JP2013195345A - Magnetic sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect a magnetic field irrespective of direction of applied magnetic field and to suppress reduction of magnetic sensitivity associated with the direction of applied magnetic field.SOLUTION: A first bridge circuit 5 is constituted of first through fourth magnetoresistive elements R1-R4. The first bridge circuit 5 has maximum sensitivity to a magnetic field applied in first and second directions D1 and D2 and generates first and second output voltages Am and Ap which vary in phase with magnetic field intensity. A second bridge circuit 6 is constituted of fifth through eighth magnetoresistive elements R5-R8. The second bridge circuit 6 has maximum sensitivity to a magnetic field applied in third and fourth directions D3 and D4 and generates third and fourth output voltages Bm and Bp which vary in reverse phase with magnetic field intensity. When no magnetic field is being applied, values of the third and fourth output voltages Bm and Bp are between the first output voltage Am and the second output voltage Ap.

Description

  The present invention relates to a magnetic sensor that detects a magnetic field using a magnetic detection element.

  In general, a magnetic sensor formed by connecting four magnetoresistive elements to a Wheatstone bridge is known (for example, see Patent Document 1). Therefore, such a conventional magnetic sensor 31 will be described with reference to FIG.

  Four magnetoresistive elements R11 to R14 constituting the magnetic sensor 31 are provided on the surface of the substrate 32 to form a bridge circuit 33. The first to fourth magnetoresistive elements R11, R12, R13, and R14 are each formed in a meander shape by connecting long strip patterns and short strip patterns alternately and orthogonally. In the first and second magnetoresistive elements R11 and R12, the short strip pattern extends in the X direction, and the long strip pattern extends in the Y direction. For this reason, the change in resistance value of the first and second magnetoresistive elements R11 and R12 is the largest for the magnetic field applied in the X direction and the smallest for the magnetic field applied in the Y direction. That is, the first and second magnetoresistive elements R11 and R12 have maximum sensitivity to the magnetic field applied in the X direction. In the third and fourth magnetoresistive elements R13 and R14, the short strip pattern extends in the Y direction, and the long strip pattern extends in the X direction. For this reason, the change in resistance value of the third and fourth magnetoresistive elements R13 and R14 is the largest for the magnetic field applied in the Y direction and the smallest for the magnetic field applied in the X direction. That is, the third and fourth magnetoresistive elements R13 and R14 have maximum sensitivity to the magnetic field applied in the Y direction. The first magnetoresistive element R11 and the third magnetoresistive element R13 are connected in series via the first connection end P11 to form a first series circuit 34, and the second magnetoresistive element R12 and the fourth magnetoresistive element R12 are connected to the fourth magnetoresistive element R12. The magnetoresistive element R14 is connected in series via the second connection end P12 to form a second series circuit 35. Further, the first magnetoresistive element R11 side of the first series circuit 34 and the fourth magnetoresistive element R14 side of the second series circuit 35 are commonly connected via the third connection end P13, and The third magnetoresistive element R13 side of the first series circuit 34 and the second magnetoresistive element R12 side of the second series circuit 35 are commonly connected via a fourth connection end P14. The power supply voltage Vcc is applied to the third connection terminal P13, and the fourth connection terminal P14 is connected to the ground GND, and it corresponds to the magnetic field intensity via the first connection terminal P11 and the second connection terminal P12. The output voltages Cm and Cp are taken out. The output voltages Cm and Cp are differentially amplified via a differential amplifier (not shown).

  Next, output voltages Cm and Cp of the magnetic sensor 31 when the magnetic field direction and the magnetic field strength of the magnetic field applied to the magnetic sensor 31 are changed will be described with reference to FIGS. As for the magnetic field direction, the angle θ rotated counterclockwise in the Y direction, which is the base line, is positive, and the angle θ rotated clockwise is negative. When the magnetic field strength is plus (+), it represents the magnetic field strength in the direction of the angle θ, and when the magnetic field strength is minus (−), the direction is opposite to the direction of the angle θ, that is, the angle (θ ± 180 °) represents the magnetic field strength. The resistance values of the magnetoresistive elements R11 to R14 are set so that the output voltage Cm is larger than the output voltage Cp when a magnetic field is not applied, that is, when the magnetic field strength is 0 [mT].

  First, the case where the angle θ of the magnetic field direction is 0 degree (θ = 0 °), that is, the case where the magnetic field direction is the Y direction will be described with reference to FIG. When the magnetic field intensity is gradually increased and applied to the magnetic sensor 31, the resistance values of the third and fourth magnetoresistive elements R13 and R14 decrease. On the other hand, since no component in the X direction is applied to the first and second magnetoresistive elements R11 and R12, the resistance values of the first and second magnetoresistive elements R11 and R12 hardly change. As a result, the output voltage Cm decreases and the output voltage CP increases. That is, the output voltages Cm and Cp change in opposite phases. Therefore, when θ = 0 °, the output voltages Cm and Cp cross at ± Ba [mT] when the magnetic field strength is gradually increased. For this reason, the detection signal of the magnetic sensor 31 is switched from, for example, a low level to a high level with ± Ba [mT] as a threshold value, so that the magnetic sensor 31 can detect a magnetic field.

  Next, the case where the absolute value of the angle θ in the magnetic field direction is 0 ° to 45 ° (0 ° <| θ | <45 °) will be described with reference to FIG. When the magnetic field strength is gradually changed greatly and applied to the magnetic sensor 31, components in the X direction and the Y direction increase. The component in the X direction is smaller than the component in the Y direction. For this reason, the resistance values of the first to fourth magnetoresistive elements R11 to R14 decrease, but the amount of change in the resistance value of the first and second magnetoresistive elements R11 and R12 is the third and fourth magnetic resistance elements. It is smaller than the change amount of the resistance value of the resistance elements R13 and R14. As a result, the output voltage Cm decreases and the output voltage CP increases. Accordingly, in the case of 0 ° <| θ | <45 °, when the magnetic field strength is gradually increased, the output voltages Cm and Cp cross at ± Bb [mT] (Cm = Cp). For this reason, the detection signal of the magnetic sensor 31 is switched from, for example, a low level to a high level with ± Bb [mT] as a threshold value, so that the magnetic sensor 31 can detect a magnetic field. Since the output voltages Cm and Cp change more slowly than when θ = 0 °, | ± Ba [mT] | <| ± Bb [mT] |.

  Next, the case where the absolute value of the angle θ in the magnetic field direction is 45 degrees (| θ | = 45 °) will be described with reference to FIG. When the magnetic field strength is gradually increased and applied to the magnetic sensor 31, the components in the X direction and the Y direction increase uniformly. For this reason, the resistance values of the first to fourth magnetoresistive elements R11 to R14 are uniformly reduced. As a result, the output voltages Cm and Cp hardly change. Therefore, when | θ | = 45 °, the output voltages Cm and Cp do not cross even if the magnetic field strength is gradually increased. For this reason, since the detection signal of the magnetic sensor 31 does not switch from the Low level to the High level, for example, the magnetic sensor 31 cannot detect the magnetic field.

  Next, the case where the absolute value of the angle θ in the magnetic field direction is 45 degrees to 90 degrees (45 ° <| θ | <90 °) will be described with reference to FIG. When the magnetic field strength is gradually changed greatly and applied to the magnetic sensor 31, components in the X direction and the Y direction increase. Note that the component in the X direction is larger than the component in the Y direction. For this reason, the resistance values of the first to fourth magnetoresistive elements R11 to R14 decrease, but the amount of change in the resistance value of the first and second magnetoresistive elements R11 and R12 is the third and fourth magnetic resistance elements. It is larger than the amount of change in the resistance values of the resistance elements R13 and R14. As a result, the output voltage Cm increases and the output voltage CP decreases. Therefore, when 45 ° <| θ | <90 °, the output voltages Cm and Cp do not cross even if the magnetic field strength is gradually increased. For this reason, since the detection signal of the magnetic sensor 31 does not switch from the Low level to the High level, for example, the magnetic sensor 31 cannot detect the magnetic field.

Japanese Patent Laid-Open No. 9-283735

  As described above, the conventional magnetic sensor has a problem that when the magnetic field direction of the magnetic field applied to the magnetic sensor is changed, a region where the magnetic field direction cannot be detected occurs. In addition, when the magnetic field direction and the magnetic field strength of the magnetic field applied to the magnetic sensor are changed, the amount of change in the resistance value of the four magnetoresistive elements constituting the magnetic sensor differs. Is different. As a result, the threshold when the magnetic sensor detects the magnetic field varies greatly depending on the magnetic field direction. That is, there is a problem that the magnetic sensitivity of the magnetic sensor is not constant depending on the direction of the magnetic field.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to provide a magnetic sensor that can detect a magnetic field without depending on the magnetic field direction.

  In order to solve the above-mentioned problems, the invention of claim 1 is characterized in that the first and second magnets have maximum sensitivity to the applied magnetic field in the first direction and output a voltage having an even function characteristic with respect to the magnetic field strength. And third and fourth magnetic sensing elements that have a maximum sensitivity to an applied magnetic field in a second direction inclined by θ1 from the first direction and that output a voltage having an even function characteristic with respect to the magnetic field strength. A first series circuit in which the first and third magnetic detection elements are connected in series via a connection end, and the second and fourth magnetic detection elements are connected in series via a connection end. The second series circuit is connected in parallel, one of the two common connection ends of the first and second series circuits is connected to the first power supply voltage and the other is grounded, From each of the connection ends of the first and second series circuits, the in-phase first A first bridge circuit for outputting an output voltage and a second output voltage; and a maximum sensitivity to an applied magnetic field in a third direction inclined by θ 2 from the first direction, and an even function characteristic with respect to the magnetic field strength Voltage having the maximum sensitivity with respect to the applied magnetic field in the fourth direction inclined by θ3 from the first direction and having an even function characteristic with respect to the magnetic field strength. A third series circuit in which the fifth and seventh magnetic detection elements are connected in series via a connection end, and the sixth and eighth magnetic detection elements. Are connected in parallel to a fourth series circuit connected in series via a connection end, and one of the two common connection ends of the third and fourth series circuits is a second power source. Is connected to the voltage and the other is grounded, A magnetic sensor comprising a second bridge circuit that outputs a third output voltage and a fourth output voltage having opposite phases from each of the connection ends of the circuit, and when the magnetic field is not applied, Offset means for making the first and second output voltages different is provided in the first bridge circuit, and when no magnetic field is applied, the voltage values of the third and fourth output voltages are different from those of the first output voltage. When the magnetic field is applied, the voltage values of the first to fourth output voltages are set such that the first output voltage> the first output voltage. 4 or the first output voltage> the third output voltage or the fourth output voltage> the second output voltage or the third output voltage> the second output voltage. Voltage value comparison means for judging whether It is characterized by providing.

  According to a second aspect of the present invention, a Wheatstone bridge is configured using the first to fourth magnetic detection elements that output a voltage having an even function characteristic with respect to the magnetic field strength, and the first and second directions on the biaxial plane are formed. When the first and second output voltages output the first and second output voltages having the maximum sensitivity to the applied magnetic field and the two output terminals change in phase with respect to the magnetic field intensity, and the magnetic field is not applied, the first and second The Wheatstone bridge is configured by using the first bridge circuit with different output voltages and the fifth to eighth magnetic detection elements that output voltages having even function characteristics with respect to the magnetic field strength, The third and fourth elements have maximum sensitivity to the applied magnetic field in the third and fourth directions different from the first and second directions, and the two output terminals change in a phase opposite to the magnetic field strength. Output voltage is output and magnetic field is applied And a second bridge circuit in which the third and fourth output voltages have a voltage value between the first output voltage and the second output voltage. When a magnetic field is applied, the magnetic field strength at which one of the first and second output voltages matches one of the third and fourth output voltages becomes the detected threshold magnetic field strength. It is characterized by.

  According to a third aspect of the present invention, there is provided the first and second magnetic detection elements that have maximum sensitivity to the applied magnetic field in the first direction and that output a voltage having an even function characteristic with respect to the magnetic field strength; And third and fourth magnetic sensing elements that have a maximum sensitivity to an applied magnetic field in a second direction inclined by θ1 from the direction and output a voltage having an even function characteristic with respect to the magnetic field strength. And a first series circuit in which the third magnetic detection elements are connected in series via a connection end, and a second series circuit in which the second and fourth magnetic detection elements are connected in series via a connection end; Are connected in parallel, and one of the two common connection ends of the first and second series circuits is connected to the first power supply voltage and the other is grounded, and the first and second series circuits are connected to each other. The first output voltage and the second output voltage of the same phase from each of the connection ends of A first bridge circuit that outputs, and fifth and second voltages that have a maximum sensitivity to an applied magnetic field in a third direction inclined by θ2 from the first direction, and that output an even function characteristic voltage with respect to the magnetic field strength. The seventh and eighth magnetic sensing elements have maximum sensitivity to an applied magnetic field in a fourth direction inclined by θ 3 from the first direction, and output a voltage having an even function characteristic with respect to the magnetic field strength. A third series circuit in which the fifth and seventh magnetic detection elements are connected in series via a connection end, and the sixth and eighth magnetic detection elements are provided via a connection end. A fourth series circuit connected in series is connected in parallel, and one of the two common connection ends of the third and fourth series circuits is connected to the second power supply voltage and the other is grounded. Each of the connection ends of the third and fourth series circuits. Comprises a third bridge voltage circuit and a second bridge circuit that outputs a fourth output voltage, and one of the first and second output voltages, and the third and fourth output voltages. It is set as the structure which detects a magnetic field by comparing with either.

  According to a fourth aspect of the present invention, a Wheatstone bridge is configured using the first to fourth magnetic detection elements that output a voltage having an even function characteristic with respect to the magnetic field strength, and the first and second directions on a biaxial plane are formed. When the first and second output voltages output the first and second output voltages having the maximum sensitivity to the applied magnetic field and the two output terminals change in phase with respect to the magnetic field intensity, and the magnetic field is not applied, the first and second The Wheatstone bridge is configured by using the first bridge circuit with different output voltages and the fifth to eighth magnetic detection elements that output voltages having even function characteristics with respect to the magnetic field strength, The third and fourth elements have maximum sensitivity to the applied magnetic field in the third and fourth directions different from the first and second directions, and the two output terminals change in a phase opposite to the magnetic field strength. Output voltage is output and magnetic field is applied A second bridge circuit in which the third and fourth output voltages have a voltage value between the first output voltage and the second output voltage. The magnetic field is detected by comparing any one of the two output voltages with any one of the third and fourth output voltages.

  According to a fifth aspect of the present invention, when no magnetic field is applied, the voltage values of the third and fourth output voltages are the same, and the third and fourth output voltages and the first output voltage are And the offset voltage between the third and fourth output voltages and the second output voltage are the same.

  According to a sixth aspect of the invention, the first and second directions are orthogonal to each other, the third and fourth directions are orthogonal to each other, and an angular difference of 45 degrees with respect to the first and second directions. The third and fourth directions are arranged.

  According to the first aspect of the present invention, the first bridge circuit outputs the first output voltage and the second output voltage having the same phase from the connection ends of the first and second series circuits, and the second bridge circuit The circuit outputs antiphase third output voltage and fourth output voltage from the connection ends of the third and fourth series circuits, respectively. In addition to this, when no magnetic field is applied, the voltage values of the third and fourth output voltages are set to be a voltage value between the first output voltage and the second output voltage.

  For this reason, when the magnetic field strength is increased, the magnitude of either the third or fourth output voltage is reversed with respect to the first output voltage. Similarly, when the magnetic field strength is increased, the magnitude of either the third or fourth output voltage is reversed with respect to the second output voltage. Therefore, when a magnetic field is applied, the first output voltage> the fourth output voltage or the first output voltage> the third output voltage or the fourth output voltage> the second output voltage or The voltage value comparison means can determine whether the output voltage of 3 is greater than the second output voltage, so that it is possible to determine whether a magnetic field has been applied, without depending on the magnetic application direction. A magnetic field can be detected.

  In addition, the voltage value comparison means may be configured such that the first output voltage> the fourth output voltage or the first output voltage> the third output voltage or the fourth output voltage> the second output voltage or the third output voltage. It is determined whether output voltage> second output voltage. For this reason, according to the magnetic application direction, a condition that is satisfied when the magnetic field intensity is the smallest among these four conditions can be appropriately selected. As a result, it is possible to suppress a decrease in magnetic sensitivity with respect to the magnetic application direction.

  In the invention of claim 2, as in the invention of claim 1, the first bridge circuit outputs the first output voltage and the second output voltage having the same phase, and the second bridge circuit is the third one having the opposite phase. And when the magnetic field is not applied, the voltage value of the third and fourth output voltages is a voltage value between the first output voltage and the second output voltage. It set so that it might become. For this reason, when a magnetic field is applied to the magnetic sensor, any one of the first and second output voltages is set to have a threshold magnetic field strength that matches one of the third and fourth output voltages. In addition, the magnetic field can be detected without depending on the magnetic application direction, and the decrease in magnetic sensitivity with respect to the magnetic application direction can be suppressed.

  According to the invention of claim 3, the first bridge circuit outputs the first output voltage and the second output voltage of the same phase from each of the common connection ends of the first and second series circuits, and the second bridge circuit The bridge circuit outputs antiphase third output voltage and fourth output voltage from each of the common connection ends of the third and fourth series circuits. For this reason, when a magnetic field is not applied, when the voltage values of the third and fourth output voltages are set to be a voltage value between the first output voltage and the second output voltage, the magnetic field strength is When it is increased, the magnitude of either the third or fourth output voltage is reversed with respect to the first output voltage. Similarly, when the magnetic field strength is increased, the magnitude of either the third or fourth output voltage is reversed with respect to the second output voltage.

  Therefore, whether the magnetic field is applied by comparing the first output voltage with the third and fourth output voltages and comparing the second output voltage with the third and fourth output voltages. The magnetic field can be detected without depending on the magnetic application direction. In addition, even when the magnetic application directions are different, the comparison result between the first output voltage and the third and fourth output voltages and the comparison result between the second output voltage and the third and fourth output voltages By appropriately selecting one of the above, it is possible to select the one whose comparison result changes when the magnetic field strength is the smallest. Thereby, the fall of the magnetic sensitivity with respect to a magnetic application direction can be suppressed.

  According to the invention of claim 4, the first bridge circuit outputs the first output voltage and the second output voltage having the same phase, and the second bridge circuit outputs the third output voltage having the opposite phase and the fourth output voltage. When the output voltage was output and the magnetic field was not applied, the voltage values of the third and fourth output voltages were set to be a voltage value between the first output voltage and the second output voltage. For this reason, one of the first and second output voltages can be compared with either the third or fourth output voltage, and the one whose comparison result changes when the magnetic field strength is the smallest can be selected. . Accordingly, it is possible to detect a magnetic field without depending on the magnetic application direction, and it is possible to suppress a decrease in magnetic sensitivity with respect to the magnetic application direction.

  According to the fifth aspect of the invention, when no magnetic field is applied, the voltage values of the third and fourth output voltages are the same, and between the third and fourth output voltages and the first output voltage. Since the offset voltage and the offset voltage between the third and fourth output voltages and the second output voltage are the same, fluctuations in magnetic sensitivity with respect to the direction of magnetic application can be reduced.

  According to the invention of claim 6, the first and second directions are orthogonal to each other, the third and fourth directions are orthogonal to each other, and have an angular difference of 45 degrees with respect to the first and second directions. Since the third and fourth directions are arranged, the maximum magnetosensitive direction of the first bridge circuit and the maximum magnetosensitive direction of the second bridge circuit can be alternately arranged at equal intervals, and magnetic Variations in magnetic sensitivity with respect to the application direction can be reduced.

It is a circuit diagram which shows the magnetic sensor by embodiment. It is a top view which shows the sensor circuit part of FIG. It is a characteristic diagram which shows the relationship between a magnetic field intensity and the 1st thru | or 4th output voltage when the angle of a magnetic field direction is 0 degree | times. It is a characteristic diagram which shows the relationship between a magnetic field intensity and the 1st thru | or 4th output voltage in the case where the angle of a magnetic field direction is between 0 degree | times and 22.5 degree | times. FIG. 6 is a characteristic diagram showing the relationship between magnetic field strength and first to fourth output voltages when the angle in the magnetic field direction is 22.5 degrees. It is a characteristic diagram which shows the relationship between a magnetic field strength and the 1st thru | or 4th output voltage in the case where the angle of a magnetic field direction is between 22.5 degree | times and 45 degree | times. It is a characteristic diagram which shows the relationship between a magnetic field intensity and the 1st thru | or 4th output voltage when the angle of a magnetic field direction is 45 degree | times. It is a characteristic diagram which shows the relationship between a magnetic field strength and the 1st thru | or 4th output voltage in the case where the angle of a magnetic field direction is between 45 degree | times and 67.5 degree | times. FIG. 6 is a characteristic diagram showing the relationship between magnetic field strength and first to fourth output voltages when the angle in the magnetic field direction is 67.5 degrees. It is a characteristic diagram which shows the relationship between a magnetic field strength and the 1st thru | or 4th output voltage in the case where the angle of a magnetic field direction is between 67.5 degree | times and 90 degree | times. It is a characteristic diagram which shows the relationship between a magnetic field intensity and the 1st thru | or 4th output voltage when the angle of a magnetic field direction is 90 degree | times. It is a characteristic diagram which shows the relationship between the angle of a magnetic field direction, and the threshold value of magnetic field intensity. It is a top view which shows the magnetic sensor by a prior art. It is a characteristic diagram which shows the relationship between a magnetic field intensity | strength and the 1st and 2nd output voltage by a prior art, when the absolute value of the angle of a magnetic field direction is 0 degree | times. It is a characteristic diagram which shows the relationship between a magnetic field strength and the 1st and 2nd output voltage by a prior art in case the absolute value of the angle of a magnetic field direction is between 0 degree | times and 45 degree | times. It is a characteristic diagram which shows the relationship between a magnetic field strength and the 1st and 2nd output voltage by a prior art in case the absolute value of the angle of a magnetic field direction is 45 degree | times. It is a characteristic diagram which shows the relationship between a magnetic field strength and the 1st and 2nd output voltage by a prior art in case the absolute value of the angle of a magnetic field direction is between 45 degree | times and 90 degree | times.

  Hereinafter, a magnetic sensor according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 shows a magnetic sensor 1. The magnetic sensor 1 includes a sensor circuit unit 2 including a magnetoresistive element formed of a magnetic thin film, and an arithmetic circuit unit 3 that performs various calculations.

  As shown in FIG. 2, the sensor circuit unit 2 includes a first bridge circuit 5 including four magnetoresistive elements R1 to R4, and a second bridge circuit 6 including four magnetoresistive elements R5 to R8. Is provided. The magnetoresistive elements R1 to R8 are formed on the surface of the substrate 4 extending along, for example, the X direction and the Y direction orthogonal to each other.

  The first to fourth magnetoresistive elements R1 to R4 are formed in a meander shape by connecting long strip patterns and short strip patterns alternately and orthogonally.

  The long strip pattern of the first and second magnetoresistive elements R1, R2 extends along the Y direction, and the long strip pattern of the third and fourth magnetoresistive elements R3, R4 extends along the X direction. For this reason, the resistance values of the first and second magnetoresistive elements R1, R2 become the smallest when a magnetic field in the first direction D1 parallel to the X direction is applied, and the second direction parallel to the Y direction. It becomes the largest when the magnetic field of D2 is applied. On the other hand, the resistance values of the third and fourth magnetoresistive elements R3 and R4 are maximized when a magnetic field in the first direction D1 is applied, and are minimized when a magnetic field in the second direction D2 is applied. . That is, the maximum magnetosensitive direction of the first and second magnetoresistive elements R1, R2 is the first direction D1, and the maximum magnetosensitive direction of the third and fourth magnetoresistive elements R3, R4 is the second direction. D2.

  The first to fourth magnetoresistive elements R1 to R4 are formed on the surface of the substrate 4, for example, a ferromagnetic thin film such as permalloy (NiFe), which is a magnetoresistive material, by microfabrication such as photolithography. It is formed into a predetermined shape using a technique. The magnetoresistive elements R1 to R4 may be AMR (anisotropic magnetoresistive element) or GMR (giant magnetoresistive element), and output a voltage having an even function characteristic with respect to the magnetic field strength. Any detection element may be used. The first direction D1, which is the maximum magnetic sensing direction of the first and second magnetoresistance elements R1, R2, and the second direction, which is the maximum magnetic sensing direction of the third and fourth magnetoresistance elements R3, R4. Although the case where the direction D2 forms an angle of 90 degrees has been illustrated, the present invention is not limited to this and may be an arbitrary angle θ1.

  The first to fourth magnetoresistive elements R 1 to R 4 are connected by a full bridge to constitute a first bridge circuit 5. Specifically, the first series circuit 7 forming a half bridge is configured by connecting the first magnetoresistive element R1 and the third magnetoresistive element R3 in series via the first connection end P1. . The second magnetoresistive element R2 and the fourth magnetoresistive element R4 are connected in series via the second connection end P2, thereby forming a second series circuit 8 forming a half bridge.

  The first magnetoresistive element R1 side of the first series circuit 7 and the second magnetoresistive element R2 side of the second series circuit 8 are commonly connected via a third connection end P3 that forms a common connection end. To do. The third magnetoresistive element R3 side of the first series circuit 7 and the fourth magnetoresistive element R4 side of the second series circuit 8 are commonly connected via a fourth connection end P4 forming a common connection end. To do. Thereby, the 1st series circuit 7 and the 2nd series circuit 8 are connected in parallel, and the 1st bridge circuit 5 which makes a Wheatstone bridge is comprised.

  The third connection terminal P3 is electrically connected to the power supply voltage terminal 9 for supplying the power supply voltage Vcc. The fourth connection end P4 is electrically connected to a ground terminal 10 for connection to an external ground GND. As a result, the first power supply voltage Vcc is applied to the bridge circuit 5 via the third connection terminal P3 and the fourth connection terminal P4.

  On the other hand, the first connection end P1 is electrically connected to the first output terminal 11 for taking out the first output voltage Am. The second connection end P2 is electrically connected to the second output terminal 12 for taking out the second output voltage Ap. As a result, the first output voltage Am and the second output voltage Ap are extracted from the first connection terminal P1 and the second connection terminal P2 of the bridge circuit 5, respectively.

  Specifically, for example, when a magnetic field in the first direction D1 is gradually and greatly applied to the magnetic sensor 1, the first output voltage Am increases and the second output voltage Ap also increases. To do. On the other hand, for example, when the magnetic field in the second direction D2 is gradually varied and applied, the first output voltage Am decreases and the second output voltage Ap also decreases. That is, the first output voltage Am and the second output voltage Ap change in phase.

  The first bridge circuit 5 has a voltage that the first output voltage Am is lower than the second output voltage Ap when the strength of the magnetic field applied to the magnetic sensor 1 is zero (0) [mT]. Offset means are provided to ensure that. The offset means, for example, makes the values of the magnetoresistive element R1 and the magnetoresistive element R2 different, makes the values of the magnetoresistive element R3 and the magnetoresistive element R4 different, or the first series circuit 7 or the second series. Various means are conceivable, such as connecting an offset resistor, a constant current source, or a constant voltage source to the circuit 8.

  The fifth to eighth magnetoresistive elements R5 to R8 are formed in the same manner as the first to fourth magnetoresistive elements R1 to R4. However, the long strip pattern of the fifth and sixth magnetoresistive elements R5 and R6 is formed to extend in a direction rotated 45 degrees counterclockwise from the X direction. Further, the long strip pattern of the seventh and eighth magnetoresistive elements R7, R8 is formed so as to extend in a direction rotated 45 degrees clockwise from the X direction. Therefore, the resistance values of the fifth and sixth magnetoresistive elements R5 and R6 are minimized when a magnetic field in the third direction D3 obtained by rotating the first direction D1 clockwise by 45 degrees is applied. When the magnetic field in the fourth direction D4 obtained by rotating the first direction D1 counterclockwise by 45 degrees is applied, the maximum value is obtained. On the other hand, the resistance values of the seventh and eighth magnetoresistive elements R7 and R8 are maximized when a magnetic field in the third direction D3 is applied, and are minimized when a magnetic field in the fourth direction D4 is applied. . That is, the maximum magnetosensitive direction of the fifth and sixth magnetoresistive elements R5 and R6 is the third direction D3, and the maximum magnetosensitive direction of the seventh and eighth magnetoresistive elements R7 and R8 is the fourth direction. D4.

  The third direction D3, which is the maximum magnetosensitive direction of the fifth and sixth magnetoresistive elements R5, R6, and the fourth direction, which is the maximum magnetosensitive direction of the seventh and eighth magnetoresistive elements R7, R8. The case where the direction D4 and the first direction D1 form an angle of 45 degrees is illustrated, but the present invention is not limited to this, and the third direction D3 and the first direction D1 form an arbitrary angle θ2, The fifth to eighth magnetoresistive elements R5 to R8 may be arranged and formed so that the four directions D4 and the first direction D1 form an arbitrary angle θ3.

  The fifth to eighth magnetoresistive elements R5 to R8 are connected by a full bridge to constitute a second bridge circuit 6. Specifically, the third series circuit 13 forming a half bridge is configured by connecting the fifth magnetoresistive element R5 and the seventh magnetoresistive element R7 in series via the fifth connection end P5. . Further, the sixth magnetoresistive element R6 and the eighth magnetoresistive element R8 are connected in series via the sixth connection end P6, thereby forming a fourth series circuit 14 forming a half bridge.

  The fifth magnetoresistive element R5 side of the third series circuit 13 and the eighth magnetoresistive element R8 side of the fourth series circuit 14 are commonly connected through a seventh connection end P7 that forms a common connection end. To do. The seventh magnetoresistive element R7 side of the third series circuit 13 and the sixth magnetoresistive element R6 side of the fourth series circuit 14 are commonly connected via an eighth connection end P8 that forms a common connection end. To do. Thereby, the 3rd series circuit 13 and the 4th series circuit 14 are connected in parallel, and the 2nd bridge circuit 6 which makes a Wheatstone bridge is comprised.

  The seventh connection terminal P7 is electrically connected to the power supply voltage terminal 15 for supplying the power supply voltage Vcc. The eighth connection end P8 is electrically connected to a ground terminal 16 for connection to an external ground GND. As a result, the second power supply voltage Vcc is applied to the bridge circuit 6 via the seventh connection terminal P7 and the eighth connection terminal P8. Note that the second power supply voltage may be the same voltage as the first power supply voltage or a different voltage.

  On the other hand, the fifth connection end P5 is electrically connected to the third output terminal 17 for taking out the third output voltage Bm. The sixth connection end P6 is electrically connected to the fourth output terminal 18 for taking out the fourth output voltage Bp. As a result, the third output voltage Bm and the fourth output voltage Bp are extracted from each of the fifth connection end P5 and the sixth connection end P6 of the bridge circuit 6.

  Specifically, for example, when a magnetic field in the third direction D3 is applied to the magnetic sensor 1 with a gradually large variation, the third output voltage Bm increases and the fourth output voltage Bp decreases. To do. On the other hand, for example, when the magnetic field in the fourth direction D4 is gradually varied and applied, the third output voltage Bm decreases and the fourth output voltage Bp increases. That is, the third output voltage Bm and the fourth output voltage Bp change in opposite phases.

  The second bridge circuit 6 is provided with offset means similar to that of the first bridge circuit 5. Thereby, the voltage values of the third output voltage Bm and the fourth output voltage Bp are the same as the first output voltage when the magnetic field strength applied to the second bridge circuit 6 is zero (0) [mT]. The same voltage value is set between Am and the voltage value of the second output voltage Ap. That is, the first to fourth output voltages Am, Ap, Bm, and Bp have the relationship expressed by the following equation 1 when the magnetic field strength applied to the magnetic sensor 1 is zero (0) [mT]. Fulfill.

  The voltage values of the third output voltage Bm and the fourth output voltage Bp may be set to different values between the first output voltage Am and the voltage value of the second output voltage Ap.

  Next, the arithmetic circuit unit 3 will be described. The arithmetic circuit unit 3 includes four comparators 21 to 24 and one OR circuit 25, and constitutes voltage value comparison means. The first connection terminal P 1 of the first bridge circuit 5 and the sixth connection terminal P 6 of the second bridge circuit 6 are connected to each of the ± input terminals of the first comparator 21. The first comparator 21 compares the voltages of the two input terminals, that is, the first output voltage Am and the fourth output voltage Bp, and the first output voltage Am is larger than the fourth output voltage Bp. A first determination signal S1 that is true when (Am> Bp) and false otherwise is output.

  The first connection terminal P 1 of the first bridge circuit 5 and the fifth connection terminal P 5 of the second bridge circuit 6 are connected to each of the ± input terminals of the second comparator 22. The second comparator 22 compares the voltages of the two input terminals, that is, the first output voltage Am and the third output voltage Bm, and the first output voltage Am is larger than the third output voltage Bm. A second determination signal S2 that is true when (Am> Bm) and false otherwise is output.

  The second connection terminal P 2 of the first bridge circuit 5 and the sixth connection terminal P 6 of the second bridge circuit 6 are connected to each of the ± input terminals of the third comparator 23. The third comparator 23 compares the voltages of the two input terminals, that is, the fourth output voltage Bp and the second output voltage Ap, and the fourth output voltage Bp is larger than the second output voltage Ap. A third determination signal S3 that is true when (Bp> Ap) and false otherwise is output.

  The second input terminal P 2 of the first bridge circuit 5 and the fifth connection terminal P 5 of the second bridge circuit 6 are connected to each of the ± input terminals of the fourth comparator 24. The fourth comparator 24 compares the voltages of the two input terminals, that is, the third output voltage Bm and the second output voltage Ap, and the third output voltage Bm is larger than the second output voltage Ap. A fourth determination signal S4 that is true when (Bm> Ap) and false otherwise is output.

  The output terminal of the first to fourth comparators 21 to 24 is connected to the input terminal of the OR circuit 25 and is true when any one of the first to fourth determination signals S1 to S4 is true. A false (eg, low level) detection signal Vout is output when all are false (eg, high level).

  Next, the detection operation of the magnetic sensor 1 will be described using the relationship between the magnetic field intensity and the output voltages Am, Ap, Bm, and Bp shown in FIGS. As for the magnetic field direction, the angle θ rotated counterclockwise in the Y direction, which is the base line, is positive, and the angle θ rotated clockwise is negative. Further, when the magnetic field strength is plus (+), it represents the magnetic field strength in the direction of the angle θ. On the other hand, when the magnetic field strength is minus (−), the direction opposite to the direction of the angle θ, that is, the angle ( This represents the magnetic field strength in the direction of θ ± 180 °.

  First, the case where the angle θ of the magnetic field direction is 0 degree (θ = 0 °), that is, the case where the magnetic field direction is the second direction D2 will be described with reference to FIG. When the magnetic field intensity is gradually increased and applied to the magnetic sensor 1, the resistance values of the third and fourth magnetoresistive elements R3 and R4 constituting the first bridge circuit 5 decrease. On the other hand, since the magnetic field component in the first direction D1 is not applied to the first and second magnetoresistive elements R1, R2, the resistance values of the first and second magnetoresistive elements R1, R2 hardly change. For this reason, the output voltage Am and the output voltage Ap decrease as the magnetic field strength increases. That is, the output voltage Am and the output voltage Ap change in phase.

  Further, when the magnetic field intensity is gradually changed greatly and applied to the magnetic sensor 1, the components in the third direction D3 and the fourth direction D4 increase uniformly. For this reason, the resistance values of the fifth to eighth magnetoresistive elements R5 to R8 constituting the second bridge circuit 6 are uniformly reduced. As a result, the output voltages Bm and Bp of the second bridge circuit 6 hardly change.

  Therefore, when the magnetic field strength is around 0 [mT], the output voltage Am is smaller than the output voltages Bm and Bp (Am <Bm, Am <Bp), and the output voltage Ap is larger than the output voltages Bm and Bp (Ap). > Bm, Ap> Bp). For this reason, the determination signals S1 to S4 are all false, and the detection signal Vout of the OR circuit 25 is false (for example, low level).

  When the magnetic field strength reaches ± B0 [mT], the output voltage Ap crosses the output voltages Bm and Bp (Ap = Bm, Ap = Bp).

  Further, when the magnetic field intensity exceeds ± B0 [mT], the output voltage Ap becomes smaller than the output voltages Bm and Bp (Ap <Bm, Ap <Bp), and the third and fourth determination signals S3 and S4 are false. Switch to true. As a result, the determination signals S3 and S4 are true, and the determination signals S1 and S2 are false. For this reason, the detection signal Vout of the OR circuit 25 switches from false to true (for example, from low level to high level) with ± B0 [mT] as a threshold, and the magnetic sensor 1 can detect the magnetic field strength.

  Next, the case where the angle θ in the magnetic field direction is between 0 ° and 22.5 ° (0 ° <θ <22.5 °) will be described with reference to FIG. When the magnetic field intensity is gradually varied and applied to the magnetic sensor 1, the components in the first direction D1 and the second direction D2 increase. The component in the first direction D1 is smaller than the component in the second direction D2. Therefore, although the resistance values of the first to fourth magnetoresistive elements R1 to R4 of the first bridge circuit 5 are reduced, the amount of change in the resistance values of the first and second magnetoresistive elements R1 and R2 is: The amount of change in the resistance values of the third and fourth magnetoresistive elements R3 and R4 is smaller. Along with this, the output voltages Am, Ap gradually decrease in phase with the case of θ = 0 °.

  Further, when the magnetic field strength is gradually changed and applied to the magnetic sensor 1, the components in the third direction D3 and the fourth direction D4 increase. The component in the third direction D3 is larger than the component in the fourth direction D4. For this reason, although the resistance values of the fifth to eighth magnetoresistive elements R5 to R8 of the second bridge circuit 6 are reduced, the amount of change in the resistance values of the fifth and sixth magnetoresistive elements R5 and R6 is: The amount of change in the resistance values of the seventh and eighth magnetoresistive elements R7 and R8 is larger. As a result, the output voltage Bm increases and the output voltage Bp decreases. That is, the output voltages Bm and Bp change in opposite phases.

  Therefore, when the magnetic field strength is around 0 [mT], the output voltage Am is smaller than the output voltages Bm and Bp (Am <Bm, Am <Bp), and the output voltage Ap is larger than the output voltages Bm and Bp (Ap). > Bm, Ap> Bp). For this reason, all the determination signals S1 to S4 are false, and the detection signal Vout of the OR circuit 25 is false (for example, low level).

  When the magnetic field strength reaches ± B1 [mT], the output voltage Ap and the output voltage Bm cross (Ap = Bm). Since the output voltage Ap decreases more slowly than when θ = 0 °, | ± B 0 [mT] | <| ± B 1 [mT] |

  Further, when the magnetic field strength exceeds ± B1 [mT], the output voltage Ap becomes smaller than the output voltage Bm (Ap <Bm), and the fourth determination signal S4 is switched from false to true. As a result, the determination signals S1 to S3 are false, and the determination signal S4 is true. For this reason, the detection signal Vout of the OR circuit 25 switches to true (for example, high level) with ± B1 [mT] as a threshold value, and the magnetic sensor 1 can detect the magnetic field strength.

  Next, the case where the angle θ in the magnetic field direction is 22.5 degrees (θ = 22.5 °) will be described with reference to FIG. When the magnetic field intensity is gradually varied and applied to the magnetic sensor 1, the components in the first direction D1 and the second direction D2 increase. The component in the first direction D1 is smaller than the component in the second direction D2. Therefore, although the resistance values of the first to fourth magnetoresistive elements R1 to R4 of the first bridge circuit 5 are reduced, the amount of change in the resistance values of the first and second magnetoresistive elements R1 and R2 is: The amount of change in the resistance values of the third and fourth magnetoresistive elements R3 and R4 is smaller. As a result, the output voltages Am and Ap gradually decrease in phase with respect to the case of 0 ° <θ <22.5 °.

  Further, when the magnetic field strength is gradually changed and applied to the magnetic sensor 1, the components in the third direction D3 and the fourth direction D4 increase. The component in the third direction D3 is larger than the component in the fourth direction D4. For this reason, although the resistance values of the fifth to eighth magnetoresistive elements R5 to R8 of the second bridge circuit 6 are reduced, the amount of change in the resistance values of the fifth and sixth magnetoresistive elements R5 and R6 is: The amount of change in the resistance values of the seventh and eighth magnetoresistive elements R7 and R8 is larger. As a result, the output voltage Bm increases and the output voltage Bp decreases. Note that the output voltages Bm and Bp change greatly as compared with the case of 0 ° <θ <22.5 °.

  Therefore, when the magnetic field strength is around 0 [mT], the output voltage Am is smaller than the output voltages Bm and Bp (Am <Bm, Am <Bp), and the output voltage Ap is larger than the output voltages Bm and Bp (Ap). > Bm, Ap> Bp). For this reason, all the determination signals S1 to S4 are false, and the detection signal Vout of the OR circuit 25 is false (for example, low level).

  When the magnetic field intensity reaches ± B2 [mT], the output voltage Ap and the output voltage Bm cross (Ap = Bm). Since the output voltage Ap gradually decreases as compared with the case of 0 ° <θ <22.5 °, | ± B1 [mT] | <| ± B2 [mT] |.

  Further, when the magnetic field strength exceeds ± B2 [mT], the output voltage Ap becomes smaller than the output voltage Bm (Ap <Bm), and the fourth determination signal S4 switches from false to true. As a result, the determination signals S1 to S3 are false and the determination signal S4 is true. Therefore, the detection signal Vout of the OR circuit 25 is switched to true (for example, high level) with ± B2 [mT] as a threshold value, and the magnetic sensor 1 can detect the magnetic field strength.

  Next, a case where the angle θ in the magnetic field direction is between 22.5 degrees and 45 degrees (22.5 ° <θ <45 °) will be described with reference to FIG. When the magnetic field intensity is gradually varied and applied to the magnetic sensor 1, the components in the first direction D1 and the second direction D2 increase. The component in the first direction D1 is smaller than the component in the second direction D2. Therefore, although the resistance values of the first to fourth magnetoresistive elements R1 to R4 of the first bridge circuit 5 are reduced, the amount of change in the resistance values of the first and second magnetoresistive elements R1 and R2 is: The amount of change in the resistance values of the third and fourth magnetoresistive elements R3 and R4 is smaller. As a result, compared to the case of θ = 22.5 °, the output voltages Am and Ap decrease slightly more gently in the same phase.

  Further, when the magnetic field strength is gradually changed and applied to the magnetic sensor 1, the components in the third direction D3 and the fourth direction D4 increase. The component in the third direction D3 is larger than the component in the fourth direction D4. For this reason, although the resistance values of the fifth to eighth magnetoresistive elements R5 to R8 of the second bridge circuit 6 are reduced, the amount of change in the resistance values of the fifth and sixth magnetoresistive elements R5 and R6 is: The amount of change in the resistance values of the seventh and eighth magnetoresistive elements R7 and R8 is larger. As a result, the output voltage Bm increases and the output voltage Bp decreases. Note that the output voltages Bm and Bp change greatly as compared with the case of θ = 22.5 °.

  Therefore, when the magnetic field strength is around 0 [mT], the output voltage Am is smaller than the output voltages Bm and Bp (Am <Bm, Am <Bp), and the output voltage Ap is larger than the output voltages Bm and Bp (Ap). > Bm, Ap> Bp). For this reason, all the determination signals S1 to S4 are false, and the detection signal Vout of the OR circuit 25 is false (for example, low level).

  When the magnetic field strength reaches ± B3 [mT], the output voltage Ap and the output voltage Bm cross (Ap = Bm). Since the output voltages Bm and Bp change greatly compared to the case of θ = 22.5 °, | ± B2 [mT] |> | ± B3 [mT] |.

  Further, when the magnetic field strength exceeds ± B3 [mT], the output voltage Ap becomes smaller than the output voltage Bm (Ap <Bm), and the fourth determination signal S4 is switched from false to true. As a result, the determination signals S1 to S3 are false and the determination signal S4 is true. For this reason, the detection signal Vout of the OR circuit 25 is switched to true (for example, High level) with ± B3 [mT] as a threshold value, and the magnetic sensor 1 can detect the magnetic field strength.

  Next, the case where the angle θ of the magnetic field direction is 45 degrees (θ = 45 °), that is, the case where the magnetic field direction is the third direction D3 will be described with reference to FIG. When the magnetic field intensity is gradually changed greatly and applied to the magnetic sensor 1, the components in the first direction D1 and the second direction D2 increase uniformly. For this reason, the resistance values of the first to fourth magnetoresistive elements R1 to R4 constituting the first bridge circuit 5 are uniformly reduced. As a result, the output voltages Am and Ap of the first bridge circuit 5 hardly change.

  When the magnetic field strength is gradually changed greatly and applied to the magnetic sensor 1, the resistance values of the fifth and sixth magnetoresistive elements R5 and R6 constituting the second bridge circuit 6 decrease. On the other hand, since the component in the fourth direction D4 is not applied to the seventh and eighth magnetoresistive elements R7, R8, the resistance values of the seventh and eighth magnetoresistive elements R7, R8 hardly change. For this reason, as the magnetic field strength increases, the output voltage Bm increases and the output voltage Bp decreases.

  Therefore, when the magnetic field strength is around 0 [mT], the output voltage Am is smaller than the output voltages Bm and Bp (Am <Bm, Am <Bp), and the output voltage Ap is larger than the output voltages Bm and Bp (Ap). > Bm, Ap> Bp). For this reason, the determination signals S1 to S4 are all false, and the detection signal Vout of the OR circuit 25 is false (for example, low level).

  When the magnetic field strength reaches ± B4 [mT], the output voltage Am and the output voltage Bp cross (Am = Bp), and the output voltage Ap and the output voltage Bm cross (Ap = Bm). Since the output voltages Bm and Bp change greatly compared with the case of 45 ° <θ <67.5 °, | ± B4 [mT] | <| ± B3 [mT] |.

  Further, when the magnetic field strength exceeds ± B4 [mT], the output voltage Am is larger than the output voltage Bp (Am> Bp), and the output voltage Ap is smaller than the output voltage Bm (Ap <Bm). The fourth determination signals S1 and S4 are switched from false to true. As a result, the determination signals S1 and S4 are true, and the determination signals S2 and S3 are false. For this reason, the detection signal Vout of the OR circuit 25 switches from false to true (for example, from the Low level to the High level) with ± B4 [mT] as a threshold value, and the magnetic sensor 1 can detect the magnetic field strength.

  Next, a case where the angle θ in the magnetic field direction is 45 ° to 67.5 ° (45 ° <θ <67.5 °) will be described with reference to FIG. When the magnetic field strength is gradually changed greatly and applied to the magnetic sensor 1, the components of the magnetic field strength in the first direction D1 and the second direction D2 increase. However, the component in the first direction D1 is larger than the component in the second direction D2. Therefore, although the resistance values of the first to fourth magnetoresistive elements R1 to R4 of the first bridge circuit 5 are reduced, the amount of change in the resistance values of the first and second magnetoresistive elements R1 and R2 is: The amount of change in the resistance values of the third and fourth magnetoresistive elements R3 and R4 is larger. Along with this, the output voltages Am and Ap gradually increase in phase.

  Further, when the magnetic field strength is gradually changed and applied to the magnetic sensor 1, the components in the third direction D3 and the fourth direction D4 increase. The component in the third direction D3 is larger than the component in the fourth direction D4. For this reason, although the resistance values of the fifth to eighth magnetoresistive elements R5 to R8 of the second bridge circuit 6 are reduced, the amount of change in the resistance values of the fifth and sixth magnetoresistive elements R5 and R6 is: The amount of change in the resistance values of the seventh and eighth magnetoresistive elements R7 and R8 is larger. As a result, the output voltage Bm increases and the output voltage Bp decreases. Note that the output voltages Bm and Bp change more slowly than when θ = 45 °.

  Therefore, when the magnetic field strength is around 0 [mT], the output voltage Am is smaller than the output voltages Bm and Bp (Am <Bm, Am <Bp), and the output voltage Ap is larger than the output voltages Bm and Bp (Ap). > Bm, Ap> Bp). For this reason, the determination signals S1 to S4 are all false, and the detection signal Vout of the OR circuit 25 is false (for example, low level).

  When the magnetic field strength reaches ± B5 [mT], the output voltage Am and the output voltage Bp cross (Am = Bp). Since the output voltages Bm and Bp change more gently than when θ = 45 °, | ± B4 [mT] | <| ± B5 [mT] |.

  Further, when the magnetic field strength exceeds ± B5 [mT], the output voltage Am becomes larger than the output voltage Bp (Am> Bp), and the first determination signal S1 is switched from false to true. As a result, the determination signal S1 is true and the determination signals S2 to S4 are false. For this reason, the detection signal Vout of the OR circuit 25 switches from false to true (for example, from the Low level to the High level) with ± B5 [mT] as a threshold value, and the magnetic sensor 1 can detect the magnetic field strength.

  Next, the case where the angle θ in the magnetic field direction is 67.5 degrees (θ = 67.5 °) will be described with reference to FIG. When the magnetic field strength is gradually changed greatly and applied to the magnetic sensor 1, the components of the magnetic field strength in the first direction D1 and the second direction D2 increase. However, the component in the first direction D1 is larger than the component in the second direction D2. Therefore, although the resistance values of the first to fourth magnetoresistive elements R1 to R4 of the first bridge circuit 5 are reduced, the amount of change in the resistance values of the first and second magnetoresistive elements R1 and R2 is: The amount of change in the resistance values of the third and fourth magnetoresistive elements R3 and R4 is larger. Along with this, the output voltages Am and Ap increase gently in the same phase.

  Further, when the magnetic field strength is gradually changed and applied to the magnetic sensor 1, the components in the third direction D3 and the fourth direction D4 increase. The component in the third direction D3 is larger than the component in the fourth direction D4. For this reason, although the resistance values of the fifth to eighth magnetoresistive elements R5 to R8 of the second bridge circuit 6 are reduced, the amount of change in the resistance values of the fifth and sixth magnetoresistive elements R5 and R6 is: The amount of change in the resistance values of the seventh and eighth magnetoresistive elements R7 and R8 is larger. As a result, the output voltage Bm increases and the output voltage Bp decreases. Note that the output voltages Bm and Bp change more slowly than in the case of 45 ° <θ <67.5 °.

  Therefore, when the magnetic field strength is around 0 [mT], the output voltage Am is smaller than the output voltages Bm and Bp (Am <Bm, Am <Bp), and the output voltage Ap is larger than the output voltages Bm and Bp (Ap). > Bm, Ap> Bp). For this reason, the determination signals S1 to S4 are all false, and the detection signal Vout of the OR circuit 25 is false (for example, low level).

  When the magnetic field strength reaches ± B6 [mT], the output voltage Am and the output voltage Bp are crossed (Am = Bp). Since the output voltages Bm and Bp change more gently than in the case of 45 ° <θ <67.5 °, | ± B5 [mT] | <| ± B6 [mT] |.

  Further, when the magnetic field intensity exceeds ± B6 [mT], the output voltage Am becomes larger than the output voltage Bp (Am> Bp), and the first determination signal S1 is switched from false to true. As a result, the determination signal S1 is true and the determination signals S2 to S4 are false. For this reason, the detection signal Vout of the OR circuit 25 switches from false to true (for example, low level to high level) with ± B6 [mT] as a threshold value, and the magnetic sensor 1 can detect the magnetic field strength.

  Next, the case where the angle θ in the magnetic field direction is 67.5 degrees to 90 degrees (67.5 ° <θ <90 °) will be described with reference to FIG. When the magnetic field strength is gradually changed greatly and applied to the magnetic sensor 1, the components of the magnetic field strength in the first direction D1 and the second direction D2 increase. However, the component in the first direction D1 is larger than the component in the second direction D2. Therefore, although the resistance values of the first to fourth magnetoresistive elements R1 to R4 of the first bridge circuit 5 are reduced, the amount of change in the resistance values of the first and second magnetoresistive elements R1 and R2 is: The amount of change in the resistance values of the third and fourth magnetoresistive elements R3 and R4 is larger. Accordingly, the output voltages Am and Ap greatly increase in phase as compared with the case of θ = 67.5 °.

  Further, when the magnetic field strength is gradually changed and applied to the magnetic sensor 1, the components in the third direction D3 and the fourth direction D4 increase. The component in the third direction D3 is larger than the component in the fourth direction D4. For this reason, although the resistance values of the fifth to eighth magnetoresistive elements R5 to R8 of the second bridge circuit 6 are reduced, the amount of change in the resistance values of the fifth and sixth magnetoresistive elements R5 and R6 is: It is larger than the amount of change in resistance value of the seventh and eighth magnetoresistive elements R7, R8. As a result, the output voltage Bm increases and the output voltage Bp decreases. Note that the output voltages Bm and Bp change more slowly than in the case of θ = 67.5 °.

  Accordingly, when the magnetic field strength is around 0 [mT], the output voltage Am is smaller than the output voltages Bm and Bp (Am <Bm, Am <Bp), and the output voltage Ap is smaller than the output voltages Bm and Bp (Ap>). Bm, Ap> Bp). For this reason, the determination signals S1 to S4 are all false, and the detection signal Vout of the OR circuit 25 is false (for example, low level).

  When the magnetic field strength reaches ± B7 [mT], the output voltage Am and the output voltage Bp cross (Am = Bp). Since the output voltages Am and Ap change greatly compared to the case of θ = 67.5 °, | ± B7 [mT] | <| ± B6 [mT] |.

  Further, when the magnetic field intensity exceeds ± B7 [mT], the output voltage Am becomes larger than the output voltage Bp (Am> Bp), and the first determination signal S1 is switched from false to true. As a result, the determination signal S1 is true and the determination signals S2 to S4 are false. For this reason, the detection signal Vout of the OR circuit 25 switches from false to true (for example, from the Low level to the High level) with ± B7 [mT] as a threshold value, and the magnetic sensor 1 can detect the magnetic field strength.

  Next, the case where the angle θ of the magnetic field direction is 90 degrees (θ = 90 °), that is, the case where the magnetic field direction is the first direction D1 will be described with reference to FIG. When the magnetic field intensity is gradually increased and applied to the magnetic sensor 1, the resistance values of the first and second magnetoresistive elements R1 and R2 decrease. On the other hand, since the component in the second direction D2 is not applied to the third and fourth magnetoresistive elements R3 and R4, the resistance values of the third and fourth magnetoresistive elements R3 and R4 hardly change. For this reason, as the magnetic field strength increases, the output voltages Am and Ap increase in phase.

  On the other hand, when the magnetic field strength is gradually varied and applied to the magnetic sensor 1, the components in the third direction D3 and the fourth direction D4 increase uniformly. For this reason, the resistance values of the fifth to eighth magnetoresistive elements R5 to R8 of the second bridge circuit 6 are uniformly reduced. As a result, the output voltages Bm and Bp of the second bridge circuit 6 hardly change.

  Therefore, when the magnetic field strength is around 0 [mT], the output voltage Am is smaller than the output voltages Bm and Bp (Am <Bm, Am <Bp), and the output voltage Ap is larger than the output voltages Bm and Bp (Ap). > Bm, Ap> Bp), the determination signals S1 to S4 are all false. For this reason, the detection signal Vout of the OR circuit 25 becomes false (for example, Low level).

  When the magnetic field intensity reaches ± B8 [mT], the output voltage Am crosses the output voltages Bm and Bp (Am = Bm, Am = Bp).

  Since the changes in the output voltages Am and Ap are larger than in the case of 67.5 ° <θ <90 °, | ± B8 [mT] | <| ± B7 [mT] |.

  Further, when the magnetic field intensity exceeds ± B8 [mT], the output voltage Am becomes larger than the output voltages Bm and Bp (Am> Bm, Am> Bp), and the first and second determination signals S1 and S2 are false. Switch to true. As a result, the determination signals S1 and S2 are true, and the determination signals S3 and S4 are false. For this reason, the detection signal Vout of the OR circuit 25 switches from false to true (for example, from the Low level to the High level) with ± B8 [mT] as a threshold value, and the magnetic sensor 1 can detect the magnetic field strength.

  Similarly, the magnetic sensor 1 can detect the magnetic field strength even when the angle θ in the magnetic field direction exceeds 90 degrees.

  When the angle θ in the magnetic field direction is 90 ° to 135 ° (90 ° ≦ θ ≦ 135 °), the output voltage Am and the output voltage Bm cross (Am = Bm) exceeding the threshold value of the magnetic field strength, When the output voltage Am becomes higher than the output voltage Bm (Am> Bm), the second determination signal S2 switches from false to true, and the magnetic sensor 1 can detect the magnetic field strength.

  When the angle θ in the magnetic field direction is 135 ° to 180 ° (135 ° ≦ θ ≦ 180 °), the output voltage Ap and the output voltage Bp cross (Ap = Bp) exceeding the threshold value of the magnetic field strength, When the output voltage Ap becomes smaller than the output voltage Bp (Ap <Bp), the third determination signal S3 switches from false to true, and the magnetic sensor 1 can detect the magnetic field strength.

  When the angle θ in the magnetic field direction is −45 ° to 0 ° (−45 ° ≦ θ ≦ 0 °), the output voltage Ap and the output voltage Bp cross (Ap = Bp). When the output voltage Ap becomes smaller than the output voltage Bp (Ap <Bp), the third determination signal S3 switches from false to true, and the magnetic sensor 1 can detect the magnetic field strength.

  When the angle θ in the magnetic field direction is −90 degrees to −45 degrees (−90 ° ≦ θ ≦ −45 °), the output voltage Am and the output voltage Bm cross (Am = Bm). When the output voltage Am exceeds the output voltage Bm (Am> Bm), the second determination signal S2 switches from false to true, and the magnetic sensor 1 can detect the magnetic field strength.

  When the angle θ in the magnetic field direction is between −135 degrees and −90 degrees (−135 ° ≦ θ ≦ −90 °), the output voltage Am and the output voltage Bp cross (Am = Bp). When the output voltage Am exceeds the output voltage Bp (Am> Bp), the first determination signal S1 switches from false to true, and the magnetic sensor 1 can detect the magnetic field strength.

  When the angle θ in the magnetic field direction is −180 degrees to −135 degrees (−180 ° ≦ θ ≦ −135 °), the output voltage Ap and the output voltage Bm cross (Ap = Bm). When the output voltage Ap becomes smaller than the output voltage Bm (Bm> Ap), the fourth determination signal S4 switches from false to true, and the magnetic sensor 1 can detect the magnetic field strength.

  The relationship between the angle θ (−90 ° ≦ θ ≦ 90 °) in the magnetic field direction based on the above description and the threshold value at which the magnetic sensor 1 detects the magnetic field intensity at the angle θ is indicated by a solid line in FIG. As a comparative example, the relationship between the angle θ (−90 ° ≦ θ ≦ 90 °) related to the conventional magnetic sensor 31 and the threshold value at which the magnetic sensor 31 detects the magnetic field strength at the angle θ is indicated by a broken line. The magnetic sensor 31 can detect a magnetic field only in the range where the absolute value of the angle θ is 0 ° to 45 ° (| θ | ≦ 45 °), whereas the magnetic sensor 1 has the absolute value of the angle θ from 0 °. A range of 90 degrees (| θ | ≦ 90 °), that is, magnetic fields in all magnetic directions can be detected.

  Further, in the magnetic sensor 31, the magnitude of the threshold varies greatly depending on the angle θ, and therefore the anisotropy in the detection direction is large. However, in the magnetic sensor 1, even when the angle θ is different, the change in the threshold is small, so the anisotropy in the detection direction is small.

  Note that the arithmetic circuit unit 3 is configured such that the first output voltage Am> the fourth output voltage Bp or the first output voltage Am> the third output voltage Bm or the fourth output voltage Bp> the second output voltage. It is determined whether Ap or the third output voltage Bm> the second output voltage Ap. For this reason, according to angle (theta), you may select suitably the conditions which are satisfied when the magnetic field intensity is the smallest among these four conditions. As a result, it is possible to suppress a decrease in magnetic sensitivity with respect to the magnetic application direction.

  Further, in the magnetic sensor 1, the first to eighth magnetoresistive elements R1 to R8 are configured to alternately connect a plurality of linear patterns formed in close proximity to each other at the tip portion. However, the present invention is not limited to this. For example, the magnetoresistive elements R1 to R8 may be configured by one linear pattern.

1 Magnetic Sensor 3 Arithmetic Circuit Unit (Voltage Value Comparison Means)
DESCRIPTION OF SYMBOLS 5 1st bridge circuit 6 2nd bridge circuit 7 1st series circuit 8 2nd series circuit 13 3rd series circuit 14 4th series circuit 21-24 Comparator 25 OR circuit R1-R8 Magnetoresistive element (Magnetic detection element)

Claims (6)

First and second magnetic sensing elements having maximum sensitivity to an applied magnetic field in a first direction and outputting a voltage having an even function characteristic with respect to the magnetic field strength;
And third and fourth magnetic sensing elements that have maximum sensitivity to a magnetic field applied in a second direction inclined by θ1 from the first direction and that output a voltage having an even function characteristic with respect to the magnetic field strength. ,
A first series circuit in which the first and third magnetic detection elements are connected in series via a connection end; and a second series circuit in which the second and fourth magnetic detection elements are connected in series via a connection end. A series circuit is connected in parallel, one of the two common connection ends of the first and second series circuits is connected to the first power supply voltage and the other is grounded, and the first and second A first bridge circuit that outputs a first output voltage and a second output voltage of the same phase from each of the connection ends of the series circuit;
Fifth and sixth magnetic sensing elements that have maximum sensitivity to an applied magnetic field in a third direction inclined by θ 2 from the first direction and that output a voltage having an even function characteristic with respect to the magnetic field strength;
And seventh and eighth magnetic detection elements that have a maximum sensitivity to a magnetic field applied in a fourth direction inclined by θ3 from the first direction and that output a voltage having an even function characteristic with respect to the magnetic field strength. ,
A third series circuit in which the fifth and seventh magnetic detection elements are connected in series via a connection end, and a fourth series in which the sixth and eighth magnetic detection elements are connected in series via a connection end A series circuit is connected in parallel, and one of the two common connection ends of the third and fourth series circuits is connected to the second power supply voltage and the other is grounded, and the third and fourth A second bridge circuit that outputs a third output voltage and a fourth output voltage having opposite phases from each of the connection ends of the series circuit, wherein the magnetic sensor comprises:
Providing the first bridge circuit with offset means for differentiating the first and second output voltages when no magnetic field is applied;
When a magnetic field is not applied, the voltage values of the third and fourth output voltages are set to be a voltage value between the first output voltage and the second output voltage,
When a magnetic field is applied,
The voltage values of the first to fourth output voltages are:
The first output voltage> the fourth output voltage or
The first output voltage> the third output voltage or
The fourth output voltage> the second output voltage or
A magnetic sensor comprising voltage value comparison means for determining whether the third output voltage is greater than the second output voltage. A Wheatstone bridge is configured using the first to fourth magnetic detection elements that output a voltage having an even function characteristic with respect to the magnetic field strength, and the maximum is applied to the applied magnetic field in the first and second directions on the biaxial plane. With sensitivity
A first bridge in which two output terminals output first and second output voltages that change in phase with respect to the magnetic field strength, and the first and second output voltages are different when no magnetic field is applied. Circuit,
A Wheatstone bridge is configured by using fifth to eighth magnetic detecting elements that output a voltage having an even function characteristic with respect to the magnetic field strength, and the third and third directions different from the first and second directions on the biaxial plane. Has maximum sensitivity to the applied magnetic field in the fourth direction,
When the two output terminals output third and fourth output voltages that change in opposite phase with respect to the magnetic field strength, and no magnetic field is applied, the third and fourth output voltages are the first output voltage. And a second bridge circuit having a voltage value between the first output voltage and the second output voltage,
When a magnetic field is applied, the magnetic field strength at which one of the first and second output voltages matches one of the third and fourth output voltages becomes the detected threshold magnetic field strength. A magnetic sensor. First and second magnetic sensing elements having maximum sensitivity to an applied magnetic field in a first direction and outputting a voltage having an even function characteristic with respect to the magnetic field strength;
And third and fourth magnetic sensing elements that have maximum sensitivity to a magnetic field applied in a second direction inclined by θ1 from the first direction and that output a voltage having an even function characteristic with respect to the magnetic field strength. ,
A first series circuit in which the first and third magnetic detection elements are connected in series via a connection end; and a second series circuit in which the second and fourth magnetic detection elements are connected in series via a connection end. A series circuit is connected in parallel, one of the two common connection ends of the first and second series circuits is connected to the first power supply voltage and the other is grounded, and the first and second A first bridge circuit that outputs a first output voltage and a second output voltage of the same phase from each of the connection ends of the series circuit;
Fifth and sixth magnetic sensing elements that have maximum sensitivity to an applied magnetic field in a third direction inclined by θ 2 from the first direction and that output a voltage having an even function characteristic with respect to the magnetic field strength;
And seventh and eighth magnetic detection elements that have a maximum sensitivity to a magnetic field applied in a fourth direction inclined by θ3 from the first direction and that output a voltage having an even function characteristic with respect to the magnetic field strength. ,
A third series circuit in which the fifth and seventh magnetic detection elements are connected in series via a connection end, and a fourth series in which the sixth and eighth magnetic detection elements are connected in series via a connection end A series circuit is connected in parallel, and one of the two common connection ends of the third and fourth series circuits is connected to the second power supply voltage and the other is grounded, and the third and fourth A second bridge circuit that outputs a third output voltage and a fourth output voltage that are opposite in phase from each of the connection ends of the series circuit.
A magnetic sensor that detects a magnetic field by comparing any one of the first and second output voltages with any of the third and fourth output voltages. A Wheatstone bridge is configured using the first to fourth magnetic detection elements that output a voltage having an even function characteristic with respect to the magnetic field strength, and the maximum is applied to the applied magnetic field in the first and second directions on the biaxial plane. With sensitivity
A first bridge in which two output terminals output first and second output voltages that change in phase with respect to the magnetic field strength, and the first and second output voltages are different when no magnetic field is applied. Circuit,
A Wheatstone bridge is configured by using fifth to eighth magnetic detecting elements that output a voltage having an even function characteristic with respect to the magnetic field strength, and the third and third directions different from the first and second directions on the biaxial plane. Has maximum sensitivity to the applied magnetic field in the fourth direction,
When the two output terminals output third and fourth output voltages that change in opposite phase with respect to the magnetic field strength, and no magnetic field is applied, the third and fourth output voltages are the first output voltage. And a second bridge circuit having a voltage value between the first output voltage and the second output voltage,
A magnetic sensor that detects a magnetic field by comparing any one of the first and second output voltages with any of the third and fourth output voltages.   When a magnetic field is not applied, the voltage values of the third and fourth output voltages are the same, and an offset voltage between the third and fourth output voltages and the first output voltage; The magnetic sensor according to claim 1, wherein an offset voltage between the third and fourth output voltages and the second output voltage is the same.   The first and second directions are orthogonal to each other, the third and fourth directions are orthogonal to each other, and the third and fourth directions have an angular difference of 45 degrees with respect to the first and second directions. The magnetic sensor according to claim 1, wherein the magnetic sensor is arranged in a direction.

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