JPH0357962A - Rotary data detection circuit - Google Patents

Abstract

PURPOSE:To detect the rotary data of a rotary body with high detection accuracy by detecting the non-equilibrium voltage contained in a magnetic field detection signal and changing a reference level corresponding to the detection result. CONSTITUTION:A clamp circuit 15 clamping a magnetic field detection signal SMO10 at the first and second clamp levels VCP1, VCP2 to send out a magnetic field detection clamp signal SMO11, an integration circuit 14 integrating the signal SMO11 to send out the non-equilibrium detection signal SOFF1 corresponding to the non-equilibrium voltage contained in the signal SMO101 and a binarizing circuit 8 comparing the signal SMO10 on the second reference level VREF1 to send out a binarization signal SB10 are provided. The non-equlibrium voltage contained in the signal SMO10 is detected in the circuits 15, 14 and, in the circuit 8, the reference level VREF1 binarizing the signal SMO10 corresponding to the detection result SOFF2 thereof is changed to make it possible to always send out the signal SB10 having desired duty regardless of the presence of the non- equilibrium voltage in the signal SMO10.

Description

DETAILED DESCRIPTION OF THE INVENTION A. Field of Industrial Application The present invention relates to a rotational information detection circuit, and is suitable for application to, for example, a circuit for detecting the rotational speed of a cab stan motor of a video tape. B Summary of the Invention The present invention detects an unbalanced voltage included in a magnetic field detection signal in a rotation information detection circuit, and changes a reference level for binarizing the magnetic field detection signal in accordance with the detection result. By doing so, regardless of the presence or absence of an unbalanced voltage in the magnetic field detection signal, the
{! It is possible to obtain the converted signal. C. Prior Art Conventionally, in a video tape recorder, for example, in order to stably drive a capstan motor at a desired rotational speed,
A capstan servo circuit is used that detects the rotation speed of the capstan motor using a rotation speed detection circuit with a magnetoresistive element structure, and controls the servo loop based on this detection result. That is, as shown in FIG. 4, in this capstan servo circuit 1, the rotation speed of the capstan motor 2 is detected by a rotation speed detection circuit 3, and the rotation speed detection signal SF obtained as a result is subjected to a subsequent frequency-voltage conversion. Send to circuit 4. The frequency-voltage conversion circuit 4 generates a rotational speed detection voltage Sv according to the inputted rotational speed detection signal SF, and uses this rotational speed detection voltage Sv to control a capstan motor supplied from a mechanical control circuit (not shown). By inputting the signal Sl4 to the adding circuit 5 and adding it together, and driving and controlling the cabstan motor 2 with this added signal SADD, a speed servo loop is formed as a whole, and thus the capstan motor 2 is driven at the desired rotation speed. It is designed to be able to drive stably.

Here, as shown in FIG. 5, the rotational speed detection circuit 3 is a rotating magnet section in which magnets with different magnetic field directions are magnetized in a ring shape at 300 to 400 pitches in the circumferential direction of the rotating shaft of the capstan motor 2. 6. Binarize the magnetic field detection unit 7 and its output signal 5MO, which is made up of a series combination of two-terminal magnetoresistive elements 7A and 7B that are placed in contact with the rotating magnet unit 6 and have magnetoresistive characteristics different by 90° from each other. 2 {! It has been warned against by the System Circuit Department 8. A ti voltage VCC having a voltage value of 5 [■] is applied to the two-terminal magnetic resistance elements 7A and 7B of the magnetic field detection unit 7, and when the capstan motor 2 rotates once, each magnetic resistance element 7A And from the connection midpoint a of 7B, the voltage value is centered at 2.5 (V)? The magnetic field detection signal SN has a sinusoidal waveform of 300 to 400 cycles. is sent. A magnetic field detection signal SN actually sent out from the magnetic field detection section 7.

is input to the non-inverting input terminal of the binarization circuit 8A consisting of an operational amplifier. This binarization circuit 8A has a reference voltage V, which has a voltage value of 2.5 C V ) obtained by dividing the power supply voltage VCC by the first and second resistors R1 and R2, input to the inverting input terminal. ．． Thus, the binarization circuit 8A generates a magnetic field detection signal SI4 having a sinusoidal waveform. (Figure 6(A)) as the reference voltage V
Binarized signal Sl (
6(B)) is sent out as the rotational speed detection signal S.

In this way, in this capstan servo circuit 1, for example, the rising cycle of the rotational speed detection signal S is counted, and the capstan motor 2 is
The rotation speed of the rotation speed detection signal SF is smoothed through a low-pass filter in the frequency-voltage conversion circuit 4, for example, to generate the rotation speed detection voltage Sv. There is. D Problems to be Solved by the Invention By the way, in the magnetic field detection section 7 of the rotational speed detection circuit 3 of this construction, there are problems in manufacturing the respective magnetoresistive elements 7A and 7B, problems in the magnetoresistive characteristics of the elements themselves, etc. From this point, variations in magnetoresistive characteristics within a predetermined range are allowed. Therefore, the magnetic field detection signal S output from the magnetic field detection section 7
．． . 1, as shown in FIG. 7(A), an unbalanced voltage V
. , F could occur. In this way, the magnetic field detection signal SI4. When an unbalanced voltage V 6, , occurs in , as shown in FIG. 7(B), the duty of the binary signal S1 sent from the rotation speed detection circuit 3 changes, causing the rotation speed detection signal SF to change. Smoothed through a low-pass filter,
In the capstan servo circuit t that generates the rotational speed detection voltage Sv, an unbalanced voltage V is applied to the rotational speed detection voltage Sv. ．． An error occurs depending on the result, and the result is Cavs? There was a problem that the rotational speed of the motor 2 could not be detected correctly.

Also, the binary signal S. In the capstan servo circuit 1, which digitally detects the rotational speed of the cabstan motor 2 based on the rise period and/or fall period of There was a problem with deterioration.

Furthermore, the magnetic field detection section 7 is replaced with two-terminal magnetic resistance elements 7A and 7B, and a sinusoidal first magnetic field detection signal Ssoz
In addition to the first magnetic field detection signal Sl4.2 (FIG. 8(A)), a cosine-shaped second magnetic field detection signal S. ．． In a rotational speed detection circuit that uses a four-terminal magnetic resistance element capable of outputting S (FIG. 8(A)) and obtains a rotational speed detection signal with a frequency twice as high as a week, for example, the second magnetic field Detection signal S. 4. ,
When an unbalanced voltage VOFFI occurs in , the duty of the 2{lI signal So changes as shown in FIG. 8(B),
As a result, there was a problem that the rotational speed of the capstan motor 2 could not be detected correctly. In order to solve such problems, conventionally, the magnetic field detection signal SMO sent from the magnetic field detection section 7 is connected to a coupling capacitor C,
A rotational speed detection circuit has been proposed in which the unbalanced voltage V REF is inputted to the binarization circuit 8 via the rotation speed detection circuit 8, thereby eliminating the influence of the unbalanced voltage V REF. However, in this case, when the capstan motor 2 rises from a stationary state to a steady rotation state, the rotation speed is slow, so the magnetic field detection signal S,4 is generated. itself fluctuates like a direct current,
There was a problem that the signal was not output as a binary signal, and this was still an insufficient solution. The present invention has been made in consideration of the above points, and aims to propose a rotation information detection circuit that can detect rotation information of a rotating body with high detection sensitivity from a stationary state to a steady rotation state. EMeans for solving the problem In order to solve the problem, the present invention includes: A rotating magnet section 6 that sequentially generates different magnetic fields in the rotational direction is arranged around the rolling body 2, and a magnetic field detection section 1l is arranged so as to come into contact with the rotating magnet section 6. A sinusoidal magnetic field detection signal SMO+ is sent out from the magnetic field detection section 1l. Binarized signal S■ is obtained by binarizing. In the rotation information detection circuit 10 that obtains rotation information of the rotating body 2 based on the magnetic field detection signal SNOI. , its magnetic field detection signal S
8. ．． Clamp circuit 1 that clamps at first and second clamp levels VCPI and vcpt set above and below the center level of and sends out a magnetic field detection clamp signal 3H011.
5 and the magnetic field detection clamp signal SNOI1 to calculate the average value of the magnetic field detection clamp signal SMOII. . ,. Unbalanced voltage v0,■ included in.

unbalance detection signal S according to. An integrating circuit 14 that sends out F■ (S0,.) and a magnetic field detection signal S. 4.1.

, the unbalance detection signal S OF is set to the first reference level
Second standard level by adding FI■1■Compared with 2
Valued signal S■. A binarization circuit 8 for transmitting .

? The magnetic field detection signal SNOI is applied to the clamping circuit 15 and the integrating circuit 14 . The unbalanced voltage V contained in ,■.

is detected, and the detection result S is detected in the 2{direction circuit 8. , n, the magnetic field detection signal SNI)l. By changing the reference level V■■ for binarizing the magnetic field detection signal 3,401. unbalanced voltage VOFF+
. 2, which always has the desired duty regardless of the presence or absence of
Valued signal S■. can be sent.

G. Embodiment An embodiment of the present invention will be described in detail below with reference to the drawings. In FIG. 1, in which parts corresponding to those in FIG. The first magnetic field detection signal SMOI is sent out from the output terminal 11A of 1. But, 2kl! The voltage is input to the unbalanced voltage detection circuit section 8 as well as to the unbalanced voltage detection circuit section 12 .

This magnetic field detection unit l1 is formed by bridge-connecting first, second, third, and fourth magnetoresistive elements MRI, MR2, MR3, and MR4, and is mounted on the rotating shaft of the capstan motor 2 (Fig. 4). With respect to the magnetoresistive characteristics of the first and third magnetoresistive elements MHI and MR3, the second and fourth magnetoresistive elements MR
2 and MR4 are arranged so that their magnetoresistive characteristics differ by 90°. Note that the connection midpoint a of the first and fourth magnetoresistive elements MHI and MR4 is connected to the power supply voltage CC with a voltage value of 5 [V], and the connection point a of the second and third magnetoresistive elements MR2 and MR3 is
The middle point C of the connection is grounded. As a result, the first and second magnetoresistive elements MR1 and M
From the first output terminal 11A formed at the connection midpoint b of R2, a voltage value of 2.5 is generated corresponding to one rotation of the capstan motor 2.
The first magnetic field detection signal SMOI has a sinusoidal waveform of 300 to 400 cycles with (V) as the center voltage. is sent. ? On the other hand, the third and fourth magnetoresistive elements MR3
A first magnetic field detection signal S. . ,. A second magnetic field detection signal S.4.2 in the form of a cosine wave having a phase difference of 90'' with respect to the second magnetic field detection signal S.4.2.

In this embodiment, the unbalanced voltage detection circuit section l2 receives the first magnetic field detection signal S,4. ,. is input to a buffer circuit 13 having an operational amplifier configuration, and its output is sent through a resistor RIO to an integrating circuit 14 consisting of a resistor Rll and a capacitor COO. Here, the connection midpoint e of this resistor RIO and the resistor Rll of the integrating circuit 14 is the clamp circuit 15
It is connected to the.

This clamp circuit 15 connects the power supply VCC and the ground with a series circuit of first to third resistors R12, R13, and R14, and includes a first resistor R12 and a second and third resistor R1.
3 and R14 to obtain the first clamp voltage (2). ? is applied to the connection midpoint e through the buffer circuit 15A of the operational amplifier structure and the diode D1 connected with opposite polarity? There is. Further, a second clamp voltage vc obtained by dividing the voltage by the first and second resistors R12 and R13 and the third resistor R14
pt is applied to the connection point e through a buffer circuit 15B having an operational amplifier structure and a diode D2 connected with forward polarity. In fact, the first and second clamp voltages ■, ■ and VCPR are calculated backward from the variations in magnetoresistive characteristics allowed within a predetermined range, and are calculated based on the undesired pressure that may occur in the magnetic field detection section l1. VOFF+,
The voltage {j! 2.5 (V) It is set to the voltage value added and subtracted from 2.5 (V). Therefore,
First magnetic field detection signal 3 sent out from buffer circuit 13
H01. is clamped at a level below the first clamp voltage VCPl and above the second clamp voltage vcpt, and the resulting magnetic field detection clamp signal S. .

．． is manually input to the integrating circuit 14. In this integrating circuit 14, the magnetic field detection clamp signal S
Integrate MOI1 and select the relevant magnetic field detection clamp? No.S. .

．． and calculate the average value of the lth unbalanced voltage detection signal S
. , ■, a level shift circuit 16 having an operational amplifier structure.
Send it to the non-inverting input terminal of . This level shift circuit l6
is negatively fed back by the resistor R15, and the power supply V.

and ground are connected by a series circuit of first and second resistors R16 and R17, and a predetermined level shift voltage V,i obtained as a result is applied to the inverting input terminal. As a result, the second unbalanced voltage detection signal S is shifted to a predetermined level in the level shift circuit 16. 2■ is input to the inverting input terminal of the binarization circuit 8A of the binarization circuit section 8,
In this way, in this binarization circuit section 8, the lth magnetic field detection signal S8.1 is generated. , the second complaint '#voltage detection signal S
. ,■ compared with the second reference voltage V■,1, which is 2
Valued signal S■. It is made to obtain.

In the above configuration, for example, as shown in FIG. 2(A), the first magnetic field detection signal S sent out from the magnetic field detection section 11
If there is no unbalanced voltage in MOIO? , the first unbalanced voltage detection signal S sent out from the integrating circuit 14 of the unbalanced voltage detection section 12. , ■ (Figure 2 (B)) is at the 0 level.

As a result, in the binarization circuit unit 8, the first magnetic field detection signal Sl. IO+. The second voltage is 2.5 (V).
The result is a binary signal S■ with a duty of 50%, as shown in FIG. 2(C). is sent.

In addition, on the other hand, as shown in FIG. 3(A), for example,
The first magnetic field detection signal Sx sent out from the magnetic field detection section 11
. ．． unbalanced voltage V. 2■. If there is an unbalanced voltage VOF■ from the integrating circuit l4. A first unbalanced voltage detection signal SOFFI according to the first unbalanced voltage detection signal SOFFI. (Figure 3 (B)) is sent. As a result, in the binarization circuit unit 8, the first magnetic field detection signal S. 4.1. The first unbalanced voltage detection signal S with respect to the reference voltage ■■, which has a voltage value of 2.5 (V). ,■. The second reference voltage with the voltage value added according to ■
■． The result is a binary signal S■ with a duty of 50%, as shown in FIG. 3(C).

? Sent out.

In this way, the rotational speed detection circuit 1 according to this embodiment
In the case of 0, the first magnetic field detection signal SMOI is sent out from the magnetic field detection unit l1. unbalanced voltage V. , F, this unbalanced voltage ■. , , and a second reference voltage corresponding to the detected unbalanced voltage V OFF.
1■ and the first magnetic field detection signal S, 4.1. Compare the values to obtain a binary signal S■. By obtaining the unbalanced voltage V. A binary signal S■ whose duty is always 50% regardless of the presence or absence of 2F.

It is possible to send . Note that the second magnetic field detection signal SMO! actually sent out from the magnetic field detection section 11! 0 is also processed in the same manner as in the rotational speed detection circuit 10, resulting in a binary signal S■.

It is possible to transmit a binary signal with a 90 degree phase delay and a duty of 50%. Further, in the case of this rotational speed detection circuit 10, the first magnetic field detection signal SN sent out from the magnetic field detection section 11. 1. the given clamp voltage■
. Unbalanced voltage V by clamping at ■ and Ver■. 7■
. Will it detect? As a result, the unbalanced voltage VOFFI can be accurately controlled even in the process of rising from a stationary state to a steady rotation state. can be detected. According to the above configuration, the first magnetic field detection signal S8 is sent out from the magnetic field detection section 11. ,. unbalanced voltage VOFF+ inside. The binary signal S■ always has a duty of 50% regardless of the presence or absence of the signal. Thus, from a stationary state to a steady rotation state,
It is possible to realize the rotational speed detection circuit 10 that can detect rotational speed with high detection accuracy.

In the above-described embodiment, the present invention is applied to detecting the rotational speed of the cab stan motor of a video tape recorder, but the present invention is not limited to this, and can be applied to a rotary drum drive motor or a spindle motor of a magnetic disk device. It can also be used to detect the rotational speed of other motors, such as those that detect the rotational speed of other motors.
It is widely applicable and suitable for detecting speed.
Furthermore, in the above embodiment, a case has been described in which a binary signal with a duty of 50% is always generated from the magnetic field detection signal, but the duty is not limited to this, and various duties can be selected as necessary, and the duty is always generated as desired. The same effect as in the above embodiment can be achieved by generating a binary signal having a duty of . Further, in the above-described embodiment, the case where the rotational speed of a rotating body is detected is described, but the present invention is not limited to this, but can be widely applied and suitable for detecting other rotational information such as the number of rotations. It is.

H Effects of the Invention As described above, according to the present invention, the unbalanced voltage included in the magnetic field detection signal is detected, and the reference level for binarizing the magnetic field detection signal is changed according to the detection result. Due to this, the complaint in the magnetic field detection signal '&T! A rotation information detection circuit that can always send a binary signal with a desired duty regardless of the presence or absence of pressure, and can detect rotation information with high detection accuracy from a stationary state to a steady rotation state. realizable.

[Brief explanation of drawings]

FIG. 1 is a connection diagram showing a rotational speed detection circuit according to an embodiment of the present invention, FIGS. 2 and 3 are signal waveform diagrams for explaining its operation, and FIG. 4 is a capacitor in which the rotational speed detection circuit is used. FIG. 5 is a block diagram showing a stun servo circuit, FIG. 5 is a connection diagram showing a conventional rotational speed detection circuit, and FIGS. 6 to 8 are signal waveform diagrams for explaining its operation. 1... Capstan servo circuit, 2...
・Capsun motor, 3, 10... Rotation speed detection circuit, 4... Frequency voltage conversion circuit, 5...
... Addition circuit, 6 ... Rotating magnet section, 7, 1
1... Magnetic field detection section, 8...2 {1! !
circuit section, 12... unbalanced voltage detection section, 14.
...Integrator circuit, 15...Clamp circuit.

Claims (1)

[Claims] A rotating magnet section that sequentially generates different magnetic fields in the rotational direction is arranged around the rotating body, and a magnetic field detection section is arranged so as to come into contact with the rotating magnet section, and the rotation of the rotating body is In a rotation information detection circuit that obtains rotation information of the rotating body based on a binary signal obtained by binarizing a sinusoidal magnetic field detection signal sent from the magnetic field detection section in response to the above, the magnetic field detection signal is A clamp circuit that outputs a magnetic field detection clamp signal by clamping at first and second clamp levels set above and below the center level of the magnetic field detection signal; an integrating circuit that calculates an average value and sends out an unbalanced detection signal according to the unbalanced voltage included in the magnetic field detection signal; and a binarization circuit that sends out a binarized signal by making a comparison at a second reference level of 1. A rotation information detection circuit characterized in that a rotation signal is obtained.