JP2012153197A - Ground fault countermeasure device of onboard electrical equipment system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable controlling of power consumption of a power supply voltage output circuit even if a ground fault of the power supply cable that supplies the power supply voltage from the supply voltage output circuit to a sensor, and to make a compact and low cost power supply voltage output circuit feasible consequently.SOLUTION: A control device 3 of an onboard electrical equipment system 1 includes: a ground fault generation monitoring means 35 that determines the presence of the occurrence of the ground fault of power supply cable 23 based on the pairs of the detection signal of sensor 5a-5c; and a power supply output control means 37 that controls the supply voltage output circuit 7 that outputs the power supply voltage for operation of the sensor 5a-5c through the power supply cable 23. The power supply output control means 37, when the ground fault for the power supply of cable 23 occurs, executes control processing to periodically repeat stop of output from the power supply voltage output circuit 7 and the resume following the stop, and when the ground fault cancels then continues the output from the supply voltage output circuit 7.

Description

  The present invention relates to a ground fault countermeasure device for an electrical system mounted on a vehicle such as an automobile.

  A vehicle such as an automobile is connected to a control device (electronic control circuit unit) including an arithmetic processing circuit such as a CPU via a cable in order to control the operation of an in-vehicle device such as an air conditioner. An electrical system including a sensor is mounted.

  In this type of electrical system, the power supply voltage for operating the sensor is supplied from the power supply voltage output circuit provided on the control device side to the sensor via the power cable, and the detection signal output from the sensor is sent to the control device. It is generally known that a signal input through a cable is A / D-converted and sequentially sampled by an arithmetic processing circuit such as a CPU of a control device (see, for example, Patent Document 1). ).

JP 2007-69741 A

  In the electrical system as described above, the cables (power supply cables and signal cables) connecting the control device, the power supply voltage output circuit, and the sensor are often along the vehicle body which is the grounding portion of the vehicle. Since the wiring is performed, the conductor wire of the cable may be electrically connected to the vehicle body, that is, a ground fault may occur due to damage to the covering portion caused by the cable biting.

  In particular, when a ground fault occurs in the power supply cable (non-grounded power supply cable) for supplying the power supply voltage to the sensor, the output side of the power supply voltage output circuit is short-circuited. In addition, an excessive current flows through the output portion of the power supply voltage output circuit. For this reason, it is required to prevent as much as possible a decrease in the power supply voltage of an arithmetic processing circuit such as a CPU and the occurrence of overheating and damage to the output section of the power supply voltage output circuit. In addition, the ground fault may be resolved due to vehicle vibration or the like. In such a case, it is required that the power supply voltage can be normally supplied to the sensor after the ground fault is resolved. The

  For this reason, in a conventional electrical system equipped with the power supply voltage output circuit, a power supply voltage is generally supplied to the sensor side from a power supply voltage output circuit configured to have a high input impedance and be capable of outputting a large current. Has been done.

  However, in the conventional electrical system, an excessive current continues to flow to the output portion of the power supply voltage output circuit on the control device side while the ground fault occurs in the power supply cable. Inconveniently, the power consumed in vain becomes excessive. In addition, if the duration of occurrence of a ground fault becomes long, the power supply voltage output circuit may become overheated due to heat generation. Therefore, in order to improve heat resistance or heat dissipation, an IC or discrete circuit that constitutes the power supply voltage output circuit may be used. There is a disadvantage that the circuit becomes large or expensive.

  The present invention has been made in view of such a background, and suppresses power consumption of the power supply voltage output circuit even when a ground fault occurs in the power supply cable that supplies the power supply voltage to the sensor from the power supply voltage output circuit. In addition, an object of the present invention is to provide a ground fault countermeasure device for an in-vehicle electrical system in which a power supply voltage output circuit can be made inexpensive and compact.

  In order to achieve the above object, a ground fault countermeasure device for an in-vehicle electrical system according to the present invention has a power supply voltage output terminal connected to a plurality of sensors mounted on a vehicle via a power cable. A power supply voltage output circuit for outputting a power supply voltage for operation of the sensor from the power supply voltage output terminal to the plurality of sensors via the power supply cable, and connected to the plurality of sensors via a signal cable; A ground fault countermeasure device for an in-vehicle electrical system including a control device for receiving detection signals output from a plurality of sensors via the signal cable, wherein the control device is input from the plurality of sensors. A ground fault occurrence monitoring means for judging whether or not a set of detection signals to be matched with the set of detection signals in a state where a ground fault has occurred in the power cable, and a judgment result of the ground fault occurrence monitoring means When the result is affirmative, the power supply voltage output circuit is controlled to periodically repeat the stop of the output of the power supply voltage from the power supply voltage output circuit and the restart of the output of the power supply voltage following the stop. Power supply output control means for executing control processing at the time of occurrence of a ground fault, wherein the power supply output control means determines the ground fault occurrence monitoring means in the resumed output state of the power supply voltage from the power supply voltage output circuit. When the result becomes negative, the control process is controlled so as to stop the control process at the time of occurrence of the ground fault and to continue the output of the power supply voltage (first invention). .

  According to the first aspect of the invention, the detection signals input from the plurality of sensors by the ground fault occurrence monitoring means of the control device in a state where the power supply voltage is output from the power supply voltage output circuit to the plurality of sensors. It is determined whether or not this set matches the set of detection signals in a state where a ground fault has occurred in the power cable.

  Here, when a ground fault occurs in the power supply cable, the power supply voltages applied to the plurality of sensors all become zero level (a level that matches or substantially matches the ground potential). A set of detection signals corresponds to a state in which a ground fault has occurred in the power supply cable, that is, a set of detection signals in a state in which the power supply voltages of the plurality of sensors are all at zero level.

  Therefore, by determining whether a set of detection signals input from the plurality of sensors matches the set of detection signals in a state where a ground fault has occurred in the power supply cable, as a result, Whether or not a ground fault has occurred in the power cable can be determined. Note that the fact that the set of detection signals matches the set of detection signals in a state where the ground fault of the power cable has occurred does not mean that the set of detection signals exactly matches, but a predetermined allowable range. It also includes the case where they almost match.

  And, when the judgment result of the ground fault occurrence monitoring means becomes affirmative, that is, when it is judged that the ground fault of the power cable has occurred, The ground fault occurrence control process is executed. Accordingly, the power supply voltage output circuit is controlled to periodically repeat the stop of the output of the power supply voltage and the restart of the output of the power supply voltage following the stop.

  For this reason, the operation in which the power supply voltage output circuit tries to resume the output of the power supply voltage to the plurality of sensors (hereinafter sometimes referred to as a power supply voltage output resuming operation) is performed intermittently. Only during the period when the power supply voltage output restart operation is performed, a current (short circuit current) resulting from the ground fault of the power supply cable is output from the power supply voltage output circuit.

  Therefore, in the occurrence state of the ground fault of the power cable, the current output from the power voltage output circuit due to the ground fault is limited to an intermittent period. As a result, power consumption of the power supply voltage output circuit in a state where a ground fault occurs in the power cable is suppressed.

  In addition, during the period when the power supply voltage output circuit performs the power supply voltage output restart operation, if the ground fault of the power supply cable is resolved, the original power supply voltage is applied to the plurality of sensors. A set of detection signals of a plurality of sensors input to the control device is a set of normal detection signals different from the one corresponding to the state where the ground fault of the power cable has occurred, and the ground fault occurrence monitoring means of the control device The judgment result of is negative.

  Therefore, in the first invention, the power supply output control means is configured to restart the output of the power supply voltage from the power supply voltage output circuit (a state where the power supply voltage output restart operation of the power supply voltage output circuit is performed). When the determination result of the ground fault occurrence monitoring means becomes negative, the control process at the time of occurrence of the ground fault is stopped and the power supply voltage output circuit is controlled so as to continue the output of the power supply voltage.

  Thus, when the ground fault is resolved after the occurrence of the ground fault of the power supply cable, the output of the power source voltage from the power source voltage output circuit to the plurality of sensors can be resumed normally.

  As described above, according to the first aspect of the present invention, the power supply voltage output circuit is controlled so that the power supply voltage output restart operation of the power supply voltage output circuit is intermittently performed when a ground fault occurs in the power supply cable. Therefore, useless power consumption of the power supply voltage output circuit due to the ground fault can be suppressed. In addition, since unnecessary power consumption of the power supply voltage output circuit can be suppressed in this way, the power supply voltage output circuit can be prevented from being overheated even if the duration of the ground fault occurrence state of the power supply cable is prolonged. . For this reason, an inexpensive and small-sized circuit can be adopted as the power supply voltage output circuit.

  Further, when a power supply cable ground fault occurs, a period during which the power supply voltage output restart operation of the power supply voltage output circuit is performed by intermittently performing the power supply voltage output restart operation of the power supply voltage output circuit From the judgment result of the ground fault occurrence monitoring means, it is possible to recognize whether or not the ground fault of the power cable has been eliminated. If the ground fault is eliminated, the power supply from the power voltage output circuit to the plurality of sensors can be recognized. The continuous output of voltage can be resumed normally.

  In the first invention, since the power supply voltage output circuit does not require high heat dissipation and heat resistance, it can be realized with various circuit configurations using a general-purpose IC, a discrete element, or the like.

  Specifically, the power supply voltage output circuit includes, for example, an operational amplifier having a negative input terminal connected to the output terminal, and a voltage having the same voltage level as the power supply voltage is applied to the positive input terminal of the operational amplifier. Thus, it is possible to employ a circuit configured to output the power supply voltage from the output terminal of the operational amplifier via the power supply cable. In this case, the ground fault occurrence control process executed by the power supply output control means controls the voltage applied to the positive input terminal of the operational amplifier to a zero level voltage when stopping the output of the power supply voltage. Then, when restarting the output of the power supply voltage, the voltage applied to the positive input terminal of the operational amplifier is controlled to a voltage having the same voltage level as the power supply voltage (second invention).

  In the second aspect of the invention, the voltage having the same voltage level as the power supply voltage does not mean only a voltage that exactly matches the power supply voltage, but substantially matches the power supply voltage within a predetermined allowable range. Such a voltage may be used. In the second invention, the output terminal of the operational amplifier corresponds to the power supply voltage output terminal.

  Alternatively, the power supply voltage output circuit includes, for example, a switching transistor that can be selectively controlled to an ON state or an OFF state, and a control signal for controlling the switching transistor to an ON state is applied to the base of the switching transistor. Accordingly, it is possible to employ a circuit configured to output the power supply voltage from the collector of the switching transistor via the power supply cable. In this case, the ground fault occurrence control process executed by the power supply output control means outputs a control signal for controlling the switching transistor to an OFF state when the output of the power supply voltage is stopped. And applying a control signal for controlling the switching transistor to the ON state when the output of the power supply voltage is resumed (third invention).

  In the third invention, the collector of the switching transistor corresponds to the power supply voltage output terminal.

  According to the second or third invention, the power supply voltage output circuit can be configured with a simple circuit using the operational amplifier or the switching transistor. In this case, since the power consumption of the operational amplifier or the switching transistor does not become excessive when the ground fault of the power supply cable is generated, the operational amplifier or the switching transistor is not required to have a high allowable upper limit or heat resistance. Can be used. Therefore, an inexpensive and small operational amplifier or switching transistor can be used.

  In the second aspect of the invention, the voltage applied to the positive input terminal of the operational amplifier is simply controlled to be periodically switched between a zero level (ground potential level) voltage and a voltage having the same voltage level as the power supply voltage. Thus, the power supply voltage output restarting operation of the power supply voltage output circuit can be intermittently performed.

  In the third aspect of the invention, the control signal to be applied to the base of the switching transistor is simply controlled to be switched periodically and alternately between the control signal for controlling the switching transistor to the OFF state and the control signal for controlling the ON state. Thus, the power supply voltage output restarting operation of the power supply voltage output circuit can be intermittently performed.

  Therefore, according to the second or third invention, it is possible to effectively realize a reduction in cost and size of the power supply voltage output circuit including the circuit configuration for controlling the operation of the operational amplifier or the switching transistor.

The figure which shows the structure of the vehicle-mounted electrical equipment system in 1st Embodiment of this invention. The timing chart for demonstrating the action | operation of the vehicle-mounted electrical equipment system of 1st Embodiment. The figure which shows the principal part structure of the vehicle-mounted electrical equipment system in 2nd Embodiment of this invention.

[First Embodiment]
A first embodiment of the present invention will be described below with reference to FIGS.

  With reference to FIG. 1, an in-vehicle electrical system 1 according to the present embodiment is an electrical system that is mounted on a vehicle such as an automobile in order to control an in-vehicle device such as an in-vehicle air conditioner, and executes control processing for the in-vehicle device. A control device 3 configured by an arithmetic processing circuit such as a CPU, a plurality of sensors 5a, 5b, 5c for detecting physical quantities used for the control processing, and a power source for operation of these sensors 5a, 5b, 5c And a power supply voltage output circuit 7 for outputting a voltage.

  The control device 3 and the power supply voltage output circuit 7 are arranged close to each other and mounted on a circuit board (not shown). Further, the sensors 5 a, 5 b, 5 c are arranged at locations away from the control device 3 and the power supply voltage output circuit 7.

  Each sensor 5a, 5b, 5c is a resistance type sensor in the example of this embodiment, and more specifically, for example, is a potentiometer. However, the type of each sensor 5a, 5b, 5c is not limited to a potentiometer, and may be another type of sensor such as a resistance temperature sensor. Further, the sensors 5a, 5b, 5c need not all be the same type of sensor, and two or more types of sensors may be included. Further, the number of sensors 5a, 5b, 5c is three in the illustrated example, but the number may be other numbers.

  In the following description, when it is not necessary to separate these sensors 5a, 5b, 5c, these are generically referred to as sensors 5.

  In this embodiment, the power supply voltage output circuit 7 includes an operational amplifier 9 and is configured to output a power supply voltage Vs for operation of the sensor 5 (hereinafter referred to as sensor power supply voltage Vs) from the operational amplifier 9.

  Specifically, the operational amplifier 9 of the power supply voltage output circuit 7 has its output terminal 9out connected to the negative input terminal 9in− via the feedback resistor 11, and the voltage at the output terminal 9out is connected to the negative input terminal via the feedback resistor 11. It is given to 9in-. In the present embodiment, the output terminal 9out of the operational amplifier 9 corresponds to the power supply voltage output terminal of the power supply voltage output circuit 7.

  The positive input terminal 9in + of the operational amplifier 9 is connected to the reference power supply potential unit 15 through the resistor 13, and the voltage V2 of the reference power supply potential unit 15 is applied to the positive input terminal 9in + through the resistor 13. It has become.

  Here, the reference power supply potential unit 15 is a part that outputs a reference power supply voltage V2 used as a power supply voltage of the control device 3 or the like. The voltage level (voltage value) of the reference power supply voltage V2 is the same as the power supply voltage Vs for operation of each sensor 5, and is, for example, 5 [V]. The reference power supply voltage V2 of the reference power supply potential unit 15 is generated from an output voltage (for example, 12 [V]) of an in-vehicle battery (not shown) through a constant voltage regulator or the like.

  Further, the positive input terminal 9in + of the operational amplifier 9 is connected to the ground potential portion 19 via the collector and emitter of the switching transistor 17 in addition to being connected to the reference power supply potential portion 15 as described above. The ground potential portion 19 is a portion grounded to the vehicle body (portion having the same potential as the vehicle body).

  In the example of the present embodiment, the switching transistor 17 is turned on (a state where the collector and the emitter are electrically connected) by applying a high level control signal to the base, and the low level is applied to the base. By applying the control signal, it becomes an OFF state (a state where the collector and the emitter are electrically disconnected). In this case, the high-level control signal means a voltage signal having the same or almost the same level as the reference power supply voltage V2, and the low-level control signal means the potential of the ground potential section 19, that is, the ground potential (0 [ V]) means a voltage signal of the same or almost the same level.

  The output terminal 9out of the operational amplifier 9 is connected to the ground potential section 19 via a capacitor 21 for smoothing the sensor power supply voltage Vs output from the output terminal 9out.

  The operational amplifier 9 is supplied with a power supply voltage V1 for operation of the operational amplifier 9 from an in-vehicle battery (not shown). In the example of this embodiment, the voltage level of the power supply voltage V1 is substantially the same voltage level as the output voltage (for example, 12 [V]) of the in-vehicle battery.

  In the power supply voltage output circuit 7 configured as described above, since the reference power supply voltage V2 is applied to the positive input terminal 9in + of the op-amp 9 when the switching transistor 17 is in the OFF state, the reference power supply is supplied from the output terminal 9out of the operational amplifier 9. A voltage having substantially the same voltage level as the voltage V2 is output as the sensor power supply voltage Vs. In the ON state of the switching transistor 17, the positive input terminal 9in + of the operational amplifier 9 is grounded via the switching transistor 17, and a voltage of zero level (≈0 [V]) is applied to the positive input terminal 9in +. Therefore, the sensor power supply voltage Vs output from the output terminal 9out of the operational amplifier 9 is controlled to a zero level voltage.

  In the present embodiment, the sensors 5a, 5b and 5c are connected via the power cable 23 to the output terminal 9out of the operational amplifier 9 of the power supply voltage output circuit 7 configured as described above.

  More specifically, on a circuit board (not shown) on which the power supply voltage output circuit 7 is mounted, a non-ground side connection terminal 25a that is conducted to the output terminal 9out of the operational amplifier 9 and a ground side that is conducted to the ground potential unit 19 are provided. A connection portion 25 having a connection terminal 25 b is provided, and one end side of the power cable 23 is connected to the connection portion 25 via a connector 27. The other end of the power cable 23 is connected to the sensors 5a, 5b, and 5c. In this case, the power cable 23 is configured such that the sensors 5a, 5b, and 5c are connected in parallel between the non-ground side connection terminal 25a and the ground side connection terminal 25b.

  By connecting the sensors 5a, 5b, and 5c to the connecting portion 25 via the power cable 23 as described above, it is generated between the non-ground side connecting terminal 25a and the ground side connecting terminal 25b of the connecting portion 25. The voltage, that is, the sensor power supply voltage Vs output from the output terminal 9out of the operational amplifier 9 is supplied in parallel to each sensor 5 via the power supply cable 23.

  The control device 3 is connected to these sensors 5a, 5b, and 5c via a signal cable 29 in order to sample the detection signals output from the sensors 5a, 5b, and 5c. More specifically, a circuit board (not shown) on which the control device 3 is mounted is provided with a connection portion 31 having connection terminals 31a, 31b, and 31c respectively connected to the signal input port of the control device 3. One end of the signal cable 29 is connected to the connection portion 31 via a connector 33. The other end side of the signal cable 29 is connected to the sensors 5a, 5b, 5c.

  In this case, the signal cable 29 is configured to conduct the signal output portions of the sensors 5a, 5b, and 5c to the connection portions 31a, 31b, and 31c, respectively. As a result, the detection signal of each sensor 5 (hereinafter sometimes simply referred to as a sensor detection signal) is input to the control device 3 via the signal cable 29.

  The control device 3 incorporates an A / D converter (not shown), and the sensor detection signal (analog signal) input to the control device 3 is A / D converted at a predetermined sampling period shown in FIG. After being converted into digital data by a device, the data is taken into the control device 3. The sampling period is, for example, 10 [ms].

  The power cable 23 and the signal cable 29 may be configured as a bundle, and the connector 27 on the power cable 23 side and the connector 33 on the signal cable 29 side may be configured integrally.

  The control device 3 further includes a port connected to the base of the switching transistor 17, and can output a control signal (low level or high level control signal) of the switching transistor 17 from the port. It has become.

  The control device 3 in which each sensor 5 and the switching transistor 17 are connected as described above has a ground fault occurrence monitoring means 35 and a power supply output control means 37 as functions realized by a program or the like installed in the ROM of the control device 3. And.

  The ground fault occurrence monitoring means 35 is a functional unit that determines whether or not a ground fault has occurred in the power supply cable 23 based on all the sensor detection signals of the sensors 5a, 5b, and 5c. Further, the power supply output control means 37 sets the voltage level of the sensor power supply voltage Vs output from the operational amplifier 9 to substantially the same level as the reference power supply voltage V2 and zero level according to the determination result of the ground fault occurrence monitoring means 35. This is a functional unit that executes control processing for selectively switching between and via the switching transistor 17.

  Next, the operation of the on-vehicle electrical system 1 described above will be described focusing on the description of more specific processing of the ground fault occurrence monitoring means 35 and the power output control means 37.

  During a normal operation in which a ground fault or the like of the power supply cable 23 does not occur, the power supply output control means 37 of the control device 3 outputs a low level control signal to the base of the switching transistor 17 and turns off the switching transistor. Control to the state.

  This state is a state before time t1 in FIG. In this state, since the reference power supply voltage V2 is applied to the positive input terminal 9in + of the operational amplifier 9 of the power supply voltage output circuit 7, the sensor power supply voltage Vs output from the output terminal 9out of the operational amplifier 9 is almost equal to the reference power supply voltage V2. The voltage is the same level. This sensor power supply voltage Vs (≈V2) is supplied to each sensor 5 via the power cable 2.

  The sensor detection signal output from each sensor 5 is input to the control device 3 via the signal cable 29 in a state where the normal sensor power supply voltage Vs (≈V2) is supplied to each sensor 5 in this way. . At this time, the control device 3 performs A / D conversion on the input sensor detection signal of each sensor 5 at a predetermined sampling period and samples it, and recognizes the value (voltage level) of each sensor detection signal.

  The value of each sensor detection signal sampled in this way is monitored by the ground fault occurrence monitoring means 35. Then, the ground fault occurrence monitoring unit 35 sequentially determines whether or not a ground fault has occurred in the power cable 23 based on the set of sampling values of the sensor detection signals of all the sensors 5a, 5b, and 5c inputted.

  Here, the ground fault for determining whether or not the ground fault occurrence monitoring means 35 has occurred is more specifically the ungrounded cable of the power cable 23, that is, the cable that is conducted to the output terminal 9 out of the operational amplifier 9 ( This is a phenomenon in which an intermediate portion of the cable connected to the non-ground side connection terminal 25a of the connection portion 25 is electrically connected to a vehicle body (specifically, a vehicle body portion having substantially the same potential as the ground potential portion 19). Hereinafter, unless otherwise specified, the ground fault of the power cable 23 means a ground fault in the above phenomenon.

  When such a ground fault occurs in the power cable 23, the output terminal 9out of the operational amplifier 9 is substantially short-circuited to the ground potential portion 19, so that a large current flows from the output terminal 9out of the operational amplifier 9. At the same time, the sensor power supply voltage Vs output from the output terminal 9out of the operational amplifier 9 is a zero level voltage (see Vs immediately after time t1 in FIG. 2). In the present embodiment, when the sensor power supply voltage Vs becomes a zero level voltage in this way, the voltage level of the sensor detection signal becomes zero level in all the sensors 5a, 5b, and 5c. In the present embodiment, in the state where the ground fault of the power cable 23 has occurred, the voltage level of the sensor detection signal becomes zero level in all the sensors 5a, 5b, and 5c as described above.

  In addition, although the ground fault of the signal cable 29 may generate | occur | produce, in this case, possibility that the ground fault of all the cables of the signal cable 29 (cable corresponding to each sensor 5) will generate | occur | produce is very low. When a ground fault occurs in any of the signal cables 29, only the sensor detection signal of the sensor 5 corresponding to the cable in which the ground fault occurs becomes a zero level signal.

  Therefore, the ground fault occurrence monitoring means 35 in this embodiment sequentially determines whether or not the sampling values of the sensor detection signals of all the sensors 5a, 5b, and 5c are at the zero level, and the determination result is affirmative. In this case, it is determined that a ground fault has occurred in the power cable 23. If the sampling value of the sensor detection signal of any one of the sensors 5 is not zero level, the ground fault occurrence monitoring unit 35 determines that no ground fault has occurred in the power cable 23.

  For example, when a ground fault occurs in the power supply cable 23 at time t1 as shown in FIG. 2 by the processing of the ground fault occurrence monitoring means 35, based on the set of sampling values of the sensor detection signal at time t2. Thus, the occurrence of a ground fault in the power cable 23 is detected.

  The judgment result of the occurrence of ground fault by the ground fault occurrence monitoring means 35 is given to the power output control means 37. When the occurrence of a ground fault in the power cable 23 is detected by the ground fault occurrence monitoring unit 35, the power source output control unit 37 causes the normal sensor power source voltage Vs from the operational amplifier 9 of the power source voltage output circuit 7 to be detected. Specifically, the output of the sensor power supply voltage Vs whose voltage level is substantially the same as the reference power supply voltage V2 is periodically stopped and the output of the normal sensor power supply voltage Vs (≈V2) following the stop is periodically performed. A ground fault occurrence control process for controlling the power supply voltage output circuit 7 so as to be repeated is executed.

  This ground fault occurrence control process is performed as follows. That is, the power output control means 37 switches the control signal applied to the base of the switching transistor 17 from the low level to the high level when the ground fault occurrence monitoring means 35 detects the occurrence of the ground fault in the power cable 23. The application of the high-level control signal to the base of the switching transistor 17 is continued during a predetermined time Toff (hereinafter referred to as output stop operation time Toff).

  When the period of the output stop operation time Toff ends, the power output control means 37 next switches the control signal applied to the base of the switching transistor 17 to the low level, and the low level control signal is switched to the switching transistor 17. Giving to the base is continued for a predetermined time Ton (hereinafter referred to as output resuming operation time Ton).

  Thereafter, the period of the output stop operation time Toff and the period of the output restart operation time Ton are alternately repeated.

  The control process at the time of occurrence of the ground fault in the present embodiment includes the control process during the output stop operation time Toff in which the control signal of the high level is applied to the base of the switching transistor 17 as described above, and the control signal at the low level. And a control process for periodically repeating the control process for the period of the output resuming operation time Ton to be applied to the base.

  In this case, since the switching transistor 17 is controlled to be in the ON state during the period of the output stop operation time Toff, the voltage level of the positive input terminal 9in + of the operational amplifier 9 becomes zero level (the period from time t2 to t3 in FIG. 2). , See period from time t4 to time t5). For this reason, in the period of the output stop operation time Toff, the power supply voltage output circuit 7 controls the sensor power supply voltage Vs output from the output terminal 9out of the operational amplifier 9 to be a zero level voltage (≈0 [V]). Will be. Therefore, in the period of the output stop operation time Toff, the operational amplifier 9 operates so that a current does not substantially flow to the output side of the operational amplifier 9 even if a ground fault occurs in the power cable 23.

  On the other hand, in the period of the output resumption operation time Ton, the switching transistor 17 is controlled to be in the OFF state, so that the reference power supply voltage V2 of the positive input terminal 9in + of the operational amplifier 9 is applied with a voltage having substantially the same voltage level (FIG. 2). (Refer to the period from time t3 to t4). For this reason, during the period of the output resumption operation time Ton, the power supply voltage output circuit 7 has the sensor power supply voltage Vs output from the output terminal 9out of the operational amplifier 9 at the voltage level (≈V2) for the operation of the original sensor 5. It will be controlled to become. Therefore, if a ground fault occurs in the power supply cable 23 during the output restart operation time Ton, a large current flows from the output terminal 9out of the operational amplifier 9 due to the ground fault. However, the state in which a large current flows from the output terminal 9out of the operational amplifier 9 in this way is limited to the period of the output restart operation time Ton.

  When a ground fault occurs in the power cable 23, the power output control means 37 executes the control process at the time of occurrence of the ground fault as described above, so that the voltage for operating the original sensor 5 is output from the output terminal 9out of the operational amplifier 9. The operation of the power supply voltage output circuit 7 that attempts to output the sensor power supply voltage Vs of level (≈V2) is intermittently performed only during the output resuming operation time Ton.

  In this case, the output stop operation time Toff and the output restart operation time Ton are the output restart operation even if the operation of the power supply voltage output circuit 7 is controlled as described above in the state where the ground fault of the power cable 23 has occurred. The time is set experimentally at such a time that the operational amplifier 9 is not excessively heated and heated due to the power consumption of the operational amplifier 9 at the time Ton, and the operational amplifier 9 is not overheated.

  In the state where the power output control means 37 is executing the control process at the time of occurrence of the ground fault as described above, the ground fault occurrence monitoring means 35 is configured to output the sensor detection signal of each sensor 5 during the output restart operation time Ton. Monitor the sampling value. Then, as described above, the ground fault occurrence monitoring unit 35 sequentially determines whether or not the ground fault has occurred in the power cable 23 based on the set of sampling values of the sensor detection signals of all the sensors 5a, 5b, and 5c inputted. to decide.

  Here, the ground fault of the power cable 23 may be eliminated by vibration of the vehicle or the like. When the ground fault of the power cable 23 is thus eliminated, the reference power source voltage V2 is applied to the positive input terminal 9in + of the operational amplifier 9 after the ground fault is eliminated (OFF state of the switching transistor 17). A set of sampling values of sensor detection signals of the obtained sensors 5a, 5b, and 5c includes a sampling value that is not zero level.

  Therefore, when the ground fault of the power cable 23 is resolved, a set of sampling values of the sensor detection signals of the sensors 5a, 5b, and 5c obtained during the output restart operation time Ton (sampling that is not zero level) The ground fault occurrence monitoring means 35 detects that the ground fault of the power cable 23 has not occurred, that is, the ground fault has been resolved, based on the group having the value.

  For example, as shown in FIG. 2, when the ground fault of the power supply cable 23 is resolved at time t6, the ground fault elimination monitoring means 35 detects that the ground fault has been eliminated at time t7. In the example shown in FIG. 2, the case where the ground fault is resolved in the middle of the period of the output resuming operation time Ton starting from time t5 is illustrated, but the power cable 23 is in the middle of the period of the output stopping operation time Toff. When the ground fault is resolved, the cancellation of the ground fault is detected during the first output resumption operation time Ton thereafter.

  When the ground fault occurrence monitoring means 35 detects the ground fault of the power cable 23 as described above, the power output control means 37 accordingly stops the ground fault occurrence control process. As in the case before the occurrence of the ground fault, the power supply voltage output circuit 7 is controlled so that the sensor power supply voltage Vs at the voltage level (≈V2) for the operation of the original sensor 5 is output from the output terminal 9out of the operational amplifier 9. To do.

  Specifically, when the ground fault occurrence monitoring unit 35 detects the elimination of the ground fault of the power cable 23, the power output control unit 37 continuously applies a low level control signal to the base of the switching transistor 17. Thus, the switching transistor 17 is continuously controlled to be in the OFF state. As a result, the reference power supply voltage V2 is continuously applied to the positive input terminal 9in + of the operational amplifier 9, as shown in the state after time t7 in FIG. Thus, the sensor power supply voltage Vs at the voltage level for operation (≈V2) is continuously supplied to each sensor 5 via the power supply cable 23.

  The above is the details of the operation of the in-vehicle electrical system 1 in the present embodiment.

  According to the present embodiment, when a ground fault occurs in the power cable 23, the operation for the operation of the original sensor 5 is performed from the output terminal 9 out of the operational amplifier 9 by the control process at the time of ground fault generation of the power output control means 37. The operation of the power supply voltage output circuit 7 which attempts to output the sensor power supply voltage Vs at the voltage level (≈V2) is intermittently performed during the output resuming operation time Ton. Then, in a period other than the period of the output restart operation time Ton, that is, in the period of the output stop operation time Toff, the operation of the power supply voltage output circuit 7 is stopped, and the power supply voltage output circuit 7 The sensor power supply voltage Vs output from the terminal 9out is controlled to be zero level.

  For this reason, in the occurrence state of the ground fault of the power supply cable 23, a large current caused by the ground fault flows from the output terminal 9 out of the operational amplifier 9 is limited to the period of the output restart operation time Ton. As a result, the power consumption of the operational amplifier 9 in the state where the ground fault of the power cable 23 is generated is suppressed, and the operational amplifier 9 is prevented from being overheated. As a result, the requirements regarding the allowable upper limit of the output current of the power supply voltage output circuit 7, heat resistance, and heat dissipation are reduced, and a small and inexpensive operational amplifier 9 can be used. Therefore, including the circuit board on which the power supply voltage output circuit 7 is mounted, the power supply voltage output circuit 7 can be made inexpensive and compact.

  Further, the control process at the time of occurrence of the ground fault in the state of occurrence of the ground fault of the power supply cable 23 can be executed only by switching the level of the control signal applied to the base of the switching transistor 17, so that the control at the time of occurrence of the ground fault is performed. Processing can be realized with a simple configuration.

  Further, when the ground fault of the power supply cable 23 is resolved, this can be detected by the ground fault occurrence monitoring means 35 in the period of the output resuming operation time Ton in the ground fault occurrence control process. Therefore, in response to the detection, the operation of the power supply voltage output circuit 7 that attempts to output the sensor power supply voltage Vs at the voltage level (≈V2) for the operation of the original sensor 5 from the output terminal 9out of the operational amplifier 9 is continued. To be able to resume.

  In the present embodiment, the voltage applied to the positive input terminal 9in + of the operational amplifier 9 is switched via the switching transistor 17. However, the switching transistor 17 is omitted, and the positive input terminal 9in + of the operational amplifier 9 is omitted from the control device 3. A high level voltage or a low level voltage may be directly applied. In this case, when a low level voltage is output from the control device 3, a zero level voltage is applied to the positive input terminal 9in + of the operational amplifier 9. Further, when a high level voltage is output from the control device 3, a voltage having substantially the same voltage level as the reference power supply voltage Vs is applied to the positive input terminal 9 in + of the operational amplifier 9.

[Second Embodiment]
Next, a second embodiment of the present invention will be described with reference to FIG.

  With reference to FIG. 3, the in-vehicle electrical system 41 of the present embodiment includes a power supply voltage output circuit 43 having a configuration different from that of the power supply voltage output circuit 7 in the first embodiment. The configuration other than the output circuit 43 is the same as that of the first embodiment. For this reason, in FIG. 3, only the principal part structure of the vehicle-mounted electrical equipment system 41 is described, and illustration of the sensors 5a, 5b, 5c, etc. is omitted. Further, in the following description of the present embodiment, the same reference numerals as those in the first embodiment are used for the same configurations or the same function units as those in the first embodiment, and detailed description thereof is omitted.

  The power supply voltage output circuit 43 in the present embodiment has a switching transistor 45 instead of the operational amplifier 9 in the first embodiment, and is configured to output the sensor power supply voltage Vs from the collector of the switching transistor 45.

  Specifically, the switching transistor 45 is a pnp type switching transistor in the example of this embodiment, and the emitter and base thereof are connected via a resistor 47. Then, a drive voltage V3 having substantially the same voltage level as the power supply voltage for operating the sensor 5 (5 [V] in the example of the present embodiment) is applied to the emitter. In this case, the drive voltage V3 is generated from the output voltage of the in-vehicle battery by a regulator circuit or the like different from the reference power supply voltage V2 (output voltage of the reference power supply potential unit 15) used as the power supply voltage of the control device 3 or the like. Voltage.

  Accordingly, in the example of this embodiment, the switching transistor 45 is turned on (conductive state between the emitter and the collector) by applying a low level (≈0 [V]) control signal to its base, A voltage having substantially the same voltage level as the drive voltage V3 is output to the collector of the switching transistor 45 as the sensor power supply voltage Vs. Further, by applying a high level (≈V3) control signal to the base of the switching transistor 45, the switching transistor 45 is turned off (emitter-collector cut-off state), and the switching transistor 45 has a collector. Voltage is not output.

  The collector of the switching transistor 45 is electrically connected to the non-ground side connection terminal 25a of the connection portion 25 so as to supply the sensor power supply voltage Vs to each sensor 5 via the power supply cable 23. The capacitor 21 (see FIG. 1) employed in the first embodiment may be interposed between the collector of the switching transistor 45 and the ground potential unit 19.

  In the present embodiment, the collector of the switching transistor 45 corresponds to the power supply voltage output terminal of the power supply voltage output circuit 43.

  The base of the switching transistor 45 is connected to the ground potential portion 19 via a resistor 49 and is connected to the reference power supply potential portion 15 via the emitter and collector of the switching transistor 51 for control.

  In the example of this embodiment, the switching transistor 51 is turned on by applying a low level (≈0 [V]) control signal to the base, and the high level (≈V2) control signal is applied to the base. Is turned OFF.

  The base of the switching transistor 51 is connected to the control device 3, and a low level or high level control signal is applied to the base of the switching transistor 51 by the control process of the power supply output control means 37 of the control device 3. It has become. Thereby, the ON / OFF state of the switching transistor 51 is controlled to be switched.

  This embodiment is the same as the first embodiment except for the configuration described above.

  In the power supply voltage output circuit 43 in this embodiment, the power supply output control means 37 of the control device 3 controls the switching transistor 51 to be turned off (a high level control signal is given to the base of the switching transistor 51). As a result, a low level control signal for controlling the switching transistor 45 to the ON state is applied to the base of the switching transistor 45. As a result, a voltage of almost the same voltage level as the drive voltage V3 is output as the sensor power supply voltage Vs from the collector of the switching transistor 45 in the ON state.

  Further, the power supply output control means 37 of the control device 3 controls the switching transistor 51 to be in an ON state (giving a low level control signal to the base of the switching transistor 51), thereby switching the switching transistor 45 to the base of the switching transistor 45. A high level control signal for controlling the transistor 45 to the OFF state is applied. As a result, the output of the sensor power supply voltage Vs from the collector of the switching transistor 45 is stopped.

  In the present embodiment, the power supply output control means 37 of the control device 3 controls the switching transistor 45 to be in the ON state via the switching transistor 51 at the normal time when the ground fault of the power cable 23 has not occurred. At this time, an original sensor power supply voltage Vs (≈V3) having a voltage level substantially equal to the drive voltage V3 is supplied from the collector of the switching transistor 45 to each sensor 5 through the power supply cable 23. Become.

  Further, when a ground fault occurs in the power cable 23, the ground fault occurrence control process of the power output control means 37 of the control device 3 is executed in the same manner as in the first embodiment, and the output stop operation time Toff is set. The period and the period of the output resuming operation time Ton are alternately and periodically repeated. In this case, the switching transistor 45 is controlled to be OFF during the output stop operation time Toff, and the output of the sensor power supply voltage Vs from the collector of the switching transistor 45 is stopped.

  Further, the switching transistor 45 is controlled to be in an ON state so that the sensor power supply voltage Vs is output from the collector of the switching transistor 45 during the output resuming operation time Ton. In this case, in the state where the ground fault of the power supply cable 23 continues, the power supply Vs actually output from the collector of the switching transistor 45 is set to the original voltage (≈V3) for the operation of the sensor 5. It becomes a zero level voltage.

  When the ground fault of the power supply cable 23 is resolved during the execution of the ground fault occurrence control process, the power output control means 37 of the control device 3 stops the ground fault occurrence control process and switches the switching transistor. 45 is continuously controlled to be ON. As a result, the original sensor power supply voltage Vs (≈V3) is continuously supplied from the collector of the switching transistor 45 to each sensor 5 via the power supply cable 23.

  In this embodiment, the same effects as those of the first embodiment can be obtained. That is, in the occurrence state of the ground fault of the power cable 23, the large current caused by the ground fault flows from the collector of the switching transistor 45 because it is limited to the period of the output restart operation time Ton. The power consumption of the switching transistor 45 in a ground fault occurrence state is suppressed, and the switching transistor 45 is prevented from being overheated. As a result, the requirements regarding the allowable upper limit, heat resistance, and heat dissipation of the output current of the power supply voltage output circuit 43 are reduced, and a small and inexpensive switching transistor 45 can be used. Therefore, including the circuit board on which the power supply voltage output circuit 43 is mounted, the power supply voltage output circuit 43 can be made inexpensive and compact.

  In addition, since the ground fault occurrence control process in the ground fault occurrence state of the power cable 23 can be executed simply by switching the level of the control signal applied to the base of the switching transistor 51, the control at the time of ground fault occurrence is performed. Processing can be realized with a simple configuration.

  When the ground fault of the power supply cable 23 is resolved, the sensor power supply voltage Vs at the voltage level (≈V3) for operating the original sensor 5 is output from the collector of the switching transistor 45 in response to the detection. Things can be resumed continuously.

  In each of the embodiments described above, the power supply voltage output circuits 7 and 43 using the operational amplifier 9 and the switching transistor 45 are exemplified. However, the power supply voltage output circuit in the present invention may adopt other configurations. For example, a tracking regulator IC may be used as the power supply voltage output circuit.

  DESCRIPTION OF SYMBOLS 1,41 ... Vehicle-mounted electrical system, 3 ... Control apparatus, 5a, 5b, 5c ... Sensor, 7, 43 ... Power supply voltage output circuit, 9 ... Operational amplifier, 9out ... Output terminal (power supply voltage output terminal), 23 ... Power supply cable , 29 ... Signal cable, 35 ... Ground fault occurrence monitoring means, 37 ... Power supply output control means, 45 ... Switching transistor.

Claims (3)

A power supply voltage output terminal connected to a plurality of sensors mounted on the vehicle via a power supply cable, and a power supply voltage for operating the plurality of sensors is transmitted from the power supply voltage output terminal to the power supply cable A power supply voltage output circuit that outputs to the plurality of sensors, and a control that is connected to the plurality of sensors via a signal cable, and a detection signal output from the plurality of sensors is input via the signal cable. A ground fault countermeasure device for an in-vehicle electrical system equipped with a device,
The control device determines whether a set of detection signals input from the plurality of sensors matches the set of detection signals in a state where a ground fault has occurred in the power supply cable. And a stop of the output of the power supply voltage from the power supply voltage output circuit and a restart of the output of the power supply voltage following the stop when the determination result of the ground fault occurrence monitoring means becomes affirmative Power supply output control means for performing control processing at the time of occurrence of a ground fault for controlling the power supply voltage output circuit so as to be repeated automatically,
The power supply output control means performs the ground fault occurrence control process when the determination result of the ground fault occurrence monitoring means in the restart state of the output of the power supply voltage from the power supply voltage output circuit becomes negative. A ground fault countermeasure device for an in-vehicle electrical system, wherein the power supply voltage output circuit is controlled to stop and continue output of the power supply voltage. In the ground fault countermeasure apparatus of the vehicle-mounted electrical system of Claim 1,
The power supply voltage output circuit includes an operational amplifier having a negative input terminal connected to an output terminal, and the power supply voltage is applied to the positive input terminal of the operational amplifier by applying a voltage having the same voltage level as the power supply voltage. A circuit configured to output from the output terminal of the operational amplifier via the power cable;
The ground fault occurrence control process executed by the power supply output control means controls the voltage applied to the positive input terminal of the operational amplifier to a zero level voltage when stopping the output of the power supply voltage, and the power supply voltage A ground fault countermeasure device for an in-vehicle electrical system, which is a process of controlling a voltage applied to a positive input terminal of the operational amplifier to a voltage having the same level as the power supply voltage when the output of the operational amplifier is resumed. In the ground fault countermeasure apparatus of the vehicle-mounted electrical system of Claim 1,
The power supply voltage output circuit has a switching transistor that can be selectively controlled to an ON state or an OFF state, and applies a control signal for controlling the switching transistor to an ON state to the base of the switching transistor. A circuit configured to output a voltage from the collector of the switching transistor via the power cable;
The ground fault occurrence control process executed by the power supply output control means applies a control signal for controlling the switching transistor to an OFF state when stopping the output of the power supply voltage to the base of the switching transistor, and A ground fault countermeasure device for an in-vehicle electrical system, which is a process of giving a control signal for controlling the switching transistor to an ON state when the output of a power supply voltage is resumed.

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