JPS6245306Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an intermittent drive circuit for intermittently driving a tape in a video tape recorder (VTR) to realize slow motion playback.

[Prior art]

Some recent VTRs perform slow motion playback by driving the tape intermittently. This is approximately the same tape speed as standard running.
Run the tape for a frame, then (m/n)
Slow motion playback is performed by stopping the tape for (n-m) frames.
is a positive integer). By repeating this cycle, (m/n) slow motion can be realized. The circuit for this purpose is shown in Fig. 1, and the waveforms of the main parts are shown in Fig. 2. 1 is the terminal for inputting the RF switching pulse A, 2 is the playback control signal E
3 is a 1/n frequency divider, 4 is a monostable monomulti MM for delay, 5 is a starting pulse
MM, 6 is a slow tracking MM, and 7 is a braking pulse MM. 8 is a capstan motor that drives the capstan, 9 is a drive circuit for the capstan motor 8, 10 is an FG coil, and 11 is a capstan motor speed control circuit that inputs FG pulses from the FG coil 10.

Reference numeral 12 denotes an R-S flip-flop FF which takes the output D of the starting pulse MM5 as a set input, the output G of the braking pulse MM7 as a reset input, and its output H becomes the gate signal for the gate circuit 13. The output of the starting pulse MM5 (starting pulse) D is the forward rotation input (B ₁ ) (B ₄ ) of the drive circuit 9 via the diode _D1 , and the output of the braking pulse MM7 (braking pulse) G is the reverse rotation input of the drive circuit 9. are applied to inputs (B ₂ ) and (B ₃ ), respectively. Further, the output of the speed control circuit 11 is applied to the forward rotation inputs (B ₁ ) (B ₄ ) of the drive circuit 9 via the diode D ₂ .

As shown in FIG. 2, in this case m=1 and n=3, and (1/3) slow motion can be realized.
Now, the RF switching pulse A input to the terminal 1 is frequency-divided by (1/3) by the (1/3) frequency divider 3B, and is applied to the delay MM4 to give a predetermined amount of delay C. The output of the delay MM4 is applied to the activation MM5 which determines the pulse width of the activation pulse, and a activation pulse such as D is output. When this starting pulse D is supplied to the drive circuit 9 , the transistors Tr ₁ and Tr ₂
turns on and the capstan motor starts rotating in the forward direction.

When the capstan motor 8 rotates in the forward direction, the tape starts running, and the control signal E is input to the terminal 2, delayed for tracking by the slow tracking MM6, and then applied to the braking pulse MM7 to generate a braking pulse. G is output. Since the braking pulse G turns on the transistors Tr ₂ and TR ₃ , a voltage for reverse rotation is applied to the capstan motor 8 . On the other hand, FF12 is set by the leading edge of the starting pulse D, so the gate circuit 13 is turned on and the capstan motor 8 is rotating, so the output of the speed control circuit 11 using the FG pulse is applied to the drive circuit. When the braking pulse G is output, the FF 12 is reset, the gate circuit 13 is turned off, and the output of the speed control circuit 11 is not supplied to the drive circuit.

That is, the speed of the capstan motor 8 is controlled while the FF 12 is set. Therefore, the capstan motor is started by a starting pulse based on the RF switching pulse, and the capstan motor rotates at substantially the same speed as during standard regeneration during the period from the end of the starting pulse to the leading edge of the braking pulse. A braking pulse based on the playback control signal instructs the drive circuit to rotate the capstan motor in the opposite direction, and as a result, the capstan motor is braked and tape running is stopped. Each of the MMs 4, 5, 6, and 7 has a variable time constant, but tracking is performed by controlling the time constant of only the slow tracking MM 6 from outside the VTR. 1st
The circuit shown in the figure is a general circuit that realizes noiseless slow motion reproduction, so further detailed explanation will be omitted.

However, in an intermittent drive circuit as shown in FIG. 1, there is a possibility that the tape will not run depending on the state in which the tape is stopped. That is, if a reproduction control signal as shown in FIG. 2E' is reproduced, a braking pulse as shown in FIG. 2G' is applied to the drive circuit 9 . In this case, since the braking pulse appears immediately after the starting pulse, there is no longer a period during which the tape is transported at substantially the same speed as during standard playback where speed control is applied. For this reason, there is a possibility that starting and braking are repeated and the tape only moves back and forth around a certain position, but the tape does not run. When this condition occurred, it was necessary to temporarily put the VTR into standard running mode and change the tape position.

[Purpose of invention]

The present invention has been devised in view of the above points, and is aimed at preventing the situation in which the tape does not run as described above in an intermittent drive circuit as shown in FIG.

[Structure of the idea]

The configuration of the present invention includes an intermittent drive circuit as shown in Figure 1,
A gate circuit that uses the starting pulse as a gate signal is added, and a braking pulse based on a reproduction control signal generated during the starting pulse period is not applied to the capstan motor by this gate circuit.

〔Example〕

An embodiment of the present invention will be described with reference to FIG. FIG. 3 is a circuit block diagram showing the vicinity of the parts that have been changed, and the same parts as in FIG. 1 are given the same figure numbers. Reference numeral 14 denotes a newly added gate circuit, which is an AND gate which receives as input an inverted version of the starting pulse MM5 (FIG. 2D) and a reproduction control signal (FIG. 2E). In this case, the activation pulse is used as a gate signal for the gate circuit, and the reproduction control signal is input to the slow tracking MM 6 only during the period when the activation pulse is not generated.

Since the configuration is as shown in Fig. 3, the reproduction control signal generated during the period in which the starting pulse D is generated is not input to the slow tracking MM6, and therefore the braking pulse based on this reproduction control signal is not output. The tape continues running. Since the gate circuit 14 is on in the control pulse to be reproduced next, a braking pulse is generated and the tape is stopped. In this case, there is a period during which the capstan motor 8 rotates at substantially the same speed as during standard playback, so the phenomenon that the tape does not run as in the conventional example does not occur.

[Effect of idea]

As described above, the present invention is practical because it can prevent tape running from stopping, which could occur with conventional intermittent drive circuits, by simply adding a simple gate circuit. Therefore, unlike the conventional example, there is no need to temporarily put the VTR into the playback state when the tape stops, and operability is improved.

[Brief explanation of the drawing]

FIG. 1 is a circuit block diagram of a conventional intermittent drive circuit, FIG. 2 is a waveform diagram of the main part of FIG. 1, and FIG. 3 is a circuit block diagram showing an embodiment of the present invention. Explanation of main drawing numbers, 4, 5, 6, 7...monostable monomultivibrator, 8...capstan motor, 9 ...drive circuit, 11...speed control circuit, 14...gate circuit.

Claims (1)

[Claims for Utility Model Registration] A capstan motor is started by a starting pulse based on an RF switching pulse, and a braking pulse based on a regeneration control signal causes the capstan motor to operate in a direction opposite to that at the time of starting. applying voltage to brake the capstan motor;
In an intermittent drive circuit that controls the speed of the capstan motor during a period defined by the starting pulse and the braking pulse, a gate circuit that uses the starting pulse as a gate signal is provided, and the starting pulse is controlled by the gate circuit. An intermittent drive circuit characterized in that a braking pulse based on a reproduction control signal generated during a pulse period is not applied to the capstan motor.