JP2000111627A - Drive circuit for magnetic impedance effect element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce power consumption and running costs by on/off controlling the supply of current to first and second excitation coils in a fixed cycle. SOLUTION: Element drive circuits 6 and coil drive circuits 7 are driven based on a clock signal supplied from one clock generator 3. The coil drive circuits 7 are on/off controlled so as not to energize excitation coils 2 at all times but to energize the excitation coils 2 intermittently corresponding to drive pulses outputted for driving magnetic impedance effect (MI) elements. The drive pulses are supplied to linear magnetic bodies (MI elements) with a fixed delay time ΔT after the energization of the excitation coils 2 is started. The delay time ΔT between 10 ns and 100 ns is suitable.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a driving circuit for a magneto-impedance effect element (hereinafter, abbreviated as "MI element"). The present invention relates to a drive circuit for an asymmetric MI element including a first excitation coil and a second excitation coil for applying a bias magnetic field to the first MI element and the second MI element, respectively.

[0002]

2. Description of the Related Art The magnetic impedance effect (hereinafter, abbreviated as MI effect) is a phenomenon in which the impedance of a magnetic material having a high magnetic permeability is changed by an external magnetic field due to a skin effect when a high-frequency current is applied to the magnetic material. It is.

FIG. 3 is a diagram showing the principle of an MI element utilizing the MI effect. An exciting coil 101 is wound around a linear magnetic body 100 having a high magnetic permeability such as an amorphous wire, and connected in series. The pulse train current generated from the oscillator 102 flows. Then, since the pulse voltage between the terminals 103, 103 connected to both ends of the linear magnetic body 100 changes according to the external magnetic field Hex, a change in the external magnetic field Hex can be detected by measuring the voltage, This principle can be applied to, for example, a magnetic sensor.

When the linear magnetic material 100 is used, MI
Since the effect generally has a symmetric characteristic with respect to the external magnetic field Hex, it is necessary to apply a DC bias magnetic field when applied to a magnetic sensor or the like.
01 is used. When the coil current flowing through the excitation coil 101 is counterclockwise and counterclockwise with respect to the wire current flowing through the linear magnetic body 100, the MI appears as an asymmetric MI effect (see FIG. 4). Applicable.

FIG. 4 is a diagram for explaining an asymmetric MI element, and is a characteristic diagram showing a relationship between an external magnetic field and a pulse voltage at both ends of a wire. 5 shows characteristic curves when the coil current flowing through the exciting coil 101 is counterclockwise and clockwise.

FIG. 5 is a drive circuit diagram of a conventional asymmetric MI element. As shown in the figure, the first linear magnetic body 100a
And the second linear magnetic body 100b are arranged in parallel with each other,
A first excitation coil 101a for applying a DC bias magnetic field is wound around the first linear magnetic body 100a, and a second excitation coil 101b is wound around the second linear magnetic body 100b. I have. The direction of the coil current flowing through the first excitation coil 101a and the second excitation coil 101b is shown in the drawing such that one direction is counterclockwise with respect to the wire current flowing through the linear magnetic body 100 and the other direction is clockwise. Thus, the winding directions of the coils are opposite to each other.

In the figure, reference numeral 105 denotes a clock generator, and 106 denotes a first linear magnetic body 100a and a second linear magnetic body 100 based on a clock signal from the clock generator 105.
b, an element driving circuit for supplying a pulse current to
07 denotes a first linear magnetic body 100a and a second linear magnetic body 1
This is a detection circuit for differentially amplifying the respective terminal outputs 00b by the operational amplifier 108 to obtain a linear output with respect to the external magnetic field Hex.

As shown in FIG. 1, in the conventional driving circuit, a coil driving circuit for driving the exciting coils 101a and 101b is provided independently of the clock generator 105 and the element driving circuit 106. , 1
01b was maintained in the excited state.

[0009] These related technologies include, for example, Journal of the Applied Magnetic Society, Vol. 21, No. 4-2, 1997 "Asymmetric magnetic-impedance effect of amorphous wire", JP-A-7-181239, JP-A-7-24
No. 8365 and the like.

[0010]

By the way, this conventional driving circuit uses an MI element (a first linear magnetic body 100a and a second linear magnetic body 100a).
A first excitation coil 101a and a second excitation coil 101 for applying a bias magnetic field to the linear magnetic body 100b) of FIG.
Since a current was constantly supplied to the point b, the power consumption was large and the running cost was high.

An object of the present invention is to solve the above-mentioned drawbacks of the prior art, and to provide a drive circuit for an MI element which consumes less power and has a low running cost.

[0012]

In order to achieve the above object, the present invention provides a first MI element and a second MI element made of a linear magnetic material such as an amorphous wire and arranged in parallel with each other. A first excitation coil and a second excitation coil for applying a bias magnetic field to the first MI element and the second MI element, respectively, and the first MI element and the second M coil.
A first element driving circuit and a second element driving circuit for respectively supplying a pulse current to the I element, and a first element having, for example, a switching element for supplying a current to each of the first excitation coil and the second excitation coil; There is provided a coil drive circuit, a second coil drive circuit, and a detection circuit having, for example, an operational amplifier for detecting a pulse voltage between both ends of the first MI element and the second MI element.

Each time a pulse current is supplied to the first MI element and the second MI element by the first element driving circuit and the second element driving circuit, the first coil driving circuit It is characterized in that it is configured to turn on and off the supply of current to the first excitation coil and the second excitation coil by a second coil drive circuit.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention is configured as described above, and each time a pulse current is supplied to each of a first MI element and a second MI element, a first coil driving circuit and a first coil driving circuit are connected. Since the current supply to the first excitation coil and the second excitation coil by the two coil drive circuits is configured to be turned on and off, power consumption is reduced and running cost can be reduced.

Next, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a driving circuit diagram of an MI element according to an embodiment, and FIG.
Is a timing chart of the driving circuit.

As shown in FIG. 1, a first linear magnetic body 1a and a second linear magnetic body 1b are arranged in parallel and integrally with each other. As the linear magnetic body 1, for example, Fe--Co--Si
A zero-magnetostrictive amorphous wire made of a -B-based alloy composition is preferable.

A first excitation coil 2a for applying a DC bias magnetic field is wound around the first linear magnetic body 1a for several tens of turns, and a second excitation is applied to the second linear magnetic body 1b. The coil 2b is similarly wound several tens of turns. The direction of the coil current flowing through the first exciting coil 2a and the second exciting coil 2b is such that one direction is counterclockwise with respect to the wire current flowing through the linear magnetic bodies 1a and 1b, and the other direction is clockwise. ing.

In the figure, 3 is a clock generator, 4 is a frequency divider,
Reference numeral 5 denotes an AND gate; 6a, a first element drive circuit for passing a pulse train current to the first linear magnetic body 1a; 6b, a second element drive circuit for passing a pulse train current to the second linear magnetic body 1b. It is.

The element driving circuit 6 is of a current output type in which the current value is set to 10 mA or more. As a specific means, the element driving circuit 6 includes at least the impedance of the linear magnetic body 1 of 10% at the gate of the digital circuit. More than double resistance R
Are connected. The reason why the element driving circuit 6 is of the current output type is that the impedance of the MI element is only several Ω, and it is difficult to drive the MI element with a normal voltage output type.

Reference numeral 7a denotes a first coil drive circuit provided with a switching element for controlling on / off of energization to the first excitation coil 2a, and 7b denotes a switching element for on / off control of energization to the second excitation coil 2b. In the second coil driving circuit provided, both coil driving circuits 7 a and 7 b are connected to the output terminal of the frequency divider 4. Reference numeral 8 denotes a detection circuit for differentially amplifying the pulse voltage between both ends of the first linear magnetic body 1a and the second linear magnetic body 1b by an operational amplifier 9 to obtain a linear output with respect to the external magnetic field Hex. It is.

FIG. 2 is a timing chart of this asymmetric MI element drive circuit diagram. In the figure, CK is a clock pulse waveform generated by the clock generator 3, Q is an output waveform of the frequency divider 4, AND is an output waveform of the AND gate 5, and differentiation is a capacitor C and a resistor R in the element driving circuit 6. Is a driving pulse waveform supplied to the linear magnetic body 1 by the element driving circuit 6, and i is a coil current waveform flowing to the exciting coil by the coil driving circuit 7.

As shown in FIG. 1, the element driving circuit 6
The coil drive circuit 7 has a circuit configuration driven based on a clock signal supplied from the same clock generator 3. Then, as shown in FIG. 2, the coil drive circuit 7 does not always energize the exciting coil 2,
On / off control is performed so that the excitation coil 2 is intermittently energized in response to the output driving pulse for driving the MI element. In addition, the drive pulse is applied to the linear magnetic body 1 (MI) with a predetermined delay time ΔT after the energization of the excitation coil 2 is started.
Element). The delay time ΔT is suitably between 10 ns and 100 ns, and the delay time ΔT is the time constant CR of the capacitor C and the resistor R of each element drive circuit 6a, 6b.
Can be adjusted individually.

When a current is applied to the exciting coil 2, the current waveform gradually rises as shown in FIG. 2i, and it takes some time until a constant magnetic field is generated. Therefore, the delay time Δ
If T is absent or too short, the detection circuit 8 will include the value when the originally required baisic magnetic field strength is not reached, thus reducing the detection accuracy. In order to avoid this, in the present embodiment, a predetermined delay time ΔT is set, and a drive pulse for driving the MI element is supplied when the intensity of the Bais magnetic field by the excitation coil 2 becomes constant.

The MI element driving circuit of the present invention can be applied to a driving circuit such as a magnetic sensor or a magnetic azimuth sensor for detecting and measuring the intensity, direction, distribution and the like of a magnetic field.

[0025]

According to the first aspect of the present invention, the first coil drive is performed each time a pulse current is supplied to each of the first MI element and the second MI element. Since the supply of current to the first excitation coil and the second excitation coil by the circuit and the second coil drive circuit is turned on and off, power consumption is reduced and running cost can be reduced.

According to the present invention, the device driving pulse is applied after the generation of a predetermined bias magnetic field, so that the measurement accuracy can be improved and the driving with high reliability can be achieved. A circuit can be provided.

[Brief description of the drawings]

FIG. 1 is a drive circuit diagram of a magneto-impedance effect element according to an embodiment of the present invention.

FIG. 2 is a timing chart of the driving circuit.

FIG. 3 is a principle diagram of a magneto-impedance effect element.

FIG. 4 is a characteristic diagram showing a relationship between an external magnetic field and a pulse voltage across a wire for describing an asymmetric magneto-impedance effect element.

FIG. 5 is a drive circuit diagram of a conventional magneto-impedance effect element.

[Explanation of symbols]

 1a first linear magnetic body 1b second linear magnetic body 2a first exciting coil 2b second exciting coil 3 clock generator 4 frequency divider 5 AND gate 6a first element driving circuit 6b second Element drive circuit 7a First coil drive circuit 7b Second coil drive circuit 8 Detection circuit 9 Operational amplifier ΔT Delay time C Capacitor R Resistance

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Shinichi Sasakawa 1-7 Yukiya Otsukacho, Ota-ku, Tokyo Alps Electric Co., Ltd. F-term (reference) 2G017 AC09 AD51 BA03 BA05

Claims (9)

[Claims] 1. A first magnetic impedance effect element and a second magnetic impedance effect element arranged in parallel with each other, and a bias magnetic field is applied to each of the first magnetic impedance effect element and the second magnetic impedance effect element. A first excitation coil and a second excitation coil, and a first element driving circuit and a second element driving circuit for supplying a pulse current to the first magnetic impedance effect element and the second magnetic impedance effect element, respectively. A first coil drive circuit and a second coil drive circuit for supplying current to the first excitation coil and the second excitation coil, respectively, the first magnetic impedance effect element, and the second magnetic impedance effect A detecting circuit for detecting a pulse voltage across each of the elements, wherein the first element driving circuit and the second element driving circuit Each time a pulse current is supplied to each of the first magneto-impedance effect element and the second magneto-impedance effect element, the first excitation coil and the second excitation coil by the second coil drive circuit and 2. A driving circuit for a magneto-impedance effect element, which is configured to turn on and off the supply of current to the second excitation coil. 2. The device according to claim 1, wherein the first magnetic impedance effect element and the second magnetic field have a predetermined delay time after the current supply to the first exciting coil and the second exciting coil is started. A drive circuit for a magneto-impedance effect element, wherein a delay means is provided so as to start supplying a pulse current to the impedance effect element. 3. The device according to claim 2, wherein the delay means is provided in each of the first element driving circuit and the second element driving circuit, and the delay time can be adjusted individually. Drive circuit for magneto-impedance effect element. 4. A driving circuit for a magneto-impedance effect element according to claim 3, wherein said delay means comprises a capacitor and a resistor of said element driving circuit. 5. The method according to claim 2, wherein
The first and second element drive circuits and the first and second coil drive circuits are driven based on a clock signal supplied from the same clock generator, and the delay time is adjustable. A drive circuit for a magneto-impedance effect element, characterized in that: 6. The method according to claim 2, wherein
The drive of the magneto-impedance effect element, wherein the delay time is a time from the start of current supply to the first excitation coil and the second excitation coil until the bias magnetic field intensity becomes substantially constant. circuit. 7. The driving circuit according to claim 6, wherein the delay time is in a range of 10 ns to 100 ns. 8. The driving circuit for a magneto-impedance effect element according to claim 1, wherein the outputs of the first and second element driving circuits are of a current output type. 9. The driving circuit for a magneto-impedance effect element according to claim 1, wherein said first and second magneto-impedance effect elements are both amorphous wires.