JPS5854599B2 - magnetic detection device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic detection device, which compares the arithmetic average voltages of the voltage terminals of each Hall element to obtain a comparison error voltage, which is connected in series to the current terminal of each Hall element according to this voltage. By controlling the current flowing through the resistor connected to the It is an object of the present invention to provide a magnetic detection device that can always accurately detect relative positions.

FIG. 1 shows a circuit diagram of an example of a general DC brushless motor using Hall elements.

The motor shown in the figure has four-phase armature windings W1 to W1, which are mounted on a stator (not shown) at intervals of 900 electrical degrees.
In the example of a Hall motor with W4, Hall elements H,,H
2 detects the relative position between the rotor (not shown) made of permanent magnets and the armature windings W1 to W4, and thereby,
The transistors X1>X4 are turned on and off depending on the relative positions, and the currents flowing through the armature windings W1 to W4 are sequentially switched to rotate the rotor in a fixed direction.

By pressing a button on the motor having the above configuration and appropriately adjusting the variable resistor VR connected to the current terminal of the Hall element H2, the transistors X1 to X4 are sequentially adjusted to 9 electrical degrees.
Turn on the armature windings W1-W'4 by shifting them by 00.
The flow angle is 90° (electrical angle) and the phase difference is 900° (
Ideally, the current should be energized at a certain angle (electrical angle), but in reality, the input resistance changes due to self-heating of the Hall elements H1 and H2, changes in ambient temperature, etc. For example, the temperature coefficient of the input resistance of an indium antimony Hall element is -2%/'C
), which varies in the range of -3%/'C), and the second
As shown in Figure A, the voltage V1 at the voltage terminal of the Hall element H1
The average voltage (DC component, straight line V) of the average voltage or voltage v3 (curve ■) of (curve I) and the average voltage of voltage v2 (curve ■) of the voltage terminal of Hall element H2 or voltage ■4 (
Curve ■) is different from the average voltage (DC component, straight line ■),
As shown in FIG. B, the flow angles of the armature currents (1) to (4) are no longer constant, resulting in uneven torque and failure to start.

In the past, in order to reduce these adverse effects, it was necessary to use Hall elements with substantially the same characteristics, but there were drawbacks such as the fact that it was extremely difficult to manufacture Hall elements.

The present invention eliminates the above-mentioned drawbacks, and one embodiment thereof will be described with reference to FIG. 3 and subsequent figures.

FIG. 3 shows a circuit diagram in which the magnetic detection device according to the present invention is applied to a four-phase Hall motor.

In the figure, X5 is a transistor, the base of which is connected to each of the two voltage terminals of the Hall element H1 (first Hall element) via resistors R1 and R3 having the same resistance value, and the collector of which is connected to the two voltage terminals of the Hall element H1 (first Hall element). It is connected to the power supply terminal 1 via R5 and to one of the two current terminals of the Hall element H1.

X6 is a transistor, the base of which is connected to each of the two voltage terminals of the Hall element H2 (second Hall element) through resistors R2 and R4 having the same resistance value, and the collector of which is connected to each of the two voltage terminals of the Hall element H2 (second Hall element) through the resistor R6. The button is connected to the power supply terminal 1 and is also connected to one of the two Hall elements H2,
Its emitter is connected to the terminal of transistor X5.

X7 is a transistor whose collector is transistor
It is connected to the connection point between the vine in step 5 and the emitter of the transistor and is connected to the power supply terminal 1'.

The emitters of each of the transistors X1□ to X14 are resistors R
It is connected to the power supply terminal 1' via IO, and the other current terminal of the Hall elements H1 and H2 is connected to the resistor R1□tR, respectively.
It is connected to the power supply terminal 1' through 1°.

The resistance values of the resistors R, , R6, R1□, and R12 are all set to approximately the same value.

Transistors X5-X7 and resistors R1-R4, R7-R
A differential amplifier is configured at 0 and forms the main part of the device of the present invention.

The rest of the configuration is similar to the circuit shown in FIG.

Next, the operation of the above-mentioned constituent circuit will be explained.

If you press the button in the same figure, the current from power supply terminal 1 will pass through Hall element H1.
, H2 and transistors X1 to X4, the rotor position is detected by Hall elements H1 and H2, and transistors X1 to X4 and transistors X11 to X14
are sequentially turned on, and a current sequentially flows through the armature windings W1 to W4, causing the rotor to rotate in a predetermined direction.

A description of the operation of the button, constant speed control circuit, and armature current amplitude control circuit will be omitted.

Here, transistors X5. X6
Considering the base voltage of , the Hall voltage V applied to the base of transistor X1 is at the base of transistor X5, which is the first input terminal of the differential amplifier.
The arithmetic average voltage v13 (first arithmetic average voltage) of the Hall voltage ■3 applied to the base of the transistor Transistor X is at the base of X6
The Hall voltage V2 applied to the base of transistor X4 and the Hall voltage v4 applied to the base of transistor X4
An arithmetic mean voltage V24 (second arithmetic mean voltage) is applied between the voltages v1 and v3. v2 and ■4
Since the alternating current components of and have opposite phases to each other, the voltages 1 and 24 are direct current voltages with almost no ripple.

Note that the collectors of the transistors X5 and X6 become the first and second output terminals of this differential amplifier.

The two current terminals of each Hall element H1 and H2 are connected to the power supply terminals 1 and 1', respectively, through resistors R5t R6tRll t R1□, which have approximately equal resistance values, so that the Hall voltages v1 to 4 are DC. Component is an abbreviation for power supply voltage,
Arithmetic average voltage V13. v24 maintains a predetermined value without being affected by the magnetoresistive effect of the Hall elements H1 and H2.

Therefore, due to variations in the characteristics of the Hall elements H1 and H2, changes in ambient temperature, etc., the voltage v13 may change to the voltage V2.
4, transistor X5. X6
detects this, and at the same time as the collector current of transistor X5 increases, the collector current of transistor X6 decreases.

As a result, the voltage drop across the resistor R5 becomes a dog, and the voltage drop across the resistor R6 becomes small, so that the voltage ■13 becomes the voltage ■
control so that it is always equal to 24.

Therefore, according to the device of the present invention, as shown in FIG. 4A, the Hall voltage V1. V3 arithmetic average voltage v13 and Hall voltage v2. ■The arithmetic mean voltage v24 of 4 always matches, and as a result, as shown in Figure B, the flow angles of the armature currents flowing through the armature windings W1 to W4, ~I4, are all equal,
The rotor can be rotated smoothly without uneven torque or uneven rotation.

Although the above embodiment uses two Hall elements, it can be similarly applied to a detection circuit using three or more Hall elements, and the two voltage terminals of each Hall element is connected to the base of each transistor constituting the differential amplifier via a resistor, and the terminal of the transistor is connected to the third
It may be connected to the collector of the transistor X7 of the constant current source shown in the figure.

If the device obtains an output signal corresponding to the Hall voltage and controls the current flowing to the current terminal of the Hall element using this output signal, it can be applied to devices other than Hall motors as well. It can similarly be applied to devices that operate with a constant static magnetic field rather than a changing magnetic field.

As described above, in the magnetic detection device according to the present invention, the Hall element is composed of at least a first Hall element and a second Hall element,
The first Hall element has two Hall voltage terminals and two current terminals, and the second Hall element has two voltage terminals and two
and a first arithmetic average voltage obtained by adding the Hall voltages generated at the two Hall voltage terminals of the first Hall element.
A second Hall voltage generated by applying the Hall voltage generated to the input terminal of and the two husband Hall voltage terminals of the second Hall element.
a second input terminal to which an arithmetic average voltage of is applied, a first output terminal connected to one current terminal of the first Hall element, and one current terminal of the second Hall element. a differential amplifier having a second output terminal connected to the differential amplifier;
The first arithmetic average voltage and the second arithmetic average voltage are compared in the differential amplifier, so that the first Hall element and the second Hall element are controlled according to the comparison error voltage. Since the current flowing through each current terminal of the element is controlled so that the first arithmetic average voltage and the second arithmetic average voltage are approximately equal, self-heating of the Hall element, changes in ambient temperature, etc. Even if there are variations in the characteristics of each Hall element, such as asymmetry in input resistance, the average voltage at the voltage terminal of the Hall element can always be made equal. Therefore, there is no need to strictly match the characteristics of multiple Hall elements. In addition, when applied to a hall motor, etc., the armature current can be passed at accurate timing, the rotor can be rotated smoothly without torque unevenness or rotational unevenness, and a decrease in starting torque can be prevented.
In particular, the waveform of the back electromotive force generated in the armature winding is not disturbed, making it ideal for motors whose speed is controlled using the back electromotive force.

[Brief explanation of the drawing]

Figures 1 and 2 A and B respectively show one example of a conventional Hall motor.
An example circuit diagram and a voltage waveform diagram to explain its operation,
Current waveform diagrams, Figures 3 and 4A. B is a circuit diagram of one embodiment of the magnetic detection device according to the present invention, and a voltage waveform diagram and a current waveform diagram for explaining its operation. Hl, H2...Hall element, X1 to X7. X1□～X
14...Transistor, R1-R1□...Resistor, W
l-w4...armature winding.

Claims (1)

[Claims] 1. In a magnetic detection device that extracts a Hall voltage from a plurality of Hall elements by applying a magnetic field from a magnetic body to a plurality of Hall elements and detects a relative position between the Hall element and the magnetic body based on the Hall voltage, the Hall element is The first Hall element has two Hall voltage terminals and two current terminals, and the second Hall element has two voltage terminals and two current terminals. a first input terminal to which a first arithmetic average voltage obtained by adding the Hall voltages generated at the two Hall voltage terminals of the first Hall element; a second input terminal to which a second arithmetic average voltage obtained by adding the Hall voltages generated at two respective Hall voltage terminals of the second Hall element; and one current of the first Hall element; a differential amplifier having a first output terminal connected to a terminal, and a second output terminal connected to one current terminal of the second Hall element; and the second arithmetic average voltage are compared in the differential amplifier, so that a current flows through each current terminal of the first Hall element and the second Hall element according to the comparison error voltage. is controlled so that the first arithmetic mean voltage and the second arithmetic mean voltage are substantially equal.