JP2010139257A - Orthogonal flux gate sensor, and detecting method of external magnetic field - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an orthogonal flux gate sensor capable of acquiring excellent linearity without using a feedback circuit. <P>SOLUTION: A pulse electric source 8 including a waveform generation circuit for supplying a pulse current to a magnetosensitive body 1 whose magnetic characteristic is changed by an external magnetic field supplies two or more rectangular pulse currents continuously to the magnetosensitive body 1. The pulse currents supplied from the pulse electric source (pulse generation circuit) 8 flow into the magnetosensitive body 1 through a first electrode pad 3 and a first connection wire 2. Then, an induced voltage is detected, which is generated by rise of a second or subsequent pulse current output through a second connection wire 5 and a second electrode pad 6 from a detection coil 4 positioned on the periphery or in the vicinity of the magnetosensitive body 1, for inducing a change of the magnetic characteristic of the magnetosensitive body 1 as a voltage change. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an orthogonal fluxgate sensor and an external magnetic field detection method using the same, and more particularly to a technology that improves an orthogonal fluxgate sensor and an external magnetic field detection method so as to have good linearity. is there.

  An orthogonal fluxgate sensor is known as a sensor that detects a minute magnetic field with high accuracy. In recent years, the orthogonal flux gate sensor has been miniaturized to be mounted on a mobile device. For example, a thin and small orthogonal flux gate sensor composed of a magnetic thin film that is a magnetosensitive material and a planar coil has been proposed (for example, Patent Documents 1 and 2). In addition, means using an MI element as an orthogonal fluxgate sensor has been proposed (see, for example, Patent Document 3).

  In these sensors, when a pulse current is applied to a magnetic thin film or a magnetic wire which is a magnetic sensitive part, a voltage is induced in the planar coil along with the rising and falling parts of the pulse. Since this induced voltage increases or decreases in proportion to the external magnetic field, the external magnetic field can be detected using the induced voltage as a sensor output. In these sensors, the pulse shape and detection timing are not specified.

  FIG. 4 shows an example of an orthogonal fluxgate sensor, and the measurement principle will be described. An orthogonal fluxgate sensor 20 shown in FIG. 4 includes a magnetosensitive body 1 and a detection coil 4. A pulse current is supplied to the magnetosensitive body 1 from a pulse power source 18 connected through the first electrode pads 3a and 3b and the first connection wirings 2a and 2b. When a pulse current is supplied to the magnetosensitive body 1, a voltage is induced in the detection coil 4, and this induced voltage has a voltage waveform generated by the oscilloscope 19 connected through the second electrode pads 6 a and 6 b and the second connection wires 5 a and 5 b. It is configured to be measured.

In FIG. 4, the magnetic sensitive body 1 is composed of two soft magnetic bodies 1A and 1B, and the detection coil 4 is composed of two planar spiral coils 4a and 4b. 5A shows the waveform of the pulse current supplied from the pulse power supply 18, and FIG. 5B shows the waveform of the voltage induced in the detection coil 4. As shown in FIG. In such orthogonal fluxgate sensor 20, the peak value V ₀ which is a voltage waveform WP, which corresponds to the rising waveform of the pulse current supplied to the measurement, based on a magnetic field applied to the magnetic sensitive member 1 to the peak value V ₀ To detect.

However, the conventional small orthogonal fluxgate sensor is not sufficiently linear as a sensor, and it is necessary to use a feedback circuit. However, when the feedback circuit is used, not only the circuit configuration becomes complicated, but also the sensor element needs to be separately wound with a coil for applying a negative feedback magnetic field, which causes a problem that the sensor becomes large.
JP 2006-201123 A JP 2003-004831 A Japanese Patent No. 3645116

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a small orthogonal fluxgate sensor that can obtain good linearity without using a feedback circuit.
It is another object of the present invention to provide an external magnetic field detection method capable of improving the linearity of an external magnetic field detected by an orthogonal fluxgate sensor.

  The inventor diligently studied the dependence of the driving current shape and the induced voltage on the external magnetic field when the orthogonal fluxgate sensor was driven by a pulse current, and the inventors obtained the following knowledge from the obtained knowledge.

  That is, the orthogonal fluxgate sensor according to claim 1 of the present invention is supplied from a magnetosensitive body whose magnetic characteristics are changed by an external magnetic field, a waveform generating circuit that supplies a pulse current to the magnetosensitive body, and the waveform generating circuit. A first electrode pad for causing a pulse current to flow through the magnetic sensitive body, a first connection wiring for connecting the magnetic sensitive body and the first electrode pad, and the magnetic sensitive body around or near the magnetic sensitive body. A detection coil that induces a change in magnetic characteristics as a change in voltage, a second electrode pad for extracting an induced voltage from the detection coil, and a second connection that connects between the detection coil and the second electrode pad In the orthogonal fluxgate sensor including at least a wiring, the waveform generation circuit supplies two or more rectangular pulse currents to the magnetosensitive body in succession, and the second electrode pad. And detecting an induced voltage due to the rise of al outputted second and subsequent pulse current.

  The orthogonal fluxgate sensor according to a second aspect of the present invention is the orthogonal fluxgate sensor according to the first aspect, wherein the second electrode pad detects the induced voltage due to a rise of the second and subsequent pulse currents. It is connected to a circuit.

  An orthogonal fluxgate sensor according to a third aspect of the present invention is the orthogonal fluxgate sensor according to the first or second aspect, wherein the waveform generation circuit is configured to perform a period from a trailing edge of a preceding pulse to a trailing edge of a subsequent pulse. The pulse current is supplied at intervals of 500 nsec or less.

  The quadrature fluxgate sensor according to claim 4 of the present invention is the quadrature fluxgate sensor according to claim 3, wherein the waveform generation circuit takes a time from the trailing edge of the previous pulse to the leading edge of the subsequent pulse. The pulse current is supplied at an interval of 100 nsec or less.

  An external magnetic field detection method using the orthogonal fluxgate sensor according to claim 5 of the present invention includes a magnetosensitive body whose magnetic characteristics are changed by an external magnetic field, a waveform generating circuit for supplying a pulse current to the magnetosensitive body, A first electrode pad for passing a pulse current supplied from the waveform generating circuit to the magnetic body, a first connection wiring connecting the magnetic body and the first electrode pad, and a periphery of the magnetic body Or a detection coil that is in the vicinity and induces a change in magnetic characteristics of the magnetosensitive body as a change in voltage; a second electrode pad for extracting an induced voltage from the detection coil; and the detection coil and the second electrode pad, In the method of detecting an external magnetic field using a second connection wiring that connects between each other and at least an orthogonal fluxgate sensor provided, a rectangular path is used as the orthogonal fluxgate sensor. In this case, a current that is supplied to the magnetosensitive body from the waveform generating circuit in succession by two or more currents is output from the second electrode pad. The external magnetic field is detected based on the induced voltage.

The orthogonal fluxgate sensor according to the present invention continuously supplies two or more rectangular pulse currents to the magnetic sensitive body, and detects an induced voltage due to the rise of the second and subsequent pulse currents output from the second electrode pad. The second electrode pad is for taking out an induced voltage from a detection coil that induces a change in magnetic characteristics of the magnetic sensitive body as a change in voltage. Therefore, by using the induced voltage due to the rise of the second and subsequent pulse currents, the peak value of the voltage waveform corresponding to the stable induced voltage can be measured without variation in output, and applied to the magnetosensitive body based on this peak value. The detected magnetic field can be detected.
Therefore, it is possible to provide a small orthogonal fluxgate sensor that can obtain good linearity without using a feedback circuit.

The external magnetic field detection method according to the present invention uses the orthogonal fluxgate sensor of the present invention described above, supplies two or more rectangular pulse currents continuously to the magnetic sensitive body from the waveform generation circuit, and outputs 2 from the detection coil. An induced voltage due to the rise of the pulse current after the first is output from the second electrode pad, and an external magnetic field is detected based on this induced voltage. Therefore, by using the orthogonal fluxgate sensor according to the present invention, the peak value of the voltage waveform corresponding to the induced voltage caused by the rising of the second and subsequent pulse currents with stable output is measured, and the external magnetic field is measured based on the peak value. Can be detected.
Therefore, it is possible to provide an external magnetic field detection method capable of improving the linearity of the external magnetic field detected by the orthogonal fluxgate sensor.

Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a schematic diagram illustrating an example of an orthogonal fluxgate sensor according to the present invention. FIG. 1A is a plan view of an orthogonal fluxgate sensor, and FIG. 1B is a cross-sectional view taken along the line AA in FIG.
As shown in FIG. 1, the orthogonal fluxgate sensor 10 according to the present embodiment includes a magnetic sensitive body 1 and a detection coil 4.

The magnetic sensitive body 1 is made of a material whose magnetic characteristics are changed by an external magnetic field. As such a magnetic sensitive body 1, for example, a conductive linear, strip-shaped, or rod-shaped soft magnetic element can be used. In the present embodiment, the magnetic sensitive body 1 is composed of two soft magnetic bodies 1A and 1B. Further, the magnetosensitive body 1 is a meander-shaped thin film magnetic body in which one ends 1Aa and 1Ba of two soft magnetic bodies 1A and 1B are electrically connected to each other by a connecting conductor 7.
A pulse current is supplied to the magnetosensitive body 1 from a pulse power source 8 connected through the first electrode pad 3 and the first connection wiring 2.

  The pulse power supply 8 includes a waveform generation circuit. This waveform generation circuit is a pulse generation circuit that supplies a pulse current to the magnetic body 1 and supplies two or more rectangular pulse currents to the magnetic body 1 in succession.

  The first electrode pad 3 is a part for allowing a pulse current supplied from a pulse power supply (waveform generation circuit) 8 to flow through the magnetic sensitive body 1 and is composed of a GND terminal 3a and a signal terminal 3b. The first electrode pad 3 is preferably made of a nonmagnetic metal such as copper (Cu) or aluminum (Al).

  The first connection wiring 2 is a nonmagnetic conductor that electrically connects between the magnetic sensitive body 1 and the first electrode pad 3, and is a connection that connects the other end 1Ab of the soft magnetic body 1A and the GND terminal 3a. The wiring 2a includes a connection wiring 2b that connects the other end 1Bb of the soft magnetic body 1B and the signal terminal 3b. The first connection wiring 2 (2a, 2b) is preferably made of a nonmagnetic metal such as copper (Cu) or aluminum (Al).

  The detection coil 4 is around or in the vicinity of the magnetic sensitive body 1 and induces a change in the magnetic characteristics of the magnetic sensitive body 1 as a change in voltage. The detection coil 4 is composed of two planar spiral coils 4a and 4b. The detection coil 4 (4a, 4b) is not particularly limited, and the same one as that used in a conventional fluxgate sensor can be used. The detection coil 4 shown in FIG. 1 is formed by connecting two planar spiral coils 4 a and 4 b wound in a rectangular shape in series, and is arranged (in the vicinity) on the upper or lower layer of the magnetic sensitive body 1. In addition, a coil wound around the magnetic sensitive body 1 can also be used. From the viewpoint of thinning the sensor, a planar spiral coil is desirable. The winding direction when two planar spiral coils 4a and 4b wound in a rectangular shape are connected in series is “the winding direction in which the current direction is opposite” or “when viewed from one side of the coil. A winding direction in which the direction from the inner peripheral end toward the outer peripheral end is reversed may be used.

  As shown in FIG. 1A, in the present embodiment, two soft magnetic bodies 1A and 1B have one end 1Aa and 1Ba located at the center of one spiral coil 4a and the other end 1Ab and 1Bb. Are located at the center of the other spiral coil 4b.

  The second electrode pad 6 is a part for taking out an induced voltage from the detection coil 4, and is composed of a GND terminal 6a and a signal terminal 6b. The second electrode pad 6 (6a, 6b) outputs a voltage (induced voltage) induced by the detection coil 4 at all rising and falling edges of the current pulse. The second electrode pad 6 is preferably made of a nonmagnetic metal such as copper (Cu) or aluminum (Al).

  The second connection wiring 5 is a nonmagnetic conductor that connects between the detection coil 4 (4a, 4b) and the second electrode pad 6 (6a, 6b), and includes a planar spiral coil 4a, a GND terminal 6a, and the like. This second connection wiring 5 comprising a connection wiring 5a for connecting the flat spiral coil 4b and the signal terminal 6b is made of a nonmagnetic metal such as copper (Cu) or aluminum (Al). It is preferable to become.

  In the orthogonal fluxgate sensor 10 according to the present invention, the second electrode pad 6 (6a, 6b) is connected to an oscilloscope 9 including a measurement circuit. This measurement circuit detects only the second and subsequent rising edges of the induced voltage output from the second electrode pad 6 (6a, 6b). Note that detecting only the second and subsequent rising edges may be detecting the second rising edge, detecting the third rising edge, or detecting the subsequent rising edges. It may be.

  Therefore, when a pulse current is supplied from the pulse power supply 8 to the magnetic sensitive body 1 (1A, 1B), a voltage is induced in the detection coil 4 (4a, 4b), and this induced voltage is generated by the second electrode pad 6 (6a, 6b). ) And the oscilloscope 9 connected through the second connection wiring 5 (5a, 5b).

The orthogonal fluxgate sensor 10 of this Embodiment is comprised as a thin sensor formed on the board | substrate 11, as shown in FIG.1 (b).
As the substrate 11, for example, a silicon (Si) substrate with an oxide film can be used as the base insulating layer 12, and a nonmagnetic substrate such as a glass substrate or a ceramic substrate can be used.

  Further, the orthogonal fluxgate sensor 10 according to the present embodiment is provided between the magnetic sensor 1 (1A, 1B) and the detection coil 4 (4a, 4b) or other conductors (2a, 2b, 3a, 3b, 5a, 5b, 6a, 6b) is provided. As the interlayer insulating layer 13, one or two or more kinds of materials can be appropriately selected and used. For example, an oxide film such as a silicon oxide film by a plasma CVD method, an organic insulating film such as a resin, etc. Can be configured.

Further, the sealing insulating layer 14 may be provided on the detection coil 4 (4a, 4b). The sealing insulating layer 14 can be composed of an insulating film similar to or different from the interlayer insulating layer 13.
In the present embodiment, the interlayer insulating layer 13 has an opening 15 exposing the first electrode pad 3 (3a, 3b) and the second electrode pad 6 (6a, 6b). It has the opening part 16 which exposes the 1st electrode pad 3 (3a, 3b) and the 2nd electrode pad 6 (6a, 6b).

  When the external magnetic field is detected using the orthogonal fluxgate sensor 10 configured as described above, two or more rectangular pulse currents are continuously supplied to the magnetic sensitive body 1 (1A, 1B). Then, the magnetic field applied to the magnetosensitive body 1 (1A, 1B) is detected based on the induced voltage caused by the rise of the second and subsequent pulse currents output from the detection coil 4 (4a, 4b). That is, when two or more pulse currents are continuously supplied from the pulse power supply 8 to the magnetic sensitive body 1 (1A, 1B), a voltage is induced in the detection coil 4 (4a, 4b), and the oscilloscope 9 A voltage waveform is measured.

As shown in FIG. 2, detection of the external magnetic field by the orthogonal fluxgate sensor 10 of the present embodiment is performed by supplying two or more rectangular pulse currents to the magnetosensitive body 1 in succession and rising of the second and subsequent pulse currents. The peak value of the voltage waveform corresponding to the induced voltage is measured, and the magnetic field applied to the magnetosensitive body is detected based on the peak value. FIG. 2A shows the waveform of the pulse current supplied from the pulse power supply 8, and FIG. 2B shows the waveform of the voltage induced in the detection coil 4 (4a, 4b). In FIG. 2B, the peak value V ₀ of the voltage waveform WP corresponding to the second rising waveform is measured, and the magnetic field applied to the magnetic sensitive body 1 (1A, 1B) is detected based on the peak value V _0. It has become a thing.

  In the orthogonal fluxgate sensor 10 of the present embodiment, when two or more rectangular pulse currents are continuously supplied to the magnetic sensitive body 1, the time from the successive falling of the previous pulse to the rising of the subsequent pulse is predetermined. The pulse current is supplied so that the interval is equal to or less than the time t. As this predetermined time t, an interval of 500 nsec or less is preferable, and an interval of 100 nsec or less is desirable.

  The orthogonal fluxgate sensor 10 detects the peak value of the induced voltage induced in the detection coil 4 in synchronization with the rising waveform of the pulse current when the pulse current is supplied to the magnetosensitive body 1. At the same time, it has a function of holding each peak value. As a method of performing control in synchronization with the rising waveform and falling waveform of the pulse current, the current value of the pulse current is time-differentiated, the differential value is compared with a predetermined threshold value, and the differential value becomes a positive positive value or more. Is detected as the rising edge of the pulse. On the other hand, there is a method of detecting when the differential value is equal to or more than a predetermined negative value as the falling edge of the pulse. Since the rising and falling of the pulse current are steep, there is an advantage that detection in this integrated circuit (IC) becomes easy.

Next, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the following examples unless it exceeds the gist.
First, an orthogonal fluxgate sensor 10 having the structure shown in FIG. 1 was manufactured. The magnetic body 1 is formed by combining two magnetic elements 1A and 1B having a line / space (L / S) of 30 μm / 20 μm, a magnetic film thickness of 1 μm, and a length of 300 μm by combining sputtering and etching. (Amorphous). The detection coil 4 is composed of conductor layers 4a and 4b formed in a spiral shape by a copper (Cu) plating method, and has a line / space (L / S) of 8 μm / 8 μm. The thickness is 5 μm. The first electrode pad 3 was connected to a pulse power supply 8 having a waveform generation circuit as a pulse generation circuit, with one electrode pad 3a serving as a pulse GND terminal and the other electrode pad 3b serving as a pulse signal terminal. The second electrode pad 6 was connected to an oscilloscope 9 having a measurement circuit with one electrode pad 6a as an output GND terminal and the other electrode pad 6b as an output signal terminal. The substrate 11 was a glass substrate, the base insulating layer 12 was an SiO film, and the interlayer insulating layer 13 and the sealing insulating layer 14 were resin films made of polyimide (PI).

<Example 1>
A pulse current having a current value of 0 to 100 mA, a rise time of 3 nsec, a pulse width of 50 nsec, and a fall time of 3 nsec is applied to the magnetosensitive body of the orthogonal fluxgate sensor configured as described above from the trailing edge of the previous pulse. Two pulses were continuously supplied at intervals of 200 nsec until the rise of the pulse, and the output voltage was measured with an oscilloscope. The pulse period is 5 μsec. In the oscilloscope, the external magnetic field was detected based on the induced voltage caused by the rising of the second and subsequent pulse currents, and the linearity was found to be 1.2% fs. Here, fs means “full scale”.

<Comparative example>
As a control, one pulse current having a current value of 0 to 100 mA, a rising time of 3 nsec, a pulse width of 50 nsec, and a falling time of 3 nsec is supplied to the magnetosensitive body of the orthogonal fluxgate sensor configured as described above, and the output voltage Was measured with an oscilloscope. The pulse period is 5 μsec. In the oscilloscope, the external magnetic field was detected based on the induced voltage due to the rise of the pulse current, and the linearity was found to be 6.5% fs.

  From the above measurement results, the linearity of the external magnetic field detected based on the induced voltage due to one pulse current was 6.5% fs. However, in the orthogonal fluxgate sensor according to the present invention, the linearity is 1. It can be seen that the linearity of the detected external magnetic field is improved by 2% fs. Therefore, sensor characteristics with good linearity and reduced hysteresis could be obtained.

<Example 2>
Further, a pulse current having a current value of 0 to 100 mA and a pulse width of 50 nsec is applied to the magnetic flux sensor of the orthogonal fluxgate sensor similarly configured, and the time from the trailing edge of the previous pulse to the rising edge of the subsequent pulse is 50 nsec. , 250 nsec, 400 nsec, 1000 nsec, and 5000 nsec were supplied in succession, and the output voltage was measured with an oscilloscope. In the oscilloscope, the external magnetic field was detected based on the induced voltage caused by the rise of the second and subsequent pulse currents, and the linearity thereof was obtained. The result is shown in the graph of FIG.

  From the above measurement results, in the orthogonal fluxgate sensor according to the present invention, the linearity is improved when the pulse current is supplied at intervals of 500 nsec or less from the trailing edge of the preceding pulse to the rising edge of the subsequent pulse. In addition, it has been found that when the pulse current is supplied at an interval of 100 nsec or less, the linearity is remarkably improved.

  INDUSTRIAL APPLICABILITY The present invention can be suitably used as a high-sensitivity and small-sized various magnetic sensor as an orthogonal fluxgate type magnetic sensor.

It is the schematic which shows an example of the orthogonal fluxgate sensor which concerns on this invention. It is a figure which shows the relationship between the rectangular pulse current applied to a magnetic body by the orthogonal fluxgate sensor which concerns on this invention, and the induced voltage waveform output. It is a figure which shows the relationship between the space | interval of the rectangular pulse current supplied with the orthogonal fluxgate sensor which concerns on this invention, and linearity. It is the schematic which shows an example of the conventional orthogonal fluxgate sensor. It is a figure which shows the relationship between the rectangular pulse current applied to a magnetic sensitive body with the conventional orthogonal fluxgate sensor, and the induced voltage waveform output.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Magnetosensitive body, 2 1st connection wiring, 3 1st electrode pad, 4 detection coil, 5 2nd connection wiring, 6 2nd electrode pad, 7 connection conductor, 8 pulse power supply (waveform generation circuit), 9 oscilloscope (measurement circuit) ) 10 orthogonal fluxgate sensor, 11 substrate, 12 base insulating layer, 13 interlayer insulating layer, 14 sealing insulating layer, 15, 16 openings.

Claims (5)

A magnetic body whose magnetic properties change due to an external magnetic field;
A waveform generating circuit for supplying a pulse current to the magnetic sensitive body;
A first electrode pad for passing a pulse current supplied from the waveform generating circuit to the magnetosensitive body;
A first connection wiring for connecting between the magnetic sensitive body and the first electrode pad;
A detection coil that is around or near the magnetic sensitive body and induces a change in magnetic properties of the magnetic sensitive body as a voltage change;
A second electrode pad for extracting an induced voltage from the detection coil;
A second connection wiring connecting between the detection coil and the second electrode pad;
In an orthogonal fluxgate sensor comprising at least
The waveform generation circuit continuously supplies two or more rectangular pulse currents to the magnetosensitive body,
Detecting an induced voltage due to a rise of the second and subsequent pulse currents output from the second electrode pad;
An orthogonal fluxgate sensor characterized by that. The second electrode pad is connected to a measurement circuit that detects the induced voltage due to rising of the second and subsequent pulse currents.
The orthogonal fluxgate sensor according to claim 1. The waveform generation circuit supplies the pulse current at intervals of 500 nsec or less from the trailing edge of the previous pulse to the rising edge of the subsequent pulse.
The orthogonal fluxgate sensor according to claim 1 or 2, characterized in that. The waveform generation circuit supplies the pulse current at intervals of 100 nsec or less from the trailing edge of the preceding pulse to the rising edge of the subsequent pulse.
The orthogonal fluxgate sensor according to claim 3. A magnetic sensing element whose magnetic characteristics are changed by an external magnetic field, a waveform generating circuit for supplying a pulse current to the magnetic sensing element, a first electrode pad for flowing the pulse current supplied from the waveform generating circuit to the magnetic sensing element, A first connection wiring that connects between the magnetic sensitive body and the first electrode pad, a detection coil that is around or near the magnetic sensitive body and induces a change in magnetic characteristics of the magnetic sensitive body as a voltage change, A second electrode pad for extracting an induced voltage from the detection coil, a second connection wiring connecting the detection coil and the second electrode pad, and an external magnetic field using at least an orthogonal fluxgate sensor. In the detection method,
As the orthogonal fluxgate sensor, two or more rectangular pulse currents are continuously supplied to the magnetic sensitive body from the waveform generating circuit,
An induced voltage due to the rise of the second and subsequent pulse currents output from the detection coil is output from the second electrode pad, and an external magnetic field is detected based on the induced voltage.
An external magnetic field detection method using an orthogonal fluxgate sensor.

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