Load drive device, diagnostic methods for load drive device

Abstract

This invention provides a high-performance and highly reliable load drive device. In this load drive device, which includes a diagnostic circuit for the drive system driver and an ESD protection capacitor, the ESD protection capacitor can be quickly charged even when the load is disconnected, and all diagnostics of the drive system driver can be completed within the required time. The invention is characterized by comprising: a load; a first switching element connected to and controlling the load; an ESD protection capacitor connected between the load and the first switching element; a charging circuit connected between the load and the first switching element and charging the ESD protection capacitor; and a second switching element connected between the ESD protection capacitor and the charging circuit.

Description

Technical Field

[0001] This invention relates to the structure and control of a load drive device, and particularly to an effective technique applicable to load drive devices equipped with ESD protection capacitors. Background Technology

[0002] In the event of a vehicle unexpectedly losing control, to prevent a major accident, it is necessary to forcibly stop the injectors, idle restart relay, electronic throttle, and other drive system actuators via a drive stop mechanism. Furthermore, to reliably stop the drive system in the event of vehicle loss of control, the proper functioning of the drive stop mechanism is diagnosed from the time the vehicle key is turned on until the crankshaft begins to turn. If the drive stop function malfunctions, the engine start-up is prevented.

[0003] In the diagnostics of the drive stop mechanism, the drive stop mechanism utilizes an arithmetic unit to monitor the output voltage of the load drive circuit when the drive is enabled and disabled. However, in the event of a load disconnection, the output voltage of the load drive circuit becomes sluggish due to the charging time of the ESD protection capacitor at the output terminal of the load drive circuit. This results in a problem where the diagnostics are not completed within the time from when the vehicle key is turned on until the crankshaft begins to turn. Therefore, in order to complete the diagnostics from when the load disconnection occurs until the crankshaft begins to turn, it is necessary to quickly charge the ESD protection capacitor.

[0004] By enabling diagnostics even when a load is disconnected, the engine can be started using a load other than the one disconnected. For example, even if one cylinder of a four-cylinder engine's injectors disconnects, the engine can be started using the injectors of the remaining cylinders, allowing the vehicle to be moved to a safe location.

[0005] As background technology, there is a technology that utilizes capacitors for ESD protection, such as that described in Patent Document 1. In the fuel injection control device of Patent Document 1, a technology is known in which an electrostatic protection capacitor and a constant current energizer are included between the downstream terminal of the injector and the downstream switch for injector drive. After the drive current flowing into the injector decreases, the constant current energizer causes a constant current to flow from the downstream terminal of the injector to GND, making it easy to detect voltage changes generated during the valve closing timing of the injector.

[0006] In addition, as another background technology, in the load driving device of Patent Document 2, there is a known technology that includes: a load, a synchronous rectifier circuit for driving the load, a voltage monitoring circuit for monitoring the voltage at the output terminal of the synchronous rectifier circuit, and a surge protection capacitor and a diagnostic current generation circuit between the output terminal of the synchronous rectifier circuit and the load. By charging and discharging the surge protection capacitor by the diagnostic current generation circuit, the voltage at the output terminal of the synchronous rectifier circuit is controlled to a certain value when the wire is disconnected, thereby detecting the wire disconnection by the monitoring circuit.

[0007] Existing technical documents

[0008] Patent documents

[0009] Patent Document 1: Japanese Patent Application Publication No. 2019-85925

[0010] Patent Document 2: International Publication No. 2019 / 220716 Summary of the Invention

[0011] The technical problem that the invention aims to solve

[0012] However, the aforementioned Patent Document 1 is a structure designed to easily detect voltage changes generated during the timing of the injector valve closing and to draw out the charge stored in the ESD protection capacitor, without considering the charging of the ESD protection capacitor.

[0013] Furthermore, in the aforementioned Patent Document 2, in order to detect the open circuit of the load, the capacitor for ESD protection is charged from the current source, and the voltage of the output terminal is controlled to a certain value, but it is not intended for the abnormal diagnosis of the driver stop mechanism.

[0014] Therefore, the purpose of this invention is to provide a high-performance and highly reliable load drive device and its diagnostic method. In a load drive device including a diagnostic circuit for the drive system driver and an ESD protection capacitor, the ESD protection capacitor can be quickly charged even when the load is disconnected, and the complete diagnostic of the drive system driver can be completed within the required time.

[0015] Technical solutions to solve technical problems

[0016] To address the aforementioned issues, the present invention includes: a load, a first switching element connected to the load and controlling the drive of the load, an ESD protection capacitor connected between the load and the first switching element, a charging circuit connected between the load and the first switching element and charging the ESD protection capacitor, and a second switching element connected between the ESD protection capacitor and the charging circuit.

[0017] Furthermore, the present invention is characterized by comprising the following steps: (a) energizing the charging circuit switch at the same time as the diagnosis of the load drive driver stop function begins; (b) after step (a), after the load drive driver switches from energized to de-energized, charging the ESD protection capacitor through the charging circuit and performing the diagnosis of the load drive driver stop function; and (c) after step (b), after the diagnosis of the load drive driver stop function is completed, switching the charging circuit switch to de-energized.

[0018] Invention Effects

[0019] According to the present invention, a high-performance and highly reliable load drive device and its diagnostic method can be realized. In the load drive device including a diagnostic circuit of the drive system driver and an ESD protection capacitor, the ESD protection capacitor can be quickly charged even when the load is disconnected, and the complete diagnosis of the drive system driver can be completed within the required time.

[0020] Therefore, even when the load is disconnected, the diagnosis of the drive stop function can be determined in a short time, thus completing the abnormal diagnosis of the drive stop function without prolonging the time from key turn to engine start (start of crank rotation).

[0021] Other technical issues, structures, and effects not mentioned above will be further clarified through the following description of the implementation methods. Attached Figure Description

[0022] Figure 1 This is a block diagram illustrating the circuit structure of the load driving device according to Embodiment 1 of the present invention.

[0023] Figure 2 This is a diagram showing the capacitor charging path of an existing load drive device.

[0024] Figure 3 This is a diagram showing the capacitor charging path of the load drive device according to Embodiment 1 of the present invention.

[0025] Figure 4 It means Figure 1 A block diagram of the circuit structure of the charging circuit switch 120.

[0026] Figure 5 This is a timing diagram illustrating an example of the operation of the load drive device according to Embodiment 1 of the present invention.

[0027] Figure 6 This is a timing diagram illustrating another operational example of the load drive device according to Embodiment 1 of the present invention.

[0028] Figure 7This is a timing diagram illustrating another operational example of the load drive device according to Embodiment 1 of the present invention.

[0029] Figure 8 This is a block diagram illustrating the circuit structure of the load driving device according to Embodiment 2 of the present invention.

[0030] Figure 9 It means Figure 8 A block diagram of the circuit structure of the charging circuit switch 120.

[0031] Figure 10 This is a timing diagram illustrating an example of the operation of the load drive device according to Embodiment 2 of the present invention.

[0032] Figure 11 This is a flowchart illustrating a diagnostic method for a representative load drive device of the present invention. Detailed Implementation

[0033] Hereinafter, embodiments of the present invention will be described using the accompanying drawings. Furthermore, in the drawings, the same reference numerals are used to denote the same structures, and detailed descriptions of repeated parts are omitted.

[0034] Example 1

[0035] Reference Figures 1 to 7 as well as Figure 11 The load drive device and its diagnostic method according to Embodiment 1 of the present invention will be described. Furthermore, Figure 2 This is a diagram illustrating the capacitor charging path of a conventional load drive device, presented as a comparative example for ease of understanding the present invention.

[0036] Figure 1 This illustrates the circuit structure of the load drive device in this embodiment. For example... Figure 1 As shown, the load drive device of this embodiment includes: a low-side driver 50 for driving a load (inductive load) 60; a terminal capacitor 70 for protecting the load drive device from ESD (Electro-Static Discharge); a voltage monitoring circuit 80 for converting the voltage of the output terminal 100 into a voltage that can be read by the arithmetic unit 1; a charging circuit 110 and a charging circuit switch 120 for charging the terminal capacitor 70; and an arithmetic unit 1 for timing the power-on of the low-side driver 50 and the charging circuit switch 120 and for monitoring the output voltage of the voltage monitoring circuit 80.

[0037] Additionally, the driver control circuit 20 is connected to the arithmetic unit 1 via the driver drive signal line 10 and to the driver stop signal line 40 via the driver stop mechanism 30. During the period when the driver stop mechanism 30 outputs a drive enable signal to the driver control circuit 20, the driver control circuit 20 energizes the gate of the low-side driver 50 by outputting a drive signal from the arithmetic unit 1 to the driver control circuit 20, and outputs a non-energized voltage.

[0038] In addition, during the period when the driver stop mechanism 30 outputs a drive inhibit signal to the driver control circuit 20, even if a drive signal is output from the computing device 1 to the driver control circuit 20, the output of a gate signal from the driver control circuit 20 to the low-side driver 50 is also prohibited, and the low-side driver 50 remains in a non-powered state.

[0039] The driver stop mechanism 30 is connected to the arithmetic unit 1. When the arithmetic unit 1 detects an abnormality, it outputs a signal notifying the abnormality to the driver stop mechanism 30. Then, the driver stop mechanism 30 outputs a drive disable signal to the driver control circuit 20. Additionally, the driver stop mechanism 30 monitors the arithmetic unit 1 and also outputs a drive disable signal to the driver control circuit 20 when an abnormality is detected in the arithmetic unit 1.

[0040] The voltage monitoring circuit 80 inputs a voltage level that can be read by the arithmetic unit 1 to the arithmetic unit 1, in place of the voltage at the output terminal 100. The current limiting resistor 81, which is a component inside the voltage monitoring circuit 80, has the function of protecting the low-side driver 50 from malfunction by preventing current from flowing through VCC when the low-side driver 50 is powered on.

[0041] In addition, the current limiting resistor 82 protects the input terminals of the arithmetic device 1 by limiting the current flowing into the arithmetic device 1 via the voltage monitoring signal line 90. Furthermore, the anode side of the protection diode 83 is connected to the current limiting resistor 81, and the cathode side is connected to the output terminal 100, preventing current from flowing back from the load power supply V into the voltage monitoring circuit 80.

[0042] When the low-side driver 50 is turned on, current flows from VCC through the current limiting resistor 81, the protection diode 83, and the drain-source of the low-side driver 50 to GND, thus inputting a voltage around the GND potential to the operational device 1.

[0043] Furthermore, when the low-side driver 50 is not conducting, since VCC < load power supply V, the reverse current prevention effect of the protection diode 83 allows the arithmetic unit 1 to input the Vcc voltage. In this embodiment, the arithmetic unit 1 detects the driving status of the low-side driver 30 by detecting the voltage variation when the input voltage from the voltage monitoring signal line 90 changes from a predetermined high-level voltage to a predetermined low-level voltage.

[0044] The charging circuit 110 is a constant current source that charges the terminal capacitor 70 immediately after the low-side driver 50 changes from energized to de-energized via the charging circuit switch 120. This charging allows for rapid determination of the voltage at the output terminal 100 even when the load 60 is disconnected. To avoid affecting the operation of the load 60, the output current of the charging circuit 110 is set to approximately one-thousandth or less of the load drive current.

[0045] Therefore, even when the load 60 is normally connected, the voltage drop at the load 60 can be significantly reduced.

[0046] Here, we will explain the technical background of how the charging circuit 110 can charge the terminal capacitor 70 in a shorter time compared to the diagnostic time. Figure 2 This indicates that in a conventional load drive device without charging circuit 110, load 60 serves as the charging path for terminal capacitor 70 during both normal and disconnected states. Under normal conditions, current primarily flows from the load power supply V through load 60 to charge terminal capacitor 70. Since the resistance RL of load 60 is several Ω to tens of Ω, the system's time constant TL (=RL×C)(T:Tau) is relatively small, allowing charging to occur within a short time.

[0047] On the other hand, when the load (inductive load) 60 is in an open state, it is mainly charged from VCC inside the voltage monitoring circuit 80 via the current limiting resistor 81. The current limiting resistor 81 does not affect the drive of the load 60, so the resistance value R81 is relatively large, ranging from several kΩ to several hundred kΩ. As a result, the system's time constant TR81 (=R81×C) is larger than TL (T:Tau), and the charging of the terminal capacitor 70 takes time.

[0048] Figure 3 This describes the charging path of the terminal capacitor (ESD protection capacitor) 70 when the load is disconnected according to the present invention. By setting the charging circuit 110 and the charging circuit switch 120 (conduction resistance: Rsw), the system with a time constant Tsw (=Rsw×C)≈TL (T:Tau) that is not affected by the current limiting resistor 81 can complete charging in a short time compared to the diagnostic time.

[0049] Figure 4This is an example of the internal structure of the charging circuit switch 120. Since the gate (G) and source (S) of the component of the charging circuit switch 120, namely the Pch-FET 121, are connected via resistors, the Pch-FET 121 becomes non-energized if the arithmetic device 1 does not control the NPN transistor 122 via the charging circuit switch control signal line 130.

[0050] In this internal structure example, the gate (G) and source (S) of Pch-FET 121 are connected via a resistor. However, to protect Pch-FET 121, a protective element connected in parallel with the resistor can also be considered. When the arithmetic device 1 outputs the charging circuit switch control signal 130, current is injected into the base (B) of NPN transistor 122, and the emitter (E) and collector (C) of NPN transistor 122 are energized. This energization lowers the gate voltage of Pch-FET 121 than the source voltage, thus Pch-FET 121 is also energized. Conversely, if the output of the charging circuit switch control signal 130 is stopped, the base current injection into NPN transistor 122 also stops, thus NPN transistor 122 becomes de-energized.

[0051] Alternatively, a reverse current prevention diode 123 with the direction of the output terminal 100 as the positive direction can be provided between the charging circuit switch 120 and the output terminal 100. This serves to prevent current from bypassing the charging circuit 110 from the load power supply V, thus preventing the charging circuit 110 from malfunctioning. Furthermore, when the load 60 is normally connected, to prevent current from flowing from the charging circuit 110 to the load power supply V, the charging voltage Vcharge of the charging circuit 110 is lower than the load power supply V. In this embodiment, the charging circuit switch 120 is configured to be controlled by the arithmetic unit 1, but other controllers may be used instead of the arithmetic unit 1.

[0052] Figure 5 This is an example of a timing diagram illustrating the abnormal diagnosis of the drive stop mechanism 30 in this embodiment. When the reference power is turned on by turning on the vehicle key, the computing device 1 and the drive stop mechanism 30 can be controlled after a certain startup period.

[0053] The arithmetic unit 1 outputs a charging circuit switch control signal 130, energizing the charging circuit switch 120. When energized, since the low-side driver 50 is not energized, the voltage monitoring signal becomes the Vcc voltage.

[0054] Next, to confirm that the driver stop mechanism 30 can properly disable the drive, a drive disable signal is output from the driver stop mechanism 30 to the driver control circuit 20 for a specified period. During this period, the arithmetic unit 1 outputs a specified number of drive signals to the driver control circuit 20 to count the number of voltage variations in the voltage monitoring signal.

[0055] Next, to confirm that the driver stop mechanism 30 can normally allow driving, a drive enable signal is output from the driver stop mechanism 30 to the driver control circuit 20 within a specified period. During this period, the arithmetic unit 1 outputs a specified number of drive signals to the driver control circuit 20 to count the number of voltage variations in the voltage monitoring signal.

[0056] After the above diagnosis is completed, the computing device 1 sets the charging circuit switch 120 to non-powered via the charging circuit switch control signal line 130.

[0057] Then, in the above diagnostic results, if the drive stop mechanism 30 is normal, the arithmetic unit 1 allows the crank to start rotating, stops the crank rotation in case of an abnormality, and notifies the user of the abnormality.

[0058] In this embodiment, the computing device 1 diagnoses the driver stop mechanism 30 as normal by detecting voltage variations in the voltage monitoring signal that do not exceed a specified threshold during the output of the drive disable signal and voltage variations in the voltage monitoring signal that correspond to the number of times the driver drive signal is sent during the output of the drive enable signal.

[0059] Based on Figure 2 In the diagnostics of the driver stop mechanism 30 of the existing load drive device circuit structure shown, because there is no charging circuit 110, when the low-side driver 50 changes from energized to de-energized when the load 60 is disconnected, the charging of the terminal capacitor 70 takes time, and the voltage at the output terminal 100 becomes sluggish. Therefore, before the voltage monitoring signal reaches a predetermined high threshold, the low-side driver 50 is energized, and the arithmetic unit 1 cannot count the predetermined number of voltage fluctuations. Thus, even if the driver stop mechanism 30 can normally allow the driver to drive, the arithmetic unit 1 determines it to be abnormal.

[0060] On the other hand, such as Figure 3 As shown, by having a charging circuit 110, the terminal capacitor 70 is quickly charged immediately after the low-side driver 50 changes from being energized to being de-energized, and the voltage monitoring signal can quickly determine the high level, thus enabling the detection of a predetermined number of voltage variations.

[0061] Furthermore, after the above diagnosis is completed, by de-energizing the charging circuit switch 120, it is possible to suppress the current from the charging circuit 110 to the load power supply V, and to suppress malfunctions of other loads or control units.

[0062] Figure 6 This indicates the power-on timing for turning on the charging circuit switch 120 when the low-side driver 50 is off. The arithmetic unit 1 outputs a disconnect signal to the driver control circuit 20 to control the timing of turning on the charging circuit switch 120 when the low-side driver 50 is not powered on.

[0063] When the low-side driver 50 is powered on, and the charging circuit switch 120 is powered on, the current flowing from the charging circuit 110 flows through the low-side driver 50 to GND, thus increasing power consumption. Therefore, by... Figure 6 The timing shown energizes the charging circuit switch 120, which can suppress unnecessary power consumption.

[0064] in addition, Figure 7 This indicates the energizing timing at which the charging circuit switch 120 is turned off after the terminal capacitor 70 has finished charging. The arithmetic unit 1 controls the charging circuit switch 120 to be energized only during the charging time of the terminal capacitor 70, calculated based on the capacitance of the terminal capacitor 70 and the output current of the charging circuit 110. Therefore, in addition to the above (… Figure 6 In addition to the same useless power reduction, it also suppresses the malfunction of other loads or control units caused by the current of the charging circuit 110 detouring upstream of the load power supply.

[0065] Figure 11 The flowchart illustrates the main process in the diagnostic method of the load drive device in this embodiment.

[0066] First, simultaneously with the start of the diagnostics for the load drive driver stop function (driver stop mechanism 30), power is supplied to the charging circuit switch 120. (Step S1)

[0067] Next, after the load drive driver (low-side driver 50) switches from powered on to powered off, the ESD protection capacitor (terminal capacitor 70) is quickly charged from the charging circuit 110 to determine the voltage of Vmon and perform a diagnostic test on the load drive driver stop function (driver stop mechanism 30). (Step S2)

[0068] Finally, after the diagnosis of the load drive driver stop function (driver stop mechanism 30) is completed, the charging circuit switch 120 is set to non-energized, and the charging circuit 110 and the drive circuit (load drive driver (low-side driver 50) and ESD protection capacitor (terminal capacitor 70)) are disconnected.

[0069] (Step S3)

[0070] According to this embodiment, even when the load 60 is disconnected, by setting a charging path with a small time constant by the charging circuit 110, the low-side driver 50 can complete the diagnosis of whether the driver stop mechanism 30 can operate normally within the time from the key being turned on to the start of crank rotation.

[0071] Example 2

[0072] Reference Figures 8 to 10 The load driving device and its diagnostic method involved in Embodiment 2 of the present invention will be described. Figure 8 This is a block diagram illustrating the circuit structure of the load drive device in this embodiment. (For example...) Figure 8 and Figure 9 As shown, the load driving device of this embodiment, in order to drive loads 60a and 60b, respectively includes the same features as in Embodiment 1 (…). Figure 1 The corresponding driving circuits and components. For parts that are common to Embodiment 1, the same symbols are used and the descriptions are omitted.

[0073] like Figure 8 As shown, the load drive device of this embodiment includes multiple load drive systems, each having loads 60a and 60b, low-side drivers 50a and 50b (first switching elements) and terminal capacitors (ESD protection capacitors) 70a and 70b, respectively. Each of the multiple load drive systems is configured to be connected in parallel with a charging circuit 110 and a charging circuit switch 120 (second switching element).

[0074] In this embodiment, as Figure 10 As shown, during the diagnosis of the driver stop mechanism 30, the arithmetic unit 1 outputs drive signals to the driver control circuits 20a and 20b respectively at the timing when loads 60a and 60b are not driven simultaneously. Therefore, at the timing when each load is driven via the voltage monitoring signal line 90, the arithmetic unit 1 detects voltage variations.

[0075] In addition, in this embodiment ( Figure 8 In the circuit structure, the two terminal capacitors 70a and 70b are charged by a charging circuit 110, but it is also possible to consider a structure with a charging circuit 110 that is equivalent to the number of terminal capacitors.

[0076] In this embodiment, by controlling the timing of the drive signal output from the computing device 1, the drives of loads 60a and 60b are overlapped. A single voltage monitoring signal line 90 can be used to diagnose whether the driver stop function of the dual-system loads is operating normally. Furthermore, even when there are two or more loads, the driver stop mechanism 30 can be diagnosed using the same circuitry and components that drive the loads.

[0077] Alternatively, the charging circuit 110 and the charging circuit switch 120 can also be respectively installed in the load drive system.

[0078] Furthermore, the present invention is not limited to the embodiments described above, but also includes various modifications. For example, the embodiments described above have been detailed to aid in understanding the present invention, and are not necessarily limited to embodiments including all the structures described. Moreover, a portion of the structure of one embodiment can be replaced with a structure of another embodiment, and a structure of another embodiment can be added to the structure of one embodiment. Additionally, regarding a portion of the structure of each embodiment, other structures can be added, deleted, or replaced.

[0079] Label Explanation

[0080] 1…Arithmetic unit; 10, 10a, 10b…Driver drive signal lines; 20, 20a, 20b…Driver control circuit; 30…Driver stop mechanism; 40, 40a, 40b…Driver stop signal lines; 50, 50a, 50b…Low-side driver; 60, 60a, 60b…Load (inductive load); 70, 70a, 70b…Terminal capacitors (ESD protection capacitors); 80…Voltage monitoring circuit; 81…Current limiting resistor; 82…Current limiting resistor; 83, 83b…Protection diodes; 90…Voltage monitoring signal lines; 100, 100a, 100b…Output terminals; 110…Charging circuit; 120…Charging circuit switch; 121…Pch-FET; 122…NPN transistor; 123, 123a, 123b…Reverse current prevention diodes; 130…Charging circuit switch control signal (line).

Claims

1. A load driving device characterized by comprising: comprising: a load; a first switching element connected to the load and controlling driving of the load; an ESD protection capacitor connected between the load and the first switching element; a charging circuit connected between the load and the first switching element and charging the ESD protection capacitor; a second switching element connected between the ESD protection capacitor and the charging circuit; an arithmetic device controlling energization timing of the first switching element and the second switching element; and a voltage monitoring circuit monitoring an output terminal voltage between the load and the first switching element, converting it into a voltage readable by the arithmetic device, and outputting it to the arithmetic device, the arithmetic device diagnosing the driving stop signal of the first switching element as normal in a case where the driving stop signal is in a driving permission period, a variation amount of the output voltage of the voltage monitoring circuit is above a prescribed range, and the driving stop signal is in a driving prohibition period, the variation amount of the output voltage of the voltage monitoring circuit being within the prescribed range.

2. The load driving device according to claim 1, wherein the second switching element is switched from off to on during a period from turning on of a vehicle key to start of cranking.

3. The load driving device according to claim 1, wherein the second switching element is made on in a case where the first switching element is off.

4. The load driving device according to claim 1, wherein the second switching element is made off after charging of the ESD protection capacitor is completed.

5. The load driving device according to claim 1, comprising a diode connected between the load and the charging circuit to take a direction from the charging circuit to the second switching element as a positive direction, an output voltage of the charging circuit is lower than a load power supply voltage of the load.

6. The load driving device according to claim 1, wherein the charging circuit supplies a current smaller than a current flowing through the load when the first switching element is energized. comprising:

7. The load driving apparatus according to claim 1, wherein an arithmetic device controlling energization timing of the first switching element and the second switching element; and a voltage monitoring circuit monitoring an output terminal voltage between the load and the first switching element, converting it into a voltage readable by the arithmetic device, and outputting it to the arithmetic device, the arithmetic device diagnosing as normal in a case where the driving stop signal of the first switching element is in a driving permission period and a variation amount of the output voltage of the voltage monitoring circuit is above a prescribed range. comprising: an arithmetic device controlling energization timing of the first switching element and the second switching element; and 8. The load driving apparatus according to claim 1, wherein a voltage monitoring circuit monitoring an output terminal voltage between the load and the first switching element, converting it into a voltage readable by the arithmetic device, and outputting it to the arithmetic device, the arithmetic device diagnosing as normal in a case where the driving stop signal of the first switching element is in a driving permission period and a variation amount of the output voltage of the voltage monitoring circuit is above a prescribed range. ​ ​ The operation device diagnoses that the drive stop signal is abnormal and stops cranking of the vehicle when the variation of the output voltage of the voltage monitoring circuit is outside the prescribed range during the drive enable period of the drive stop signal of the first switching element.

9. The load driving device according to claim 1, wherein a plurality of load driving systems each including the load, the first switching element, and the ESD protection capacitor, each of the plurality of load driving systems is connected in parallel with one of the charging circuits and one of the second switching elements.

10. A diagnosis method of diagnosing the load driving apparatus according to any one of claims 1 to 9, characterized by, has the steps of: (a) a step of turning on the charging circuit switch at the same time as the start of diagnosis of the load driving driver stop function; (b) a step of diagnosing the load driving driver stop function by charging the ESD protection capacitor through the charging circuit after the load driving driver is switched from being turned on to being turned off after the step (a); and (c) a step of turning off the charging circuit switch after the end of diagnosis of the load driving driver stop function after the step (b), the drive stop signal is diagnosed as normal when the variation of the voltage between the load driving driver and the load is above the prescribed range during the drive enable period of the drive stop signal of the load driving driver and the variation of the voltage between the load driving driver and the load is within the prescribed range during the drive disable period of the drive stop signal.

11. A diagnosis method of diagnosing the load driving apparatus according to any one of claims 1 to 9, characterized by, has the steps of: (a) a step of turning on the charging circuit switch at the same time as the start of diagnosis of the load driving driver stop function; (b) a step of diagnosing the load driving driver stop function by charging the ESD protection capacitor through the charging circuit after the load driving driver is switched from being turned on to being turned off after the step (a); and (c) a step of turning off the charging circuit switch after the end of diagnosis of the load driving driver stop function after the step (b), the drive stop signal is diagnosed as normal when the variation of the voltage between the load driving driver and the load is above the prescribed range during the drive enable period of the drive stop signal of the load driving driver.

12. A diagnostic method of diagnosing the load driving apparatus according to any one of claims 1 to 9, characterized by, has the steps of: (a) a step of turning on the charging circuit switch at the same time as the start of diagnosis of the load driving driver stop function; (b) a step of diagnosing the load driving driver stop function by charging the ESD protection capacitor through the charging circuit after the load driving driver is switched from being turned on to being turned off after the step (a); and (c) a step of turning off the charging circuit switch after the end of diagnosis of the load driving driver stop function after the step (b), the drive stop signal is diagnosed as abnormal and the cranking of the vehicle is stopped when the variation of the voltage between the load driving driver and the load is outside the prescribed range during the drive enable period of the drive stop signal of the load driving driver.

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