JPH065174B2 - Hall element unbalance voltage automatic correction method in magnetic type rotation angle sensor - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a Hall element unbalanced voltage automatic correction method in a magnetic rotation angle sensor using a multi-pole permanent magnet rotor and a Hall element.

[Prior art]

FIG. 4 is a block diagram showing a system configuration example of a conventional magnetic rotation angle sensor for an internal combustion engine. In the figure, 1
1 is a permanent magnet rotor having a large number of poles, 1
Reference numeral 2 is a Hall element, 13 is an operational amplifier, 14 is a waveform converter (comparator), 15 is an output section, and 16 is a reference voltage source for generating a first reference voltage Vrefl.

In the magnetic rotation angle sensor having the above structure, a rotating magnetic field from the permanent magnet rotor 11 is applied to the hall element 12, the hall output from the hall element 12 is amplified by the amplifier 13, and the direct current component is cut by the capacitor C. , Applying only the rotation signal component to the waveform converter 14,
The sine wave is converted into a square wave and output from the output unit 15.

The reference voltage Vrefl from the reference voltage source 16 is the reference potential when the circuit is operated by a single power supply (operated by a positive or negative single-polarity power supply), which is a power supply voltage Vcc of about Vcc / 3.
Is a bias power supply for the above, and also serves as a waveform comparison voltage of the waveform converter 14.

Further, the resistance R of the waveform converter 14 is a bias resistance for applying a DC reference voltage to the input signal.

FIG. 5 is a waveform diagram showing the waveform of each part of the magnetic rotation angle sensor circuit. (1) shows the output voltage waveform of the Hall element 12, and (2) shows the input waveform of the waveform converter 14 at high rotation. The output waveform of the output unit 15 and (3) show the input waveform of the waveform converter 14 and the output waveform of the output unit 15 during low rotation, respectively.

[Problems to be solved by the invention]

However, when the permanent magnet rotor 11 rotates at a low speed in the above circuit, the time constant τ = C · R is compared with the signal period (the period of the input voltage signal of the waveform converter 14),
If it is not made sufficiently large, there is a drawback that the phase shift Δt occurs as shown in FIG. 5 (3), and the crankshaft angle is shifted.

Also, at the time of starting, the charging time τ = C · R of the capacitor C causes the reference potential of the input signal of the waveform converter 14 to fluctuate, and the intervals of the output pallets are not aligned. Therefore, when angular accuracy at the time of starting is required. However, since the charging time τ cannot be increased unnecessarily, there is a drawback that it conflicts with the demand that the time constant τ be sufficiently large.

The present invention has been made in view of the above points, and is a waveform conversion method for removing fluctuations of a signal reference potential due to an unbalanced voltage or an offset voltage of an amplifier by using the output signal of the conventional Hall element as an AC coupling (C coupling). In the above, the Hall element unbalance voltage automatic correction method in the magnetic rotation angle sensor with good output waveform conversion accuracy for the rotation angle has been eliminated by eliminating the drawbacks of phase shift deviation at low speed rotation and output waveform settling time at startup. To provide.

[Means for solving problems]

In order to solve the above-mentioned problems, the present invention relates to a magnetic rotation angle sensor using a multi-pole permanent magnet rotor and a Hall element, and after amplifying an output voltage (sine wave) of the Hall element using an operational amplifier, a waveform converter. To the operational amplifier by detecting the fluctuation of the signal reference voltage due to the Hall element unbalanced voltage generated by the DC coupling and the offset voltage of the operational amplifier, and comparing with the set DC reference voltage. A circuit that automatically corrects the applied bias voltage and approximates the reference potential of the output voltage to the set DC reference voltage, and removes the sine wave signal component from the amplified signal voltage of the waveform conversion reference potential of the waveform converter. It is characterized in that a circuit using a signal reference voltage as a reference power source is provided.

[Action]

With the above-mentioned configuration, the operational amplifier and the waveform converter are coupled to each other by direct current. Therefore, there is a drawback of the conventional AC coupling (C coupling) method, which is a drawback of low-speed rotation and phase shift. The problem of requiring waveform settling time is eliminated, and the fluctuation of the signal reference potential due to the unbalanced voltage of the Hall element and the offset voltage of the operational amplifier, which occurs when performing the waveform conversion by the DC coupling method, is automatically corrected, and By using the signal reference voltage obtained by removing the sine wave signal from the amplified signal voltage, the conversion accuracy of the output waveform with respect to the rotation angle can be improved.

〔Example〕

 Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing a system configuration of a magnetic rotation angle sensor according to an embodiment of the present invention, FIG. 2 is a waveform diagram of each part thereof, and FIG. 3 is a circuit diagram embodying the block diagram of FIG. Is.

In FIGS. 1 and 3, 11 is a permanent magnet rotor, 12 is a Hall element, 13 is an operational amplifier, 1
4 is a waveform converter (comparator), 15 is an output unit, 16
Reference voltage source for generating a first reference voltage Vrefl is 17 Yuru衡amplifier, 18 the correction _{amplifier, R, R S, R 1} ~R 16 is resistance, C, C ₁ is a capacitor, Q ₁ the output transistor Is.

In FIG. 2, (1) is the output voltage waveform of the Hall element 12, (2) is the output of the operational amplifier 13, that is, the input voltage waveform of the waveform converter 14, and (3) is the reference voltage of each part, that is, the first to the first. Four
Voltage levels of the reference voltages Vref1 to Vref3, and (4) shows the output waveform of the waveform converter 14, respectively.

Prior to explaining the operation of the magnetic rotation angle sensor shown in FIGS. 1 and 3, first, the Hall element 12 will be described with reference to FIG.
The cause of the unbalanced voltage generated at the output of the amplification stage will be described.

From the principle, the Hall element 12 is considered to be a bridge resistor having the same resistance value on each side, and in the circuit shown in FIG.
FIG. 7 is a diagram in which the DC potential between the output terminals and the alternating signal voltage due to the rotating magnetic field are separated to form an equivalent circuit.

Here, assuming that the resistors R ₁ = R ₃ and R ₂ = R ₄ and the gain of the operational amplifier 13 is A 1, A 1 = R ₂ / R ₁ = R ₃ / R ₄ , and therefore the output voltage V of the operational amplifier 13 _{OA1 is, V OA1 = -A1 · e OHE} sinθ + Vrefl + {(1 + A 1) · (V + -V -)} ...... (1) where, -A1 · e _OHE sinθ is alternating signal voltage term, Vrefl Is the DC reference potential term, {(1 + A1) · (V ₊ −V ₋ )} is the unbalanced voltage amplification component of the Hall element 12, and (V ₊ −V ₋ ) is the unbalanced voltage term of the Hall element 12. Also, V ₊ , V
_- the voltage of the positive input terminal of each operational amplifier 13, -
This is the voltage at the input terminal.

In the above formula (1), _- a = When _{± Vu, V OA1 = -A1 ·} e OHE sinθ + {Vrefl + (± Vu) + (A1 · ± Vu)} ...... (2) (V + -V) Become. Where −A1 · e _OHE sin θ is the alternating voltage term, {Vrefl
+ (± Vu) + (A1 · ± Vu)} becomes a DC reference potential term, and this DC reference potential term becomes the reference potential of the alternating voltage term, which varies depending on the unbalanced voltage Vu of the hall element 12. . FIG. 8 is a waveform diagram showing the waveform.
(1) is the same figure when the DC reference potential fluctuation of (2) is -Vu
(2) shows the case where the DC reference potential fluctuation of equation (2) is + Vu.

Next, the operation of the magnetic rotation angle sensor of FIG. 1 which is an embodiment of the present invention will be described. DC potential applied to the operational amplifier 13 is the output voltage V of the correction amplifier 18 _OA2 = Vref3 because has a (third reference voltage), the output voltage V _OA1 of the operational amplifier 13 is above (2) as well as V _OA1 = -A1 ・ e _OHE sin θ + {Vref3 + (± Vu) + (A1 ・ ± Vu)} (3) Where A1 · e _OHE sin θ is the alternating voltage term, {Vref3
+ (± Vu) + (A1 · ± Vu)} is a current reference voltage term.

On the other hand, the input signal V _'OA1 of the buffer amplifier 17 is a DC voltage alternating signal voltage component by a signal filter comprising a resistor R ₆ and the capacitor C ₁ from the output voltage V _OA1 of the operational amplifier 13 is substantially removed, the output If Vref2 (second reference voltage) is used, Vref2 can be calculated by using the DC voltage term {Vref3
Since it is + (± Vu) + (A1 · ± Vu)}, Vref2 = Vref3 + (± Vu) + (A1 · ± Vu) (4).

Further, since the correction amplifier 18 operates as an inverting amplifier using the DC reference voltage as the first reference voltage Vref1, the resistance R
_{If 13} = R ₁₄ , the gain A2 is A2 = R ₁₅ / R ₁₄ . Output voltage V _OA2 correction amplifier 18 _{V OA2 = -A2 · (V +} -V -) + Vref1 = Vref3 becomes ...... (5). Note that V ₊ and V ₋ are the voltage at the + input terminal and the voltage at the − input terminal of the correction amplifier 18, respectively. here,
Assuming that (V ₊ −V ₋ ) = ± Vd is the correction voltage, this correction voltage ± Vd becomes ± Vd = Vref1-Vref2 (6), which is corrected from the above equations (5) and (6). The third reference voltage Vref3 output from the amplifier 18 is Vref3 = -A2. (+ Vd) + Vref1 (7) where -A2. (. +-. Vd) is a DC fluctuation voltage term. the above
Substituting equation (7) into equation (3), V _OA1 = -A1 ・ e _OHE sin θ + {-[A2 ・ (± Vd) + Vref1] + (± Vu) + (A1 ・ ± Vu)} = -A1・ E _OHE sin θ + Vref1 + (± Vu) + (A1 ・ ± Vu)-(A2 ・ ± Vd) …… (8) In formula (8), A1 ・ e _OHE sin θ is the alternating signal voltage term, Vref1
+ (± Vu) is the DC reference voltage term, (A1 ・ ± Vu)-(A2 ・ ± Vd)
Is a correction term. In the above formula (8), the correction term (A1 ・ ± Vu)
If − (A2 ・ ± Vd) becomes zero, DC reference voltage term Vref1 +
The fluctuation of (± Vu) is only the unbalanced voltage of the Hall element 12, and the object of the present invention can be achieved.

Next, it will be described that the correction term (A1 · ± Vu) − (A2 · ± Vd) becomes zero.

Substituting Vd = Vref1-Vref2 in the above equation (6) into equation (4), Vd = Vref1- {Vref3 + (± Vu) + (A1 ・ ± Vu)} ...... (6) ′ (6) ′ , Vref3 = Vref1 + (± Vu)-(A1 ・ ± Vu) Therefore, from equation (7), -A2 ・ (± Vd) + Vref1 ＝ Vref1- (± Vu)-(A1 ・ ± Vu) -A2 -(± Vd) =-(± Vu)-(A1. ± Vu) Here, if the gain A1 of the operational amplifier 13 and the gain A2 of the correction amplifier 18 are made equal, -A1. (± Vd) =-(± Vu )-(A1 ・ ± Vu) ± Vd ＝ {-(± Vu)-(A1 ・ ± Vu)} /-A1 ＝ (± Vu) / A1 + (± Vu)} ≒ ± Vu …… (9) Therefore, Correction term of the above formula (8) (A1 ・ ± Vu)-(A2 ・ ± Vd)
Is A1 · (± Vu) − (A2 · ± Vd) = A1 · (± Vu) − (A1 · ± Vu) = 0, and the present invention is achieved.

〔The invention's effect〕

As described above, according to the present invention, after the output of the Hall element is amplified, in the DC coupling method, the fluctuation of the signal reference potential due to the Hall element unbalanced voltage and the offset voltage of the amplifier, which occurs when the waveform conversion is performed, is automatically performed. By using the signal reference voltage obtained by removing the sine wave signal component from the corrected and amplified signal voltage as the reference power source of the waveform converter, the excellent effect of improving the output waveform conversion accuracy with respect to the rotation angle can be obtained. In addition, it is a circuit composed of a single-power-supply operational amplifier, which reduces cost, and can be applied not only as an on-vehicle crank angle sensor but also as a rotation angle sensor for all devices that have a rotation axis. The effect is obtained.

[Brief description of drawings]

FIG. 1 is a block diagram showing a Hall element unbalanced voltage automatic correction circuit in a magnetic type rotation angle sensor according to the present invention, and FIG. 2 is a view for explaining the operation of the Hall element unbalanced voltage automatic correction circuit of FIG. FIG. 3 is a voltage waveform diagram of each part, FIG. 3 is a circuit diagram embodying the Hall element unbalanced voltage automatic correction circuit of FIG. 1, and FIG. 4 is a block diagram showing a system configuration example of a conventional magnetic rotation angle sensor for an internal combustion engine. 5 and 5 are voltage waveform diagrams of respective portions for explaining the operation of the magnetic type rotation angle sensor of FIG. 4, and FIG. 6 is a Hall element 12 and operational amplifier 1 of FIG.
3 is a circuit diagram, FIG. 7 is an equivalent circuit diagram of FIG. 6, and FIG. 8 is a waveform diagram of each part of FIG. In the figure, 11 ... Permanent magnet rotor, 12 ...
... Hall element, 13 ... Operational amplifier, 14 ... Waveform converter, 15 ... Output section, 16 ... Reference voltage source, 17 ... Buffer amplifier, 18 ... Correction amplifier.

Claims (1)

[Claims] 1. A permanent magnet rotor having a plurality of poles and a hall element, wherein an output voltage of the hall element is DC-amplified by an operational amplifier, and the amplified signal voltage is waveform-converted by a waveform converter. In the magnetic rotation angle sensor, the fluctuation of the reference voltage due to the Hall element unbalanced voltage generated when the output voltage of the Hall element is DC-amplified by the operational amplifier is detected and compared with the set DC voltage, and the bias of the operational amplifier is detected. A circuit for automatically correcting the voltage and maintaining the output reference potential is provided, and a circuit for using the signal reference voltage obtained by removing the sine wave signal component from the signal voltage amplified by the operational amplifier as the reference power source of the waveform converter is provided. Hall element unbalance voltage automatic correction method in magnetic rotation angle sensor characterized by the above.