ELECTRONIC CONTROL DEVICE AND ELECTRONIC CONTROL METHOD

An electronic control device comprises a reverse connection protection relay, a voltage detector, and a control device. The reverse connection protection relay comprises a switching element and a rectifying element. The switching element and the rectifying element are connected in parallel. A negative electrode of the rectifying element and a positive electrode of the rectifying element are connected to a negative electrode of a power source and a load, respectively, the load consuming power supplied from the power source. Opening and closing of the switching element are controlled on the basis of a switching control signal indicating presence or absence of power supply from the power source. The voltage detector is configured to detect a potential difference between both ends of the reverse connection protection relay. The control device is configured to determine a state of the reverse connection protection relay on the basis of the potential difference.

TECHNICAL FIELD

The present disclosure relates to an electronic control device and an electronic control method.

BACKGROUND ART

Patent Document 1 describes an electronic control device including: a reverse connection protector including a MOSFET as a switching element and a Zener diode as a reverse flow prevention element; a power source circuit that generates a positive power source voltage; a voltage detector that detects a voltage between a positive power source voltage and a ground of a battery; an A/D convertor that performs A/D conversion on a voltage output from the voltage detector; and a failure diagnosis unit that performs failure diagnosis on the reverse connection protector on the basis of an output value output from the A/D convertor. Patent Document 1 describes providing an electronic control device capable of diagnosing a failure of a reverse connection protection element using a MOSFET as a reverse connection protection element between a load and a ground.

CITATION LIST

Patent Document

SUMMARY OF INVENTION

Technical Problem

In the electronic control device described in Patent Document 1, when a positive voltage is applied from a positive electrode of a battery to a gate of the MOSFET, a drain and a source of the MOSFET are electrically connected. Therefore, a short-circuit failure in the MOSFET cannot be detected solely by monitoring a positive power source voltage. When the battery is reversely connected at the time of short-circuit failure, a current flows reversely. The reverse flow of the current causes a failure of the electronic control device. In order to avoid the reverse flow of the current, redundancy of a reverse connection protection relay or addition of a drive device for applying a positive power source voltage to a gate of the MOSFET is also conceivable. These measures require additional elements or peripheral circuits, thus leading to an increase in circuit scale or cost.

One object of the present disclosure is to provide an electronic control device and an electronic control method that solve the above-described problems.

Solution to Problem

A first aspect is an electronic control device comprising a reverse connection protection relay, a voltage detector, and a control device, in which the reverse connection protection relay comprises a switching element and a rectifying element, the switching element and the rectifying element are connected in parallel, a negative electrode of the rectifying element and a positive electrode of the rectifying element are connected to a negative electrode of a power source and a load, respectively, the load is configured to consume power supplied from the power source, opening and closing of the switching element are controlled on the basis of a switching control signal indicating presence or absence of power supply from the power source, the voltage detector is configured to detect a potential difference between both ends of the reverse connection protection relay, and the control device is configured to determine a state of the reverse connection protection relay on the basis of the potential difference.

A second aspect is an electronic control method in an electronic control device comprising a reverse connection protection relay, a voltage detector, and a control device, in which the reverse connection protection relay comprises a switching element and a rectifying element, the switching element and the rectifying element are connected in parallel, a negative electrode of the rectifying element and a positive electrode of the rectifying element, the negative electrode of the rectifying element and the positive electrode of the rectifying element, are connected to a negative electrode of a power source and a load, respectively, the load is configured to consume power supplied from the power source, and opening and closing of the switching element are controlled on the basis of a switching control signal indicating presence or absence of power supply from the power source, the method including: a first step of detecting, by the voltage detector, a potential difference between both ends of the reverse connection protection relay; and second step of determining, by the control device, a state of the reverse connection protection relay on the basis of the potential difference.

Advantageous Effects of Invention

According to the present disclosure, it is possible to economically detect a failure of a reverse connection protection relay.

DESCRIPTION OF EMBODIMENTS

Hereinafter, embodiments will be described with reference to the drawings. Elements common to or corresponding to the drawings are denoted by the same reference numerals, and description thereof is applied unless otherwise specified.

First Embodiment

A first embodiment will be described with reference to the drawings.FIG.1is a circuit diagram illustrating a configuration example of an electronic control device1according to the present embodiment. In the example ofFIG.1, it is assumed that the electronic control device1is mounted on the same vehicle (not illustrated) together with a power source8, a power source switch9, and an electric motor7, and is used to control an operation of an operation mechanism of the vehicle. The power source switch9controls necessity of power supply from the power source8to the electronic control device1. The power source switch9receives an operation from a user, for example, and generates a switching control signal indicating the necessity of power supply according to the received operation. The power source switch9switches the necessity of power supply from the power source8to the electronic control device1according to the generated switching control signal, and outputs the generated switching control signal to the electronic control device1. The necessity of power supply from the power source8to the electronic control device1is instructed using the switching control signal provided from the power source switch9.

A battery and an ignition switch can be applied as the power source8and the power source switch9, respectively. The battery is a storage battery capable of supplying DC power to the electronic control device1. A driver of the vehicle can be a main user of the electronic control device1. The ignition switch generates an ignition signal as an example of the switching control signal. The ignition signal is used to control activation (ON) or stop (OFF) of an operation mechanism of the vehicle. The operation mechanism of the vehicle includes, for example, electric power steering (EPS). The electric motor7forms a part of the operation mechanism.

The electronic control device1includes an electric motor drive circuit5as a load that consumes power supplied from the power source8. The electric motor drive circuit5supplies power from the power source8to the electric motor7to drive the electric motor7. The electric motor7also functions as a load that consumes power supplied from the power source8. The number of electric motors7included in the operation mechanism of the vehicle is not limited to one, and can be two or more. In this case, the electric motor drive circuit5supplies power required for an operation of each electric motor7. Note that, in the following description, a case where the number of electric motors7is one will be mainly described.

The electronic control device1, the power source8, the power source switch9, and the electric motor7may be individually manufactured or transferred. In addition, the electronic control device1, the power source8, the power source switch9, and the electric motor7may be attached to and detached from the vehicle at the time of maintenance, inspection, repair, or the like. For example, a positive electrode terminal and a negative electrode terminal of a battery as the power source8are connected to the electronic control device1using a power source plug (not illustrated). When the battery is replaced, the battery, which is a DC power source, may be connected to the power source plug in error of polarity. Connection with a polarity different from a predetermined polarity is called reverse connection. When the battery is connected with a wrong polarity, a current from the battery flows reversely in the electronic control device1. The reverse flow of the current may cause a fault or a failure of the electronic control device1. For protection from reverse connection, the electronic control device1includes a reverse connection protection relay2. As described below, the electronic control device1can autonomously determine a state of the reverse connection protection relay2.

The electronic control device1includes the reverse connection protection relay2, a voltage detector3, a control device4, the electric motor drive circuit5, a power source output holding circuit6, and a power source circuit10.

The reverse connection protection relay2protects the electric motor drive circuit5from a reverse flow of a current that may occur at the time of reverse connection of the power source8. The reverse connection protection relay2includes a switching element2sand a rectifying element14. The switching element2sand the rectifying element14are connected in parallel. That is, at one end of the reverse connection protection relay2, one end of the rectifying element14and one end of the switching element2sare electrically connected. At the other end of the reverse connection protection relay2, the other end of the rectifying element14and the other end of the switching element2sare electrically connected. The one end of the reverse connection protection relay2is connected to a negative electrode of the power source8.

Opening and closing of both ends of the switching element2sare controlled on the basis of a switching control signal applied from the power source switch9to the switching element2s.Whether or not a current flows from one end to the other end of the switching element2sis controlled in conjunction with presence or absence of power supply from the power source8to the electronic control device1indicated by the switching control signal. Even if the power source8is connected with a polarity reverse to the illustrated polarity, the reverse connection protection relay2cuts off a current from the power source8to the electric motor drive circuit5. Therefore, the electric motor drive circuit5is protected from the reverse flow of the current.

A digital electric signal indicating necessity of power supply from the power source8depending on whether a voltage is a high voltage or a low voltage may be used as the switching control signal. The high voltage and the low voltage indicate a higher voltage and a lower voltage of two-stage voltages, respectively. When a signal with a high voltage is not supplied, a detected voltage may be a low voltage. In the present application, the high voltage may be referred to as High. The low voltage may be referred to as Low.

The switching element2sis, for example, a metal-oxide-semiconductor field-effect transistor (MOSFET). The MOSFET generally comprises a source, a drain, and a gate. The MOSFET comprises a source terminal, a drain terminal, and a gate terminal in a source region, a drain region, and a gate region, respectively. The MOSFET as the switching element2sis connected to the rectifying element14with its source terminal and drain terminal as one end and the other end, respectively. The switching control signal input from the power source switch9is applied to the gate terminal.

Note that the MOSFET as the switching element2smay be any type of MOSFET such as an n-type MOSFET or a p-type MOSFET. The present embodiment exemplifies a case where an n-type MOSFET is used as the switching element2s.In the n-type MOSFET, a silicon oxide film and a gate electrode are disposed in a gate region set on a p-type semiconductor substrate. In each of a drain region and a source region, an n-type semiconductor is disposed on the p-type semiconductor substrate. The n-type semiconductor is formed by ion implantation with impurity concentration higher than the p-type semiconductor.

The rectifying element14causes a current to flow from one end thereof to the other end of the rectifying element14, and cuts off a current from the other end to the one end. The rectifying element14is, for example, a diode. The diode generally includes an anode and a cathode. The diode as the rectifying element14is connected to the switching element2swith the anode and the cathode as one end thereof and the other end of the rectifying element14.

For example, a parasitic diode may be used as the rectifying element14. The parasitic diode is also referred to as a body diode. The parasitic diode is configured to have a pn junction between a source region and a drain region of the n-type MOSFET. The pn junction is formed by disposing a p-type semiconductor together with an n-type semiconductor in a source region and disposing an n-type semiconductor in a drain region such that the n-type semiconductor is not in contact with the p-type semiconductor. As the rectifying element14, a parasitic diode configured in a MOSFET as the switching element2smay be used. As a result, a MOSFET in which the switching element2sand the rectifying element14are integrally configured can be used as the reverse connection protection relay2.

The voltage detector3detects a voltage at one end of the reverse connection protection relay2. As described later, a voltage detected on the basis of a reference potential GND_PCB corresponds to a potential difference between both ends of the reverse connection protection relay2. The voltage detector3generates an electric signal indicating the detected voltage, and outputs the generated electric signal to the control device4as a detection voltage signal.

The control device4consumes power supplied from the power source8via the power source switch9and the power source circuit10, and executes and controls various processes for exerting functions of the electronic control device1. The control device4includes, for example, a central processing unit (CPU). The control device4determines a state of the reverse connection protection relay2on the basis of the detection voltage signal input from the voltage detector3. The control device4includes, for example, an analog to digital (A/D) converter. The A/D converter converts the input analog detection voltage signal into a digital detection voltage signal, and determines a state of the reverse connection protection relay2on the basis of a voltage value indicated by the converted detection power signal. As the state of the reverse connection protection relay2, for example, presence or absence of an open failure and/or presence or absence of a short-circuit failure is detected. A specific example of a method for determining the state of the reverse connection protection relay2will be described later.

The control device4may acquire a notification signal for providing a notification of the determined state and output the acquired notification signal to a notifier16. The notifier16provides a notification of the state of the reverse connection protection relay2on the basis of the notification signal input from the control device4. The notifier16may be a member that can present information to a user, for example, a light emitting diode or a speaker. When a light emitting diode and a speaker are used as the notifier16, DC power and an acoustic signal are used, respectively. The light emitting diode emits light according to DC power supplied from the control device4. The speaker emits sound on the basis of an acoustic signal input from the control device4. As the notifier16, for example, a warning lamp, an audio speaker, or the like disposed in front of a driver's seat of the vehicle may be applied. The notifier16may be integrated with the electronic control device1or may be configured separately.

The control device4controls an operation of the electric motor drive circuit5on the basis of a known control method. The control device4controls the electric motor drive circuit5on the basis of, for example, an ignition signal input to the control device4. The control device4causes the electric motor drive circuit5to operate the electric motor7when a voltage of the ignition signal is High. At this time, the control device4generates a drive control signal for instructing the operation of the electric motor7, and outputs the generated drive control signal to the electric motor drive circuit5. When the voltage of the ignition signal is Low, the control device4causes the electric motor drive circuit5to stop the operation of the electric motor7. At this time, the control device4stops outputting the drive control signal to the electric motor drive circuit5.

Various signals are input to the control device4from devices included in the vehicle as vehicle-side input signals. The vehicle-side input signals include a torque signal from a torque sensor that detects a steering operation, a vehicle speed signal from a vehicle speed sensor, and the like. The control device4may execute an arithmetic process and a drive instruction for driving an operation mechanism of the vehicle using the vehicle-side input signals.

The electric motor drive circuit5drives the electric motor7under control of the control device4. As a power supply state, for example, necessity of power supply to the electric motor7is instructed. When a drive control signal indicating that an operation of the electric motor7is necessary is input from the control device4to the electric motor drive circuit5, the electric motor drive circuit5supplies power from the power source8to the electric motor7. When the drive control signal is not input from the control device4to the electric motor drive circuit5, the electric motor drive circuit5stops power supply from the power source8to the electric motor7. The electric motor drive circuit5includes, for example, a bridge circuit and a motor relay switching element. The bridge circuit includes a high-side switching element and a low-side switching element for supplying power to each of one or more coils included in the electric motor7. The motor relay switching element cuts off power supplied to the electric motor7when the drive control signal indicates that the operation is not necessary.

When a switching control signal is input from the power source switch9to the power source output holding circuit6or when a power request signal is input from the control device4to the power source output holding circuit6, the power source output holding circuit6outputs an operation permission signal to the power source circuit10. The power request signal is an electric signal for indicating that power supply is necessary. The power request signal indicates that power supply is necessary with a voltage being High. The operation permission signal is an electric signal for instructing holding of an operating voltage of the control device4. The operation permission signal indicates holding of the operating voltage with a voltage being High. The control device4outputs the power request signal to the power source output holding circuit6during the operation.

The power source output holding circuit6has, for example, a diode OR configuration. The power source output holding circuit6includes, for example, two diodes and one resistance element, and one end of each of the diodes serves as an input end of the power source output holding circuit6. The other end of each of the diodes is connected to one end of the resistance element and serves as an output end of the power source output holding circuit6. The other end of the resistance element is grounded.

According to this configuration, when a voltage of the switching control signal input from power source switch9changes from High to Low, the power source circuit10can hold an operating voltage of the control device4. Note that each of the power source output holding circuit6and the power source circuit10may comprise a storage battery that stores power supplied from the power source8. Even if power from the power source8is interrupted, an output of the operation permission signal from the power source output holding circuit6is maintained. At this time, power is supplied from the storage battery of the power source circuit10to the control device4. Thus, power supply from the power source8via the power source circuit10is prevented from being immediately cut off during the operation of the control device4. Therefore, opportunities for termination of the operation of the electric motor drive circuit5by the control device4, a finalization of the control device4itself, and the like can be ensured. The finalization comprises, for example, a process of writing internal data of the control device4at that time into a memory included in the control device4. Immediately after the voltage of the switching control signal changes from High to Low, the control device4can terminate the operation at a predetermined timing without immediately terminating the operation.

After completion of the finalization, the control device4terminates outputting the power request signal to the power source output holding circuit6. When an input of the switching control signal from the power source switch9and an input of the power request signal from the control device4are terminated, the power source output holding circuit6terminates outputting the operation permission signal to the power source circuit10. When no power is supplied from the power source8via the power source switch9and no operation permission signal is input from the power source output holding circuit6, the power source circuit10terminates holding the operating voltage. At this time, power supply from the power source circuit10to the control device4is terminated.

Next, a circuit configuration example around the reverse connection protection relay2according to the present embodiment will be described.FIG.2is a circuit diagram illustrating a circuit configuration example around the reverse connection protection relay2according to the present embodiment. In the example ofFIG.2, a case where the switching element2sis a MOSFET, and a parasitic diode formed in the MOSFET is applied as the rectifying element14is illustrated. The reverse connection protection relay2is configured to include one MOSFET. A gate terminal of the MOSFET as the switching element2sis connected to the power source switch9via a resistance element12and a rectifying element11. An anode and a cathode of a Zener diode13are connected to a gate terminal and a source terminal of the MOSFET, respectively. A switching control signal supplied from the power source switch9is applied to the gate terminal of the MOSFET. The rectifying element11is a charge holding diode for holding a charge when a voltage of the switching control signal is Low. The resistance element12is a current limiting resistor for preventing an excessive current. The Zener diode13is provided to avoid a reverse flow of a current due to the switching control signal, thereby protecting the electric motor drive circuit51.

According to the configuration ofFIG.2, the source terminal and the drain terminal of the MOSFET as the switching element2sare electrically connected (ON) while a voltage of the switching control signal is High. The source terminal of the MOSFET is cut off from the drain terminal (OFF) while the voltage of the switching control signal is Low. Note that, in the example ofFIG.2, the rectifying element11, the resistance element12, and the Zener diode13are not essential. Some or all of the rectifying element11, the resistance element12, and the Zener diode13may be omitted, or may be replaced with other members.

Next, a specific example of a method for determining a state of the reverse connection protection relay2will be described.FIG.3is an explanatory diagram for describing a specific example of the method for determining a state of the reverse connection protection relay2according to the present embodiment. First, a specific example of a method for detecting an open failure as a state of the reverse connection protection relay2will be described. The open failure of the reverse connection protection relay2refers to a failure in which connection between both ends of the switching element2sis cut off (OFF) when both ends of the switching element2sshould be electrically connected (ON). In the following description, it is assumed that power is initially supplied from the power source8to the power source circuit10via the power source switch9, the control device4operates, and the electric motor drive circuit5does not operate.

FIG.3illustrates time courses of the switching control signal, a state of the reverse connection protection relay, the operation permission signal, and an operation state of the control device. In the illustrated example, a voltage of the switching control signal supplied from the power source switch9is initially High. When no open failure occurs, both ends of the reverse connection protection relay2are electrically connected (ON). Thus, a current from a positive electrode terminal to a negative electrode terminal of the power source8passes through the switching element2s.When an open failure occurs, connection between both ends of the reverse connection protection relay2is cut off (OFF). Therefore, a current from a positive electrode terminal to a negative electrode terminal of the power source8passes through the rectifying element14connected in parallel with the switching element2s.Accordingly, a potential difference generated between both ends of the reverse connection protection relay2is different between the case where a current passes through the switching element2sand the case where the current passes through the rectifying element14.

As an example, it is assumed that a resistance between a drain and a source of the MOSFET as the switching element2sis 1 mΩ, a forward voltage Vf of the parasitic diode as the rectifying element14is 700 mV, and power consumption of the electronic control device1is 1 A. When a current passes through the MOSFET, the potential difference is 1 mV. When a current passes through the parasitic diode, the potential difference corresponds to 700 mV, which is a forward voltage of the parasitic diode. The forward voltage depends on characteristics of each rectifying element14, but has a value sufficiently larger than the potential difference when a current passes through the switching element2s.A reference potential may be preset such that a voltage corresponding to this potential difference can be detected by the voltage detector3.

As illustrated inFIG.1, a reference potential GND of the voltage detector3is set so as to be equal to a potential of a negative electrode of the power source8. A reference potential GND_PCB of a control component including the power source circuit10and the control device4is set so as to be equal to a potential between the reverse connection protection relay2and the electric motor drive circuit5. A position where the reference potential GND is set and a position where the reference potential GND_PCB is set are separated across both ends of the reverse connection protection relay2.

As described above, a potential difference generated between the reference potential GND and the reference potential GND_PCB is significantly different between the case where an open failure occurs in the reverse connection protection relay2and the case where the open failure does not occur in the reverse connection protection relay2. Therefore, the control device4determines presence or absence of an open failure of the switching element2son the basis of a detection voltage signal input from the voltage detector3. A voltage based on the reference potential GND_PCB is a potential difference between both ends of the reverse connection protection relay2. More specifically, the control device4compares a voltage indicated by the detection voltage signal with a preset open failure threshold, and can determine presence or absence of an open failure by whether or not the voltage indicated by the detection voltage signal is higher than the open failure threshold. The open failure threshold may be preset between a voltage (potential difference) detected in case of an open failure and a voltage (potential difference) detected not in case of the open failure.

Note that, when the electric motor7is driven in a state where an open failure occurs in the reverse connection protection relay2, a drive current passes through the rectifying element14. Power consumption of the rectifying element14corresponds to a product of a potential difference between both ends of the rectifying element14and the drive current. The power consumption is larger than power consumption of the switching element2swhen the drive current passes through the switching element2s.An increase in calorific value may cause abnormal heat generation, leading to failure, smoking, or ignition. Therefore, the control device4may determine presence or absence of an open failure of the reverse connection protection relay2before the operation of the electric motor drive circuit5starts. When determining occurrence of an open failure, the control device4does not have to output a drive control signal to the electric motor drive circuit5regardless of whether or not an ignition signal is input. Thus, abnormal heat generation due to current flow to the rectifying element14can be avoided without operating the electric motor drive circuit5.

Next, a specific example of a method for detecting a short-circuit failure in the reverse connection protection relay2will be described. The short-circuit failure in the reverse connection protection relay2refers to a failure in which both ends of the switching element2sare electrically connected (ON) when connection between both ends of the switching element2sshould be cut off (OFF). In the following description, as illustrated inFIG.3, it is assumed that a voltage of a switching control signal from the power source switch9changes from High to Low at time T0. At this time, a voltage of an operation permission signal output from the power source output holding circuit6is maintained at High. Therefore, even when the time passes T0, the operation of the control device4continues. The control device4terminates the operation of the electric motor drive circuit5and performs a finalization of the control device4. Thereafter, at time T1, the control device4terminates the operation. At this time, the voltage of the operation permission signal output from the power source output holding circuit6changes from High to Low. The control device4can ensure an opportunity to execute failure detection of the reverse connection protection relay2in an output holding period from time T0to time T1.

Since the voltage of the control signal is Low in the output holding period, connection between both ends of the switching element2sis cut off (OFF) unless a short-circuit failure occurs. Therefore, a current from a positive electrode terminal to a negative electrode terminal of the power source8passes through the rectifying element14. On the other hand, when a short-circuit failure occurs, the current from the positive electrode terminal to the negative electrode terminal of the power source8passes through the switching element2s.As described above, a potential difference between both ends of the reverse connection protection relay2varies depending on whether the current passes through the rectifying element14or passes through the switching element2s.

As an example, it is assumed that a resistance between a drain and a source of the MOSFET as the switching element2sis 1 mΩ, a forward voltage Vf of the parasitic diode as the rectifying element14is 700 mV, and power consumption of the electronic control device1is 1 A. When a current passes through the MOSFET, the potential difference is 1 mV. When a current passes through the parasitic diode, the potential difference corresponds to 700 mV, which is a forward voltage of the parasitic diode.

Thus, the control device4may determine presence or absence of a short-circuit failure in the switching element2son the basis of a detection voltage signal input from the voltage detector3. The detection voltage signal indicates a voltage detected by the voltage detector3. More specifically, the control device4compares a voltage indicated by the detection voltage signal with a preset short-circuit failure threshold, to determine presence or absence of a short-circuit failure based on whether or not the voltage indicated by the detection voltage signal is lower than the short-circuit failure threshold. The short-circuit failure threshold may be preset a value between a voltage (potential difference) detected in case of short-circuit failure and a voltage (potential difference) detected not in case of the short-circuit failure. In addition, as described above, the reference potential GND of the voltage detector3may be preset so as to be equal to a potential of the negative electrode of the power source8. In addition, a reference potential GND_PCB of a control component including the power source circuit10and the control device4is set so as to be equal to a potential between the reverse connection protection relay2and the electric motor drive circuit5. With this setting, a voltage indicated by the detection voltage signal corresponds to a potential difference between both ends of the reverse connection protection relay2.

When determining a short-circuit failure, the control device4supplies DC power to a warning lamp mounted on the vehicle, for example, as a notification signal for providing a notification of the short-circuit failure. The warning lamp emits light according to DC power from the control device4. A driver who has visually recognized the light-emitting warning lamp is notified of occurrence of the short-circuit failure. When an ignition switch is applied as an example of the power source switch9, protection from a current by battery connection as the power source8is provided during an ignition OFF period. The ignition OFF period corresponds to a duration when an ignition signal with a High voltage is not input. Generally, the battery is not replaced while the vehicle is traveling. Therefore, it can be practically sufficient that a short-circuit failure is detected during the ignition OFF period.

Note that the above description exemplifies a case where the reverse connection protection relay2is driven on the basis of a switching control signal from the power source switch9in place of power supplied from the power source8, and an operating voltage of the control device4is held using the power source output holding circuit6. When power is not supplied from the power source8, even if electrical connection between both ends of the reverse connection protection relay is cut off using the switching control signal, the operating voltage of the control device4is maintained by the power source output holding circuit6. Even in such a case, the control device4can autonomously detect a short-circuit failure in the reverse connection protection relay2.

Second Embodiment

A second embodiment will be described with reference to the drawings. The following description will mainly focus on a difference from the first embodiment. Unless otherwise specified, the description in the first embodiment is applied to other matters. An electronic control device1according to the present embodiment can detect presence or absence of a short-circuit failure as a state of a reverse connection protection relay2even in a case where power supply from a power source8is started in addition to a case where the power supply from the power source8is cut off. Thereafter, opening and closing of the reverse connection protection relay2are controlled on the basis of a switching control signal.

FIG.4is a circuit diagram illustrating a configuration example of the electronic control device1according to the present embodiment.

The electronic control device1according to the present embodiment includes a reverse connection protection relay drive control circuit24in addition to the reverse connection protection relay2, a voltage detector3, a control device4, an electric motor drive circuit5, a power source output holding circuit6, and a power source circuit10. The reverse connection protection relay drive control circuit24is disposed between and connected to a power source switch9and the reverse connection protection relay2. When receiving, as an input, a switching control signal indicating power supply on from the power source switch9and a switching command signal indicating a switching command for the reverse connection protection relay2from the control device4, the reverse connection protection relay drive control circuit24outputs the switching control signal indicating power supply on to the reverse connection protection relay2. When receiving a switching control signal indicating power supply off from the power source switch9, or when not receiving a switching command signal indicating a switching command for the reverse connection protection relay2from the control device4, the reverse connection protection relay drive control circuit24outputs the switching control signal indicating power supply off to the reverse connection protection relay2. Necessity of the switching command is indicated by, for example, whether a voltage of the switching command signal is High or Low.

Therefore, when the switching command is acquired from the control device4, the reverse connection protection relay drive control circuit24can control opening and closing of the reverse connection protection relay2according to the switching control signal from the power source switch9. When the switching command is not acquired, the reverse connection protection relay drive control circuit24cuts off connection between both ends of the reverse connection protection relay2regardless of whether or not a switching control signal having a High voltage is input. In this state, the control device4can determine presence or absence of a short-circuit failure in the reverse connection protection relay2on the basis of a voltage indicated by a detection power signal input from the voltage detector3. After determining presence or absence of a short-circuit failure, the control device4outputs a switching command signal indicating a switching command for the reverse connection protection relay2to the reverse connection protection relay drive control circuit24. The switching command is represented, for example, with a voltage of the switching command signal being High. The control device4includes, for example, a general purpose input/output (GPIO) port, and can output the switching command signal using the GPIO.

Note that the control device4executes an initialization process when power supply from the power source circuit10is started. The initialization process includes, for example, processes such as reading of internal data stored in a memory and detection of various devices connected to the control device4. After completing the initialization process, the control device4can determine presence or absence of a short-circuit failure. After determining that there is no short-circuit failure, the control device4outputs a switching command signal to the reverse connection protection relay drive control circuit24. As a result, opening and closing of the reverse connection protection relay2based on the switching control signal from the power source switch9can be controlled. At this stage, the control device4may start control of the electric motor drive circuit5based on an ignition signal.

Next, a specific example of a method for detecting a short-circuit failure in the reverse connection protection relay2will be described.FIG.5is an explanatory diagram for describing an example of a method for detecting a short-circuit failure in the reverse connection protection relay2according to the present embodiment. In the following description, it is assumed that power is not initially supplied from the power source8to the power source circuit10via the power source switch9, and both the control device4and the electric motor drive circuit5do not operate.FIG.5illustrates time courses of the switching control signal, an output of the power source circuit, an operation state of the control device4, the switching command, and a state of the reverse connection protection relay2. In the illustrated example, a voltage of the switching control signal supplied from the power source switch9is initially Low. When a short-circuit failure does not occur, electrical connection between both ends of the reverse connection protection relay2is cut off (OFF). In this state, power is not supplied from the power source8to the power source circuit10via the power source switch9. Therefore, a voltage of power supplied from the power source circuit10to the control device4is 0 V (OFF). At this time, since the control device4does not operate (OFF), the switching command signal is not output from the control device4(OFF).

Next, it is assumed that the voltage of the switching control signal from the power source switch9changes from Low to High at time T0. At this time, a voltage of power supplied from the power source circuit10to the control device4starts to rise from 0 V (OFF) and reaches a operating voltage (ON) at time T1, the operating voltage preset in the control device4. At this time, the voltage is stabilized, and an initialization process is started as an operation of the control device4(ON). After the initialization process is ended, at time T2, the control device4starts outputting a switching command signal indicating a switching command to the reverse connection protection relay drive control circuit24(ON). At this time, the reverse connection protection relay drive control circuit24starts outputting a switching control signal having a High voltage to the reverse connection protection relay2. If no short-circuit failure occurs, both ends of the reverse connection protection relay2begin to change from a cut-off state (OFF) to an electrically connected state (ON). Therefore, the control device4can determine presence or absence of a short-circuit failure in the reverse connection protection relay2on the basis of a voltage value indicated by a detection power signal input from the voltage detector3during a period until the switching command signal is output at time T2after the initialization process is ended.

In this period, since the power source circuit10and the control device4operate, a current is generated from a positive electrode terminal to a negative electrode terminal of the power source8. When no short-circuit failure occurs in the reverse connection protection relay2, connection between both ends of the switching element2sshould be cut off (OFF). In this state, the generated current passes through the rectifying element14connected in parallel with the switching element2s.When a short-circuit failure occurs, both ends of the switching element2sare electrically connected (ON). Therefore, a current from a positive electrode terminal to a negative electrode terminal of the power source8passes through the switching element2s.Therefore, a potential difference generated between both ends of the reverse connection protection relay2is different between the case where a current passes through the rectifying element14and the case where the current passes through the switching element2s.

As an example, it is assumed that a resistance between a drain and a source of the MOSFET as the switching element2sis 1 mΩ, a forward voltage Vf of the parasitic diode as the rectifying element14is 700 mV, and power consumption of the electronic control device1is 1 A. When a current passes through the parasitic diode, the potential difference corresponds to 700 mV, which is a forward voltage of the parasitic diode. When a current passes through the MOSFET, the potential difference is 1 mV.

Therefore, the control device4determines presence or absence of a short-circuit failure in the switching element2son the basis of a detection voltage signal input from the voltage detector3. More specifically, the control device4compares a voltage indicated by the detection voltage signal with a preset short-circuit failure threshold, and can determine presence or absence of a short-circuit failure by whether or not the voltage indicated by the detection voltage signal is lower than the short-circuit failure threshold. The short-circuit failure threshold may be preset between a voltage in case of a short-circuit failures and a voltage not in case of the short-circuit failure.

Accordingly, the reverse connection protection relay drive control circuit24can control the electrical connection between both ends of the reverse connection protection relay2to be cut off, even when power is supplied from the power source8. Therefore, the control device4can determine presence or absence of a short-circuit failure in the reverse connection protection relay2even after power supplied from the power source8is consumed and the operation is started.

Next, a modification of the electronic control devices1according to the above embodiments will be described. The electronic control device1may include, for example, any one of the power source switch9, the electric motor7, and the notifier16, or a combination of any of these, and may be integrally configured. The electronic control device1may further include the power source8. The electronic control device1may have a function of controlling another device mounted on the vehicle. The other device may be, for example, any one of an acoustic device, an air conditioning device, a navigation device, a driving assistance system, and the like, or a combination of any of these. The electronic control device1may be configured as an electronic control unit (ECU).

The power source8is not limited to a portable power source such as a battery, and may be a stationary power source. Power supply from the power source8to the electronic control device1is not limited to wired power supply, and may be wireless power supply. When a wireless charger is used as the power source8, the electronic control device1may include a wireless power receiver and receive power transmitted from the wireless charger. The load is not limited to the electric motor drive circuit5, and may be another device as long as the device consumes power supplied from the power source8. The device serving as the load does not have to be configured integrally with the electronic control device1.

The switching element2sis not necessarily limited to a MOSFET, and may be another type of bipolar transistor. The rectifying element14is not necessarily limited to a diode, and may be a selenium rectifier or the like.

A display may be used as the notifier16. The control device4may generate a signal representing information indicating a determined state by characters, symbols, or images as the above notification signal, and output the signal to the display. When a speaker is used as the notifier16, a signal representing the information indicating the determined state by voice may be generated as the above signal and output to the speaker. The notification information may include, in addition to the information indicating the determined state, information indicating a countermeasure (for example, component replacement or contact with a sales store) for the state.

As described above, the electronic control device1according to the present disclosure includes the reverse connection protection relay2, the voltage detector3, and the control device4. The reverse connection protection relay2comprises the switching element2sand the rectifying element14, and the switching element2sand the rectifying element14are connected in parallel. A negative electrode of the rectifying element14and a positive electrode of the rectifying element14are connected to a negative electrode of the power source8and a load (for example, the electric motor drive circuit5), respectively. The load is configured to consume power supplied from the power source8. Opening and closing of the switching element2sare controlled on the basis of a switching control signal indicating presence or absence of power supply from the power source. The voltage detector3is configured to detect a potential difference between both ends of the reverse connection protection relay2. The control device4is configured to determine a state of the reverse connection protection relay2on the basis of the detected potential difference.

In general, electrical resistance of the reverse connection protection relay2depends on a state of the reverse connection protection relay2. According to this configuration, the state of the reverse connection protection relay2is determined on the basis of the potential difference generated between both ends of the reverse connection protection relay2by a current through the reverse connection protection relay2in response to power supply from the power source8. Therefore, the state of the reverse connection protection relay2is autonomously detected without an increase in circuit scale or cost.

The control device4may detect presence or absence of an open failure as the state of the reverse connection protection relay2in case of power supply from the power source8.

According to this configuration, when electrical connection of both ends of the reverse connection protection relay2is instructed, presence or absence of an open failure can be determined on the basis of the potential difference between both ends of the reverse connection protection relay2.

The electronic control device1may include the power source circuit10and the power source output holding circuit6. The power source circuit10may convert a power source voltage of power supplied from the power source8into an operating voltage of the control device4. The power source output holding circuit6may cause the power source circuit10to hold the operating voltage in case of interruption of power supply from the power source8. The control device4may detect presence or absence of a short-circuit failure as a state of the reverse connection protection relay2.

According to this configuration, even when the power supply from the power source8is cut off, the operating voltage of the control device4is maintained. On the other hand, control is performed such that electrical connection between both ends of the reverse connection protection relay2is cut off. The control device4can determine presence or absence of a short-circuit failure on the basis of the potential difference between both ends of the reverse connection protection relay2without terminating the operation.

The electronic control device1may further comprise a drive control circuit (for example, the reverse connection protection relay drive control circuit24). The drive control circuit may cause both ends of the switching element2sto be electrically connected in case of power supply from the power source8and the switching command is acquired from the control device4. The control device4may detect presence or absence of a short-circuit failure as a state of the reverse connection protection relay2before the power supply from the power source8and the switching command acquired from the control device4.

According to this configuration, even when power is supplied from the power source8, electrical connection between both ends of the switching element2sis cut off at a stage where a switching command is not acquired from the control device4. Even before a switching command is input, the control device4is operated by the power supply from the power source8, whereby presence or absence of a short-circuit failure can be determined on the basis of a potential difference between both ends of the reverse connection protection relay2.

A reference potential serving as a reference of the operating voltage of the control device4and a reference potential of the voltage detector3may be separated across both ends of the reverse connection protection relay2.

According to this configuration, by setting the reference potential of the control device4to one end of the reverse connection protection relay2, the voltage detector3can detect the voltage at the one end of the reverse connection protection relay2as a potential difference between both ends of the reverse connection protection relay2.

The switching element2smay be a MOSFET, and the rectifying element14may be a parasitic diode formed by joining a source and a drain of the MOSFET.

According to this configuration, one MOSFET is configured as the reverse connection protection relay2. Reducing the number of components contributes to miniaturization and cost reduction of the electronic control device1.

The load may be the electric motor drive circuit5that is configured to drive the electric motor7. Opening and closing of the switching element2smay be controlled on the basis of an ignition signal input from an ignition switch as the switching control signal.

According to this configuration, opening and closing of the switching element2scan avoid a reverse flow of a current to the electric motor drive circuit5due to a reverse connection of the power source8in conjunction with power supply to the electric motor drive circuit5by the ignition switch. In addition, a state of the reverse connection protection relay2can be detected without delay by using the ignition signal in control of the switching element2s.

Although the embodiments of the present disclosure have been described above, the present disclosure is not limited to these embodiments and a modification thereof. Addition, omission, replacement, and other changes of the configuration can be made without departing from the gist of the present disclosure.

A direction of an arrow illustrated in the block diagrams and other drawings are for convenience of description, and do not limit flow directions of information, data, signals, and the like in implementation.

In addition, the present disclosure is not limited by the above description, but is limited solely by the attached claims.

INDUSTRIAL APPLICABILITY

According to the electronic control device and the electronic control method according to the present disclosure, a state of the reverse connection protection relay2is determined on the basis of a potential difference generated between both ends of the reverse connection protection relay2by a current through the reverse connection protection relay2in response to power supply from the power source8. Therefore, the state of the reverse connection protection relay2is autonomously detected without an increase in circuit scale or cost.

REFERENCE SIGNS LIST