JP7286932B2 - magnetic sensor - Google Patents

Description

The present invention relates to a magnetic sensor including a plurality of magnetoresistive elements.

Patent Literature 1 listed below discloses a magnetic field detection sensor capable of detecting minute magnetic fields. This magnetic field detection sensor includes four magnetoresistive elements forming a bridge circuit and a magnetic body. The fixed magnetization directions of the four magnetoresistive elements are the same. The magnetic body collects the magnetic field to be detected that is perpendicular to the bridge circuit, and makes the collected detection magnetic field substantially parallel to the fixed magnetization direction of the four magnetoresistive elements that constitute the bridge circuit. change direction. A differential output from the bridge circuit is input to the differential arithmetic circuit, and the differential arithmetic circuit causes a feedback current to flow through the magnetic field generating conductors. The magnetic field generating conductor through which the feedback current flows generates a magnetic field in the direction opposite to the direction of the magnetic field to be detected for the four magnetoresistive elements. The magnetic field to be detected is measured by measuring the feedback current.

JP 2015-219061 A

In the magnetic sensor of Patent Document 1, even if bias magnetic fields (non-detection target magnetic fields such as disturbance magnetic fields) are applied to the four magnetoresistive elements in the same direction or phase, the resistance changes of the four magnetoresistive elements are the same. , the bridge circuit does not detect the bias magnetic field. However, the bias magnetic field changes the operating point of the magnetoresistive element and affects the output of the magnetic sensor. That is, when the magnetic field strength in the magnetization direction of the pinned layer increases above a certain value, the magnetoresistive effect element loses its resistance value change (sensitivity) to changes in the magnetic field. , there is a problem that an expected output cannot be obtained with respect to the magnetic field to be detected (see also FIGS. 17 and 18).

SUMMARY OF THE INVENTION The present invention has been made in recognition of such circumstances, and an object of the present invention is to provide a magnetic sensor capable of suppressing the influence of a bias magnetic field.

One aspect of the present invention is a magnetic sensor. This magnetic sensor
a magnetic detection unit including first and second magnetoresistive effect elements to which the first magnetic field to be detected is applied and whose pinned layer magnetization directions are the same;
The magnetic field applied to the magnetic detection unit is connected in series between the high-voltage terminal and the low-voltage terminal, and the resistance value change due to the magnetic field applied to the magnetic detection unit is suppressed or due to the magnetic field applied to the magnetic detection unit. A resistive element whose resistance value does not change,
a first magnetic field generating conductor through which a current corresponding to a ratio between the resistance value of the magnetic detection unit and the resistance value of the resistance element flows,
the first magnetic field has magnetic field components parallel to the pinned layer magnetization direction and in opposite directions at the positions of the first and second magnetoresistive elements;
A magnetic field generated by a current flowing through the first magnetic field generating conductor is applied to the first and second magnetoresistive elements, and parallel to the magnetization direction of the pinned layer and to each other at the positions of the first and second magnetoresistive elements. A change in the resistance values of the first and second magnetoresistive elements due to a bias magnetic field having magnetic field components in the same direction is suppressed.

The first magnetic field generating conductor may be provided between an interconnection point between the magnetic detection section and the resistive element and a medium voltage terminal.

a first differential amplifier that amplifies a difference between a voltage at an interconnection point between the magnetic detection unit and the resistance element and a voltage at a medium voltage terminal;
The first magnetic field generating conductor may be provided between the output terminal of the first differential amplifier and the medium voltage terminal.

The resistive element may be a magnetically shielded magnetoresistive element.

The resistive element may be a fixed resistor.

a second differential amplifier to which the output voltage of the magnetic detection unit is input;
The flow of the first negative feedback current output by the second differential amplifier causes the first and second magnetic detection elements to detect a second magnetic field that cancels the first magnetic field detected by the first and second magnetic detection elements. and a second magnetic field generating conductor for applying to the element.

A magnetic body may be provided that changes the direction of the first magnetic field so that the first magnetic field to be detected has magnetic field components in opposite directions at the positions of the first and second magnetoresistive elements.

Any combination of the above constituent elements, and conversion of expressions of the present invention between methods and systems are also effective as embodiments of the present invention.

According to the present invention, it is possible to provide a magnetic sensor capable of suppressing the influence of a bias magnetic field.

1 is a schematic cross-sectional view of a magnetic sensor 1A according to Embodiment 1 of the present invention; FIG. FIG. 2 is a schematic plan view of the magnetic sensor 1A; Wiring pattern explanatory drawing of the 1st magnetic field generation conductor 75 of 1 A of magnetic sensors. A schematic circuit diagram of the magnetic sensor 1A. 7 is a graph showing an example of the bias magnetic field applied to the magnetic detection section 7, the resistance change of the magnetic detection section 7 in the comparative example, and the resistance change of the magnetic detection section 7 of the magnetic sensor 1A. FIG. 2 is a schematic cross-sectional view of a magnetic sensor 1B according to Embodiment 2 of the present invention; The schematic circuit diagram of the magnetic sensor 1C based on Embodiment 3 of this invention. FIG. 10 is a schematic cross-sectional view of a magnetic sensor 1D according to Embodiment 4 of the present invention; FIG. 4 is a wiring pattern explanatory diagram of the second magnetic field generating conductor 70 of the magnetic sensor 1D. Schematic circuit diagram of magnetic sensor 1D. FIG. 10 is a schematic cross-sectional view of a magnetic sensor 1E according to Embodiment 5 of the present invention; FIG. 10 is a schematic circuit diagram of a magnetic sensor 1F according to Embodiment 6 of the present invention; FIG. 11 is a schematic circuit diagram of a magnetic sensor 1G according to Embodiment 7 of the present invention; FIG. 11 is a schematic cross-sectional view of a magnetic sensor 1H according to Embodiment 8 of the present invention; FIG. 11 is a schematic cross-sectional view of a magnetic sensor 1J according to Embodiment 9 of the present invention; 16 is a schematic circuit diagram of the magnetic sensor of FIGS. 14 and 15; FIG. FIG. 4 is a characteristic diagram showing an example of change in resistance value with respect to magnetic field strength in the magnetization direction of the pinned layer of the magnetoresistive effect element; FIG. 4 is a characteristic diagram showing an example of change in sensitivity of the magnetoresistive element with respect to the magnetic field strength in the magnetization direction of the pinned layer;

Preferred embodiments of the present invention will be described in detail below with reference to the drawings. The same or equivalent constituent elements, members, etc. shown in each drawing are denoted by the same reference numerals, and duplication of description will be omitted as appropriate. Moreover, the embodiments are illustrative rather than limiting the invention, and not all features and combinations thereof described in the embodiments are necessarily essential to the invention.

(Embodiment 1)
A magnetic sensor 1A according to Embodiment 1 of the present invention will be described with reference to FIGS. 1 to 5. FIG. In FIGS. 1 and 2, XYZ axes, which are three orthogonal axes, are defined. 1 and 2 also show the lines of magnetic force of the magnetic field to be detected. In the magnetic sensor 1</b>A, the first magnetoresistive element 10 , the second magnetoresistive element 20 , the third magnetoresistive element 30 , and the fourth magnetoresistive element 40 are connected together with the first magnetic field generating conductor 75 to the laminate 5 . provided in A magnetic body 80 is provided on the surface of the laminate 5 . As shown in FIG. 2, the positions of the first magnetoresistive element 10 and the third magnetoresistive element 30 in the X direction are equal to each other. Similarly, the second magnetoresistive element 20 and the fourth magnetoresistive element 40 have the same position in the X direction. In addition, the positions of the first magnetoresistive element 10 and the second magnetoresistive element 20 are equal to each other in the Y direction. Similarly, the positions of the third magnetoresistive element 30 and the fourth magnetoresistive element 40 are equal to each other in the Y direction.

In FIG. 2, the arrangement of the first magnetoresistive effect element 10 and the third magnetoresistive effect element 30 and the arrangement of the second magnetoresistive effect element 20 and the fourth magnetoresistive effect element 40 are symmetrical in the X direction. Let A be the center line. Further, the center line in the Y direction where the arrangement of the first magnetoresistive effect element 10 and the second magnetoresistive effect element 20 and the arrangement of the third magnetoresistive effect element 30 and the fourth magnetoresistive effect element 40 are line symmetrical be B. The magnetic body 80 is preferably arranged at a position where the center line in the X direction and the center line in the Y direction of the magnetic body 80 coincide with A and B, respectively. In addition, the magnetic body 80 extends in the Y direction of the first magnetoresistive element 10 and the second magnetoresistive element 20, and also extends between the third magnetoresistive element 30 and the fourth magnetoresistive element . It preferably extends in the Y direction. Further, the magnetic body 80 is arranged such that the end face on the side of the laminated body 5 is closest to the first to fourth magnetoresistance effect elements (10, 20, 30, 40) in the Z direction, that is, the end face on the side of the laminated body 5 is the laminated body. It is preferably in contact with the surface of body 5 . By arranging in this way, the resistance change of the first to fourth magnetoresistive effect elements (10, 20, 30, 40) according to the change of the magnetic field to be detected is efficiently and evenly generated. Become.

The layer forming the first magnetic field generating conductor 75 in the laminate 5 is a lower layer (on the -Z direction side) than the layer forming the first to fourth magnetoresistive elements (10, 20, 30, 40). layer). By arranging the first magnetic field generating conductor 75 below the layer in which the first to fourth magnetoresistance effect elements (10, 20, 30, 40) are formed, the magnetic body 80 and the first to fourth magnetoresistance effects The distance of the elements (10, 20, 30, 40) in the Z direction can be shortened, so that the first to fourth magnetoresistive elements (10, 20, 30, 40) can efficiently respond to changes in the magnetic field to be detected. become responsive. The magnetic body 80 may be a soft magnetic body.

The magnetic body 80 collects the magnetic field to be detected in the Z direction, and distributes the collected magnetic field to be detected in the magnetization direction (X direction). The magnetic field to be detected is a magnetic field parallel to the Z direction as a whole if the magnetic body 80 does not exist, and is partially bent by the presence of the magnetic body 80 to form the first to fourth magnetoresistive elements (10 , 20, 30, 40) have components in the X direction. By the magnetic body 80, the X component of the magnetic field to be detected at the positions of the first magnetoresistive effect element 10 and the third magnetoresistive effect element 30 and the detection at the positions of the second magnetoresistive effect element 20 and the fourth magnetoresistive effect element 40 The X component of the target magnetic field is in the opposite direction to each other, and when the magnetic field to be detected is an alternating current, a differential magnetic field with a phase difference of 180 degrees (opposite phase).

FIG. 3 is a wiring pattern explanatory diagram of the first magnetic field generating conductor 75 of the magnetic sensor 1A. In FIG. 3, the wiring pattern of the first magnetic field generating conductors 75 in the laminate 5 is indicated by solid lines. The first magnetic field generating conductor 75 is formed in the same laminate 5 as the first to fourth magnetoresistive elements (10, 20, 30, 40). In the example of FIG. 3, the first magnetic field generating conductor 75 has a meandering conductor pattern. Specifically, the first magnetic field generating conductor 75 extends in the +Y direction with one end at the same X direction position as the fourth magnetoresistive element 40 and the -Y direction side of the fourth magnetoresistive element 40, and the second magnetoresistive element It reaches the +Y direction side of the effect element 20, extends in the +X direction from there, reaches the same X direction position as the magnetic body 80, extends in the -Y direction from there, reaches the -Y direction side of the magnetic body 80, and from there +X. direction to reach the same X-direction position as the third magnetoresistive effect element 30, and then extend in the +Y direction to reach the +Y-direction side of the first magnetoresistive effect element 10 (the same X direction as the first magnetoresistive effect element 10). The direction position and the +Y direction side of the first magnetoresistive effect element 10 is the other end). The first magnetic field generating conductor 75 generates a correction magnetic field having a magnetic field component that cancels out the X direction component (magnetosensitive direction component) of the bias magnetic field at the position of each magnetoresistive effect element. In this embodiment, the bias magnetic field is assumed to be a uniform magnetic field in an arbitrary direction if the magnetic body 80 does not exist, and the X-direction component of the bias magnetic field is canceled by the correction magnetic field. Here, the cancellation is preferably approximately 0, but may be partial cancellation.

FIG. 4 is a schematic circuit diagram of the magnetic sensor 1A. The magnetic detection unit 7 of the magnetic sensor 1A is a bridge circuit composed of a first magnetoresistive element 10, a second magnetoresistive element 20, a third magnetoresistive element 30, and a fourth magnetoresistive element 40. FIG. The pinned layer magnetization directions of the first to fourth magnetoresistive elements (10, 20, 30, 40) are the same (+X direction). A direction parallel to the magnetization direction of the pinned layer is the magnetosensitive direction of each magnetoresistive element. The resistor R is a resistive element whose resistance value change due to the magnetic field applied to the magnetic detection section is suppressed or whose resistance value change does not occur due to the magnetic field applied to the magnetic detection section. The resistor R may be a fixed resistor or a magnetically shielded magnetoresistive element. When the resistor R is a magnetoresistive element, it is preferable that it has the same temperature characteristics as those of the first to fourth magnetoresistive elements (10, 20, 30, 40). The resistance value of the resistor R matches the resistance value of the magnetic detection section 7 in the absence of a bias magnetic field, that is, the combined resistance value of the first to fourth magnetoresistive elements (10, 20, 30, 40).

One end of the resistor R is connected to a high voltage terminal supplied with the power supply voltage Vcc. The other end of the resistor R is connected to one end of the first magnetoresistive element 10 and one end of the second magnetoresistive element 20 . The other end of the first magnetoresistive element 10 is connected to one end of the fourth magnetoresistive element 40 . The other end of the second magnetoresistive element 20 is connected to one end of the third magnetoresistive element 30 . The other end of the third magnetoresistive element 30 and the other end of the fourth magnetoresistive element 40 are connected to a low voltage terminal to which the power supply voltage -Vcc is supplied. The other end of the resistor R, one end of the first magnetoresistive element 10 and one end of the second magnetoresistive element 20 (point P1 in FIG. 4) are connected to one end of the first magnetic field generating conductor 75 . The other end of the first magnetic field generating conductor 75 is connected to a ground terminal as a medium voltage terminal. The voltage Va output to the interconnection point of the first magnetoresistive effect element 10 and the fourth magnetoresistive effect element 40 is output to the interconnection point of the second magnetoresistive effect element 20 and the third magnetoresistive effect element 30. Let the voltage be Vb. The difference between the voltages Va and Vb is the sensor output voltage of the magnetic sensor 1A.

When the magnetic field to be detected is in the state shown in FIG. 2, in the first magnetoresistive effect element 10, the direction of the magnetic field to be detected has a component in the same direction as the magnetization direction of the fixed layer. The resistance value of the first magnetoresistive effect element 10 changes by -ΔR from the resistance value R0 in the absence of the magnetic field. On the other hand, in the second magnetoresistance effect element 20, the direction of the magnetic field to be detected has a component opposite to the magnetization direction of the pinned layer, so the magnetization direction of the free layer is opposite to the magnetization direction of the pinned layer. The resistance value of the effect element 20 changes by +ΔR from the resistance value R0 in the absence of the magnetic field. Similarly, the resistance value of the third magnetoresistive effect element 30 changes by -ΔR compared to when there is no magnetic field, and the resistance value of the fourth magnetoresistive effect element 40 changes by +ΔR compared to when there is no magnetic field. Due to such resistance changes of the first to fourth magnetoresistive elements (10, 20, 30, 40), the voltage Va becomes higher than in the absence of magnetic field, and the voltage Vb becomes lower than in the absence of magnetic field. Become. Therefore, the bridge circuit of the first to fourth magnetoresistive elements (10, 20, 30, 40) provides a differential output, that is, a voltage Va and a voltage Vb that change opposite to each other according to changes in the magnetic field to be detected. output is possible.

In the circuit of FIG. 4, point P1 is at ground potential when no bias magnetic field is present. Therefore, no current flows through the first magnetic field generating conductor 75 . When a bias magnetic field having a component in the +X direction is applied to the magnetic detection section 7, the resistance values of the first to fourth magnetoresistive elements (10, 20, 30, 40) decrease, and the magnetic detection section 7 Since the resistance drops, the voltage at point P1 becomes negative (below ground potential). The negative degree increases as the component of the bias magnetic field in the +X direction increases. When the voltage at point P1 becomes negative, current flows in the direction of the ground terminal, first magnetic field generating conductor 75, and point P1. As a result, the first magnetic field generating conductor 75 generates a correction magnetic field having a -X direction component at the position of each magnetoresistive effect element, that is, canceling out the bias magnetic field at the position of each magnetoresistive effect element.

When a bias magnetic field having a component in the −X direction is applied to the magnetic detection section 7, the resistance values of the first to fourth magnetoresistive elements (10, 20, 30, 40) increase, and the magnetic detection section 7 increases, the voltage at point P1 becomes positive (exceeds ground potential). The degree of plus increases as the component of the bias magnetic field in the -X direction increases. When the voltage at the point P1 becomes positive, current flows in the direction of the point P1, the first magnetic field generating conductor 75, and the ground terminal. As a result, the first magnetic field generating conductor 75 generates a correction magnetic field having a +X direction component at the position of each magnetoresistive effect element, that is, canceling out the bias magnetic field at the position of each magnetoresistive effect element.

Since the first magnetic field generating conductor 75 forms the current path shown in FIG. equal. The current (negative feedback current) flowing through the first magnetic field generating conductor 75 increases as the X direction component of the bias magnetic field increases. At the position of each magnetoresistive element, a magnetic equilibrium state is established between the bias magnetic field and the correction magnetic field.

The operating point at which the magnetic equilibrium state of the bias magnetic field and correction magnetic field is established is
- magnetic coupling between the first magnetic field generating conductor 75 and each magnetoresistive effect element;
The magnetic field generation efficiency of the first magnetic field generating conductor 75 alone (inductance value of the first magnetic field generating conductor 75),
・Determined by three conditions of resolution of each magnetoresistive effect element. If the three conditions are ideal, that is, the magnetic coupling between the first magnetic field generating conductor 75 and each magnetoresistive effect element is sufficiently strong, the magnetic field generating efficiency of the first magnetic field generating conductor 75 alone is sufficiently high, and each If the resolution of the magneto-resistive effect element is sufficiently high, the magnetic equilibrium state will be established only by a slight current flowing through the first magnetic field generating conductor 75, and X The components sum to essentially zero.

FIG. 5 is a graph showing an example of the bias magnetic field applied to the magnetic detection section 7, the resistance change of the magnetic detection section 7 in the comparative example, and the resistance change of the magnetic detection section 7 of the magnetic sensor 1A. A comparative example is a configuration in which the resistor R is removed from the configuration of FIGS. As shown in FIG. 5, in the configuration of the comparative example, the resistance value of the magnetic detection section 7 fluctuates greatly due to fluctuations in the bias magnetic field. On the other hand, in the magnetic sensor 1A of the present embodiment, the variation of the resistance value of the magnetic detection section 7 with respect to the variation of the bias magnetic field is greatly suppressed, and the resistance value of the magnetic detection section 7 is almost the same as when there is no bias magnetic field. It is almost constant with a value that does not change. That is, the sum of the X components of the bias magnetic field and correction magnetic field is substantially zero at the position of each magnetoresistive element.

As shown in FIGS. 17 and 18, the magnetoresistive element exhibits a linear relationship between the magnetic field strength and the resistance value when the magnetic field strength in the magnetization direction of the pinned layer is within a certain value, resulting in high sensitivity. exceeds a certain value, the change (gradient) of the resistance value with respect to the change in the magnetic field intensity becomes small, resulting in a decrease in sensitivity. Therefore, the magnetoresistive element has high sensitivity at the operating point when the bias magnetic field shown in FIGS. the largest possible). On the other hand, at the operating point when the bias magnetic field is small as shown in FIG. 17, the sensitivity is lower than the operating point when the bias magnetic field is 0, and a large linear resistance value change cannot be obtained. Also, at the operating point when the bias magnetic field is large, as shown in FIG. 17, the magnetoresistive element cannot operate due to saturation.

In this embodiment, a resistor R is connected in series with the magnetic detection section 7, a first magnetic field generating conductor 75 is connected between the interconnection point of the resistor R and the magnetic detection section 7, and a ground terminal. A current corresponding to the ratio between the resistance value and the resistance value of the magnetism detecting section 7 is caused to flow through the first magnetic field generating conductor 75 . Here, the ratio between the resistance value of the resistor R and the resistance value of the magnetic detection section 7 changes depending on the X direction component of the bias magnetic field applied to the magnetic detection section 7 . The correction magnetic field generated by the current flowing through the first magnetic field generating conductor 75 cancels the X-direction component of the bias magnetic field applied to the magnetic detection section 7, and the ratio of the resistance value of the resistor R to the resistance value of the magnetic detection section 7 is to approximate, and preferably substantially match, the ratio in the absence of the bias field.

According to this embodiment, the following effects can be obtained.

(1) Since the X direction component of the bias magnetic field applied to the magnetic detection section 7 is canceled by the correction magnetic field generated by the first magnetic field generating conductor 75, the influence of the bias magnetic field can be suppressed. Specifically, it is possible to suppress the risk of inoperability due to desensitization or saturation of the first to fourth magnetoresistive elements (10, 20, 30, 40) due to the bias magnetic field.

(2) Only the resistor R and the first magnetic field generating conductor 75 are sufficient for generating the correction magnetic field. Therefore, the circuit configuration for suppressing the influence of the bias magnetic field is simple and the cost is low.

(3) When the resistor R is a magnetoresistive element having the same temperature characteristics as those of the first to fourth magnetoresistive elements (10, 20, 30, 40), a change in temperature affects the effect of suppressing the influence of the bias magnetic field. Fluctuations can be suppressed.

(4) Since the resistance value of the resistor R is matched with the resistance value of the magnetic detector 7 when no bias magnetic field exists, the voltage at the point P1 in FIG. 4 when no bias magnetic field exists is the ground potential. Therefore, the ground terminal can be used as a medium voltage terminal to which the other end of the first magnetic field generating conductor 75 is connected, and the circuit configuration can be simplified.

In the present embodiment, the ratio between the resistance value of the resistor R and the resistance value of the magnetic detection section 7 in the absence of a bias magnetic field is not limited to 1:1, and can be set arbitrarily. In any ratio, the medium voltage terminal to which the other end of the first magnetic field generating conductor 75 is connected should be a terminal with a voltage that matches the voltage at point P1 in FIG. 4 when no bias magnetic field exists. For example, if the ratio is 1:3, a reference power source of +Vcc×1/2 is provided, and the reference power source terminal of +Vcc×1/2 is used as a medium voltage terminal to which the other end of the first magnetic field generating conductor 75 is connected. do it. In this case, although it is necessary to provide a reference power source, the voltage drop due to the resistor R can be reduced, and the amplitude of the output voltage of the magnetic detection section 7 can be increased. The resistor R may be connected between a connection point between the other ends of the third magnetoresistive element 30 and the fourth magnetoresistive element 40 and a low voltage terminal to which the power supply voltage -Vcc is supplied.

(Embodiment 2)
FIG. 6 is a schematic cross-sectional view of a magnetic sensor 1B according to Embodiment 2 of the present invention. In the magnetic sensor 1B of the present embodiment, as compared with the magnetic sensor 1A of the first embodiment, the first magnetic field generating conductor 75 provided inside the laminate 5 in the magnetic sensor 1A is outside the laminate 5. The difference is that the provided first magnetic field generating conductors 75a and 75b are replaced, and the other points are the same. The first magnetic field generating conductors 75a and 75b are, for example, coils (solenoid coils or the like) whose winding axis direction is parallel to the X direction, and are provided on both sides of the laminate 5 in the X direction. The first magnetic field generating conductors 75a and 75b are preferably configured to apply a uniform magnetic field parallel to the X direction to the first to fourth magnetoresistive elements (10, 20, 30, 40). The first magnetic field generating conductors 75a and 75b may be connected in series or in parallel with each other. This embodiment can also achieve the same effect as the first embodiment.

(Embodiment 3)
FIG. 7 is a schematic circuit diagram of a magnetic sensor 1C according to Embodiment 3 of the present invention. Compared to the magnetic sensor 1A of the first embodiment, the magnetic sensor 1C of the present embodiment additionally includes a first operational amplifier 76 as a first differential amplifier. A non-inverting input terminal of the first operational amplifier 76 is connected to an interconnection point (point P1 in FIG. 7) of the resistor R and the magnetic detection section 7 . The inverting input terminal of the first operational amplifier 76 is connected to the ground terminal. The output terminal of the first operational amplifier 76 is connected to one end of the first magnetic field generating conductor 75 . The other end of the first magnetic field generating conductor 75 is connected to the ground terminal.

When a bias magnetic field having a component in the +X direction is applied to the magnetic detection section 7 and the voltage at the point P1 becomes negative, the output voltage of the first operational amplifier 76 becomes negative, and the ground terminal, the first magnetic field generating conductor 75, the first Current flows in the direction of the output terminal of operational amplifier 76 . As a result, the first magnetic field generating conductor 75 generates a correction magnetic field having a -X direction component at the position of each magnetoresistive effect element, that is, canceling out the bias magnetic field at the position of each magnetoresistive effect element. When a bias magnetic field having a component in the −X direction is applied to the magnetic detection section 7 and the voltage at the point P1 becomes positive, the output voltage of the first operational amplifier 76 becomes positive, and the output terminal of the first operational amplifier 76 and the first A current flows in the direction of the magnetic field generating conductor 75 ground terminal. As a result, the first magnetic field generating conductor 75 generates a correction magnetic field having a +X direction component at the position of each magnetoresistive effect element, that is, canceling out the bias magnetic field at the position of each magnetoresistive effect element. Since a virtual short is established between the non-inverting input terminal and the inverting input terminal of the first operational amplifier 76, the voltage at point P1 substantially matches the voltage at the ground terminal. That is, in the magnetic equilibrium state of the bias magnetic field and the correction magnetic field, the sum of the X components of the bias magnetic field and the correction magnetic field becomes substantially 0 at the position of each magnetoresistance effect element.

Other points of this embodiment are the same as those of the first embodiment. According to the present embodiment, although the addition of the first operational amplifier 76 is required as compared with the first embodiment, the amplifying action of the first operational amplifier 76 allows each magnetic resistance in the magnetic equilibrium state of the bias magnetic field and the correction magnetic field. The sum of the X components of the bias field and correction field at the location of the effect element can be brought closer to zero. In the present embodiment, the first magnetic field generating conductors 75 may be replaced with first magnetic field generating conductors 75a and 75b provided outside the laminate 5 as in the second embodiment shown in FIG.

(Embodiment 4)
FIG. 8 is a schematic cross-sectional view of a magnetic sensor 1D according to Embodiment 4 of the present invention. FIG. 9 is a wiring pattern explanatory diagram of the second magnetic field generating conductor 70 of the magnetic sensor 1D. In FIG. 9, the wiring pattern of the second magnetic field generating conductor 70 in the laminated body 5 is indicated by a solid line, and the illustration of the first magnetic field generating conductor 75 in the laminated body 5 is omitted. FIG. 10 is a schematic circuit diagram of the magnetic sensor 1D. While the magnetic sensors of Embodiments 1 to 3 are of the magnetic proportional type in which the sensor output voltage corresponding to (proportional to) the magnetic field to be detected appears between the output terminals of the magnetic detection unit 7, the magnetic sensor of the present embodiment The magnetic sensor 1D is of a magnetic balance type. The magnetic sensor 1D includes, in addition to the configuration of the magnetic sensor 1A of the first embodiment, a second magnetic field generating conductor 70, a second operational amplifier 50 as a second differential amplifier, and a detection resistor Rs.

As shown in FIGS. 8 and 9, the second magnetic field generating conductor 70 is formed in a single layer within the same laminate 5 as the first to fourth magnetoresistive elements (10, 20, 30, 40). be. In the example of FIG. 9, the second magnetic field generating conductor 70 is a U-shaped planar coil with less than one turn, but it may be a planar coil with a plurality of spiral turns. Note that the layer in which the second magnetic field generating conductor 70 is formed in the laminate 5 is a layer above the layer in which the first magnetic field generating conductor 75 is formed in the example of FIG. It may be a layer below the layer to be formed. As will be described later, the second magnetic field generating conductor 70 has a magnetic field component that cancels the detection target magnetic field (first magnetic field) detected by each magnetoresistive effect element (has a magnetic field component that offsets the magnetosensitive direction component of the detection target magnetic field). 2 Generate a magnetic field. Here, the cancellation is preferably approximately 0, but may be partial cancellation.

As shown in FIG. 10, the second operational amplifier 50 has an inverting input terminal connected to the interconnection point of the first magnetoresistive element 10 and the fourth magnetoresistive element 40, and a non-inverting input terminal connected to the second magnetoresistive element. It is connected to the interconnection point of the effect element 20 and the third magnetoresistive effect element 30 , and its output terminal is connected to one end of the second magnetic field generating conductor 70 . The second operational amplifier 50 receives the output voltages (voltages Va, Vb) of the magnetic detection section and supplies a negative feedback current to the second magnetic field generating conductor 70 . The negative feedback current output from the second operational amplifier 50 flows through the second magnetic field generating conductor 70 to generate a second magnetic field that cancels out the first magnetic field (magnetic field to be detected) detected by each magnetoresistive effect element. In other words, the second operational amplifier 50 causes the second magnetic field generating conductor 70 to generate a second magnetic field having a magnetic field component that cancels the magnetosensitive direction component of the first magnetic field at the position of each magnetoresistive effect element. That is, a negative feedback current is supplied to the second magnetic field generating conductor 70 so that the magnetic equilibrium state of the first and second magnetic fields is established at the position of each magnetoresistive effect element.

Since the second magnetic field generating conductor 70 forms the current path shown in FIG. The second magnetic field at the position of the magnetoresistive element 40 is parallel to the X direction and directed in opposite directions. The detection resistor Rs is connected between the other end of the second magnetic field generating conductor 70 and the ground terminal. The voltage across the detection resistor Rs is the sensor output voltage Vout. Assuming that the negative feedback current is I as shown in FIG. 10, the output voltage Vout is Vout=Rs×I. The negative feedback current is proportional to the magnitude of the magnetic field to be detected (first magnetic field). Therefore, the output voltage Vout is also proportional to the magnetic field to be detected, and the magnetic field to be detected can be detected from the output voltage Vout. Other points of this embodiment are the same as those of the first embodiment. This embodiment can also achieve the same effect as the first embodiment.

(Embodiment 5)
FIG. 11 is a schematic cross-sectional view of a magnetic sensor 1E according to Embodiment 5 of the present invention. In the magnetic sensor 1E of the present embodiment, as compared with the magnetic sensor 1D of the fourth embodiment, the first magnetic field generating conductor 75 provided inside the laminate 5 in the magnetic sensor 1D is outside the laminate 5. The difference is that the provided first magnetic field generating conductors 75a and 75b are replaced, and the other points are the same. The configuration of the first magnetic field generating conductors 75a and 75b is the same as that of the second embodiment (FIG. 6). This embodiment can also achieve the same effects as those of the fourth embodiment.

(Embodiment 6)
FIG. 12 is a schematic circuit diagram of a magnetic sensor 1F according to Embodiment 6 of the present invention. Compared to the magnetic sensor 1D of the fourth embodiment, the magnetic sensor 1F of the present embodiment additionally includes a first operational amplifier 76 as a first differential amplifier. The connection form of the first operational amplifier 76 and the principle of generation of the correction magnetic field are the same as in the third embodiment (FIG. 7). Other points of this embodiment are the same as those of the fourth embodiment. According to the present embodiment, the amplifying action of the first operational amplifier 76 reduces the sum of the X components of the bias magnetic field and the correction magnetic field at the position of each magnetoresistive element in the magnetic equilibrium state of the bias magnetic field and the correction magnetic field. can be brought closer to In the present embodiment, the first magnetic field generating conductors 75 may be replaced with first magnetic field generating conductors 75a and 75b provided outside the laminate 5 as in the fifth embodiment shown in FIG.

(Embodiment 7)
FIG. 13 is a schematic circuit diagram of a magnetic sensor 1G according to Embodiment 7 of the present invention. In each of the above-described embodiments, the X component of the bias magnetic field applied to the magnetic detection section 7 is detected from the ratio between the resistance value of the resistor R and the resistance value of the magnetic detection section 7 . On the other hand, in the present embodiment, the X component of the bias magnetic field applied to the magnetic detection section 7 is detected by the current flowing through the magnetic detection section 7 . The following description focuses on differences from the first embodiment.

The bias magnetic field detection means of this embodiment includes a resistor R, a first operational amplifier 76 as a first differential amplifier, a first magnetic field generating conductor 75, a third operational amplifier 77 as a third differential amplifier, and a reference voltage. source 78; The resistor R converts the current flowing through the magnetic detection section 7 into voltage. The current flowing through the magnetic detection section 7 is inversely proportional to the resistance value of the magnetic detection section 7 . The resistance value of the magnetic detection section 7 changes depending on the X direction component of the bias magnetic field applied to the magnetic detection section 7 . When the voltage across the resistor R is specified, the X direction component of the bias magnetic field applied to the magnetic detection section 7 is specified.

A non-inverting input terminal of the first operational amplifier 76 is connected to one end of the resistor R. An inverting input terminal of the first operational amplifier 76 is connected to the other end of the resistor R. The output terminal of the first operational amplifier 76 is connected to the inverting input terminal of the third operational amplifier 77 . A reference voltage source 78 is connected between the non-inverting input terminal of the third operational amplifier 77 and the ground terminal. An output terminal of the third operational amplifier 77 is connected to one end of the first magnetic field generating conductor 75 . The other end of the first magnetic field generating conductor 75 is connected to the ground terminal. By making the resistance value of the resistor R sufficiently lower than the resistance value of the magnetic detection section 7, the amplitude of the output voltage of the magnetic detection section 7 can be increased.

A first operational amplifier 76 amplifies the voltage across resistor R. FIG. The output voltage of the first operational amplifier 76 is proportional to the current flowing through the magnetic detector 7 . The third operational amplifier 77 supplies current to the first magnetic field generating conductor 75 so that the difference between the output voltage of the first operational amplifier 76 and the output voltage of the reference voltage source 78 is substantially zero. The output voltage of the reference voltage source 78 is preferably equal to the output voltage of the first operational amplifier 76 in the absence of the bias magnetic field (corresponding to the current flowing through the magnetic detector 7 in the absence of the bias magnetic field). As a result, the sum of the X-direction component of the bias magnetic field and the X-direction component of the correction magnetic field at the position of each magnetoresistive element becomes substantially 0 and constant (the current flowing through the magnetic detection unit 7 is the current in the absence of the bias magnetic field). approximately equal to).

The current (negative feedback current) output by the third operational amplifier 77 flows through the first magnetic field generating conductor 75, thereby generating a correction magnetic field that cancels out the bias magnetic field at the position of each magnetoresistive effect element. In other words, the third operational amplifier 77 operates so that the first magnetic field generating conductor 75 generates a correction magnetic field having a magnetic field component that cancels the magnetosensitive direction component of the bias magnetic field at the position of each magnetoresistive element. A current is supplied to the first magnetic field generating conductor 75 so that the magnetic equilibrium state of the bias magnetic field and the correction magnetic field is established at the position of the magnetoresistive element.

According to the present embodiment, although the addition of the first operational amplifier 76, the third operational amplifier 77, and the reference voltage source 78 is required as compared with the first embodiment, the first operational amplifier 76 and the third operational amplifier 77 can bring the sum of the X components of the bias magnetic field and the correction magnetic field closer to zero at the position of each magnetoresistive element in the magnetic equilibrium state of the bias magnetic field and the correction magnetic field.

(Embodiments 8 and 9)
FIG. 14 is a schematic cross-sectional view of a magnetic sensor 1H according to Embodiment 8 of the present invention. FIG. 15 is a schematic cross-sectional view of a magnetic sensor 1J according to Embodiment 9 of the present invention. 16 is a schematic circuit diagram of the magnetic sensor of FIGS. 14 and 15; FIG. In the present embodiment, the X-direction component of the bias magnetic field is detected by the magnetic detection element 79 for bias magnetic field detection. In the configuration example of FIG. 14 , the magnetic detection element 79 is arranged inside the laminate 5 and directly below the magnetic body 80 . In the configuration example of FIG. 15, the magnetic detection element 79 is arranged outside the laminate 5 .

In FIG. 16, the magnetic detection element 79 is two magnetoresistive elements 79a and 79b. The fixed layer magnetization directions of the magnetoresistive elements 79a and 79b are, for example, both parallel to the X direction and opposite to each other. The magnetoresistive elements 79a and 79b are connected in series between a high voltage terminal to which the power supply voltage Vcc is supplied and a low voltage terminal to which the power supply voltage -Vcc is supplied. The interconnection point of the magnetoresistive elements 79 a and 79 b is connected to the inverting input terminal of the third operational amplifier 77 . The third operational amplifier 77 applies the first magnetic field so that the difference between the voltage at the interconnection point of the magnetoresistive elements 79a and 79b (the output voltage of the magnetic detection element 79) and the output voltage of the reference voltage source 78 is substantially zero. A negative feedback current is supplied to the generator conductor 75 . When the operating points of the first to fourth magnetoresistive elements (10, 20, 30, 40) are the operating points when the bias magnetic field is 0, the output voltage of the reference voltage source 78 is 0 (reference voltage source 78 is a short circuit). This embodiment can also achieve the same effect as the seventh embodiment.

Although the present invention has been described above with reference to the embodiments, it will be understood by those skilled in the art that various modifications can be made to each component and each processing process of the embodiments within the scope of the claims. By the way. Modifications will be discussed below.

In the embodiments, the case where the correction magnetic field is generated corresponding to the X-direction component of the bias magnetic field has been described, but instead of or in addition to the X-direction component of the bias magnetic field, a non-X-direction component of the bias magnetic field (for example, the Y-direction component) may be generated. The number of magnetoresistive elements forming the magnetic detection unit 7 is not limited to four as exemplified in the embodiment, and may be any number of two or more. In the embodiment, an example in which four magnetoresistive effect elements are connected in a full-bridge connection as the magnetic detection section 7 has been described. may Each element driven by a dual power supply may be driven by a single power supply.

In order to further improve the detection accuracy of the first to fourth magnetoresistive elements (10, 20, 30, 40), the magnetic body 80 and the first to fourth magnetoresistive elements (10, 20, 30, 40) A yoke may be formed between By forming the yoke, more magnetic fields can be efficiently guided to the first to fourth magnetoresistive elements (10, 20, 30, 40), so that minute magnetic fields can be detected with high accuracy. becomes possible. In addition, by forming the yoke by a thin film process, not only can it be arranged with high precision in terms of dimensions and position, but it can also be formed in the same lamination process, so that the cost is lower than that of externally attached parts, and the product can be made smaller and the manufacturing cost can be reduced. can be reduced.

1A to 1H, 1J magnetic sensor, 5 laminate, 7 magnetic detection unit, 10 first magnetoresistive effect element, 20 second magnetoresistive effect element, 30 third magnetoresistive effect element, 40 fourth magnetoresistive effect element, 50 Second operational amplifier (second differential amplifier), 70 Second magnetic field generating conductor, 75 First magnetic field generating conductor, 76 First operational amplifier (first differential amplifier), 77 Third operational amplifier (third differential amplifier) ), 78 reference voltage source, 79 magnetic detection element, 80 magnetic body

Claims (7)

a magnetic detection unit including first and second magnetoresistive effect elements to which a first magnetic field to be detected is applied and whose pinned layer magnetization directions are the same;
The magnetic field applied to the magnetic detection unit is connected in series between the high-voltage terminal and the low-voltage terminal, and the resistance value change due to the magnetic field applied to the magnetic detection unit is suppressed or due to the magnetic field applied to the magnetic detection unit. A resistive element whose resistance value does not change,
a first magnetic field generating conductor through which a current corresponding to a ratio between the resistance value of the magnetic detection unit and the resistance value of the resistance element flows,
the first magnetic field has magnetic field components parallel to the pinned layer magnetization direction and in opposite directions at the positions of the first and second magnetoresistive elements;
A magnetic field generated by a current flowing through the first magnetic field generating conductor is applied to the first and second magnetoresistive elements, and parallel to the magnetization direction of the fixed layer and to each other at the positions of the first and second magnetoresistive elements. A magnetic sensor in which a change in the resistance values of the first and second magnetoresistive elements due to a bias magnetic field having magnetic field components in the same direction is suppressed. 2. The magnetic sensor according to claim 1, wherein said first magnetic field generating conductor is provided between an interconnection point between said magnetic detecting portion and said resistive element and a medium voltage terminal. a first differential amplifier that amplifies a difference between a voltage at an interconnection point between the magnetic detection unit and the resistance element and a voltage at a medium voltage terminal;
2. The magnetic sensor according to claim 1, wherein said first magnetic field generating conductor is provided between an output terminal of said first differential amplifier and said medium voltage terminal. 4. The magnetic sensor according to claim 1, wherein said resistance element is a magnetically shielded magnetoresistive element. 4. The magnetic sensor according to claim 1, wherein said resistive element is a fixed resistor. a second differential amplifier to which the output voltage of the magnetic detection unit is input;
The flow of the first negative feedback current output by the second differential amplifier causes the first and second magnetic detection elements to detect a second magnetic field that cancels the first magnetic field detected by the first and second magnetic detection elements. A magnetic sensor according to any one of claims 1 to 5, comprising a second magnetic field generating conductor for applying to the element. 7. The apparatus according to any one of claims 1 to 6 , comprising a magnetic body that changes the direction of the first magnetic field so that the first magnetic field to be detected has magnetic field components in opposite directions at the positions of the first and second magnetoresistive elements. A magnetic sensor according to any one of the preceding claims.

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