Control device, program, and control method

Abstract

This control device is applied to a system comprising an ignition switch (60) operated for transmitting either a connection command for instructing connection between an electrical apparatus (20) and a DC power supply (30), or a disconnection command. The control device controls the on / off state of a first switch (SMRL) and a second switch (SMRP) that connect the electrical apparatus and the DC power supply. A series connection body of the second switch and a resistor (40) is connected in parallel to the first switch. The control device performs: first processing for keeping the first and second switches in the off state if it is determined that the temperature of the resistor is higher than a first threshold, even if it is determined that the switches are in a state in which the connection command has been received; and second processing for keeping the first switch in the on state and keeping the second switch in the off state if it is determined that the temperature of the resistor is higher than a second threshold, even if it is determined that the switches are in a state in which the disconnection command has been received.

Description

Control device, program and control method CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is based on Japanese Application No. 2024-084125, filed on May 23, 2024, the contents of which are incorporated herein by reference.

[0002] The present disclosure relates to a control device, a program, and a control method.

[0003] A known system includes a main relay that connects an electrical device to a DC power source, and a series connection of a precharge relay and a resistor that are connected in parallel to the main relay, and a control device that is applied to the system. An example of such a technology is disclosed in Patent Document 1.

[0004] The control device described in Patent Document 1 performs a process of temporarily turning on a precharge relay as a system initialization process when it determines that it has received a power supply connection request from an external device. This electrically connects the DC power supply and the electrical device via a resistor, thereby preventing an inrush current from flowing from the DC power supply to the electrical device. The control device then performs a process of turning on a main relay as an initialization process. This electrically connects the DC power supply and the electrical device via the main relay. On the other hand, when it determines that it has received a power supply interruption request from an external device, the control device turns off the main relay.

[0005] When the precharge relay is turned on and current flows through the resistor, the resistor heats up. If power connection requests and power cutoff requests are repeated alternately, the resistor does not have enough time to dissipate heat, and current flows through the resistor before its temperature has sufficiently decreased. As a result, there is a risk that the resistor may overheat.

[0006] Therefore, the control device measures the elapsed time since the precharge relay was turned off. Even if the control device determines that a power cutoff request has been received, if the measured elapsed time has not reached a predetermined specified time, the control device keeps the main relay on without turning it off. This ensures time for the resistor to dissipate heat and prevents the resistor from overheating. Furthermore, because the main relay is kept on, when the next power connection request is input from the outside to the control device, power supply from the DC power source to the electrical device can be started quickly. As a result, a decrease in convenience for the system user can be prevented.

[0007] JP 2011-114974 A

[0008] In the control device described in Patent Document 1, if the measured elapsed time reaches a specified time, the main relay is turned off when a power cut-off request is input to the control device. When a power connection request is then input to the control device, the control device performs the initial processing of temporarily turning on the precharge relay and then turning on the main relay, as described above.

[0009] Here, after a power-off request is input to the control device, when a power-on request is next input to the control device, the initializing process may be performed while the resistor temperature is high. In this case, the precharge relay is turned on, causing current to flow through the resistor, which is at a high temperature. As a result, the resistor may overheat. Furthermore, if the initializing process is repeated for some reason, the resistor may also overheat.

[0010] As described above, there is still room for improvement in the technology for preventing the resistor from overheating while preventing a decrease in the convenience of the system user.

[0011] A main object of the present disclosure is to provide a control device, a program, and a control method that can prevent a situation in which a resistor becomes overheated while suppressing a decrease in user convenience.

[0012] The present disclosure relates to a control device that is applied to a system including: an electric device; a DC power supply that supplies power to the electric device; a first switch that connects the electric device to the DC power supply; a series connection of a second switch and a resistor connected in parallel to the first switch; and a start-up switch that is operated to issue either a connection command that instructs the electric device to connect to the DC power supply or a disconnection command that instructs the electric device to disconnect from the DC power supply, the control device comprising: a switch control unit that controls the on / off of the first switch and the second switch; a first command determination unit that, when the first switch is in an off state, determines whether the connection command has been received or the disconnection command has been received; and a second command determination unit that, when the first switch is on and the second switch is off, determines whether the connection command has been received or the disconnection command has been received.

[0013] In the present disclosure, when the first command determination unit determines that the connection command has been received, the switch control unit sets the second switch to a precharge state in which it turns on the second switch, and then sets the second switch to an off state and the first switch to an on state, and when the second command determination unit determines that the disconnection command has been received, sets the first switch to an off state.

[0014] The present disclosure comprises a first temperature judgment unit that judges whether the temperature of the resistor is higher than a first threshold, and a second temperature judgment unit that judges whether the temperature of the resistor is higher than a second threshold that is a value less than the first threshold, wherein the switch control unit performs a first process of keeping the first switch and the second switch off when the first temperature judgment unit judges that the temperature of the resistor is higher than the first threshold, even if the first command judgment unit judges that the state has received the connection command, and performs a second process of keeping the first switch on and the second switch off when the second temperature judgment unit judges that the temperature of the resistor is higher than the second threshold, even if the second command judgment unit judges that the state has received the disconnection command.

[0015] In the present disclosure, even if the second command determination unit determines that a shutoff command has been received with the first switch on and the second switch off, if the second temperature determination unit determines that the temperature of the resistor is higher than the second threshold, a second process is performed to maintain the first switch on and the second switch off, thereby preventing the resistor from overheating.

[0016] The second threshold for the second process, which keeps the first switch on and the second switch off even when a disconnection command is input, is lower than the first threshold for the first process, which keeps the first and second switches off even when a connection command is input. Therefore, after a disconnection command is input to the control device and the second process is executed, the temperature of the resistor is usually lower than the first threshold when the next connection command is input. As a result, when the next connection command is input, the first temperature determination unit determines that the temperature of the resistor is equal to or lower than the first threshold, and the precharge state and the subsequent connection of the electrical device and the DC power source can be quickly achieved. This prevents a decrease in user convenience.

[0017] Furthermore, due to some factors, such as the environment surrounding the system or the operating status of the system, the temperature of the resistor may be high when the first switch is off. In the present disclosure, even if the first command determination unit determines that a connection command has been received when the first switch is off, if the first temperature determination unit determines that the temperature of the resistor is higher than the first threshold, a first process is performed to maintain the first and second switches off. Therefore, even if the temperature of the resistor is high when the first switch is off, heat dissipation time for the resistor can be ensured, and damage to the resistor can be prevented. On the other hand, if the temperature of the resistor is equal to or lower than the first threshold when the first switch is off, and the first command determination unit determines that a connection command has been received, a precharge state in which the second switch is turned on and a state in which the second switch is subsequently turned off and the first switch is turned on can be quickly achieved.

[0018] In this way, according to the present disclosure, it is possible to prevent the resistor from overheating while preventing a decrease in convenience for the user of the system.

[0019] Unlike the above disclosure, the following configuration can also be adopted. More specifically, this configuration is a control device applied to a system including: an electric device; a DC power source that supplies power to the electric device; a first switch that connects the electric device to the DC power source; a series connection of a second switch and a resistor connected in parallel to the first switch; and a start-up switch that is operated to issue either a connection command that instructs the electric device to connect the electric device to the DC power source or a disconnection command that instructs the electric device to disconnect the electric device from the DC power source, the control device comprising: a switch control unit that controls the on / off of the first switch and the second switch; and a command determination unit that, when the first switch is in an off state, determines whether the connection command or the disconnection command has been received, and when the command determination unit determines that the connection command has been received, the switch control unit sets the second switch to a precharge state in which it turns on, and then turns off the second switch and turns on the first switch; and a temperature determination unit that determines whether the temperature of the resistor is higher than a threshold value. The switch control unit performs processing to keep the first switch and the second switch off if the command determination unit determines that the connection command has been received, but if the temperature determination unit determines that the temperature of the resistor is higher than the threshold value.

[0020] Due to some factors, such as the system's surrounding environment or system operation status, the temperature of the resistor may be high when the first switch is off. In the above configuration, even if the command determination unit determines that a connection command has been received when the first switch is off, if the temperature determination unit determines that the resistor temperature is higher than a threshold, processing is performed to maintain the first and second switches off. Therefore, even if the resistor temperature is high when the first switch is off, heat dissipation time for the resistor can be ensured, and damage to the resistor can be prevented. On the other hand, if the command determination unit determines that a connection command has been received when the first switch is off and the resistor temperature is below the threshold, a precharge state in which the second switch is turned on and a state in which the second switch is subsequently turned off and the first switch is turned on can be quickly achieved.

[0021] The above and other objects, features, and advantages of the present disclosure will become more apparent from the following detailed description taken in conjunction with the accompanying drawings, in which Fig. 1 is an overall configuration diagram of a system according to one embodiment, Fig. 2 is a functional block diagram showing processing by a microcomputer, Fig. 3 is a flowchart showing the procedure for switch control processing, Fig. 4 is a time chart showing transitions in the control modes of the switches, Fig. 5 is a time chart showing transitions in the control modes of the switches, and Fig. 6 is a flowchart showing the procedure for switch control processing according to another embodiment.

[0022] Hereinafter, an embodiment of a control device according to the present disclosure will be described with reference to the drawings. The control device of this embodiment is installed in a power supply system of a mobile body, such as an electric vehicle or a hybrid vehicle.

[0023] As shown in FIG. 1 , the power supply device of the system includes a motor 10, an inverter 20, a high-potential side path 22H, and a low-potential side path 22L. The motor 10 is a three-phase synchronous machine and includes star-connected armature windings of U, V, and W phases, and a rotor. The armature windings of each phase are arranged with an electrical angle of 120°. The motor 10 is, for example, a permanent magnet synchronous machine. The rotor is capable of transmitting power to the drive wheels of the vehicle. Therefore, the motor 10 serves as a source of torque for propelling the vehicle. However, since the armature windings and rotor are not essential parts of the motor 10, the armature windings and the like are not shown in FIG. 1 .

[0024] The inverter 20 includes three phases of series-connected upper and lower arm switches. Upper arm diodes, which are freewheel diodes, are connected in anti-parallel to the upper arm switches, and lower arm diodes, which are also freewheel diodes, are connected in anti-parallel to the lower arm switches. In this embodiment, the upper and lower arm switches are IGBTs. However, since the inverter 20 includes the upper and lower arm switches and upper and lower arm diodes, the upper and lower arm switches are not shown in FIG. 1 because they are not essential.

[0025] The power supply device includes a smoothing capacitor 21. A high-potential side path 22H is connected to a high-potential side terminal of the smoothing capacitor 21. A low-potential side path 22L is connected to a low-potential side terminal of the smoothing capacitor 21. The high-potential side path 22H and the low-potential side path 22L are, for example, electrical paths such as bus bars. The smoothing capacitor 21 may be provided inside the inverter 20.

[0026] The system includes a battery 30. The battery 30 serves as a power supply source for driving the rotor of the motor 10 to rotate. The battery 30 is a rechargeable secondary battery, and has a terminal voltage of, for example, 100 V or more. The battery 30 is, for example, a lithium-ion battery or a nickel-metal hydride battery.

[0027] The power supply device includes a high-side switch SMRH, a low-side switch SMRL, and a pre-charge switch SMRP for electrically connecting or disconnecting the battery 30 and the inverter 20. In this embodiment, the switches SMRH, SMRL, and SMRP are mechanical relays. When turned off, the switches SMRH, SMRL, and SMRP block bidirectional current flow, and when turned on, allow bidirectional current flow. A series connection of the pre-charge switch SMRP and a pre-charge resistor 40 is connected in parallel to the low-side switch SMRL. Note that the switches SMRH, SMRL, and SMRP are not limited to mechanical relays and may be, for example, semiconductor switching elements.

[0028] The power supply device includes a temperature sensor 50 that detects the temperature of the precharge resistor 40, and a voltage sensor 51 that detects the voltage across the smoothing capacitor 21. The power supply device also includes a rotation angle sensor (not shown) that detects the rotation angle (electrical angle) of the rotor as another sensor.

[0029] The system includes a control device 70. The control device 70 is an electronic control unit that is mainly composed of a microcomputer 71.

[0030] The microcomputer 71 includes a CPU (Central Processing Unit). The functions provided by the microcomputer 71 can be provided by software stored in a physical memory device and a computer executing the software, software alone, hardware alone, or a combination thereof. For example, if the microcomputer 71 is provided by a hardware electronic circuit, the function can be provided by a digital circuit including multiple logic circuits or an analog circuit. For example, the microcomputer 71 executes a program stored in a non-transitory tangible storage medium serving as a storage unit of the microcomputer 71. The program includes, for example, a program for the process shown in FIG. 3 (described later). A method corresponding to the program is executed by executing a set of instructions constituting the program. The storage unit is, for example, a non-volatile memory. The program stored in the storage unit can be updated via a communication network such as the Internet, for example, via OTA (Over the Air).

[0031] The system includes a start switch 60. The start switch 60 is a switch used by a user of the mobile vehicle to start or stop the system. When the user turns on the start switch 60, a connection command is input to the control device 70 to electrically connect the inverter 20 and the battery 30. On the other hand, when the user turns off the start switch 60, a disconnection command is input to the control device 70 to disconnect the electrical connection between the inverter 20 and the battery 30. As in a general case, the presence of a signal from the start switch 60 is a command to connect, and the absence of a signal from the start switch 60 is a command to disconnect. In addition, the control device 70 receives a detection value from the temperature sensor 50 (hereinafter referred to as the detected temperature Tr) and a detection value from the voltage sensor 51 (hereinafter referred to as the detected voltage Vr). The control device 70 controls the switches SMRH, SMRL, and SMRP based on the connection command or disconnection command from the start switch 60, the detected temperature Tr, and the detected voltage Vr.

[0032] In this embodiment, the low-potential-side switch SMRL corresponds to a “first switch,” the pre-charge switch SMRP corresponds to a “second switch,” and the high-potential-side switch SMRH corresponds to a “third switch.” Also, the pre-charge resistor 40 corresponds to a “resistor.”

[0033] 2 , the control device 70 includes a first command determination unit 101, a second command determination unit 102, a third command determination unit 103, and a switch control unit 104. When the user of the mobile object turns on the start switch 60, a connection command between the inverter 20 and the battery 30 is input to the first command determination unit 101, the second command determination unit 102, and the third command determination unit 103. When the start switch 60 is turned off, a disconnection command between the inverter 20 and the battery 30 is input to the first command determination unit 101, the second command determination unit 102, and the third command determination unit 103. The first command determination unit 101, the second command determination unit 102, and the third command determination unit 103 determine whether a connection command or a disconnection command has been input, and output the determination result to the switch control unit 104. The first command determining unit 101, the second command determining unit 102, and the third command determining unit 103 also receive information on the on / off states of the high potential side switch SMRH, the low potential side switch SMRL, and the precharge switch SMRP.

[0034] When at least one of the high-potential side switch SMRH and the low-potential side switch SMRL is in the off state, the first command judgment unit 101 judges whether a connection command or a disconnection command has been received based on a signal indicating the operation state (specifically, off or on) of the start switch 60.

[0035] When the high-side switch SMRH and the low-side switch SMRL are in the on state and the precharge switch SMRP is in the off state, the second command judgment unit 102 judges, based on the operation status signal of the start-up switch 60, whether a connection command has been received or a disconnection command has been received.

[0036] When the low potential side switch SMRL is in the OFF state and the high potential side switch SMRH and the precharge switch SMRP are in the ON state, the third command judgment unit 103 judges whether a connection command has been received or a disconnection command has been received based on a signal indicating the operation state of the start switch 60.

[0037] The control device 70 includes a first temperature determination unit 105 and a second temperature determination unit 106. The first temperature determination unit 105 determines whether the temperature of the precharge resistor 40 (specifically, the detected temperature Tr) is higher than a first threshold value Tth1. The second temperature determination unit 106 determines whether the detected temperature Tr is higher than a second threshold value Tth2. Here, the second threshold value Tth2 is set to a value lower than the first threshold value Tth1.

[0038] The control device 70 includes a voltage determination unit 107. The voltage determination unit 107 determines whether or not the voltage across the terminals of the smoothing capacitor 21 (specifically, the detected voltage Vr) has reached a predetermined voltage Vth.

[0039] The switch control unit 104 receives the determination results output from the first command determination unit 101, the second command determination unit 102, and the third command determination unit 103, the determination results from the first temperature determination unit 105 and the second temperature determination unit 106, and the determination result from the voltage determination unit 107. The switch control unit 104 outputs on / off signals for the switches SMRH, SMRL, and SMRP based on the determination results. Specifically, even if the first command determination unit 101 determines that a connection command has been received, if the first temperature determination unit 105 determines that the detected temperature Tr is higher than the first threshold value Tth1, the switch control unit 104 executes a first process of maintaining the high-side switch SMRH, the low-side switch SMRL, and the pre-charge switch SMRP off.

[0040] In addition, even if the second command judgment unit 102 judges that a shut-off command has been received, if the second temperature judgment unit 106 judges that the detected temperature Tr is higher than the second threshold value Tth2, the switch control unit 104 executes a second process of keeping the high-potential side switch SMRH and the low-potential side switch SMRL on and keeping the pre-charge switch SMRP off.

[0041] 3 is a flowchart showing the procedure of the control process for the switches SMRH, SMRP, and SMRL. This process is executed by the control device 70.

[0042] As shown in step S10, the initial state of each of the switches SMRH, SMRP, and SMRL at the start of the flowchart is the off state.

[0043] In step S11, the first command determination unit 101 determines whether a connection command or a disconnection command has been input based on the signal indicating the operation state of the start switch 60. If it is determined that a connection command has been input, the process proceeds to step S12.

[0044] In step S12, the first temperature determination unit 105 determines whether the detected temperature Tr is equal to or lower than the first threshold value Tth1. The first threshold value Tth1 is set to a value (e.g., 100°C) that prevents the precharge resistor 40 from overheating. If it is determined that the detected temperature Tr is equal to or lower than the first threshold value Tth1, the process proceeds to step S13. On the other hand, if it is determined that the detected temperature Tr is higher than the first threshold value Tth1, the process returns to step S11, and the switches SMRH, SMRP, and SMRL are maintained in the OFF state. Unless it is determined in step S11 that a shut-off command has been input, the determination in step S12 is repeated, and the switches SMRH, SMRP, and SMRL are maintained in the OFF state. In this embodiment, the processes in steps S11 and S12 correspond to the "first process."

[0045] Incidentally, while the determination in step S12 is being repeated, control may be performed such that a change in the signal indicating the operating state of the start switch 60 is not determined. In this case, a loop may be created in which step S12 is repeated without returning from step S12 to step S11.

[0046] In step S13, the switch control unit 104 turns on the high-side switch SMRH and the pre-charge switch SMRP. As a result, current starts to flow from the battery 30 to the smoothing capacitor 21 via the pre-charge switch SMRP and the pre-charge resistor 40, and the smoothing capacitor 21 starts to be charged.

[0047] After completing the process of step S13, the process proceeds to step S14, where the voltage determination unit 107 determines whether the detected voltage Vr has reached a predetermined voltage Vth. The predetermined voltage Vth is set to a value that is the same as or equivalent to the terminal voltage of the battery 30 (for example, the rated voltage of the battery 30). Note that, when the rated voltage of the battery 30 is Vrt, the value Ve that is equivalent to the terminal voltage of the battery 30 is, for example, "0.9×Vrt<Ve<Vrt," "0.93×Vrt≦Ve<Vrt," or "0.95×Vrt≦Ve<Vrt."

[0048] If it is determined in step S14 that the detected voltage Vr has not reached the predetermined voltage Vth, the process proceeds to step S15. In step S15, it is determined whether a connect command or a disconnect command has been input based on a signal indicating the operation state of the start switch 60. If it is determined that the input command remains a connect command, the process returns to step S13. With the start switch 60 in an on position, the loop of steps S14, S15, S13, and S14 is repeated until it is determined in step S14 that the detected voltage Vr has reached the predetermined voltage Vth.

[0049] If it is determined in step S14 that the detected voltage Vr has reached the predetermined voltage Vth, the process proceeds to step S16. In step S16, the switch control unit 104 switches the pre-charge switch SMRP off and switches the low-side switch SMRL on. This stops current from flowing through the pre-charge resistor 40.

[0050] If it is determined in step S14 that the detected voltage Vr has not reached the predetermined voltage Vth, and then it is determined in step S15 that a shutoff command has been input, the process proceeds to step S17. In step S17, the high-side switch SMRH, the precharge switch SMRP, and the low-side switch SMRL are all turned off. Then, this series of processes ends.

[0051] After the process of step S16 is completed, in step S18, the second command determination unit 102 determines whether a disconnect command or a connect command has been input based on the signal indicating the operation state of the start switch 60. If it is determined that a disconnect command has been input, the process proceeds to step S19.

[0052] In step S19, the second temperature determination unit 106 determines whether the detected temperature Tr is equal to or lower than the second threshold value Tth2. If it is determined that the detected temperature Tr is equal to or lower than the second threshold value Tth2, the process proceeds to step S17. In step S17, the switch control unit 104 switches the high-side switch SMRH and the low-side switch SMRL to OFF. Thereafter, discharge control is performed to discharge the smoothing capacitor 21, for example, by controlling the switching of the inverter 20.

[0053] On the other hand, if it is determined that the detected temperature Tr is higher than the second threshold value Tth2, the low-side switch SMRL is kept on and the precharge switch SMRP is kept off, and the process returns to step S18 to determine whether a disconnect command or a connect command has been input. Here, the second threshold value Tth2 is, for example, a value between 60% and 90% of the first threshold value Tth1, or a value between 70% and 80% of the first threshold value Tth1. In this embodiment, the processes of steps S18 and S19 correspond to the "second process."

[0054] When a connection command between the inverter 20 and the battery 30 is input, the control device 70 executes a precharge process to suppress an inrush current from flowing through the inverter 20. In the precharge process, the control device 70 turns on the precharge switch SMRP and the high-side switch SMRH to charge the smoothing capacitor 21. As a result, a current flows through the precharge switch SMRP and the precharge resistor 40, causing the temperature of the precharge resistor 40 to rise.

[0055] When the control device 70 determines that the connection command has been switched to a disconnection command and that the detected temperature Tr exceeds the second threshold value Tth2 while the high-side switch SMRH and the low-side switch SMRL are on and the pre-charge switch SMRP is off, the control device 70 executes a second process to maintain the high-side switch SMRH and the low-side switch SMRL on and the pre-charge switch SMRP off. In the second process, the inverter 20 and the battery 30 are connected via the low-side switch SMRL. Therefore, when the input command subsequently switches to a connection command, the power supply device can be quickly started. Furthermore, because the pre-charge switch SMRP is off, heat is dissipated from the pre-charge resistor 40. This allows heat to be dissipated from the pre-charge resistor 40 while minimizing degradation of user convenience.

[0056] For some reason, for example, a drop in the power supply voltage to the microcomputer 71 or a reset signal being sent to the microcomputer 71 from an ECU higher than the control device 70, the microcomputer 71 may be reset, and then the microcomputer 71 may return from the reset state. Incidentally, the microcomputer 71 is reset, for example, when the power supply voltage to the microcomputer 71 becomes lower than a threshold voltage. The threshold voltage is a value set to implement under voltage lock out (UVLO) of the microcomputer 71.

[0057] When the microcomputer 71 returns from the reset state, the switches SMRH, SMRL, and SMRP are temporarily turned off. Even during execution of the second process, the switches SMRH, SMRL, and SMRP remain off. However, because the activation switch 60 remains turned on, when the microcomputer 71 is released from the reset state and returns to the reset state, control by the microcomputer 71 is restarted. Based on the input of a connection command by turning on the activation switch 60, the high-side switch SMRH and the pre-charge switch SMRP are turned on and the low-side switch SMRL is turned off from the off state, and the pre-charge process is executed again. Thus, when the microcomputer 71 returns from the reset state, even if the pre-charge resistor 40 has not yet completed heat dissipation and the temperature of the pre-charge resistor 40 is high, current may still flow through the pre-charge resistor 40, potentially causing the pre-charge resistor 40 to overheat. In particular, there is a concern that such a state may occur if the microcomputer 71 is repeatedly reset and restored from the reset state.

[0058] Below, the cases of [1-1], [1-2], [2-1], and [2-2] will be explained in conjunction with the processing of each step in the flowchart.

[0059] [1-1] If the first command determination unit 101 (step S11) determines that a connection command has been input, and if the first temperature determination unit 105 (step S12) determines that the detected temperature Tr is equal to or lower than the first threshold value Tth1, the switch control unit 104 turns on the pre-charge switch SMRP corresponding to the "second switch" while keeping the low-side switch SMRL off. In this embodiment, in which the high-side switch SMRH is provided on the high-side bus (specifically, for example, electrical wiring), the high-side switch SMRH is also turned on (step S13). These determinations are repeated until the detected voltage Vr reaches the predetermined voltage Vth, i.e., until an inrush current can be avoided. When an inrush current can be avoided (step S14), the switch control unit 104 turns on the low-side switch SMRL and turns off the pre-charge switch SMRP (step S16). In the case where the high-potential-side switch SMRH corresponding to the "third switch" is provided, the high-potential-side switch SMRH is kept on (step S16), thereby connecting the inverter 20 and the battery 30.

[0060] [1-2] Even if the first command determination unit 101 (step S11) determines that a connection command has been input, if the first temperature determination unit 105 (step S12) determines that the detected temperature Tr is higher than the first threshold Tth1, the switch control unit 104 restricts the switching on of the low-side switch SMRL corresponding to the “first switch” and the pre-charge switch SMRP corresponding to the “second switch.” That is, the low-side switch SMRL and the pre-charge switch SMRP are kept off. Incidentally, if the microcomputer 71 enters a reset state and then returns from the reset state while the temperature of the pre-charge resistor 40 is high, control by the microcomputer 71 is restarted, but as described above, the pre-charge switch SMRP is not switched on. Therefore, the pre-charge process is not started until the temperature of the pre-charge resistor 40 has reliably dropped, thereby preventing damage to the pre-charge resistor 40. In particular, if the microcomputer 71 is reset and released multiple times, the temperature of the precharge resistor 40 will continue to rise, and in such a case, the above effect is significant. On the other hand, if the temperature of the precharge resistor 40 is low, the precharge process can be performed immediately as usual.

[0061] [2-1] After the inverter 20 and the battery 30 are connected, even if the second command determination unit 102 (step S18) determines that a shutoff command has been input, the switch control unit 104 keeps the low-side switch SMRL corresponding to the “first switch” and the pre-charge switch SMRP corresponding to the “second switch” in their current states, i.e., keeps the low-side switch SMRL on and the pre-charge switch SMRP off, while the second temperature determination unit 106 (step S19) determines that the detected temperature Tr is higher than the second threshold value Tth2 (loop of steps S18 and S19), and returns to step S18 to repeat the determination by the second command determination unit 102 (loop related to step S18). Here, the second threshold value Tth2 is set lower than the first threshold value Tth1.

[0062] [2-2] While the second temperature determination unit 106 (step S19) determines that the detected temperature Tr is higher than the second threshold value Tth2 (loop of steps S18 and S19), the switch control unit 104 returns to step S18. If the second command determination unit 102 (step S18) determines that a connection command has been input, the switch control unit 104 waits until the second command determination unit 102 (step S18) determines that a disconnection command has been input, while keeping the low-side switch SMRL corresponding to the "first switch" on and the pre-charge switch SMRP corresponding to the "second switch" off (step S18).

[0063] If the second command judgment unit 102 (step S18) judges that a shut-off command has been input, and the second temperature judgment unit 106 (step S19) judges that the detected temperature Tr is equal to or lower than the second threshold value Tth2, the low potential side switch SMRL is turned off and the precharge switch SMRP is turned off (step S17).

[0064] By executing the processes [2-1] and [2-2] above, even if it is determined that a disconnection command has been input, the connection between the inverter 20 and the battery 30 is not immediately disconnected, but the connection is maintained while waiting for the temperature of the pre-charge resistor 40 to sufficiently decrease. Even during this waiting period, the connection between the inverter 20 and the battery 30 is maintained. Therefore, when the second command determination unit 102 determines that the command has been switched to a connection command, the inverter 20 can continue to operate without again performing a process to pass current through the pre-charge resistor 40 to prevent inrush current. In this way, the unnecessary waiting time of disconnecting the connection and executing the pre-charge process is eliminated, improving convenience for the vehicle user.

[0065] The following will explain why a distinctive effect can be obtained by setting the second threshold value Tth2 lower than the first threshold value Tth1.

[0066] In this embodiment, the ON state of the low-potential-side switch SMRL and the OFF state of the pre-charge switch SMRP can be maintained for a longer period of time than when the temperature threshold value in the second temperature determination unit 106 (step S19) is set to the first threshold value Tth1 instead of the second threshold value Tth2. Therefore, even if the user turns the start switch 60 OFF and then ON again, the inverter 20 can be immediately driven without current flowing through the pre-charge resistor 40. Furthermore, when the second threshold value Tth2 is set lower than the first threshold value Tth1, the standby time is longer than when the second threshold value Tth2 is set equal to the first threshold value Tth1. Therefore, there are more opportunities to immediately drive the inverter 20, which improves user convenience.

[0067] By executing the process [2-2], the inverter 20 and the battery 30 are disconnected and power supply to the inverter 20 is terminated after the temperature of the pre-charge resistor 40 has sufficiently dropped. Therefore, when the start switch 60 is turned on again to start the power supply device, even if the first process (the loop of steps S11 and S12) is performed, there is no need to wait for the temperature of the pre-charge resistor 40 to drop. In particular, by using the detection value of the temperature sensor 50, the determination in step S12 can be made accurately, and there is no need to waste time for the pre-charge resistor 40 to dissipate heat.

[0068] In principle, the high-side switch SMRH is turned on when the start switch 60 is turned on, and turned off when the start switch 60 is turned off. However, in this embodiment, the inverter 20 and the battery 30 may be electrically disconnected even when the start switch 60 is turned on. Also, the inverter 20 and the battery 30 may be electrically connected even when the start switch 60 is turned off. The high-side switch SMRH is turned on mainly when the pre-charge switch SMRP or the low-side switch SMRL is on, and the high-side switch SMRH is turned off when the pre-charge switch SMRP and the low-side switch SMRL are off. Note that if there is a low-side switch SMRL connected in parallel to the pre-charge resistor 40, the high-side switch SMRH is not necessary, and the high-side path may simply be connected by a bus.

[0069] 4 and 5 show examples of waveforms when start-up or stop control of the power supply device is executed. In Figures 4 and 5, (a) shows the transition of the connection command (H) or the disconnection command (L) based on the signal indicating the operation state of the start-up switch 60, (b) shows the transition of the detected temperature Tr, (c) shows the transition of the switching command for the high-side switch SMRH, (d) shows the transition of the switching command for the pre-charge switch SMRP, and (e) shows the transition of the switching command for the low-side switch SMRL.

[0070] 4 shows an example in which the activation switch 60 is frequently turned on and off by the user. At time t1 in FIG. 4, the activation switch 60 is turned on, and a connection command is input to the control device 70. Since the connection command is input to the control device 70 and the detected temperature Tr is determined to be equal to or lower than the first threshold value Tth1, the high-side switch SMRH and the pre-charge switch SMRP are turned on. As a result, the temperature of the pre-charge resistor 40 gradually increases.

[0071] At time t2, before a state in which an inrush current can be avoided is reached (step S14), the start switch 60 is turned off (step S15), and a shut-off command is input to the control device 70. When the shut-off command is input to the control device 70, the high-side switch SMRH and the pre-charge switch SMRP are switched off (step S17), causing the temperature of the pre-charge resistor 40 to gradually decrease.

[0072] At time t3, the start switch 60 is turned on again (step S11). In this case, a connection command is input to the control device 70, and it is determined that the temperature of the pre-charge resistor 40 is equal to or lower than the first threshold value Tth1 (step S12). Therefore, the high-side switch SMRH and the pre-charge switch SMRP are turned on (step S13). This charges the smoothing capacitor 21. Furthermore, the temperature of the pre-charge resistor 40 gradually increases.

[0073] At time t4, the detected voltage Vr of the voltage sensor 51 reaches the predetermined voltage Vth (step S14), the precharge switch SMRP is turned off, and the low-side switch SMRL is turned on (step S16). In this state, the inverter 20 and the battery 30 are connected, so that the inverter 20 can be driven.

[0074] At time t5, when the start switch 60 is turned off (step S18), a shut-off command is input to the control device 70. Here, at time t5, the control device 70 determines that the temperature of the pre-charge resistor 40 is equal to or lower than the second threshold value Tth2 (step S19). Therefore, the control device 70 turns off the high-side switch SMRH and the low-side switch SMRL (step S17).

[0075] After time t5, the activation switch 60 is turned on and off in the same manner as at times t1, t2, and t3, and the process proceeds in the same manner as from time t1 to t4. However, the temperature of the pre-charge resistor 40 continues to rise overall due to the multiple energizations of the pre-charge resistor 40. When the activation switch 60 is turned off at time t6 (step S18), a shut-off command is input to the control device 70. Here, at time t6, the control device 70 determines that the temperature of the pre-charge resistor 40 is higher than the second threshold value Tth2 (step S19). Therefore, despite the input of the shut-off command, the control device 70 keeps the high-side switch SMRH and the low-side switch SMRL on (corresponding to a loop of steps S18 and S19).

[0076] At time t7, when the start switch 60 is turned on (step S18), a connection command is input to the control device 70. Here, at time t7, the high-side switch SMRH and the low-side switch SMRL are maintained on, so the connection between the inverter 20 and the battery 30 is also maintained, and no processing is required to avoid inrush current. Therefore, the control device 70 does not turn on the pre-charge switch SMRP. As a result, if the user turns on the start switch 60 shortly after turning off the start switch 60, the inverter 20 can be driven immediately without spending time pre-charging the smoothing capacitor 21. Note that, because no current is applied to the pre-charge resistor 40, the temperature of the pre-charge resistor 40 gradually decreases.

[0077] Thereafter, the start switch 60 is turned off, and a shut-off command is input to the control device 70. In this case, it is determined that the detected temperature Tr is lower than the second threshold value Tth2, and based on the shut-off command, the control device 70 turns off the high-side switch SMRH and the low-side switch SMRL.

[0078] FIG. 5 shows an example in which the user frequently switches the start switch 60 on and off, and the microcomputer 71 is frequently reset due to a drop in power to the microcomputer 71, or due to a command from a higher-level ECU.

[0079] In Fig. 5, the state in which the start switch 60 is turned on and off twice from the start of control is roughly the same as the state in which the operation up to t1 and t2 in Fig. 4 is repeated twice. The third turning on and off of the start switch 60 is roughly the same as the operation from t3 to t5 in Fig. 4.

[0080] 5, some factor causes the microcomputer 71 to enter a reset state, and the switches SMRH, SMRP, and SMRL are turned off.

[0081] At time t2, the microcomputer 71 returns from the reset state. Because the start switch 60 remains ON (step S11), a connection command is input to the control device 70, and the temperature of the precharge resistor 40 is equal to or lower than the first threshold value Tth1 (step S12), the control device 70 switches the high-side switch SMRH and the precharge switch SMRP ON (step S13). This causes current to flow through the precharge resistor 40, and the temperature of the precharge resistor 40 begins to gradually increase. Next, as described with respect to times t3 and t4 in FIG. 4 , when the detection voltage Vr reaches the predetermined voltage Vth, it is determined that an inrush current can be avoided (step S14), and the precharge switch SMRP is switched OFF and the low-side switch SMRL is switched ON. In this state, the high-side switch SMRH and the low-side switch SMRL are ON, and the inverter 20 and the battery 30 are connected (step S16). In this state, the inverter 20 can be driven. Note that, since no current flows through the precharge resistor 40, the temperature of the precharge resistor 40 gradually decreases.

[0082] During the period from time t3 to time t4, the same control as that during the period from time t1 to time t2 is executed. That is, at time t3, the microcomputer 71 enters a reset state due to some factor. The switches SMRH, SMRP, and SMRL are turned off. Upon returning from the reset state, the control process for the switches SMRH, SMRP, and SMRL is restarted. Because the activation switch 60 remains turned on, a connection command is input to the control device 70 at time t4. Because it is determined that the temperature of the pre-charge resistor 40 is equal to or lower than the first threshold value Tth1 (step S12), the high-side switch SMRH and the pre-charge switch SMRP are switched on (step S13). This charges the smoothing capacitor 21. Furthermore, the temperature of the pre-charge resistor 40 further increases.

[0083] When it is determined that the detected voltage Vr has reached the predetermined voltage Vth (step S14), an inrush current can be avoided, so the precharge switch SMRP is switched off and the low-side switch SMRL is switched on (step S16). In this state, the high-side switch SMRH and the low-side switch SMRL are on, the inverter 20 and the battery 30 are connected, and the inverter 20 can be driven (step S16).

[0084] Next, just before time t5, the start switch 60 is turned off (step S18). The control device 70 determines that the detected temperature Tr exceeds the second threshold value Tth2 (step S19), and therefore keeps the high-side switch SMRH and the low-side switch SMRL on despite the input of a shut-off command (corresponding to a loop of steps S18 and S19).

[0085] From the above state in which the detected temperature Tr is waiting to become lower than the second threshold value Tth2 (corresponding to the loop of steps S18 and S19), at time t5, the microcomputer 71 enters a reset state due to some factor. As a result, the switches SMRH, SMRP, and SMRL are turned off. At the same time t5, the activation switch 60 is switched on. At time t6, the microcomputer 71 returns from the reset state. Because the activation switch 60 remains on, the control process of the switches SMRH, SMRP, and SMRL by the microcomputer 71 is restarted. Despite the input of a connection command to the control device 70, because the detected temperature Tr is higher than the first threshold value Tth1, the control device 70 maintains the switches SMRH, SMRP, and SMRL off (corresponding to the loop of steps S11 and S12). This prevents the precharge resistor 40 from overheating, and prevents the temperature of the precharge resistor 40 from exceeding an upper limit Tmax (e.g., an absolute maximum rating) of the temperature of the precharge resistor 40. The upper limit Tmax is a value greater than the first threshold value Tth1.

[0086] According to the present embodiment described above, the following effects can be achieved.

[0087] - If the second command determination unit 102 determines that a connection command has been received while the switch control unit 104 is continuing in the second processing state, the switch control unit 104 continues to turn on the high-side switch SMRH and the low-side switch SMRL and continues to turn off the pre-charge switch SMRP without going through the pre-charge state in which the pre-charge switch SMRP is turned on.

[0088] Even if the user turns off the activation switch 60 and a shut-off signal is input to the control device 70, the high-side switch SMRH and the low-side switch SMRL are maintained on and not turned off as long as the temperature of the pre-charge resistor 40 is higher than the second threshold value Tth2. In other words, if the activation switch 60 is turned on again shortly after being turned off, there is no need to switch the pre-charge switch SMRP on and enter a pre-charge state. This allows the inverter 20 to resume operation immediately. Furthermore, because the second threshold value Tth2 is set to a value lower than the first threshold value Tth1, there are more opportunities to resume operation of the inverter 20 even if it takes a long time for the activation switch 60 to be switched from off to on. This improves user convenience compared to when the first threshold value Tth1 and the second threshold value Tth2 are set to the same value.

[0089] The control device 70 includes a third command determination unit 103 that determines whether a connection command has been received or a disconnection command has been received in a precharge state in which the high-side switch SMRH and the precharge switch SMRP are on. If the third command determination unit 103 determines that a connection command has been received, the switch control unit 104 performs processing to maintain the precharge state, and if the third command determination unit 103 determines that a disconnection command has been received, the switch control unit 104 turns off the high-side and low-side switches SMRH and SMRL and the precharge switch SMRP.

[0090] As a result, when the start switch 60 is switched off during the execution of the precharge process and the control device 70 receives a disconnection signal, the high-potential and low-potential side switches SMRH and SMRL and the precharge switch SMRP are turned off, and the electrical connection between the inverter 20 and the battery 30 is interrupted. As a result, even during the execution of the precharge process, it is possible to appropriately respond to changes in the operation state of the start switch 60.

[0091] The system including the power supply device and the control device 70 is configured so that the switches SMRH, SMRL, and SMRP are turned off when the control device 70 enters a reset state. When the control device 70 returns from the reset state, the switch control unit 104 starts the control process (processing in FIG. 3) of the switches SMRH, SMRL, and SMRP.

[0092] When the control device 70 is reset while the temperature of the precharge resistor 40 is high, and then returns from the reset state, the control process is restarted with the switches SMRH, SMRL, and SMRP turned off. Even in this case, if the switch control unit 104 determines that the detected temperature Tr is higher than the first threshold value Tth1, it performs a first process that prohibits the switches SMRH, SMRL, and SMRP from being switched on. This prevents the precharge switch SMRP from being switched on and the precharge process from being performed, and prevents the precharge resistor 40 from becoming overheated.

[0093] The power supply device includes a high-side switch SMRH. When the low-side switch SMRL or the pre-charge switch SMRP is turned on, the switch control unit 104 also turns on the high-side switch SMRH, and when the low-side switch SMRL or the pre-charge switch SMRP is turned off, the switch control unit 104 also turns off the high-side switch SMRH.

[0094] By setting the on / off states of the low potential switch SMRL and the precharge switch SMRP and the on / off state of the high potential side switch SMRH as described above, it is possible to electrically connect and disconnect the inverter 20 and the battery 30, and to start and stop precharging appropriately. Furthermore, even if the low potential side switch SMRL fails due to sticking or the like, it is possible to accurately cut off the current flowing from the battery 30 to the inverter 20.

[0095] The power supply device includes a temperature sensor 50 that detects the temperature of the precharge resistor 40. The switch control unit 104 uses the detected value of the temperature sensor 50 as the temperature of the precharge resistor 40 to be compared with the first threshold value Tth1 and the second threshold value Tth2.

[0096] This allows accurate comparison of the magnitude between the actually measured temperature of the precharge resistor 40 (specifically, the value detected by the temperature sensor 50, for example) and each of the threshold values ​​Tth1 and Tth2.

[0097] Unlike the configuration using the temperature detection value, a configuration is also possible in which the heat dissipation time required for the temperature of the precharge resistor 40 to fall below a threshold is determined in advance, and processing proceeds based on whether the measured elapsed time reaches the heat dissipation time. However, the heat dissipation time depends on the ambient temperature of the power supply device. As a result, a configuration that compares the elapsed time with the heat dissipation time cannot ensure accuracy in determining whether the temperature of the precharge resistor 40 has sufficiently dropped, and the precharge process may be performed while the temperature of the precharge resistor 40 is high. In this case, the temperature of the precharge resistor 40 may exceed the rated temperature of the precharge resistor 40.

[0098] Other Embodiments The above embodiment may be modified as follows.

[0099] The process of step S14 in Fig. 3 may be changed to step S20 shown in Fig. 6. Specifically, the time elapsed since the start of the precharge process in step S13 may be measured, and it may be determined whether the measured elapsed time has reached a predetermined time. If the control device 70 determines that the elapsed time has reached the predetermined time, it proceeds to step S16, and if it determines that the elapsed time has not reached the predetermined time, it proceeds to step S15. The predetermined time is the time required for charging of the smoothing capacitor 21 to be completed, and may be set in advance by testing or the like.

[0100] In steps S12 and S19, instead of the detected value of the temperature sensor 50, an estimated value of the temperature of the precharge resistor 40 by a temperature estimator may be used.

[0101] The switches of the inverter 20 are not limited to IGBTs and may be, for example, N-channel MOSFETs having body diodes. In this case, the high-potential terminal of the N-channel MOSFET serves as the drain, and the low-potential terminal serves as the source.

[0102] Instead of the low-side switch SMRL, a series connection of the pre-charge switch SMRP and the pre-charge resistor 40 may be connected in parallel to the high-side switch SMRH. In this case, the high-side switch SMRH corresponds to the "first switch." In this case, the low-side switch SMRL does not need to be provided.

[0103] The motor is not limited to a star-connected motor, but may be a delta-connected motor. The motor and inverter are not limited to a three-phase motor, but may be a two-phase motor, or a four-phase or more phase motor. The motor is not limited to a permanent magnet synchronous machine having a permanent magnet as a field pole on the rotor, but may be a wound field synchronous machine having a field winding as a field pole on the rotor. In this case, the rotor may be provided with both a field winding and a permanent magnet. The motor is not limited to a synchronous machine, but may be an induction machine.

[0104] The DC power supply may be, for example, a large-capacity electric double layer capacitor, or may include both a DC power supply and an electric double layer capacitor. The DC power supply may also be a fuel cell.

[0105] The mobile body on which the system is mounted is not limited to a vehicle, but may be, for example, an aircraft or a ship. The system is also not limited to a mobile body, but may be a stationary device.

[0106] The control device and method described herein may be implemented by a special-purpose computer configured with a processor and memory programmed to execute one or more functions embodied in a computer program. Alternatively, the control device and method described herein may be implemented by a special-purpose computer configured with a processor comprising one or more dedicated hardware logic circuits. Alternatively, the control device and method described herein may be implemented by one or more special-purpose computers configured with a combination of a processor and memory programmed to execute one or more functions and a processor configured with one or more hardware logic circuits. Furthermore, the computer program may be stored in a computer-readable non-transitory tangible recording medium as instructions to be executed by a computer.

[0107] The following describes characteristic configurations extracted from the above-described embodiments. [Configuration 1] A control device applied to a system including an electric device (20), a DC power supply (30) that supplies power to the electric device, a first switch (SMRL) that connects the electric device to the DC power supply, a series connection of a second switch (SMRP) and a resistor (40) connected in parallel to the first switch, and a start switch (60) that is operated to transmit either a connection command that instructs the electric device to connect to the DC power supply or a disconnection command that instructs the electric device to disconnect from the DC power supply, the control device comprising: a switch control unit (104) that controls on / off of the first switch and the second switch; a first command determination unit (101) that determines, when the first switch is in an off state, whether the connection command has been received or the disconnection command has been received; and a second command determination unit (102) that determines, when the first switch is in an on state and the second switch is in an off state, whether the connection command has been received or the disconnection command has been received. the switch control unit, when it is determined by the first command determination unit that the connection command has been received, sets the second switch to a precharge state in which it turns on, and then turns off the second switch and turns on the first switch, and when it is determined by the second command determination unit that the disconnection command has been received, sets the first switch to an off state; a first temperature determination unit (105) that determines whether or not the temperature of the resistor is higher than a first threshold (Tth1); and a second temperature determination unit (106) that determines whether or not the temperature of the resistor is higher than a second threshold (Tth2) that is a value less than the first threshold; the switch control unit, when it is determined by the first command determination unit that the connection command has been received, performs a first process of maintaining the first switch and the second switch off;The control device performs a second process of maintaining the first switch on and the second switch off when the second temperature determination unit determines that the temperature of the resistor is higher than the second threshold, even when the second command determination unit determines that the disconnection command has been received. [Configuration 2] The control device according to Configuration 1, wherein, if the second command determination unit determines that the connection command has been received while the second process is continuing, the switch control unit continues to keep the first switch on and the second switch off without going through a pre-charge state in which the second switch is turned on. [Configuration 3] The control device according to Configuration 1 or 2, further comprising: a command third determination unit (103) that, in a pre-charge state in which the second switch is on, determines whether the connection command has been received or the disconnection command has been received, and the switch control unit performs a process of maintaining the pre-charge state when the third command determination unit determines that the connection command has been received, and turns off the second switch when the third command determination unit determines that the disconnection command has been received. [Configuration 4] The control device according to any one of configurations 1 to 3, wherein when the control device enters a reset state, the first switch and the second switch are turned off, and the switch control unit starts controlling the on or off of the first switch and the second switch when the control device returns from the reset state. [Configuration 5] The control device according to any one of configurations 1 to 4, wherein the system further includes a third switch (SMRH) that is provided on a path of a different potential from the first switch and connects the electrical device to the DC power supply, and the switch control unit turns the third switch on when the first switch or the second switch is turned on, and turns the third switch off when the first switch and the second switch are turned off. [Configuration 6] The system includes a temperature sensor (50) that detects the temperature of the resistor,The control device according to any one of configurations 1 to 5, wherein the switch control unit uses a detection value of the temperature sensor as the temperature of the resistor to be compared with the first threshold value and the second threshold value.

[0108] Although the present disclosure has been described with reference to the embodiments, it is understood that the present disclosure is not limited to the embodiments or structures. The present disclosure also encompasses various modifications and equivalent modifications. In addition, various combinations and forms, including only one element, more than one element, or less than one element, are also within the scope and spirit of the present disclosure.

Claims

1. A control device applied to a system including an electric device (20), a DC power supply (30) that supplies power to the electric device, a first switch (SMRL) that connects the electric device to the DC power supply, a series connection of a second switch (SMRP) and a resistor (40) connected in parallel to the first switch, and a start switch (60) that is operated to transmit either a connection command that instructs the electric device to connect to the DC power supply or a disconnection command that instructs the electric device to disconnect from the DC power supply, the control device comprising: a switch control unit (104) that controls the on / off of the first switch and the second switch; a first command determination unit (101) that determines, when the first switch is in an off state, whether the connection command has been received or the disconnection command has been received; and a second command determination unit (102) that determines, when the first switch is in an on state and the second switch is in an off state, whether the connection command has been received or the disconnection command has been received. the switch control unit, when it is determined by the first command determination unit that the connection command has been received, sets the second switch to a precharge state in which it turns on, and then turns off the second switch and turns on the first switch, and when it is determined by the second command determination unit that the disconnection command has been received, sets the first switch to an off state; a first temperature determination unit (105) that determines whether or not the temperature of the resistor is higher than a first threshold (Tth1); and a second temperature determination unit (106) that determines whether or not the temperature of the resistor is higher than a second threshold (Tth2) that is a value less than the first threshold; the switch control unit, when it is determined by the first command determination unit that the connection command has been received, performs a first process of maintaining the first switch and the second switch off; A control device that performs a second process of keeping the first switch on and the second switch off when the second temperature judgment unit judges that the temperature of the resistor is higher than the second threshold value even if the second command judgment unit judges that the shutdown command has been received.

2. The control device according to claim 1, wherein, if the second command determination unit determines that the connection command has been received while the second processing state is continuing, the switch control unit continues to keep the first switch on and the second switch off without going through a precharge state in which the second switch is turned on.

3. A control device as described in claim 1 or 2, further comprising a third command determination unit (103) that determines whether the state is one in which the connection command has been received or the disconnection command has been received in a pre-charge state in which the second switch is on, wherein the switch control unit performs processing to maintain the pre-charge state when the third command determination unit determines that the state is one in which the connection command has been received, and turns off the second switch when the third command determination unit determines that the state is one in which the disconnection command has been received.

4. A control device as described in claim 1 or 2, wherein when the control device is in a reset state, the first switch and the second switch are turned off, and when the control device returns from the reset state, the switch control unit begins to control the on or off of the first switch and the second switch.

5. The control device according to claim 1 or 2, wherein the system further comprises a third switch (SMRH) that is a switch provided in a path of a different potential from that of the first switch and connects the electrical device to the DC power supply, and wherein the switch control unit turns the third switch on when the first switch or the second switch is turned on, and turns the third switch off when the first switch and the second switch are turned off.

6. The control device according to claim 1 or 2, wherein the system includes a temperature sensor (50) for detecting the temperature of the resistor, and the switch control unit uses the detected value of the temperature sensor as the temperature of the resistor to be compared with the first threshold value and the second threshold value.

7. A control device applied to a system including an electric device (20), a DC power source (30) that supplies power to the electric device, a first switch (SMRL) that connects the electric device to the DC power source, a series connection of a second switch (SMRP) and a resistor (40) connected in parallel to the first switch, and a start switch (60) that is operated to issue either a connection command that instructs the electric device to connect to the DC power source or a disconnection command that instructs the electric device to disconnect from the DC power source, the control device comprising: a switch control unit (104) that controls the on / off of the first switch and the second switch; and a command determination unit (101) that determines, when the first switch is in an off state, whether the connection command has been received or the disconnection command has been received, wherein, when the command determination unit determines that the connection command has been received, the switch control unit sets the second switch to a precharge state in which it is on, and then sets the second switch to a state in which it is on and the first switch to a state in which it is a temperature determination unit (105) that determines whether the temperature of the resistor is higher than a threshold value (Tth1), and the switch control unit performs processing to maintain the first switch and the second switch off when the temperature determination unit determines that the temperature of the resistor is higher than the threshold value, even if the command determination unit determines that the connection command has been received.

8. The control device according to claim 7, wherein when the control device is in a reset state, the first switch and the second switch are turned off, and when the control device returns from the reset state, the switch control unit starts controlling the on or off of the first switch and the second switch.

9. A program applied to a system including an electric device (20), a DC power supply (30) that supplies power to the electric device, a first switch (SMRL) that connects the electric device to the DC power supply, a series connection of a second switch (SMRP) and a resistor (40) connected in parallel to the first switch, and a start switch (60) that is operated to transmit either a connection command that instructs the electric device to connect to the DC power supply or a disconnection command that instructs the electric device to disconnect from the DC power supply, the program causing a computer (71) to execute: a switch control process that controls the on / off of the first switch and the second switch; a first command determination process that determines, when the first switch is in an off state, whether the connection command has been received or the disconnection command has been received; and a second command determination process that determines, when the first switch is in an on state and the second switch is in an off state, whether the connection command has been received or the disconnection command has been received. In the switch control process, when it is determined by the first command determination process that the connection command has been received, the second switch is placed in a precharge state where it is turned on, and then the second switch is turned off and the first switch is turned on; and when it is determined by the second command determination process that the disconnection command has been received, the first switch is turned off; the computer is caused to execute a first temperature determination process that determines whether the temperature of the resistor is higher than a first threshold (Tth1), and a second temperature determination process that determines whether the temperature of the resistor is higher than a second threshold (Tth2) that is a value less than the first threshold; and in the switch control process, even when it is determined by the first command determination process that the connection command has been received, when it is determined by the first temperature determination process that the temperature of the resistor is higher than the first threshold, a first process that keeps the first switch and the second switch off;A program that performs a second process of keeping the first switch on and the second switch off when the second temperature determination process determines that the temperature of the resistor is higher than the second threshold value even if the second command determination process determines that the shut-off command has been received.

10. A control method applicable to a system including an electric device (20), a DC power supply (30) that supplies power to the electric device, a first switch (SMRL) that connects the electric device to the DC power supply, a series connection of a second switch (SMRP) and a resistor (40) connected in parallel to the first switch, and a start switch (60) that is operated to transmit either a connection command that instructs the electric device to connect to the DC power supply or a disconnection command that instructs the electric device to disconnect from the DC power supply, the control method comprising: a switch control step that controls the on / off of the first switch and the second switch; a first command determination step that, when the first switch is in an off state, determines whether the connection command has been received or the disconnection command has been received; and a second command determination step that, when the first switch is in an on state and the second switch is in an off state, determines whether the connection command has been received or the disconnection command has been received. In the switch control step, when it is determined in the first command determination step that the connection command has been received, a precharge state is established in which the second switch is turned on, and then the second switch is turned off and the first switch is turned on; and when it is determined in the second command determination step that the disconnection command has been received, the first switch is turned off; a first temperature determination step of determining whether or not the temperature of the resistor is higher than a first threshold (Tth1); and a second temperature determination step of determining whether or not the temperature of the resistor is higher than a second threshold (Tth2) that is a value less than the first threshold; In the switch control step, even when it is determined in the first command determination step that the connection command has been received, if it is determined in the first temperature determination step that the temperature of the resistor is higher than the first threshold, a first process is performed to maintain the first switch and the second switch off;A control method in which, even if the second command determination step determines that the shut-off command has been received, if the second temperature determination step determines that the temperature of the resistor is higher than the second threshold, a second process is performed to keep the first switch on and the second switch off.

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