Electronic control device and method for detecting disconnection of ground line

Abstract

This electronic control device includes: a drive unit that includes a first load drive circuit for driving a first load, a second load drive circuit for driving a second load, and a common ground that is common to the first and second load drive circuits, the common ground being connected to a dedicated ground; and a control unit that is capable of individually controlling the first and second load drive circuits and that is connected to a dedicated ground which differs from the dedicated ground of the drive unit. The first load is connected to the common ground, and the second load is connected to the dedicated ground of the drive unit. The output side of the second load drive circuit is connected to the common ground via a diode which enables current to flow toward the output side. A current detection circuit is disposed between the common ground and the dedicated ground of the drive unit. The control unit detects, according to the output of the current detection circuit, whether the ground line connected to the dedicated ground of the drive unit is disconnected.

Description

Electronic control device and ground line disconnection detection method

[0001] The present invention relates to an electronic control device capable of detecting a break in a ground line, and a method for detecting a break in a ground line.

[0002] As described in Japanese Patent Laid-Open No. 2009-133815 (Patent Document 1), an electronic control device that drives a load needs to detect whether a break has occurred in a ground line that connects a ground terminal and ground, which defines the reference potential of the electronic circuit. The electronic control device described in Patent Document 1 has a drive unit that drives the load and a control unit that controls the drive unit. A diode that passes current from the ground line to the drive unit is disposed in an electrical path inside the electronic control device that connects the ground line of the control unit and the output side of the drive unit, and a break in the ground line is detected depending on whether current flows through this diode.

[0003] JP 2009-133815 A

[0004] In an electronic control device that drives a load, it is possible to prevent abnormal operation due to a break in the ground line by separating the ground line of the control unit and the ground line of the drive unit to provide redundancy. In this case, in an electronic control device that applies the technology described in Patent Document 1, even if a break occurs in the ground line of the drive unit, the break cannot be detected because the current that passed through a certain load flows to ground via the electrical path connecting the ground line of the control unit and the output side of the drive unit and via other loads.

[0005] Therefore, an object of the present invention is to provide an electronic control device and a method for detecting a break in a ground line that is capable of detecting a break in the ground line of a drive unit even in a configuration in which the ground line of the control unit and the ground line of the drive unit are separated and made redundant.

[0006] According to one aspect of the present invention, an electronic control device includes a first load drive circuit that drives a first load, a second load drive circuit that drives a second load, and a common ground shared by the first load drive circuit and the second load drive circuit, the common ground being connected to a dedicated ground, and a control unit that can individually control the first load drive circuit and the second load drive circuit and is connected to a dedicated ground different from the dedicated ground of the drive unit. The first load is connected to the common ground, the second load is connected to the dedicated ground of the drive unit, and the output side of the second load drive circuit is connected to the common ground via a diode that allows current to flow toward the common ground. A current detection circuit is disposed between the common ground and the dedicated ground of the drive unit, and the control unit detects whether the ground line connected to the dedicated ground of the drive unit is broken based on the output of the current detection circuit.

[0007] According to another aspect of the present invention, an electronic control device includes a drive unit including a first load drive circuit for driving a first load, a second load drive circuit for driving a second load, and a common ground shared by the first load drive circuit and the second load drive circuit, the common ground being connected to a dedicated ground, and a control unit capable of individually controlling the first load drive circuit and the second load drive circuit and connected to a dedicated ground different from the dedicated ground of the drive unit. The first load is connected to the common ground, the second load is connected to the dedicated ground of the drive unit, and the dedicated ground of the control unit and the common ground of the drive unit are connected via a diode that allows current to flow from the dedicated ground of the control unit to the common ground of the drive unit. A current detection circuit is disposed between the common ground and the dedicated ground of the drive unit, and the control unit detects whether a ground line connected to the dedicated ground of the control unit is broken or not based on the output of the current detection circuit.

[0008] According to the present invention, even in an electronic control device in which the ground line of the control unit and the ground line of the drive unit are separated for redundancy, it is possible to detect a break in the ground line of the drive unit.

[0009] 1 is a schematic diagram showing an example of an electronic control device that drives multiple loads; FIG. 1 is a schematic diagram showing an example of the internal structure of an electronic control device; FIG. 2 is a flowchart showing an example of a ground line disconnection detection process; FIG. 3 is an explanatory diagram of a current that flows through a drive unit when an electric motor is driven in a state where the ground line of the drive unit is normal; FIG. 4 is an explanatory diagram of a current that flows through a drive unit when an electric motor is driven in a state where the ground line of the drive unit is disconnected; FIG. 5 is an explanatory diagram of a current that flows through a control unit when an electric motor is not driven in a state where the ground line of the control unit is normal; and FIG. 6 is an explanatory diagram of a current that flows through a control unit when an electric motor is not driven in a state where the ground line of the control unit is disconnected.

[0010] Hereinafter, an embodiment for carrying out the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 shows an example of an electronic control unit (ECU) 100 that drives multiple loads. Here, the loads may be, for example, electric motors such as three-phase brushless motors, or well-known actuators such as solenoids. The electronic control unit 100 controls the loads in response to commands from a higher-level electronic control unit (e.g., an engine control unit). Note that, although the following description will be directed to an electronic control unit 100 that drives an electric motor M and a solenoid S, this embodiment is also applicable to a configuration in which any number of loads or any loads are driven.

[0011] The electronic control device 100 includes a water-resistant and dust-resistant casing 120, and a reverse connection protection circuit 140, a drive unit 160, a control unit 180, a diode 200, and a current detection circuit 220 housed inside the casing 120. In addition to the above configuration, the electronic control device 100 may also include a known constant voltage circuit.

[0012] The casing 120 is a box-shaped case manufactured, for example, by aluminum die-casting. It includes a box-shaped main body with an open side and a lid that is rectangular in plan view and detachably closes the opening of the main body. Here, well-known sealing members such as O-rings and gaskets are disposed at the interface between the main body and the lid to prevent water, dust, and the like from entering the internal space. Also, a battery terminal 120A, a motor output terminal 120B, a motor input terminal 120C, a solenoid output terminal 120D, a ground terminal 120E of the drive unit 160, and a ground terminal 120F of the control unit 180 are attached to predetermined locations on the casing 120. Note that in reality, each terminal is implemented as a terminal of a connector (not shown) that detachably connects a harness attached to predetermined locations on the casing 120.

[0013] The battery terminal 120A is connected to a dedicated ground PG (hereinafter referred to as "driver ground PG") of the drive unit 160 via a battery BATT, which is an example of a DC power supply. The motor output terminal 120B and the motor input terminal 120C are respectively connected to two terminals (an input terminal and an output terminal) of the electric motor M. The solenoid output terminal 120D is connected to the drive unit ground PG via a solenoid S. The ground terminal 120E of the drive unit 160 is connected to the drive unit ground PG. The ground terminal 120F of the control unit 180 is connected to a dedicated ground LG (hereinafter referred to as "controller ground LG") of the control unit 180, which is different from the drive unit ground PG. Here, the electric motor M is an example of a first load, and the solenoid S is an example of a second load.

[0014] The reverse connection protection circuit 140 is a well-known circuit that protects the electronic control device 100 when the polarity of the battery BATT is connected incorrectly, and its input terminal is connected to the battery terminal 120A. The output terminals of the reverse connection protection circuit 140 are connected to the drive unit 160 and the control unit 180, respectively. Note that a well-known circuit can be used for the reverse connection protection circuit 140, and therefore a detailed description thereof will be omitted.

[0015] The drive unit 160 includes a motor drive circuit 160A that controls the current supplied to the electric motor M, a solenoid drive circuit 160B that controls the current supplied to the solenoid S, a current detection circuit 160C that detects the drive current of the electric motor M, a first diode 160D, and a second diode 160E. The motor drive circuit 160A and the solenoid drive circuit 160B include, for example, N-channel metal oxide semiconductor field effect transistors (MOSFETs). Hereinafter, for convenience of explanation, the MOSFET in the motor drive circuit 160A will be referred to as the "motor drive FET 160A," and the MOSFET in the solenoid drive circuit 160B will be referred to as the "solenoid drive FET 160B." The motor drive FET 160A and the solenoid drive FET 160B are not limited to N-channel MOSFETs, and may be well-known semiconductor switching elements such as P-channel MOSFETs, bipolar transistors, and insulated gate bipolar transistors. Here, the motor drive FET 160A is an example of a first load drive circuit, the solenoid drive FET 160B is an example of a second load drive circuit, and the second diode 160E is an example of a diode that allows current to flow toward the second load.

[0016] The drain of the motor drive FET 160A is connected to the output terminal of the reverse connection protection circuit 140. The source of the motor drive FET 160A is connected to the motor output terminal 120B and is also connected to a common ground PG_ECU via a first diode 160D arranged to pass current toward the source of the motor drive FET 160A. The gate of the motor drive FET 160A is connected to an analog signal output terminal of the control unit 180. Here, the common ground PG_ECU is an internal ground common to (shared with) the motor drive FET 160A and the solenoid drive FET 160B in the drive unit 160 of the electronic control unit 100.

[0017] The drain of the solenoid drive FET 160B is connected to the output terminal of the reverse connection protection circuit 140. The source of the solenoid drive FET 160B is connected to the solenoid output terminal 120D, and is also connected to the common ground PG_ECU via a second diode 160E arranged to pass current toward the source of the solenoid drive FET 160B. In addition, the gate of the solenoid drive FET 160B is connected to an analog signal output terminal of the control unit 180 that is different from the analog signal output terminal of the motor drive FET 160A.

[0018] The current detection circuit 160C includes a shunt resistor 160C1 disposed in an electrical path connecting the motor input terminal 120C and the common ground PG_ECU, and an operational amplifier 160C2 that amplifies the voltage difference between both ends of the shunt resistor 160C1. The output terminal of the operational amplifier 160C2 is connected to an analog signal input terminal of the control unit 180.

[0019] The control unit 180 is configured to include, for example, a microcomputer (not shown) so as to be able to individually control the motor drive FET 160A and the solenoid drive FET 160B of the drive unit 160, and is connected to a ground terminal 120F of the control unit 180. Specifically, as shown in Fig. 2, the control unit 180 has a processor 180A such as a CPU (Central Processing Unit), a non-volatile memory 180B, a volatile memory 180C, an input / output circuit 180D, a communication circuit 180E, and an internal bus 180F that connects these so that they can communicate with each other.

[0020] The processor 180A is hardware that executes an instruction set (such as data transfer, calculation, processing, control, and management) written in an application program, and is composed of an arithmetic unit, registers that store instructions and data, and peripheral circuits. The non-volatile memory 180B is composed of, for example, a flash ROM (Read Only Memory) that can retain data even when the power supply is cut off, and stores an application program (computer program) for implementing this embodiment. The volatile memory 180C is composed of, for example, a dynamic RAM (Random Access Memory) that loses data when the power supply is cut off, and provides a memory area for temporarily storing data during the calculation process of the processor 180A.

[0021] The input / output circuit 180D includes an A / D converter, a D / A converter, a D / D converter, etc., and provides an input / output function for analog signals and digital signals to / from external devices. The communication circuit 180E includes, for example, a CAN transceiver, etc., and provides a function for connecting to an in-vehicle network such as a CAN (Controller Area Network) (not shown). The internal bus 180F is a path for exchanging data between devices, and includes an address bus for transferring addresses, a data bus for transferring data, and a control bus for exchanging timing and control information for actual input / output via the address bus and data bus.

[0022] The diode 200 is arranged in an electrical path connecting the common ground PG_ECU and the ground terminal 120F of the control unit 180 so that a current flows from the ground terminal 120F of the control unit 180 to the common ground PG_ECU. Therefore, the drive unit 160 and the control unit 180 are electrically separated by the diode 200, and a dedicated drive unit ground PG for the drive unit 160 and a dedicated control unit ground LG for the control unit 180 can be realized.

[0023] Further, current detection circuit 220 is disposed on an electrical path connecting common ground PG_ECU and ground terminal 120E of drive unit 160. Specifically, current detection circuit 220 includes a shunt resistor 220A disposed on the electrical path connecting common ground PG_ECU and ground terminal 120E, and an operational amplifier 220B that amplifies the voltage difference between both ends of shunt resistor 220A. An output terminal of operational amplifier 220B is connected to an analog signal input terminal of control unit 180 that is different from current detection circuit 160C in drive unit 160.

[0024] According to the electronic control device 100, when the control unit 180 outputs a predetermined voltage from the analog signal output terminal to the gate of the motor drive FET 160A to drive the electric motor M, a voltage difference is generated between the gate and source of the motor drive FET 160A. This turns the motor drive FET 160A ON, and current supplied from the battery BATT passes through the reverse connection protection circuit 140, flows from the drain to the source of the motor drive FET 160A, and is then supplied to the electric motor M via the motor output terminal 120B. At this time, because the first diode 160D is located downstream (on the output side) of the source of the motor drive FET 160A, the current output from the source of the motor drive FET 160A does not flow to the common ground PG_ECU. Furthermore, the current passing through the electric motor M flows to the common ground PG_ECU via the motor input terminal 120C, and then flows from the common ground PG_ECU to the drive unit ground PG via the ground terminal 120E of the drive unit 160. At this time, the control unit 180 detects the current that actually drives the electric motor M using the current detection circuit 160C, and feedback controls the voltage output to the gate of the motor drive FET 160A.

[0025] Furthermore, when driving the solenoid S, the control unit 180 outputs a predetermined voltage from the analog signal output terminal to the gate of the solenoid drive FET 160B, generating a voltage difference between the gate and source of the solenoid drive FET 160B. This turns the solenoid drive FET 160B ON, and current supplied from the battery BATT passes through the reverse connection protection circuit 140, flows from the drain to the source of the solenoid drive FET 160B, and is then supplied to the solenoid S via the solenoid output terminal 120D. At this time, because the second diode 160E is located downstream (on the output side) of the source of the solenoid drive FET 160B, the current output from the source of the solenoid drive FET 160B does not flow to the common ground PG_ECU. The current that has passed through the solenoid S then flows to the drive unit ground PG.

[0026] The control unit 180 is configured to detect whether or not the ground line connected to the drive unit ground PG and the ground line connected to the control unit ground LG are broken, depending on the output of the current detection circuit 220, as will be described in detail below.

[0027] 3 shows an example of a ground line disconnection detection process that is repeatedly executed by the processor 180A of the control unit 180 at predetermined time intervals upon startup of the electronic control unit 100. The processor 180A of the control unit 180 executes the ground line disconnection detection process using an application program pre-stored in the non-volatile memory 180B.

[0028] In step 10 (abbreviated as "S10" in FIG. 3, and the same applies below), the processor 180A of the control unit 180 determines whether the electric motor M is being driven. If the processor 180A of the control unit 180 determines that the electric motor M is being driven (Yes), the process proceeds to step 11. On the other hand, if the processor 180A of the control unit 180 determines that the electric motor M is not being driven (No), the process proceeds to step 14.

[0029] In step 11, the processor 180A of the control unit 180 reads the output of the current detection circuit 220 of the drive unit 160 and determines whether a current is flowing in the electrical path connecting the common ground PG_ECU and the ground terminal 120E, in other words, whether a current has been detected. If the processor 180A of the control unit 180 determines that a current is flowing in the electrical path connecting the common ground PG_ECU and the ground terminal 120E (Yes), the process proceeds to step 12. On the other hand, if the processor 180A of the control unit 180 determines that a current is not flowing in the electrical path connecting the common ground PG_ECU and the ground terminal 120E (No), the process proceeds to step 13.

[0030] In step 12, the processor 180A of the control unit 180 determines that the ground line connecting the ground terminal 120E of the drive unit 160 to the drive unit ground PG is normal, that is, that the ground line is not broken. Then, the processor 180A of the control unit 180 ends the ground line break detection process for the current control cycle.

[0031] In step 13, the processor 180A of the control unit 180 determines that the ground line connecting the ground terminal 120E of the drive unit 160 to the drive unit ground PG is abnormal, that is, that the ground line is broken. Then, the processor 180A of the control unit 180 ends the ground line break detection process for the current control cycle.

[0032] In step 14, the processor 180A of the control unit 180 reads the output of the current detection circuit 220 of the drive unit 160 and determines whether or not a current is flowing in the electrical path connecting the common ground PG_ECU and the ground terminal 120E, in other words, whether or not a current has been detected. If the processor 180A of the control unit 180 determines that a current is flowing in the electrical path connecting the common ground PG_ECU and the ground terminal 120E (Yes), the process proceeds to step 15. On the other hand, if the processor 180A of the control unit 180 determines that a current is not flowing in the electrical path connecting the common ground PG_ECU and the ground terminal 120E (No), the process proceeds to step 16.

[0033] In step 15, the processor 180A of the control unit 180 determines that the ground line connecting the ground terminal 120F of the control unit 180 to the control unit ground LG is abnormal, that is, that the ground line is broken. Then, the processor 180A of the control unit 180 ends the ground line break detection process for the current control cycle.

[0034] In step 16, the processor 180A of the control unit 180 determines that the ground line connecting the ground terminal 120F of the control unit 180 to the control unit ground LG is normal, that is, that the ground line is not broken. Then, the processor 180A of the control unit 180 ends the ground line break detection process for the current control cycle.

[0035] According to the electronic control device 100 that is equipped with such a ground line disconnection detection process, if a current flows in the electrical path connecting the common ground PG_ECU and the ground terminal 120E while the electric motor M is running, it is determined that there is no disconnection in the ground line of the drive unit 160. Furthermore, if a current does not flow in the electrical path connecting the common ground PG_ECU and the ground terminal 120E while the electric motor M is running, it is determined that there is a disconnection in the ground line of the drive unit 160.

[0036] 4, when the motor drive FET 160A is turned ON to drive the electric motor M, the current supplied from the battery BATT flows to the drive unit ground PG through the battery terminal 120A, the reverse connection protection circuit 140, the motor drive FET 160A, the motor output terminal 120B, the electric motor M, the motor input terminal 120C, the current detection circuit 160C, and the current detection circuit 220. At this time, a current flows through the electrical path in which the current detection circuit 220 is located, and by detecting this current, it can be determined that the ground line of the drive unit 160 is normal.

[0037] 5, when the motor drive FET 160A is turned ON to drive the electric motor M, the current supplied from the battery BATT flows to the drive unit ground PG through the battery terminal 120A, reverse connection protection circuit 140, motor drive FET 160A, motor output terminal 120B, electric motor M, motor input terminal 120C, current detection circuit 160C, second diode 160E, solenoid output terminal 120D, and solenoid S. At this time, no current flows through the electrical path in which the current detection circuit 220 is located, and by detecting this, it can be determined that the ground line of the drive unit 160 is broken.

[0038] On the other hand, when the electric motor M is not being driven, if a current flows in the electrical path connecting the common ground PG_ECU and the ground terminal 120E, the electronic control device 100 determines that the ground line of the control unit 180 is disconnected. Also, when the electric motor M is not being driven, if a current does not flow in the electrical path connecting the common ground PG_ECU and the ground terminal 120E, the electronic control device 100 determines that the ground line of the control unit 180 is normal.

[0039] That is, if the ground line of the control unit 180 is normal and the electric motor M is not being driven, the current supplied from the battery BATT passes through the battery terminal 120A, the reverse connection protection circuit 140, the control unit 180, and the ground terminal 120F and flows to the control unit ground LG, as shown by the bold line in Fig. 6. At this time, no current flows through the electrical path in which the current detection circuit 220 is located, and by detecting this, it can be determined that the ground line of the control unit 180 is normal.

[0040] On the other hand, if the ground line of the control unit 180 is broken and the electric motor M is not being driven, the current supplied from the battery BATT passes through the battery terminal 120A, the reverse connection protection circuit 140, the control unit 180, the diode 200, the current detection circuit 220, and the ground terminal 120E to the drive unit ground PG, as shown by the bold line in Fig. 7. At this time, a current flows through the electrical path in which the current detection circuit 220 is located, and by detecting this, it can be determined that the ground line of the control unit 180 is broken.

[0041] Therefore, according to the electronic control device 100 of this embodiment, even if the ground line of the drive unit 160 and the ground line of the control unit 180 are configured separately for redundancy, it is possible to detect a break in each ground line.

[0042] Furthermore, a person skilled in the art will easily understand that new embodiments can be created by omitting parts of the technical ideas of the above embodiments, combining parts as appropriate, or replacing parts with well-known technology.

[0043] For example, the load is not limited to the electric motor M and the solenoid S, but may be any known load such as a heater or an electromagnet.

[0044] 100...Electronic control device, 160...Driver, 160A...Motor drive FET (first load drive circuit), 160B...Solenoid drive FET (second load drive circuit), 160E...Second diode (diode), 180...Controller, 200...Diode, 220...Current detection circuit, 220A...Shunt resistor, 220B...Operational amplifier, M...Electric motor (first load), S...Solenoid (second load), PG_ECU...Common ground, PG...Driver ground (dedicated ground for drive unit), LG...Controller ground (dedicated ground for control unit)

Claims

1. An electronic control device having: a drive unit including a first load drive circuit that drives a first load, a second load drive circuit that drives a second load, and a common ground common to the first load drive circuit and the second load drive circuit, the common ground being connected to a dedicated ground; and a control unit that is capable of individually controlling the first load drive circuit and the second load drive circuit and is connected to a dedicated ground different from the dedicated ground of the drive unit, wherein the first load is connected to the common ground, and the second load is connected to the dedicated ground of the drive unit, the output side of the second load drive circuit is connected to the common ground via a diode that can pass a current toward the second load drive circuit, a current detection circuit is disposed between the common ground and the dedicated ground of the drive unit, and the control unit is configured to detect whether or not a ground line connected to the dedicated ground of the drive unit is broken according to the output of the current detection circuit.

2. The electronic control device according to claim 1, wherein the control unit is configured to diagnose whether or not a ground line of the drive unit is disconnected when the control unit controls the first load drive circuit to drive the first load.

3. The electronic control device according to claim 2, wherein the control unit diagnoses that the ground line of the drive unit is disconnected when no current is detected by the current detection circuit.

4. The electronic control device according to claim 1, wherein the current detection circuit includes a shunt resistor disposed between the common ground and a dedicated ground of the drive unit, and an operational amplifier that amplifies the potential difference between both ends of the shunt resistor.

5. An electronic control device as described in claim 1, wherein the dedicated ground of the control unit and the common ground of the drive unit are connected via a diode that allows current to flow from the dedicated ground of the control unit to the common ground of the drive unit, and when the control unit is not controlling the first load drive circuit to drive the first load and a current is detected by the current detection circuit, the electronic control device is configured to diagnose that the ground line connected to the dedicated ground of the control unit is broken.

6. An electronic control device having a drive unit including a first load drive circuit that drives a first load, a second load drive circuit that drives a second load, and a common ground common to the first load drive circuit and the second load drive circuit, the common ground being connected to a dedicated ground, and a control unit that is capable of individually controlling the first load drive circuit and the second load drive circuit and is connected to a dedicated ground different from the dedicated ground of the drive unit, wherein the first load is connected to the common ground, and the second load is connected to the dedicated ground of the drive unit, the dedicated ground of the control unit and the common ground of the drive unit are connected via a diode that can pass a current from the dedicated ground of the control unit to the common ground of the drive unit, a current detection circuit is disposed between the common ground and the dedicated ground of the drive unit, and the control unit is configured to detect whether or not a ground line connected to the dedicated ground of the control unit is broken according to an output of the current detection circuit.

7. The electronic control device according to claim 6, wherein the control unit is configured to diagnose whether or not a ground line of the control unit is disconnected when the control unit is not controlling the first load drive circuit to drive the first load.

8. The electronic control device according to claim 6, wherein the control unit is configured to diagnose that a ground line of the control unit is disconnected when a current is detected by the current detection circuit.

9. The electronic control device according to claim 6, wherein the current detection circuit includes a shunt resistor disposed between the common ground and a dedicated ground of the drive unit, and an operational amplifier that amplifies the voltage difference between both ends of the shunt resistor.

10. A method for detecting a break in a ground line of an electronic control device comprising: a drive unit including a first load drive circuit that drives a first load, a second load drive circuit that drives a second load, and a common ground common to the first load drive circuit and the second load drive circuit, the common ground being connected to a dedicated ground; and a control unit that is capable of individually controlling the first load drive circuit and the second load drive circuit and is connected to a dedicated ground different from the dedicated ground of the drive unit, wherein the first load is connected to the common ground, and the second load is connected to the dedicated ground of the drive unit, an output side of the second load drive circuit is connected to the common ground via a diode that can pass a current toward the second load drive circuit, and a current detection circuit is disposed between the common ground and the dedicated ground of the drive unit, wherein the control unit detects whether or not the ground line connected to the dedicated ground of the drive unit is broken in accordance with the output of the current detection circuit.

11. The method for detecting a break in a ground line as described in claim 10, wherein the control unit diagnoses whether or not there is a break in the ground line of the drive unit while controlling the first load drive circuit to drive the first load.

12. The method for detecting a break in a ground line according to claim 11, wherein the control unit diagnoses that the ground line of the drive unit is broken when no current is detected by the current detection circuit.

13. A method for detecting a break in a ground line of an electronic control device, comprising: a drive unit including a first load drive circuit that drives a first load, a second load drive circuit that drives a second load, and a common ground common to the first load drive circuit and the second load drive circuit, the common ground being connected to a dedicated ground; and a control unit that is capable of individually controlling the first load drive circuit and the second load drive circuit and is connected to a dedicated ground different from the dedicated ground of the drive unit, wherein the first load is connected to the common ground and the second load is connected to the dedicated ground of the drive unit, the dedicated ground of the control unit and the common ground of the drive unit are connected via a diode that can pass a current from the dedicated ground of the control unit to the common ground of the drive unit, and a current detection circuit is disposed between the common ground and the dedicated ground of the drive unit, wherein the control unit detects whether or not the ground line connected to the dedicated ground of the control unit is broken in accordance with an output of the current detection circuit.

14. The method for detecting a break in a ground line according to claim 13, further comprising diagnosing whether or not the ground line of the control unit is broken when the control unit is not controlling the first load drive circuit to drive the first load.

15. The method for detecting a break in a ground line according to claim 14, wherein the control unit diagnoses that the ground line of the control unit is broken when a current is detected by the current detection circuit.

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