JPS5972882A - Intermittent driving circuit - Google Patents

Abstract

PURPOSE:To have a quick shift from a continuous drive state to an intermittent drive state, by shaping a start pulse and/or damping pulse of a capstan motor. CONSTITUTION:When a switch indicating a still or slow motion reproduction is applied, a command signal (b) is set at a high level. Then and RF pulse (a) is supplied to a divider 4, and MM5 and 6 are driven by the output of the divider 4. Then a driving pulse (e) is delivered. In this case, the output K of a D-FF15 is kept at a low level. Therefore the first start pulse is not delivered. An FF7 is set by the pulse (e) to deliver a driving pulse (h). Thus a CTL signal C triggers MM11 and 12 to deliver a damping pulse (g). While a pulse is impressed to a clock input (CLK) of the D-FF15 by an inverter 16 and a differentiating circuit 17 in the falling timing of the pulse (e). Thus an output Q is set at a high level, and an AND gate 18 is opened. Then the subsequent start pulses (l) are impressed to the driving circuit of a capstan motor.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a video tape recorder (VTR) stealth,
This invention relates to an intermittent drive circuit that drives tape intermittently during slow motion playback.

[Prior art]

A circuit block diagram and a main part waveform diagram of an intermittent drive circuit which has been commonly used in the past are shown in FIGS. 1 and 2, respectively. In Fig. 1, (1) is the terminal for inputting the RF switching pulse (RF) 1, (2) is the input terminal for the command signal that is used as a signal during still and slow motion playback, and (3) is the terminal for both terminals 111 ( 2) an AND gate connected to (4)
is the slow ratio? +5* is a monostable multivibrator (MM) for RF delay which inputs the output of the frequency divider (4), and f61 is a starting MM that determines the width of the starting pulse. The output of M i63 is the set input (SE
#IC, N dynamic pulse output terminal (81
VC supplied.

(9J is a terminal that inputs the playback control signal (CTI), ``AND'' gate that inputs the CTL signal and the drive pulse from FF (described later), aυ is MM (slow MM) for slow tracking, σ4 is slow MMα
vJM which determines the width of the braking pulse triggered by υ
It is M. The output of the brake MM [121 is applied to the brake pulse output terminal 13 and is also given to the 9 set input (RESET) of the FF (71).Therefore, the FF (7) is set by the activation pulse and reset by the brake pulse. Therefore, the output of FF (7) is AND game as a drive pulse) 11 (1 and drive pulse output terminal 04)
supplied to

Next, the operation will be briefly explained according to the main waveform diagram of FIG. 2.

When the input terminal (2) becomes a high level as shown in Figure 2 (F), the RF pulse (gradient) is divided into 14 by the divider (4).The fCRF pulse divided by 14 is RF delayed MM [5].
and the output of the RF delay M M (5) is activated M
By triggering M(6)1, a starting pulse C) whose rising edge within the PIF pulse is also delayed is output.

The starting pulse (C) is the capstan motor drive circuit (
When K (not shown) is applied, the capstan motor starts one rotation and the tape runs. FF (7) is the starting pulse ((
1) Vc is reset and drive pulse 0 becomes high level.

When the tape starts running and the CTL signal W (B) is detected, the drive pulse (because the crow is a helepel, the AND gate signal is opened and the slow MM signal is triggered).

The output of the slow MM11υ brings the loop control @MMa■ into a quasi-stable state, and a braking pulse 0 delayed from the rise of the CTL signal (B) is output. The capstan motor drive circuit receives a braking pulse, and the capstan motor receives a voltage opposite to that at startup. By applying this voltage, the capstan motor KIJ is activated to stop tape running. On the other hand, the FF (73) is reset at the timing of the leading edge of the braking pulse. The drive pulse (g) is used to subject the capstan motor to speed control.

Therefore, the coupe is activated based on the RF pulse, accelerated to approximately the same speed as during standard regeneration, runs with no speed control applied, and is stopped by the braking pulse based on the CTL number. Become. This is done in order to draw in noise when stopping.2C1Each M M (5) (6)
uH2Jf) R constant is +l! Adjustments are made so that the i+ side color noise disappears. #M slow M when actually using it
Tracking in slow motion and still playback is adjusted using only the Mαυ variable resistor (VR). Slow motion playback can be achieved by sequentially driving the tape intermittently using the intermittent drive circuit described above. On the other hand, noiseless still playback can be achieved using a special method that disables the capstan motor drive circuit at the next stage after the tape stops.

Now, let us consider a case where the state of the VTR immediately before the slow motion or still playback mode is the playback or double speed playback mode. In this case, before the intermittent drive is performed, there is a state in which the tape is continuously driven and comes and goes. If the intermittent drive state is entered in this state, a situation will occur where the tape is running when it should be stopped, as shown in FIG. 3(A). In other words, in the conventional example, the cycle of start-up and braking is repeated, so the tape is running before entering the intermittent drive operation, and when the tape enters the intermittent drive operation, the speed is first increased to VD, and then the brake is applied. This is because it is added (see Figure 3).

Even if the tape is in the intermittent drive state as described above, if the tape does not stop when it should be in the stop state, the noise cannot be drawn into the vertical blanking period during that period, until the tape returns to the normal intermittent drive state. The screen becomes unsightly. In addition, in the case of still playback, the time until the noise is drawn in is longer than in the normal case, so if you take this into account and set a longer time from the still playback command to the actual tape stop, it may be unreasonable. There was a risk that the screen for still playback would end, and an improvement was desired.

[Purpose of the invention]

The present invention has been made in view of the above-mentioned points, and is a state in which the tape is continuously driven and running (continuous running state).
That is, to provide an intermittent drive circuit that can quickly shift from modes such as normal playback and double-speed playback to a state in which the tape is intermittently driven in slow motion playback and still playback (intermittent drive running state). With the goal.

[Structure of the invention]

In the conventional intermittent drive cycle, the present invention provides a capstan motor control system when transitioning from a continuous running state to an intermittent drive running state. The above-mentioned tFJ is achieved by shaping the starting pulse for starting and the braking pulse for braking the capstan motor, or any one of them.

〔Example〕

FIGS. 4 and 5 show a circuit block diagram of an embodiment of the present invention and waveform diagrams of its essential parts. See Figure 4. 1151 is D
It is a type of flip-flop (D-FF), and a steal and slow motion reproduction command is applied to the data input (Da). D-FF (151 Tsukurotsuku Hachiriki (CL
K ) K C, gvJM M[61c/) output is inverted by inverter 11υ, and further differentiated circuit α7J
'Ik. Output of D-FF [151 (Q
is input to 18 along with the activation pulse.

The output of AND gate [L8 is used as a new activation pulse.

Next, the operation will be explained according to the main waveform diagram of FIG. 5.

V in which the tape is running continuously under standard playback conditions.
In TR, when you turn on the switch to instruct stealth or slow motion playback, the corresponding command number (
b) is at a high level11. The RF pulse (a) is input to the splitter (4). MM (
5) and (6) are driven, and a starting pulse (6) from MM+6J is output. At this time, the output (k) of the D-FF (151), which is the other input of the AND gate, remains at a low level, so the first activation pulse is not output.

“The CTL value number (1) is set by the starting pulse (6), and the FF (7) is set and the drive pulse () is output.
q passes through the AND gate (1 (1) and triggers the MM ring 14, so the braking pulse (2) is output. On the other hand, at the timing when the starting pulse (8) falls, the inverter 1lt
9 and the differentiating circuit αη, the signal as shown in FIG.
It is applied to the clock input (CLK) of FF (151).

Since the data input (Da) of D-FF151 is always at high level, the output of D-FFaS (Q goes to high level at the timing of clock input (Fig. 5)) A
After 11G opens, the starting pulse (1) is applied to the capstan motor drive circuit. Therefore, according to time FjIIVc in FIG. 4, the first starting pulse immediately after the command for still playback or through playback is muted. The transition to the drive running state is quickly realized.

FIG. 7 is a circuit block diagram showing a portion of the second embodiment. In this embodiment, the starting pulse is masked for a certain period of time after a still playback or slow playback command is issued. The command signal for still or slow playback (high level during stealth or slow playback) is applied to the clock input (CLK) of D-FFtll, and the data input (Da) is connected to the power supply voltage and is always high. level condition. Between the output (Q) of D-FFl19 and the reset input (R8T), a time constant circuit 4 as shown in the figure is constructed.The output Q is connected to the diode Cυ
The base 1C of the transistor (Trl) of the starting pulse output circuit (221) is connected through the transistor (Trl).
The output from MIJf6J (not shown) is also applied to the base of 1).

Therefore, in the circuit of Fig. 7, a D type flip-flop (T
C4015)'P It will be used as a monostable multivibrator. This is because when the clock input (CLKJ) becomes irregular, the data input (Da) is at a high level, so the output (Q is 8 (L/bevel output) is at a low level. Therefore, the base of the transistor (Trl) is grounded. Even if the output is output, it is not supplied to the capstan motor drive circuit (not shown).The capacitor of the time constant circuit is charged and the voltage of the 9th set input (R8T) is set to a predetermined value. When the value increases, D-FF (
11 is reset, output (Q is low level, output (Q
is at a high level. Therefore, the starting pulse is masked for a predetermined time determined by the time constant circuit for returning the steal or slow regeneration command, but thereafter it is applied to the drive circuit of the capstan motor.

The time during which the output Q of D-FFnl is at the low level (i.e., the metastable time of the monostable multivibrator) is determined by the period of the control signal, the pulse width of MM (5) (11t), and the pulse width of MM161 (width of the starting pulse). ) is sufficient. direction, time constant circuit (2(l
The capacitor is quickly discharged to the diode inside,
This is to prevent malfunctions when still or slow playback commands are repeated.

Figure WJa is a circuit block diagram showing the third embodiment.

In this embodiment, a case is considered in which a transition from double speed playback mode to slow or still playback is made.

During double speed playback, the tape is literally driven at twice the speed of normal playback, and since there is a risk that the tape may not stop just by muting the first starting pulse, the first braking pulse is also shaped. .

In FIG. 8, the same parts as in FIG. 4 are given the same figure numbers and their explanations are omitted. D type Fujitsubu flop (/additional data input (Da) has a voltage holding capacitor (C1)
A command signal that becomes high level in the double speed mode is applied through &. D-FFq clock input (CLK
) is given a command for still or slow playback, and the output (Q) is controlled by the analog switch (241 and (c)).
goods) are added to the inputs (24a) and (25a). D-
FFf23J reset input (R8T) K is MMt-1
The braking pulse from 21 is inverted by an inverter (261) and is applied via a differentiating circuit ta71.

Therefore, D -F F (a3+ is reset at the timing of the fall of the braking pulse. Analog switch f24J
and 12th limit are for changing the time constants in the time constant circuits of MM(13) and MM13, respectively.

Figure 9 is a waveform diagram of the main parts in Figure 8. When transitioning from 2x speed mode to still or slow playback mode Q, the command signal (b) for still or slow playback becomes high level and was applied before the command signal for 2x speed playback, and data input (Da) K maintains the voltage. Since the capacitor (C1) for
Switch to something suitable for still or slow motion. At this time D
The first activation pulse is muted by FF1151 and AND game)019.

When the control signal is regenerated, MMQυ and MMfi
3 is activated according to the time constant that is switched.
5 is output. When the braking pulse (output of MMf+3) decreases, D-FFQ31 is reset and MMαυ and M
The time constant of M(13 returns to the normal case.The delay time and the width of the braking pulse when moving from double speed to still or slow playback may be determined so that noise is drawn in and the playback stops quickly.

It is obvious that the present invention also includes a technique of shaping only the braking pulse while leaving the starting pulse unchanged.

〔Effect of the invention〕

According to the present invention, a starting pulse is applied to the capstan motor when transitioning from a state in which the tape is continuously running to a state in which the tape is driven intermittently (for convenience, still playback is also included in this state). By shaping the and/or braking pulses, the transition can be effected quickly without noise and is effective.

[Brief explanation of drawings]

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, FIG. 3 is an explanatory diagram for explaining the drawbacks of the conventional example, and FIG. A circuit block diagram of one embodiment, FIG. 5 is a waveform diagram of the main part of FIG. 4, and FIG. 6 is a tape drive according to the present invention. Is the explanatory drawing to be explained, FIG. 7, a part of the second embodiment? FIG. 8 is a circuit block diagram of the sixth embodiment, and FIG. 9 is a waveform diagram of the main part of FIG. 8. Explanation of main drawing numbers (RF)...RF switching pulse, (CTL)
...Playback control signal.

Claims (1)

[Claims] (The capstan motor is started by a starting pulse based on the 13 RF switching pulse, and a voltage opposite to that at the time of starting is applied to the capstan motor by a braking pulse based on a regeneration control signal. In an intermittent drive mode for braking a stun motor, the transition from the continuous drive state to the intermittent drive drive state is achieved by shaping the starting pulse and/or the braking pulse when transitioning from the continuous drive state to the intermittent drive drive state. Intermittent drive 11-'J 1B characterized by prompt operation
. (2) The intermittent drive circuit according to claim 1, wherein said shaping is to remove an initial starting pulse upon transition from said continuous running state to said intermittent drive state. (3) The intermittent drive circuit according to claim 1, wherein the shaping is to change the width and/or position of the first braking pulse when transitioning from the continuous running state to the intermittent drive state.