JP2008059517A - External load interface circuit, electronic control device, and method for switching driving voltage in external load interface circuit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To cope with a plurality of kinds of external loads arranged outside an ECU without increasing the footprint of an ASIC and a production cost, in relation to an external load interface for supplying a driving voltage for driving an external load such as a Hall effect element sensor or the like according to a control command to be input from a microcomputer within a mobile object, an electronic control device, and a method for switching driving voltages in the external load interface. <P>SOLUTION: The external load interface circuit is constituted so that a plurality of driving voltages are switched according to the kinds of the external loads SE1-SE3; and a reference voltage to be generated inside the external load interface circuit and an arbitrary external voltage to be applied to an external terminal are switched so as to output respective driving voltages. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention provides an external load interface circuit having a function of supplying a driving voltage for driving an external load such as a Hall effect element sensor to the external load in accordance with various control commands input from a microcomputer in a moving body such as a vehicle. The present invention relates to an electronic control device having the external load interface circuit, and a drive voltage switching method in the external load interface circuit.

  In general, an electronic control device having a microcomputer and an ASIC (Application Specific Integrated Circuit) is provided in a moving body such as a vehicle. Such an electronic control device is usually called an ECU (Electronic Control Unit). In this ECU, when it is detected that a collision of a vehicle or the like has occurred, in order to reduce the influence of the collision of such a vehicle or the like as much as possible, an electronic controlled device (for example, It is required that the fail-safe process is executed by correctly controlling an air bag, an electronically controlled engine, or the like). Here, “fail-safe processing” refers to damage caused by collision or failure by causing the electronically controlled device in the moving body to act on the safe side in the event of a vehicle collision or some failure in the ECU. It means to perform processing to minimize the.

  For example, an external load composed of various external sensors such as a Hall effect element sensor is provided outside the airbag ECU for controlling the airbag. This external load has a function of detecting an event related to the occurrence of a collision of a vehicle or the like. Further, an external load interface circuit for supplying a driving voltage necessary for the external load is mounted as an ASIC. Here, in order to make it easy to understand the problems related to the conventional external load interface circuit, the configuration of the conventional external load interface circuit will be described with reference to the attached drawing (FIG. 1).

  FIG. 1 is a block diagram showing a configuration of a conventional external load interface circuit. However, in FIG. 1, the structure of the conventional external load interface circuit mounted as ASIC10 in moving bodies, such as a vehicle, is simplified and shown. Here, only the features of the main part of the conventional external load interface circuit will be described briefly, and the details of the configuration of each part of the external load interface circuit will be described later. [Best Mode for Carrying Out the Invention] It will be explained in the section.

  As shown in FIG. 1, an ECU 90 such as an airbag ECU incorporates an ASIC 10 and a microcomputer 9 connected to the ASIC 10. As the ASIC 10, a conventional external load interface circuit is mounted. Further, an external load including an external sensor SEext such as a Hall effect element sensor is provided outside the ECU 90. The external sensor SEext is connected to an external terminal of the ASIC 10 via an external resistor Rext and an external capacitor Cext. In general, a plurality of types of external sensors can be considered as the external sensor SExt. Here, when a collision of a vehicle or the like occurs, a Hall effect element sensor for detecting whether or not the seat belt is operating normally Is shown as a representative.

  The conventional external load interface circuit of FIG. 1 recognizes a communication signal COMIN in the serial communication format including input information of various control commands input from the microcomputer 9 and performs bidirectional communication with the microcomputer 9. The serial communication unit 7 is provided, and the constant voltage control unit 4 outputs a drive voltage corresponding to the reference voltage Vref in accordance with the on / off control signal Soc from the serial communication unit 7. The drive voltage sent from the operational amplifier 40 in the constant voltage control unit 4 includes a drive voltage output transistor 50 such as an n-channel MOS transistor (hereinafter abbreviated as nMOS transistor), an external resistor Rext, and a capacitor Cext. Via, it is supplied to an external sensor SEext such as a Hall effect element sensor. Here, the voltage value of the drive voltage is determined by the operation power supply unit 53 including the operation power supply connected to the ECU internal power supply VBACK, the power supply side resistor 55, the drive voltage output transistor 50, the output side resistor 51, and the drive voltage setting transistor 52. The voltage value suitable for driving the external sensor SExt is set in advance.

  Further, the external load interface circuit of FIG. 1 includes a load current detection unit 7 for detecting a load current flowing through the external sensor Sext. The load current detection unit 7 includes a current mirror amplifier 70, a mirror current detection transistor 72, and resistors 71 and 73, detects a mirror current proportional to the load current flowing through the external sensor Sext, and detects the load current. It has a function of sending to the load current detection resistor 75 and the load current detection capacitor 76 via the terminal (SWREF). Finally, by inputting the voltage between both terminals of the load current detection resistor 75 to the microcomputer 9, it is possible to confirm the change in the load current flowing through the external sensor Sext.

  In general, when a vehicle collision occurs, the seat belt is actuated by the action of an electromagnet or the like, and a relatively large tension is instantaneously applied to the seat belt to fix the occupant to the seat. For example, when a Hall effect element sensor is provided as the external sensor SEext in the vicinity of the seat belt, the current flowing through the Hall effect element sensor changes due to a change in the magnetic field in the vicinity of the seat belt due to the action of an electromagnet or the like. The microcomputer 9 detects that the seat belt is operating normally by a change in the current flowing through the Hall effect element sensor, and determines that a collision of the vehicle or the like has occurred based on the detection result. Based on such a determination result by the microcomputer 9, an electronic controlled device such as an airbag or an electronically controlled engine (none of which is shown) is correctly controlled (for example, the ignition timing of the airbag, the electronic control) The fail-safe process can be executed by appropriately controlling the fuel injection amount of the engine.

  Further, in the external load interface circuit of FIG. 1, the drive voltage of the external sensor SExt and the voltage values of several voltages 81 in the ECU are switched according to a multiplexer control unit (abbreviated as MPX control unit in FIG. 1) 84. A multiplexer 8 to be selected (abbreviated as MPX in FIG. 1) is formed. By inputting a multiplexer output voltage that can be switched from the multiplexer 8 according to the multiplexer control unit 84 to the microcomputer 9 via the multiplexer output terminal (MPXOUT), an arbitrary output voltage corresponding to the multiplexer output voltage can be obtained. Whether it is normal or not can be diagnosed.

  Generally, in a moving body such as a vehicle, when a vehicle collision occurs, the electronic device to be controlled such as an airbag or an electronically controlled engine is more accurately controlled to execute the fail-safe process quickly and accurately. In order to be able to do so, a plurality of types of external sensors such as a resistive load sensor are provided in addition to the Hall effect element sensor. Usually, the drive voltage required to drive these external sensors differs depending on the type of external sensor.

  However, since the conventional external load interface circuit as shown in FIG. 1 is configured to output only a predetermined driving voltage, one type of external sensor (for example, Hall effect element sensor) is configured. It was possible to cope only with. In other words, in order to supply drive voltages necessary for a plurality of types of external sensors, it is necessary to form an ASIC by mounting a plurality of external load interface circuits respectively corresponding to all types of external sensors. Come.

  Therefore, in the conventional external load interface circuit, the occupying area of the ASIC is increased, and the manufacturing process for manufacturing the ASIC is increased, resulting in an increase in manufacturing cost.

  Here, for reference, two prior art documents (Patent Document 1 and Patent Document 2) describing technical contents related to a conventional external load interface circuit are presented.

  In Patent Document 1 (Japanese Patent Laid-Open No. 5-197420), in a driving means for driving a load, a load driving output terminal and a load abnormality detection input terminal are shared by one terminal. A configuration of a load driving device that reduces the number of terminals of the processing circuit as the driving means is disclosed.

  Patent Document 2 (Japanese Patent Laid-Open No. 2005-17091) has a function of operating a vehicle device in accordance with a control command supplied from the outside, so that the number of input / output terminals is reduced and the chip size is reduced. A configuration of an integrated circuit device for a vehicle device is disclosed.

  However, in both Patent Document 1 and Patent Document 2, an external load interface capable of supporting a plurality of types of external sensors provided outside the ECU without increasing the chip size or the like of the integrated circuit. It does not mention a specific technique for providing a circuit. Therefore, both Patent Document 1 and Patent Document 2 still have the same problems as those of the conventional external load interface circuit as described above.

JP-A-5-197420 JP 2005-17091 A

  The present invention has been made in view of the above problems, and in order to more accurately control electronic controlled devices and to perform fail-safe processing quickly and accurately in the event of a collision of a vehicle or the like, External load interface circuit, electronic control device, and external load interface circuit capable of dealing with external loads composed of a plurality of types of external sensors provided outside the ECU without increasing the occupied area and manufacturing cost It is an object of the present invention to provide a driving voltage switching method.

  In order to solve the above problems, the present invention has a function of supplying a drive voltage for driving an external load to the external load in accordance with a control command input from a microcomputer, and according to the type of the external load. An external load interface circuit (ie, ASIC) configured to switch a plurality of drive voltages is provided.

  Further, preferably, by switching between a reference voltage generated inside the external load interface circuit of the present invention and an arbitrary external voltage applied to the external terminal, the corresponding driving voltage is output. It is supposed to be.

  Further preferably, in the external load interface circuit of the present invention, switching information for switching the driving voltage is assigned to the control command, and control for switching the driving voltage is performed.

  Further, preferably, in the external load interface circuit of the present invention, an arbitrary external voltage applied to the external terminal is output from the multiplexer, and an abnormality of the arbitrary external voltage can be diagnosed.

  Further preferably, in the external load interface circuit of the present invention, the external load interface circuit has a function of sending a divided voltage value obtained by dividing the drive voltage to the microcomputer, and based on the divided voltage value, the drive It is possible to diagnose whether the voltage is switched normally.

  Further preferably, in the external load interface circuit of the present invention, when the divided voltage value is switched by the on / off operation of a plurality of control channels respectively corresponding to the plurality of external loads, each of the control channels is turned on. It is possible to determine whether or not the drive voltage is normal during the period, and to detect a power fault of the external load during the off-state.

  Further preferably, in the external load interface circuit of the present invention, a load current detection unit for detecting a load current flowing through the external load is shared by a plurality of control channels.

  Further, preferably, the operating power supply for operating the external load interface circuit of the present invention is connected to a power supply boosted from the voltage of the battery power supply, and when one external load is in a power fault, The detection performance is not affected.

  Further, preferably, in the external load interface circuit of the present invention, the external load interface circuit has a function of monitoring the voltage of the boosted power supply, and the detection performance of the other external load at the time of a fault of one of the external loads When it is detected that the voltage has dropped to an abnormal voltage, the supply of the drive voltage to the external load is stopped.

  Furthermore, preferably, in the external load interface circuit of the present invention, the drive voltage to the external load is only detected when a decrease in the voltage of the boosted power supply and a power supply fault of any one of the external loads are detected. The supply is stopped.

  Furthermore, the present invention provides an electronic control device (ie, ECU) including the external load interface circuit configured as described above and a microcomputer connected to the external load interface circuit.

  Furthermore, the present invention provides an external load interface circuit for supplying a drive voltage for driving an external load to the external load in accordance with a control command input from a microcomputer, wherein a plurality of drive voltages are set according to the type of the external load. Provided is a drive voltage switching method in an external load interface circuit for switching.

  In summary, according to the present invention, when driving a plurality of types of external loads (for example, a plurality of types of external sensors such as a Hall effect element sensor and a resistance load sensor) in accordance with a control command input from a microcomputer in the moving body. In addition, a plurality of drive voltages are switched in accordance with the types of these external loads within one external load interface circuit to supply the external loads corresponding to the drive voltages.

  Preferably, in the present invention, switching is performed between a single or a plurality of reference voltages generated inside one external load interface circuit and an arbitrary external voltage applied to an external terminal, and each corresponds. Drive voltage is output.

  Therefore, according to the present invention, an ASIC is formed by mounting one external load interface circuit corresponding to a plurality of types of external loads by switching a plurality of drive voltages inside the external load interface circuit. Therefore, in the event of a collision of a vehicle or the like, the electronic controlled device is more accurately controlled to execute the fail-safe process quickly and accurately, and the ASIC occupying area and manufacturing than the conventional external load interface circuit are possible. Costs can be saved.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings (FIGS. 2 to 5).

  FIG. 2 is a block diagram showing a configuration of an external load interface circuit according to an embodiment of the present invention. However, here, the configuration of the external load interface circuit according to the above-described embodiment that is mounted as the ASIC 10 in a moving body such as a vehicle is simplified. Hereinafter, the same components as those described above are denoted by the same reference numerals.

  As shown in FIG. 2, an ECU 90 such as an airbag ECU incorporates an ASIC 10 and a microcomputer 9 connected to the ASIC 10. As the ASIC 10, an external load interface circuit according to an embodiment of the present invention is mounted. Further, an external load including a plurality of types of external sensors such as a Hall effect element sensor and a resistance load sensor is provided outside the ECU 90. However, here, as the plurality of types of external sensors, only the three types of external sensors of the first sensor SE1, the second sensor SE2, and the third sensor SE3 are shown as representatives.

  In accordance with an instruction from the microcomputer 9 in the ECU 90, one of the first sensor SE1, the second sensor SE2, and the third sensor SE3 is selected, and is externally attached to the ASIC 10. It is connected to the switching external terminal (SWOUT1, SWOUT2, or SWOUT2) of the ASIC 10 via a resistor (R1, R2, or R3) and an external capacitor C1, C2, or C3). At the present time, the first sensor SE1 is connected to the switching external terminal SWOUT1 of the ASIC 10 via the external resistor R1 and the external capacitor C1. An external sensor connected to the terminal can be switched from the first sensor SE1 to the second sensor SE2 or the third sensor SE3.

  The external load interface circuit according to the embodiment of FIG. 2 recognizes the communication signal COMIN in the serial communication format including the input information of various control commands input from the microcomputer 9 as in the case of FIG. A serial communication unit 7 that performs bidirectional communication with the microcomputer 9, and a constant voltage control unit 4 that outputs a drive voltage corresponding to the reference voltage Vref in accordance with an on / off control signal Soc from the serial communication unit 7. It has.

  Here, when bidirectional communication is performed between the microcomputer 9 and the serial communication unit 7, the clock signal COMCLK, the chip enable signal CE, and the communication signal COMIN in the serial communication format, which are the basis of communication, are stored in the microcomputer. 9 is transferred to the serial communication unit 7, and a serial communication communication signal COMOUT for notifying the microcomputer 9 of an abnormality in the ECU is transferred from the serial communication unit 7 to the microcomputer 9.

  Further, in the external load interface circuit according to the embodiment of FIG. 2, the constant voltage control unit 4 has an operational amplifier 40. The non-inverting input terminal (+) of the operational amplifier 40 is connected to the reference voltage switching setting unit 2 for generating the switchable reference voltage Vref, and the inverting input terminal (−) of the operational amplifier 40 has three types. Are connected to the input side control channel switching unit 3 for switching the input side control channel in correspondence with any one of the external sensors. On the other hand, the output terminal of the operational amplifier 40 is connected to the output-side control channel switching unit 5 that switches the output-side control channel corresponding to any one of the three types of external sensors. Further, the output terminal of the operational amplifier 40 is connected to the inverting input terminal (−) of the operational amplifier 40 via the output side control channel switching unit 5 and the input side control channel switching unit 3. In such a configuration, the operational amplifier 40 has a voltage gain of about 1 time, and the voltage value of the drive voltage output from the operational amplifier 40 is substantially equal to the voltage value of the reference voltage Vref.

  Here, the reference voltage switching setting unit 2 connected to the non-inverting input terminal (+) of the operational amplifier 40 generates three types of reference voltages Vref for driving the three types of external sensors. It should be noted that the corresponding drive voltage is output from the output terminal of the operational amplifier 40 by appropriately switching the type of reference voltage.

  Furthermore, the external load interface circuit according to the embodiment of FIG. 2 includes a drive voltage switching control unit 1 that performs control to switch a plurality of drive voltages according to the type of external sensor selected by an instruction from the microcomputer 9. Yes. When one of the three types of external sensors is selected in accordance with an instruction from the microcomputer 9, an external load selection signal (included in the communication signal COMIN) indicating that the external sensor has been selected is serially displayed. It is supplied from the communication unit 7 to the drive voltage switching control unit 1. Here, the drive voltage switching control unit 1 sends the drive voltage switching control signal Sds corresponding to the external load selection signal to the reference voltage switching setting unit 2, so that the currently selected external sensor (for example, the first sensor) The reference voltage switching setting unit 2 is controlled to switch to the reference voltage Vref corresponding to the sensor SE1).

  At this time, the input side control channel switching unit 3 corresponds to the currently selected external sensor (for example, the first sensor SE1) based on the input side control channel switching signal Schi supplied from the serial communication unit 7. Then, the input side control channel (for example, the first input side control channel) is switched. On the other hand, the output side control channel switching unit 5 corresponds to the currently selected external sensor (for example, the first sensor SE1) based on the output side control channel switching signal Scho supplied from the serial communication unit 7. Then, the output side control channel (for example, the first output side control channel) is switched. In this manner, by switching the input side control channel and the reference voltage Vref according to the type of the external sensor selected by the instruction of the microcomputer 9, the drive voltage corresponding to the currently selected external sensor is changed to the output side. The data is output from the corresponding output side control channel of the control channel switching unit 5.

  Furthermore, the external load interface circuit according to the embodiment of FIG. 2 includes first drive voltage output transistors 50-1 to 50-1 having gates respectively connected to the first output side control channel to the third output side control channel. Three drive voltage output transistors 50-3 and first outputs connected between the sources of the first drive voltage output transistors 50-1 to 50-3 and the third drive voltage output transistors 50-3 and the ground, respectively. Side resistor 51-1 to third output side resistor 51-3 and first drive voltage setting transistor 52-1 to third drive voltage setting transistor 52-3. Preferably, each of the first driving voltage output transistor 50-1 to the third driving voltage output transistor 50-3 is configured by an nMOS transistor, and the first driving voltage setting transistor 52-1 to the third driving voltage setting transistor 52-1 The drive voltage setting transistor 52-3 is composed of a bipolar npn transistor.

  Further, the drains of the first drive voltage output transistor 50-1 to the third drive voltage output transistor 50-3 are connected to the operation power supply unit 53 via the reverse current prevention diode 54 and the power supply side resistor 55. Is done. The operation power supply unit 53 includes an operation power supply connected to the ECU internal power supply VBACK. Based on the ECU internal power supply VBACK, a voltage necessary for operating each part of the external load interface circuit is generated by this operating power supply.

  For example, when the first sensor SE1 is selected, the corresponding drive voltage is output from the first output side control channel (or the first input side control channel) of the output side control channel switching unit 5, One drive voltage output transistor 50-1, an external resistor R1, and an external capacitor C1 are supplied to the first sensor SE1. On the other hand, when the second sensor SE2 is selected, the corresponding drive voltage is output from the second output side control channel (or the second input side control channel), and the second drive voltage output transistor 50-2, the external resistor R2, and the external capacitor C2 are supplied to the second sensor SE2. On the other hand, when the third sensor SE3 is selected, the corresponding drive voltage is output from the third output side control channel (or the third input side control channel), and the third drive voltage output transistor is output. 50-3, the external resistor R3, and the external capacitor C3 are supplied to the third sensor SE3.

  Here, the voltage values of the three types of driving voltages are as follows: the operating power supply unit 53, the power supply side resistor 55, the first driving voltage output transistor 50-1 to the third driving voltage output transistor 50-3, and the first driving voltage output transistor 50-3. The first sensor SE1 to the third sensor 51-3 are output by the output-side resistor 51-1 to the third output-side resistor 51-3 and the first drive voltage setting transistor 52-1 to the third drive voltage setting transistor 52-3. The voltage value is set in advance so as to be suitable for driving each sensor SE3.

  Furthermore, the external load interface circuit according to the embodiment of FIG. 2 includes a load current detector 7 for detecting the load current flowing through the first sensor SE1 to the third sensor SE3. The load current detection unit 7 includes a current mirror amplifier 70, a mirror current detection transistor 72, and resistors 71 and 73. Here, the load current detection unit 7 includes the first output side control channel to the third output side control channel (or the first input side control channel) corresponding to the first sensor SE1 to the third sensor SE3, respectively. Note that it is shared for the third input side control channel).

  In such a shared load current detection unit 7, a mirror voltage Vmir proportional to a load current flowing through an external load such as the first sensor SE 1, the second sensor SE 2, or the third sensor SE 3 is generated from the power supply side resistor 55. The current is input to the non-inverting input terminal (+) of the current mirror amplifier 70. By setting the mirror voltage Vmir to an appropriate voltage value, a mirror current having a load current reduced to 1 / n (n is an arbitrary positive integer: for example, n = 50) is detected by the current mirror amplifier 70. The Such a mirror current corresponding to 1 / n of the load current includes a mirror current detection transistor 72 such as a p-channel MOS transistor (usually abbreviated as a pMOS transistor), a resistor 73, and a 5V clamp unit (a reference voltage of 5V). Via the load current detection terminal (SWREF) to the load current detection resistor 75 and the load current detection capacitor 76. Finally, the voltage between the two terminals of the load current detection resistor 75 (that is, the load current detection voltage) is input to the A / D (analog / digital) port of the microcomputer 9, thereby the first sensor SE1, A change in load current flowing through an external load such as the second sensor SE2 or the third sensor SE3 can be confirmed.

  Here, when a collision of a vehicle or the like occurs, the seat belt is actuated by the action of an electromagnet or the like, and a relatively large tension is instantaneously applied to the seat belt to fix the occupant to the seat. For example, when a Hall effect element sensor is provided in the vicinity of the seat belt as the first sensor SE1, the current flowing through the Hall effect element sensor changes due to a change in the magnetic field in the vicinity of the seat belt due to the action of an electromagnet or the like. The microcomputer 9 detects that the seat belt is operating normally by a change in the current flowing through the Hall effect element sensor, and determines that a collision of the vehicle or the like has occurred based on the detection result. Furthermore, the microcomputer 9 can easily detect an event related to the occurrence of a collision of a vehicle or the like with respect to another external sensor (for example, a resistance load sensor). Based on the determination results of the plurality of types of external sensors by the microcomputer 9 as described above, the electronic controlled device such as an air bag and an electronically controlled engine (none of which are shown) is controlled more accurately (for example, The fail-safe process can be executed quickly and accurately by appropriately controlling the ignition timing of the airbag and the fuel injection amount of the electronically controlled engine.

  Until now, the drive voltage switching control unit 1 outputs the corresponding drive voltage by switching the reference voltage Vref of the reference voltage switching setting unit 2, but alternatively, within the predetermined voltage range. It is also possible to store the plurality of drive voltages in the drive voltage switching control unit 1 and select and output one of these drive voltages so as to be switchable.

  Further, the external load interface circuit according to the embodiment of FIG. 2 is a multiplexer (in FIG. 2, abbreviated as MPX) that switches and selects the driving voltage of the first sensor SE1 to the third sensor SE3 and other various output voltages. 8) and a multiplexer control unit (abbreviated as MPX control unit in FIG. 2) 84 for controlling the switching selection operation of the multiplexer 8 in accordance with the multiplexer control signal Smp from the microcomputer 9.

  More specifically, in the multiplexer 8, the 5V clamp unit 30 from the first output side control channel to the third output side control channel (or the first input side control channel to the third input side control channel) and In addition to the driving voltages of the first sensor SE1 to the third sensor SE3 input via a multiplexer channel switching unit (abbreviated as MPX channel switching unit in FIG. 2), several voltages 81 inside the ECU The multiplexer output voltage (for example, the first sensor SE1 to the third sensor SE3 is selected from the multiplexer 8 in accordance with the multiplexer control unit 84). Drive voltage, or voltage values of some other voltages 81 inside the ECU), buffer 85 and multiplexer outputs A child (MPXOUT) is input to the A / D port of the microcomputer 9. In the microcomputer 9, it is diagnosed whether any output voltage corresponding to the multiplexer output voltage is normal. it can.

  Heretofore, a configuration has been described in which three types of driving voltages for driving the three types of external sensors, the first sensor SE1 to the third sensor SE3, are switched and output. Of course, it is also possible to employ a configuration in which four or more types of drive voltages for driving four or more types of external sensors are switched and output.

  According to the embodiment of FIG. 2, a single external load interface circuit corresponding to an external load such as a plurality of types of external sensors is mounted by switching a plurality of drive voltages inside the external load interface circuit. Since the ASIC can be formed, the area occupied by the ASIC and the manufacturing cost can be reduced as compared with the conventional external load interface circuit.

  Preferably, in the embodiment of FIG. 2, the operation power supply of the operation power supply unit 53 of FIG. 2 can be configured to be connected to the ECU internal power supply VBACK boosted from the voltage of the battery power supply. Generally, the voltage value of the driving voltage of the external sensor is about 5V (volt), and the voltage value of the boosted power supply is set to a voltage value much higher than 5V. In such a configuration, even when one external sensor has a power fault, it is connected to the boosted ECU internal power supply, so that the power supply voltage does not decrease, and the detection performance of other external sensors It will be possible to avoid affecting.

  Furthermore, preferably, in the embodiment of FIG. 2, the operation power supply unit 53 in the external load interface circuit can have a function of monitoring the voltage of the boosted power supply. Here, when the operating power supply 53 detects that a certain external sensor has fallen to a voltage causing an abnormality in the detection performance of the other external sensor, the drive voltage to the other external sensor is detected. It is also possible to configure so as to stop the supply.

  Alternatively, as an alternative example, the drive voltage is supplied to the other external sensor only when a drop in the voltage of the boosted power source is detected and a power supply fault of one external load is detected. It can also be configured to stop.

  FIG. 3 is a block diagram showing a configuration of an external load interface circuit according to another embodiment of the present invention. However, also here, the configuration of the external load interface circuit according to the above-described embodiment that is mounted as the ASIC 10 in a moving body such as a vehicle is simplified and shown.

  The configuration of the external load interface circuit according to the embodiment of FIG. 3 is substantially the same as the configuration of the external load interface circuit of FIG. However, in the external load interface circuit of FIG. 3, between the reference voltage generated by the reference voltage switching setting unit 2a of the external load interface circuit and any external voltage applied from the external voltage generation unit 20 to the external terminal. And a divided voltage value obtained by dividing the drive voltages of the first sensor SE1 to the third sensor SE3 by the load-side channel switching unit 56 and the external load abnormality detection unit 57. 2 is different from the aforementioned external load interface circuit shown in FIG.

  Therefore, in the external load interface circuit according to the embodiment of FIG. 3, the description of the same configuration as that of the external load interface circuit of FIG. 2 is omitted, and functions different from those of the external load interface circuit of FIG. Only the part which has is demonstrated.

  As described above, the external load interface circuit according to the embodiment of FIG. 3 is applied to the reference voltage Vref generated by the reference voltage switching setting unit 2a of the external load interface circuit and the external voltage generation unit 20 to the external terminal. It has a function of switching between any external voltage.

  More specifically, the external load interface circuit according to the embodiment of FIG. 3 includes an external voltage generating unit 20 that generates an arbitrary external voltage other than the reference voltage Vref, and a reference voltage switching setting unit 2a that amplifies the external voltage. And an amplifying unit 21 for sending out the signal. The external voltage generated by the external voltage generation unit 20 is input to the amplification unit 21 via an external terminal. In the amplifying unit 21, the external voltage is amplified with a preset gain (magnification) and sent to the reference voltage switching setting unit 2a.

  The drive voltage switching control unit 1 in FIG. 3 sends three types of external sensors (for example, the first sensor SE1 to the third sensor SE3) by sending a drive voltage switching control signal Sds to the reference voltage switching setting unit 2a. Is controlled to select any one of the three types of reference voltages Vref corresponding to each of the reference voltages Vref, and an arbitrary external voltage supplied from the external voltage generation unit 20 to the reference voltage switching setting unit 2a via the amplification unit 21. Control to select the voltage is also performed. The above three types of reference voltages Vref are selected by the first input side control channel to the third input side control channel, respectively, and the above arbitrary external voltages are selected by the fourth input side control channel. The

  Here, an arbitrary external voltage applied to the external terminal from the external voltage generation unit 20 is applied to the 5V clamp unit 30 and the multiplexer channel switching unit 80 in the same manner as the drive voltages of the first sensor SE1 to the third sensor SE3. To the multiplexer 8. Further, the above arbitrary external voltage is selectively output from the multiplexer 8 according to the multiplexer control unit 84, and is input to the A / D port of the microcomputer 9 through the buffer 85 and the multiplexer output terminal (MPXOUT). Finally, in the microcomputer 9, it is possible to diagnose whether or not any of the above external voltages is normal.

  On the other hand, as described above, the external load interface circuit according to the embodiment of FIG. 3 uses the load side channel switching unit 56 and the external load abnormality detection unit 57 to drive the first sensor SE1 to the third sensor SE3. It has a function of sending a divided value obtained by dividing the voltage to the microcomputer.

  More specifically, the external load interface circuit according to the embodiment of FIG. 3 switches three types of driving voltages respectively corresponding to three types of external sensors (for example, the first sensor SE1 to the third sensor SE3). A load-side channel switching unit 56 to be selected and an external load abnormality detecting unit 57 that detects an abnormality of the external sensor by dividing the drive voltage selected by the load-side channel switching unit 56 are provided.

  Here, the drive voltage selected by the load-side channel switching unit 56 based on the output-side control channel switching signal Scho is divided by the pair of voltage dividing resistors 58 and 59 in the external load abnormality detection unit 57. A predetermined partial pressure value is obtained. The partial pressure value obtained in this way is input to the microcomputer 9. Finally, in the microcomputer 9, it is possible to diagnose whether or not the drive voltage is normally switched based on the above-mentioned divided voltage value.

  In the embodiment of FIG. 3, a configuration has been described in which three types of driving voltages for driving the three types of external sensors are switched and output. However, naturally, four or more types of driving voltages are output. It is also possible to employ a configuration in which four or more types of drive voltages for driving each external sensor are switched and output.

  According to the embodiment of FIG. 3, a plurality of reference voltages generated inside the external load interface circuit are switched, and a plurality of types of external sensors and the like are switched by switching between arbitrary external voltages. Since an ASIC can be formed by mounting a single external load interface circuit corresponding to the external load, it is possible to reduce the occupied area and manufacturing cost of the ASIC as compared with the conventional external load interface circuit. .

  FIG. 4 is a data format diagram showing a state in which switching information is assigned to the external load interface circuit control command used in the present invention.

  Here, the control commands for the external load interface circuit included in the communication signal in the serial communication format in the above-described embodiments of FIGS. 2 and 3 are used to switch various drive voltages according to the type of the external sensor. Switching information is assigned.

  More specifically, the control command for the external load interface circuit includes various types of switching information such as on / off control information, control channel switching information, and drive voltage switching information in addition to the control command bits for the external load interface circuit. . Here, the on / off control information is a control for turning on or off a plurality of input side control channels (or output side control channels) (that is, whether or not each input side control channel is selected). Information in a bit format for performing, control channel switching information is information in a bit format for switching and selecting a plurality of input side control channels (or output side control channels), and a plurality of drive voltage switching information Information in a bit format for switching and selecting a plurality of drive voltages respectively corresponding to external sensors of the above types.

  In the external load interface circuit according to the embodiment of the present invention, the switching information in the bit format as described above is read by a serial communication unit (for example, see FIG. 2), so that a plurality of drive voltages are provided according to the type of external sensor. Can be easily supplied to an external sensor corresponding to the drive voltage.

  FIG. 5 is a timing chart for explaining the on / off control and drive voltage switching of each control channel according to the present invention. Here, according to the control command for the external load interface circuit shown in FIG. 4 described above, control is performed to turn on or off a plurality of input side control channels (or output side control channels), or a plurality of drive voltages are switched. The manner of doing this will be described with reference to a timing chart.

  FIG. 5A illustrates input information of a control command input to the serial communication unit (for example, see FIG. 2) of the external load interface circuit. FIG. 5B shows output information of a control command output from the serial communication unit (for example, see FIG. 2) of the external load interface circuit.

  Further, FIGS. 5C to 5E show changes in voltage values of three types of drive voltages respectively output from the ASIC switching external terminals (SWOUT1, SWOUT2, and SWOUT3).

  FIG. 5 (f) shows a change in the voltage value of the load current detection voltage inputted from the load current detection terminal (SWREF) of the ASIC to the A / D port of the microcomputer.

  FIG. 5G shows how the voltage value of the multiplexer output voltage inputted from the multiplexer output terminal (MPXOUT) of the ASIC to the A / D port of the microcomputer is changed.

  Here, based on the input information and output information of the control command in FIG. 5A, each input side control channel is turned on (ie, selected) or turned off (ie not selected). The control for switching the drive voltage corresponding to each input side control channel is executed (see (c) to (e) of FIG. 5). As such an input side control channel, as described in the embodiment of FIG. 3, in addition to the first input side control channel (CH # 1) to the third input side control channel (CH # 3), a fourth Input side control channels (CH # 4) are also included. In FIGS. 5C to 5E, for the sake of simplicity, the first input side control channel to the third input side control channel are included. Only the state of changes in the voltage values of the three types of drive voltages respectively output from the switching external terminals (SWOUT1, SWOUT2, and SWOUT3) is shown.

  As is clear from (c) to (e) of FIG. 5, during the period in which each input-side control channel is on (that is, during the selected period), a high voltage value voltage is output. During a period in which each input-side control channel is in an off state (that is, a period during which each input-side control channel is not selected), a low voltage value is output.

  Further, as shown in FIG. 5 (f), during the period in which each input-side control channel is in the ON state, the load current detection voltage when each input-side control channel is ON is the load current detection terminal ( SWREF) is input to the A / D port of the microcomputer. In this microcomputer, it is possible to determine whether or not the drive voltage corresponding to each input side control channel is normally output by detecting whether or not the load current detection voltage is normal. .

  Further, as shown in FIG. 5 (g), during the period in which each input side control channel is in the OFF state, the multiplexer output voltage when each input side control channel is OFF is the multiplexer output terminal (MPXOUT). To the A / D port of the microcomputer. In this microcomputer, by detecting whether or not the voltage value of the multiplexer output voltage is changing normally, it is possible to detect the power supply fault of the external sensor corresponding to each input side control channel.

  The external load interface circuit, the electronic control device, and the drive voltage switching method in the external load interface circuit of the present invention are provided in a moving body such as a vehicle in order to control an electronic controlled device such as an airbag or an electronically controlled engine. It can be applied to other ECUs. In particular, the drive voltage switching method in the external load interface circuit, the electronic control device, and the external load interface circuit according to the present invention is a damage caused by a collision or a failure when a vehicle or the like or some failure occurs in a part of the ECU. In order to minimize the error, the electronic controlled device in the moving body can be used in a computer system for quickly and accurately performing the fail-safe process.

It is a block diagram which shows the structure of the conventional external load interface circuit. It is a block diagram which shows the structure of the external load interface circuit which concerns on one Embodiment of this invention. It is a block diagram which shows the structure of the external load interface circuit which concerns on other embodiment of this invention. It is a data format figure which shows the state which allocated switching information to the control command for external load interface circuits used for this invention. It is a timing chart for demonstrating the mode of ON / OFF control of each control channel of this invention, and drive voltage switching.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Drive voltage switching control part 2 Drive voltage switching setting part 2a Drive voltage switching setting part 3 Input side control channel switching part 4 Constant voltage control part 5 Output side control channel switching part 7 Serial communication part 8 Multiplexer 9 Microcomputer 10 ASIC
DESCRIPTION OF SYMBOLS 20 External voltage generation part 21 Amplification part 40 Operational amplifier 50-1 1st drive voltage output transistor 50-2 2nd drive voltage output transistor 50-3 3rd drive voltage output transistor 53 Operation | movement power supply part 56 Load side channel switching Unit 57 external load abnormality detection unit 70 current mirror amplifier 72 mirror current detection transistor 80 multiplexer channel switching unit 84 multiplexer control unit 85 buffer 90 ECU (electronic control unit)

Claims (12)

In an external load interface circuit for supplying a drive voltage for driving an external load in accordance with a control command input from a microcomputer to the external load,
An external load interface circuit configured to switch a plurality of drive voltages in accordance with a type of the external load.   By switching between a reference voltage generated inside the external load interface circuit and an arbitrary external voltage applied to the external terminal, the corresponding driving voltage is output. The external load interface circuit according to claim 1.   3. The external load interface circuit according to claim 1, wherein switching information for switching the drive voltage is assigned to the control command to perform control to switch the drive voltage.   3. The external load interface circuit according to claim 2, wherein an arbitrary external voltage applied to the external terminal is output from a multiplexer, and abnormality of the arbitrary external voltage can be diagnosed.   It has a function of sending a divided voltage value obtained by dividing the drive voltage to the microcomputer, and diagnoses whether or not the drive voltage is normally switched based on the divided voltage value The external load interface circuit according to claim 2, wherein the external load interface circuit is capable of performing the operation.   Whether the drive voltage is normal during a period in which each of the control channels is on when the divided voltage value is switched by turning on / off the plurality of control channels corresponding to the plurality of external loads. 6. The external load interface circuit according to claim 5, wherein the external load interface circuit is capable of detecting a power supply fault of the external load during a period in which it is determined to be off.   7. The external load interface circuit according to claim 1, wherein a load current detection unit that detects a load current flowing through the external load is shared by a plurality of control channels. 8.   The operating power supply for operating the external load interface circuit is connected to a power supply boosted from the voltage of the battery power supply, and does not affect the detection performance of other external loads when a certain external load fails. 8. The external load interface circuit according to claim 7, wherein the external load interface circuit is configured as described above.   When it has a function of monitoring the voltage of the boosted power supply, and when it is detected that the voltage has dropped to a voltage causing an abnormality in the detection performance of the other external load at the time of a fault of one of the external loads 9. The external load interface circuit according to claim 8, wherein supply of the drive voltage to the external load is stopped.   The supply of the drive voltage to the external load is stopped only when a decrease in the voltage of the boosted power supply and a power supply fault of any one external load are detected. The external load interface circuit according to claim 9.   An electronic control device comprising: the external load interface circuit according to claim 1; and a microcomputer connected to the external load interface circuit.   An external load interface circuit that supplies a drive voltage for driving an external load to the external load in accordance with a control command input from a microcomputer, wherein a plurality of drive voltages are switched according to the type of the external load. And driving voltage switching method in external load interface circuit.

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