JPS6010414A - Shaping circuit of deflecting voltage - Google Patents

Abstract

PURPOSE:To prevent a mechanical oscillation in a bimorph by shaping a saw tooth wave deflecting voltage so that it has a gentle amplitude characteristic in the period when the amplitude characteristic of the deflecting voltage is changed rapidly. CONSTITUTION:Integral characteristics 6 and 7 are changed in accordance with the frequency of the control pulse from a control pulse generator 5, and integrators integrate hardly a voltage when the control pulse is >=300kHz. A switching pulse (a) or (b) is inputted to a terminal 10. Monostable multivibrators 15 and 16 output pulses (i) and (j) corresponding to periods when the amplitude of the saw tooth wave deflecting voltage is changed rapidly. The control pulse generator 5 outputs control pulses (a) and (b) having frequencies 1kHz and 500kHz from terminals A and B. Both pulses are selected alternately by switches 31 and 34 and are given to the integrator 6. They are given to the integrator 7 also similarly. Consequently, saw tooth deflecting voltage (d) and (c) are integrated in periods of pulses (i) and (j) by said characteristics of integrators, and integral outputs (m) and (k) are taken out from integrators. An error output from a tracking control circuit 4 is superposed onto integral outputs (m) and (k), and they are given to a pair of bimorph plates.

Description

[Detailed description of the invention]

TECHNICAL FIELD The present invention relates to a video tape recorder that uses a bimorph as a support member for a magnetic head and controls the deflection of the magnetic head by driving the bimorph, and more particularly to a deflection voltage shaping circuit for driving the bimorph. BACKGROUND ART In video tape recorders, it is important to prevent l/race deviation of the magnetic head with respect to the video track during playback, and a pilot system has been proposed for this tracking adjustment. This pilot method uses four types of pilot signals f1 to f that are predetermined in a frequency region lower than the low-pass conversion color signal.
4 are sequentially written to each trunk. If a trunk misalignment occurs during playback, the pilot signal of the trunk being played back and the pilot signal due to the cross stroke from the adjacent track on the side where the head is closer to each other are obtained. The direction and amount of deviation are detected, and the obtained error output is used to control the phase and deviation of the magnetic head, thereby correcting the locus traced by the magnetic head. In this case, the magnetic head is fixed to a rotating base using a bimorph plate as a support member, and the bimorph plate is bent by the above-mentioned error output to control the deviation of the magnetic nod. In a video tape recorder that uses this type of pilot system, recording tracks are written in a standard recording format and a suitably sized magnetic tape is played back at a variable tape running speed that is different from the standard tape running speed, such as fast forwarding. playback, slow playback,
So-called special playback such as still playback is being performed. In this case, if the magnetic head rotates drawing the same locus, the inclination angle at which the magnetic head traces the tape changes as the tape running speed changes, causing the magnetic head to trace across a plurality of recording tracks. In this case, noise accompanying track crossing appears on the playback screen, which is inconvenient. Therefore, the first
As shown in the figure, the deflection voltage generator IK generates a sawtooth deflection voltage (FIG. 4 C, 2) that has an amplitude corresponding to the tape running speed and is synchronized with the rotation of the magnetic head. The signal is applied to the bimorph plate supporting the magnetic head via amplifiers 2 and 3, and the rotation locus of the magnetic head is controlled in accordance with the tape running speed. Then, the tracking control signal generating circuit 4 generates the above-mentioned error output, and the deflection voltages C, d
The amount of deviation of the magnetic head is controlled with high accuracy, and sufficient tracking can be achieved even during special playback, thereby preventing noise caused by track crossing from appearing on the screen. The magnetic head extracts a reproduction signal effective for displaying on a screen from a recording track on the magnetic tape when the bimorph plate is controlled during a period in which the deflection voltage has linear characteristics in which it rises gradually. Just before the deflection voltage reaches the peak value of one polarity, the deflection voltage suddenly drops.
During a certain period of time immediately after reaching the peak value of the other polarity, even if the magnetic head extracts a signal from the magnetic tape, this extracted signal is not used as a reproduction signal for display on the screen. ing. In the conventional configuration described above, the deflection of the bimorph plate is controlled by a sawtooth deflection voltage, so there is a period during which the deflection voltage rapidly changes from the peak value of one polarity to the peak value of the other polarity. Since the mechanical amplitude motion of the bimorph plate is suddenly reversed, mechanical vibrations occur regardless of the control of the deflection voltage, resulting in slight deviations in tracking during special playback. DISCLOSURE OF THE INVENTION The present invention has been invented in view of the above points, and provides that the amplitude characteristic of the sawtooth deflection voltage that controls the deflection of the bimorph changes rapidly from the peak value of one polarity to the peak value of the other polarity. During the period, the deflection voltage is shaped so that when it reaches the peak value of one polarity, it gradually reaches the peak value of the other polarity.

[7] It is an object of the present invention to provide a deflection voltage shaping circuit that obtains a control output such that the above-described mechanical vibration does not occur in the bimorph. Therefore, in the present invention, the sawtooth waveform deflection voltage generator is reliably integrated during the period in which the amplitude characteristic rapidly changes, and in this period, the sharp part of the deflection voltage waveform is removed and the sawtooth waveform deflection voltage is gradually changed. The structure is such that the signal is not integrated at all or is integrated to the extent that it is not substantially integrated during the period in which the signal rises linearly. As a result, when performing special playback on a video tape recorder,
While unnecessary mechanical vibrations are no longer generated on the bimorph plate, and the magnetic head is still tracing the recording track to extract the necessary reproduction signal, the characteristics of the deflection voltage that controls the deflection of the bimorph plate are similar to those on the tape. Since the period of the gradual linear rise of the sawtooth wave with the amplitude set according to the running speed is used without being substantially shaped, it is practical without any inconvenience caused by shaping the deflection voltage. DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings. FIG. 2 is a circuit diagram showing one embodiment of the present invention, and FIG. 3 is an integrator circuit 6 of FIG.
FIG. 4 is a waveform diagram of each part of FIG. 2. The same reference numerals shown in the drawings indicate the same thing. In Figure 2, 6,711-1: 8 switches as shown in Figure 3, a suinotide capacitor consisting of S2 and a capacitor C], an operational amplifier 11, and a feedback capacitor C
The integrator is constructed by combining two draw-pass filters 12 and has almost the same configuration, and the integral characteristic is determined according to the frequency of the control pulse given from the control pulse generator 5 via the switches 31 to 34. Change. When the frequency of this control pulse reaches a high frequency of 300 KH2 or more, the integrators 6 and 7 hardly integrate the passing signal. This integrator 6 will be further explained. For example, when each switch SI + 82 making up the switched capacitor is connected to the opposite contact point as shown, capacitor C] is charged, and when switches S, S2 are connected as shown, capacitor C is charged as an operational amplifier. It is discharged to the 11 side. This switch S1. S2 is controlled in conjunction with control pulses applied from terminals 63 and 64, one of which is alternately grounded, and the circuit consisting of capacitor C, switch Sl, and S2 is controlled according to the frequency of the control pulse. Since the resistance component changes, it acts as an equal resistance of the integrator 6, and together with the operational amplifier 11 and the feedback capacitor C2, an integration circuit is formed. This fine characteristic is expressed by the capacitor CI and 0
It is determined by the capacitance ratio of 2 and the sampling frequency of the control pulse. When a sawtooth deflection voltage is input from the terminal 61, an intermittent integrated output is taken out from the operational amplifier 11. This intermittent integral output is input to the low-pass filter 12, and digital noise due to sampling of the control pulse is removed, and the low-pass filter 12 outputs a continuous integral output as shown in FIG. Ru. The above is the explanation of the integrators 6 and 7. Numeral 10 is a pulse for selecting a signal section to be displayed on the screen from among the signals taken out from the magnetic tape by a magnetic head (not shown); if there are multiple magnetic heads, the signal from each head is switched and reproduced. The pulses (a) and (b), which are commonly called switching pulses because they are used as signals, are the input terminals of (b). 11 is a quadruple multiplier for this pulse (A), which outputs a pulse (E) of four times the frequency synchronized with the pulse (A). 12゜13 is the frequency divider and the pulse (E) is the frequency divider 12
The frequency is output as a noise pulse (to), and the frequency divider 1
In step 3, the frequency of the pulse (g) is halved and output as a pulse (t). 】4 is an inverter that inverts the polarity of the pulse (g) and outputs a pulse (force). Pulse (IJ) corresponding to a period of rapid change from one peak value to the other peak value
. side) is output. Pulses (January, 0) are respectively terminal 2
0°22 and is also applied via an inverter 17.18 to a terminal 21.23. Further, when pulses with opposite polarities are output from the control pulse generators 22 and 23, these pulses are output from the switch 31.
34 is alternately switched to select one of the control pulses a and b. This selected pulse has its ti Ff
The signal is applied to the terminal 64 of the 9-divider 6, and at the same time, it is inverted by the inverter 9 and applied to the terminal 63 of the integrator 6. For example, the switch 31 is
is closed, and a control pulse a of 1KH2 is applied to the integrator 6, which integrates the sawtooth deflection voltage. The switch 34 is closed by a pulse of opposite polarity to the pulse ray still sent from the terminal 23, and during this period a control pulse b of 5QQKHz is applied to the integrator 6, but in this case the sawtooth deflection voltage passing through the integrator 6 No is almost never integrated. On the other hand, when the switch 32.33 is controlled by the pulse output from the terminal 20.21, one of the control pulses a and b is alternately applied to the integrator 7. In this case as well, the sawtooth deflection voltage 2 during the pulse period is integrated, and the integrator 7 outputs the integral output shown in . The error output from the tracking control generating circuit 4 is superimposed on each of these integral quantities Cal and wo, and is applied to a pair of bimorph plates (not shown) via amplifiers 2 and 3, thereby controlling the deflection of the bimorph plates. FIG. 5 shows another embodiment of the present invention, in which the switch s
w, , sw2 are connected as shown in the figure during the period when the pulse signal is not supplied from the terminal 22, and the switch S
W3. SW4 is also connected as shown in the figure during a period when the pulse signal is not supplied from the terminal 21. Then, when a pulse is supplied from the terminal 22, in response to this pulse, the connections of the switches EIW, , sw2 are changed, and both switches SW1 . A disqualifier 24 is connected between SWz. Similarly, when a pulse signal is supplied from the child 21, in response to this pulse signal, the switch sw3. sw, switch ρ switch SW3. Connect the IN divider 25 between SW4. In this case, the sawtooth wave-like deflection voltages are integrated by selecting a period in which the amplitude characteristics of the deflection blood pressure change rapidly, and shaped into the integral output shown in FIGS. The following operation is already explained in FIG. 2, so it will be omitted. As described above, according to the present invention, when special playback is performed in a video tape recorder, unnecessary mechanical vibrations are not generated in the bimorph plate, and the magnetic head traces the recording track exactly as required. During the period in which a reproduction signal is taken out, the voltage characteristics of the deflection voltage are not shaped, so there is no inconvenience caused by the shaping of the deflection voltage, and this is practical.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing a control output generation part of a bimorph according to the present invention, FIG. 2 is a circuit diagram showing an embodiment of the present invention, and FIG. 3 is a circuit diagram showing the main part of FIG. 2. Figure 4 1 is the second
FIG. 5 is a circuit diagram showing another embodiment of the present invention. ■ - Deflection voltage signal generator, 6.7, 24.25 - Integrating means, 31-34. sw, ~SW4... switch. ', -7

Claims (1)

[Claims] A magnetic head is mounted on a bimorph plate fixed to a rotating base, and a tape recorded at a first tape running speed is transferred to a second tape running speed different from the first tape running speed. When reproducing at the tape running speed, the deflection of the bimorph plate is controlled by a sawtooth deflection voltage that is synchronized with the rotation of the first six-dimensional head and has an amplitude level corresponding to the second tape running speed. , tracking of the magnetic head is performed by bending and deflecting the bimorph plate so that the magnetic head does not cross a plurality of tracks, and the magnetic head is moved during a certain period of the linear rise of the deflection voltage. A video tape recorder that uses a reproduced signal extracted from the tape as a signal to be displayed on a screen, wherein the deflection voltage shaping circuit is characterized in that the deflection voltage is integrated over a period other than the certain period.