JPS60126972A - Television receiver - Google Patents

Abstract

PURPOSE:To stabilize vertical deflection and stabilize a screen by detecting whether an additional pulse generated in a vertical synchronizing signal is present or not from the output signal of a synchronous separating circuit, and supplying a counted-down vertical synchronizing signal and a vertical synchronizing signal obtained from the output signal of the synchronous separating circuit to a vertical driving circuit selectively according to said detection result. CONSTITUTION:When a VTR is switched to a special reproduction mode, an additional pulse is generated for the vertical synchronizing signal generated in a reproduced signal to obtain an impulsive additional waveform W in a frequency signal Vf, and the crest value becomes higher than reference voltages VREF11 and VREF2. Consequently, a high-level output signal Vf'' is obtained from a voltage comparator 23 and a high level output signal Vf''' is obtained from a voltage comparator 24. A counter 31 is reset with an output signal Vf<4>' and terminals (b) and (c) of a switch SW1 are connected electrically to drive the input of a vertical driving circuit 34 by the rising of the additional waveform W of the output of the voltage comparator 23, through a buffer amplifier.

Description

[Detailed description of the invention] [Technical field] The present invention relates to a receiver such as a television.

[Background technology]

On the other hand, in recent years, a method has been proposed for television receivers in which a horizontal synchronization signal and a vertical synchronization signal are obtained from the output signal of a synchronization separation circuit using a counting circuit, that is, a countdown synchronization processing method.

In a television receiver using such a countdown synchronization processing method, the vertical oscillation circuit is omitted (therefore, the complicated work of adjusting the free-running oscillation frequency of the vertical oscillation circuit, which was conventionally necessary) can be omitted.

By the way, the nominal frequency width of the horizontal synchronization signal in NTSO broadcasting received by a television receiver is 15750H.
z, which is the nominal frequency of the vertical synchronization signal.By the way, a television receiver can be used for many purposes, not just receiving broadcast waves and displaying a screen. For example, a television receiver may be connected to a magnetic recording/reproducing device (hereinafter referred to as a VTR) to reproduce video and audio signals recorded on the magnetic tape. When the VTR is in the normal playback mode, the plurality of recording tracks sequentially formed on the magnetic tape match the trajectories of the first and second playback heads. Then, nine color video signals and horizontal and vertical synchronization signals are obtained for each field from the first and second playback heads, and a stable screen is displayed on the television receiver.

That is, when the VTR is in the normal playback mode, the frequency width of the horizontal synchronization signal and the frequency fv of the vertical synchronization signal included in the video signals detected by these playback heads have the above-mentioned ratio (f, that is, 262.5). Therefore, the synchronization condition is satisfied in horizontal and vertical deflection, and a stable screen can be obtained.

However, VTRs have so-called special playback functions such as still image playback, slow motion playback, and high speed playback. Taking high-speed playback as an example, as the running speed of the magnetic tape increases, the trajectories of the first and second playback heads begin to trace a plurality of adjacent recording tracks. Therefore, the recording trunk and the trajectories of the first and second playback heads no longer match.

Furthermore, as is well known, since a plurality of recording trunks are arranged diagonally with respect to the longitudinal direction of the magnetic tape, the starting point of two adjacent recording trunks is equivalent to 1.5 times in terms of time.
There is a distance difference of H (H is 15,750 seconds, that is, synchronization of the horizontal synchronization signal). Similarly, the distance between the starting point and the ending point of one recording trunk has a length of 262.5 hours in terms of time.

On the other hand, one playback head can trace N adjacent recording tracks during high-speed playback of a VTR. The distance between the starting point and the ending point of this high-speed trace is 2'62.5H-N (N-1)X 1.5H when converted to 1 hour.
becomes. Therefore, during high-speed playback of a VTR, one playback head traces N recording tracks, and as a result, the ratio of the frequency of the horizontal synchronization signal and the vertical synchronization signal included in the video signal detected by the playback head is as described above. 262.5
becomes smaller than the value.

Therefore, during high-speed playback of such a VTR, the VTR
If the ratio of the horizontal and vertical deflection frequencies of the television receiver connected to it is held at the above-mentioned value of 262.5, the vertical synchronization of the high-speed trace of the VTR and the vertical synchronization of the television receiver becomes inconsistent.

On the other hand, as a matter of course, in a VTR, a video signal, horizontal synchronization signal, vertical synchronization signal, etc. recorded on one recording track can only be reproduced by one reproduction head. Therefore, during high-speed playback of a VTR, while one playback head shifts from the first recording track to the next adjacent recording track, normal video signals and synchronization signals cannot be obtained, and the output signal of the playback head is only noise. becomes.

On the other hand, during such high-speed playback, one playback head performs two traces on 2N adjacent recording tracks, and this playback head performs two traces between the first and second traces. It is necessary to detect the vertical synchronization signal. However, while the playback head shifts from the first trace to the second trace, no vertical synchronization signal is obtained from the playback head and only noise is obtained, resulting in a synchronization error and the screen on the television receiver being distorted. Or it starts to flow downward.

To prevent this phenomenon, when playing back a VTR at high speed, V
TR is a pulse signal with a time width corresponding to 3 to 5 horizontal synchronization signals and a period of 262.5H-(N-1)Xl, 5H between the horizontal synchronization signal and the vertical synchronization signal. Add to equivalent pulse. This additional pulse is added only during special reproduction, and is not recorded on the magnetic tape.

When a general television receiver having a horizontal oscillation circuit and a vertical oscillation circuit receives a video signal from a VTR during high-speed playback, the oscillation frequency of the horizontal oscillation circuit is the frequency of the horizontal synchronization signal in this video signal. The oscillation frequency of the vertical oscillation circuit matches the frequency of the additional pulse in this video signal. Therefore, the ratio of the horizontal deflection frequency to the vertical deflection frequency of this television receiver is smaller than 262.5,
A match is obtained between the vertical synchronization of the VTR's high-speed trace and the vertical synchronization of the television receiver.

On the other hand, when a television receiver using the conventional countdown processing method is connected to a VTR, the VTR will respond with a constant count regardless of whether the VTR is in normal playback mode or special playback mode.
A vertical output signal is formed by counting horizontal synchronization signals from the TR.

Therefore, in this case, the ratio of the horizontal deflection frequency to the vertical deflection frequency of the television receiver using the countdown processing method is 2.
62.5, a synchronization error occurs and the screen of the television receiver moves upward or downward.

OBJECTS OF THE INVENTION It is an object of the present invention to provide a television receiver that can display a stable screen on a picture tube even during special playback of a VTR.

[Summary of the invention]

A brief summary of the invention disclosed in this application is as follows. That is, a sync separation circuit for obtaining a horizontal sync signal and a vertical sync signal, a phase detection circuit to which the horizontal sync signal from the output of the sync separation circuit is applied to one input terminal, and an output signal of the phase detection circuit. a voltage controlled oscillation circuit whose oscillation frequency is controlled by a voltage controlled oscillation circuit; a 1/2 frequency divider and a 11525 frequency divider connected to the output of the voltage controlled oscillation circuit; a low pass filter connected to the output of the synchronous separation circuit; first and second voltage comparison circuits connected to the output of the low-pass filter;
a phase comparator, a horizontal drive circuit, and a vertical drive circuit to which the output of the frequency divider and the output of the first voltage comparison circuit are applied, and the output signal of the 1/2 frequency divider is subjected to the phase detection. The other input terminal of the circuit is made responsive and the input of the horizontal drive circuit is driven by the output signal of the 172 frequency divider, and the phase of the output signal of the 11525 frequency divider and the output signal of the first voltage comparator circuit are adjusted. When the phases match, the input of the vertical drive circuit is controlled by the output signal of the phase comparator.
The second voltage comparator is made to respond to the output signal of the 1525 frequency dividing circuit, and when the output of the synchronization separation circuit includes an additional pulse during special reproduction of the VTR, the second voltage comparator detects the presence of this additional pulse, By controlling this detection output, the input of the vertical drive circuit is made to respond to the additional pulse,
This achieves the stabilization of the screen, which is the object of the present invention.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. 1 to 4.

First, regarding Fig. 1, the horizontal synchronizing signal sieve and the vertical synchronizing signal f
The causes of fluctuations in the frequency ratio with respect to v will be described below.

In each of the recording tracks OH, OH, . Also, 0 is an audio signal track, and D is a control signal track.

Note that the magnetic tape T runs in the direction of arrow a.

When the VTR is in normal playback mode, recording tracks OH,
and the trajectory A of the first playback head (not shown) match,
A detection output signal for one field is obtained. Furthermore, the recording track OH and the locus of the second reproducing head (not shown) match, and a detection output signal for one primary field is obtained. The output points of each recording trunk OH,,OH,...oHn have a time difference (carrier shift) of 1.5H in terms of time, and it is assumed that the so-called H is rounded off. . And recording track OH,,OH.

One frame of screen is displayed on a picture tube of a television receiver, which will be described later, by the reproduction signal obtained from the reproduction head, that is, the detection output signal of the first and second reproduction heads.

By the way, to take the case of high-speed reproduction as an example, the magnetic tape T is run at high speed in the direction of arrow a, and the trajectory A of the first reproduction head is
As shown by the shaded area A' in FIG. 1, a plurality of recording tracks are traced. The second reproducing head also traces a plurality of recording trunks, as shown by the shaded area B' in FIG.

During high-speed playback as described above, a playback signal f having a waveform as shown in FIG. 2 is sent from the VTR to the television receiver.
, is supplied. In other words,■.

is a vertical synchronizing pulse, vP' is an equivalent pulse, and ■,'' are additional pulses.The additional pulse vP' supplied from the VTR during special playback of the VTR corresponds to 3 to 5 periods of the horizontal synchronizing pulse H1. In addition, the second
The video signal ■i indicated by a dotted line in the figure is reproduced in the normal reproduction mode.

The distance from the starting point to the ending point of one recording track (one field) is 262.5H when converted into time. As shown in FIG. 1, when one playback head diagonally traces three adjacent recording tracks during high-speed playback of a VTR, the distance between the starting point and end point of this high-speed tracing is 262. 5) (-(3-1) Xl, 5
H=259.5H. Then, the reproduced signal f shown in FIG. 2 is supplied from the VTR to the input terminal (usually a UHF antenna terminal) of the television receiver.

First, the circuit operation during normal broadcast wave reception will be described with reference to FIG.

1 is a receiving antenna, and a received signal f1 is supplied to a high frequency amplification circuit 2. Among the received signals f, the selected signal f is supplied to the mixing circuit-3.

The local oscillation circuit 4 generates a local frequency f, and supplies it to the mixing circuit 3. The mixing circuit 3 receives the frequency signals f,
Perform frequency mixing of f, and generate a frequency signal f4 of the difference between the two.
is obtained as an intermediate frequency signal.

A so-called color television signal fv is obtained from the intermediate frequency amplification and video detection circuit 5. The color television signal fv is
Audio circuit system (filter circuit.

6, video signal amplification system 8,
The color signal reproduction yarn 10 is supplied to the synchronous separation circuit 11. Audio is obtained by an audio circuit system 6 and a speaker 7. A video signal (Y signal) Y is obtained by the video signal amplification system 8 and is supplied to the picture tube 9 . Color difference signals of R (red), G (green), and B (blue) are obtained by the color signal reproduction thread 10 and supplied to the picture tube 9.

By the way, the synchronous separation circuit 11 receives the color television signal fV
The horizontal synchronizing signal fH is obtained from the horizontal synchronizing signal fH. The horizontal synchronization signal f□ is supplied to each circuit making up the synchronization signal processing system 21.

The synchronization signal processing system 21 can be roughly divided into a circuit system A for performing horizontal scanning and a circuit system B for performing vertical scanning.

The circuit system A performs the following circuit operation.

That is, the detection circuit 22 supplies the voltage controlled oscillation circuit 25 with a control signal vc necessary for automatic frequency control. This detection circuit 22 is for comparing the phases of two frequency signals and obtaining a voltage signal whose level changes in accordance with the phase difference. The voltage controlled oscillation circuit 25 receives a frequency signal f of 2fH. oscillates and supplies it to the 1/2 frequency divider 27 and the 17525 frequency divider 26.

From the 1/2 frequency divider 27, a frequency signal f1t with a frequency width is output.
' is obtained and supplied to the horizontal drive circuit 28.

The horizontal drive circuit 28 generates a sawtooth wave signal fT with a frequency width and supplies it to the horizontal deflection coil L.

Further, the output signal fT' of the horizontal drive circuit 28 is supplied to a flyback circuit 29, and the high voltage output Hv is supplied to the anode (not shown) of the picture tube 9. Furthermore, a frequency component H'' of frequency f□ is obtained from the flyback circuit 29 and fed back to the detection circuit 22. As a result, a control signal ■ obtained from the detection circuit 22 is obtained.

The voltage level corresponds to the phase difference between the horizontal synchronizing signal sieve and the frequency of the frequency signal fH'', and is equal to one, and the frequency signal Hv is controlled by the voltage level difference.

Next, the circuit operation of circuit system B will be described.

The low-pass filter 12 includes resistors R, l, capacitor 01
A frequency signal f of 60 Hz is obtained.

The frequency signal f is supplied to each positive phase input terminal of the voltage comparators 23 and 24. During normal broadcast radio wave reception, no additional pulses are formed in the vertical synchronization signal, and the number of pulses in the horizontal synchronization signal does not decrease. And the frequency signal V
The voltage level of f is the reference voltage vKl) FI S ■RWF
2 is set so that VREFI<■f<<REF2.

As a result, the voltage comparator 23 outputs a high level output signal vf
" is obtained, and no high level output signal is obtained from the pressure comparator 24. The output signal f" is supplied to the fixed terminal of the phase comparator 30 and the switch SW.

On the other hand, the other input terminals of the 5-phase comparator 30 have 2fH”&
A 60 Hz frequency signal (8) divided into 11,525 is supplied. Note that the frequency signal f8 is transmitted by the switch SW! It is also supplied to the fixed contact a.

During normal broadcast reception, the phases of one frequency multiple V, , Vf" are the same, and the counter 31 is switched to the reset state by the comparison output. When the counter 31 is in the reset state, its operation mode is a latch circuit. The movable contact C of the switch SW1 is switched to the fixed contact a by the output signal o of the latch circuit 32.

The output signal vs of the 11525 frequency divider 26 is the switch 5W.
The output signal V8' of the buffer amplifier 33 is supplied to the vertical drive circuit 34 through the IV.A sawtooth wave signal V8 with a frequency of 60 Hz is obtained, and the vertical deflection coil L, is supplied.

Therefore, when receiving normal broadcast waves, horizontal and vertical deflection is performed without frequency error.

You can get a stable screen.

Next, the circuit operation when a VTR reproduction signal is supplied will be described.

When the VTR is in normal playback mode, the playback signal is similar to normal broadcast radio waves. Therefore, when a reproduction signal is supplied to a television receiver, in the normal reproduction mode, the same circuit operation as described above will be performed.
You can get a stable screen.

Next, the circuit operation of the synchronous signal processing system when the VTR is switched to the special reproduction mode will be described.

In this case, an additional pulse is formed in the vertical synchronization signal formed in the reproduced signal. By forming the additional pulse, a pulse-like additional waveform W as shown in FIG. 2 appears on the frequency signal f. In addition, the dotted line part shown in Figure 2 is 5
This shows the waveform of one frequency multiple V (when receiving normal broadcast radio waves and when the VTR is operating in normal playback mode).

As the additional waveform W appears in the frequency signal vf, the peak value of the frequency signal f becomes the reference voltage R1, Fl.

It becomes a higher level than vREF2. Therefore, a high level output signal f' is obtained from the voltage comparator 23, and a high level output signal f' is obtained from the voltage comparator 24. The counter 31 is switched to the reset state by the output signal f"', terminals S and C of the switch SW1 are electrically connected, and the rising edge of the 7JD waveform W of the output of the voltage comparator 23 is passed through the buffer amplifier 33. The vertical drive circuit 340 input is driven by.

For the above reasons, when the television receiver according to this embodiment receives the signal fP from the VTR during high-speed reproduction, the frequency of the horizontal sawtooth current obtained from the horizontal drive circuit 28 is equal to the horizontal frequency included in this signal f. The frequency of the vertical sawtooth current obtained from the vertical drive circuit 34 matches the frequency of the synchronous pulse H1, and the frequency of the additional pulse 2' included in this signal f. Therefore, the ratio of the horizontal deflection frequency to the vertical deflection frequency of this television receiver is 26
2.5, and the vertical synchronization of the high-speed trace of the VTR matches the vertical synchronization of the television receiver.

Similarly, during high-speed playback of a VTR, as shown in FIG.
'f! Due to this, several horizontal synchronizing pulses HP are missing from the detection output signal obtained from the first reproducing head during the gap between the recording tracks OH.

However, the automatic phase control circuit 22. ! The pressure controlled oscillator circuit 25 and the 1/2 frequency divider circuit 27 are so-called PLL (Phase Locked) circuits with a large electrical moment of inertia.
Loop) circuit, the frequency of the horizontal sawtooth current fHv finally obtained from the water tap drive circuit 28 does not vary even if the horizontal synchronizing pulse HP is slightly missing.

That is, in the case of VTR1J''-special reproduction mode, vertical deflection is performed not by obtaining a vertical synchronizing signal counted down from a horizontal synchronizing signal sieve, but by using a vertical synchronizing signal obtained in an analog manner.

(1) Detect the presence or absence of an additional pulse formed in the vertical synchronization signal from the output signal of the synchronization separation circuit, and count down the vertical synchronization signal based on this detection result and the output signal of the synchronization separation circuit. By selectively supplying the vertical synchronization signal to the vertical drive circuit, when an additional pulse is formed in the vertical synchronization signal, the vertical synchronization signal obtained from the output signal of the synchronization separation circuit is supplied to the vertical drive circuit. The effect of stabilizing the screen is achieved by stabilizing the vertical deflection.

(2) The switching operation in (1) above is automatically performed during special playback of V'TR.

(3) - The circuit configuration is simple and there are no external parts, making it easy to integrate into a semiconductor integrated circuit.

Above, the invention made by the present inventors has been specifically explained based on the examples thereof, but the present invention is not limited to the above examples, and can be modified in various ways without departing from the gist thereof. Needless to say, it is.

For example, instead of the counter 31 and the latch circuit 32, a switch SW may be switched by the output signal f''.Furthermore, although the switch SW is shown as a switch having a mechanical structure, the switch SW may be an analog switch. An electronic switch such as a switch may also be used.

[Application field]

In the above description, a case has been described in which the invention made by the present inventors is applied to a television receiver, which is the background field of application, but the invention is not limited thereto.

For example, it can be applied to deflection circuits for VTRs, video cameras, etc., and is particularly effective when configuring VTRs, video cameras, etc. with semiconductor integrated circuits.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing the relationship between the recording track and the trajectory of the playback head during special playback in a VTR, FIG. 2 is a waveform diagram showing an example of additional pulses during special playback, and FIG. FIG. 4 is a block diagram showing a non-embodiment of the applied television receiver, and FIG. 4 is a waveform diagram of the frequency signal vf for explaining the operation of the same circuit. 21... Synchronous signal processing system, 23124... Operational amplifier circuit, 25... Voltage controlled oscillator, 26... Bow 1525
Frequency divider, 31... Phase comparator, 34... Vertical drive circuit, SW,... Switch, Import... Horizontal synchronizing signal, f
v...Color television signal, vf'', ■f'''...output signal, Vs...phase comparison output, ■T...vertical sawtooth signal.

Claims (1)

[Claims] 1. A sync separation circuit for obtaining a horizontal sync signal and a vertical sync signal, a phase detection circuit to which the horizontal sync signal from the output of the sync separation circuit is applied to one input terminal, and a phase detection circuit for the phase detection circuit. A voltage controlled oscillation circuit whose oscillation frequency is controlled by an output signal, a 1/2 frequency divider and a 11525 frequency divider connected to the output of the voltage controlled oscillation circuit, and a low pass filter connected to the output of the synchronous separation circuit. , first and second voltage comparison circuits connected to the output of the low-pass filter, - a phase comparator to which the output of the 11525 frequency divider and the output of the first voltage comparison circuit are applied, and a horizontal drive. circuit and a vertical drive circuit, the other input terminal of the phase detection circuit is made to respond to the output signal of the 172 frequency divider, and the input of the horizontal drive circuit is driven by the output signal of the 172 frequency divider. , when the phase of the output signal of the 17525 frequency divider and the phase of the output signal of the first voltage comparison circuit match, the input of the vertical drive circuit is controlled by the output signal of the phase comparator to the 11525 frequency divider. If the output of the synchronization separation circuit includes an additional pulse during special playback of the VTR, the second voltage comparator examines the presence of this additional pulse and calculates the output of this detection output. A television receiver characterized in that the input of the vertical drive circuit is controlled to respond to an additional pulse.