Semiconductor switch control device and semiconductor switch control method

Abstract

A controller (10) for controlling a semiconductor switch (11) connected between a power source (1) and a load (2) acquires a voltage applied to the semiconductor switch (11) and a current flowing through the semiconductor switch (11), calculates the resistance value of the semiconductor switch (11) on the basis of the acquired voltage and current, estimates a predicted reaching temperature which the semiconductor switch (11) is predicted to reach in the future on the basis of the resistance value, and controls on / off of the semiconductor switch (11) on the basis of the predicted reaching temperature.

Description

Semiconductor switch control device and semiconductor switch control method

[0001] The present invention relates to a semiconductor switch control device and a semiconductor switch control method.

[0002] A technology is known that determines whether a semiconductor switch has poor heat dissipation based on the temperature difference between the actual temperature of the semiconductor switch and an estimated temperature based on the current supplied to the semiconductor switch, and if poor heat dissipation is detected, manages the operation of the semiconductor switch so that the actual temperature is below an overtemperature threshold (Patent Document 1).

[0003] International Publication No. 2023 / 281786

[0004] However, the technology described in Patent Document 1 is a technology for managing the operation of a semiconductor switch based on the temperature of the semiconductor switch, and therefore, when a semiconductor switch experiences a half-on failure, it is not possible to predict a temperature abnormality from the temperature at the time of the half-on failure, and the operation of the semiconductor switch cannot be managed appropriately.

[0005] An object of the present invention is to provide a semiconductor switch control device and a semiconductor switch control method that can appropriately manage the operation of a semiconductor switch when the semiconductor switch has a half-on failure.

[0006] The present invention solves the above problem by calculating the resistance value of a semiconductor switch based on the voltage applied to the semiconductor switch and the current flowing through the semiconductor switch, estimating the predicted temperature that the semiconductor switch will reach in the future based on the resistance value, and controlling the on / off of the semiconductor switch based on the predicted temperature.

[0007] According to the present invention, when a half-on fault occurs in a semiconductor switch, the operation of the semiconductor switch can be appropriately managed.

[0008] Fig. 1 is a schematic diagram of a power supply system according to an embodiment of the present invention. Fig. 2 is a diagram showing an example of a flowchart of a semiconductor switch control method executed by a controller according to the embodiment. Fig. 3 is a graph showing the relationship between the resistance value of a semiconductor switch and the temperature reached in the embodiment. Fig. 4 is a diagram for explaining semiconductor switch control in the embodiment when a half-on failure occurs in the semiconductor switch. Fig. 5 is a diagram for explaining setting of a priority according to the state of a vehicle in the embodiment.

[0009] Fig. 1 is a schematic diagram of a power supply system according to an embodiment of the present invention. In this embodiment, the power supply system is mounted on a vehicle equipped with a battery. As shown in Fig. 1, the power supply system 100 includes a battery 1, a load 2, and a semiconductor switch control device 3. In the following description, an embodiment in which a battery is mounted on a vehicle will be described, but a generator may also be used, or both a battery and a generator may also be mounted on the vehicle.

[0010] The battery 1 is a low-voltage power supply for operating a load 2 such as an auxiliary device. The battery 1 is a battery of 50 volts or less, for example, a 12 V battery. In other words, the battery 1 is a battery of 50 volts or less and / or a battery for an auxiliary device. The battery 1 is connected to the load 2 via a semiconductor switch 11. The battery 1 is, for example, a secondary battery such as a lithium-ion battery or a lead battery.

[0011] The load 2 is a load that operates using power supplied from the battery 1. The load 2 includes at least on-board equipment related to the operation of the vehicle. In this embodiment, the power supply system 100 is configured to include a plurality of different loads, but this is not limited thereto, and the number of loads 2 may be one. Also, in FIG. 1 , three loads 2 (2 a, 2 b, 2 c) are connected to the semiconductor switch control device 3 as an example of the plurality of different loads, but this is not limited thereto, and the plurality of different loads 2 may include two loads 2, or four or more loads 2.

[0012] The semiconductor switch control device 3 is a supply device that supplies power from the battery 1 to the load 2, and controls a semiconductor switch 11 to switch between electrical conduction and cut-off between the battery 1 and the load 2. The semiconductor switch control device 3 is electrically connected to the battery 1 located upstream and the load 2 located downstream, and includes a controller 10, a semiconductor switch 11, and a detection unit 12.

[0013] The semiconductor switch 11 is connected between the battery 1 and the load 2 and switches between electrical conduction and interruption between the battery 1 and the load 2. The semiconductor switch 11 uses a semiconductor element as a switching device and is connected to a power supply circuit for outputting power supplied from the battery 1 to the load 2. The semiconductor switch 11 is a transistor switch such as a MOSFET or an IGBT. The semiconductor switch 11 may also function as a fuse (semiconductor fuse) that interrupts current between the battery 1 and the load 2. For example, an IPD (Intelligent Power Device) having a protection circuit may be used as the semiconductor switch 11. The semiconductor switch 11 is also communicatively connected to the controller 10 and receives commands transmitted from the controller 10.

[0014] A power supply circuit includes a plurality of semiconductor switches 11. For example, the semiconductor switches 11 may include different types of semiconductor switches. The semiconductor switches 11 include a shutoff semiconductor switch 11a and a drive semiconductor switch 11b. The shutoff semiconductor switch 11a is a semiconductor switch that shuts off the power supply when a failure occurs in which the semiconductor switch 11b is stuck ON. The drive semiconductor switch 11b is a semiconductor switch that drives a load 2 and is installed for each load 2. In FIG. 1 , the drive semiconductor switches 11b(1), 11b(2), and 11b(3) correspond to the loads 2a, 2b, and 2c, respectively. The drive semiconductor switch 11b connected to the load 2 to be driven is turned on when an on switching command is input. When the semiconductor switch is on, power is supplied to the corresponding load 2, enabling it to be driven. When an off switching command is input, the drive semiconductor switch 11b is turned off and cuts off the power flowing to the corresponding load 2. The power supply circuit branches to each load 2 downstream of the shutoff semiconductor switch 11a and is connected to each drive semiconductor switch 11b. That is, the power supply circuit has a branch point 4 downstream of the shutoff semiconductor switch 11a. The power supply circuit has branch wiring from the branch point 4, and each load 2 has wiring connecting to the branch point 4. In the power supply circuit, each drive semiconductor switch 11b and the shutoff semiconductor switch 11a are connected in series. The shutoff semiconductor switch 11a is an example of an "upstream semiconductor switch" as defined in the claims. The drive semiconductor switch 11b is an example of a "downstream semiconductor switch" as defined in the claims.

[0015] In addition to on-failures and off-failures, the semiconductor switch 11 may also experience a half-on failure. A half-on failure is a phenomenon in which the resistance across the semiconductor switch, e.g., an FET, remains in a voltage range outside the range of voltages that should be applied, resulting in the semiconductor switch not being adjusted to a sufficiently high or low value. When a half-on failure occurs, the resistance across the semiconductor switch is not sufficiently high, so current flows through the semiconductor switch. The amount of heat generated is proportional to the square of the current, resulting in the semiconductor switch generating a large amount of heat. In a half-on failure, the semiconductor switch 11 does not experience a sufficient increase in resistance even in the off state, so current flows, generating heat proportional to the square of the current, and the temperature of the semiconductor switch rises. However, the current flowing is within a normal current range, and if a half-on failure does not occur, the current value would not be such that excessive heat would be generated. Therefore, conventional methods for shutting off the semiconductor switch 11 based on temperature measurement cannot detect a half-on failure, and therefore the shutoff control of the semiconductor switch 11 is not executed or the current value cannot be suppressed. Furthermore, after a half-on failure, the semiconductor switch 11 experiences a sudden temperature rise, but conventional shutoff methods based on temperature measurement cause a delay equivalent to the time it takes to measure the temperature, making it impossible to shut off the semiconductor switch within the required time. In this embodiment, as will be described below, when the semiconductor switch 11 experiences a half-on failure, the controller 10 outputs an OFF command to the driving semiconductor switch 11b to shut off the current flowing through the load 2. This makes it possible to prevent temperature abnormalities from occurring.

[0016] The detector 12 detects the voltage applied to the semiconductor switch 11a and the current flowing through the semiconductor switch 11a. In this embodiment, the detector 12 may detect the voltages upstream and downstream of the semiconductor switch 11a. The voltage downstream of the semiconductor switch 11a may be detected, and the voltage upstream of the semiconductor switch 11a may be calculated as, for example, the battery voltage, to detect the voltage difference. However, because the voltage of the power source mounted on the vehicle is unstable, the voltage upstream of the semiconductor switch 11a may be detected. For example, the detector 12 includes a detector 12a connected upstream of the semiconductor switch 11a, i.e., between the battery 1 and the semiconductor switch 11a, and a detector 12b connected downstream of the semiconductor switch 11a, i.e., between the semiconductor switch 11a and the branch point 4. For example, the detector 12 has voltage detection terminals (voltage sensors) and detects the voltages upstream and downstream of the semiconductor switch 11a. The detector 12 has a shunt resistor 12c connected to the semiconductor switch 11a, and detects the current flowing through the semiconductor switch 11a by measuring the current flowing through the shunt resistor 12c with a current sensor. The detector 12 is communicably connected to the controller 10, and the detected values ​​(detected voltage and detected current) of the detector 12 are output to the controller 10. Note that in this embodiment, it is not essential to provide the detector 12 both upstream and downstream of the semiconductor switch 11a, and the detector 12 may be provided upstream or downstream of the semiconductor switch 11a.

[0017] The controller 10 is an electronic control device for controlling the on / off switching of the semiconductor switch 11. The controller 10 outputs a switching command to switch the semiconductor switch 11 on / off to the semiconductor switch 11. For example, the controller 10 identifies a load 2 to be driven, and outputs an on switching command (on command) to a driving semiconductor switch 11b connected to the load 2 to be driven. Furthermore, when turning off the operation of the load 2, the controller 10 outputs an off switching command (off command) to the semiconductor switch 11b connected to the load 2.

[0018] The controller 10 is configured, for example, by a microcomputer integrating a CPU, ROM, RAM, etc. The CPU reads out program code of software that realizes each function according to this embodiment from the ROM, loads it into the RAM, and executes it. The controller 10 includes functional blocks including a current acquisition unit 20, a voltage acquisition unit 30, a determination unit 40, and a control unit 50.

[0019] The current acquiring unit 20 acquires a detected value of the current flowing through the semiconductor switch 11a from the detecting unit 12. The voltage acquiring unit 30 acquires detected values ​​of the voltage downstream and upstream of the semiconductor switch 11a from the detecting unit 12. For example, the current acquiring unit 20 and the voltage acquiring unit 30 acquire the detected values ​​of the current and the voltage at regular intervals while power is being supplied from the battery 1.

[0020] The determination unit 40 calculates the resistance value of the semiconductor switch 11a based on the voltage and current of the semiconductor switch 11a. The determination unit 40 estimates a predicted temperature that the semiconductor switch 11a is expected to reach in the future based on the calculated resistance value. The predicted temperature is a future predicted value and is different from the current temperature of the semiconductor switch 11a (actual temperature and estimated temperature). The correspondence between the resistance value and the predicted temperature is obtained in advance by experiment, etc. The determination unit 40 determines whether the estimated predicted temperature is equal to or higher than a predetermined temperature threshold.

[0021] The control unit 50 controls the on / off of the semiconductor switch 11b based on the predicted temperature to be reached. This switches between conduction and interruption of the current flowing through the load 2. For example, when the predicted temperature to be reached is equal to or higher than a predetermined temperature threshold, the control unit 50 outputs an off command to the semiconductor switch 11b to turn off the semiconductor switch 11b. At this time, the control unit 50 may turn off all of the driving semiconductor switches 11b connected to each of the multiple loads 2, or may turn off the driving semiconductor switch 11b connected to one of the loads 2 and maintain current conduction in the driving semiconductor switches 11b connected to the remaining loads 2.

[0022] Here, an example of a procedure for executing the semiconductor switch control method according to this embodiment will be described with reference to FIG. 2 . FIG. 2 is a diagram showing an example of a flowchart of the semiconductor switch control method executed by the controller according to this embodiment. In this embodiment, for example, when power supply from the battery 1 to the load 2 starts, the controller 10 starts the control flow from step S1. In step S1, the controller 10 acquires voltages and currents upstream and downstream of the cutoff semiconductor switch 11a. In step S2, the controller 10 calculates the resistance value of the semiconductor switch 11a based on the voltage and current of the semiconductor switch 11a acquired in step S1. In step S3, the controller 10 estimates the predicted temperature of the semiconductor switch 11a based on the resistance value calculated in step S2. In step S4, the controller 10 controls the on / off of the driving semiconductor switch 11b based on the predicted temperature. For example, the controller 10 turns off the driving semiconductor switch 11b when the predicted temperature is equal to or higher than a predetermined temperature threshold.

[0023] Next, referring to FIG. 3 , we will explain how the relationship between the resistance value and the ultimate temperature of a semiconductor switch changes when the semiconductor switch is shut off. FIG. 3 is a graph showing the relationship between the resistance value and the ultimate temperature of a semiconductor switch in this embodiment. In FIG. 3 , the horizontal axis represents the resistance value (Ω) of the semiconductor switch 11a, and the vertical axis represents the temperature (ultimate temperature) that the semiconductor switch 11a reaches when maintained at that resistance value. The temperature Ti is a predetermined temperature threshold (e.g., 200°C), which indicates the temperature at which, for example, the substrate on which the semiconductor switch is mounted may deform or emit smoke. The predetermined temperature threshold is obtained in advance through experiments, etc. Graph A shows the ultimate temperature of the semiconductor switch 11a when the semiconductor switch 11a is in a half-on fault state and the current flowing at that resistance value continues. Graph B shows the ultimate temperature for each resistance value when one driving semiconductor switch 11b is shut off. Graph C shows the ultimate temperature for each resistance value when two driving semiconductor switches 11b are shut off. The number of semiconductor switches 11b to be turned off is not limited to the example shown in FIG. 3, and may be set appropriately depending on the number of loads 2, etc.

[0024] As shown in FIG. 3 , when the driving semiconductor switch 11b is turned off (graphs B and C), the temperature is lower than when the driving semiconductor switch 11b is not turned off (graph A). In this embodiment, the control unit 50 selects the driving semiconductor switch 11b to be turned off depending on the resistance value. For each resistance value, the driving semiconductor switch 11b that needs to be turned off to make the predicted target temperature below a predetermined temperature threshold is stored in advance. For example, if the semiconductor switch 11a experiences a half-on failure when the resistance value is 1 Ω, the control unit 50 turns off the selected semiconductor switch 11b. When the semiconductor switch 11b is turned off, the temperature is lower than when the semiconductor switch 11b is not turned off (graph A), as shown in graph B.

[0025] Furthermore, if the semiconductor switch 11a experiences a half-on failure when the resistance value is 2 Ω, the control unit 50 shuts off two selected semiconductor switches 11b. When two semiconductor switches 11b are shut off, the temperature is lower than the temperature when the semiconductor switch 11b is shut off (graph B), as shown in graph C. Also, as shown in FIG. 3, when the resistance value is 2 Ω, the temperature (predicted temperature) when the semiconductor switch 11b is not shut off (graph A) exceeds temperature Ti, but the temperature when two semiconductor switches 11b are shut off (graph C) is lower than temperature Ti. As described above, in this embodiment, the control unit 50 shuts off the semiconductor switch 11b to lower the temperature of the semiconductor switch 11a to below the predetermined temperature threshold. Furthermore, when the semiconductor switch 11a experiences a half-on failure when the resistance value is 4 Ω, the control unit 50 shuts off all semiconductor switches 11b.

[0026] Using Figure 4, the shutoff of a semiconductor switch according to the semiconductor switch control method of this embodiment will be described in comparison with the conventional technique. Figure 4 is a diagram for explaining semiconductor switch control in the present embodiment when a half-on failure occurs in the semiconductor switch. In Figure 4, the horizontal axis represents time and the vertical axis represents the temperature of the semiconductor switch 11a. Note that temperature response delays inside and outside the semiconductor switch 11a are ignored. Note that the values ​​of temperature, time, etc. shown in Figure 4 are merely examples and are not limited to these.

[0027] In the example of FIG. 4 , the temperature of the semiconductor switch 11a normally remains at a normal temperature (e.g., 100°C). At time t1, a half-on fault occurs in the semiconductor switch 11a. As a result, the temperature of the semiconductor switch 11a begins to rise from time t1. It takes 180 msec for the temperature of the semiconductor switch 11a to reach a temperature (e.g., 300°C) set as the abnormal temperature. In this embodiment, the controller 10 periodically acquires the voltage and current of the semiconductor switch 11a and calculates the resistance value to estimate the predicted temperature. As a result, as soon as a half-on fault occurs, it is determined that the predicted temperature will be equal to or greater than a predetermined temperature threshold. Therefore, the controller 10 can quickly output an OFF command to turn off the semiconductor switch 11b. In the example of FIG. 4 , the controller 10 can complete the turning off of the semiconductor switch 11b at time t2. Note that time t2 is 50 msec after time t1, taking into account the time required for three voltage measurements (20 msec), resistance value calculation (10 msec), and processing of the turn-off command (10 msec). That is, in this embodiment, the semiconductor switch 11b can be completely turned off within 50 msec after the occurrence of a half-on fault.

[0028] On the other hand, in conventional technology that performs shutoff control of a semiconductor switch based on temperature measurement, a temperature (e.g., 250°C) lower than a temperature (e.g., 300°C) set as an abnormal temperature is set as the temperature at which shutoff control of the semiconductor switch is initiated. Therefore, in the conventional technology, shutoff control of the semiconductor switch is initiated when the temperature of the semiconductor switch reaches 250°C at time t3. Then, the conventional technology performs temperature measurement and degradation determination, and completes shutoff of the semiconductor switch at time t4. Assuming that it takes 135 msec for the temperature of the semiconductor switch to reach 250°C, and 10 msec each for temperature measurement, degradation determination, and shutoff command processing, in the conventional technology, it takes 165 msec from time t1 when the half-on failure occurs to time t4 when shutoff is completed. As described above, the semiconductor switch control method according to this embodiment can complete shutoff of the semiconductor switch more quickly than the conventional technology.

[0029] In the present embodiment, a priority for cutting off current may be set for each load 2 depending on the state of the vehicle. That is, the priority set for each load 2 differs depending on the state of the vehicle. When a priority is set for each load, the control unit 50 identifies the semiconductor switch 11b to be cut off in accordance with the priority of each load 2, and cuts off the identified semiconductor switch 11b. For example, the control unit 50 compares the priorities of multiple loads and identifies the semiconductor switch 11b corresponding to the load 2 with a higher priority as the semiconductor switch 11b to be cut off. Furthermore, the control unit 50 may identify the semiconductor switch 11b corresponding to the load 2 with a priority equal to or higher than a predetermined priority as the semiconductor switch 11b to be cut off.

[0030] First, the control unit 50 sets a priority for each load 2 according to the state of the vehicle. The control unit 50 sets the priority for each load 2, for example, so that functions necessary for maintaining vehicle movement are not shut off while the vehicle is moving, and so that functions for immobilizing the vehicle are not shut off after the vehicle has stopped. For each load 2, a vehicle state and a priority corresponding to the vehicle state are associated and stored. Examples of vehicle states include moving, parked, and collision. The control unit 50 then determines the current vehicle state when it determines that the predicted target temperature is equal to or higher than a predetermined temperature threshold. The determination of the vehicle state is performed, for example, based on vehicle information acquired from the vehicle's on-board equipment. For each load 2, the control unit 50 sets a priority for the load 2 corresponding to the determined vehicle state. The control unit 50 compares the priorities of each load 2 and controls the on / off of the semiconductor switch 11b so that a load 2 with a higher priority is shut off from the multiple loads 2 with priority over a load 2 with a lower priority.

[0031] For example, when the vehicle is in a running state (driving), the control unit 50 sets a lower priority for the load 2 that executes a function necessary to maintain the running state than for the load 2 that executes a function unrelated to maintaining the running state. Functions necessary to maintain the running state include, for example, a steering control function and a braking function. The control unit 50 then preferentially turns off the semiconductor switch 11b corresponding to the load 2 that has a higher priority when the vehicle is in a running state, i.e., the load 2 that executes a function unrelated to maintaining the running state. Furthermore, when the vehicle is in a stopped state (parked), the control unit 50 sets a lower priority for the load that executes a function necessary to maintain the stopped state than for the load that executes a function unrelated to maintaining the stopped state. Functions necessary to maintain the stopped state include, for example, a parking brake and a door lock. The control unit 50 then preferentially turns off the semiconductor switch 11b corresponding to the load 2 that has a higher priority when the vehicle is in a stopped state, i.e., the load 2 that executes a function unrelated to maintaining the stopped state.

[0032] Furthermore, the control unit 50 may prioritize shutting off loads 2 with a greater temperature reduction effect over loads 2 with a smaller temperature reduction effect, even among loads with the same priority. A load 2 with a greater temperature reduction effect is a load 2 that can reduce the temperature of the semiconductor switch 11a more effectively when the corresponding semiconductor switch 11b is shut off. An example of a load 2 with a greater temperature reduction effect is a load 2 with a larger current consumption. By preferentially shutting off loads 2 with a greater temperature reduction effect, the controller 10 can more quickly suppress temperature increases while maintaining functions required for each vehicle state. For example, when there are multiple loads 2 with the same priority (state priority) set based on the vehicle state, the control unit 50 sets a lower priority for loads 2 with a smaller current consumption than for loads 2 with a larger current consumption. Hereinafter, the priority set based on the magnitude of the temperature reduction effect is also referred to as a reduction priority. The control unit 50 then compares the reduction priorities of the loads 2 and identifies the semiconductor switch 11b corresponding to the load 2 with the higher reduction priority as the semiconductor switch 11b to be shut off.

[0033] Here, a method for setting priorities according to vehicle states according to this embodiment will be described with reference to FIG. 5 . FIG. 5 is a diagram for explaining the setting of priorities according to vehicle states according to this embodiment. In the table of FIG. 5 , state priorities for the vehicle states of driving, parking, and collision are pre-associated and stored for each load. In addition to the state priorities, reduction priorities are pre-associated and stored for each load. Note that, although FIG. 5 lists power steering, VDC, electronic parking brake, headlamps, airbags, air conditioner, motor fan, audio, and seat heater as examples of load 2, examples of load 2 are not limited to these.

[0034] The control unit 50 refers to the state priority of each load 2 according to the state of the vehicle and identifies the load 2 with the highest state priority. For example, when the state of the vehicle is "driving," the control unit 50 identifies the load 2 with the highest state priority of "3," which are the electronic parking brake, audio, and seat heater. Furthermore, a reduction priority is pre-associated with each load 2. When there are loads 2 with the same state priority, the control unit 50 may identify the load 2 according to the reduction priority of those loads 2. For example, among the loads 2 with the state priority of "3," which are the electronic parking brake, audio, and seat heater, the control unit 50 identifies the load 2 with the highest reduction priority of "8," which is the seat heater. The control unit 50 first turns off the semiconductor switch 11b corresponding to the seat heater. When further turning off the semiconductor switch 11b, the control unit 50 turns off the semiconductor switches 11b corresponding to the audio and electronic parking brake in descending order of reduction priority. 5, the semiconductor switches 11b corresponding to the loads 2 are turned off in order from the highest priority, but the identification of the loads 2 according to priority is not limited to this. For example, all the semiconductor switches 11b corresponding to the loads whose state priorities are equal to or higher than a predetermined priority may be turned off.

[0035] Furthermore, in this embodiment, the control unit 50 may control the on / off of the semiconductor switch 11 based on the predicted temperature when the ambient temperature of the semiconductor switch 11 is equal to or higher than a predetermined temperature threshold. The predetermined temperature threshold is a temperature higher than the normal ambient temperature, i.e., the ambient temperature in a high-temperature atmosphere. When the ambient temperature of the semiconductor switch 11a is high, even if the semiconductor switch 11a is in a normal state without a half-on failure, the temperature of the semiconductor switch 11a is higher than the temperature of the semiconductor switch 11a when the ambient temperature is normal. Therefore, when the semiconductor switch 11a experiences a half-on failure in a high-temperature atmosphere, the time it takes for the temperature of the semiconductor switch 11a to reach the temperature set as a temperature abnormality is shortened. Even in such a case, the semiconductor switch control device 3 according to this embodiment can quickly complete the shutoff of the semiconductor switch 11b.

[0036] As described above, in the semiconductor switch control device and semiconductor switch control method according to the present embodiment, the controller acquires the voltage applied to the semiconductor switch and the current flowing through the semiconductor switch, calculates the resistance of the semiconductor switch based on the acquired voltage and current, estimates the predicted temperature that the semiconductor switch will reach in the future based on the resistance, and controls the on / off of the semiconductor switch based on the predicted temperature. This makes it possible to appropriately manage the operation of the semiconductor switch when a half-on failure occurs in the semiconductor switch.

[0037] Furthermore, in the semiconductor switch control device and semiconductor switch control method according to the present embodiment, the controller turns off the semiconductor switch when the predicted temperature is equal to or higher than a predetermined temperature threshold, thereby making it possible to prevent temperature abnormalities from occurring.

[0038] In the semiconductor switch control device and semiconductor switch control method according to the present embodiment, the semiconductor switches include an upstream semiconductor switch whose predicted temperature is to be estimated, and a plurality of downstream semiconductor switches each connected to a wiring branching downstream of the upstream semiconductor switch, and the controller controls the on / off of the downstream semiconductor switches based on the predicted temperature. This makes it possible to cut off current flowing through some of the wiring when a semiconductor switch experiences a half-on failure.

[0039] Furthermore, in the semiconductor switch control device and semiconductor switch control method according to the present embodiment, when a vehicle is equipped with multiple loads, the controller sets priorities for interrupting current for each of the multiple loads according to the vehicle state, and controls the on / off of the semiconductor switches so that current flowing through loads with higher priorities is interrupted in preference to loads with lower priorities. This makes it possible to suppress the occurrence of temperature abnormalities while maintaining necessary vehicle functions according to the vehicle state.

[0040] Furthermore, in the semiconductor switch control device and semiconductor switch control method according to the present embodiment, when the vehicle is in a running state, the controller sets a lower priority for the loads that execute functions necessary to maintain the running state than for the loads that execute functions unrelated to maintaining the running state, thereby making it possible to suppress the occurrence of temperature abnormalities while maintaining the vehicle functions necessary for vehicle running.

[0041] Furthermore, in the semiconductor switch control device and semiconductor switch control method according to the present embodiment, when the vehicle is stopped, the controller sets a lower priority for the loads that execute functions necessary to maintain the stopped state than for the loads that execute functions unrelated to maintaining the stopped state, thereby making it possible to suppress the occurrence of temperature abnormalities while maintaining the vehicle functions necessary for stopping the vehicle.

[0042] Furthermore, in the semiconductor switch control device and semiconductor switch control method according to this embodiment, when there are multiple loads with the same priority, the controller controls the on / off of the semiconductor switch so as to cut off the current flowing through the load with a higher current consumption, prioritizing the load with a lower current consumption over the load with a lower current consumption, thereby more efficiently suppressing the occurrence of temperature abnormalities.

[0043] In the semiconductor switch control device and semiconductor switch control method according to the present embodiment, the controller controls the on / off of the semiconductor switch based on the predicted temperature when the ambient temperature of the semiconductor switch is equal to or higher than a predetermined temperature threshold. This makes it possible to appropriately manage the operation of the semiconductor switch even when the semiconductor switch experiences a half-on failure in a high-temperature environment around the semiconductor switch.

[0044] Furthermore, in the semiconductor switch control device and semiconductor switch control method according to the present embodiment, the controller acquires the voltages upstream and downstream of the semiconductor switch, respectively, thereby enabling more accurate measurement of the voltage applied to the semiconductor switch.

[0045] It should be noted that the above-described embodiments have been described to facilitate understanding of the present invention, and are not intended to limit the present invention. Therefore, the elements disclosed in the above embodiments are intended to include all design modifications and equivalents that fall within the technical scope of the present invention.

[0046] REFERENCE SIGNS LIST 100 power supply system 1 battery 2 load 3 semiconductor switch control device 10 controller 20 current acquisition unit 30 voltage acquisition unit 40 determination unit 50 control unit 11 semiconductor switch 12 detection unit

Claims

1. A semiconductor switch control device comprising a controller that controls a semiconductor switch connected between a power source and a load, wherein the controller: acquires a voltage applied to the semiconductor switch and a current flowing through the semiconductor switch; calculates a resistance value of the semiconductor switch based on the acquired voltage and current; estimates a predicted temperature that the semiconductor switch is expected to reach in the future based on the resistance value; and controls the on / off of the semiconductor switch based on the predicted temperature.

2. A semiconductor switch control device according to claim 1, wherein the controller turns off the semiconductor switch when the predicted temperature to be reached is equal to or higher than a predetermined temperature threshold.

3. A semiconductor switch control device according to claim 1 or 2, wherein the semiconductor switches include an upstream semiconductor switch that is the target of estimation of the predicted temperature to be reached, and a plurality of downstream semiconductor switches that are each connected to wiring that branches off downstream of the upstream semiconductor switch, and the controller controls the on / off of the downstream semiconductor switches based on the predicted temperature to be reached.

4. A semiconductor switch control device according to any one of claims 1 to 3, wherein the controller, when a plurality of the loads are mounted on a vehicle, sets a priority for cutting off the current for each of the plurality of loads in accordance with the state of the vehicle, and controls the on / off of the semiconductor switch so that the current flowing through a load with a higher priority is cut off in preference to a load with a lower priority among the plurality of loads.

5. A semiconductor switch control device according to claim 4, wherein the controller, when the vehicle is in a running state, sets the priority of the load that executes a function necessary to maintain the running state to be lower than the priority of the load that executes a function unrelated to maintaining the running state.

6. A semiconductor switch control device according to claim 4 or 5, wherein the controller, when the vehicle is in a stopped state, sets the priority of the load that executes a function necessary to maintain the stopped state to be lower than the priority of the load that executes a function unrelated to maintaining the stopped state.

7. A semiconductor switch control device according to any one of claims 4 to 6, wherein when there are a plurality of loads with the same priority, the controller controls the on / off of the semiconductor switch so as to cut off the current flowing through the load with a larger current consumption, giving priority to the load with a smaller current consumption.

8. A semiconductor switch control device according to any one of claims 1 to 7, wherein the controller controls the on / off of the semiconductor switch based on the predicted temperature to be reached when the ambient temperature of the semiconductor switch is equal to or higher than a predetermined temperature threshold.

9. A semiconductor switch control device according to any one of claims 1 to 8, wherein the controller acquires the voltages upstream and downstream of the semiconductor switch, respectively.

10. A semiconductor switch control method executed by a controller that controls a semiconductor switch connected between a power supply and a load, wherein the controller: acquires a voltage applied to the semiconductor switch and a current flowing through the semiconductor switch; calculates a resistance value of the semiconductor switch based on the acquired voltage and current; estimates a predicted temperature that the semiconductor switch is expected to reach in the future based on the resistance value; and controls the on / off of the semiconductor switch based on the predicted temperature.

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