WO2025017778A1 - Semiconductor switch control device, control system, and semiconductor switch control method - Google Patents

Abstract

This semiconductor switch control device comprises: a controller that outputs a switching command for switching between on and off to a semiconductor switch 12 connected between a low-voltage power supply and a load; and a detection circuit 11 that is connected between the semiconductor switch 12 and a load 2 and detects a voltage and/or a current on the downstream side of the semiconductor switch 12. The controller determines an energization state on the downstream side of the semiconductor switch 12 on the basis of a detection value of the detection circuit 11 during the output of an off command for turning off the semiconductor switch 12, and makes a diagnosis that the semiconductor switch 12 is in an on-fixed state when it is determined that the downstream side of the semiconductor switch 12 is energized.

Description

Semiconductor switch control device, control system, and semiconductor switch control method

The present invention relates to a semiconductor switch control device, a control system, and a semiconductor switch control method.

　Vehicle control devices equipped with multiple ECUs connected via an in-vehicle network have been known for some time. For example, the vehicle control device described in Patent Document 1 diagnoses whether an electric parking brake activation switch is stuck on, monitors a wake-up signal linked to the state of the activation switch, and diagnoses the switch as stuck on when the wake-up signal remains at a high level for a predetermined period of time.

International Publication No. 2016/137793

However, the above vehicle braking system has the problem that it takes a long time to diagnose a stuck-on brake.

The problem that this invention aims to solve is to provide a semiconductor switch control device, control system, and semiconductor switch control method that enable the diagnosis of a stuck-on state in a short period of time.

The present invention solves the above problem by determining the electrical current state downstream of the semiconductor switch based on the detection value of the detection circuit while an OFF command to turn off the semiconductor switch is being output, and diagnosing that the semiconductor switch is stuck ON if it is determined that electrical current is flowing downstream of the semiconductor switch.

The present invention makes it possible to diagnose ON-state fixation in a short period of time.

FIG. 1 is a schematic diagram of a power supply system according to an embodiment of the present invention. FIG. 2 is a block diagram of the ECU, the load, the low-voltage battery, and the power supply box. FIG. 3 is a block diagram of the load, the low voltage battery, and the power box.

FIG. 1 is a schematic diagram of a power supply system (control system) 100 according to this embodiment. In this embodiment, the power supply system is mounted on a vehicle equipped with a high-voltage battery and a low-voltage battery. The vehicle is an electric vehicle that uses power stored in the high-voltage battery to drive a traction motor. Note that the power supply system 100 is not limited to electric vehicles, and may also be mounted on hybrid vehicles equipped with an engine and a motor, or vehicles (ICE vehicles) that obtain power from an engine rather than a motor. In other words, the power supply system 100 is applicable to a variety of powertrains.

As shown in FIG. 1, the power supply system 100 includes a low-voltage battery 1, a load 2, a power supply box 3, a power distribution box 4, a DCDC converter 5, a drive motor 6, an inverter 7, and a high-voltage battery 8.

The low-voltage battery 1 is a low-voltage power source for operating a load 2 such as auxiliary equipment. The rated voltage of the low-voltage battery 1 is lower than the rated voltage of the high-voltage battery 8, and the battery capacity of the low-voltage battery is also lower than the battery capacity of the high-voltage battery 8. The low-voltage battery 1 is a battery of 50 volts or less, for example a 12 V battery. In other words, the low-voltage battery 1 is a battery of 50 volts or less and/or a battery for auxiliary equipment. The low-voltage battery 1 is connected to the load 2 via a semiconductor switch 12. The low-voltage battery 1 is a secondary battery such as a lithium-ion battery or a lead battery. The low-voltage battery 1 can be charged by the power of the high-voltage battery 8. When the vehicle is stopped/parked, the low-voltage battery 1 can be charged by the power of the high-voltage battery 8, and the remaining capacity of the low-voltage battery 1 is maintained at or above a predetermined value.

The power supply box 3 is a supply device that supplies power from the low-voltage battery 1 to the load 2, and has a first ECU 10, a detection circuit 11, and a semiconductor switch 12. The first ECU 10 is an electronic control device that controls the on/off switching of the semiconductor switch 12 and diagnoses whether the semiconductor switch 12 is stuck on. The first ECU 10 determines the electrical current state downstream of the semiconductor switch 12 based on the detection value of the detection circuit 11, and diagnoses whether the semiconductor switch 12 is stuck on based on the determination result.

The detection circuit 11 is connected between the semiconductor switch 12 and the load 2, and detects the voltage and/or current downstream of the semiconductor switch 12. Since the power of the low-voltage battery 1 is output from the semiconductor switch 12 to the load 2, the detection circuit 11 is provided on the output side from the semiconductor switch 12 to the load. The detection circuit 11 has a voltage detection terminal (voltage sensor), a shunt resistor, a current sensor, or the like. The detection circuit 11 is connected to the first ECU 10, and the detection value of the detection circuit (detected voltage and/or detected current) is output to the first ECU 10.

The semiconductor switch 12 is connected between the low-voltage battery 1 and the load 2, and switches between electrical conduction and cut-off between the low-voltage battery 1 and the load 2. The semiconductor switch 12 may function as a fuse (semiconductor fuse) that cuts off the current between the low-voltage battery 1 and the load 2. For example, an IPD (Intelligent Power Device) with a protection circuit may be used as the load 2 semiconductor switch 12.

Load 2 is a load that operates using power supplied from the low-voltage battery. Load 2 includes at least on-board equipment related to driving, such as windshield wipers, headlights, and EPS. Distribution box 4 branches the current path of the flowing current into a path that flows to low-voltage battery 1 and a path that flows the current of low-voltage battery 1 to load 2.

The DCDC converter 5 is connected between the low-voltage battery 1 and the high-voltage battery 8, and converts the output voltage of the high-voltage battery 8 and outputs it as a charging voltage for the low-voltage battery 1. The DCDC converter 5 may convert the output voltage of the high-voltage battery 8 and output the converted voltage to the load 2. The drive motor 6 is connected to the high-voltage battery 8 via an inverter 7. The drive motor 6 is connected to the wheels and is driven by power from the high-voltage battery 8. The inverter 7 is a power converter that converts the power supplied from the high-voltage battery 8 during power running and supplies it to the drive motor 6. During regeneration, the inverter 7 converts the power generated by the drive motor 6 and outputs it to the high-voltage battery 8.

The high-voltage battery 8 comprises multiple secondary batteries (lithium ion batteries) connected in series and/or parallel. The rated voltage and battery capacity of the high-voltage battery 8 are higher than those of the low-voltage battery 1. The high-voltage battery 8 is a drive battery, and is connected to the drive motor 6 via an inverter 7. The high-voltage battery 8 is also connected to the low-voltage battery 1 and the load 2 via a DCDC converter 5.

The high-voltage battery 8 is connected to a high-voltage power line. The high-voltage line may be a pair of power lines connected to the positive and negative poles of the high-voltage battery 8, respectively. A relay switch may be connected to electrically isolate the high-voltage battery 8 from the drive motor 6. The cutoff mechanism using a relay switch or the like may have the function of being able to cut off the positive and negative pole lines, respectively. On the other hand, since the line between the low-voltage battery 1 and the load 2 is a low-voltage line, it is not necessary to connect a cutoff mechanism for the high-voltage battery 8, and a semiconductor switch 12 may be connected instead.

Next, referring to FIG. 2, the ECU and power supply box 3 connected to the vehicle network will be described. FIG. 2 is a block diagram of the low-voltage battery 1, the load 2, the power supply box 3, and the second ECU 20. Note that the device including the first ECU 10 and the detection circuit 11 corresponds to the "semiconductor switch control device" of the present invention, and the method of diagnosing a stuck-on state by the first ECU 10 corresponds to the "semiconductor switch control method" of the present invention. Also, the ECU system including at least the first ECU 10 corresponds to the "control system" of the present invention.

The power supply box 3 is electrically connected to the low-voltage battery 1 located upstream, and has multiple detection circuits 11, multiple semiconductor switches 12, and a first ECU 10. The first ECU 10 and the second ECU 20 are mounted on the vehicle.

The first ECU 10 outputs a switching command to switch the semiconductor switch 12 on and off to the semiconductor switch 12 in response to an operation command from the second ECU 20 having a control function for the load 2. The second ECU 20 is an ECU that controls the control function for the load 2, and transmits an operation command to the first ECU 10 to operate the load 2 in response to a user's operation command or a command on the vehicle's system. The operation command specifies the load 2 to be operated, but does not specify the semiconductor switch 12 to be turned on or off. For example, the first ECU 10 specifies the load 2 to be operated based on the operation command for the load 2 transmitted from the second ECU 20, and outputs an on switching command (on command) to the semiconductor switch 12 connected to the load 2 to be operated. In addition, when the first ECU 10 receives an operation command from the ECU to turn off the operation of the load 2, it outputs an off switching command (off command) to the semiconductor switch 12. In the example of FIG. 2, for convenience, the second ECU 20 is illustrated as controlling multiple loads 2, but a second ECU 20 may be provided for each load 2.

The first ECU 10 can also switch the semiconductor switch 12 on and off without responding to an operation command from the second ECU 20. For example, there are cases where the headlights and steering included in the load 2 maintain an on state if they are headlights, and a steering wheel maintains a steerable state if they are steering, regardless of whether or not there is an operation command from the second ECU 20. For example, suppose that the operation command from the second ECU 20 is temporarily cut off or delayed (signal delay) for some reason while driving at night. In such a case, the first ECU 10 outputs an ON command to the semiconductor switch 12 based on its own judgment, even if no operation command is input from the second ECU 20. The first ECU 10 can also output an OFF command to the semiconductor switch 12 based on its own judgment, without responding to an operation command from the second ECU 20. In other words, the first ECU 10 can separate the master-slave relationship in control between the second ECU 20 and the first ECU 10, and the first ECU 10 becomes the main controller of the load 2 and can control the ON and OFF of the semiconductor switch 12.

Next, the stuck-on diagnosis of the first ECU 10 will be described with reference to FIG. 2. While the first ECU 10 is outputting an OFF command to turn off the semiconductor switch 12, the first ECU 10 determines the current flow state on the downstream side of the semiconductor switch 12 based on the detection value of the detection circuit 11. If the first ECU 10 determines that the downstream side of the semiconductor switch 12 is conducting, it diagnoses that the semiconductor switch 12 is stuck on (stuck on).

If the detection circuit 11 has a voltage detection terminal, the first ECU 10 may perform a stuck-on diagnosis in the following manner. The first ECU 10 obtains the downstream voltage of the semiconductor switch 12 (hereinafter also referred to as the downstream voltage) by detecting the voltage applied to the voltage detection terminal of the detection circuit 11 while outputting an OFF command to the semiconductor switch 12. The first ECU 10 diagnoses that the semiconductor switch 12 is stuck-on when the difference between the upstream voltage of the semiconductor switch 12 (hereinafter also referred to as the upstream voltage) and the downstream voltage is equal to or less than the voltage difference threshold. On the other hand, if the difference between the upstream voltage and the downstream voltage of the semiconductor switch 12 is greater than the voltage difference threshold, the first ECU 10 diagnoses that the semiconductor switch 12 is not stuck-on (not stuck-on). The upstream voltage is the output voltage of the low-voltage battery 1. For example, if a 12V voltage is used for the low-voltage battery 1, the upstream voltage is 12V. It should be noted that the first ECU 10 does not necessarily have to detect the upstream voltage. If the low-voltage battery 1 has a function of automatically recovering its charging voltage by being charged with the power of the high-voltage battery 8 when the remaining capacity of the low-voltage battery 1 becomes low, the upstream voltage may be a fixed voltage.

The upstream voltage may be detected using a detection circuit having a voltage detection terminal (voltage sensor), a shunt resistor, a current sensor, or the like, in order to detect the voltage and/or current upstream of the semiconductor switch 12. The first ECU 10 obtains a power supply voltage from the low-voltage battery 1, and has a function of measuring the power supply voltage (power supply voltage of the first ECU 10). Therefore, the first ECU 10 may use the measured power supply voltage as the upstream voltage.

The voltage difference threshold corresponds to the voltage drop of the semiconductor switch 12 in a stuck-on state, i.e., when the semiconductor switch 12 is short-circuited, and is preferably set to a value close to 0V. The voltage difference threshold is also preferably set according to the capacitance of the capacitor included in the load 2. That is, the voltage difference threshold is preferably set according to the type of load 2. If the load 2 has an element with a capacitive component such as a capacitor, the downstream voltage of the semiconductor switch 12 may be maintained by the capacitive component (does not immediately become 0V) after the semiconductor switch 12 is switched from on to off. The maintained voltage is determined according to the capacitance of the capacitor included in the load 2. Therefore, for example, if the load 2 maintains the downstream voltage at a high voltage after the semiconductor switch 12 is turned off, the voltage difference threshold is set to a value closer to 0V. This allows the first ECU 10 to diagnose whether the semiconductor switch 12 is stuck on while it is off, for example, in a scene where the semiconductor switch 12 switches from on to off and then from off to on in a short time, i.e., when the time between turning off (switching from on to off) and turning on (switching from off to on) the semiconductor switch 12 is short. Also, it is possible to diagnose whether the semiconductor switch 12 is stuck on without waiting for the charge stored in the capacitance component of the load 2 to be discharged.

When the first ECU 10 receives an operation command from the ECU to operate the load 2, it determines the power-on state downstream of the semiconductor switch 12 and diagnoses the stuck-on state before outputting an ON command for the semiconductor switch 12. When the first ECU 10 receives a stop command from the ECU to stop the operation of the load 2, it outputs an OFF command for the semiconductor switch 12 to the semiconductor switch 12, and while the OFF command is being output, it determines the power-on state downstream of the semiconductor switch 12 and diagnoses the stuck-on state. In other words, even when an operation command is input, the first ECU 10 performs a stuck-on diagnosis in addition to controlling the semiconductor switch 12 corresponding to the operation command. This increases the number of times the semiconductor switch 12 is diagnosed as being stuck-on, making it possible to obtain a diagnosis result as quickly as possible when a stuck-on state occurs.

The first ECU 10 also performs a stuck-on diagnosis at its own timing even when it does not receive an operation command from the second ECU 20. For example, when the first ECU 10 is in a sleep state, such as when the vehicle is parked and the ACC power of the vehicle is on, the first ECU 10 goes from a sleep state to a wake-up state when it receives a command to operate the load 2, and turns on the semiconductor switch 12 in response to the command. At this time, the first ECU 10 diagnoses a stuck-on state before outputting an ON command to the semiconductor switch 12, that is, while outputting an OFF command to the semiconductor switch 12. Also, for example, if an abnormality occurs that makes it impossible to stop the load 2 in operation (for example, an abnormality in which the headlights included in the load 2 remain on and cannot be turned off), the first ECU 10 may diagnose a stuck-on state while outputting an OFF command to the semiconductor switch 12, even if the second ECU 20 is in a sleep state. That is, the first ECU 10 performs a stuck-on diagnosis regardless of whether an operation command is input from the ECU.

The low-voltage battery 1 may have a function (auxiliary charging function) to be charged by the high-voltage battery 8 when the remaining capacity becomes low. Therefore, if the semiconductor switch 12 is stuck on, the low-voltage battery 1 and the load 2 cannot be electrically disconnected, and the power of the low-voltage battery 1 is consumed. Even if the power of the low-voltage battery 1 continues to be consumed, the auxiliary charging function operates and the low-voltage battery 1 is charged. As a result, the remaining capacity of the high-voltage battery 8 decreases. In particular, in the case of an electric vehicle that does not have an engine, if the power of the high-voltage battery 8 is consumed due to such a stuck on switch, this may affect the running of the vehicle.

However, many vehicles up to now do not have a function for recharging the low-voltage battery 1, and when the semiconductor switch 12 is stuck on, the power of the low-voltage battery 1 is consumed, resulting in a state in which the capacity of the low-voltage battery 1 is insufficient. Therefore, the user can easily notice the abnormality caused by the stuck on from the decrease in the capacity of the low-voltage battery 1. On the other hand, if a function for recharging the low-voltage battery 1 is provided, even if the stuck on occurs, the low-voltage battery 1 is charged, so the user does not easily notice the occurrence of the stuck on from the decrease in capacity. By diagnosing the stuck on of the semiconductor switch 12 as in this embodiment, it becomes possible to easily notice the occurrence of the stuck on even if the vehicle has a function for recharging the low-voltage battery 1. In other words, the diagnosis of the stuck on as in this embodiment is highly useful for a system with a function for recharging the low-voltage battery 1.

In this embodiment, the first ECU 10 diagnoses the stuck-on state by its own judgment even when it does not receive an operation command for the semiconductor switch 12, so that a diagnosis result can be obtained as soon as possible when the stuck-on state occurs. Furthermore, when the first ECU 10 receives an operation command for the load 2 from a source other than the second ECU 20, it diagnoses the stuck-on state before turning on the semiconductor switch 12 and while outputting an OFF command. This makes it possible to increase the number of times the semiconductor switch 12 is diagnosed as stuck-on.

The first ECU 10 transmits the diagnosis result of the stuck-on state to an ECU that controls loads such as warning lights and buzzers. The ECU to which the diagnosis result is transmitted has a load control function for meters, buzzers, etc., and a function for switching the power supply to the load on and off, and when it receives a diagnosis result of a stuck-on state from the first ECU 10, it issues a warning using a warning light in the meter or a buzzer. Note that if the first ECU 10 has a function for controlling loads such as warning lights and buzzers, the first ECU 10 may also issue a warning.

As described above, in the semiconductor switch control device and semiconductor switch control method according to this embodiment, the first ECU 10 determines the current flow state downstream of the semiconductor switch 12 based on the detection value of the detection circuit 11 while outputting an OFF command to turn off the semiconductor switch 12, and if it determines that the downstream side of the semiconductor switch 12 is current flowing, it diagnoses that the semiconductor switch 12 is stuck on. In other words, in this embodiment, the stuck on state is diagnosed using the determination result of the current flow state downstream of the semiconductor switch 12, so communication with the load 2 is not required. Therefore, the stuck on state can be diagnosed in a short period of time.

If the stuck-on diagnosis time is long, normal control and functions cannot be operated until the diagnosis is completed, resulting in a long wait time. For example, if the semiconductor switch control device according to this embodiment is applied to a vehicle power supply system, the functions of the auxiliary devices cannot be operated by the low-voltage battery 1 until the diagnosis of the stuck-on of the semiconductor switch 12 is completed. Therefore, if the stuck-on diagnosis time is long, there is a problem that the wait time before the auxiliary devices can be operated becomes long. Furthermore, there is also a problem that the discharge of the low-voltage battery 1 increases until the diagnosis of the stuck-on is completed. In this embodiment, such problems can be solved because the stuck-on can be diagnosed in a short period of time.

In addition, in this embodiment, the first ECU 10 obtains the downstream voltage of the semiconductor switch 12 by detecting the voltage applied to the voltage detection terminal included in the detection circuit 11 while outputting the OFF command, and diagnoses that the semiconductor switch 12 is stuck on when the difference between the upstream voltage and the downstream voltage of the semiconductor switch 12 is equal to or less than the voltage difference threshold. This makes it possible to diagnose the semiconductor switch 12 as stuck on in a short period of time, without making the detection circuit 11 have a complex circuit configuration.

In addition, in this embodiment, the first ECU 10 inputs an operation command to operate the load 2 from the second ECU 20, which is responsible for controlling the load 2, outputs a switching command to the semiconductor switch 12 in response to the operation command, and performs a stuck-on diagnosis regardless of whether an operation command is input. This makes it possible to increase the number of times the stuck-on diagnosis is performed, and to obtain a diagnosis result as soon as possible when a stuck-on occurs.

In addition, in this embodiment, the voltage difference threshold is set according to the capacitance of the capacitor included in the load 2. This makes it possible to diagnose a stuck-on state without waiting for the charge accumulated in the capacitance component of the load 2 to be discharged.

The first ECU 10 may ensure a time for diagnosing the stuck-on state by estimating the time it takes for the capacitor included in the load 2 to discharge and for the voltage downstream of the semiconductor switch 12 to drop. If the capacitance of the capacitor differs for each load 2, the diagnosis time may be set for each load. In other words, if the discharge rate of the charge stored in the capacitive component of the load 2 is slow, the diagnosis time may be set long.

In this embodiment, the first ECU 10 may transmit the diagnosis result of stuck on to an ECU that determines whether or not to output a warning. When the ECU that determines whether or not to output a warning (hereinafter also referred to as the warning determination ECU) receives the diagnosis result of stuck on, it stores the diagnosis result in memory and determines whether or not to output a warning depending on the diagnosis content. The diagnosis content is not limited to whether or not the switch is stuck on, but also includes other diagnosis content such as abnormalities in the power supply system. The warning determination ECU then determines whether or not to output a warning depending on the diagnosis content. If the diagnosis content does not require a warning, the warning determination ECU does not issue a warning. For example, if the diagnosis result is of high importance, such as stuck on, the warning determination ECU may issue a warning.

In this embodiment, the ECU system includes the first ECU 10 and at least one other ECU other than the first ECU 10, the start-up time of the first ECU 10 is shorter than that of the other ECUs, and the other ECUs do not have a diagnostic function for a semiconductor switch stuck on. The other ECUs are ECUs with a longer start-up time than the first ECU 10. For example, if the other ECU has a microcomputer with a large processing capacity or a system-on-chip with a high calculation function, the start-up time will be longer. In addition, if the other ECU is connected to many devices such as multiple sensors, multiple actuators, and a network bus such as CAN, the start-up time will be longer because it takes time to check the interface. Furthermore, if the other ECU has a large capacity memory (e.g. RAM), the start-up time will also be longer. An ECU with such a long start-up time does not have the diagnostic function for a semiconductor switch 12 stuck on, which is a function of the first ECU 10. The stuck on diagnosis is performed after the ECU is started up from the sleep state. Therefore, if a stuck-on diagnostic function is provided for an ECU with a long startup time, time is added for the diagnosis, and it takes time for the ECU to reach a state where it can control the controlled object. Even if an ECU with a short startup time such as the first ECU 10 has a stuck-on diagnostic function, the time from inputting an operation command to operating the load 2 is not that long. The first ECU 10 corresponds to the "first ECU" of the present invention.

In addition, in this embodiment, the ECU system includes a first ECU 10 and at least one other ECU other than the first ECU 10, the power consumption of the first ECU 10 is smaller than that of the other ECUs, and the other ECUs do not have a diagnostic function for a semiconductor switch stuck on. An ECU with high power consumption is, for example, an ECU with a microcomputer with high computational processing power. If a stuck on diagnostic function is provided for an ECU with high power consumption, the power consumption will become even larger. Therefore, in this embodiment, an ECU with low power consumption is provided with a stuck on diagnostic function. Note that the first ECU 10 corresponds to the "first ECU" in the present invention.

As a modification of this embodiment, the power supply system 100 may have multiple semiconductor switches 12a to 12c connected in series between the low-voltage battery 1 and the load 2. FIG. 3 is a block diagram of the low-voltage battery 1, the load 2, and the power supply box 3. The power supply box 3 has a first ECU 10, detection circuits 11a to 11c, and semiconductor switches 12a to 12c. The semiconductor switch 12a and the semiconductor switch 12b are connected in series, and the semiconductor switch 12a and the semiconductor switch 12c are connected in series. The semiconductor switch 12a is provided to cut off the circuit between the low-voltage battery 1 and the load 2 when a half-on failure occurs in the semiconductor switch 12b or the semiconductor switch 12c. The detection circuits 11a to 11c are connected downstream of the multiple semiconductor switches 12a to 12c, respectively. The semiconductor switch 12a may be an FET, and the semiconductor switches 12b and 12c may be IPDs.

The first ECU 10 judges the power-on state of the downstream side of the semiconductor switches 12a to 12c based on the detection values of the detection circuits 11a to 11c, and diagnoses whether the semiconductor switches 12a to 12c are stuck on or not based on the judgment result. The first ECU 10 performs a stuck-on diagnosis of the upstream semiconductor switch 12a in the following manner. The first ECU 10 outputs an OFF command to the semiconductor switches 12a to 12c. While outputting the OFF command to the semiconductor switches 12a to 12c, the first ECU 10 judges the power-on state of the downstream side of the semiconductor switch 12a based on the detection value of the detection circuit 11a. If the first ECU 10 judges that the downstream side of the semiconductor switch 12a is powered on, it diagnoses that the semiconductor switch 12a is stuck on. On the other hand, if the first ECU 10 judges that the downstream side of the semiconductor switch 12a is not powered on, it diagnoses that the semiconductor switch 12a is not stuck on.

The first ECU 10 also performs a stuck-on diagnosis of the semiconductor switches 12b and 12c in the following manner. With the semiconductor switch 12a in the on state, the first ECU 10 outputs an OFF command to the semiconductor switches 12b and 12c. While outputting the OFF command to the semiconductor switches 12b and 12c, the first ECU 10 determines the current-carrying state of the downstream sides of the semiconductor switches 12b and 12c based on the detection values of the detection circuits 11b and 11c. If the first ECU 10 determines that the downstream sides of the semiconductor switches 12b and 12c are conducting, it diagnoses that the semiconductor switches 12b and 12c are stuck-on. On the other hand, if the first ECU 10 determines that the downstream sides of the semiconductor switches 12b and 12c are not conducting, it diagnoses that the semiconductor switches 12b and 12c are not stuck-on.

The first ECU 10 performs a stuck-on diagnosis of the upstream semiconductor switch 12a among the semiconductor switches 12a to 12c after the previous vehicle run. The first ECU 10 performs a stuck-on diagnosis of the downstream semiconductor switches 12b and 12c among the semiconductor switches 12a to 12c when the first ECU 10 is started.

Unlike the modified example, if the stuck-on diagnosis of the upstream semiconductor switch 12a and the stuck-on diagnosis of the downstream semiconductor switches 12b and 12c are performed in a single diagnostic flow, the diagnostic time will be long. For example, when the vehicle starts traveling, if the stuck-on diagnosis of the upstream semiconductor switch 12a and the downstream semiconductor switches 12b and 12c is performed after the first ECU 10 is started, the diagnostic time will be approximately twice as long as the time required to diagnose only one of the upstream semiconductor switch 12a and the downstream semiconductor switches 12b and 12c. In other words, the diagnostic time after the first ECU 10 is started will be approximately twice as long.

On the other hand, as in the modified example, by performing a stuck-on diagnosis of the upstream semiconductor switch 12a after the previous vehicle run, the next time the first ECU 10 is started, it is only necessary to perform a stuck-on diagnosis of the downstream semiconductor switches 12b and 12c. Therefore, the time required for diagnosing a stuck-on state when the first ECU 10 is started can be shortened.

The "first ECU" in this embodiment corresponds to the "controller" of the present invention.

1 Low voltage battery 2 Load 10 First ECU
11 Detection circuit 12 Semiconductor switch 30 Power supply box 100 Power supply system (control system)

Claims (9)

a controller that outputs a switching command to switch a semiconductor switch connected between a low-voltage power supply and a load between on and off;
a detection circuit connected between the semiconductor switch and the load to detect a voltage and/or a current downstream of the semiconductor switch;
The controller:
determining a conduction state of the downstream side of the semiconductor switch based on a detection value of the detection circuit while an OFF command to turn off the semiconductor switch is being output;
The semiconductor switch control device diagnoses the semiconductor switch as being stuck on when it is determined that the downstream side of the semiconductor switch is conducting. 2. The semiconductor switch control device according to claim 1,
the detection circuit includes a voltage detection terminal;
The controller:
A downstream voltage, which is a voltage on a downstream side of the semiconductor switch, is obtained by detecting a voltage applied to the voltage detection terminal during the output of the OFF command;
The semiconductor switch control device diagnoses the semiconductor switch as being stuck on when a difference between an upstream voltage, which is a voltage on the upstream side of the semiconductor switch, and the downstream voltage is equal to or smaller than a voltage difference threshold. 3. The semiconductor switch control device according to claim 1,
The controller:
An operation command for operating the load is input from an ECU that controls the load;
outputting a switching command to the semiconductor switch in response to the operation command;
A semiconductor switch control device that performs the stuck-on diagnosis regardless of whether the operation command is input or not. 3. The semiconductor switch control device according to claim 2,
The voltage difference threshold is set according to the capacitance of a capacitor included in the load. 4. The semiconductor switch control device according to claim 3,
The controller transmits the result of the stuck-on determination to an ECU that determines whether or not to output a warning. The semiconductor switch control device according to any one of claims 1 to 5,
The semiconductor switch control device, wherein the low voltage power supply is a battery of 50 volts or less and/or a battery for auxiliary equipment. A control system including the semiconductor switch control device according to any one of claims 1 to 6,
A plurality of ECUs including a first ECU and another ECU are provided,
The start-up time of the one ECU is shorter than that of the other ECU,
The one ECU has a function of diagnosing whether the semiconductor switch is stuck on by the controller,
The other ECU is a control system that does not have a diagnostic function for determining whether the semiconductor switch is stuck on. A control system including the semiconductor switch control device according to any one of claims 1 to 6,
A plurality of ECUs including a first ECU and another ECU are provided,
The power consumption of the one ECU is smaller than that of the other ECU,
The one ECU has a function of diagnosing whether the semiconductor switch is stuck on by the controller,
The other ECU is a control system that does not have a diagnostic function for determining whether the semiconductor switch is stuck on. A semiconductor switch control method for diagnosing a semiconductor switch connected between a low-voltage power supply and a load, the method comprising:
The controller:
determining a conduction state of the downstream side of the semiconductor switch based on a detection value of a detection circuit that is connected between the semiconductor switch and the load and detects a voltage and/or a current of the downstream side of the semiconductor switch while an OFF command for turning off the semiconductor switch is being output;
The semiconductor switch control method further comprises determining that the semiconductor switch is stuck on when it is determined that the downstream side of the semiconductor switch is conducting.

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