JP2003149309A - Multi-channel magnetic detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce cost and power consumption of a multi-channel magnetic detector using a plurality of elements having a magnetic impedance (MI) effect. SOLUTION: The detector comprises MI elements 1a and 1b having a magnetic impedance effect; alternating current supply means 3, 4a, 4b, 5a and 5b for applying alternating current to the elements; supply means 13a and 14a for supplying bias current to bias coils 2a and 2b; detection means 6a and 6b for detecting the peak of voltage change in response to the impedance change of the MI elements 1a and 1b; switches 7a and 7b; holding means 8a; and amplifying means 11a. The detector can detect each channel (each MI element) by selectively operating switches 4a, 4b, 7a, 7b and 14a, thereby reducing power consumption and cost.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement of a magnetic detection element utilizing a magnetic impedance (MI) effect, and more particularly to a multi-channel type magnetic detection device using a plurality of such magnetic detection elements.

[0002]

2. Description of the Related Art Hall elements and magnetoresistive elements have hitherto been widely used as magnetic detection devices, but one of them is still unsatisfactory in terms of detection sensitivity. Therefore, as a high-sensitivity magnetic detection element replacing a Hall element or a magnetoresistive element, for example, a magneto-impedance element using an amorphous wire disclosed in Japanese Patent Laid-Open No. 06-281712 or Japanese Patent Laid-Open No. 08-075835 is disclosed. Thin film-shaped ones have been proposed.

However, no matter which shape of the magneto-impedance element is used, in principle, the magneto-impedance element generates a magneto-impedance effect, so that it is necessary to apply a high-frequency current of at least several MHz to several mA. Therefore, there is a problem that the power consumption increases and it becomes difficult to apply it to portable devices and the like.

[0004]

Further, it is desired to obtain a plurality of magnetic information by arranging a plurality of magnetic detection elements and providing multi-channels with the recent increase in accuracy of information equipment and measurement / control equipment. Although there is a demand for this, there is a problem that the component cost increases in accordance with the number of installed elements.

FIG. 12 shows a conventional example using a magneto-impedance element.

This is an example in which the oscillating circuit 3'and the bias current applying means 13a 'are made common, but a current of several mA and a bias current of 10 mA are constantly applied to the magnetic detecting elements 1a and 1b. Therefore, the power consumption increases in proportion to the number of elements. Further, the detecting means 6a ', 6b'
, Holding means 8a ', 8b', amplification means 11a ', 11
Since b'is required for the number of elements, the circuit scale increases and the component cost also increases.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a multi-channel type magnetic detection device with low power consumption and low cost.

[0008]

In order to solve such a problem, according to the invention of claim 1, a plurality of magnetic detecting elements having a magnetic impedance effect, and one oscillating means and a magnetic detecting element are provided. AC current supply means comprising one switch and a first current applying means for applying an AC current to the magnetic detection element via the first switch, a bias coil wound around the magnetic detection element, and a third coil. Bias current supply means comprising a switch and a second current application means for supplying a current to each of the bias coils via the third switch; and a bias current supply means provided corresponding to the magnetic detection element for converting respective impedance changes into voltages. A detection means for passing the peak of the voltage, a second switch provided corresponding to each of the detection means and selecting its output, Holding means for holding the output of the the said detection means, and a amplifying means for amplifying the held voltage, by selective operation of the first to third switches,
The feature is that magnetic detection is enabled for each channel.

According to a second aspect of the present invention, a plurality of magnetic detection elements having a magnetic impedance effect, a first switch and a first switch provided corresponding to one oscillating means and the magnetic detection element.
AC current supply means for applying an alternating current to the magnetic detection element via the first switch, a bias coil wound around the magnetic detection element, a second current application means, and a second current application means, respectively. Bias current supply means for supplying a current to each of the bias coils at the first and second timings, and a frequency dividing means connected to the oscillating means via three switches to divide the output of the oscillating means.
A detection means provided corresponding to the magnetic detection element for converting each impedance change into a voltage and passing a peak of the voltage, a second switch provided corresponding to each of the detection means and selecting its output, and a selection First holding means for holding the output of the detected detection means, and two fourth holding means for selecting the held voltage at the first and second timings.
A switch, two second holding means for holding the two selected voltages, and an amplification means for amplifying an output difference between the two second holding means are provided, and the selective operation of the first to fourth switches. By this, magnetic detection is enabled for each channel.

In the invention of claim 1 or 2,
A first switch and a second switch provided for the magnetic detection element.
When at least one of the switches is selected, the third switch can be selected (the invention of claim 3), and in any one of the inventions of claims 1 to 3, it corresponds to the magnetic detection element. A first switch provided,
The oscillating means can be operated when at least one of the second switches is selected (claim 4).
Invention).

In the invention according to any one of claims 1 to 4, the magnetic detection element, a terminal for applying an alternating current to the magnetic detection element, the bias coil and a bias current supplied to the bias coil. Or a terminal for applying an alternating current to the magnetic detection element, the bias coil, and A terminal for supplying a bias current to this,
A circuit portion that outputs a signal proportional to the output of the magnetic detection element can be integrated by resin molding (the invention of claim 6).

Furthermore, in the invention of any one of claims 1 to 6, a thin film type can be used as the magnetic detection element (the invention of claim 7).

[0013]

1 is a block diagram showing a first embodiment of the present invention.

In the figure, 1a and 1b are MI elements, and the element shape may be a wire or a thin film. 2a,
2b is a coil for applying a bias to the MI elements 1a and 1b, 3 is an oscillation circuit, 4a and 4b are first switches, 5
Reference numerals a and 5b are first current applying means, and the output of the oscillation circuit 3 is switched by the first switches 4a and 4b.
A high-frequency alternating current is applied to the MI elements 1a and 1b via a and 5b. Reference numeral 13a is a second current applying means for applying a current to the bias coils 2a and 2b, and the current application is turned on and off by the third switch 14a. 6a,
Reference numeral 6b is a detection means for outputting the peak value of the impedance change of the MI elements 1a, 1b converted into the voltage change, 7a,
7b is a second switch for taking out the output of the detecting means according to the selected MI element, 8a is a first holding means for holding the outputs of the detecting means 6a, 6b, and 11a is a first holding means 8
It is an amplification means for amplifying the output of a.

Further, the control means 15 controls the MI elements 1a, 1b by the control signals A1, A2, B1, B2 for the first and second switches 4a, 4b and 7a, 7b.
Either one of 1b is selected, and the control signal C1 is output to allow a bias current to flow.

That is, MI is controlled by the control signals A1 and A2.
In the element 1a, the MI element 1b is selected by the control signals B1 and B2, respectively, and the bias current is applied by the control signal C1, so that the current and bias current applied to the MI element, which occupies most of the power consumption, are The control signal can be applied only for the selected time, and the current consumption can be minimized. For example, the first switch 4
Low power consumption can be realized by outputting the control signal C1 and turning on the third switch 14a only when at least one of the switches a, 4b or the second switches 7a, 7b is turned on. Also, the first holding means 8a and the amplification means 11
Since only one system is required for a, low power consumption and low cost can be realized.

FIG. 2 shows a specific example of FIG.

The oscillation circuit 3 has various methods using a crystal oscillator or a transistor, but here, as an example, a CMO is used.
The S-gate is used, and the first current applying means 5a and 5b are formed of a CMOS gate and a current limiting resistor. Although the detection means 6a and 6b can be configured by analog switches,
Here, as an example, it is configured by a diode, and the first holding means 8a is configured by a resistor and a capacitor. Although the amplifying means 11a can be configured by a transistor, it is configured by an operational amplifier as an example here. First, second,
The third switch is composed of a relay or an analog switch, and the control means 15 is composed of a one-chip microcomputer or the like.

The devices shown in FIGS. 1 and 2 are characterized in that magnetic detection is possible with a simple structure, but the output accuracy is not very good. This is because the change in impedance of the amorphous wire element with respect to the magnetic field has nonlinearity as shown in FIG. 13, for example.

FIG. 3 shows a second configuration example in which the above-mentioned non-linear characteristic is improved. This is different from that shown in FIG. 1 in that positive and negative bias magnetic fields are alternately applied to the MI elements 1a and 1b, and the difference between the detected voltages when the respective bias magnetic fields are applied is calculated to obtain linearity of the output. It is different in that it is designed to improve.

Reference numeral 12 is a frequency dividing means for dividing the output of the oscillating means 3 and outputs a signal having a frequency lower than the alternating current applied to the MI elements 1a and 1b. 13b is a frequency dividing means 12
The second current applying means for alternately applying the positive and negative bias magnetic fields in accordance with the positive and negative output timing from the oscillating means 3 divided by the frequency dividing means 12 via the third switch 14b.
Is applied to the bias coils 2a and 2b. Furthermore, the first holding means 8b that holds the voltage corresponding to the impedance change of the MI elements 1a and 1b due to the positive and negative bias magnetic fields, the second holding means 10a and 10b that holds the output at each positive and negative timing, and the timing D thereof.
It is provided with fourth switches 9a and 9b which operate at 1 and D2, and differential amplification means 11b which differentially amplifies the outputs of the second holding means 10a and 10b.

FIG. 4 is an explanatory diagram of the operation of positive and negative bias.
The characteristic of the sensor with respect to the magnetic field in the figure shows the characteristic of a general magneto-impedance element.

In case 1 of the figure, when the external magnetic field is zero,
Since the output on the plus side and the output on the minus side as seen from the output of the MI element are equal, the second holding means 10 in FIG.
The outputs of a and 10b are equal, and the output of the differential amplifier 11b is zero.

In case 2, the difference between the plus side output and the minus side output seen from the output of the MI element is ΔV when the external magnetic field ΔH is applied, so the second holding means 10 of FIG.
The output difference between a and 10b becomes ΔV, and the differential amplifier 11b
Output is α × ΔV (α: gain of the differential amplification means).

A specific example of FIG. 3 is shown in FIG. This is shown in Figure 2.
The second holding means 10a, 10b, the differential amplification means 11b, and the frequency dividing means 12 are added to the second holding means 10a, 10b.
Here, the holding means 10a and 10b are composed only of capacitors, the differential amplification means 11b is composed of a differential amplifier by an operational amplifier, and the frequency dividing means 12 is composed of a flip-flop.

If, instead of the oscillating means shown in FIGS. 2 and 5, a device that oscillates only when the control signal C1 is at a high level, as shown in FIG. 6, is used, the first switches 4a, 4a.
b or at least one of the second switches 7a and 7b
The third switch 14b to the signal C1 only when one is turned on.
It is possible to further reduce the power consumption by turning it on.

Next, the structure of the magnetic detection element section is shown in FIG.
Will be described with reference to.

In the figure, 21 is a thin film magnetic detecting element, and 23 is a resin bobbin formed outside the magnetic detecting element 21, which is manufactured by insert molding or the like. Reference numeral 24 is a coil for applying a bias magnetic field to the magnetic detection element 21,
25 is a coil for applying a negative feedback magnetic field to the magnetic detection element 21, and 26 is the magnetic detection element 21 and the coils 24, 2.
A resin case for protecting 5 from the environment, which is also manufactured by insert molding or the like. Reference numeral 22 denotes a terminal for applying a high frequency current to both ends of the magnetic detection element 21 and the coil 2.
It is a terminal for applying a current to 4, 25. The magnetic detection element portion configured in this way is indicated by reference numeral 20. Although the example in which the coil for applying the negative feedback magnetic field is provided to the magnetic detection element 21 is shown here, it may be omitted.

FIG. 8 shows an example of an assembling flow of the magnetic detecting element section.

First, the magnetic detection element 21 is joined between a pair of terminals of the lead frame 27 as shown by.
Examples of this joining method include soldering, adhesion, and bonding. Next, the bobbin 23 is resin-molded on the lead frame 27 to which the magnetic detection element 21 is bonded as described above.
Next, after cutting the lead frame 27 as described above, the bias coil 24 and the negative feedback coil 25 are wound.
Then, the case 26 is resin-molded as in, and the terminal 22 is bent to be completed.

Since the thin film magnetic detecting element can be manufactured to have a size of about 1 mm square, the outer shape of the magnetic detecting element portion 20 is about 5 mm.
The magnetic sensing element 21 and the coil 24,
The magnetic resistance with 25 can be reduced significantly.

FIG. 9 shows a mounting example of the magnetic detection element section. The figure (a) is a perspective view and the figure (b) is a top view.

As shown in FIG. 3A, the magnetic detection element section 20 is mounted on the substrate 31 having the wiring 32 for guiding the current 30, and the magnetic flux generated by the current 30 as shown by the dotted line in FIG. Since the output sensitivity of the magnetic detection element unit 20 is determined by the arrangement of the magnetic detection element unit, the output sensitivity of the magnetic detection element unit 20 according to the magnitude of the current 30 can be considered by considering the arrangement of the magnetic detection element unit. Adjustment is possible.

FIG. 10 shows an example of the magnetic shield structure.

This is the same as the magnetic shield 3 shown in FIG.
3 is added, and the shape thereof is an elliptical shape here, but it is desirable to optimize it according to the magnitude of the current 30.

FIG. 11 shows a specific example of the magnetic detection device.

This is the magnetic detection element section 20 as shown in FIG.
In addition, it is characterized in that the detection circuit unit 40 is incorporated (integrated). By doing so, it is possible to increase the S / N ratio of the detection signal, and by incorporating various correction data at the time of automatic calibration as described with reference to FIG.

Although the above description uses two MI elements, the number of MI elements may be three or more.
Even if the number of elements is increased, there is an advantage that the power consumption is almost the same as the case of one element.

[0039]

According to the present invention, in the multi-channel magnetic detection device, since the current is applied only to the selected magnetic detection element, the power consumption can be reduced. In addition, by energizing the bias coil or operating the oscillating means only during measurement, it is possible to further reduce power consumption.

Since the holding means and the amplifying means need only be one system,
Low cost and low power consumption can be realized.

Further, by applying positive and negative biases alternately to the magnetic detection element and calculating the difference between the detected voltages at that time,
The linearity of the output can be improved.

Furthermore, by integrating the magnetic detection element and its AC current application terminal with the bias winding and its current application terminal by resin molding, the magnetic resistance and the bias current can be reduced, and the size is small and the power consumption is low. A magnetic detection device can be provided.

By integrating the magnetic detection element and its AC current application terminal, the bias winding and its current application terminal, and the circuit section which outputs a signal proportional to the output of the magnetic detection element, a high S / N ratio is achieved. Can be realized. In particular, by incorporating various correction data to achieve high functionality, it is possible to realize a magnetic detection device with excellent environment resistance, high accuracy, and low power consumption. Further, by using the thin film type magnetic detection element, there is no influence of the output change due to strain which is a problem in the wire type, and as a result, it is possible to provide a highly accurate and low power consumption magnetic detection device.

[Brief description of drawings]

FIG. 1 is a block diagram showing a first embodiment of the present invention.

FIG. 2 is a configuration diagram showing a specific example of FIG.

FIG. 3 is a block diagram showing a second embodiment of the present invention.

FIG. 4 is an explanatory diagram of positive / negative bias.

5 is a configuration diagram specifically showing each component of FIG. 3. FIG.

FIG. 6 is a circuit diagram showing another example of the oscillating means.

FIG. 7 is a perspective view showing a specific configuration example of a magnetic detection element section.

FIG. 8 is an explanatory diagram of a manufacturing process of the magnetic detection element unit of FIG. 7.

9 is an explanatory view of a mounting form of the magnetic detection element unit of FIG. 7.

FIG. 10 is an explanatory diagram of an example of a magnetic shield.

FIG. 11 is a perspective view showing a specific configuration example of a magnetic detection device.

FIG. 12 is a block diagram showing a conventional example of a magnetic detection device.

FIG. 13 is an explanatory diagram of magnetic impedance characteristics of an amorphous wire.

[Explanation of symbols]

1a, 1b, 21 ... Magnetic detection element (MI element), 2a,
2b ... Bias coil, 3 ... Oscillation circuit, 4a, 4b, 7
a, 7b, 9a, 9b, 14a, 14b ... switch, 5
a, 5b, 13a, 13b ... Current applying means, 6a, 6b
... Detecting means, 8a, 8b, 10a, 10b ... Holding means,
11a, 11b ... Amplifying means, 12 ... Dividing means, 15 ... Control means, 20 ... Magnetic detection element section, 22 ... Terminal, 23 ... Bobbin, 24, 25 ... Coil, 26 ... Resin case, 27
... lead frame, 31 ... substrate, 32 ... wiring, 33 ... magnetic shield, 40 ... detection circuit.

Claims (7)

[Claims] 1. A plurality of magnetic detection elements having a magneto-impedance effect, one oscillating means, and a first switch and a first current applying means provided corresponding to the magnetic detection element. An alternating current supply means for applying an alternating current to each of the detection elements, a bias coil wound around each of the magnetic detection elements, a third switch, and a second current application means, each bias coil including the third switch. Bias current supplying means for supplying a current through the detecting means, detecting means provided corresponding to the magnetic detecting element for converting the impedance change of each to voltage and passing the peak of the voltage, and provided for each of the detecting means. And a second switch that selects its output,
Holding means for holding the output of the selected detection means,
A multi-channel type magnetic detecting device comprising: an amplifying means for amplifying the held voltage, and enabling magnetic detection for each channel by selective operation of the first to third switches. 2. A plurality of magnetic detection elements having a magneto-impedance effect, one oscillating means, and a first switch and a first current applying means provided corresponding to the magnetic detection element. An alternating current supply means for applying an alternating current to the detection element, a bias coil respectively wound around the magnetic detection element, a second current application means, and a third switch are connected to the oscillation means to divide the output. Bias current supply means for supplying a current to each of the bias coils at the first and second timings, and frequency change means for circling, and impedance changes of the bias current supply means provided corresponding to the magnetic detection element and converted into a voltage. Detection means for passing a peak of voltage, second switches provided corresponding to each of the detection means for selecting the output thereof, and selection The first holding means for holding the output of the detected detection means, and the held voltage for the first and second
Two fourth switches selected at the timing of, and two second holding means for holding the two selected voltages,
A multi-channel type magnetic device, comprising: an amplifying unit for amplifying an output difference between two second holding units, and enabling magnetic detection for each channel by selective operation of the first to fourth switches. Detection device. 3. A first device provided corresponding to the magnetic detection element.
3. The multi-channel magnetic detection device according to claim 1, wherein the third switch is selected when at least one of the switch and the second switch is selected. 4. A first device provided corresponding to the magnetic detection element.
4. The multi-channel magnetic detection device according to claim 1, wherein the oscillating means is operated when at least one of the switch and the second switch is selected. 5. The magnetic detection element, a terminal for applying an alternating current to the magnetic detection element, the bias coil and a terminal for supplying a bias current thereto are integrated by resin molding. The multi-channel magnetic detection device according to any one of claims 1 to 4, which is characterized in that. 6. The magnetic detection element, a terminal for applying an alternating current to the magnetic detection element, the bias coil and a terminal for supplying a bias current thereto.
5. The multi-channel magnetic detection device according to claim 1, wherein a circuit section that outputs a signal proportional to the output of the magnetic detection element is integrated by resin molding. 7. The multi-channel magnetic detection device according to claim 1, wherein a thin film type is used as the magnetic detection element.