JPS5911966B2 - kaitenhetsudogatajikikugasaiseisouchi - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a rotary head type magnetic recording and reproducing device (hereinafter referred to as VTR) having two rotary heads, which stably controls the rotational phase of the rotary heads and The structure is such that switching of the rotary head can also be performed satisfactorily.

A conventional VTR rotary head control system and head switching signal generation system has the configuration shown in FIG.
In FIG. 1, a magnetic piece 4 is provided on a rotating head disc 1 provided with two rotating magnetic heads (not shown), and approximately 18
52 detection heads 2 arranged with an angle difference of 0.00
, 3, a signal corresponding to the rotational phase of the rotary magnetic head is detected.

This detection signal is amplified by amplification circuits 5 and 6, and the amplified signals are passed through monostable multivibrators □ and 8 to adjust the detection phase of the detection heads 2 and 3. The bistable multivibrator 9 is triggered by the output of the multivibrator □, 8. The output of the bistable multivibrator 9 is used as a head switching signal during reproduction, and the next trapezoidal wave adjustment circuit 10 is triggered to obtain a trapezoidal wave. 15 The trapezoidal wave and the external reference signal input from the terminal 11 are compared with the signal passed through the sample pulse shaping circuit 12 in the phase comparison circuit 13, and the resulting error signal is sent to the rotating magnetic head circle via the phase compensation circuit 14. The plate 1 is superimposed on the strayness control circuit 1620 of the driving DC motor 15 to perform phase control (here, the DC motor is used, but a synchronous motor may also be used).

To explain the details of the speed control circuit 16, the rotating shaft 1 of the DC motor 15? The detection signal from the rotational speed detection device 18 connected to the The output signal and the output of the bistable multivibrator 20 are gated by an AND gate circuit 22, and the rotational speed of the DC motor 15 is controlled to be constant via a motor drive circuit 2330. Then, the output of the phase compensation circuit 14 is applied to the monostable multivibrator 21, and its delay amount is controlled to make the rotational phase of the motor 15 coincide with the external reference signal. In this method, accurate rotational phase control and head switching cannot be performed due to changes in temperature characteristics of the monostable multivibrators 1 and 8 for correcting mounting errors of the detection heads 2 and 3. The present invention aims to perform phase adjustment using a method different from the above-described monostable multi for rotational phase adjustment, and to simplify the circuit configuration.

An embodiment of the invention will be described with reference to FIG. The detection signals detected by the detection heads 2 and 3 and the magnetic piece 4 provided for detecting the rotational phase of the rotating magnetic head disk 1 are amplified by amplification circuits 5 and 6, respectively, to produce the amplified signals. The bistable multivibrator 24 is triggered, and the obtained signal is used to operate a trapezoidal wave shaping circuit 25 that generates a trapezoidal wave having both slopes and is composed of a constant current circuit provided for constant current charging and constant current discharging. , the obtained trapezoidal wave is applied to the shot trigger circuit 26 having a "0N" level and "0FF" level variable means, the obtained output is used as a reproduction head switching signal, and the output of the trapezoidal wave shaping circuit 25 and the terminal 11 are The input external reference signal is compared with the signal passed through the sample pulse shaping circuit 12 by the phase comparator circuit 13, and the obtained signal is superimposed on the speed control circuit 16 of the DC motor 15 that drives the rotating magnetic head disk 1. and performs phase control. This speed control circuit 16 has the same configuration as described above. A circuit example of the trapezoidal wave shaping circuit 25 will be explained with reference to FIG.

Resistors 27 and 28 determine the first bias, resistor 29 determines the constant current value, and transistor 30 connects the capacitor 31.
The resistor 29 operates to photoelectrically apply a constant current determined by the resistor 29. Resistors 35 and 36 determine the second bias, resistor 33 determines the constant current value, and transistor 32
The capacitor 31 operates to discharge a current determined by 3 from the capacitor 31. The transistor 34 and the terminal 37 form an input section, and the signal input to the terminal 37 causes the transistor 34 to perform ION'' and ``0FF'' operations, photodischarging a current into the capacitor 31.The terminal 38 is a DC voltage source. Now, when a "High" signal is input to the input terminal 37, the transistor 34 is in the "0N" state, the base potential of the transistor 32 is "LOW" potential, and it is "0FF".
Since it is in the I state, the capacitor 31 is charged with a current of i1. When the input signal of the input terminal 37 becomes FLOw, the transistor 34 becomes "0FF" state and the transistor 3
2 is biased by resistors 35 and 36 that determine the second bias, and the current of I2 becomes "0N" state and the current of I2 flows to capacitor 3.
It is discharged from 1. By the above-described operation, the mouth output having the slope of the output trapezoidal wave T, t2 is obtained for the input waveform A shown in FIG. Further, a circuit example of the Schmitt trigger circuit 26 will be explained with reference to FIG.

Transistors 39 and 40 represent a differential amplifier, and transistor 41 and resistor 42 represent a detection circuit.

The transistor 43 is a switching transistor. The DC voltage V1 applied to the base of the transistor 39 via the resistor 44 and the DC voltage V2 applied to the base of the transistor 40 via the resistor 45 are the DC voltage source 4.
By setting a level difference between the voltages caused by 9 using the variable resistor 46 and making V1 higher than V2, the transistor 39
is in the "ON" state, and the transistor 40 is in the "0FF" state. When the potential of the transistor 40 becomes equal to or becomes higher than the base potential of the transistor 39 due to the input signal from the terminal 51, the collector potential of the transistor 40 decreases to VBE or lower than the DC voltage source 52. If the gain of the differential amplifier determined by the constant current source 50 and the resistor 48 is selected as shown in FIG.
1 becomes the "0N" state. Transistor 41 is "0N"
When the state is reached, the transistor 43 becomes "0N" state, and the connection point between the collector of the transistor 43 and the variable resistor 47 becomes "0N" state.
At this time, the base potential of the transistor 39 becomes the divided potential of the resistor 44 and the variable resistor 47 from V1, so the input signal level applied to the transistor 40 puts the transistor 41 in the "0N" state and the transistor 43
Even if the voltage decreases to the level at which it was brought into the "0N" state, the transistor 40 will no longer be brought into the "0FF" state. For the transistor 40 to enter the "0FF" state, the base voltage applied to the transistor 40 must be made equal to or less than the divided potential of the resistor 44 and the variable resistor 47, depending on the input signal. Since the transistor 43 is in the "0N" state while the base potential of the transistor 40 is higher than the base potential of the transistor 39 due to the input signal, the connection point between the variable resistor 47 and the collector of the transistor 43 is "0N".
When the base potential of the transistor 40 becomes lower than the divided voltage of the resistor 44 and the transformer resistor 47 due to the input signal that maintains the LOW" potential, the transistor 41 becomes the "0FF" state, and the transistor 43 also becomes the "0FF" state. Therefore, the DC voltage of square V1 returns to the base of the transistor 39. From the above operation explanation, the variable resistors 46 and 47
Since it is possible to set the 0N" level and the "0FF" level, each phase delay can be applied to the trapezoidal wave input. This will be explained in the waveform diagram of FIG. 6. Rotary phase detection heads 2 and 3
The detection signals of are waveforms A and b, and the output of the bistable multivibrator 24 triggered by the detection signals A and b is the waveform shown in c. The signal waveform obtained by operating is shown in d. As shown in the figure, the trapezoidal wave d is at 0N level,
In addition to the Schmitt Trigger circuit 26 which operates at 0FF level and operates at 0FF, an output e is obtained. and is used as a head switch signal.The above trapezoidal wave d can be used as a detection signal for phase braking and speed braking.As described above, the present invention can detect the detection head without using two stages of monostable multivibrators. Phase adjustment can be performed by using a trapezoidal wave created to control the rotating body and a simple shot trigger circuit. Since it is generated at the same timing as the detection signal of , the dead time element of the control system due to phase delay is reduced, and the design of the control system is facilitated.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing the configuration of a conventional control system, Fig. 2 is a block diagram showing the configuration of an embodiment of the present invention, and Fig. 3 is a circuit example of a trapezoidal wave shaping circuit constituting the present invention. 4 is a waveform diagram showing the input and output of the trapezoidal wave shaping circuit, FIG. 5 is a wiring diagram showing an example of the Schmitt trigger circuit constituting the present invention, and FIG. 6 is a waveform diagram showing the operation waveforms of the present invention. FIG. 1...Rotating magnetic head disk, . 2, 3...
...Detection head, 5, 6...Amplifier, 11...
...External reference signal input terminal, 13...Phase comparison circuit, 15...Motor, 16...
Speed control circuit, 24... Bistable multivibrator, 25... Trapezoidal wave shaping circuit, 26...
... Schmitt trigger circuit.

Claims (1)

[Claims] 1 Set the rotational phase of the two rotating magnetic heads to the first and second
A bistable multivibrator is triggered by the detection signal, and a trapezoidal wave having slopes on both sides is created by applying the output signal to a trapezoidal wave shaping circuit, and the trapezoidal wave is set to the ON level. In addition to a Schmitt trigger circuit whose OFF level is variable, the output of the Schmitt trigger circuit is used as a switching signal for the rotating magnetic head, and the phase of the trapezoidal wave and an external reference signal is compared, and the error signal is used as a switching signal for the rotating magnetic head. A rotary head type magnetic recording and reproducing device characterized by controlling the rotational phase of a drive system.