JP2022014161A - Current sensor - Google Patents

Abstract

To perform high-precision current measurement while securing a wide measurement range.SOLUTION: A current sensor for measuring current flowing through a conductor includes a detection element having a first end and a second end. The detection element includes: n+1 (n is a natural number ) magnetic materials; n connection parts; a first connection terminal connected to the first end; a second connection terminal connected to the second end; and a third connection terminal connected to one of the n connection parts. The n+1 magnetic materials extend in a second direction perpendicular to a first direction in which the current flows. The n+1 magnetic materials are arranged in a third direction perpendicular to the first direction and the second direction. The n connection parts connect ends of the adjacent magnetic materials of the n+1 magnetic materials so that the detection element are formed in a meander shape.SELECTED DRAWING: Figure 1

Description

The present invention relates to a current sensor.

The magnetic impedance (MI) element is a magnetic sensor using the magnetic impedance effect. Patent Document 1 discloses a current sensor using this MI element.

In Patent Document 1, the magnetic field generated by the current flowing through the measurement target is measured by a plurality of MI elements. Since the plurality of MI elements are arranged so that the distances from the measurement target are different from each other, the magnitudes of the magnetic fields measured by the plurality of MI elements are different from each other. In Patent Document 1, the difference in the magnitude of the measured magnetic field is used to enable current measurement in a wide measurement range from a small current to a large current.

Japanese Patent No. 4910290

However, in the technique disclosed in Patent Document 1, since a plurality of MI elements are used, a positional deviation (distance, angle) between the plurality of MI elements may occur. This misalignment reduces the accuracy of current measurement.

Therefore, an object of the present invention is to perform highly accurate current measurement while ensuring a wide measurement range.

In order to solve the above problems, the current sensor of the present invention is a current sensor that measures a current flowing through a conductor, and has a detection element having a first end portion and a second end portion, and the detection element is , N + 1 (n is a natural number) magnetic material, n connection portions, and a first connection terminal connected to the first end portion and a second connection portion connected to the second end portion. It has two connection terminals and a third connection terminal connected to one of the n connection portions, and each of the n + 1 magnetic materials is in the first direction in which the current flows. Extending in a vertical second direction, the n + 1 magnetic bodies are arranged in the first direction and a third direction perpendicular to the second direction, and the n connections are arranged. The end portions of the adjacent magnetic bodies of the n + 1 magnetic bodies are connected so that the detection element has a meander shape.

The current sensor further includes a control unit connected to the first connection terminal, the second connection terminal, and the third connection terminal, and the control unit is the first of the detection elements. The impedance of the portion between the connection terminal and the third connection terminal, and the impedance of the portion of the detection element between the second connection terminal and the third connection terminal are measured and measured. The value of the current may be calculated based on the impedance.

n is a natural number of 2 or more, and the current sensor may further have a fourth connection terminal connected to a connection portion different from the connection portion to which the third terminal is connected.

The current sensor may further have a bus bar for a bias magnetic field covering the detection element.

According to the present invention, it is possible to perform highly accurate current measurement while ensuring a wide measurement range.

It is a figure which shows the current sensor 100 which concerns on one Embodiment of this invention. It is a figure which shows the MI element 110 which concerns on one Embodiment of this invention. It is a figure which shows the impedance characteristic with respect to the current IB of the MI element 110 which concerns on one Embodiment of this invention. It is a figure which shows the MI element 110 which concerns on one Embodiment of this invention. It is a figure which shows the MI element 110 which concerns on one Embodiment of this invention.

<Current sensor 100>
FIG. 1 is a diagram showing a current sensor 100 according to an embodiment of the present invention. 1 (A) is a perspective view of the current sensor 100, and FIG. 1 (B) is a view of the current sensor 100 as viewed from the right side of FIG. 1 (A). The current sensor 100 has a magnetic impedance (MI) element 110 mounted on the circuit board S and a control unit 120 so that the MI element 110 is inserted into the bias magnetic field bus bar 130 formed in a U shape. It is composed of. The current sensor 100 may have a housing (not shown) that houses the MI element 110, the control unit 120, and the bias magnetic field bus bar 130.

The current sensor 100 according to the present embodiment measures the current flowing through the measurement target in a non-contact manner. In the example shown in FIG. 1, the current sensor 100 is arranged in the vicinity of the measurement target bus bar BB so as not to come into contact with the measurement target bus bar BB when measuring the current IB flowing through the measurement target bus bar BB.

When the current IB flows through the measurement target bus bar BB, a magnetic field HB is generated around the measurement target bus bar BB. The magnitude of this magnetic field HB changes according to the value of the current IB flowing through the measurement target bus bar BB and the distance from the measurement target bus bar BB. On the other hand, the impedance of the MI element 110 changes according to the change of the external magnetic field. Therefore, when the distance between the MI element 110 and the measurement target bus bar BB is kept constant, the impedance of the MI element 110 of the current sensor 100 arranged in the vicinity of the measurement target bus bar BB is the current flowing through the measurement target bus bar BB. It changes according to the change of IB. Therefore, in the present embodiment, the control unit 120 measures the impedance of the MI element 110 and calculates the value of the current IB flowing through the measurement target bus bar BB based on the measured impedance.

FIG. 2 is a diagram showing an MI element 110 according to the present embodiment. FIG. 2A is a diagram showing details of the MI element 110 according to the present embodiment, and FIG. 2B is a diagram showing a positional relationship between the MI element 110 according to the present embodiment and the measurement target bus bar BB. Is.

The MI element 110 has a meander shape, and has a first end portion 111 and a second end portion 112 at both ends thereof.

The MI element 110 includes four magnetic bodies 113 (first magnetic body 1131, second magnetic body 1132, third magnetic body 1133, fourth magnetic body 1134) and three connecting portions 114 (first magnetic body 1134). Connection unit 1141, second connection unit 1142, third connection unit 1143) and three connection terminals 115 (first connection terminal 1151, second connection terminal 1152, third connection terminal 1153). Have.

As shown in FIG. 2, each of the four magnetic bodies 113 extends in a second direction D2 perpendicular to the first direction D1 (direction in which the measurement target bus bar BB extends) through which the current IB in the measurement target bus bar BB flows. It has ends at both ends. As shown in FIG. 2, the first end 111 is one of the two ends of the first magnetic material 1131 and one of the two ends of the fourth end 1134.

As shown in FIG. 2, the four magnetic bodies 113 are arranged in a third direction D3 perpendicular to the first direction D1 and the second direction D2.

As shown in FIG. 2, the MI element 110 has a meander shape by connecting the ends of adjacent magnetic bodies among the four magnetic bodies 113 by the three connecting parts 114. Specifically, the end of the two ends of the first magnetic body 1131 that is not the first end 111 and one end of the second magnetic body 1132 are connected by the first connecting portion 1141. , The other end of the second magnetic body 1132 and one end of the third magnetic body 1133 are connected by the second connecting portion 1142, and the other end of the third magnetic body 1133 and the two ends of the fourth magnetic body 1134. The end of the portion that is not the second end 112 is connected by the third connecting portion 1143.

The magnetic material 113 is a magnetic material having a high magnetic permeability. Therefore, the impedance of the magnetic body 113 changes according to the change of the external magnetic field due to the magnetic impedance effect.

It is desirable that the connecting portion 114 is a non-magnetic good conductor metal (copper or gold).

The first connection terminal 1151 is connected to the first end 111, the second connection terminal 1152 is connected to the second end 112, and the third connection terminal 1153 is the second connection 1152. It is connected to the.

In the present embodiment, the four magnetic bodies 113 extending in the second direction D2 perpendicular to the first direction D1 through which the current IB in the measurement target bus bar BB flows are in the first direction D1 and the second direction D2. They are lined up in the vertical third direction D3. Therefore, the distances of the four magnetic materials 113 from the measurement target bus bar BB are different from each other. In the example shown in FIG. 2, the first magnetic body 1131 is arranged closest to the measurement target bus bar BB, and the fourth magnetic body 1134 is arranged farthest from the measurement target bus bar BB.

The magnitude of the magnetic field HB generated by the current IB flowing through the measurement target bus bar BB becomes smaller as the distance from the measurement target bus bar BB increases. Therefore, the four magnetic materials 113 are exposed to magnetic fields HB having different sizes from each other. In the example shown in FIG. 2, the magnitude of the magnetic field HB to which the first magnetic body 1131 arranged closest to the measurement target bus bar BB is exposed is the largest, and is arranged farthest from the measurement target bus bar BB. The magnitude of the magnetic field HB to which the magnetic material 1134 is exposed becomes the smallest. Therefore, the four magnetic materials 113 have different impedance characteristics with respect to the current IB flowing through the bus bar BB to be measured.

FIG. 3 is a diagram showing impedance characteristics with respect to the current IB flowing through the measurement target bus bar BB of the MI element 110 according to the present embodiment. The broken line in FIG. 3 indicates the first portion of the MI element 110 between the first connection terminal 1151 and the third connection terminal 1153 (that is, the first magnetic body 1131, the second magnetic body 1132, and the first one. It is the impedance characteristic of the connection portion 1141 and the MI element portion composed of the second connection portion 1142), and the one-point chain wire is the second of the MI element 110 between the second connection terminal 1152 and the third connection terminal 1153. (That is, the MI element portion composed of the third magnetic body 1133, the fourth magnetic body 1134, the second connecting portion 1141, and the third connecting portion 1142). The solid line in FIG. 3 is the combined impedance of the first portion and the second portion of the MI element 110.

As shown in FIG. 3, the combined impedance (solid line) is the MI element in the unstable region (near zero current IB in FIG. 2) where the change in impedance with respect to the current IB flowing through the bus bar BB to be measured is not stable. Although it is almost the same as the impedance characteristic (broken line) of the first part of the 110, the impedance characteristic (broken line) of the first part of the MI element 110 is where the value of the current IB flowing through the measurement target bus bar BB is large. The change in impedance is large compared to.

Therefore, in the present embodiment, the control unit 120 is connected to the first connection terminal 1153 and the second connection terminal 1152, and the impedance of the MI element 110 is measured to widen the current IB flowing through the bus bar BB to be measured. It becomes possible to measure in the range. That is, in the present embodiment, it is possible to measure whether the current IB flowing through the measurement target bus bar BB is a minute current or a large current.

Further, as shown in FIG. 3, the impedance characteristic (broken line) of the first portion of the MI element 110 is the second portion of the MI element 110 where the value of the current IB flowing through the measurement target bus bar BB is small. Compared to the impedance characteristic (dashed line) of, the change in impedance is large. On the other hand, the impedance characteristic (dashed line) of the second portion of the MI element 110 is higher than the impedance characteristic (broken line) of the first portion of the MI element 110 where the value of the current IB flowing through the measurement target bus bar BB is large. The change in impedance is large.

Therefore, in the present embodiment, the control unit 120 is connected to the first connection terminal 1153, the second connection terminal 1152, and the third connection terminal 1153, and the control unit 120 determines the impedance of the entire MI element 110 and the MI element. The impedance of the first portion of the 110 and the impedance of the second portion of the MI element 110 are measured, and the current IB flowing through the bus bar BB to be measured is measured based on the measured impedance.

Therefore, in the present embodiment, when the impedance component of the first portion of the MI element 110 and the impedance component of the second portion of the MI element 110 are combined, the change in impedance is as shown by the solid line in FIG. Therefore, it becomes possible to measure the current IB flowing through the measurement target bus bar BB in a wide range.

Further, the control unit 120 may have a function of switching the output from the current sensor 100, for example. That is, the control unit 120 outputs the output from the current sensor 100 to the output based on the entire MI element 110, the output based on the first part of the MI element 110, and the output based on the second part of the MI element 110. It is good to have a function to switch between. By doing so, in the present embodiment, the output of the current sensor 100 can be switched according to the magnitude of the current IB flowing through the bus bar BB to be measured, and the current IB can be measured with high sensitivity in a wide range. It will be possible to do.

Further, in the present embodiment, unlike the technique disclosed in Patent Document 1, the current sensor 100 is composed of one MI element 110. Therefore, unlike the technique disclosed in Patent Document 1, there is no problem that the measurement accuracy of the current IB is lowered due to the positional deviation (distance, angle) between the plurality of MI elements. Therefore, in the present embodiment, it is possible to perform highly accurate current measurement while ensuring a wide measurement range.

The connection portion to which the third connection terminal 1153 is connected is not limited to the second connection portion 1142. For example, the third connection terminal 1153 may be connected to the first connection portion 1141 as shown in FIG. 4 (A). Further, the third connection terminal 1153 may be connected to the third connection portion 1143.

Further, the number of connecting portions 115 is not limited to three. For example, the MI element 110 has a fourth connection connected to the first connection portion 1142 as shown in FIG. 4B, in addition to the third connection portion 1153 connected to the second connection portion 1142. It may have a terminal 1154. Further, the MI element 110 may have another connection terminal connected to the third connection portion 1143. By doing so, it becomes possible to further divide the MI element 110 into smaller pieces and measure the impedance of each portion. As a result, it becomes possible to perform a measurement more suitable for the current IB flowing through the bus bar BB to be measured.

Further, in the example shown in FIG. 2, the MI element 110 has four magnetic bodies 113 and three connecting portions 114, but as shown in FIG. 5A, the MI element 110 has two magnetic bodies 113. It may have one connecting portion 114, or as shown in FIG. 5B, it may have six magnetic materials 113 and five connecting portions 114. That is, the MI element 110 may have n + 1 (n is a natural number) magnetic material and n connecting portions. For example, by increasing the number of magnetic materials 113, the magnitude of the magnetic field HB to which the magnetic material 113 closest to the measurement target bus bar BB is exposed and the magnetic field HB to which the magnetic material 113 farthest to the measurement target bus bar BB is exposed. The difference between the size and the size becomes large, and as a result, sensitive current measurement can be performed in a wider range.

<Bias magnetic field bus bar 130>
As shown in FIG. 1, the bias magnetic field bus bar 130 has a U-shape and covers the MI element 110. That is, in the present embodiment, the MI element 110 is sandwiched between the U-shaped portions 131 of the U-shaped bias magnetic field bus bar 130. A current is passed through the bias magnetic field bus bar 130 in a direction substantially perpendicular to the second direction D2 in which the magnetic body 113 of the MI element 110 extends in order to generate a bias magnetic field for avoiding the unstable region. Is done.

When the MI element is placed in the coil (bias coil) to generate the bias magnetic field, the bias coil exists between the MI element and the measurement target, which makes it difficult to bring the MI element closer to the measurement target. Become. On the other hand, in the present embodiment, since the bias magnetic field bus bar 130 has a U-shape, the bias magnetic field bus bar 130 does not exist between the MI element 110 and the measurement target bus bar BB. Therefore, in the present embodiment, the MI element 110 can be brought closer to the measurement target bus bar BB than the current sensor using the bias coil. As a result, it becomes possible to measure a smaller current than a current sensor using a bias coil.

Further, in the present embodiment, the MI element 110 is simply inserted into the U-shaped portion 131 of the U-shaped bias magnetic field bus bar 130, and the configuration of the current sensor 100 according to the present embodiment is to insert the MI element into the bias coil. The configuration is easier to manufacture than the configuration arranged in the above, and as a result, in the present embodiment, it is possible to reduce the manufacturing cost as compared with the current sensor using the bias coil.

Further, when a permanent magnet is used to generate a bias magnetic field as in the technique disclosed in Patent Document 1, the direction of the bias magnetic field cannot be changed, and the direction of the current flowing through the measurement target is determined. I can't. On the other hand, in the present embodiment, the bus bar 130 is used to generate the bias magnetic field, and the direction of the bias magnetic field can be changed. Therefore, the direction of the current flowing through the measurement target can be determined. The current sensor 100 according to the present embodiment can also be used for measuring the current flowing through a circuit connected to a livestock battery or the like.

Compared to the coil, the resistance of the bus bar can be reduced by several orders of magnitude. Therefore, in the present embodiment, it is possible to suppress the power consumed for generating the bias magnetic field as compared with the current sensor using the bias coil.

In the present embodiment, it is preferable to form the MI element 110 so that the magnetic material of the MI element 110 is located at the center of the U-shaped portion 131 of the bias magnetic field bus bar 130 by using flip chip bonding or the like. By doing so, it is not necessary to use the element protective material, and it becomes possible to suppress the thickness of the MI element 110. As a result, the width W of the U-shaped portion 131 of the U-shaped bias magnetic field bus bar 130 can be reduced, and a large bias magnetic field can be generated.

The present invention has been described above according to a preferred embodiment of the present invention. Although the present invention has been described here with reference to specific examples, various modifications and modifications can be made to these specific examples without departing from the spirit and scope of the invention described in the claims.

100 Current sensor 110 MI element 111 First end 112 Second end 113 Magnetic material 1131 First magnetic material 1132 Second magnetic material 1133 Third magnetic material 114 Connection part 1141 First connection part 1142 Second 2 Connection 1143 3rd Connection 115 Connection Terminal 1151 1st Connection Terminal 1152 2nd Connection Terminal 1153 3rd Connection Terminal 120 Control Unit 130 Bias Magnetic Bus Bar 131 U-shaped Part BB of Bias Magnetic Bus Bar 130 Measurement target bus bar IB Current flowing through the measurement target bus bar BB HBB Current magnetic field generated by IB D1 First direction D2 Second direction D3 Third direction

Claims (4)

A current sensor that measures the current flowing through a conductor.
It has a detection element with a first end and a second end,
The detection element is
n + 1 (n is a natural number) magnetic material and
It has n connections and
The first connection terminal connected to the first end and
The second connection terminal connected to the second end,
It has a third connection terminal connected to one of the n connection portions.
Each of the n + 1 magnetic materials extends in a second direction perpendicular to the first direction in which the current flows.
The n + 1 magnetic materials are arranged in the first direction and the third direction perpendicular to the second direction.
The n connection portions are current sensors that connect the ends of adjacent magnetic bodies among the n + 1 magnetic materials so that the detection element has a meander shape. Further having a control unit connected to the first connection terminal, the second connection terminal, and the third connection terminal.
The control unit includes the impedance of the portion of the detection element between the first connection terminal and the third connection terminal, and the second connection terminal of the detection element and the third connection. The current sensor according to claim 1, wherein the impedance of the portion between the terminals is measured, and the value of the current is calculated based on the measured impedance. n is a natural number of 2 or more,
The current sensor according to claim 1 or 2, further comprising a fourth connection terminal connected to a connection portion different from the connection portion to which the third terminal is connected. The current sensor according to any one of claims 1 to 3, further comprising a bus bar for a bias magnetic field covering the detection element.

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