JPS60237662A - Video tape recorder - Google Patents

Abstract

PURPOSE:To cease speedily the fluctuation of a speed error voltage during switching from high-speed operation to low-speed operation by suppressing a rise in speed voltage above a set reference voltage through a control system. CONSTITUTION:When a signal for constant-speed reproducing operation is supplied to the system controller of VTR during fast searching operation, a brake voltage is applied from a terminal 10 to a synthesizing circuit 7 and a negative impulsive reverse signal is supplied from a terminal 12 to a driving circuit 9. Then, if the fluctuation of the output voltage of a sample-hold circuit 6 begins to increase at the switching point of frequency division ratios of a frequency divider 4, a switch 14 is turned on with the output of a comparator 13 once the voltage exceeds the reference voltage E0 and the brake voltage turned off only during the on period of the switch. Consequently, the speed error voltage from the circuit 6 is limited to the reference voltage E0.

Description

DETAILED DESCRIPTION OF THE INVENTION (A) Field of Industrial Application The present invention relates to a VTR (video tape recorder), and particularly to a VTR that performs a braking operation when transitioning from high-speed operation to constant-speed operation.

(b) Conventional technology In order to smoothly transition from high-speed operation such as high-speed search or n-times speed mode to constant-speed operation without tape loosening, the capstan, which had previously rotated at high speed, was It is necessary to apply a brake to the motor to bring it to normal driving speed.

This kind of thing has been done, for example, in Japanese Patent Laid-Open No. 58-35757.

In the conventional example shown in FIG.
) The output (a) of the divider (4), which divides the output of
The sample and hold circuit (6) produces a triangular wave that rises with a further delay of time σ) from the rising edge of
) is as shown in FIG. 5(C). The relationship when the rotational frequency of the capstan motor t11 increases is shown in taf(b)'(c/ in FIG. 5. In the synthesis circuit (7), the speed error voltage ( C) is applied to the key stan motor +11 through the DC amplifier (8) and the drive circuit <9). In this control p-p, the n-times speed operation in search etc. is performed using the voltage applied during constant speed (
For example, a DC voltage amplifier (
8) to the control valve and by setting the division ratio of the frequency divider (4) to i.

At the time of transition from n-times speed operation to constant speed operation, a brake voltage (Pl) is applied via the combining circuit (7) to prevent the tape from becoming slack.

At that time, a signal for rotating the motor in the opposite direction is given to the drive circuit (9) from the terminal Q''4. Note that the terminal 02)
If the signal applied from the motor is at a high level μ, the motor is rotated in the forward direction, and if it is at a low level μ, the motor is rotated in the reverse direction.

FIG. 6 shows waveforms of various parts when transitioning from n-times high-speed operation to constant-speed operation. In Figure 6, (Pl) is the terminal (
brake voltage applied from lO) to the composite circuit (7),
(P2) is the motor forward/reverse signal given to the drive circuit (9) from the terminal (+), (c) is the speed error voltage generated from the #-j sample μ hold circuit (6).Speed error voltage (
When the voltage C) is switched from the high-speed operation mode to the constant-speed operation mode (B) at time (tl), the voltage becomes oscillating as shown in the figure, and then it oscillates and then settles down.

In this way, there are variations in the starting force depending on the rotation angle of the motor and the starting force of individual motors, so the conventional method of applying a constant brake voltage for a certain period of time reduces the rise time from high-speed operation such as search to constant operation speed. (The time it takes for the oscillating voltage to settle to a predetermined voltage) is long and unstable.

(c) Object of the Invention Therefore, it is an object of the present invention to provide a video tape recorder that can quickly shift from high-speed operation to constant-speed operation.

B) Structure of the Invention The present invention suppresses vibrations in the speed error voltage that occur when switching from high-speed operation to constant-speed operation by providing a suppressing means that prevents the speed voltage in the speed braking system from exceeding a predetermined paper voltage. I wanted to finish it quickly.

(One Embodiment In FIG. 1 in which the present invention is implemented, the same parts as in FIG. 4 are given the same symbols and redundant explanations are omitted. In FIG. 1, 031 is the reference voltage (EO) and sample hold. (14) Fi is a comparator that compares the speed error voltage (C) from the circuit (6) and generates an output when the speed error voltage (C) becomes equal to or higher than the reference voltage. This switch means is turned on by the output and deactivates the brake voltage (Pl) applied from the terminal (10) to the combining circuit (7).

The operation of the praying circuit will be explained with reference to FIG.

First, the signal dEVT for constant speed playback operation during high speed search operation.
When the brake voltage (Pl) is applied to the system controller (not shown) of R, the brake voltage (Pl) is applied from the terminal (10) to the combining circuit (7) accordingly, and the brake voltage (Pl) is applied to the driving circuit (9).
A negative pulse-like reverse signal (P2) is applied from the terminal (I2) to the terminal (I2). At this time, the voltage #in at the terminal (lI) doubles the voltage (nEl) to the voltage in the normal constant speed operation mode (El
), and the frequency division ratio of the divider (4) is also switched to the division ratio in the constant speed operation mode. From the switching point (11), the voltage of the sample and hold circuit (6) (
C) tends to oscillate greatly, but the reference voltage (EO
), an output is generated from the comparator (13+) and turns on the switch means (141), so the brake voltage (
Pi) #'i, its on period 1i1 (D) becomes inactive. Therefore, the speed error voltage (c) #dll quasi-voltage (EO) from the sun 1μ hold circuit (6) becomes a limit, and the vibration energy μ is suppressed. Where the speed error voltage is lower than the reference voltage, the brake voltage is input to the combining circuit (7). In this way, as shown by the solid line in FIG. 2(C), the voltage quickly converges to a predetermined voltage without repeating subsequent oscillations. Incidentally, the dotted line waveform indicates vibration in a case other than the present invention. In this way, the time from the search operation to the constant speed operation is shortened, and the transient operation is also stabilized. In particular, in the past, it took a long time for the speed error voltage to converge due to variations in the starting force of the motor, but the disadvantages caused by such variations can be improved. Figure 3 shows a specific example of the main part, where (+5) is an IC with the product number BA6321 manufactured by ROHM, the output of the frequency divider circuit (4) is input to pin 8, and this output is The signal is supplied to a sawtooth waveforming circuit (6) and a sump-hold circuit (6). 061(16)#-! , No. 9 bin (2), and No. 100 bottle are charging/discharging capacitors externally attached, and form part of the sawtooth wave forming circuit (6) and the sump μ-hord circuit (6), respectively. The speed error voltage that is the output of the sampling hold circuit (6) is connected to the -tan IC (1
5) Externally through resistors (R1) (R2) 133
Enter the IC (+5+) again from the number bin. At that time, terminal Q9
) is combined with the phase error voltage of the phase servo system applied through the resistor (R8). Is the speed error voltage etc. input from pin 133 an operational amplifier? It is added as a positive input of υ and output from pin 15 [phase]. Q indicates a terminal connected to the DC amplifier (8) in FIG.

(R4) and (R6) are bleeder resistors connected between bin 111 and ground, and (Q) is a switching transistor whose base is connected to the middle point of the connection. Its collector is for inputting the brake voltage. The emitter is connected to the terminal via a resistor (R7), and the emitter is connected to ground. In this embodiment, the reference voltage (Eo) mentioned above is the voltage that appears at pin 111 when the switching transistor (0) is turned on. The output signal is applied to the speed control system through a resistor (R6) and a switching diode CDI. The brake voltage (Pl) applied to the terminal (I81) is also applied to the speed control system through the resistor (R7) and the switching diode (D2). However, according to the present invention, when the switching transistor (Q) is turned on, the brake voltage is Voltage is disabled.

As for the synthesis circuit (7) in Fig. 1, in the case of Fig. 3,
This applies to the external line from bin 111 to bin 133.

In addition, in the configuration as shown in Fig. 3, a comparator is provided with a predetermined reference voltage as one input and the output of the 111th bin as the other input, and the output of this comparator is used to control the switching transistor (Q). Needless to say, it may be configured to be driven.

(F) Effects of the Invention According to the present invention, there is an advantageous effect that the transient operation when moving from high-speed operation to constant-speed operation ends quickly, and the transient operation is also stabilized.

[Brief explanation of the drawing]

FIG. 1 is a block circuit diagram showing the configuration of the main parts of a video tape recorder embodying the present invention, and FIG. 4s2 is an operational waveform diagram thereof. FIG. 3 is a circuit diagram showing essential parts of another embodiment of the present invention. FIG. 4 is a block circuit diagram showing the configuration of the main parts of a conventional video tape recorder, and FIGS.
The figure shows its operating waveform diagram. (C)...Speed error voltage, (Eo)...Reference voltage,
(Q)...Switching transistor, ring...Comparator, -...Switching means. Applicant Tamyo Wki Co., Ltd. Agent Patent Attorney Shizuo Sano Ward Figure 4 Figure 5 Figure 6 (Pθ - "Ko., 9P" 2 ov (n>ol Kai 1

Claims (1)

[Claims] +1) Via'off that applies a brake voltage to the speed control system when transitioning from high-speed operation to constant-speed operation.
-7'' video tape recorder, characterized in that a suppressing means for suppressing a speed error voltage in the speed control system from exceeding a predetermined reference voltage is provided. 2. A video tape recorder according to claim 1, further comprising a comparator for comparing the voltage with a reference voltage, and switch means for inactivating said brake voltage during an output period of said comparator.