JPH0694817A - Self-energized magnetic sensor - Google Patents

Abstract

PURPOSE:To provide a self-energized type magnetic sensor which has a simplified circuit configuration and can enhance the accuracy and sensitivity. CONSTITUTION:An energizing coil 2 is wound for changing the magnetic intensity within a core 1 and is energized by the output of a driver circuit 8 of self- energized type, and the X- and Y-components of the magnetic field to be measured are sensed by an X- and a Y-sensing coil 3, 4 which are wound on the core 1. Change of the magnetic flux in the core 1 is sensed by a feedback coil 9 wound on the core 1 and fed back to the driver circuit 8 for generating self- energized oscillation. This allows eliminating any oscillator circuit, simplifying the circuit, and enhancing the accuracy and sensitivity.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fluxgate type magnetic sensor for detecting weak magnetism such as geomagnetism.

[0002]

2. Description of the Related Art FIG. 11 shows, for example, Japanese Patent Publication No. 49-46.
It is a figure which shows the conventional magnetic sensor of the flux gate type shown by the publication 90, and in the figure, 1 is an annular core. An exciting coil 2 is wound around the core 1. Further, an X-direction detection coil 3 and a Y-direction detection coil 4 are wound around the core 1 so as to be orthogonal to each other. The detection signals from the X-direction detection coil 3 and the Y-direction detection coil 4 are input to the signal processing circuit 6.

The exciting coil 2 is driven by a drive circuit 5, and the drive circuit 5 is mainly composed of transistors Tr1 to Tr4 arranged in an H-bridge type. The transistor is the signal generation circuit 17
It is designed to be driven by the output of. The output of the oscillation circuit 7 is input to the signal generation circuit 17 and the signal processing circuit 6. The oscillator circuit 7 controls the timings of the drive circuit 5 and the signal processing circuit 6.

Next, the operation will be described. When a current is applied to the exciting coil 2 from the drive circuit 5 in a magnetic field in the surroundings, a magnetic flux is generated in the core 1. further,
When the exciting current flowing through the exciting coil 2 increases, the magnetic flux in the core 1 becomes saturated. From this time, the surrounding magnetic flux concentrated in the core 1 cannot pass through the core 1 until it passes through the space.

This is equivalent to the fact that the surrounding magnetic flux concentrated inside the X-direction detection coil 3 and the Y-direction detection coil 4 has been driven out and decreased, and the X-direction detection coil 3 and Y
A pulsed voltage is generated in the direction detection coil 4. This pulsed voltage is proportional to the intensity of the magnetism that has been driven out, that is, the ambient magnetism.

The signal processing circuit 6 detects the pulsed voltage in synchronization with the excitation cycle of the exciting coil 2.
The output of the signal processing circuit 6 is voltage or current.
The synchronization timing and the excitation timing are the oscillation circuit 7
Is supervised by. The timing and waveform are shown in Figure 1.
2 is shown.

FIG. 12A shows an exciting voltage of the exciting coil 2,
12 (b) is the exciting current, FIG. 12 (c) is the voltage generated in the X-direction detection coil 3 and the Y-direction detection coil 4, and FIG.
12D shows the detection synchronization signal, and FIG. 12E shows the output signal of the oscillation circuit 7.

The X-direction detection coil 3 and the Y-direction detection coil 4 are synchronized with the pulsed excitation voltage of FIG. 12 (a) in synchronization with the excitation cycle of the excitation coil 2 by the excitation current shown in FIG. 12 (b). The output is detected by the signal processing circuit 6 (Fig. 12 (d)).
To do.

As described above, the fluxgate type magnetic sensor applies magnetic modulation to the magnetic field to be detected by saturating or non-saturating the ring-shaped core 1, and the X-direction detection coil 3 generated at that time. , Y direction detection coil 4
It is intended to detect the strength of the magnetic field to be detected based on the voltage.

[0010]

In the conventional fluxgate type magnetic sensor, the oscillation circuit 7 for determining the excitation timing of the core 1 and synchronizing with the signal processing circuit 6 is required.

The frequency of the oscillator circuit 7 is the same as that of the core 1
In addition, it is necessary to set an appropriate period in consideration of the magnetic saturation characteristic of the exciting coil 2, that is, a time for which the exciting current continues to flow until it is sufficiently saturated. In other words, it was necessary to set the excitation time to a sufficient length by anticipating the lowest power supply voltage to be used. In normal use, even if the core 1 reaches saturation, an unnecessary current continues to flow within the set time, and there is a problem that the exciting current, and eventually the power supply current, becomes large.

In order to reduce this enormous exciting current and to reduce the rating and heat generation of the parts used, the exciting current is also set in the configuration in which the current limiting resistor is inserted in series in the exciting coil, but it is set. There is no difference in that unnecessary current continues to flow over time.

Further, by inserting the current limiting resistor, the time from the start of excitation to the saturation is extended, and the excitation cycle cannot be shortened. In other words, this is the saturation per unit time −
This means that the number of times of non-saturation is reduced, and the magnetic energy that can be taken out per unit time is reduced, resulting in a problem that the sensitivity of the sensor is suppressed low.

The present invention has been made to solve the above problems, and immediately after the core reaches magnetic saturation, the exciting current is cut off to eliminate unnecessary exciting current and reduce the power supply current. With the elimination of unnecessary excitation current, the limiting resistance inserted in series in the excitation coil can be reduced or omitted, and the time from the start of excitation to saturation can be shortened. ,
The purpose is to obtain a self-excited magnetic sensor that can improve the sensitivity, and the purpose is to obtain a self-excited magnetic sensor that can simplify the entire circuit configuration. Furthermore, a feedback coil is not required and the cost can be reduced. Aiming to obtain a self-excited magnetic sensor, and to obtain a self-excited magnetic sensor that can obtain a power supply output other than the input voltage and can secure an operating voltage that allows circuit operation even at low voltage input. In addition, the present invention provides a self-excited magnetic sensor that can be stably operated without stopping oscillation in the case of the current feedback type.

[0015]

A self-exciting magnetic sensor according to the present invention comprises an exciting coil wound around a core and a drive circuit for driving the exciting coil by self-excited oscillation.

Further, a feedback coil, which is wound around the core separately from the exciting coil, detects the magnetic flux of the core and feeds back the detection output to the drive circuit.

Further, a detection coil for detecting the exciting current of the exciting coil wound around the core, and a drive circuit for driving the exciting coil by self-excited oscillation by feedback of the detection output of the detecting coil are provided. is there.

Further, the magnetic energy stored in the exciting coil during driving of the exciting coil is transferred to a capacitor through a diode when the exciting current is turned off, or electric energy is transferred to a power source system other than the input power source simultaneously with the excitation of the core. It is provided with a circuit.

In addition, when the power supply voltage of the drive circuit is low, or when the drive circuit is started from a low voltage, an auxiliary starter circuit for stably operating the drive circuit is provided.

[0020]

The drive circuit of the self-exciting magnetic sensor constructed as described above excites the exciting coil wound around the core at a constant cycle and excites without separately providing an oscillating circuit.

Further, the magnetic flux in the core is detected by a feedback coil wound around the core separately from the exciting coil, and the detected output is fed back to the drive circuit, so that the drive circuit self-oscillates and its oscillation output To excite the exciting coil.

Further, when the exciting current flowing in the exciting coil is detected by the detecting coil and the detection output of the detecting coil is fed back to the driving circuit, the driving circuit oscillates by self-excitation,
The excitation coil is excited by the oscillation output.

While the exciting coil is being driven by the drive circuit, the electric energy stored in the exciting coil is
When the exciting coil is turned off, it is transferred from the drive circuit to the capacitor through the diode, or simultaneously with the excitation of the core, the electric energy stored in the exciting coil is transferred to the power supply system other than the input power supply.

In addition, when the power supply voltage of the drive circuit is low or when the drive circuit is started in the low voltage state, the auxiliary start-up circuit detects these states and stabilizes the self-oscillation action of the drive circuit.

[0025]

【Example】

Example 1. 1 is a block diagram showing an embodiment of the present invention. In FIG. 1, the same parts as those in FIG. 11 are designated by the same reference numerals. In FIG. 1, an exciting coil 2 is wound around an annular core 1, and the exciting coil 2 is driven by a drive circuit 8.
Is excited by.

The magnetic flux generated by the excitation of the exciting coil 2 is X
The direction detection coil 3 and the Y-direction detection coil 4 are used for detection. X direction detection coil 3 and Y
The direction detection coil 4 is wound around the core 1 so as to be orthogonal to each other, and a detection signal obtained by detecting the magnetic flux by the X direction detection coil 3 and the Y direction detection coil 4 is input to the signal processing circuit 6. It has become.

The signal processing circuit 6 includes the X-direction detection coil 3 and Y.
The detection signal of the direction detection coil 4 is converted into direct current, and the X direction output and the Y direction output are output.

A feedback coil 9 is also wound around the core 1. The feedback coil 9 is
The magnetic flux in the core 1 is detected and magnetically fed back to the drive circuit 1. The output of the feedback coil 9 causes the drive circuit 1 to perform self-excited oscillation.

The drive circuit 1 is composed mainly of a transistor Tr, the base of which is connected to one end of a feedback coil 9 via a resistor R1.
The other end of is grounded. The base of the transistor Tr is connected to the power supply via the resistor R2, and is also connected to the collector of the transistor Tr via the exciting coil 2.

The collector of the transistor Tr is connected to the input terminal of the waveform shaping circuit 10. The waveform shaping circuit 10 outputs the output of the transistor Tr, that is, the drive circuit 8.
Is input to determine the detection timing and output to the signal processing circuit 6. The signal processing circuit 6 detects the detection signals of the X-direction detection coil 3 and the Y-direction detection coil 4 by the output of the waveform shaping circuit 10 and converts them into DC as described above.

Next, the operation will be described. By saturating or non-saturating the core 1, the magnetic field to be detected is magnetically modulated, and the voltage generated in the X-direction detection coil 3 and the Y-direction detection coil 4 at that time causes the original magnetic field to be detected. The basics for detecting the drive circuit are the same as those in the conventional example of FIG. 11, and the description thereof is omitted here.
The self-excited oscillation circuit and its timing will be described.

If the transistor Tr of the drive circuit 8 is turned on as shown in FIG. 2 (a), the exciting current of the exciting coil 2 gradually increases, as shown in FIG. 2 (b).
Along with that, the magnetic flux in the core 1 also gradually increases, and reaches saturation from non-saturation to finally saturation. At this time, like the conventional example,
The X-direction detection coil 3 and the Y-direction detection coil 4 are shown in FIG.
As shown in (d), a pulsed voltage proportional to the intensity of the magnetic field to be detected is generated.

On the other hand, the voltage V1 in the feedback coil 9 becomes 0 at the moment of saturation as shown in FIG. 2 (c), and immediately the transistor Tr of the drive circuit 8 starts turning off. When the transistor Tr starts to turn off, the exciting current gradually decreases, the magnetic flux in the core 1 decreases, and at the same time, a voltage is generated in the feedback coil 9 in the opposite direction to completely turn off the transistor Tr.

When the magnetic flux in the core 1 stabilizes, the voltage of the feedback coil 9 disappears and the base current from the pull-up resistor (resistor R1) causes the transistor T to disappear.
r begins to turn on. When the transistor Tr starts to turn on, the magnetic flux in the core 1 increases, a voltage is generated in the feedback coil 9, and the transistor Tr is completely turned on.

By repeating such an operation, the drive circuit 8 and the exciting coil 2 self-excited and oscillate. In the process, the X-direction detecting coil 3 and the Y-direction detecting coil 4 are shown in FIG. 2 (d). Such a pulsed voltage is generated. The on / off signals of the transistor Tr are taken into the waveform shaping circuit 10, the detection timing is determined there, and the signal is sent to the signal processing circuit 6, so that the signal processing circuit 6 detects, integrates, and takes out as a DC component. it can.

With such a configuration, the drive circuit 8 and the exciting coil 2 self-excitedly oscillate by the feedback coil 9, so that it is not necessary to separately provide an oscillating circuit.

Further, when the core 1 is saturated, the excitation of the exciting coil 2 is immediately stopped. Therefore, as in the conventional case, even after the saturation,
It is not necessary to keep the saturation current flowing for a certain period of time, and it is possible to reduce unnecessary excitation current, and immediately after saturation, the next excitation operation is started, so that the oscillation frequency can be increased and the sensitivity can be increased.

Example 2. FIG. 3 is a circuit diagram showing the configuration of the second embodiment. In FIG. 3, the same parts as those in FIG. 1 are denoted by the same reference numerals, and the parts different from those in FIG. 1 will be mainly described.

In FIG. 3, reference numeral 11 is a drive circuit using a royal type self-excited oscillation circuit. One end of the feedback coil 9 is connected to the base of the transistor Tr2 via the resistor R3, and the other end of the feedback coil 9 is directly connected to the base of the transistor Tr3. The base of the transistor Tr2 is connected to the power supply. The emitters of the transistors Tr2 and Tr3 are directly connected and grounded, and the collector of the transistor Tr2 and the emitter of the transistor Tr3 are connected to the input end of the waveform shaping circuit 10.

The exciting coil 12 is connected between the power source and the collector of the transistor Tr2, and similarly, the exciting coil 13 is connected between the power source and the collector of the transistor Tr3. These exciting coils 1
Both 2 and 13 are wound around the core 1, and the exciting coils 12 and 13 alternately excite the core 1.

Next, the operation will be described. Since the core 1 is alternately excited by the exciting coils 12 and 13, the core 1
The direction of the magnetic flux therein can be changed alternately to reduce the influence of the residual magnetic flux of the core 1 and to reduce the error contained in the voltage generated in the X-direction detection coil 3 and the Y-direction detection coil 4. Therefore, accuracy and sensitivity can be improved at the same time.

Example 3. FIG. 4 is a circuit diagram of the third embodiment, and 14 is a drive circuit. This drive circuit 14 connects the transistors Tr1 to Tr4 in an H-bridge type,
The exciting coil 2 is excited. The drive circuit 12 has current detection resistors R5 and R6 built therein, and the current detection resistors R5 and R6 are connected between the emitters of the transistors Tr3 and Tr4 and the ground, respectively.

By these current detection resistors R5 and R6,
The current flowing through the exciting coil 2 is converted into a voltage, and the converted voltage is input to the timing adjusting circuit 16 through the differentiating circuits 15a and 15b, respectively.

The timing adjusting circuit 16 includes the exciting coil 2
The excitation timing and the detection timing of the magnetic flux of the X-direction detection coil 3 and the Y-direction detection coil 4 are determined, and a signal is sent to the signal generation circuit 17 and the waveform shaping circuit 10.

The signal generating circuit 17 is included in the driving circuit 14, and by inputting the output of the timing adjusting circuit 16, the transistors Tr1 and Tr4 and Tr2 and T2.
The r3 is alternately turned on and off. Further, the waveform shaping circuit 10 inputs the output of the timing adjustment circuit 16, determines the detection timing, and outputs it to the signal processing circuit 6.

FIG. 5 is a circuit diagram showing an example of the internal configuration of the timing adjusting circuit 16, and the output voltages of the differentiating circuits 15a and 15b are input to the inverting input terminals of the comparators 16a and 16b, respectively. . Comparators 16a and 16b
A predetermined reference voltage is applied to the non-inverting input terminal of, and this reference voltage is obtained by connecting resistors R7 and R8 in series between the power source and ground.

The outputs of the comparators 16a and 16b are rise delay circuits 16c and 16 formed by resistors and capacitors.
It is connected to the output end side of the signal generation circuit 17, that is, the base side of the transistors Tr4 and Tr3 of the drive circuit 14 via the d, the buffers 16e and 16f, and the resistors R9 and R10.

The output terminal of the buffer 16e has an integrating circuit 16g composed of a resistor and a capacitor, an inverter 16h,
Via a differentiation circuit 16i composed of a capacitor and a resistor,
It is connected to a reset terminal R of a flip-flop circuit 17a (hereinafter referred to as FF) of the signal generation circuit 17.
Similarly, the output end of the buffer 16f has an integrating circuit 16
j, the buffer 16k, and the differentiation circuit 16l, FF1
It is connected to the set terminal S of 7a.

The output terminal Q of the FF 17a is connected to the base of the transistor Tr2 of the drive circuit 14 via the resistor R11, and is connected to the base of the transistor Tr1 via the inverter 17b and the resistor R12. The D terminal and the inverting output terminal of the FF 17a are connected to the base of the transistor Tr3 via the resistor R13, and are connected to the base of the transistor Tr4 via the inverter 17c and the resistor R14.

The comparator 16a of the timing adjustment circuit 16,
The output end of 16b is connected to the input end of the waveform shaping circuit 10.

Next, the operation will be described with reference to the waveform chart of FIG. The waveforms in FIGS. 6A to 6R show the waveforms at points a to r in FIG. The resistance R5 of the drive circuit 14
A signal a obtained by converting the exciting current of the exciting coil 2 into a voltage by R6 is as shown in FIG. 6 (a). This signal passes through the differentiating circuit 15a, and the output of the differentiating circuit as shown in FIG. 6B is obtained.

The output of the differentiating circuit 15a is the comparator 16a.
Applied to the inverting input of. A predetermined reference voltage is applied to the non-inverting input terminal of the comparator 16a. The reference voltage is compared with the output voltage of the differentiating circuit 15a, and the comparator 16a is compared.
An output signal c as shown in FIG. 6C is obtained at the output end of a.

This output signal c is a signal from excitation to saturation, and the waveform shaping circuit 10 is used as the timing for detecting the signals of the X-direction detection coil 3 and the Y-direction detection coil 4 generated at the time of saturation. Output to. A waveform as shown in FIG. 6D is obtained by a rising delay circuit (by a resistor, a capacitor, and a diode) in order to turn off the excitation with a slight delay from the end of the detection timing. By shaping the output signal d of the rising delay circuit 16 in the buffer 16e, the waveform shown in FIG.
An excitation off signal e as shown in (1) is obtained.

Next, the transistor Tr1 of the drive circuit 14
The upper and lower transistors Tr1 and Tr3 of Tr4,
In order to prevent Tr2 and Tr4 from turning on at the same time, the integration circuit 16g integrates and delays the integrated output f as shown in FIG. 6 (f). This integrated output f
Waveform is shaped by the buffer 16h and the shaped output g is shown in FIG.
Obtained as shown in (g).

That is, the excitation ON signal g (FIG. 16) appearing at the output end of the buffer 16h after a slight delay from the excitation OFF signal e (FIG. 6E) output from the buffer 16e.
(G)), and the waveform of the excitation ON signal h (FIG. 16 (h)) obtained by integrating and delaying this by the integration circuit 16i. This excitation ON signal h is sent to FF1 of the signal generation circuit 17.
By sending to the reset terminal R of 7a, the upper and lower transistors being driven, that is, the transistors Tr1 and Tr1.
3, it is possible to prevent Tr2 and Tr4 from turning on at the same time.

The next excitation starts from the excitation ON signal h,
The output i of the FF 17a from the inverting output end of the FF 17a is shown in FIG.
As shown in (i), the transistor Tr3 is turned on, and the output r (FIG. 16 (r)) of the opposite polarity from the output terminal Q of the FF 17a is added to the base of the transistor Q2. It turns on.
As a result, an exciting current flows through the exciting coil 2. Similarly, the signals j to q are also obtained, the signals shown in FIGS. 6 (j) to 6 (q) are obtained, and the excitation coil 2 is obtained by repeating the operations based on the signals a to i and the signals j to q. The exciting current flows alternately to the cores 1, and therefore the core 1 is excited alternately.

In this way, the signal generating circuit 17 drives the transistors Tr1 and Tr4 and Tr2 and Tr3 in the drive circuit 14 by the signals h and q. In addition, the waveform shaping circuit 10 uses the excitation timing signals c and l (FIG. 6C, FIG.
(L)) determines the detection timing and outputs it to the signal processing circuit 6.

That is, as described above, the feedback in the self-excited oscillation is performed not by magnetism but by current, so that there is no need to wind a troublesome feedback coil and there is an advantage that the magnetic sensor can be inexpensive.

Example 4. FIG. 7 is a circuit diagram showing the configuration of the fourth embodiment. In FIG. 7, the magnetic sensor part is the same as that in FIG. 1, but in FIG. 7, a positive power supply output is added to the configuration of FIG.

That is, the transistor T in the drive circuit 8
The collector of r is connected to the positive power supply output terminal T1 via a diode 18, the cathode of this diode 18 is grounded via a capacitor 19, and when the exciting coil 2 is turned off to the capacitor 19 through the diode 18. The electric energy stored in the exciting coil 2 is transferred when the exciting coil 2 is turned on, and a positive power source other than the input power source can be configured.

Similarly, FIG. 8 shows an example applied to the circuit of FIG. 3, showing an embodiment in which electric energy in the coil 1 is transferred to the capacitor 19 through the two diodes 18a and 18b. is there. In FIG. 8, the diode 18 is connected to the collectors of the transistors Tr2 and Tr3.
is connected to the capacitor 19 via a and 18b,
It is also connected to the positive power supply output terminal T1.

FIG. 9 shows an example applied to the circuit of FIG. 4 in a similar manner. The transistor Tr of the drive circuit 14 is shown in FIG.
A diode 18 for preventing backflow on the collector side of 1 and Tr2.
c and 18d are inserted, and the cathodes of the diodes 18c and 18d are connected to the capacitor 19 via the diodes 18a and 18b, respectively, and are also connected to the positive power supply output terminal T1.

By configuring as shown in FIGS. 8 and 9, the energy generated in the exciting coil 2 can be used without waste. Further, even when a low input power supply voltage is used, it is possible to secure a high power supply voltage that allows the signal processing circuit 6 and the like to operate sufficiently, and a magnetic sensor that can be used even at a low voltage can be configured. Although FIG. 8 and FIG. 9 are all positive power supply configurations, the transistor and diode 18a, 1
It is also possible to change to a negative power source by changing the configuration of 8b.

If a secondary coil insulated from the input power supply system is provided as in a general transformer structure, it is possible to form a power supply insulated from the input power supply system. Further, as shown in FIG. 8, when one exciting coil is in operation and has another coil that does not contribute to excitation, in addition to the energy released in the coil when the energy is stored in the coil, the core There is also electric energy generated by the non-operating coil when the magnetic flux by the operating coil that excites is increased, and by adding this, a power source with a larger output can be configured. The separate power source isolated from the positive, negative and input power systems is a so-called DC-D.
Like the C power supply, it can be set to any voltage.

Example 5. FIG. 10 is a block diagram showing the configuration of the fifth embodiment. In FIG. 10, the auxiliary starting circuit 20 is provided in the configuration of FIG. In the current feedback type self-excited oscillation, when the power supply voltage is low, the amount of change in the current is reduced and the differential value thereof is also a low value, and the output signals of the comparators 16a and 16b shown in FIG. 5 are obtained. And the timing adjustment circuit 16 cannot operate, and thus becomes unstable. Further, when starting from a low voltage, the output may be fixed to either side and may not oscillate.

Therefore, when the auxiliary starting circuit 20 is provided and the outputs of the comparators 16a and 16b cannot be obtained, the auxiliary starting circuit 20 detects it and the signal generating circuit 17 is excited by the auxiliary starting circuit 20. However, the self-excited oscillation is stabilized.

[0067]

Since the present invention is constructed as described above, it has the following effects.

By driving the exciting coil by self-excited oscillation, an oscillation circuit is not required, and since the excitation is turned off immediately after the core is saturated, useless exciting current can be reduced, and power source current and heat generation can be reduced. And moreover,
The excitation cycle is also made faster, and accuracy and sensitivity are improved.

Further, a feedback coil is provided in addition to the exciting coil, the magnetic flux in the core is detected by the feedback coil, self-excited oscillation is performed by the detected output, and the exciting coil is driven, thereby simplifying the entire circuit. Can be achieved.

Further, by detecting the current flowing through the exciting coil and feeding it back to the drive circuit, the feedback coil is not required and the cost is reduced.

Further, the electric energy stored in the exciting coil during driving of the exciting coil is stored in the capacitor through the diode when the exciting current is turned off, or the electric energy is supplied to the power supply system other than the input power supply simultaneously with the excitation of the core. By shifting, the power supply output below the input voltage can be obtained, and even when the low voltage is input, the operating voltage at which the circuit can operate can be secured, and there is no waste.

In addition, the self-excited oscillation of the drive circuit can be stabilized even if the auxiliary adjustment circuit is provided for the current feedback type self-excited oscillation and the timing adjustment circuit cannot operate.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a configuration of a self-excited magnetic sensor according to a first embodiment of the present invention.

FIG. 2 is a waveform diagram for explaining the operation of the first embodiment.

FIG. 3 is a circuit diagram showing a configuration of a self-excited magnetic sensor according to a second embodiment of the present invention.

FIG. 4 is a circuit diagram showing a configuration of a self-excited magnetic sensor according to Embodiment 3 of the present invention.

5 is a circuit diagram showing an internal configuration of a timing adjustment circuit in the self-excited magnetic sensor of FIG. 4. FIG.

6 is a waveform diagram for explaining the operation of the timing adjustment circuit of FIG.

FIG. 7 is a circuit diagram showing a configuration of a self-excited magnetic sensor according to a third embodiment of the present invention.

FIG. 8 is a circuit diagram showing a configuration of a self-excited magnetic sensor showing a modification of the fourth embodiment of the present invention.

FIG. 9 is a circuit diagram showing a configuration of a self-excited magnetic sensor showing a further modified example of the fourth embodiment of the present invention.

FIG. 10 is a circuit diagram showing the configuration of a self-excited magnetic sensor according to Embodiment 5 of the present invention.

FIG. 11 is a circuit diagram showing a configuration of a conventional separately excited magnetic sensor.

FIG. 12 is a waveform diagram of each part for explaining the operation of the conventional separately excited magnetic sensor.

[Description of Reference Signs] 1 core 2 exciting coil 3 X-direction detecting coil 4 Y-direction detecting coil 5 driving circuit 6 signal processing circuit 8 driving circuit 9 feedback coil 10 waveform shaping circuit 11 driving circuit 12 exciting coil 13 exciting coil 14 driving circuit 15a Differentiation circuit 15b Differentiation circuit 16 Timing adjustment circuit 17 Signal generation circuit 18a Diode 18b Diode 19 Capacitor 20 Auxiliary starting circuit

Claims (5)

[Claims] 1. An exciting coil for changing a magnetic flux of a core, a drive circuit for driving the exciting coil by self-excited oscillation, a detecting coil for detecting X and Y direction components of measured magnetic field, and this detecting coil. A self-excited magnetic sensor including a signal processing circuit for converting a signal generated in the signal and a waveform shaping circuit for determining a detection timing of the signal processing circuit. 2. The drive circuit is wound around the core in addition to the exciting coil, and a detection output for detecting the magnetic flux of the core is fed back from a feedback coil to self-oscillate to drive the exciting coil. The self-excited magnetic sensor according to claim 1, wherein 3. The self-exciting type according to claim 1, wherein the drive circuit drives the exciting coil by detecting a current flowing through the exciting coil and feeding back a detection output from the detecting coil. Magnetic sensor. 4. The driving circuit charges the energy stored in the exciting coil during driving of the exciting coil into a capacitor via a diode when the exciting current is off, or other than an input power source at the same time as exciting the core. 2. The self-excited magnetic sensor according to claim 1, wherein electric energy is transferred to the power supply system. 5. The self-excited magnetic sensor according to claim 3, wherein the drive circuit stabilizes the self-excited oscillation by the auxiliary start-up circuit when the power supply voltage is low or when starting from a low voltage. .