JPS5851339B2 - Rotational phase control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a rotational phase control device, such as a magnetic recording and reproducing device having a simultaneous recording and reproducing function for recording and reproducing digital signals, which uses a reference frame synchronization signal and a capstan motor during recording. The rotation detection pulse signals of the motor must be synchronized, the reference frame synchronization signal and the playback frame synchronization signal must be synchronized during playback, and the rotation speed of the motor and the frequency of the playback frame signal must be different, and the recording Because it is necessary to change the characteristics of the motor control system during recording and the characteristics of the motor control system during playback, motor rotation phase control is used by switching between the motor phase control circuit during recording and the motor phase control circuit during playback. It is related to circuits.

A block diagram of a conventional rotational phase control device having the above-mentioned functions is shown in FIG. 1 and will be described.

In FIG. 1, 1 is an input terminal that receives a reference frame synchronization signal, and this signal is divided by a frequency dividing circuit 2 to a frequency equal to the number of rotations of the capstan motor 3 during steady tape running. , the waveform is shaped into a trapezoidal wave by the integrating circuit 4, and the waveform is supplied to the sample hold circuit 5.

On the other hand, a rotation detection pulse from a rotation pulse generator 6 that generates a detection pulse every rotation of the rotating shaft of the capstan motor 3 is amplified by an amplifier 7, and the waveform is shaped by a waveform shaping circuit 8. It is supplied to circuit 5.

This sample/hold circuit 5 samples the output trapezoidal wave of the integrating circuit 4 using the output pulse of the waveform shaping circuit 8.
The output is smoothed by a phase compensation circuit 9, amplified by an amplifier 10, and supplied to a switch 11.

In addition, the reference frame synchronization signal input to input terminal 1 is
The reproduction frame synchronization signal which is waveformed into a trapezoidal wave by the integrating circuit 12 and inputted to the input terminal 14 by the sample/hold circuit 13 is compared in phase with the signal pulsed by the waveform shaping circuit 15. The hold output is smoothed by the phase compensation circuit 16, amplified by the amplifier 17, and supplied to the switch 11.

With the recording/playback switching signal input to the input terminal 18.

By switching the switch 11, the output of the amplifier 10 is set to the capstan during recording, and the output of the amplifier 17 is set to the capstan during playback.
The signal is supplied to a motor drive circuit 19, and this capstan motor drive circuit 19 drives the capstan motor 3.

However, during recording, the control loop of the playback system is open, so in a magnetic recording and playback device using the simultaneous recording and playback method, the phase relationship between the reference frame synchronization signal and the playback frame synchronization signal is not necessarily the same as the phase relationship during normal operation. Because they do not match, the output power of the sample-and-hold circuit 13 does not necessarily match the value during normal operation, and when switching to the control loop of the reproduction system, synchronization pull-in may be delayed due to the time constant of the phase compensation filter 16. Similarly, when switching from playback to recording, the control loop of the recording system is open during playback, so the phase relationship between the reference frame synchronization signal and the motor rotation detection pulse is the same as the phase during normal operation. Since the output of the sample/hold circuit 5 does not necessarily match the value during steady operation, when switching to the recording system control loop,
There is a drawback that synchronization may be delayed due to the time constant of the phase compensation filter 9.

This invention is intended to shorten the synchronization pull-in time when switching the control loop from recording to playback or from playback to recording.

FIG. 2 is a block diagram showing an embodiment of the present invention, and the same reference numerals are the same as those in the conventional example described above.

In FIG. 2, during recording, the gate circuit 20 is activated by the recording/reproduction switching signal input to the input terminal 18.
The output pulse of the waveform shaping circuit 15 generated from the reproduction frame synchronization signal supplied to the sample and hold circuit 21 is cut off, and sampling in the sample and hold circuit 21 is stopped.

During playback, the gate circuit 22 is activated by the recording/playback switching signal input to the input terminal 18, and the output pulse of the waveform shaping circuit 7, which is generated from the motor rotation detection pulse supplied to the sample/hold circuit 23, is cut off. Then, sampling in the sample/hold circuit 23 is stopped.

The sample and hold circuits 21 and 23 have a circuit configuration such that the outputs of the sample and hold circuits 21 and 23 asymptotically approach a certain set value during a period in which the sample and hold circuits 21 and 23 are stopped for a long period of time compared to the sampling cycle. do.

An example of this is shown in the circuit diagram of FIG.

In FIG. 3, 24 is an input terminal for a trapezoidal wave generated from a reference frame synchronization signal, 25 is an input terminal for a motor rotation detection pulse or a sampling pulse generated from a reproduction frame synchronization signal, and a gate transistor At 26, the trapezoidal wave input to the input terminal 24 is extracted by the sampling pulse input to the input terminal 25, and is stored in the hold capacitor 27.

28 and 29 are high impedance resistors, which control the potential at point A and the voltage of the DC power supply 30 when no sampling pulse is input for a period longer than the sampling period.
It has the role of maintaining the value divided by 90 resistance ratio.

31 is a voltage follower operational amplifier, which functions as an impedance converter, and 32 is an output terminal.

Note that 33 is a protective resistor. If the sampling pulse is normally input to the input terminal 25, 28.29
Since the 0 resistance is high impedance, the value sampled by the transistor 26 determines the potential at point A, and as mentioned above, if sampling is stopped for a long time, the transistor 26 In order to turn off, the potential at point A is determined by the value obtained by dividing the voltage of the DC power supply 30 by a resistance ratio of 28°29, and this potential at point A is obtained from the output terminal 32.

28. The value of the 290 resistance is determined by the potential at point A when no sampling pulse is input to the input terminal 25 for a period longer than the sampling period, and the potential at point A when the control system is in steady operation.
If the resistance ratio is determined to be equal to the potential at the point, the output of the output terminal 32 will maintain the value during steady operation of the control system in terms of DC even during the period when sampling is stopped. Therefore, even when switching from recording to reproduction or from reproduction to recording, there is no delay due to the time constant of the phase compensation circuit 9 or 16 for the DC component, so the synchronization pull-in time is shortened.

As explained above, when the capstan motor is used by switching between two different phase control circuits for recording and playback, one phase control circuit controls the capstan motor. When driving, sampling is stopped by cutting off the sampling pulse of the sample-and-hold circuit of the other phase control circuit, and when sampling is stopped, the output of the sample-and-hold circuit is By making the value equal to the value when the control system is in steady operation, there is an effect that the synchronization pull-in time when switching the two systems of phase control circuits is shortened.

[BRIEF DESCRIPTION OF THE DRAWINGS] FIG. 1 is a block diagram showing a conventional rotary phase control device similar to the present invention, FIG. 2 is a block diagram of a rotary phase control device showing an embodiment of the present invention, and FIG. The figure is a circuit diagram in which the output of the sample/hold circuit is set to a certain set value when sampling is stopped. In the figure, 1 is the input terminal for the reference frame synchronization signal, 2
3 is a frequency dividing circuit, 3 is a capstan motor, 6 is a rotation detection pulse generator, 11 is a changeover switch, 14 is an input terminal for a playback frame synchronization signal, 18 is an input terminal for a recording/playback switching signal, 20 and 22 are Gate circuits 21 and 23 are sample and hold circuits. Note that the same reference numerals in each figure indicate the same or corresponding parts.

Claims (1)

[Claims] 1. During recording, the phase of the signal obtained by dividing the reference frame synchronization signal and the motor rotation detection pulse is compared in a sample-and-hold circuit to control the phase of the capstan motor.
It is equipped with a phase synchronization circuit for controlling the phase of the capstan motor by comparing the phases of the reference frame synchronization signal and the reproduction frame synchronization signal in another sample-and-hold circuit during playback. In a rotary phase control device that drives a capstan motor using first and second phase synchronization circuits in each mode, when the capstan motor is driven by the phase control circuit of one system, the capstan motor of the other system is driven. Sampling in the sample-and-hold circuit of the phase control circuit is stopped, and during the period when sampling is stopped, the output of the sample-and-hold circuit is made to be approximately equal to the center value of C during steady operation. A rotational phase control device characterized by: