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

Technical Field

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

Background Art

[0002] Conventionally, a vehicle control device including a plurality of ECUs connected by an in-vehicle network is known. For example, the vehicle control device described in Patent Document 1 diagnoses the presence or absence of on-sticking of an operation switch of an electric parking brake, monitors a wake-up signal linked to the state of the operation switch, and diagnoses on-sticking when the wake-up signal continues at a high level for a predetermined time.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, the above vehicle control device has a problem that the diagnosis time of on-sticking is long.

[0005] The problem to be solved by the present invention is to provide a semiconductor switch control device, a control system, and a semiconductor switch control method that enable diagnosis of on-sticking in a short period of time.

Means for Solving the Problems

[0006] The present invention solves the above problems by diagnosing that the semiconductor switch is in an on-sticking state when, during the output of an off command for turning off the semiconductor switch, based on the detection value of a detection circuit, it is determined that the energization state on the downstream side of the semiconductor switch is energized. [Effects of the Invention]

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

[0008] [Figure 1] Figure 1 is a schematic diagram of the power supply system according to an embodiment of the present invention. [Figure 2] Figure 2 is a block diagram of the ECU, load, low-voltage battery, and power box. [Figure 3] Figure 3 is a block diagram of the load, low-voltage battery, and power box. [Modes for carrying out the invention]

[0009] Figure 1 is a schematic diagram of the configuration of the 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 the power stored in the high-voltage battery to drive the traction motor. Note that the power supply system 100 is not limited to electric vehicles, but may also be installed in hybrid vehicles equipped with an engine and a motor, or vehicles that obtain power from an engine rather than a motor (ICE vehicles). In other words, the power supply system 100 is applicable to various powertrains.

[0010] As shown in Figure 1, the power supply system 100 includes a low-voltage battery 1, a load 2, a power supply box 3, a distribution box 4, a DC-DC converter 5, a drive motor 6, an inverter 7, and a high-voltage battery 8.

[0011] Low-voltage battery 1 is a low-voltage power supply for operating load 2 such as auxiliary equipment. The rated voltage of low-voltage battery 1 is lower than the rated voltage of high-voltage battery 8. 1The battery capacity of the low-voltage battery 1 is also lower than that of the high-voltage battery 8. The low-voltage battery 1 is a battery of 50 volts or less, for example, a 12V battery. In other words, the low-voltage battery 1 is a battery of 50 volts or less, and / or an auxiliary battery. 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-acid battery. The low-voltage battery 1 can be charged by the power of the high-voltage battery 8. While 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 above a predetermined value.

[0012] The power box 3 is a power 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 for controlling the on / off switching of the semiconductor switch 12 and diagnosing whether the semiconductor switch 12 is stuck in the on position. Based on the detection value of the detection circuit 11, the first ECU 10 determines the energized state downstream of the semiconductor switch 12, and based on the determination result, diagnoses whether the semiconductor switch 12 is stuck in the on position.

[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 detects the voltage and / or current downstream of the semiconductor switch 12. 2 It is provided on the output side to the detection circuit 11. The detection circuit 11 has a voltage detection terminal (voltage sensor), a shunt resistor, or a current sensor, etc. The detection circuit 11 is connected to the first ECU 10, and the detection circuit 11 The detected values ​​(detected voltage and / or detected current) are output to the first ECU10.

[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 the current between the low-voltage battery 1 and the load 2. halfThe conductor switch 12 may be, for example, an IPD (Intelligent Power Device) with a protection circuit.

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

[0016] The DC-DC 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 to output as the charging voltage for the low-voltage battery 1. The DC-DC 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 connected to the wheels and is driven by the power of the high-voltage battery 8. The inverter 7 is a power converter that converts the power supplied from the high-voltage battery 8 and supplies it to the drive motor 6 during powering. During regeneration, the inverter 7 converts the power generated by the drive motor 6 and outputs it to the high-voltage battery 8.

[0017] 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 the inverter 7. The high-voltage battery 8 is also connected to the low-voltage battery 1 and load 2 via the DC-DC converter 5.

[0018] Incidentally, the high-voltage battery 8 is connected to a power line in the high-voltage system. A pair of power lines respectively connected to the positive and negative electrodes of the high-voltage battery 8 may be used for the high-voltage system line. Further, a relay switch may be connected to electrically disconnect the high-voltage battery 8 and the drive motor 6. Also, the cutoff mechanism using the relay switch or the like may have a function capable of cutting off the positive-side line and the negative-side line respectively. On the other hand, since the line between the low-voltage battery 1 and the load 2 is a low-voltage system line, it is not necessary to connect a cutoff mechanism for the high-voltage battery 8, and a semiconductor switch 12 may be connected.

[0019] Next, referring to FIG. 2, the ECU connected to the vehicle network and the power box 3 will be described. FIG. 2 is a block diagram of the low-voltage battery 1, the load 2, the power 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 the on-sticking 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.

[0020] The power box 3 is electrically connected to the low-voltage battery 1 located upstream, and has a plurality of detection circuits 11, a plurality of semiconductor switches 12, and the 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 for switching on and off the semiconductor switch 12 to the semiconductor switch 12 according to an operation command from the second ECU 20 having the control function of the load 2. The second ECU 20 is an ECU in charge of the control function of the load 2, and transmits an operation command for operating the load 2 to the first ECU 10 according to a user operation command or a command on the vehicle system. In the operation command, the load 2 to be the operation target is specified, but the semiconductor switch 12 to be turned on or off is not specified. For example, the first ECU 10 specifies the load 2 to be the operation target according to the operation command of 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 that is the operation target. Further, when the first ECU 10 inputs an operation command for turning off the operation of the load 2 from the ECU, the first ECU 10 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] Also, the first ECU 10 can also switch on and off the semiconductor switch 12 without responding to the operation command from the second ECU 20. For example, there are cases where the headlights and steering included in the load 2 maintain the on state for the headlights and the steerable state for the steering regardless of the presence or absence of an operation command from the second ECU 20. For example, during night driving, assume that the operation command from the second ECU 20 is temporarily interrupted or the operation command is delayed (signal delay) for some reason. In such a case, the first ECU 10 outputs an on command to the semiconductor switch 12 even when no operation command is input from the second ECU 20 based on its own determination. Also, the first ECU 10 can output an off command to the semiconductor switch 12 based on its own judgment without responding to the operation command from the second ECU 20. That is, the first ECU 10 can disconnect the master-slave relationship in control with the second ECU 20, and the first ECU 10 can become the control subject of the load 2 and control the on and off of the semiconductor switch 12.

[0023] Next, referring to Figure 2, the ON-fixation diagnosis of the first ECU 10 will be explained. While the first ECU 10 is outputting an OFF command to turn off the semiconductor switch 12, it determines the energized state of the downstream side of the semiconductor switch 12 based on the detected value of the detection circuit 11. If the first ECU 10 determines that the downstream side of the semiconductor switch 12 is energized, it diagnoses that the semiconductor switch 12 is in an ON-fixed state (ON-fixed).

[0024] If the detection circuit 11 is equipped with a voltage detection terminal, the first ECU 10 may perform an ON-lock diagnosis in the following manner. 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 an OFF command is being output to the semiconductor switch 12. The first ECU 10 diagnoses that the semiconductor switch 12 is in an ON-lock state if the difference between the upstream voltage (hereinafter also referred to as the upstream voltage) and the downstream voltage of the semiconductor switch 12 is less than or equal to a 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 in an ON-lock state (no ON-lock). 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 will be 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 that automatically restores its charging voltage by charging it with the power of the high-voltage battery 8 when its remaining capacity becomes low, the upstream voltage may be set to a fixed voltage.

[0025] The upstream voltage may be detected using a detection circuit that includes a voltage detection terminal (voltage sensor), shunt resistor, or current sensor to detect the voltage and / or current upstream of the semiconductor switch 12. Furthermore, the first ECU 10 obtains a power supply voltage from the low-voltage battery 1 and has a function to measure this power supply voltage (the 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 when it is in the ON-fixed state, i.e., in the short-circuit state, and should be set to a value close to 0V. Furthermore, the voltage difference threshold should be set according to the capacitance of the capacitor included in the load 2. In other words, the voltage difference threshold should be set according to the type of load 2. If the load 2 has an element with a capacitive component, such as a capacitor, after switching the semiconductor switch 12 from ON to OFF, the downstream voltage of the semiconductor switch 12 may be maintained by the capacitive component (it will not immediately become 0V). The voltage that is maintained is determined according to 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 should be set to a value closer to 0V. This allows the first ECU 10 to diagnose ON-locking of semiconductor switch 12 during the OFF period, for example, in a scenario where semiconductor switch 12 switches from ON to OFF and then quickly switches from OFF to ON, that is, when the time from turn-off (switching from ON to OFF) to turn-on (switching from OFF to ON) of semiconductor switch 12 is short. Furthermore, it can diagnose ON-locking without waiting for the charge accumulated in the capacitive component of load 2 to discharge.

[0027] When the first ECU 10 receives an operation command from the ECU to operate load 2, it determines the energized state downstream of semiconductor switch 12 and diagnoses ON-lock before outputting an ON command for semiconductor switch 12. Furthermore, when the first ECU 10 receives a stop command from the ECU to stop the operation of load 2, it outputs an OFF command to semiconductor switch 12, and while the OFF command is output, it determines the energized state downstream of semiconductor switch 12 and diagnoses ON-lock. In other words, even when an operation command is input, the first ECU 10 performs ON-lock diagnosis in addition to controlling the semiconductor switch 12 corresponding to the operation command. This increases the number of ON-lock diagnoses for semiconductor switch 12, allowing for the earliest possible diagnosis when ON-lock occurs.

[0028] Furthermore, even if the first ECU 10 does not receive an operation command from the second ECU 20, it performs an ON-fixed diagnosis at its own timing. For example, when the first ECU 10 is in a sleep state, such as when the vehicle is parked and the vehicle's ACC power is on, when the first ECU 10 receives a command to operate load 2, it switches from the sleep state to the wake state and turns on the semiconductor switch 12 in accordance with the command. At this time, the first ECU 10 diagnoses ON-fixed before outputting an ON command to the semiconductor switch 12, that is, while the semiconductor switch 12 is outputting an OFF command. Also, for example, if an abnormality occurs that prevents the operation of load 2 from being stopped (for example, an abnormality where the headlights included in load 2 remain on and cannot be turned off), the first ECU 10 may diagnose ON-fixed while the semiconductor switch 12 is outputting an OFF command, even if the second ECU 20 is in a sleep state. In other words, the first ECU 10 diagnoses ON-fixed regardless of whether or not it receives an operation command from the ECU.

[0029] The low-voltage battery 1 may have a function (supplementary 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 gets stuck in the "on" position, it becomes impossible to electrically disconnect the low-voltage battery 1 from the load 2, causing the power of the low-voltage battery 1 to be consumed. Furthermore, even when the power of the low-voltage battery 1 is continuously being consumed, the supplementary charging function activates, 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 electric vehicles that do not have an engine, if the power of the high-voltage battery 8 is consumed due to such an "on" position, it may affect the vehicle's operation.

[0030] Incidentally, many conventional vehicles do not have a supplemental charging function for the low-voltage battery 1. When the semiconductor switch 12 gets stuck in the "on" position, the power of the low-voltage battery 1 is consumed, resulting in a state where the capacity of the low-voltage battery 1 is insufficient. Therefore, users could easily notice the abnormality caused by the on-fixation from the decrease in the capacity of the low-voltage battery 1. On the other hand, if a supplemental charging function for the low-voltage battery 1 is provided, the low-voltage battery 1 will be charged even if on-fixation occurs, so users would have difficulty noticing the on-fixation from the decrease in capacity. As in this embodiment, by diagnosing the on-fixation of the semiconductor switch 12, it becomes possible to easily notice the occurrence of on-fixation even when the low-voltage battery 1 has a supplemental charging function. In other words, diagnosing on-fixation as in this embodiment is highly useful for systems that have a supplemental charging function for the low-voltage battery 1.

[0031] In this embodiment, the first ECU 10 diagnoses ON-locking by its own determination even when it does not receive an operation command for the semiconductor switch 12, so that it can obtain a diagnosis result as quickly as possible when ON-locking occurs. Furthermore, when the first ECU 10 receives an operation command for load 2 from a source other than the second ECU 20, it diagnoses ON-locking before turning on the semiconductor switch 12 and while the OFF command is being output. This increases the number of times ON-locking diagnoses for the semiconductor switch 12 can be performed.

[0032] The first ECU 10 transmits the diagnosis result of the "on" sticking to an ECU that controls the load, such as a warning light or buzzer. The ECU to which the diagnosis result is transmitted has load control functions such as a meter or buzzer, and a function to switch the power supply to the load on and off. When the first ECU 10 receives the diagnosis result of the "on" sticking, it issues a warning using a warning light or buzzer in the meter. If the first ECU 10 has a function to control the load, such as a warning light or 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 energized state of the downstream side of the semiconductor switch 12 based on the detection value of the detection circuit 11 while an off command is output to turn off the semiconductor switch 12. If it determines that the downstream side of the semiconductor switch 12 is energized, it diagnoses that the semiconductor switch 12 is stuck in the ON state. In other words, in this embodiment, since the ON state is diagnosed using the determination result of the energized state downstream of the semiconductor switch 12, communication with the load 2, etc., is unnecessary. Therefore, the ON state can be diagnosed in a short period of time.

[0034] If the diagnostic time for ON-locking is long, normal control and functions cannot operate until the diagnosis is complete, resulting in a long waiting time. For example, when the semiconductor switch control device according to this embodiment is applied to a vehicle power supply system, the functions of auxiliary equipment cannot be operated by the low-voltage battery 1 until the diagnosis of ON-locking of the semiconductor switch 12 is complete. Therefore, if the diagnostic time for ON-locking is long, there is a problem that the waiting time before auxiliary equipment can be operated will be long. Furthermore, there is also the problem that the discharge of the low-voltage battery 1 increases until the diagnosis of ON-locking is complete. In this embodiment, ON-locking can be diagnosed in a short period of time, so these problems can be solved.

[0035] 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 an off command is output. If the difference between the upstream voltage and the downstream voltage of the semiconductor switch 12 is less than or equal to a voltage difference threshold, it diagnoses that the semiconductor switch 12 is stuck in the on state. This allows for quick diagnosis of on-fixation without requiring a complex circuit configuration for the detection circuit 11.

[0036] In this embodiment, the first ECU 10 receives an operation command to operate load 2 from the second ECU 20, which controls load 2, and outputs a switching command to the semiconductor switch 12 in response to the operation command. Regardless of whether an operation command is input or not, the first ECU 10 diagnoses on-fixed state. This increases the number of on-fixed state diagnoses and allows for obtaining a diagnosis result as quickly as possible when on-fixed state occurs.

[0037] In this embodiment, the voltage difference threshold is set according to the capacitance of the capacitor included in the load 2. This allows for diagnosis of on-locking without waiting for the discharge of the charge accumulated in the capacitive component of the load 2.

[0038] Furthermore, the first ECU 10 may ensure a diagnostic time for ON-lock by considering the time it takes for the capacitor included in 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 diagnostic time may be set for each load. In other words, if the discharge rate of the charge accumulated in the capacitive component of load 2 is slow, the diagnostic time may be set to be longer.

[0039] In this embodiment, the first ECU 10 may transmit the ON-fixed diagnosis result 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 ON-fixed diagnosis result, it stores the diagnosis result in memory and determines whether or not to issue a warning according to the diagnosis content. The diagnosis content is not limited to whether or not there is an ON-fixed condition, but also includes other diagnosis content such as a power supply system abnormality. The warning determination ECU then determines whether or not a warning is necessary according to 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 ON-fixed condition, 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 besides the first ECU 10, the startup time of the first ECU 10 is shorter than that of the other ECUs, and the other ECUs are semiconductor switches 12The first ECU does not have a diagnostic function for ON-locking. Other ECUs have longer startup times than the first ECU 10. For example, if another ECU has a microcomputer with high processing power or a system-on-a-chip with high computing power, the startup time will be longer. Also, if another ECU is connected to many devices such as multiple sensors, multiple actuators, and network buses such as CAN, the startup time will be longer because it takes time to check the interfaces. Furthermore, if another ECU has a large amount of memory (e.g., RAM), the startup time will also be longer. ECUs with such long startup times do not have the diagnostic function for ON-locking of the semiconductor switch 12, which is a function of the first ECU 10. ON-locking diagnosis is performed after the ECU is started from sleep state. Therefore, if an ON-locking diagnostic function is provided for an ECU with a long startup time, the time required for diagnosis will be added, and it will take longer 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 an on-fixed diagnostic function, the time from the input timing of the operation command to the operation timing of load 2 is not very long. Note that the first ECU 10 corresponds to "one ECU" in the present invention.

[0041] In this embodiment, the ECU system includes a first ECU 10 and at least one other ECU besides the first ECU 10, the power consumption of the first ECU 10 is lower than that of the other ECUs, and the other ECUs are semiconductor switches. 12 It does not have a diagnostic function for ON-locking. ECUs with high power consumption are, for example, ECUs with high processing power of microcontrollers. If an ON-locking diagnostic function is provided for an ECU with high power consumption, the power consumption will increase even further. Therefore, in this embodiment, the ON-locking diagnostic function is provided for an ECU with low power consumption. Note that the first ECU 10 corresponds to "one ECU" of the present invention.

[0042] As a modification of this embodiment, the power supply system 100 may have a plurality of semiconductor switches 12a to 12c connected in series between the low-voltage battery 1 and the load 2. Figure 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. Semiconductor switch 12a and semiconductor switch 12b are connected in series, and semiconductor switch 12a and semiconductor switch 12c are connected in series. 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 semiconductor switch 12b or semiconductor switch 12c. Detection circuits 11a to 11c are connected to the downstream side of the plurality of semiconductor switches 12a to 12c, respectively. A FET may be used for semiconductor switch 12a, and IPDs may be used for semiconductor switches 12b and 12c.

[0043] The first ECU 10 determines the energized state of the downstream semiconductor switches 12a to 12c based on the detected values ​​of the detection circuits 11a to 11c, and based on the determination result, the first ECU 10 determines the energized state of the downstream semiconductor switches 12a to 12c. c The first ECU 10 diagnoses whether the semiconductor switch 12a is stuck in the ON state. The first ECU 10 diagnoses whether the semiconductor switch 12a is stuck in the ON state in the following manner. The first ECU 10 outputs an OFF command to semiconductor switches 12a to 12c. While the first ECU 10 is outputting the OFF command to semiconductor switches 12a to 12c, it determines the energized state of the downstream side of the semiconductor switch 12a based on the detected value of the detection circuit 11a. If the first ECU 10 determines that the downstream side of the semiconductor switch 12a is energized, it diagnoses that the semiconductor switch 12a is stuck in the ON state. On the other hand, if the first ECU 10 determines that the downstream side of the semiconductor switch 12a is not energized, it diagnoses that the semiconductor switch 12a is not stuck in the ON state.

[0044] Furthermore, the first ECU 10 performs an ON-fixation diagnosis of semiconductor switch 12b or 12c in the following manner. With semiconductor switch 12a turned ON, the first ECU 10 outputs an OFF command to semiconductor switches 12b and 12c. While outputting the OFF command to semiconductor switches 12b and 12c, the first ECU 10 determines the energized state of the downstream side of semiconductor switches 12b and 12c based on the detected values ​​of the detection circuits 11b and 11c. If the first ECU 10 determines that the downstream side of semiconductor switches 12b and 12c is energized, it diagnoses that semiconductor switches 12b and 12c are in an ON-fixed state. On the other hand, if the first ECU 10 determines that the downstream side of semiconductor switches 12b and 12c is not energized, it diagnoses that semiconductor switches 12b and 12c are not in an ON-fixed state.

[0045] The first ECU 10 performs an ON-fixation diagnosis of the upstream semiconductor switch 12a among the semiconductor switches 12a to 12c after the last vehicle run. The first ECU 10 performs an ON-fixation diagnosis of the downstream semiconductor switches 12b and 12c among the semiconductor switches 12a to 12c when the first ECU 10 is started up.

[0046] Unlike the modified example, if the ON-fixation diagnosis of the upstream semiconductor switch 12a and the ON-fixation diagnosis of the downstream semiconductor switches 12b and 12c are performed in a single diagnostic flow, the diagnostic time will be longer. For example, if the ON-fixation diagnosis of the upstream semiconductor switch 12a and the downstream semiconductor switches 12b and 12c are performed after the first ECU 10 is started when the vehicle starts driving, the diagnostic time will be approximately twice as long as the time it takes to diagnose only one of the upstream semiconductor switch 12a or the downstream semiconductor switches 12b and 12c. In other words, the diagnostic time after starting the first ECU 10 will be approximately twice as long.

[0047] On the other hand, as shown in the modified example, by performing an ON-fixation diagnosis of the upstream semiconductor switch 12a after the last vehicle run, when the first ECU 10 is started again, it is only necessary to perform an ON-fixation diagnosis of the downstream semiconductor switches 12b and 12c. Therefore, the time required to diagnose ON-fixation when the first ECU 10 is started can be shortened.

[0048] In this embodiment, the "first ECU" corresponds to the "controller" of the present invention. [Explanation of Symbols]

[0049] 1 Low-voltage battery 2 loads 3 Power box 10 1st ECU 11 Detection circuit 12 Semiconductor switches 100 Power supply system (control system)

Claims

1. A controller that outputs switching commands to switch a semiconductor switch connected between a low-voltage power supply and a load on or off, The semiconductor switch and the load are connected to a detection circuit that detects the voltage and / or current downstream of the semiconductor switch, The aforementioned controller, During the output of the off command to turn off the semiconductor switch, the energized state of the downstream side of the semiconductor switch is determined based on the detected value of the detection circuit. A semiconductor switch control device that determines that the downstream side of the semiconductor switch is energized, and diagnoses that the semiconductor switch is stuck in the ON position.

2. In the semiconductor switch control device according to claim 1, The detection circuit is equipped with a voltage detection terminal, The aforementioned controller, During the output of the OFF command, the voltage applied to the voltage detection terminal is detected to obtain the downstream voltage, which is the voltage downstream of the semiconductor switch. A semiconductor switch control device that diagnoses that the semiconductor switch is stuck in the ON state when the difference between the upstream voltage, which is the voltage on the upstream side of the semiconductor switch, and the downstream voltage is less than or equal to a voltage difference threshold.

3. In the semiconductor switch control device according to claim 1 or 2, The aforementioned controller, The ECU, which controls the load, inputs an operation command to operate the load. A switching command is output to the semiconductor switch in accordance with the aforementioned operation command. A semiconductor switch control device that diagnoses the ON-fixation regardless of whether or not the aforementioned operation command is input.

4. In the semiconductor switch control device according to claim 2, The aforementioned voltage difference threshold is set according to the capacitance of the capacitor included in the load.

5. In the semiconductor switch control device according to claim 3, The controller is a semiconductor switch control device that transmits the ON-fixation determination result to an ECU that determines whether or not to output a warning.

6. In the semiconductor switch control device according to claim 1 or 2, The low-voltage power supply is a battery of 50 volts or less, and / or an auxiliary battery, in the semiconductor switch control device.

7. In a control system including a semiconductor switch control device according to claim 1 or 2, It has multiple ECUs, including one ECU and other ECUs. The startup time of the first ECU is shorter than that of the other ECUs. The aforementioned ECU has a diagnostic function for the ON-fixation of the semiconductor switch by the controller, The aforementioned other ECU is a control system that does not have a diagnostic function for the ON-fixation of the semiconductor switch.

8. In a control system including a semiconductor switch control device according to claim 1 or 2, It has multiple ECUs, including one ECU and other ECUs. The power consumption of the first ECU is smaller than that of the other ECUs. The aforementioned ECU has a diagnostic function for the ON-fixation of the semiconductor switch by the controller, The aforementioned other ECU is a control system that does not have a diagnostic function for the ON-fixation of the semiconductor switch.

9. A semiconductor switch control method, performed by a controller, for diagnosing a semiconductor switch connected between a low-voltage power supply and a load, The aforementioned controller, During the output of the off command to turn off the semiconductor switch, the energized state of the downstream side of the semiconductor switch is determined based on the detected value of a detection circuit connected between the semiconductor switch and the load, which detects the voltage and / or current downstream of the semiconductor switch. A semiconductor switch control method that determines that the downstream side of the semiconductor switch is energized, and diagnoses that the semiconductor switch is stuck in the ON state.

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