JPH10234005A - Vertical period buzz reduction circuit and video incorporating television receiver having the circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the vertical period buzz reduction circuit that provides a surer operation without the need for severe and difficult adjustment for a coil for eliminating buzz in a conventional technology. SOLUTION: A reproduction video signal from a video head of a VTR is given to a synchronizing signal separate circuit 3, in which a synchronizing signal is separated, a horizontal synchronizing signal is eliminated and a vertical synchronizing signal is extracted by an integration circuit 4, the phase of the vertical synchronizing signal is inverted by a phase inversion circuit 5, the result is waveform-shaped by a waveform shaping circuit 6, and a vertical synchronizing pulse that is positive for a period when the vertical synchronizing signal is in existence is obtained. Then a buzz reduction circuit 7 makes a transistor(TR) of the circuit conductive for the vertical synchronizing signal period only and a control section to attenuate the signal reduces a vertical period buzz (produced by a linear audio head to pick up leakage magnetic flux of a vertical deflection coil) included in an output of an audio output amplifier circuit 2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the elimination of buzz in a reproduction audio signal of a VTR, and more particularly to a measure for reducing a vertical cycle buzz (buzz caused by a leakage magnetic flux of a vertical deflection coil of a television). It can be mainly used for TVs with built-in video, TVs with built-in tape recorders, etc., and can also be used for VTRs with TVs around.

[0002]

2. Description of the Related Art As an example of the prior art, a technique for reducing a vertical cycle buzz of a linear audio reproduction signal in a television with a built-in video will be described. The vertical cycle buzz is VT
R, which naturally occurs in the linear audio reproduction circuit of the tape recorder, but when incorporated in a television, the vertical deflection leakage flux leaks from the deflection coil of the television, and the linear audio head picks up the leakage flux to reproduce the audio. The signal mixes with the signal, resulting in a vertical cycle buzz that is incomparably larger than that of a non-TV built-in VTR or tape recorder.

[0003] Conventionally, as a measure against this buzz,
As shown in FIG. 5, a coil L1 '(COLD side) or L2' (HOT side) is attached in series with the linear audio head, and the angle of attachment to the deflection coil of the television, which is a source of buzz, is adjusted to adjust the angle of the linear audio head. An output having a phase opposite to the reproduction output is obtained, and the coil L1 'or L1'
By adjusting the inductance value of 2 'and adjusting the level of the opposite-phase output thereof, a means for canceling only the vertical bus having a large output without significantly affecting the reproduced audio signal which is a small signal is used. I have.

In FIG. 1, reference numeral 1 'denotes an audio amplifier circuit for amplifying a reproduction signal from a linear audio head. The amplified signal is further amplified by the audio output amplifier circuit 2 ', and the DC component is cut by the capacitor C1' and output. R1 'and C2' are for removing external noise. In some cases, the audio output level is controlled by R2 '.

The buzz removing circuit of the same vertical period of the television with a built-in video shown in FIG. 5 is a coil L1 '(peaking coil of about 15 .mu.H) and one end of the linear audio head (in the figure, the COLD side, that is, the GND side). In another model, the coil is a coil L2 ', which is inserted between the HOT side, that is, between the audio amplifier circuit 1' and the linear audio head, and its mounting position is slightly changed for each model to change the deflection coil of the television (actually, the vertical deflection coil in the coil). ), The coil L2 'picks up the magnetic flux leaking from the vertical deflection coil, and adjusts the phase of the pickup component of the vertical magnetic flux. Further, the operation of canceling the buzz component picked up by the linear audio head by adjusting the inductance and the amplitude is performed.
Depending on the size of T, the size and mounting position of the deflecting coil vary, and variations among products differ from model to model, and even the same model may differ from lot to lot or one by one. Since the phase and amplitude of the buzz component picked up by the head change, it is very difficult to select the optimum value of the mounting angle and inductance of the coil L1 'or L2' for canceling it. Further, the adjustment of the mounting angle is quite severe, and depending on the deviation of the mounting angle, instead of canceling, there may be a case where a reverse output is output as shown in FIG. 6 (broken line portion in FIG. 6). Actually, the effect is not surely obtained.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems in the prior art, and does not require a difficult and difficult adjustment of a peaking coil for removing buzz in the prior art, which is more reliable. It is an object of the present invention to provide a vertical cycle buzz mitigation circuit in which buzz is reduced.

[0007]

According to the first aspect of the present invention, there is provided a vertical cycle buzz reducing circuit for reducing a vertical cycle buzz contained in an audio signal reproduced by a magnetic head and generated by a vertical leakage magnetic flux from a deflection coil of a television. A vertical synchronizing pulse generating means for generating a vertical synchronizing pulse from a video signal which is a source of the vertical leakage magnetic flux, and operating during a period based on the vertical synchronizing pulse generated by the vertical synchronizing pulse generating means, and This is provided with a buzz reduction circuit acting on the vertical period buzz.

According to a second aspect of the present invention, in the first aspect of the present invention, a reproduced video signal is used as a video signal from which the vertical leakage magnetic flux is generated.

According to a third aspect of the present invention, in the first or second aspect of the present invention, a coil for picking up a vertical leakage magnetic flux from a deflection coil of the television is provided to the audio signal reproducing circuit provided before the buzz reducing circuit. And the coil generates a signal for canceling the vertical period buzz in the audio signal.

According to a fourth aspect of the present invention, in the third aspect of the present invention, the coil is adjusted so that a buzz component in an audio signal affected by the coil has a positive polarity.

The invention according to claim 5 is the invention according to claims 1 to 4.
VT provided with the vertical cycle buzz mitigation circuit according to any one of the above.
This is a television with a built-in video having a vertical cycle buzz mitigation circuit having R as a component.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. FIG. 1 is a block diagram showing one embodiment of a vertical cycle buzz mitigation circuit according to the present invention. FIG. 2 is a diagram showing an example of a specific circuit of the circuit shown in FIG. FIG. 3 is a diagram showing another embodiment of the embodiment of the circuit shown in FIG. FIG. 4 is a diagram showing an output waveform in a main part of the circuit shown in FIG.

1 and 2, a linear audio head, a coil L1 or L2, an audio amplifier 1, an audio output amplifier 2, capacitors C1 and C2, and resistors R1 and R2 are different from those of the conventional circuit (see FIG. 5). Instead, the description refers to the description of the conventional circuit. The reproduced video signal from the video head of the VTR is input to a synchronizing signal separating circuit 3 where the synchronizing signal is separated (the separated synchronizing signal has a positive polarity). In the embodiment shown in FIG.
The horizontal synchronizing signal is deleted and the vertical synchronizing signal is taken out by the integrating circuit 4 shown as 3, R4, C4. The extracted vertical synchronizing signal is supplied to a resistor R
5, the phase is inverted by a phase inverting circuit 5 shown as a transistor Q1, and the waveform is shaped by a waveform shaping circuit 6 including a capacitor C5 and an amplifier Q2. Get sync pulse.

Next, resistors R6 and R7, transistor Q
3, in the buzz mitigating circuit 7 composed of the capacitor C6, the transistor Q3 is turned ON only during the vertical synchronizing signal period by setting the resistors R6, R7 and the transistor Q3.
The capacitor C6 for attenuating the signal reduces the vertical cycle buzz generated by the linear audio head picking up the leakage flux of the vertical deflection coil included in the output of the audio output amplifier circuit 2.

In this embodiment, the coils L1 or L2
The mounting position and the inductance are determined with the main focus on making the buzz output of the audio output amplifier circuit 2 a positive polarity. In this case, it is necessary to perform the adjustment operation in the canceling direction. The reason is that the buzz may increase to the positive polarity due to the addition of the coil L1 or L2 instead of canceling the reverse by merely having the positive polarity, and when the buzz amplitude increases, the width of the buzz period portion increases, This is because if the pulse width of the vertical synchronizing signal extracted as a collector output from the amplifier Q2 is wider than the pulse width of the vertical synchronizing signal, even if the circuit of the present invention operates, it cannot be completely erased.

In order to make the effect of the circuit according to the present invention sufficient, it is natural that the smaller the output buzz amplitude of the audio output amplifier circuit 2 is, the better it is. Therefore, the coil L1 or L2 should be mounted in the direction in which the buzz is canceled. In this case, it is not necessary to set it so severely. At this time, it is necessary to set a positive output polarity and to obtain a rough effect that is somewhat smaller than when there is no coil L1 or L2. Is fine. If the coil L1 or L2 is mounted in such a direction as to obtain such an effect, the circuit according to the present invention eliminates the remaining buzz.

In the above-described embodiment, the coils L1, L2 for canceling the buzz used in the prior art are also used.
2, and a mitigation circuit which is a component specific to the present invention is added. However, the buzz output has a positive polarity compared to the specified output of linear audio of the audio output amplifier circuit 2 (in this case, -8 dBS). If the amplitude is reasonably small, the desired effect may not be obtained due to the above-mentioned variation even with the addition of the coil L1. In such a case, this coil is not attached and only the mitigation circuit is used. The desired objectives can be achieved by the method.

Next, an embodiment of the present invention will be described with reference to FIG. 3 which constitutes means for the case where the vertical buzz component of the audio output amplifier circuit 2 has a negative polarity based on the relationship between the position of the deflection coil and the position of the linear audio head. Although it may be shifted to the positive polarity side by adding the coil L1 or L2, a means for reversing the operation polarity of the circuit of the present invention is conceivable, and FIG. 3 shows an example thereof. In FIG. 3, the output of the amplifier Q2 is inverted by the amplifier Q4,
5. The negative buzz component is eliminated by the capacitor C6.
In this case as well, the coil L1 or L
If the addition of No. 2 can reduce the amplitude of the negative component, this is added, and the coil L
Even if there is no 1 or L2, it is unnecessary if the negative component is small.

[0019]

【The invention's effect】

According to the first aspect, it is possible to reliably reduce the vertical cycle buzz generated during the period based on the vertical synchronization pulse generated from the video signal without using the conventional coil for buzz elimination.

Effect of Claim 2 In addition to the effect of Claim 1, it is proposed to use a reproduced video signal as a means for embodying a video signal used to generate a vertical synchronizing pulse. large. In particular, VTR
By using the video signal and the audio signal reproduced in the apparatus, the mitigation circuit can be configured as an internal circuit of the apparatus.

Effect of Claim 3: In addition to the effects of Claims 1 and 2, since the effect of the coil L1 or L2 conventionally implemented in a television with a built-in video is too severe, a sufficient effect can be obtained. According to the present invention, the effect of the coil L1 or L1 is large.
In order to limit the effect of the second embodiment to the one that provides the primary effect, the selection of the mounting angles and the inductance values of the coils L1 and L2 becomes rough, and unnecessary buzz is eliminated by the secondary reduction circuit means. Variations between products are reduced and are ensured.

Effect of Claim 4 In addition to the effect of Claim 3, the buzz mitigation circuit can be configured even if the buzz remaining as a result of the buzz elimination by the coil is either positive or negative. However, a positive polarity simplifies the circuit configuration.

According to the fifth aspect of the present invention, there is provided a television with a built-in VTR having the buzz reduction effect of the first to fourth aspects.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of a vertical cycle buzz mitigation circuit according to the present invention.

FIG. 2 is a diagram showing an embodiment of an embodiment of the circuit shown in FIG. 1;

FIG. 3 is a diagram showing another embodiment of a specific circuit of the circuit shown in FIG. 1;

FIG. 4 is a diagram showing an output waveform in a main part of the circuit shown in FIG. 1;

FIG. 5 is a diagram showing an example of a conventional reproducing circuit which takes a countermeasure against vertical period buzz.

FIG. 6 is a diagram illustrating a waveform of a reproduced linear audio output signal in which buzz has a negative polarity.

[Explanation of symbols]

1, 1 'audio amplifier circuit, 2, 2' audio output amplifier circuit, 3 synchronizing signal separation circuit, 4 integration circuit, 5 phase inversion circuit, 6 waveform shaping circuit, 7 buzz reduction circuit , C
1, C1 ', C2, C2', C3, C4, C5, C6 ...
Capacitor, L1, L1 ', L2, L2' ... coil, Q
1, Q3, Q5: transistor, Q2, Q4: amplifier,
R1, R1 ', R2, R2', R3, R4, R5, R
6, R7, R8 ... resistance.

Claims (5)

[Claims] 1. A vertical cycle buzz reducing circuit for reducing a vertical cycle buzz included in an audio signal reproduced by a magnetic head and generated by a vertical leak magnetic flux from a deflection coil of a television. Vertical synchronizing pulse generating means for generating a vertical synchronizing pulse from a video signal, and a buzz reducing circuit which operates during a period based on the vertical synchronizing pulse generated by the vertical synchronizing pulse and acts on a vertical cycle buzz of the audio signal. A vertical cycle buzz mitigation circuit characterized by comprising: 2. The vertical cycle buzz reducing circuit according to claim 1, wherein a reproduced video signal is used as a video signal from which the vertical leakage magnetic flux is generated. 3. The audio signal reproducing circuit provided at a stage preceding the buzz reducing circuit includes a coil for picking up a vertical leakage magnetic flux from a deflection coil of the television, and the coil controls the vertical period in the audio signal. 3. The vertical cycle buzz mitigation circuit according to claim 1, wherein a signal for canceling buzz is generated. 4. The vertical cycle buzz mitigation circuit according to claim 3, wherein said coil is adjusted so that a buzz component in an audio signal affected by said coil has a positive polarity. 5. A video built-in television having a vertical cycle buzz mitigation circuit comprising a VTR having the vertical cycle buzz mitigation circuit according to claim 1 as a component.