JP6115501B2 - Current sensor - Google Patents

Description

  The present invention includes a magnetoresistive effect element, a bias magnet that transmits a bias magnetic field to the magnetoresistive effect element, and a calculation unit that calculates a current to be measured based on an electric signal output from the magnetoresistive effect element. It relates to sensors.

  As shown in Patent Document 1, a current sensor in which a magnetoelectric conversion element is formed on a sensor substrate and the sensor substrate is surrounded by a magnetic shield is known as a prior art. In the magnetic shield, a bias magnet for applying a bias magnetic field to the magnetoelectric conversion element and a circuit board for processing an output signal of the magnetoelectric conversion element are provided. Each of the sensor substrate, the bias magnet, and the circuit substrate is fixed to a support substrate made of a nonmagnetic material.

JP 2013-11469 A

  As described above, in the current sensor disclosed in Patent Document 1, the sensor substrate, the bias magnet, and the circuit substrate are each fixed to a support substrate. Therefore, the heat generated in the circuit board is transferred to the sensor board and the bias magnet through the support board. Since the bias magnetic field has temperature characteristics, it is necessary to calculate the bias magnetic field according to the temperature of the bias magnet. In order to calculate the bias magnetic field in this way, the temperature of the bias magnet must be detected. However, since the bias magnet does not have a function of detecting the temperature, the temperature of the bias magnet is detected by the temperature measuring element. . However, if the amount of heat transferred from the circuit board to the thermometer and the amount of heat transferred from the circuit board to the bias magnet are different, the temperature of the bias magnet cannot be detected accurately, and as a result, the calculation accuracy of the bias magnetic field cannot be detected. May decrease.

  In view of the above problems, an object of the present invention is to provide a current sensor in which a decrease in accuracy of calculating a bias magnetic field is suppressed.

  In order to achieve the above object, the present invention includes a magnetoresistive element (10) that transmits a magnetic field to be measured generated by the flow of a current to be measured, and a bias magnet (20) that transmits a bias magnetic field to the magnetoresistive element. A current sensor that calculates a current to be measured based on an electrical signal output from the magnetoresistive element, the magnetoresistive element having a pinned layer with a fixed magnetization direction, An angle formed by the magnetization directions of the pinned layer and the free layer, each of which includes a free layer whose magnetization direction changes according to the transmitted magnetic field, and a nonmagnetic intermediate layer provided between the pinned layer and the free layer. As the magnetoresistive effect element, the first magnetoresistive effect element (11) and the first magnetoresistive effect element differ in the magnetization direction of the pinned layer by 90 ° as the magnetoresistive effect element. Effect element (12) and The bridge circuit (13, 14, 15) is assembled by the first magnetoresistive element and the second magnetoresistive element, and the midpoint potential is an electric signal for detecting the magnetic field to be measured. , The relative distance between the bridge circuit and the calculation unit, and the relative distance between the bias magnet and the calculation unit are equal, the amount of heat transferred from the calculation unit to the bridge circuit, and the amount of heat transferred from the calculation unit to the bias magnet And the calculation unit calculates the first temperature characteristic of the combined resistance of the first magnetoresistive effect element and the second magnetoresistive effect element forming the bridge circuit, and the second temperature characteristic of the bias magnetic field of the bias magnet. And a bias magnet temperature is calculated based on the first temperature characteristic, and a bias magnetic field is calculated based on the calculated temperature and the second temperature characteristic.

  Thus, according to the present invention, the resistance value of the magnetoresistive element (10) varies depending on the angle formed by the magnetization directions of the pinned layer and the free layer. Therefore, when each of the magnetic field to be measured and the bias magnetic field is transmitted through the magnetoresistive element (10), the resistance value varies regardless of the temperature. However, the magnetization direction of the pinned layer differs by 90 ° between the first magnetoresistive element (11) and the second magnetoresistive element (12). Therefore, when the resistance value of one of the two magnetoresistive effect elements (10) decreases, the resistance value of the other increases by the same amount. Therefore, the total resistance (synthetic resistance) of the bridge circuit (13, 14, 15) assembled by these two magnetoresistance effect elements (10) is invariant to the magnetic field. Thus, the temperature of the bridge circuit (13, 14, 15) can be calculated based on the temperature characteristic of the combined resistance.

  In the present invention, the amount of heat transferred from the calculation unit (30) to the bridge circuit (13, 14, 15) is equal to the amount of heat transferred from the calculation unit (30) to the bias magnet (20). . Therefore, the temperature of the bridge circuit (13, 14, 15) and the bias magnet (20) are compared with a configuration in which the amount of heat transferred from the calculation unit to the bridge circuit is different from the amount of heat transferred from the calculation unit to the bias magnet. ) Temperature values are close. On the other hand, since the calculation unit (30) calculates the temperature of the bias magnet (20) based on the first temperature characteristic of the combined resistance of the bridge circuit (13, 14, 15), the accuracy of the calculated temperature is reduced. It is suppressed. As described above, based on the calculated temperature of the bias magnet (20) and the second temperature characteristic of the bias magnetic field, a decrease in the accuracy of calculating the bias magnetic field is suppressed. Furthermore, unlike the configuration having a temperature sensing element for detecting the temperature of the bias magnet (20), the magnetoresistive effect element (10) assumes its function, and thus the increase in the size of the current sensor is suppressed.

  A bridge circuit, a bias magnet, and a mounting unit (40) for mounting each of the calculation units on one surface (40a), a relative distance between the bridge circuit and the calculation unit on one surface of the mounting unit, and a bias magnet and a calculation unit The relative distances from each other are equal.

  According to this, from the calculation unit (30) to the bridge circuit (13, 14, 15) and from the calculation unit (30) to the bias magnet (20) through the same mounting unit (40), the calculation unit ( 30) heat is transferred. Therefore, the bridge circuit (13, 14, 15) is compared with the configuration in which the heat of the calculation unit is transferred to the bridge circuit and the bias magnet through different members from the calculation unit to the bridge circuit and from the calculation unit to the bias magnet. ) And the bias magnet (20) are prevented from being different in heat quantity.

  A bridge circuit is mounted on one surface (30a) of the calculation unit, and a bias magnet is mounted on the back surface (30b) of the one surface of the calculation unit.

  According to this, a member different from the calculation unit (30) between the calculation unit (30) and the bridge circuit (13, 14, 15) and between the calculation unit (30) and the bias magnet (20). Therefore, the amount of heat transferred to the bridge circuit (13, 14, 15) and the bias magnet (20) is suppressed from being different due to quality variations such as the composition ratio of the interposed members.

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

It is sectional drawing which shows schematic structure of a current sensor. It is a schematic diagram explaining the magnetic field which permeate | transmits a magnetoresistive effect element. It is a circuit diagram which shows a full bridge circuit. It is a top view which shows the relative distance of a full bridge circuit and a calculation part, and a bias magnet and a calculation part. It is sectional drawing which shows the modification of a current sensor. It is a top view which shows the relative distance of a full bridge circuit, a calculation part, a bias magnet, and a calculation part, and a temperature sensing element and a calculation part.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
(First embodiment)
The current sensor according to the present embodiment will be described with reference to FIGS. Hereinafter, the three directions orthogonal to each other are referred to as an x direction, a y direction, and a z direction. A plane orthogonal to the z direction is referred to as a detection plane. The y direction corresponds to the flow direction described in the claims, and the z direction corresponds to the height direction described in the claims.

  The current sensor 100 includes the magnetoresistive effect element 10, the bias magnet 20, and the calculation unit 30, and detects a measured current flowing through the measured conductor 90. The magnetoresistive effect element 10 transmits a bias magnetic field generated from the bias magnet 20 and a measured magnetic field generated by the flow of the measured current. Therefore, the magnetoresistive effect element 10 generates an electrical signal corresponding to the combined magnetic field composed of the bias magnetic field and the measured magnetic field. The calculation unit 30 calculates the current to be measured based on the electrical signal output from the magnetoresistive effect element 10.

  The current sensor 100 according to the present embodiment includes a mounting portion 40, a magnetic shield 50, and a fixing portion 60 in addition to the above-described components. The mounting unit 40 mounts the magnetoresistive effect element 10, the bias magnet 20, and the calculation unit 30. The magnetic shield 50 prevents an external magnetic field different from the measured magnetic field and the bias magnetic field from passing through the magnetoresistive element 10. The fixing unit 60 fixes the magnetoresistive element 10, the bias magnet 20, the mounting unit 40 on which the calculation unit 30 is mounted, and the magnetic shield 50 to the conductor 90 to be measured.

  The magnetoresistive element 10 has a resistance value that varies according to a magnetic field that passes through the magnetoresistive element 10 (transmitted magnetic field). As shown in FIG. 1, since the measured current flows in the y direction, a measured magnetic field is generated around it. The bias magnet 20 forms a bias magnetic field around the x direction. Therefore, as shown in FIG. 2, the magnetic field component along the x direction in the magnetic field to be measured and the magnetic field component along the y direction in the bias magnet 20 are transmitted through the magnetoresistive element 10. As described above, since the composite magnetic field is composed of the bias magnetic field and the magnetic field to be measured, when the magnetic field to be measured is zero, the composite magnetic field is equal to the bias magnetic field. Therefore, the angle θ between the combined magnetic field and the bias magnetic field on the detection plane orthogonal to the z direction is zero when the measured magnetic field is zero, but when the measured magnetic field is finite, the angle θ is also finite. Thus, the value of the angle θ varies depending on the strength of the magnetic field to be measured.

  The magnetoresistive element 10 detects only the magnetic field along the detection plane. Although not shown, the magnetoresistive effect element 10 has a pinned layer whose magnetization direction is fixed, a free layer whose magnetization direction changes in accordance with the transmitted magnetic field, and a nonmagnetic intermediate layer provided therebetween. When the intermediate layer has non-conductivity, the magnetoresistive effect element 10 is a giant magnetoresistive effect element, and when the intermediate layer has conductivity, the magnetoresistive effect element 10 is a tunnel magnetoresistive effect element.

  The resistance value of the magnetoresistive effect element 10 varies depending on the angle formed by the magnetization directions of the pinned layer and the free layer. The magnetization direction of the pinned layer is along the detection plane, and the magnetization direction of the free layer is determined by the transmitted magnetic field along the detection plane. As described above, the combined magnetic field is transmitted through the magnetoresistive element 10. Therefore, the magnetization direction of the free layer is determined by the direction of the combined magnetic field (angle θ), and thereby the resistance value of the magnetoresistive element 10 is also determined. The resistance value is the smallest when the magnetization directions of the free layer and the fixed layer are parallel, and is the largest when the magnetization directions are antiparallel.

  As the magnetoresistive effect element 10 described above, the same number of first magnetoresistive effect elements 11 and the same number of second magnetoresistive effect elements 12 as the first magnetoresistive effect elements 11 are different in the magnetization direction of the pinned layer by 90 °. As described above, since the magnetization directions of the pinned layers are different by 90 °, the fluctuations in the resistance values of the magnetoresistive elements 11 and 12 are reversed. That is, when the resistance value of one of the two magnetoresistive effect elements 11 and 12 decreases, the resistance value of the other increases by the same amount.

  In this embodiment, as shown in FIG. 3, the magnetoresistive effect element 10 includes two magnetoresistive elements 11 and 12. The first magnetoresistive element 11 and the second magnetoresistive element 12 are sequentially connected in series from the power supply to the ground to form the first half bridge circuit 13, and the second magnetoresistive effect from the power supply to the ground. The second half bridge circuit 14 is configured by connecting the element 12 and the first magnetoresistive element 11 in series in order. Thus, in the two half-bridge circuits 13 and 14, the arrangement of the magnetoresistive effect elements 11 and 12 is reversed. Accordingly, the midpoint potential of each of the two half-bridge circuits 13 and 14 increases as one potential decreases. In this embodiment, these two half-bridge circuits 13 and 14 are combined to form a full-bridge circuit 15, and the above-described difference value V1 between the two midpoint potentials is an electric signal for detecting the current to be measured. Is output to the calculation unit 30.

  Further, as shown in FIG. 3, a resistor 16 is provided between the magnetoresistive effect elements 11 and 12 on the low side of the half bridge circuits 13 and 14 and the ground. As described above, since the fluctuations in the resistance values of the magnetoresistive effect elements 11 and 12 are reversed, the total resistance (combined resistance) of each of the half bridge circuits 13 and 14 formed by these two magnetoresistive effect elements 11 and 12 is reversed. ) Is invariant to the magnetic field. The resistor 16 has a property that does not change with respect to the magnetic field, and each of the magnetoresistive effect elements 11 and 12 and the resistor 16 has a property that depends on temperature. As described above, the midpoint potential V <b> 2 between the combined resistor and the resistor 16 is output to the calculation unit 30 as an electrical signal for detecting the temperature of the full bridge circuit 15.

  The bias magnet 20 allows the magnetoresistive element 10 to transmit a bias magnetic field. The bias magnetic field has a temperature characteristic, and its strength is inversely proportional to the temperature. The amount of heat transferred from the calculation unit 30 to the full bridge circuit 15 is equal to the amount of heat transferred from the calculation unit 30 to the bias magnet 20. Therefore, the temperature of the full bridge circuit 15 and the bias magnet 20 is close to each other.

  The calculation unit 30 calculates the current to be measured based on the above-described difference value V1, and calculates the temperature of the full bridge circuit 15 based on the midpoint potential V2. Further, as described above, since the amount of heat transferred from the calculation unit 30 to each of the full bridge circuit 15 and the bias magnet 20 is equal, the calculation unit 30 uses the calculated temperature of the full bridge circuit 15 as the temperature of the bias magnet 20. Considering this, the bias magnetic field is calculated.

  As described above, the difference value V1 is determined by the resistance values of the magnetoresistive elements 11 and 12, and the resistance value is determined by the direction of the combined magnetic field (angle θ). On the other hand, the calculation unit 30 stores a correlation between the difference value V1 and the angle θ, and a correlation between the angle θ and the measured magnetic field (measured current). The calculation unit 30 calculates a measured current based on the correlation and the difference value V1.

  As described above, the midpoint potential V 2 depends on the combined resistance of the magnetoresistive effect elements 11 and 12 that form the half bridge circuits 13 and 14, and the combined resistance is determined by the temperature of the full bridge circuit 15. In contrast, the calculation unit 30 has a first temperature characteristic of the combined resistance and a second temperature characteristic of the bias magnetic field. The calculating unit 30 calculates the temperature of the bias magnet 20 based on the first temperature characteristic, and calculates a bias magnetic field based on the calculated temperature and the second temperature characteristic.

  Strictly speaking, the midpoint potential V2 depends on the combined resistance and the resistance 16, respectively. Therefore, the calculation unit 30 has the combined resistance and the temperature characteristic of the resistor 16 as the first temperature characteristic. However, the resistor 16 is merely illustrated as an example for convenience in order to detect the temperature of the combined resistor, and the calculation unit 30 may have this detection resistor. An important technique in the present invention is that although the combined resistance of the magnetoresistive effect elements 11 and 12 depends on the magnetic field, the combined resistance does not depend on the magnetic field. This is used to calculate the temperature of the bridge circuit 15. As described above, the temperature characteristic of the resistor 16 is not a matter related to the essence of the invention, and thus is not described strictly in the text.

  The mounting unit 40 mounts the magnetoresistive effect element 10 (full bridge circuit 15), the bias magnet 20, and the calculation unit 30 on one surface 40a. The mounting portion 40 is a wiring board in which a wiring pattern is formed on an insulating substrate. Therefore, the mounting unit 40 not only mounts the full bridge circuit 15, the bias magnet 20, and the calculation unit 30 but also functions to electrically connect them. The back surface 40 b of the mounting part 40 is in contact with the conductor to be measured 90. Further, as indicated by double-ended arrows in FIG. 4, the relative distance between the full bridge circuit 15 and the calculation unit 30 and the relative distance between the bias magnet 20 and the calculation unit 30 on the one surface 40 a are equal. Therefore, the amount of heat transferred from the calculation unit 30 to the full bridge circuit 15 is equal to the amount of heat transferred from the calculation 30 unit to the bias magnet 20.

  The magnetic shield 50 prevents the external magnetic field from passing through the magnetoresistive effect element 10. The magnetic shield 50 has shields 51 and 52 made of a magnetic material. Each of the shields 51 and 52 has a flat plate shape in which the main surface having the largest area is orthogonal to the z direction. The shields 51 and 52 are arranged in the z direction, and the mounting portion 40 on which the magnetoresistive effect element 10, the bias magnet 20, and the calculation unit 30 are mounted, and the conductor to be measured 90 are provided in the space therebetween. Yes.

  The fixing part 60 fixes the mounting part 40 and the magnetic shield 50 to the conductor 90 to be measured. The fixing portion 60 is nonmagnetic and is made of a nonconductive resin material.

  Next, the function and effect of the current sensor 100 according to this embodiment will be described. As described above, the combined resistance of each of the bridge circuits 13 to 15 assembled by the magnetoresistive effect elements 11 and 12 is invariant to the magnetic field. Thereby, the temperature of the bridge circuits 13 to 15 can be calculated based on the first temperature characteristic of the combined resistance.

  Further, the amount of heat transferred from the calculation unit 30 to the full bridge circuit 15 is equal to the amount of heat transferred from the calculation 30 unit to the bias magnet 20. Therefore, compared to a configuration in which the amount of heat transferred from the calculation unit to the bridge circuit is different from the amount of heat transferred from the calculation unit to the bias magnet, the values of the temperature of the full bridge circuit 15 and the temperature of the bias magnet 20 are different. It ’s close. On the other hand, since the calculation unit 30 calculates the temperature of the bias magnet 20 based on the first temperature characteristic of the combined resistance of the magnetoresistive effect elements 11 and 12, a decrease in accuracy of the calculated temperature is suppressed. As described above, based on the calculated temperature of the bias magnet 20 and the second temperature characteristic of the bias magnetic field, a decrease in the accuracy of calculating the bias magnetic field is suppressed. More specifically, unlike the configuration having a temperature sensing element for detecting the temperature of the bias magnet, the magnetoresistive effect elements 11 and 12 serve the function, so that an increase in the size of the current sensor 100 is suppressed.

  The relative distance between the full bridge circuit 15 and the calculation unit 30 on the one surface 40a of the mounting unit 40 and the relative distance between the bias magnet 20 and the calculation unit 30 are equal. According to this, the heat of the calculation unit 30 is transferred from the calculation unit 30 to the full bridge circuit 15 and from the calculation unit 30 to the bias magnet 20 via the same mounting unit 40. Accordingly, the full bridge circuit 15 and the bias magnet are compared with the configuration in which the heat of the calculation unit is transferred to the bridge circuit and the bias magnet through different members from the calculation unit to the full bridge circuit and from the calculation unit to the bias magnet, respectively. It is suppressed that the amount of heat transmitted to each of 20 is different.

  The magnetic shield 50 suppresses the transmission of the external magnetic field through the magnetoresistive element 10. According to this, it is suppressed that the detection accuracy of the magnetic field to be measured is lowered by the external magnetic field.

  Plate-shaped shields 51 and 52 whose main surfaces are orthogonal to the z-direction are arranged in the z-direction, and a mounting portion 40 in which the magnetoresistive effect element 10, the bias magnet 20, and the calculation unit 30 are mounted in the space between them. In addition, a conductor to be measured 90 is provided. The magnetoresistive effect element 10 detects only a magnetic field along a detection plane orthogonal to the z direction.

  In the case of this configuration, when an external magnetic field orthogonal to the z direction attempts to pass through the current sensor 100 as indicated by an outlined arrow in FIG. 1, the external magnetic field is bent due to the shields 51 and 52, and the magnetoresistive effect Transmission through the element 10 is suppressed. However, when the external magnetic field is along the z-direction, the external magnetic field is transmitted without being bent by the shields 51 and 52, and thus is transmitted through the magnetoresistive effect element 10. On the other hand, as described above, the magnetoresistive element 10 detects only the magnetic field along the detection plane orthogonal to the z direction. Therefore, even if the external magnetic field along the z direction is transmitted through the magnetoresistive effect element 10 through the shields 51 and 52, it is possible to prevent the detection accuracy of the magnetic field to be measured from being lowered. In addition, since a simple flat plate shape is adopted as the shape of the shields 51 and 52 as described above, the manufacture of the shields 51 and 52 is facilitated.

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

  An example in which the current sensor 100 according to the present embodiment has the mounting portion 40, the magnetic shield 50, and the fixing portion 60 has been shown. However, the current sensor 100 may have at least one of these, or may not have one.

  The magnetoresistive effect element 10 showed the example which detects only the magnetic field along a detection plane. However, if the magnetic shield 50 shields not only the detection direction but also the external magnetic field in the z direction orthogonal thereto, the magnetoresistive effect element 10 may detect not only the detection direction but also the magnetic field in the z direction.

  In the present embodiment, an example in which the full bridge circuit 15 is configured by combining the two half bridge circuits 13 and 14 is shown. However, only one of the two half-bridge circuits 13 and 14 may be configured. For example, when only the first half-bridge circuit 13 is configured, the midpoint potential is output to the calculation unit 30 as an electrical signal for detecting the current to be measured. Further, the midpoint potential between the combined resistance of the magnetoresistive effect elements 11 and 12 constituting the first half bridge circuit 13 and the resistor 16 is output to the calculation unit 30 as an electric signal for detecting the temperature of the full bridge circuit 15. Is done.

  In the present embodiment, an example is shown in which the calculation unit 30 stores the correlation between the difference value V1 and the angle θ, and the correlation between the angle θ and the magnetic field to be measured (current to be measured). However, the calculation unit 30 may store the relationship between the difference value V1 and the magnetic field to be measured (current to be measured). Thus, the calculation unit 30 only needs to have data necessary for calculating the current to be measured based on the difference value V1.

  In the present embodiment, an example in which the resistor 16 is provided in the full bridge circuit 15 in order to detect the temperature change of the combined resistance of the full bridge circuit 15 is shown. However, if there is another configuration (element) that can detect the above-described temperature change as an electrical signal, the resistor 16 is not necessary. Such an electric signal can be easily taken out by those skilled in the art, and the illustration thereof is omitted.

  In the present embodiment, an example in which the magnetoresistive effect element 10 (full bridge circuit 15), the bias magnet 20, and the calculation unit 30 are mounted on one surface 40a of the mounting unit 40 is shown. However, as shown in FIG. 5, the bias magnet 20 is directly mounted on the one surface 40 a, the calculation unit 30 is mounted on the one surface 40 a via the bias magnet 20, and the full bridge circuit is formed on the one surface 40 a via the bias magnet 20 and the calculation unit 30. A configuration in which 15 is mounted can also be adopted. That is, a configuration in which the bias magnet 20 is mounted on the one surface 40 a, the calculation unit 30 is mounted on the bias magnet 20, and the full bridge circuit 15 is mounted on the calculation unit 30 can be adopted. In other words, a configuration in which the full bridge circuit 15 is mounted on one surface 30a of the calculation unit 30 and the bias magnet 20 is mounted on the back surface 30b of the calculation unit 30 may be employed. According to this, a member different from the calculation unit 30 is not interposed between the calculation unit 30 and the bridge circuit 15 and between the calculation unit 30 and the bias magnet 20. Therefore, it is suppressed that the amount of heat transferred from the calculation unit 30 to the bridge circuit 15 and the bias magnet 20 differs due to quality variations such as the composition ratio of the interposed members.

  In the present embodiment, an example in which the temperature of the bias magnet 20 is detected based on an electrical signal output from the bridge circuits 13 to 15 including the magnetoresistive elements 11 and 12 has been described. However, as shown in FIG. 6, the current sensor 100 may have a temperature measuring element 70 for detecting the temperature of the bias magnet 20. As shown in FIG. 6, the magnetoresistive effect element 10 (full bridge circuit 15), the bias magnet 20, the calculation unit 30, and the temperature measuring element 70 are each mounted on one surface 40 a. As indicated by double-ended arrows in FIG. 6, the relative distance between the temperature measuring element 70 and the calculation unit 30 on the one surface 40 a and the relative distance between the bias magnet 20 and the calculation unit 30 are equal. Therefore, the amount of heat transferred from the calculation unit 30 to the temperature measuring element 70 is equal to the amount of heat transferred from the calculation 30 unit to the bias magnet 20. In this modification, the calculation unit 30 detects the temperature of the bias magnet 20 based on the detection signal of the temperature measuring element 70, and calculates the bias magnetic field based on the detected temperature and the second temperature characteristic.

  In FIG. 6, the relative distance between the full bridge circuit 15 and the calculation unit 30 and the relative distance between the bias magnet 20 and the calculation unit 30 are also equal, and heat is transferred from the calculation unit 30 to the full bridge circuit 15. The amount of heat and the amount of heat transferred from the calculation unit 30 to the bias magnet 20 are also equal. Therefore, the calculation unit 30 may detect the temperature of the bias magnet 20 based on the detection signal of the temperature detecting element 70 and the midpoint potential V2 of the full bridge circuit 15. According to this, compared with the structure which detects the temperature of a bias magnet based on either one of the detection signal of a temperature sensing element and the midpoint potential of a full bridge circuit, the temperature of the bias magnet 20 can be detected with higher accuracy. . Therefore, a decrease in the calculation accuracy of the bias magnetic field is suppressed.

  In this embodiment, the back surface 40b of the mounting part 40 showed the example which is contacting the to-be-measured conductor 90. FIG. However, the mounting portion 40 may not be in contact with the conductor to be measured 90.

  Each of the shields 51 and 52 shows an example in which the main surface has a flat plate shape orthogonal to the z direction. However, the shape of the shields 51 and 52 is not limited to the above example. The shape of the shields 51 and 52 may be any shape that suppresses the transmission of the external magnetic field that interferes with the detection of the magnetic field to be measured.

DESCRIPTION OF SYMBOLS 10 ... Magnetoresistive effect element 11 ... 1st magnetoresistive effect element 12 ... 2nd magnetoresistive effect element 13 ... 1st half bridge circuit 14 ... 2nd half bridge circuit 15 ... Full bridge circuit 20 ... Bias magnet 30 ... Calculation unit 100 ... Current sensor

Claims (7)

A magnetoresistive element (10) through which a magnetic field to be measured generated by the flow of the current to be measured passes;
A bias magnet (20) that transmits a bias magnetic field to the magnetoresistive element;
A calculation unit (30) for calculating the current to be measured based on an electrical signal output from the magnetoresistive element,
The magnetoresistive element includes a pinned layer having a fixed magnetization direction, a free layer whose magnetization direction changes according to a transmitted magnetic field, and a nonmagnetic intermediate layer provided between the pinned layer and the free layer And the resistance value varies according to the angle formed by the magnetization directions of the pinned layer and the free layer,
As the magnetoresistive effect element, the same number of first magnetoresistive effect elements (11) and the same number of second magnetoresistive effect elements (12) in which the magnetization directions of the pinned layers differ from each other by 90 °. Have
A bridge circuit (13, 14, 15) is assembled by the first magnetoresistive element and the second magnetoresistive element, and a midpoint potential thereof is an electric signal for detecting the measured magnetic field,
The relative distance between the bridge circuit and the calculation unit, and the relative distance between the bias magnet and the calculation unit are equal, the amount of heat transferred from the calculation unit to the bridge circuit, and the bias from the calculation unit The amount of heat transferred to the magnet is equal,
The calculation unit has a first temperature characteristic of a combined resistance of the first magnetoresistive effect element and the second magnetoresistive effect element forming the bridge circuit, and a second temperature characteristic of a bias magnetic field of the bias magnet. A current sensor that calculates a temperature of the bias magnet based on the first temperature characteristic and calculates the bias magnetic field based on the calculated temperature and the second temperature characteristic. The bridge circuit, the bias magnet, and the calculation unit each having a mounting portion (40) for mounting on one surface (40a),
2. The current sensor according to claim 1, wherein a relative distance between the bridge circuit and the calculation unit on one surface of the mounting unit and a relative distance between the bias magnet and the calculation unit are equal to each other. .   The current sensor according to claim 1, wherein the bridge circuit is mounted on one surface (30a) of the calculation unit, and the bias magnet is mounted on a back surface (30b) of the one surface of the calculation unit.   The magnetic shield (50) which suppresses that the external magnetic field different from each of the said to-be-measured magnetic field and the said bias magnetic field permeate | transmits the said magnetoresistive effect element, The magnetic shield (50) characterized by the above-mentioned. Current sensor. The magnetic shield has two plate-shaped shields (51, 25) whose principal surfaces are orthogonal to the height direction orthogonal to the flow direction of the current to be measured,
Each of the two shields is arranged in the height direction, and in the space between them, the bias magnet, the magnetoresistive effect element, and the measured conductor (90) through which the measured current flows are provided,
The current sensor according to claim 4, wherein the magnetoresistive effect element detects only a magnetic field along a detection plane orthogonal to the height direction.   The current sensor according to claim 1, wherein the intermediate layer is non-conductive, and the magnetoresistive element is a giant magnetoresistive element.   The current sensor according to claim 1, wherein the intermediate layer has conductivity, and the magnetoresistive element is a tunnel magnetoresistive element.

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