JPH0355049B2 - - Google Patents

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to a level setting circuit, and particularly to an AC output (waveform) such as a rotation detection signal of a motor (rotating body).
The present invention relates to a level setting circuit that sets a setting level (comparison input level) for obtaining a predetermined output by comparing the level of a signal with a certain setting level.

(Prior art) The applicant previously filed the
Patent applications (title of the invention: ``Motor drive device'') were filed on April 12, 2007, and April 12, 2015, respectively.

This involves magnetizing a rotating body that is integrated with the rotor of the drum motor (DC brushless motor) of a magnetic recording/reproducing device (VTR) in a predetermined pattern, and then detecting this magnetization pattern using a sensor such as a Hall element. By detecting and generating a rotation detection signal, and processing this signal waveform based on this rotation detection signal, a drive current to be passed through the coils of each phase of the motor is output,
Furthermore, the phase information signal and velocity information signal of the rotating body are also extracted.

Here, a general description will be given of the "motor drive device" filed on April 12, 1985, among the earlier patent applications by the present applicant.

It should be noted that the magnetization pattern of the embodiment of the above invention described below is slightly different from that of the embodiment shown in the "motor drive device" of the patent application dated April 12, 1985 (changes). (the position of point a ₁ ' is different), but this can naturally be an embodiment of the claimed scope of the invention.

FIG. 6 shows a block system diagram of the motor drive device according to the invention of the applicant mentioned above.

In the figure, the marker section 1 has a magnetized pattern (magnetic pole) magnetized under the conditions described below, and is, for example, a rotating drum (cylinder).
It is constructed by magnetizing a rotating body that is integrated with the rotor of the motor that drives the motor.

The sensor section 2 is provided at a position always close to the marker section 1, and includes, for example, one Hall element (sensor) 4 that detects the magnetic flux of the magnetic poles forming the marker section 1. The output detected by this sensor 4 is supplied to a differential amplifier 5. The output of this differential amplifier 5 is supplied to comparators 6A, 6B, 6C,
Through the digital signal processing circuit 7, a pulse (PG signal) is output as phase information at a rate of once (emission) for each rotation of the rotating drum, and a plurality of pulses (FG signal) exist at equal intervals. is output as speed information.

Note that the comparators 6A, 6B, 6C and the digital signal processing circuit 7 constitute the FG signal and PG signal generation circuit 3.

As the PG signal which is phase information, a pulse as shown in waveform a in FIG. 7 is obtained. This pulse can be triggered on its rising edge by a monomulti 8
By passing the signal through a monomulti 9 which is triggered at the falling edge, waveforms b and c shown in FIG. 7 are obtained.
These waveforms b and c are the flip-flop 10.
This flip-flop 10 is supplied with waveform b
It is set at the falling edge of waveform c, and reset at the falling edge of waveform c. Therefore, if the rotating drum is e.g.
Drum pulse (DP) like waveform d, corresponding to the switching position of the video head with a repetition rate of 30 Hz and a duty ratio of 50% when rotating at 30 rps.
get.

This signal of waveform d (drum pulse) is used as a switching pulse and is also supplied to the trapezoidal wave generator 11.

This trapezoidal wave generator 11 generates a trapezoidal wave synchronized with the signal of waveform d, and the sample and hold circuit 1
Supply to 2.

On the other hand, the composite video signal 13 is supplied to a vertical synchronization signal separation circuit (V synchronization separation circuit) 14. And, by this vertical synchronization signal separation circuit 14, 60Hz
Only the vertical synchronization signal of
5. Therefore, this 1/2 frequency divider circuit 15
A pulse synchronized with a 30 Hz video signal is outputted from the output of the switch circuit 16, and this pulse is supplied to one terminal 16a (REC) of the switch circuit 16.

On the other hand, the pulse generated by the reference frequency oscillator 17 is passed through the frequency dividing circuit 18 to obtain a 30 Hz reference pulse, and this reference pulse is supplied to the other terminal 16b (PB) of the switch circuit 16.

The switch circuit 16 is switched to the terminal 16a side during recording and to the terminal 16b side during playback, thereby selecting the pulses from the 1/2 frequency divider circuit 15 and the frequency divider circuit 18, and selects the pulses from the monomultiplier 19. We are trying to make sure that it is supplied to the public.

A monomulti 19 generates a sampling pulse that is delayed by a certain period of time with respect to the vertical synchronization signal of the video signal during recording.

The sample and hold circuit 12 samples and holds the slope part of the trapezoidal wave using this sampling pulse to obtain a phase error voltage. This phase error voltage is supplied to a loop filter 20 whose purpose is to improve the transient characteristics of the servo loop.
Its output (phase error voltage) is supplied to a mixing amplifier 21.

Further, the FG signal output from the digital signal processing circuit 7 is transmitted to the FG pulse amplifier 22 and the F/V
It is supplied to the mixing amplifier 21 via a (frequency/voltage) converter 23. Further, this FG signal is also supplied to the motor drive circuit 24. That is, in this invention, the FG signal is used for the timing of switching the coil current of the motor.

The motor drive circuit 24 includes a pulse generation circuit 25,
It is composed of a switch circuit means 26, a waveform conversion circuit 27, and a driver circuit 28. Further, the output terminal of the driver circuit 28 is connected to the coil of the motor 29.
is connected.

In the motor drive circuit 24 having the above configuration, FG
The FG signal obtained from the output end of the digital signal processing circuit 7 constituting the signal and PG signal generation circuit 3 is supplied to the retriggerable monomulti 30 and the terminal 31a of the changeover switch 31.

At startup or at low speed, the changeover switch 31 is switched to the terminal 31b side, and the output from the pulse generation circuit 25 is supplied to the ring counter 32 and the waveform conversion logic circuit 33, respectively. Therefore,
At the output terminals Q ₁ , Q ₂ , Q ₃ of the ring counter 32,
Pulses are output in the order of the output signal Q ₁ → Q ₂ → Q ₃ . Then, this pulse is transmitted to the waveform conversion logic circuit 33.
The voltage is applied to transistors T ₁ , T ₂ , and T ₃ via , and further turns on (ON) transistors T ₁₁ , T ₁₂ , and T ₁₃ in sequence. As a result, the coil,,
The drive current is switched in the order of , , , . . . , and a rotating magnetic field in the forward rotation direction is generated. Therefore,
The main magnetic pole of the rotor of the motor rotates in the forward rotation direction in synchronization with the rotating magnetic field generated.

On the other hand, the motor has a certain speed or higher (steady rotation speed)
Then, the changeover switch 31 is switched to the terminal 31a side by the output of the retriggerable monomulti 30, and the FG signal is supplied to the ring counter 32. As a result, a rotating magnetic field is generated in the forward rotation direction, and the drive current of the motor can be switched at the correct current switching point, so that the rotor of the motor rotates continuously.

Further, in the embodiment of the present invention, as shown in FIG. 8, the rotation of the rotating drum is controlled by a direct drive motor in which the rotating drum (cylinder) and the driven motor are directly connected. . The structure of the driven motor includes a rotating body 3 integrally attached to a rotor 35 provided with a main magnetic pole (main magnet) 34.
6, there is a marker 37 that is magnetized on the circumference so as to satisfy the conditions described below. Further, the stator 38 is provided with an armature coil (hereinafter referred to as a coil), and further a sensor 4 is attached at a position facing the marker 37. Further, a rotating drum 40 is connected by a motor shaft 39, and two video heads (magnetic heads) 41a and 41b are attached to this rotating drum 40 at an interval of 180 degrees.

FIG. 9 is a diagram showing the arrangement relationship when the main parts of the driven motor shown in FIG. position, marker 37 of rotating body 36
represents the magnetized state of Furthermore, the positions of the two video heads 41a and 41b are also noted. In addition, in the same figure, the forward rotation direction of the motor is counterclockwise (in the same figure,
(indicated by arrow R).

Here, the following conditions are required for the magnetization pattern of the marker 37 magnetized on the circumference of the rotating body 36.

The magnetic pole change points that change from N pole to S pole in the reverse rotation direction of the motor are sequentially a ₁ , a ₂ , ..., a ₁₂
Expressed as , the magnetic poles between the magnetic pole change points a ₁ and a ₁₂ exist at equal intervals, and between the change points a ₁₂ and a ₁ there is a change point a ₁ ′ that changes from the S pole to the N pole. To exist.

The maximum value of the detected waveform of the magnetic flux density of the N pole adjacent to the magnetic pole change point _a1 ' (the peak value at which the output waveform changes from increasing to decreasing) is the maximum value of the detected waveform of the magnetic flux density of the other N pole of marker 37. The minimum value of the detected waveform of the magnetic flux density of S (the peak value at which the output waveform changes from decreasing to increasing) that is smaller than and adjacent to the magnetic pole change point a ₁ ' is the same as that of the magnetic flux density of the other S pole of the marker 37. Must be larger than the minimum value of the detected waveform.

That is, as shown in FIG.
In waveform A, which is the output of the sensor unit 2 (output of the differential amplifier 5) that detects the magnetization pattern _of The maximum value of the detected waveform for the magnetic flux density of the adjacent north pole is smaller than the maximum value of the detected waveform for the magnetic flux density of the other north pole, and similarly, the detected waveform for the magnetic flux density of the south pole of the marker 37 is Among the minimum values, the magnetic pole change point
The minimum value of the detected waveform for the magnetic flux density of the S pole adjacent to a ₁ ' is larger than the minimum value of the detected waveform for the magnetic flux density of the other S poles.

Here, the output of sensor section 2 (differential amplifier output)
are comparators (level comparators) 6A, 6B,
6C respectively. The purpose of the comparator 6A is to detect all magnetic pole change points, and the voltage V _B is set as the comparison input level to achieve this purpose. That is, in the timing chart of FIG. 10, the output waveform B of the comparator 6A
The falling part is the magnetic pole change of marker 37.
Exactly matches a ₁₁ , a ₁₂ , a ₁ , a ₂ , a ₃ , ….

Further, the comparator 6B detects a portion of the maximum value of the waveform A in FIG. ₁₀ that is smaller than other maximum values (N
The comparison input level of the comparator 6B is set to voltage V _C so as to detect only the polar portion.
If the input level of the comparator 6B is larger than the voltage V _C , the output will be "H level", and if it is smaller, the output will be "L level", so the output waveform of the comparator 6B will change at the timing shown in FIG. The chart will look like waveform C.

Further, the comparator 6C detects a portion of the minimum value of the waveform A shown in _FIG .
The comparison input level of the comparator 6C is set to the voltage V _D so as to detect only the pole part).
If the input level of the comparator 6C is larger than the voltage V _D , the output will be "L level", and if it is smaller, the output will be "H level", so the output waveform is as shown in the timing chart of FIG. Waveform D
become that way.

Next, the output waveforms B, C, and D of these comparators 6A, 6B, and 6C are supplied to the digital signal processing circuit 7. Various methods can be considered for the circuit configuration of this digital signal processing circuit 7, but in short,
Using waveforms B, C, and D in FIG.
Pulses at timings corresponding to the magnetic pole change points a ₁ to _{a 12} of the marker 37 and pulses at timings corresponding to the magnetic pole change point a ₁ ' of the marker 37 are extracted.

As mentioned above, marker 3 under these conditions
The output waveform A obtained by detecting the magnetization pattern No. 7 by the sensor unit 2 is supplied to the comparators 6A, 6B, and 6C, and the output waveforms B, C, and D are obtained. Based on these output waveforms B, C, and D, these signals (pulses) are processed by the FG signal and PG signal generation circuit 3 shown in Fig. 6, and are sent to the coils of each phase of the motor. Outputs the drive current, and also outputs the phase information signal (PG signal) of the motor (rotor) mentioned above.
It is also possible to extract speed information signals (FG signals).

(Problems to be Solved by the Invention) However, when the magnetization pattern of the marker 37 is detected by the sensor unit 2 as described above, for example, variations may occur in the sensor (Hall element) 4 of the sensor unit 2. If so, it appears as a variation (fluctuation) in the detection output of the sensor section 2.

Therefore, the sensor section 2 as shown in FIG.
The output waveform A appears as waveforms A ₁ ', A ₂ ', and A ₃ ' whose amplitudes vary as shown in FIG.

However, in the motor drive circuit proposed by the applicant as described above, the comparators 6A, 6B, 6C
Since the comparison voltage levels (comparison input levels) V _C and V _D are constant values, if there is variation in the detection output of the sensor section 2 as described above, the comparators 6B and 6C
The outputs of the comparators 6B and 6C also have different waveforms. For example, in the case of the waveform A ₃ ' in FIG. 11, no outputs are obtained from the comparators 6B and 6C. In addition, in the case of waveform A ₁ ', comparator 6B,
The output from 6C includes "↑" in Figure 11,
Pulses are also output at the timing corresponding to the part indicated by "↓", so the correct waveforms (pulses) C and D shown in FIG. 10 are not supplied to the digital signal processing circuit 7, and therefore the correct PG signal cannot be obtained.

Therefore, in view of the above, the present invention has been developed so that even when there are variations (variations) in the amplitude of the output due to variations in the sensor section,
It is an object of the present invention to provide a level setting circuit that can always obtain an appropriate setting level (comparison input level) so that the output of a comparator can be obtained at the correct setting level (comparison input level).

That is, for example, the level of the maximum value (V _H in FIG. 12) among the maximum values of the output (waveform A) of the sensor section as shown in FIG. V _L ) in the figure is detected,
The level (V _C ) in between is set, and the level of the minimum value (Vl in Fig. 12) of the minimum values of the output (waveform) of the sensor section and the minimum value of the higher level (Vl) are set. It is an object of the present invention to provide a level setting circuit that can detect Vh) in the figure and set a level (V _D ) therebetween.

(Means for Solving the Problems) In order to achieve the above object, the present invention provides the local maximum value (or local minimum value) of an AC signal waveform whose amplitude changes periodically; however, if the value in parentheses is selected, the following also select the maximum (or minimum) value of
This is a level setting circuit that sets a level between a maximum value (or minimum value) of a lower (or higher) level, and the AC signal waveform supplied via the input terminal 40 is A first discrimination circuit 4 that discriminates whether the level is higher or lower than the reference level.
1, a first detection circuit 42 that detects the moment when the signal waveform output from the first discrimination circuit 41 becomes larger (or smaller) than the reference level, and a signal output from the first discrimination circuit 41. A second detecting moment when the waveform becomes smaller (or larger) than the reference level.
a third detection circuit 44 that detects the maximum value (or minimum value) of the AC signal waveform supplied via the input terminal 40 and is reset by the output of the first detection circuit 42; Third detection circuit 4
A sample hold circuit 4 which takes the output of 4 as an input and is sampled by the output of the second detection circuit 43.
5, a fourth detection circuit 46 which receives the output of the sample and hold circuit 45 as an input and detects the minimum value (or maximum value) of the signal waveform; A fifth detection circuit 47 receives the output of the detection circuit 44 as an input and detects the maximum value (or minimum value) of the signal waveform or output;
An adder circuit 48 adds the output of the detection circuit 47 and outputs a predetermined set level, and the AC signal waveform supplied via the input terminal 40 is larger or smaller than the output set level from the adder circuit 48. A second discriminating circuit 49 is configured to determine whether the adder circuit 48 has a predetermined level or not, and from the output terminal of the second discriminating circuit 49, a predetermined output whose level has been discriminated based on a predetermined set level outputted from the adder circuit 48 is obtained. It provides a level setting circuit.

(Function) In the level setting circuit having the above configuration, when setting a predetermined level for an AC signal waveform whose amplitude changes periodically, even if there is variation (fluctuation) in the amplitude of the processed signal waveform, , always at an appropriate setting level, that is, a setting level between the maximum value of the local maximum values of the AC signal waveform and the local maximum value of a lower level (or the minimum value of the local minimum values of the AC signal waveform and higher Depending on the set level (between the minimum value of the level), a set level that can process the processed signal waveform can be obtained.

(Configuration of the Invention) FIG. 1 is a block diagram showing the configuration of a level setting circuit according to the present invention.

In the figure, reference numeral 40 denotes an input signal whose amplitude changes periodically, such as the output waveform (waveform A shown in FIG. 10) of the sensor unit 2 of the motor drive device shown in FIG. 6 as described above. This is an input terminal to which an AC signal waveform is supplied. This input terminal 4
0 is connected to the input terminal of a discrimination circuit 41, and the output terminal of this discrimination circuit 41 is connected to the input terminals of detection circuits 42 and 43, respectively.

The determination circuit 41 is a circuit that determines whether the signal waveform (AC waveform) supplied via the input terminal 40 is larger or smaller than a "reference level" that is a reference for the signal waveform. Further, the detection circuit 42 is a circuit that detects the moment when the supplied signal waveform becomes larger (or smaller) than the above-mentioned "reference level",
Further, the detection circuit 43 is a circuit that detects the moment when the supplied signal waveform becomes smaller (or larger) than the above-mentioned "reference level".

The output terminal of the detection circuit 42 is connected to the reset terminal of the detection circuit 44, and the input terminal 40 is connected to the input terminal of the detection circuit 44. Furthermore, the output terminal of this detection circuit 44 is connected to one terminal a of the changeover switch S, and is also connected to the input terminal of a sample and hold circuit 45. Further, the reset terminal of this sample and hold circuit 45 is connected to the detection circuit 4.
The output end of No. 3 is connected.

The detection circuit 44 detects the maximum value (or minimum value) of the AC signal waveform supplied via the input terminal 40, and is reset by the output of the detection circuit 42. Further, the sample and hold circuit 45 has a sample and hold function in which the output of the detection circuit 44 is input and the output of the detection circuit 43 is sampled.

The output terminal of the sample and hold circuit 45 is connected to one input terminal of an adding circuit 48 via a detection circuit 46.

The detection circuit 46 receives the output of the sample and hold circuit 45 as an input, and detects the minimum value (or maximum value) of the signal waveform.

On the other hand, the input terminal 40 is connected to the other terminal b of the changeover switch S, and the movable contact terminal c of the changeover switch S is connected to the adder circuit 4 through the detection circuit 47.
It is connected to the other input terminal of 8.

The detection circuit 47 receives as input the AC signal waveform supplied via the input terminal 40 or the output of the detection circuit 44, and detects the maximum value (or minimum value) of the signal waveform or output.

The adder circuit 48 adds the output of the detection circuit 46 and the output of the detection circuit 47, and outputs an appropriate setting level.

The output terminal of the adder circuit 48 is connected to one input terminal of a discrimination circuit 49, and the input terminal 40 is connected to the other input terminal of the discrimination circuit 49.

The determination circuit 49 is a circuit that determines whether the signal waveform input via the input terminal 40 is larger or smaller than the output setting level from the adder circuit 48.

The output terminal of the discrimination circuit 49 is connected to an output terminal 50, and a predetermined output whose level has been discriminated based on the appropriate setting level outputted from the addition circuit 48 is obtained at this output terminal 50. In addition, the changeover switch S
The movable contact piece may be switched to either side.

The above is the configuration of the level setting circuit according to the present invention.

(Example) Next, an example of the level setting circuit according to the present invention having the above-described configuration will be described below with reference to the drawings.

FIG. 2 is a diagram showing a specific circuit example of the level setting circuit according to the present invention. In this figure, the same components as those in FIG. 1 are designated by the same reference numerals.

Now, let us consider detecting the marker section 1 in the motor drive device shown in FIG. 6 with the sensor section 2 and obtaining its output waveform.

FIG. 3 shows the magnetization pattern of the marker 37 constituting the marker section 1, and also shows an output waveform A when the marker 37 is detected by the sensor 4 of the sensor section 2.

The circuit shown in FIG. 2 is used to obtain the voltage level V _C shown in waveform A in FIG. This is a circuit (for setting).

In FIG. 3, it is assumed that the motor starts rotating from the position indicated by "▲" in waveform A. However, in reality, the marker 37 (magnet) moves to the left in the drawing, but here we assume that the sensor moves to the right in the drawing with respect to the marker 37, and the detected waveform corresponding to this movement is as shown in FIG. The waveform is obtained in the right direction from the position indicated by ▲.

Waveform B is the comparator 41 that constitutes the discrimination circuit 41.
This is the output of comparator 41a, similar to waveform B in the timing chart of FIG.
The voltage (reference level) V _B at the inverting input terminal of the comparator 41a is set as the comparison input level, and if the input level at the non-inverting input terminal of the comparator 41a is greater than the voltage V _B , the output becomes "H level"; In this case, the output is at "L level", so waveform B in FIG. 3 is obtained.

This waveform B is supplied to monomulti 42a and 43a, and monomulti 42a is triggered by the rising edge of waveform B and outputs a pulse (waveform E) with a pulse width (time constant) τ, and monomulti 43a
is triggered by the falling edge of waveform B, and similarly outputs a pulse (waveform F) with a pulse width (time constant) τ.
Here, mono multi 4 to create waveforms E and F.
It is assumed that the time constant τ of 2a and 43a is sufficiently smaller than the period T determined by the rotation speed.

The detection circuit (maximum peak hold circuit) 44 holds (maintains) the maximum peak value of the waveform A input to the non-inverting input terminal of the comparator 44a via the input terminal 40, and the waveform E output from the monomulti 42a. At this timing, the switch 44s is turned on and reset. Therefore, a waveform G is obtained at the output terminal 44o of the detection circuit 44.

This waveform G is supplied to a sample and hold circuit 45, and the output of this sample and hold circuit 45 becomes a waveform H. That is, the switch 45s of this sample hold circuit 45 is the monomulti 43
It is turned ON at the timing of waveform F output from the input waveform G, and the level of the input waveform G at that time is held and becomes waveform H. The waveform H is input to the non-inverting input terminal of the comparator 45a so as to be at the level of the power supply voltage Vcc until the first pulse of the waveform F is input after the motor starts rotating (that is, the level of the waveform G is obtained). Connected resistor R and capacitor C
is connected to the power supply (Vcc) side.

Waveform H is supplied to the non-inverting input terminal of comparator 46a of detection circuit (minimum peak hold circuit) 46, and since the minimum peak value of waveform H is held as the output of this detection circuit 46, the broken line of waveform H The waveform becomes H ₀ as shown by , and from then on, this level is held (maintained) as long as the motor is rotating.

On the other hand, the waveform G, which is the output of the detection circuit 44, is generated by the comparator 4 of the detection circuit (maximum peak hold circuit) 47.
The output of the detection circuit 47 becomes a waveform I since the maximum peak value of the waveform G is held. In addition, the detection circuit 47
The input terminal 4 is connected to the non-inverting input terminal of the comparator 47a.
Even if the waveform A input via 0 is directly supplied, it does not change to the waveform I.

The waveform I and the waveform H ₀ are added by the adder circuit 48 and output from the connection point between the resistors R ₁ and R ₂ , and supplied to the inverting input terminal of the comparator 49 a of the discrimination circuit 49 .

In the circuit of FIG. 2, the voltage level VJ of the output of the adder circuit 48 is given by the following equation.

VJ=R ₂・VI+R ₁・VH ₀ /R ₁ +R ₂ However, VI is the voltage level of waveform I, and VH ₀ is the waveform
The voltage level is H ₀ .

Now, if R ₁ =R ₂ , then VJ=VI+VH ₀ /2, and the output waveform of the adder circuit 48 becomes waveform J in FIG.

Therefore, the magnetic pole change point _a1 of the marker 37 is determined by the sensor 4.
From the moment when the comparator 49 of the discrimination circuit 49 passes
The comparison input level supplied as waveform J to the inverting input terminal of a is held at the level of V _C in waveform A of FIG. That is, the level of V _C is between the maximum value of the maximum values of waveform A and the maximum value of a lower level.

Therefore, the discrimination circuit 49 compares the level of the waveform J (level of V _C ) supplied to the inverting input terminal of the comparator 49 with the waveform A supplied to the non-inverting input terminal via the input terminal 40. As a result, a waveform C shown in FIG. 10 is obtained at the output terminal 50a.

By inputting this waveform C and the waveform B shown in FIGS. 3 and 10 into a digital signal processing circuit, that is, a counter, as shown in FIG. A waveform K shown in FIG. 3 is obtained. In other words, a phase information signal is obtained.

As described above, even if there is variation (fluctuation) in the level of the output (waveform A) of the sensor section due to variation in the sensor section, correct phase information can always be obtained.

The above is the comparison input level input to comparator 6B.
This is a circuit to obtain (set) V _C , but
Next, a circuit for obtaining (setting) the comparison input level V _D (a level between the level of the minimum value among the minimum values of waveform A and the minimum value of a higher level) will be described.

FIG. 4 is a diagram showing a specific circuit example of the level setting circuit according to the present invention. In this figure, the same components as those in FIG. 1 are designated by the same reference numerals.

Similar to FIG. 2 described above, we will now consider detecting the marker section 1 in the motor drive device shown in FIG. 6 described above with the sensor section 2 and obtaining its output waveform.

FIG. 5 shows the magnetization pattern of the marker 37' constituting the marker section 1 (the position of the change point a ₁ ' is different from that shown in FIG. 3), and furthermore, this marker 37' A waveform A' detected by the sensor 4 of the sensor section 2 is also shown.

The circuit shown in Figure 4 obtains the voltage level V _D shown in waveform A' in Figure 5 (a level between the level of the minimum value of the minimum values of waveform A and the minimum value of a higher level). This is a circuit for setting (setting).

In FIG. 5, it is assumed that the motor starts rotating from the position indicated by "▲" in waveform A'. However, in reality, the marker 37' (magnet) moves to the left in the drawing, but here, with respect to the marker 37',
Assuming that the sensor moves to the right in the drawing, a detected waveform corresponding to the movement is obtained as a rightward waveform from the position indicated by "▲" in FIG.

Waveform B' is the comparator 4 that constitutes the discrimination circuit 41.
1a, and similar to the waveform B in the timing chart of FIG. 10 described above, the comparator 41
The voltage (reference level) V _B at the inverting input terminal of comparator 41a is set as the comparison input level, and if the input level at the non-inverting input terminal of comparator 41a is higher than voltage V _B , the output becomes "H level" and the In this case, the output becomes "L level", so that waveform B' shown in FIG. 5 is obtained.

This waveform B' is supplied to monomulti 42a and 43a, and monomulti 42a is triggered by the falling edge of waveform B and outputs a pulse (waveform E') with a pulse width (time constant) τ. 43
A is triggered by the rising edge of waveform B', and similarly outputs a pulse (waveform F') with a pulse width (time constant) τ. Here, it is assumed that the time constant τ of the monomultis 42a and 43a for creating the waveforms E' and F' is sufficiently smaller than the period T determined by the rotation speed.

The detection circuit (maximum peak hold circuit) 44 holds (maintains) the minimum peak value of the waveform A' input to the non-inverting input terminal of the comparator 44a via the input terminal 40, and outputs the waveform from the monomulti 42a. At timing E', switch 44s is turned on and reset. Therefore, a waveform G' is obtained at the output terminal 44o of the detection circuit 44.

This waveform G' is supplied to a sample and hold circuit 45, and the output of this sample and hold circuit 45 becomes a waveform H'. That is, the switch 45s of the sample and hold circuit 45 is turned on at the timing of the waveform F' output from the monomulti 43, and the level of the input waveform G' at that time is held and becomes the waveform H'. The waveform H' is controlled by the comparator 45a so that the ground voltage is 0 (V) until the motor starts rotating and the first pulse of the waveform F' is input (that is, the level of the waveform G' is obtained). A resistor R and a capacitor C connected to the non-inverting input terminal are connected to the GND {0 (V)} side.

The waveform H' is supplied to the non-inverting input terminal of the comparator 46a of the detection circuit (maximum peak hold circuit) 46, and since the maximum peak value of the waveform H' is held as the output of this detection circuit 46, the waveform H' is The waveform becomes H' ₀ as indicated by the broken line at ', and from then on, this level is held (maintained) as long as the motor is rotating.

On the other hand, the waveform G' which is the output of the detection circuit 44 is supplied to the non-inverting input terminal of the comparator 47a of the detection circuit (minimum peak hold circuit) 47, and the output of this detection circuit 47 is the minimum peak value of the waveform G'. is held, so the waveform becomes I'. Further, even if the waveform A' input through the input terminal 40 is directly supplied to the non-inverting input terminal of the comparator 47a of the detection circuit 47, it does not change to the waveform I'.

The waveform I' and the waveform _H'0 are added by the adder circuit 48, outputted from the connection point between the resistor _R1 and the resistor _R2 , and supplied to the inverting input terminal of the comparator 49a of the discrimination circuit 49. .

In the circuit of FIG. 4, the voltage level VJ' of the output of the adder circuit 48 is given by the following equation.

VJ′=R ₂・VI′+R ₁・VH′ ₀ /R ₁ +R ₂ However, VI′ is the voltage level of waveform I′, and VH′ ₀ is the waveform
The voltage level is H′ ₀ .

Now, if R ₁ =R ₂ , then VJ'=VI'+ _VH'0 /2, and the output waveform of the adder circuit 48 becomes waveform J' in FIG.

Therefore, from the moment when the sensor 4 passes the magnetic pole change point a ₁ ' of the marker 37', the comparator 4 of the discrimination circuit 49
The comparison input level supplied as waveform J' to the inverting input terminal of 9a is held at the level of V _D in waveform A' of FIG. That is, the level of V _D is between the minimum value of the minimum values of waveform A' and the minimum value of a higher level.

Therefore, the discrimination circuit 49 determines the waveform J' (level of V _D ) supplied to the non-inverting input terminal of the comparator 49.
By comparing the levels of the signal and the waveform A' supplied to the inverting input terminal via the input terminal 40, the waveform D shown in FIG. 10 is obtained at the output terminal 50b.

By inputting this waveform D and the waveform B' shown in FIGS. 5 and 10 into a digital signal processing circuit, that is, a counter, as shown in FIG. Fifth
A waveform K' shown in the figure is obtained. In other words, a phase information signal is obtained.

As described above, even if there is variation (fluctuation) in the level of the output of the sensor section (waveform A') due to variation in the sensor section, correct phase information can always be obtained.

As mentioned above, the circuit of FIG. 2 and the circuit of FIG.
By using the circuit shown in the figure, V _C and V _D , which are the comparison input levels of the comparator, can be maintained at appropriate values (set levels) even if there are variations in the sensor output (waveforms A and A'). For example, by applying this to the motor drive device shown in FIG.
The comparison input level of the comparator constituting the FG signal and PG signal generation circuit 3 of the device can be set to an appropriate value (set level).

Similarly, the present applicant previously applied for patents on March 20, 1985 and April 10, 1985, for which a sensor is used to detect a marker portion of a rotating body, such as a motor drive device, which has a detected portion (marker portion). Even if there are variations in the output of the sensor section that detects the marker section of the rotating body, the comparison input levels V _C and V _D of the comparator must be adjusted to an appropriate level. value (setting level), and therefore correct rotational speed information and rotational phase information can be obtained.

(Effects of the Invention) As described above, according to the level setting circuit of the present invention, when setting a predetermined level for an AC signal waveform whose amplitude changes periodically, variations in the amplitude of the processed signal waveform ( Even if there is a fluctuation), the setting level is always at an appropriate setting level (or one of the minimum values of the AC signal waveform), that is, between the maximum value of the local maximum values of the AC signal waveform and the local maximum value of a lower level. It has the advantage of being able to obtain a setting level that can process the processed signal waveform by setting a level between the minimum value and a higher level minimum value.

[Brief explanation of drawings]

FIG. 1 is a block system diagram showing the configuration of the level setting circuit according to the present invention, FIGS. 2 and 4 are diagrams showing specific circuit examples of the level setting circuit according to the present invention, and FIGS. The figures are magnetization patterns and signal waveform diagrams for explaining the operation of the specific circuit of the present invention shown in Figs. 2 and 4, respectively, and Fig. 6 is a block system diagram of a motor drive device for which the present applicant previously applied for a patent. , FIG. 7 is a signal waveform diagram for explaining the operation of the motor drive device shown in FIG. 6, FIGS. 8 and 9 are diagrams showing an example of the structure of the driven motor of the motor drive device shown in FIG. 6, FIG. 10 is a magnetization pattern and signal waveform diagram for explaining the operation of the motor drive device shown in FIG. 6, FIG. 11 is a signal waveform diagram for explaining the problems of the prior art, and FIG. Signal waveform diagram for explaining the configuration of the level setting circuit, Part 1
3 and 14 are diagrams showing examples of digital signal processing circuits for obtaining phase information signals. 40...Input terminal, 41, 49...Discrimination circuit,
41a, 44a, 45a, 46a, 47a, 49
a... Comparator, 42, 43, 44, 46, 47...
...Detection circuit, 42a, 43a...Mono multi, 4
4s, 45s...Switch, 45...Sample hold circuit, 48...Addition circuit, 50, 50a,
50b...Output terminal, S...Selector switch, R ₁ ,
R ₂ , R...resistance, C... capacitor.

Claims (1)

[Claims] 1. The maximum value (or minimum value) among the maximum values (or minimum values; however, if the value in parentheses is selected, the following values are selected in the same manner) of an AC signal waveform whose amplitude changes periodically. ) and a local maximum value (or minimum value) of a lower (or higher) level, the AC signal waveform supplied via the input terminal is a first discrimination circuit that discriminates whether the signal waveform is larger than or smaller than the reference level; and a first discrimination circuit that detects the moment when the signal waveform output from the first discrimination circuit becomes larger (or smaller) than the reference level. a second detection circuit that detects the moment when the signal waveform output from the first discrimination circuit becomes smaller (or larger) than the reference level; a third detection circuit that detects the maximum value (or minimum value) of the AC signal waveform and is reset by the output of the first detection circuit; a sample and hold circuit sampled by the output of the detection circuit; and an output of the sample and hold circuit as input,
a fourth detection circuit that detects the minimum value (or maximum value) of the signal waveform; and a fourth detection circuit that receives the AC signal waveform supplied via the input terminal or the output of the third detection circuit; Maximum (or minimum) output value
a fifth detection circuit that detects; an addition circuit that adds the output of the fourth detection circuit and the output of the fifth detection circuit and outputs a predetermined set level; and a supply via the input terminal. a second discrimination circuit that discriminates whether the AC signal waveform to be output is larger or smaller than the output setting level from the adder circuit, and from the output terminal of the second discrimination circuit, the AC signal waveform output from the adder circuit is A level setting circuit configured to obtain a predetermined output whose level is determined at a predetermined set level.