Control device

Abstract

To provide a control device capable of detecting a failure of a monitoring part and improving safety of a system.SOLUTION: A control device C includes a control part MCU that operates by receiving a power supply from a power supply Bat, a switch SW provided on a PL provided on a supply line that supplies a power from the power supply Bat to a control target Sol controlled by the control part MCU, and a monitoring part 2 that monitors a voltage input from the power supply Bat to the control part MCU and turns off the switch SW when an overvoltage occurs. The control part MCU detects a failure of the monitoring part 2 based on an output of the monitoring part 2 when a diagnosis signal for recognizing an overvoltage is input to the monitoring part 2.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a control device. [Background technology]

[0002] Vehicles are equipped with control devices to control controlled objects such as engines and variable damping shock absorbers, and such control devices are equipped with microcontrollers that start up when the ignition switch is turned on and control the supply of power to the controlled objects.

[0003] The microcontroller receives power from the vehicle's battery, but because the battery voltage is higher than the operating voltage of the microcontroller, it receives power via a step-down circuit that reduces the battery voltage to a voltage suitable for the operation of the microcontroller (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2019-80402 Summary of the Invention [Problem to be solved by the invention]

[0005] If a high voltage exceeding the operating voltage is applied to a microcontroller, it may cause problems in the operation of the microcontroller, making it unable to control the controlled object normally. For this reason, the control device is equipped with a monitoring unit that monitors the voltage stepped down by the step-down circuit and input to the microcontroller, and if the monitoring unit detects an overvoltage that makes it impossible to guarantee normal operation of the microcontroller, it opens a switch installed between the controlled object and the power supply to stop the flow of power to the controlled object.

[0006] Therefore, in conventional control devices, if the voltage input to the microcontroller becomes excessive, creating an environment in which the microcontroller cannot operate normally and there is a possibility of control failure, the power supply to the controlled object can be stopped and fail-safe operation can be performed.

[0007] In this way, conventional control devices can perform fail-safe operations in situations where a control failure may occur if the monitoring unit itself is operating normally, but they have no way of confirming whether the monitoring unit is operating normally.

[0008] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a control device that can detect a failure in a monitoring unit and improve the safety of the system. [Means for solving the problem]

[0009] In order to achieve the above object, the control device of the present invention includes a control unit that operates by receiving power from a power source, a switch provided on a supply line that supplies power from the power source to a control target controlled by the control unit, and a monitoring unit that monitors the voltage input from the power source to the control unit and turns off the switch if an overvoltage occurs, and the control unit detects a failure of the monitoring unit based on the output of the monitoring unit when it receives a diagnostic signal that makes the monitoring unit recognize an overvoltage. With a control device configured in this way, it is possible to determine if the monitoring unit itself has failed, thereby improving the safety of the system.

[0010] The control device may also include a voltage adding circuit having a voltage divider circuit that divides the voltage input from the monitoring unit to the control unit, and a comparator that compares the output of the voltage divider circuit with a reference voltage, and turning off a switch when the voltage becomes an overvoltage, and an additional line connected to the voltage divider circuit, and an additional circuit switch and resistor provided on the additional line, and turning on the additional circuit switch when a diagnostic signal is input from the control unit, thereby making the output of the voltage divider circuit equal to or higher than the reference voltage. With a control device configured in this way, the monitoring unit can be made to recognize an overvoltage simply by adding the voltage adding circuit to the circuit configuration of the monitoring unit, so that a failure detection function for the monitoring unit can be added inexpensively without changing the circuit configuration of the monitoring unit. [Effects of the Invention]

[0011] According to the control device of the present invention, it is possible to detect a failure in the monitoring unit and improve the safety of the system. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 2 is a circuit configuration diagram of a control device according to an embodiment. [Figure 2] FIG. 2 is a circuit configuration diagram of a monitoring unit according to an embodiment. [Figure 3] 10 is a flowchart illustrating a procedure for self-diagnosis processing of a control unit in one embodiment. [Figure 4] FIG. 10 is a circuit configuration diagram of a monitoring unit according to a modified example of an embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0013] The present invention will be described below based on the embodiments shown in the drawings. As shown in Fig. 1, the control device C is configured to include a microcontroller MCU as a control unit that operates by receiving power supply from a power supply Bat via a step-down circuit 1, a switch SW provided on a supply line PL that supplies power from the power supply Bat to a solenoid Sol as a control target controlled by the microcontroller MCU, and a monitoring unit 2 that receives power directly from the power supply Bat, monitors the output voltage of the step-down circuit 1, and turns off the switch SW when it detects an overvoltage in the voltage input to the microcontroller MCU.

[0014] The following is a detailed description of each part of the control device C of this example. A power supply Bat supplies power to a microcontroller MCU serving as a control unit via a branch supply line DL branching from a supply line PL that supplies power to the solenoid Sol and a step-down circuit 1.

[0015] The power supply Bat is connected to a drive circuit DC that controls the supply of power to the solenoid Sol that is the object of control via a supply line PL. A switch SW is provided in the middle of this supply line PL between the power supply Bat and the drive circuit DC, which, when turned on, connects the power supply Bat and the drive circuit DC, enabling the supply of power to the solenoid Sol.

[0016] In this example, the switch SW is an N-channel MOSFET, and when a high signal is input to its gate, it turns on, connecting the power supply Bat and the drive circuit DC and enabling power to be supplied to the solenoid Sol. Note that the switch SW may be a switch other than a MOSFET as long as it turns on when a high signal is input.

[0017] A step-down circuit 1 is provided on the branch supply line DL, and in this example, the step-down circuit 1 steps down the voltage of the power supply Bat, which is 12 V, to 5 V and outputs the resulting voltage. The microcontroller MCU is connected to the step-down circuit 1 via the branch supply line DL, and operates on the voltage stepped down to 5 V by the step-down circuit 1.

[0018] The microcontroller MCU is a control unit that controls a solenoid Sol that drives a damping force adjustment valve in a shock absorber with adjustable damping force mounted on a vehicle (not shown). The microcontroller MCU is also connected to a drive circuit DC that drives the solenoid Sol via a drive circuit signal line DSL, and is also connected to the gate of a switch SW via a signal line SL. In performing the control, the microcontroller MCU outputs a PWM drive signal to the drive circuit DC that drives the solenoid Sol so that the current flowing through the solenoid Sol becomes a target current corresponding to the target damping force that the shock absorber should output.

[0019] As described above, the drive circuit DC is provided on the supply line PL connecting the power supply Bat and the solenoid Sol to be controlled, and is controlled by the microcontroller MCU. Specifically, the drive circuit DC drives the solenoid Sol by applying a PWM drive signal input from the microcontroller MCU to the winding (not shown) of the solenoid Sol at an on-duty ratio indicated by the PWM drive signal. The drive circuit DC may be any suitable drive circuit for driving the solenoid Sol, and may include, for example, a switching element (not shown) that turns on and off the connection between the winding of the solenoid Sol and the power supply Bat. The drive circuit DC may be any suitable drive circuit for driving the controlled object. Therefore, if the controlled object is a motor, a drive circuit such as a circuit with only one switch, a half-bridge circuit, an H-bridge circuit, or an inverter may be appropriately selected depending on the motor's structure and rotation direction.

[0020] An AND logic circuit 4 is provided along the signal line SL. One of the input terminals of the logic circuit 4 is connected to the microcontroller MCU, and the other input terminal is connected to the output terminal of the watchdog WD. The microcontroller MCU outputs a high signal to one of the input terminals of the logic circuit 4 during control, and outputs a low signal to the other input terminal of the logic circuit 4 when power is cut off. The watchdog WD receives power via a branch supply line DL and monitors the watchdog pulses output by the microcontroller MCU. The watchdog WD monitors the watchdog pulses output by the microcontroller MCU, and determines that an abnormality has occurred in the processing of the microcontroller MCU if the microcontroller MCU stops outputting watchdog pulses at regular intervals. Furthermore, if the microcontroller MCU is normal, the watchdog WD outputs a high signal from its output terminal to the AND logic circuit 4, and if an abnormality occurs, it outputs a low signal to the logic circuit 4.

[0021] Therefore, when the microcontroller MCU is normal, the logic circuit 4 outputs a high signal since high signals are input to both input terminals. On the other hand, if the power supply to the microcontroller MCU is stopped, or if the microcontroller MCU becomes abnormal or stops operating, a low signal is input to at least one of the input terminals of the logic circuit 4, and the output of the logic circuit 4 becomes a low signal.

[0022] The output terminal of the logic circuit 4 is connected to the gate of the switch SW through a signal line SL. In addition, the output terminal 26 of the monitoring unit 2 is connected to the middle of the signal line SL, as shown in FIG.

[0023] The monitoring unit 2 operates by receiving power directly from the power supply Bat, and includes a voltage divider circuit 21 that divides and outputs the voltage output from the step-down circuit 1 and input to the microcontroller MCU, a first comparator 22 for detecting overvoltage, a first switching element 23 that switches on and off in accordance with the output of the first comparator 22, a second comparator 24 for detecting undervoltage, and a second switching element 25 that switches on and off in accordance with the output of the second comparator 24, and a voltage adding circuit 3 that adds voltage to the output of the voltage divider circuit 21 in the monitoring unit 2 when a diagnostic input signal is input from the microcontroller MCU.

[0024] In this embodiment, the monitoring unit 2 monitors the voltage input to the microcontroller MCU, and when it detects an overvoltage, that is, the voltage exceeds the voltage at which the microcontroller MCU can operate normally, or when it detects an undervoltage, that is, the voltage is below the voltage at which the microcontroller MCU can operate normally, it turns on the first switching element 23 or the second switching element 25 to ground the signal line SL and turn off the switch SW. On the other hand, when the voltage is within the voltage range at which the microcontroller MCU can operate normally, the first switching element 23 and the second switching element 25 are turned off, and the output of the monitoring unit 2 becomes high impedance.

[0025] The voltage-dividing circuit 21 includes a voltage detection line 21a having one end grounded and the other end connected to the branch supply line DL, and three resistors 21b, 21c, and 21d connected in series to the voltage detection line 21a. The resistors 21b, 21c, and 21d connected to the voltage detection line 21a divide the output voltage of the step-down circuit 1 and output an overvoltage detection voltage to be input to the first comparator 22 and an undervoltage detection voltage to be input to the second comparator 24. Specifically, the voltage-dividing circuit 21 outputs the voltage between the resistors 21b and 21c on the voltage detection line 21a to the first comparator 22 as the overvoltage detection voltage, and outputs the voltage between the resistors 21c and 21d on the voltage detection line 21a to the second comparator 24 as the undervoltage detection voltage.

[0026] In this embodiment, the resistance values ​​of resistors 21b, 21c, and 21d are set so that, for example, when step-down circuit 1 outputs a voltage of 5V, the voltage at the junction between resistors 21b and 21c is 1.10V, and the voltage at the junction between resistors 21c and 21d is 1.46V. Meanwhile, the reference voltages input to first comparator 22 and second comparator 24 are set to 1.27V. Since the median between 1.10V and 1.46V is 1.28V, the reference voltage is a threshold for detecting an abnormality in the output voltage of step-down circuit 1. It may be set around the median value, but it may also be tuned according to the upper and lower limit voltages that are allowable for normal operation of the microcontroller MCU. The settings of resistors 21b, 21c, and 21d and the reference voltage described above are merely examples and can be changed as desired.

[0027] As the output voltage of the step-down circuit 1 increases, the overvoltage detection voltage at the junction between resistors 21b and 21c on the voltage detection line 21a and the undervoltage detection voltage at the junction between resistors 21c and 21d also increase. Conversely, as the output voltage of the step-down circuit 1 decreases, the overvoltage detection voltage and the undervoltage detection voltage also decrease. Therefore, the monitoring unit 2 uses the first comparator 22 and the second comparator 24 to compare the voltage at the junction between resistors 21b and 21c with a reference voltage, and also compares the reference voltage with the voltage at the junction between resistors 21c and 21d, thereby detecting whether the output voltage of the step-down circuit 1 is within the allowable upper and lower voltage limits. The upper voltage limit is set to 5.73 V in this example, a voltage that, if applied, would cause the microcontroller MCU to malfunction or become unable to operate normally. The lower voltage limit is set to 4.34 V, a voltage that, if applied, would cause the microcontroller MCU to become unable to operate normally.

[0028] The first comparator 22 compares the overvoltage detection voltage at the connection point between resistors 21b and 21c on the voltage detection line 21a with a reference voltage, and outputs a high signal if the overvoltage detection voltage is equal to or greater than the reference voltage, and outputs a low signal if the overvoltage detection voltage is less than the reference voltage. The first switching element 23 in this example is an N-channel MOSFET, with its drain connected to the middle of the signal line SL via the output terminal 26 of the monitoring unit 2, its source grounded, and its gate connected to the output terminal of the first comparator 22. Therefore, when the output voltage of the step-down circuit 1 exceeds the allowable upper limit voltage and becomes an overvoltage, the overvoltage detection voltage exceeds the reference voltage, causing the first comparator 22 to output a high signal. The first switching element 23 then grounds the signal line SL and sets the signal input to the switch SW to a low level.

[0029] On the other hand, when the output voltage of the step-down circuit 1 is less than the allowable upper limit voltage and the overvoltage detection voltage is less than the reference voltage, the first comparator 22 outputs a low signal, and the first switching element 23 becomes high impedance, does not ground the signal line SL, and does not allow current to flow.

[0030] The second comparator 24 compares the undervoltage detection voltage at the connection point between resistors 21c and 21d on the voltage detection line 21a with a reference voltage, and outputs a low signal if the undervoltage detection voltage is equal to or greater than the reference voltage, and outputs a high signal if the undervoltage detection voltage is less than the reference voltage. The second switching element 25 in this example is an N-channel MOSFET, with its drain connected to the middle of the signal line SL via the output terminal 26 of the monitoring unit 2, its source grounded, and its gate connected to the output terminal of the second comparator 24. Therefore, when the output voltage of the step-down circuit 1 falls below the allowable lower limit voltage and becomes an undervoltage, the undervoltage detection voltage falls below the reference voltage, and the second comparator 24 outputs a high signal. The second switching element 25 then grounds the signal line SL and sets the signal input to the switch SW to a low level.

[0031] On the other hand, when the output voltage of the step-down circuit 1 is equal to or higher than the allowable lower limit voltage and the undervoltage detection voltage is equal to or higher than the reference voltage, the second comparator 24 outputs a low signal, and the second switching element 25 becomes high impedance, does not ground the signal line SL, and does not allow current to flow.

[0032] As described above, the logic circuit 4 outputs a high signal when the microcontroller MCU is normal and outputs a low signal when the microcontroller MCU is abnormal. When the microcontroller MCU is normal and the logic circuit 4 outputs a high signal, and the voltage input to the microcontroller MCU is not an overvoltage or undervoltage but is within the normal range and the output of the monitoring unit 2 is high impedance, a high signal is input to the gate of the switch SW, causing the switch SW to turn on and connect the power supply Bat and the drive circuit DC. On the other hand, even if the microcontroller MCU is normal and the logic circuit 4 outputs a high signal, if the voltage input to the microcontroller MCU is an overvoltage or undervoltage, the gate of the switch SW is grounded by the monitoring unit 2 and a low signal is input to the switch SW, causing the switch SW to turn off and disconnect the power supply Bat and the drive circuit DC. If the microcontroller MCU is abnormal and the logic circuit 4 outputs a low signal, and the voltage input to the microcontroller MCU is within the normal range and the output of the monitoring unit 2 is high impedance, a low signal is input to the switch SW, causing the switch SW to turn off and disconnect the power supply Bat from the drive circuit DC. In this way, the switch SW turns on only when the microcontroller MCU is normal and the voltage input to the microcontroller MCU is within the normal range, but turns off if the microcontroller MCU is abnormal or the voltage input to the microcontroller MCU is an overvoltage or undervoltage. As described above, the monitoring unit 2 receives power directly from the power supply Bat and monitors the output voltage of the step-down circuit 1, and turns off the switch SW if the output voltage of the step-down circuit 1 becomes an overvoltage or undervoltage, regardless of the state of the microcontroller MCU.

[0033] Furthermore, the output of the monitoring unit 2 is output from the output terminal 26 to which the drain sides of the first switching element 23 and the second switching element 25 are connected, and input to the microcontroller MCU. In this way, when the overvoltage detection voltage is equal to or greater than the reference voltage, or when the undervoltage detection voltage is less than the reference voltage, the monitoring unit 2 drops the signal line SL to ground and outputs a low-level voltage from the output terminal 26, preventing voltage from being applied to the gate of the switch SW and turning off the switch SW. The low-level voltage output from the output terminal 26 of the monitoring unit 2 is input to the microcontroller MCU.

[0034] Furthermore, when the overvoltage detection voltage is less than the reference voltage and the undervoltage detection voltage is equal to or greater than the reference voltage, the first switching element 23 and the second switching element 25 become high impedance, and the voltage at the output terminal 26 of the monitoring unit 2 becomes approximately equal to the voltage applied to the gate of the switch SW. Thus, when the overvoltage detection voltage is less than the reference voltage and the undervoltage detection voltage is equal to or greater than the reference voltage, the output terminal 26 of the monitoring unit 2 becomes high impedance. The output level of the monitoring unit 2 becomes the same as the output level of the logic circuit 4. The output of the monitoring unit 2 is input to the microcontroller MCU. The first switching element 23 may be a switching element other than an N-channel MOSFET, as long as it is turned on by a high signal from the first comparator 22 and turned off by a low signal from the first comparator 22. The second switching element 25 may also be a switching element other than an N-channel MOSFET, as long as it is turned on by a high signal from the second comparator 24 and turned off by a low signal from the second comparator 24.

[0035] In this embodiment, a resistor 27 is provided on the signal line SL between the logic circuit 4 and the gate of the switch SW, closer to the logic circuit 4 than the connection point of the output terminal 26. The resistor 27 is provided for the purpose of generating a potential difference between the logic circuit 4 and the output terminal 26 so that it can be accurately determined whether the microcontroller MCU is outputting a low signal or a high signal, regardless of the output of the logic circuit 4.

[0036] Next, the voltage addition circuit 3 includes an additional line 31 having one end connected to the branch supply line DL and the other end connected between resistors 21b and 21c in the voltage detection line 21a of the monitoring unit 2, a resistor 32 provided on the additional line 31, and a transistor 33 provided on the additional line 31 as an additional circuit switch.

[0037] In this embodiment, the transistor 33 is a PNP transistor. The emitter is connected to the branch supply line DL, the collector is connected to the voltage detection line 21a, and the base receives a diagnostic signal from the microcontroller MCU. When the diagnostic signal is received from the microcontroller MCU, the transistor 33 turns on, connecting the branch supply line DL to the resistors 21b and 21c of the voltage detection line 21a via the additional line 31 and the resistor 32. This connects the resistor 32 installed on the additional line 31 in parallel with the resistors 21c and 21d connected in series to the voltage detection line 21a. This reduces the combined resistance of the resistors 21c, 21d, and 32, and the overvoltage detection voltage becomes higher than the voltage obtained by dividing the voltage output by the step-down circuit 1 at a predetermined ratio by the resistors 21b, 21c, and 21d in the voltage-dividing circuit 21. The resistance value of the resistor 32 is set so that the overvoltage detection voltage is equal to or higher than the reference voltage, even if the step-down circuit 1 is operating normally and outputting a voltage of 5V. Therefore, when a diagnostic signal is input from the microcontroller MCU, the voltage addition circuit 3 increases the overvoltage detection voltage, and the monitoring unit 2 detects an overvoltage and sets the output of the output terminal 26 to a low-level voltage.

[0038] On the other hand, when there is no diagnostic signal input from the microcontroller MCU and the diagnostic signal output terminal of the microcontroller MCU becomes high impedance, the transistor 33 stops passing current, so that the voltage detection line 21a is not connected to the branch supply line DL via the additional line 31 and resistor 32, and the overvoltage detection voltage becomes equal to the voltage output from the step-down circuit 1 divided at a predetermined ratio by the resistors 21b, 21c, and 21d in the voltage divider circuit 21. Note that although the voltage addition circuit 3 in this embodiment uses the transistor 33 as the additional circuit switch, a switch that can be turned on by input of a diagnostic signal from the microcontroller MCU can be used instead of the transistor 33 as the additional circuit switch. Furthermore, the microcontroller MCU can output a diagnostic signal suitable for turning on the switch used in the voltage addition circuit 3.

[0039] Furthermore, the microcontroller MCU monitors the voltage that the monitoring unit 2 outputs from the output terminal 26 when the diagnostic signal is output. When the microcontroller MCU outputs the diagnostic signal, if the output of the output terminal 26 of the monitoring unit 2 is a low-level voltage, it determines that the monitoring unit 2 is operating normally, and conversely, if the output terminal 26 is at high impedance and the output of the output terminal 26 of the monitoring unit 2 is a high-level voltage, it determines that the monitoring unit 2 is faulty.

[0040] Specifically, as shown in FIG. 3, when the main switch (not shown) is turned on and the microcontroller MCU receives power from the power supply Bat and starts up, the switch SW turns on, while the drive circuit DC sets the on-duty ratio to 0 so that no voltage is applied to the solenoid Sol, and executes self-diagnosis processing. When the microcontroller MCU receives power from the power supply Bat and starts up, it outputs a diagnostic signal and increases the overvoltage detection voltage above the reference voltage via the voltage addition circuit 3 so that the first comparator 22 can detect an overvoltage (step F1). The microcontroller MCU reads the voltage at the output terminal 26 of the monitoring unit 2 (step F2) and determines whether the output of the output terminal 26 is a low-level voltage (step F3). If the output of the output terminal 26 is a low-level voltage, the monitoring unit 2 has properly detected an overvoltage, and the microcontroller MCU determines that the monitoring unit 2 is normal. The microcontroller MCU then stops outputting the diagnostic signal (step F4), terminates the self-diagnosis processing at startup, and then controls the solenoid Sol. On the other hand, if the output of the output terminal 26 is a high-level voltage, the microcontroller MCU determines that the monitoring unit 2 is faulty because it cannot detect an overvoltage. Therefore, the microcontroller MCU stops the diagnostic signal, outputs a low signal to the logic circuit 4, turns off the switch SW, and terminates the startup self-diagnosis process (step F5). Therefore, when the control device C receives power from the power supply Bat and starts up, it executes a self-diagnosis process to determine whether the monitoring unit 2 is faulty. If the monitoring unit 2 is operating normally, it stops outputting the diagnostic signal, keeps the switch SW on, and controls the solenoid Sol. However, if the monitoring unit 2 is faulty, it turns off the switch SW to prevent power from being supplied to the solenoid Sol. If the microcontroller MCU diagnoses that the monitoring unit 2 is faulty, it outputs a low signal to the logic circuit 4 to turn off the switch SW. The output of the faulty monitoring unit 2 is a low-level voltage or high impedance. However, because the resistor 27 is provided in the signal line SL, when a low signal is input from the logic circuit 4 to the switch SW, the gate voltage drops and the switch SW is turned off.

[0041] The control device C of this example is configured as described above, and its operation will be described below. First, as described above, when the control device C receives power from the power supply Bat and starts up, it executes a self-diagnosis process, outputs a diagnostic signal from the microcontroller MCU, and determines whether the monitoring unit 2 is operating normally or has failed. If the monitoring unit 2 is operating normally, it turns on the switch SW and executes a process to control the solenoid Sol. On the other hand, if the control device C determines in the self-diagnosis process that the monitoring unit 2 has failed, it turns off the switch SW and does not control the solenoid Sol. Therefore, if the monitoring unit 2 has failed, it is unclear whether the voltage supplied to the microcontroller MCU is within the normal range, so the control device C does not control the solenoid Sol and executes a fail-safe operation.

[0042] Next, we will explain the case where the step-down circuit 1 is functioning normally and its output voltage is below the upper limit voltage and above the lower limit voltage, within the normal range. The step-down circuit 1 supplies the microcontroller MCU with a voltage suitable for normal operation. When the microcontroller MCU is processing normally, the microcontroller MCU and watchdog WD output a high signal to the logic circuit 4. This causes the logic circuit 4 to output a high signal. When the output voltage of the step-down circuit 1 is normal, the monitoring unit 2 sets the output terminal 26 to high impedance and does not ground the switch SW. This causes the high signal from the logic circuit 4 to be input to the gate of the switch SW, turning it on. This causes the microcontroller MCU to execute control processing and input a PWM drive signal to the drive circuit DC via the drive circuit signal line DSL.

[0043] Therefore, when the microcontroller MCU functions normally and the output voltage of the step-down circuit 1 is normal, the switch SW is turned on and the solenoid Sol, which is the object to be controlled, is appropriately controlled by the microcontroller MCU.

[0044] Next, we will explain the case where the step-down circuit 1 is functioning normally, but the watchdog WD detects an abnormality in the microcontroller MCU. In this case, the abnormal microcontroller MCU inputs a high or low signal to the logic circuit 4, but the watchdog WD inputs a low signal to the logic circuit 4. As a result, the logic circuit 4 outputs a low signal. If the output voltage of the step-down circuit 1 is normal, the monitoring unit 2 sets the output terminal to high impedance and does not ground the switch SW. As a result, only a low signal is input to the gate of the switch SW, and the switch SW is turned off. In the case of an abnormality in the microcontroller MCU, even though a high or low signal is input from the microcontroller MCU to the logic circuit 4, the watchdog WD outputs a low signal to the logic circuit 4, so the switch SW is turned off. As such, operation is not guaranteed due to an abnormality in the microcontroller MCU, but turning the switch SW off prevents power from being supplied to the solenoid Sol.

[0045] Therefore, when the microcontroller MCU is abnormal and the output voltage of the step-down circuit 1 is normal, the switch SW is turned off, and the solenoid Sol, which is the object of control, is not driven.

[0046] Next, we will explain the case where the step-down circuit 1 is abnormal and the output voltage becomes an overvoltage exceeding the upper limit voltage or an undervoltage below the lower limit voltage. In this case, the step-down circuit 1 supplies an abnormal voltage that is not suitable for normal operation, so the monitoring unit 2 sets the voltage at the output terminal 26 to low. Regardless of whether the signals output by the microcontroller MCU and the watchdog timer WD are high or low, the switch SW is grounded, so the gate of the switch SW is not applied and the switch SW is forcibly turned off. Thus, when the output voltage of the step-down circuit 1 becomes abnormal, the monitoring unit 2 activates and forcibly turns off the switch SW, disconnecting the solenoid Sol from the power supply Bat and forcibly terminating the operation of the solenoid Sol. If the output voltage of the step-down circuit 1 becomes abnormal, the microcontroller MCU may malfunction. However, as described above, if the output voltage of the step-down circuit 1 becomes abnormal, the power supply to the solenoid Sol is forcibly stopped, ensuring fail-safe operation.

[0047] In this way, the control device C of the present invention comprises a microcontroller (control unit) MCU that operates by receiving power from a power supply Bat, a switch SW provided on a supply line PL that supplies power from the power supply Bat to a solenoid (controlled object) Sol controlled by the microcontroller (control unit) MCU, and a monitoring unit 2 that monitors the voltage input from the power supply Bat to the microcontroller (control unit) MCU and turns off the switch SW when an overvoltage occurs, and the microcontroller (control unit) MCU detects a fault in the monitoring unit 2 based on the output of the monitoring unit 2 when a diagnostic signal that causes the monitoring unit 2 to recognize an overvoltage is input.

[0048] The control device C configured in this manner can determine whether the monitoring unit 2 itself has failed, thereby improving the safety of the system. Furthermore, the control device C of this embodiment detects a failure in the monitoring unit 2 at startup, so it can quickly discover that the monitoring unit 2 is in a state where it cannot operate normally, and if there is a possibility that it cannot control the solenoid (control object) Sol normally, it can turn off the switch SW to prevent control of the solenoid (control object) Sol.

[0049] Furthermore, the monitoring unit 2 in the control device C of this embodiment has a voltage divider circuit 21 that divides the voltage input to the microcontroller (control unit) MCU, and a first comparator 22 that compares the output of the voltage divider circuit 21 with a reference voltage, and turns off a switch SW when the voltage becomes an overvoltage, and is equipped with a voltage addition circuit 3 that has an additional line 31 connected to the voltage divider circuit 21, and a transistor (additional circuit switch) 33 and a resistor 32 provided on the additional line 31, and when the diagnostic signal is input from the control unit, the additional circuit switch turns on, and when the diagnostic signal is input from the microcontroller (control unit) MCU, the transistor (additional circuit switch) 33 turns on, making the output of the voltage divider circuit 21 higher than the reference voltage.

[0050] According to the control device C configured in this manner, the monitoring unit 2 can be made to recognize an overvoltage simply by adding the voltage addition circuit 3 to the circuit configuration of the monitoring unit 2, so that a fault detection function of the monitoring unit 2 can be added inexpensively to the monitoring unit 2 without changing the circuit configuration of the monitoring unit 2. In this embodiment, the voltage addition circuit 3 connects the additional line 31 to the branch supply line DL and, when the additional circuit switch is turned on, connects the branch supply line DL to the voltage divider circuit 21 to make the output of the voltage divider circuit 21 equal to or higher than the reference voltage, but the additional line 31 may also be connected to the supply line PL or an external power source in addition to the branch supply line DL.

[0051] 4, instead of providing the voltage addition circuit 3 in the monitoring unit 2, a diagnostic signal may be directly added, the voltage being such that the overvoltage detection voltage input from the microcontroller MCU to the first comparator 22 of the monitoring unit 2 is equal to or higher than the reference voltage. However, the voltage addition circuit 3 of this embodiment adds voltage using the voltage of the branch supply line DL. The microcontroller MCU only needs to output a signal that operates the transistor 33 in the voltage addition circuit 3, which is convenient as it does not need to output a high voltage.

[0052] In this embodiment, the monitoring unit 2 turns off the switch SW when it detects not only an overvoltage but also an undervoltage, thereby stopping control when the undervoltage prevents the microcontroller MCU from operating normally. However, since it is sufficient for the monitoring unit 2 to detect an overvoltage, the second comparator 24 and the second switching element 25 that detect an undervoltage may be eliminated, and an undervoltage monitoring unit that monitors whether the voltage input to the microcontroller MCU is an undervoltage may be provided instead. In this case, the undervoltage monitoring unit may be configured to output a high signal to the logic circuit 4 when the voltage input to the microcontroller MCU is equal to or higher than the lower limit voltage, and to output a low signal to the logic circuit 4 when the voltage is below the lower limit voltage. The logic circuit 4 may be configured to receive signals from the microcontroller MCU, the watchdog timer WD, and the undervoltage monitoring unit, and to output a high signal only when the microcontroller MCU is normal, the microcontroller MCU and the watchdog timer WD each output a high signal, and the undervoltage monitoring unit outputs a high signal.

[0053] The control device C of this embodiment includes a step-down circuit 1 that steps down and outputs the voltage of a power supply Bat; a microcontroller (controller) MCU that operates by receiving power from the step-down circuit 1; a switch SW provided on a supply line PL that supplies power from the power supply Bat to a solenoid (control object) Sol controlled by the microcontroller (controller) MCU; and a monitoring unit 2 that receives power directly from the power supply Bat and monitors the output voltage of the step-down circuit 1 and turns off the switch SW when it detects an overvoltage in the output voltage. The control device C configured in this manner can forcibly stop the power supply to the solenoid (control object) Sol if the output voltage of the step-down circuit 1 becomes an overvoltage that could cause the microcontroller (controller) MCU to malfunction or operate abnormally. Therefore, the control device C turns off the switch SW when the output voltage of the step-down circuit 1 becomes an overvoltage that could cause the microcontroller (controller) MCU to malfunction or operate abnormally, preventing the microcontroller (controller) MCU from continuing control even when it appears to be operating normally.

[0054] It should be noted that the control device C of the present invention may naturally be used to control a control target other than the solenoid Sol of a shock absorber with adjustable damping force.

[0055] Although the preferred embodiment of the present invention has been described in detail above, modifications, variations and changes can be made without departing from the scope of the appended claims. [Explanation of symbols]

[0056] 2 ··· Monitoring unit, 3 ··· Voltage addition circuit, 21 ··· Voltage divider circuit, 22 ··· First comparator (comparator), 31 ··· Additional line, 32 ··· Resistor, 33 ··· Transistor (additional circuit switch), Bat ··· Power supply, C ··· Control device, MCU ··· Microcontroller (control unit), PL ··· Supply line, Sol ··· Solenoid (controlled object), SW ··· Switch

Claims

1. a control unit that operates by receiving power from a power source; a switch provided on a supply line that supplies power from the power source to a control target controlled by the control unit; a monitoring unit that monitors a voltage input from the power supply to the control unit and turns off the switch when an overvoltage occurs; The control unit detects a failure of the monitoring unit based on an output of the monitoring unit when a diagnostic signal for causing the monitoring unit to recognize an overvoltage is input. A control device characterized by:

2. the monitoring unit has a voltage dividing circuit that divides the voltage input to the control unit, and a comparator that compares the output of the voltage dividing circuit with the reference voltage, and turns off the switch when the voltage becomes an overvoltage; a voltage addition circuit having an additional line connected to the voltage dividing circuit, an additional circuit switch and a resistor provided on the additional line, and configured to turn on the additional circuit switch when the diagnostic signal is input from the control unit, thereby making the output of the voltage dividing circuit equal to or higher than the reference voltage; 2. The control device according to claim 1.

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