JP2016050841A - Magnetism detection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnetism detection device that suppresses manufacturing costs.SOLUTION: A rotation angle detection device 1 is roughly configured, as shown in Figure 2(a), with a magnetism detection unit for detecting a change in a magnetic field 25 corresponding to the displacement of an object to be detected and outputting a detection signal differing in phase, a switching unit 7 having a plurality of magnetism detection units (first MR sensor 5 and second MR sensor 6) electrically connected thereto and periodically switching the connection with each of the plurality of magnetism detection units, and an operational amplifier 8 for differentially amplifying the detection signal differing in phase for each of the plurality of magnetism detection units that is inputted via the switching unit 7.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a magnetic detection device.

  As a conventional technique, a magnet that rotates in conjunction with a steering and four magnetoresistors are arranged in a substantially rectangular shape, and two opposing magnetoresistors are electrically connected to form two pairs of magnetoresistors. Two magnetic detection elements formed, switching means disposed at both ends of a pair of magnetic resistances of one magnetic detection element, and two pairs of magnetic detection elements electrically connected to each of the two magnetic detection elements There is known a rotation angle detection device comprising two operational amplifiers for differentially amplifying the intermediate potential of a resistor, and control means for controlling the switching means and detecting the rotation angle of the magnet based on the outputs of the two operational amplifiers. (For example, refer to Patent Document 1).

  In this rotation angle detection device, one of the two magnetic detection elements is rotated by 45 ° with respect to the other, and is further arranged so that both are overlapped.

JP 2012-78207 A

  However, since the conventional rotation angle detection device requires the same number of operational amplifiers as the magnetic detection elements, the number of operational amplifiers increases as the number of magnetic detection elements increases, resulting in an increase in manufacturing cost.

  Accordingly, an object of the present invention is to provide a magnetic detection device that suppresses manufacturing costs.

  According to one embodiment of the present invention, a magnetic detection unit that detects a change in a magnetic field according to a displacement of a detection target and outputs detection signals having different phases and a plurality of magnetic detection units are electrically connected, and a plurality of magnetic detection units Magnetic detection unit comprising: a switching unit that periodically switches connections to each of the units; and a differential amplification unit that differentially amplifies detection signals having different phases for each of the plurality of magnetic detection units input via the switching unit Providing equipment.

  According to the present invention, the manufacturing cost can be suppressed.

FIG. 1A is a schematic diagram of a rotation angle detection device according to the first embodiment, and FIG. 1B shows a first MR (Magneto Resistive) sensor, a second MR sensor, and a magnet. FIG. 1C is a schematic diagram for explaining the arrangement of the first MR sensor and the second MR sensor. FIG. 2A is a block diagram of the rotation angle detection device according to the first embodiment, and FIG. 2B is a graph of detection signals output from the first MR sensor. FIG. 2C is a graph of detection signals output from the second MR sensor, and FIG. 2D is a graph of amplified signals obtained by differentially amplifying the respective detection signals. FIG. 3 is a block diagram of a rotation angle detection device according to the second embodiment.

(Summary of embodiment)
A magnetic detection device according to an embodiment detects a change in a magnetic field according to a displacement of a detection target, and outputs a detection signal having a different phase and a plurality of magnetic detection units electrically connected to each other. A switching unit that periodically switches connection to each of the magnetic detection units, and a differential amplification unit that differentially amplifies detection signals having different phases for each of the plurality of magnetic detection units input via the switching unit. It is roughly structured.

  Since this magnetic detection device performs differential amplification by switching the connection between the magnetic detection unit and the differential amplification unit by the switching unit, it does not require the same number of differential amplification units as the magnetic detection unit, thereby reducing the manufacturing cost. can do.

[First embodiment]
(Overall configuration of the rotation angle detection device 1)
FIG. 1A is a schematic diagram of the rotation angle detection device according to the first embodiment, and FIG. 1B shows the positional relationship between the first MR sensor, the second MR sensor, and the magnet. FIG. 1C is a top view for explaining, and FIG. 1C is a schematic diagram for explaining the arrangement of the first MR sensor and the second MR sensor. FIG. 2A is a block diagram of the rotation angle detection device according to the first embodiment, and FIG. 2B is a graph of detection signals output from the first MR sensor. FIG. 2C is a graph of detection signals output from the second MR sensor, and FIG. 2D is a graph of amplified signals obtained by differentially amplifying the respective detection signals. In FIG. 2B to FIG. 2D, the vertical axis is the voltage [V], and the horizontal axis is the rotation angle θ [°]. FIG. 2B to FIG. 2D illustrate a range of 0 ° to 180 °. Note that, in each drawing according to the embodiment described below, the ratio between figures may be different from the actual ratio. In FIG. 2A and FIG. 3 described later, main signals and information flows are indicated by arrows.

  A rotation angle detection device 1 as a magnetic detection device detects a rotation angle of a detection target through direct detection of a rotation angle of a detection target or detection of a rotation angle of a member that rotates in conjunction with the detection target. It is. This detection target is, for example, an operation knob or the like of an electronic device in which a vehicle is steered or rotated.

  In the present embodiment, a case where a magnet 2 is attached to a detection target will be described as shown in FIG. It is assumed that the rotation axis to be detected coincides with the rotation axis 200 of the magnet 2. Moreover, the rotation angle detection apparatus 1 shall be electrically connected to the electronic device mounted in the vehicle as an example.

  As shown in FIG. 2A, the rotation angle detection device 1 detects a change in the magnetic field 25 according to the displacement of the detection target, and outputs a detection signal having a different phase, and a plurality of magnetic detection units. Are electrically connected, and the switching unit 7 that periodically switches the connection to each of the plurality of magnetic detection units, and the detection signals having different phases for the plurality of magnetic detection units input via the switching unit 7 are differentially And an operational amplifier 8 as a differential amplifier for amplifying.

  The rotation angle detection device 1 includes a first MR sensor 5 and a second MR sensor 6 as a magnetic detection unit. The first MR sensor 5, the second MR sensor 6, and the switching unit 7 are disposed on the substrate 3 as a one-chip magnetic sensor IC (Integrated Circuit) 4 as an example. This substrate 3 is, for example, a printed wiring board.

The rotation angle detection device 1 converts the amplified signal S ₁ output from the operational amplifier 8 into a digital signal and outputs a digital signal S _2. The A / D conversion unit 9 outputs the digital signal S ₂ and outputs from the A / D conversion unit 9. A rotation angle calculation unit 10 as a calculation unit that calculates the rotation angle θ to be detected based on the digital signal S ₂ and a clock signal generation unit 11 that generates the clock signal S ₄ are provided.

  The operational amplifier 8, A / D converter 9, rotation angle calculator 10 and clock signal generator 11 are arranged on the substrate 3.

(Configuration of magnet 2)
The magnet 2 is, for example, a permanent magnet such as an alnico magnet, a ferrite magnet, or a neodymium magnet, or a magnetic material such as a ferrite-based, neodymium-based, samakoba-based, or samarium-iron-nitrogen-based material, and a polystyrene-based, polyethylene-based, polyamide-based, It is a plastic magnet formed by mixing a synthetic resin material such as acrylonitrile / butadiene / styrene (ABS) into a desired shape. The magnet 2 may be an electromagnetic magnet.

  As shown in FIG. 1A, the magnet 2 has a cylindrical shape. The magnet 2 is magnetized so that one of the semi-cylinders has an N pole and the other has an S pole. Therefore, the magnet 2 springs out from the north pole and forms a magnetic field 25 that is sucked into the south pole. In FIG. 1A, the magnetic field 25 on the front surface 20 of the magnet 2 is illustrated. On the back surface 21 side facing the substrate 3, the magnetic field 25 acts on the detection regions of the first MR sensor 5 and the second MR sensor 6. A magnetic field 25 is generated.

  The magnetic field 25 on the back surface 21 side generates a magnetic vector 250 that crosses the detection regions of the first MR sensor 5 and the second MR sensor 6 as shown in FIGS. 1B and 1C. Note that the magnetic vector 250 in FIGS. 1B and 1C schematically shows a part of the magnetic vector of the magnetic field 25.

  The magnet 2 rotates clockwise (in the direction of arrow A) and counterclockwise (in the direction of arrow B) about the rotating shaft 200 shown in FIG. The magnetic vector 250 rotates about the rotation axis 200 as the magnet 2 rotates.

  As shown in FIG. 1B, the rotation angle θ of the magnet 2, that is, the rotation angle θ of the detection object is such that the boundary between the N pole and the S pole is between the first MR sensor 5 and the second MR sensor 6. The position is the reference position (θ = 0 °), and the clockwise direction is positive. The magnet 2 and the magnetic sensor IC 4 are arranged so that the rotation shaft 200 passes through the midpoint of the first MR sensor 5 and the second MR sensor 6.

(Configuration of magnetic sensor IC4)
As an example, the magnetic sensor IC 4 is formed by sealing with resin so that the first MR sensor 5, the second MR sensor 6, and the switching unit 7 become one chip. The sealing with the resin is performed using, for example, a thermosetting molding material in which an epoxy resin is a main component and a silica filler is added. The first MR sensor 5, the second MR sensor 6, and the switching unit 7 may be separately disposed on the substrate 3.

  As shown in FIG. 1C, the first MR sensor 5 includes a first magnetoresistive element 51 to a fourth magnetoresistive element 54. The second MR sensor 6 includes a first magnetoresistive element 61 to a fourth magnetoresistive element 64. The first magnetoresistive element 51 to the fourth magnetoresistive element 54 and the first magnetoresistive element 61 to the fourth magnetoresistive element 64 are the same magnetoresistive elements although they are arranged differently. Accordingly, the first magnetoresistive element 51 to the fourth magnetoresistive element 54 and the first magnetoresistive element 61 to the fourth magnetoresistive element 64 have the same resistance value when the magnetic field 25 is not acting. It is configured.

  In the first MR sensor 5, adjacent magnetoresistive elements are arranged at an angle of 90 °, and a bridge circuit is formed by the first magnetoresistive element 51 to the fourth magnetoresistive element 54. The second MR sensor 6 has an arrangement in which the bridge circuit, that is, the first MR sensor 5 is rotated by 45 °.

A power supply voltage VCC is applied to one end of the first magnetoresistive element 51, and the other end is electrically connected to one end of the second magnetoresistive element 52. The other end of the second magnetoresistive element 52 is grounded. A midpoint potential is generated between the first magnetoresistive element 51 and the second magnetoresistive element 52, and a detection signal V ₁ indicating a change in the midpoint potential accompanying the rotation of the magnet 2 is output.

The power supply voltage VCC is applied to one end of the third magnetoresistive element 53, and the other end is electrically connected to one end of the fourth magnetoresistive element 54. The other end of the fourth magnetoresistive element 54 is grounded. A midpoint potential is generated between the third magnetoresistive element 53 and the fourth magnetoresistive element 54, and a detection signal V ₂ indicating a change in the midpoint potential accompanying the rotation of the magnet ₂ is output.

The detection signal V ₁ and the detection signal V ₂ output from the first MR sensor 5 are signals having different phases according to the rotation angle θ of the magnet 2 as shown in FIG. Specifically, when the magnet 2 is at the reference position (θ = 0 °), the magnetic vector 250 is changed from the first magnetoresistive element 51 to the second magnetoresistive element 54 as shown in FIG. And the first magnetoresistive element 51 to the second magnetoresistive element 54 have the same magnetoresistance. Therefore, the detection signal V ₁ and the detection signal V ₂ are sine waves whose phases are different by 90 °.

The detection signal V ₁ of the first MR sensor 5 is input to the non-inverting input terminal (+) of the operational amplifier 8 via the switch SW ₁ of the switching unit 7. The detection signal V ₂ is the inverting input terminal of the operational amplifier 8 via a switch SW ₂ of the switch unit 7 - is input to ().

The detection signal V ₃ and the detection signal V ₄ output from the second MR sensor 6 are signals having different phases according to the rotation angle θ of the magnet 2 as shown in FIG. Specifically, since the second MR sensor 6 is arranged by rotating the first MR sensor 5 by 45 °, the detection signal V ₃ and the detection signal V ₄ are the detection signal V ₁ and the detection signal V _2. And the phase is 45 ° different. Therefore, the detection signal V ₃ and the detection signal V ₄ are cosine waves whose phases are different by 90 °.

The detection signal V ₃ of the second MR sensor 6 is input to the inverting input terminal (−) of the operational amplifier 8 through the switch SW ₄ of the switching unit 7. The detection signal V ₄ is input to the non-inverting input terminal (+) of the operational amplifier 8 via the switch SW ₃ of the switching unit 7.

The amplified signal S _{1a in} FIG. 2D shows a signal obtained by differentially amplifying the detection signal V ₁ and the detection signal V ₂ of the first MR sensor 5. An amplified signal S _{1b in} FIG. 2D shows a signal obtained by differentially amplifying the detection signal V ₃ and the detection signal V ₄ of the second MR sensor 6. The amplified signal S _1a and the amplified signal S _1b are alternately generated according to the switching cycle of the switches SW ₁ to SW ₄ of the switching unit 7. Thus amplified signal _{S 1} is output as a signal including the amplified signal _{S 1a} and the amplified signal _{S 1b} alternately to the A / D converter 9.

(Configuration of the switching unit 7)
The switching unit 7 is, for example, a multiplexer. As shown in FIG. 2A, the switching unit 7 includes switches SW ₁ to SW ₄ and a control unit 70 that periodically switches the switches SW ₁ to SW ₄ based on the clock signal S _4. It is equipped with.

For example, the control unit 70 includes a semiconductor memory that stores a table 71 that is referred to when the switches SW ₁ to SW ₄ are switched. For example, the control unit 70 refers to the table 71 and is configured to periodically switch the switches SW ₁ to SW ₄ according to the input clock signal S ₄ .

In this table 71, switch SW ₁ and switch SW ₂ are closed, switch SW ₃ and switch SW ₄ are opened, switch SW ₁ and switch SW ₂ are opened, and switch SW ₃ and switch SW ₄ are closed. ₁ of opening and closing of the ~ switch SW ₄ combinations are stored.

(Configuration of A / D converter 9)
A / D converter 9 is output from the first MR sensor 5 and the second MR sensor 6, the amplified signals S ₁ which is an analog signal obtained through the differential amplification by the operational amplifier 8, on the basis of the clock signal S ₄ It is configured to convert the digital signal S ₂ by sampling based on predetermined sampling period.

This digital signal S ₂ is obtained by differentially amplifying the detection signal V ₁ and the detection signal V _{2 of} the first MR sensor 5 when the first MR sensor 5 is connected to the operational amplifier 8 via the switching unit 7. is generated based on the amplified signals S ₁ was. The digital signal S _2, when the second MR sensor 6 is connected to the operational amplifier 8 via a switching unit 7, the detection signal V ₃ and the detection signal V ₄ of the second MR sensor 6 is differential amplifier is generated based on the amplified signals S ₁ was. Therefore the digital signal S _2, a digital signal of the first MR sensor 5 and the digital signal of the second MR sensor 6 is included alternately on the basis of the clock signal S _4.

(Configuration of the rotation angle calculation unit 10)
For example, the rotation angle calculation unit 10 is configured to separate the digital value of the first MR sensor 5 and the digital value of the second MR sensor 6 from the digital signal S ₂ based on the clock signal S ₄ . .

Specifically, the rotation angle calculation unit 10, for example, a digital signal based on the amplified signal S ₁ a of the first MR sensor 5 output based on the clock signal S ₄ and an amplified signal of the second MR sensor 6. generates Sinθ and Cos? separates the digital signal based on the S _1b, by calculating the inverse tangent function (arctan) from Sinθ and Cos?, is configured to calculate the rotation angle theta. The rotation angle calculation unit 10 is configured to calculate a rotation angle θ of 180 ° or more and a rotation angle θ in the direction of arrow B, for example, by holding a history of the calculated rotation angle θ.

Rotation angle calculation unit 10 generates the rotational angle information S ₃ is calculated information of the rotation angle θ, and outputs the connected electronic equipment.

(Configuration of clock signal generation unit 11)
Clock signal generator 11 generates a clock signal S ₄ for synchronizing the switching unit 7, A / D converter 9 and the rotation angle calculation unit 10, and outputs these.

  Below, an example of operation | movement of the rotation angle detection apparatus 1 is demonstrated.

(Operation)
The clock signal generating unit 11 of the rotation angle detection device 1, when the power supply voltage VCC is applied, and outputs to the switching unit 7, A / D converter 9 and the rotation angle calculation unit 10 generates a clock signal S _4.

The control unit 70 of the switching unit 7 switches the switches SW ₁ to SW ₄ based on the clock signal S ₄ and the table 71. By this switching, the switching unit 7 periodically sends the detection signal V ₁ and detection signal V _{2 of} the first MR sensor 5 and the detection signal V ₃ and detection signal V ₄ of the second MR sensor 6 to the operational amplifier 8. Output.

The operational amplifier 8 differentially amplifies the detection signal V ₁ and the detection signal V ₂ and the detection signal V ₃ and the detection signal V ₄ that are periodically input to generate and output an amplified signal S ₁ .

A / D converting unit 9 based on the clock signal S _4, the amplified signals S ₁ digitizes generates and outputs a digital signal S ₂ to be input.

Rotation angle calculation unit 10 based on the clock signal S _4, and separates the digital signal S ₂ to be input to calculate the inverse tangent function to calculate the rotation angle theta. Subsequently, the rotation angle calculation unit 10 generates the rotational angle information S ₃ based on the rotation angle θ calculated rotation angle detecting device 1 is outputted to the connected electronic equipment.

(Effects of the first embodiment)
The rotation angle detection device 1 according to the present embodiment can reduce the manufacturing cost. Specifically, the rotation angle detection device 1 switches the connection between the first MR sensor 5 and the second MR sensor 6 and the operational amplifier 8 by the switching unit 7 and differentially detects the detection signals V ₁ to V ₄ . It is configured to amplify. The switching unit 7 and the operational amplifier 8 have a smaller circuit scale than the case where the same number of two operational amplifiers as the magnetic detection unit are provided. Therefore, since the rotation angle detection device 1 does not require the same number of operational amplifiers as the first MR sensor 5 and the second MR sensor 6, the circuit scale is reduced and the manufacturing cost is suppressed. The rotation angle detection device 1 can be miniaturized because the circuit scale is small.

  Further, in the case of a detection apparatus having a plurality of differential amplification units, there is a possibility that a difference in amplification factor due to individual differences of the differential amplification units occurs and detection accuracy is lowered. However, since the rotation angle detection device 1 differentially amplifies the detection signals of all the magnetic detection units by the operational amplifier 8, it is possible to suppress a decrease in detection accuracy due to individual differences and improve the detection accuracy. In the rotation angle detection device 1, the switching unit 7 serves as a resistor, but the input impedance can be sufficiently increased, so that the influence on the detection accuracy of the rotation angle θ is suppressed.

[Second Embodiment]
The second embodiment is different from the first embodiment in that it further includes a pair of magnetic detection units of the first MR sensor 5 and the second MR sensor 6.

  FIG. 3 is a block diagram of a rotation angle detection device according to the second embodiment. In the embodiments described below, parts having the same functions and configurations as those of the first embodiment are denoted by the same reference numerals as those of the first embodiment, and description thereof is omitted.

As shown in FIG. 3, the rotation angle detection apparatus 1 according to the present embodiment includes a first MR sensor 5, a second MR sensor 6, a third MR sensor 5a, a fourth MR sensor 6a, and a switch. And a switching unit 7 having SW ₁ to switch SW ₈ . The rotation angle detection apparatus 1 includes, for example, a first MR sensor 5, a second MR sensor 6, a third MR sensor 5a, and a fourth MR sensor 6a in order to obtain redundancy.

  For example, the first MR sensor 5 and the second MR sensor 6 are arranged so that the element centers formed by the four magnetic detection elements coincide with each other, and the outer shape formed by both of them is a regular octagon. Similarly, the third MR sensor 5a and the fourth MR sensor 6a are arranged, for example, so that the element centers coincide with each other and the outer shape formed by both is a regular octagon.

  As an example, the magnetic sensor in which the first MR sensor 5 and the second MR sensor 6 are integrated is disposed at the position of the first MR sensor 5 of the first embodiment. The magnetic sensor in which the third MR sensor 5a and the fourth MR sensor 6a are integrated is disposed at the position of the second MR sensor 6 of the first embodiment as an example.

  The first MR sensor 5, the second MR sensor 6, the third MR sensor 5a, and the fourth MR sensor 6a may be arranged at each vertex with the center of the cross as the rotation axis 200. Arrangements not limited to are possible.

As shown in FIG. 3, in the third MR sensor 5a, the magnetoresistive elements are arranged in the same direction as the first MR sensor 5, and the first to fourth magnetoresistive elements 54 to 54 are arranged. Is used to form a bridge circuit. A first magnetoresistive element 51 of the third MR sensor 5a midpoint potential of the second magnetoresistance element 52 has a non-inverting input terminal of the operational amplifier 8 via a switch SW ₅ for switching portion 7 as a detection signal V _1a Enter in (+). Midpoint potential of the third magnetoresistance element 53 and the fourth magnetoresistive element 54 of the third MR sensor 5a is an inverting input terminal of an operational amplifier 8 via a switch SW ₆ of the switching unit 7 as a detection signal V _2a ( -)

As shown in FIG. 3, in the fourth MR sensor 6a, each magnetoresistive element is arranged in the same direction as the second MR sensor 6, and the first magnetoresistive element 61 to the fourth magnetoresistive element 64. Is used to form a bridge circuit. A first magnetoresistive element 61 of the fourth MR sensor 6a midpoint potential of the second magnetoresistance element 62, the inverting input terminal of the operational amplifier 8 via a switch SW ₈ for switching portion 7 as a detection signal V _3a ( -) Midpoint potential of the third magnetoresistance element 63 and the fourth magnetoresistive element 64 of the fourth MR sensor 6a has a non-inverting input terminal of the operational amplifier 8 via a switch SW ₇ for switching portion 7 as a detection signal V _4a Enter in (+).

The control unit 70 of the switching unit 7 is configured to periodically switch the switches SW ₁ to SW ₈ based on the clock signal S ₄ and the table 71. Specifically, the control unit 70 periodically closes with a combination of the switch SW ₁ and the switch SW ₂ , the switch SW ₃ and the switch SW ₄ , the switch SW ₅ and the switch SW ₆ , and the switch SW ₇ and the switch SW _8. To control. The table 71 stores combinations of opening and closing of the switches SW ₁ to SW ₈ .

The A / D converter 9 is output from the first MR sensor 5, the second MR sensor 6, the third MR sensor 5 a, and the fourth MR sensor 6 a, and the amplified signal S differentially amplified by the operational amplifier 8. It is configured to convert the ₁ to a digital signal S _2. The digital signal _{S 2,} the first MR sensor 5, the second MR sensor 6, a digital signal of the third MR sensor 5a and the fourth MR sensor 6a is contained alternately on the basis of the clock signal _{S 4} It is.

Rotation angle calculation unit 10, for example, the first MR sensor 5 from the digital signal _{S 2} on the basis of the clock signal _{S 4,} the second MR sensor 6, a digital third MR sensor 5a and the fourth MR sensor 6a Configured to separate values.

The rotation angle calculation unit 10 is configured to calculate the rotation angle θ by calculating an arctangent function based on the separated digital signal. Therefore, the rotation angle calculation unit 10 calculates two rotation angles θ that have the same value within the allowable range. Rotation angle calculation unit 10 generates and outputs the rotation angle information S ₃ based on the two rotation angle θ calculated.

  As a modification, for example, when the difference between the two rotation angles θ is larger than a predetermined threshold, the rotation angle calculation unit 10 outputs failure information indicating that one of the MR sensors has failed. It may be configured. As another modification, the rotation angle detection device 1 may include a determination unit that determines a failure based on, for example, two calculated rotation angles θ.

(Effect of the second embodiment)
The rotation angle detection device 1 according to the present embodiment can have redundancy. Moreover, since the rotation angle detection apparatus 1 is comprised with the one operational amplifier 8 with respect to four MR sensors, it can suppress manufacturing cost.

As a modification, the magnetic detection device may be configured to detect a displacement other than the rotation of the detection target. In this case, the magnetic detection apparatus includes a position determination unit that determines the position of the magnet 2 based on the digital signal S ₂ instead of the rotation angle calculation unit 10. As an example, this magnetic detection device detects an operation position of a shift lever of a vehicle shift device, an operation position of a lever of a lever combination switch device that instructs on / off of a light, and an operation position of an operation unit such as a joystick. can do.

  As a modification, the magnetic detection device may include more than four magnetic detection units.

  The magnetic detection devices according to the above-described embodiments and modifications are, for example, partly based on a program executed by a computer, an ASIC (Application Specific Integrated Circuit), an FPGA (Field Programmable Gate Array), or the like depending on the application. It may be realized.

  As mentioned above, although some embodiment and modification of this invention were demonstrated, these embodiment and modification are only examples, and do not limit the invention based on a claim. These novel embodiments and modifications can be implemented in various other forms, and various omissions, replacements, changes, and the like can be made without departing from the scope of the present invention. In addition, not all combinations of features described in these embodiments and modifications are necessarily essential to the means for solving the problems of the invention. Furthermore, these embodiments and modifications are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

DESCRIPTION OF SYMBOLS 1 ... Rotation angle detection apparatus, 2 ... Magnet, 3 ... Board | substrate, 5 ... 1st MR sensor, 5a ... 3rd MR sensor, 6 ... 2nd MR sensor, 6a ... 4th sensor, 7 ... Switching part , 8 ... operational amplifier, 9 ... conversion unit, 10 ... rotation angle calculation unit, 11 ... clock signal generation unit, 20 ... front surface, 21 ... back surface, 25 ... magnetic field, 51 to 54 ... first magnetoresistive element to fourth magnetoresistive element, 61 to 64 ... first magnetoresistive element to the fourth magnetoresistive element, 70 ... control unit, 71 ... table, 200 ... rotary shaft, 250 ... magnetic vector, _SW 1 to SW 8 _... switch

Claims (3)

A magnetic detection unit that detects a change in the magnetic field according to the displacement of the detection target and outputs detection signals having different phases;
A plurality of the magnetic detection units are electrically connected, and a switching unit that periodically switches connection with each of the plurality of magnetic detection units,
A differential amplifier for differentially amplifying detection signals having different phases for each of the plurality of magnetic detectors input via the switching unit;
A magnetic detection device. The plurality of magnetic detection units include a first magnetic detection unit in which a first bridge circuit is formed by four magnetoresistive elements, and a second bridge that is arranged by rotating the first bridge circuit by 45 °. Having at least one pair of magnetic detection units constituted by a second magnetic detection unit having a circuit;
The magnetic detection apparatus according to claim 1. A converter that digitally converts the amplified signal output from the differential amplifier and outputs a digital signal; and
A calculation unit that calculates a rotation angle of the detection target based on the digital signal output from the conversion unit;
The magnetic detection apparatus according to claim 1, further comprising:

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