JP2015055543A - Magnetic element controller and magnetic element control method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnetic element controller which suppresses abnormal oscillation of a voltage current conversion circuit which generates an excitation signal of current control, suppresses noise in a wide temperature range, and suppresses variation by offset temperature.SOLUTION: A magnetic element controller performs control so as to measure a stationary magnetic field applied to an FG type magnetic element composed of driving and detection coils by a magnetic balance type and has: an excitation signal adjustment part which performs voltage current conversion by a differential amplifier where a capacitor and a resistor are serially connected to either an output terminal or an input terminal and generates an excitation signal to be a current signal to be applied to an exciting coil from an alternate signal; a detection signal comparison part which detects a detection signal generated by a change of a current direction of the excitation signal; a feedback signal conversion part which converts a time width between detection signals into voltage information; a feedback signal adjustment part which generates a feedback signal from the voltage information; and a data signal conversion part which outputs the feedback signal as a data signal showing magnetic field intensity. An excitation signal where the feedback signal is superimposed on the alternate signal is generated.

Description

  The present invention relates to a signal processing circuit and a physical quantity measuring apparatus using the signal processing circuit, and in particular, a magnetic element control device and a magnetic element control for driving a magnetic element of a time-resolved fluxgate method (hereinafter referred to as FG method). Regarding the method.

In general, FG magnetic elements have higher sensitivity to detect magnetic fields and can be miniaturized compared to Hall elements and magnetoresistive elements, which are magnetic elements that detect similar magnetism. Used in azimuth detection devices.
FIG. 22 is a diagram illustrating a configuration example of a time-resolved FG type magnetic element (magnetic field proportional measurement). As shown in FIG. 22, in the FG magnetic element, an excitation winding and a detection winding are wound around the outer peripheral surface of a magnetic core 53 made of a high permeability material. The region around which the excitation winding is wound is driven by the excitation signal as the excitation coil 52, and the region around which the detection winding is wound outputs the detection signal as the detection coil 51.

  FIG. 23 is a waveform diagram for explaining the principle of magnetic field detection in the magnetic field proportional type using a time-resolved FG type magnetic element. FIG. 23A shows the exciting current supplied to the exciting coil 52 of the magnetic element, the vertical axis shows the current value of the exciting current, and the horizontal axis shows the time. FIG. 23B shows the magnetic flux density of the magnetic field generated in the magnetic core 50 by the exciting coil 52 of the magnetic element of FIG. 22, the vertical axis shows the magnetic flux density, and the horizontal axis shows the time. FIG. 23C shows voltage values of pulses generated by the induced electromotive force in the detection coil 51 of the magnetic element in FIG. 22, and the horizontal axis shows time.

In order to drive the excitation coil 52 in FIG. 23, an excitation current Id signal (hereinafter referred to as an excitation signal) is exchanged between a terminal TI1 and a terminal TI2 of the excitation coil 52, an alternating current excitation signal having a constant period, That is, as shown in FIG. 23B, it is applied as a triangular wave-shaped excitation signal (that is, a triangular wave current signal).
Thus, in the case of FIG. 23C in the time when the direction of the excitation current flowing through the excitation coil 52 changes (positive and negative alternating time zone of the excitation current), the detection coil is induced at time t1 and time t2. Positive and negative pulses are generated by electric power, and the voltage Vp of this pulse is used as a detection signal. This detection signal is generated between the terminals of the detection coil as a pulse having a positive and negative polarity voltage continuously corresponding to the period of the triangular wave current signal.

When a stationary magnetic field Hex that passes through a cylindrical space formed by the excitation winding and the detection winding of the magnetic core 53 is applied to this magnetic element, a stationary current corresponding to the stationary magnetic field flows in the excitation winding. That is, the above-described steady current is superimposed as an offset on the excitation current Id of the excitation signal applied to the excitation winding.
As a result, due to this offset, the driving state of the excitation coil 52 by the alternating excitation signal changes, that is, the time when the direction in which the excitation current Id flows changes between when the stationary magnetic field Hex is applied and when the stationary magnetic field Hex is applied. It will vary depending on when no is applied.

  At this time, as shown in FIG. 23A, the stationary magnetic field Hex is applied in the same direction as the magnetic field generated by the exciting coil as compared with the case where the stationary magnetic field Hex is not applied (Hex = 0). In the case of (Hex> 0), the horizontal axis L1 in which the direction in which the excitation current Id flows changes to the position of the horizontal axis L2. On the other hand, as compared with the case where the stationary magnetic field Hex is not applied, when the stationary magnetic field Hex in the direction opposite to the magnetic field generated by the exciting coil 52 is applied (Hex <0), the change in the direction in which the exciting current Id flows. The horizontal axis L1 is changed to the position of the horizontal axis L3.

As a result, the change in the magnetic flux density φ in the magnetic core 53, which changes according to the change timing of the direction in which the excitation current Id flows, also changes corresponding to the steady current superimposed on the excitation current Id. .
When the direction of the magnetic flux is changed, an induced electromotive force is generated in the direction to cancel the change of the magnetic flux with respect to the detection coil 51, that is, the detection signal is a pulse of a negative voltage at the timing when the excitation current Id changes from positive to negative. Occurs as. On the other hand, the detection signal is generated as a positive voltage pulse at the timing when the excitation current Id changes from negative to positive.

Therefore, the FG type magnetic element compares the output timing of the detection signal when the steady current Hex is not applied with the output timing of the detection signal when the steady current Hex is applied. Thus, the magnitude of the stationary magnetic field Hex can be indirectly measured. That is, when a steady magnetic field Hex is applied, a specific steady current flows through the excitation coil 52, so that a certain offset is superimposed on the excitation signal, and the time interval between the negative and positive voltage pulsed detection signals changes. .
Therefore, the magnetic field detection device using the FG type magnetic element measures the intensity of the stationary magnetic field Hex applied from the outside by measuring the time interval at which the negative and positive voltage pulse detection signals are generated. (For example, refer to Patent Document 1, Patent Document 2, and Patent Document 3).

Here, the maximum value of the excitation current Id applied to the excitation coil 52 is set to a value that generates a magnetic field that is equal to or higher than the saturation magnetic flux density of the magnetic core 53. Thereby, the measurement magnetic field range of the magnetic element includes a time of one period of the excitation signal and a time change (hereinafter referred to as excitation efficiency) corresponding to the current value of the steady current as an offset by applying the steady magnetic field Hex. Determined from.
That is, from time t0 to time t3 is one period of the excitation signal, and this period width is time T. When no stationary magnetic field Hex is applied (Hex = 0), a positive voltage detection signal (hereinafter referred to as a second detection signal) is output from time t1 when a negative voltage detection signal (hereinafter referred to as a first detection signal) is output. The time until the time t2 at which the detection signal is detected is a half period of the excitation signal, and thus is time T / 2.

  In addition, when a stationary magnetic field Hex is applied, a time width (hereinafter referred to as a measurement time width) from when the first detection signal is output until the second detection signal is detected changes with respect to time T / 2. To do. Here, as shown in FIG. 23C, when the magnetic flux direction of the stationary magnetic field Hex is a solid arrow (Hex> 0), the time width Tm is equal to the time Tm because it is the same direction as the magnetic flux direction generated by the exciting coil. / 2 (T0> Tm), on the other hand, when the magnetic flux direction of the stationary magnetic field Hex is a broken arrow (Hex <0), the time width Tp is the time because the direction is opposite to the magnetic flux direction generated by the exciting coil. It becomes longer than T / 2 (Tp> T0). Here, T0 = T / 2.

  Next, FIG. 24 is a diagram illustrating a configuration example of a time-resolved FG type magnetic element (magnetic field balance type measurement) 100. As shown in FIG. 24, the magnetic element of the FG method in the magnetic field balance measurement is different from the magnetic element of FIG. 22 on the outer peripheral surface of the magnetic core 53 made of a high permeability material and the excitation winding and the detection winding. In addition to the wire, a feedback (hereinafter FB) winding coil is wound. The region where the excitation winding is wound is driven by the excitation signal as the excitation coil 52, the region where the detection winding is wound outputs the detection signal as the detection coil 51, and the region where the feedback winding is wound is The FB coil 54 is driven by a feedback signal.

Next, FIG. 25 is a waveform diagram illustrating the principle of magnetic field detection in a magnetic field balance type using a time-resolved FG type magnetic element.
FIG. 25A shows the excitation current (current of the excitation signal) supplied to the excitation coil of the magnetic element, the vertical axis shows the current value of the excitation current, and the horizontal axis shows the time. The exciting current is a positive / negative alternating signal with a reference current value of 0 A (zero ampere) as a boundary. FIG. 25B shows the FB signal (that is, the feedback signal) by the current applied to the FB coil 54 of the magnetic element, the vertical axis shows the current value of the FB signal, and the horizontal axis shows the time. FIG. 25C shows voltage values of pulses generated by the induced electromotive force in the detection coil 51 of the magnetic element, and the horizontal axis shows time.

As shown in FIG. 25, in the magnetic field balance type measurement, the FB coil 54 generates a magnetic field that cancels out a stationary magnetic field applied to the magnetic element (a stationary magnetic field that passes through the magnetic core). Then, the stationary magnetic field applied to the magnetic element is measured from the current value when the FB coil 54 generates a magnetic field that cancels the stationary magnetic field.
In the magnetic field balance type, as described above, in addition to the detection coil 51 and the excitation coil 52, the FB coil 54 is provided in the magnetic element as a coil for generating a magnetic field for canceling the stationary magnetic field in the magnetic core. ing.
Hereinafter, in the present specification, the FB coil FB control is a method in which the FB signal is applied to cancel the stationary magnetic field in the magnetic core 53 and measure the magnetic field.

In the case of the magnetic field balance type measurement, the time interval of the pulses generated by the detection coil 51 is measured in the positive and negative alternating time zones of the excitation signal applied to the excitation coil 52, as in the magnetic field proportional expression already described. Then, the FB signal is output to the FB coil 54 so that the time from the time t1 at which the measured negative voltage detection signal is output to the time t2 at which the positive voltage detection signal is detected is T / 2. Apply.
For example, in FIG. 25C, when the time width between time t1 and time t2 becomes wider than T / 2, a stationary magnetic field in the negative direction is applied as shown in FIG. The signal curve has changed from the curve L0 to the curve L2. For this reason, in order to return the curve L2 of the excitation signal to the position of the curve L0 where the time width between the time t1 and the time t2 is T / 2, the current of the line FB2 in FIG. Apply the value FB signal.

On the other hand, in FIG. 25C, when the time width between time t1 and time t2 becomes narrower than T / 2, a stationary magnetic field in the positive direction is applied as shown in FIG. The signal curve is changed from the curve L0 to the curve L1. For this reason, in order to return the curve L1 of the excitation signal to the position of the curve L0, the FB signal having the current value of the line FB1 in FIG. 25B is applied to the FB coil.
Then, the strength of the stationary magnetic field applied to the magnetic element is obtained from the current value of the FB signal applied to the FB coil so that the time width between time t1 and time t2 is T / 2.
In the above description, the case where the vertical axis component in FIG. 25A is the current and the excitation signal applied to the excitation coil is described as a current signal, but the vertical axis component is the voltage value at both ends of the excitation coil terminal. It may be expressed as In this case, in FIG. 25A, the voltage on the vertical axis intersecting the horizontal axis is represented as Vref (0 A in current notation) as the reference reference voltage.

Next, FIG. 26 is a block diagram illustrating a configuration example of a magnetic detection device using the magnetic element control device in the FB coil FB control. 26, the magnetic element 100 has the configuration shown in FIG. 22, and includes a detection coil 51, an excitation coil 52, and an FB coil.
The magnetic element control device 200 includes a magnetic element control unit 201, a clock signal generation unit 202, and a clock signal adjustment unit 203.
The clock signal generation unit 202 generates a clock with a period T and outputs it to the clock signal adjustment unit 203.
The clock signal adjustment unit 203 adjusts the signal level of the supplied clock and outputs the adjusted clock to the magnetic element control unit 201.

The magnetic element control unit 201 includes a detection signal amplification unit 2012, a detection signal comparison unit 2013, a feedback signal adjustment unit 2014, a feedback signal conversion unit 2015, a data signal conversion unit 2016, an excitation signal adjustment unit 2017, and an excitation signal generation unit 2018. ing.
The excitation signal generation unit 2018 generates a triangular wave as an excitation signal shown in FIG. 25A from the clock supplied from the clock signal adjustment unit 203.
The excitation signal adjustment unit 2017 adjusts the voltage level of the excitation signal supplied from the excitation signal generation unit 2018 and supplies it to the excitation coil 52 as an excitation signal.

The exciting coil 52 generates a magnetic field corresponding to the triangular wave in the magnetic core 53 of the magnetic element 100.
The detection coil 51 generates a pulse in the positive and negative alternating time zones of the excitation signal in the magnetic core 53.
The detection signal amplification unit 2012 amplifies the voltage level of the pulse supplied from the detection coil 51 and outputs the amplified voltage level to the detection signal comparison unit 2013 as a detection signal.
The detection signal comparison unit 2013 obtains the difference between the time width between the time t1 and the time t2 of the pulse (detection signal) and T / 2, and outputs this difference to the feedback signal conversion unit 2015.
The feedback signal converter 2015 obtains the current value of the FB signal supplied to the FB coil 54 from the supplied difference.

Here, the feedback signal conversion unit 2015 reads the current value corresponding to the difference from the FB current value table previously written and stored in the internal storage unit, and obtains the current value of the FB signal. The FB current value table is a table showing the correspondence between the difference and the current value (digital value) that cancels the stationary magnetic field in the magnetic core.
The feedback signal adjustment unit 2014 performs D / A (Digital / Analog) conversion on the current value of the FB signal supplied from the feedback signal conversion unit 2015, and converts the generated current as the FB signal to the FB coil. Output. Further, the feedback signal adjustment unit 2014 outputs the current value of the FB signal supplied from the feedback signal conversion unit 2015 to the feedback signal adjustment unit 2014.

  The feedback signal adjustment unit 2014 obtains the strength of the stationary magnetic field canceled in the magnetic core 53, that is, the strength of the stationary magnetic field applied to the magnetic element 100 from the current value of the supplied FB signal. Here, the feedback signal adjustment unit 2014 reads out the magnetic field intensity corresponding to the current value of the FB signal from the current value magnetic field table previously written and stored in the internal storage unit, and is applied to the magnetic element 100. Find the strength of the stationary magnetic field. The current value magnetic field table is a table in which the current value of the FB signal corresponds to the intensity of the applied stationary magnetic field.

When performing magnetic field detection in the magnetic field proportional type using the time-resolved FG type magnetic element described above, the amount of magnetic field generated per current applied to the coil due to the material and structure of the magnetic core 53 of the magnetic element 100 ( Hereinafter, the measurable magnetic field range is determined by the excitation efficiency) and the intensity of the excitation signal.
On the other hand, when magnetic field detection in a magnetic field balance type is performed using a time-resolved FG type magnetic element, a detection signal is detected at a constant time interval (T / 2) regardless of a stationary magnetic field applied to the magnetic element 100. So that the magnetic field in the magnetic core is kept in an equilibrium state. For this reason, the magnetic field can be measured within a range that is limited by the power supply voltage of the entire magnetic element 100, that is, the current value of the FB signal can be supplied.

When a time-resolved FG type magnetic element is used to perform magnetic field detection in a magnetic field proportional type, the time interval at which the detection signal is output changes according to the magnetic field. It will be reflected directly in the characteristics.
On the other hand, when using a time-resolved FG type magnetic element and performing magnetic field detection in the magnetic field balance type, the magnetic field characteristic of the excitation efficiency is small as a characteristic of the magnetic element, so that the detection signal waveform and the detection signal are generated. The continuity of the time interval is easily maintained.
Therefore, when applied to a magnetic element that measures a magnetic field generated by a current of about several hundred A (ampere) as a measurement object while maintaining linearity in the entire measurement current range, compared to the conventional magnetic field proportional expression Magnetic field detection in a magnetic field balance type is mainly used.

JP 2008-292325 A JP 2007-078423 A JP 2007-078422 A

When performing magnetic field detection by the magnetic field proportional method using the time-resolved FG type magnetic element described above, the measurable magnetic field range is limited by the excitation efficiency and the excitation signal of the magnetic element 100 as described above.
For this reason, when a magnetic field proportional magnetic element is applied as a current sensor having a maximum measurement current of about several hundred A, in addition to the dependence of the linearity of the output of the single magnetic element on the strength of the magnetic field, the magnetic element is driven. There is a problem that the measurement range of the magnetic field that can obtain high-accuracy output linearity is limited by the limitation of the power supply voltage and the allowable maximum current value.

  Further, when the waveform of the detection signal generated by the detection coil 51 changes depending on the intensity of the stationary magnetic field Hex and the temperature of the magnetic core, the time differential value of the rise of the detection signal waveform and the output fluctuation of the detection signal There is a correlation. For this reason, the time fluctuation value of the output of the detection signal changes depending on the strength of the magnetic field, so that in the measurement of the magnetic field strength, the time fluctuation value increases, particularly as the magnetic field strength increases. The magnetic field cannot be detected.

On the other hand, when the magnetic field detection is performed by the magnetic field balance type using the time-resolved FG type magnetic element, the FB signal is generally applied by current control in the FB coil FB control.
As already described, the current value in the FB control signal and the intensity of the magnetic field generated by this current value are in a proportional relationship, and the FB coil 54 corresponds to the temperature due to the difference in the current value of the FB signal. Even if the resistance of the FB signal changes, the current value of the FB signal is controlled by a constant current. For this reason, the linearity of the sensitivity of the magnetic element can be maintained even in a high-strength magnetic field where the current value of the FB signal increases.

Even when the excitation efficiency of each of the excitation coil 52 and the FB coil 54 changes due to individual deviations in the characteristics of the magnetic element, the convergence state of the magnetic field balance between the magnetic field and the stationary magnetic field by the FB signal is output as the FB signal It is limited by the characteristics of the control circuit, and the residual (error) in convergence does not change.
Furthermore, when the ratio between the excitation efficiency of the excitation coil 52 and the excitation efficiency of the FB coil 54 is kept constant, the ratio of the magnetic sensitivity between the excitation coil 52 and the FB coil 54 does not change. The convergence time until the stationary magnetic field is balanced with the magnetic field does not change.
Therefore, when the exciting coil 52 and the FB coil 54 in the magnetic element 100 are simultaneously formed by a semiconductor process or the like, even if the resistances of the exciting coil 52 and the FB coil 54 change, the ratio of the coil resistance is maintained. The residual in the equilibrium state, which is an index of convergence of the magnetic field balance, and the time to reach the equilibrium state do not change.

However, when magnetic field detection is performed by a magnetic field balance type using a time-resolved FG type magnetic element, an amount of FB signal proportional to the magnetic field is required. There is a growing problem. Furthermore, when the strength of the magnetic field generated by the FB coil is controlled by the current value of the FB signal, it is necessary to perform constant current control on the current value corresponding to the strength of the magnetic field. For this reason, a voltage-current conversion circuit that performs constant current control must be mounted, the circuit scale of the control unit that controls the current applied to the FB coil increases, and the current consumption also increases.
Further, since the internal reference potential when the constant current in the voltage-current conversion circuit is generated fluctuates with time as the current value of the FB signal increases, the reference potential becomes unstable. Will fluctuate.

  Further, the temperature of the output value of the magnetic sensor under a constant magnetic field environment due to the temperature dependence of the offset of the amplifier of the voltage-current conversion circuit (excitation signal adjustment unit) 2017 as well as the characteristics of the excitation signal in the magnetic proportional type. There is a problem that changes occur. Further, although the measurement magnetic field range is limited by the FB current amount, it is effective to increase the excitation current in order to expand the measurement magnetic field range. However, since the amplification factor of the operational amplifier (differential amplifier) used in the voltage-current converter circuit is small, there is a problem that abnormal oscillation is likely to occur.

As described above, each type of control method of the magnetic element 100 has advantages and disadvantages with respect to linearity of magnetic sensitivity and current consumption in magnetic field detection.
However, it can be seen that the temperature-dependent characteristics of the offset and the magnetic sensitivity are common to the excitation signal control method. By controlling the excitation signal applied to the magnetic element 100, the temperature dependence of the magnetic sensitivity is reduced, but the temperature dependence of the offset is increased.
On the other hand, by using voltage control as the excitation signal applied to the magnetic element, the temperature dependence of the offset (output value of the magnetic element) is reduced, but the temperature dependence of the magnetic sensitivity occurs. For this reason, it is difficult to simultaneously reduce the temperature dependence of the magnetic sensitivity and the temperature dependence of the output value.

Therefore, when current control is performed on the excitation signal, it is necessary to compensate the output signal (output value) of the magnetic element in order to achieve highly accurate temperature characteristics. As a method for compensating an output signal, there is known a method of adjusting a setting value of an offset or an amplification factor of an operational amplifier provided in an output signal adjustment unit at the final stage in a control circuit that controls a magnetic element.
However, it is necessary to individually compensate for the temperature dependence of the offset generated in the output signal and the magnetic sensitivity by the combination of the specific control circuit and the specific magnetic element. When this compensation is performed, the technique realized by individually adjusting the constants of the passive elements of the analog electronic circuit in the control circuit maintains the compensation accuracy for each combination of the control circuit and the magnetic element at a certain level. There are problems that make it difficult.

In addition to the individual adjustment of the constants of the passive elements of the analog electronic circuit, a technique for compensating the output signal by numerical calculation using the measured value of the temperature sensor is known. This numerical calculation method measures the output signal at a specific temperature and magnetic field environment before compensation, and determines the coefficient of the approximate expression that correlates the temperature dependence of magnetic sensitivity and offset from each measured value. Once, the output signal is converted into a digital value using an A / D converter (analog / digital converter).
Therefore, the accuracy of compensation for the temperature dependence of the output signal is limited by the resolution of the converted digital value (resolution of the A / D converter).

  Digital circuits are often clock-controlled during operation. In particular, in the case of a semiconductor integrated circuit, spike-shaped noise caused by clock signal jitter, clock signal crosstalk, and ringing that occurs at the rise (or fall) of the clock is caused by analog noise in the semiconductor integrated circuit. Input to the circuit. As a result, the spike-shaped noise is superimposed on the excitation signal output from the analog electronic circuit. When the phase margin of the voltage-current converter for generating the excitation signal for current control is small and abnormal oscillation is likely to occur, spike-shaped noise superimposed on the excitation signal is the starting point, and the excitation that is the voltage-current converter Abnormal oscillation occurs in the signal adjustment unit 2017.

  In addition, in the excitation signal adjustment unit 2017, when an AC signal such as a triangular wave whose signal polarity is inverted via the reference potential of an operational amplifier (differential amplifier 20155 described later) that performs voltage-current conversion is used as the excitation signal, it depends on the type of the operational amplifier. May cause distortion in the signal in the time zone where the signal polarity is inverted (hereinafter referred to as crossover distortion). Generation of crossover distortion can be prevented by superimposing a bias current on the excitation signal so that the reference potential does not fall within the signal amplitude range of an AC signal such as a triangular wave. However, since the bias current is constantly applied, the current consumption of the control circuit increases. An amplifier that performs such an operation is called a class A amplifier.

On the other hand, the above-described crossover distortion occurs in an amplifier that operates with zero bias current, that is, a class B amplifier.
In addition, a class AB amplifier, which is a general general-purpose amplifier, is applied with an appropriate bias current in order to perform an intermediate operation between class A and class B. Even in this class AB amplifier, when an amplifier with a small maximum drive current is used for the purpose of reducing the consumption current of the amplifier, a crossover distortion is generated. When a detection signal is generated in the time zone when crossover distortion occurs, the linearity of magnetic sensitivity is reduced not only in magnetic proportional control but also in magnetic balance control, and it is in a constant temperature and constant magnetic field environment. The stability of the output value decreases.
Further, when the phase margin of the voltage / current converter circuit is small and abnormal oscillation is likely to occur, spike-shaped noise superimposed on the excitation signal and caused by crossover distortion is the starting point and abnormal oscillation occurs.

As described above, the current control of a relatively large amount of current is aimed at reducing the temperature dependence of the magnetic sensitivity with respect to the signal processing circuit of the FG type magnetic sensor regardless of the control method of the magnetic element. When the excitation signal circuit is used, the amplification factor of the operational amplifier for the current conversion circuit decreases. When the amplification factor of the operational amplifier is decreased, abnormal oscillation is likely to occur as described above.
In addition, as described above, abnormal oscillation may occur due to spike-shaped noise superimposed on the excitation signal. Examples of the noise source of the spike-shaped noise include a clock signal of a digital circuit and a crossover distortion caused by an amplifier operation of a generation circuit of an excitation signal. Spike-shaped noise increased the linearity error of the excitation signal slope. For this reason, the linearity error of the sensor output (output value) output from the magnetic sensor increases.

Further, when abnormal oscillation occurs and the amplitude and frequency of abnormal oscillation change with temperature, as a result, the offset of the sensor output changes at the temperature range where the oscillation state changes.
Therefore, in particular, when designing an FG magnetic sensor using a current-controlled excitation signal for a magnetic element, in order to maintain the temperature dependence of the sensor output, abnormal oscillation in the entire temperature range using the magnetic sensor It is necessary to suppress the occurrence.

  The present invention has been made in view of such circumstances, and suppresses abnormal oscillation of a voltage-current conversion circuit that generates an excitation signal for current control over a wide temperature range, so that it is superimposed on the excitation signal over the entire operating temperature range. It is an object of the present invention to provide a magnetic element control device and a magnetic element control method that reduce noise caused by the offset and prevent fluctuation due to offset temperature.

  The present invention has been made to solve the above-described problems, and the magnetic element control device of the present invention is capable of time-resolving the strength of a stationary magnetic field applied to a fluxgate type magnetic element including an excitation coil and a detection coil. This is a magnetic element control device that controls the magnetic element when detecting by a magnetic balance type, and has an excitation signal generation unit that generates an alternating signal and a voltage-current conversion circuit using a differential amplifier, A series circuit in which a capacitor and a resistor are connected in series is provided at either the output terminal or the input terminal of the amplifier, and is inserted between the output terminal and the input terminal based on the alternating signal. An excitation signal adjusting unit that generates an excitation signal that is a current signal to be applied to the excitation coil, and a detection signal for a positive or negative voltage generated by an induced electromotive force when the current direction of the excitation signal is switched. A detection signal comparator for detecting, a feedback signal converter for converting a time width between detection signals of a positive voltage and a negative voltage into voltage information, and a magnetic field for canceling a stationary magnetic field applied to the magnetic element from the voltage information A feedback signal adjustment unit that generates a feedback signal for generating the signal and a data signal conversion unit that outputs the feedback signal as a data signal indicating a magnetic field strength, and the excitation signal adjustment unit converts the alternating voltage signal into Converting into an alternating current, converting the feedback signal into a feedback current, superimposing the feedback current on the alternating current to generate the excitation signal, and applying the generated excitation signal to the excitation coil It is characterized by.

  In the magnetic element control device of the present invention, the series circuit is connected between the output terminal and a ground point, between the input terminal and the ground point, or between the input terminal and another input terminal in the differential amplifier. It is characterized by being inserted in between.

  In the magnetic element control device of the present invention, the capacitance value of the capacitor and the cutoff frequency of the differential amplifier are between the frequency of the alternating signal and the frequency of abnormal oscillation superimposed on the excitation signal. Each resistance value of the resistor is set.

  In the magnetic element control device of the present invention, the data signal converter has the feedback signal set in advance, and the magnetic field strength generated by the voltage value of the feedback signal and the voltage value of the feedback signal has linearity. The output is amplified by an amplification factor at which a voltage value outside the voltage range of the feedback signal is saturated and output.

  The magnetic element control device of the present invention superimposes an offset voltage corresponding to a magnetic field due to an ambient environment for measuring a steady magnetic field on the feedback signal, and the feedback signal on which the offset voltage is superimposed is sent to the feedback signal adjustment unit. It further has an offset voltage adjusting unit for outputting.

  The magnetic element control device according to the present invention further includes an adjustment signal generation unit that generates an offset signal for canceling an offset component superimposed on the data signal, and the excitation signal adjustment unit receives an alternating current from the alternating signal, A feedback current is generated from the feedback signal and an offset current is generated from the offset signal, and the excitation current applied to the excitation coil is generated by superimposing the feedback current and the offset current on the alternating current. It is characterized by.

  In the magnetic element control device of the present invention, the offset signal is set to a voltage that cancels the offset component, which is a difference between a data signal measured in a zero magnetic field and an expected value of a designed data signal in the zero magnetic field. It is characterized by being.

  The magnetic element control device of the present invention detects the strength of a stationary magnetic field applied to a fluxgate type magnetic element composed of an excitation coil, a detection coil, and a feedback coil by using a time-resolved magnetic balance type. A magnetic element control device that controls a magnetic element, an excitation signal generation unit that generates an alternating signal, and an electric current signal that generates an alternating voltage signal from the alternating signal and that is applied to the excitation coil based on the alternating voltage signal An excitation signal adjustment unit that generates an excitation signal, a detection signal comparison unit that detects a detection signal of a positive or negative voltage generated by an induced electromotive force when the current direction of the excitation signal is switched, a positive voltage and a negative voltage A feedback signal converter for converting a time width between voltage detection signals into voltage information; and a magnetic field for canceling a stationary magnetic field applied to the magnetic element from the voltage information in the feedback coil. A feedback signal adjustment unit that generates a feedback signal that is a current signal to be applied; a data signal conversion unit that outputs the feedback signal as a data signal indicating magnetic field strength; and at least one of the excitation signal and the feedback signal An adjustment signal generation unit that outputs a DC adjustment signal that has been adjusted in advance, and that is superimposed, and the excitation signal adjustment unit or the feedback signal adjustment unit has a voltage-current conversion circuit using a differential amplifier, A series circuit in which a capacitor and a resistor are connected in series is provided at either the output terminal or the inverting input terminal of the differential amplifier, and the excitation signal or the feedback signal is generated based on the DC adjustment signal. The detection signal applied to the excitation coil or the feedback coil interposed between the output terminal and the inverting input terminal and detected by the detection signal comparison unit Generates staggered with respect to the non-linear region of the excitation signal, characterized in that.

  In the magnetic element control device of the present invention, the adjustment signal generation unit includes a first resistor having one end connected to an input terminal capable of inputting an adjustment voltage, and the excitation signal adjustment unit or the feedback signal adjustment unit includes: One end has a second resistor connected to the excitation signal generator and the feedback signal converter, respectively, and the first resistor and the second resistor are connected to the inverting input terminal of the differential amplifier, A normal rotation input terminal of the differential amplifier is connected to a preset reference voltage, the excitation coil or the feedback coil is connected between an output terminal of the differential amplifier and the inverting input terminal, and the difference The dynamic amplifier is characterized in that a current is passed through the exciting coil or the feedback coil so that the voltage level of the inverting input terminal is equal to the voltage level of the normal input terminal.

  The magnetic element control method of the present invention controls the magnetic element when detecting the strength of a stationary magnetic field applied to a fluxgate type magnetic element composed of an excitation coil and a detection coil by a time-resolved magnetic balance type. This is a magnetic element control method for performing an excitation signal generation process for generating an alternating signal, and a voltage / current generated by a differential amplifier provided with a series circuit in which a capacitor and a resistor are connected in series to either the output terminal or the input terminal. An excitation signal, which is a current signal, is converted, generates an alternating voltage signal from the alternating signal, and is applied to the excitation coil interposed between the output terminal and the input terminal based on the alternating voltage signal An excitation signal adjustment process for generating a positive signal, a detection signal comparison process for detecting a positive or negative voltage detection signal generated by an induced electromotive force when the current direction of the excitation signal is switched, And a feedback signal conversion process for converting a time width between detection signals of negative voltage and voltage into voltage information, and a feedback signal for generating a magnetic field for canceling a stationary magnetic field applied to the magnetic element from the voltage information. A feedback signal adjustment process; and a data signal conversion process for outputting the feedback signal as a data signal indicating magnetic field strength. In the excitation signal adjustment process, the alternating voltage signal is converted into an alternating current, and the feedback signal is The excitation signal is converted into a feedback current, the feedback current is superimposed on the alternating current to generate the excitation signal, and the generated excitation signal is applied to the excitation coil.

  When the magnetic element control method of the present invention detects the strength of a stationary magnetic field applied to a flux gate type magnetic element composed of an excitation coil, a detection coil, and a feedback coil by a time-resolved magnetic balance type, A magnetic element control method for controlling a magnetic element, an excitation signal generation process for generating an alternating signal, and an electric current signal for generating an alternating voltage signal from the alternating signal and applying the alternating voltage signal to the excitation coil based on the alternating voltage signal An excitation signal adjustment process for generating an excitation signal, a detection signal comparison process for detecting a detection signal of a positive or negative voltage generated by an induced electromotive force when the current direction of the excitation signal is switched, a positive voltage and a negative voltage A feedback signal generation process for converting a time width between voltage detection signals into voltage information, and a magnetic field for canceling a stationary magnetic field applied to the magnetic element from the voltage information. A feedback signal adjustment process for generating a feedback signal that is a current signal applied to the coil, a data signal conversion process for outputting the feedback signal as a data signal indicating a magnetic field strength, and at least one of the excitation signal and the feedback signal. An adjustment signal generation process for outputting a pre-adjusted DC adjustment signal to be superimposed on the signal, and in the excitation signal adjustment process or the feedback signal adjustment process, either the output terminal or the inverting input terminal Voltage-current conversion by a differential amplifier provided with a series circuit in which a capacitor and a resistor are connected in series, and generating the excitation signal or the feedback signal based on the DC adjustment signal, the output terminal and the The detection signal detected by the detection signal comparison unit is applied to the excitation coil or the feedback coil inserted between the inverting input terminal and the feedback coil. Generating shifted relative to the non-linear region of the excitation signal, characterized in that.

  According to the present invention, when the excitation signal for current control is generated by the voltage-current conversion circuit, the capacitor is connected to either the output terminal or the input terminal in which the excitation coil is inserted in the differential amplifier circuit of the voltage-current conversion circuit. By providing a series circuit consisting of a resistor and a resistor, it is possible to reduce noise superimposed on the excitation signal in the entire operating temperature range by suppressing abnormal oscillation in the voltage-current converter circuit over a wide temperature range. Can prevent fluctuations.

It is a figure which shows the structural example of the magnetic element control apparatus 110 by the 1st embodiment. It is a figure which shows the structural example of the magnetic element 50 which is a fluxgate type | mold magnetic element. It is a graph which shows the principle of operation of a fluxgate type magnetic element. It is a figure which shows the structural example of the excitation signal adjustment part 1016 in FIG. It is a figure which shows the other structural example of the excitation signal adjustment part 1016 in FIG. It is a figure explaining the structure which suppresses the abnormal oscillation in the excitation signal adjustment part 1016 of FIG. It is a figure which shows the output waveform of the excitation signal of the excitation signal adjustment part 1016 shown in FIG. 6 in 25 degreeC. It is a figure which shows the output linearity error in the output waveform of the excitation signal of the excitation signal adjustment part 1016 shown in FIG. 6 in 25 degreeC. It is a figure which shows the output waveform of the excitation signal of the excitation signal adjustment part 1016 shown in FIG. 6 in 125 degreeC. It is a figure which shows the frequency dependence of the amplification factor of the excitation signal adjustment part 1016 shown in FIG. 6 in 25 degreeC. It is a figure which shows the relationship between the offset value (offset output) of the output of the excitation signal adjustment part 1016 of the structure of type3 shown in FIG.6 (c), and temperature. It is a figure which shows the structural example of the excitation signal adjustment part 1016 in 1st Embodiment. It is a figure which shows the other structural example of the excitation signal adjustment part 1016 in 1st Embodiment. It is a flowchart which shows the operation example of the magnetic element control apparatus 110 in 1st Embodiment. It is a figure which shows the structural example of the magnetic element control apparatus 210 in 2nd Embodiment. FIG. 16 is a diagram illustrating a configuration example of an excitation signal adjustment unit 1016 and an adjustment signal generation unit 1100 in FIG. FIG. 16 is a diagram illustrating another configuration example of the excitation signal adjustment unit 1016 in FIG. 15. It is a figure which shows the structural example of the magnetic element control apparatus 310 by 3rd Embodiment. It is a figure which shows the structural example of the excitation signal adjustment part 1016 in FIG. It is a figure which shows the other structural example of the excitation signal adjustment part 1016 in FIG. It is a figure for demonstrating the principle of 3rd Embodiment. It is a figure which shows the structural example of the magnetic element (magnetic field proportional measurement) of a time-resolved FG system. It is a wave form diagram explaining the principle of the magnetic field detection in a magnetic field proportional type using a time-resolved FG type magnetic element. It is a figure which shows the structural example of the magnetic element (magnetic field balance type | mold measurement) of a time-resolved FG system. It is a wave form diagram explaining the principle of the magnetic field detection in a magnetic field balance type | mold using the time-resolved FG type magnetic element. It is a block diagram which shows the structural example of the magnetic detection apparatus using the magnetic element control apparatus in FB coil FB control.

<First Embodiment>
With reference to FIG. 1, the magnetic element control apparatus 110 by the 1st Embodiment of this invention is demonstrated. FIG. 1 is a diagram illustrating a configuration example of the magnetic element control device 110 according to the first embodiment. In FIG. 1, the magnetic element control device 110 includes a magnetic element control unit 111, a clock signal generation unit 102, a clock signal adjustment unit 103, and a data signal determination unit 104. The magnetic element control device 110 according to the present invention detects an intensity of a stationary magnetic field applied to a flux gate type magnetic element 50 including a detection coil 51 and an excitation coil 52 by a time-resolved magnetic balance type. The excitation signal applied to 52 (for example, the already explained triangular wave current signal) is controlled.
The magnetic element control unit 111 includes a detection signal amplification unit 1011, a detection signal comparison unit 1012, a feedback signal adjustment unit 1013, a feedback signal conversion unit 1014, a data signal conversion unit 1015, an excitation signal adjustment unit 1016, an excitation signal generation unit 1017, and an offset. A voltage adjustment unit 1018 is provided.

The clock signal generation unit 102 includes an oscillator that generates a clock signal having a predetermined period, and outputs the generated clock signal to the clock signal adjustment unit 103.
The clock signal adjustment unit 103 performs processing such as amplifying the signal level of the supplied clock signal or changing the cycle of the clock signal, and outputs the processing result clock signal to the excitation signal generation unit 1017.
The data signal determination unit 104 determines whether the voltage value of the data signal indicating the strength of the stationary magnetic field supplied from the data signal conversion unit 1015 is a numerical value in a preset data range.

Based on the clock signal supplied from the clock signal adjustment unit 103, the excitation signal generation unit 1017 generates an alternating signal, for example, a triangular wave signal as an alternating voltage signal that alternates using 0 V as a reference potential.
The excitation signal adjustment unit 1016 amplifies the triangular wave signal generated by the excitation signal generation unit 1017 with a predetermined amplification factor, and generates a triangular wave voltage signal. Further, the excitation signal adjustment unit 1016 converts the generated triangular wave voltage signal into a voltage-to-current signal, generates an excitation signal that is a triangular wave current signal (hereinafter sometimes simply referred to as a current signal), and applies the excitation signal to the excitation coil 52. .

Next, FIG. 2 is a diagram illustrating a configuration example of a magnetic element 50 that is a fluxgate magnetic element.
In the magnetic element 50, two windings are wound around the magnetic core 53, and a detection coil 51 constituted by one winding and an exciting coil 52 constituted by another winding. Consists of.

  Next, FIG. 3 is a graph showing the operation principle of the fluxgate type magnetic element. FIG. 3A is a graph showing the time change of the triangular wave current signal for generating the excitation signal supplied to the excitation coil 52, with the vertical axis indicating the current and the horizontal axis indicating the time. In FIG. 3A, the triangular wave current signal supplied to the exciting coil 52 is a positive / negative alternating signal with the reference reference current 0A as a boundary. 3B, the vertical axis indicates voltage and the horizontal axis indicates time, and the direction of the excitation current flowing in the excitation coil 52 by the triangular wave current signal of FIG. The detection signal (first detection signal at time t1) generated in the detection coil 51 by the induced electromotive force when the polarity of the current changes and thereby the polarity of the current value of the excitation signal (excitation current) that is a current signal changes) , A second detection signal at time t2).

Here, FIG. 3A shows a stationary magnetic field in which the reference current value generated by the exciting current applied to the exciting coil 52 is applied when the stationary magnetic field (Hex) is applied to the magnetic element 50. It is shown that there is a deviation from the reference current value by the DC voltage that generates In addition, the generation timing of the first detection signal (time t1) and the second detection signal (time t2) is shifted in time corresponding to the deviation due to the stationary magnetic field (Hex) from the reference current of the excitation current. ing.
Further, as can be seen from FIG. 3B, the time width Tw between the time t1 of the first detection signal and the time t2 of the second detection signal and the time T / 2 which is ½ of the period T of the triangular wave. If the difference Td is 0, no stationary magnetic field (Hex) is applied to the magnetic element 50. If the difference Td is positive, a negative stationary magnetic field (Hex <0) is applied, and the difference Td is negative. If so, a positive stationary magnetic field (Hex> 0) is applied.

Returning to FIG. 1, the detection signal amplifying unit 1011 amplifies the voltage across the detection coil 51 of the magnetic element 50 with a preset amplification factor.
The detection signal comparison unit 1012 compares the voltage value of the amplified detection signal supplied from the detection signal amplification unit 1011 with a predetermined threshold voltage value, and compares the first detection signal and the second detection signal (FIG. 3). (B) is detected.
Here, as shown in FIG. 3, the first detection signal is a negative pulse and is generated by the induced electromotive force in a voltage region where the polarity of the voltage applied to the exciting coil 52 changes from positive to negative. To do. On the other hand, the second detection signal is a positive pulse, and induction in the boundary region where the polarity of the current of the excitation signal applied to the excitation coil 52 changes from negative (negative current) to positive (positive current). Generated by electricity.

  In the above description, the excitation signal applied to the excitation coil 52 is a current signal. That is, the vertical axis component in FIG. 3A is the current value of the excitation signal. For this reason, the reference current value of the alternating signal in FIG. 3A is the current value on the vertical axis that intersects the horizontal axis, and is 0 A (zero amperes).

  In the first embodiment, as a configuration for generating a voltage of a feedback signal that is an FB signal, a configuration in which digital processing is performed using a digital value and a configuration in which analog processing is performed using an analog value. In any case, the magnetic element control device 110 can be configured. Hereinafter, a configuration for generating the voltage of the feedback signal by digital processing and a configuration for generating the feedback voltage by analog processing will be described in order.

The configuration for generating the voltage of the feedback signal by digital processing The detection signal comparison unit 1012 measures the time width from the first detection signal to the second detection signal, and the time width Tw is a half time of the period T of the triangular wave. That is, a difference Td (= Tw− (T / 2)) from T / 2 is obtained and output to the feedback signal converter 1014.
When the difference Td that is time information is supplied from the detection signal comparison unit 1012, the feedback signal conversion unit 1014 generates voltage information that generates a voltage of the feedback signal as the FB signal from the difference Td.
Here, in the feedback signal conversion unit 1014, a time voltage information table indicating the correspondence between the difference Td and the voltage information of the digital value corresponding to the difference Td is written and stored in advance in the internal storage unit.

  The feedback signal conversion unit 1014 reads voltage information corresponding to the supplied difference Td from the time voltage information table stored in the internal storage unit, and outputs the voltage information to the feedback signal adjustment unit 1013. For example, the voltage information is digital value data indicating the voltage value of the feedback signal. The voltage information has a polarity of the difference Td, that is, has a positive polarity when the difference Td is positive, and has a negative polarity when the difference td is negative. Therefore, when a stationary magnetic field (Hex) having a positive polarity is applied to the magnetic element 50, a feedback current of a negative polarity current is obtained with respect to the current signal resulting from the voltage-current conversion of the triangular wave voltage signal. On the other hand, when a stationary magnetic field (Hex) having a negative polarity is applied, a feedback current having a positive polarity current is superimposed on a current signal obtained by converting a triangular wave voltage signal into a voltage / current.

The feedback signal adjustment unit 1013 generates a feedback signal having a voltage value indicated by the voltage information based on the voltage information supplied from the feedback signal conversion unit 1014, and outputs the feedback signal to the excitation signal adjustment unit 1016 as an FB signal.
Here, since the voltage information is a digital value, the feedback signal adjustment unit 1013 includes, for example, a D / A converter therein, and inputs the voltage information that is the supplied digital value to the D / A converter to generate a direct current. A voltage is obtained and output to the excitation signal adjustment unit 1016 as a feedback signal.
The excitation signal adjustment unit 1016 converts the feedback signal, which is the FB signal supplied from the feedback signal adjustment unit 1013, into a feedback current, and superimposes the internally generated triangular wave voltage signal on the voltage-current converted current signal. An excitation signal is applied to the excitation coil 52.

When the feedback current is superimposed on the excitation signal, the time interval between the first detection signal and the second detection signal detected by the detection signal comparison unit 1012 is in the vicinity of T / 2.
Therefore, when the feedback signal is already superimposed on the excitation signal, the detection signal comparison unit 1012 uses an error indicating an error between the feedback signal to be T / 2 and the feedback signal currently applied as time information to be output. Voltage. Therefore, when the excitation signal is applied, the detection signal comparison unit 1012 outputs the difference Td to the feedback signal conversion unit 1014 as time information indicating the error voltage described above.

Further, when the difference Td that is time information indicating the error voltage is supplied, the feedback signal conversion unit 1014 stores the voltage information corresponding to the difference Td in the internal storage unit as described above. Read from the time voltage information table and output to the feedback signal adjustment unit 1013.
The feedback signal adjustment unit 1013 includes a storage unit therein, and voltage information is accumulated and stored in the storage unit, and a feedback signal is generated using the accumulated voltage information.
Here, the feedback signal adjustment unit 1013 determines whether or not the voltage information corresponding to the difference Td is included in a preset voltage range.

When the voltage information is not included in the set voltage range, the feedback signal adjustment unit 1013 has a voltage that does not affect the cancellation of the stationary magnetic field applied to the magnetic element 50 (less than the measurement accuracy). A voltage indicating a stationary magnetic field).
In other words, the feedback signal adjustment unit 1013 determines that the time width of the first detection signal and the second detection signal is approximately T / 2 due to an error in control accuracy. At this time, the feedback signal adjustment unit 1013 discards the voltage information within the error range without adding it to the time information until immediately before the internal storage unit.

The data signal conversion unit 1015 amplifies the voltage information supplied from the feedback signal adjustment unit 1013 with a preset amplification factor and outputs the amplified voltage information to the outside.
The amplification degree in the data signal conversion unit 1015 is set to a value that outputs only the voltage value range of the feedback signal in a linearly measurable range in advance as a data signal. In other words, this amplification degree is a voltage obtained by amplifying only the range in which the magnetic field that cancels the stationary magnetic field and the feedback signal of the voltage value that generates this magnetic field maintain linearity, and the voltage outside the range is saturated to a constant voltage. It is what. That is, the data signal conversion unit 1015 performs a preset amplification in which the voltage value of the feedback signal is saturated with the voltage value of the feedback signal and the magnetic field strength generated by the voltage value is outside the voltage range of the feedback signal having linearity. Depending on the rate, the feedback signal is amplified and output.

The offset voltage adjustment unit 1018 in the magnetic element control unit 111 is based on the time width of the first detection signal and the second detection signal in a state where the stationary magnetic field (Hex) to be measured is not applied to the magnetic element 50. When it deviates from the time width, for example, T / 2 which is half the period T of the triangular wave, an offset voltage for correcting this deviation is generated. This offset voltage has a steady magnetic field of 0, and is set as a voltage that cancels the magnetic field due to the environment corresponding to the intensity of the magnetic field generated by the environment around the installation position of the magnetic element 50.
Then, the offset voltage adjustment unit 1018 adds the offset voltage generated by itself to the feedback signal supplied from the feedback signal adjustment unit 1013, and uses the addition result as a new feedback signal to the excitation signal adjustment unit 1016. Output.

The data signal determination unit 104 determines whether or not the voltage value of the data signal supplied from the data signal conversion unit 1015 is included in a preset data range (output data designation range). In the data signal determination unit 104, the data range is previously written and stored in an internal storage unit. This data range determines whether or not the voltage value indicated by the data signal amplified and output by the data signal conversion unit 1015 is included in a region where the magnetic field and the voltage value indicating the magnetic field are in a linear relationship. It is a range of voltage values.
Here, when the voltage value of the data signal is not included in the data range, the data signal determination unit 104 outputs a data signal (error signal) indicating an error to the external magnetic field strength detection device. In addition, when the voltage value of the data signal is included in the data range, the data signal determination unit 104 outputs a data signal indicating the voltage value to the external magnetic field strength detection device.

Therefore, this data signal indicates the magnetic field voltage for obtaining the strength of the magnetic field for canceling the stationary magnetic field, that is, the strength of the stationary magnetic field. An external magnetic field strength detection device (not shown) converts the voltage value of the magnetic field voltage indicated by the data signal into the magnetic field strength, and outputs the converted magnetic field strength.
Here, in the magnetic field strength detection device, a magnetic field strength table indicating the correspondence between the voltage value of the magnetic field voltage and the strength of the magnetic field corresponding to the voltage value of the magnetic field voltage is written and stored in advance in the internal storage unit. ing.
The magnetic field strength detection device reads out the magnetic field strength corresponding to the voltage value of the magnetic field voltage indicated by the data signal supplied from the magnetic element control device 110 from the magnetic field strength table and sets it as a numerical value of the strength of the stationary magnetic field (Hex). , Display on the display unit provided in itself. In the present invention, the magnetic element control device 110 and the magnetic field intensity detection device (not shown) described above constitute a magnetic detection device.

Configuration for Generating Feedback Signal Voltage by Analog Processing The detection signal comparison unit 1012 outputs the first detection signal and the second detection signal to the feedback signal conversion unit 1014.
The feedback signal conversion unit 1014 generates a pulse having a duty ratio as voltage information based on the period (interval between time t1 and time t2, that is, the time width) in which the first detection signal and the second detection signal are output. The pulse is output to the feedback signal adjustment unit 1013 as voltage information. That is, the feedback signal conversion unit 1014 obtains a duty ratio indicating the voltage value of the feedback signal from the time width as voltage information, and outputs a rectangular wave having a duty ratio indicating the voltage value of the feedback signal to the feedback signal adjustment unit 1013. Output.
When the information is indicated by a rectangular wave signal, the feedback signal adjustment unit 1013 generates a DC voltage corresponding to the duty ratio by a PWM (Pulse Width Modulation) circuit or the like and outputs it as a feedback signal.

For example, when the time width from the first detection signal to the second detection signal is longer than the time width from the second detection signal to the first detection signal, the stationary magnetic field needs to be negative. Therefore, the feedback signal adjustment unit 1013 generates a DC voltage feedback signal that generates a positive magnetic field that cancels the stationary magnetic field.
On the other hand, when the time width from the second detection signal to the first detection signal is longer than the time width from the first detection signal to the second detection signal, since the stationary magnetic field is positive, the feedback signal adjustment unit 1013 is A DC voltage feedback signal that generates a negative magnetic field that cancels the stationary magnetic field is generated.

That is, when a pulse as voltage information is supplied, the feedback signal adjustment unit 1013 generates a feedback signal having a voltage value corresponding to the duty ratio of the pulse, and the generated feedback signal is sent to the excitation signal adjustment unit 1016. Output.
Here, the feedback signal adjustment unit 1013 is provided with, for example, a voltage-current conversion circuit configured using an operational amplifier. In this voltage-current converter circuit, an amplifier with an operational amplifier function is used, and this amplifier functions so that the potential difference between the positive input and the negative input is maintained at zero. Therefore, the current signal from the amplifier output to the positive input And is proportional. Then, by applying a signal proportional to the current signal as a feedback signal to the exciting coil 52, a magnetic field is generated by the feedback signal so that the magnetic field applied to the magnetic core in the magnetic element 50 becomes constant. Adjust to. As a result, the time interval between the first detection signal and the second detection signal can be kept constant without depending on the external stationary magnetic field.

As in the case of digital processing, the excitation signal adjustment unit 1016 converts a feedback current obtained by converting the feedback signal supplied from the feedback signal adjustment unit 1013 into a voltage-current, and converts a triangular wave voltage signal generated inside the control circuit into a voltage current. The excitation signal superimposed with the converted current signal is applied to the excitation coil 52 with the feedback current superimposed.
Since the operation of the data signal conversion unit 1015 is the same as that of digital processing except that the analog value is amplified, description thereof is omitted.
Further, the external magnetic field strength detection device converts the analog value data signal supplied from the magnetic element control device 110 into a digital value by A / D (Analog / Digital) conversion, and performs the same operation as described in the digital processing. Obtain the magnetic field strength.

  Next, FIG. 4 is a diagram illustrating a configuration example of the excitation signal adjustment unit 1016 in FIG. That is, in FIG. 4, the excitation signal adjustment unit 1016 provides feedback (FB) when the excitation signal adjustment unit 1016 of the magnetic element control unit 111 generates an excitation signal from the triangular wave signal output from the excitation signal generation unit 1017 using a differential signal. ) Signals are added by current. In FIG. 4, an excitation signal adjustment unit 1016 generates an excitation signal based on the difference between the triangular wave signal from the excitation signal generation unit 1017 and the inverted signal of the triangular wave signal, and outputs the excitation signal from the output terminal.

The excitation signal adjustment unit 1016 includes a resistor 20170, an amplifier circuit 20171, an inverting circuit 20172, a resistor 20153, an amplifier circuit 20174, and an amplifier 20175. The resistor 500 is a resistance component of the exciting coil 52. Here, the resistance value 20170 has a resistance value Rf, and the resistance 20153 has a resistance value R. The amplifier 20155 performs voltage-current conversion by converting a voltage signal excitation signal into a current signal excitation signal using a resistor 20113.
In the case of the excitation signal adjustment unit 1016 having the circuit configuration shown in FIG. 4, the feedback current of the FB signal (the same applies when a steady current is added) is supplied to the (−) input terminal (inverting input terminal) of the amplifier 20155. . That is, the resistor 20170 is interposed between the output of the offset voltage adjustment unit 1018 and the (−) input terminal of the amplifier 20155. The resistor 20170 converts the voltage (feedback voltage) of the feedback signal output from the offset voltage adjustment unit 1018 into a voltage-current, and outputs it as a feedback current If to the (−) input terminal of the amplifier 20155. Further, the resistance value Rf is set so that the current value of the feedback current If corresponds to the amount of shift of the magnetic field indicated by the feedback voltage and becomes a current value that changes the excitation current Iex.

  Next, FIG. 5 is a diagram illustrating another configuration example of the excitation signal adjustment unit 1016 in FIG. That is, in FIG. 5, the excitation signal adjusting unit 1016 is a current signal obtained by converting the triangular wave signal output from the excitation signal generating unit 1017 into a voltage-current converted by the excitation signal adjusting unit 1016 of the magnetic element control unit 111, as in the case of FIG. On the other hand, a feedback current obtained by converting the FB signal into a voltage / current is added to generate an excitation signal used for current control. In FIG. 5, the excitation signal adjustment unit 1016 generates an excitation signal based on the difference between the triangular wave signal from the excitation signal generation unit 1017 and the reference voltage Vref, and outputs the excitation signal from the output terminal.

  The excitation signal adjustment unit 1016 includes a resistor 20170, a resistor 20176, and an amplifier 20175. The resistor 500 is a resistance component of the exciting coil 52. Here, the resistor 20170 has a resistance value Rf, and the resistor 20176 has a resistance value R. The amplifier 20175 performs voltage-current conversion by converting a voltage signal excitation signal into a current signal excitation signal using a resistor 20176. Further, the resistor 20170 converts the voltage of the feedback signal (feedback voltage) output from the offset voltage adjustment unit 1018 into voltage-current and outputs it as a feedback current If to the (−) input terminal of the amplifier 20155. Further, the resistance value Rf is set so that the current value of the feedback current If corresponds to the amount of shift of the magnetic field indicated by the feedback voltage and becomes a current value that changes the excitation current Iex.

  In the case of the excitation signal adjustment unit 1016 having the circuit configuration shown in FIG. 5, the FB signal is supplied to the (−) input terminal of the amplifier 20155. Thus, a feedback loop in the magnetic balance method of the magnetic element control unit 111 using the inspection circuit 10 in the present embodiment is formed. The resistor 20176 converts the triangular wave signal, which is a voltage signal, into a current signal, and supplies it to the (−) input terminal of the amplifier 20175. That is, the excitation signal adjustment unit 1016 is a voltage / current conversion circuit.

FIG. 6 is a diagram illustrating a configuration for suppressing abnormal oscillation in the excitation signal adjustment unit 1016 of FIG. FIG. 5 shows three types of configurations of the excitation signal adjustment unit 1016. FIG. 6A shows the configuration of type 1 and is the same as FIG.
FIG. 6B shows the configuration of type 2 and shows the configuration of the excitation signal adjustment unit 1016 provided with a capacitor 20107 for suppressing abnormal oscillation. The capacitor 20117 is inserted between the output terminal of the amplifier 20175 and the ground point, and is a phase compensation capacitor.
FIG. 6C shows the configuration of type 3 and shows the configuration of an excitation signal adjustment unit 1016 provided with a capacitor 20187 and a resistor 2018 to suppress abnormal oscillation. The capacitor 20107 and the resistor 20178 are inserted in series between the output terminal of the amplifier 20175 and the ground point. The capacitor 20117 is a phase compensation capacitor.

FIG. 7 is a diagram showing an output waveform of the excitation signal of the excitation signal adjustment unit 1016 shown in FIG. In FIG. 7, the horizontal axis indicates time, and the vertical axis indicates the amplitude value of the excitation signal. FIG. 7A shows the output waveform (excitation signal) of the configuration of type 1, FIG. 7B shows the output waveform of the configuration of type 2, and FIG. 7C shows the output waveform of the configuration of type 3. .
Each excitation signal adjustment unit 1016 in FIG. 6 has a current value I obtained by dividing the voltage value (Vref) of the reference signal input to the (+) input terminal (non-inverting input terminal) by the resistance value R of the resistor 20176. Be controlled. This control is the same not only in the configuration of the single-ended signal in FIGS. 5 and 6, but also in the configuration of the differential signal in FIG.

  FIG. 8 is a diagram showing an output linearity error in the output waveform of the excitation signal of the excitation signal adjustment unit 1016 shown in FIG. In FIG. 8, the horizontal axis represents the applied magnetic field, and the vertical axis represents the numerical value of the output linear error. 8A shows the output linearity error in the output waveform of the configuration of type 1, FIG. 8B shows the output linearity error in the output waveform of the configuration of type 2, and FIG. 8C shows the output linearity error of the configuration of type 3. The output linearity error in the output waveform is shown. The output linearity error is a numerical value obtained by linearly approximating the correspondence between the applied magnetic field and the output value of the magnetic sensor, and standardizing the distance of the output value from the straight line.

  FIG. 9 is a diagram showing an output waveform of the excitation signal of the excitation signal adjustment unit 1016 shown in FIG. In FIG. 9, the horizontal axis indicates time, and the vertical axis indicates the amplitude of the excitation signal. FIG. 9A shows an output waveform of the excitation signal having the configuration of type 2, and FIG. 9B shows an output waveform of the excitation signal having the configuration of type 3.

  FIG. 10 is a diagram showing the frequency dependence of the amplification factor of the excitation signal adjusting unit 1016 shown in FIG. 6 at 25 ° C. In FIG. 10, the horizontal axis indicates the frequency, and the vertical axis indicates the amplification factor of the operational amplifier. FIG. 10A shows the frequency dependency of the configuration of type 2, and FIG. 10B shows the frequency dependency of the configuration of type 3. In FIG. 10, the frequency fc is a cut frequency. The frequency fp is a frequency at which a resonance peak occurs.

  FIG. 11 is a diagram illustrating the relationship between the offset value (offset output) of the output of the excitation signal adjustment unit 1016 having the type 3 configuration illustrated in FIG. 6C and the temperature. In FIG. 11, the horizontal axis indicates the temperature, and the vertical axis indicates the offset output (voltage value). FIG. 11 is a diagram showing the temperature dependence of the offset output in the case of changing the resistance value of the resistor 20178 connected in series with the capacitor 20107 and each resistance value. In FIG. 11, “×” indicates that the resistance value of the resistor 20178 is 0Ω (same configuration as type 2 without adding a resistor), “◇” indicates that the resistance value of the resistor 20178 is 5Ω, and “□” indicates that the resistance value of the resistor 20178 is 10Ω. , “Δ” indicates that the resistance value of the resistor 20178 is 20Ω, and “◯” indicates that the resistance value of the resistor 20178 is 30Ω.

In the case of a differential signal, as shown in FIG. 4, in-phase alternating current signals having different polarities at the (+) input terminal and the (−) input terminal are supplied as a positive feedback signal and a negative feedback signal.
In the case of a single end signal, as shown in FIG. 5, a DC voltage having a constant voltage value is supplied as a reference voltage Vref to the (+) input terminal.
In the amplifier 20155, the output signal from the output terminal is input to the (−) input terminal. The amplifier 20155 is in a state where abnormal oscillation is likely to occur when the gain is small and the phase margin is small.

In general, an operational amplifier has a characteristic that abnormal oscillation is suppressed when the phase shift (hereinafter referred to as phase margin) of an output signal with respect to an input signal when the amplification factor is 0 dB is as large as possible within a range of ± 180 °. is there.
As shown in FIG. 4, in the case of a circuit composed of a plurality of operational amplifiers including an inverting circuit 20172 and an amplifier 20155 that are voltage followers, the output signal is input at the same magnification as a negative feedback signal to the (−) input terminal. Therefore, abnormal oscillation is likely to occur. In addition, when the inverting circuit 20172 that is a voltage follower and the amplifier 20175 are combined, the maximum value of the amplifier (hereinafter referred to as a resonance peak) due to the resonance frequency of each operational amplifier may occur.

Furthermore, in the case of the time-resolved FG method, in order to expand the measurement magnetic field range, it is necessary to increase the excitation current as much as possible. For this reason, it is necessary to reduce the set value of the amplification factor of the amplifier 20175, so that abnormal oscillation in the amplifier 20175 is likely to occur.
As can be seen from FIG. 7, in the case of the type 1 configuration shown in FIG. 6A in which no countermeasure against abnormal oscillation is taken, an abnormal oscillation AC signal is superimposed on the excitation signal.

As described above, when the abnormal oscillation is superimposed on the excitation signal that is an AC signal, distortion may occur in the rising and falling slopes of the waveform of the excitation signal.
Here, in the circuit configuration shown in FIG. 6A, the excitation signal generator generates an AC signal having an arbitrary voltage peak value. In other words, an oscillation circuit having an arbitrary frequency is formed by the amplifier 20115.

On the other hand, the amplifier 20155 and the inverting circuit 20172 are feedback circuits in which the output from the output terminal is fed back to the (−) input terminal. For this reason, when the phase margin is small, abnormal oscillation may occur at an oscillation frequency caused by the amplifier characteristics of the amplifier 20155 and the inverting circuit 20152. This abnormal oscillation propagates to both the (−) input terminal side and the output terminal side of the amplifier 20155 and the inverting circuit 20172. For this reason, it is also superimposed on the AC signal of the excitation signal generator 1017.
In particular, when the excitation signal is a differential signal and the positive signal and the negative signal are generated by separate operational amplifiers, the amount and phase in which abnormal oscillation is superimposed on the positive signal and the negative signal may be different. When the frequency of abnormal oscillation is higher than the frequency of the excitation signal, the linearity of the slope of the excitation signal may deteriorate as a result, and the slope may be distorted.

  Due to the distortion of the slope, as shown in FIG. 8A, in the configuration of type 1 shown in FIG. 6A, a non-linear region is seen in the slope in the region where the polarity of the excitation signal is reversed. The output linearity error of the sensor output has a maximum value, and the linearity of the sensor output with respect to the magnetic field deteriorates. On the other hand, as shown in FIGS. 7B and 7C, each of type 2 and type 3 taking measures against abnormal oscillation suppresses the superimposition of the abnormal oscillation AC signal in the output waveform of the excitation signal. At the same time, it can be seen that there is no nonlinear region on the slope.

In order to suppress the abnormal oscillation described above, as a method of stopping oscillation caused by the phase difference characteristic (Board diagram) of the output signal of the gain of the operational amplifier (amplifier 20175) alone, a phase compensation capacitor 20117 is provided in the operational amplifier. The installation method is generally known. A Bode diagram is a diagram showing the frequency characteristics of a transfer function in a linear time-invariant system, and is usually used as a combination of a gain diagram and a phase diagram.
When a phase compensation capacitor 20107 is added to the output terminal of the operational amplifier, as shown in FIG. 10B, in the type 2 configuration, the frequency fc (hereinafter, cut frequency) at which the amplification factor of the amplifier 20175 starts to decrease. Decrease). For this reason, in the configuration of type 2, there is an effect that the phase margin of the operational amplifier is increased and the occurrence of abnormal oscillation is suppressed.

In addition, it is possible to suppress abnormal oscillation by connecting a capacitor 20107 in addition to the output terminal of the amplifier 20175 described above. As other connection points to the amplifier 20155, the following three locations are conceivable. Including the configuration in which the capacitor 20117 is added to the output terminal of the amplifier 20155, the phase margin can be increased in all of the following configurations a, b, and c.
a. A capacitor 20117 is connected between the (−) input terminal and the (+) input terminal of the amplifier 20075.
b. A capacitor 20117 is inserted between the (−) input terminal of the amplifier 20155 and the ground point.
c. A capacitor 20117 is inserted between the output terminal of the amplifier 20115 and the ground point.

Excitation coil 52 (which may be indicated as resistance 500 as the resistance component of excitation coil 52) is connected between the (−) input terminal and output terminal of amplifier 20155. For this reason, when the excitation signal generation unit 1017 and the amplifier 20175 are integrated, the configuration b and the configuration c can be applied.
In the case of type 2 shown in FIG. 6B, a capacitor 20117 having an appropriate capacitance value is connected between the exciting coil connection terminal of the integrated circuit and the ground.
As a result, as shown in FIG. 7B, abnormal oscillation superimposed on the excitation signal is suppressed as compared with the excitation signal of type 1 in FIG.
And generation | occurrence | production of abnormal oscillation is suppressed and distortion on the slope of an excitation signal is relieve | moderated as shown to type2 of FIG.7 (b). By reducing the distortion on the slope, as a result, as shown in FIG. 8B, the maximum value of the linearity error of the sensor output in the vicinity of the zero magnetic field is reduced in the configuration of type 2. is there.

However, by adding the capacitor 20117, the cut frequency of the amplifier 20155 is reduced. Thereby, when the cut frequency approaches the frequency of the excitation signal, the linearity of the slope of the output waveform of the excitation signal is deteriorated, and as a result, the linearity error of the sensor output is increased.
Further, when the capacitance value of the capacitor 20117 decreases due to the temperature rise, the phase margin becomes small, and abnormal oscillation occurs in the amplifier 20175 at a high temperature (125 ° C.) in the configuration of type 2 as shown in FIG. There is a case.

  Therefore, by increasing the capacitance value of the capacitor 20117, abnormal oscillation is suppressed even at high temperatures. However, since the cut frequency fc is lowered, there is a problem that the gain of the excitation signal is also lowered. Therefore, although the cut frequency of the amplifier 20155 is reduced, in order to suppress the generation of resonance peaks in a multi-stage operational amplifier configuration, it is necessary to set the amplification factor at the frequency fp at which resonance peaks occur to 0 dB or less.

  As shown in FIG. 10C, it is effective to realize the lag lead characteristic obtained by the configuration of type 3 as a state where the amplification factor at the frequency fp at which the resonance peak occurs is 0 dB or less. As a method of obtaining the lag lead characteristics, there is a configuration in which a resistor 20178 is connected in series to a capacitor 20107 and then grounded as in the configuration of type 3 shown in FIG. That is, a series circuit in which a capacitor 20107 and a resistor 2018 are connected in series is inserted between the output terminal of the amplifier 20155 and the ground point.

As shown in FIG. 10 (c), the amplifier 20105 having the configuration of type 3 suppresses a decrease in the amplification factor in the high frequency region as compared with type 2, and the amplification factor at the resonance peak is set to 0 dB or less. it can. Here, it was confirmed that good lag lead characteristics can be obtained by connecting a resistor 20178 having an appropriate resistance value in series with a capacitor 201077 added to the output terminal of the amplifier 20175.
Further, in the configuration of type 3 shown in FIG. 6C, a series connection of a capacitor 20117 and a resistor 2017 is added to the output terminal of the amplifier 20155. With this type 3 circuit configuration, as shown in FIG. 9B, it can be seen that the occurrence of abnormal oscillation in the high temperature range (125 ° C.) is suppressed compared to type 2 shown in FIG. 9A. .

On the other hand, as shown in FIG. 11, when the capacitance value of the capacitor 201077 is made constant and the resistance value of the resistor 20178 is changed, the offset temperature characteristic of the sensor output changes depending on the resistance value of the resistor 20178. When the resistance value of the resistor 20178 is increased, the offset in the low temperature region changes greatly. On the other hand, it was found from the results shown in FIG. 11 that the offset above a specific temperature hardly changes.
Here, when the resistance value of the resistor 20178 is increased, the amount of current flowing to the grounding point is reduced due to this resistance value, so that the offset superimposed on the excitation signal is reduced.

Although the resistance value of the resistor 20178 has temperature dependence, there is a correlation between the amount of current flowing through the resistor 20178 and the offset voltage of the excitation signal. For this reason, it is considered that the temperature change of the offset is reduced by increasing the resistance value of the resistor 20178.
Therefore, it is possible to connect the offset value in the low temperature region closer to the offset value in the high temperature region as shown in FIG. As a result, the change in offset in the output value of the magnetic sensor can be reduced in all temperature ranges in the operating temperature range of the magnetic sensor. As described above, in FIG. 11, the horizontal axis indicates the temperature, and the vertical axis indicates the offset output (voltage value).

In the configuration of type 3 shown in FIG. 6C, an example in which a capacitor 20107 and a resistor 20178 are connected to the output terminal of the amplifier 20175 is shown.
However, for the purpose of suppressing the occurrence of abnormal oscillation in a high temperature region and adjusting the temperature change of the offset value, the (−) input terminal of the amplifier 20175 or the output terminal of the amplifier 20175 and the ( -) It is good also as a structure which connected the capacitor | condenser 201077 and the resistor 20178 to both the input terminals.
Further, in the excitation signal adjustment unit 1016 of the magnetic element control unit 111 shown in FIG. Add a circuit.

  Therefore, the excitation signal adjustment unit 1016 in the present embodiment has the configuration shown in FIG. 12 or FIG. FIG. 12 is a diagram illustrating a configuration example of the excitation signal adjustment unit 1016 in the first embodiment. FIG. 13 is a diagram illustrating another configuration example of the excitation signal adjustment unit 1016 according to the first embodiment. In each of FIGS. 12 and 13, a series circuit in which a capacitor 20107 and a resistor 2018 are connected in series is interposed between the output terminal of the amplifier 20175 and the ground point. In addition, in each of FIGS. 12 and 13, the same reference numerals are given to the same configurations as those in FIGS. 4 and 5.

  As described above, the present embodiment sets the cut frequency between the frequency of the excitation signal and the frequency of abnormal oscillation, and the capacitor 20177 and the resistor 20178 as an external connection circuit of the amplifier 20175 aimed at the lag lead characteristic. The amplifier 20105 is connected in series between the output terminal and the grounding point. With this configuration, according to the present embodiment, abnormal oscillation can be suppressed up to a high temperature region, so that it is possible to suppress the abnormal oscillation having a higher frequency than the excitation signal from being superimposed on the excitation signal that is an AC signal. . As a result, the slope of the excitation signal is prevented from being distorted, and the slope linearity is improved. In addition, according to the present embodiment, the amount of change in the offset output in a wide temperature range can be reduced by adjusting the capacitance value of the capacitor 20117 and the resistance value of the resistor 20178 and suppressing the amount of current flowing to the ground point. Can do.

With the configuration described above, according to the present embodiment, the feedback signal is superimposed on the excitation signal, and this excitation signal is applied to the excitation coil 52. Therefore, a magnetic element generally used in a magnetic proportional expression can be used. Compared to the conventional magnetic element provided with the FB coil used in the measurement of the magnetic field strength by the time-resolved magnetic balance type, it is possible to configure an inexpensive and small-sized magnetic detection device. Here, in addition to reducing the size of the magnetic element, when the size of the magnetic element is equivalent to the magnetic balance type, the excitation efficiency is increased by using the FB coil region and increasing the number of excitation coils and detection coils. Thus, the measurement range of the stationary magnetic field can be further expanded, and the S / N (Signal / Noise) ratio of the detection signal in the detection coil can be improved.
Further, in the present embodiment, the cut-off frequency is set between the frequency of the excitation signal and the frequency of abnormal oscillation, and as an external connection circuit of the amplifier 20175 aiming at the lag lead characteristics, a capacitor 20107 and a resistor 20178 are provided. It is connected in series between the output terminal and the grounding point. With this configuration, according to the present embodiment, abnormal oscillation can be suppressed up to a high temperature region, so that it is possible to suppress the abnormal oscillation having a higher frequency than the excitation signal from being superimposed on the excitation signal that is an AC signal. . As a result, the slope of the excitation signal is prevented from being distorted, and the slope linearity is improved. In addition, according to the present embodiment, the amount of change in the offset output in a wide temperature range can be reduced by adjusting the capacitance value of the capacitor 20117 and the resistance value of the resistor 20178 and suppressing the amount of current flowing to the ground point. Can do.
The configuration of the present embodiment described above performs magnetic field balance measurement by superimposing the feedback signal on the excitation signal without using the FB coil. However, even in the configuration of the FB coil FB control in which a feedback signal (current signal) is applied to the FB coil and the magnetic field balance type measurement is performed, in the excitation signal adjustment unit for supplying the excitation current to the excitation coil for this embodiment and the issue As a nautical chart connection circuit aiming at lag lead characteristics, the capacitor 20107 and the resistor 20178 in this embodiment are connected in series between an output terminal of an amplifier that applies an excitation current (AC signal) to an excitation coil and a ground point. Similar to the present embodiment, it is possible to suppress the superposition of abnormal oscillation with a frequency higher than that of the excitation signal.

In addition, according to the present invention, the magnetic element generally used in the magnetic proportional expression is used, but the range of the strength of the stationary magnetic field applied to the magnetic element as compared with the case of magnetic field detection by the magnetic proportional expression. Can be taken widely.
In addition, according to the present invention, since the feedback signal is superimposed as the FB signal on the triangular wave voltage signal, the constant current (FB) is compared with the case where the FB signal is applied as the current to the conventional FB coil. The time variation of the reference voltage of the differential signal when generating the signal) can be stabilized, and the time variation of the output data signal can be suppressed.

Further, according to the present invention, when the excitation signal generation unit 1017 generates a triangular wave, a nonlinear region near the reference potential (hereinafter referred to as crossover distortion) due to the characteristics of the operational amplifier used for generation is avoided. The time interval of the detection signals (first detection signal, second detection signal) can be corrected by FB control.
For example, in order to accurately determine the timing at which the magnetic equilibrium is reached, an offset is given to the triangular wave voltage signal in advance, and the reference potential is adjusted so as to cross a triangular wave region having no crossover distortion. Even in the magnetic balance type using the FB coil, it is possible to perform control to avoid the above-described crossover distortion. However, it is necessary to once convert the feedback current used as the FB signal into a feedback signal that is a voltage signal. Therefore, constant current control is not performed. As a result, the accuracy of detecting the magnetic field strength is deteriorated depending on the temperature of the magnetic element 50.

  Next, the operation of the magnetic element control device 110 in this embodiment will be described with reference to FIGS. 1 and 14. FIG. 14 is a flowchart illustrating an operation example of the magnetic element control device 110 according to the first embodiment. In the first embodiment, a case where a feedback signal is generated by digital processing will be described. The configuration for generating the feedback signal by analog processing can be similarly performed by the operation of the flowchart of FIG.

Step S1:
The detection signal amplification unit 1011 amplifies the voltage across the detection coil 51 and outputs the amplified voltage to the detection signal comparison unit 1012.
Then, the detection signal comparison unit 1012 subtracts the reference time width T / 2 from the time width Tw between the time t1 when the first detection signal is detected and the time t2 when the second detection signal is detected, The difference Td of the subtraction result is output as time information to the feedback signal converter 1014. Moreover, when this time information is converted into a digital value, it is desirable to use TDC (Time to Digital Converter) or the like.

Step S2:
Next, the feedback signal conversion unit 1014 reads voltage information indicating the voltage value of the feedback signal corresponding to the difference Td, which is the supplied time information, from the time voltage information table stored in the storage unit.
Then, the feedback signal conversion unit 1014 outputs the read voltage information to the feedback signal adjustment unit 1013.

Step S3:
Next, the feedback signal converter 1014 reads voltage information indicated by the immediately preceding feedback (FB) signal stored in the internal storage unit. The immediately preceding feedback signal is voltage-to-current converted and superimposed as a feedback current on the current signal obtained by changing the current triangular wave voltage signal.
Then, the feedback signal conversion unit 1014 adds the voltage information supplied from the detection signal to the voltage information read from the storage unit.
The feedback signal conversion unit 1014 generates a feedback signal having a voltage value indicated by the voltage information based on the voltage information of the addition result, and outputs the feedback signal to the offset voltage adjustment unit 1018.
Further, the feedback signal conversion unit 1014 writes and stores the voltage information of the addition result as new immediately previous voltage information in the internal storage unit, and stores this voltage information (digital value) to the data signal conversion unit 1015. Output.

Step S4:
Next, the offset voltage adjusting unit 1018 adds the offset voltage generated by itself to the supplied feedback signal, and outputs the added feedback signal to the excitation signal adjusting unit 1016 as a new feedback signal.
The offset voltage adjustment unit 1018 outputs offset information, which is a digital value indicating the offset voltage, stored in the internal storage unit, to the data signal conversion unit 1015.
Then, the excitation signal adjustment unit 1016 converts the triangular wave voltage signal synchronized with the clock signal output from the clock signal adjustment unit 103 into a voltage-current converter, generates a current signal, and converts the feedback signal supplied from the offset voltage adjustment unit 1018 into the voltage current. The converted feedback current is superimposed and applied to the excitation coil 52 as an excitation signal.

Step S5:
Next, the data signal conversion unit 1015 subtracts the offset information supplied from the offset voltage adjustment unit 1018 from the voltage information supplied from the feedback signal adjustment unit 1013, and sets the subtraction result as new voltage information.
Then, the data signal conversion unit 1015 amplifies the voltage information of the subtraction result with a preset amplification degree, and outputs the amplification result to the data signal determination unit 104 as a data signal.

Step S6:
Next, the data signal determination unit 104 determines whether or not the voltage value indicated by the data signal is included in a preset data range.
At this time, when the voltage value indicated by the data signal is included in the data range, the data signal determination unit 104 proceeds with the process to step S7, while when the voltage value indicated by the data signal is not included in the data range. Then, the process proceeds to step S8.

Step S7:
Next, since the data signal is included in the data range, the data signal determination unit 104 outputs the data signal as it is to a magnetic field strength detection device arranged outside.
Then, the external magnetic field strength detection device reads the magnetic field strength corresponding to the voltage value indicated by the supplied data signal from the magnetic field strength table stored in the internal storage unit, and reads the magnetic field strength read to its own display unit. indicate.

Step S8:
On the other hand, since the data signal is not included in the data range, the data signal determination unit 104 discards the data signal and outputs an error signal to the magnetic field strength detection device arranged outside.
At this time, for example, when an error signal is supplied, the magnetic field intensity detection device displays information for notifying the user that the measurement range is exceeded on its own display unit.
When power is supplied, the magnetic element control device 110 performs the processing from step S1 to step S8 according to the flowchart shown in FIG.

Here, when measuring the magnetic field strength of the measurement target, the measurement from step S1 to step S8 described above is performed in a state where there is no magnetic field to be measured, and the obtained measurement value is set to the offset voltage adjustment unit 1018. .
And after setting an offset voltage to the offset voltage adjustment part 1018, the measurement of the magnetic field intensity of a measuring object is performed by the process of step S1 to step S8.
Further, when the magnetic element control device 110 is powered on, the feedback signal adjustment unit 1013 resets the accumulated data of the voltage information in the internal storage unit and writes 0 as the initial value.

<Second Embodiment>
With reference to FIG. 15, the magnetic element control apparatus 210 in the 2nd Embodiment of this invention is demonstrated. FIG. 15 is a diagram illustrating a configuration example of the magnetic element control device 210 according to the second embodiment. The same code | symbol is attached | subjected to the structure similar to 1st Embodiment. In FIG. 15, the magnetic element control device 210 includes a magnetic element control unit 112, a clock signal generation unit 102, a clock signal adjustment unit 103, and a data signal determination unit 104. The magnetic element control device 210 according to the present embodiment uses the time-resolved magnetic balance type to detect the strength of the steady magnetic field applied to the fluxgate type magnetic element 50 including the detection coil 51 and the excitation coil 52. The excitation signal applied to the coil 52 is controlled.

The magnetic element control unit 112 includes a detection signal amplification unit 1011, a detection signal comparison unit 1012, a feedback signal adjustment unit 1013, a feedback signal conversion unit 1014, a data signal conversion unit 1015, an excitation signal adjustment unit 1016, an excitation signal generation unit 1017, and an adjustment. A signal generation unit 1100 is provided.
This embodiment is different from the first embodiment in that the offset voltage adjustment unit in the first embodiment is eliminated and an adjustment signal generation unit 110 is newly provided. The different configurations and operations will be described below.

  Next, FIG. 16 is a diagram illustrating a configuration example of the excitation signal adjustment unit 1016 and the adjustment signal generation unit 1100 in FIG. In FIG. 16, the excitation signal adjustment unit 1016 converts the FB signal into a voltage-to-current conversion with respect to the current signal obtained by converting the triangular wave signal output from the excitation signal generation unit 1017 by the excitation signal adjustment unit 1016 of the magnetic element control unit 112. The added feedback current is added to generate an excitation signal used for current control. In FIG. 16, the excitation signal adjustment unit 1016 generates an excitation signal based on the difference between the triangular wave signal from the excitation signal generation unit 1017 and the inverted signal of this triangular wave signal, and outputs it from the output terminal.

The excitation signal adjustment unit 1016 includes a resistor 20170, an amplifier circuit 20171, an inverting circuit 20172, a resistor 20153, an amplifier circuit 20174, an amplifier 20175, a capacitor 20107, and a resistor 20178. The resistor 500 is a resistance component of the exciting coil 52. Here, the resistance value 20170 has a resistance value Rf, and the resistance 20153 has a resistance value R. The amplifier 20155 performs voltage-current conversion by converting a voltage signal excitation signal into a current signal excitation signal using a resistor 20113.
In the case of the excitation signal adjustment unit 1016 having the circuit configuration shown in FIG. 16, the feedback current of the FB signal (the same applies when a steady current is added) is supplied to the (−) input terminal (inverting input terminal) of the amplifier 20155. . That is, the resistor 20170 is interposed between the output of the offset voltage adjustment unit 1018 and the (−) input terminal of the amplifier 20155. The resistor 20170 converts the voltage (feedback voltage) of the feedback signal output from the offset voltage adjustment unit 1018 into a voltage-current, and outputs it as a feedback current If to the (−) input terminal of the amplifier 20155. Further, the resistance value Rf is set so that the current value of the feedback current If corresponds to the amount of shift of the magnetic field indicated by the feedback voltage and becomes a current value that changes the excitation current Iex. That is, the excitation signal adjustment unit 1016 is a voltage / current conversion circuit.

  The amplifier 20115 has a (−) input terminal connected to the output terminal of the adjustment signal generation unit 1100. Here, the adjustment signal generation unit 1100 is a circuit that outputs a constant current. The adjustment signal generator 1100 generates an offset current Ia as a constant current. That is, the adjustment signal generation unit 1100 includes a variable resistor 1101, and an offset voltage Va (an offset signal that is a DC adjustment signal) that is a DC adjustment voltage supplied from an input terminal is generated by the variable resistor 1101 having a resistance value Ra. The voltage-current conversion is performed, and the offset current Ia is output from the output terminal to the (−) terminal of the amplifier 20155. Here, the offset voltage Va is supplied from an external power source (not shown) via an adjustment voltage input terminal. Further, a power supply for supplying the offset voltage Va may be provided inside the magnetic element control device 210.

In the differential amplifier 2001, the terminals of the exciting coil 52 are connected to the output terminal and the (−) terminal, respectively. Here, the resistance value of the exciting coil 52 is Rex, and Iex is applied from the output terminal of the differential amplifier 2001 as the exciting current of the triangular wave current signal.
With this configuration, the exciting current Iex flowing in the exciting coil 52 is the above-described triangular wave current signal, and the addition of the drive current I (alternating current obtained by converting the triangular wave voltage signal into a voltage current), the feedback current If, and the offset current Ia. Value.

Here, the offset current Ia is a current obtained by converting the offset voltage Va given from the outside by the variable resistor 1101. The offset voltage Va is generated due to manufacturing variations of the magnetic elements 50, the circuit elements constituting the magnetic element control unit 112, the clock signal generation unit 102, the clock signal adjustment unit 103, and the data signal determination unit 104 in the magnetic element control device 210. This is a voltage for canceling an offset (offset component in magnetic intensity data) superimposed on the data signal to be transmitted.
That is, if the circuit elements described above are created as designed, basically, when the magnetic detection device is placed in a magnetic shielding box having a stationary magnetic field Hex of “0” and the magnetic field is measured, the data signal is magnetic. Is a numerical value indicating “0”. The temperature at which this offset is measured is room temperature.

However, as described above, due to manufacturing variations of circuit elements, even when the stationary magnetic field Hex is “0”, the data signal may not have a value indicating the magnetic intensity “0”.
That is, in the design of the magnetic element control device 210, the magnetic strength of the data signal should be “0”, but may not be the expected value “0” due to the above-described variation in characteristics of the circuit elements and the like. At this time, in a state where the stationary magnetic field Hex is “0” (and at room temperature), a calibration process is performed to adjust the offset voltage Va to a voltage at which the data signal has a value indicating “0”. At this time, the resistance value Ra of the variable resistor 1101 is constant, but both the offset voltage Va and the resistance value Ra may be adjusted. Thereby, an offset current Ia indicating the magnetic field intensity corresponding to the offset superimposed on the data signal flows to the (−) terminal of the amplifier 20155 in FIG. A feedback current If including a current that cancels the offset current Ia flows, and the feedback current If, that is, the feedback voltage is corrected by the offset current Ia, so that the offset superimposed on the data signal can be canceled.

  Further, in FIG. 16 of the present embodiment, a series circuit in which a capacitor 20107 and a resistor 20178 are connected in series is connected to the output terminal of the amplifier 20175 similarly to the excitation signal adjustment unit 1016 of the first embodiment shown in FIG. It is inserted between the ground point. In addition, a series circuit of a capacitor 201077 and a resistor 20178 may be connected as in configurations b and c.

  Next, FIG. 17 is a diagram illustrating another configuration example of the excitation signal adjustment unit 1016 in FIG. That is, in FIG. 17, the excitation signal adjustment unit 1016 converts the excitation signal from the triangular wave signal output from the excitation signal generation unit 1017 by the excitation signal adjustment unit 1016 of the magnetic element control unit 111 as a differential signal, as in FIG. The feedback (FB) signal in the case of generating by the above is added by current. In FIG. 17, an excitation signal adjustment unit 1016 generates an excitation signal based on the difference between the triangular wave signal from the excitation signal generation unit 1017 and the reference voltage Vref, and outputs the excitation signal from the output terminal.

  The excitation signal adjustment unit 1016 includes a resistor 20170, a resistor 20176, an amplifier 20175, a capacitor 201077, and a resistor 20178. The resistor 500 is a resistance component of the exciting coil 52. Here, the resistance value of the resistor 20170 is Rf, and the resistance value of the resistor 20176 is R. The amplifier 20175 performs voltage-current conversion by converting a voltage signal excitation signal into a current signal excitation signal using a resistor 20176.

In the case of the excitation signal adjustment unit 1016 having the circuit configuration shown in FIG. 17, the feedback current of the FB signal (the same applies when a steady current is added) is supplied to the (−) input terminal (inverting input terminal) of the amplifier 20155. . That is, the resistor 20170 is interposed between the output of the offset voltage adjustment unit 1018 and the (−) input terminal of the amplifier 20155. The resistor 20170 converts the voltage (feedback voltage) of the feedback signal output from the offset voltage adjustment unit 1018 into a voltage-current, and outputs it as a feedback current If to the (−) input terminal of the amplifier 20155. Further, the resistance value Rf is set so that the current value of the feedback current If corresponds to the amount of shift of the magnetic field indicated by the feedback voltage and becomes a current value that changes the excitation current Iex. That is, the excitation signal adjustment unit 1016 is a voltage / current conversion circuit.
In FIG. 17 of the present embodiment, as in the first embodiment, a series circuit in which a capacitor 20107 and a resistor 20178 are connected in series is inserted between the output terminal of the amplifier 20175 and the ground point. Yes. In addition, a series circuit of a capacitor 201077 and a resistor 20178 may be connected as in configurations b and c.

With the configuration described above, the present embodiment is similar to the first embodiment in that the present embodiment sets the cut frequency between the excitation signal frequency and the abnormal oscillation frequency, and aims at the lag lead characteristics. As an external connection circuit of 20155, a capacitor 20187 and a resistor 20178 are connected in series between the output terminal of the amplifier 20175 and the ground point. With this configuration, according to the present embodiment, abnormal oscillation can be suppressed up to a high temperature region, so that it is possible to suppress the abnormal oscillation having a higher frequency than the excitation signal from being superimposed on the excitation signal that is an AC signal. . As a result, the slope of the excitation signal is prevented from being distorted, and the slope linearity is improved. In addition, according to the present embodiment, the amount of change in the offset output in a wide temperature range can be reduced by adjusting the capacitance value of the capacitor 20117 and the resistance value of the resistor 20178 and suppressing the amount of current flowing to the ground point. Can do.
In addition, the present embodiment includes an excitation coil adjustment signal generation unit 1100 that outputs a DC adjustment signal that has been adjusted in advance and is superimposed on the excitation signal. Then, the excitation signal adjustment unit 1016 generates an excitation signal based on the DC adjustment signal and applies it to the excitation coil 52. The time interval of the detection signal detected by the detection signal comparison unit 1012 depends on the reference potential of the feedback signal generation circuit (feedback signal generation unit 1014), but the crossover distortion of the excitation triangle wave (excitation triangle wave) It depends on the reference potential of the (excitation signal generator 1017). Depending on the amount of the DC adjustment current, the crossover distortion occurrence time zone changes relative to the triangular wave (excitation triangular wave). Therefore, the detection signal comparison unit 1012 can be generated by shifting the region (nonlinear region) where the crossover distortion of the excitation signal is generated without changing the time interval of the detection signal detected by the detection signal comparison unit 1012. A stationary magnetic field can be measured while maintaining linearity from the lower limit value to the measurement upper limit value.
Therefore, according to the present embodiment, the magnetic element control device performs magnetic field balance type magnetic field detection using a time-resolved FG type magnetic element without being affected by signal distortion generated in the excitation signal. The output stability of the apparatus can be improved. In the present embodiment, the current addition type EX coil FB control has been described. However, the same effect can be achieved in the voltage addition type EX coil FB control in which the FB signal is added to the triangular wave voltage signal in a voltage state.

<Third Embodiment>
Next, a magnetic element control apparatus 310 according to the third embodiment of the present invention will be described with reference to FIG. FIG. 18 is a diagram illustrating a configuration example of the magnetic element control device 310 according to the third embodiment. The same components as those in the first embodiment in FIG. 1 are denoted by the same reference numerals.
The magnetic element control device 310 includes a magnetic element control unit 113, a clock signal generation unit 102, a clock signal adjustment unit 103, and a data signal determination unit 104. When the magnetic element control device 110 detects the strength of the stationary magnetic field applied to the flux gate type magnetic element 50 including the detection coil 51, the excitation coil 52, and the FB coil 54 by a time-resolved magnetic balance type, The excitation signal applied to the excitation coil 52 and the feedback signal applied to the FB coil 54 are controlled. The configuration of the magnetic element 100, which is a fluxgate type magnetic element, is the same as the configuration shown in FIG.

  The magnetic element control unit 113 includes a detection signal amplification unit 1011, a detection signal comparison unit 1012, a feedback signal adjustment unit 1013, a feedback signal conversion unit 1014, a data signal conversion unit 1015, an excitation signal adjustment unit 1016, an excitation signal generation unit 1017, and An excitation coil adjustment signal generator 1200 is provided.

The clock signal generation unit 102 includes an oscillator that generates a clock signal (periodic clock signal) having a predetermined period, and outputs the generated clock signal to the clock signal adjustment unit 103.
The clock signal adjustment unit 103 performs processing such as amplifying the signal level of the supplied clock signal or changing the cycle of the clock signal, and outputs the processing result clock signal to the excitation signal generation unit 1017.
Based on the clock signal supplied from the clock signal adjustment unit 103, the excitation signal generation unit 1017 generates an alternating signal, for example, a triangular wave signal as an alternating voltage signal that alternates with 0V as a reference potential.
The excitation signal adjustment unit 1016 amplifies the triangular wave signal generated by the excitation signal generation unit 1017 with a predetermined amplification factor, generates a triangular wave current signal, and applies it to the excitation coil 52. At this time, the excitation signal adjustment unit 1016 superimposes the offset current signal generated by the excitation coil adjustment signal generation unit 1200 on the triangular wave current signal (excitation signal) (details will be described later).

The exciting coil 52 generates a magnetic field corresponding to the triangular wave in the magnetic core of the magnetic element 100.
The detection coil 51 generates a pulse (pu signal) during positive and negative alternating time zones of the excitation signal in the magnetic core 53.
The detection signal amplification unit 1011 amplifies the voltage level of the pulse supplied from the detection coil 51 and outputs the amplified voltage level to the detection signal comparison unit 1012 as a detection signal.

  Next, FIG. 19 is a diagram illustrating a configuration example of the excitation signal adjustment unit 1016 in FIG. That is, in FIG. 19, the excitation signal adjustment unit 1016 converts the FB signal into a voltage current with respect to the current signal obtained by converting the triangular wave signal output from the excitation signal generation unit 1017 by the excitation signal adjustment unit 1016 of the magnetic element control unit 111. The converted feedback current is added to generate an excitation signal used for current control. In FIG. 19, the excitation signal adjustment unit 1016 generates an excitation signal based on the difference between the triangular wave signal from the excitation signal generation unit 1017 and the inverted signal of the triangular wave signal, and outputs the excitation signal from the output terminal.

The excitation signal adjustment unit 1016 includes a resistor 20170, an amplifier circuit 20171, an inverting circuit 20172, a resistor 20153, an amplifier circuit 20174, and an amplifier 20175. The resistor 500 is a resistance component of the exciting coil 52. Here, the resistance value 20170 has a resistance value Rf, and the resistance 20153 has a resistance value R. The amplifier 20155 performs voltage-current conversion by converting a voltage signal excitation signal into a current signal excitation signal using a resistor 20113.
In FIG. 19 of the present embodiment, as in the configuration of FIG. 12 of the first embodiment, a series circuit in which a capacitor 20187 and a resistor 20178 are connected in series is provided between the output terminal of the amplifier 20175 and the ground point. Is inserted. In addition, a series circuit of a capacitor 201077 and a resistor 20178 may be connected as in configurations b and c.

  In the case of the excitation signal adjustment unit 1016 having the circuit configuration shown in FIG. 19, the feedback current of the FB signal (the same applies when a steady current is added) is supplied to the (−) input terminal (inverting input terminal) of the amplifier 20155. . That is, the resistor 20170 is interposed between the output of the offset voltage adjustment unit 1018 and the (−) input terminal of the amplifier 20155. The resistor 20170 converts the voltage (feedback voltage) of the feedback signal output from the offset voltage adjustment unit 1018 into a voltage-current, and outputs it as a feedback current If to the (−) input terminal of the amplifier 20155. Further, the resistance value Rf is set so that the current value of the feedback current If corresponds to the amount of shift of the magnetic field indicated by the feedback voltage and becomes a current value that changes the excitation current Iex.

  The excitation coil adjustment signal generator 1200 is composed of a variable resistor 1201 (adjustment resistance value Ra), one end of which is connected to the (−) input terminal of the amplifier 20155 and the other end connected to the excitation coil adjustment voltage input terminal. (See FIG. 18). The adjustment voltage (adjustment voltage value Va) is supplied to the excitation coil adjustment voltage input terminal (input terminal capable of inputting the adjustment voltage).

With the above configuration, the excitation signal adjustment unit 1016 performs excitation so that V− = Vref when the voltage level (V−) of the input terminal of the amplifier 20150 (+) and the voltage level Vex of the triangular wave change. A current Iex is passed through the coil 52 (500). That is, assuming that the power supply voltage level of the amplifier 20115 is Vcc and the peak value of the excitation voltage (voltage across the excitation coil 52) is in the range of Iex × Rex <Vcc / 2, Iex = (Vex−Vref) / R is established. To do. Thereby, since Vex is voltage-controlled, an excitation signal for current control is generated.
In addition, the offset DC current Ia (reference current) of (Va− (V −)) / Ra is superimposed on the excitation signal applied to the excitation coil 52 in terms of current.
The adjustment of the adjustment voltage value Va and the adjustment resistance value Ra will be described below with reference to FIG. 21 (described later).
The adjustment voltage values Va and Ra are adjusted, for example, when the magnetic element control device 310 is activated.

  Next, FIG. 20 is a diagram illustrating another configuration example of the excitation signal adjustment unit 1016 in FIG. That is, in FIG. 20, the excitation signal adjustment unit 1016 converts the excitation signal from the triangular wave signal output from the excitation signal generation unit 1017 by the excitation signal adjustment unit 1016 of the magnetic element control unit 113, as in the case of FIG. The feedback (FB) signal in the case of generating by the above is added by current. In FIG. 20, the excitation signal adjustment unit 1016 generates an excitation signal based on the difference between the triangular wave signal from the excitation signal generation unit 1017 and the reference voltage Vref, and outputs the excitation signal from the output terminal.

The excitation signal adjustment unit 1016 includes a resistor 20170, a resistor 20176, an amplifier 20175, a capacitor 201077, and a resistor 20178. The resistor 500 is a resistance component of the exciting coil 52. Here, the resistor 20170 has a resistance value Rf, and the resistor 20176 has a resistance value R. The amplifier 20175 performs voltage-current conversion by converting a voltage signal excitation signal into a current signal excitation signal using a resistor 20176. The resistor 20170 converts the voltage (feedback voltage) of the feedback signal output from the offset voltage adjustment unit 1018 into a voltage-current, and outputs it as a feedback current If to the (−) input terminal of the amplifier 20155. Further, the resistance value Rf is set so that the current value of the feedback current If corresponds to the amount of shift of the magnetic field indicated by the feedback voltage and becomes a current value that changes the excitation current Iex.
In FIG. 20 of the present embodiment, as in the configuration of FIG. 13 of the first embodiment, a series circuit in which a capacitor 20187 and a resistor 20178 are connected in series is provided between the output terminal of the amplifier 20175 and the ground point. Is inserted. In addition, a series circuit of a capacitor 201077 and a resistor 20178 may be connected as in configurations b and c.

  In the case of the excitation signal adjustment unit 1016 having the circuit configuration shown in FIG. 20, the feedback current of the FB signal (the same applies when a steady current is added) is supplied to the (−) input terminal (inverting input terminal) of the amplifier 20155. . That is, the resistor 20170 is interposed between the output of the offset voltage adjustment unit 1018 and the (−) input terminal of the amplifier 20155. The resistor 20170 converts the voltage (feedback voltage) of the feedback signal output from the offset voltage adjustment unit 1018 into a voltage-current, and outputs it as a feedback current If to the (−) input terminal of the amplifier 20155. Further, the resistance value Rf is set so that the current value of the feedback current If corresponds to the amount of shift of the magnetic field indicated by the feedback voltage and becomes a current value that changes the excitation current Iex.

  The excitation coil adjustment signal generator 1200 is composed of a variable resistor 1201 (adjustment resistance value Ra), one end of which is connected to the (−) input terminal of the amplifier 20155 and the other end connected to the excitation coil adjustment voltage input terminal. (See FIG. 18). The adjustment voltage (adjustment voltage value Va) is supplied to the excitation coil adjustment voltage input terminal (input terminal capable of inputting the adjustment voltage).

With the above configuration, the excitation signal adjustment unit 1016 performs excitation so that V− = Vref when the voltage level (V−) of the input terminal of the amplifier 20150 (+) and the voltage level Vex of the triangular wave change. A current Iex is passed through the coil 52 (500). That is, assuming that the power supply voltage level of the amplifier 20115 is Vcc and the peak value of the excitation voltage (voltage across the excitation coil 52) is in the range of Iex × Rex <Vcc / 2, Iex = (Vex−Vref) / R is established. To do. Thereby, since Vex is voltage-controlled, an excitation signal for current control is generated.
In addition, the offset DC current Ia (reference current) of (Va− (V −)) / Ra is superimposed on the excitation signal applied to the excitation coil 52 in terms of current.
The adjustment of the adjustment voltage value Va and the adjustment resistance value Ra will be described below with reference to FIG. 21 (described later).
The adjustment voltage values Va and Ra are adjusted, for example, when the magnetic element control device 310 is activated, as in the case of FIG.

  In the present embodiment, as in the first embodiment, this embodiment sets the cut frequency between the frequency of the excitation signal and the frequency of abnormal oscillation, and an external connection circuit of the amplifier 20155 aimed at the lag lead characteristics Are connected in series between the output terminal of the amplifier 20155 and the ground point. With this configuration, according to the present embodiment, abnormal oscillation can be suppressed up to a high temperature region, so that it is possible to suppress the abnormal oscillation having a higher frequency than the excitation signal from being superimposed on the excitation signal that is an AC signal. . As a result, the slope of the excitation signal is prevented from being distorted, and the slope linearity is improved. In addition, according to the present embodiment, the amount of change in the offset output in a wide temperature range can be reduced by adjusting the capacitance value of the capacitor 20117 and the resistance value of the resistor 20178 and suppressing the amount of current flowing to the ground point. Can do.

Next, FIG. 21 is a diagram for explaining the principle of the third embodiment. In FIG. 21, FIGS. 21A and 21C are graphs showing the time change of the triangular wave current signal supplied to the exciting coil 52, with the vertical axis indicating voltage and the horizontal axis indicating time. . In FIG. 21A and FIG. 21C, the triangular wave current signal supplied to the exciting coil 52 is a positive / negative alternating signal with a reference current (in this embodiment, a reference current value 0A as an example) as a boundary. is there. In FIG. 21 (b) and FIG. 21 (d), the vertical axis represents voltage and the horizontal axis represents time. 21B and 21D respectively show changes in the direction of the excitation current flowing in the excitation coil 52 due to the triangular wave voltage signal in FIGS. 21A and 21B. Detection signal (first detection signal, second detection signal) generated in the detection coil 51 by the induced electromotive force when the polarity of the voltage value of the triangular wave voltage signal changes, thereby changing the polarity of the current value of the exciting current. It is a graph which shows the time change of a signal.
The excitation signal applied to the excitation coil 52 may be a voltage signal. That is, the vertical axis component in FIG. 21A may be a voltage value. In this case, the reference voltage value of the alternating signal in FIG. 21A is the reference reference voltage Vref.

Here, FIG. 21A shows that a stationary magnetic field (Hex) is applied to the magnetic element 50, so that the reference current of the triangular wave current signal applied to the exciting coil 52 generates the applied stationary magnetic field. It shows that the current is deviated from the reference current value 0A by the DC current. Further, it corresponds to the deviation due to the stationary magnetic field (Hex) from the reference current value 0A of the triangular wave current signal, and the generation timings of the first detection signal and the second detection signal are shifted in time.
In FIG. 21A, when a steady magnetic field is not applied to the magnetic element 50, the current value supplied to the exciting coil 52 shows a change corresponding to the curve L0d. In FIG. 21A, from the time T / 2 when the adjustment voltage value Va and the adjustment resistance value Ra start to be adjusted, the time width of the pu signal by the curve L0d is ½ of the period T of the triangular wave. The short case is shown.
When a stationary magnetic field in the negative direction (lower limit of measurable magnetic field) is applied, the curve of the excitation signal substantially changes from the curve L0d to the curve L2d. Further, when a stationary magnetic field in the positive direction (upper limit value of a measurable magnetic field) is applied, the excitation signal curve substantially changes from the curve L0d to the curve L1d.

The adjustment resistance value Ra and the adjustment voltage value Va are such that the straight line Lai indicating the reference current after the offset current is superimposed and the curve L1d are outside the linear range of the triangular wave current signal, that is, the crossover distortion indicated by the curve L1d. Is set to cross.
That is, the adjustment resistance value Ra and the adjustment voltage value Va are set so that the constant current La flows from the inverting input terminal of the amplifier 20155 to the excitation coil adjustment voltage input terminal (La <0). Note that the state in which the time width of the detection signal is shorter than the time T / 2 that is ½ of the period T of the triangular wave can be confirmed by data output from the data signal output terminal at the start of adjustment.

  At this time, as shown in FIG. 21A, in the curves L0d and L2d, the intersections with the reference current (indicated by the straight line Lai) are the respective crossover distortion ranges (nonlinear regions where the excitation signal does not change linearly). ) Never enter. Therefore, as shown in FIG. 21B, the time width of the detection signal is set to time Tc (La <0). As a result, the detection signal detected by the detection signal comparison unit can be generated by being shifted with respect to the nonlinear region of the excitation signal, so that a stationary magnetic field is measured while maintaining linearity from the measurement lower limit value to the measurement upper limit value. can do. That is, when generating the triangular wave current signal, the output stability of the apparatus can be improved without being affected by the signal distortion generated in the excitation signal.

FIG. 21C shows a DC in which the reference current of the triangular wave current signal applied to the excitation coil 52 generates the applied stationary magnetic field when the stationary magnetic field (Hex) is applied to the magnetic element 50. It shows that the current component deviates from the reference current value 0A. Further, it corresponds to the deviation due to the stationary magnetic field (Hex) from the reference current value 0A of the triangular wave current signal, and the generation timings of the first detection signal and the second detection signal are shifted in time.
In FIG. 21C, when a steady magnetic field is not applied to the magnetic element 50, the current value supplied to the exciting coil 52 shows a change corresponding to the curve L0e. FIG. 21C shows a case where the time width of the detection signal is longer than the time T / 2 which is ½ of the period T of the triangular wave at the start of adjustment of the adjustment voltage value Va and the adjustment resistance value Ra. Show. When a stationary magnetic field in the negative direction (lower limit of measurable magnetic field) is applied, the excitation signal curve substantially changes from the curve L0e to the curve L2e. When a stationary magnetic field in the positive direction (upper limit value of a measurable magnetic field) is applied, the excitation signal curve substantially changes from the curve L0e to the curve L1e.

In the adjustment resistance value Ra and the adjustment voltage value Va, the straight line Lad indicating the reference current after the offset current is superimposed and the curve L2e are outside the linear range of the triangular wave current signal, that is, the crossover distortion range indicated by the curve L2e. Is set to cross.
That is, the adjustment resistance value Ra and the adjustment voltage value Va are set so that the constant current La flows from the excitation coil adjustment voltage input terminal to the inverting input terminal in the direction of the amplifier 20155 (La> 0). Note that the state in which the time width of the detection signal is longer than the time T / 2 that is ½ of the period T of the triangular wave can be confirmed by the data output from the data signal output terminal at the start of adjustment.

  At this time, as shown in FIG. 21 (c), in the curves L0e and L1e, the intersections with the reference current (indicated by the straight line Lad) do not fall within the respective crossover distortion ranges. Therefore, as shown in FIG. 21 (d), the time width of the detection signal is set to time Tc (La> 0). As a result, the detection signal detected by the detection signal comparison unit can be shifted from the excitation signal crossover distortion region (non-linear region), so that the measurement lower limit value is changed to the measurement upper limit value. The stationary magnetic field can be measured while maintaining linearity. That is, the output stability of the apparatus can be improved without being affected by the signal distortion generated in the excitation signal.

  As can be seen from FIG. 21B and FIG. 21D, the time width (between detection signals) between the generation time of the first detection signal and the generation time of the second detection signal, and the time Tc (preliminary) If the difference Td from the set reference time width is zero, no stationary magnetic field (Hex) is applied to the magnetic element 50, and if the difference Td is positive, a negative stationary magnetic field (Hex < 0) is applied, and if the difference Td is negative, a positive stationary magnetic field (Hex> 0) is applied. These differences Td are calculated in a detection signal comparison unit 1012 described later.

Returning to FIG. 18, the detection signal amplifying unit 1011 amplifies the voltage across the detection coil 51 of the magnetic element 50 by a preset amplification factor.
The detection signal comparison unit 1012 compares the voltage value of the amplified detection signal supplied from the detection signal amplification unit 1011 with a predetermined threshold voltage value, and compares the first detection signal and the second detection signal (FIG. 21). (B) and FIG. 21 (d)) are detected.
Here, as shown in FIG. 21, the first detection signal is a negative polarity (negative voltage) pulse, and the current applied to the exciting coil 52 is larger than the reference current from the reference current. It is generated by the induced electromotive force in the region that changes to a small state. On the other hand, the second detection signal is a positive polarity (positive voltage) pulse, and a region in which the current applied to the exciting coil 52 changes from a small state with respect to the reference current to a large state with respect to the reference current. It is generated by induced electromotive force.

  In the present embodiment, as a configuration for generating the voltage of the feedback signal that is an FB signal, either a configuration that is performed by digital processing using a digital value or a configuration that is performed by analog processing using an analog value is used. The magnetic element control device 310 can be configured. Since this description is the same as that of the magnetic element control apparatus 110 in the first embodiment, the description of the processing is omitted.

As described above, the third embodiment includes the excitation coil adjustment signal generation unit 1200 that outputs a DC adjustment signal that has been adjusted in advance and is superimposed on the excitation signal. Then, the excitation signal adjustment unit 1016 generates an excitation signal based on the DC adjustment signal and applies it to the excitation coil 52. The time interval of the detection signal detected by the detection signal comparison unit 1012 depends on the reference potential of the feedback signal generation circuit (feedback signal conversion unit 1014), but the crossover distortion of the excitation triangle wave (excitation triangle wave) is the excitation triangle wave generation circuit. It depends on the reference potential of the (excitation signal generator 1017). Depending on the amount of the DC adjustment current, the crossover distortion occurrence time zone changes relative to the triangular wave (excitation triangular wave). Therefore, the detection signal comparison unit 1012 can be generated by shifting the region (nonlinear region) where the crossover distortion of the excitation signal is generated without changing the time interval of the detection signal detected by the detection signal comparison unit 1012. A stationary magnetic field can be measured while maintaining linearity from the lower limit value to the measurement upper limit value.
Therefore, according to the present invention, in a magnetic element control apparatus that performs magnetic field detection of a magnetic field balance type using a time-resolved FG type magnetic element, the output of the apparatus is not affected by the signal distortion generated in the excitation signal. Stability can be improved.

  Also, a program for realizing the functions of each of the magnetic element control unit 111 in FIG. 1, the magnetic element control unit 112 in FIG. 15, and the magnetic element control unit 113 in FIG. 18 (arithmetic processing for generating a feedback signal using a digital value). May be recorded on a computer-readable recording medium, and a program recorded on the recording medium may be read into a computer system and executed to perform magnetic element control processing. Here, the “computer system” includes an OS and hardware such as peripheral devices.

Further, the “computer system” includes a homepage providing environment (or display environment) if a WWW system is used.
The “computer-readable recording medium” refers to a storage device such as a flexible medium, a magneto-optical disk, a portable medium such as a ROM and a CD-ROM, and a hard disk incorporated in a computer system. Furthermore, the “computer-readable recording medium” dynamically holds a program for a short time like a communication line when transmitting a program via a network such as the Internet or a communication line such as a telephone line. In this case, a volatile memory in a computer system serving as a server or a client in that case, and a program that holds a program for a certain period of time are also included. The program may be a program for realizing a part of the functions described above, and may be a program capable of realizing the functions described above in combination with a program already recorded in a computer system.

  The embodiment of the present invention has been described in detail with reference to the drawings. However, the specific configuration is not limited to this embodiment, and includes design and the like within a scope not departing from the gist of the present invention.

  DESCRIPTION OF SYMBOLS 50 ... Magnetic element 51 ... Detection coil 52,500 ... Excitation coil 53 ... Magnetic body core 54 ... FB coil 110,210,310 ... Magnetic element control apparatus 111,112,113 ... Magnetic element control part 102 ... Clock signal generation part 103 DESCRIPTION OF SYMBOLS ... Clock signal adjustment part 104 ... Data signal determination part 1011 ... Detection signal amplification part 1012 ... Detection signal comparison part 1013 ... Feedback signal adjustment part 1014 ... Feedback signal conversion part 1015 ... Data signal conversion part 1016 ... Excitation signal adjustment part 1017 ... Excitation Signal generation unit 1018 ... Offset voltage adjustment unit 1100 ... Adjustment signal generation unit 1101, 1201 ... Variable resistor 1200 ... Excitation coil adjustment signal generation unit 20170, 20171, 20176, 20178 ... Resistance 20171, 20174 ... Amplification circuit 20152 ... Inversion circuit 0175 ... amplifier 20177 ... capacitor

Claims (11)

A magnetic element control device that controls the magnetic element when detecting the strength of a stationary magnetic field applied to a fluxgate type magnetic element composed of an excitation coil and a detection coil by a time-resolved magnetic balance type,
An excitation signal generator for generating an alternating signal;
A voltage-current conversion circuit using a differential amplifier is provided, and a series circuit in which a capacitor and a resistor are connected in series is provided at either the output terminal or the input terminal of the differential amplifier. Based on the alternating signal An excitation signal adjusting unit that generates an excitation signal that is a current signal applied to the excitation coil that is interposed between the output terminal and the input terminal;
A detection signal comparator for detecting a positive or negative voltage detection signal generated by an induced electromotive force when the current direction of the excitation signal is switched;
A feedback signal converter that converts a time width between detection signals of positive voltage and negative voltage into voltage information;
A feedback signal adjusting unit that generates a feedback signal for generating a magnetic field that cancels a stationary magnetic field applied to the magnetic element from the voltage information;
A data signal converter that outputs the feedback signal as a data signal indicating the magnetic field strength, and
The excitation signal adjustment unit converts the alternating voltage signal into an alternating current, converts the feedback signal into a feedback current, and generates the excitation signal by superimposing the feedback current on the alternating current. And applying the excitation signal to the excitation coil. The series circuit is interposed between the output terminal and a ground point, or between the input terminal and the ground point, or between the input terminal and another input terminal in the differential amplifier. The magnetic element control apparatus according to claim 1. Each of the capacitance value of the capacitor and the resistance value of the resistor is set such that the cutoff frequency of the differential amplifier is between the frequency of the alternating signal and the frequency of abnormal oscillation superimposed on the excitation signal. The magnetic element control apparatus according to claim 1, wherein the magnetic element control apparatus is a magnetic element control apparatus. The data signal converter is
The feedback signal is amplified by a preset amplification factor at which the voltage value of the feedback signal and the magnetic field strength generated by the voltage value of the feedback signal are linear and the voltage value outside the voltage range of the feedback signal is saturated. The magnetic element control device according to any one of claims 1 to 3, wherein the magnetic element control device outputs the output.   An offset voltage adjustment unit that superimposes an offset voltage corresponding to a magnetic field due to an ambient environment for measuring a stationary magnetic field on the feedback signal and outputs the feedback signal on which the offset voltage is superimposed to the feedback signal adjustment unit. The magnetic element control device according to claim 1, wherein the magnetic element control device is a magnetic element control device. An adjustment signal generating unit that generates an offset signal for canceling an offset component superimposed on the data signal;
The excitation signal adjustment unit is
An alternating current is generated from the alternating signal, a feedback current is generated from the feedback signal, and an offset current is generated from the offset signal. The feedback current and the offset current are superimposed on the alternating current and applied to the exciting coil. The magnetic element control device according to claim 1, wherein the exciting current is generated. The offset signal is
The magnetic element according to claim 6, wherein the magnetic element is set to a voltage that cancels the offset component that is a difference between a data signal measured in a zero magnetic field and an expected value of a designed data signal in the zero magnetic field. Control device. Magnetic element control that controls the magnetic element when detecting the strength of a stationary magnetic field applied to a fluxgate magnetic element composed of an excitation coil, a detection coil, and a feedback coil by a time-resolved magnetic balance type Device,
An excitation signal generator for generating an alternating signal;
An excitation signal adjusting unit that generates an alternating voltage signal from the alternating signal and generates an excitation signal that is a current signal applied to the excitation coil based on the alternating voltage signal;
A detection signal comparator for detecting a positive or negative voltage detection signal generated by an induced electromotive force when the current direction of the excitation signal is switched;
A feedback signal converter that converts a time width between detection signals of positive voltage and negative voltage into voltage information;
A feedback signal adjustment unit that generates a feedback signal that is a current signal that applies a magnetic field that cancels a stationary magnetic field applied to the magnetic element from the voltage information to the feedback coil;
A data signal converter that outputs the feedback signal as a data signal indicating magnetic field strength;
An adjustment signal generation unit that outputs a DC adjustment signal that has been adjusted in advance and is superimposed on at least one of the excitation signal and the feedback signal;
Have
The excitation signal adjustment unit or the feedback signal adjustment unit has a voltage-current conversion circuit using a differential amplifier, and a capacitor and a resistor are connected in series to either the output terminal or the inverting input terminal of the differential amplifier. A series circuit is provided to generate the excitation signal or the feedback signal based on the DC adjustment signal, and to the excitation coil or the feedback coil interposed between the output terminal and the inverting input terminal The detection signal detected by the detection signal comparison unit is shifted with respect to the nonlinear region of the excitation signal,
A magnetic element control device. The adjustment signal generator includes a first resistor having one end connected to an input terminal capable of inputting an adjustment voltage,
The excitation signal adjustment unit or the feedback signal adjustment unit is
One end has a second resistor connected to the excitation signal generator and the feedback signal converter,
The first resistor and the second resistor are connected to an inverting input terminal of the differential amplifier, and a normal input terminal of the differential amplifier is connected to a preset reference voltage,
The excitation coil or the feedback coil is connected between the output terminal of the differential amplifier and the inverting input terminal;
The differential amplifier allows a current to flow through the excitation coil or the feedback coil so that the voltage level of the inverting input terminal is equal to the voltage level of the normal input terminal.
The magnetic element control apparatus according to claim 8. A magnetic element control method for controlling a magnetic element when detecting the strength of a stationary magnetic field applied to a fluxgate magnetic element composed of an excitation coil and a detection coil by a time-resolved magnetic balance equation,
An excitation signal generation process for generating an alternating signal;
Voltage / current conversion is performed by a differential amplifier provided with a series circuit in which a capacitor and a resistor are connected in series to either the output terminal or the input terminal, and the alternating voltage signal is generated from the alternating signal. An excitation signal adjustment process for generating an excitation signal, which is a current signal, applied to the excitation coil interposed between the output terminal and the input terminal,
A detection signal comparison process for detecting a positive or negative voltage detection signal generated by an induced electromotive force when the current direction of the excitation signal is switched;
A feedback signal conversion process for converting a time width between detection signals of positive voltage and negative voltage into voltage information;
A feedback signal adjustment process for generating a feedback signal for generating a magnetic field for canceling a stationary magnetic field applied to the magnetic element from the voltage information;
A data signal conversion process of outputting the feedback signal as a data signal indicating the magnetic field strength,
In the excitation signal adjustment process, the alternating voltage signal is converted into an alternating current, the feedback signal is converted into a feedback current, and the excitation signal is generated by superimposing the feedback current on the alternating current. And applying the excitation signal to the excitation coil. Magnetic element control that controls the magnetic element when detecting the strength of a stationary magnetic field applied to a fluxgate magnetic element composed of an excitation coil, a detection coil, and a feedback coil by a time-resolved magnetic balance type Is the way
An excitation signal generation process for generating an alternating signal;
An excitation signal adjustment process for generating an alternating voltage signal from the alternating signal and generating an excitation signal that is a current signal applied to the excitation coil based on the alternating voltage signal;
A detection signal comparison process for detecting a positive or negative voltage detection signal generated by an induced electromotive force when the current direction of the excitation signal is switched;
A feedback signal generation process for converting a time width between detection signals of positive voltage and negative voltage into voltage information;
A feedback signal adjustment process for generating a feedback signal which is a current signal for applying a magnetic field for canceling a stationary magnetic field applied to the magnetic element from the voltage information to the feedback coil;
A data signal conversion process of outputting the feedback signal as a data signal indicating magnetic field strength;
An adjustment signal generation process for outputting a pre-adjusted DC adjustment signal that is superimposed on at least one of the excitation signal and the feedback signal;
Have
In the excitation signal adjustment process or the feedback signal adjustment process, voltage / current conversion is performed by a differential amplifier provided with a series circuit in which a capacitor and a resistor are connected in series to either the output terminal or the inverting input terminal, The excitation signal or the feedback signal is generated based on a DC adjustment signal and applied to the excitation coil or the feedback coil interposed between the output terminal and the inverting input terminal, and the detection signal The detection signal detected by the comparison unit is generated by shifting with respect to the nonlinear region of the excitation signal.
Magnetic element control method characterized by the above.