JPH03105703A - Crosstalk reduction circuit for rotary transformer - Google Patents

Abstract

PURPOSE:To reduce switching noise by providing a switching transistor (TR) short-circuiting a stator side rotary transformer coil and a recording amplifier amplifying a recording signal during the generating period of a recording amplifier drive pulse and supplying its output to the stator side rotary transformer coil. CONSTITUTION:An integration circuit 8 is connected to an input terminal of a short pulse ST and an integration output IT is fed to the base of a 1st NPN TR. Moreover, an emitter side of a 2nd TR Q2 connects to a fixed voltage VC and the collector side connects to a recording reproduction IC respectively and a recording amplifier 9 and a reproduction amplifier 10 driven only during the generating period of a amplifier drive pulse are incorporated in the recording reproduction IC and any amplifier and a 1st stator transformer coil S1 are selectively connected via a recording reproduction switch SW1 depending on the mode. Thus, switching noise is reduced or eliminated.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to a crosstalk reduction circuit for a rotary transformer of a time recording/reproducing device.

(b) Conventional technology For miniaturization, camera-integrated VTRs such as 8mm video cameras set the tape winding amount to just over 270 degrees, and perform recording and playback by sequentially switching four rotating heads. There is.

When employing such an llm, a small rotary transformer is provided with coils for at least four channels, and the rotary transformer coils on the stator side are short-circuited during non-reproduction scanning periods in order to eliminate crosstalk between channels.

(c) Problems to be Solved by the Invention However, the above-mentioned conventional technology has the drawback that switching noise due to short circuits is mixed into the recorded signal and the reproduced signal. It has also been confirmed that when a recording current including a DC bias current is supplied to the stator-side rotary transformer coil during a recording scan period, noise due to the DC bias occurs at the recording start and end timings.

Therefore, it is necessary to reduce switching noise caused by short circuits and DC bias.

(2) Means for Solving the Problems The present invention provides a pulse generating means that generates a short circuit pulse that is energized before the start of a reproduction scan period and deactivated after the end of the reproduction scan period, and a pulse generator that integrates the short circuit pulse. an integrating circuit that
A first feature is that switching transistors that input the output of the integrating circuit and short-circuit the rotary transformer coil on the stator side are respectively disposed in the regeneration circuit,
A short circuit pulse that is deactivated before the start of a recording scan period and activated after the end of the recording scan period, and a recording amplifier that is activated before the short circuit pulse is deactivated and is deactivated before the short circuit pulse is activated. pulse generating means for generating respective drive pulses; an integrating circuit for integrating the short-circuiting pulse; a switching transistor for inputting the output of the integrating circuit to short-circuit the rotary transformer coils on the stator side; and a generation period of the recording amplifier drive pulse. A second feature is that a recording amplifier is provided for amplifying the medium recording signal and supplying its output to the rotary transformer coil on the stator side.

(E) Accordingly, according to the present invention, during regeneration, the stator side rotary transformer coil is gradually short-circuited and short-circuited,
The generation of switching noise is reduced, and during recording, the short circuit is gradually released after the recording signal is supplied to the stator side rotary transformer coil, and the short circuit is gradually removed before the recording signal supply is terminated.

(f) Example DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below according to an illustrative embodiment.

In this embodiment, a small 8-inch tape is wound around a cylinder by a little more than 270 degrees, and four rotating heads are sequentially switched to perform recording and playback, while a rotating erasing head enables editing and recording.
The present invention is applied to millivideo.

Therefore, in this embodiment, as shown in FIG.
E, the short ring coil pair SS, RS on the second turn, the coil village S4, R4 for the fourth head on the third turn, and the coil pair 32, R2 for the second head on the fourth turn. , a coil pair S3, R3 for the third head is provided in the fifth round, and a coil pair Sl, Rl for the first head is provided in the sixth round, respectively.

Furthermore, in this embodiment, various timing pulses are derived by a microcomputer shown in the functional block diagram of FIG. As is clear from this figure, the microcomputer generates four pulses in synchronization with the rotation of the cylinder.
5Hz PG pulse PG and 720Hz FG pulse FG
is input, and three periods of PG pulse form a pulse of four field periods. Therefore, the PG pulse is first converted into a frequency-divided pulse of 15 Hz by the 1/3 frequency dividing means 1. Further, the FG pulse is inputted to the 12-decimal counter 2 and the 48-decimal counter 3 as counting pulses, respectively. Both counters 2.3 use the frequency-divided pulse as a reset input, the 12-decimal counter 2 repeats counting in a field period, and the 48-decimal counter 3 performs counting in a 4-field period.

The count value of the 12-way counter 2 is input to the decoding means 4, and the time counter 6 for counting the master clock is reset at the timing when the count value becomes "2".

Note that the master clock is generated by the master clock generating means 5.

Furthermore, the counting outputs of each counter 2, 3.6 are inputted to a pulse generation stage 7, and four-phase switching pulses SWI, S
W2, SW3, SW4 and 4-phase short pulse STI
, ST2, ST3, and ST4, and four-phase recording amplifier drive pulses API, AP2, AP3, and AP4 are respectively shaped or derived.

Note that FIG. 3 shows the first phase switching pulse SW1, short pulse STI, and recording amplifier drive pulse API during recording. As is clear from this figure, the short pulses S are deenergized before the switching pulse SW is energized, and are energized after the switching pulse SW is deenergized. Furthermore, the recording amplifier drive pulse is
It is activated 50 μsec before the short pulse is deactivated, and deactivated 50 μsec before the short pulse is activated.

FIG. 3 also shows a second phase switching pulse SW2 and a short pulse ST2 during reproduction. As is clear from this figure, short pulse S
T is 200 μs from the activation of the switching pulse SW.
The switching pulse SW is deenergized before ec.
is deenergized and energized at the same time.

Note that each of the above-mentioned pulses is generated in common for all four phases, and the pulse waveform shown in FIG. 3 is merely an example for one phase.

Further, FIG. 2 specifically illustrates only the recording/reproducing circuit connected to the first rotary head Hl.

In the figure, an integrating circuit 8 is connected to the input terminal of the short pulse ST, and the integrated output IT is supplied to the base of the first NPN transistor Ql.

Moreover, the collector of this first transistor Ql has a PNP
A first stator transformer coil S1 is connected between the emitter and the collector of the second transistor Q2.

Further, the emitter side of the second transistor Q2 is connected to a fixed voltage vc, and the collector side is connected to a recording/reproducing IC, and the recording/reproducing IC includes a recording amplifier 9 that is driven only during the period when an amplifier drive pulse is generated. and a playback amplifier 10, and a recording/playback switch S depending on the mode.
Any amplifier and the first stator transformer coil Sl are selectively connected via the WI.

Therefore, during recording, the sheet pulse STI remains at a high level during the non-recording scanning period, and the first and second transistors Q
1 and Q2 are in a conductive state, and the first stator transformer coil S1 is in a short-circuited state.

When the start of a recording scan approaches in such a state, the recording amplifier 9 is first activated and supplies a recording signal to the first stator transformer coil S1, but since the second transistor Q2 is in a conductive state, the start of the first rotation and first drive is delayed. No recording signal is supplied to H i. After driving the recording amplifier 9, when the short pulse STI is deactivated, the integral output ITI gradually falls, the second transistor Q2 is gradually turned off, and a recording signal is supplied to the first rotary head H1. After this recording signal supply start timing, the switching pulse SWI rises. However, although this switching pulse SW1 is not used for switching during recording, recording scanning must be guaranteed during the generation period of this switching pulse. Next, before the end of the recording scan, a switching pulse S
WI is deactivated, followed by short pulse STI.

This short pulse STI is integrated and gradually shortens the first stator transformer coil S1.

Thereafter, the amplifier drive pulse API is deenergized and the non-recording scanning state is entered again. Therefore, one recording trunk is formed by this recording scan, and recording tracks are sequentially formed in a continuous manner.

On the other hand, during reproduction, the short pulse ST2 is in an energized state during non-reproduction scanning, and the first stator transformer coil S1 is in a short-circuited state. Before starting the playback scan,
When the short pulse is deenergized 200 μsec before the activation of the switching pulse SW2, the first stator transformer coil Sl gradually becomes non-conducting due to the integral output IT2 before the activation of the switching pulse SW2, and the reproduction signal is supplied to the reproduction amplifier 10.

Before the reproduction scan ends, the switching pulse SW2 is deactivated and the short pulse ST2 is activated at the same time. Therefore, after the switching pulse SW2 is deenergized, the first stator transformer coil S1 is gradually short-circuited and enters the non-regenerative scanning state again. The reproduction signal obtained from each reproduction amplifier by the above-mentioned reproduction scan is selected by the switching pulse and is derived as a continuous signal.

(G) Effects of the Invention According to the present invention, it is possible to reduce or eliminate switching noise for removing crosstalk of a rotary transformer that occurs during recording and reproduction, and the effect is significant.

[Brief explanation of drawings]

Each of the figures shows one embodiment of the present invention, and FIG. 1 is a functional block diagram of a microcomputer for pulse generation, and FIG. 2 is a functional block diagram of a microcomputer for pulse generation.
The figure shows a recording/reproducing circuit diagram for one channel, FIG. 3 shows an explanatory diagram of main part signal waveforms, and FIG. 4 shows a sectional view of the rotary transformer core.

Claims (2)

[Claims] (1) In a magnetic recording and reproducing apparatus of a type in which the stator-side rotary transformer coil is short-circuited during the non-reproducing scanning period of the rotary head and a reproduction signal is derived from the stator-side rotary transformer coil only during the reproducing scanning period, the above-mentioned pulse generating means for generating a short circuit pulse that is energized before the start of the regeneration scan period and deactivated after the end of the regeneration scan period; an integrating circuit that integrates the short circuit pulse; A rotary transformer crosstalk reduction circuit consisting of switching transistors that short-circuit the rotary transformer coil on the stator side. (2) In a magnetic recording/reproducing device of a type in which a recording signal is supplied together with a DC bias current to the stator-side rotary transformer coil only during the recording scanning period of the rotary head, the power is deenergized before the recording scanning period starts. pulse generating means for respectively generating a short circuit pulse that is activated after the end of the recording scan period and a recording amplifier drive pulse that is activated before the short circuit pulse is deactivated and is deactivated before the short circuit pulse is activated; an integrating circuit that integrates the short-circuiting pulse; a switching transistor that inputs the output of the integrating circuit and short-circuits the rotary transformer coils on the stator side; A rotary transformer crosstalk reduction circuit consisting of a recording amplifier that supplies the side rotary transformer coils, respectively.