KR910007644Y1 - Head switching signal generating circuit for vtr - Google Patents

Abstract

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Description

VTR Head Switching Signal Generation Circuit

1 is a conventional circuit diagram.

FIG. 2 (a) is a state diagram showing the positional relationship between the conventional head and the dipole.

Figure 2 (b) is a state diagram showing the positional relationship between the head and the S pole of the present invention.

3 is a circuit diagram of the present invention.

4 is an output waveform diagram of each part of FIG.

* Explanation of symbols for main parts of the drawings

101: D-FG signal input terminal 102: D-FG signal input terminal

111a, 111b: Schmitt trigger 112: Inverter

113, 116: Divider 114a, 114b: Monostable multivibrator

115: AND gate 120: head switching signal output terminal

124a: error correction circuit VR ₁ , VR ₂ : variable resistance

C ₁ , C ₂ : condenser

The present invention relates to a head switching signal generation circuit that can be used for a drum servo control circuit or a head switching circuit of a VTR. In particular, the head and head switching signals are generated by using only one PG (Phase Generator) signal. The present invention relates to a head switching signal generation circuit of a VTR that solves the difficulty of phase adjustment and achieves a cost reduction effect.

Conventionally, as shown in FIG. 1, a Schmitt Trigger (Schmitt Trigger: 111a, 111b) and an inverter (for converting a D-PG (Drum-Phase Generator) signal and a D-FG (Drum-Freqrency Generator) signal into a square wave) 112), a monostable multivibrator (114a, 114b), a condenser (C ₁ ) (C ₂ ), a variable resistor (VR ₁ ) (for correcting the phase error between the video head and the head switching signal) VR ₂ ), an end gate 115, and a divider 116 are used to generate the head switching signal necessary for video head switching. In this case, the -D-FG signal is used only to control the drum speed. (A) of FIG. 2 shows the positional relationship between the conventional video head and the dipole. As shown in FIG. 2, two multivibrators are provided by using the dipoles of the N pole and the S pole which are attached to the drum rotator as described above. And variable resistor, capacitor There is a defect that is expensive because it has to be done, and there is a defect that the screen state becomes unstable due to difficulty of adjustment and unbalance during phase control, and there is a fear that there may be a level difference in the dipole assembly process of the drum rotor. there was.

In view of this, the present invention utilizes the fact that the D-PG signal and the D-FG signal are simultaneously detected when the drum motor rotates, thereby lowering the frequency of the D-FG signal to generate not only the drum speed but also the head switching signal. By using the 1PG signal by eliminating the N pole of the dipole, as shown in (b) of FIG. 2, it is possible to solve the difficulty in reducing and adjusting the circuit elements when correcting the phase error, and using only one pole (S pole). It is intended to halve the difficulty in the assembly process of the rotator and to reduce the cost, which will be described by the accompanying drawings as follows.

As shown in FIG. 3, in a circuit composed of Schmitt triggers 111a and 111b for converting a D-FG signal and a D-PG signal into a square wave, the D-FG signal input terminal 101 and D-PG The signal input terminal 102 is connected to the Schmitt triggers 111a and 111b, respectively, and the Schmitt trigger 111a is connected to a drum speed control system, and the frequency divider 113 lowering the frequency of the D-FG signal. The Schmitt trigger 111b is connected directly to the divider 113, and the divider 113 includes a monostable multivibrator 114a, a condenser C ₁ , and a variable resistor VR ₁ . The error correction circuit 124a corrects the mechanical phase error between the video head and the S-pole, and is connected to a frequency divider 116 that lowers the output frequency of the error correction circuit 124a by 1/2. The cycle 116 is connected to the drum phase control system and the head switching signal output It is configured to connect to the party (120).

Hereinafter, an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

In this embodiment, as shown in FIG. 2 (b), the head switching signal can be generated with only 1PG signal by using only the S pole by removing the N pole from the dipoles attached to the drum rotator. (Not shown) is applied to the Schmitt trigger 111a through the D-PG signal and the D-FG signal input terminal 101 and the D-PG signal as shown in FIG. The PG signal is applied to the Schmitt trigger 111b through the D-PG signal input terminal 102. At this time, the Schmitt trigger 111a, 111b converts the input signal into a square wave using a hysteresis characteristic and outputs the Schmitt trigger. As shown in (c) of FIG. 4, the trigger 111a outputs a D-PG signal converted into a square wave, is applied to the drum speed control system, and is applied to the divider 113, and from the Schmitt trigger 111b. 4th As shown in (d), the D-PG signal converted into the square wave is output and applied to the divider 113.

At this time, the divider 113 lowers the frequency of the D-FG signal by 1 / N counter as needed. If the D-PG signal frequency is 720Hz The 1 / N counter should be composed of 1/12 counters. Therefore, the D-PG signal passed through the divider 113 has a lower frequency as shown in (e) of FIG. Is applied to the monostable multivibrator 114a.

Here, the error correction circuit 124a is used to correct the mechanical phase error between the S pole and the video head attached to the drum rotator to the monostable multivibrator 114a by adjusting the variable resistor VR ₁ . The error can be corrected by adjusting the time constant of the applied signal. As shown in (f) of FIG. 4, when a signal whose time constant is adjusted by the variable resistor VR ₁ and the capacitor C ₁ is applied, From the monostable multivibrator 114a, it is possible to obtain a square wave signal delayed by the time constant as shown in (g) of FIG. 4, wherein the phase relationship between the video head and the S pole is an angle σ. Since the square wave signal is triggered on a divider 116 composed of 1/2 counters, a signal as shown in (h) of FIG. 4 can be obtained from the divider 116. It is the signal being applied as soon at the same time output through the head switching signal output terminal 120 to the drum phase control system it is possible to obtain a head switching signal which corresponds with the position of the video head.

As described above, the present invention has the effect of halving the assembly process by only assembling one magnetic pole (S-pole) on the drum rotator, and eliminating screen instability due to unbalance and difficulty in adjusting the phase error by using only 1PG signal. It is effective and cost-effective by eliminating N-pole and reducing circuit elements.

Claims (1)

A circuit for generating a head switching signal using a D-PG signal, comprising: waveform converting means for converting an input D-PG signal into a rectangle, and converting the square wave using only 1PG signal obtained by eliminating the N pole of a dipole. The phase error between the video head and the S-pole is obtained by using a first division means for lowering the frequency of the pre-determined D-PG signal and a multivibrator input signal whose time constant is adjusted by the divided D-PG signal and the variable resistor. An error correction means for correction and a second division means for lowering the frequency of the corrected signal secondly to obtain a head switching signal matching the position of the head; .