JP2011043338A - Current sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a current sensor capable of more accurately detecting a current value. <P>SOLUTION: The current sensor includes a first detection unit 11 having first and second magnetoresistive elements 14a, 14b which are perpendicular to each other in their extending directions and connected at their ends to each other and a second detection unit 13 having third and fourth magnetoresistive elements 14c, 14d which are perpendicular to each other in their extending directions and connected at their ends to each other. The first detection unit 11 is approximated to a conductor 12, the second detection unit 13 is disposed apart from the conductor 12 more than the first detection unit 11, and the surface on which the first to the fourth magnetoresistive elements 14a to 14d of the first and second detection elements 11, 13 is made approximately parallel to a tangent of a signal magnetic field. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a current sensor for detecting a current flowing in a conductor of various electronic devices.

  In the conventional current sensor of this type, as shown in FIG. 5, the first detection unit 1 and the second detection unit 2 each having a magnetoresistive element are positioned on opposite sides of the conductor 3. .

  Then, the output obtained by the first detector 1 and the output obtained by the second detector 2 are differentially processed to take measures against the external magnetic field B0.

  As prior art document information relating to the invention of this application, for example, Patent Document 1 is known.

JP 2005-517937

  In the above-described conventional current sensor, it is difficult to accurately attach the position of the first detection unit 1 and the position of the second detection unit 2 so as to be symmetric with respect to the conductor 3, and it is symmetric. There was a case where it shifted from the position. If the first detection unit 1 and the second detection unit 2 are affected by the external magnetic field B0 differently from each other even if they are slightly shifted from the symmetrical position, there is a problem that a more accurate current value cannot be detected. Had.

  The present invention solves the above-described conventional problems, and an object of the present invention is to provide a current sensor capable of more accurate current value detection.

  In order to achieve the above object, the present invention has the following configuration.

  According to a first aspect of the present invention, in a current sensor for detecting a signal magnetic field generated from a current flowing through a conductor and detecting a current flowing through the conductor, the extending directions are orthogonal and connected to each other at the end. A first detection unit having a first magnetoresistive element and a second magnetoresistive element, and a third magnetoresistive element and a fourth magnetoresistive element whose extending directions are orthogonal and connected to each other at the ends. A second detection unit having the first detection unit to be close to the conductor, and the distance from the conductor to the second detection unit is larger than that of the first detection unit. The signal obtained by the first detector is arranged and the surface of the first and second detectors on which the first to fourth magnetoresistive elements are provided is substantially parallel to the tangent to the signal magnetic field. And detecting the difference between the signals obtained by the second detector The current flowing in the conductor is detected by eliminating the influence of the external magnetic field. According to this configuration, the second detection unit detects the magnetic field of only the external magnetic field, Since the detection unit 1 detects the combined magnetic field of both the external magnetic field and the signal magnetic field, the signal obtained by the first detection unit and the signal obtained by the second detection unit are differentially processed. By doing so, it is possible to obtain an output only by the signal magnetic field, and as a result, the surface on which the first to fourth magnetoresistive elements are provided is substantially parallel to the tangent to the signal magnetic field, and the first and second to the conductors. Since the influence of the external magnetic field can be eliminated simply by defining the distance of the detection section, the effect of more accurate current value detection can be obtained.

  According to a second aspect of the present invention, in the current sensor for detecting the signal magnetic field generated from the current flowing through the conductor and detecting the current flowing through the conductor, the extending directions are orthogonal and connected to each other at the end. A first detection unit having a first magnetoresistive element and a second magnetoresistive element, and a third magnetoresistive element and a fourth magnetoresistive element whose extending directions are orthogonal and connected to each other at the ends. A surface of the first detection unit on which the first and second magnetoresistive elements are provided is substantially parallel to a tangent line of the signal magnetic field, and the second detection unit. The surface on which the third and fourth magnetoresistive elements are provided is substantially perpendicular to the tangent to the signal magnetic field, and the signal obtained by the first detector and the signal obtained by the second detector are By detecting the difference, the influence of the external magnetic field is eliminated and the conductor is According to this configuration, since the second detection unit is not affected by the signal magnetic field, only the external magnetic field is detected. Since the detection unit 1 detects the combined magnetic field of both the external magnetic field and the signal magnetic field, the signal obtained by the first detection unit and the signal obtained by the second detection unit are differentially processed. As a result, an output by only the signal magnetic field can be obtained. As a result, the surface on which the first to fourth magnetoresistive elements are provided is substantially parallel to the tangent of the signal magnetic field and the first to the tangent of the signal magnetic field. Since the influence of the external magnetic field can be eliminated simply by defining the angle of the second detection unit, the effect of more accurate current value detection can be obtained.

  As described above, in the current sensor of the present invention, the first detection unit is disposed close to the conductor, and the second detection unit is disposed such that the distance from the conductor is greater than that of the first detection unit, and The surface on which the first to fourth magnetoresistive elements in the first and second detection units are provided is substantially parallel to the tangent to the signal magnetic field, and the signal obtained by the first detection unit and the second detection are detected. Since the current flowing through the conductor is detected by detecting the difference between the signals obtained by the part and eliminating the influence of the external magnetic field, the second detection part detects the magnetic field of only the external magnetic field. On the other hand, the first detection unit detects a combined magnetic field of both the external magnetic field and the signal magnetic field, whereby the signal obtained by the first detection unit and the second detection unit are detected. By differentially processing the signal obtained in step 1, only the signal magnetic field is used. Since the force can be obtained, the surface on which the first to fourth magnetoresistive elements are provided is made substantially parallel to the tangent line of the signal magnetic field, and the distance between the first and second detectors with respect to the conductor is specified. Thus, it is possible to eliminate the influence of the external magnetic field, thereby producing an excellent effect that a more accurate current value can be detected.

The schematic diagram when the current sensor in Embodiment 1 of this invention is seen from the side. The top view when the first detection part of the current sensor is viewed from the conductor The top view when the 2nd detection part of the same current sensor is seen from the conductor Schematic when the current sensor according to Embodiment 2 of the present invention is viewed from the side. Schematic view of a conventional current sensor as viewed from the side

(Embodiment 1)
Hereinafter, the first aspect of the present invention will be described with reference to the first embodiment.

  1 is a schematic diagram when the current sensor according to Embodiment 1 of the present invention is viewed from the side, FIG. 2 is a plan view when the first detection portion of the current sensor is viewed from a conductor, and FIG. 3 is the same current. It is a top view when the 2nd detection part of a sensor is seen from the conductor.

  As shown in FIGS. 1 to 3, the current sensor according to the first embodiment of the present invention brings the first detection unit 11 close to the conductor 12 and the second detection unit 13 with respect to the conductor 12. The surface of the first and second detectors 11 and 13 where the first to fourth magnetoresistive elements 14a to 14d are provided is tangent to the signal magnetic field B. And almost parallel. In addition, although the 1st detection part 11 and the 2nd detection part 13 are not illustrated, they are integrally formed in the holder. 1 and 3, the current flowing through the conductor 12 flows in the direction from the back side to the front side of the page.

  The first detection unit 11 includes first and second magnetoresistive elements 14a and 14b provided on the upper surface of an insulating substrate 15a made of alumina or the like. As shown in FIG. 2, the first and second magnetoresistive elements 14a and 14b are connected so that their extending directions are orthogonal to each other, and the first and second magnetoresistive elements 14a and 14b are connected to each other. A first output portion 17 is formed in the connection portion 16 of 14b.

  The second detector 13 is also provided with third and fourth magnetoresistive elements 14c and 14d provided on the upper surface of an insulating substrate 15b made of alumina or the like. As shown in FIG. 3, the third and fourth magnetoresistive elements 14c and 14d are configured so that the extending directions are orthogonal to each other, and the third and fourth magnetoresistive elements 14c, 14c, A second output portion 19 is formed at the connection portion 18 of 14d.

  At this time, for the end portions of the first to fourth magnetoresistive elements 14a to 14d that are not connected to the connecting portions 16 and 18, the voltage terminals are connected to the first and third magnetoresistive elements 14a and 14c, and The second and fourth magnetoresistive elements 14b and 14d are connected to the ground.

  The first to fourth magnetoresistive elements 14a to 14d are formed on the substrates 15a and 15b by a method such as vapor deposition, and the shape thereof is shown as a rectangular shape in FIGS. Actually, it is configured in a meandering manner so as to be folded at the longitudinal side. And when the magnetic field is not applied, each resistance value of the 1st-4th magnetoresistive elements 14a-14d is substantially the same. Furthermore, the first to fourth magnetoresistive elements 14a to 14d are protected by a protective film (not shown).

  In addition, the patterns and positional relationships of the first and second magnetoresistive elements 14 a and 14 b and the output unit 17 in the first detection unit 11, and the third and fourth magnetoresistive elements 14 c in the second detection unit 13. , 14d, the output unit 19 and the like, and the pattern and the positional relationship are made substantially the same, productivity can be improved.

  The second detection unit 13 is arranged at a position farther than the first detection unit 11 with respect to the conductor 12, and the surface on which the third and fourth magnetoresistive elements 14c and 14d are provided is a signal magnetic field. The tangent of B is substantially parallel to the surface of the first detector 11 where the first and second magnetoresistive elements 14a and 14b are provided. At this time, since the resistance value of the magnetoresistive element changes when the current flowing through the magnetoresistive element and the magnetic field are orthogonal, the resistance value of the first to fourth magnetoresistive elements 14a to 14d is changed by the signal magnetic field B. Accordingly, signals are output from the first and second output units 17 and 19.

  Further, the second detection unit 13 needs to detect a magnetic field of only an external magnetic field without generating an output by the signal magnetic field B. For that purpose, it must be arranged far from the conductor 12, but this distance is appropriately determined according to the current flowing through the conductor 12, the required detection accuracy, etc., and can be set to 50 mm, for example.

  By arranging in this way, the influence of the external magnetic field (disturbance magnetic field) received by both the first detection unit 11 and the second detection unit 13 can be made the same. At this time, in the first to fourth magnetoresistive elements 14a to 14d, a voltage is applied between the voltage terminal and the ground, and the output (voltage V01) obtained from the first output unit 17 and the second output unit 19 are obtained. Since the influence of the external magnetic field can be canceled by the output obtained by differentially processing the output (voltage V02), only the signal magnetic field B can be detected. Then, the current value flowing through the conductor 12 is calculated from the signal magnetic field B.

  In the above-described current sensor according to the first embodiment of the present invention, the surface on which the first to fourth magnetoresistive elements 14a to 14d are provided is substantially parallel to the tangent to the signal magnetic field B, and the first, Since the influence of the external magnetic field can be eliminated simply by defining the distance between the second detectors 11 and 13, an effect that a more accurate current value can be detected can be obtained.

  And while making the 1st detection part 11 adjoin to the conductor 12, the 2nd detection part 13 is arrange | positioned so that the distance from the said conductor 12 may become larger than the said 1st detection part 11, and said 1st, The surface of the second detectors 11 and 13 on which the first to fourth magnetoresistive elements 14a to 14d are provided is substantially parallel to the tangent to the signal magnetic field B, and the signal obtained by the first detector 11 By detecting the difference between the signals obtained by the second detector 13, the current flowing in the conductor 12 is detected by eliminating the influence of the external magnetic field. As a result, the second detection unit 13 detects only the magnetic field of the external magnetic field, while the first detection unit 11 detects the combined magnetic field of both the external magnetic field and the signal magnetic field B. Therefore, an output based only on the signal magnetic field can be obtained by differentially processing the signal obtained by the first detection unit 11 and the signal obtained by the second detection unit 13.

  That is, both the external magnetic field and the signal magnetic field B are incident on the first detection unit 11, but in order to detect the current value flowing through the conductor 12, the output from only the signal magnetic field B generated in the conductor 12 is used. Because it is necessary, it is necessary to know the influence of the output by the external magnetic field. For this reason, if an output by only the external magnetic field can be obtained by the second detection unit 13 at a distant position that is not affected by the signal magnetic field B, an output can be obtained only by the signal magnetic field B by taking the difference between them. it can.

  In addition, it is not necessary to accurately attach the position of the first detection unit 11 and the position of the second detection unit 13 so as to be symmetric with respect to the conductor 12, and the first detection unit 11 and the second detection unit. For each of 13, it is only necessary to provide these at predetermined locations, and it is only necessary to form them in one direction with respect to the conductor 12, so that high mounting accuracy is not required, thereby reducing the influence of the external magnetic field due to mounting. .

  Furthermore, if the 1st detection part 11 and the 2nd detection part 13 are integrally formed in a holder, the 1st detection part 11 and the 2nd detection part 13 can be easily located in a predetermined location. it can.

  In addition, even when the signal magnetic fields of the plurality of conductors 12 are detected, only one detection unit for detecting the external magnetic field is required. Therefore, the same number of first detection units 11 and one second detection unit as the number of conductors 12 are used. It suffices if there is a detection unit 13, thereby reducing the number of detection units.

  Moreover, since the external magnetic field itself is detected by the second detection unit 13 unlike the conventional case, the subsequent processing is facilitated.

(Embodiment 2)
The second aspect of the present invention will be described below with reference to the second embodiment.

  FIG. 4 is a schematic view of the current sensor according to Embodiment 2 of the present invention when viewed from the side. In the second embodiment of the present invention, components having the same configurations as those of the first embodiment of the present invention are denoted by the same reference numerals, and the description thereof is omitted.

  The difference between the second embodiment of the present invention and the first embodiment of the present invention is that, as shown in FIG. 4, the third and fourth magnetoresistive elements 14c and 14d in the second detection unit 13 are different. The surface provided is not substantially parallel to the tangent line of the signal magnetic field B, but is substantially perpendicular to the tangent line of the signal magnetic field B.

  At this time, the third and fourth magnetoresistive elements 14c and 14d need to be substantially parallel to the first and second magnetoresistive elements 14a and 14b in the first detection unit 11.

  With such a configuration, since the signal magnetic field B is applied in the film thickness direction to the third and fourth magnetoresistive elements 14c and 14d in the second detection unit 13, the third and fourth The magnetoresistive elements 14c and 14d of FIG. 4 do not change their resistance values and detect only the external magnetic field, and the first detection unit 11 combines the magnetic field of both the external magnetic field and the signal magnetic field B. Therefore, by performing a differential process on the signal obtained by the first detection unit 11 and the signal obtained by the second detection unit 13, it is possible to obtain an output based only on the signal magnetic field. An effect is obtained.

  In the first embodiment of the present invention described above, it is difficult to eliminate the influence of the signal magnetic field B depending on the position of the second detection unit 13 (distance from the conductor 12), but in the second embodiment of the present invention. Can more reliably eliminate the influence of the signal magnetic field B regardless of the distance from the conductor 12.

  In the current sensor according to the first and second embodiments of the present invention described above, the magnetoresistive elements constituting the first and second detection units 11 and 13 are each configured as a half bridge circuit. Alternatively, a full bridge circuit may be configured.

  Further, since the detected output has linearity, a magnet made of BaFe, SrFe or the like is provided on the lower surface of the substrates 15a and 15b, and a bias magnetic field is applied to the first detection unit 11 and the second detection unit 13. May be.

  The current sensor according to the present invention has an effect that a more accurate current value can be detected, and is particularly useful when applied to a current sensor or the like for detecting a current flowing through a conductor of various electronic devices. It is.

DESCRIPTION OF SYMBOLS 11 1st detection part 12 Conductor 13 2nd detection part 14a-14d 1st-4th magnetoresistive element

Claims (2)

In a current sensor for detecting a signal magnetic field generated from a current flowing through a conductor to detect a current flowing in the conductor, a first magnetoresistive element and a second magnetism whose extending directions are orthogonal to each other and connected to each other at an end portion A first detector having a resistance element; and a second detector having a third magnetoresistive element and a fourth magnetoresistive element that are perpendicular to each other and connected to each other at the ends, The first detection unit is disposed close to the conductor, the second detection unit is disposed such that a distance from the conductor is larger than the first detection unit, and the first and second detection units are arranged. The surface on which the first to fourth magnetoresistive elements are provided is substantially parallel to the tangent to the signal magnetic field, and the signal obtained by the first detector and the signal obtained by the second detector are By detecting the difference, the influence of the external magnetic field is eliminated and the difference is Current sensor to detect the current flowing through the body. In a current sensor for detecting a signal magnetic field generated from a current flowing through a conductor to detect a current flowing in the conductor, a first magnetoresistive element and a second magnetism whose extending directions are orthogonal to each other and connected to each other at an end portion A first detector having a resistance element; and a second detector having a third magnetoresistive element and a fourth magnetoresistive element that are perpendicular to each other and connected to each other at the ends, The surface of the first detection unit on which the first and second magnetoresistive elements are provided is substantially parallel to the tangent line of the signal magnetic field, and the third and fourth magnetoresistive elements in the second detection unit are By making the provided surface substantially perpendicular to the tangent of the signal magnetic field and detecting the difference between the signal obtained by the first detection unit and the signal obtained by the second detection unit, the influence of the external magnetic field can be reduced. The electric current which is excluded and detects the current flowing through the conductor Sensor.

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