JP2014071101A - Signal processing circuit and magnetic field detection device using the same - Google Patents

Abstract

A signal processing circuit for improving the detection accuracy of the strength of a magnetic field applied to a magnetic element by increasing the rising or falling slope of the detection signal without increasing the amplification degree of the detection signal amplification unit.
A signal processing circuit according to the present invention includes a clock signal generator for generating a synchronization signal, a drive signal generator for generating a triangular wave signal to be supplied to a drive coil of an FG magnetic element, and the triangular wave signal. An excitation signal adjustment unit that generates a triangular wave signal for superimposing the detection signal and a reference potential of a positive or negative voltage detection signal generated by an induced electromotive force when the current direction of the triangular wave current in the detection coil of the magnetic element is switched. Compared with the detection signal processing unit that outputs a differential signal in which the triangular wave signal for signal superimposition is superimposed and the slope of the voltage change of the detection signal is increased, and the threshold value set for the polarity of the difference signal, And a signal processing unit for determining the strength of the magnetic field applied to the FG magnetic element from the time width.
[Selection] Figure 1

Description

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

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. 9 is a diagram illustrating a configuration example of an FG magnetic element. As shown in FIG. 9, in the FG magnetic element, an excitation winding and a detection winding are wound around the outer peripheral surface of a magnetic core made of a high permeability material. A region around which the excitation winding is wound is driven by a drive signal as a drive coil (excitation coil), and a region around which the detection winding is wound outputs a detection signal as a detection coil.

  FIG. 10 is a timing chart for explaining the principle of magnetic detection in the FG type magnetic element. FIG. 10A shows the drive current (excitation current) supplied to the drive coil of the magnetic element, the vertical axis shows the current value of the drive current, and the horizontal axis shows the time. FIG. 10B shows the magnetic flux density of the magnetic field generated in the magnetic core by the drive coil of the magnetic element, the vertical axis shows the magnetic flux density, and the horizontal axis shows the time. FIG. 10C shows the voltage value of the induced electromotive force generated in the detection coil of the magnetic element, and the horizontal axis shows the time.

In order to drive the drive coil in FIG. 10, a drive current Id signal (hereinafter referred to as a drive signal) between a drive coil terminal TI1 and a terminal TI2 is a drive signal of an alternating current having a constant period, that is, FIG. As shown in FIG. 10B, it is applied as a triangular wave drive signal (that is, a triangular wave current signal).
Thereby, the direction of the magnetic field generated in the magnetic core is reversed between positive and negative in synchronization with the change in the direction of the drive current. Then, at the timing (time t1 and time t2) when the direction of the magnetic field in the magnetic core is reversed, positive and negative pulses are generated in the detection coil due to the induced electromotive force, and the voltage Vp of this pulse is used as a detection signal. This detection signal is generated between the terminals TO1 and TO2 of the detection coil as a pulse voltage having continuous positive and negative polarities corresponding to the period of the triangular wave current signal.

When a stationary magnetic field Hex passing through a cylindrical space formed by the excitation winding and the detection winding of the magnetic core is applied to the 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 drive current Id of the drive signal applied to the excitation winding.
As a result, due to this offset, the driving state of the drive coil by the alternating drive signal changes, that is, the time when the direction in which the drive current Id flows changes when the stationary magnetic field Hex is applied and when the stationary magnetic field Hex is It will change depending on when it is not applied.

  At this time, as shown in FIG. 10A, the stationary magnetic field Hex is applied in the same direction as the magnetic field generated from the drive 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 changes to the position of the horizontal axis L2 corresponding to the direction in which the drive current Id flows. On the other hand, when the stationary magnetic field Hex in the direction opposite to the magnetic field generated by the exciting coil is applied (Hex <0) as compared with the case where the stationary magnetic field Hex is not applied, this corresponds to the direction in which the drive current Id flows. Thus, the horizontal axis L1 changes to the position of the horizontal axis L3.

As a result, as shown in FIG. 10, the change in the magnetic flux density φ in the magnetic core, which changes according to the change timing of the direction in which the drive current Id flows, also corresponds to the steady current superimposed on the drive current Id. Will change.
When the direction of the magnetic flux changes, an induced electromotive force is generated in a direction that cancels the change of the magnetic flux with respect to the detection coil, that is, the detection signal is a pulse of the negative voltage Vp at the timing when the drive current Id changes from positive to negative. Occurs as. On the other hand, the detection signal is generated as a pulse of the positive voltage Vp at the timing when the drive current Id changes from negative to positive.

Therefore, the FG magnetic element compares the timing at which the detection signal is output when the steady current Hex is not applied with the timing at which the detection signal is output 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 drive coil, so that a constant offset is superimposed on the drive 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 drive current Id applied to the drive coil 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. As a result, the measurement magnetic field range of the magnetic element includes the time of one cycle of the drive signal and the 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 the stationary magnetic field Hex is not applied (Hex = 0), a positive voltage detection signal (hereinafter referred to as second detection) from time t1 when a negative voltage detection signal (hereinafter referred to as first detection signal) is output. The time until the time t2 when the 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. 10, when the magnetic flux direction of the stationary magnetic field Hex is a solid arrow (Hex> 0), the time width Tm is from the time T / 2 because it is the same direction as the magnetic flux direction generated by the drive coil. On the other hand, when the magnetic flux direction of the stationary magnetic field Hex is a dashed arrow (Hex <0), the time width Tp is the time T / 2 because the direction is opposite to the magnetic flux direction generated by the drive coil. It becomes longer (Tp> T0). Here, T0 = T / 2.

Next, FIG. 11 shows an example of the configuration of a conventional magnetic field detection apparatus including an FG magnetic element 200 and a signal processing circuit 100 that outputs the intensity of a stationary magnetic field Hex from a detection signal output from the magnetic element 200. FIG. In FIG. 11, a magnetic element 200 is an FG magnetic element having the configuration shown in FIG. The signal processing circuit 100 includes a drive signal generation unit 101, a clock signal generation unit 102, a clock signal control unit 103, a detection signal amplification unit 104, a detection signal comparison unit 105, and a signal processing unit 106. .
The drive signal generation unit 101 generates an excitation signal shown in FIG. 10 based on the triangular wave signal generated by the clock signal generation unit 102 that generates a synchronization signal having a constant period, and generates a drive coil (excitation coil) of the magnetic element 200. Supply.

Next, FIG. 12 is a waveform diagram showing the amplified first detection signal and the amplified second detection signal, which are output by the detection signal amplification unit 104 amplifying and outputting the first detection signal and the second detection signal, which are mutually inverted waveforms. It is. In FIG. 12, the peak value Hout1 of the amplified first detection signal and the peak value Hout2 of the amplified second detection signal are shown. Further, the threshold value VthL and the threshold value VthH are indicated by a one-dot chain line.
Returning to FIG. 11, the clock signal control unit 103 generates a periodic signal for detecting one period of the triangular wave current signal having a constant period supplied from the clock signal generation unit 102, and sends the periodic signal to the signal processing unit 106. Output. For example, in FIG. 10, the clock signal control unit 103 detects the top of the triangular wave current signal at times t0 and t3, and outputs a periodic signal at the timing when the top is detected.
The detection signal amplification unit 104 amplifies the first detection signal and the second detection signal that are output from the detection coil of the magnetic element 200 and have mutually inverted waveforms, and amplifies the amplified first detection signal and the amplified second detection signal. Are output to the detection signal comparison unit 105.

  The detection signal comparison unit 105 includes, for example, a hysteresis comparator, and outputs the first level detection signal to the signal processing unit 106 when the peak value Hout1 of the amplified first detection signal exceeds the threshold value VthH. Further, the detection signal comparison unit 105 outputs the second level detection signal to the signal processing unit 106 when the peak value Hout2 of the amplified second detection signal falls below the threshold value VthL. Here, VthH <VthL.

The signal processing unit 106 has a timer counter inside, starts counting processing of the timer counter at the timing when the first level detection signal is supplied, and timers at the timing when the second level detection signal is supplied. The counter counting process is terminated. Thereby, the signal processing unit 106 can measure the time between the first detection signal and the second detection signal output from the detection coil of the magnetic element 200.
Further, when the periodic signal is supplied, the signal processing unit 106 reads the count value of the timer counter and obtains the strength of the stationary magnetic field Hex from the count value. For example, the signal processing unit 106 previously includes a correspondence table between the count value and the strength of the stationary magnetic field Hex, and outputs the strength of the magnetic field corresponding to the count value to a circuit (not shown) in the next stage.

Here, the threshold value VthH and the threshold value VthL are set in accordance with the operation of the comparator in the detection signal comparison unit 105 and the stability of the operation of the entire signal processing circuit 100 (in consideration of the degree of noise and the like). .
Further, in the detection signal amplification unit 104, the amplification degree is a voltage peak value that is a signal intensity at which each voltage Vp of the first detection signal and the second detection signal can be determined by the threshold value VthH and the threshold value VthL. It is set to be Hout1 or the peak value Hout2.

Further, the first detection signal and the second detection signal amplified in accordance with the magnitude of the voltage Vp of each of the first detection signal and the second detection signal output from the magnetic element 200 and the frequency characteristics of the detection signal amplifier 104. Each half width (the time width of the waveform at a voltage value half the level of the peak value) Wout1 and Wout2 and the signal delays delay1 and delay2 are determined.
Here, each of the threshold value VthH to be compared with the peak value Hout1 of the amplified first detection signal and the threshold value VthL to be compared with the peak value Hout2 of the amplified second detection signal is the stability of the voltage value of the power supply voltage. Accordingly, there may be a voltage fluctuation (jitter1, jitter2) corresponding to a constant voltage value fluctuation.

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

Next, FIG. 13 is a diagram showing the relationship between the time variation of the amplified first detection signal and the maximum value of time differentiation (hereinafter referred to as slope) of the rising portion of the waveform of the amplified first detection signal. In FIG. 13, the vertical axis represents the time variation (standard deviation) of the inverted first detection signal, and the horizontal axis represents the slope value. Here, the larger the slope, the steeper the rising of the waveform of the inverted first detection signal.
Next, FIG. 14 is a diagram for explaining slope by time differentiation at the rising portion of the amplified first detection signal. In FIG. 14, the vertical axis represents voltage and the horizontal axis represents time. As shown in the figure, the portion where the slope of the rising portion of the amplified first detection signal is maximum is defined as slope.

Returning to FIG. 13, when the peak value H 1 of the first detection signal is at a voltage level that cannot be detected by the detection signal comparison unit 105, it is necessary to perform amplification by the detection signal amplification unit 104. In this case, as described above, the signal waveform of the amplified first detection signal after amplification changes according to the half-value width Wout1 and the signal delay delay1 corresponding to the frequency characteristic of the detection signal amplification unit 104, and the first detection The shape is different from the signal. For the same reason, the amplified second detection signal has a different shape from the second detection signal.
In FIG. 13, the peak value H of the first detection signal is in a relationship of H1 <H2 <H3 <H4.

  As shown in FIG. 13, when the amplification factor setting is constant, it can be seen that the time variation of the amplified first detection signal decreases as the peak value H of the amplified first detection signal increases. The reason for this is that when the amplification factor of the first detection signal is constant, the slope of the rising edge of the waveform increases as the peak value H increases, so the time variation of the voltage value in the half-value width portion of the amplified first detection signal Because it becomes difficult to receive. That is, a constant voltage fluctuation is superimposed on the first detection signal. For this reason, when the slope is small, in the detection process in the detection signal comparison unit 105, the timing at which the first detection signal is detected is shifted due to the voltage fluctuation of the amplified first detection signal.

In FIG. 13, when the peak value is constant, increasing the amplification factor of the first detection signal in the detection signal amplification unit 104 increases the slope, but also increases the time variation at the same time. This is because, when the amplification degree for amplifying the detection signal is increased, the fluctuation level of the time variation as the noise component superimposed on the detection signal is also amplified, and the amplified first detection signal is detected. This is because the timing is more shifted. The above description also applies to the second detection signal and the amplified second detection signal.
As described above, in order to reduce the temporal fluctuation of the voltage level of the amplified first detection signal and the amplified second detection signal, the amplification first detection signal and the amplification are not increased without increasing the amplification degree of the detection signal amplification unit 104. It is necessary to increase the slope at the rising edge of the signal waveform of the second detection signal.

In order to satisfy the above-described conditions, it is necessary to increase the peak values Vp of the first detection signal and the second detection signal output from the magnetic element 200.
However, the peak value Vp has an upper limit value depending on the structure of the magnetic element 200, and the lower limit value of the fluctuation level of the first detection signal and the second detection signal is limited by the peak value as the upper limit value (a constant value). The lower limit that cannot be below).
In addition, when the deviation of the detection timing of the detection signal due to the fluctuation level is larger than the time corresponding to the magnetic field resolution of the magnetic element, naturally, the accuracy of the magnetic field detected by the magnetic field detection device is lowered.
Furthermore, it is conceivable that the slope of the magnetic element 200 changes depending on the strength of the stationary magnetic field Hex to which the magnetic element 200 is applied or the temperature characteristics, and the slope changes. For this reason, there is also a problem that the accuracy of the magnetic field detected by the magnetic field detection device varies depending on the strength of the stationary magnetic field Hex or the ambient temperature.

  The present invention has been made in view of such circumstances, and can increase the slope at the rise or fall of the signal waveform of the detection signal without increasing the amplification factor of the detection signal amplification unit. It is an object of the present invention to provide a signal processing circuit capable of improving detection accuracy and a magnetic field detection device using the signal processing circuit.

  The present invention has been made to solve the above-described problems. A signal processing circuit according to the present invention includes a clock signal generator that generates a synchronization signal having a constant period, and a drive coil for a fluxgate (FG) magnetic element. A driving signal generator for generating a triangular wave current signal to be supplied from the triangular wave signal; an excitation signal adjusting unit for generating a triangular wave voltage waveform signal from the triangular wave current signal; and a current of the triangular wave current in the detection coil of the magnetic element The triangular wave voltage waveform signal is superimposed on the reference potential of the positive or negative voltage pulse detection signal generated by the induced electromotive force generated when switching the direction, and the slope of the voltage change of the detection signal is A detection signal processing unit that increases the signal change of the triangular wave voltage waveform signal and outputs it as a differential signal, and the differential signal of positive voltage or negative voltage Compared to a preset threshold value corresponding to each polarity, the time width from the time of occurrence of one of the positive voltage or the negative voltage to the time of occurrence of the other was measured, and this measurement was performed. A signal processing unit that obtains the strength of the magnetic field applied to the magnetic element from the time width.

  The signal processing circuit of the present invention is characterized in that the triangular wave voltage waveform signal is also superimposed on the threshold value.

  In the signal processing circuit of the present invention, the detection signal processing unit performs differential amplification of the detection signal and an inverted signal of the triangular wave voltage waveform signal, and outputs the triangular wave voltage waveform signal with respect to a reference potential of the detection signal. It is characterized by overlapping. Corresponding to the first embodiment, the detection signal processing unit is a detection signal amplification unit 104 and a detection signal comparison unit 105.

  In the signal processing circuit of the present invention, the detection signal processing unit generates a first waveform signal by adding the voltage value of the triangular wave voltage waveform signal to the voltage value of the detection signal, and an inverted signal of the detection signal A voltage value of an inverted signal of the triangular wave voltage waveform signal is added to a voltage value of the second waveform signal to generate a second waveform signal, differential amplification is performed on the first waveform signal and the second waveform signal, and the difference signal is The signal processing circuit according to claim 1, wherein the signal processing circuit is obtained. Corresponding to the second embodiment, the detection signal processing unit is a detection signal addition amplification unit 13 and a detection signal comparison unit 105.

  In the signal processing circuit of the present invention, the detection signal processing unit generates an amplified signal and an inverted amplified signal of the detection signal, and adds the voltage value of the triangular wave voltage waveform signal to the voltage value of the amplified signal. A first waveform signal is generated, a voltage value of the inverted signal of the triangular wave voltage waveform signal is added to a voltage value of the inverted amplified signal to generate a second waveform signal, and the voltage value of the first waveform signal is The difference signal is generated by subtracting the voltage value of the second waveform signal. Corresponding to the third embodiment, the detection signal processing unit is a detection signal amplification unit 14 and a detection signal addition comparison unit 15.

  A magnetic field detection apparatus according to the present invention includes a fluxgate magnetic element and any one of the signal processing circuits described above.

  According to the present invention, since the triangular wave waveform signal synchronized with the triangular wave signal applied as the excitation signal to the FG magnetic element is superimposed on the detection signal, the change in the voltage of the triangular wave signal is the voltage change in the waveform of the detection signal. Is added to. For this reason, it is possible to increase the slope at the rise (or fall) of the signal waveform of the detection signal without increasing the amplification degree of the detection signal amplification unit, and the time width between the detection signals due to voltage fluctuation of the detection signal. The intensity of the magnetic field applied to the FG magnetic element can be measured with high accuracy while suppressing fluctuations.

It is a schematic block diagram which shows the structural example of the magnetic field detection apparatus using the signal processing circuit by one Embodiment of this invention. It is a wave form diagram explaining the production | generation process of the difference signal performed in the detection signal amplification part 104. FIG. It is a schematic block diagram which shows the structural example of the magnetic field detection apparatus using the signal processing circuit by the 2nd Embodiment of this invention. It is a wave form diagram explaining the production | generation process of the difference signal performed in the detection signal addition amplification part. It is a schematic block diagram which shows the structural example of the magnetic field detection apparatus using the signal processing circuit by the 3rd Embodiment of this invention. It is a wave form diagram explaining the production | generation process of the difference signal performed in the detection signal addition comparison part 15. FIG. It is a schematic block diagram which shows the structural example of the magnetic field detection apparatus using the signal processing circuit by the 4th Embodiment of this invention. FIG. 5 is a waveform diagram illustrating a differential signal generation process performed by a detection signal addition unit 16 and a detection signal calculation comparison unit 17. It is a figure which shows the structural example of the magnetic element of FG system. It is a timing chart explaining the principle of the magnetic detection in the FG-type magnetic element. It is a figure which shows the structural example of the conventional magnetic field detection apparatus which consists of the magnetic element 200 of FG system, and the magnetic field detection circuit 100 which outputs the intensity | strength of the stationary magnetic field Hex from the detection signal which this magnetic element outputs. It is a timing chart explaining the principle of the magnetic detection in the FG-type magnetic element. It is a figure which shows the relationship between the time fluctuation | variation of an amplification 1st detection signal, and the maximum value of the time differentiation of the rising part of the waveform of an amplification 1st detection signal. It is a figure explaining the slope by time differentiation in the rising part of an amplification 1st detection signal.

<First Embodiment>
Hereinafter, a first embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a schematic block diagram showing a configuration example of a magnetic field detection apparatus using a signal processing circuit according to the first embodiment of the present invention. Also, in FIG. 1, parts corresponding to those in FIG. 11 are denoted by the same reference numerals, description of similar operations is omitted, and only different operations are described.
The signal processing circuit 1 includes an excitation signal adjustment unit 11, a drive signal generation unit 101, a clock signal generation unit 102, a clock signal control unit 103, a detection signal amplification unit 104, a detection signal comparison unit 105, and a signal processing unit 106. .

The clock signal generation unit 102 generates a triangular wave signal with a preset period T as a synchronization signal that is the basis of the excitation signal in FIG. 10, and outputs it to each of the drive signal generation unit 101 and the clock signal control unit 103.
The drive signal generation unit 101 generates a triangular wave current signal to be supplied to the drive coil (excitation coil) of the magnetic element 200 from the triangular wave signal supplied from the clock signal generation unit 102.
The drive signal generator 101 supplies the generated triangular wave current signal to the drive coil of the magnetic element 200 and outputs it to the excitation signal adjuster 11.

  Next, FIG. 2 is a waveform diagram for explaining a differential signal generation process performed by the detection signal amplification unit 104. FIG. 2B shows a detection signal (first induced by the induced electromotive force already described) supplied from the detection coil (detection coil) of the magnetic element 200 to the (+) side terminal of the differential amplifier in the detection signal amplification unit 104. Detection signal and second detection signal), the horizontal axis indicates the time, and the vertical axis indicates the voltage value of the detection signal. FIG. 2C is a waveform of a triangular wave voltage waveform signal (described later) supplied from the excitation signal adjustment unit 11 to the (−) side terminal of the differential amplifier of the detection signal amplification unit 104, and the horizontal axis indicates the time. The vertical axis indicates the voltage value of the triangular wave voltage signal. FIG. 2A shows the waveform of the differential signal output from the differential amplifier in the detection signal amplification unit 104, where the horizontal axis indicates time and the vertical axis indicates the voltage value of the differential signal.

  Returning to FIG. 1, the excitation signal adjustment unit 11 converts the triangular wave signal supplied from the drive signal generation unit 101 into a triangular wave signal for detection signal superimposition. In other words, the excitation signal adjustment unit 11 adjusts the peak value of the triangular wave signal and outputs the adjusted triangular wave signal to the (−) side terminal of the differential amplifier in the detection signal amplification unit 104 ( FIG. 2 (c)). Here, the triangular wave signal for superimposing the detection signal is synchronized with the triangular wave signal supplied from the excitation signal generator.

  The detection signal amplification unit 104 performs differential amplification processing of the voltage value of the detection signal supplied to the (+) side terminal of the differential amplifier and the triangular wave signal for superimposing the detection signal supplied to the (−) side terminal. Do. Further, the detection signal amplifying unit 104 sends a difference signal (a first detection difference signal, a second detection difference signal) indicating a difference in voltage value between the detection signal and the triangular signal for superimposing the detection signal to the detection signal comparison unit 105. Output. Here, the first detection difference signal corresponds to the first detection signal, and the second detection difference signal corresponds to the second detection signal. In this differential amplification process, the reference potential of the differential signal changes in synchronization with the change in the current value of the current-controlled triangular wave signal applied to the drive coil of the magnetic element 200 by superimposing the triangular wave signal by voltage control. Will do.

The detection signal comparison unit 105 compares the voltage value of the first detection difference signal supplied from the detection signal amplification unit 104 with a preset threshold value VthH, and the voltage value of the first detection difference signal sets the threshold value VthH. When it falls below, a 1st determination signal is output with respect to the signal processing part 106. FIG.
Similarly, the detection signal comparison unit 105 compares the voltage value of the second detection difference signal supplied from the detection signal amplification unit 104 with a preset threshold value VthL, and the voltage value of the second detection difference signal is determined. When the threshold value VthL is exceeded, a second determination signal is output to the signal processing unit 106.

Here, the slope of the rising edge of the waveform of the first detection differential signal is increased by the slope of the rising edge of the triangular wave voltage waveform signal with respect to the slope of the first detection signal (pulse signal having a positive polarity voltage). By being subtracted by amplification, the slope of the first detection signal is steeper.
Similarly, the second detection differential signal has a slope at the falling edge of the waveform, and a slope at the falling edge of the triangular wave voltage waveform signal with respect to the slope of the second detection signal (pulsed signal having a negative polarity voltage). By subtracting by differential amplification, the slope of the second detection signal is steeper.
Thereby, the detection signal amplification unit 104 increases the slope of each of the falling edge of the waveform of the first detection signal and the rising edge of the waveform of the second detection signal, so that it is not necessary to increase the amplification degree. Therefore, in this embodiment, without increasing the fluctuation of the detection signal, the slope of the waveform of the detection signal is increased, and the detection accuracy of the detection signal comparison unit 105 at the next stage is improved.

Further, in the detection signal comparison unit 105, when comparing the detection signal and the threshold value, since the slope of the waveform of the detection signal is large, the detection signal comparison unit 105 compares the fluctuation of the detection signal voltage and the threshold voltage. Thus, the comparison process can be performed with less error.
Therefore, as described above, the detection signal comparison unit 105 can reduce the influence of the voltage fluctuation on the first determination signal and the second determination signal corresponding to the magnetic field strength of the stationary magnetic field Hex, and can perform the first determination signal with high accuracy. It can output based on the 1st detection signal and the 2nd detection signal.

When the periodic signal is supplied from the clock signal control unit 103, the signal processing unit 106 resets the internal timer counter. When the first determination signal is supplied, the signal processing unit 106 starts the counting process and is supplied with the second determination signal. The counting process is stopped at the timing. That is, the time width between the first determination signal and the second determination signal, that is, the time width between the first detection signal and the second detection signal is obtained as the count value of the timer counter.
When the periodic signal is supplied and the timer counter is reset, the signal processing unit 106 reads out the magnetic field intensity corresponding to the count value of the timer counter from the internal correspondence table and outputs it to the external circuit. Here, instead of the timer counter, a counter that counts a fixed-cycle clock generated by a clock circuit (not shown) may be used, and the count value of this counter may be changed to the magnetic field strength. The length of this constant period is the accuracy of magnetic field detection.
Further, as already described, the signal processing unit 106 determines that the first determination signal and the second inverted signal supplied from the detection signal comparison unit 105 are the first detection signal and the second detection signal, respectively, with high accuracy. Since it is detected, the magnetic field strength of the stationary magnetic field Hex can be detected with high accuracy.

Next, the operation of the magnetic field detection apparatus using the signal processing circuit in this embodiment will be described with reference to FIG.
Time t0:
The clock signal control unit 103 generates a periodic signal from the peak value of the triangular wave signal supplied from the clock signal generation unit 102 and outputs the periodic signal to the signal processing unit 106.
When the periodic signal is supplied, the signal processing unit 106 reads the magnetic field strength corresponding to the count value of the internal timer counter from the internal table, and uses the read magnetic field strength as the magnetic field strength of the current steady magnetic field Hex. Output for.
Then, the signal processing unit 106 resets the count value of the internal timer counter to zero.

At this time, the drive signal generator 101 supplies a triangular wave current signal generated from the triangular wave signal supplied from the clock signal generator 102 to the drive coil of the magnetic element 200.
In addition, the detection coil of the magnetic element 200 causes an offset in the drive current (excitation current) Id due to the stationary magnetic field Hex with respect to the triangular wave current signal, and the first detection signal and the first detection signal shifted from the T / 2 period according to the offset amount. 2 detection signals are generated.
At this time, the excitation signal adjustment unit 11 adjusts the triangular wave current signal supplied from the drive signal generation unit 101 and outputs it as a triangular wave voltage waveform signal to the (−) side terminal of the differential amplifier of the detection signal amplification unit 104. To do.

Then, the detection signal amplification unit 104 performs differential amplification between the voltage of the detection signal (the first detection signal and the second detection signal) and the voltage of the triangular wave voltage waveform signal that is a waveform inverted with respect to the detection signal, A difference signal (a first detection difference signal and a second detection difference signal) is output.
Here, when the positive peak value of the triangular wave voltage waveform signal is amplified by the detection signal amplification unit 104, the excitation signal adjustment unit 11 does not exceed the threshold VthH and the angle θ of the slope of the first detection difference signal θ The triangular wave signal is adjusted to a size that does not exceed 90 degrees.
Similarly, when the negative peak value of the triangular wave voltage waveform signal is amplified by the detection signal amplification unit 104, the excitation signal adjustment unit 11 does not fall below the threshold VthL and the angle θ of the slope of the second detection difference signal The triangular wave signal is adjusted to a size that does not exceed 90 degrees.

Time t1:
In the difference signal including the first detection difference signal and the second detection difference signal, the detection signal comparison unit 105 determines whether the voltage value of the first detection difference signal is lower than the threshold value VthL or the voltage value of the second detection difference signal is the threshold value. It is determined whether or not VthH is exceeded.
Here, since the voltage value of the first detection difference signal is lower than the threshold value VthL, the detection signal comparison unit 105 outputs the first determination signal to the signal processing unit 106 at a timing lower than the threshold value VthL.
As a result, the signal processing unit 106 starts the counting process of the timer counter from the time when the first determination signal is supplied.

Time t2:
In the difference signal including the first detection difference signal and the second detection difference signal, the detection signal comparison unit 105 determines whether the voltage value of the first detection difference signal is lower than the threshold value VthL and the voltage value of the second detection difference signal is It is determined whether or not the threshold value VthH is exceeded.
Here, since the voltage value of the second detection difference signal exceeds the threshold value VthH, the detection signal comparison unit 105 outputs the second determination signal to the signal processing unit 106 at a timing exceeding this.
Thereby, the signal processing unit 106 stops the counting process of the timer counter at the time when the second determination signal is supplied.

Time t3 (corresponding to time t0):
When the periodic signal is supplied, the signal processing unit 106 reads the magnetic field strength corresponding to the count value of the internal timer counter from the internal table, and uses the read magnetic field strength as the magnetic field strength of the current steady magnetic field Hex. Output for.
Then, the signal processing unit 106 resets the count value of the internal timer counter to zero.
The processing from time t0 to time t2 described above is repeated, and the magnetic field strength of the stationary magnetic field Hex is output to the next stage circuit at every predetermined period T.

<Second Embodiment>
The second embodiment of the present invention will be described below with reference to the drawings. FIG. 3 is a schematic block diagram showing a configuration example of a magnetic field detection device using a signal processing circuit according to the second embodiment of the present invention. Also, in FIG. 3, the same reference numerals are given to portions corresponding to the respective portions in the first embodiment of FIG. 1, description of similar operations is omitted, and only different operations will be described.
The signal processing circuit 1A includes an excitation signal adjustment unit 12, a drive signal generation unit 101, a clock signal generation unit 102, a clock signal control unit 103, a detection signal addition amplification unit 13, a detection signal comparison unit 105, and a signal processing unit 106. Yes.

The second embodiment is different from the first embodiment in that the excitation signal adjustment unit 11 is replaced with an excitation signal adjustment unit 12 and the detection signal amplification unit 104 is replaced with a detection signal addition amplification unit 13. is there.
The excitation signal adjustment unit 12 adjusts the peak value of the triangular wave signal from the triangular wave current signal supplied from the drive signal generation unit 101, and superimposes the triangular wave signal for superimposing the detection signal and the detection signal superposition of the waveform obtained by inverting the triangular wave signal. And an inverted triangular wave signal.
Then, the excitation signal adjustment unit 12 outputs the generated triangular signal for superimposing the detection signal and the inverted triangular wave signal for superimposing the detection signal to the detection signal addition amplification unit 13. Here, each of the triangular wave signal for superimposing the detection signal and the inverted triangular wave signal for superimposing the detection signal is synchronized with the triangular wave signal.

  Next, FIG. 4 is a waveform diagram for explaining a differential signal generation process performed by the detection signal addition amplification unit 13. FIG. 4B shows the voltage value between the detection signal (first detection signal and second detection signal) supplied from the detection coil of the magnetic element 200 and the triangular wave voltage waveform signal supplied from the excitation signal adjustment unit 12. The horizontal axis indicates time and the vertical axis indicates the voltage value of the first waveform signal. FIG. 4C shows an inversion signal of the detection signals (first detection signal and second detection signal) supplied from the detection coil of the magnetic element 200, and an inverted triangular wave voltage waveform signal supplied from the excitation signal adjustment unit 12. FIG. 6 is a diagram illustrating a second signal waveform obtained by the addition processing between the voltage values of the two, wherein the horizontal axis indicates time and the vertical axis indicates the voltage value of the second waveform signal. FIG. 4A shows a differential signal (differential amplification signal) obtained by amplifying the difference between the voltage value of the first waveform signal and the voltage value of the second waveform signal, which is output from the differential amplifier in the detection signal amplification unit 104. The horizontal axis indicates the time, and the vertical axis indicates the voltage value of the difference signal.

Returning to FIG. 3, the detection signal addition amplification unit 13 includes two adders, a first adder and a second adder, and one differential amplifier. In the detection signal addition amplification unit 13, each of the first adder, the second adder, and the differential amplifier performs the following signal processing.
The first adder performs addition processing of the voltage value of the detection signal of the detection coil of the magnetic element 200 and the voltage value of the triangular wave voltage waveform signal supplied from the excitation signal adjustment unit 12, and the voltage value of the triangular wave voltage waveform signal Is superimposed on the first waveform signal of FIG. 4B. The second adder performs addition processing of the voltage value of the inverted signal of the detection signal of the detection coil of the detection coil of the magnetic element 200 and the voltage value of the inverted triangular wave voltage waveform signal supplied from the excitation signal adjustment unit 12 to invert The second waveform signal of FIG. 4C on which the voltage value of the triangular wave voltage waveform signal is superimposed is generated.
Then, the differential amplifier obtains a difference obtained by subtracting the voltage value of the second waveform signal from the voltage value of the first waveform signal, amplifies the difference by a preset amplification degree, and the amplification result of the difference is a difference. It outputs to the detection signal comparison part 105 as a signal (a 1st detection difference signal and a 2nd detection difference signal).
Accordingly, the detection signal comparison unit 105 determines whether the voltage value of the first detection difference signal is lower than the threshold value VthL or the voltage of the second detection difference signal in the difference signal including the first detection difference signal and the second detection difference signal. It is determined whether the value exceeds the threshold value VthH.
Then, the detection signal comparison unit 105 outputs each of the first determination signal and the second determination signal obtained as a result of the determination to the signal processing unit 106.
The operation of the magnetic field detection apparatus in the timing chart of FIG. 4 is the same as that of the first embodiment except for the differences in the configurations of the excitation signal adjustment unit 12 and the detection signal addition amplification unit 13 described above.

As described above, in the present embodiment, by performing differential amplification between the voltage value of the first waveform signal generated by the first adder and the voltage value of the second waveform signal generated by the second adder. The detection difference signal (the first detection difference signal and the second detection difference signal) is generated.
For this reason, in the present embodiment, the first waveform signal and the first waveform signal generated by each of the first adder and the second adder are compared with the first embodiment in which the detection difference signal is directly obtained by differential amplification processing. Since the differential amplification with the two waveform signals is performed, it is possible to reduce the voltage fluctuation of the differential signal supplied to the detection signal comparison unit 105 by reducing the amplification degree in the differential amplifier.

That is, in the differential amplifier, even with the same amplification factor, the amplification factor with respect to a signal with a small amount of time change is effectively larger than the amplification factor with respect to a signal with a large amount of time change due to frequency characteristics.
Therefore, in comparison with the first embodiment, the inverted triangular wave signal and the triangular wave signal are given, and the differential in which the amplification degree of the differential amplifier is reduced by the addition processing of each of the first adder and the second adder. Amplification is performed to increase the magnitude of the slope, and it is possible to reduce the noise due to the voltage fluctuation ratio of the first waveform signal and the second waveform signal, that is, the voltage fluctuation of the detection difference signal. Furthermore, since it is a differential signal, in-phase noise can be removed, and noise components due to in-phase voltage fluctuations can be removed.

<Third Embodiment>
The third embodiment of the present invention will be described below with reference to the drawings. FIG. 5 is a schematic block diagram showing a configuration example of a magnetic field detection device using a signal processing circuit according to the third embodiment of the present invention. In FIG. 5, the same reference numerals are given to the portions corresponding to the respective portions in the first embodiment of FIG. 1, description of similar operations is omitted, and only different operations will be described.
The signal processing circuit 1B includes an excitation signal adjustment unit 12, a drive signal generation unit 101, a clock signal generation unit 102, a clock signal control unit 103, a detection signal amplification unit 14, a detection signal addition comparison unit 15, and a signal processing unit 106. Yes.

The third embodiment differs from the first embodiment in that the excitation signal adjustment unit 11 is the excitation signal adjustment unit 12, the detection signal amplification unit 104 is the detection signal amplification unit 14, and the detection signal comparison unit 105. Is replaced by the detection signal addition comparison unit 15.
The excitation signal adjustment unit 12 adjusts the peak value of the triangular wave signal from the triangular wave signal supplied from the drive signal generation unit 101, and detects a waveform in which the triangular wave signal for superimposing the detection signal and the triangular wave voltage waveform signal are inverted. An inverted triangular wave voltage waveform signal for signal superposition is generated.
Then, the excitation signal adjustment unit 12 outputs the generated triangular signal for superimposing the detection signal and the inverted triangular wave signal for superimposing the detection signal to the detection signal addition amplification unit 13. Here, each of the triangular wave voltage waveform signal for detection signal superimposition and the inverted triangular wave voltage waveform signal for detection signal superposition is synchronized with the triangular wave signal.
The detection signal amplification unit 14 outputs each of an amplification signal obtained by amplifying the detection signal output from the detection coil of the magnetic element 200 and an inverted amplification signal obtained by inverting and amplifying the detection signal to the detection signal addition comparison unit 15. To do.

  Next, FIG. 6 is a waveform diagram for explaining the difference signal generation processing performed by the detection signal addition comparison unit 15. FIG. 6B shows an amplified signal obtained by amplifying the detection signals (first detection signal and second detection signal) supplied from the detection coil of the magnetic element 200, and a triangular wave voltage waveform signal supplied from the excitation signal adjustment unit 12. Is a first signal waveform obtained by the addition processing between the voltage values, and the horizontal axis indicates time and the vertical axis indicates the voltage value of the first waveform signal. FIG. 6C shows an inverted amplified signal obtained by inverting and amplifying the detection signals (first detection signal and second detection signal) supplied from the detection coil of the magnetic element 200 and an inverted triangular wave supplied from the excitation signal adjustment unit 12. It is the 2nd signal waveform obtained by addition processing between voltage values with a voltage waveform signal, a horizontal axis shows time, and a vertical axis shows a voltage value of the 2nd waveform signal. FIG. 6A is a waveform of a differential signal that is differentially amplified from the voltage value of the first waveform signal, which is output from the adder in the detection signal addition / comparison unit 15, and the horizontal axis Indicates the time, and the vertical axis indicates the voltage value of the differential signal.

Returning to FIG. 5, the detection signal addition / comparison unit 15 includes two adders, a first adder and a second adder, one subtractor, and a comparator. In the detection signal addition comparison unit 15, each of the first adder, the second adder, and the subtracter performs the following signal processing.
The first adder adds the triangular wave signal for superimposing the detection signal supplied from the excitation signal adjusting unit 12 from the amplified signal obtained by amplifying the detection signal of the detection coil of the magnetic element 200, and the triangular wave signal is superimposed. A first waveform signal 6 (b) is generated. The second adder adds the voltage value of the inverted triangular wave signal for superimposing the detection signal supplied from the excitation signal adjusting unit 12 from the inverted amplification signal obtained by inverting and amplifying the detection signal of the detection coil of the magnetic element 200. Thus, the second waveform signal in FIG. 6C on which the inverted triangular wave signal for superimposing the detection signal is superimposed is generated.
The subtracter subtracts the second waveform signal from the first waveform signal to obtain a difference, and generates a difference signal (a first detection difference signal and a second detection difference signal) from the difference.
In the differential signal including the first detection differential signal and the second detection differential signal, the comparator has a voltage value of the first detection differential signal that is lower than the threshold value VthL, and a voltage value of the second detection differential signal is the threshold value VthH. Judge whether or not it exceeds
Then, the comparator outputs each of the first determination signal and the second determination signal obtained as a result of the determination to the signal processing unit 106.
The operation of the magnetic field detection apparatus in the timing chart of FIG. 6 is the same as that of the first embodiment except for the differences in the configurations of the excitation signal adjustment unit 12, the detection signal amplification unit 14, and the detection signal addition comparison unit 15 described above.

In the present embodiment, an amplified signal and an inverted amplified signal for taking a difference are directly input from the detection signal amplification unit 14 to the detection signal addition comparison unit 15.
For this reason, in the present embodiment, unlike the first embodiment, the differential amplification signal and the ground line are paired and the differential amplification signal is not output to the detection signal addition comparison unit 15. .
Therefore, in this embodiment, even if noise due to the operation of an electronic component or the like is superimposed on the ground line, the noise does not give a voltage fluctuation to the amplified signal and the inverted amplified signal, and the detected signal addition comparison unit 15 is not affected. Can communicate.
Thereby, according to this embodiment, the voltage fluctuation in the 1st detection signal and the 2nd detection signal in the detection signal addition comparison part 15 is reduced, and a 1st determination signal and a 2nd determination signal are made into 1st Embodiment. Can be output to the signal processing unit 106 more accurately than the above. That is, in the third embodiment, since the differential signal is the same as in the second embodiment, the S / N ratio is improved compared to the first embodiment by removing the common-mode noise. be able to. Since the triangular wave signal is superimposed after the detection signal is amplified, the slope can be increased when the peak value of the detection signal is set to a peak value equivalent to that of the second embodiment, and as a result. As a result, it is possible to reduce the time fluctuation of the output.

<Fourth Embodiment>
Hereinafter, a fourth embodiment of the present invention will be described with reference to the drawings. FIG. 7 is a schematic block diagram showing a configuration example of a magnetic field detection device using a signal processing circuit according to the fourth embodiment of the present invention. Also, in FIG. 7, the same reference numerals are given to portions corresponding to the respective portions in the first embodiment of FIG. 1, description of similar operations is omitted, and only different operations will be described.
The signal processing circuit 1C includes an excitation signal adjustment unit 12, a drive signal generation unit 101, a clock signal generation unit 102, a clock signal control unit 103, a detection signal amplification unit 14, a detection signal addition unit 16, a detection signal calculation comparison unit 17, a signal A processing unit 106 is provided.

The fourth embodiment is different from the first embodiment in that the excitation signal adjustment unit 11 is the excitation signal adjustment unit 12, the detection signal amplification unit 104 is the detection signal amplification unit 14, and the detection signal comparison unit 105. Is replaced with a detection signal calculation comparison unit 17 and a detection signal addition unit 16 is added.
The excitation signal adjusting unit 12 adjusts the peak value of the triangular wave signal from the triangular wave current signal supplied from the drive signal generating unit 101, and generates a triangular wave voltage waveform signal and an inverted triangular wave voltage waveform signal.

Then, the excitation signal adjustment unit 12 outputs the generated triangular signal for superimposing the detection signal and the inverted triangular wave signal for superimposing the detection signal to the detection signal addition amplification unit 13. Here, each of the triangular wave signal for superimposing the detection signal and the inverted triangular wave signal for superimposing the detection signal is synchronized with the triangular wave signal.
The detection signal amplification unit 14 outputs each of an amplification signal obtained by amplifying the detection signal output from the detection coil of the magnetic element 200 and an inverted amplification signal obtained by inverting and amplifying the detection signal to the detection signal addition comparison unit 15. To do.

Next, FIG. 8 is a waveform diagram for explaining the difference signal generation processing performed by the detection signal addition unit 16 and the detection signal calculation comparison unit 17. In FIG. 8, the triangular wave voltage waveform signal is superimposed on the threshold value VthL and the threshold value VthH. The waveform of the differential signal is obtained by adding the voltage value of the second waveform signal output from the second adder to the voltage value of the first waveform signal output from the first adder in the detection signal adding unit 16. The axis indicates the time, and the vertical axis indicates the voltage value of the difference signal.
The triangular wave voltage waveform signal is synchronized with the triangular wave current signal output from the drive signal generator 101.

Returning to FIG. 7, the detection signal adding unit 16 includes two adders, a first adder and a second adder.
The detection signal calculation / comparison unit 17 includes a subtracter, a third adder, and a fourth adder.
Similarly to the third embodiment, the detection signal adding unit 16 is supplied with the amplified signal and the inverted amplified signal from the detection signal amplifying unit 14.
Then, the detection signal adding unit 16 adds the amplified signal and the triangular signal for superimposing the detection signal by the first adder, and generates the first waveform signal by superimposing the triangular signal on the amplified signal. The first waveform signal is output to the detection signal calculation / comparison unit 17. Further, the detection signal adding unit 16 performs addition processing of the inverted amplified signal for superimposing the detection signal and the inverted triangular wave signal by the second adder, and superimposes the inverted triangular wave signal for overlapping the detection signal on the inverted amplified signal. Then, a second waveform signal is generated, and this second waveform signal is output to the detection signal calculation comparison unit 17.

The detection signal calculation comparison unit 17 obtains a difference between the voltage values of the first waveform signal and the second waveform signal supplied from the detection signal addition unit 16 by a subtracter, and calculates a difference signal (the first detection difference signal and the second detection signal). A detection difference signal) is generated (FIG. 8A).
Further, the detection signal calculation comparison unit 17 adds the triangular wave voltage waveform signal to the threshold value VthL by the third adder, and generates a synchronous threshold value VthLS in which the voltage changes in synchronization with the change of the triangular wave voltage waveform signal. .
Similarly, the detection signal calculation comparison unit 17 adds a triangular wave voltage waveform signal to the threshold value VthH by the fourth adder, and generates a synchronous threshold value VthHS in which the voltage changes in synchronization with the change of the triangular wave voltage waveform signal. To do.

In addition, the detection signal calculation comparison unit 17 compares the voltage value of the difference signal with the above-described synchronization threshold value VthLS and the synchronization threshold value VthHS, and the voltage value of the first detection difference signal is less than the synchronization threshold value VthLS, or 2 It is detected whether the voltage value of the detection difference signal has reached the threshold value VthHS.
Then, when the voltage value of the first detection difference signal falls below the synchronization threshold VthLS, the detection signal calculation comparison unit 17 outputs the first determination signal to the signal processing unit 106 at this timing.
On the other hand, when the voltage value of the second detection difference signal exceeds the synchronization threshold VthLH, the detection signal calculation comparison unit 17 outputs the second determination signal to the signal processing unit 106 at this timing.
The operation of the magnetic field detection apparatus in the timing chart of FIG. 8 is the first implementation except for the differences in the configuration of the excitation signal adjustment unit 12, the detection signal amplification unit 14, the detection signal addition unit 16, and the detection signal calculation comparison unit 17 described above. It is the same as the form.

If each of the threshold value VthL and the threshold value VthH is constant and there is no voltage fluctuation in the reference potential of the first detection difference signal and the second detection difference signal, the detection of the first detection signal and the second detection signal is performed with higher accuracy. Can be done. However, when the reference potentials of the first detection difference signal and the second detection difference signal change in synchronization with the triangular wave current signal, the triangular wave signal is superimposed on the detection signal even in the range of the stationary magnetic field where the detection signal is generated. Therefore, it may be difficult to detect the detection signal by the comparator.
Therefore, according to the present embodiment, using the triangular wave voltage waveform signal, the synchronization thresholds VthLS and VthHS that change in synchronization with the triangular wave current signal are generated, and the differential signal (reference signal that also has the reference potential synchronized with the triangular wave current signal) In order to determine the voltage value of the first detection difference signal and the second detection difference signal), the difference signal is compared with the case where the difference signal is not changed in synchronization with the triangular wave current signal (from the first embodiment to the third embodiment). Thus, a wider magnetic field range can be detected within the range of all the stationary magnetic fields in which the detection signal is generated. The configuration for generating the synchronization threshold values VthLS and VthHS may be applied to the first to third embodiments.

Further, a temperature sensor is added to each of the signal processing circuits 1, 1A, 1B and 1C in the first to fourth embodiments, and a measured temperature value obtained by measuring the ambient temperature of the temperature sensor is obtained. obtain.
Then, a control circuit that controls the magnitude of the slope is loaded on the circuit that generates each of the triangular wave signal and the inverted triangular wave signal by controlling the peak values of the triangular wave signal and the inverted triangular wave signal. Here, this control circuit has a table indicating the correspondence between the measured temperature value and the coefficient α, and reads the coefficient α corresponding to the measured temperature value. Then, the control circuit changes the amplification degree of the internal amplifier by this coefficient α, and controls the magnitude of the slope of the triangular wave voltage waveform signal and the inverted triangular wave voltage waveform signal. The coefficient α is a triangular wave voltage waveform signal and inverted so that the slope angle θ of the falling edge of the first detection differential signal and the angle θ of the slope of the rising edge of the second detection differential signal are constant regardless of the temperature. This is a coefficient for controlling the magnitude of the slope of the triangular wave voltage waveform signal.

In the first to fourth embodiments, the connection is made only to the magnetic element 200. However, in order to change the connection between the magnetic element 200 and a plurality of other magnetic elements. The switching element may be provided.
That is, the signal processing circuit (1, 1A, 1B, and 1C) is switched between the plurality of magnetic elements by switching the terminal of the signal processing circuit, the terminals TI1 and TI2 of the driving coil of the magnetic element, and the terminals TO1 and TO2 of the detection coil. ) May be used in common among, for example, time division among a plurality of magnetic elements.
Further, in the first to fourth embodiments, one period of the triangular wave signal in the measurement is from the peak value of the positive voltage to the peak value of the positive voltage, but the peak value of the negative voltage and the peak value of the negative voltage Signal processing circuit (1, 1A, 1B, 1C) with a positive voltage pulsed detection signal as a first detection signal and a negative voltage pulsed detection signal as a second detection signal. May be configured. Further, in the first to fourth embodiments, the signal processing unit has shown the method of detecting the signal obtained by converting the time interval of the detection signal into the pulse wave by the counter. However, the duty ratio of the pulse wave is changed. A pulse width modulation method (PWM method) may be used as a method for converting into a DC signal.

  In addition, a program for realizing the functions of the signal processing circuits 1, 1A, 1B, and 1C in each of FIGS. 1, 3, 5, and 6 is recorded on a computer-readable recording medium. The magnetic field detection processing may be performed by causing the computer system to read and execute the program recorded on the computer. 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 1,1A, 1B, 1C ... Signal processing circuit 11, 12 ... Excitation signal adjustment part 13 ... Detection signal addition amplification part 14, 104 ... Detection signal amplification part 15 ... Detection signal addition comparison part 16 ... Detection signal addition part 101 ... Drive Signal generation unit 102 ... Clock signal generation unit 103 ... Clock signal control unit 105 ... Detection signal comparison unit 106 ... Signal processing unit 200 ... Magnetic element

Claims (6)

A clock signal generator for generating a synchronization signal having a constant period;
A drive signal generator for generating a triangular wave signal to be supplied to the drive coil of the fluxgate magnetic element;
An excitation signal adjusting unit that generates a triangular wave signal for superimposing a detection signal from the triangular wave signal, and a positive voltage generated by an induced electromotive force generated when switching the current direction of the triangular wave current in the detection coil of the magnetic element or The triangular wave signal for superimposing the detection signal is superimposed on the reference potential of the negative pulse detection signal, and the slope of the signal change of the detection signal is increased by the signal change of the triangular signal for detection signal superposition. A detection signal processing unit that outputs a difference signal;
A detection signal comparison unit that compares the differential signal of positive voltage or negative voltage with a preset threshold value corresponding to each polarity, and generation of either the differential signal of positive voltage or negative voltage A signal processing circuit comprising: a signal processing unit that measures a time width from the time point to the other occurrence time point, and obtains the strength of the magnetic field applied to the magnetic element from the measured time width.   The signal processing circuit according to claim 1, wherein the triangular wave signal is also superimposed on the threshold value. The detection signal processing unit is
3. The signal processing according to claim 1, wherein differential detection of the detection signal and an inverted signal of the triangular wave signal is performed, and the triangular wave signal is superimposed on a reference potential of the detection signal. circuit. The detection signal processing unit is
The triangular wave signal is added to the voltage value of the detection signal to generate a first waveform signal, and the inverted signal of the triangular wave signal is added to the inverted signal of the detection signal to generate a second waveform signal. The signal processing circuit according to claim 1, wherein the differential signal is obtained by performing differential amplification with the first waveform signal and the second waveform signal. The detection signal processing unit is
Generates an amplified signal and an inverted amplified signal of the detection signal, adds the triangular wave signal to the amplified signal to generate a first waveform signal, and adds an inverted signal of the triangular wave signal to the inverted amplified signal The signal processing circuit according to claim 1, wherein a second waveform signal is generated, and the difference signal is generated by subtracting the second waveform signal from the first waveform signal. A fluxgate magnetic element;
A magnetic field detection apparatus comprising: the signal processing circuit according to claim 1.

Images