JP6331853B2 - Sensor device - Google Patents

Description

  The present invention relates to a magnetic sensor and a sensor device having a processing unit that processes a sensor signal output from the magnetic sensor.

  As shown in Patent Document 1, there is known a processing circuit that processes a sensor voltage that periodically changes following the rotation of a rotating body. This processing circuit includes an amplifier circuit capable of adjusting an offset voltage and an amplification factor, an extreme value storage circuit that stores an output voltage of the amplifier circuit, and an adjustment circuit that outputs an adjustment signal of the offset voltage and the amplification factor to the amplifier circuit. And. The extreme value storage circuit stores the maximum value and the minimum value of the output voltage of the amplification circuit, and the adjustment circuit stores the maximum value or the minimum value stored in the amplification circuit based on the output voltage of the amplification circuit and the extreme value storage circuit. In contrast, an offset voltage and gain adjustment signal is output. The adjustment circuit outputs a signal for correcting the extreme value stored in the extreme value storage circuit to the extreme value storage circuit.

JP 2011-196904 A

  As described above, in the processing circuit disclosed in Patent Document 1, the offset voltage and the amplification factor are adjusted by correcting the extreme value stored in the extreme value storage circuit. In the case of this configuration, if the extreme value stored in the extreme value storage circuit disappears due to noise or the like, the extreme value (data) suitable for adjusting the offset voltage and the amplification factor must be calculated again.

  In view of the above problems, an object of the present invention is to provide a sensor device in which data loss is suppressed.

The first invention for achieving the above-described object is to detect a magnetic flux whose transmission direction periodically changes due to rotation of a rotating body, and to output a sensor signal that changes like a triangular wave according to the period of the magnetic flux. a sensor (10), processing unit for processing the sensor signal (30), a storage unit for storing the processed data in the processing unit (50), the first power supply unit for applying a first voltage to the processing unit (71) and a second power supply unit (72) for applying a second voltage to the storage unit, and the storage unit is composed of a volatile memory in which data retained by the disappearance of the applied voltage is lost. The common power supply (73) is connected to each of the first power supply unit and the second power supply unit, and a common voltage is output from the common power supply. The first power supply unit generates a first voltage based on the common voltage. 1 generation circuit (81), the second power supply unit is connected to the common voltage Therefore, when the noise is applied to the second generation circuit (82) that generates the second voltage and the common power supply, and the operation of the second generation circuit becomes unstable, the voltage that applies the second voltage to the storage unit The processing unit includes a holding unit (83) , an amplification unit (31) that amplifies the sensor signal, a conversion unit (33) that converts an output signal of the amplification unit from an analog signal to a digital signal, and an output from the conversion unit A calculation unit (32) that calculates the amplitude and center value of the sensor signal based on the peak value and the bottom value of the sensor signal based on the output signal of the amplification unit, and the amplification unit is an amplifier (36) A gain adjusting unit (37) for adjusting the gain of the amplifier, and an offset adjusting unit (38) for adjusting the offset voltage of the amplifier, and the calculating unit calculates the amplification unit from the amplitude and the center value. Amplitude and center of sensor signal output from An adjustment value for adjusting the gain adjustment unit and the offset adjustment unit is calculated so that and become a predetermined value, and the gain and offset voltage of the amplifier are determined based on the calculated adjustment value. The processing unit includes a check unit (35) for performing a cyclic redundancy check included in the data stored in the storage unit, and the check unit performs a cyclic redundancy check based on the peak value, the bottom value, and the adjustment value. The CRC value to be calculated is calculated, and when the peak value, bottom value, adjustment value, and CRC value are all prepared as data, the peak value, bottom value, adjustment value, and CRC value are stored in the storage unit. It is memorized at the same time .

  According to this, even when noise is applied to the common power source (73), and the operations of the first generation circuit (81) and the second generation circuit (82) become unstable, the voltage holding unit (83) The second voltage is applied to the storage unit (50). Therefore, loss of data stored in the storage unit (50) due to noise is suppressed, and time for calculating the data again and storing it in the storage unit (50) becomes unnecessary.

  In the second invention, the voltage holding unit is a capacitor, and one end of the voltage holding unit is connected to the output terminal (77b) of the second generation circuit. According to this, when the second generation circuit (82) is operating normally, the second voltage is applied to the voltage holding unit (83), and thereby the voltage holding unit (83) is charged. Therefore, even when the operation of the second generation circuit (83) becomes unstable, the second voltage is output from the output terminal of the second generation circuit (83) by the voltage holding unit (83).

  In addition, although the elements described in the claims and the means for solving the problems are attached with parentheses, the parentheses are attached to each component described in the embodiment. This is to simply show the correspondence with the elements, and does not necessarily indicate the elements themselves described in the embodiments. The description of the reference numerals with parentheses does not unnecessarily narrow the scope of the claims.

It is a block diagram showing a schematic structure of a sensor device concerning a 1st embodiment. It is a circuit diagram which shows a common power supply, a 1st power supply part, and a 2nd power supply part. It is a timing chart which shows the amplified sensor signal and the binarized sensor signal. It is a timing chart which shows an adjustment value, a peak value, a bottom value, a CRC value, a data signal, and a memory signal. It is a timing chart which shows the change of the common voltage by the noise application, the 1st voltage, and the 2nd voltage. It is a circuit diagram which shows the modification of a 2nd power supply part.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
(First embodiment)
The sensor device 100 detects the rotation state of a rotating body (not shown). As the rotator, for example, there is a gear of a transmission, and as its type, there are an automatic transmission (AT) and a continuously variable transmission (CVT). In AT and CVT, the output signal of the sensor device 100 is used for speedometer control, and in CVT, pulley rotation detection and belt position control. In addition to the transmission, the rotating body includes, for example, an engine camshaft and a crank. Due to the rotation of the rotating body, a magnetic flux whose transmission direction periodically changes passes through the sensor device 100. The sensor device 100 detects the rotational state of the rotating body based on this magnetic flux. This magnetic flux is output from the sensor device 100 to the rotating body or from the rotating body to the sensor device 100.

  As shown in FIG. 1, the sensor device 100 includes a magnetic sensor 10, a processing unit 30, a storage unit 50, and a power supply unit 70. A part of the processing unit 30, the magnetic sensor 10, and the power supply unit 70 are analog circuits, and a part of the processing unit 30 and the storage unit 50 are digital circuits. The magnetic sensor 10 converts the magnetic flux whose transmission direction periodically fluctuates due to the rotation of the rotating body into an electrical signal, and the processing unit 30 binarizes the sensor signal output from the magnetic sensor 10. As shown in FIG. 3, the sensor signal changes like a triangular wave according to the period of the magnetic flux, and when the voltage level of the sensor signal is higher than the threshold indicated by the broken line, it becomes Hi level, and when it is low, it becomes Lo level. The sensor signal is binarized.

  As described above, since there are various types of rotating bodies, the strength of the magnetic flux that passes through the sensor device 100 also varies. Therefore, the voltage level of the sensor signal output from the magnetic sensor 10 also changes variously. However, in order to process the electrical signal in the processing unit 30, it is necessary to adjust the voltage level of the sensor signal to a voltage level suitable for the processing. As will be described in detail later, the processing unit 30 includes an amplification unit 31 that amplifies the sensor signal, and a calculation unit 32 that adjusts the amplification factor (gain) and the offset voltage of the amplification unit 31. The calculating unit 32 adjusts the voltage level of the sensor signal to a voltage level suitable for processing by adjusting the gain and the offset voltage of the amplifying unit 31, but the adjustment value for adjusting the gain and the offset voltage is stored as described above. Stored in the unit 50. This adjustment value is calculated by the calculation unit 32 when the sensor device 100 is driven and stored in the storage unit 50. The storage unit 50 is composed of a volatile memory, and when the applied voltage is lost, the stored data is lost. Therefore, in order to avoid losing data in the storage unit 50 when the sensor device 100 is driven, the power supply unit 70 includes a first power supply unit 71 that applies a first voltage to the magnetic sensor 10 and the processing unit 30, and a storage unit 50. And a second power supply unit 72 for applying a second voltage. As will be described later, the second power supply unit 72 is more resistant to noise than the first power supply unit 71.

  The magnetic sensor 10 has a magnetoelectric conversion function for converting magnetic flux into an electric signal. Although not shown, the magnetic sensor 10 according to the present embodiment includes a plurality of magnetoresistive elements and a bridge circuit formed by these elements. The resistance value of the magnetoresistive effect element also periodically varies according to the above-described periodic variation of the magnetic flux, and accordingly, the output voltage (sensor voltage) of the bridge circuit also varies periodically. Therefore, the sensor signal behaves like a triangular wave, and the peak value with the highest voltage level and the bottom value with the lowest voltage level appear periodically in the sensor signal. The magnetic sensor 10 may have, for example, a Hall element instead of the magnetoresistive effect element. When the magnetic flux is transmitted from the sensor device 100 to the rotating body, the magnetic sensor 10 may include a magnet that transmits the magnetic flux to the rotating body via the bridge circuit described above.

  The processing unit 30 binarizes the sensor signal. The processing unit 30 includes an AD conversion unit 33, an output circuit 34, and a check unit 35 in addition to the amplification unit 31 and the calculation unit 32 described above. The amplification unit 31 is an analog circuit, and the calculation unit 32, the check unit 35, and the output circuit 34 are digital circuits. The output signal of the amplification unit 31 is converted from an analog signal to a digital signal by the AD conversion unit 33, and the output signal of the amplification unit 31 converted into this digital signal is input to the calculation unit 32. The output signal of the amplifying unit 31 is binarized by the calculating unit 32, and the binarized sensor signal is output to an external device via the output circuit. The calculation unit 32 and the storage unit 50 are electrically connected via a check unit 35, and data calculated by the calculation unit 32 is stored in the storage unit 50 by the check unit 35 and stored in the storage unit 50. The read data is read by the check unit 35. Then, the data read by the check unit 35 is output to the calculation unit 32. The check unit 35 will be described in detail later.

  The amplifying unit 31 includes an amplifier 36, a gain adjusting unit 37 for adjusting the gain of the amplifier 36, and an offset adjusting unit 38 for adjusting the offset voltage of the amplifier 36. The gain adjusting unit 37 is a variable resistor such as a ladder resistor, and is provided in a feedback wiring that connects the input terminal and the output terminal of the amplifier 36. This resistance value is adjusted by the calculation unit 32. The offset adjustment unit 38 is a DA conversion circuit that converts the adjustment voltage output from the calculation unit 32 from a digital signal to an analog signal. The offset adjustment of the amplifier 36 is performed by the adjustment voltage output from the offset adjustment unit 38.

  As described above, the calculation unit 32 adjusts the gain and offset voltage of the amplifier 36, and an adjustment value for achieving the adjustment is calculated based on the following processing. First, the calculation unit 32 calculates the peak value and the bottom value of the sensor signal based on the sensor signal input via the amplification unit 31 and the AD conversion unit 33. The calculation unit 32 calculates the amplitude and center value of the sensor signal based on the calculated peak value and bottom value. Next, the calculating unit 32 uses the resistance value of the gain adjusting unit 37 and the offset adjusting unit 38 so that the amplitude and center value of the sensor signal amplified by the amplifying unit 31 from the calculated amplitude and center value become values suitable for processing. An adjustment value for adjusting each of the adjustment voltages input to is calculated. The adjustment value is calculated when the sensor device 100 is driven, and the calculated adjustment value is stored in the storage unit 50. After calculating the adjustment value, the calculation unit 32 determines the gain and offset voltage of the amplifier 36 based on the adjustment value. Further, the calculation unit 32 sequentially obtains the peak value and the bottom value of the sensor signal based on the sensor signal input via the amplification unit 31 and the AD conversion unit 33, and sequentially transmits them to the check unit 35 to store the storage unit 50. To remember. Then, the calculation unit 32 uses the midpoint of the calculated peak value and bottom value as a threshold value, and binarizes the sensor signal output from the AD conversion unit 33 based on the threshold value. The gain and the offset voltage when driving the sensor device 100 are set to predetermined values. Based on the adjustment value, the predetermined value is revised so that the voltage level of the sensor signal becomes a value suitable for processing in the calculation unit 32. A value suitable for processing in the calculation unit 32 corresponds to a predetermined value described in the claims.

  Next, the check unit 35 will be described. The check unit 35 performs a cyclic redundancy check. The check unit 35 receives the peak value and the bottom value from the calculation unit 32 and the adjustment value stored in the storage unit 50. The check unit 35 calculates a CRC value for performing a cyclic redundancy check based on the input peak value, bottom value, and adjustment value. FIG. 4 is a timing chart showing the timing at which data is calculated by increasing the voltage level. The data signal shown in FIG. 4 is a signal indicating that all the data of the peak value, the bottom value, the adjustment value, and the CRC value are prepared, and the stored signal is the peak value, the bottom value, the adjustment value, and the CRC. It is a signal for storing a value in the storage unit 50. The check unit 35 inputs the storage signal to the storage unit 50 when all the data of the peak value, the bottom value, the adjustment value, and the CRC value are prepared (the data signal rises), thereby the peak value and the bottom value. The adjustment value and the CRC value are stored simultaneously. The first writing is performed at time t1, and the second writing is performed at time t2. In FIG. 4, in order to indicate that the adjustment value is once calculated and is not recalculated, the voltage level of the adjustment value is constantly increased after being calculated once.

  The check unit 35 performs the following cyclic redundancy check when its drive is instantaneously interrupted and restored by noise applied to the common power source 73 described later. That is, the check unit 35 calculates a new CRC value based on the peak value and the bottom value output from the calculation unit 32 and the adjustment value stored in the storage unit 50. Then, the check unit 35 compares the calculated new CRC value with the CRC value stored in the storage unit 50. If they are different, the check unit 35 determines that an error has occurred in the adjustment value stored in the storage unit 50 and discards the adjustment value stored in the storage unit 50. Then, the check unit 35 requests the calculation unit 32 to calculate a new adjustment value, and stores the calculated new adjustment value in the storage unit 50. In contrast, when both are the same, the check unit 35 determines that no error has occurred in the adjustment value stored in the storage unit 50 and does not discard the adjustment value stored in the storage unit 50. As described above, the adjustment value is calculated when the sensor device 100 is driven and stored in the storage unit 50. However, unless an error occurs in the adjustment value due to application of noise, the adjustment value is calculated again and stored in the storage unit 50. Not remembered.

  The storage unit 50 stores data processed by the processing unit 30. The data processed by the processing unit 30 includes the above-described peak value, bottom value, adjustment value, and CRC value. The storage unit 50 is composed of a volatile memory in which stored data is lost due to the disappearance of the applied voltage, and a D latch can be adopted as the volatile memory. Any one of the peak value, the bottom value, the adjustment value, and the CRC value is input from the check unit 35 to at least one D terminal of the plurality of D latches constituting the storage unit 50. Then, when the peak value, the bottom value, the adjustment value, and the CRC value are all input to the corresponding D latch, the storage signal is simultaneously input from the check unit 35 to the G terminals of all the D latches. By doing so, the peak value, the bottom value, the adjustment value, and the CRC value are simultaneously stored in the plurality of D latches constituting the storage unit 50.

  The power supply unit 70 includes a first power supply unit 71 and a second power supply unit 72. As shown in FIG. 1, a common power supply 73 is commonly connected to each of the first power supply unit 71 and the second power supply unit 72, and the common voltage of the common power supply 73 is applied to each of the first power supply unit 71 and the second power supply unit 72. Applied. As shown in FIG. 2, the power supply units 71 and 72 and the common power supply 73 are electrically connected to each other via a common wiring 77. The common power source 73 includes a power source 74 connected to the common wiring 77, a reference voltage circuit 75 that generates a reference voltage, and noise suppression that suppresses the application of noise to each of the reference voltage circuit 75 and the power source units 71 and 72. Part 76. The noise suppression unit 76 and the reference voltage circuit 75 are sequentially connected to the common wiring 77 so as to be away from the power source 74, and the voltage (common voltage) of the power source 74 via the resistor 78 of the noise suppression unit 76 is the reference voltage circuit 75. It is the structure applied to. The reference voltage circuit 75 is a so-called band gap circuit.

  The noise suppression unit 76 includes a resistor 78 provided in the common wiring 77 and three Schottky barrier diodes 79 provided in the ground wiring 80 that connects the common wiring 77 and the ground. One end of the ground wiring 80 is connected between the resistor 78 and the reference voltage circuit 75 in the common wiring 77, and the other end is connected to the ground. The anode electrode of each of the three Schottky barrier diodes 79 is connected to the ground side, and the cathode electrode is connected to the common wiring 77 (power supply 74) side. Thus, even if a common voltage is applied to the cathode electrode of the Schottky barrier diode 79 via the resistor 78, no current flows through the three Schottky barrier diodes 79 toward the ground. However, for example, when noise is applied between the power supply 74 and the resistor 78 in the common wiring 77, noise flows to the ground via each of the three Schottky barrier diodes, and the noise flows to the reference voltage circuit 75 and the power supply units 71 and 72. Is suppressed from being input.

  As shown in FIG. 2, the first power supply unit 71 and the second power supply unit 72 are sequentially connected to the common wiring 77 so as to be away from the common power supply 73, and the first power supply unit 71 and the second power supply unit 72 are connected via the common wiring 77. A common voltage is applied to each power supply unit 72. The first power supply unit 71 includes a first generation circuit 81 that generates a first voltage based on the common voltage. The first generation circuit 81 is provided between the first amplifier 84 that amplifies the difference value between the reference voltage and the common voltage, the common wiring 77, and the first output terminal 77a. A first switch 85 in a driving state. The first switch 85 is an npn transistor, the collector electrode of which is connected to the common wiring 77, and the emitter electrode of which is connected to the first output terminal 77a. When the first switch 85 is turned on, the common wiring 77 and the first output terminal 77a are electrically connected via the first switch 85. As a result, the common voltage dropped by the resistance of the first switch 85 is output from the first output terminal 77a as the first voltage. The first output terminal 77 a is electrically connected to the processing unit 30 and the magnetic sensor 10.

  On the other hand, in the second power supply unit 72, noise is applied to the second generation circuit 82 that generates the second voltage based on the common voltage and the common power supply 73, and the operation of the second generation circuit 82 becomes unstable. In this case, the storage unit 50 includes a voltage holding unit 83 that applies the second voltage. The second generation circuit 82 is provided between the second amplifier 86 that amplifies the difference value between the reference voltage and the common voltage, the common wiring 77, and the second output terminal 77b. And a second switch 87 which is in a driving state. The second switch 87 is a P-channel MOSFET, and its source electrode is connected to the common wiring 77, and its drain electrode is connected to the second output terminal 77b. When the second switch 87 is turned on, the common wiring 77 and the second output terminal 77 b are electrically connected via the second switch 87. As a result, the common voltage dropped by the resistance of the second switch 87 is output from the second output terminal 77b as the second voltage. The second output terminal 77b is electrically connected to the storage unit 50.

  The voltage holding unit 83 is a capacitor. As shown in FIG. 2, the voltage holding unit 83 is provided in the ground wiring 88 that connects the drain electrode of the second switch 87 and the ground, one end of which is connected to the drain electrode of the second switch 87, and the other end. Connected to ground. Thus, when the second switch 87 is turned on, the voltage holding unit 83 is charged by the second voltage output from the second switch 87, and the voltage difference between both ends of the voltage holding unit 83 becomes the second voltage. Therefore, even if the operation of the second switch 87 becomes indefinite, the second voltage is output from the second output terminal 77b for the voltage holding unit 83. The drain electrode of the second switch 87 corresponds to the output terminal of the second generation circuit described in the claims.

  The second power supply unit 72 according to the present embodiment includes a backflow prevention element 89 in addition to the second generation circuit 82 and the voltage holding unit 83 described above. The backflow prevention element 89 suppresses the flow of current to the common power source 73 due to the charge stored in the voltage holding unit 83. The backflow prevention element 89 according to the present embodiment is a diode, and is provided between the second switch 87 and the common wiring 77. The anode electrode of the backflow prevention element 89 is connected to the common wiring 77 side, and the cathode electrode is connected to the second switch 87 side.

  Next, functions and effects of the sensor device 100 according to the present embodiment will be described. As described above, even if the operation of the second switch 87 becomes indefinite, the second voltage is output from the second output terminal 77b for the voltage holding unit 83, and the second voltage is applied to the storage unit 50. . FIG. 5 shows the behavior of the common voltage, the first voltage, and the second voltage when noise is applied to the common wiring 77. As shown in FIG. 5, when the voltage value of the common voltage varies greatly due to noise applied at the timing of time t3, the voltage value of the first voltage also varies greatly. However, the fluctuation of the voltage value of the second voltage is smaller than that of the first voltage, and it can be seen that the fluctuation of the second voltage is suppressed by the application of noise. Thus, since the fluctuation | variation of the 2nd voltage by application of noise is suppressed, it is suppressed that the data (adjustment value) memorize | stored in the memory | storage part 50 are lost by noise. Therefore, time for calculating the adjustment value again and storing it in the storage unit 50 becomes unnecessary. The broken line shown in FIG. 5 indicates the ground potential.

  The voltage holding unit 83 is a capacitor, and the voltage holding unit 83 is provided in the ground wiring 88 that connects the drain electrode of the second switch 87 and the ground. Accordingly, when the second switch 87 is turned on, the voltage holding unit 83 is charged by the second voltage output from the second switch 87. Therefore, even if the operation of the second switch 87 becomes unstable due to the application of noise, the second voltage is output from the second output terminal 77 b for the voltage holding unit 83.

  A backflow prevention element 89 that suppresses a current from flowing to the common power source 73 due to the electric charge stored in the voltage holding unit 83 is provided between the second switch 87 and the common wiring 77. According to this, even when the operation of the second generation circuit 82 becomes unstable, it is possible to suppress the current from flowing into the common power source 73 due to the voltage holding unit 83.

  The magnetic sensor 10 converts a magnetic flux whose transmission direction periodically varies with the rotation of the rotating body into an electrical signal. The rotating body is constantly turning, whereby the sensor signal output from the magnetic sensor 10 is also constantly changing. Therefore, when the adjustment value for adjusting the gain and the offset voltage of the amplifier 36 is lost from the storage unit 50 due to noise, the rotation of the rotating body is performed while the adjustment value is calculated again despite the rotation of the rotating body. The state cannot be detected. However, as described above, the loss of the adjustment value stored in the storage unit 50 due to noise is suppressed. Therefore, time for calculating the adjustment value again and storing it again in the storage unit 50 becomes unnecessary.

  The check unit 35 causes the storage unit 50 to simultaneously store the peak value, the bottom value, the adjustment value, and the CRC value when all of the peak value, the bottom value, the adjustment value, and the CRC value are collected. According to this, power consumption is reduced as compared with the configuration in which the peak value, the bottom value, the adjustment value, and the CRC value are stored in the storage unit at different timings.

  The check unit 35 checks whether or not an error has occurred in the adjustment value stored in the storage unit 50 when its drive is instantaneously interrupted and restored by noise applied to the common power source 73. Thereby, the reliability of the adjustment value is improved.

  The preferred embodiments of the present invention have been described above. However, the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present invention.

  In the present embodiment, an example in which the offset adjustment unit 38 is a DA conversion circuit is shown. However, the offset adjustment unit 38 is not limited to the above example, and may be appropriately adopted as long as it adjusts the offset voltage of the amplifier 36 according to the signal (adjustment signal) output from the calculation unit 32 based on the adjustment value. Can do.

  In this embodiment, the example which has the check part 35 for the process part 30 to perform cyclic redundancy check was shown. However, the processing unit 30 may not include the check unit 35. In this case, the calculation unit 32 writes and reads data to and from the storage unit 50. The CRC value is not calculated, and the adjustment value check (cyclic redundancy check) is not performed.

  In the present embodiment, an example is shown in which the peak value, the bottom value, the adjustment value, and the CRC value are stored in the storage unit 50 at the time when all the data are prepared. However, the peak value, the bottom value, the adjustment value, and the CRC value may be stored in the storage unit 50 at different timings.

  In the present embodiment, an example in which the storage unit 50 includes a plurality of D latches is shown. However, the element constituting the storage unit 50 is not limited to the above example, and, for example, a flip-flop may be employed.

  In the present embodiment, an example in which the common power source 73 includes the reference voltage circuit 75 is shown. However, the common power source 73 may not have the reference voltage circuit 75. In this case, the reference voltage input to each of the first amplifier 84 and the second amplifier 86 is the ground potential.

  In this embodiment, the common power supply 73 has shown the example which has the noise suppression part 76. FIG. However, the common power source 73 may not include the noise suppression unit 76. In this case, the voltage itself output from the power supply 74 corresponds to the common voltage. The common power supply 73 may have a resistor 78 that is a part of the noise suppression unit 76.

  In the present embodiment, an example in which the noise suppression unit 76 includes three Schottky barrier diodes 79 is shown. However, the number of Schottky barrier diodes 79 is not limited to the above example, and may be one, two, or four or more. The noise suppression unit 76 may have a simple diode instead of the Schottky barrier diode 79.

  In the present embodiment, an example in which the first switch 85 is an npn transistor has been described. However, the first switch 85 is not limited to the above example, and, for example, a pnp transistor or a MOSFET can be employed.

  In the present embodiment, an example in which the second switch 87 is a P-channel MOSFET has been described. However, the second switch 87 is not limited to the above example, and for example, an N-channel MOSFET or a transistor can be employed.

  In the present embodiment, an example in which the second power supply unit 72 includes the backflow prevention element 89 is shown. However, the second power supply unit 72 may not have the backflow prevention element 89.

  In the present embodiment, an example in which the backflow prevention element 89 is a diode is shown. However, the backflow preventing element 89 is not limited to the above example. For example, as illustrated in FIG. 6, a configuration in which the backflow prevention element 89 includes a pnp transistor 90, a second voltage holding unit 91, and a noise suppression unit 92 can be employed. The emitter electrode and base electrode of the pnp transistor 90 are connected to the common wiring 77, and the collector electrode is connected to the source electrode of the second switch 87. Thus, a diode is formed by the PN junction that forms the emitter electrode and the base electrode in the pnp transistor 90. The second voltage holding unit 91 stably applies a common voltage to the base electrode of the pnp transistor 90 even when noise is applied to the common wiring 77. The second voltage holding unit 91 is a capacitor. As shown in FIG. 6, one end of the second voltage holding unit 91 is connected to the common wiring 77 and the base electrode of the pnp transistor 90, and the other end is connected to the ground. Yes. Thereby, when the common power supply 73 is normal, the common voltage is applied to the second voltage holding unit 91 and the second voltage holding unit 91 is charged. When the operation of the common power source 73 becomes unstable, the common voltage is applied from the second voltage holding unit 91 to the base electrode of the pnp transistor. This suppresses fluctuations in the driving state of the pnp transistor. The noise suppression unit 92 suppresses application of noise to the base electrode of the pnp transistor 90 when noise is applied to the common wiring 77. The noise suppression unit 92 includes a resistor 93 provided in a ground wiring 94 that connects the base electrode of the pnp transistor 90 and the ground. When noise is applied to the common wiring 77, the noise flows into the ground via the ground wiring 94 provided with the resistor 93.

DESCRIPTION OF SYMBOLS 10 ... Magnetic sensor 30 ... Processing part 50 ... Memory | storage part 71 ... 1st power supply part 72 ... 2nd power supply part 73 ... Common power supply 81 ... 1st generation circuit 82 ... 2nd generation circuit 83 ... Voltage holding part 100 ... Sensor apparatus

Claims (4)

A magnetic sensor (10) for detecting a magnetic flux whose transmission direction is periodically changed by rotation of a rotating body, and outputting a sensor signal that changes like a triangular wave according to the period of the magnetic flux ;
Processing unit for processing the sensor signal (30),
A storage unit (50) for storing data processed by the processing unit;
A first power supply unit (71) for applying a first voltage to the processing unit;
A second power supply unit (72) for applying a second voltage to the storage unit,
The storage unit is composed of a volatile memory in which the data held by loss of applied voltage is lost,
A common power supply (73) is connected in common to each of the first power supply unit and the second power supply unit, and a common voltage is output from the common power supply,
The first power supply unit includes a first generation circuit (81) that generates the first voltage based on the common voltage,
In the second power supply unit, noise is applied to the second generation circuit (82) that generates the second voltage based on the common voltage, and the common power supply, and the operation of the second generation circuit becomes indefinite. A voltage holding unit (83) for applying the second voltage to the storage unit ,
The processing unit includes an amplification unit (31) that amplifies the sensor signal, a conversion unit (33) that converts an output signal of the amplification unit from an analog signal to a digital signal, and the amplification unit that is output from the conversion unit. A calculation unit (32) for calculating an amplitude and a center value of the sensor signal based on a peak value and a bottom value of the sensor signal based on the output signal of
The amplification unit includes an amplifier (36), a gain adjustment unit (37) for adjusting the gain of the amplifier, and an offset adjustment unit (38) for adjusting an offset voltage of the amplifier,
The calculation unit adjusts the gain adjustment unit and the offset adjustment unit so that the amplitude and the center value of the sensor signal output from the amplification unit have predetermined values from the amplitude and the center value. An adjustment value for the amplifier is calculated, and the gain and offset voltage of the amplifier are determined based on the calculated adjustment value.
The adjustment value is included in the data stored in the storage unit,
The processing unit includes a check unit (35) for performing a cyclic redundancy check,
The check unit calculates a CRC value for performing the cyclic redundancy check based on the peak value, the bottom value, and the adjustment value, and the data includes the peak value, the bottom value, the adjustment value, And when all the said CRC values are gathered, the said peak value, the said bottom value, the said adjustment value, and the said CRC value are memorize | stored simultaneously in the said memory | storage part, The sensor apparatus characterized by the above-mentioned . The voltage holding unit is a capacitor,
The sensor device according to claim 1, wherein one end of the voltage holding unit is connected to an output terminal of the second generation circuit.   A backflow prevention element (89 to 93) is provided between the second generation circuit and the common power source to suppress a current from flowing to the common power source due to the electric charge stored in the voltage holding unit. The sensor device according to claim 2, wherein: The check unit
When the drive of itself is instantaneously interrupted by the noise applied to the common power supply and returns, the new CRC value is calculated based on the peak value, the bottom value, and the adjustment value output from the calculation unit. Calculate
The calculated new CRC value is compared with the CRC value stored in the storage unit,
When both are different, the adjustment value stored in the storage unit is discarded, the calculation unit is requested to calculate a new adjustment value, and the calculated new adjustment value is stored in the storage unit. And
The sensor device according to any one of claims 1 to 3 , wherein when both are the same, the adjustment value stored in the storage unit is not discarded.

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