JP4582050B2 - Electronic control unit - Google Patents

Description

  The present invention relates to an electronic control device including two types of power supply circuits, a power supply circuit that generates a power supply voltage when a power switch is turned on, and a power supply circuit that always generates a power supply voltage regardless of the state of the power switch.

  2. Description of the Related Art Conventionally, as an engine control electronic control unit (hereinafter referred to as ECU) 50 mounted on a vehicle, as illustrated in FIG. 9, a main microcomputer (not shown) that operates when the ignition switch 4 is turned on to control the engine. (Hereinafter referred to as a main microcomputer) 12, a backup microcomputer (hereinafter referred to as a sub-microcomputer) 14 for monitoring the operation of the main microcomputer 12 when the ignition switch 4 is turned on, and holding control data when the ignition switch 4 is turned off, The one with is known.

  This type of ECU 50 receives a power supply from the battery 2 when the ignition switch 4 is turned on, generates a power supply voltage Vma, and supplies power to each part of the control system including the main microcomputer 12 (main power control unit). 16 and a power supply circuit (standby power supply control unit) that generates a power supply voltage Vst by always receiving power supply from the battery 2 regardless of the on / off state of the ignition switch 4 and supplies power to the sub-microcomputer 14 and its peripheral circuits. 22 is mounted (see, for example, Patent Documents 1 and 2).

Further, since the sub-microcomputer 14 monitors the operation of the main microcomputer 12, the sub-microcomputer 14 includes the main microcomputer 12 and peripheral devices common to the main microcomputer 12 (sensors and detection signals from the sensors as digital data). Various signals are input from an AD converter or the like to be converted), but when these input signals are captured on the sub-microcomputer 14 side, it is necessary to identify the input signals with the same reference voltage Vref as the main microcomputer 12. The same power supply voltage as the main microcomputer 12 (that is, the power supply voltage Vma from the main power supply control unit 16) is input to the sub-microcomputer 14 as the reference voltage Vref for signal input.
Japanese Patent Laid-Open No. 09-261853 JP 2000-166086 A

  By the way, in the electronic control device, in a microcomputer that can be used as a control circuit, a parasitic diode D0 is formed between the input line of the power supply voltage Vcc and the input line of the reference voltage Vref, and the reference voltage Vref is input. If the line has a higher potential than the input line of the power supply voltage Vcc and a current flows through the parasitic diode D0 in the forward direction, some may break down.

  Therefore, as shown in FIG. 9, when this type of microcomputer is used as the sub-microcomputer 14 of the electronic control device, a current flows through the parasitic diode D0 of the sub-microcomputer 14 and the sub-microcomputer 14 may fail. Conceivable.

  That is, in the electronic control device described above, the main power supply control unit 16 and the standby power supply control unit 22 are usually configured to generate the power supply voltages Vma and Vst of the same voltage (for example, 5 V). When the circuits 16 and 22 are operating normally, the sub-microcomputer 14 does not fail.

  However, when the ignition switch (in other words, the power switch) 4 is turned on, the battery voltage decreases and the power supply circuits 16 and 22 cannot generate the normal power supply voltages Vma and Vst, or when the ignition switch 4 is turned on. When the microcomputer 14 starts to write control data to the flash memory and the power consumed by the sub-microcomputer 14 exceeds the amount of power that can be supplied from the standby power control unit 22, the standby power control unit 22 It is conceivable that the power supply voltage Vst from the main power supply control unit 16 becomes lower than the power supply voltage Vma from the main power supply control unit 16 and a current flows in the forward direction to the parasitic diode D0 of the sub-microcomputer 14 and the sub-microcomputer 14 breaks down.

  In addition to the configuration described above, the ECU 50 shown in FIG. 9 also includes a power supply IC 20, a battery low voltage detection unit 24, a flash write permission unit 26, diodes D1 and D2, and the like, which will be described later. Since it is the same as the electronic control unit (ECU 10) of the embodiment, detailed description is omitted here.

  The present invention has been made in view of such problems, and in an electronic control device including two types of power supply circuits, a main power supply that operates when a power switch is turned on and a standby power supply that operates constantly, a power supply voltage from the main power supply As a reference voltage, a control circuit that operates by receiving power supply from a standby power supply is prevented from failing due to a voltage difference between power supply voltages from the power supply circuits.

  The electronic control device according to claim 1, which has been made to achieve the above object, includes two power supply circuits of a first power supply circuit and a second power supply circuit, and the first power supply circuit includes a power switch. When the power is turned on, a power supply voltage is generated, and the generated power supply voltage is supplied to the first control circuit via the first power supply line. The second power supply circuit always generates a power supply voltage regardless of the on / off state of the power switch, and supplies the generated power supply voltage to the second control circuit via the second power supply line.

  On the other hand, the first control circuit operates by receiving power supply from the first power supply circuit via the first power supply line, and takes in a signal from an external device by using the potential of the first power supply line as a reference potential. Execute control processing. The second control circuit operates by receiving power supply from the second control circuit via the second power supply line. Similar to the first control circuit, the second control circuit uses the potential of the first power supply line as a reference potential from an external device. The second control process is executed by capturing the signal.

  For this reason, when the above-described microcomputer (sub-microcomputer) is used as the second control circuit, the data to the non-volatile memory (flash memory or the like) in the second control circuit or when the power supply voltage of the external power supply is reduced. At the time of writing or the like, it is conceivable that the power supply voltage of the second control circuit decreases and a forward current flows through the parasitic diode, causing the second control circuit to fail.

  However, in the electronic control device according to claim 1, when the potential of the second power supply line is lowered by a predetermined voltage or more with respect to the potential of the first power supply line, a current flows from the first power supply line to the second power supply line. And a protection circuit for limiting a potential drop of the second power supply line with respect to the first power supply line.

  Therefore, according to the electronic control device of the present invention, even if the above-described microcomputer (sub-microcomputer) is used as the second control circuit, the second difference is caused by the potential difference generated between the first power supply line and the second power supply line. The control circuit does not fail, and the second control circuit can be protected from fluctuations in the power supply voltage.

  Here, as the protection circuit, for example, as described in claim 2, the protection circuit may be configured with a Schottky barrier diode (Shotkey Barrier Diode) provided between the first power supply line and the second power supply line. it can.

  That is, by connecting the anode of the Schottky barrier diode to the first power supply line and connecting the cathode of the Schottky barrier diode to the second power supply line, the potential of the first power supply line is shot to the potential of the second power supply line. This is limited to a potential equal to or lower than the potential obtained by adding the forward voltage Vf of the key barrier diode.

  In this case, the Schottky barrier diode can lower the forward voltage Vf as compared with a general PN diode such as a parasitic diode, and the voltage value can be appropriately selected. When the potential of the two power supply lines is lower than the potential of the first power supply line, the current is supplied from the first power supply line to the second power supply line before the current starts to flow through the parasitic diode in the second control circuit. To protect the second control circuit.

  By the way, when the power switch is turned off and the operation of the first power supply circuit is stopped, the first power supply line is in a floating state, and the first control circuit and the first control circuit connected to the first power supply line are connected. It is also conceivable that a current flows through the connected electrical load (sensor or the like), causing a problem.

  Therefore, in order to prevent such a problem, a ground circuit for grounding the first power supply line and holding the potential of the first power supply line at the ground potential when the power switch is turned off is provided as described in claim 3. You may do it.

  As the ground circuit, for example, the voltage of the power supply line that supplies power from the external power supply to the first power supply circuit is monitored, and the power switch is turned off when the voltage falls below a predetermined threshold value. It can be configured by a comparator that determines and grounds the first power supply line.

  In addition, although the Schottky barrier diode can lower the forward voltage Vf as compared with the PN diode, the reverse current increases, so that the power switch is turned off and the operation of the first power supply circuit is stopped. Sometimes, the dark current flowing from the second power supply line to the first power supply line via the Schottky barrier diode may be increased.

Therefore, in order to reduce this dark current, the protection circuit is connected in series to the Schottky barrier diode in addition to the Schottky barrier diode, and the first power supply line and the second power supply are connected to the protection circuit. Conditions under which a transistor that conducts / cuts off a current path between the power supply line and a potential difference that degrades the second control circuit may be generated between the first power supply line and the second power supply line when the power switch is turned on. And a control means for conducting the transistor.

And by doing in this way, by making the transistor conductive under a condition where a potential difference that degrades the second control circuit may occur between the first power supply line and the second power supply line when the power switch is turned on, The second control is performed by limiting the potential difference between the first power supply line and the second power supply line to a voltage equal to or lower than the voltage obtained by adding the forward voltage Vf of the Schottky barrier diode and the voltage drop (ON voltage) when the transistor is on The circuit can be protected, and when the power switch is turned off, the current path between the first power supply line and the second power supply line is interrupted by the transistor, so that the second power supply line to the first power supply line is cut off. A dark current can be prevented from flowing.

  Further, as in the device according to claim 4, the potential difference between the first power supply line and the second power supply line that occurs when the power switch is turned on is suppressed, and the first power supply is supplied from the second power supply line when the power switch is turned off. In order to prevent the dark current from flowing to the line, it is not always necessary to use a Schottky barrier diode. As described in claim 5, the protection circuit is simply composed of a transistor and a control means. Also good.

  If the protection circuit is configured in this way, the potential difference between the first power supply line and the second power supply line can be limited to be equal to or lower than the on-voltage of the transistor when the power switch is turned on. The potential difference can be further reduced as compared with the case of using.

  Here, in the device according to claim 4 or 5, the control means includes a transistor when the power supply voltage is output from the first power supply circuit to the first power supply line as described in claim 6. It is good to comprise so that it may conduct | electrically_connect.

  That is, if the control means is configured in this way, when the power supply voltage is output from the first power supply circuit to the first power supply line, the on-voltage of the transistor is between the first power supply line and the second power supply line. Or, when a potential difference exceeding the voltage obtained by adding the ON voltage and the forward voltage Vf of the Schottky barrier diode is generated, a current flows from the first power supply line to the second power supply line, and the potential difference is determined by the transistor ON voltage. Or the voltage obtained by adding the ON voltage and the forward voltage Vf of the Schottky barrier diode is limited to the following, and the second control circuit can be protected from the potential difference.

  In the device according to claim 4 or 5, the control means generates a potential difference between the first power supply line and the second power supply line so as to degrade the second control circuit when the power switch is turned on. When the power switch is turned on or when the first power supply circuit is operating, it is not always necessary to turn on the transistor continuously. As described in Item 8, the transistor may be made to conduct under a condition that a potential difference is generated between the first power supply line and the second power supply line.

  That is, when the second control circuit writes control data to a non-volatile memory such as a flash memory, the power consumption in the second control circuit may increase and the power supply voltage of the second power supply line may decrease. Thus, as described in claim 7, the control means may be configured to turn on the transistor when the second control circuit is writing data to the nonvolatile memory.

  In addition, when the supply voltage from the external power supply to each power supply circuit decreases and the power supply voltage generated in each power supply circuit decreases, the potential of the second power supply line becomes lower than the potential of the first power supply line. Therefore, as described in claim 8, the control means may be configured to turn on the transistor when the supply voltage from the external power source decreases.

Embodiments of the present invention will be described below with reference to the drawings.
[First Embodiment]
FIG. 1 is a block diagram showing a schematic configuration of an electronic control unit (ECU) 10 of a first embodiment to which the present invention is applied.

  The ECU 10 of the present embodiment is for controlling an engine mounted on an automobile. The ECU 10 operates when the ignition switch of the vehicle is turned on to control the engine, and when the ignition switch is turned on, the main microcomputer 12 A sub-microcomputer 14 that monitors the operation and retains control data when the ignition switch is turned off, and a power supply IC 20 for supplying power to these units are provided.

  Further, the ECU 10 has a battery terminal Tb directly connected to the positive electrode side of the battery 2 mounted on the vehicle, and a power supply terminal Ti connected to the positive electrode side of the battery 2 via the power switch 4 when the ignition switch is turned on. And a ground terminal Tg connected to the ground of the same potential as the negative electrode side of the battery 2, and a ground line in the ECU 10 is connected to the ground terminal Tg.

  Further, a power supply IC is connected to the battery terminal Tb via a backflow prevention diode D1 having an anode connected to the battery terminal Tb side, and a power supply IC 20 is directly connected to the power supply terminal Ti. Between the cathode side of the diode D1 in the power supply path from the battery terminal Tb to the power supply IC 20 and the power supply path from the power supply terminal Ti to the power supply IC 20, there is a backflow prevention diode D2 with the power supply terminal Ti side as an anode. It is connected.

  Next, the power supply IC 20 receives a power supply voltage (hereinafter referred to as a battery supply voltage) V (BATT) input from the battery 2 via the battery terminal Tb and the diode D1, and receives the sub-microcomputer 14 and its peripheral circuit (this) Is provided with a standby power supply control unit 22 for generating a standby power supply voltage Vst for operating the second control circuit and supplying the generated standby power supply voltage Vst to the sub-microcomputer 14 via the power supply line L2. Yes.

  Further, the ECU 10 receives a battery voltage (hereinafter referred to as IG supply voltage) V (+ B) input from the battery 2 via the power switch 4 to the power supply terminal Ti, and receives the main microcomputer 12 and its peripheral circuit (this) A main power supply voltage Vma for operating peripheral devices (sensors, etc.) connected to the main microcomputer 1 and the main power supply voltage Vma to the main microcomputer 12 and the like via the power supply line L1. A main power supply control unit 16 for supplying is also provided.

  When the IG supply voltage V (+ B) is input from the power supply terminal Ti via the power switch 4, the power supply IC 20 operates the main power supply control unit 16 to supply power to the main microcomputer 12 and its peripheral devices. Start.

  Note that the standby power supply voltage Vst and the main power supply voltage Vma generated by the standby power supply control unit 22 and the main power supply control unit 16, respectively, have the same voltage value. Only the difference. That is, the standby power control unit 22 only needs to be able to supply power for operation to the sub-microcomputer 14, and thus has a smaller power capacity than the main power control unit 16 that supplies power to the main microcomputer 12 and its peripheral devices. Yes.

  Next, the main microcomputer 12 takes in the main power supply voltage Vma supplied from the main power supply control unit 16 via the power supply line L1 as the drive voltage Vcc for its own operation, and starts engine control. In this case, the main power supply voltage Vma is also used as a reference voltage Vref for signal input, and an input signal from a peripheral device is captured.

  Further, the sub-microcomputer 14 takes in the standby power supply voltage Vst supplied from the standby power supply control section 22 via the power supply line L2 as a drive voltage Vcc for its own operation, monitors the operating state of the main microcomputer 12, and controls data. However, when the main microcomputer 12 is monitored, the same main power supply voltage Vma as that of the main microcomputer 12 is used as a reference voltage Vref for signal input, and an input signal from the main microcomputer 12 and its peripheral devices is used. Capture.

  Further, the power supply IC 20 has a battery low voltage that outputs a low voltage detection signal DI to the main microcomputer 12 and the sub microcomputer 14 when the IG supply voltage V (+ B) falls below a preset low voltage determination voltage (for example, 8V). When a data update command is input from the detection unit 24 or an external device for maintenance and inspection at the time of maintenance and inspection of the ECU 10, the flash write permission signal VPP is output to the main microcomputer 12 and the sub-microcomputer 14. A flash write permission unit 26 is also provided for permitting data writing to the flash memory provided in each of the microcomputers 12 and 14.

  Then, when the low voltage detection signal DI is input from the battery low voltage detection unit 24, each of the microcomputers 12 and 14 executes a control process that shifts from a normal control operation to a control operation when the battery voltage decreases, and the flash memory When the flash write enable signal VPP is input from the write enable unit 26, update processing is performed to write data input from an external device for maintenance and inspection to the flash memory via a bus line (not shown) and update various control data. Execute.

  By the way, when the battery low voltage detection unit 24 detects a decrease in the battery voltage (specifically, the IG supply voltage V (+ B)) or the flash write permission unit 26 outputs the flash write permission signal VPP. When the microcomputer 14 is writing data to the flash memory, or when the power supply voltages Vma, Vst fluctuate due to overshoot when the main power supply voltage Vma is generated, instantaneous interruption of the battery 2, sudden change in current consumption, etc. The standby power supply voltage Vst is lower than the main power supply voltage Vma, and a current flows in a forward direction through a parasitic diode D0 formed between the input line of the reference voltage Vref and the input line of the drive voltage Vcc of the sub-microcomputer 14. The sub-microcomputer 14 may fail.

  That is, in the automobile, since various electric loads are connected to the battery 2 in addition to the ECU 10 for engine control, the output voltage of the battery 2 temporarily decreases as the power consumption due to these electric loads increases. There is.

  Then, as shown in FIG. 7A, the output voltage of the battery 2 starts to decrease (time point t1), and the IG supply voltage V (+ B) is a low voltage determination voltage (for example, 8V) in the battery low voltage detection unit 24. (Time t2), the low voltage detection signal DI is output from the battery low voltage detection unit 24. Thereafter, the output voltage of the battery 2 further decreases, and the battery 2 supplies the power supply control units 16 and 22. Supply voltage (IG supply voltage V (+ B), battery supply voltage V (BATT)) required for generating a normal power supply voltage (5V) in each power supply control unit 16, 22 (for example, 5.5V) ), The output voltage (main power supply voltage Vma, standby power supply voltage Vst) from each of the power supply control units 16 and 22 decreases from the normal power supply voltage (5V).

  Further, the battery supply voltage V (BATT) directly supplied from the battery 2 is supplied with the IG supplied from the battery 2 via the power switch 4 because the backflow prevention diode D1 is provided in the power supply path. In the process in which the output voltage from the battery 2 decreases as the power consumption of the battery 2 increases, the forward voltage Vf (about 0.7V) of the diode D1 becomes lower than the voltage V (+ B). The power supply voltage Vst starts to decrease from the normal voltage value (5 V) earlier than the main power supply voltage Vma (see time points t3 and t4).

  Therefore, when the battery voltage is lowered, the drive voltage Vcc in the sub-microcomputer 14 becomes lower than the reference voltage Vref, and a current flows through the parasitic diode D0 in the sub-microcomputer 14 and the sub-microcomputer 14 may break down. It is.

  For example, as shown in FIG. 5A, when the sub-microcomputer 14 receives the flash write permission signal VPP from the flash write permission unit 26 and writes data to the flash memory (time t11 to time t14). In some cases, the current consumption in the sub-microcomputer 14 temporarily increases and the standby power supply voltage Vst decreases (time t12 to time t13).

  Even when the standby power supply voltage Vst drops during writing of data to the flash memory in this way, a current flows through the parasitic diode D0 in the sub-microcomputer 14 and the sub-microcomputer 14 may break down.

  In addition, when writing data to the flash memory, the current limiter of the standby power supply control unit 22 limits the supply current from the standby power supply control unit 22 to the submicrocomputer 14, so that the submicrocomputer 14 does not fail. Even in such a case, the sub-microcomputer 14 may not operate normally because the standby power supply control unit 22 cannot supply the required current Isb necessary for writing data to the flash memory on the sub-microcomputer 14 side.

  Therefore, in the ECU 10 of the present embodiment, the power line L1 side is an anode and the power line L2 side is a cathode between the power line L1 from the main power control unit 16 and the power line L2 from the standby power control unit 22. By connecting the Schottky barrier diode D3, the standby power supply voltage Vst becomes lower than the main power supply voltage Vma, and the voltage Δ (Vma−Vst) at which current begins to flow to the parasitic diode D0 in the sub-microcomputer 14 Δ Before reaching V (for example, 0.46 V), a current is passed from the power supply line L1 to the power supply line L2 by the Schottky barrier diode D3, and the potential difference (Vma−Vst) between the power supply lines L1 and L2 is set to the voltage ΔV. The voltage is limited to a predetermined potential difference that is less than a predetermined value.

  That is, in the present embodiment, the Schottky barrier diode D3 having a forward voltage Vf smaller than the voltage ΔV specific to the sub-microcomputer 14 is connected between the power supply line L1 and the power supply line L2, thereby The potential difference (Vma−Vst) with respect to the power supply line L2 is limited to a predetermined voltage or less determined by the forward voltage Vf of the Schottky barrier diode D3.

  Therefore, according to the ECU 10 of the present embodiment, it is possible to prevent the sub-microcomputer 14 from being damaged or deteriorated due to a potential difference generated between the power supply line L1 and the power supply line L2 when the power switch 4 is turned on.

In the present embodiment, the main power supply control unit 16 corresponds to the first power supply circuit of the present invention, the standby power supply control unit 22 corresponds to the second power supply circuit of the present invention, and the main microcomputer 12 and its peripheral circuits are The sub-microcomputer 14 and its peripheral circuit correspond to the second power supply circuit of the present invention, the power supply line L1 corresponds to the first power supply line of the present invention, and the power supply line L2 corresponds to the first control circuit of the present invention. It corresponds to the second power supply line of the invention, and the Schottky barrier diode D3 corresponds to the protection circuit of the invention.
[Second Embodiment]
FIG. 2 is a block diagram showing a schematic configuration of an electronic control unit (ECU) 10 of the second embodiment to which the present invention is applied.

  The ECU 10 of this embodiment is basically configured in the same manner as that of the first embodiment. The difference from the first embodiment is that the power switch 4 is turned off and the IG supply voltage V (+ B from the battery 2 is turned off. ) Is interrupted, the power supply line L1 from the main power supply control unit 16 is grounded to the ground line, and a grounding circuit is provided to prevent a malfunction due to the voltage rise of the power supply line L1.

  This ground circuit is configured around a comparator 30 that operates in response to the battery supply voltage V (BATT). Then, to-be-determined voltage obtained by dividing the IG supply voltage V (+ B) by the resistors R1 and R2 is input to the non-inverting input terminal of the comparator 30, and to the resistors R3 and R4 to the inverting input terminal of the comparator 30. The reference voltage for determination obtained by dividing the battery supply voltage V (BATT) is input, and the power supply line L1 is connected to the output terminal of the comparator 30 via the resistor R5.

  Therefore, the comparator 30 turns the power supply line L1 to the ground line via the resistor R5 when the power switch 4 is turned off and the voltage to be determined (in other words, the IG supply voltage V (+ B)) falls below the reference voltage. It will be grounded.

  Therefore, according to the comparator 30, when the power switch 4 is turned off, the voltage of the power supply line L1 is floated, so that the electrical load (peripheral devices such as the main microcomputer 12 and the sensor) connected to the first power supply line is applied. Current can flow and trouble can be prevented.

  The resistor R5 is a protection for preventing a large current from flowing into the comparator 30 from the power supply line L1 due to charges accumulated in the main power supply control unit 16 and the power supply line L1 after the power switch 4 is turned off. Resistance.

For the same purpose as this protective resistor, the other end of the capacitor C1 whose one end is grounded to the ground line is also connected to the non-inverting input terminal of the comparator 30. That is, the capacitor C1 delays the time until the output of the comparator 30 is inverted from the high level to the low level after the power switch 4 is turned off, and the charge remaining in the power line L1 and the like during the delay period. Is consumed by the electric load connected to the power supply line L1.
[Third Embodiment]
FIG. 3 is a block diagram showing a schematic configuration of an electronic control unit (ECU) 10 of a third embodiment to which the present invention is applied.

  The ECU 10 of the present embodiment is basically configured in the same manner as that of the first embodiment. The difference from the first embodiment is that between the cathode of the Schottky barrier diode D3 and the power supply line L2, This is the point that a transistor TR1 is provided for conducting / cutting off the current path between them.

  The transistor TR1 is composed of a PNP-type bipolar transistor. The emitter is connected to the cathode of the Schottky barrier diode D3, the collector is connected to the power supply line L2, and the emitter-base is connected via the resistor R6. ing.

  The base of the transistor TR1 is connected to the main microcomputer 12. During the operation of the main microcomputer 12, the transistor TR1 is controlled to be turned on by the main microcomputer 12, and the main microcomputer 12 is reduced as the main power supply voltage Vma decreases. When the transistor 12 stops operating, the transistor TR1 is turned off.

  Therefore, according to the present embodiment, the power supply line L1 by the Schottky barrier diode D3 is only supplied from the main power supply control unit 16 to the power supply line L1 when the power supply voltage capable of operating the main microcomputer 12 is supplied. The energization operation to the power supply line L2 is allowed, the potential of the power supply line L1 falls below the potential of the power supply line L2 (standby power supply voltage Vst), and the sub microcomputer 14 breaks down due to the potential difference between these power supply lines L1 and L2. When this is not done, the energization path by the Schottky barrier diode D3 can be cut off.

  Therefore, according to the present embodiment, the standby power supply voltage Vst decreases when the power switch 4 is turned on to prevent the sub-microcomputer 14 from being damaged, and the Schottky barrier diode is turned off when the power switch 4 is turned off. It is possible to prevent the dark current from flowing from the power supply line L2 to the power supply line L1 via D3, and to suppress unnecessary power consumption of the battery 2.

In the present embodiment, the main microcomputer 12 corresponds to the control means of the present invention.
[Fourth Embodiment]
FIG. 4 is a block diagram showing a schematic configuration of an electronic control unit (ECU) 10 of a fourth embodiment to which the present invention is applied.

  The ECU 10 of this embodiment is basically configured in the same manner as that of the first embodiment, and differs from the first embodiment in that a power line L1 and a power line L2 are used instead of the Schottky barrier diode D3. Is provided with a transistor TR2 for conducting / interrupting the current path between them, and the transistor TR2 is turned on by the flash write enable signal VPP output from the flash write enable unit 26. It is.

  That is, the transistor TR2 is composed of a PNP-type bipolar transistor, the emitter is connected to the power supply line L1 of the main power supply voltage Vma, the collector is connected to the power supply line L2 of the standby power supply voltage Vst, and the emitter-base is connected. Are connected via a resistor R7. The flash write permission signal VPP is input to the base of the transistor TR2 via the inverting circuit 32.

  As a result, according to the present embodiment, as shown in FIG. 5B, the flash write enable signal VPP (high level) is output from the flash write enable unit 26, and the sub-microcomputer 14 sends data to the flash memory. Is written (time t11 to time t14), the transistor TR2 is turned on, and the potential difference between the power supply lines L1 and L2 is limited to be equal to or lower than the on-voltage (for example, 0.1 V) of the transistor TR2. When the sub-microcomputer 14 writes data to the flash memory, it is possible to prevent current from flowing through the parasitic diode D0 in the sub-microcomputer 14 and failure of the sub-microcomputer 14.

  Further, when data is written to the flash memory of the sub-microcomputer 14, power can be supplied to the sub-microcomputer 14 from both the standby power control unit 22 and the main power control unit 16. By supplying the required current Isb necessary for writing data to the flash memory, the data updating operation on the sub-microcomputer 14 side can be executed normally.

In the present embodiment, the flash write permission unit 26 and the inverting circuit 32 correspond to the control means of the present invention.
[Fifth Embodiment]
FIG. 6 is a block diagram showing a schematic configuration of an electronic control unit (ECU) 10 of the fifth embodiment to which the present invention is applied.

  The ECU 10 of this embodiment is basically configured in the same manner as that of the first embodiment, and differs from the first embodiment in that a power line L1 and a power line L2 are used instead of the Schottky barrier diode D3. Is provided with a transistor TR3 for conducting / interrupting the current path between them, and this transistor TR3 is configured to be turned on by a low voltage detection signal DI output from the battery low voltage detection unit 24. is there.

  That is, the transistor TR3 is formed of a PNP-type bipolar transistor like the transistor TR2 of the fourth embodiment, the emitter is connected to the power supply line L1 of the main power supply voltage Vma, and the collector is the power supply of the standby power supply voltage Vst. It is connected to the line L2, and the emitter and base are connected via a resistor R8. The low voltage detection signal DI is input to the base of the transistor TR3 via the inverting circuit 34.

  As a result, according to the present embodiment, as shown in FIG. 7B, the IG supply voltage V (+ B) falls below the low voltage determination voltage (for example, 8V) in the battery low voltage detection unit 24, and the battery low When the low voltage detection signal DI (high level) is output from the voltage detection unit 24 (time point t2), the transistor TR3 is turned on, and the potential difference between the power supply lines L1 and L2 is changed to the ON voltage (for example, 0. 1V) or less, it is possible to prevent the sub-microcomputer 14 from being damaged due to a current flowing through the parasitic diode D0 in the sub-microcomputer 14 when the battery voltage is lowered.

In the present embodiment, the battery low voltage detection unit 24 and the inverting circuit 34 correspond to the control means of the present invention.
[Sixth Embodiment]
FIG. 8 is a block diagram showing a schematic configuration of an electronic control unit (ECU) 10 of a sixth embodiment to which the present invention is applied.

  The ECU 10 of this embodiment is basically configured in the same manner as that of the first embodiment, and differs from the first embodiment in that a power line L1 and a power line L2 are used instead of the Schottky barrier diode D3. Is provided between the power supply line L1 and the power supply line L2 so that the transistor TR4 is turned on only during the operation of the main microcomputer 12. It is the point which comprised so that it might conduct | electrically_connect.

  That is, the transistor TR4 is composed of a PNP-type bipolar transistor like the transistors TR2 and TR3 described above, the emitter is connected to the power supply line L1 of the main power supply voltage Vma, and the collector is the power supply line L2 of the standby power supply voltage Vst. The emitter and base are connected via a resistor R6. The base of the transistor TR4 is connected to the main microcomputer 12. During the operation of the main microcomputer 12, the transistor TR4 is controlled to be turned on by the main microcomputer 12, and as the main power supply voltage Vma decreases, the main microcomputer 12 When the operation stops, the transistor TR4 is turned off.

  Therefore, according to the present embodiment, the transistor TR4 is turned on only when the power supply voltage capable of operating the main microcomputer 12 is supplied from the main power supply control unit 16 to the power supply line L1, and the power supply line L1, The potential difference between L2 is limited to the ON voltage (for example, 0.1V) or less of the transistor TR4, and the potential of the power supply line L1 falls below the potential of the power supply line L2 (standby power supply voltage Vst). When the sub-microcomputer 14 does not fail due to the potential difference between the power supply lines L1 and L2, the power supply lines L1 and L2 are blocked.

  Therefore, according to the present embodiment, not only can the sub-microcomputer 14 be prevented from being damaged by the standby power supply voltage Vst being lowered when the power switch 4 is turned on, but also from the power line L2 when the power switch 4 is turned off. It is possible to prevent dark current from flowing to the power supply line L1, and to suppress unnecessary power consumption of the battery 2.

In the present embodiment, the main microcomputer 12 corresponds to the control means of the present invention.
As mentioned above, although embodiment of this invention was described, this invention is not limited to the said embodiment, A various aspect can be taken in the range which does not deviate from the summary of this invention.

  For example, in the fourth embodiment and the fifth embodiment, when the power switch 4 is turned on, the standby power supply voltage Vst is lower than the main power supply voltage Vma and the sub-microcomputer is likely to break down. The TR3 is made conductive, and the potential difference between the power supply lines L1 and L2 is limited to be equal to or lower than the ON voltage of each of the transistors TR2 and TR3. However, the fourth embodiment and the fifth embodiment are combined to perform flash writing. When the flash write permission signal VPP is output from the permission unit 26 and when the low voltage detection signal DI is output from the battery low voltage detection unit 24, the transistor provided between the power supply lines L1 and L2 is turned on. You may make it make it.

  In the above-described embodiment, the ECU 10 has been described as an electronic control device that controls an engine mounted on a vehicle. However, the present invention is not limited to other devices (such as an automatic transmission or a braking device) mounted on a vehicle. Even an electronic control device that controls a control object other than a vehicle-mounted device can be applied in the same manner as in the above embodiment. In other words, the present invention can be applied to the same embodiment as in the above-described embodiment to provide the same effect as long as it is an electronic control device that includes two control circuits composed of a microcomputer or the like and supplies power to these components from different power supply circuits. Obtainable.

It is a block diagram showing schematic structure of the electronic controller of 1st Embodiment. It is a block diagram showing schematic structure of the electronic controller of 2nd Embodiment. It is a block diagram showing schematic structure of the electronic controller of 3rd Embodiment. It is a block diagram showing schematic structure of the electronic controller of 4th Embodiment. It is explanatory drawing explaining the operation | movement at the time of flash memory writing in the apparatus of 4th Embodiment compared with a conventional apparatus. It is a block diagram showing schematic structure of the electronic controller of 5th Embodiment. It is explanatory drawing explaining the operation at the time of the battery voltage fall in the apparatus of 5th Embodiment compared with a conventional apparatus. It is a block diagram showing schematic structure of the electronic controller of 6th Embodiment. It is a block diagram showing schematic structure of the conventional electronic control apparatus.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 2 ... Battery, 4 ... Power switch, 10 ... ECU (electronic control unit), 12 ... Main microcomputer, 14 ... Sub microcomputer, D0 ... Parasitic diode, 16 ... Main power supply control part, Vma ... Main power supply voltage, 20 ... Power supply IC , 22 ... standby power supply control unit, Vst ... standby power supply voltage, D1, D2 ... diode, L1, L2 ... power supply line, 24 ... battery low voltage detection unit, 26 ... flash write enable unit, D3 ... Schottky barrier diode, DESCRIPTION OF SYMBOLS 30 ... Comparator, C1 ... Capacitor, R1-R8 ... Resistance, TR1-TR4 ... Transistor, 32, 34 ... Inversion circuit, 50 ... ECU (conventional electronic control unit).

Claims (8)

A first power supply circuit that receives a power supply from an external power supply when the power switch is turned on, generates a power supply voltage of a predetermined voltage value, and outputs the power supply voltage to the first power supply line;
A second power supply circuit that receives a constant power supply from the external power supply, generates a power supply voltage having the same voltage value as the first power supply, and outputs the power supply voltage to a second power supply line;
A first control circuit that operates by receiving power supply from the first power supply line and executes a first control process by taking a signal from an external device with the potential of the first power supply line as a reference potential;
A second control circuit that operates by receiving power supply from the second power supply line and executes a second control process by taking a signal from an external device with the potential of the first power supply line as a reference potential;
An electronic control device comprising:
When the potential of the second power supply line decreases by a predetermined voltage or more with respect to the potential of the first power supply line, a current is passed from the first power supply line to the second power supply line, and the second power supply line An electronic control device comprising a protection circuit for limiting a potential drop with respect to the first power supply line.   The electronic control device according to claim 1, wherein the protection circuit includes a Schottky barrier diode provided between the first power supply line and the second power supply line.   The electronic control device according to claim 2, further comprising a ground circuit that grounds the first power supply line and maintains the potential of the first power supply line at a ground potential when the power switch is turned off. The protection circuit is
A transistor connected in series to the Schottky barrier diode and conducting / blocking a current path between the first power supply line and the second power supply line formed via the Schottky barrier diode;
Control means for conducting the transistor under a condition where a potential difference that degrades the second control circuit may occur between the first power supply line and the second power supply line when the power switch is turned on;
The electronic control device according to claim 2, further comprising: The protection circuit is
A transistor provided between the first power supply line and the second power supply line, which conducts / cuts off between the power supply lines;
Control means for conducting the transistor under a condition where a potential difference that degrades the second control circuit may occur between the first power supply line and the second power supply line when the power switch is turned on;
The electronic control device according to claim 1, further comprising:   The electronic control device according to claim 4, wherein the control unit conducts the transistor when a power supply voltage is output from the first power supply circuit to a first power supply line.   6. The electronic control device according to claim 4, wherein the control means turns on the transistor when the second control circuit is writing data to the nonvolatile memory.   8. The electronic control device according to claim 4, wherein the control unit conducts the transistor when a supply voltage from the external power supply is lowered.

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