JP5504488B2 - Current sensor - Google Patents

Description

  The present invention relates to a current sensor that measures the magnitude of a current. In particular, the present invention relates to a current sensor in which a decrease in measurement accuracy due to the influence of a magnetic field is suppressed.

  In fields such as motor drive technology in electric vehicles and hybrid cars, a relatively large current is handled, and thus a current sensor capable of measuring a large current in a non-contact manner is required for such applications. As such a current sensor, a system that detects a change in a magnetic field caused by a current to be measured by a magnetic sensor has been put into practical use. A current sensor using a magnetic sensor has a problem in that the measurement accuracy is deteriorated due to the influence of an external magnetic field.

  As a method for suppressing a decrease in measurement accuracy due to the influence of an external magnetic field, for example, a method of taking a differential between output signals of two magnetic sensors has been proposed (see Patent Document 1). In this configuration, in the output signals of the two magnetic sensors, the influence of the magnetic field formed by the current to be measured appears in the opposite phase, and the influence of the external magnetic field appears in the same phase. It can be removed to some extent.

JP 2002-243766 A

  However, even when the configuration described in Patent Document 1 is adopted, measurement accuracy may be reduced due to the influence of an induced magnetic field or an external magnetic field due to the current to be measured. This invention is made | formed in view of this point, and it aims at providing the current sensor which can fully suppress the fall of an electric current measurement precision.

  The current sensor according to the present invention includes a pair of magnetic sensors each having a current line through which a current to be measured flows, a sensor unit, and a circuit and wiring connected to the sensor unit, and is connected to the pair of magnetic sensors. And an arithmetic unit that differentially calculates the output signals of the pair of magnetic sensors, wherein in the pair of magnetic sensors, the sensor units are arranged such that the respective sensitivity axis directions are the same, The circuits or / and the wirings of a pair of magnetic sensors are arranged so as to have a symmetrical relationship with each other on a plane perpendicular to a direction in which the current to be measured flows.

  According to this configuration, the sensitivity axis directions of the sensor portions of the pair of magnetic sensors are the same, and the circuits and wirings of the pair of magnetic sensors are arranged symmetrically on a plane perpendicular to the direction in which the current to be measured flows. Therefore, it is possible to remove the influence of the external magnetic field by differential calculation while equalizing the influence of the magnetic field applied to the circuit and wiring outside the sensor unit. Thereby, the fall of an electric current measurement precision can fully be suppressed.

  In the present specification, the expression “symmetric” regarding the arrangement is used to include a substantial symmetrical relationship that does not lose the effect of the invention. For example, a difference that does not affect the measurement accuracy (a difference from a symmetrical arrangement) is allowed.

  In the current sensor of the present invention, the circuits or / and the wirings of the pair of magnetic sensors are arranged so as to have a two-dimensional point-symmetric relationship with each other on a plane perpendicular to a direction in which the current to be measured flows. May be. According to this configuration, the influence from the induced magnetic field caused by the current to be measured flowing through the current line can be made equal in the circuit and wiring outside the sensor unit. For this reason, it is possible to sufficiently suppress a decrease in current measurement accuracy.

  In the current sensor of the present invention, the circuits or / and the wirings of the pair of magnetic sensors are arranged so as to have a two-dimensional line-symmetric relationship with each other on a plane perpendicular to a direction in which the current to be measured flows. May be. According to this configuration, the influence from the external magnetic field can be made equal in circuits and wiring outside the sensor unit. For this reason, it is possible to sufficiently suppress a decrease in current measurement accuracy.

  In the current sensor of the present invention, the sensor units of the pair of magnetic sensors may have different configurations. According to this configuration, by changing the configuration of the sensor unit, it is possible to use the same circuit and wiring outside the sensor unit, so that the circuit and wiring outside the sensor unit are symmetrical (for example, It becomes easy to arrange in point symmetry or line symmetry. Thereby, the fall of an electric current measurement precision can be suppressed easily.

  In the current sensor of the present invention, the sensitivity axis directions of the sensor portions of the pair of magnetic sensors are the same, and the circuits and wirings of the pair of magnetic sensors are symmetrical on a plane perpendicular to the direction in which the current to be measured flows. Since they are arranged so as to have a relationship, it is possible to remove the influence of the external magnetic field by the differential calculation while making the influence of the magnetic field received by the circuit and the wiring outside the sensor section equal. Thereby, the fall of an electric current measurement precision can fully be suppressed.

It is a schematic diagram which shows the structure of a current sensor. It is a schematic diagram which shows the structure of a current sensor. It is a schematic diagram which shows the circuit structure of a current sensor. It is a circuit diagram which shows a sensor part, a circuit part, and its connection relation. It is a circuit diagram of a pair of magnetic sensors. It is a schematic diagram which shows the structure of a current sensor. It is a circuit diagram of a pair of magnetic sensors. It is a figure shown about the output of a pair of magnetic sensor. It is a schematic diagram which shows the structure of a current sensor. It is a circuit diagram of a pair of magnetic sensors. It is a schematic diagram which shows the structure of a current sensor. It is a circuit diagram of a pair of magnetic sensors.

  In a current sensor using a magnetic sensor, it is difficult to sufficiently increase the measurement accuracy of the current sensor by reducing the influence of various magnetic fields including an external magnetic field only by taking the differential of the two magnetic sensors. This is because there is a difference in the influence of these on the magnetic field depending on the arrangement of the circuit and wiring. For example, when the circuit and wiring layout is asymmetric, the influence of the induced magnetic field and the external magnetic field due to the current to be measured flowing through the current line differs for each magnetic sensor. (Differential matching) is reduced, and the problem that the external magnetic field cannot be sufficiently removed may occur.

  The present inventors pay attention to this point, and arrange the circuits and wirings of the pair of magnetic sensors in the current sensor so as to have a symmetrical relationship in a plane perpendicular to the direction in which the current to be measured flows. The present inventors have found that the measurement accuracy of the current sensor can be sufficiently increased by making the influence of the magnetic field applied to the circuit and the wiring equal to suppress the decrease in the current measurement accuracy.

  That is, the gist of the present invention employs a configuration in which the influence of the induced magnetic field due to the current to be measured and the influence of the external magnetic field appears equally in a pair of magnetic sensors, thereby sufficiently canceling the influence of the external magnetic field by differential calculation. Thus, it is intended to suppress a decrease in current measurement accuracy. Hereinafter, the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a schematic diagram showing an example of the arrangement of a current sensor 10 according to the present invention. The current sensor 10 includes a current line 15 and a first magnetic sensor 11A and a second magnetic sensor 11B arranged so as to sandwich the current line 15 therebetween. In FIG. 1, the letters X, Y, and Z attached to the first magnetic sensor 11A and the second magnetic sensor 11B indicate the corresponding circuits or wirings, respectively. That is, in the first magnetic sensor 11A, for example, a circuit or wiring represented by X corresponds to a circuit or wiring represented by X in the second magnetic sensor 11B. In FIG. 1A, the white arrow indicates the direction of the induced magnetic field generated by the current to be measured, and in FIG. 1B, the hatched arrow indicates the direction of the external magnetic field.

  FIG. 1A shows a plane (current line 15 is extended) in which the circuit and wiring of the first magnetic sensor 11A and the circuit and wiring of the second magnetic sensor 11B are perpendicular to the direction in which the current to be measured flows. This is an example of an arrangement having a two-dimensional point symmetry (two-fold symmetry) relationship in a plane perpendicular to the existing direction. As shown in FIG. 1A, the circuit or wiring of the first magnetic sensor 11A is arranged in the order of X, Y, Z in the direction of the induced magnetic field by the current to be measured, and the second magnetic sensor 11B The circuit or wiring is arranged in the order of X, Y, and Z in the direction of the induced magnetic field due to the current to be measured. In such an arrangement, the influence of the first magnetic sensor 11A from the induced magnetic field due to the current to be measured is substantially equal to the influence of the second magnetic sensor 11B from the induced magnetic field due to the current to be measured. And the influence of the external magnetic field can be sufficiently removed by differential calculation.

  In the current sensor 10, the first magnetic sensor 11A and the second magnetic sensor 11B include a sensor unit including a bridge circuit and a feedback coil, a differential / current amplifier outside the sensor unit, an I / V amplifier, and the like. (Not shown), all of which need not satisfy the symmetry. For example, the sensor unit does not have to have the above symmetry. Further, the symmetry need not be strict, and the influence of the current to be measured from the magnetic field may be almost equal. In addition, the point of symmetry in the point symmetry usually exists inside the current line 15.

  If the symmetry is considered three-dimensionally, it becomes three-dimensional line symmetry (two-fold symmetry). Therefore, in the configuration of the current sensor 10 in FIG. 1A, the circuit and wiring of the first magnetic sensor 11A and the circuit and wiring of the second magnetic sensor 11B have a three-dimensional line-symmetric relationship. It is possible to express that they are arranged as follows. However, the symmetry axis faces the direction in which the current to be measured flows. In addition, since there is no change in the two-dimensional or three-dimensional symmetry, the circuit and wiring of the first magnetic sensor 11A and the circuit and wiring of the second magnetic sensor 11B are It may be expressed as a two-fold symmetry relationship. In this case, the rotating shaft faces the direction in which the current to be measured flows. Further, in the current sensor 10 of FIG. 1A, the circuit and wiring of the first magnetic sensor 11A and the circuit and wiring of the second magnetic sensor 11B are affected by the direction of the induced magnetic field caused by the current to be measured (each of which affects the circuit). It is also possible to express that they are arranged in the same configuration with respect to the direction of the magnetic field received.

  FIG. 1B shows a plane (current line 15 is extended) in which the circuit and wiring of the first magnetic sensor 11A and the circuit and wiring of the second magnetic sensor 11B are perpendicular to the direction in which the current to be measured flows. This is an example of an arrangement having a two-dimensional line symmetry relationship in a plane perpendicular to the existing direction. As shown in FIG. 1B, in the first magnetic sensor 11A, the circuits or wirings are arranged in the order of X, Y, and Z in the direction of the external magnetic field. The wiring is arranged in the order of X, Y, and Z in the direction of the external magnetic field. In such an arrangement, the influence of the first magnetic sensor 11A from the external magnetic field is almost equal to the influence of the second magnetic sensor 11B from the external magnetic field. It is possible to remove.

  Note that it is not necessary for all the configurations in the first magnetic sensor 11A and the second magnetic sensor 11B to satisfy the symmetry. For example, the sensor unit may not have the above symmetry. Further, the symmetry need not be strict, and the influence of the current to be measured from the magnetic field may be almost equal. The symmetry axis in the line symmetry usually exists so that a part thereof overlaps the current line 15 in a plane perpendicular to the direction in which the current to be measured flows.

  When the symmetry is considered three-dimensionally, it becomes plane symmetry. Therefore, in the configuration of the current sensor 10 in FIG. 1B, the circuit and wiring of the first magnetic sensor 11A and the circuit and wiring of the second magnetic sensor 11B are arranged so as to have a plane symmetry relationship. It can be expressed as In this case, the symmetry plane is a plane parallel to the direction in which the current to be measured flows. In the current sensor 10 of FIG. 1B, the circuit and wiring of the first magnetic sensor 11A and the circuit and wiring of the second magnetic sensor 11B are arranged in the same configuration with respect to the direction of the external magnetic field. It can also be expressed as

  As shown in FIGS. 1A and 1B, depending on the type of symmetry that the circuit and wiring of the first magnetic sensor 11A and the circuit and wiring of the second magnetic sensor 11B have, The types of magnetic fields that can be equally affected are different. Therefore, any configuration may be selected as appropriate in accordance with the type of magnetic field that has a large influence on the current measurement accuracy.

  As described above, in the current sensor 10 of the present invention, the plane perpendicular to the direction in which the current to be measured flows through the circuit and wiring of the first magnetic sensor 11A and the circuit and wiring of the second magnetic sensor 11B. Are arranged so as to have a symmetrical relationship. With such an arrangement, the influence of the induced magnetic field and the external magnetic field due to the current to be measured appears equally in the first magnetic sensor 11A and the second magnetic sensor 11B, so that the influence of the external magnetic field is sufficiently canceled by the differential operation. Thus, it is possible to suppress a decrease in current measurement accuracy. In the following embodiments, specific examples of the current sensor 10 of the present invention will be described in more detail.

(Embodiment 1)
In this embodiment, as a specific example of the current sensor 10 of the present invention, an example in which the circuit or wiring of the magnetic sensor has a two-dimensional point-symmetric relationship in a plane perpendicular to the direction in which the current to be measured flows Will be described with reference to the drawings. FIG. 2A is a schematic diagram showing the configuration of the current sensor 10 when viewed from the direction in which the current to be measured flows, and FIG. 2B is perpendicular to the direction in which the current to be measured flows. It is a schematic diagram which shows the structure of the current sensor 10 when it sees from a direction. In FIG. 2A, the mark attached to the current line 15 indicates that the current to be measured flows from the back to the front. In FIG. 2B, the solid arrow indicates the direction of the current to be measured. The white arrow indicates the direction of the induced magnetic field due to the current to be measured. 2A and 2B, the solid arrow indicates the direction of the sensitivity axis, and in FIG. 2A, the broken arrow indicates the A side or B side in FIG. 2B, respectively. It corresponds to. Moreover, what is attached | subjected with the same number among the pins (terminal) of sensor part 12A and sensor part 12B shows that it is connected to the element which has the same function, respectively.

  Current sensor 10 in the present embodiment includes current line 15, first magnetic sensor 11A disposed on substrate 16A, and second magnetic sensor 11B disposed on substrate 16B. The first magnetic sensor 11A includes a sensor unit 12A including a bridge circuit and a feedback coil, and a circuit unit 13A including a differential / current amplifier and an I / V amplifier. The second magnetic sensor 11B includes a sensor unit 12B including a bridge circuit and a feedback coil, and a circuit unit 13B including a differential / current amplifier and an I / V amplifier.

  In the current sensor 10 of the present embodiment, the arrangement of the pins (terminals) of the sensor unit 12A in the first magnetic sensor 11A and the arrangement of the pins (terminals) of the sensor unit 12B in the second magnetic sensor 11B are as follows. In a plane perpendicular to the direction in which the current to be measured flows, there is a two-dimensional point-symmetrical relationship (see FIG. 2A). Further, the wiring connected to the sensor unit 12A in the first magnetic sensor 11A and the wiring connected to the sensor unit 12B in the second magnetic sensor 11B are on a plane perpendicular to the direction in which the current to be measured flows. Two-dimensional point symmetry. Similarly, the circuit unit 13A included in the first magnetic sensor 11A and the circuit unit 13B included in the second magnetic sensor 11A have a two-dimensional point-symmetric relationship in a plane perpendicular to the direction in which the current to be measured flows. It is in. In this case, the symmetry point exists inside the current line 15.

  By having such a symmetric relationship, the influence of the first magnetic sensor 11A from the induced magnetic field due to the current to be measured can be substantially equal to the influence of the second magnetic sensor 11B from the induced magnetic field due to the current to be measured. The matching (differential matching) at the time of differential calculation can be improved. Thereby, the influence of an external magnetic field is fully removed, and the fall of measurement accuracy can be suppressed.

  Note that the above expression is merely an example when the current sensor 10 is viewed two-dimensionally, and other expressions are possible. For example, the wiring connected to the sensor unit 12A in the first magnetic sensor 11A and the wiring connected to the sensor unit 12B in the second magnetic sensor 11B have axes extending in the direction in which the current to be measured flows. The three-dimensional line-symmetric relationship with the axis of symmetry is such that the circuit portion 13A of the first magnetic sensor 11A and the circuit portion 13B of the second magnetic sensor 11B pass in the direction in which the current to be measured flows. It can be said that there is a three-dimensional line-symmetric relationship with the extended axis as the symmetry axis. Similarly, it may be said that there is a two-fold symmetric relationship with the axis extending in the direction of passing the current to be measured as the rotation axis. Furthermore, the circuit part 13A and the wiring of the first magnetic sensor 11A and the circuit part 13B and the wiring of the second magnetic sensor 11B are in the direction of the induced magnetic field (the direction of the magnetic field that is affected by each) measured current. On the other hand, it can also be expressed as being arranged in the same configuration.

  Next, the circuit configuration of the current sensor 10 according to the present invention will be described. FIG. 3 is an example of a block diagram of the current sensor 10 according to the present invention. The current sensor 10 shown in FIG. 3 is a differential amplifier that performs a differential operation of outputs of the first magnetic sensor 11A and the second magnetic sensor 11B in addition to the first magnetic sensor 11A and the second magnetic sensor 11B. 14.

  The first magnetic sensor 11A shown in FIG. 3 is a magnetic balance sensor, and includes a feedback coil 111A arranged so as to be able to generate a magnetic field in a direction that cancels the magnetic field generated by the current to be measured, and two magnets that are magnetic detection elements. The sensor unit 12A includes a bridge circuit 113A including a resistance effect element and two fixed resistance elements. Also, a differential / current amplifier 121A that amplifies the differential output of the bridge circuit 113A and controls the feedback current of the feedback coil 111A, and an I / V amplifier 123A that converts the feedback current of the first magnetic sensor 11A into a voltage , Including a circuit portion 13A. Here, the sensor unit 12A including the feedback coil 111A and the bridge circuit 113A may be built in one chip. In some cases, the differential / current amplifier 121A and the I / V amplifier 123A are based on an operational amplifier having the same configuration and whose connection is changed.

  Similarly to the first magnetic sensor 11A, the second magnetic sensor 11B includes a sensor unit 12B including a feedback coil 111B and a bridge circuit 113B, and a circuit unit 13B including a differential / current amplifier 121B and an I / V amplifier 123B. Have In addition, the sensor unit 12B including the feedback coil 111B and the bridge circuit 113B may be built in one chip. In some cases, the differential / current amplifier 121A and the I / V amplifier 123A are based on an operational amplifier having the same configuration and whose connection is changed.

  The feedback coils 111A and 111B are arranged in the vicinity of the magnetoresistive effect elements of the bridge circuits 113A and 113B, and generate a canceling magnetic field that cancels the induced magnetic field generated by the current to be measured. As the magnetoresistive effect element of the bridge circuits 113A and 113B, a GMR (Giant Magneto Resistance) element, a TMR (Tunnel Magneto Resistance) element, or the like can be used. The magnetoresistive element has a characteristic that the resistance value is changed by an induced magnetic field from the current to be measured. By configuring the bridge circuits 113A and 113B using two magnetoresistive elements having such characteristics and two fixed resistance elements, a highly sensitive current sensor can be realized. Further, by using the magnetoresistive effect element, it becomes easy to arrange the sensitivity axis in a direction parallel to the substrate surface on which the current sensor is installed, and a planar coil can be used.

  Each of the bridge circuits 113A and 113B includes two output terminals that generate a potential difference corresponding to an induced magnetic field caused by a current to be measured. Two outputs from the two output terminals of each of the bridge circuits 113A and 113B are differentially amplified by the differential / current amplifiers 121A and 121B, and the differentially amplified outputs are supplied to the feedback coils 111A and 111B as current (feedback current). ). When the feedback current is applied to the feedback coils 111A and 111B, a cancellation magnetic field that cancels the induced magnetic field is generated by the feedback current. Then, the current flowing in the feedback coils 111A and 111B is converted into a voltage by the I / V amplifiers 123A and 123B when an equilibrium state in which the induction magnetic field and the canceling magnetic field cancel each other is generated and becomes a sensor output.

  In the differential / current amplifiers 121A and 121B, the power supply voltage is set to a value close to the reference voltage for I / V conversion + (maximum value within the rated value of feedback coil resistance × feedback coil current at full scale). The feedback current is limited, and the effect of protecting the magnetoresistive effect element and the feedback coil can be obtained. Here, the differential of the two outputs of the bridge circuits 113A and 113B is amplified and used as a feedback current. However, only the midpoint potential is output from the bridge circuits 113A and 113B, and the potential difference from a predetermined reference potential is set. The original feedback current may be used.

  The differential amplifier 14 outputs a differential value of output signals of the first magnetic sensor 11A and the second magnetic sensor 11B (that is, output signals of the I / V amplifiers 123A and 123B). By such differential calculation processing, the influence of an external magnetic field such as geomagnetism on the output signals of the first magnetic sensor 11A and the second magnetic sensor 11B is canceled, and the current can be measured with high accuracy.

  Next, the configuration of the sensor units 12A and 12B and the circuit units 13A and 13B and the connection relationship thereof in the first magnetic sensor 11A and the second magnetic sensor 11B will be described. FIG. 4 is a circuit diagram showing the basic configuration and connection relationship of the sensor units 12A and 12B and the circuit units 13A and 13B. FIG. 5 is a circuit diagram showing the configuration of the first magnetic sensor 11A and the second magnetic sensor 11B. The circuit diagram of FIG. 5 corresponds to the schematic diagram of FIG. 2B, in which the solid arrow indicates the direction of the current to be measured, and the white arrow indicates the direction of the induced magnetic field due to the current to be measured. Show. In FIG. 4, the numbers assigned to the pins (terminals) of the sensor units 12A and 12B and the circuit units 13A and 13B correspond to the pins assigned the same numbers in FIG.

  As can be seen from FIGS. 4 and 5, in the first magnetic sensor 11A, the two outputs of the bridge circuit 113A become the two inputs of the differential / current amplifier 121A. That is, the two pins (6, 7) of the sensor unit 12A and the two pins (3, 2) of the circuit unit 13A are connected to each other. The pin (1) of the circuit unit 13A corresponding to the output of the differential / current amplifier 121A and the pin (2) of the sensor unit 12A corresponding to one terminal of the feedback coil 111A are connected.

  Also, the pin (3) of the sensor unit 12A corresponding to the other terminal of the feedback coil 111A and the pin (5) of the circuit unit 13A corresponding to one input terminal of the I / V amplifier 123A are connected, These are connected to a ground potential (GND) through a resistor. Further, the pin (6) of the circuit unit 13A corresponding to the other input terminal of the I / V amplifier 123A and the pin (7) of the circuit unit 13A corresponding to the output terminal of the I / V amplifier 123A are output from the sensor. Connected to the terminal. A predetermined voltage (V +, V−) is applied to the two pins (5, 8) of the sensor unit 12A, and a predetermined voltage is applied to the two pins (4, 8) of the circuit unit 13A. (V +, V-) is given.

  The connection relationship of the second magnetic sensor 11B is the same. For this reason, as shown in FIG. 5, the circuit portion 13A and the wiring in the first magnetic sensor 11A and the circuit portion 13B and the wiring in the second magnetic sensor 11B are perpendicular to the direction in which the current to be measured flows. A configuration having a two-dimensional point-symmetric relationship in the plane is realized by arranging the same circuit and wiring by rotating 180 degrees.

  On the other hand, the sensor unit 12A and the sensor unit 12B in the configuration shown in FIG. 5 are not realized even when the same sensor unit is rotated 180 °. This is because it is necessary to match the direction of the sensitivity axis between the first magnetic sensor 11A and the second magnetic sensor 11B. Therefore, strictly speaking, the relationship between the sensor unit 12A and the sensor unit 12B does not become two-dimensional point symmetry in a plane perpendicular to the direction in which the current to be measured flows. However, this has little effect on the current measurement accuracy.

  Next, in FIGS. 6 and 7, the circuit portion 13A and the wiring in the first magnetic sensor 11A and the circuit portion 13B and the wiring in the second magnetic sensor 11B are perpendicular to the direction in which the current to be measured flows. An example of a case where the plane is not in a two-dimensional point symmetry relationship is shown. 6A is a schematic diagram when viewed from the direction in which the current to be measured flows, and FIG. 6B is a schematic diagram when viewed from the direction perpendicular to the direction in which the current to be measured flows. FIG. FIG. 7 is a circuit diagram showing the configuration of the first magnetic sensor 11A and the second magnetic sensor 11B. 6 and 7, the solid arrows indicate the direction of the current to be measured, and the white arrows indicate the direction of the induced magnetic field due to the current to be measured.

  In this case, as can be seen from FIG. 6B, the first magnetic sensor 11A and the second magnetic sensor 11B have a two-dimensional point-symmetric relationship in a plane parallel to the direction in which the current to be measured flows. . On the other hand, in a plane perpendicular to the direction in which the current to be measured flows, the arrangement of the pins (terminals) of the sensor unit 12A in the first magnetic sensor 11A and the pins (terminals) of the sensor unit 12B in the second magnetic sensor 11B. ) Is not in a two-dimensional point-symmetric relationship (see FIG. 6A). Further, the wiring connected to the sensor unit 12A in the first magnetic sensor 11A and the wiring connected to the sensor unit 12B in the second magnetic sensor 11B are on a plane perpendicular to the direction in which the current to be measured flows. There is no two-dimensional point symmetry. Similarly, the circuit unit 13A included in the first magnetic sensor 11A and the circuit unit 13B included in the second magnetic sensor 11B have a two-dimensional point-symmetric relationship in a plane perpendicular to the direction in which the current to be measured flows. Not.

  Such a configuration can be easily realized by rotating the magnetic sensor having the same configuration in a plane parallel to the direction in which the current to be measured flows, but in this case, an induced magnetic field generated by the current to be measured Therefore, the influence received by the first magnetic sensor 11A may not be equal to the influence received by the second magnetic sensor 11B from the induced magnetic field caused by the current to be measured. For example, when spike noise is applied to the current line 15 of the current sensor, as shown in FIG. 8, the output of the first magnetic sensor 11A and the output of the second magnetic sensor 11B do not match. Then, matching (differential matching) at the time of differential calculation is lowered, and the influence of the external magnetic field cannot be sufficiently removed.

  The current sensor 10 shown in the present embodiment has been conceived to solve such a problem. At least a part of the wiring or circuit of the pair of magnetic sensors is perpendicular to the direction in which the current to be measured flows. By arranging so as to have a two-dimensional point-symmetrical relationship on a smooth surface, the influence from the induced magnetic field by the current to be measured is made equal, and an appropriate differential operation is realized.

  Here, although the magnetic balance type sensor is used as the first magnetic sensor 11A and the second magnetic sensor 11A, a magnetic proportional type sensor may be used. Further, the configuration of the current sensor 10 according to FIGS. 3 to 5 is merely an example, and other configurations can naturally be adopted.

(Embodiment 2)
In the present embodiment, as a specific example of the current sensor 10 of the present invention, another case where the circuit or wiring of the magnetic sensor has a two-dimensional point symmetry relationship in a plane perpendicular to the direction in which the current to be measured flows. An example will be described with reference to the drawings. FIG. 9 is a schematic diagram showing the configuration of the current sensor 10 when viewed from the direction in which the current to be measured flows. In FIG. 9, the mark attached to the current line 15 indicates that the current to be measured flows from the front to the back, the white arrow indicates the direction of the induced magnetic field due to the current to be measured, and the solid arrow indicates the sensitivity. Indicates the direction of the axis. Moreover, what is attached | subjected with the same number among the pins (terminal) of sensor part 12A and sensor part 12B shows that it is connected to the element which has the same function, respectively.

  Current sensor 10 in the present embodiment includes current line 15, first magnetic sensor 11 </ b> A and second magnetic sensor 11 </ b> B arranged on substrate 16. The first magnetic sensor 11A includes a sensor unit 12A including a bridge circuit and a feedback coil, and a circuit unit 13A including a differential / current amplifier and an I / V amplifier. The second magnetic sensor 11B includes a sensor unit 12B including a bridge circuit and a feedback coil, and a circuit unit 13B including a differential / current amplifier and an I / V amplifier.

  In the current sensor 10 of the present embodiment, the arrangement of the pins (terminals) of the sensor unit 12A in the first magnetic sensor 11A and the arrangement of the pins (terminals) of the sensor unit 12B in the second magnetic sensor 11B are as follows. In a plane perpendicular to the direction in which the current to be measured flows, there is a two-dimensional point-symmetric relationship (see FIG. 9). Further, the wiring connected to the sensor unit 12A in the first magnetic sensor 11A and the wiring connected to the sensor unit 12B in the second magnetic sensor 11B are on a plane perpendicular to the direction in which the current to be measured flows. Two-dimensional point symmetry. Similarly, the circuit unit 13A included in the first magnetic sensor 11A and the circuit unit 13B included in the second magnetic sensor 11A have a two-dimensional point-symmetric relationship in a plane perpendicular to the direction in which the current to be measured flows. It is in. In this case, the symmetry point exists inside the current line 15.

  By having such a symmetric relationship, the influence of the first magnetic sensor 11A from the induced magnetic field due to the current to be measured can be substantially equal to the influence of the second magnetic sensor 11B from the induced magnetic field due to the current to be measured. Differential matching can be enhanced. Thereby, the influence of an external magnetic field is fully removed, and the fall of measurement accuracy can be suppressed.

  Note that the above expression is merely an example when the current sensor 10 is viewed two-dimensionally, and other expressions are possible. For example, the wiring connected to the sensor unit 12A in the first magnetic sensor 11A and the wiring connected to the sensor unit 12B in the second magnetic sensor 11B have axes extending in the direction in which the current to be measured flows. The three-dimensional line-symmetric relationship with the axis of symmetry is such that the circuit portion 13A of the first magnetic sensor 11A and the circuit portion 13B of the second magnetic sensor 11B pass in the direction in which the current to be measured flows. It can be said that there is a three-dimensional line-symmetric relationship with the extended axis as the symmetry axis. Similarly, it may be said that there is a two-fold symmetric relationship with the axis extending in the direction of passing the current to be measured as the rotation axis. Furthermore, the circuit part 13A and the wiring of the first magnetic sensor 11A and the circuit part 13B and the wiring of the second magnetic sensor 11B are in the direction of the induced magnetic field (the direction of the magnetic field that is affected by each) measured current. On the other hand, it can also be expressed as being arranged in the same configuration.

  The circuit configuration of the current sensor 10 is the same as that of the first embodiment. That is, in addition to the first magnetic sensor 11A and the second magnetic sensor 11B, there is a differential amplifier that performs a differential operation on the outputs of the first magnetic sensor 11A and the second magnetic sensor 11B. Details are omitted here because the description of Embodiment Mode 1 and FIG. 3 may be referred to.

  Next, the configuration of the sensor units 12A and 12B and the circuit units 13A and 13B and the connection relationship thereof in the first magnetic sensor 11A and the second magnetic sensor 11B will be described. FIG. 10 is a circuit diagram showing the configuration of the first magnetic sensor 11A and the second magnetic sensor 11B. The circuit diagram of FIG. 10 corresponds to the schematic diagram of FIG. 9. The mark attached to the current line 15 indicates that the current to be measured flows from the front to the back, and the white arrow indicates the covered line. The direction of the induced magnetic field due to the measurement current is shown. Note that the details of the basic configurations and connection relationships of the sensor units 12A and 12B and the circuit units 13A and 13B may be referred to the description in Embodiment 1, FIG.

  As can be seen from FIG. 10, two pins (6, 7) of the sensor unit 12A corresponding to the two outputs of the bridge circuit 113A and two of the circuit unit 13A corresponding to the two inputs of the differential / current amplifier 121A. The pins (3, 2) are connected to each other. The pin (1) of the circuit unit 13A corresponding to the output of the differential / current amplifier 121A and the pin (2) of the sensor unit 12A corresponding to one terminal of the feedback coil 111A are connected.

  Also, the pin (3) of the sensor unit 12A corresponding to the other terminal of the feedback coil 111A and the pin (5) of the circuit unit 13A corresponding to one input terminal of the I / V amplifier 123A are connected, These are connected to a ground potential (GND) through a resistor. Further, the pin (6) of the circuit unit 13A corresponding to the other input terminal of the I / V amplifier 123A and the pin (7) of the circuit unit 13A corresponding to the output terminal of the I / V amplifier 123A are output from the sensor. Connected to the terminal. A predetermined voltage (V +, V−) is applied to the two pins (5, 8) of the sensor unit 12A, and a predetermined voltage is applied to the two pins (4, 8) of the circuit unit 13A. (V +, V-) is given.

  The connection relationship of the second magnetic sensor 11B is the same. Therefore, as shown in FIG. 10, the circuit portion 13A and the wiring in the first magnetic sensor 11A and the circuit portion 13B and the wiring in the second magnetic sensor 11B are perpendicular to the direction in which the current to be measured flows. A configuration having a two-dimensional point-symmetric relationship in the plane is realized by arranging the same circuit and wiring by rotating 180 degrees.

  On the other hand, the sensor unit 12A and the sensor unit 12B in the configuration shown in FIG. 10 are not realized even if the same sensor unit is rotated 180 °. This is because it is necessary to match the direction of the sensitivity axis between the first magnetic sensor 11A and the second magnetic sensor 11B. Therefore, strictly speaking, the relationship between the sensor unit 12A and the sensor unit 12B does not become two-dimensional point symmetry in a plane perpendicular to the direction in which the current to be measured flows. However, this has little effect on the current measurement accuracy.

  As described above, by arranging at least a part of the wiring or circuit of the pair of magnetic sensors so as to have a two-dimensional point-symmetric relationship in a plane perpendicular to the direction in which the current to be measured flows, An appropriate differential operation can be realized by equalizing the influence of the induced magnetic field from the induced magnetic field.

  Here, although the magnetic balance type sensor is used as the first magnetic sensor 11A and the second magnetic sensor 11A, a magnetic proportional type sensor may be used. Further, the configuration of the current sensor 10 according to FIGS. 9 and 10 is merely an example, and other configurations can naturally be adopted.

(Embodiment 3)
In the present embodiment, as a specific example of the current sensor 10 of the present invention, an example in which the circuit or wiring of the magnetic sensor has a two-dimensional line-symmetric relationship in a plane perpendicular to the direction in which the current to be measured flows. Will be described with reference to the drawings. FIG. 11A is a schematic diagram showing the configuration of the current sensor 10 when viewed from the direction in which the current to be measured flows, and FIG. 11B is perpendicular to the direction in which the current to be measured flows. It is a schematic diagram which shows the structure of the current sensor 10 when it sees from a direction. In FIG. 11A, the mark attached to the current line 15 indicates that the current to be measured flows from the back to the front. In FIG. 11B, the solid arrow indicates the direction of the current to be measured. The hatched arrows indicate the direction of the external magnetic field. In FIGS. 11A and 11B, the solid line arrow indicates the direction of the sensitivity axis. Moreover, what is attached | subjected with the same number among the pins (terminal) of sensor part 12A and sensor part 12B shows that it is connected to the element which has the same function, respectively.

  Current sensor 10 in the present embodiment includes current line 15, first magnetic sensor 11A disposed on substrate 16A, and second magnetic sensor 11B disposed on substrate 16B. The first magnetic sensor 11A includes a sensor unit 12A including a bridge circuit and a feedback coil, and a circuit unit 13A including a differential / current amplifier and an I / V amplifier. The second magnetic sensor 11B includes a sensor unit 12B including a bridge circuit and a feedback coil, and a circuit unit 13B including a differential / current amplifier and an I / V amplifier.

  In the current sensor 10 of the present embodiment, the arrangement of the pins (terminals) of the sensor unit 12A in the first magnetic sensor 11A and the arrangement of the pins (terminals) of the sensor unit 12B in the second magnetic sensor 11B are as follows. In a plane perpendicular to the direction in which the current to be measured flows, there is a two-dimensional line-symmetric relationship (see FIG. 11A). Further, the wiring connected to the sensor unit 12A in the first magnetic sensor 11A and the wiring connected to the sensor unit 12B in the second magnetic sensor 11B are on a plane perpendicular to the direction in which the current to be measured flows. Two-dimensional line symmetry. Similarly, the circuit unit 13A included in the first magnetic sensor 11A and the circuit unit 13B included in the second magnetic sensor 11A have a two-dimensional line-symmetric relationship in a plane perpendicular to the direction in which the current to be measured flows. It is in. In this case, the symmetry axis 17 exists so that a part thereof overlaps the current line 15 in a plane perpendicular to the direction in which the current to be measured flows.

  By having such a symmetrical relationship, the influence received by the first magnetic sensor 11A by the external magnetic field and the influence received by the second magnetic sensor 11B can be made substantially equal. Therefore, it is possible to suppress a decrease in measurement accuracy.

  Note that the above expression is merely an example when the current sensor 10 is viewed two-dimensionally, and other expressions are possible. For example, the wiring connected to the sensor unit 12A in the first magnetic sensor 11A and the wiring connected to the sensor unit 12B in the second magnetic sensor 11B are parallel to the direction in which the current to be measured flows. A plane that is symmetrical with respect to the plane of symmetry and that is parallel to the direction in which the current to be measured flows through the circuit portion 13A of the first magnetic sensor 11A and the circuit portion 13B of the second magnetic sensor 11B. It can be said that they are in a plane-symmetrical relationship with the plane of symmetry. In addition, the circuit unit 13A and the wiring of the first magnetic sensor 11A and the circuit unit 13B and the wiring of the second magnetic sensor 11B are expressed in the same configuration with respect to the direction of the external magnetic field. Is also possible.

  The circuit configuration of the current sensor 10 is the same as that of the first embodiment. That is, in addition to the first magnetic sensor 11A and the second magnetic sensor 11B, there is a differential amplifier that performs a differential operation on the outputs of the first magnetic sensor 11A and the second magnetic sensor 11B. Details are omitted here because the description of Embodiment Mode 1 and FIG. 3 may be referred to.

  Next, the configuration of the sensor units 12A and 12B and the circuit units 13A and 13B and the connection relationship thereof in the first magnetic sensor 11A and the second magnetic sensor 11B will be described. FIG. 12 is a circuit diagram showing the configuration of the first magnetic sensor 11A and the second magnetic sensor 11B. The circuit diagram of FIG. 12 corresponds to the schematic diagram of FIG. 11, and the hatched arrows indicate the direction of the external magnetic field.

  Details of the basic configurations and connection relationships of the sensor units 12A and 12B and the circuit units 13A and 13B may be referred to the description of Embodiment 1, FIG. However, in the second magnetic sensor 11B of the present embodiment, the operational amplifier used as the differential / current amplifier and the operational amplifier used as the I / V amplifier in FIG. 4 are used interchangeably. That is, in the present embodiment, the circuit portion 13A of the first magnetic sensor 11A and the circuit portion 13B of the second magnetic sensor 11B are in the plane shown in FIG. 12 (parallel to the direction in which the current to be measured flows). In such a manner that the relationship is rotated by 180 °. In this case, the pins (1, 2, 3, 5, 6, 7) of the circuit unit 13A correspond to the pins (7, 6, 5, 3, 2, 1) of the circuit unit 13B, respectively. The reason why the circuit unit 13A and the circuit unit 13B are arranged in such a manner is to ensure as much as possible the symmetry of the wiring (two-dimensional line symmetry in a plane perpendicular to the direction in which the current to be measured flows). It is. Instead of using operational amplifiers of the same configuration for the circuit unit 13A and the circuit unit 13B, the design is changed so that the circuit unit 13A and the circuit unit 13B have the above-described symmetry, and the first magnetic sensor You may further improve the symmetry of 11A and the 2nd magnetic sensor 11B.

  Note that the sensor unit 12A and the sensor unit 12B are designed so that the arrangement of the pins has the above-described symmetrical relationship, and therefore the configurations thereof are different from each other. However, since the symmetry with respect to the external magnetic field is high, it is preferable from the viewpoint of equalizing the influence of the external magnetic field.

  As described above, by arranging at least a part of the wiring or circuit of the pair of magnetic sensors so as to have a two-dimensional line-symmetrical relationship in a plane perpendicular to the direction in which the current to be measured flows, the external magnetic field Therefore, the appropriate differential operation can be realized.

  Here, although the magnetic balance type sensor is used as the first magnetic sensor 11A and the second magnetic sensor 11A, a magnetic proportional type sensor may be used. Further, the configuration of the current sensor 10 according to FIGS. 11 and 12 is merely an example, and it is naturally possible to adopt other configurations.

  The current sensor of the present invention can be used, for example, to detect the magnitude of a current for driving a motor of an electric vehicle or a hybrid car.

  The present application is based on Japanese Patent Application No. 2010-204719 filed on Sep. 13, 2010. All this content is included here.

Claims (4)

A current line through which the current to be measured flows;
A pair of magnetic sensors each having a sensor unit and wiring connected to the sensor unit;
An arithmetic device connected to the pair of magnetic sensors and differentially calculating output signals of the pair of magnetic sensors;
Comprising
In the pair of magnetic sensors, the sensor units are arranged so that the respective sensitivity axis directions are the same, and the wiring of the pair of magnetic sensors is on a plane perpendicular to the direction in which the current to be measured flows. The current sensors are arranged so as to have a symmetrical relationship with each other.   The wiring of the pair of magnetic sensors is arranged so as to have a two-dimensional point-symmetric relationship with each other on a plane perpendicular to a direction in which the current to be measured flows. Current sensor.   The wiring of the pair of magnetic sensors is arranged to have a two-dimensional line-symmetric relationship with each other on a plane perpendicular to a direction in which the current to be measured flows. Current sensor.   The current sensor according to any one of claims 1 to 3, wherein the sensor units of the pair of magnetic sensors have different configurations.

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