JPH11337368A - Magnetic detection circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnetism detection circuit in which the burden of its maintenance and its cost including a sensor can be reduced sharply. SOLUTION: A sensor 10, by which the change state of an object to be detected is detected as a change in magnetism, is provided. An output circuit 20 in which an output voltage Vm from the sensor 10 is compared with a reference voltage Vf and which outputs a pulse-shaped output voltage Vout according to the change state of the object to be detected is provided. A correction circuit 30, in which the reference voltage Vf is supplied to the output circuit 20 as a change-absorption reference voltage Vf' according to a change in the output voltage Vm, is installed between the sensor 10 and the output circuit 20.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic detection circuit used for detecting a change state such as displacement or rotation of a detection target using a magnetoresistive element.

[0002]

2. Description of the Related Art In recent years, a circuit for detecting a change state such as displacement or rotation of an object using a magnetoresistive element and processing the output signal is disclosed in, for example, Japanese Patent No. 2715997,
As shown in FIG. 3 and disclosed in Japanese Utility Model Registration No. 2525199, two magnetoresistive elements 11 and 12 whose resistance values change according to a magnetic change are connected to a power supply Vcc and a ground G.
ND are connected in series with each other.
By comparing with the reference voltage Vf set in FIG. 2, as shown in FIG.
A magnetic change is detected by a change in a binary pulse-like output voltage Vout (see FIG. 2B) corresponding to a change in the output voltage Vm of the sensor 10 (see FIG. 2A), and a subsequent stage. To the measuring device (not shown) connected to
ut is output. Reference numeral 23 denotes a resistor for forming a hysteresis width (see FIG. 3C) serving as a high / low determination value in the output circuit 20.

[0003]

In such a configuration, as shown in FIG. 5, which is an operation waveform diagram with the horizontal axis representing time T due to variations in the magnetic field strength due to the displacement of the position of the sensor 10, etc. If the characteristic of the output voltage Vm of the output circuit 10 differs between the design time (see FIG. 7A) and the actual one (see FIG. 7B), the initial characteristic cannot be obtained as the output voltage Vout of the output circuit 20. There is a problem to say.

[0004]

According to the present invention, there is provided a sensor for detecting a change state of an object to be detected as a change in magnetism, and comparing an output voltage Vm from the sensor with a reference voltage Vf. An output circuit that outputs a pulsed output voltage Vout in accordance with the change state of the detection target, and sets the reference voltage Vf as a fluctuation absorption reference voltage Vf ′ in accordance with a change in the output voltage Vm. And a correction circuit for supplying the correction signal to the power supply.

Also, a sensor for detecting a change state of a detection target as a change in magnetism, and an output voltage V from the sensor.
and an output circuit that compares m with the reference voltage Vf and outputs a pulsed output voltage Vout in accordance with the change state of the detection target. A correction circuit is provided for supplying a fluctuation absorption reference voltage Vf ′ obtained by adding the average value Vr to the reference voltage Vf to the output circuit.

Also, a sensor for detecting a change state of a detection target as a change in magnetism, and an output voltage V from the sensor.
and an output circuit for comparing the reference voltage Vf with the reference voltage Vf and outputting a pulsed output voltage Vout according to the change state of the detection target. The output voltage Vm is varied by a smoothing circuit including a resistor and a capacitor. The average value Vr is detected, and the fluctuation average value Vr is added to the reference voltage Vf.
A correction circuit for supplying f ′ to the output circuit is provided.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A sensor 10 for detecting a change state of an object to be detected as a change in magnetism, and an output voltage Vm from this sensor 10 and a reference voltage Vf are compared to determine the change state of the object to be detected. An output circuit 20 for outputting a pulsed output voltage Vout, and a correction circuit 30 for supplying the reference voltage Vf to the output circuit 20 as the fluctuation absorption reference voltage Vf 'according to the fluctuation of the output voltage Vm.

As a result, even if the sensor 10 has variations in characteristics, the sensor 10 is corrected by the correction circuit 30 to improve the yield, and the positional relationship between the sensor 10 and the object to be detected is initially shifted and time-dependent. The target characteristics can be maintained by automatically correcting the target change.

Further, a sensor 10 for detecting a change state of the object to be detected as a magnetic change, and comparing an output voltage Vm from the sensor 10 with a reference voltage Vf, a pulse corresponding to the change state of the object to be detected. An output circuit 20 for outputting a V-shaped output voltage Vout, detecting a variation average value Vr of the output voltage Vm, and adding a variation absorption reference voltage Vf ′ obtained by adding the variation average value Vr to the reference voltage Vf. And a correction circuit 30 for supplying to the power supply.

As a result, even if the sensor 10 has a variation in characteristics, the yield is improved by the correction by the correction circuit 30, and the initial positional deviation and the aging of the positional relationship between the sensor 10 and the object to be detected are improved. The target characteristics can be maintained by automatically correcting the target change.

Further, a sensor 10 for detecting the change state of the object to be detected as a magnetic change, and comparing an output voltage Vm from the sensor 10 with a reference voltage Vf to generate a pulse corresponding to the change state of the object to be detected. And an output circuit 20 for outputting a V-shaped output voltage Vout. The output voltage Vm is detected by a smoothing circuit including a resistor and a capacitor to detect a variation average value Vr, and the variation average value Vr is added to the reference voltage Vf. Correction circuit 3 for supplying absorption reference voltage Vf 'to output circuit 20
0 was provided.

As a result, even if the sensor 10 has a variation in characteristics, the yield is improved by the correction by the correction circuit 30, and the initial positional deviation and the aging of the positional relationship between the sensor 10 and the object to be detected are improved. The target characteristics can be maintained by automatically correcting the target change.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described with reference to the embodiments shown in FIGS. 1 and 2. The same or corresponding parts as those in the conventional example shown in FIGS. Omit the explanation.

The present invention is characterized in that the sensor 10 and the output circuit 2
Since the correction circuit 30 is interposed between 0 and 0, the correction circuit 30 includes a smoothing circuit including a resistor 31 and a capacitor 32 and resistors 33 and 34.

A series circuit of a resistor 31 and a capacitor 32 is connected between the connection midpoint of the magnetoresistive elements 11 and 12 and the ground GND, and the connection midpoint of this series resistor and the resistors 21 and 22 are connected.
The output circuit 2 is connected to the connection middle point through resistors 33 and 34, respectively.
The reference input terminal of the output circuit 20 is connected to the middle point of connection between the magnetoresistive elements 11 and 12 as in the conventional example.

That is, the output voltage Vm of the sensor 10 is inputted to the comparison input terminal of the output circuit 20, and the reference voltage Vf set by the resistors 21 and 22, the resistor 31, and the capacitor 32 are inputted to the reference input terminal of the output circuit 20. Will be input as the fluctuation absorption reference voltage Vf ′.

According to such a configuration, the output voltage of the sensor 10 is changed as shown in FIG. 2, which is an operation waveform diagram in which the horizontal axis represents time T, due to variations in the magnetic field intensity due to the displacement of the position of the sensor 10. Even if the characteristic of Vm fluctuates from the design time (see FIG. 3A) to the actual (see FIG. 3B),
At the same time, the fluctuation absorption reference voltage Vf ′ of the output circuit 20 has the same ratio, that is, the output voltage Vm is
2, the detection voltage Vout of the output circuit 20 does not change as a result.

That is, the output voltage Vm of the sensor 10 is averaged by the circuit of the resistor 31 and the capacitor 32 to become the voltage Vr of the DC level, while the resistors 33 and 34 use the initial reference voltage Vf as the voltage Vr. Is corrected and applied to the output circuit 20 as the fluctuation absorption reference voltage Vf ′. Therefore, if the resistance 34 is set to 0Ω, Vf ′ = Vf, so that no correction is performed, and the resistance 33 is set to 0Ω.
Then, Vf ′ = Vr, and the fixed Vf becomes ineffective.

Therefore, the reference voltage Vf at the time of design and the average value Vr of the change of the output voltage Vm caused by the mounting fluctuation of the sensor 10 and the like are added, and the fluctuation absorbing reference voltage Vf ′ = Vf +
By setting Vr, the detection of the output circuit 20 can be performed stably.

The magnetic detection circuit according to the present invention can be applied to, for example, a magnetoresistive element used for detecting the traveling speed of a vehicle, and the sensor 1 detects vibrations during traveling of the vehicle.
Even if a mechanical position of a gear (not shown) interlocked with the rotation of the axle, which is a detection target for detection of 0, changes, a determination can be made in the output circuit 20 in accordance with the changed output Vm. Therefore, it is not necessary to perform a special periodic inspection, and the reliability is improved.

The sensor 10 is constructed by connecting two magnetoresistive elements 11 and 12 and connecting four magnetoresistive elements as disclosed in the above-mentioned prior art document in a bridge-like manner. However, the same is applicable.

The resistances 21 and 21 for determining the reference voltage Vf
2 may be configured such that at least one of the resistors is a variable resistor and the user can arbitrarily adjust the level.

[0023]

According to the present invention, the yield can be improved because the sensor operates as a sensor even if the magnetoresistive elements constituting the sensor have variations in characteristics. In addition, the initial deviation and the change over time of the positional relationship between the sensor and the detection target can be automatically corrected to maintain the initial characteristics. Therefore, maintenance and cost burden of the magnetoresistive circuit including the sensor can be greatly reduced.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of an embodiment of the present invention.

FIG. 2 is an operation waveform diagram of the above.

FIG. 3 is a circuit diagram of a conventional example.

FIG. 4 is an operation waveform chart of the above.

FIG. 5 is an operation waveform chart of the above.

[Explanation of symbols]

 Reference Signs List 10 sensor 11, 12 magnetoresistive element 20 output circuit 30 correction circuit

Claims (3)

[Claims] 1. A sensor for detecting a change state of an object to be detected as a change in magnetism, and comparing an output voltage Vm from the sensor with a reference voltage Vf to generate a pulse-like signal corresponding to the change state of the object to be detected. An output circuit that outputs an output voltage Vout, and a correction circuit that supplies the reference voltage Vf to the output circuit as a variation absorption reference voltage Vf ′ in accordance with a variation in the output voltage Vm. Magnetic detection circuit. 2. A sensor for detecting a change state of a detection target as a change in magnetism, and comparing an output voltage Vm from the sensor with a reference voltage Vf to generate a pulse-like signal corresponding to the change state of the detection target. An output circuit for outputting an output voltage Vout, detecting a variation average value Vr of the output voltage Vm, and adding a variation absorption reference voltage Vf ′ obtained by adding the variation average value Vr to the reference voltage Vf to the output circuit. A magnetic detection circuit comprising a correction circuit for supplying the magnetic field. 3. A sensor for detecting a change state of a detection target as a change in magnetism, and comparing an output voltage Vm from the sensor with a reference voltage Vf to generate a pulse-like signal corresponding to the change state of the detection target. An output circuit for outputting an output voltage Vout, wherein the output voltage Vm is detected by a smoothing circuit composed of a resistor and a capacitor to detect a fluctuation average value Vr, and the fluctuation average value Vr is added to the reference voltage Vf. A magnetic detection circuit comprising a correction circuit for supplying a reference voltage Vf 'to the output circuit.