JP5832751B2 - Electronic circuit and magnetic field detection device capable of self-diagnosis - Google Patents

Description

  The present invention relates to an electronic circuit capable of self-diagnosis capable of determining whether or not the electronic circuit is functioning normally.

  Conventionally, in an electronic circuit having a detection circuit for detecting a magnetic field, for example, in a configuration in which only a magnetic field detection signal can be acquired, even if a failure occurs in the electronic circuit, the microprocessor correctly outputs the magnetic field detection signal. As a result, the calculation process is performed and the reliability is low.

  For example, in Patent Document 1, a channel for measuring a reference voltage of 0 volts is provided in a measurement channel of a multiplexer-type voltage measuring element, this reference voltage is measured, and a measurement result is compared with a reference voltage value. A configuration for determining whether or not the voltage measurement device can normally communicate is disclosed (see [0029] column of Patent Document 1).

  However, as in the configuration described in Patent Document 1, if only one reference voltage is used, for example, the multiplexer is faulty and the switching is not successful and the lock state occurs, and the measurement result that coincides with one reference voltage happens to appear. Therefore, the reliability is not sufficiently improved.

  Further, in Patent Document 1, for example, an operational amplifier is connected in an electronic circuit, and even if the operational amplifier fails, since the reference voltage is set to 0 V, failure of the operational amplifier cannot be properly determined.

  The invention described in Patent Document 2 is an electronic circuit configuration configured to switch a plurality of drive voltages according to the type of external load, and determines whether or not the drive voltage has been switched normally. Judgment is made based on the divided voltage value obtained by dividing the voltage by the voltage dividing resistor (see the [0068] column of Patent Document 2).

  However, in Patent Document 2, as in Patent Document 1, determination is made only with one reference voltage (divided voltage value), and reliability cannot be sufficiently improved.

JP 2006-113699 A JP 2008-59517 A

  An object of the present invention is to solve the above-described conventional problems, and an object thereof is to provide an electronic circuit and a magnetic field detection device that can perform self-diagnosis with higher reliability than those of the conventional art.

The present invention relates to a detection circuit, an operational amplifier for amplifying a detection signal from the detection circuit, a multiplexer connected between the detection circuit and the operational amplifier, and a microprocessor for processing the detection signal from the operational amplifier. In an electronic circuit having
A diagnostic circuit for generating a high-voltage first diagnostic signal and a low-voltage second diagnostic signal, respectively;
The diagnostic circuit is connected to the multiplexer, and each diagnostic signal selected by the multiplexer can be input to the microprocessor via the operational amplifier.
In the microprocessor, based on the first diagnostic signal and the second diagnostic signal, whether or not the operational amplifier and the multiplexer are functioning normally can be diagnosed and input to the microprocessor. A first reference voltage for comparison with the first diagnostic signal and a second reference voltage for comparison with the second diagnostic signal input to the microprocessor are stored in the microprocessor. And a reference voltage adjusting unit provided in the microprocessor converts the first reference voltage and the second reference voltage to the input voltages in accordance with fluctuations in the input voltage of the diagnostic circuit. On the other hand, it is adjusted to a predetermined ratio.

  As described above, in the present invention, since the microprocessor determines whether or not the electronic circuit is functioning normally based on the two diagnostic signals of the high voltage and the low voltage, the reliability is higher than the conventional one. An electronic circuit capable of self-diagnosis can be configured. In addition, since the detection circuit and the diagnosis circuit are connected to the multiplexer and the single operational amplifier and the microprocessor are provided, the circuit configuration is not complicated and the cost increase can be suppressed.

In addition, since the first reference voltage and the second reference voltage can be corrected, an electronic circuit that can perform self-diagnosis with higher reliability can be configured.

In the present invention, the microprocessor diagnoses whether or not the electronic circuit is functioning normally based on the first diagnosis signal and the second diagnosis signal input to the microprocessor. Have a self-diagnosis department
The self-diagnosis unit includes an evaluation unit for evaluating whether or not the first diagnosis signal and the second diagnosis signal input to the microprocessor are within a normal range;
A counter unit for accumulating a predetermined counter value when the first diagnostic signal and the second diagnostic signal deviate from a normal range by the evaluation unit;
It is preferable that an error signal is output when it is determined that there is an abnormality when the counter value exceeds a predetermined value. Thus, even when the evaluation unit determines that the first diagnostic signal and the second diagnostic signal are out of the normal range, the first time when the counter value becomes equal to or greater than a predetermined value without immediately issuing an error signal. By issuing an error signal, the driving stability of the electronic circuit can be improved.

  In the present invention, it is preferable that the diagnostic circuit can output the first diagnostic signal having a high voltage and the second diagnostic signal having a low voltage, respectively, by a resistance voltage dividing circuit. As a result, a simple diagnostic circuit can be configured, and the circuit configuration is not complicated, thereby suppressing an increase in cost.

  In the present invention, the detection circuit can be constituted by a bridge circuit of a plurality of magnetic field detection elements.

Moreover, the magnetic field detection apparatus in the present invention is
A magnetic sensor and a magnet are arranged to face each other with an interval, and the magnetic sensor is for detecting a change in a magnetic field generated from the magnet,
The magnetic circuit includes the electronic circuit including the magnetic field detection element. As a result, the risk of erroneous magnetic field detection can be effectively avoided, and magnetic field detection accuracy can be improved.

  In the present invention, since the microprocessor determines whether or not the electronic circuit is functioning normally based on the two diagnostic signals of high voltage and low voltage, self-diagnosis can be performed with higher reliability than in the past. An electronic circuit can be constructed. In addition, since the detection circuit and the diagnosis circuit are connected to the multiplexer and the single operational amplifier and the microprocessor are provided, the circuit configuration is not complicated and the cost increase can be suppressed.

A perspective view of the magnetic field detection device, Electronic circuit diagram in this embodiment The block diagram of the microprocessor in this embodiment, Based on the change of the magnetic field accompanying the rotation of the magnet, the SIN signal generated from the detection circuit shown in FIG. 2 through the operational amplifier, and the COS signal image diagram ((a) is the SIN signal, (b) is the COS signal), The flowchart figure for self-diagnosis whether the electronic circuit in this embodiment is functioning normally.

FIG. 1 is a perspective view of a magnetic field detection apparatus according to this embodiment.
A magnetic field detection device 9 shown in FIG. 1 includes a magnetic sensor 10 and a magnet 14. As shown in FIG. 1, the magnetic sensor 10 includes a printed wiring board 11 and a sensor element 12 electrically connected to the printed wiring board 11. The magnetic sensor 10 and the magnet 14 are spaced apart (non-contacting).

FIG. 2 is a circuit diagram of the electronic circuit 20 incorporated in the magnetic sensor 10.
As shown in FIG. 2, the electronic circuit 20 includes a detection circuit 21 as a magnetic field detection unit, a multiplexer 22, an operational amplifier (differential amplifier) 23, a microprocessor 24, and a diagnostic circuit 25. Yes.

  As shown in FIG. 2, the detection circuit 21 includes bridge circuits 26 and 27 of a plurality of magnetic field detection elements S1, S2, S3, S4, S5, S6, S7, and S8.

As shown in FIG. 2, when the magnet 14 (shown schematically by a dotted line in FIG. 2) rotates, the electrical characteristics of the magnetic field detection elements S <b> 1 to S <b> 8 change, and the first bridge circuit 26 outputs SIN as a magnetic field detection signal. ^{The +} signal and the SIN ⁻ signal are output, and the COS ⁺ signal and the COS ⁻ signal are output from the second bridge circuit 27 as magnetic field detection signals. The SIN ⁺ and SIN ⁻ signals and the COS ⁺ and COS ⁻ signals are 180 degrees out of phase. Further, the SIN ⁺ signal and the COS ⁺ signal, and the SIN ⁻ signal and the COS ⁻ signal are each 90 degrees out of phase.

When the SIN ⁺ signal and the SIN ⁻ signal are selected by the multiplexer 22 shown in FIG. 2 and inputted to the operational amplifier 23, an amplified SIN signal 34 is obtained by the operational amplifier 23 as shown in FIG. be able to.

When the COS ⁺ signal and the COS ⁻ signal are selected by the multiplexer 22 shown in FIG. 2 and inputted to the operational amplifier 23, the COS signal 35 amplified by the operational amplifier 23 as shown in FIG. Can be obtained.

  As shown in FIG. 2, for example, the input voltage (power supply voltage) of each of the bridge circuits 26 and 27 is 5V, so that the midpoint potential is 2.5V as shown in FIGS. 4 (a) and 4 (b).

  For example, the SIN signal 34 and the COS signal 35 generated by the operational amplifier 23 are input to the arithmetic processing unit 19 shown in FIG. 3 of the microprocessor 24 in a state of being converted into a digital signal. The angle of the magnet is calculated by the “tan” function, and output indicating the angle value is performed. For example, it is converted into an analog value by a D / A converter (not shown) and output as a voltage value. At this time, the output voltage changes in proportion to the angle change during one rotation of the magnet 14, that is, a voltage that changes in a linear function with respect to the angle change, or changes to approximate a linear function. And is transmitted as a rotation angle and angular velocity signal 43 of the magnet 14 to a control unit (for example, ECU) 44 on the apparatus body side.

The element configuration of the plurality of magnetic field detection elements S <b> 1 to S <b> 8 shown in FIG. 2 is not particularly limited as long as the electrical characteristics change in response to a magnetic field change accompanying the rotation of the magnet 14. For example, the magnetic field detection elements S1 to S8 are GMR elements and have a laminated structure of a fixed magnetic layer / nonmagnetic layer / free magnetic layer. The GMR element is an element whose electric resistance varies depending on the magnetization relationship between the fixed magnetization direction (PIN direction) of the fixed magnetic layer and the magnetization direction of the free magnetic layer whose magnetization direction varies depending on the direction of the external magnetic field. The outputs obtained from the bridge circuits 26 and 27 vary from the midpoint potential based on the resistance change of each of the magnetic field detection elements S1 to S8, and the SIN ⁺ signal is output from the first bridge circuit 26 as the magnet 14 rotates. The SIN ⁻ signal and the COS ⁺ signal and the COS ⁻ signal are output from the second bridge circuit 27, respectively. At this time, the fixed magnetization direction (PIN) of the fixed magnetic layer of the magnetic field detection element between the magnetic field detection elements connected in series in each of the bridge circuits 26 and 27 and between the first bridge circuit 26 and the second bridge circuit 27. The SIN ⁺ signal and the SIN ⁻ signal are output from the first bridge circuit 26, and the COS ⁺ signal and the COS ⁻ signal are output from the second bridge circuit 27, respectively.

  As shown in FIG. 2, the electronic circuit 20 of this embodiment includes a diagnostic circuit 25. In the diagnostic circuit 25, three fixed resistors 28a to 28c are connected in series to obtain different voltage dividing resistors from between the fixed resistors 28a and 28b and between the fixed resistors 28b and 28c. The voltage dividing resistor circuit is configured.

  As shown in FIG. 2, the input terminal 30 is connected to the fixed resistor 28a side, and the ground terminal 31 is connected to the fixed resistor 28c side. The input terminal 30 can be shared with the first bridge circuit 26 and the second bridge circuit 27. Therefore, if the input voltage of the first bridge circuit 26 and the second bridge circuit 27 is 5V, the input voltage of the diagnostic circuit 25 is also 5V.

  The first diagnostic signal 32 obtained from the connection between the fixed resistor 28a and the fixed resistor 28b by the diagnostic circuit 25 shown in FIG. 2 becomes a high voltage, and from the connection between the fixed resistor 28b and the fixed resistor 28c. The obtained second diagnostic signal 33 has a low voltage. It is desirable that the first diagnostic signal 32 after passing through the operational amplifier 23 is higher than the midpoint potential (2.5V) and the second diagnostic signal 33 is lower than the midpoint potential (2.5V).

In the multiplexer 22 shown in FIG. 2, the SIN ⁺ signal and the SIN ⁻ signal generated by the first bridge circuit 26 in response to the channel select signal 36 from the microprocessor 24, and the COS ⁺ signal generated by the second bridge circuit 27. And the COS ⁻ signal, the first diagnostic signal 32 and the second diagnostic signal 33 generated by the diagnostic circuit 25 are sequentially selected and sent to the operational amplifier 23.

  As shown in FIG. 3, the SIN signal 34, the COS signal 35, the first diagnostic signal 32, and the second diagnostic signal 33 that are amplified by the operational amplifier 23 are sequentially input to the microprocessor 24. The COS signal 35 is sent to the arithmetic processing unit 19 as described above.

  On the other hand, the first diagnosis signal 32 and the second diagnosis signal 33 are sent to the self-diagnosis unit 37 of the microprocessor 24. Hereinafter, a self-diagnosis method for diagnosing whether or not the electronic circuit 20 is functioning normally will be described with reference to the flowchart shown in FIG.

  As shown in FIG. 3, the self-diagnosis unit 37 includes an evaluation unit 38, a counter unit 39, a reference voltage adjustment unit 40, and the like. The evaluation unit 38 determines whether or not the first diagnostic signal 32 input to the microprocessor 24 is within a normal range with respect to the first reference voltage, and the second diagnostic signal input to the microprocessor 24. It is evaluated whether 33 is within the normal range with respect to the second reference voltage.

  The first reference voltage and the second reference voltage to be compared with each diagnostic signal 32, 33 are stored in the microprocessor 24, and the first reference voltage is in a state where the electronic circuit 20 is functioning normally. The second reference voltage matches the voltage value of the first diagnostic signal 32 input to the microprocessor 24, and the second reference voltage is input to the microprocessor 24 with the electronic circuit 20 functioning normally. It corresponds to the voltage value of the signal 33.

  In the reference voltage adjustment unit 40 shown in FIG. 3, when the input voltage of the diagnostic circuit 25 fluctuates, the first reference voltage and the second reference voltage are corrected accordingly. By regulating each reference voltage at a predetermined ratio (percentage) with respect to the input voltage, the first reference voltage and the second reference voltage can be adjusted with high accuracy in accordance with fluctuations in the input voltage.

  The counter unit 39 shown in FIG. 3 accumulates a predetermined counter value when the evaluation unit 38 determines that the first diagnostic signal 32 and the second diagnostic signal 33 are out of the normal range. Alternatively, it has a function of decreasing the counter value when it is within the normal range.

  As shown in the flowchart of FIG. 5, the counter value is initially zero. A high-voltage first diagnostic signal 32 and a low-voltage second diagnostic signal 33 generated by the diagnostic circuit 25 shown in FIG. 2 are selected by the multiplexer 22, and are sent to the microprocessor 24 via the operational amplifier 23. The evaluation unit 38 of the microprocessor 24 compares the first diagnostic signal 32 with the first reference voltage to evaluate whether it is within the normal range and outputs the second diagnostic signal 33 to the second diagnostic signal 33. It is evaluated whether it is within the normal range as compared with the reference voltage (steps ST1 and ST2 in FIG. 5). For example, the “normal range” has a certain width from the reference voltage.

  If the first diagnostic signal 32 and the second diagnostic signal 33 are within the normal range, it is determined whether or not the current counter value of the counter unit 39 is greater than zero (step ST3 in FIG. 5). If the value is zero, the microprocessor 24 reads the SIN signal 34 and the COS signal 35 which are magnetic field detection signals (step ST4 in FIG. 5). Then, after calculation of the rotation angle and angular velocity of the magnet 14 (step ST5 in FIG. 5), if it is the CAN transmission timing (step ST6 in FIG. 5), the signal of the rotation angle and angular velocity of the magnet 14 is the magnetic field in FIG. It is transmitted to an electronic device, an in-vehicle device or the like incorporating the detection device 9 (step ST7 in FIG. 5). If it is not the CAN transmission timing (step ST6 in FIG. 5), the process returns to step ST1 again. If the counter value is larger than 0 in step ST3 in FIG. 5, the counter value is decreased by 1 (step ST11), and the process proceeds to step ST4.

  As shown in FIG. 5, when it is determined in step ST2 that the first diagnostic signal 32 or the second diagnostic signal 33 deviates from the normal range, the counter value in the counter unit 39 is increased by 3 for example. (Step ST8 in FIG. 5).

  Subsequently, it is determined whether or not the counter value is equal to or greater than a predetermined error threshold (step ST9 in FIG. 5). If the counter value exceeds the error threshold, an error is determined (step ST10 in FIG. 5). The error signal 45 is transmitted to a control unit such as an electronic device or an in-vehicle device incorporating the magnetic field detection device 9 of FIG. 1 (see FIG. 3). How to handle the error signal 45 in the control unit is arbitrarily determined. For example, upon receiving the error signal 45, the driving of the electronic device or the in-vehicle device can be completely stopped.

  As shown in FIG. 5, if the counter value is below the error threshold value in step ST9, the process proceeds to step ST4.

  Thus, even if the evaluation unit 38 determines that the first diagnostic signal 32 and the second diagnostic signal 33 are out of the normal range, the counter value becomes equal to or greater than a predetermined value without immediately issuing an error signal. When an error signal (steps ST9 and ST10 in FIG. 5) is output for the first time, there is no failure in the electronic circuit 20, and even if an abnormal diagnostic signal is accidentally output due to noise or the like, an error does not occur immediately. The driving stability of the electronic circuit 20 can be improved.

  The present embodiment is characterized in that the microprocessor 24 determines whether or not the electronic circuit 20 is functioning normally based on the two diagnostic signals 32 and 33 of high voltage and low voltage.

  Conventionally, since the diagnosis circuit 25 is not provided and only the detection signal from the detection circuit 21 is processed, the microprocessor 24 detects that the detection signal from the detection circuit 21 is correct even if the multiplexer 22, the operational amplifier 23, or the like is faulty. Since the calculation and the predetermined output processing are performed as a thing, it was inferior in reliability.

  Alternatively, conventionally, there is a circuit configuration in which one diagnostic voltage is input to a microprocessor and compared with a reference voltage set in the microprocessor to self-diagnose whether there is a failure in the electronic circuit. However, if only one diagnostic voltage is used, for example, when a failure occurs in which the multiplexer 22 is locked, if the voltage that coincides with the reference voltage set in the microprocessor 24 continues to be inputted, the microprocessor 24 An erroneous determination is made that the circuit 20 is operating normally.

  On the other hand, in the present embodiment, the microprocessor 24 determines whether or not the electronic circuit 20 is functioning normally based on the two diagnostic signals 32 and 33 of the high voltage and the low voltage. There is no problem, and the electronic circuit 20 capable of self-diagnosis with higher reliability than the conventional one can be configured. That is, by using the two diagnostic signals 32 and 33 of the high voltage and the low voltage, the first diagnostic signal 32 or the first diagnostic signal 32 input to the microprocessor 24 when the electronic circuit 20 fails and does not function normally. Since at least one of the two diagnostic signals 33 always deviates from the normal range as compared with the reference voltage, the state of the electronic circuit 20 can be checked with high accuracy.

  Further, as shown in FIG. 2, the detection circuit 21 and the diagnostic circuit 25 are connected to the multiplexer 22, and the operational amplifier 23 and the microprocessor 24 are provided, so that the circuit configuration is not complicated and the cost increase is suppressed. can do.

  In the present embodiment, as shown in FIG. 3, the self-diagnosis unit 37 of the microprocessor 24 is provided with a reference voltage adjustment unit 40. A first reference voltage for comparison with the first diagnostic signal input to the processor 24 and a second reference voltage for comparison with the second diagnostic signal input to the microprocessor 24 are respectively corrected. It is possible. Thereby, the electronic circuit 20 with higher reliability and capable of self-diagnosis can be configured.

  In the present embodiment, the diagnostic circuit 25 can output a high-voltage first diagnostic signal 32 and a low-voltage second diagnostic signal, respectively, by a resistance voltage dividing circuit. As a result, a simple diagnostic circuit 25 can be configured, and the circuit configuration is not complicated, and an increase in cost can be suppressed.

And by incorporating the electronic circuit 20 in this embodiment in the magnetic sensor 10 arranged to face the magnet 14, the risk of erroneous magnetic field detection can be avoided and the magnetic field detection accuracy can be improved.
The electronic circuit 20 in the present embodiment is applicable to other than the magnetic sensor 10.

DESCRIPTION OF SYMBOLS 9 Magnetic field detection apparatus 10 Magnetic sensor 11 Printed wiring board 14 Magnet 20 Electronic circuit 21 Detection circuit 22 Multiplexer 23 Operational amplifier 24 Microprocessor 25 Diagnosis circuit 26, 27 Bridge circuit 28a-28c Fixed resistance 32 1st diagnostic signal 33 2nd diagnosis Signal 34 SIN signal 35 COS signal 37 Self-diagnosis unit 38 Evaluation unit 39 Counter unit 40 Reference voltage adjustment unit

Claims (5)

An electronic circuit comprising: a detection circuit; an operational amplifier that amplifies a detection signal from the detection circuit; a multiplexer connected between the detection circuit and the operational amplifier; and a microprocessor that performs an arithmetic process on the detection signal from the operational amplifier. In the circuit
A diagnostic circuit for generating a high-voltage first diagnostic signal and a low-voltage second diagnostic signal, respectively;
The diagnostic circuit is connected to the multiplexer, and each diagnostic signal selected by the multiplexer can be input to the microprocessor via the operational amplifier.
In the microprocessor, based on the first diagnostic signal and the second diagnostic signal, whether or not the operational amplifier and the multiplexer are functioning normally can be diagnosed and input to the microprocessor. A first reference voltage for comparison with the first diagnostic signal and a second reference voltage for comparison with the second diagnostic signal input to the microprocessor are stored in the microprocessor. And a reference voltage adjusting unit provided in the microprocessor converts the first reference voltage and the second reference voltage to the input voltages in accordance with fluctuations in the input voltage of the diagnostic circuit. An electronic circuit capable of self-diagnosis characterized by being adjusted to a predetermined ratio. The microprocessor includes a self-diagnosis unit for diagnosing whether or not the electronic circuit is functioning normally based on the first diagnosis signal and the second diagnosis signal input to the microprocessor. Have
The self-diagnosis unit includes an evaluation unit for evaluating whether or not the first diagnosis signal and the second diagnosis signal input to the microprocessor are within a normal range;
A counter unit for accumulating a predetermined counter value when the first diagnostic signal and the second diagnostic signal deviate from a normal range by the evaluation unit;
2. The electronic circuit capable of self-diagnosis according to claim 1, wherein when the counter value exceeds a predetermined value, it is determined that there is an abnormality and an error signal is output. 3. The self-diagnosis is possible according to claim 1, wherein the diagnostic circuit can output the first diagnostic signal at a high voltage and the second diagnostic signal at a low voltage by a resistance voltage dividing circuit, respectively. Electronic circuit.   The electronic circuit according to any one of claims 1 to 3, wherein the detection circuit includes a bridge circuit of a plurality of magnetic field detection elements. A magnetic sensor and a magnet are arranged to face each other with an interval, and the magnetic sensor is for detecting a change in a magnetic field generated from the magnet,
5. The magnetic field detection apparatus, wherein the magnetic circuit includes the electronic circuit including the magnetic field detection element according to claim 4.

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