JP2001305163A - Current sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a small-sized, low-cost current sensor which is affected by neither a disturbing magnetic field due to a transient current, terrestrial magnetism, etc., nor temperature characteristics that an element originally has. SOLUTION: This current sensor is provided with a means for providing 1st and 2nd magnetic impedance elements 1 and P (MI element) so that one is in the opposite direction from the magnetic field produced with a current to be measured. The 1st and 2nd MI elements are wound with DC bias coils 2 and 2' and negative feedback coils 3 and 3' and both ends of the 1st and 2nd MI elements are connected to the negative feedback bias coils through detecting circuits 4 and 4'; and the ends of the negative feedback coils are connected to one-end sides of elements 5 and 5' for output detection and outputs are detected at both the ends of the elements for output detection and regarded as one current output.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a current sensor, and more particularly to a current sensor using an MI element which has high sensitivity and can detect a detection magnetic field over a wide range, and more particularly to the influence of a disturbance magnetic field such as geomagnetism. The present invention relates to a current sensor which is not affected by the temperature characteristic and has no relation to the temperature characteristic of the MI element.

[0002]

2. Description of the Related Art In recent years, there has been an increasing demand for a magnetic sensor having a small size, a low cost, a high sensitivity and a high speed response. Accordingly, MI that can detect a weak external magnetic field with high sensitivity
Devices are becoming necessary. In addition, demand for high-sensitivity sensors that can be used for nondestructive inspection and banknote inspection has been increasing. Further, there is an increasing demand for a current sensor having high sensitivity and capable of sensing over a wide range of a detected magnetic field as a current sensor for an automobile.

Here, the MI effect will be briefly described. The MI effect is an electromagnetic phenomenon in which when a high-frequency current or a pulse current of several MHz that causes a skin effect on a highly permeable magnetic material is applied, the magnitude of the impedance changes greatly due to an external magnetic field. A highly sensitive MI device utilizing this phenomenon was proposed in 1993 by Professor Mori of Nagoya University. The MI element utilizing the MI effect is an amorphous magnetic wire type shown below.
When a high-frequency current of the order of Hz is applied, not only the amplitude of the induced voltage but also the amplitude between both ends of the wire significantly changes due to the external magnetic field Hex in the wire length direction. This is H
The reason for this is that, in addition to the inductance inside the wire, the ohmic resistance due to the skin effect also changes at the same time.
The use of the zero magnetostrictive or negative magnetostrictive amorphous wire also causes the MI effect to be prominent even in a sample having a small size of several tens of μm in diameter and a length of 1 to 2 mm, and no coil for excitation or detection is required at all. Further, the MI effect does not require a circuit for canceling the ohmic voltage, so that the sensor configuration can be simplified, and the excitation frequency can be up to several hundred MHz, so that a high-frequency device can be configured.

As a feature, since a change in magnetic flux in the circumferential direction (closed magnetic path) is used due to energization, there is no demagnetizing field due to excitation, not only the head becomes micro-sized, but also no magnetic flux due to excitation is generated outside. No coil is required for excitation and detection, and there is no problem of stray capacitance in high-frequency excitation. It is possible to suppress a characteristic change due to a temperature change of the magnetic wire. Since the detection sensitivity is high, it is expected to be applied to a magnetic head or a high-precision magnetic head for a rotary encoder of an HDD or FDD spindle motor.

The MI element is made thinner by forming a magnetic thin film using a sputtering method or the like,
MI elements that produce I characteristics have been proposed. This M
The I element can control the magnetic properties of the film by annealing in a magnetic field or film formation in a magnetic field, and the flexibility in structure can be increased by lamination and patterning, and it can be used as an on-chip device, and This is advantageous in comparison with wire elements. This thin film type MI element has a slightly lower magnetic field detection sensitivity than the magnetic wire type. In order to configure a magnetic field sensor with this MI element, since the MI effect is symmetric with respect to the positive and negative of the external magnetic field, it is necessary to make the characteristics asymmetric using a DC bias magnetic field generated by a coil or a permanent magnet. In particular, the magnetic thin film MI element generally has a lower magnetic field detection sensitivity of 1/3 to 1/4 as compared with an amorphous wire, so that power consumption increases when a DC bias magnetic field is generated by a coil current. Further, there is a problem that the element becomes large by winding a coil or disposing a permanent magnet. Further, a laminated type crossed magnetic anisotropic film MI element in which two soft magnetic thin films such as a CoFeB film improved from the above-mentioned MI element are laminated has been proposed.

[0006] The latter cross-type magnetic thin film MI element is a cross-type magnetic anisotropic film MI element having a magnetic anisotropy that crosses using the easy axis of magnetization of the soft magnetic thin film.
The MI effect that is asymmetric with respect to the sign of the external magnetic field can be obtained. This makes it possible to construct a magnetic field sensor without using a DC bias magnetic field at all. Since a coil for generating a DC bias magnetic field is not required, low power consumption and ultra-miniaturization have become possible. Further, since the magnitude of the magnetic field at which the magnitude of the impedance is maximum is 1/5 of that of the magnetic thin film MI element, it is expected that a sensor with higher sensitivity can be manufactured.

However, although the above-described MI element has high sensitivity, it is difficult to obtain linearity over a wide range of the detected magnetic field, and thus it is necessary to improve the control device. FIG. 17 is a block diagram showing a conventional control device 40 for the MI element 31. A bias magnetic field is applied by a DC bias coil 32, amplified by an amplifier 35 through a detection circuit 34, and subjected to negative feedback through a negative feedback resistor 37 and a wound negative feedback bias coil 33 to obtain an output 36. The external magnetic field H _ex [Oe] −the output voltage V _OUT [V] is represented by FIG.
The linearity as shown in is obtained.

As described above, in the current sensor, the conventional MI
Even with the element control device 40, linearity could be obtained only in the range of ± 3 [Oe] as shown in FIG. The MI element has high sensitivity but an external magnetic field Hex-
Looking at the MI characteristics such as the impedance change rate [%], the peak of the impedance change rate [%] is ± several [O].
e] and the characteristics are symmetric, so that the bias magnetic field H _b
The output could be detected only in the linear region where the characteristics were shifted and asymmetric by applying. For example,
As shown in FIG. 18, a linear region could be obtained only within the range of ± 3 [Oe]. ± 4 [Oe], ± 5 [O
In [e], the output was in a saturation region and the output could not be detected. In addition, in the conventional MI element control device, the first and second MI elements are arranged so as to apply bias magnetic fields in directions opposite to each other with respect to the direction of the magnetic field due to the detected current when considering the current sensor for the vehicle. However, in order to use it for vehicles, it is necessary to consider the influence of disturbance magnetic fields such as magnetic fields due to transient currents and geomagnetism, and the temperature characteristics of MI elements. There is a need for a current sensor that is not affected by the temperature characteristics of the MI element.

At present, a current sensor using a ball element is used as a current sensor for a vehicle. This is because the current sensor using the ball element has an advantage that the current can be detected over a wide range without being affected by disturbance magnetic fields or temperature characteristics. Further, in a current sensor for a vehicle, a transient current, a disturbance magnetic field due to geomagnetism, and a temperature characteristic are more important than the necessity of high sensitivity. FIG.
FIG. 2 is a simplified view of a conventional current sensor using a ball element. In such a current sensor using a ball element, a method is used in which a magnetic core using a member such as ferrite is used to measure a current flowing in a conductive substrate for a current to be detected. Not only is the cost high, but it is not suitable for downsizing the current sensor.

[0010]

SUMMARY OF THE INVENTION The applicant of the present invention has found that in a current sensor, the output of the MI element having any MI characteristic may be saturated by using a new MI element control device. The magnetic field can be detected over a wide range (infinity) as well as the Hall element with high sensitivity, and the influence of the disturbance magnetic field due to transient current, geomagnetism, etc.
The current flowing through the conductive substrate for the current to be detected is detected in the same manner as in FIG. 19 while the current to be detected is output over a wide range without being affected by the temperature characteristics of the MI element and without using the magnetic core. It has become possible to provide a current sensor that is small, inexpensive, and not affected by a disturbance magnetic field.

[0011]

SUMMARY OF THE INVENTION The present invention is a current sensor for solving the above-mentioned problems. In the present invention, the first and second current sensors are arranged so that one of them is in the opposite direction with respect to the direction of the magnetic field due to the current to be detected. Means for providing first and second magnetic impedance elements (hereinafter referred to as MI elements); winding a DC bias coil and a negative feedback bias coil around the first and second MI elements; Respectively connected to the negative feedback bias coils from both ends of the MI element via detection circuits,
3. An end of each of the negative feedback bias coils is connected to one end of an output detecting element, an output is detected at both ends of the output detecting element, and each detected output is made one current output.
Means for providing first and second magnetic impedance elements (hereinafter, MI elements) so that one direction is opposite to the direction of the magnetic field due to the detected current; Negative feedback bias coils for magnetic flux cancellation are wound respectively, and are wound around the first and second MI elements from both ends of the first and second MI elements via respective detection circuits and initial offset circuits. Each of the negative feedback bias coils is connected, the terminal of the negative feedback bias coil is connected to one end of an output detection element, and the output is detected at both ends of the output detection element. Claim 3 provides means for providing first and second magnetic impedance elements (hereinafter referred to as MI elements) so that one side is opposite to the direction of the magnetic field due to the current to be detected. And the second MI Are connected to respective negative feedback bias coils wound around the first and second MI elements through respective detection circuits from both ends of the element, and the ends of the respective negative feedback biases are respectively connected to one end of an output detecting element. 5. A current sensor connected to the output detecting element to detect an output at both ends of the output detecting element, and to use each detected output as one current output.
Provides a current sensor that solves the problem by being characterized in that the one current output is the difference between the respective detection outputs detected at both ends of the respective output detection elements.

According to a fifth aspect of the present invention, the first and second MI elements read a voltage between both ends of the MI element, which is changed by an external magnetic field, by the detection circuit to generate a current and supply the current to the negative feedback bias coil. Providing a current sensor characterized by generating a magnetic field in which a tall magnetic field becomes zero and balancing the current. According to a sixth aspect of the present invention, the detected current is supplied to a detected current substrate formed of a conductive substrate, and the first and second MI elements are respectively provided on both surfaces of the detected current conductive substrate. The problem is solved by being provided.

According to a seventh aspect of the present invention, the first and second MI elements have symmetric MI characteristics.
Claim 8 is the current sensor according to Claim 3, wherein the first and second MI elements have asymmetric MI characteristics. The current sensor according to any one of claims 1 to 3, wherein the means for providing the first and second MI elements is formed in a U shape by an insulating resin molding member. This will solve the problem.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Here, an embodiment of the current sensor of the present invention will be described using an MI element using a magnetic thin film, but the same effect can be obtained with any MI element. As a first embodiment, FIG. 1 shows a magnetic thin film MI element 1 as first and second MI elements according to the present invention,
FIG. 2 is a diagram showing a configuration of 1 ^′ . FIG. 2A is a diagram illustrating MI characteristics of the first and second MI elements when an external magnetic field Hex [Oe] is applied from the plus side and when an external magnetic field Hex [Oe] is applied from the minus side. FIG. 2B is a diagram showing MI characteristics of first and second MI elements having different MI characteristics. In FIG. 2B, in order to simplify the description, the impedance when the external magnetic field Hex [Oe] is applied from the plus side is shown.
The MI characteristic is represented only by the dance change rate. FIG. 3 shows a magnetic thin film MI when a bias magnetic field H _b [Oe] is applied.
1 shows a configuration diagram of elements 1 and 1 ^′ . FIG. 4A is a characteristic diagram of the magnetic thin film MI element when the bias magnetic field H _b [Oe] is applied. FIG. 4b shows a bias magnetic field H _b [O applied to first and second magnetic thin film MI elements having different MI characteristics.
FIG. 7 is a characteristic diagram of the magnetic thin film MI element when [e] is applied. FIG. 5 shows a control device 10 for the first and second magnetic thin film MI elements 1, 1 ^' as a first embodiment according to the present invention.
FIG. 1 is a diagram schematically showing a current sensor to which the present invention is applied. FIG.
FIGS. 6A and 6B are diagrams showing an example in which the electronic circuit of the current sensor according to the present invention is schematically represented by blocks. FIG.
As a first embodiment according to the present invention, the external magnetic field H _ex [Oe] −the output voltage V _OUT [V] of the current sensor to which the control device 10 of the first and second magnetic thin film MI elements 1 and 1 ^′ is applied. 6 is a graph showing the relationship of. FIG. 7B shows a detected current value I of a current sensor to which the first and second magnetic thin film MI element control devices are applied as a first embodiment according to the present invention.
₅ is a graph showing a relationship between _ex [A] and output voltage V _OUT [V].

FIG. 1 shows a magnetic thin film MI element (hereinafter referred to as thin film MI element 1 or 1 ^′ ), and the substrate is omitted in the figure, but the thin film MI element 1 is an Al ₂ O ₃ ceramic wafer. CoF which is a soft magnetic thin film on a non-magnetic substrate with enhanced surface smoothness such as Si wafer, glass wafer, etc.
plating film of eNi, NiFe, etc., or FeCoSi
When a soft magnetic thin film such as an amorphous sputtered film such as B, CoZrNb, FeSiB, or CoSiB, or a NiFe sputtered film is formed and then heat-treated in a rotating magnetic field or a static magnetic field, the magnetic properties can be improved.

[0016] Both ends of the first and second thin-film MI elements 1 and 1 ^' for obtaining a skin effect by applying a time-varying current are respectively connected to both ends by electrodes made of aluminum wire bonding, Au wire or the like, or by direct soldering. Several [MHz]
A high frequency current of the above (preferably 10 to 40 [MHz]) is applied to both ends. At this time, the external magnetic field Hex [Oe]
FIG. 2A shows the relationship (MI characteristic) between the impedance change rate (%) and the impedance change rate (%). In FIG. 3, the DC bias coil 2,
The bias magnetic field H _b [Oe] is applied to shift the operating point at which the maximum sensitivity is obtained by winding 2 ^′ N times. FIG. 4A shows the MI characteristics at this time. This will be described with reference to FIG.
At this time, the thin-film MI elements 1 and 1 provided in opposite directions to a magnetic field (hereinafter, an external magnetic field) generated by the detected current.
^The DC bias coils 2, 2 ^' wound around the coil are insulated or the outer periphery of the coil is insulated, and the negative feedback bias coils 3, 3 ^' are wound N times as much as the DC bias coil. Next, a current I flowing through a conductive substrate (hereinafter referred to as a detected current bar) 8 made of a conductor such as a copper plate for a detected current.
_{When ex} flows, it generates an external magnetic field. The external magnetic field H _ex [Oe] changes the voltage of the thin-film MI elements 1, 1 ^′ . The bias magnetic field H _b [Oe] applied to each of the thin film MI elements 1 and 1 ^′ is in the opposite direction, and the disturbance magnetic field due to the geomagnetism and the transient current is canceled. The detected output 6 is output as a difference between one current value, which is suitable for a current sensor for a vehicle or the like.

The external current generated by the above-mentioned detected current
Bias magnetic fields H in directions opposite to each other with respect to the magnetic field_bIs applied
Elements 1, 1 arranged so that^'From both ends of
Detection circuits 4, 4^'Voltage V₁, V_TwoRead,
I₁And I₂And a thin film MI element 1,
1^'Negative feedback bias coils 3 and 3 wound around^'To
The respective thin-film MI elements 1, 1^'Total magnetism
H where the world is zero₁And H₂By generating
I₁And I₂Always equilibrate. (This each player
The principle of zeroing the magnetic field is as follows:
MI element 1, 1 ^'Each will be described. ) Each H₁And H
₂To the respective detection elements 5, 5^'(Resistance R ₁, Resistance R₂)
Is output as one current output difference. Respectively
DC bias coils 2, 2^', Each negative feedback bias
Coil 3, 3^'Are the MI elements 1 and 1 shown in FIG.^'In the main part of
Has been disclosed. An example of the electronic circuit at this time is shown in FIG.
a and FIG. 6b schematically shows a block diagram.

The principle of making each total magnetic field zero is described below.
And the first and second thin-film MI elements 1, 1^'Divided into theories
I will tell. External magnetic field H generated_ex[Oe] is applied
The first and second MI elements 1, 1^'Set
The current I flowing through the detected current bar 8_exBy
External magnetic field H_ex[Oe] and H₁[Oe] Total
The external magnetic field of the thin-film MI element 1
World H_exMagnetic field in the region where the voltage change with respect to [Oe] is saturated
But we can detect linearly. On the other hand, the current
Current I_exExternal magnetic field H generated by [A]_ex[O
e] and H₂Total field of [Oe] is always zero
And thin film MI element 1^'External magnetic field H_exElectricity for [Oe]
Even a magnetic field in a region where the pressure change is saturated can be detected linearly.
The difference between these two detected outputs is one current output
Output. Therefore, in the past, ± numbers as shown in FIG.
Detection was possible only in the narrow magnetic field range of [Oe].
As shown in Fig. 7a, a wide range (physically infinite) of external magnetism
World H_exMagnetic field balanced type that obtains a linear output over [Oe]
Can be obtained. This also
The output voltage V as shown in FIG._OUT[V] -current to be detected
It has become possible to obtain the relationship of the value [A]. Next, FIG.
b, MI elements 1 and 1 having different MI characteristics a shown in FIG.^'
And MI elements 1 and 1 having MI characteristics b^'Control device 10
And a current sensor using the same. MI element
1, 1^'MI characteristics vary slightly depending on the element
For this reason, MI elements with different characteristics are used.
And experimented. FIG. 4b shows the respective MI characteristics of FIG. 2b.
a, b bias magnetic field H_b[Oe] was applied and shifted
FIG. The detailed explanation is not described because it has been described above, but the solid line
7A together with the MI characteristic a shown by the dotted line and the MI characteristic b shown by the dotted line.
As shown in the figure, a completely similar (physical infinity)
External magnetic field H_exMagnetic field balanced type with linear output over
It was verified that it was the control device 10 of FIG. Figure 7b
The same was true. Thus, a wide range (physically infinite
Large) Magnetic field capable of detecting linear output over current measurement
This is a current sensor that uses a balanced MI element controller.
Was verified. Also, as shown in FIG.
In configuring the semiconductor device, the MI elements 1, 1 ^'Is the detected
Reverse magnetic field (external magnetic field) generated by energizing flow bar 8
Elements 1, 1 provided in the directions^'Is each MI element
1, 1^'The direction of the best sensitivity matches the external magnetic field
It is preferable that they are arranged as follows. Because the electricity
The magnetic field generated by the current is the MI element 1, 1^'External magnet
This is because a better sensitivity can be obtained. Furthermore,
In the figure, MI elements 1, 1^'Are above the detected current bar 8 and
Although provided below, it is generated by the detected current bar 8.
It only needs to be in a position where the generated magnetic field can be detected.
No. However, be careful not to be affected by disturbance magnetic fields or temperature characteristics.
Are located at the same distance from the detected current bar 8
Is preferred. Such an MI element 1, 1^'And detected power
Against the external magnetic field generated by the current flowing through the flow bar 8.
And the first and second MI elements 1, 1^'In the opposite direction,
Furthermore, in order to keep the same distance from the detected current bar 8, heat resistance and
Insulating resin moldings and ceramic
Insert a U-shaped part into the detected current bar 8
Shape can further simplify the process and reduce costs
It is possible to plan.

Next, as a second embodiment according to the present invention, a current sensor to which the control device 20 for the first and second thin-film MI elements 11, 11 ^' is applied will be described. FIG. 8 is a diagram showing a configuration of the first and second thin film MI elements 11 and 11 ^′ using the MI effect according to the present invention. FIG. 9A is a diagram showing MI characteristics of the first and second MI elements 11 and 11 ^′ when an external magnetic field Hex [Oe] is applied from the plus side and when an external magnetic field Hex [Oe] is applied from the minus side. It is. FIG. 9B is a diagram showing MI characteristics c and d of the first and second MI elements 11 and 11 ^′ having different MI characteristics. In FIG. 9B, for simplicity of description, the MI characteristic is expressed only by the impedance change rate when the external magnetic field Hex [Oe] is applied from the plus side. FIG. 10A shows that ΔH [Oe] is obtained by applying a current to the negative feedback bias coils 13 and 13 ^′ in advance by the initial offset circuits 17 and 17 ^′ .
FIG. 3 shows a characteristic diagram in which the MI characteristic is shifted to be asymmetric. FIG.
0b is set to the negative feedback bias coil 1 in advance by the initial offset circuits 17, 17 ^' to the first and second MI elements 11, 11 ^' having different MI characteristics c, d, respectively.
A characteristic diagram is shown in which the MI characteristic is made asymmetric by passing a current through 3, 13 ^' . FIG. 11 is a diagram schematically showing a current sensor to which the control device 20 for the thin film MI elements 11, 11 ^{'according to} the present invention is applied. 12A and 12B are diagrams schematically illustrating an example of an electronic circuit of the current sensor according to the present invention by using blocks. Further, the relationship between the external magnetic field H _ex [Oe] -output voltage V _OUT [V] and the detected current value I _ex [A] − of the current sensor to which the control device 20 of the MI elements 11 and 11 ^{′ according} to the present invention is applied. The graph showing the relationship of the output voltage V _OUT [V] is the same as that of the first embodiment, and will be described with reference to the graphs of FIGS. 7A and 7B.

FIG. 11 shows a thin-film MI element 11, 11 to which a bias magnetic field _ΔH [Oe] is applied in the second embodiment according to the present invention so that magnetic fields generated by currents to be detected are in different directions. ^'is a current sensor which applies a control device 20, wherein the thin film MI elements 11, 11 using the MI element to obtain the applied skin effect current time ^varying' the structure of the current sensor which applies a control device 20 It is the figure which showed typically. Specifically, the first and second MI elements 11,
It is a principle diagram of current detection by 11 ^' . As shown in FIG. 9A, when using the first and second MI elements 11 and 11 ^′ whose voltage changes symmetrically with respect to the direction of the magnetic field, they are generated by the respective initial offset circuits 17 and 17 ^′ . The current is supplied to each of the negative feedback bias coils 13 and 1 in advance.
3 flowed to ^'keep asymmetrically shifted the MI characteristic [Delta] H [Oe] only as shown in Figure 10a. The external magnetic field generated by the current I _ex [A] flowing through the detected current bar 18 is represented by H
_ex [Oe], the first and second MI elements 11 and 11 ^′
Voltage changes. The voltages V ₁ and V ₂ are read from both ends of the MI elements 11 and 11 ^{′ by} the detection circuits 14 and 14 ^′ to generate currents I ₁ and I ₂ , respectively. H is supplied to the negative feedback bias coils 13, 13 ^' wound around the elements 11, 11 ^{' so} that the total magnetic field of each of the thin film MI elements 11, 11 ^' becomes zero.
By generating the _first and _{H 2,} always be equilibrium respectively _{I 1} and _{I 2.} (The respective bets -. The principle of the barrel magnetic field to zero is omitted because described in the first embodiment for each first and second thin film MI elements 1, 1 ^') each of an H ₁
And H ₂ are respectively detected by the detection elements 15 and 15 ^′ (resistors R ₁ ,
The current is output as a difference between one current output via the resistor R ₂ ). Each negative feedback bias coil 13, 13 ^' is disclosed in the main part of the MI element 11, 11 ^{' in} this figure. Further, an example of the electronic circuit at this time is schematically shown by blocks in FIGS. 12A and 12B.

Therefore, conventionally, ± number [O
e] could be detected only in the narrow magnetic field range,
As shown in FIG. 7A, a magnetic field balanced control device 20 that obtains a linear output voltage over a wide range of external magnetic field H _ex [Oe] was obtained. As a result, as shown in FIG. 7B, the sensitivity is higher than that of the Hall element, such as the detected current value _Iex [A] _-the output voltage V _OUT [V]. ) Can be detected, a low-cost and ultra-small current sensor can be obtained without using a magnetic core, and the process is not complicated. In addition, D
Without requiring C bias coil could be obtained asymmetric characteristic as shown in FIG. 10a, a negative feedback bias coil 13, 13 of respective ^'only a thin film MI elements 11, ^11'
V changed by the detection circuits 14, 14 ^' from both ends of the
Reads _1, V _2, to generate a current to be _{I 1,} I _2,
Thin film MI elements 11 and 11 is supplied to the ^"negative feedback bias coil 13, 13 each wound in ^'APPLICATION - Tal magnetic field to generate a H _{1, H 2} becomes zero, and always balance the I _{1, I 2} Let me. Next, the different MI characteristics c and d shown in FIG.
The control device 20 was verified with MI elements 11 and 11 ^′ having Although not described in detail because it has been described above, both the MI characteristic c shown by the solid line and the MI characteristic d shown by the dotted line are caused to flow in advance by the initial offset circuits 17 and 17 ^'in advance and shifted by ΔH [Oe] as shown in FIG. 10b. It has an asymmetric characteristic. The external magnetic field H _ex [Oe] −the output voltage V _OUT [V] of the control device 20 of the first and second MI elements 11 and 11 ^′ used for the current sensor even for different MI characteristics c and d.
And the detected current value I _ex [A] _−the output voltage V
It was verified that the graph showing the relationship of _OUT [V] was the same as in the first embodiment. In constituting the current sensor, as shown in FIG. 11, the first and second MI elements 11, 11 ^', energization current I _ex of the current to be detected bar -18
It is preferable to arrange the MI elements 11, 11 ^' to which the bias magnetic fields are applied in such a manner that the magnetic fields generated by [A] are opposite to each other so as to coincide with the direction of the best sensitivity of the MI elements 11 and 11 ^' and the direction of the external magnetic field. This is because the magnetic field generated by the energizing current is the external magnetic field of the first and second MI elements 11 and 11 ^' , and can be detected with the best sensitivity. Further, in the figure, the MI elements 11 and 11 ^′
8 are provided above and below the detected current bar -1.
It suffices if it is located at a position in a range where the magnetic field generated by 8 can be detected. However, it is preferable that they are provided at the same distance from the detected current bar 18 so as not to be affected by a disturbance magnetic field or temperature characteristics. Such an MI element 1
1, 11 ^' and an external magnetic field generated by the current flowing through the detected current bar 18, the first and second MI elements 1
1, 11 ^' are provided in opposite directions, and furthermore, in order to make the same distance from the current bar 18 to be detected, a heat-resistant and insulating resin molded member or ceramic is used to integrally form a U-shaped part. By making the shape fit into the detected current bar 18,
This makes it possible to further simplify the process and reduce the cost. By setting the external magnetic field to H _ex [Oe], the thin film M
The voltages of the I elements 11, 11 ^' change. Each of the thin film MI elements 11 and 11 ^′ has an applied external magnetic field H _ex [Oe].
Are opposite to each other, and a disturbance magnetic field due to terrestrial magnetism and transient current is cancelled. Further, the difference between the current outputs is detected as one current output, and is suitable as a current sensor for vehicles and the like.

Next, a third embodiment according to the present invention will be described with reference to the drawings.
Will be explained. FIG. 13 shows the magnetic properties of the soft magnetic thin film according to the present invention.
Crossed magnetic anisotropy stacked to cross the direction of gas anisotropy
Thin film MI element 21, 21^'FIG. 3 is a diagram showing the configuration of FIG.
FIG. 14A shows that an external magnetic field Hex [Oe] is applied from the plus side.
And when an external magnetic field Hex [Oe] is applied from the minus side
Cross-type magnetically anisotropic thin-film MI elements 21, 21^'MI
It is a figure showing a characteristic. FIG. 14b shows the difference in variation.
Crossed magnetically anisotropic thin film MI elements 21 ^'MI
The characteristics e and f are shown. FIG. 14b simplifies the description.
When an external magnetic field Hex [Oe] is applied from the plus side
FIG. 6 is a diagram showing MI characteristics of FIG. FIG. 15 shows a crossed magnetic anisotropic
Thin film MI element 21, 21^'Of the control device 30
FIG. 3 is a diagram schematically illustrating a structure of a current sensor. FIG.
a, FIG. 16b shows a crossed magnetic anisotropic thin film according to the present invention.
MI element 21, 21^'Current control using the control device 30 of FIG.
Diagram showing an example of an electronic circuit of a sensor
It is. In addition, the crossing used in the current sensor according to the present invention.
-Type magnetic anisotropic thin-film MI element 21, 21^'Control device 30
External magnetic field H_ex[Oe] −Output voltage V_OUT[V] relationship and
Detected current value I_ex[A] -Output voltage V_OUT[V] relation
Is the same as in the first embodiment,
This will be described with reference to the graphs of FIGS. 7A and 7B.

As shown in FIG. 13, the thin-film MI elements 21 and 21 have a structure in which the directions of the magnetic anisotropy of the soft magnetic thin film are crossed.
^' Indicates an Al ₂ O ₃ ceramic wafer (not shown),
Plating films of soft magnetic thin films such as CoFeNi and NiFe on substrates such as Si wafers and glass wafers, or FeCoSiB, CoZrNb, FeSiB, CoSi
A soft magnetic thin film such as an amorphous sputtered film such as B or a NiFe sputtered film is laminated so that the directions of magnetic anisotropy intersect.

FIG. 14A shows a cross-type thin-film MI element 21 or 21 ^′ that obtains a skin effect by applying a time-varying current.
As shown in FIG.
Not only there is an advantage that it is not necessary to use a C bias or an initial offset circuit, but also the detection sensitivity is very good. FIG. 15 is a principle diagram of current detection schematically showing the structure of a current sensor to which the control device 30 for the cross-type magnetic anisotropic thin film MI elements 21 and 21 ^{′ according to} the present invention is applied.

The cross-type MI elements 21 and 21 ^' utilizing the easy axis of magnetization of the soft magnetic thin film are not shown in the figure, but are provided at both ends with electrodes made of aluminum wire bonding, Au wire or the like, or lead wires formed by direct soldering. To 10 [MH
z] or more, and preferably a high-frequency current of 10 to 40 [MHz] is applied to both ends. The external magnetic field Hex [O
FIG. 14A shows the relationship between [e] and the impedance change rate [%]. As shown in FIG. 14A, when using a cross-type magnetically anisotropic thin-film MI element 21 in which the voltage changes asymmetrically with respect to the direction of the magnetic field, the MI characteristics are made asymmetric by a DC bias or an initial offset circuit. No need.

Referring to FIG. 15, the detected current bar
An external magnetic field generated by a current I _ex [A] flowing through the cross-type magnetic anisotropic thin-film MI element 2 is represented by H _ex [Oe].
The voltage at 1, 21 ^' changes. The above-described MI elements 1, 1
^The voltages V ₁ [V] and V ₂ [V] are read from the both ends of ^' ₁ by the detection circuits 24 and 24 ^' , respectively, and I ₁ [A] and I ₁ [A], respectively.
₂ [A] is generated, and the negative feedback bias coil 2 wound around the cross-type magnetic anisotropic thin film MI element 21, 21 ^′
Is supplied to the 3 and 23 ^', respectively bets - H ₁ barrel magnetic field is zero [Oe], to generate _{H 2} [Oe], respectively I ₁ [A], I
₂ Always balance [A]. This I ₁ [A], I
₂ [A] is output via the output detecting elements 25 and 25 ^′ (resistors R ₁ and R ₂ ) as the difference between the respective detected outputs as one current value. The cross-type magnetic anisotropic thin-film MI elements 21 and 21 ^' provided in a direction opposite to a magnetic field (hereinafter referred to as an external magnetic field) generated by the detected current bar 28 include a detected current bar made of a conductor such as a copper plate. Current I flowing through −28
_{When ex} [A] is supplied, an external magnetic field is generated.
The cross-type magnetic anisotropic thin film M is generated by the external magnetic field H _ex [Oe].
The respective voltages of the I elements 21 and 21 ^' change. Each of the cross-type magnetic anisotropic thin-film MI elements 21 and 21 ^′
The applied external magnetic field H _ex [Oe] is in the opposite direction,
The disturbance magnetic field due to the transient current is canceled. FIGS. 16A and 16B schematically show an example of an electronic circuit at this time by using blocks.

Therefore, in the conventional product, the magnetic field can be detected only in a narrow magnetic field range of ± several [Oe] as shown in FIG. 18, but the current I flowing through the current bar to be detected as shown in FIG. An external magnetic field H _ex generated by _ex can be used as a current sensor by obtaining a magnetic field balanced control device 30 that obtains a linear output voltage over a wide range of the detection magnetic field H _ex . Further, an asymmetric characteristic as shown in FIG. 14A can be obtained without the need for a DC bias coil and an initial offset circuit.
^'Only crossover anisotropy thin film MI elements 21, ^21' respectively of the voltage V from both ends by the detection circuit 24, 24 ^'of the
₁ [V] and V ₂ [V] are read, and I ₁ [A] and I ₂
A current that becomes [A] is generated. Next, the negative feedback bias coils 23, 2 wound around the respective MI elements 21, 21 ^'
3 ^'respective current is supplied to the respective bets - H ₁ barrel magnetic field is zero [Oe], generating monkey the H 2 _[Oe]. As described above, by using a magnetic field balanced type current sensor in which the magnetic field is always balanced by flowing I ₁ [A] and I ₂ [A], the output can be detected even in a region where the magnetic field is saturated. Furthermore, since a DC bias coil and an initial offset circuit are not required, the number of steps can be reduced and the cost can be reduced. Next, verification was performed by applying the MI device control device 30 as a current sensor to the crossed magnetic anisotropic thin film MI device having different MI characteristics e and f shown in FIG. 14B. Although not described in detail because it has been described above, the MI characteristic e shown by a solid line and the MI characteristic f shown by a dotted line are also asymmetrical characteristics. Even in this case, as shown in FIGS. 7A and 7B, the external magnetic field _Hex of the control device 30 of the MI elements 21 and 21 ^' used for the current sensor also has different MI characteristics e and f.
[Oe] -Output voltage V _OUT [V] relationship and detected current value I
_The graph showing the relationship between _ex [A] and output voltage V _OUT [V] shows that linear output is obtained over a wide range (physically infinite) of the external magnetic field _Hex just like the first embodiment. It can be verified that the same is true for the detected current value _Iex [A] _-output voltage _VOUT [V] even when the control device 30 is of the magnetic field equilibrium type and is applied to a current sensor. In configuring the current sensor as shown in FIG. 15, the MI elements 21 and 21 ^′
Is preferably arranged so that the direction of the magnetic field generated by the current flowing through the detected current bar 28 coincides with the direction of the maximum sensitivity of the MI elements 21 and 21 ^' . This is because the magnetic field generated by the energizing current becomes the external magnetic field of the MI elements 21 and 21 ^′ , so that the sensitivity is better. Although the MI elements 21 and 21 ^′ are provided above and below the detected current bar 28 in the figure, the MI elements 21 and 21 ^′ may be located in a position where a magnetic field generated by the detected current bar 28 can be detected. I just need. However, it is preferable that they are provided at the same distance from the detected current bar 28 so as not to be affected by a disturbance magnetic field or temperature characteristics.

The first and second MI elements 21 and 21 ^′ are provided in opposite directions with respect to such an external magnetic field generated by the current flowing through the MI elements 21 and 21 ^′ and the current bar 28 to be detected. In order to make the same distance from the detected current bar 28, a heat-resistant and insulating resin molded member or ceramic is used to fit a U-shaped part integrally into the detected current bar 28. By doing so, it is possible to further simplify the process and reduce the cost. Assuming that the external magnetic field is H _ex [Oe], the thin film MI element 2 is formed by H _ex [Oe].
The voltage at 1, 21 ^' changes. The external magnetic field H _ex [Oe] applied to each of the thin film MI elements 21 and 21 ^′ is in a direction opposite to each other, and a disturbance magnetic field due to terrestrial magnetism and a transient current is canceled. Further, the difference between the current outputs is detected as one current output, which is optimal as a current sensor for a vehicle or the like. It is self-evident that the coil is used with an insulative coating or the element is insulated and the coil is wound. Although not particularly shown, stabilizing the characteristics by using an initial offset circuit for the cross-type magnetic anisotropic thin film MI elements 21 and 21 ^' is also included in the present application. In this case, it is preferable to supply a current in advance by the initial offset and shift the current to the position of the maximum sensitivity.

Accordingly, the present invention has been verified with respect to a current sensor to which a control device provided with first and second MI elements in a direction opposite to a direction in which an external magnetic field generated by the above-described detected current is applied is applied. The control devices for the first and second MI elements used in the above-described current sensor in the above-described method always generate a magnetic field in which the total magnetic field is zero, thereby controlling the external magnetic field _Hex generated by the current bar to be detected. Even a magnetic field in a region where the voltage change is saturated can be detected linearly. This is a current sensor that can obtain linearity over a wide range of detected magnetic fields (physically infinite) in the same manner as the Hall element with ultra-high sensitivity compared to the Hall element, and without applying a bias magnetic field. Can also be achieved. Further, M
The output can be detected without being affected by variations in the MI characteristics of the I element. Further, by providing the first and second MI elements in a direction opposite to a direction in which an external magnetic field generated by the detected current is applied to these MI elements, a disturbance magnetic field due to terrestrial magnetism, a transient current, and the temperature of the MI element It has become possible to provide a current sensor suitable for vehicles without being affected by characteristics. It should be further noted that, in order to provide the above-described first and second MI elements above and below the detected current bar, a shape that can be fitted into the detected current bar in a U-shape is suitable for assembly. , So that the first and second M
An I element is provided. For example, the first and second MI elements are provided on a U-shaped molded article integrally formed of a heat-resistant and insulating plastic or a molded article integrally formed of an insulator such as ceramic to be detected. By incorporating it into the current bar, the process can be prevented from becoming complicated, and further cost reduction can be expected.

[0030]

As described above, according to the present invention, the external magnetic field in the direction opposite to the direction of the magnetic field due to the current to be detected can be obtained by using the control device for the MI element having any MI characteristics in the current sensor. Providing first and second applied magnetic impedance elements (hereinafter referred to as MI elements)
A magnetic field where the total magnetic field is always zero is generated,
By maintaining the equilibrium state at all times, linearity can be obtained over a wide range of the detected magnetic field (physically infinite) as in the case of the Hall element with ultra-high sensitivity. Further, similar effects can be achieved without applying a bias magnetic field. Also,
Since a magnetic core is not used, an ultra-small and low-cost current sensor can be obtained as compared with a current sensor using a ball element.

[Brief description of the drawings]

FIG. 1 shows first and second magnetic thin films MI using the MI effect in a first embodiment of a current sensor according to the present invention.
FIG. 3 is a diagram showing a configuration of an element.

FIG. 2A is a graph showing the MI when the external magnetic field is applied from the plus side and the MI when the external magnetic field is applied from the minus side to the first and second magnetic thin film MI elements in the first embodiment of the current sensor according to the present invention; It is a figure showing a characteristic.

FIG. 2B is a diagram illustrating a current sensor according to the first embodiment of the present invention in which an external magnetic field is applied from the plus side to first and second magnetic thin film MI elements having different characteristics.
It is a figure showing an I characteristic.

FIG. 3 shows a configuration diagram of first and second magnetic thin film MI elements when a bias magnetic field _Hb is applied in the first embodiment of the current sensor according to the present invention.

FIG. 4a is a characteristic diagram of the magnetic thin film MI element when a bias magnetic field _Hb is applied to the first and second magnetic thin film MI elements in the first embodiment of the current sensor according to the present invention.

FIG. 4B is a diagram illustrating a current sensor according to the first embodiment of the present invention in which a bias magnetic field _Hb is applied to a magnetic thin film MI element having different MI characteristics; It is a characteristic diagram.

FIG. 5 is a diagram schematically showing a current sensor to which a first and second magnetic thin film MI element control devices using a soft magnetic thin film are applied as a first embodiment of the current sensor according to the present invention. It is.

FIG. 6a is a block diagram of an example of an electronic circuit of a current sensor to which a first and second magnetic thin film MI element control devices using a soft magnetic thin film are applied as a first embodiment of the current sensor according to the present invention; FIG.

FIG. 6B is a block diagram showing an example of an electronic circuit of a current sensor to which a first and second magnetic thin film MI element control devices using a soft magnetic thin film are applied as a first embodiment of the current sensor according to the present invention; FIG.

FIG. 7A is a graph showing a relationship between an external magnetic field H _ex [Oe] and an output voltage V _OUT [V] of a control device of the first and second MI elements in the current sensor according to the present invention.

FIG. 7B is a diagram showing a detected current value I _ex [A] − of the control device of the first and second MI elements in the current sensor according to the present invention;
It is a graph which shows the relationship of output voltage V _OUT [V].

FIG. 8 shows first and second magnetic thin films MI using the MI effect in the second embodiment of the current sensor according to the present invention.
FIG. 3 is a diagram showing a configuration of an element.

FIG. 9A shows MI characteristics of the current sensor according to the second embodiment of the present invention when an external magnetic field is applied to the first and second magnetic thin film MI elements from the plus side and when an external magnetic field is applied from the minus side. FIG.

FIG. 9b is a diagram showing MI characteristics of first and second magnetic thin film MI elements having different characteristics in the second embodiment of the current sensor according to the present invention.

FIG. 10A is a diagram illustrating a current sensor according to a second embodiment of the present invention, in which a bias magnetic field _ΔH [Oe] is applied to a magnetic thin film MI element by an initial offset circuit; It is a characteristic diagram.

FIG. 10B is a diagram illustrating a current sensor according to a second embodiment of the present invention, in which a bias magnetic field _ΔH [Oe] is applied at initial offset to a magnetic thin film MI element having different MI characteristics. FIG. 4 is a characteristic diagram of the thin film MI element of FIG.

FIG. 11 is a diagram schematically showing a current sensor to which a control device for a first and second magnetic thin film MI element using a soft magnetic thin film in a second embodiment of the current sensor according to the present invention is applied. It is.

FIG. 12a shows an example of an electronic circuit of a current sensor to which a control device for a first and second magnetic thin film MI element using a soft magnetic thin film in a second embodiment of the current sensor according to the present invention is applied. FIG.

FIG. 12b shows an example of an electronic circuit of a current sensor to which the first and second magnetic thin film MI element control devices using the soft magnetic thin film in the second embodiment of the current sensor according to the present invention are applied. FIG.

FIG. 13 shows the configuration of first and second crossed magnetic thin film MI elements stacked so as to intersect the direction of the magnetic anisotropy of the soft magnetic thin film in the third embodiment of the current sensor according to the present invention. FIG.

FIG. 14A is a diagram illustrating a current sensor according to a third embodiment of the present invention, which is added to the first and second crossed magnetic thin film MI elements stacked so as to intersect the direction of the magnetic anisotropy of the soft magnetic thin film. FIG. 7 is a diagram showing MI characteristics when an external magnetic field is applied from the side and when an external magnetic field is applied from the minus side.

FIG. 14b shows characteristics of a current sensor according to a third embodiment of the present invention when an external magnetic field is applied from the plus side to first and second crossed magnetic thin film MI elements having different MI characteristics. FIG.

FIG. 15 shows a third embodiment of a current sensor according to the present invention, in which a control device for a first and second cross-type magnetic thin film MI element laminated so as to cross the magnetic anisotropy of a soft magnetic thin film is applied. FIG. 3 is a diagram schematically illustrating a current sensor that has been used.

FIG. 16a is a diagram schematically showing, in a block diagram, an electronic circuit of a current sensor to which a first and second cross-type magnetic thin film MI element control devices in a third embodiment of the current sensor according to the present invention are applied. This is an example.

FIG. 16b is a diagram schematically showing, in a block diagram, an electronic circuit of a current sensor to which a first and second cross-type magnetic thin film MI element control devices in a third embodiment of the current sensor according to the present invention are applied. This is an example.

FIG. 17 is a block diagram showing an electronic circuit of a conventional MI element control device.

FIG. 18 shows an external magnetic field H by a conventional MI element control device.
FIG. 6 is a diagram showing _ex -output (voltage) V _OUT characteristics.

FIG. 19 is a diagram showing a simplified structure of a current sensor using a conventional ball element.

[Explanation of symbols]

1, 11, 21 ... first MI element 1 ^' , 11 ^' , 21 ^' , ... second MI element 2, 2 ^' , ... DC bias coil 3, 3 ^' , 13, 13 ^' , 23, 23 ^' ... negative feedback bias coil 4, 4 ^', 14, ^14', 24, 24 ^'... detection circuits 5 and ^5', 15, 15 ^', 25, ^25' ... output detection element (resistor R _1, resistor _R 2) 6, 6 ^' , 16, 16 ^' , 26, 26 ^' ... output 8, 18, 28 ... conductive substrate for detected current (detected current bar) 10, 20, 30 ... MI element control device 17, 17 ^'... initial offset circuit H _b ... bias field H _ex ... external magnetic field I _1, I 2 _... negative feedback current (balanced current) I _ex · · · the current to be detected bar - applied current H ₁ of, _{H 2} ... Equilibrium magnetic field where the total magnetic field with the external magnetic field becomes zero (negative feedback magnetic field)

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Masaaki Hatsumi 1-3-1 Edanishi, Aoba-ku, Yokohama-shi, Kanagawa Prefecture Inside Stanley Electric Co., Ltd. Yokohama Technical Center (72) Inventor Chihiro Funaoka Eda, Aoba-ku, Yokohama-shi, Kanagawa 1-3-1 Nishi, Stanley Electric Co., Ltd. Technical Research Institute (72) Inventor Katsura Tsukada 1-3-1 Edanishi, Aoba-ku, Yokohama-shi, Kanagawa Prefecture Stanley Electric Co., Ltd. Technical Research Institute (72) Inventor Hiroyuki Sano Yokohama, Kanagawa Prefecture 1-3-1 Eda Nishi, Aoba-ku, Tokyo Stanley Electric Co., Ltd. (72) Inventor Hiroo Yokoyama 1-3-1 Eda Nishi, Aoba-ku, Aoba-ku, Yokohama-shi, Kanagawa Pref. Stanley Electric Co., Ltd. (72) Inventor Iritono Kimihiro 1-33-1 Edanishi, Aoba-ku, Yokohama-shi, Kanagawa Prefecture Stanley Electric Co., Ltd. Technology Research house F-term (reference) 2G017 AA01 AB01 AB02 AB05 AC02 AC04 AC09 AD51 AD53 AD65 BA02 BA03 BA05 2G025 AA05 AA09 AA11 AA13 AB01

Claims (9)

[Claims] A means for providing first and second magnetic impedance elements (hereinafter referred to as MI elements) such that one direction is opposite to the direction of a magnetic field due to a current to be detected; A DC bias coil and a negative feedback bias coil are respectively wound around the MI element, and both ends of the first and second MI elements are connected to the respective negative feedback bias coils via detection circuits, respectively. A current sensor, wherein a terminal of a coil is connected to one end of each output detection element, an output is detected at both ends of each output detection element, and each detection output is made into one current output. . 2. A means for providing first and second magnetic impedance elements (hereinafter referred to as MI elements) so that one direction is opposite to the direction of a magnetic field due to a current to be detected; A negative feedback bias coil is wound around each of the MI elements, and both ends of the first and second MI elements are respectively wound around the first and second MI elements via respective detection circuits and initial offset circuits. , The ends of the negative feedback bias coils are respectively connected to one ends of output detection elements, outputs are detected at both ends of each output detection element, and the respective detection outputs are connected to one end. A current sensor having two current outputs. 3. Means for providing first and second magnetic impedance elements (hereinafter referred to as MI elements) so that one direction is opposite to the direction of a magnetic field due to a current to be detected; Through both detection circuits from both ends of the MI element,
Each of the negative feedback bias coils wound around the first and second MI elements is connected, and the terminal of each negative feedback bias is connected to one end of an output detection element, and both ends of the output detection element are connected. A current output, wherein each of the detected outputs is a current output. 4. The current sensor according to claim 1, wherein said one current output is a difference between said respective detection outputs detected at both ends of said respective output detecting elements. 5. The first and second MI elements read a voltage between both ends of the MI element, which is changed by an external magnetic field, by the detection circuit to generate a current, supply the current to the negative feedback bias coil, and supply a total magnetic field to the negative feedback bias coil. The current sensor according to claim 1, wherein a magnetic field in which is zero is generated to balance the current. 6. The detection current is passed through a detection current substrate formed of a conductor, and the first and second MI elements are
The current sensor according to claim 1, wherein the current sensor is provided on both surfaces of the conductive substrate for the current to be detected. 7. The current sensor according to claim 1, wherein the first and second MI elements have symmetric MI characteristics. 8. The current sensor according to claim 3, wherein the first and second MI elements have asymmetric MI characteristics. 9. The method according to claim 1, wherein said means for providing said first and second MI elements is formed in a U-shape by an insulating resin molding member. Current sensor.