Magnetic field detection sensor

Abstract

A magnetic field detection sensor with: a magnetic impedance element designed to exploit a magnetic impedance effect; a bias coil designed to apply a bias field to the magnetic impedance element; an oscillator circuit designed to apply an alternating current to the magnetic impedance element; a differentiating circuit designed to differentiate an output signal of the magnetic impedance element; a flip-flop circuit configured to output a high-level signal and a low-level signal based on a trigger signal output by the differentiating circuit; and a computing unit configured to detect an external magnetic field based on a time course with high and low of the high-level signal and low-level signal output by the flip-flop circuit, wherein the magnetic field detection sensor is configured to detect the external magnetic field based on an output signal obtained by applying the alternating current to the magnetic impedance element, the magnetic impedance element comprises a non-magnetic substrate and a magnetic layer provided on a surface of the non-magnetic substrate, wherein a magnetic field detection direction coincides with a longitudinal direction of the magnetic impedance element and the magnetic layer is configured to have magnetic anisotropy such that a direction of an axis of its easy magnetizability coincides with the magnetic field detection direction, and The computing unit is configured to send a reset signal to the flip-flop circuit at the time of a drop in an AC bias frequency, and to detect the external magnetic field based on the duration of an initial high-level signal following the reset signal.

Description

Area

[0001] The present invention relates to a magnetic field detection sensor. background

[0002] Conventionally, a magnetic field detection sensor is disclosed with a magnetic impedance (MI) element that utilizes the magnetoresistive or magnetic impedance effect of an amorphous wire. Size reduction is easier with an MI element compared to a flux-gate sensor, and sensors using an MI element exhibit a detection sensitivity equivalent to that of flux-gate sensors.

[0003] An example of such a magnetic field detection sensor using the MI element will now be explained. An oscillator circuit supplies an alternating current (AC) bias current to a coil wound around an MI element. This generates an AC bias field in the MI element, and an amplitude-modulated (AM) waveform, whose peak values ​​alternately exhibit a magnitude difference, is obtained as an output signal. A detector circuit is configured to detect the output signal and remove the direct current (DC) component, and the resulting waveform is fed into a comparator. The magnetic field detection sensor then receives an output signal with a digital waveform that is pulse-modulated based on the magnitude difference.Such a magnetic field detection sensor determines the magnitude of the external magnetic field not based on the absolute value of the amplitude of the output signal from the oscillator circuit, but rather on the magnitude of the change in amplitude. Therefore, such a magnetic field detection sensor is less affected by fluctuations in the supply voltage, the temperature characteristics of the element, and the like. This not only eliminates the need for precise adjustment of the oscillator circuit, but also allows for the provision of a magnetic field detection sensor that is robust with respect to noise (see patent reference 1).

[0004] Furthermore, a magnetic field detection sensor is disclosed which includes an oscillator circuit that applies a sinusoidal high-frequency current to both ends of a magnetic core, a buffer circuit arranged between the oscillator circuit and the magnetic core of a thin-film magnetic impedance element, and which adjusts the mismatch between an output impedance of the oscillator circuit and an input impedance of the thin-film magnetic impedance element, a detector circuit for detecting the magnitude of a magnetic change in the external magnetic field based on the magnitude of the change in the high-frequency current, which changes according to the external magnetic field acting on the magnetic impedance element, and a hysteresis cancellation circuit that cancels out the hysteresis in the magnetic impedance element.Since such a magnetic field detection sensor is equipped with a buffer circuit, for example, the output signal resulting from the high-frequency current applied by the oscillator circuit can be provided without loss (see patent reference 2). Since the slope, which represents the change in magnitude, depends on the external magnetic field applied to the magnetic impedance element, the magnetic detection sensor is steepest at 400 A / m, as shown in [reference missing]. Fig. As shown in patent literature 2, a constant current, which shifts the operating point to the point at which the magnitude of the change becomes steepest, must be impressed into the bias coil. List of citations from patent literature Patent literature 1: Japanese published patent application number 9-127218 Patent literature 2: published Japanese patent application number 2000-180521 Overview Technical Problem

[0005] However, the magnetic field detection sensors disclosed in patent literature 1 and patent literature 2 are not capable of performing a very sensitive measurement unless an AC bias voltage is applied at a level at which the slope of the impedance becomes steep (up to ± 400 A / n). Fig. 5, which is disclosed in patent literature 2), since the impedance, which depends on the magnetic field of the MI element, changes in an M-shape. This increases the current draw. Similarly, a method of applying a DC bias at a level where the slope of the impedance change becomes steep requires a larger amount of current draw.

[0006] Furthermore, since the hysteresis is increased in the M-shaped properties, the detection accuracy is affected by the size of the hysteresis. Additionally, since the magnetic field can only be measured with high sensitivity within the range where a steep incline or gradient is guaranteed, only a limited detection range is available.

[0007] The present invention was conceived to solve the problem described above, and it is an object of the present invention to provide a magnetic field detection sensor that is able to reduce power consumption, improve detection accuracy and increase the detection range. Solution to the problem

[0008] A magnetic field detection sensor according to the present invention comprises a magnetic impedance element configured to exploit a magnetic impedance effect;and a premagnetizing coil configured to apply a premagnetizing field to the magnetic impedance element, wherein the magnetic field detection sensor is configured to detect an external magnetic field based on an output signal obtained by applying an alternating current to the magnetic impedance element, and the magnetic impedance element comprises a non-magnetic substrate and a magnetic layer provided on a surface of the non-magnetic substrate, wherein a magnetic field detection direction coincides with a longitudinal direction of the magnetic impedance element, and the magnetic layer is configured to have a magnetic anisotropy such that a direction of an axis of easy magnetizability coincides with the magnetic field detection direction.

[0009] In the magnetic field detection sensor, the magnetic field detection direction coincides with the longitudinal direction of the magnetic impedance element within the sensor, and the magnetic layer is provided with magnetic anisotropy such that one direction of the axis of slight magnetizability extends along the longitudinal direction. Due to the alignment of the magnetic field detection direction with the axis of slight magnetizability of the magnetic layer, pyramidal magnetic impedance characteristics can be achieved in the magnetic field detection sensor. These pyramidal magnetic impedance characteristics eliminate the need for a DC or AC bias voltage at a level where the slope of the impedance change becomes steep for the M-shaped properties.Furthermore, since a magnetic field detection sensor with pyramidal properties exhibits smaller hysteresis compared to a sensor with M-shaped properties, detection accuracy can be improved. Additionally, because the pyramidal properties represent a certain degree of inclination or slope across the entire area, a wider detection range can be ensured. The magnetic field detection sensor can therefore reduce power consumption, improve detection accuracy, and provide a wider detection range.

[0010] It is preferred that the magnetic field detection sensor according to the present invention further comprises an oscillator circuit configured to impress the alternating current into the magnetic impedance element; a differentiating circuit configured to differentiate an output signal of the magnetic impedance element; and a computing unit configured to detect the external magnetic field on the basis of a trigger signal output by the differentiating circuit.

[0011] Since the magnetic field detection sensor detects the external magnetic field based on the trigger signal output by the differentiating circuit, it provides a sensor that is more robust against noise compared to a setup that detects the external magnetic field based on the difference in amplitude and compared to a configuration using an integrated circuit. The magnetic field detection sensor can therefore further improve detection accuracy.

[0012] In the magnetic field detection sensor according to the present invention, it is preferred that the premagnetization coil is constructed from a single premagnetization coil for negative feedback, which is configured to apply the premagnetization field and a magnetic field for negative feedback to the magnetic impedance element.

[0013] In the magnetic field detection sensor, the magnetic field detection sensor can avoid an increase in size and cost compared to the design in which a coil for negative feedback and a premagnetization coil are provided separately. Advantageous effects of the invention

[0014] According to the present invention, it is possible to provide a magnetic field detection sensor that is able to reduce power consumption, improve detection accuracy, and ensure a wider detection range. Brief description of drawings Fig. Figure 1 is a circuit diagram that schematically represents a magnetic field detection sensor according to one embodiment. Fig. Figure 2A is a perspective view that shows in detail a first example of a magnetic impedance element and structures around the magnetic impedance element according to the embodiment. Fig. Figure 2B is a perspective view that shows in detail a second example of the magnetic impedance element and the structures around the magnetic impedance element according to the embodiment. Fig. Figure 3 is a view showing magnetic impedance properties or magnetoresistive properties. Fig. Figure 4A shows an output signal from a sensor with the magnetic impedance element and a resistor according to the embodiment when an external magnetic field is 0 [H / m]. Fig. Figure 4B is a view showing an output signal from the sensor with the magnetic impedance element and the resistance according to the embodiment when the external magnetic field is negative (for example, -40 [H / m]). Fig. Figure 5 is a time sequence diagram showing various signals when the external magnetic field is 0 [H / m]. Fig. Figure 6 is a time sequence diagram showing various signals when the external magnetic field is positive. Fig. Figure 7 is a time sequence diagram showing various signals when the external magnetic field is negative. Fig. Figure 8 is a view that shows a correlation between the time a signal is at a HIGH level and the magnitude of the external magnetic field. Description of embodiments.

[0015] An illustrative embodiment of the present invention will now be explained with reference to some drawings. However, the scope of protection of the present invention is not limited to these embodiments.

[0016] Fig. Figure 1 is a circuit diagram schematically representing a magnetic field detection sensor according to one embodiment. This magnetic field detection sensor 1, which is located in Fig. The device shown in Figure 1, which is equipped with a magnet detector, is configured to detect an external magnetic field (the direction, azimuth, and magnitude of the magnetic field) based on an output signal from a magnetic impedance element 12 into which an AC current is impressed. This element is used, for example, as a component in a current sensor, an azimuth sensor, a torque sensor, or a rotation angle sensor. Such a magnetic field detection sensor 1, serving as a detector for magnetism, comprises an oscillator circuit 10, the magnetic impedance element or magnetoresistive element 12, a resistor R, and a bias coil for negative feedback (bias coil) 14.

[0017] The oscillator circuit 10 is a source of an AC voltage for driving the magnetic impedance element 12, which, for example, comprises a crystal oscillator and is configured to output an alternating current signal (AC voltage). The AC voltage output by the oscillator circuit 10 is applied to the magnetic impedance element 12. The magnetic impedance element 12 comprises an amorphous magnetic body with zero magnetostriction or, for example, a magnetic thin film and is suitable for exhibiting a magnetic impedance effect or magnetoresistive effect. The magnetic impedance effect is a phenomenon in which the impedance changes when a high-frequency current is applied, for example, due to a change in penetration depth. This occurs because the magnetic permeability changes significantly in the circumferential direction when an external magnetic field is applied.One end of the magnetic impedance element 12 is connected to the oscillator circuit 10, and the other end is connected to one end of the resistor R. The other end of the resistor R is grounded.

[0018] The bias coil for negative feedback 14 is a coil wound around the magnetic impedance element 12. However, the bias coil for negative feedback 14 need not be wound around the magnetic impedance element 12, which serves as a core, as long as the bias coil for negative feedback 14 is capable of applying a bias field to the magnetic impedance element 12. Furthermore, in the example described above, the magnetic impedance element 12 and the resistor R are configured as a half-bridge, but the circuit can have a full-bridge configuration with three resistors and is not limited to the half-bridge configuration.

[0019] Fig. 2A and Fig. Figure 2B shows perspective views that depict the magnetic impedance element 12 according to the embodiment and the structures around the magnetic impedance element 12 in detail. Fig. 2A shows a first example and Fig. 2B shows a second example. As in Fig. As shown in Figure 2A, the magnetic impedance element 12 has a non-magnetic substrate 12a, a magnetic thin film (magnetic layer) 12b and electrodes 12c and 12d.

[0020] The non-magnetic substrate 12a is a substrate made of a non-magnetic material and is arranged on a printed circuit board 100. This non-magnetic substrate 12a is made, for example, of calcium titanate, oxide glass, titanium dioxide, or aluminum oxide and, in this embodiment, has a substantially cubic shape.

[0021] The magnetic thin film 12b is a magnetic metal layer with high magnetic permeability, arranged on a surface of the non-magnetic substrate 12a opposite a surface on which the printed circuit board 100 is arranged, and has a meandering shape (serpentine shape) in a top view, as shown in Fig. 2A is shown. More precisely, the magnetic thin film 12b has the shape of a rectangular profile, with its rise and fall extending in the longitudinal direction of the non-magnetic substrate 12a, which has an essentially cubic shape.

[0022] The magnetic thin film 12b is formed such that it exhibits magnetic anisotropy such that one direction for an axis of slight magnetizability is aligned with the longitudinal direction of the magnetic thin film 12b on the layer surface, and that the entire direction of the axis of slight magnetizability of the magnetic thin film 12d is aligned with the longitudinal direction of the non-magnetic substrate 12a. The direction of the axis of slight magnetizability here refers to the orientation of a crystal in which the magnetic thin film (magnetic body) 12b, which exhibits anisotropy, can be easily magnetized.

[0023] Electrodes 12c and 12d are provided on the surface of the non-magnetic substrate 12a at respective ends of the magnetic thin film 12b. Electrodes 12c and 12d are connected by bond wires to corresponding electrodes 100a and 100b, which are provided on the circuit board 100. The electrodes 100a and 100b, which are provided on the circuit board 100, are connected accordingly to the oscillator circuit 10 and the resistor R, which are located in Fig. 1 are shown.

[0024] The circuit board 100 also has a notch 100c on each side of the magnetic impedance element 12 in the width direction in such a way that it forms a gap to the magnetic impedance element 12, as shown in Fig. 2A is shown. The cutouts 100c extend from one end of the circuit board 100 towards the vicinity of the center of the circuit board 100.

[0025] The bias coil for negative feedback 14 is wound around the magnetic impedance element 12 by means of the cutouts 100c in the printed circuit board 100. The direction of the coil axis of the bias coil for negative feedback 14 is therefore aligned with the longitudinal direction of the non-magnetic substrate 12a, and thus the magnetic field detection direction coincides with the longitudinal direction of the magnetic impedance element 12. Since the direction of the axis of slight magnetizability is aligned with the longitudinal direction of the non-magnetic substrate 12a, as mentioned previously, it can be said that the magnetic thin film 12b is provided with a magnetic anisotropy such that an axis of slight magnetizability coincides with the magnetic field detection direction.

[0026] The magnetic thin film 12b can be provided on the back side of the non-magnetic substrate 12a, i.e., on the surface on which the printed circuit board 100 is arranged, as shown in Fig. Figure 2B illustrates this arrangement. In such a configuration, electrodes 12c and 12d are located at respective ends of the magnetic thin film 12b on the rear surface of the non-magnetic substrate 12a. Electrodes 100a and 100b are also located on the side of the circuit board 100 facing the rear surface of the non-magnetic substrate 12a.

[0027] It was back on Fig. 1 referred back, wherein the magnetic field detection sensor 1 also includes an instrumentation amplifier 16, a first amplifier 18, a first differentiating circuit 20, a second amplifier 22, a second differentiating circuit 24, a comparator 26, a flip-flop circuit 28 and a microcomputer (computing unit) 30 in addition to the units described above, and these units are connected to each other in the sequence listed here.

[0028] The instrumentation amplifier 16 receives as its input an output signal from the half-bridge circuit, which comprises the magnetic impedance element 12 and the resistor R. The first amplifier 18 is connected downstream of the instrumentation amplifier 16. The output voltage from the half-bridge circuit is amplified by the instrumentation amplifier 16 and the first amplifier 18 and then fed to the first differentiator circuit 20.

[0029] The first differentiating circuit 20 is configured to detect a point of change in the voltage amplified by the instrumentation amplifier 16 and the first amplifier 18. The first differentiating circuit 20 outputs this point of change in the output voltage from the half-bridge circuit as a trigger signal. The second amplifier 22 then amplifies the output signal from the first differentiating circuit 20. The second differentiating circuit 24 is configured to detect a point of change in the voltage amplified by the second amplifier 22. The second amplifier 22 and the second differentiating circuit 24 ensure that the trigger signal is output in a more pronounced form.Although the magnetic field detection sensor 1 according to the embodiment is provided with the first differentiating circuit 20 for differentiating the output signal of the magnetic impedance element 12, the second amplifier 22 and the second differentiating circuit 24 for differentiating the output signal of the magnetic impedance element 12, the magnetic field detection sensor can alternatively be provided with a single differentiating circuit for differentiating the output signal of the magnetic impedance element 12.

[0030] The trigger signal output by the second differentiator circuit 24 is fed to the comparator 26. The flip-flop circuit 28 outputs a HIGH-level signal and a LOW-level signal based on the trigger signal. The microcomputer 30 then records the time for HIGH and LOW. The time profile for HIGH and LOW represents the external magnetic field, as explained below in the description of its operation. The microcomputer 30 therefore detects the external magnetic field based on the time profile of HIGH and LOW. A JK flip-flop circuit is used as the flip-flop circuit 28.

[0031] The microcomputer 30 further generates a pulse voltage to apply a bias field to the bias coil for negative feedback 14. The magnetic field detection sensor 1 has a filter 32 and a third amplifier 34. The filter 32 converts the pulse output by the microcomputer 30 into a triangular signal, and the triangular signal output by the filter 32 is applied as an AC bias voltage to the bias coil for negative feedback 14 via the third amplifier 34. In this way, the bias field is applied to the magnetic impedance element 12.

[0032] The microcomputer 30 also outputs a signal (negative feedback signal) to apply a magnetic field in a direction opposite to the detected external magnetic field to the magnetic impedance element 12. The magnetic field detection sensor 1 has a high-current output amplifier 36 and an adder 38. The high-current output amplifier 36 amplifies the negative feedback signal output by the microcomputer 30. The adder 38 is arranged between the filter 32 and the third amplifier 34 and sums the triangular signal output by the filter 32 and the negative feedback signal amplified by the high-current output amplifier 36. In this way, the bias voltage and the negative feedback voltage are supplied to the negative feedback bias coil 14 via the third amplifier 34.

[0033] Since, as previously described, the magnetic field detection sensor 1 according to the embodiment provides a premagnetization and a negative feedback in a single premagnetization coil for negative feedback 14, the magnetic field detection sensor 1 can avoid an increase in size and cost compared to a design in which a coil for negative feedback and a premagnetization coil are provided separately.

[0034] The function, operating mode, and other features of the magnetic field detection sensor 1 according to the embodiment are now explained. By adapting the magnetic field detection direction to the axis of the magnetic thin film 12b's easy magnetizability, pyramidal magnetic impedance characteristics can be achieved.

[0035] Fig. Figure 3 is a diagram illustrating magnetic impedance characteristics. Fig. 3. The solid lines represent the properties according to the embodiment, and the dotted lines represent conventional properties. In Fig. 3 The horizontal axis represents a magnetic field H [Oe], and the vertical axis represents an impedance Z [Ohm]. As indicated by the dotted lines in Fig. As indicated in Figure 3, the conventional magnetic impedance characteristics correspond to an M-shape. With M-shaped characteristics, the change in impedance in an external magnetic field near 0 [Oe] is extremely small. Therefore, a very sensitive measurement is not possible using conventional methods unless the AC bias is applied at a level where the slope of the impedance change is steep (4 [Oe] to 8 [Oe]). Consequently, the current draw increases. Applying a DC bias at a level where the slope of the impedance change is steep also requires increased current draw.

[0036] Furthermore, the hysteresis is increased in the M-shaped properties, where the impedance changes occur with a large slope, as in Fig. Figure 3 shows that the detection accuracy deteriorates with increasing hysteresis. Furthermore, the highly sensitive magnetic field measurement is only possible in the range where impedance changes exhibit a steep slope. Therefore, only a limited detection range is available.

[0037] In contrast, pyramidal magnetic impedance properties are achieved in this embodiment by aligning the magnetic field detection direction and the axis of easy magnetizability of the magnetic thin film 12b with each other. The pyramidal properties, as in Fig. As shown in Figure 3, a certain amount of impedance change is ensured even near an external magnetic field of 0 [Oe]. In other words, the characteristics represent a certain slope even near 0 [Oe]. Therefore, applying a DC or AC bias voltage at a level where the slope of the impedance change is steep, as required for the M-shaped characteristics, becomes unnecessary, and the power consumption can be reduced.

[0038] Furthermore, pyramidal properties generally exhibit smaller hysteresis compared to some M-shaped properties, where the impedance change is steep. Therefore, pyramidal properties can improve detection accuracy compared to M-shaped properties. Additionally, since pyramidal properties represent a certain degree of slope across their entire range, a wider detection range can be ensured.

[0039] Fig. 4A and Fig. Figure 4B shows the output signals of a sensor with the magnetic impedance element 12 and the resistor R according to the embodiment. Fig. Figure 4A shows an example in which the external magnetic field is 0 [H / m], and Fig. Figure 4B shows an example where the external magnetic field is negative (for example, -40 [H / m]). Fig. 4A and Fig. 4B represents the horizontal axis as the magnitude (H [A / m] of the magnetic field and the vertical axis as the impedance Z [Ω].

[0040] As in Fig. As shown in 4A, the AC bias oscillates bi-symmetrically with respect to the apex of the pyramid (bi-symmetrically in Fig. 4) since the magnetic field detection sensor 1 according to the embodiment exhibits pyramidal magnetic impedance characteristics when the external magnetic field is 0 [H / m], and a frequency of impedance change output by the sensor according to the AC bias becomes twice the AC bias frequency.

[0041] More precisely, the magnetic field detection sensor 1 exhibits an impedance Z1 with respect to the AC bias at time Ta1, and an impedance Z2 with respect to the AC bias at time Ta2. The magnetic field detection sensor 1 also exhibits the impedance Z1 with respect to the AC bias at time Ta3, the impedance Z2 with respect to the AC bias at time Ta4, and the impedance Z1 with respect to the AC bias at time Ta5. In this way, the frequency of the sensor output is obtained as twice the AC bias frequency.

[0042] Conversely, if the external magnetic field is negative, the center of the AC bias oscillation is shifted from the apex of the pyramid, as shown in Fig. 4B is shown, and the sensor output signal changes accordingly.

[0043] More precisely, magnetic field detection sensor 1 exhibits an impedance Z3 with respect to the AC bias at time Tb1, and exhibits the impedance Z1 with respect to the AC bias at time Tb2. Magnetic field detection sensor 1 exhibits an impedance Z4 with respect to the AC bias at time Tb3, exhibits the impedance Z1 with respect to the AC bias at time Tb4, and exhibits the impedance Z3 with respect to the AC bias at time Tb5. Magnetic field detection sensor 1 exhibits the impedance Z5 with respect to the AC bias at time Tb6 and exhibits the impedance Z3 with respect to the AC bias at time Tb7.

[0044] When the external magnetic field is negative, the sensor output signal has a different shape compared to when the external magnetic field is 0 [H / m], and the sensor output signal assumes two maximum and two minimum values. These maximum and minimum values ​​are used as the trigger signal in the first differentiating circuit 20, the second amplifier 22, and the second differentiating circuit 24, as will be explained later. With reference to Fig. 4B is an example explained in which the external magnetic field is negative, but the same applies when the external magnetic field is positive, except that the center of the AC bias is shifted in the opposite direction.

[0045] Fig. Figure 5 is a time sequence diagram that represents various signals when the external magnetic field is 0 [H / m]. The time sequences shown in Fig. 5 and Fig. 6 and Fig. Figure 7, which are explained below, is shown with the horizontal axis representing the time axis [t] and the vertical axis representing, in order from top to bottom, “the pulse voltage output by the microcomputer to the filter”, “the AC bias applied to the bias coil for negative feedback”, “the output signal of the half-bridge circuit”, “the output signal of the second differentiator circuit”, and “the output signal of the flip-flop circuit” [V]. In the following explanation, “the voltage output by the microcomputer to the filter” is sometimes referred to as a first line, and “the AC bias applied to the bias coil for negative feedback” is sometimes referred to as a second line.“The output signal of the half-bridge circuit” is sometimes referred to as a third line, “the output signal of the second differentiating circuit” is occasionally referred to as a fourth line, and “the output signal of the flip-flop circuit” is occasionally referred to as a fifth line.

[0046] As in the first line in Fig. As specified in 5, the microcomputer 30 outputs a signal with a predetermined frequency (AC bias frequency f0). In particular, the frequency signal increases at time t. 10 on, occurs at time t 20 from, rises at time t 30 on, occurs at time t 40 from and rises at time t 50 The signal with such a frequency is converted into a triangular signal by the filter 32, and is amplified by the third amplifier 34, and the AC bias voltage, which is shown in the second line in Fig. The voltage specified in point 5 is generated. This AC bias voltage increases at time t. 10 the maximum value, takes on a value at time t 20 the minimum value, takes on a value at time t 30 the maximum value, takes on a value at time t 40 the minimum value and takes on a value at time t 50 the maximum value. Such an AC bias voltage is applied to the bias coil for negative feedback 14, and an alternating current magnetic field is applied to the magnetic impedance element 12.

[0047] When the previously described bias voltage is applied to the bias coil for negative feedback 14, assuming that the external magnetic field is 0 [H / m], the output signal of the half-bridge circuit is at twice the AC bias frequency, as with reference to Fig. 4A is explained. In particular, the output signal of the half-bridge circuit reaches its minimum value at time t. 10 , t20 , t 30 , t 40 and t 50 as in the third line in Fig. The output signal of the half-bridge circuit reaches its maximum value at time t. 60 , which between time t 10 and the time t 20 lies at time t 70 , which between time t 20 and the time t 30 lies at time t 80 , which between time t 30 and the time t 40 lies, and at time t 90 , which between time t 40 and the time t 50 lies.

[0048] The output signal of the half-bridge circuit is then converted into a trigger signal by means of the first differentiator circuit 20, the second amplifier 22, and the second differentiator circuit 24. Specifically, the trigger signal is output according to the maximum and minimum values ​​of the half-bridge circuit's output signal, as shown in the fourth line in Fig. 5 is specified. In other words, the trigger signal is given at time t. 10 , t 20 , t 30 , t 40 , t 50 , t 60 , t 70 , t 80 and t 90 won. The trigger signal takes the form of a positive trigger signal at time t. 10 , t 20 , t 30 , t 40 and t 50 on, and takes place at time t 50 , t 70 , t 80 and t 90 a trigger signal on the negative side.

[0049] The flip-flop circuit 28, which receives such a trigger signal, continuously outputs a HIGH-level signal during the time the trigger signal is on the negative side. The duration of the negative trigger signal, i.e., the time T during which the HIGH-level signal is output, changes depending on the external magnetic field. The microcomputer 30 therefore detects the external magnetic field based on the duration T during which the signal is at the HIGH level. In the Fig. In the example shown in Figure 5, the time T = 1 / 2f0, and therefore the microcomputer 30 recognizes that the external magnetic field is 0 [H / m].

[0050] Fig. Figure 6 is a time sequence diagram showing the various signals when the external magnetic field is positive.

[0051] First, as in the first line in Fig. As shown in Figure 6, the microcomputer 30 outputs a signal with a predetermined frequency (AC bias frequency f0). This signal is the same one shown in the first line in Figure 6. Fig. 5 is shown, and increases at time t 1+ on, occurs at time t 2+ from, rises at time t 3+ on, occurs at time t 4+ from, and rises at time t 5+ The signal, which has such a frequency, is converted into a triangular signal by the filter 32 and amplified by the third amplifier 34, and the AC bias voltage, which is in the second line in Fig. The voltage specified in line 6 is generated by this. This AC bias is the same as the one in the second line in Fig. The preload shown in section 5 reaches its maximum value at time t. 1+ on, takes on the minimum value at time t 2+ on, takes on the maximum value at time t 3+ on, takes on the minimum value at time t4+ and takes on the maximum value at time t 5+ An such AC bias voltage is supplied to the bias coil for negative feedback 14 and an alternating current magnetic field is applied to the magnetic impedance element 12.

[0052] When the previously described bias voltage is applied to the bias coil for negative feedback 14, the output signal of the half-bridge circuit, assuming that the external magnetic field is positive, is equal to the output signal that is in Fig. Figure 4B shows the signal, but it is shifted in the positive direction. In particular, the output signal of the half-bridge circuit reaches its minimum value at time t. 1+, t 2+ , t 3+ , t 4+ and t 5+ as in the third line in Fig. The output signal of the half-bridge circuit reaches its maximum value at time t. 6+ , which between time t1+ and the time t 2+ lies, at the time t 7+ , which between time t 2+ and the time t 2+ lies, at the time t 8+ , which is between time t3, and time t 4+ lies, and at that time t 9+ , which between time t 4+ and the time t 5+ lies.

[0053] The time t 6+ and the time t 7+ , which correspond to the maximum value, lie close to time t 2+ , and the time t 8+ and the time t 9+ lie near time t 4+ .

[0054] The output signal of the half-bridge circuit is then converted into a trigger signal by means of the first differentiator circuit 20, the second amplifier 22, and the second differentiator circuit 24. Specifically, a trigger signal corresponding to the maximum and minimum values ​​of the output signal of the half-bridge circuit is output, as shown in the fourth line in Fig. 6 is specified. In other words, the trigger signal is given at time t. 1+, t 2+ , t 3+ , t 4+ , t 5+ , t 6+ , t 7+ , t 8+ and t 9+ won. The trigger signal takes the form of a positive trigger signal at time t. 1+, t 2+ , t 3+ , t 4+ and t 5+ and takes the form of a negative trigger signal at time t 6+ , t 7+ , t 8+ and t 9+ to.

[0055] The flip-flop circuit 28, which receives such a trigger signal, continuously outputs a HIGH-level signal during the time in which the trigger signal is negative. Assuming that the external magnetic field is positive, the time t 6+ and the time t 7+ , at which the trigger signal with a negative sign is generated, each near time t 2+ , and the time t 8+ and the time t 9+ lie near time t 4+ Therefore, the time T during which the signal is at the HIGH level is longer than in the Fig. Example 5. The microcomputer 30 therefore detects the external magnetic field based on the time period T during which the signal is at a HIGH level. In the example shown in Fig. In the example shown in 6, the time T > 1 / 2f0, and therefore the microcomputer 30 recognizes that the external magnetic field is positive.

[0056] Fig. Figure 7 is a time sequence diagram showing the various signals when the external magnetic field is negative.

[0057] First, as in the first line in Fig. As indicated in figure 7, the microcomputer 30 outputs a signal with a predetermined frequency (AC bias frequency f0). This signal is the same one shown in the first line in Fig. 5 is shown, and increases at time t1, and decreases at time t 2- from, rises at time t 3- on, occurs at time t 4+ from and rises at time t 5- The signal, which has such a frequency, is converted into a triangular signal by the filter 32 and amplified by the third amplifier 34, and the AC bias voltage, which is shown in the second line in Fig. The voltage specified in line 7 is generated. This AC bias is the same as that shown in the second line in Fig. 5 is shown, and takes the maximum value at time t. 1-on, takes on the minimum value at time t 2- on, takes on the maximum value at time t 3- one takes on the minimum value at time t 4- and takes the maximum value at time t 5- An such AC bias signal is applied to the bias coil for negative feedback 14, and an alternating current magnetic field is applied to the magnetic impedance element 12.

[0058] When the previously described bias voltage is applied to the bias coil for negative feedback 14, assuming that the external magnetic field is negative, the output signal of the half-bridge circuit is equal to that which is obtained with reference to Fig. 4B is explained. In particular, the output signal of the half-bridge circuit reaches its minimum value at time t. 1- , t 2- , t 3- , t 4- and t 5- as in the third line in Fig. The output signal of the half-bridge circuit reaches its maximum value at time t. 6- , which is between time 0 and time t 1- lies, at time t 7- , which between time t 1- and the time t 2- lies, at time t 8- , which between time t 2- and the time t 3- lies, at time t 9- , which between time t 3- and the time t 4- lies, at time t 10- , which between time t 4- and the time t 5- lies, and at time t 11- , which is at time t 5- follows.

[0059] The time t 6- and the time t 7- , which correspond to the maximum value, lie close to time t 1- , and the time t 8- and the time t 9- are also close to time t3- The time t 10- and the time t 11- are also close to time t 5- .

[0060] The output signal of the half-bridge circuit is then converted into a trigger signal by means of the first differentiator circuit 20, the second amplifier 22, and the second differentiator circuit 24. Specifically, the trigger signal is output according to the maximum and minimum values ​​of the output signal of the half-bridge circuit, as shown in the fourth line in Fig. 7 is specified. In other words, the trigger signal is given at time t. 1- , t 2- , t 3- , t 4- , t 5- , t 6- , t 7- , t 8- , t 9- , t 10- and t 11- . won. The trigger signal becomes a positive trigger signal at time t. 1- , t 2- , t 3- , t 4- and t 5-, and becomes a negative trigger signal at time t 6- , t 7- , t 8- , t 9- , t 10- and t 11- .

[0061] The flip-flop circuit 28, which receives such a trigger signal, continuously outputs a HIGH-level signal during the time in which the trigger signal is negative. When the external magnetic field is negative, the time t 6- and the time t 7- , at which the negative trigger signal is generated, each time close to time t 1- , and the time t 8- and the time t 9- are also close to time t 3- The time t 10- and the time t 11- are also close to time t 5- The time T during which the signal is at a HIGH level is therefore shorter than in the example above. Fig. Example 5. The microcomputer 30 therefore detects the external magnetic field based on the time period T during which the signal is at the HIGH level. In the example shown in Fig. In the example shown in 5, this applies to the time T < 1 / 2f0, and therefore the microcomputer 30 recognizes that the external magnetic field is negative.

[0062] In the previously described example, it is preferred for the microcomputer 30 to send a RESET signal to the flip-flop circuit 28 when the AC bias frequency f0 drops (at the time indicated by the star marking in Fig. 5, Fig. 6 to Fig. (as specified in 7) sends, and it is preferred for the microcomputer 30 that it detects the external magnetic field based on the time period T corresponding to the first HIGH-level signal after the RESET signal. In this way, it is possible to react to a situation in which the second differentiating circuit 24 is unable to output a trigger signal accurately.

[0063] Fig. Figure 8 is a diagram showing a correlation between the duration T during which the signal is at a HIGH level and the magnitude of the external magnetic field. In this embodiment, the microcomputer 30 can detect not only the direction (positive, negative) but also the magnitude of the external magnetic field by measuring the Fig. The data shown in the 8 images will be stored in advance.

[0064] As previously described, in the magnetic field detection sensor 1 according to the embodiment, the longitudinal direction of the magnetic impedance element 12 is adapted to the magnetic field detection direction, and the magnetic impedance element 12 is designed to exhibit magnetic anisotropy such that an axis of slight magnetizability of the magnetic thin film 12b coincides with the longitudinal direction. By aligning the direction of the magnetic field detection direction and the axis of slight magnetizability of the magnetic thin film 12b in the magnetic field detection sensor 1, pyramidal magnetic impedance characteristics can be achieved. Achieving these pyramidal magnetic impedance characteristics in the magnetic field detection sensor 1 eliminates the need to apply a DC or AC bias voltage at a level where the slope of the impedance change becomes steep, as would have been required in a sensor with M-shaped characteristics.Furthermore, since the magnetic field detection sensor 1 with pyramidal properties exhibits smaller hysteresis than a sensor with M-shaped properties, the detection accuracy can be improved. Additionally, since the pyramidal properties have a certain degree of inclination or slope across their entire area, a wider detection range can be ensured. Therefore, the current consumption of the magnetic field detection sensor 1 can be reduced, the detection accuracy improved, and a wider detection range achieved.

[0065] Furthermore, since the magnetic field detection sensor 1 detects the external magnetic field based on the trigger signal output by the second differentiating circuit 24, a sensor with higher noise robustness can be provided compared to a configuration in which the external magnetic field is detected based on the amplitude difference and compared to a configuration using an integrated circuit. Therefore, the detection accuracy of the magnetic field detection sensor 1 can be further improved.

[0066] Furthermore, the magnetic field detection sensor 1 can avoid an increase in size and cost compared to a configuration that has a separate negative feedback coil and bias coil.

[0067] The present invention has been previously explained on the basis of an illustrative embodiment, but the present embodiment is not limited thereto, and further modifications within the scope of protection are possible without deviating from the basic idea of ​​the present invention.

[0068] For example, the magnetic field detection sensor 1 according to the embodiment is provided with a single bias coil for negative feedback 14, but a coil for negative feedback and a bias coil can be provided separately without being limited to the integrated bias coil for negative feedback 14.

[0069] Furthermore, in the embodiment, the magnetic thin film 12b of the magnetic impedance element 12 has a meandering shape (serpentine shape) in the top view, but it can also, for example, have a straight shape without being limited to the meandering shape.

[0070] Furthermore, in the embodiment of the micro-computer 30, the external magnetic field is detected based on the duration of the HIGH-level signal being output; however, it is not limited to this, but can detect the external magnetic field based on the duration that begins, for example, at the AC bias frequency f0, until the time of the drop of the HIGH-level signal, since the same effects can be achieved thereby. List of reference symbols 1 magnetic field detection sensor 10 Oscillator circuit 12 Magnetic impedance element 12a non-magnetic substrate 12b magnetic thin film (magnetic layer) 12c, 12d Electrodes 14. Pre-magnetization coil for negative feedback (pre-magnetization coil) 16 instrument amplifiers 18 first amplifier 20 first differentiating circuit 22 second amplifier 24 second differential circuit 26 Comparator 28 flip-flop circuit 30 microcomputers (processing units) 32 filters 34 third amplifier 36 high-current output amplifiers 38 Adders R resistance

Claims

A magnetic field detection sensor comprising: a magnetic impedance element configured to utilize a magnetic impedance effect; a bias coil configured to apply a bias field to the magnetic impedance element; an oscillator circuit configured to apply an alternating current to the magnetic impedance element; a differentiator circuit configured to differentiate an output signal of the magnetic impedance element; a flip-flop circuit configured to output a high-level signal and a low-level signal based on a trigger signal output by the differentiator circuit; and a computation unit configured to detect an external magnetic field based on a time series with high and low phases of the high-level and low-level signals output by the flip-flop circuit, wherein the magnetic field detection sensor is configuredto detect the external magnetic field based on an output signal obtained by applying alternating current to the magnetic impedance element, the magnetic impedance element comprising a non-magnetic substrate and a magnetic layer provided on a surface of the non-magnetic substrate, wherein a magnetic field detection direction coincides with a longitudinal direction of the magnetic impedance element, and the magnetic layer is configured to have magnetic anisotropy such that a direction of an axis of its easy magnetizability coincides with the magnetic field detection direction, and the computing unit is configured to send a reset signal to the flip-flop circuit at the time of a drop in an alternating current bias frequency, and to detect the external magnetic field based on the duration of an initial high-level signal following the reset signal. The magnetic field detection sensor according to claim 1, wherein the premagnetization coil is composed of a single premagnetization coil for negative feedback configured to apply the premagnetization field and a magnetic field for negative feedback to the magnetic impedance element.

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