electronic equipment

Abstract

Provided is an electronic device capable of diagnosing failure of loads and suppressing damage to a switching element.　This electronic device comprises a plurality of loads, a switching element provided on a current path connected to the plurality of loads, a failure diagnosis unit that diagnoses a failure on the basis of voltages applied to the plurality of loads, and a drive circuit that drives the switching element. The drive circuit outputs, to the switching element, a drive control signal representing the result of comparing a load signal, which is obtained by converting a current flowing through the current path to a voltage, with a reference signal serving as a reference for operation of the switching element, and the failure diagnosis unit determines that the loads are abnormal in a case when a voltage outside a normal voltage range is detected.

Description

[Technical Field]

[0001] The present disclosure relates to electronic devices. [Background technology]

[0002] A conventional inductive load short-circuit detection device includes a load drive circuit having an inductive load and a field-effect transistor connected to a DC power supply, and a detection circuit including a comparator connected between the inductive load and the field-effect transistor, and detects whether or not the inductive load is short-circuited by comparing an input voltage to the detection circuit with a reference voltage using the comparator when the field-effect transistor of the load drive circuit is driven.When the inductive load is not short-circuited, a diagnostic drive signal is applied to the gate of the field-effect transistor so short that almost no current flows through the inductive load even when the field-effect transistor is turned on (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 10-142284 Summary of the Invention [Problem to be solved by the invention]

[0004] However, conventional inductive load short circuit detection devices drive field effect transistors with extremely short pulse-shaped drive voltages, which can lead to false detection of a short circuit in the inductive load, or, if the inductive load is short-circuited, excessive current can flow through the field effect transistor, potentially damaging the field effect transistor (switching element).

[0005] Therefore, an object of the present invention is to provide an electronic device that can reliably perform a fault diagnosis of a load and can prevent damage to a switching element. [Means for solving the problem]

[0006] An electronic device according to an embodiment of the present disclosure includes a plurality of loads, a switching element provided in a current path connected to the plurality of loads, a fault diagnosis unit that performs fault diagnosis based on a voltage applied to the plurality of loads, and a drive circuit that drives the switching element, wherein the drive circuit outputs a drive control signal to the switching element that represents a comparison result between a load signal obtained by converting a current flowing in the current path into a voltage and a reference signal that serves as a basis for the operation of the switching element, and when the fault diagnosis unit detects a voltage outside the normal voltage range, it determines that the load is in an abnormal state. [Effects of the Invention]

[0007] It is possible to provide an electronic device that can reliably perform a fault diagnosis on a load and prevent damage to a switching element. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a diagram illustrating an electronic device according to a first embodiment. [Figure 2A] FIG. 10 is a diagram showing current flow in a normal state. [Figure 2B] FIG. 10 is a diagram showing the current flow when an open fault occurs in the actuator. [Figure 2C] FIG. 10 is a diagram showing the flow of current when a short circuit fault occurs in the actuator. [Figure 3A] 10A and 10B are diagrams showing voltage waveforms at various parts of the electronic device when a fault diagnosis is performed when the actuator is in a normal state. [Figure 3B] 10A and 10B are diagrams illustrating voltage waveforms at various parts of an electronic device when a fault diagnosis is performed when one of the actuators is in an open fault state. [Figure 3C] 10A and 10B are diagrams showing voltage waveforms at various parts of the electronic device when a fault diagnosis is performed when one of the actuators is in a short-circuit fault state. [Figure 4] FIG. 4 is a diagram showing voltage data used by a fault diagnosis unit in fault diagnosis. [Figure 5] 4 is a flowchart showing a fault diagnosis process executed by a fault diagnosis unit. [Figure 6] FIG. 10 is a diagram illustrating an electronic device according to a second embodiment. [Figure 7A] FIG. 10 is a diagram showing current flow in a normal state. [Figure 7B] FIG. 10 is a diagram showing the current flow when an open fault occurs in the actuator. [Figure 7C] FIG. 10 is a diagram showing the flow of current when a short circuit fault occurs in the actuator. [Figure 8A] 10A and 10B are diagrams showing voltage waveforms at various parts of the electronic device when a fault diagnosis is performed when the actuator is in a normal state. [Figure 8B] 10A and 10B are diagrams illustrating voltage waveforms at various parts of an electronic device when a fault diagnosis is performed when one of the actuators is in an open fault state. [Figure 8C] 10A and 10B are diagrams showing voltage waveforms at various parts of the electronic device when a fault diagnosis is performed when one of the actuators is in a short-circuit fault state. [Figure 9] FIG. 10 is a diagram showing voltage data used by the fault diagnosis unit in fault diagnosis according to the second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, an embodiment to which the electronic device of the present disclosure is applied will be described.

[0010] <Embodiment 1> <Configuration of Electronic Device 100> FIG. 1 is a diagram illustrating an electronic device 100 according to a first embodiment. The electronic device 100 includes a power supply terminal 101, actuators 110A and 110B, a field effect transistor (FET) 120, an operational amplifier 130, an analog-to-digital converter (ADC) 140, a microcomputer 150, and resistors R1 to R7. The voltage applied to the power supply terminal 101 is higher than the rated voltage for operating the operational amplifier 130, the ADC 140, and the microcomputer 150. The actuators 110A and 110B are an example of a plurality of loads. The FET 120 is an example of a switching element. The operational amplifier 130 is an example of a drive circuit.

[0011] The actuators 110A and 110B are vibration elements such as piezoelectric elements. The vibration elements may be eccentric motors, solenoids, LRAs (linear resonant actuators), etc. The actuators 110A and 110B have the same resistance and are the same product, for example. The electronic device 100 is a device that generates vibrations by driving the actuators 110A and 110B, for example. The actuators 110A and 110B are attached to an operation unit of an input device or the like that incorporates the electronic device 100, and are driven to vibrate when a hand or the like touches the operation unit, thereby presenting a tactile sensation to the user through the hand or the like. For this reason, the electronic device 100 can also be regarded as a tactile sensation presentation device.

[0012] The multiple loads included in the electronic device 100 are not limited to vibration elements, but may be, for example, LEDs (light emitting diodes), motors, heaters, etc. The electronic device 100 is a device that drives the multiple loads and performs fault diagnosis on the loads. The fault diagnosis is performed by a microcomputer 150.

[0013] The actuators 110A and 110B are inserted in series into two wires connected to a power supply terminal 101 that outputs DC power. The two wires connected to the power supply terminal 101 are connected to the drain terminal (D) of the FET 120.

[0014] The FET 120 has a drain terminal (D), a source terminal (S), and a gate terminal (G). The drain terminal is connected to the actuators 110A and 110B. The source terminal is connected to the inverting input terminal of the operational amplifier 130 via a resistor R4 and is grounded via a resistor R5. A current path extending from the power supply terminal 101 through the actuators 110A and 110B, the FET 120, and the resistor R5 to the ground potential point is a current path that supplies current to the actuators 110A and 110B. The FET 120 and the operational amplifier 130 form a constant current circuit.

[0015] The operational amplifier 130 has a non-inverting input terminal to which a reference signal is input from the microcomputer 150, an inverting input terminal connected to the source terminal of the FET 120 via a resistor R4, and an output terminal connected to the gate terminal of the FET 120 via a resistor R2. A resistor R1 is connected as a negative feedback resistor between the inverting input terminal and the output terminal of the operational amplifier 130. A resistor R3 is also connected branching from between the resistor R2 and the gate terminal of the FET 120, with the other end of the resistor R3 being grounded. The resistor R3 has the function of determining the voltage applied to the gate terminal of the FET 120 to prevent the FET 120 from being unintentionally turned on due to noise or the like.

[0016] A load signal obtained by converting the current flowing through the current path between actuators 110A and 110B and resistor R5 into a voltage is input to the inverting input terminal. A reference signal input to the non-inverting input terminal is a signal that serves as a reference for the operation of FET 120. Operational amplifier 130 outputs a drive control signal, which indicates the result of comparing the load signal input to the inverting input terminal with the reference signal, to the gate terminal of FET 120.

[0017] The ADC 140 is connected to the wiring (current path) between the actuators 110A and 110B and the drain terminal of the FET 120 via a voltage divider circuit including resistors R6 and R7. The ADC 140 converts the voltage value into a digital value and outputs it to the microcomputer 150. The resistors R6 and R7 are set so that the voltage of the power supply terminal 101 applied to the ADC 140 is lower than the rated voltage of the ADC 140.

[0018] The microcomputer 150 includes a reference signal generating unit 151, a fault diagnosis unit 152, and a memory 153. The microcomputer is a microcontroller implemented by a computer including a CPU (Central Processing Unit), RAM (Random Access Memory), ROM (Read Only Memory), HDD (Hard Disk Drive), an input / output interface, an internal bus, etc. The reference signal generating unit 151 and the fault diagnosis unit 152 are functional blocks representing the functions of a program executed by the microcomputer 150. The memory 153 is a functional representation of the memory of the microcomputer 150.

[0019] The reference signal generation unit 151 generates a reference signal and outputs it to the non-inverting input terminal of the operational amplifier 130. When a drive command is input from an input device or the like built into the electronic device 100 while the actuators 110A and 110B are in a normal state, the reference signal generation unit 151 generates a reference signal for driving the actuators 110A and 110B in accordance with the drive command. Furthermore, when the fault diagnosis unit 152 performs fault diagnosis, the reference signal generation unit 151 generates and outputs a reference signal for fault diagnosis so that a predetermined voltage lower than the operating voltage at which the actuators 110A and 110B operate is applied to the actuators 110A and 110B. This will be described in detail later.

[0020] The fault diagnosis unit 152 performs fault diagnosis on the actuators 110A and 110B based on the voltage input from the ADC 140. The voltage input from the ADC 140 represents the voltage applied to the two loads, the actuators 110A and 110B. The fault diagnosis is a diagnosis that determines whether an open circuit fault (disconnection), a short circuit fault (short circuit), or other abnormality has occurred in the actuator 110A or 110B. If no open circuit fault, short circuit fault, or other abnormality has occurred, the actuators 110A and 110B are in a normal state.

[0021] The memory 153 stores programs and data necessary for the reference signal generating unit 151 to perform the process of generating a reference signal, programs and data necessary for the fault diagnosing unit 152 to perform fault diagnosis, and the like.

[0022] <Current flow under normal conditions> 2A is a diagram showing the flow of current in a normal state. When the actuators 110A and 110B are in a normal state, current flows from the power supply terminal 101 through the actuators 110A and 110B and the FET 120 toward the resistor R5, as shown by the arrows in FIG. 2A.

[0023] <Current Flow in an Open Fault State of Actuator 110B> FIG. 2B is a diagram showing the current flow when an open circuit fault occurs in actuator 110B. When actuator 110A is in a normal state and an open circuit fault occurs in actuator 110B, if FET 120 is driven, all of the current passes through actuator 110A, as shown in FIG. 2B. Compared to the state in FIG. 2A where current flows through parallel actuators 110A and 110B, as shown in FIG. 2B, when current flows only through actuator 110A, the combined resistance between power supply terminal 101 and FET 120 increases, and the drain terminal voltage of FET 120 decreases, resulting in a decrease in the voltage value input from ADC 140 to microcomputer 150. This allows fault diagnosis unit 152 to determine that an open circuit fault has occurred in actuator 110A or 110B.

[0024] <Current flow when actuator 110A is short-circuited> FIG. 2C is a diagram showing the current flow when a short circuit occurs in actuator 110A. When actuator 110B is in a normal state and a short circuit occurs in actuator 110A, if FET 120 is driven, all of the current passes through actuator 110A, as shown in FIG. 2C. Compared to the state in FIG. 2A where current flows through parallel actuators 110A and 110B, a short circuit in actuator 110A causes a short circuit between power supply terminal 101 and FET 120, as shown in FIG. 2C, and the drain terminal voltage of FET 120 increases, resulting in an increase in the voltage value input from ADC 140 to microcomputer 150. Therefore, fault diagnosis unit 152 can determine that a short circuit has occurred in actuator 110A or 110B.

[0025] <Voltage Applied to Actuators 110A and 110B During Fault Diagnosis> 2A to 2C, fault diagnosis can be performed by passing a current through the actuators 110A and 110B. However, when the actuators 110A and 110B are driven to perform fault diagnosis of the actuators 110A and 110B, an operation unit of an input device or the like built into the electronic device 100 vibrates, presenting an unwanted tactile sensation to the user.

[0026] For this reason, when performing a fault diagnosis, the electronic device 100 sets the voltage value of the reference signal for fault diagnosis so that the voltage applied to the actuators 110A and 110B is a predetermined voltage lower than the operating voltage at which the actuators 110A and 110B operate. In this way, a current is passed through the actuators 110A and 110B to perform a fault diagnosis without driving the actuators 110A and 110B, so that an operation unit of an input device or the like built into the electronic device 100 is not vibrated and unnecessary tactile sensations are not presented to the user. The operating voltage is the lower limit of the voltage at which the actuators 110A and 110B can operate.

[0027] <Voltage waveforms of each part during fault diagnosis under normal conditions> 3A is a diagram showing voltage waveforms of various parts of the electronic device 100 when a fault diagnosis is performed when the actuators 110A and 110B are in a normal state. In FIG. 3A, the horizontal axis represents time, and the vertical axis represents voltage values. FIG. 3A shows example waveforms of the reference signal, the drive control signal, the drain-source voltage Vds of the FET 120, the load signal, and the input voltage of the fault diagnosis unit 152. The input voltage of the fault diagnosis unit 152 is a voltage input from the ADC 140 to the microcomputer 150. The drain-source voltage Vds indicates the level of the drain-source voltage Vds when the FET 120 is in an on (ON) state and an off (OFF) state, as indicated by ON and OFF.

[0028] When the reference signal rises at time t1, the drive control signal also begins to rise, and the drain-source voltage Vds begins to fall. Also at time t1, the load signal begins to rise, and the input voltage of fault diagnosis unit 152 begins to fall due to the fall in drain-source voltage Vds.

[0029] When the reference signal rises completely at time t2, the drive control signal also rises completely, and the drain-source voltage Vds drops to Vds1. Also, at time t2, the load signal rises completely, and the input voltage of the fault diagnosis unit 152 starts to drop to Vadc1.

[0030] When the reference signal starts to fall at time t3, the drive control signal also starts to fall, and the drain-source voltage Vds starts to increase. Also at time t3, the load signal starts to fall, and the input voltage of fault diagnosis unit 152 starts to increase due to the increase in drain-source voltage Vds.

[0031] In this way, when the drain-source voltage Vds drops to Vds1, it is close to the voltage value when the FET 120 is in the off state, so the FET 120 does not turn on completely, and the current flowing between the drain terminal and the source terminal of the FET 120 during fault diagnosis is very small. Also, when the drain-source voltage Vds drops to Vds1, a predetermined voltage lower than the operating voltage is applied to the actuators 110A and 110B, so the actuators 110A and 110B do not operate. Therefore, fault diagnosis can be performed without operating the actuators 110A and 110B.

[0032] Furthermore, the period between times t2 and t3 can be a relatively long time, on the order of several tens of milliseconds to several seconds, so that a sufficiently long time can be taken for fault diagnosis, and erroneous determinations can be suppressed.

[0033] <Voltage waveforms at each part during fault diagnosis in an open fault state> 3B is a diagram showing voltage waveforms of various parts of electronic device 100 when a fault diagnosis is performed when one of actuators 110A or 110B is in an open-circuit fault state. In FIG. 3B, the horizontal axis represents time, and the vertical axis represents voltage values. FIG. 3B shows an example of waveforms of the drain-source voltage Vds of FET 120, the load signal, and the input voltage of fault diagnosis unit 152, with the reference signal and drive control signal being omitted because they are the same as those in FIG. 3A. In the following, a description will be given assuming that an open-circuit fault has occurred in actuator 110B as shown in FIG. 2B, but the same applies when an open-circuit fault has occurred in actuator 110A.

[0034] When the reference signal (see FIG. 3A) rises at time t1, the drive control signal (see FIG. 3A) also begins to rise, and the drain-source voltage Vds begins to drop. Also, at time t1, the load signal begins to rise, and the input voltage of fault diagnosis unit 152 begins to drop due to the drop in drain-source voltage Vds.

[0035] When the reference signal rises completely at time t2, the drive control signal also rises completely, and the drain-source voltage Vds drops to Vds2. At this time, an open circuit fault occurs in actuator 110B, and the resistance between power supply terminal 101 and the drain terminal of FET 120 is higher than when actuators 110A and 110B are in a normal state. This causes the drain terminal voltage of FET 120 to be lower than in the normal state. Therefore, the drain-source voltage Vds2 at time t2 is lower than the drain-source voltage Vds1 shown in FIG. 3A. Also, at time t2, the load signal rises completely, and the input voltage of fault diagnosis unit 152 begins to drop to Vadc2. Because the drop in drain-source voltage Vds is greater than in FIG. 3A, the input voltage Vadc2 of fault diagnosis unit 152 is lower than the input voltage Vadc1 of fault diagnosis unit 152 shown in FIG. 3A.

[0036] When the reference signal starts to fall at time t3, the drive control signal also starts to fall, and the drain-source voltage Vds starts to increase. Also at time t3, the load signal starts to fall, and the input voltage of fault diagnosis unit 152 starts to increase due to the increase in drain-source voltage Vds.

[0037] In this way, the input voltage Vadc2 of the fault diagnosis unit 152 when an open circuit fault occurs in the actuator 110B is lower than the input voltage Vadc1 of the fault diagnosis unit 152 in a normal state, so the fault diagnosis unit 152 can determine that an open circuit fault has occurred based on the input voltage.

[0038] <Voltage waveforms at each part during fault diagnosis in a short-circuit fault state> 3C is a diagram showing voltage waveforms of various parts of electronic device 100 when a fault diagnosis is performed when one of actuators 110A or 110B is in a short-circuit fault state. In FIG. 3C, the horizontal axis represents time, and the vertical axis represents voltage value. FIG. 3C shows an example of waveforms of drain-source voltage Vds of FET 120, a load signal, and an input voltage of fault diagnosis unit 152, with the reference signal and drive control signal omitted because they are the same as those in FIG. 3A. In the following, a description will be given assuming that a short-circuit fault has occurred in actuator 110A as shown in FIG. 2C, but the same applies when a short-circuit fault has occurred in actuator 110B.

[0039] When the reference signal (see FIG. 3A) rises at time t1, the drive control signal (see FIG. 3A) also begins to rise, and the drain-source voltage Vds begins to drop. Also, at time t1, the load signal begins to rise, and the input voltage of fault diagnosis unit 152 begins to drop due to the drop in drain-source voltage Vds.

[0040] When the reference signal rises completely at time t2, the drive control signal also rises completely, and the drain-source voltage Vds drops to Vds3. At this time, a short circuit occurs in actuator 110A, and compared to when actuators 110A and 110B are in a normal state, a short circuit occurs between power supply terminal 101 and the drain terminal of FET 120, causing the drain terminal voltage of FET 120 to be higher than in the normal state. Therefore, the drain-source voltage Vds3 at time t2 is higher than the drain-source voltage Vds1 shown in FIG. 3A. Also, at time t2, the load signal rises completely, and the input voltage of fault diagnosis unit 152 begins to drop to Vadc3. Because the drop in drain-source voltage Vds is smaller than in FIG. 3A, the input voltage Vadc3 of fault diagnosis unit 152 is higher than the input voltage Vadc1 of fault diagnosis unit 152 shown in FIG. 3A.

[0041] When the reference signal starts to fall at time t3, the drive control signal also starts to fall, and the drain-source voltage Vds starts to increase. Also, at time t3, the load signal starts to fall, and the input voltage of the fault diagnosis unit 152 starts to increase due to the increase in the drain-source voltage Vds.

[0042] Thus, since the input voltage Vadc3 of the fault diagnosis unit 152 when a short circuit fault occurs in the actuator 110A is higher than the input voltage Vadc1 of the fault diagnosis unit 152 in the normal state, the fault diagnosis unit 152 can determine that a short circuit fault has occurred based on the input voltage.

[0043] <Fault diagnosis by the fault diagnosis unit 152> FIG. 4 is a diagram showing voltage data used by the fault diagnosis unit 152 for fault diagnosis. The voltage values included in the voltage data shown in FIG. 4 are obtained by simulation. The voltage data is stored in the memory 153.

[0044] The input voltage of the fault diagnosis unit 152 is the voltage output by the ADC 140 to the microcomputer 150. When the output voltage of the ADC 140 is between V1 and V2, the fault diagnosis unit 152 determines that the actuators 110A and 110B are in a normal state. V1 < V2, and V1 and V2 are positive voltages. The input voltage Vadc1 of the fault diagnosis unit 152 shown in FIG. 3A (normal state) is a voltage between V1 and V2.

[0045] Also, when the output voltage of the ADC 140 is out of the range between V1 and V2, the fault diagnosis unit 152 determines that a fault has occurred. The fault is an open circuit fault, a short circuit fault, or other abnormal states of the actuators 110A or 110B. Other abnormal states are, for example, abnormal high resistance states or abnormal low resistance states of the actuators 110A and 110B. When the fault diagnosis unit 152 determines that a fault has occurred, it notifies a higher-level control unit such as an input device incorporating the electronic device 100.

[0046] The fault diagnosis unit 152 does not determine what kind of fault has occurred in the actuator 110A or 110B. However, in addition to the voltages V1 and V2, the following voltages VL1, VL2, VH1, and VH2 may be used to discriminate the fault state.

[0047] When the output voltage of the ADC 140 is lower than V1 and not less than VL2, the fault diagnosis unit 152 determines that either one of the actuators 110A and 110B is in an abnormal high-resistance state. VL2 < V1, and VL2 is a positive voltage. The abnormal high-resistance state means that although the actuator 110A or 110B is not open-circuited, damage has occurred in the wiring or the like, and the resistance value has become extremely higher than that in the normal state.

[0048] When the output voltage of the ADC 140 is lower than VL2 and not less than VL1, the fault diagnosis unit 152 determines that either one of the actuators 110A and 110B is in an open-fault state. VL1 < VL2, and VL1 is a positive voltage. The input voltage Vadc2 of the fault diagnosis unit 152 shown in FIG. 3B (open state) is lower than VL2 and not less than VL1.

[0049] When the output voltage of the ADC 140 is lower than VL1, the fault diagnosis unit 152 determines that both of the actuators 110A and 110B are in an abnormal high-resistance state.

[0050] When the output voltage of the ADC 140 is higher than V2 and not more than VH1, the fault diagnosis unit 152 determines that either one of the actuators 110A and 110B is in an abnormal low-resistance state. VH1 > V2. The abnormal low-resistance state means that although the actuator 110A or 110B is not short-circuited, damage has occurred in the wiring or the like, and the resistance value has become extremely lower than that in the normal state.

[0051] When the output voltage of ADC 140 is higher than VH1 and equal to or lower than VLH2, fault diagnosis unit 152 determines that one or both of actuators 110A and 110B are in a short-circuit fault state. VH2>VH1. The input voltage Vadc3 of fault diagnosis unit 152 shown in FIG. 3C (short-circuit state) is higher than VH1 and equal to or lower than VLH2.

[0052] Voltage data representing voltage values ​​V1 and V2, or voltage data representing voltage values ​​VL1, VL2, V1, V2, VH1, and VH2 are stored in memory 153, and fault diagnosis unit 152 reads the voltage data from memory 153, compares it with the output voltage of ADC 140, and performs fault diagnosis.

[0053] <Fault diagnosis processing> Fig. 5 is a flowchart showing the fault diagnosis process executed by fault diagnosis unit 152. Fault diagnosis unit 152 repeatedly executes the process shown in Fig. 5. As a prerequisite, fault diagnosis unit 152 reads out voltage data from memory 153.

[0054] The fault diagnosis unit 152 acquires the output voltage of the ADC 140 (step S1).

[0055] The fault diagnosis unit 152 compares the acquired output voltage of the ADC 140 with the voltage values ​​V1 and V2 included in the voltage data (step S2).

[0056] The fault diagnosis unit 152 performs fault diagnosis based on the comparison result (step S3). When the output voltage of the ADC 140 is equal to or greater than V1 and equal to or less than V2, the fault diagnosis unit 152 determines that the actuators 110A and 110B are in a normal state, and when the output voltage of the ADC 140 is out of the range of equal to or greater than V1 and equal to or less than V2, the fault diagnosis unit 152 determines that a fault has occurred.

[0057] The fault diagnosis unit 152 ends the series of processes (END). The fault diagnosis unit 152 repeatedly executes the processes from START to END at a predetermined cycle or at a predetermined timing.

[0058] In addition, using voltages L1, VL2, V1, V2, VH1, and VH2, it may be determined whether actuators 110A and 110B are in a normal state, one of them is in an abnormally high resistance state, one of them is in an open fault state, both are in an abnormally high resistance state, one of them is in an abnormally low resistance state, or one or both are in a short fault state.

[0059] As described above, the operational amplifier 130 that drives the FET 120 outputs to the FET 120 a drive control signal that represents the result of a comparison between a load signal, which is a voltage converted from the current flowing through the current path, and a reference signal that serves as the basis for the operation of the FET 120, and when the fault diagnosis unit 152 detects a voltage outside the normal voltage range, it determines that the actuators 110A and 110B are in an abnormal state.

[0060] Therefore, the FET 120 is gradually turned on by the drive control signal, so that even if the actuator 110A or 110B is broken, the current flowing through the FET 120 can be suppressed and damage to the FET 120 can be prevented.

[0061] Therefore, it is possible to provide electronic device 100 that can perform a fault diagnosis on actuator 110A or 110B and can prevent damage to FET 120.

[0062] Furthermore, the fault diagnosis unit 152 determines whether the actuators 110A, 110B are in an abnormal state or a normal state, and an abnormal state is an open fault or short fault of the actuators 110A, 110B. Therefore, a fault in the actuator 110A or 110B can be detected based on the voltage of the actuators 110A, 110B.

[0063] Furthermore, the voltages of the actuators 110A, 110B detected by the fault diagnosis unit 152 are such that the normal voltage of the actuators 110A, 110B in a normal state is higher than the open voltage in the event of an open fault in the actuators 110A, 110B, and the short voltage in the event of a short fault in the actuators 110A, 110B is higher than the normal voltage. Therefore, it is possible to detect open faults and short faults in the actuators 110A or 110B based on the voltages of the actuators 110A, 110B.

[0064] The fault diagnosis unit 152 performs fault diagnosis based on the voltage of the current path between the multiple actuators 110A, 110B and the FET 120, and can therefore detect a fault in the actuator 110A or 110B based on the voltage of the actuators 110A, 110B obtained through the current path.

[0065] Furthermore, when performing fault diagnosis, the fault diagnosis unit 152 sets the voltage of the reference signal to a voltage applied to the actuators 110A and 110B that is lower than the operating voltage at which the actuators 110A and 110B operate, so that fault diagnosis can be performed without operating the actuators 110A and 110B.

[0066] The above describes a configuration in which the fault diagnosis unit 152 determines whether an open circuit failure, a short circuit failure, or another abnormal state (e.g., an abnormally high resistance state or an abnormally low resistance state) has occurred in the actuators 110A and 110B based on the output voltage of the ADC 140. However, even if the electronic device 100 includes only one of the actuators 110A and 100B, the output voltage of the ADC 140 changes if an open circuit failure, a short circuit failure, or another abnormal state (e.g., an abnormally high resistance state or an abnormally low resistance state) has occurred. For this reason, the electronic device 100 may be configured to include only one actuator. It is sufficient that the fault diagnosis unit 152 determines whether an open circuit failure, a short circuit failure, or another abnormal state (e.g., an abnormally high resistance state or an abnormally low resistance state) has occurred in one actuator based on the output voltage of the ADC 140.

[0067] <Embodiment 2> <Configuration of Electronic Device 200> 6 is a diagram showing an electronic device 200 according to embodiment 2. The electronic device 200 includes a power supply terminal 101, actuators 110A and 110B, a FET 120, an operational amplifier 130, amplifiers 135A and 135B, an ADC 140, a microcomputer 150, and resistors R1 to R5 and R8 to R17. Here, among the components of the electronic device 200 according to embodiment 2, the same components as those of the electronic device 100 according to embodiment 1 are denoted by the same reference numerals, and description thereof will be omitted.

[0068] The electronic device 200 of the second embodiment is configured such that the voltage divider circuit including resistors R6 and R7 of the electronic device 100 of the first embodiment is omitted, and instead resistors R8 and R9 are provided which are connected in series to the actuators 110A and 110B, respectively, and a voltage is input to the ADC 140 via amplifiers 135A and 135B. The resistors R8 and R9 are resistors for converting the current flowing through the actuators 110A and 110B into a voltage, and have the same resistance value. Resistors R10 to R17 are connected around the amplifiers 135A and 135B.

[0069] More specifically, the terminal of resistor R8 connected to actuator 110A is designated as T81, the terminal of resistor R8 connected to the drain terminal of FET 120 is designated as T82, the terminal of resistor R9 connected to actuator 110B is designated as T91, and the terminal of resistor R9 connected to the drain terminal of FET 120 is designated as T92. Terminal T81 is an example of a first terminal of resistor R8, and T82 is an example of a second terminal of resistor R8. Terminal T91 is an example of a first terminal of resistor R9, and T92 is an example of a second terminal of resistor R9.

[0070] Resistor R10 is connected between terminal T81 and the non-inverting input terminal of amplifier 135A, and resistor R12 is connected between terminal T82 and the inverting input terminal of amplifier 135A. One end of resistor R11 is connected between resistor R10 and the non-inverting input terminal of amplifier 135A, and the other end of resistor R11 is grounded. Resistor R13 is connected as a negative feedback resistor between the output terminal and the inverting input terminal of amplifier 135A. The output terminal of amplifier 135A is connected to one of the two input terminals of ADC 140.

[0071] Resistor R14 is connected between terminal T91 and the non-inverting input terminal of amplifier 135B, and resistor R16 is connected between terminal T92 and the inverting input terminal of amplifier 135B. One end of resistor R15 is connected between resistor R14 and the non-inverting input terminal of amplifier 135B, and the other end of resistor R15 is grounded. Resistor R17 is connected as a negative feedback resistor between the output terminal and inverting input terminal of amplifier 135B. The output terminal of amplifier 135B is connected to the other of the two input terminals of ADC 140.

[0072] The ADC 140 converts the voltage values ​​output from the amplifiers 135A and 135B into digital values ​​and outputs the converted values ​​to the microcomputer 150. The fault diagnosis unit 152 of the microcomputer 150 of the second embodiment performs fault diagnosis based on the two voltage values ​​amplified by the amplifiers 135A and 135B and digitally converted by the ADC 140.

[0073] The resistors R10 to R17 are adjusted so that the voltage values ​​output from the amplifiers 135A and 135B are applied to the actuators 110A and 110B in a normal state and in an abnormal state, respectively.

[0074] Fault diagnosis unit 152 performs fault diagnosis on actuators 110A and 110B based on the two voltages input from ADC 140. The two voltages input from ADC 140 represent voltages applied to actuators 110A and 110B, which are two loads. Memory 153 stores programs and data necessary for reference signal generation unit 151 to perform reference signal generation processing, programs and data necessary for fault diagnosis unit 152 to perform fault diagnosis, and also stores voltage data used by electronic device 200 of the embodiment.

[0075] <Current flow under normal conditions> 7A is a diagram showing the flow of current in a normal state. When the actuators 110A and 110B are in a normal state, current flows from the power supply terminal 101 through the actuators 110A and 110B and the FET 120 toward the resistor R5, as shown by the arrows in FIG. 7A.

[0076] <Current Flow in an Open Fault State of Actuator 110B> FIG. 7B is a diagram showing the current flow when an open circuit fault occurs in actuator 110B. When actuator 110A is in a normal state and an open circuit fault occurs in actuator 110B, if FET 120 is driven, all current passes through actuator 110A and no current flows through actuator 110B, as shown in FIG. 7B. As a result, the voltage across resistor R8 connected in series with actuator 110A becomes higher than in the normal state, and the voltage across resistor R9 connected in series with actuator 110B becomes 0 V. Based on these voltage changes, fault diagnosis unit 152 can determine that an open circuit fault has occurred in actuator 110A or 110B.

[0077] <Current flow when actuator 110A is short-circuited> FIG. 7C is a diagram showing the current flow when a short circuit occurs in actuator 110A. When actuator 110B is in a normal state and a short circuit occurs in actuator 110A, if FET 120 is driven, all of the current passes through actuator 110A, as shown in FIG. 7C. As a result, the voltage across resistor R8 connected in series with actuator 110A becomes higher than in the normal state, and the voltage across resistor R9 connected in series with actuator 110B becomes significantly lower than in the normal state because the current therethrough becomes nearly zero. Based on these voltage changes, fault diagnosis unit 152 can determine that a short circuit has occurred in actuator 110A or 110B.

[0078] <Voltage Applied to Actuators 110A and 110B During Fault Diagnosis> As described with reference to FIGS. 7A to 7C, fault diagnosis can be performed by passing a current through the actuators 110A and 110B. As with the electronic device 100 of the first embodiment, when performing fault diagnosis, the electronic device 200 sets the voltage value of the reference signal for fault diagnosis so that the voltage applied to the actuators 110A and 110B becomes a predetermined voltage lower than the operating voltage at which the actuators 110A and 110B operate. In this way, fault diagnosis can be performed by passing a current through the actuators 110A and 110B without driving the actuators 110A and 110B. This prevents the operation unit of an input device or the like built into the electronic device 200 from vibrating, and avoids presenting an unnecessary tactile sensation to the user.

[0079] <Voltage waveforms of each part during fault diagnosis under normal conditions> FIG. 8A is a diagram showing voltage waveforms of various components of the electronic device 200 when a fault diagnosis is performed when the actuators 110A and 110B are in a normal state. In FIG. 8A, the horizontal axis represents time, and the vertical axis represents voltage values. FIG. 8A also shows example waveforms of the reference signal, the drive control signal, the drain-source voltage Vds of the FET 120, the load signal, and two input voltages Va and Vb of the fault diagnosis unit 152. The two input voltages Va and Vb of the fault diagnosis unit 152 are voltages input from the ADC 140 to the microcomputer 150 and detected by resistors R8 and R9, respectively. That is, the input voltages Va and Vb represent the values ​​of the currents flowing through the actuators 110A and 110B, respectively. Note that the drain-source voltage Vds is indicated by ON and OFF, respectively, to represent the levels of the drain-source voltage Vds when the FET 120 is in an on (ON) state and an off (OFF) state.

[0080] When the reference signal rises at time t1, the drive control signal also begins to rise, and the drain-source voltage Vds begins to fall. Also at time t1, the load signal begins to rise, and current flows through the actuators 110A and 110B as the drain-source voltage Vds falls, so that the two input voltages Va and Vb of the fault diagnosis unit 152 begin to rise.

[0081] When the reference signal rises completely at time t2, the drive control signal also rises completely, and the drain-source voltage Vds drops to Vds1. Also, at time t2, the load signal rises completely, and the two input voltages Va and Vb of the fault diagnosis unit 152 increase to Va1 and Vb1, respectively.

[0082] When the reference signal starts to fall at time t3, the drive control signal also starts to fall, and the drain-source voltage Vds starts to increase. Also at time t3, the load signal starts to fall, and the increase in the drain-source voltage Vds reduces the current flowing through the actuators 110A and 110B, so the two input voltages Va and Vb of the fault diagnosis unit 152 start to decrease.

[0083] As described above, when the drain-source voltage Vds drops to Vds1, it is close to the voltage value when the FET 120 is in the off state. Therefore, the FET 120 does not turn on completely, and the current flowing between the drain terminal and the source terminal of the FET 120 during fault diagnosis is very small. Furthermore, when the drain-source voltage Vds drops to Vds1, a predetermined voltage lower than the operating voltage is applied to the actuators 110A and 110B, so the actuators 110A and 110B do not operate. Therefore, fault diagnosis can be performed without operating the actuators 110A and 110B. Note that the drain-source voltage Vds1 does not have to be equal to the drain-source voltage Vds1 of the first embodiment.

[0084] Furthermore, the period between times t2 and t3 can be a relatively long time, on the order of several tens of milliseconds to several seconds, so that a sufficiently long time can be taken for fault diagnosis, and erroneous determinations can be suppressed.

[0085] <Voltage waveforms at each part during fault diagnosis in an open fault state> 8B is a diagram showing voltage waveforms of various parts of electronic device 200 when a fault diagnosis is performed when one of actuators 110A or 110B is in an open-circuit fault state. In FIG. 8B, the horizontal axis represents time, and the vertical axis represents voltage values. FIG. 8B shows an example of waveforms of drain-source voltage Vds of FET 120, a load signal, and an input voltage of fault diagnosis unit 152, with the reference signal and drive control signal omitted because they are the same as those in FIG. 8A. In the following, a description will be given assuming that an open-circuit fault has occurred in actuator 110B as shown in FIG. 7B, but the same applies when an open-circuit fault has occurred in actuator 110A.

[0086] When the reference signal (see FIG. 8A) rises at time t1, the drive control signal (see FIG. 8A) also begins to rise, and the drain-source voltage Vds begins to drop. Also, at time t1, the load signal begins to rise, and the input voltage of fault diagnosis unit 152 begins to drop due to the drop in drain-source voltage Vds.

[0087] When the reference signal has completely risen at time t2, the drive control signal has also completely risen, and the drain-source voltage Vds drops to Vds2. At this time, if an open fault occurs in actuator 110B and FET 120 is driven, all of the current passes through actuator 110A and no current flows through actuator 110B, so that input voltage Va to fault diagnosis unit 152 becomes Va2, which is higher than Va1 in the normal state, and input voltage Vb to fault diagnosis unit 152 becomes 0 V because actuator 110B is in the open state.

[0088] When the reference signal starts to fall at time t3, the drive control signal also starts to fall, and the drain-source voltage Vds starts to increase. Also at time t3, the load signal starts to fall, and the increase in drain-source voltage Vds reduces the current flowing through actuator 110A, so the input voltage Va of fault diagnosis unit 152 starts to decrease.

[0089] In this way, the input voltage Va2 of the fault diagnosis unit 152 when an open fault occurs in actuator 110B is higher than the input voltage Va1 of the fault diagnosis unit 152 in a normal state, and the input voltage Vb of the fault diagnosis unit 152 corresponding to actuator 110B in which an open fault (disconnection) has occurred is 0V, so the fault diagnosis unit 152 can determine that a fault (open fault or short fault) has occurred in actuator 110A or 110B based on the two input voltages Va and Vb.

[0090] <Voltage waveforms at each part during fault diagnosis in a short-circuit fault state> 8C is a diagram showing voltage waveforms of various parts of electronic device 200 when a fault diagnosis is performed when one of actuators 110A or 110B is in a short-circuit fault state. In FIG. 8C, the horizontal axis represents time, and the vertical axis represents voltage value. FIG. 8C shows an example of waveforms of drain-source voltage Vds of FET 120, a load signal, and an input voltage of fault diagnosis unit 152, with the reference signal and drive control signal being omitted because they are the same as those in FIG. 8A. In the following, a description will be given assuming that a short-circuit fault has occurred in actuator 110A as shown in FIG. 7C, but the same applies when a short-circuit fault has occurred in actuator 110B.

[0091] When the reference signal (see FIG. 8A) rises at time t1, the drive control signal (see FIG. 8A) also begins to rise, and the drain-source voltage Vds begins to drop. Also, at time t1, the load signal begins to rise, and the input voltage of fault diagnosis unit 152 begins to drop due to the drop in drain-source voltage Vds.

[0092] When the reference signal has fully risen at time t2, the drive control signal has also fully risen, and the drain-source voltage Vds drops to Vds3. If FET 120 is driven when actuator 110B is in the normal state and a short circuit fault occurs in actuator 110A, all of the current passes through actuator 110A, as shown in Figure 7C, and the voltage of resistor R8 connected in series with actuator 110A becomes Va3, which is higher than Va1 in the normal state, and the voltage Vb of resistor R9 connected in series with actuator 110B drops to Vb3, which is significantly lower than Vb1 in the normal state.

[0093] When the reference signal starts to fall at time t3, the drive control signal also starts to fall, and the drain-source voltage Vds starts to increase. Also at time t3, the load signal starts to fall, and the increase in the drain-source voltage Vds reduces the current flowing through actuator 110A, and the input voltage Va of fault diagnosis unit 152 starts to decrease.

[0094] Thus, when a short circuit fault occurs in the actuator 110A, the input voltage Va3 of the fault diagnosis unit 152 is higher than the input voltage Va1 of the fault diagnosis unit 152 in the normal state, and the input voltage Vb is significantly lower than the input voltage Vb1 in the normal state. Therefore, the fault diagnosis unit 152 can determine that a fault (short circuit fault or open circuit fault) has occurred in the actuator 110A or 110B based on the input voltage.

[0095] <Fault diagnosis by the fault diagnosis unit 152> FIG. 9 is a diagram showing voltage data used by the fault diagnosis unit 152 in the fault diagnosis of Embodiment 2. The voltage values included in the voltage data shown in FIG. 9 are obtained by simulation. The voltage data is stored in the memory 153.

[0096] The two input voltages Va and Vb of the fault diagnosis unit 152 are voltages output by the amplifiers 135A and 135B, digitally converted by the ADC 140, and output to the microcomputer 150. The fault diagnosis unit 152 determines that the actuators 110A and 110B are in a normal state when the input voltage Va is greater than or equal to Va11 and less than or equal to Va12, and the input voltage Vb is greater than or equal to Vb11 and less than or equal to Vb12. Va11 < Va12, Vb11 < Vb12, Va11 = Vb11, and Va12 = Vb12. Also, Va11, Va12, Vb11, and Vb12 are positive voltages. The input voltage Va1 of the fault diagnosis unit 152 shown in FIG. 8A (normal state) is a voltage greater than or equal to Va11 and less than or equal to Va12, and the input voltage Vb1 is a voltage greater than or equal to Vb11 and less than or equal to Vb12.

[0097] In addition, the fault diagnosis unit 152 determines that the actuator 110A or 110B is in a fault state when the input voltage Va deviates from the range of greater than or equal to Va11 and less than or equal to Va12, or the input voltage Vb deviates from the range of greater than or equal to Vb11 and less than or equal to Vb12. The fault state is an open circuit fault of the actuator 110A and / or 110B, a short circuit fault of the actuator 110A or 110B, an abnormal high resistance state or an abnormal low resistance state of either the actuator 110A or 110B.

[0098] The fault diagnosis unit 152 does not determine which of the above fault states the actuator 110A or 110B is in, but when the voltage Va or Vb is 0V in Figure 9, an open fault or short fault has occurred, and when the voltages Va and Vb are 0V, an open fault has occurred in the actuators 110A and 110B.

[0099] As described above, the operational amplifier 130 that drives the FET 120 outputs to the FET 120 a drive control signal that represents the result of a comparison between a load signal, which is a voltage converted from the current flowing through the current path, and a reference signal that serves as the basis for the operation of the FET 120, and when the fault diagnosis unit 152 detects a voltage outside the normal voltage range, it determines that the actuators 110A and 110B are in an abnormal state.

[0100] Therefore, the FET 120 is gradually turned on by the drive control signal, so that even if the actuator 110A or 110B is broken, the current flowing through the FET 120 can be suppressed and damage to the FET 120 can be prevented.

[0101] Therefore, it is possible to provide the electronic device 200 that can perform a fault diagnosis on the actuator 110A or 110B and can prevent the FET 120 from being damaged.

[0102] Furthermore, similar to the electronic device 100 of embodiment 1, the electronic device 200 of embodiment 2 can detect a failure of the actuator 110A or 110B based on the voltage applied to the actuators 110A, 110B, and can detect an open failure and a short failure of the actuator 110A or 110B. Furthermore, when performing a failure diagnosis, the failure diagnosis unit 152 sets the voltage of the reference signal to a voltage applied to the plurality of actuators 110A and 110B that is lower than the operating voltage at which the actuators 110A and 110B operate, and therefore can perform a failure diagnosis without operating the actuators 110A and 110B.

[0103] The electronic device 200 further includes a plurality of resistors R8 and R9 connected in series to the plurality of actuators 110A and 110B, respectively, and a plurality of amplifiers 135A and 135B that amplify the voltages across the resistors R8 and R9. The resistors R8 and R9 have first terminals T81 and T91 connected to the actuators 110A and 110B, respectively, and second terminals T82 and T92 connected to the FET 120. The non-inverting input terminals of the amplifiers 135A and 135B are connected to the first terminals T81 and T91, respectively, and the inverting input terminals of the amplifiers 135A and 135B are connected to the second terminals T82 and T92. The fault diagnosis unit 152 performs fault diagnosis based on the output voltages of the amplifiers 135A and 135B. This allows the provision of an electronic device 200 that can perform fault diagnosis based on the currents flowing through the actuators 110A and 110B.

[0104] The above describes a configuration in which the fault diagnosis unit 152 determines whether an open circuit failure, a short circuit failure, or another abnormal state (e.g., an abnormally high resistance state or an abnormally low resistance state) has occurred in the actuators 110A and 110B based on the output voltage of the ADC 140. However, even if the electronic device 200 includes only one of the actuators 110A and 110B, the output voltage of the ADC 140 changes if an open circuit failure, a short circuit failure, or another abnormal state (e.g., an abnormally high resistance state or an abnormally low resistance state) occurs. Therefore, the electronic device 200 may be configured to include only one actuator. In this case, for example, if the electronic device 200 includes the actuator 110A in FIG. 6 but does not include the actuator 110B, the components included in the path from the power supply terminal 101 through the actuator 110B to the drain terminal (D) of the FET 120 and the path from the actuator 110B to the ADC 140 are unnecessary. The fault diagnosis unit 152 may determine, based on the output voltage of the ADC 140, that an open circuit fault, short circuit fault, or other abnormal state (for example, an abnormally high resistance state or an abnormally low resistance state) has occurred in one of the actuators 110A.

[0105] The above describes electronic devices according to exemplary embodiments of the present disclosure, but the present disclosure is not limited to the specifically disclosed embodiments, and various modifications and variations are possible without departing from the scope of the claims.

[0106] This international application claims priority based on Japanese Patent Application No. 2022-003500, filed on January 13, 2022, the entire contents of which are incorporated herein by reference. [Explanation of symbols]

[0107] 100, 200 electronic equipment 101 Power terminal 110A, 110B Actuators 120FET 130 operational amplifiers 135A, 135B amplifiers 140 ADC 150 microcomputers 151 Reference signal generation section 152 Fault diagnosis section 153 memory R1~R17 Resistor

Claims

1. A current path including a plurality of paths connecting in parallel between a power supply terminal and a connection point, and a path connecting the connection point and a ground potential point; a plurality of loads inserted in series into the plurality of paths, respectively; an N-channel FET provided in a path connecting the connection point and the ground potential point in the current path; a reference signal generating unit that generates a reference signal that serves as a reference for the operation of the FET; a fault diagnosis unit connected to the connection point and performing fault diagnosis based on a voltage at the connection point; an operational amplifier that drives the FET and forms a constant current circuit together with the FET; Including, the FET has a drain terminal connected to the connection point, a source terminal connected to the ground potential point via a resistor, and a gate terminal connected to the output terminal of the operational amplifier; the operational amplifier has a non-inverting input terminal connected to the reference signal generating unit and to which the reference signal is input, and an inverting input terminal connected to a path of the current path that connects the source terminal and the resistor and to which a load signal obtained by converting into a voltage a current flowing through a path of the current path that connects the source terminal and the ground potential point is input, the operational amplifier compares the load signal input to the inverting input terminal with the reference signal input to the non-inverting input terminal so that a constant current flows through the current path, and outputs a drive control signal representing the comparison result to the gate terminal of the FET; the fault diagnosis unit determines that the load is in an abnormal state when the voltage at the connection point is outside a normal voltage range; The electronic device wherein the reference signal generation unit sets a voltage value of the reference signal for fault diagnosis so that when the fault diagnosis unit performs fault diagnosis, the voltage applied to the plurality of loads becomes a predetermined voltage that is lower than the operating voltage at which the plurality of loads operate.

2. the fault diagnosis unit determines whether the plurality of loads are in an abnormal state or a normal state based on the voltages at the connection points; The electronic device according to claim 1 , wherein the abnormal state is an open circuit fault, a short circuit fault, or another abnormal state of the load.

3. 2. The electronic device according to claim 1, wherein the input voltage input from the connection point to the fault diagnosis unit is a normal voltage in a normal state of the load that is higher than an open voltage in the event of an open fault in the load, and a short voltage in the event of a short fault in the load that is higher than the normal voltage.

4. A current path having a plurality of paths connecting in parallel between a power supply terminal and a connection point, and a path connecting the connection point and a ground potential point; a plurality of loads inserted in series into the plurality of paths, respectively; a plurality of first resistors connected in series to the plurality of loads in the plurality of paths, respectively; a plurality of amplifiers that respectively amplify voltages across both terminals of the plurality of first resistors; an N-channel FET provided in a path connecting the connection point and the ground potential point in the current path; a reference signal generating unit that generates a reference signal that serves as a reference for the operation of the FET; a fault diagnosis unit connected to output terminals of the plurality of amplifiers and performing fault diagnosis based on outputs of the plurality of amplifiers; an operational amplifier that drives the FET and forms a constant current circuit together with the FET; Including, the FET has a drain terminal connected to the connection point, a source terminal connected to the ground potential point via a second resistor, and a gate terminal connected to the output terminal of the operational amplifier; the operational amplifier has a non-inverting input terminal connected to the reference signal generating unit and to which the reference signal is input, and an inverting input terminal connected to a path of the current path that connects the source terminal and the second resistor and to which a load signal obtained by converting into a voltage a current flowing through a path of the current path that connects the source terminal and the ground potential point is input, the operational amplifier compares the load signal input to the inverting input terminal with the reference signal input to the non-inverting input terminal so that a constant current flows through the current path, and outputs a drive control signal representing the comparison result to the gate terminal of the FET; Each first resistor has a first terminal connected to the load and a second terminal connected to the node; non-inverting input terminals of the plurality of amplifiers are respectively connected to the first terminals of the plurality of first resistors, and inverting input terminals of the plurality of amplifiers are respectively connected to second terminals of the plurality of first resistors; the fault diagnosis unit determines that the load is in an abnormal state when any of the output voltages of the plurality of amplifiers is outside a normal voltage range; The electronic device wherein the reference signal generation unit sets a voltage value of the reference signal for fault diagnosis so that when the fault diagnosis unit performs fault diagnosis, the voltage applied to the plurality of loads becomes a predetermined voltage that is lower than the operating voltage at which the plurality of loads operate.

5. A load connected to a power supply terminal; an N-channel FET provided in a current path extending from the power supply terminal through the load to a ground potential point; a reference signal generating unit that generates a reference signal that serves as a reference for the operation of the FET; a fault diagnosis unit that performs fault diagnosis based on a voltage in a section of the current path between the load and a drain terminal of the FET; an operational amplifier that drives the FET and forms a constant current circuit together with the FET; Including, the FET has a drain terminal connected to the load, a source terminal connected to the ground potential point via a resistor, and a gate terminal connected to the output terminal of the operational amplifier; the operational amplifier has a non-inverting input terminal connected to the reference signal generating unit and to which the reference signal is input, and an inverting input terminal connected to a section of the current path between the source terminal and the resistor and to which a load signal obtained by converting a current flowing in a section of the current path between the source terminal and the ground potential point into a voltage is input; the operational amplifier compares the load signal input to the inverting input terminal with the reference signal input to the non-inverting input terminal so that a constant current flows through the current path, and outputs a drive control signal representing the comparison result to the gate terminal of the FET; the fault diagnosis unit determines that the load is in an abnormal state when a voltage in a section of the current path between the load and the drain terminal of the FET becomes a voltage outside a normal voltage range; The electronic device wherein the reference signal generation unit sets a voltage value of the reference signal for fault diagnosis so that when the fault diagnosis unit performs fault diagnosis, the voltage applied to the load becomes a predetermined voltage that is lower than the operating voltage at which the load operates.

6. the fault diagnosis unit determines whether the load is in an abnormal state or a normal state based on a voltage in a section of the current path between the load and the drain terminal of the FET; The electronic device according to claim 5 , wherein the abnormal state is an open circuit fault, a short circuit fault, or another abnormal state of the load.

7. An electronic device as described in claim 5, wherein the input voltage input to the fault diagnosis unit from the section of the current path between the load and the drain terminal of the FET is a normal voltage of the load in a normal state that is higher than the open voltage in the event of an open fault of the load, and a short voltage in the event of a short fault of the load that is higher than the normal voltage.

8. A load connected to a power supply terminal; a first resistor connected in series with the load; an amplifier that amplifies the voltage across the first resistor; an N-channel FET provided in a current path from the power supply terminal through the load and the first resistor to a ground potential point; a reference signal generating unit that generates a reference signal that serves as a reference for the operation of the FET; a fault diagnosis unit connected to an output terminal of the amplifier and performing fault diagnosis based on the output voltage of the amplifier; an operational amplifier that drives the FET and forms a constant current circuit together with the FET; Including, the first resistor has a first terminal connected to the load and a second terminal connected to the drain terminal of the FET; a non-inverting input terminal of the amplifier connected to the first terminal of the first resistor, and an inverting input terminal of the amplifier connected to the second terminal of the first resistor; the FET has a drain terminal connected to the second terminal of the first resistor, a source terminal connected to the ground potential point via a second resistor, and a gate terminal connected to the output terminal of the operational amplifier; the operational amplifier has a non-inverting input terminal connected to the reference signal generating unit and to which the reference signal is input, and an inverting input terminal connected to a section of the current path between the source terminal and the second resistor and to which a load signal obtained by converting a current flowing in a section of the current path between the source terminal and the ground potential point into a voltage is input, the operational amplifier compares the load signal input to the inverting input terminal with the reference signal input to the non-inverting input terminal so that a constant current flows through the current path, and outputs a drive control signal representing the comparison result to the gate terminal of the FET; the fault diagnosis unit determines that the load is in an abnormal state when the output voltage of the amplifier is outside a normal voltage range; The electronic device wherein the reference signal generation unit sets a voltage value of the reference signal for fault diagnosis so that when the fault diagnosis unit performs fault diagnosis, the voltage applied to the load becomes a predetermined voltage that is lower than the operating voltage at which the load operates.

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