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

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

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

[0002] A vehicle control device including a plurality of ECUs connected via an in-vehicle network has been known for some time. For example, a vehicle control device described in Patent Document 1 diagnoses whether an electric parking brake activation switch is stuck on, by monitoring a wake-up signal linked to the state of the activation switch, and diagnosing the switch as stuck on when the wake-up signal remains at a high level for a predetermined period of time.

[0003] International Publication No. 2016 / 137793

[0004] However, the above-described vehicle braking system has a problem in that it takes a long time to diagnose a stuck-on state.

[0005] An object of the present invention is to provide a semiconductor switch control device, a control system, and a semiconductor switch control method that enable a stuck-on diagnosis to be performed in a short period of time.

[0006] The present invention solves the above problem by determining the electrical conduction 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 conduction is occurring downstream of the semiconductor switch.

[0007] According to the present invention, stuck-on can be diagnosed in a short period of time.

[0008] 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 an ECU, a load, a low-voltage battery, and a power supply box, and Fig. 3 is a block diagram of the load, the low-voltage battery, and the power supply box.

[0009] 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 installed in 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 installed in 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.

[0010] 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 DC-DC converter 5 , a drive motor 6 , an inverter 7 , and a high-voltage battery 8 .

[0011] The low-voltage battery 1 is a low-voltage power source for operating a load 2 such as an auxiliary device. 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, such as 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 devices. 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 using power from the high-voltage battery 8. While the vehicle is stopped / parked, the low-voltage battery 1 can be charged using power from the high-voltage battery 8, and the remaining capacity of the low-voltage battery 1 is maintained at or above a predetermined value.

[0012] The power supply box 3 is a supply device that supplies power from the low-voltage battery 1 to the load 2, and includes 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 conduction 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.

[0013] 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, etc. 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.

[0014] The semiconductor switch 12 is connected between the low-voltage battery 1 and the load 2, and switches between electrical conduction and interruption between the low-voltage battery 1 and the load 2. The semiconductor switch 12 may also function as a fuse (semiconductor fuse) that interrupts current between the low-voltage battery 1 and the load 2. For example, an IPD (Intelligent Power Device) having a protection circuit may be used as the load 2 semiconductor switch 12.

[0015] The load 2 is a load that operates using power supplied from the low-voltage battery. The load 2 includes at least on-board devices related to driving, such as wipers, headlights, EPS, etc. The distribution box 4 branches the current path into a path that flows to the low-voltage battery 1 and a path that flows the current of the low-voltage battery 1 to the load 2.

[0016] 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 also 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 coupled to the wheels and is driven by power from the high-voltage battery 8. The inverter 7 is a power converter that converts power supplied from the high-voltage battery 8 and supplies it to the drive motor 6 during power running. The inverter 7 converts power generated by the drive motor 6 and outputs it to the high-voltage battery 8 during regeneration.

[0017] The high-voltage battery 8 includes a plurality of 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 DC-DC converter 5.

[0018] The high-voltage battery 8 is connected to a high-voltage power supply line. The high-voltage line may preferably comprise a pair of power supply 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 interrupting mechanism, such as a relay switch, may have the function of being able to interrupt both the positive and negative pole lines. On the other hand, the line between the low-voltage battery 1 and the load 2 is a low-voltage line, so there is no need to connect an interrupting mechanism for the high-voltage battery 8; instead, a semiconductor switch 12 may be connected.

[0019] Next, the ECUs and power supply box 3 connected to the vehicle network will be described with reference to Figure 2. Figure 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 for diagnosing a stuck-on state using the first ECU 10 corresponds to the "semiconductor switch control method" of the present invention. Furthermore, the ECU system including at least the first ECU 10 corresponds to the "control system" of the present invention.

[0020] The power supply box 3 is electrically connected to the low-voltage battery 1 located upstream, and includes a plurality of detection circuits 11, a plurality of semiconductor switches 12, and a first ECU 10. The first ECU 10 and the second ECU 20 are mounted on the vehicle.

[0021] The first ECU 10 outputs a switching command to the semiconductor switch 12 to switch the semiconductor switch 12 on and off in response to an operation command from a 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 operation command or a command from a vehicle 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. Furthermore, 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 a plurality of loads 2, but the second ECU 20 may be provided for each load 2.

[0022] 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 wheel included in the load 2 maintain an on state and the steering wheel maintain a steerable state regardless of whether or not an operation command is received from the second ECU 20. For example, suppose that the operation command from the second ECU 20 is temporarily interrupted or delayed (signal delay) for some reason while driving at night. In such a case, the first ECU 10 independently outputs an on command to the semiconductor switch 12 even when no operation command is received from the second ECU 20. The first ECU 10 can also independently output an off command to the semiconductor switch 12 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 with the second ECU 20, and the first ECU 10 can become the main controller of the load 2 and control the on and off of the semiconductor switch 12.

[0023] 2, the stuck-on diagnosis of the first ECU 10 will be described. While the first ECU 10 is outputting an OFF command to turn off the semiconductor switch 12, the first ECU 10 determines the conduction state of 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, the first ECU 10 diagnoses that the semiconductor switch 12 is in a stuck-on state (stuck-on present).

[0024] If the detection circuit 11 has a voltage detection terminal, the first ECU 10 may perform a stuck-on diagnosis as follows. The first ECU 10 obtains the voltage downstream 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 the semiconductor switch 12 as being stuck-on if the difference between the voltage upstream 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 and downstream voltages of the semiconductor switch 12 is greater than the voltage difference threshold, the first ECU 10 diagnoses the semiconductor switch 12 as not being stuck-on (no 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. Note that the first ECU 10 does not necessarily have to detect the upstream voltage. If the low-voltage battery 1 has a function in which the charging voltage of the low-voltage battery 1 is automatically restored 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.

[0025] 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 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.

[0026] The voltage difference threshold corresponds to the voltage drop across 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 0 V. The voltage difference threshold is also preferably set according to the capacitance of a 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 includes an element with a capacitive component, such as a capacitor, the downstream voltage of the semiconductor switch 12 may be maintained (does not immediately reach 0 V) ​​by the capacitive component after the semiconductor switch 12 is switched from on to off. The maintained voltage is determined by the capacitance of the capacitor included in the load 2. Therefore, for example, if the load 2 maintains a high downstream voltage after the semiconductor switch 12 is turned off, the voltage difference threshold is set to a value closer to 0 V. As a result, for example, in a scenario 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 from turning off (switching from on to off) to turning on (switching from off to on) of the semiconductor switch 12 is short, the first ECU 10 can diagnose whether the semiconductor switch 12 is stuck on while the semiconductor switch 12 is off. In addition, the first ECU 10 can diagnose whether the semiconductor switch 12 is stuck on without waiting for the charge accumulated in the capacitance component of the load 2 to be discharged.

[0027] When the first ECU 10 receives an operation command from the ECU to operate the load 2, it determines the conduction state downstream of the semiconductor switch 12 and diagnoses whether the semiconductor switch 12 is stuck on 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 to the semiconductor switch 12, and while outputting the OFF command, it determines the conduction state downstream of the semiconductor switch 12 and diagnoses whether the semiconductor switch 12 is stuck on. 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 for a stuck-on state, making it possible to obtain a diagnostic result as quickly as possible when a stuck-on state occurs.

[0028] 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's ACC power is on while the vehicle is parked, the first ECU 10 switches from the sleep state to an active state upon receiving 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, i.e., while outputting an OFF command to the semiconductor switch 12. Furthermore, for example, if an abnormality occurs that makes it impossible to stop the operating load 2 (e.g., 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. In other words, the first ECU 10 performs a stuck-on diagnosis regardless of whether an operation command is input from an ECU.

[0029] The low-voltage battery 1 may have a function (auxiliary charging function) that allows it to be charged by the high-voltage battery 8 when its 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, resulting in the consumption of power from the low-voltage battery 1. Even if the power of the low-voltage battery 1 continues to be consumed, the auxiliary charging function operates, causing the low-voltage battery 1 to be charged. As a result, the remaining capacity of the high-voltage battery 8 decreases. In particular, in the case of an electric vehicle without an engine, if power from the high-voltage battery 8 is consumed due to such a stuck on switch, this may affect the running of the vehicle.

[0030] However, many conventional vehicles do not have a function for auxiliary charging the low-voltage battery 1. When the semiconductor switch 12 is stuck on, the power of the low-voltage battery 1 is consumed, resulting in a state where the low-voltage battery 1 is insufficient in capacity. Therefore, the user can easily notice an abnormality caused by the stuck-on state from a decrease in the capacity of the low-voltage battery 1. On the other hand, when a function for auxiliary charging the low-voltage battery 1 is provided, the low-voltage battery 1 is charged even when the stuck-on state occurs, making it difficult for the user to notice the occurrence of the stuck-on state from a decrease in capacity. By diagnosing the stuck-on state of the semiconductor switch 12 as in this embodiment, it becomes possible to easily notice the occurrence of the stuck-on state even in a system that has a function for auxiliary charging the low-voltage battery 1. In other words, the stuck-on state diagnosis as in this embodiment is highly useful for systems that have a function for auxiliary charging the low-voltage battery 1.

[0031] In this embodiment, the first ECU 10 independently diagnoses the semiconductor switch 12 for stuck-on status even when it does not receive an operation command for the semiconductor switch 12, thereby obtaining a diagnostic result as soon as possible after the occurrence of the stuck-on status. 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 semiconductor switch 12 for stuck-on status before turning on the semiconductor switch 12 and while outputting an OFF command. This increases the number of times the semiconductor switch 12 is diagnosed for stuck-on status.

[0032] The first ECU 10 transmits the diagnostic result of the stuck-on state to an ECU that controls loads such as a warning light and a buzzer. The ECU to which the diagnostic result is transmitted has a load control function for a meter, a buzzer, etc., and a function for switching the power supply to the load on and off, and when it receives the diagnostic result of the 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 a warning light and a buzzer, the first ECU 10 may issue a warning.

[0033] As described above, in the semiconductor switch control device and semiconductor switch control method according to this embodiment, the first ECU 10 determines the conduction 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 conducting, 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 conduction 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.

[0034] If the stuck-on diagnosis takes a long time, 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 stuck-on diagnosis 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 is long. Furthermore, there is a problem that the discharge of the low-voltage battery 1 increases until the stuck-on diagnosis is completed. In this embodiment, such a problem can be solved by diagnosing the stuck-on in a short period of time.

[0035] In this embodiment, the first ECU 10 detects the voltage applied to a voltage detection terminal included in the detection circuit 11 while outputting the OFF command, thereby obtaining the downstream voltage of the semiconductor switch 12, and if 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, the first ECU 10 diagnoses that the semiconductor switch 12 is stuck on. This allows the detection circuit 11 to be diagnosed as stuck on in a short period of time without having a complex circuit configuration.

[0036] In this embodiment, the first ECU 10 receives an operation command to operate the load 2 from the second ECU 20, which controls 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 or not the operation command is input. This increases the number of times the stuck-on diagnosis can be performed, and enables the diagnosis result to be obtained as quickly as possible when a stuck-on occurs.

[0037] 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.

[0038] The first ECU 10 may ensure a diagnostic time for a stuck-on state by estimating the time it takes for the capacitor included in the load 2 to discharge and the voltage downstream of the semiconductor switch 12 to drop. If the capacitance of the capacitor differs for each load 2, the diagnostic time may be set for each load. In other words, if the discharge rate of the charge stored in the capacitance component of the load 2 is slow, the diagnostic time may be set long.

[0039] In this embodiment, the first ECU 10 may transmit the diagnostic result of stuck-on to an ECU that determines whether or not to issue a warning. When the ECU that determines whether or not to issue a warning (hereinafter also referred to as the warning determination ECU) receives the diagnostic result of stuck-on, it stores the diagnostic result in memory and determines whether or not to issue a warning based on the diagnostic content. The diagnostic content is not limited to whether or not there is a stuck-on, but also includes other diagnostic content such as an abnormality in the power supply system. The warning determination ECU then determines whether or not there is a need for a warning based on the diagnostic content. If the diagnostic content does not require a warning, the warning determination ECU does not issue a warning. For example, if the diagnostic result is of high importance, such as stuck-on, the warning determination ECU may issue a warning.

[0040] In this embodiment, the ECU system includes a first ECU 10 and at least one other ECU other than the first ECU 10. The startup 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 being stuck on. The other ECUs have a longer startup time than the first ECU 10. For example, the startup time is longer if the other ECU has a microcomputer with large processing capacity or a system-on-chip with high computing capabilities. Furthermore, if the other ECU is connected to many devices, such as multiple sensors, multiple actuators, and a network bus such as a CAN, the startup time is longer because it takes time to check the interfaces. Furthermore, the startup time is also longer if the other ECU has a large memory (e.g., RAM). An ECU with such a long startup time does not have the diagnostic function for a semiconductor switch 12 being stuck on, which is a function of the first ECU 10. The stuck-on diagnosis is performed after the ECU is started from a sleep state. Therefore, if a stuck-on diagnostic function is provided for an ECU with a long startup time, the time required for the diagnosis is added, and it takes a long time for the ECU to be able to 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 the input timing of the operation command to the operation timing of the load 2 is not that long. The first ECU 10 corresponds to the "first ECU" in the present invention.

[0041] In this embodiment, the ECU system includes a first ECU 10 and at least one other ECU other than the first ECU 10. The first ECU 10 consumes less power than the other ECUs, and the other ECUs do not have a diagnostic function for determining whether a semiconductor switch is stuck on. An ECU with high power consumption is, for example, an ECU with a high microcomputer processing capability. If a stuck-on diagnostic function is provided for an ECU with high power consumption, the power consumption will increase even further. Therefore, in this embodiment, the stuck-on diagnostic function is provided for an ECU with low power consumption. The first ECU 10 corresponds to the "first ECU" in the present invention.

[0042] 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 includes 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 interrupt the circuit between the low-voltage battery 1 and the load 2 in the event of a half-on failure 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.

[0043] The first ECU 10 determines the conduction 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 based on the determination 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 determines the conduction 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 determines that the downstream side of the semiconductor switch 12a is conducting, it diagnoses that the semiconductor switch 12a is stuck on. On the other hand, if the first ECU 10 determines that the downstream side of the semiconductor switch 12a is not conducting, it diagnoses that the semiconductor switch 12a is not stuck on.

[0044] The first ECU 10 also diagnoses whether the semiconductor switch 12b or 12c is stuck on as follows: The first ECU 10 outputs an OFF command to the semiconductor switches 12b and 12c while the semiconductor switch 12a is turned on. While the first ECU 10 is outputting the OFF command to the semiconductor switches 12b and 12c, the first ECU 10 determines the conduction 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, the first ECU 10 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, the first ECU 10 diagnoses that the semiconductor switches 12b and 12c are not stuck on.

[0045] The first ECU 10 performs a stuck-on diagnosis on the upstream semiconductor switch 12a among the semiconductor switches 12a to 12c after the previous vehicle run, and performs a stuck-on diagnosis on the downstream semiconductor switches 12b and 12c among the semiconductor switches 12a to 12c at startup of the first ECU 10.

[0046] 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.

[0047] On the other hand, by performing the stuck-on diagnosis of the upstream semiconductor switch 12a after the previous vehicle run, as in the modified example, the next time the first ECU 10 is started, it is only necessary to perform the stuck-on diagnosis of the downstream semiconductor switches 12b and 12c, thereby shortening the time required for the stuck-on diagnosis when the first ECU 10 is started.

[0048] The "first ECU" in this embodiment corresponds to the "controller" of the present invention.

[0049] REFERENCE SIGNS LIST 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

1. A semiconductor switch control device comprising: 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; and a detection circuit that is connected between the semiconductor switch and the load and detects the voltage and / or current downstream of the semiconductor switch, wherein the controller determines the conductive state of the downstream side of the semiconductor switch based on the detection value of the detection circuit while outputting an off command to turn the semiconductor switch off, and when it determines that the downstream side of the semiconductor switch is conductive, diagnoses the semiconductor switch as being stuck on.

2. A semiconductor switch control device as claimed in claim 1, wherein the detection circuit has a voltage detection terminal, and the controller obtains a downstream voltage, which is the voltage on the downstream side of the semiconductor switch, by detecting a voltage applied to the voltage detection terminal while the OFF command is being output, and diagnoses that the semiconductor switch is stuck on when a difference between an upstream voltage, which is the voltage on the upstream side of the semiconductor switch, and the downstream voltage is equal to or less than a voltage difference threshold.

3. A semiconductor switch control device according to claim 1 or 2, wherein the controller inputs an operation command for operating the load from an ECU which controls the load, outputs a switching command to the semiconductor switch in response to the operation command, and performs a stuck-on diagnosis regardless of whether the operation command has been input.

4. A semiconductor switch control device according to claim 2, wherein the voltage difference threshold is set in accordance with a capacitance of a capacitor included in the load.

5. A semiconductor switch control device according to claim 3, wherein the controller transmits the result of the stuck-on determination to an ECU which determines whether or not a warning should be output.

6. A semiconductor switch control device according to any one of claims 1 to 5, wherein the low-voltage power supply is a battery of 50 volts or less and / or a battery for auxiliary equipment.

7. A control system including a semiconductor switch control device according to any one of claims 1 to 6, comprising a plurality of ECUs including a first ECU and another ECU, wherein the start-up time of the first ECU is shorter than that of the other ECUs, the first ECU has a diagnostic function for determining whether the semiconductor switch is stuck on by the controller, and the other ECUs do not have a diagnostic function for determining whether the semiconductor switch is stuck on.

8. A control system including a semiconductor switch control device according to any one of claims 1 to 6, comprising a plurality of ECUs including a first ECU and another ECU, the first ECU consuming less power than the other ECUs, the first ECU having a diagnostic function for determining whether the semiconductor switch is stuck on by the controller, and the other ECUs not having a diagnostic function for determining whether the semiconductor switch is stuck on.

9. A semiconductor switch control method executed by a controller for diagnosing a semiconductor switch connected between a low-voltage power supply and a load, wherein the controller, while outputting an off command to turn off the semiconductor switch, determines a conductive state of the downstream side of the semiconductor switch based on a detection value of a detection circuit connected between the semiconductor switch and the load and detecting a voltage and / or current on the downstream side of the semiconductor switch, and when it is determined that the downstream side of the semiconductor switch is conductive, determines that the semiconductor switch is stuck on.

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