JP4340966B2 - Microcomputer power supply voltage monitoring system - Google Patents

Description

  The present invention relates to a system for monitoring power supplied to a microcomputer of an automotive electronic control device.

In order to respond to social needs such as informatization and safety improvement for automobiles, improvement of driving performance, driving operability, route guidance, anti-theft convenience, safety improvement, ITS-related predictive safety and information communication, etc. A large number of electronic control devices related to, have been mounted on automobiles. Many of these electronic control devices employ a microcomputer to perform high-performance and high-security digital control. In recent years, a one-chip microcomputer in which peripheral circuits such as RAM / ROM / Interface are integrated into a single chip is often used for this microcomputer from the viewpoint of downsizing of the apparatus and low cost. In such an environment of advanced automobile electronics, it is important to improve the safety and reliability of various controls by microcomputers.

In addition, there are ROM ROM types that can be rewritten, such as Flash ROM that can be rewritten and Mask ROM that cannot be rewritten. As described above, various microcomputers are properly used in the electronic control apparatus for automobiles depending on the application, but the required voltage differs depending on the type of microcomputer to be used. For this reason, power supplies mounted on electronic control devices for automobiles are often equipped with a function of switching a plurality of voltage outputs, and are often used by switching the voltage output in order to obtain a voltage necessary for the microcomputer to be mounted. . At this time, it is necessary to determine whether an appropriate voltage is output from the power supply to the microcomputer from the viewpoint of safety and reliability of microcomputer control. In order to solve this problem, Patent Document 1 discloses a method for permitting output of a power supply when a power supply output and a voltage value set outside the electronic control device are compared and matched.
JP-A-7-231562

However, in order to determine whether the power supply output is a power supply voltage that guarantees the operation of the microcomputer (hereinafter, this voltage is referred to as the “appropriate power supply voltage”), it is necessary to provide a power supply monitoring function outside the electronic control unit. There is. However, there has been a problem that a power supply monitoring function must be provided inside the electronic control device in order to reduce the size of the electronic control device and reduce the number of parts.

An object of the present invention is to provide a highly reliable and safe microcomputer power supply voltage monitoring system for determining whether or not a power supply voltage supplied to a microcomputer is appropriate.

Means for Solving the Problems and Effects of the Invention

A microcomputer power supply voltage monitoring system according to the present invention is an electronic control device for an automobile which performs electric power steering control of an automobile using a microcomputer which is a one-chip microcomputer in which peripheral circuits such as RAM / ROM / Interface are integrated on a single chip. in either power supply voltage is the voltage of the power supply voltage supply line which connects the power supply terminals of the output terminal and the microcomputer of the power supply unit you supply power to the microcomputer, a power supply with a power supply voltage to ensure operation of the microcomputer Power supply monitoring means for monitoring whether the power supply voltage falls within an appropriate power supply voltage range that is a range between a predetermined upper threshold voltage and a lower threshold voltage. When the power supply voltage of the power supply section exceeds the upper threshold voltage and when the power supply voltage of the power supply section falls below the lower threshold voltage, The output driver for controlling the external load is stopped in response to the control signal output from the controller, or the operation of the microcomputer is stopped.

  In this way, it is monitored whether the power supply voltage matches the appropriate power supply voltage stored in the microcomputer in the electronic control device itself, so the power supply monitoring function is not provided outside the electronic control device. It is possible to prevent the malfunction of the microcomputer based on the influence of the voltage. As a result, prevent malfunctions in microcomputer control caused by human error or incorrect setting of power supply voltage due to failure of changeover switch, or abnormal power supply voltage due to sudden power supply circuit failure. Can do.

In the microcomputer power supply voltage monitoring system of the present invention, the power supply unit includes output voltage switching means for switching the output voltage output to the microcomputer,
The power supply voltage may be configured to be an output voltage switched by the output voltage switching unit.

  In this way, the output voltage switching means is integrated with the power supply unit, and the microcomputer power supply voltage monitoring system can be reduced in size and cost.

In the microcomputer power supply voltage monitoring system of the present invention, the power supply monitoring means is provided in the microcomputer, the microcomputer stores information on the appropriate power supply voltage range or the appropriate power supply voltage, and the power supply monitoring means stores the value of the power supply voltage. A power supply voltage detecting means for detecting may be provided, and it may be configured to monitor whether or not the value of the detected power supply voltage is within an appropriate power supply voltage range or whether it is an appropriate power supply voltage .

In this way, the microcomputer itself performs the power supply monitoring function for determining whether or not the power supply voltage is an appropriate voltage, so there is no need to provide a new circuit, and the microcomputer power supply voltage monitoring system can be reduced in size and cost. .

The microcomputer power supply voltage monitoring system of the present invention can also be configured such that the power supply monitoring means is provided in the power supply section.

In this way, the power supply monitoring function is integrated into the power supply unit, and the wiring is simpler than when the power supply monitoring function is provided outside the power supply unit. Improvement and cost reduction can be achieved.

In the microcomputer power supply voltage monitoring system according to the present invention, the power supply voltage detecting means includes an A / D converter for A / D converting the power supply voltage, and the power supply monitoring means has a value obtained by A / D converting the power supply voltage. It is configured to monitor whether the power supply voltage is stored in the appropriate power supply voltage range stored as the voltage A / D conversion value or whether the power supply voltage is stored in the microcomputer as the voltage A / D conversion value. It is also possible to do.

In this way, the microcomputer itself can quantitatively analyze whether the power supplied to the microcomputer is appropriate, and make detailed and accurate judgments including noise superimposed on the power supply voltage and high frequency induction. can do. [Power supply monitoring means by means of numerical calculation of microcomputer]

In addition, the microcomputer power supply voltage monitoring system of the present invention is a vehicle electronic device that performs electric power steering control of an automobile using a microcomputer that is a one-chip microcomputer in which peripheral circuits such as RAM / ROM / Interface are integrated into a single chip. In the control device, the power supply voltage that is the voltage on the power supply voltage supply line that connects the output terminal of the power supply unit that supplies power to the microcomputer and the power supply terminal of the microcomputer is the appropriate power supply voltage that guarantees the operation of the microcomputer. Power supply monitoring means for monitoring whether or not, the power supply unit generates a voltage signal output circuit that generates a voltage signal corresponding to the output of a plurality of power supply circuits prepared in the power supply unit and outputs to the microcomputer The microcomputer stores the necessary voltage information corresponding to the voltage value necessary for the operation of the microcomputer and the input voltage Power supply voltage information is generated based on the signal, and the power supply monitoring means receives a control signal output from the microcomputer when the power supply voltage information does not match the required voltage information even when the power supply voltage is an appropriate power supply voltage. The output driver that controls the external load is stopped, or the operation of the microcomputer is stopped.

In this case, the power supply flag synchronized with the output switching of the power supply circuit (that is, the power supply voltage information of the present invention, the same applies hereinafter) and the necessary voltage flag corresponding to the appropriate voltage of the microcomputer (that is, the necessary voltage of the present invention) It is possible to easily determine whether or not the power supply voltage is an appropriate voltage by comparing the information (the same applies to the following) . As a result, even when either the microcomputer itself or the power supply unit fulfills this power monitoring function, the function can be easily realized. Specifically, when the microcomputer itself performs the power monitoring function, the microcomputer itself does not need the A / D conversion function, and only one I / O port is provided, and the power supply flag and the necessary voltage flag can be simply set. This can be achieved by performing a logical operation (details of the configuration of the logical operation will be described later) . [Power supply monitoring means by logic operation means]

The appropriate power supply voltage in the microcomputer power supply voltage monitoring system of the present invention is determined as an appropriate power supply voltage range that is a range between a predetermined upper threshold voltage and a lower threshold voltage, and the appropriate power supply voltage range is stored in the microcomputer. The power supply monitoring means includes power supply voltage detection means for detecting the value of the power supply voltage, and the power supply monitoring means determines whether or not the detected power supply voltage value falls within an appropriate power supply voltage range. You may comprise so that it may determine .

In this way, the power supply monitoring function for determining whether or not the power supply voltage is an appropriate voltage can be realized by a simple analog circuit or the like. [Power supply monitoring means by analog calculation means]

In the microcomputer power supply voltage monitoring system according to the present invention, the voltage signal is a high level or low level voltage signal output corresponding to the power supply voltage, and the power supply voltage information is based on a high level or low level voltage signal. The necessary voltage information is a 1-bit binary code corresponding to an appropriate power supply voltage that is stored in advance in the microcomputer and guarantees the operation of the microcomputer. Ri DOO the exclusive oR of the voltage information and the required voltage information, it is preferably configured to said power supply voltage information and the required voltage information to determine whether to match.

In this way, whether the microcomputer itself performs the power monitoring function or the power supply unit performs the power monitoring function, it can be realized by exclusive ORing the power flag and the necessary voltage flag. For example, when this function is performed in the power supply unit, it can be realized by using a simple logic gate circuit such as EX-OR (Exclusive OR).

The microcomputer power supply voltage monitoring system of the present invention is a microcomputer power supply voltage monitoring system applied to an electric power steering device for assisting the steering force of a steering wheel.
The external load is preferably configured to be one of a motor relay of the electric power steering device, a semiconductor switching element that drives a motor of the electric power steering device, and a power supply relay of the electric power steering device.

In this way, in the electric power steering device that improves the operability of the steering, when the power supply voltage monitoring system detects an abnormality, control of the external load by the microcomputer, that is, the motor relay, the power relay, the motor, etc. is stopped. can do. As a result, the safety and reliability of the electric power steering device can be further improved.

Further, the microcomputer power supply voltage monitoring system of the present invention is an operation monitoring means for monitoring whether the operation of the microcomputer is normal, at least one of a watchdog and a homework answer,
You may comprise so that the power supply monitoring means which monitors whether the power supply voltage supplied to a microcomputer is an appropriate power supply voltage may be used together. If it does in this way, the safety | security with respect to the vehicle control which uses a microcomputer can be doubled, and the reliability can be improved further.

Hereinafter, the best mode of a microcomputer power supply voltage monitoring system of the present invention will be described with reference to the accompanying drawings. FIG. 1 shows a circuit block configuration of a microcomputer power supply voltage monitoring system according to the present invention. The microcomputer power supply voltage monitoring system 1 includes a microcomputer 10 that controls an external load 60 and a power supply unit 20 that supplies a power supply voltage having a voltage switching function thereto. The microcomputer 10 is connected to an operation monitoring circuit 30 [consisting of a W / D circuit and homework answer (details will be described later)] as operation monitoring means for monitoring whether the operation is normal. The power supply voltage supplied by switching from the constant voltage power supply 21 of the power supply unit 20 to a voltage corresponding to the type of the microcomputer is applied to the power supply terminal of the microcomputer 10 and is simultaneously taken in from the I / O port of the microcomputer 10. The power supply voltage input from the port is compared with the appropriate power supply voltage value 11 indicating the “power supply voltage range in which operation is guaranteed” of the microcomputer 10, and the power supply voltage is set to the proper power supply voltage (“power supply in which operation is guaranteed”). Whether or not the voltage range is “) is monitored by the power supply 12 (as power supply monitoring means). On the other hand, the microcomputer 10 controls the control signal S _c to output an external load (described in detail later) output driver 40 connected to 60. When this power supply monitoring output and the output of the operation monitoring circuit 30 are led to a logical operation circuit 50 such as an OR circuit, when the power supply voltage supplied to the microcomputer 10 is not an appropriate power supply voltage or when the operation of the microcomputer 10 is not normal, Inhibit the output driver 40 that controls the external load 60 and the microcomputer to stop the control of the external load 60.

Next, another best mode when the power supply monitoring function is provided outside the microcomputer 10 will be described with reference to FIG. The microcomputer 10 is similarly connected with an operation monitoring circuit 30 as an operation monitoring means for monitoring whether or not the operation is normal. Similarly, the power supply voltage supplied from the constant voltage power supply 21 of the power supply unit 20 by switching to the voltage corresponding to the type of the microcomputer is supplied to the power supply terminal of the microcomputer 10. When power is supplied, the microcomputer 10 controls the control signal S _c to an output driver 40 connected to the external load 60. On the other hand, the power supply voltage is input to the power supply monitoring circuit 28 (as power supply monitoring means) and compared with the appropriate power supply voltage value 11 output by the microcomputer 10 to monitor whether the power supply voltage is the proper power supply voltage. Is done. The output of the power supply monitoring circuit 28 and the output of the operation monitoring circuit 30 are led to a logical operation circuit 50 such as an OR circuit, and the power supply voltage supplied to the microcomputer 10 is not an appropriate power supply voltage or the operation of the microcomputer 10 is normal. If not, the output driver 40 that controls the external load 60 is reset to inhibit the microcomputer and the control of the external load 60 is stopped.

  Hereinafter, four representative embodiments will be sequentially described with reference to a circuit block diagram and a flowchart. First, the configuration and function of the first embodiment will be described with reference to the block diagram of FIG. The microcomputer power supply voltage monitoring system 1 includes a microcomputer 10 that controls an external load 60 and a power supply unit 20 that supplies a power supply voltage thereto. An operation monitoring circuit 30 composed of a W / D circuit and a homework answer is connected to the microcomputer 10 as operation monitoring means for monitoring whether or not the operation is normal.

The microcomputer 10 has a counter called a watchdog timer, and the counter is counted up by a clock signal as the program is executed. By generating a reset signal for each cycle of program execution and resetting its Counter, it is monitored that the program is being executed normally. If the microcomputer 10 goes out of control for some reason, the Counter overflows and resets the microcomputer system operation. The W / D [Watch Dog] circuit monitors the generation state of the reset signal. Also, homework answers are sent periodically to microcomputer 10 to solve problems such as numerical computation, and the answers of microcomputer 10 are received and the contents are checked to monitor whether the functions of microcomputer 10 are normal. To do.

Switching from the constant voltage power supply 21 of the power supply unit 20 to a voltage according to the type of microcomputer (in the figure, two types for 2.5V / 1.5V for example), the supplied power supply voltage is applied to the power supply terminal of the microcomputer 10 At the same time, it is taken in from the I / O port of the microcomputer 10. The power supply voltage input from the port is A / D converted 13 to become a binary code (including binary and hexadecimal numbers) X, and compared with a binary code Y indicating the appropriate power supply voltage (range) value 11 of the microcomputer 10 Then, power supply monitoring 12 (power supply monitoring means: as numerical value calculation means) is performed to determine whether or not the power supply voltage is within the appropriate power supply voltage (range). On the other hand, the microcomputer 10 outputs a control signal S _c, electric power stearyl § ring motor relay 61, (such as MOS FET) power supply relay 62 and the semiconductor switching element for driving the motor external load 63 is at least one of The output driver 40 that controls 60 is controlled. The output of the power supply monitor 12 and the output of the operation monitor circuit 30 are led to a logical operation circuit 50 such as an OR circuit, and when the power supply voltage supplied to the microcomputer 10 is not an appropriate power supply voltage (range), or the operation of the microcomputer 10 When not normal, the output driver 40 for controlling the external load 60 is inhibited and the microcomputer is reset to stop the control of the external load 60 by the microcomputer 10.

Next, an outline of the operation of the first embodiment will be described using the flowchart of FIG. In P1, power is supplied from the constant voltage power supply 21 to the microcomputer 10. At P2, Watchdog monitoring [W / D circuit] and operation monitoring by homework answer are performed, and at P3, it is determined whether the operation of the microcomputer 10 is normal. If No: abnormal, the process immediately shifts to P8, the output driver 40 is inhibited and the microcomputer is reset, the output is prohibited, and the control of the external load 60 is stopped. Yes at P3: When normal, the power supply voltage is taken from the I / O at P4 and A / D converted at P5 to become binary X. At P6, the appropriate power supply voltage value Y is read from the internal memory or the like, and at P7, power supply monitoring is performed to compare X of the A / D conversion output with the appropriate power supply voltage (range) value Y. When the power supply voltage is within the range of the appropriate power supply voltage value, that is, Yes: normal, the process returns to P2, and the operation monitoring of the microcomputer 10 and the power supply monitoring of the power supply voltage are periodically performed at a predetermined cycle. If the power supply voltage deviates from the appropriate power supply voltage value, that is, No: abnormal, the output driver 40 is inhibited and the microcomputer is reset at P8, the output is prohibited, and the control of the external load 60 is stopped. The The steps from P5 to P7 are referred to as “numerical calculation means”.

Next, the configuration and function of the second embodiment will be described with reference to the block diagram of FIG. In [4A], the microcomputer power supply voltage monitoring system 1 includes a microcomputer 10 that controls the external load 60 and a power supply unit 20 that supplies the power supply voltage thereto. An operation monitoring circuit 30 composed of a W / D circuit and a homework answer is connected to the microcomputer 10 as operation monitoring means for monitoring whether or not the operation is normal.

The power supply voltage supplied from the constant voltage power supply 21 of the power supply unit 20 is applied to the power supply terminal of the microcomputer 10 and simultaneously input to the overvoltage / undervoltage monitor circuit 22. The power supply unit 20 generates a power flag (High: for 2.5 V / Low: for 1.5 V) in synchronization with the selection switching of the two types of power supply voltages of the constant voltage power supply 21 (for 2.5 V / 1.5 V) A power flag circuit 23 is prepared. The two reference reference voltages of the overvoltage / undervoltage monitor circuit 22, ie, the upper threshold voltage V _ref-H and the lower threshold voltage V _ref-L are selected and switched in synchronization with this power flag (for 2.5 V / 1.5 V) Is made. Specifically, when 1.5V is used, upper threshold voltage: V _re-H = 1.65V, lower threshold voltage: V _re-L = 1.35V is selected, and when 2.5V is used, upper threshold voltage: V _re-H = 2.7V, lower threshold voltage: V _re-L = 2.3V is selected. In the microcomputer 10, a power supply voltage that guarantees the operation of the microcomputer, that is, a necessary voltage flag corresponding to an appropriate power supply voltage [2.5 V: High, 1.5 V: Low] X is read from the built-in memory 15. A power supply flag Y corresponding to the selection of the power supply voltage of the constant voltage power supply 21 is output from the power supply flag circuit 23 and is taken in from the I / O port of the microcomputer 10. The power flag Y (binary code) and the necessary flag X (binary code) described above are input to the power supply monitor 16 that performs a logical operation of exclusive OR, and the difference between them is monitored.

The power supply voltage V _IN input from the constant voltage power supply 21 to the overvoltage / undervoltage monitor circuit 22 (as analog calculation means) is a reference corresponding to the selection of the power supply voltage of the constant voltage power supply 21 in the W / C [Window Comparator] 22A Compared with the reference voltages V _ref-H and V _ref-L , whether or not the power supply voltage V _IN is within the appropriate power supply voltage (range) of the upper threshold voltage V _ref-H and the lower threshold voltage V _ref-L Monitored. Here, the configuration and operation of the W / C 22A will be briefly described with reference to the circuit diagram [4B]. The W / C 22 includes a Comparator 221 that functions as an inverting input comparator, a Comparator 222 that functions as a non-inverting input comparator, and a NAND circuit 223 that performs a NAND operation on the outputs of both. When the power supply voltage V _IN is V _ref−L <V _IN <V _ref−H, that is, when the power supply voltage is an appropriate power supply voltage (range), the output of the W / C 22 becomes zero (Low).

Returning to [4A], the control for the external load 60 is as follows. The microcomputer 10 outputs a control signal S _c, to control the external load 60 is at least one of the electric power stearyl § ring motor relay 61, the power supply relay 62 and the semiconductor switching element for driving the motor (such as MOS FET) 63 Controls the output driver 40. When the power supply flag Y corresponding to the selection of the power supply voltage of the constant voltage power supply 21 and the required voltage flag X do not match, the output V _O which is the exclusive OR output Z becomes “1” level (High), and the power supply voltage for some reason when V _iN is not proper power supply voltage, i.e. the output V _M of the overvoltage and low voltage monitoring circuit 22 when the power supply voltage V _iN does not fit between the lower threshold voltage V _ref- L and an upper threshold voltage V _ref-H is " Level 1 ”. Further, when the operation of the microcomputer 10 is not normal, the output V _s of the operation monitoring circuit 30 becomes “1” level. The three outputs V ₀ , V _M , and V _s are input to the OR circuit 50, and a logical sum of the three is obtained. Therefore, when the power supply voltage is not an appropriate power supply voltage or when the operation of the microcomputer 10 is not normal, the output of the OR circuit 50 becomes “1” level, and the output driver 40 that controls the external load 60 is inhibited and the microcomputer is reset. Stop control of load 60.

Next, the outline of the operation of the second embodiment will be described using the flowchart of FIG. In P1, power is supplied from the constant voltage power supply 21 to the microcomputer 10. At P2, Watchdog monitoring [W / D circuit] and operation monitoring by homework answer are performed, and at P3, it is determined whether the operation of the microcomputer 10 is normal. If No: abnormal, the process immediately shifts to P8, the output driver 40 is inhibited and the microcomputer is reset, the output is prohibited, and the control of the external load 60 is stopped. Yes in P3: If normal, the process proceeds to P4 and the power supply voltage V _IN is monitored. Whether or not the power supply voltage is in the proper power supply voltage (range) in P5 (V _ref-L <V _IN <V _ref- Whether it is _H ) or not. If No: abnormal voltage, the process immediately shifts to P8, the output driver 40 inhibits the microcomputer and the microcomputer is reset, the output is prohibited, and the control of the external load 60 is stopped. Yes in P5: If the power supply voltage is within the appropriate power supply voltage range, the power supply flag Y corresponding to the selection of the power supply voltage is fetched into the microcomputer 10 in P6. At the same time, the necessary voltage flag X stored in the built-in memory 15 of the microcomputer 10 is read at P7, and the power flag Y and the necessary flag X are compared at P8. If No: The power flag Y and the required flag X do not match (that is, the power supply voltage supplied from the constant voltage power supply 21 to the microcomputer 10 does not match the power supply voltage required by the microcomputer 10), P9 The output of the output driver 40 is prohibited and the control of the external load 60 is stopped. Yes in P8: When the power flag Y and the necessary flag X match, the process returns to P2, and the operation monitoring and power monitoring of the microcomputer 10 are periodically performed at a predetermined cycle. The steps P4 and P5 are referred to as “analog calculation means”.

Next, the configuration and function of the third embodiment will be described with reference to the block diagram of FIG. The difference between the third embodiment and the second embodiment is that the power monitor 16 function that performs a logical operation of exclusive OR of the power flag Y and the necessary flag X in the microcomputer 10 of FIG. 3 is replaced with the power monitor circuit 24 of FIG. That is. Therefore, the power supply monitoring circuit 24 will be described here, and the functions of other parts are the same, and the description thereof will be omitted. The necessary voltage flag X read from the built-in memory 15 of the microcomputer 10 and the power supply flag Y corresponding to the selection of the power supply voltage are converted into a power supply monitoring circuit 24 (power supply monitoring means: logic operation means) that is an EX-OR [Exclusive OR] circuit. ) To obtain the exclusive OR. Therefore, when the necessary voltage flag X and the power supply flag Y do not match, the output V ₀ which is the exclusive OR output Z of the power supply monitoring circuit 24 becomes “1” level.

Next, the outline of the operation of the third embodiment will be described with reference to the flowchart of FIG. The flowchart of FIG. 9 is the same as the flowchart of FIG. 8 except for Steps P6, P7, and P8, and thus the description of the other steps is omitted. Yes in P5: When the power supply voltage _VIN is in the appropriate power supply voltage range, the necessary voltage flag X is read from the microcomputer 10 in P6, and then the power supply flag Y and the necessary voltage flag X are input to the power supply monitoring circuit 24 in P7. At P8, the power supply monitoring circuit 24 takes an exclusive OR of the power supply flag Y and the necessary voltage flag X to determine whether or not they match. The steps P6, P7, and P8 are referred to as “logical operation means”.

Next, the configuration and function of the fourth embodiment will be described with reference to the block diagram of FIG. In the fourth embodiment, there is provided a microcomputer power supply monitoring circuit 25 in which both functions of the power supply flag circuit 23 and the power supply monitoring circuit 24 of the third embodiment shown in FIG. Yes. Therefore, the function of the microcomputer power supply monitoring circuit 25 will be mainly described. The power supply voltage V _IN determined by the power supply voltage selection (for 1.5V / 2.5V) of the constant voltage power supply 21 is supplied to the microcomputer 10 and simultaneously input to the W / C [WindowComparator] 25A of the microcomputer power supply monitoring circuit 25. The A necessary voltage flag X corresponding to this power supply voltage selection is read from the built-in memory 15 and sent from the microcomputer 10 to the microcomputer power supply monitoring circuit 25. The necessary voltage flag X is used to selectively switch between the upper threshold voltage V _ref-H and the lower threshold voltage V _ref-L , which are two reference standard voltages of W / C25. Specifically, when the required voltage flag X is Low (for 1.5V), the upper threshold voltage: V _ref-H = 1.65V and the lower threshold voltage: V _ref−L = 1.35V are selected, and the required voltage flag When X is High (for 2.5V), the upper threshold voltage: V _ref−H = 2.7V and the lower threshold voltage: V _ref−L = 2.3V are selected. W / C25 in the power supply voltage VIN and these upper threshold voltage V _ref-H, comparing the lower threshold voltage V _ref-L is performed in the same manner as described above for W / C22A, power supply voltage V _IN is proper supply voltage (range ) Is monitored for power. Since the inhibit of the output driver 40 and the reset of the microcomputer are the same as described above, they are omitted.

Next, the operation of the fourth embodiment will be described using the flowchart of FIG. In P1, power is supplied from the constant voltage power supply 21 to the microcomputer 10. At P2, monitoring of the microcomputer by watchdog monitoring [W / D circuit] and homework answer is performed, and at P3, it is determined whether the operation of the microcomputer 10 is normal. If No: abnormal, the process immediately shifts to P8, inhibits the output driver 40 and resets the microcomputer, prohibits the output, and stops the control of the external load 60. Yes in P3: If normal, the required voltage flag X corresponding to the selection of the power supply voltage is sent from the microcomputer 10 to the microcomputer power supply monitoring circuit 25 in P4. In P5, the upper threshold voltage V _ref-H and the lower threshold voltage V _ref-L are respectively selected according to the contents (High / Low) of the necessary voltage flag X. In P6, the power supply voltage V _IN is compared with these upper threshold voltage V _ref-H and lower threshold voltage V _ref-L . If the power supply voltage V _IN is within the range of the appropriate power supply voltage range (V _ref-L <V _IN <V _ref-H ), that is, Yes: if normal, return to P2, monitor the operation of the microcomputer 10 and the power supply voltage The power supply monitoring is periodically performed at a predetermined cycle. If the power supply voltage is not in the proper power supply voltage range, that is, No: abnormal, the output driver 40 is inhibited and the microcomputer is reset in P8, the output is prohibited, and the control of the external load 60 is stopped.

The circuit block diagram which shows the basic composition of the best form of the microcomputer power supply voltage monitoring system of this invention. The circuit block diagram which shows the basic composition of another best form of the microcomputer power supply voltage monitoring system of this invention. The circuit block diagram which shows the structure of Embodiment 1 of the microcomputer power supply voltage monitoring system of this invention. The circuit block diagram which shows the structure of Embodiment 2 of the microcomputer power supply voltage monitoring system of this invention. The circuit block diagram which shows the structure of Embodiment 3 of the microcomputer power supply voltage monitoring system of this invention. The circuit block diagram which shows the structure of Embodiment 4 of the microcomputer power supply voltage monitoring system of this invention. The flowchart which shows operation | movement of Embodiment 1 of the microcomputer power supply voltage monitoring system of this invention. The flowchart which shows operation | movement of Embodiment 2 of the microcomputer power supply voltage monitoring system of this invention. The flowchart which shows operation | movement of Embodiment 3 of the microcomputer power supply voltage monitoring system of this invention. The flowchart which shows operation | movement of Embodiment 4 of the microcomputer power supply voltage monitoring system of this invention.

Explanation of symbols

1 Microcomputer power supply voltage monitoring system Microcomputer power supply operation monitoring circuit (W / D circuit, homework answer, operation monitoring means)
Output driver logic operation circuit (OR circuit)
60 Appropriate power supply voltage value for external load (appropriate power supply voltage range value)
12 Power supply monitoring (Power supply monitoring means, numerical calculation means)
A / D conversion
15 Built-in memory power monitoring (power monitoring means)
Constant voltage power supply overvoltage / undervoltage monitor circuit (analog calculation means)
22A, 25A W / C (Window Comparator)
23 Power supply flag circuit
24 Power monitoring circuit (Power monitoring means, logical operation means, Exclusive OR)
Power supply monitoring circuit (power supply monitoring means)
Motor relay power relay main conductor switching element (MOS FET)

Claims (11)

In an automotive electronic control device that performs electric power steering control of an automobile using a microcomputer that is a one-chip microcomputer in which peripheral circuits such as RAM / ROM / Interface are integrated into a single chip ,
Or the power supply voltage is the voltage of the power supply voltage supply line which connects the power supply terminals of the output terminal and the microcomputer of the power supply unit that to supply power to the microcomputer, a power supply with a power supply voltage to ensure operation of the microcomputer Power supply monitoring means for monitoring whether or not,
The power monitoring means is
Determining whether the power supply voltage falls within an appropriate power supply voltage range that is a range between a predetermined upper threshold voltage and a lower threshold voltage;
When the power supply voltage of the power supply unit is higher than the upper threshold voltage, and when the power supply voltage of the power supply unit is lower than the lower threshold voltage,
A microcomputer power supply voltage monitoring system, which receives a control signal output from the microcomputer and stops an output driver that controls an external load, or stops the operation of the microcomputer. The power supply unit includes output voltage switching means for switching an output voltage to be output to the microcomputer.
The microcomputer power supply voltage monitoring system according to claim 1, wherein the power supply voltage is the output voltage switched by the output voltage switching means. In an automotive electronic control device that performs electric power steering control of an automobile using a microcomputer that is a one-chip microcomputer in which peripheral circuits such as RAM / ROM / Interface are integrated into a single chip,
Whether the power supply voltage, which is the voltage on the power supply voltage supply line that connects the output terminal of the power supply unit that supplies power to the microcomputer and the power supply terminal of the microcomputer, is an appropriate power supply voltage that guarantees the operation of the microcomputer Power monitoring means for monitoring
The power supply unit includes a voltage signal output circuit that generates voltage signals corresponding to outputs of a plurality of power supply circuits prepared in the power supply unit and outputs the voltage signals to the microcomputer.
The microcomputer stores necessary voltage information corresponding to a voltage value necessary for the operation of the microcomputer, and generates power supply voltage information based on the input voltage signal.
The power monitoring means is
Even when the power supply voltage is the appropriate power supply voltage, when the power supply voltage information and the necessary voltage information do not match,
A microcomputer power supply voltage monitoring system, which receives a control signal output from the microcomputer and stops an output driver that controls an external load, or stops the operation of the microcomputer. The power supply unit includes output voltage switching means for switching an output voltage to be output to the microcomputer.
4. The microcomputer power supply voltage monitoring system according to claim 3 , wherein the power supply voltage is the output voltage switched by the output voltage switching means . 5. The microcomputer power supply voltage monitoring system according to claim 3, wherein the voltage signal output circuit outputs the voltage signal in synchronization with a switch for switching outputs of a plurality of power supply circuits prepared in the power supply unit . The appropriate power supply voltage is determined as an appropriate power supply voltage range that is a range between a predetermined upper threshold voltage and a lower threshold voltage, and the appropriate power supply voltage range depends on the necessary voltage information stored in the microcomputer. Switched,
The power supply monitoring means includes power supply voltage detection means for detecting the value of the power supply voltage,
The microcomputer power supply voltage monitoring system according to any one of claims 3 to 5, wherein the power supply monitoring unit determines whether or not the detected value of the power supply voltage falls within the proper power supply voltage range . The voltage signal is a high-level or low-level voltage signal output corresponding to the power supply voltage,
The power supply voltage information is a 1-bit binary code generated based on the high level or low level voltage signal.
The necessary voltage information is a 1-bit binary code stored in advance in the microcomputer and corresponding to an appropriate power supply voltage that guarantees the operation of the microcomputer.
7. The power supply monitoring unit according to any one of claims 3 to 6, wherein the power supply monitoring unit takes an exclusive OR of the power supply voltage information and the necessary voltage information, and determines whether or not the power supply voltage information and the necessary voltage information match. the microcomputer power supply voltage monitoring system according to an item or. The power monitoring means is provided in the microcomputer;
The microcomputer stores information on the appropriate power supply voltage range or the appropriate power supply voltage,
The power supply monitoring means includes power supply voltage detection means for detecting the value of the power supply voltage,
The microcomputer power supply voltage monitoring according to any one of claims 1 to 7, wherein the detected value of the power supply voltage is monitored to determine whether or not the value of the power supply voltage falls within the appropriate power supply voltage range or the appropriate power supply voltage. system. The power supply voltage detecting means includes an A / D converter for A / D converting the power supply voltage,
The power supply monitoring means determines whether the value obtained by A / D converting the power supply voltage falls within the appropriate power supply voltage range stored in the microcomputer as a voltage A / D conversion value, or whether the voltage A is stored in the microcomputer. 9. The microcomputer power supply voltage monitoring system according to claim 8 , which monitors whether or not the power supply voltage is stored as a / D conversion value . The microcomputer power supply voltage monitoring system according to any one of claims 1 to 7, wherein the power supply monitoring unit is provided in the power supply unit . In the microcomputer power supply voltage monitoring system applied to the electric power steering device for assisting the steering force of the steering,
The external load is any one of a motor relay of the electric power steering device, a semiconductor switching element that drives a motor of the electric power steering device, and a power supply relay of the electric power steering device. The microcomputer power supply voltage monitoring system described in the section .

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