JP2011078178A - Device and system for driving load - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a device and a system for driving a load wherein it is possible to carry out drive control and overcurrent protection according to the type of a load to be driven or the like. <P>SOLUTION: The load drive system 1 includes multiple load driving portions 4 (drive circuits 20 and protection circuits 30) and drives multiple loads under the control of a microcomputer 2. When an overcurrent is produced in the current path between the load and the drive circuit 20 of each load driving portion 4, each current path is repeatedly interrupted and interruption is released each time a predetermined time passes after the current path is interrupted. Each protection circuit 30 can interrupt a current path or release the interruption by a first interruption method or a second interruption method. In the first interruption method, a current path is kept interrupted when the number of times of repeated interruption and release of interruption reaches a predetermined number. In the second interruption method, interruption of and release of interruption of a current path are repeatedly carried out regardless of the number of times of repetition. Each protection circuit 30 individually changes the method for interruption under the control of the microcomputer 2. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a load driving device and a load driving system capable of driving an electric load such as a motor or a lamp and protecting the load and a driving circuit from an overcurrent.

  Conventionally, electronic control of vehicles has progressed, and the number of loads such as motors and lamps mounted on the vehicle tends to increase. In order to drive these plural loads, a large number of drive circuits are mounted on the ECU (Electronic Control Unit) of the vehicle. When a failure or the like occurs in the load or the drive circuit, a large current (overcurrent) may flow from the drive circuit to the load or from the load to the drive circuit. For this reason, it is desirable to mount an overcurrent protection circuit together with the drive circuit in the ECU.

  In recent years, with the development of semiconductor manufacturing technology, IC (Integrated Circuit) chips can be highly integrated and enlarged. As a result, a large number of drive circuits can be mounted on one IC chip, and the number of ECU parts and cost can be reduced. In particular, when a plurality of driving circuits are mounted on one IC chip and a plurality of loads are driven, when an overcurrent flows in any one of the loads and driving circuits, the operation of other loads and driving circuits Therefore, the need for a protection circuit is high.

  In Patent Document 1, a plurality of MOS (Metal Oxide Semiconductor) transistors and driving circuits for driving a plurality of loads, a current detection circuit for detecting a current flowing through each transistor, and a plurality of MOS transistors are closely coupled. When the detected temperature of the temperature detection circuit exceeds the threshold temperature, it is determined that abnormal heat generation has occurred in any of the MOS transistors that are on-driven, and current among the plurality of MOS transistors is determined. There has been proposed a load control device that can selectively protect and control only a switching element that causes abnormal heat generation by driving off a detection current detected by a detection circuit that exceeds a threshold current.

  In Patent Document 2, a comparator is provided that outputs a detection signal indicating that the current flowing through the semiconductor element has reached a protection level, and when the detection signal of the comparator is output more than a set number of times within a predetermined time, the semiconductor There has been proposed a protection circuit for a semiconductor element that can be protected from heat generated by switching at the same time as overcurrent protection of the semiconductor element by continuously turning off the element. This protection circuit counts the detection signal of the comparator with a counter, holds the count-up signal of the counter with a flip-flop for a certain period of time, and has a period longer than the time from the count start until the count-up signal is output Thus, the counter is reset to control on / off of the semiconductor element based on the output signal of the flip-flop.

JP 2002-232280 A Japanese Patent No. 3231450

  However, the load control device described in Patent Document 1 has a problem that it is necessary to mount a temperature detection circuit in order to detect an abnormality in the drive circuit, which is expensive. In addition, since only one temperature detection circuit is mounted for a plurality of drive circuits, it is difficult to detect the abnormality of each drive circuit equally, and each drive circuit is provided with a temperature detection circuit. In this case, there is a problem that the cost of the load driving device is further increased. In addition, since a certain amount of time is required until the temperature rises after an abnormality such as an overcurrent occurs in the drive circuit, the circuit may not be protected depending on the degree or type of abnormality.

  The protection circuit described in Patent Document 2 is such that when an overcurrent is detected at a timing when a semiconductor element is turned on, the semiconductor element is turned off for the period when the semiconductor element is repeatedly turned on / off at a predetermined period. If overcurrent is detected a predetermined number of times within a certain time (ie, during a predetermined number of ON / OFF cycles), the circuit is protected by completely turning off the semiconductor element and stopping the operation. It is to do. For this reason, it is difficult to apply the configuration of the protection circuit when the semiconductor element is not turned on / off periodically but is turned on / off at an arbitrary timing (so-called DC energization).

  Further, in order to reduce the development cost of an ECU or the like, it is desired to use an IC chip equipped with a plurality of drive circuits as a general-purpose component. In this case, there are various loads driven by each drive circuit of the IC chip, and it is necessary to perform drive control suitable for the type of load. As described above, the IC chip is equipped with a drive circuit and a protection circuit against overcurrent. However, since the loads to be driven are various, the type or cause of the failure that causes the overcurrent is also different for each load. There are various.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a load drive device and a load capable of performing drive control and overcurrent protection according to the type of load to be driven. It is to provide a drive system.

  A load driving apparatus according to the present invention detects a current flowing through a current path between a driving means for driving a load in response to a control signal relating to driving on / off given from the control apparatus, and between the driving means and the load. Current detection means, determination means for determining whether or not the current detected by the current detection means exceeds a threshold, and when the determination means determines that the current exceeds the threshold, the load and the A blocking means for blocking the current path between the driving means, a releasing means for releasing the blocking after a lapse of a predetermined time after the blocking of the current path by the blocking means, a blocking by the blocking means, or a blocking release by the releasing means When the control device gives a drive-off control signal after the number of repetitions exceeds a predetermined number, the counted number of repetitions is reset. And a counter that, if the number of iterations the counter has counted exceeds the predetermined number, and wherein that you have to continue the shut-off without releasing the current path.

  In addition, the load driving device according to the present invention, when the number of repetitions exceeds the predetermined number of times, whether to continue the interruption of the current path, or to continue the interruption of the current path and release of the interruption? Are switched according to control from the control device.

  The load drive system according to the present invention includes a plurality of the load drive devices described above, and each load drive device drives a different load, and the number of repetitions depends on the control from the control device. When the predetermined number of times is exceeded, switching means for individually switching for each load driving device whether to continue the interruption of the current path or to continue the interruption and release of the interruption of the current path is provided. It is characterized by that.

  In addition, the load driving system according to the present invention further includes a communication unit that transmits and receives control information to and from the control device, and the switching unit performs switching according to information received by the communication unit. It is characterized by the above.

  In addition, the load drive system according to the present invention is further characterized by further comprising: a cut-off state transmission unit that transmits information related to an operation state of the cut-off unit of each load drive device to the control device by the communication unit.

In the present invention, the driving means drives a load in accordance with a control signal from a control device (for example, a CPU (Central Processing Unit) or an MPU (Micro Processing Unit)), and an overcurrent (threshold value) is present in the current path between the loads. The load driving device is provided with a blocking means for cutting off the current path when a current exceeding the current path is detected and a release means for releasing the blocking of the current path after a predetermined time has elapsed since the blocking. Thereby, in a state where a control signal for turning on the driving of the load is given from the control device, it is possible to repeatedly interrupt the current path and release the interruption in a predetermined time according to the overcurrent.
Also, the number of times the current path is interrupted / released is counted by the counter. If the counted number exceeds the specified number, the current path is interrupted without releasing the current path and the load is driven. To stop. As a result, the drive of the load can be resumed when the abnormality is resolved by the interruption of the current path, and the drive of the load is completely stopped when the abnormality is not resolved even if the current path is interrupted. it can.
Note that the number of times the counter counts is reset when a drive-off control signal is given from the control device after the current path is completely cut off exceeding the predetermined number as described above. As a result, when the drive of the load is stopped, the control device can reset the counter by setting the control signal to drive off and then attempt to drive the load again by setting the control signal to drive on.

Further, in the present invention, when the number of times counted by the counter exceeds the predetermined number as described above, the driving of the load is completely stopped without releasing the interruption of the current path (first method), or Even if the number of times the counter has counted exceeds the predetermined number of times (that is, regardless of the number of times of the counter), whether or not to continue the current path interruption and interruption release (second method) is determined from the control device. It is possible to switch by controlling.
Thereby, since the control apparatus can switch the interruption | blocking method of an electric current path | route according to the classification etc. of the load used as a drive object, suitable protection according to the drive object is realizable. Moreover, the versatility of the load driving device can be improved.

In the present invention, a load driving system is configured by mounting a plurality of load driving devices capable of switching the blocking method to the first method or the second method as described above. In the load drive system, each load drive device drives a load, and current detection, determination, interruption, and release of interruption can be performed individually for each current path between the drive means and the load. Further, each load driving device is configured to be able to individually switch the current path blocking method.
Thereby, when a plurality of load driving devices respectively drive different types of loads, the current path blocking method by each load driving device can be individually set according to the type of load. Therefore, since it can drive by connecting various load to one load drive system, the versatility of a load drive system can be improved.

  In the present invention, communication such as serial communication is performed between the load driving system and the control device, and information related to control can be transmitted and received. The load driving system individually switches the current path blocking method by each load driving device in accordance with information from the control device. As a result, even when the load drive system includes a large number of load drive devices, it is possible to switch the current path blocking method of each load drive device by communication from the control device to the load drive system. Each individual setting can be easily and reliably performed.

  Further, in the present invention, information related to the operating state of the shut-off means of each load driving device (such as whether or not the current supply path is shut off) is transmitted from the load driving system to the control device. Accordingly, the control device can detect that an abnormality has occurred in the load or the driving means based on the information received from the load driving system, and can execute processing for this abnormality.

In the case of the present invention, when an overcurrent is detected by driving a load in accordance with a control signal from the control device, the current path is cut off and the cut-off is released after a predetermined time has elapsed, and the number of repetitions of the cut-off / cut-off release If the current path exceeds the predetermined number of times, the current path is completely cut off, so that a drive-on signal is given from the control device for a long period of time, and so-called DC energization that continues to drive the load during this period is performed. Even a drive device that has been enabled can repeatedly try to interrupt the current path and then release the interruption in response to an overcurrent. Further, even when a control signal for periodically turning on / off the drive is given from the control device, the current path can be completely cut off after the cut-off and cut-off return are repeatedly performed.
As a result, the current path can be appropriately interrupted with respect to overcurrent regardless of whether DC driving or periodic driving is performed according to the type of load to be driven. The versatility of the apparatus can be improved.

  In addition, by configuring a load drive system with a plurality of load drive devices that can switch the current path interruption method, and by switching the interruption method by each load drive device individually according to the control from the control device, Even when a plurality of various loads are connected to one load drive system for driving, an appropriate blocking method can be set according to the characteristics of each load. Can be improved.

  Therefore, it is possible to reliably realize a general-purpose product of the load driving device and the load driving system, and it is possible to realize a reduction in development cost and a reduction in the number of parts of the ECU using the load driving device and the load driving system.

It is a block diagram which shows the structure of the load drive system which concerns on this invention. It is a block diagram which shows the structure of the load drive part which concerns on this invention. It is a schematic diagram for demonstrating the 1st interruption | blocking method. It is a schematic diagram for demonstrating the 2nd interruption | blocking method.

  Hereinafter, the present invention will be specifically described with reference to the drawings showing embodiments thereof. FIG. 1 is a block diagram showing a configuration of a load driving system according to the present invention. The thick solid line in FIG. 1 represents a 5-bit bus, and the thin solid line extending from the bus represents a 1-bit signal line. In the figure, reference numeral 1 denotes a load drive system. The load drive system 1 drives a plurality of loads such as a door lock relay 3a, a light relay 3b, a horn relay 3c, and an indicator 3d under the control of a microcomputer 2 (control device). Do. The load drive system 1 includes a plurality of load drive units (load drive devices) 4, a drive function control unit 11, a serial communication unit (communication unit) 12, and a protection function control unit (switching unit) 13. Yes. Each load drive unit 4 includes a drive circuit (drive means) 20 and a protection circuit (blocking means, release means) 30.

  A load is connected to each of a plurality (four in the figure) of load drive units 4 included in the load drive system 1, and the drive circuit 20 controls a predetermined drive voltage or drive according to the control of the drive function control unit 11. The load is driven by outputting a current. The drive circuit 20 operates individually according to the drive signals individually given from the drive function control unit 11, and outputs a drive voltage or a drive current when the drive signal given as, for example, a 1-bit digital signal is at a high level. However, when the drive signal is at a low level, the output is stopped (drive off).

  The drive function control unit 11 controls the drive on / off of the drive circuit 20 of each load drive unit 4 in accordance with the drive command from the microcomputer 2 received by the serial communication unit 12. For example, the microcomputer 2 transmits data of plural bits (4 bits in this example) instructing driving on / off of each load driven by the load driving system 1 to the load driving system 1 through serial communication together with a driving command. The serial communication unit 12 of the load drive system 1 that has received this gives the received data to the drive function control unit 11. The drive function control unit 11 outputs a drive signal to the drive circuit 20 of each load drive unit 4, and determines the output level of each drive signal according to a plurality of bits of data given from the serial communication unit 12. To do.

  The serial communication unit 12 transmits and receives data to and from the microcomputer 2 by serial communication. As described above, the microcomputer 2 transmits a drive command for instructing driving on / off to the load to the load driving system 1 and switches a blocking method (described later) related to the operation of the protection circuit 30 of the load driving unit 4. The command is transmitted to the load driving system 1. When the serial communication unit 12 receives a drive command from the microcomputer 2, the serial communication unit 12 provides the drive function control unit 11 with data supplied together with the drive command. Data given together with the switching command is given to the protection function control unit 13. Further, the serial communication unit 12 is provided with information on the operation state of the protection circuit 30 of each load driving unit 4 from the protection function control unit 13, and transmits this information in response to a request from the microcomputer 2.

  Each load drive unit 4 is provided with one drive circuit 20 and one protection circuit 30 in a one-to-one correspondence. The protection circuit 30 is for protecting the drive circuit 20 and the load from being destroyed by the overcurrent by blocking the current path when an overcurrent flows in the current path between the drive circuit 20 and the load. is there. Although the details will be described later, the protection circuit 30 can perform the interruption and release of the interruption of the current path by two kinds of methods, and the interruption method is switched according to the switching signal individually given from the protection function control unit 13. Do. For example, the protection circuit 30 performs current path blocking / unblocking by the first blocking method when a switching signal given as a 1-bit digital signal is at a low level, and performs a second blocking when the switching signal is at a high level. The current path is cut off / released by the method.

  The protection circuit 30 outputs a status signal indicating its own operating state to the protection function control unit 13 (note that the status signal is not shown in FIG. 1). For example, the protection circuit 30 outputs a 1-bit digital signal that becomes a high level when an overcurrent is detected and a cutoff operation is performed, and that is a low level when the cutoff operation is not performed as a status signal.

  The protection function control unit 13 performs switching control of the blocking method for the protection circuit 30 of each load driving unit 4 in accordance with the switching command from the microcomputer 2 received by the serial communication unit 12. For example, the microcomputer 2 transmits a plurality of bits of data instructing a method of cutting off the current path by the protection circuit 30 to the load driving system 1 through serial communication together with the switching command, and receives the received serial communication unit of the load driving system 1 12 gives the received data to the protection function control unit 13. The protection function control unit 13 outputs a switching signal to the protection circuit 30 of each load protection unit 4, and determines the output level of each switching signal according to the multi-bit data given from the serial communication unit 12. To do. Further, the protection function control unit 13 is given a status signal from the protection circuit 30 of each load protection unit 4, and the operation state of each protection circuit 30 indicated by the status signal is data of a plurality of bits (4 bits in this example). To the serial communication unit 12.

  FIG. 2 is a block diagram showing the configuration of the load driving unit 4 according to the present invention. In FIG. 2, the door lock relay 3a, the light relay 3b, the horn relay 3c, the indicator 3d and the like shown in FIG. The protection circuit 30 includes an interruption control unit 31, a current detection unit (current detection unit) 32, a comparison unit (determination unit) 33, a switching element 34, a counter 35, and the like. As described above, the protection circuit 30 is provided in one-to-one correspondence with the drive circuit 20, and the drive signal given from the drive function control unit 11 to the drive circuit 20 is also given to the corresponding protection circuit 30. Yes.

  The current detection unit 32 is arranged in the current path of the drive circuit 20 and the load 3 and detects a current flowing through the current path. The current value detected by the current detection unit 32 is given to the comparison unit 33. The comparison unit 33 determines whether or not an overcurrent has occurred in the current path by comparing the current value detected by the current detection unit 32 with a predetermined threshold value. The comparison unit 33 notifies the interruption control unit 31 of the comparison result, that is, the presence or absence of overcurrent.

  The switching element 34 is a transistor such as a FET (Field Effect Transistor) or an element such as a relay, and is arranged in a current path between the drive circuit 20 and the load 3 to connect / cut off this current path. The switching element 34 operates in accordance with a cutoff signal given from the cutoff control unit 31, for example, when the cutoff signal is high level, cuts off the current path, and when the cutoff signal is low level, connects the current path.

  The shutoff control unit 31 turns off / on the switching element 34 (that is, the current) according to the drive signal given to the drive circuit 20, the switching signal given from the protection function control unit 13, and the comparison result of the comparison unit 33. Controls route blocking / blocking release). Further, the cutoff control unit 31 generates a status signal indicating the operating state of the protection circuit 30 and outputs the status signal to the protection function control unit 13. The counter 35 is used when the cutoff control unit 31 performs a cutoff process by the switching element 34.

  Moreover, the interruption | blocking control part 31 performs interruption | blocking / canceling cancellation | release of an electric current path according to either of the following two interruption | blocking methods. It can be switched by the switching signal given from the protection function control part 13 by which interruption | blocking method the interruption | blocking control part 31 performs interruption | blocking / disconnection cancellation | release of an electric current path. For example, the shut-off control unit 31 performs shut-off / shut off with the first shut-off method when the switching signal is at a low level, and performs shut-off / shut-off with the second shut-off method when the switch signal is at a high level. Do.

(First blocking method)
FIG. 3 is a schematic diagram for explaining the first cutoff method, and an example of the operation is illustrated as a timing chart of a drive signal, a detection current, a cutoff signal, a count value, and a status signal. In the first cutoff method, the protection circuit 30 is driven by repeatedly turning off / on the switching element 34 and repeatedly cutting off / breaking off the current path when the detection current of the current detection unit 32 exceeds a threshold value. The current path between the circuit 20 and the load 3 is repeatedly interrupted / released. However, in the first interruption method, the counter 35 counts the number of times the current path is interrupted / released, and when the count value reaches 7, that is, when the interruption / release cancellation is repeated 7 times, the protection is performed. The circuit 30 turns off the switching element 34 and maintains the current path in a cut-off state.

  When the detected current exceeds the threshold value, the protection circuit 30 repeats the interruption / cancellation release at a predetermined time. As the time from the interruption of the current path to the release of the interruption, for example, a time sufficient for the drive target load 3 to return from the abnormal state to the normal state is set in advance according to the type of the load 3. In addition, as the time from the release of the interruption of the current path to the interruption again, a minimum time required for the current detection unit 32 to measure the detected current is set in advance. These times may be configured such that the microcomputer 2 can be set by serial communication.

  For example, when the drive signal changes to a high level at time t1 and the detection current of the current detection unit 32 does not exceed the threshold value, the cutoff control unit 31 of the protection circuit 30 maintains the switching element 34 in the ON state. The drive circuit 20 drives the load 3 until the drive signal becomes low level.

  When the drive signal changes to the high level at time t2 and the detected current of the current detection unit 32 exceeds the threshold value, the cutoff control unit 31 repeatedly switches the cutoff signal between the low level and the high level to switch the switching element 34. Are repeatedly turned off / on, and the current paths of the drive circuit 20 and the load 3 are repeatedly cut off / released. At this time, the cutoff control unit 31 counts up the counter 35 in response to the rise of the cutoff signal (change from low level to high level), and when the count value of the counter 35 reaches 7 at time t3, The repetition of the blocking / unblocking of the path is stopped, the blocking signal is maintained at a high level, and the current path is maintained in the blocking state. The interruption state of the current path is maintained until the drive signal changes to the low level, and the interruption of the current path is not released before the drive signal changes to the low level. Moreover, the interruption | blocking control part 31 outputs a status signal as a high level until the detection electric current falls below a threshold value after the electric current exceeding a threshold value is detected.

  When the drive signal changes to the low level at time t4, the cutoff control unit 31 sets the cutoff signal to the low level to cancel the cutoff state of the current path, and resets the count value of the counter 35. Even in this case, the cutoff control unit 31 maintains the status signal at a high level.

  When the drive signal changes to the high level again at time t5, the interruption control unit 31 repeats interruption / release of the current path until the count value of the counter 35 reaches 7, and the count value reaches 7. After that, the current path is maintained in an interrupted state. Even if the drive signal changes to the low level before the count value of the counter 35 reaches 7, the count value of the counter 35 is not reset (see t6).

  Thereafter, when the drive signal changes to high level at time t7 and the detected current of the current detection unit 32 falls below the threshold value, the cutoff control unit 31 sets the cutoff signal to low level and maintains the switching element 34 in the on state. To restore the current path. As a result, the drive circuit 20 drives the load 3 until the drive signal becomes low level. Moreover, the interruption | blocking control part 31 outputs a status signal as a low level, when the detection electric current of the electric current detection part 32 is less than a threshold value.

  Thus, in the first interruption method, when a current exceeding the threshold is detected, the protection circuit 30 repeats interruption / release of the current path until the detected current falls below the threshold, and the number of repetitions is a predetermined number of times. When the current exceeds the value, the current path is maintained in a cut-off state. For example, when the load 3 to be driven has a large overcurrent when it is in an abnormal state or a load that requires time to return from the abnormal state to the normal state, the current applied to the protection circuit 30 by the first interruption method The route can be blocked.

(Second blocking method)
FIG. 4 is a schematic diagram for explaining the second cutoff method, and an example of the operation is shown as a timing chart of a drive signal, a detection current, a cutoff signal, and a status signal. In the second cutoff method, the protection circuit 30 repeatedly turns off and on the switching element 34 when the current detected by the current detection unit 32 exceeds the threshold when the drive signal is at a high level, thereby driving the drive circuit 20. In addition, the current path between the load 3 is repeatedly interrupted / released. While the drive signal is at a high level, the protection circuit 30 continues to repeat the interruption / release of the current path. Further, after detecting the current exceeding the threshold, the protection circuit 30 sets the status signal to the high level. Thereafter, when the current detection unit 32 detects a current that is lower than the threshold value, the protection circuit 30 ends the repetition of the interruption / cancellation of the current path, and maintains the switching element 34 in the on state to connect the current path. At the same time, the status signal is set to a low level.

  That is, in the second shutoff method, the counter 35 does not count the number of shutoff / shutoff repetitions (or ignores the count value of the counter 35), and the current detected by the current detector 32 exceeds the threshold value. In, the current path is continuously cut off / released. This can be realized simply by stopping the operation of the counter 35 (or ignoring the output signal of the counter 35) with respect to the first shut-off method.

  For example, when the drive signal changes to a high level at time t1, the drive circuit 20 outputs a drive voltage. At this time, the cutoff signal is at a low level and the switching element 34 is not cut off. Is applied, and the current detection unit 32 detects the current. If the detected current does not exceed the threshold value, the cutoff control unit 31 of the protection circuit 30 maintains the switching element 34 in the ON state, and the load 3 is driven until the drive signal becomes low level.

  When the drive signal is changed to a high level at time t2 and the load 3 is driven, when the current detection unit 32 detects a current exceeding the threshold value, the cutoff control unit 31 sets the cutoff signal to a high level. As a result, the switching element 34 is turned off to interrupt the current path. After that, the interruption control unit 31 repeatedly turns off / on the switching element 34 to repeatedly interrupt / release the current path, and when the current path is restored, the current detection unit 32 detects the current detected by the current detection unit 32. Comparison with the threshold is performed, and the current path is repeatedly interrupted / released until the detected current falls below the threshold. Moreover, the interruption | blocking control part 31 outputs a status signal as a high level until the detection electric current falls below a threshold value after the electric current exceeding a threshold value is detected.

  When the drive signal changes to the low level without the detected current falling below the threshold at time t3, the cutoff control unit 31 temporarily stops the switching element 34 from being turned on / off. At this time, the interruption control unit 31 maintains the interruption signal at a high level, maintains the current path in an interruption state, and maintains the status signal at a high level.

  When the drive signal changes to a high level at times t4 and t5, and the detected current of the current detection unit 32 exceeds the threshold value, the cutoff control unit 31 restarts the switching element 34 off / on repeatedly. Thereafter, when the drive signal changes to a high level at time t6 and the detection current of the current detection unit 32 falls below the threshold, the cutoff control unit 31 sets the cutoff signal to a low level and maintains the switching element 34 in the on state. Restore the current path. As a result, the drive circuit 20 drives the load 3 until the drive signal becomes low level. Moreover, the interruption | blocking control part 31 outputs a status signal as a low level, when the detection electric current of the electric current detection part 32 is less than a threshold value.

  As described above, in the second cutoff method, when the current exceeding the threshold value, that is, the overcurrent is detected, the protection circuit 30 repeatedly turns off and on the switching element 34 until the detected current falls below the threshold value. Repeat blocking / unblocking of the route. For example, when the load 3 to be driven is in an abnormal state and has a high possibility of returning to a normal state in a short period of time, the protection circuit 30 is provided with a current path by the second interruption method. Blocking / unblocking can be performed.

  The load drive unit 4 of the load drive system 1 having the above configuration is configured such that the current flowing through the current path between the drive circuit 20 and the load 3 when the drive circuit 20 drives the load 3 according to the drive signal from the microcomputer 2. When the threshold value exceeds the threshold value, the interruption control unit 31 repeatedly turns off / on the switching element 34 to repeatedly interrupt the current path and release the interruption after a predetermined time has elapsed since the interruption, and the number of repetitions exceeds the predetermined number of times. By adopting a configuration in which the current path is maintained in the cut-off state (first cut-off method), the overcurrent can be applied regardless of whether the drive circuit 20 performs DC drive or periodic drive. If the failure is not resolved even if the current path is interrupted, the current path is completely interrupted after a predetermined number of repetitions and the load 3 and It can be protected driving circuit 20 and the like.

  Further, the counter 35 that counts the number of repetitions of interruption / release of the current path is configured to be reset when a drive-off drive signal is given from the microcomputer 2 after the number of repetitions exceeds a predetermined number. When the drive of the load 3 is stopped by the protection circuit 30, the microcomputer 2 outputs a drive-off drive signal and resets the counter 35, then outputs a drive-on drive signal and tries to drive the load 3 again. be able to.

  Therefore, the current path can be appropriately interrupted with respect to overcurrent regardless of whether DC driving or periodic driving is performed according to the type of the load 3 to be driven. The versatility of the load drive unit 4 of the drive system 1 can be improved, and the development cost of the ECU and the like using this can be reduced and the number of parts can be reduced.

  In addition, the protection circuit 30 of the load driving unit 4 is independent of the first interruption method for maintaining the current path in the interruption state when the number of repetitions of the interruption / release of interruption of the current path reaches a predetermined number, or regardless of the number of repetitions. The current path can be interrupted / disengaged by any one of the second interrupting methods in which the current path is interrupted / interrupted, and the protection circuit 30 of each load drive unit 4 is controlled according to the control of the microcomputer 2. By adopting a configuration in which the shut-off method can be switched individually, the shut-off method can be individually set according to the type of the load 3 driven by each drive circuit 20, so that the versatility of the load drive system 1 can be increased. Can be improved.

  Further, the microcomputer 2 and the serial communication unit 12 of the load drive system 1 transmit and receive data related to switching of the blocking method by serial communication, and the protection function control unit 13 protects each load drive unit 4 according to the received data. By adopting a configuration in which the switching method is switched by outputting a switching signal to the circuit 30, even when the number of the load driving units 4 provided in the load driving system 1 is large, the load driving unit 4 is provided with respect to the protection circuit 30. Switching of the blocking method can be performed easily and reliably.

  Further, the protection circuit 30 of each load driving unit 4 outputs a status signal that becomes a high level when an overcurrent is detected to the protection function control unit 13, and the protection function control unit 13 is based on these status signals. Data indicating the operation state of each protection circuit 30 is created, and this data is transmitted from the serial communication unit 12 to the microcomputer 2. Thereby, the microcomputer 2 can detect an abnormality related to driving of each load 3 and can execute a process for the abnormality.

  In the present embodiment, the load driving system 1 is configured to include the four load driving units 4 (the driving circuit 20 and the protection circuit 30). However, the present invention is not limited to this, and the number is three or less or five or more. The load drive unit 4 may be provided. Further, although the protection circuit 30 of the load driving unit 4 is configured to perform the current path interruption / break release by either the first interruption method or the second interruption method, the present invention is not limited to this. However, the current path may be blocked / released using only the first blocking method. 1 shows a door lock relay 3a, a light relay 3b, a horn relay 3c, and an indicator 3d as an example of the load 3, the load 3 is not limited to these, and the load driving system 1 includes Various other loads 3 may be connected. In addition, the microcomputer 2 and the load driving system 1 are configured to transmit and receive data by serial communication. However, the present invention is not limited to this, and may be configured to transmit and receive data by other communication methods such as parallel communication. . The signal waveforms shown in FIGS. 3 and 4 are examples, and the present invention is not limited to these. In FIG. 2, the counter 35 is provided separately from the shut-off control unit 31. However, the configuration is not limited to this, and the counter 35 may be provided in the shut-off control unit 31.

1 Load drive system 2 Microcomputer (control device)
3 Load 4 Load drive unit (load drive device)
11 Drive Function Control Unit 12 Serial Communication Unit (Communication Means)
13 Protection function controller (switching means)
20 Drive circuit (drive means)
30 Protection circuit (shut-off means, release means)
31 Blocking control unit 32 Current detection unit (current detection means)
33 Comparison unit (determination means)
34 Switching element 35 Counter

Claims (5)

Drive means for driving a load in response to a control signal relating to drive on / off given from the control device;
Current detecting means for detecting a current flowing in a current path between the driving means and the load;
Determination means for determining whether or not the current detected by the current detection means exceeds a threshold;
A blocking unit that blocks a current path between the load and the driving unit when the determination unit determines that the current exceeds a threshold;
Release means for releasing the interruption after a predetermined time has elapsed since the interruption of the current path by the interruption means;
Counting the number of repetitions of the blocking by the blocking means or the cancellation of the blocking by the releasing means, and counting the number of repetitions when the control device gives a drive-off control signal after the number of repetitions exceeds a predetermined number And a counter to reset
The load driving device, wherein when the number of repetitions counted by the counter exceeds the predetermined number, the interruption is continued without releasing the current path. When the number of repetitions exceeds the predetermined number, whether to continue the interruption of the current path or to continue the interruption of the current path and the release of the interruption according to the control from the control device The load driving device according to claim 1, wherein the load driving device is switched. A plurality of load drive devices according to claim 2 are provided, and each load drive device drives a different load,
In response to control from the control device, when the number of repetitions exceeds the predetermined number, whether to continue the interruption of the current path, or to continue the interruption of the current path and release of the interruption. A load driving system comprising switching means for individually switching for each of the load driving devices. It further comprises communication means for transmitting and receiving information related to control with the control device,
The load driving system according to claim 3, wherein the switching unit is configured to perform switching according to information received by the communication unit. The load drive system according to claim 4, further comprising: a cut-off state transmission unit that transmits information related to an operation state of the cut-off unit of each load drive device to the control device by the communication unit.

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