the downstream switch Ga is maintained on. This controls the power supply to the load E1. However, the control unit 33 may also instruct the downstream switch Ga to be switched on or off while the upstream switch F1 is maintained on. In this configuration, when the control unit 33 instructs the downstream switch Ga to be switched off, it determines whether or not a current is flowing through the downstream switch Ga. If the control unit 33 determines that a current is flowing through the downstream switch Ga, it instructs the upstream switch F1 to be switched off. In this case, the upstream switch F1 and the downstream switch Ga function as a second switch and a first switch, respectively.

[0161] In this configuration, the ECU 12 detects the current value of the current flowing through the downstream switch Ga. The control unit 33 determines whether or not a current is flowing through the downstream switch Ga based on the current value of the current flowing through the downstream switch Ga. In the second, third, and fifth embodiments, the control unit 33 may also instruct the downstream switch Ga to be switched on or off while keeping the upstream switch F1 on. The control unit 33 detects a short-circuit fault in the downstream switch Ga.

[0162] When the number of loads is increased from 1 to n in a configuration that detects the occurrence of a short-circuit fault in the downstream switch Ga, a common upstream switch and n downstream switches are used. One downstream switch is arranged downstream of each load. In this case, the n downstream switches are controlled in the same manner as the n upstream switches F1, F2, . . . , Fn in embodiment 4. The common upstream switch is controlled in the same manner as the common downstream switch Ga in embodiment 4.

[0163] In the configuration for detecting a short-circuit fault in the downstream switch Ga, two downstream switches may be arranged downstream of the load. Furthermore, two upstream switches may be arranged upstream of the load.

[0164] In the first to fifth embodiments, the upstream switch is not limited to an N-channel MOSFET and may be another switch. Examples of other switches include a P-channel MOSFET, a FET other than a MOSFET, a bipolar transistor, and a relay contact. When a switch that does not form a parasitic diode is used, there is no need to connect two upstream switches in series.

[0165] Similarly, in the first to fifth embodiments, the downstream switch is not limited to an N-channel MOSFET and may be another switch. Examples of other switches include a P-channel MOSFET, a FET other than a MOSFET, a bipolar transistor, and a relay contact. When a switch that does not form a parasitic diode is used, there is no need to connect two downstream switches in series.

[0166] In the first to fifth embodiments, the number of sensors 13 connected to the microcomputer 21 of the ECU 12 is not limited to one, and may be two or more. In this case, in each of steps S31 and S33 of the power supply control process, the control unit 33 of the microcomputer 21 may use at least one of the communication data received by the communication unit 30 and the multiple sensor data input from the multiple sensors 13. The process unrelated to the power supply control is not limited to the transmission process, and may be a process different from the transmission process.

[0167] The technical features (constituent elements) described in the first to fifth embodiments can be combined with each other, and by combining them, new technical features can be formed. The disclosed embodiments 1 to 5 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 meaning described above, and is intended to include all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0168] 1 Power System 10 DC power supply 11. Fuse 12 ECU (power supply control unit) 13 Sensors 20 Regulator 21 Microcomputer 30 Communications Department 31 Input section 32 Storage section 33 Control section (processing section) 34 Internal Bus A storage medium C vehicle E1,E2,...,En load F1, F2,..., Fn Upstream switches (first switch, second switch) Ga, Gb downstream switch (first switch, second switch) H1, H2, , Hn, Ja, Jb Parasitic diodes K1, K2,..., Kn drive circuit Lc communication line M1, M2, , Mn voltage detection circuit P Computer Program Q1 Current output circuit R1 Resistor T1, T2, , Tn First output section U Second output section X1, X2,..., Xn A / D conversion section

Claims

1. A power supply control device that controls power supply to a load, an upstream switch disposed upstream of the load in a current path of a current flowing through the load; a downstream switch disposed downstream of the load in the current path; a processing unit for executing processing; Equipped with The processing unit instructing a first switch included in the upstream switch and the downstream switch to be switched on or off; determining whether or not a current is flowing through the first switch while instructing the first switch to be turned off; instructing a second switch included in the upstream switch and the downstream switch to be switched off when it is determined that a current is flowing through the first switch; the current path is a path of a current output from a fuse, power is supplied to the processing unit from a connection node between the fuse and the upstream switch; the processing unit executes a transmission process for transmitting data to an external device, Even if a short circuit failure occurs in the upstream switch, power continues to be supplied to the processing unit via the fuse. Power supply control device.

2. The processing unit Instructing the upstream switch to be switched on or off; determining whether current is flowing through the upstream switch while instructing the upstream switch to be switched off; If it is determined that a current is flowing through the upstream switch, it instructs the downstream switch to be switched off. The power supply control device according to claim 1 .

3. The processing unit When the upstream switch is being instructed to be switched off, Obtain the voltage value at one end, If the acquired voltage value is equal to or greater than the voltage threshold, it is determined that a current is flowing through the upstream switch. The power supply control device according to claim 2 .

4. the number of downstream switches is two; Each of the two downstream switches is a semiconductor switch; a parasitic diode is connected across each of the two downstream switches; The anode of the parasitic diode of one downstream switch is connected to the anode of the parasitic diode of the other downstream switch. The power supply control device according to claim 2 or 3.

5. the number of downstream switches is two; Each of the two downstream switches is a semiconductor switch; a parasitic diode is connected across each of the two downstream switches; The cathode of the parasitic diode of one downstream switch is connected to the cathode of the parasitic diode of the other downstream switch. The power supply control device according to claim 2 or 3.

6. A load is placed on each of the current paths of the multiple currents, the number of the upstream switches is two or more; An upstream switch is disposed on the upstream side of the load in each current path, the plurality of currents flow through a common downstream switch; The processing unit instructing each of the plurality of upstream switches to be switched on or off; determining whether or not a current is flowing through one of the upstream switches that has been instructed to be switched off while the switch is instructed to be switched off; Instructing the downstream switch to be switched off when it is determined that a current is flowing through the upstream switch that has been instructed to be switched off. The power supply control device according to any one of claims 2 to 5.

7. A power supply control method for controlling power supply to a load, comprising: instructing switching on or off of a first switch included in an upstream switch arranged upstream of the load in a current path of a current flowing through the load and a downstream switch arranged downstream of the load in the current path; determining whether current is flowing through the first switch while instructing the first switch to be turned off; instructing a second switch included in the upstream switch and the downstream switch to be switched off when it is determined that a current is flowing through the first switch; The computer executes the current path is a path of a current output from a fuse, the computer is supplied with power from a connection node between the fuse and the upstream switch; The computer executes a transmission process for transmitting data to an external device, Even if a short circuit occurs in the upstream switch, power continues to be supplied to the computer via the fuse. Power supply control method.

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