JPS5854886A - Control circuit for direct current motor - Google Patents

Abstract

PURPOSE:To stop a tape at an aimed stopping position with high accuracy by generating positional signals indicating the position of the tape among control signals on the basis of frequency signals from a frequency generator. CONSTITUTION:The terminal voltage Ep of a capacitor 54 rises only by iO. T5/C every time the frequency signals 8FG of time width T5 are inputted to an input terminal 60. When the frequency signals 8FG are inputted only by the moving number of the distance tape corresponding to the pitches of control signals CTL, the terminal voltage Ep is changed into reference voltage Es, and the capacitor 54 is reset by a switch 53. When the control signals CTL are regenerated during movement, the capacitor 54 is clamped to voltage Ec. The terminal voltage Ep is outputted as the positional signals. When the positional signals Ep are turned into reference voltage EB, brake starting signals Bs are outputted.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a DC motor control circuit suitable for application to a VTR that enables slow playback.

First, with reference to FIG. 1, an example of a control circuit for a DC motor that directly drives a capstan in a conventional VTR that enables variable speed playback will be described.

In such a VTR, slow playback at a desired speed is achieved by alternately repeating the process of stopping the running of the magnetic tape for a predetermined period and the process of running the magnetic tape at the standard speed for one pitch of the control (CTL) signal. I try to do it. This VTR is equipped with a pair of rotating magnetic heads H with a 180° angular division with different azimuths of the normal magnetic gap.
In addition to a and Hb, the magnetic head Hb has the same azimuth as the magnetic head Ha, and has the same azimuth as the magnetic head Hb. ) are provided with auxiliary rotary magnetic heads Ha' arranged at angular intervals corresponding to . Then, the tracks of the same field on the magnetic tape are tracked by (N-1)7L using the magnetic head Ha, )ia'.
The still playback is performed for a frame period, then the two-field track is played back for one frame period using the magnetic heads Ha and Hb, and then the above still playback is performed again. By repeating this, the standard speed X I'm trying to play it in slow motion.

FIG. 1 shows a control circuit for a direct current motor that directly drives a capstan in order to intermittently feed the magnetic tape in this manner. (1) is the DC motor that drives the capstan, (
2) is the control amount M (drive circuit). (3) is a controller that controls whether or not the motor (1) rotates and the direction. (4) and (5) are control signal input terminals, (6) to (9)
is a monostable multivibrator. The controller (3) is supplied with output pulses from the vibrators (7) and (9).

An RF switching pulse SWP whose waveform is shown in FIG. 2 is supplied to the input terminal (4). This pulse SWP
The period corresponds to one frame period.

FIG. 2 shows magnetic heads Ha, Hb, and Ha' whose RF reproduction signals are switched by this pulse.

The vibrator (6) is triggered on the falling edge of pulse SWP. FIG. 2B shows the waveform of the output pulse M (6) of the vibrator (6), which rises at the falling edge of the pulse SWP. The time constant of this vibrator (6) is made variable according to the above-mentioned N, and here, for example, l'J=3 is selected, so the output pulse M(6
The time constant is selected so that the time width of ) is longer than the 2-frame period and does not exceed the 3-frame period □
.

The vibrator (7) is triggered on the rising edge of the output pulse M(6). FIG. 2C shows the waveform of the output pulse M(7) of the vibrator (7), the rising edge of which coincides with the rising edge of the output pulse M(6).

This output pulse M(7) is a pulse for forward rotation of the motor (1), and a forward DC voltage is applied to the motor (1) for a period of time width Tf. This time width Tl is selected so as not to exceed one frame period.

A reproduction control signal CTL whose waveform is shown in the second figure is supplied to the input terminal (5). Vibrator (8)
is triggered by this signal C'l'L.

FIG. 2E shows the waveform of the output pulse M(8) of the vibrator (8). The time constant of this vibrator (8) is made variable, and the time width T of its output pulse M(8)
is the tracking volume installed in the time constant circuit (
(not shown), tracking adjustment becomes possible.

The vibrator (9) is triggered on the falling edge of the output pulse M (8). Ibrator (9) shown in Figure 2 1
), which rises at the falling edge of the output pulse M(8) and has a time width Tr. This output pulse M(9) is a pulse for reversing the motor (1), that is, braking the motor (1), and a DC voltage in the opposite direction is applied to the motor (1) for a period of time width Tr.

This time width Tr is selected to a value that is sufficient for the motor (1) to stop and not to reverse rotation.

If there are multiple standard running speeds of the magnetic tape, the time constants of the vibrators (7) and (9), that is, the time width of their output pulses, are varied accordingly.

Thus, during slow playback of the VTR, the magnetic tape is intermittently fed by the motor (1).

By the way, in the conventional DC motor control circuit described above,
To control the tape stop position, a control signal reproduced from the tape is used as a reference, and after a certain time delay from that timing, a braking pulse of a predetermined time width is generated, and this is supplied to a DC motor as a capstan motor. I was doing it.

Note that tracking adjustment is performed by adjusting this delay time. However, such conventional DC motor control circuits have the following problems.

That is, if there is a dropout in the reproduction of the control signal, the tape cannot stop running until the next control signal is reproduced, resulting in mistracking. In addition, since a braking pulse cannot be generated before the timing of the reproduced control signal, if the target tape stop position is close to the recording position of the tape control signal, the actual tape stop position may not match the target stop position. If the value is significantly exceeded, tracking will still occur.

In view of this, the present invention relates to a control circuit for a DC motor that drives a tape to run, and generates a stop signal at any point in the positive or negative range with respect to the timing of a control signal, regardless of the lack of a control signal. for any [
The purpose is to propose a control circuit that can stop the vehicle at a single target stop position with high precision.

In a control circuit for a DC motor that drives a tape, the present invention uses a DC Tanabata-related frequency generator and a tape position between control signals based on a frequency signal from the DC Tanabata generator. means for generating a position signal indicative of the position;
It has means for regulating this position signal using a control signal, and means for detecting that the position signal has reached a predetermined value and supplying a stop signal to the DC motor.

Next, the present invention will be described in detail with reference to FIG. 3 and subsequent figures. This embodiment is constructed by combining the circuits shown in FIGS. 3 and 5. This embodiment is also a case in which the present invention is applied to a control circuit for a DC motor that directly connects and drives a capstan in a VTR similar to that described in FIG.

First, the circuit shown in FIG. 3 will be explained. (1) is a DC motor that is directly connected to a capstan (not shown). During slow playback, the magnetic tape is fed in steps by the motor (1), that is, by the capstan. The rotation speed of the capstan is, for example, 2 Hz when the tape runs at a standard speed. (2) Drive circuit for the dove motor (1), (
2o) is a frequency generator provided in connection with the motor (1). This generator (a) consists of a magnetic disk (the circumferential surface of which is magnetized as N, 8, N, 8. Yes) (2
1) and a pair of flux-responsive fixed magnetic heads (22A) and (22B) facing the surface of the magnet disk (21). The distance between the magnetic heads (22A) and (22B) is such that the phase difference between the reproduction frequency signals FGA and FGB is 90
°. Therefore, magnetic spatula)” (2
2A), (22B) ノflJ]MwoLh, ai
If the pitch of N, 8 is Lm, then Lb −(n+”
) becomes Lm. However, n is 11"' 0.1.2,
...becomes... This means that this frequency signal FGA, F
This is to supply GB to the frequency multiplier circuit (2) to obtain a frequency signal 8FG (see Figure 4) multiplied by 8. This frequency signal 8FG is the same whether the motor (1) rotates forward or reverse. This frequency multiplier circuit (
The multiplication ratio of 23) is arbitrary. The interval between the magnetic heads (22A) and (22B) may be selected depending on the multiplication ratio.

Next, a part of the drive circuit (2) will be explained in detail.

(3) is a controller that controls whether or not the motor (1) rotates and the direction. The controller (3) has two input terminals (3a)
, (3b), one input terminal (3a) is supplied with a pulse width modulation double old PWM as a motor drive signal,
A rotation direction switching signal RD is supplied to the other input terminal (3b).

From the input terminal Q4) to the D-type flip-flop circuit t26)
A start signal ST' (not shown) is input to the D input terminal of
'A switching pulse swp (see FIG. 2A) is supplied, and a start signal ST (see FIG. 4A) is output from its non-inverting output terminal. Start signal 8T is at time P
This is a signal that rises in synchronization with pulse 5WP (see FIG. 2A).

A brake start signal BS (see Fig. 4B, a signal having a predetermined timing with respect to the control signal CTL in Fig. 2, which will be described later) is sent from the input terminal 07 to the non-inverting signal of the monostable multivibrator (28). Supplied to the trigger input terminal. This brake start signal BS is at time P
Stand up on 2. The time width of the output pulse M (28) (see Fig. 4G) of the monostable multivibrator (28) is determined by the motor (
1) is set to have an appropriate time width for applying a voltage in the opposite direction to apply a brake to the motor (1). Output pulse M (28
) is a signal that rises at time P2 and falls at time P3.

A frequency signal 8FG (see the fourth diagram) from the multiplier circuit (23) is supplied from the input terminal L29) to the inverting trigger input terminal of the retrigger monostable multivibrator 00) via an inverter. (131, (14) are capacitors forming a time constant circuit, and are connected in parallel to each other.

A switch 0ω is inserted in series with the capacitor αa. An output pulse MQO) (see FIG. 4C) which rises in synchronization with the rise of the frequency signal 8FG is obtained from the non-inverting output terminal of the vibrator (10). Output pulse M
The time width of O■ is τ6゛ when switch 0!51 is off,
When on, τ1 (τl>τ0, for example, τl−1,5τo
). Note that the output pulse M00) of the inverted output terminal of the vibrator 0) is not shown in FIG.

Start signal ST from flip-flop circuit (2G)
is supplied to each cellar (8) input terminal of the R8 type flip-flop circuit O(υ, C3]). In addition, the input terminal (
The brake start signal 138 from c) is supplied to the reset (it) input terminal of the flip-flop circuit 00.

Output pulse of flip-flop circuit (to) F C30)
(See FIG. 4C) is a pulse that rises at time P1 and falls at time P2.

Frequency signal 8FG and vibrator 00) output pulse M
(11) is supplied to the AND circuit 02, and its output pulse is supplied to the reset (R) input terminal of the flip-flop circuit 01. The output pulse (Fell) of the flip-flop circuit c31) (see FIG. 4C is supplied to the OR circuit 0. This output pulse F C3) rises at the rising edge of the start signal 8T, and the repetition period of the frequency signal 8FG This is a pulse that falls when becomes less than τl.

Thus, the vibrator aα, the flip-flop circuit O
I) and a first control circuit (1) which supplies DC voltage to the DC motor (1) when the DC motor (1) starts up by operating the AND circuit until the rotational speed of the DC motor (1) reaches a predetermined value. property).

Output pulse F C31 of flip-flop circuit c31)
) is supplied as a control signal to the switch (151) of the vibrator aα via the OR circuit (c), and the output pulse F
Gt) period switch Q! 9 is turned on to set the time width of the output pulse M(10) of the vibrator aω to τl, and when the repetition period of the frequency signal 8F'G becomes smaller than τl, the switch (151 is turned off and the output pulse of the vibrator 0■ M00) is switched to τ0. Also, the period of the output pulse M of the vibrator (28I (Je is supplied as a control signal to one switch of the vibrator (10) through the OR circuit 0ω, Jl, its output pulse MO8), the time of the output pulse MQO of the vibrator 00) The width is switched from τ0 to τl (this τl may be any other value).

The output pulse Mθ0) of the vibrator 00) is an OR circuit (
33). The output of the OR circuit (, 33) is then supplied to the AND circuit (06). AND circuit αj)
is the output pulse F (30) on the flip-flop circuit side.
will also be supplied.

Furthermore, the output pulse Mα01 of the vibrator (rule, Kan),
MCI! al is supplied to an AND circuit C37).

Vibrator (101, Coal and AND circuit 67)
Therefore, when the DC motor (1) falls, a predetermined period (P2
~P3) constitutes the second control circuit for supplying the pulse width modulated signal to the DC converter (1).

The output of AND circuit C16), 07) is OR circuit C3G
1, and its output becomes the Norms width modulation signal PWM (see Fig. 4, ■I), which is supplied to the DC motor (1). Therefore, when the DC motor (1) starts rotating, that is, when the motor (1) starts up, the duty ratio is 100% until the repetition period of the frequency signal sFG becomes smaller than τ1.
The pulse width modulation signal voltage becomes a DC voltage (flat light voltage) with a constant amplitude, and the rise of the DC motor (1) becomes faster.After that, the frequency signal 8FG is set so that the angular velocity of the DC motor (1) becomes constant. The repetition period τ0 (<
A pulse width variable signal voltage of τ1) is supplied to the DC motor (1) to apply speed servo, and when braking the DC motor (1),
That is, at the time of falling, a frequency modulation signal voltage with a repetition period τl (>τ0) is applied to the DC motor (1) for a predetermined period (P2 to P3) to speed up the falling of the DC motor (], ) and to prevent the magnetic tape from falling. The motor (1) is stopped so that it stops at a predetermined position.

Further, the output pulse M (28) of the vibrator (28) and the forward running control signal FWD (not shown in FIG. 4) for the tape from the input terminal (43) are connected to an AND circuit Ω.
Q, and its output is supplied to the OR circuit (421). Also, the output of the flip-flop circuit 00/(Rus F
(to) and input terminal (reno for tape from 4) (
- The running control signal REV (not shown in Fig. 4) is supplied to the AND circuit (currently), and its output is supplied to the OR circuit (4 circuits). This rotation direction switching signal RD becomes "1" when the DC motor (1) is rotating when the tape is running forward, becomes "0" when braking, and becomes "0" when the tape is running in reverse. During running, the value is "0" when the DC motor (1) is rotating, and "1" when braking.

Next, the circuit shown in FIG. 5 will be explained. 154) is a hold capacitor (capacitance is C) constituting a hold circuit, one end of which is grounded. The negative pole of the DC power supply (G) is grounded, and its positive pole (from which a reference voltage (clamp voltage) EC is obtained) is connected to the other end of the on-off switch (also the capacitor 4 via 5η). The negative pole of a constant current source (constant current is io) 6ω is grounded, and its positive pole is connected to [Capacitor +! 54) is connected to the other end. Also, there is an on/off switch 5 on both ends of the capacitor ←
3+ are connected in parallel.

5η is a magnetic head that reproduces the control signal from the tape, and the reproduced control signal CTL (see FIG. 6C) is amplified by an amplifier 681 and supplied from the input terminal to the switch 61) as a switching control signal. . This switch (51) is on for a short period when the control signal CTL is "1", and is off when it is "0".

Also, the frequency signal 8PG (
(see Fig. 4) is supplied from the input terminal - to the switch 621 as a switching control signal. This switch 62
is on for a short period when the frequency signal sPG is "11", and is off when it is "0".

switch 6]), 62 and capacitor I! 54) is connected via a buffer amplifier 6υ to the output terminal - from which the terminal voltage LEp (FIG. 6A) of the position signal (capacitor 64) is obtained.

Wow, Kasumi is a comparator, the above-mentioned position signal Ep is supplied to each non-inverting input terminal, and each reference voltage BS, EB (4th
(see Art and Crafts). Then, the first comparison output of the comparator is supplied to the delay amount l1i8 of the minute delay amount τr, and the obtained output is supplied to the switch 53 as a reset pulse R8T (see the sixth diagram). This switch←1 is on for a short period when the reset pulse R8T is "1", and is off when it is "0".

Then, the brake start signal BS (see Fig. 4) is obtained from the output terminal (material), which is the input terminal (2?) shown in Fig. 3.
). Incidentally, FIG. 6F shows the tape speed, and N8 shows the standard running speed.

Next, the operation of the circuit shown in FIG. 5 will be explained.

Now, suppose that the switch 6η, ←■ is in the off state, and the frequency signal sFG with a constant time width T5 (25 μs) is input to the input terminal (60), then the capacitor 64)
The terminal voltage (position signal) Ep is a constant voltage ΔEp-io@ every time one pulse of the frequency signal sFG occurs.
Increase by T5/C. Therefore, the position signal Ep rises in a stepwise manner, but when it exceeds a preset reference voltage Es, an output is obtained from the comparator line, and after being delayed by a minute time τr, it is switched as a reset signal R8T ( ), which turns on. Thus, the capacitor 64) is reset and the position signal Ep becomes the ground potential (OV).

The operating time of this reset loop is equal to the time τr if there is no delay from other circuit elements, and the value of the time τr is set to be sufficiently smaller (approximately 100 μs) than the pulse interval (approximately 1 m5) of the frequency signal 8FG. degree).

The capstan shaft controls the tape with the signal C'l'L.
Since the machine is configured so that N pulses of the frequency signal 8FG are generated when the machine is moved by a distance corresponding to the pitch of
B (N, ΔEp), the capacitor (54
) terminal voltage F3p is the tape control signal CTL.
It becomes a staircase wave of N steps that is reset every time it moves by one pitch.

On the other hand, when the control signal CTL is reproduced from the moving tape, the switch 6υ is instantly turned on and the position signal (staircase wave) EP is clamped to a preset reference voltage (clamp voltage) EC.

Similar to the above-mentioned reset operation, this clamp operation is completed in a sufficiently short time with respect to the period of the frequency signal sFG. In addition, the reference voltage (clamp voltage) EC is the highest value of the staircase wave E5
shall not exceed.

Through the above processing, the position signal Ep (Figure 6 person) is obtained,
Furthermore, the rising edge of the brake start signal BS is determined by comparing it with the variable reference voltage DB using a comparator. In this case, since the tape stops after traveling a certain braking distance from the braking start point (corresponding to ΔEl), tracking control is performed by appropriately selecting voltage EB with respect to voltage EC.

Note that the slip that occurs between the capstan shaft and the tape is a problem, but as a result of investigation, this slip ratio is S: o,
i%. This error is eliminated by the clamping operation by the control signal CTL and will not be accumulated, but even if the control signal CTL cannot be reproduced continuously for 20 to 30 steps, the position signal H
The error occurring in p is estimated to be about one step of a staircase wave.

Also, the value of the reference voltage (clamp voltage) EC is strictly n
-Δ'FJP(n-0,1,2##11N), but if N is sufficiently large and an error within one step of the staircase wave is allowed, the configuration becomes simple.

Further, since tracking is determined only by the relative relationship between the reference voltage EC and the variable reference voltage EB, even if the voltage EB is fixed and the voltage Ec is variable, the result is substantially the same as described above.

Incidentally, the circuit shown in FIG. 5 can also be realized by a digital processing circuit (microbe processor). That is, digital data NC corresponding to voltage EC is set in a register, and digital data NB corresponding to voltage EB is set in another register. An N-advance counter is provided, to which a frequency signal 8FG is supplied as a clock signal, and a control signal CTL is supplied as a preset signal. When the control signal CTL arrives, the counter is preset to digital data NC. Then, the digital data NP corresponding to the position signal from the counter is supplied to the digital comparator and compared with the digital data NB, and when the data NP exceeds the data N13, the brake start signal BS is output as a comparison output. Just do it.

Now, with the circuit shown in FIG. 5, there is no problem in forward playback, but there is the following problem in reverse slow playback. Therefore, this point will be considered below, and then an embodiment of a control circuit that can stop the tape at an arbitrary target stop position in both forward and reverse slow playback will be described.

As shown in FIG. 7, when the target stop position (optimum stop position) is displaced from the control signal position CTLP on the tape TP by ΔS in the direction shown, two adjacent stop positions 81 and 82 (dotted chain line ), consider the case where step feeding is performed alternately using forward steps and reverse steps. In addition, ΔS is S/4 for a 2-hour mode tape,
If the tape is used in 3-hour mode, it will be S/10.

However, S is one pitch of the control signal position.

At this time, the distance that the tape TP must move is equal to one pitch S of the control signal position, but the distance from the control signal position CTLP to the target stop position differs depending on the feeding direction of the tape TP. Therefore, the aforementioned clamp voltage EC and brake threshold voltage EB
is associated with correct tracking in the forward step, it can be used as is.
When applied to the reverse step, as shown in Figure 8, an inappropriate end ramp operation is performed (indicated by the solid line), and as a result, the tape TP returns too far by 2.ΔS with respect to the target stop position S1, as shown in Figure 7. I end up. This problem is solved by changing the clamp voltage to EC during the reverse step (without changing the voltage EB), as shown by the dotted line in FIG. However, the voltages EC and EC are the voltage (stop voltage) corresponding to the stop position of the position signal EP no(-Bg-ΔEB
), and is expressed as the following equation.

Eo = (Ec + Ec) / 2 On the other hand, the stopping position of the compatible tape is, for example, at the position indicated by the dotted line in Fig. 7,
For these (without changing the voltage EB), the clamp voltage E
Correct tracking operation is performed by differentially changing C and EC (indicated by triangles and circles in FIG. 8A). FIG. 8B shows a control signal CTL for self-recording, and FIG. 8C shows a control signal CTL' for a compatible tape.

FIG. 9 shows a circuit for reliably stopping the tape at the target stop position in both forward and reverse slow playback, and this can also be combined with the circuit shown in FIG. 3 to provide another embodiment of the present invention. A control circuit is constructed. Furthermore, the 9th
In the figure, parts corresponding to those in FIG. 5 are designated by the same reference numerals, and redundant explanation will be omitted.

In FIG. 9, the DC power source 66) is made variable (for tracking adjustment) and the DC power source 1Gl is fixed. σ■ is a changeover switch, which has fixed contacts FD and RV on the forward side and reverse side, and the positive pole of the DC power supply side) connects the capacitor 64) and Switch I!
5, 6□□□ are connected to the connection midpoints.

Biwa is a subtracter that generates a voltage Ee (-Es-Ec) and supplies it to the reverse side fixed contact of the switch (70). (71) is an operational amplifier, and Q2 to υ (g) are resistors with equal resistance values (represented by R). A DC power supply (63') whose negative electrode is grounded is provided. Then, the voltages BS and EC of the positive electrodes of the DC power supplies (63) and -) are supplied to the subtractor ff1), and the voltage Ec (=Es-Ec
) is being made.

Next, the operation of the circuit shown in FIG. 9 will be explained. As shown in FIG. 10A, the brake threshold voltage EB is the stopping voltage E
o is fixed at a value such that it is equal to the midpoint electrode of voltage E8 (Eo"Bs/2) (En-Bs / 2-ΔBn
). Also, tracking adjustment is performed by changing the clamp voltage EC, but a new switch σQ
, the voltage EC is selected during forward operation, and the voltage Ec is selected during reverse operation. However, the voltage EC is the subtractor σ
The stop voltage Eo (-Es/'2) is inverted by υ to a value symmetrical to the voltage EC (Ec = B
s-Be). In Δ' in FIG. 10, ΔEB is the voltage of the position signal Bp corresponding to ΔS in FIG. 7. FIG. 10B shows the control signal CTL.

Further, the tracking range in the case of such a configuration is shown in FIGS. 11 and 12. If the variable range of voltages EC and EC is equal to the voltage Es1C, the control signal position C'
The trunking range for one pitch is obtained with l"LP as the center, but as mentioned above, the optimum stopping position is displaced by ΔS with respect to the control signal position @CTLP, so the effective tracking range is as shown in the figure. It becomes asymmetrical with respect to the optimum stop position.Therefore, the middle D of the tracking control
comes at a point offset by -ΔEs from the midpoint (-Es/2) of the variable range.

FIG. 13 shows an example of a circuit that uses a volume with a center tap and allows the middle point of the tracking control range to be obtained at the click point. In the case of this Fig. 13, the circuit from which voltages EC and EC are obtained has a partially different configuration from that in Fig. 9, and parts corresponding to those in Fig. 9 are given the same reference numerals. Some redundant explanations will be omitted.

One end of the center-tapped volume example is grounded, and the other end is connected to a DC power source (63') with voltage ES.

Let the voltage at the center tap of the volume wire be t.

(c) is the subtractor, (83) is its operational amplifier, (84
), (86), and (87) have resistance values ranging from resistor 6 to (75
), and S51 is a resistor with a resistance value R' different from these resistors. In addition, W/几 is 1-2
Selected as ΔEB/ES. Then, the voltage Et of the center tap of the volume ■ is supplied to the subtractor 3) via the buffer amplifier (supplied), and from this the voltage 2ΔE of the power supply section is supplied to the subtractor 3).
S is subtracted and the resulting voltage (2ΔEB − Et)
is supplied to a subtracter σ1) and subtracted from the voltage ES to output the voltage EC. This voltage EC is the voltage 2ΔES
is equal to These voltages EC and EC are connected to the switch (70
) is supplied to terminals FD and KV.

FIG. 14 shows the characteristics of voltage EC and change in EC with respect to change in tracking control voltage Et.

According to the present invention described above, in the control circuit of the DC motor that drives the tape, the timing can be set within any positive or negative range (maximum 1 pitch of the control signal), regardless of the lack of the control signal. It is possible to obtain a control circuit that can generate a stop signal at a time point (up to ±T) and stop the tape at an arbitrary target stop position with high precision.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing a control circuit of a DC motor of a conventional VTR, Fig. 2 is a waveform diagram, Fig. 3 is a Plutz diagram showing a part of an embodiment of the present invention, and Fig. 4 is a waveform diagram. , FIG. 5 is a circuit diagram showing other parts of an embodiment of the present invention, FIG. 6 is a waveform diagram, FIG. 7 is an explanatory diagram showing the tape, FIG. 8 is a waveform diagram, and FIG.
10 is a waveform diagram, FIG. 11 is a characteristic curve diagram, FIG. 12 is an explanatory diagram showing the tape, and FIG. FIG. 14 is a circuit diagram showing a part of a modified example of the circuit shown in the figure, and FIG. 14 is a characteristic curve diagram. (1) is a DC motor, (2) is a drive circuit, (3) is a controller, (20 is a frequency generator, and 154 is a hold circuit).

Claims (1)

[Claims] 1. In a control circuit for a DC motor that drives a tape to run, a frequency generator associated with the DC motor and a tape position between control signals based on a frequency signal from the frequency generator are provided. means for generating a position signal indicating the position signal; and means for regulating the position signal by the above-mentioned CON) 0-left signal;
A control circuit for a DC motor, comprising means for detecting that the position signal reaches a predetermined value and supplying a stop signal to the DC motor. 2. The control circuit for a DC motor as set forth in Patent No. 1, wherein the regulating means comprises a hold circuit that provides a reference value as the position signal for each control signal. 3. The DC motor control circuit according to claim 2, wherein the reference value takes a first value and a second value depending on the running direction of the tape. 4. The magnitude of the position signal corresponding to the stop position of the tape is selected to be approximately 1 of the maximum value of the position signal, and the first and second values are set as the position signal corresponding to the stop position of the tape. 4. The control circuit for a DC motor according to claim 3, wherein the control circuit is selected to be symmetrical with respect to the control circuit.