Patent ID: 12222406

DESCRIPTION OF EMBODIMENTS

Hereinafter, embodiments of the present invention will be described with reference to the drawings. It should be noted that the drawings are simplified and thus the technical scope of the present invention should not be narrowly interpreted based on the description of the drawings. In addition, the same elements are denoted by the same reference numerals with redundant description omitted.

First Embodiment

A first embodiment of the present invention will be described below with reference toFIGS.1to6.

(Configuration of Integrated Circuit Device)

FIG.1is a configuration diagram of an integrated circuit device according to the first embodiment of the present invention. An integrated circuit device10according to the present embodiment is provided in an electronic control device1mounted in a vehicle system such as an automobile and is connected to a load50such as a solenoid to control the load current supplied to the load50. The load50is, for example, a solenoid for operating a vehicular automatic transmission, and the integrated circuit device10performs automatic transmission control by controlling the load current flowing through the load50. The integrated circuit device10is configured to include a control circuit20, a drive circuit30, a rectifier circuit60, a diagnostic circuit70, and a diagnostic current supply circuit90.

It should be noted that although a plurality of loads are controllable in a general vehicular electronic control device, in the present embodiment, an example in which one load50is connected to the integrated circuit device10and the load current flowing through this load50is controlled by one drive circuit30will be described in order to describe the operation of the integrated circuit device10in an easy-to-understand manner.

The control circuit20generates an operating power supply25or a control signal26necessary for the operation of the drive circuit30and outputs the operating power supply25or the control signal26to the drive circuit30. The control circuit20is supplied with electric power via a power terminal15from a vehicular battery (not illustrated) mounted in the vehicle system and operates using this power supply. The control circuit20is connected to a ground line21, and the ground line21is connected via a GND terminal22to the common ground of the electronic control device1provided outside the integrated circuit device10. As a result of this connection, the control circuit20is grounded via the ground line21and the GND terminal22.

The drive circuit30operates in accordance with the control signal26from the control circuit20using the operating power supply25supplied from the control circuit20. The drive circuit30has a high-side switch element40and a low-side switch element45connected in series between a power terminal16and a GND terminal32and uses these switch elements to switch between the conduction and interruption of the load current supplied from the vehicular battery (not illustrated) to the load50and switch the conduction path. Turning on the high-side switch element40and off the low-side switch element45leads to low-loss conduction between the power terminal16and a LOAD output47connected to the load50, and turning on the low-side switch element45and off the high-side switch element40leads to low-loss conduction between the GND terminal32and the LOAD output47. As a result, it is possible to switch between the conduction and interruption of the load current flowing through the load50and switch the conduction path of the load current.

The drive circuit30has a switch element control circuit35. The switch element control circuit35outputs switch control signals36and37to the high-side switch element40and the low-side switch element45in accordance with the control signal26from the control circuit20, respectively. As a result, each of the high-side switch element40and the low-side switch element45can be switched to the ON state or the OFF state and the load current can be controlled as described above.

The drive circuit30is connected to a ground line31, and the ground line31is connected via the GND terminal32to the common ground of the electronic control device1provided outside the integrated circuit device10. As a result of this connection, the drive circuit30is grounded via the ground line31and the GND terminal32.

In general, a load controlled by a vehicular electronic control device, such as the load50, requires ampere-order current supply. In the present embodiment, the ground line21of the control circuit20and the ground line31of the drive circuit30are separated in the integrated circuit device10in order to prevent the control circuit20from deteriorating in performance or malfunctioning due to ground noise generated by this current.

As described above, these ground lines are connected to the common ground of the electronic control device1via the mutually different GND terminals22and32, respectively.

The rectifier circuit60is connected between the ground line21and the ground line31. In the integrated circuit device10of the present embodiment, the rectifier circuit60is inserted between the ground lines21and31from the viewpoint of electrostatic withstand voltage protection between the ground lines21and31connected to the common ground independently of each other. The rectifier circuit60is configured using rectifying elements61and62such as diodes connected in mutually opposite directions and has a bidirectional rectification function. As a result, in the case of an open (non-conduction) state between one of the ground lines and the common ground and a constant potential difference between the ground lines attributable to poor connection of the GND terminals22and32or the like, a current is caused to flow from the ground line on the high-potential side to the ground line on the low-potential side via the rectifier circuit60and the charge is discharged.

It should be noted that in order to protect the control circuit20or the drive circuit30in a case where the potential of the ground line21or the ground line31has risen due to poor connection of the GND terminals22and32or the like, a protective diode may be disposed on the input side of the control signal26serving as an interface therebetween.FIG.2is a diagram illustrating an example in which a protective diode is disposed on the input side of the control signal26. In the example ofFIG.2, protective diodes65and66are disposed between the control signal26and the ground lines21and31in the control circuit20and the drive circuit30, respectively.

Here, almost no current flows through the rectifier circuit60and the protective diodes65and66on a normal occasion when the ground lines21and31and the common ground of the electronic control device1are conducted via the GND terminals22and32, respectively. In this case, the current consumed by the control circuit20flows from the ground line21to the common ground via the GND terminal22. In addition, the current consumed by the drive circuit30flows from the ground line31to the common ground via the GND terminal32.

A load termination51on the side opposite to the end of the load50to which the LOAD output47is connected is connected to either the vehicular battery or the common ground. In a case where the connection destination of the load termination51is the vehicular battery, with the drive circuit30operating, the current consumption of the switch element control circuit35or the load current supplied to the load50by switching the low-side switch element45to the ON state flows into the ground line31. On the other hand, in a case where the connection destination of the load termination51is the common ground, with the drive circuit30operating, the current consumption of the switch element control circuit35flows into the ground line31by switching the high-side switch element40to the OFF state. In these states, when the connection between the ground line31and the common ground is interrupted and the ground line31is opened due to poor connection of the GND terminal32or the like, the current that has flowed into the ground line31does not flow out to the common ground via the GND terminal32and the potential of the ground line31rises. As a result, a forward bias is applied to the rectifying element62in the direction from the ground line31toward the ground line21. The rectifying element62causes a current corresponding to this forward voltage to flow from the ground line31to the ground line21and discharges the current to the common ground of the electronic control device1via the GND terminal22. In other words, the rectifying element62works so as to generate a voltage such that a current flows from the ground line31to the ground line21and generate a potential difference between the ground line31and the ground line21.

Therefore, the diagnostic circuit70diagnoses the grounding state of the ground line31by measuring the potential difference between the ground line31and the ground line21and determining whether or not this potential difference corresponds to the forward voltage generated in the rectifying element62described above. The diagnostic circuit70is configured using a monitor circuit71and a comparative determination circuit74. The monitor circuit71measures the potential difference between the ground line31and the ground line21and outputs the measurement result as a monitor circuit output72. The comparative determination circuit74compares the monitor circuit output72output from the monitor circuit71with a predetermined comparison voltage73and outputs the comparison result as a diagnostic result75regarding the grounding state of the ground line31. Specifically, when the monitor circuit output72is equal to or lower than the comparison voltage73, it is determined that the grounding state of the ground line31is normal and the determination result is output as the diagnostic result75. On the other hand, when the monitor circuit output72is higher than the comparison voltage73, it is determined that the grounding state of the ground line31is abnormal and poor opening attributable to poor connection of the GND terminal32or the like has occurred in the ground line31and the determination result is output as the diagnostic result75.

The diagnostic result75output from the comparative determination circuit74of the diagnostic circuit70is input to the control circuit20. The control circuit20records the diagnostic result75and outputs the diagnostic result75to another device (not illustrated) provided separately from the integrated circuit device10in the electronic control device1or takes a predetermined safety measure based on the diagnostic result75. For example, in a case where the diagnostic result75indicating that the grounding state of the ground line31is abnormal is input, the drive circuit30is stopped and the load current supply to the load50is interrupted.

Here, it is preferable to set the comparison voltage73in the diagnostic circuit70to a value larger than the potential difference generated between the ground line31and the ground line21when the grounding state of the ground line31is normal. As mentioned above, the load current supplied from the integrated circuit device10to the load50may reach the order of amperes. Accordingly, even with the grounding state of the ground line31normal, the parasitic impedance between the ground line31and the GND terminal32and between the GND terminal32and the common ground causes the potential of the ground line31to rise. For example, at a parasitic impedance of 0.1Ω, a potential rise of 200 mV occurs in the ground line31with respect to a load current of2A. The comparison voltage73needs to be sufficiently large so as not to erroneously detect this as poor opening. It should be noted that although not particularly illustrated inFIG.1, a filter circuit or the like may be added in the stage subsequent to the comparative determination circuit74in order to remove, for example, spike noise generated in the ground line31due to instantaneous current fluctuation or the like or noise generated in the event of control switching.

The diagnostic current supply circuit90is connected to the ground line31and supplies a predetermined diagnostic current to the ground line31. In a state where the integrated circuit device10does not control the load50and the drive circuit30is stopped, no current consumption occurs at the switch element control circuit35, and thus the current flowing into the ground line31from the switch element control circuit35is 0 or minute. Accordingly, even in a case where the ground line31has been opened, a sufficient potential difference does not occur between the ground line31and the ground line21and poor opening cannot be reliably detected at the diagnostic circuit70in some cases. Therefore, in the present embodiment, the diagnostic current supply circuit90is provided in the integrated circuit device10and a predetermined diagnostic current is supplied from the diagnostic current supply circuit90to the ground line31so that a sufficient potential difference is generated between the ground line31and the ground line21regardless of the operating state of the drive circuit30in a case where the ground line31is open and poor opening can be reliably detected at the diagnostic circuit70.

Considering damage to the integrated circuit device10or another device in the electronic control device1, it is preferable that poor opening of the ground line31can be detected before the integrated circuit device10starts controlling the load current supplied to the load50. In the present embodiment, by installing the diagnostic current supply circuit90in the integrated circuit device10, poor opening can be reliably detected at the diagnostic circuit70regardless of the operating state of the drive circuit30as described above. Accordingly, there is an advantage that it is possible to ensure that the grounding state of the ground line31is normal before the load current flows through the load50.

(Comparison Voltage)

Next, the comparison voltage73in the diagnostic circuit70will be described. As described above, when the ground line31is opened due to poor connection of the GND terminal32or the like, a potential difference corresponding to the forward voltage of the rectifying element62is generated between the ground line31and the ground line21. On the other hand, even with the grounding state of the ground line31normal, a rise in potential corresponding to the parasitic impedance between the ground line31and the GND terminal32and between the GND terminal32and the common ground occurs in the ground line31. Accordingly, in order for the diagnostic circuit70to accurately detect poor opening of the ground line31, it is necessary to set the comparison voltage73to a value smaller than the forward voltage of the rectifying element62and sufficiently larger than the potential rise attributable to the parasitic impedance described above.

FIG.3is a diagram illustrating an example of the electrical characteristics of the rectifying element62. InFIG.3, the solid-line graph indicated by reference numeral101indicates the relationship between the forward voltage and the forward current of the rectifying element62at a standard temperature. Meanwhile, the dashed-line graph indicated by reference numeral102indicates the relationship between the forward voltage and the forward current of the rectifying element62at a low temperature, and the broken-line graph indicated by reference numeral103indicates the relationship between the forward voltage and the forward current of the rectifying element62at a high temperature. In these graphs, the horizontal axis represents the forward current value and the vertical axis represents the forward voltage value.

As indicated by the graphs101to103inFIG.3, the forward voltage generated in the rectifying element62increases as the forward current increases and as the temperature decreases. In other words, the forward voltage of the rectifying element62has current dependency and temperature dependency. Accordingly, in view of these relationships, the value of the comparison voltage73is set such that the minimum value of the forward voltage generated in the rectifying element62exceeds the comparison voltage73with respect to the minimum forward current flowing through the rectifying element62when the ground line31is open.

For example, in a case where the minimum value of the forward current flowing through the rectifying element62is 100 μA, the value of the comparison voltage73should be set to 0.4 V or less from the intersection of the graph103and dotted line104inFIG.3. It can be determined that the ground line31is poorly open when the potential difference between the ground line31and the ground line21measured by the monitor circuit71is greater than the set value of the comparison voltage73.

It can be seen that the presence or absence of poor opening of the ground line31can be reliably detected with respect to a forward current and a temperature within predetermined ranges in this manner.

However, even in a case where the same forward current is applied to the rectifying element62at the same temperature, an individual difference occurs in the forward voltage generated in the rectifying element62due to, for example, a variation in a manufacturing process. Therefore, it is preferable to determine the set value of the comparison voltage73in consideration of such an individual difference. For example, a semiconductor element manufactured in the same manufacturing process as the rectifying element62is provided in the diagnostic circuit70and the comparison voltage73is generated by the voltage at the time when the same forward current as the rectifying element62is passed through the semiconductor element. By using the comparison voltage73generated in this manner, the comparison voltage73can be changed in accordance with the temperature of the rectifying element62based on the temperature dependency of the forward voltage of the rectifying element62. As a result, it is possible to realize the diagnostic circuit70that is highly tolerant of the individual difference or temperature dependency of the rectifying element62.

(Diagnostic Current)

Next, the diagnostic current supplied to the ground line31by the diagnostic current supply circuit90will be described.

In the integrated circuit device10, in a case where the grounding state of the ground line31is normal, the diagnostic current supplied from the diagnostic current supply circuit90to the ground line31is a wasted current consumption that flows out from the ground line31to the common ground of the electronic control device1via the GND terminal32. Accordingly, in a case where the ground line31is open, it is preferable that the diagnostic current supply circuit90supplies, as a diagnostic current, the minimum current required to generate a potential difference equal to or greater than the comparison voltage73between the ground line31and the ground line21.

Here, the current value of the diagnostic current supplied by the diagnostic current supply circuit90may be changed in accordance with the operating state of the drive circuit30or the implementation status of the opening diagnosis by the diagnostic circuit70. For example, in a case where the drive circuit30is in operation and a potential difference equal to or greater than the comparison voltage73can be obtained between the ground line31and the ground line21by the forward voltage of the rectifying element62corresponding to the current consumption thereof, the diagnostic current supply circuit90is stopped and the diagnostic current becomes zero. On the other hand, in a case where the operation of the drive circuit30is stopped or a potential difference equal to or greater than the comparison voltage73cannot be obtained between the ground line31and the ground line21with the current consumption of the drive circuit30, a diagnostic current corresponding to the current shortfall is supplied from the diagnostic current supply circuit90. Further, by stopping the diagnostic current supply circuit90when the opening diagnosis is not performed by the diagnostic circuit70, the diagnostic current is supplied only when the diagnosis is performed. In this manner, further efficiency improvement can be achieved.

(Switch Element)

Next, the configurations of the high-side switch element40and the low-side switch element45will be described. In general, the high-side switch element40and the low-side switch element45mounted in the integrated circuit device10and used for load current control are configured using MOS transistors.

FIG.4is a diagram illustrating a configuration example of a switch element using a MOS transistor. As illustrated inFIG.4, parasitic diodes41and46are respectively formed in a direction from the low side to the high side in the high-side switch element40and the low-side switch element45configured by MOS transistors. It should be noted that inFIG.4, parts other than the high-side switch element40and the low-side switch element45are the same as the configuration diagram of the integrated circuit device10illustrated inFIG.1.

By the low-side switch element45having the parasitic diode46, in a case where the connection destination of the load termination51is the common ground, even when the low-side switch element45is in the OFF state, a current path may be formed that reaches the common ground from the ground line31via the parasitic diode46and, further, through the LOAD output47and the load50. As for the potential difference generated between the ground line31and the ground line21at this time, the forward voltage generated by the current flowing through the parasitic diode46, not the rectifying element62, becomes dominant.

Therefore, in a case where the load50is an inductive load solenoid and the connection destination of the load termination51is the common ground, when the diagnostic circuit70performs opening diagnosis with the drive circuit30stopped, a diagnostic current set in accordance with the forward voltage and current characteristics of the parasitic diode46is supplied from the diagnostic current supply circuit90. As a result, in a case where the grounding state of the ground line31is open, the diagnostic circuit70is capable of reliably detecting poor opening of the ground line31by causing the potential difference generated between the ground line31and the ground line21by the current flowing through the parasitic diode46to become equal to or greater than the comparison voltage73.

(Method for Detecting Poor Opening in Case Where Load Termination is Connected to Common Ground)

Next, a method for detecting poor opening in a case where the load termination51is connected to the common ground will be described with reference toFIG.5. It should be noted that in the following description, the integrated circuit device10has the configuration illustrated inFIG.4and the switch element control circuit35in the drive circuit30repeats the operation of alternately switching the high-side switch element40and the low-side switch element45to the ON state or the OFF state in a complementary and exclusive manner at a constant cycle in response to the control signal26from the control circuit20. It is also assumed that the load50is an inductive load solenoid and the load termination51is connected to the common ground.

InFIG.5, reference numeral111indicates a state where the integrated circuit device10is yet to start controlling the load50and the operation of the drive circuit30is stopped. In this state, the current consumption of the switch element control circuit35is 0 and both the high-side switch element40and the low-side switch element45are in the OFF state. At this time, the diagnostic current from the diagnostic current supply circuit90flows into the ground line31.

It is assumed that a connection abnormality has occurred between the GND terminal32and the common ground and the ground line31has been opened in the above state111. In this case, as indicated by the dotted line in the drawing, the diagnostic current that has flowed into the ground line31is divided and flows through the current path that reaches the common ground via the rectifying element62, the ground line21, and the GND terminal22and the current path that reaches the common ground via the parasitic diode46of the low-side switch element45, the LOAD output47, and the load50.

The low-side switch element45is larger in size than the rectifying element62because it is necessary to conduct a large current of ampere order as a return current of the load50. Accordingly, when the parasitic diode46in the low-side switch element45and the rectifying element62are compared as to the magnitude of the current flowing with respect to the same forward voltage, the parasitic diode46is larger than the rectifying element62. Accordingly, most of the diagnostic current that has flowed into ground line31flows through the current path that reaches the common ground via the parasitic diode46, the LOAD output47, and the load50. The potential difference generated between the ground line31and the ground line21at this time is approximately equal to the forward voltage of the parasitic diode46with respect to the diagnostic current.

When the ground line31is opened with the load termination51connected to the common ground and the operation of the drive circuit30stopped as described above, a potential difference approximately equal to the forward voltage of the parasitic diode46corresponding to the diagnostic current is generated between the ground line31and the ground line21. In the diagnostic current supply circuit90, it is necessary to set the value of the diagnostic current such that the diagnostic circuit70is capable of detecting the potential difference as the grounding state abnormality of the ground line31. For example, a current value at which the forward voltage of the parasitic diode46is equal to or greater than the comparison voltage73is calculated in advance based on the forward voltage and current characteristics of the parasitic diode46and the current value is stored in advance in the diagnostic current supply circuit90. When the operation of the drive circuit30is stopped, the diagnostic current is supplied from the diagnostic current supply circuit90to the ground line31using this as the set value of the diagnostic current. As a result, in a case where the ground line31has been opened, a potential difference equal to or greater than the comparison voltage73is generated between the ground line31and the ground line21, and thus poor opening of the ground line31can be reliably detected by the diagnostic circuit70.

InFIG.5, reference numeral112indicates a state where the load50is controlled by the integrated circuit device10operating the drive circuit30and a load current is supplied to the load50from the vehicular battery (not illustrated). In this state, by the switch element control circuit35switching the high-side switch element40from the OFF state to the ON state, the load current is supplied from the vehicular battery (not illustrated) to the load50via the power terminal16, the high-side switch element40, and the LOAD output47as indicated by the dotted line in the drawing. At this time, in addition to the diagnostic current from the diagnostic current supply circuit90, the current consumption of the switch element control circuit35flows into the ground line31.

It is assumed that a connection abnormality has occurred between the GND terminal32and the common ground and the ground line31has been opened in the above state112. In this case, as indicated by the dotted line in the drawing, the current that has flowed into the ground line31flows through the current path that reaches the common ground via the rectifying element62, the ground line21, and the GND terminal22. Accordingly, a potential difference corresponding to the forward voltage of the rectifying element62with respect to the total value of the diagnostic current and the current consumption of the switch element control circuit35is generated between the ground line31and the ground line21.

It should be noted that, in the above state, the high-side switch element40is in the ON state and thus the potential of the LOAD output47reaches the same level as the power terminal16. Accordingly, the parasitic diode46is not forward-biased by the current flowing into the ground line31and no current path is formed from the ground line31to the load50.

When the ground line31is opened with the load termination51connected to the common ground and the high-side switch element40switched to the ON state and the low-side switch element45switched to the OFF state during the operation of the drive circuit30as described above, a potential difference corresponding to the forward voltage of the rectifying element62corresponding to the total value of the diagnostic current and the current consumption of the switch element control circuit35is generated between the ground line31and the ground line21. Accordingly, in the diagnostic current supply circuit90, the value of the diagnostic current should be set such that the diagnostic circuit70is capable of detecting the potential difference as the grounding state abnormality of the ground line31. It should be noted that in a case where a sufficient potential difference can be obtained by the current consumption of the switch element control circuit35, the diagnostic current may become zero by stopping the diagnostic current supply circuit90.

InFIG.5, reference numeral113indicates a state where the load50is controlled by the integrated circuit device10operating the drive circuit30and the load current supply from the vehicular battery (not illustrated) to the load50is interrupted. In this state, the switch element control circuit35switches the high-side switch element40from the ON state to the OFF state and switches the low-side switch element45from the OFF state to the ON state, and thus the load current supplied from the vehicular battery to the load50is interrupted. At this time, since the load50is an inductive load, the energy accumulated in the load50is released and, as indicated by the dotted line in the drawing, a return current flows from the ground line31to the load50via the low-side switch element45and the LOAD output47. As a result, the potential of the LOAD output47drops.

It should be noted that although not illustrated inFIG.5, in the event of a state112-to-state113transition, a dead time is provided during which both the high-side switch element40and the low-side switch element45are switched to the OFF state. During this dead time, a return current flows from the ground line31to the load50via the parasitic diode46of the low-side switch element45.

It is assumed that a connection abnormality has occurred between the GND terminal32and the common ground and the ground line31has been opened in the above state113. In this case, the return path that reaches the ground line31from the common ground via the GND terminal32is interrupted and the potential of the ground line31drops along with the LOAD output47. As a result, a forward bias from the ground line21to the ground line31is applied to the rectifying element61and a current corresponding to the forward voltage flows through the rectifying element61. As a result, as indicated by the dotted line in the drawing, a return current flows through the load50from the common ground via the GND terminal22, the ground line21, the ground line31, the low-side switch element45, and the LOAD output47.

The diagnostic circuit70determines that the grounding state of the ground line31is abnormal by detecting a rise in the potential of the ground line31with respect to the potential of the ground line21. Here, immediately after a state112-to-state113transition by the high-side switch element40being switched off and the low-side switch element45being switched on, the potential of the LOAD output47drops as described above and thus the potential of the ground line31also drops. In addition, in the state113, the ground line31is connected to the common ground via the low-side switch element45and the load50, and thus the potential of the ground line31converges to the ground level over time. Accordingly, in the state113, the diagnostic circuit70is incapable of detecting the grounding state abnormality of the ground line31even with the ground line31open. However, during the load current control by the integrated circuit device10, the state112and the state113appear alternately by each of the high-side switch element40and the low-side switch element45being periodically switched on and off. Accordingly, the grounding state abnormality of the ground line31can be detected in the state112and no operational problems arise.

(Method for Detecting Poor Opening in Case Where Load Termination is Connected to Vehicular Battery)

Next, a method for detecting poor opening in a case where the load termination51is connected to the vehicular battery (not illustrated) will be described with reference toFIG.6. It should be noted that in the following description, as in the case ofFIG.5, the integrated circuit device10has the configuration illustrated inFIG.4and the switch element control circuit35in the drive circuit30repeats the operation of alternately switching the high-side switch element40and the low-side switch element45to the ON state or the OFF state in a complementary manner at a constant cycle in response to the control signal26from the control circuit20. It is also assumed that the load50is an inductive load solenoid and the load termination51is connected to the vehicular battery (not illustrated).

InFIG.6, reference numeral121indicates a state where the integrated circuit device10is yet to start controlling the load50and the operation of the drive circuit30is stopped. In this state, the current consumption of the switch element control circuit35is 0 and both the high-side switch element40and the low-side switch element45are in the OFF state. At this time, the diagnostic current from the diagnostic current supply circuit90flows into the ground line31.

It is assumed that a connection abnormality has occurred between the GND terminal32and the common ground and the ground line31has been opened in the above state121. In this case, as indicated by the dotted line in the drawing, the diagnostic current that has flowed into the ground line31flows through the current path that reaches the common ground via the rectifying element62, the ground line21, and the GND terminal22. Accordingly, a potential difference corresponding to the forward voltage of the rectifying element62with respect to the diagnostic current is generated between the ground line31and the ground line21. Accordingly, in the diagnostic current supply circuit90, the value of the diagnostic current should be set such that the diagnostic circuit70is capable of detecting the potential difference as the grounding state abnormality of the ground line31. It should be noted that the value of the diagnostic current at this time can be made smaller than the diagnostic current required in the state111inFIG.5.

InFIG.6, reference numeral122indicates a state where the load50is controlled by the integrated circuit device10operating the drive circuit30and a load current is supplied to the load50from the vehicular battery (not illustrated). In this state, by the switch element control circuit35switching the low-side switch element45from the OFF state to the ON state, the load current supplied from the vehicular battery (not illustrated) to the load50flows into the ground line31via the LOAD output47and the low-side switch element45. In addition, the diagnostic current from the diagnostic current supply circuit90and the current consumption of the switch element control circuit35also flow into the ground line31.

It is assumed that a connection abnormality has occurred between the GND terminal32and the common ground and the ground line31has been opened in the above state122. In this case, as indicated by the dotted line in the drawing, the current that has flowed into the ground line31flows through the current path that reaches the common ground via the rectifying element62, the ground line21, and the GND terminal22. Accordingly, a potential difference corresponding to the forward voltage of the rectifying element62with respect to the total value of the load current, the diagnostic current, and the current consumption of the switch element control circuit35is generated between the ground line31and the ground line21. Accordingly, in the diagnostic current supply circuit90, the value of the diagnostic current should be set such that the diagnostic circuit70is capable of detecting the potential difference as the grounding state abnormality of the ground line31. In general, the load current is sufficiently large, and thus the value of the diagnostic current can be zero.

InFIG.6, reference numeral123indicates a state where the load50is controlled by the integrated circuit device10operating the drive circuit30and the load current supply from the vehicular battery (not illustrated) to the load50is interrupted. In this state, the switch element control circuit35switches the high-side switch element40from the OFF state to the ON state and switches the low-side switch element45from the ON state to the OFF state, and thus the load current supplied from the vehicular battery to the load50is interrupted. At this time, since the load50is an inductive load, the energy accumulated in the load50is released and, as indicated by the dotted line in the drawing, a return current flows via the high-side switch element40and the power terminal16between the vehicular battery and the load50. In addition, the current consumption of the switch element control circuit35flows into the ground line31in addition to the diagnostic current from the diagnostic current supply circuit90.

It is assumed that a connection abnormality has occurred between the GND terminal32and the common ground and the ground line31has been opened in the above state123. In this case, as indicated by the dotted line in the drawing, the current that has flowed into the ground line31flows through the current path that reaches the common ground via the rectifying element62, the ground line21, and the GND terminal22. Accordingly, a potential difference corresponding to the forward voltage of the rectifying element62with respect to the total value of the diagnostic current and the current consumption of the switch element control circuit35is generated between the ground line31and the ground line21. Accordingly, in the diagnostic current supply circuit90, the value of the diagnostic current should be set such that the diagnostic circuit70is capable of detecting the potential difference as the grounding state abnormality of the ground line31. In a case where a sufficient potential difference can be obtained by the current consumption of the switch element control circuit35, the diagnostic current may become zero by stopping the diagnostic current supply circuit90.

It should be noted that, in the above state, the high-side switch element40is in the ON state and thus the potential of the LOAD output47reaches the same level as the power terminal16. Accordingly, the parasitic diode46is not forward-biased by the current flowing into the ground line31and no current path is formed from the ground line31to the load50.

As described above, in a case where the load termination51is connected to the vehicular battery, the potential of the LOAD output47does not become lower than the ground line31and the parasitic diode46is not forward-biased even when the drive circuit30is stopped or in operation. As a result, when the ground line31is opened due to a connection abnormality of the GND terminal32or the like, the current flowing into the ground line31flows out to the ground line21via the rectifying element62and is discharged from the GND terminal22to the common ground. Accordingly, when the current flowing into the ground line31is ensured by the diagnostic current supplied by the diagnostic current supply circuit90, opening detection is possible at the diagnostic circuit70regardless of the operating state of the drive circuit30.

According to the first embodiment of the present invention described above, regardless of the connection destination of the load termination51or the operating state of the drive circuit30, it is possible to diagnose the grounding state of the ground line31with certainty and reliability by a simpler method and poor opening can be detected. As a result, an abnormality can be detected early, and thus it is possible to suppress the operation period of the integrated circuit device10in a large-loss abnormal state and prevent damage to the integrated circuit device10mounted in the electronic control device1and other devices.

According to the first embodiment of the present invention described above, the following actions and effects are obtained.

(1) The integrated circuit device10is connected to the load50and controls the load current supplied to the load50. The integrated circuit device10includes the drive circuit30, the control circuit20controlling the operation of the drive circuit30, the ground lines21and31, the diagnostic current supply circuit90, the bidirectional rectifying elements61and62, and the diagnostic circuit70. The drive circuit30has the switch elements40and45and uses the switch elements40and45to switch between the conduction and interruption of the load current. The ground line31is grounded via the GND terminal32to the common ground provided outside the integrated circuit device10and is connected to the drive circuit30. The ground line21is grounded to the common ground via the GND terminal22and is connected to the control circuit20. The diagnostic current supply circuit90supplies a predetermined diagnostic current to the ground line31. The rectifying elements61and62are connected between the ground line21and the ground line31. The diagnostic circuit70measures the potential difference between the ground line31and the ground line21and compares the potential difference with the predetermined comparison voltage73to diagnose the grounding state of the ground line31. In this manner, regardless of the connection state of the load50and the operating state of the drive circuit30, poor opening can be detected with certainty and reliability with respect to the ground line31of the integrated circuit device10.

(2) The switch elements of the drive circuit30include the high-side switch element40and the low-side switch element45, and each of the switch elements can be switched to the ON state or the OFF state. The drive circuit30uses the high-side switch element40to conduct or interrupt the load current between the vehicular battery supplying the load current and the load50and uses the low-side switch element45to conduct or interrupt the load current between the ground line31and the load50. The control circuit20repeatedly performs control with respect to the drive circuit30to alternately and complementarily switch the high-side switch element40and the low-side switch element45to the ON state or the OFF state. In this manner, the integrated circuit device10is capable of appropriately controlling the load current flowing through the load50.

(3) The high-side switch element40and the low-side switch element45are configured using, for example, MOS transistors. In this manner, the high-side switch element40and the low-side switch element45used in controlling the load current flowing through the load50can be easily realized at a reasonable cost.

(4) The diagnostic current supply circuit90is capable of changing the diagnostic current in accordance with the operating state of the drive circuit30. In this manner, wasteful current consumption can be reduced and efficiency can be improved.

(5) The diagnostic circuit70is capable of changing the comparison voltage in accordance with the temperature of the rectifying element62based on the temperature dependency of the forward voltage of the rectifying element62. In this manner, the grounding state of the ground line31can be accurately diagnosed even with respect to temperature fluctuations.

(6) The control circuit20may stop the operation of the drive circuit30in a case where the diagnostic circuit70has diagnosed that the grounding state of the ground line31is abnormal. In this manner, safety can be ensured in a case where the ground line31has been opened due to poor connection of the GND terminal32or the like.

Second Embodiment

A second embodiment of the present invention will be described below with reference toFIG.7.

FIG.7is a configuration diagram of an integrated circuit device according to the second embodiment of the present invention. As in the case of the integrated circuit device10described in the first embodiment, an integrated circuit device10A according to the present embodiment is provided in the electronic control device1mounted in a vehicle system such as an automobile, is connected to the load50such as a solenoid, and controls a load current supplied to the load50.

The integrated circuit device10A of the present embodiment is provided with a diagnostic circuit70A instead of the diagnostic circuit70of the integrated circuit device10described in the first embodiment. The diagnostic circuit70A has the same configuration as the diagnostic circuit70except that an input polarity switching unit76is provided on the input side of the monitor circuit71.

The input polarity switching unit76switches the polarity of the voltage input to the monitor circuit71based on a switching state signal38output from the switch element control circuit35. The switching state signal38indicates the switching state of the high-side switch element40and the low-side switch element45. Specifically, in a case where the load termination51is connected to the common ground, the input polarity switching unit76switches the polarity of the input voltage to the monitor circuit71when the high-side switch element40has been switched off and the low-side switch element45has been switched on. As a result, in the state113ofFIG.5described in the first embodiment, in a case where a connection abnormality has occurred between the GND terminal32and the common ground and the ground line31has been opened, the potential difference generated between the ground line21and the ground line31in accordance with the forward voltage generated in the rectifying element61can be detected by the monitor circuit71and compared with the comparison voltage73.

As described above, according to the second embodiment of the present invention, the load50is connected between the drive circuit30and the common ground, and the diagnostic circuit70A inverts the polarity of the potential difference between the ground line31and the ground line21and performs comparison with the comparison voltage73when the high-side switch element40has been switched from the ON state to the OFF state. As a result, the grounding state of the ground line31can be diagnosed even with the load termination51connected to the common ground, the load current supply from the vehicular battery to the load50interrupted, and a return current flowing through the load50.

It should be noted that although the drive circuit30and the load50in each of the embodiments described above have been described as one representative example in order to describe the present invention in an easy-to-understand manner, a plurality thereof may be provided. Regardless of the numbers of drive circuits30and loads50, the present invention can be applied with each having the same configuration. In addition, the control and signal lines illustrated in each embodiment are those considered to be necessary for description, and not all control and signal lines are necessarily shown on the product.

The embodiments and various modification examples described above are merely examples, and the present invention is not limited to the content thereof insofar as the features of the invention are not impaired. In addition, although various embodiments and modification examples have been described above, the present invention is not limited to the content thereof. Other aspects conceivable within the scope of the technical idea of the present invention are also included in the scope of the present invention.

REFERENCE SIGNS LIST

1electronic control device10,10A integrated circuit device15,16power terminal20control circuit21ground line22GND terminal30drive circuit31ground line32GND terminal35switch element control circuit40high-side switch element41parasitic diode45low-side switch element46parasitic diode47LOAD output50load51load termination60rectifier circuit61,62rectifying element65,66protective diode70,70A diagnostic circuit71monitor circuit72monitor circuit output73comparison voltage74comparative determination circuit75diagnostic result76input polarity switching unit90diagnostic current supply circuit