JP3743143B2 - Television receiver - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a television receiver that detects a reference pulse provided outside an effective screen of a video signal, for example, and compensates for individual differences and aging of a cathode ray tube (CRT).
[0002]
[Prior art]
For example, a television receiver has been proposed in which a reference pulse is inserted outside the effective screen of a video signal to compensate for individual differences or aging of cathode ray tubes. That is, in FIG. 2, video signals of three primary colors (R, G, B) from a demodulation circuit (not shown) are supplied to input terminals 21R, 21G, 21B. These video signals are supplied to the switch circuits 22R, 22G, and 22B, and a reference pulse of a predetermined level is inserted at an arbitrary position outside the effective screen according to a control signal from the terminal 20, for example.
[0003]
The three primary color video signals into which these reference pulses are inserted are supplied to the drive circuits 24R, 24G, and 24B through the level shift circuits 23R, 23G, and 23B, respectively. Here, for example, in the drive circuit 24R, the supplied video signal is amplified by the transistor Q and supplied to the cathode electrode of the cathode ray tube (CRT) 25 through the transistor P. Since the drive circuits 24G and 24B have the same configuration as the drive circuit 24R, detailed illustration is omitted.
[0004]
Furthermore, currents flowing through the transistors P of these drive circuits 24R, 24G, and 24B are taken out through the switches 26R, 26G, and 26B, respectively. Here, the switches 26R, 26G, and 26B are turned on, for example, at the timing when the reference pulse from the terminal 20 is inserted. As a result, cathode currents corresponding to the respective reference pulses inserted into the three primary color video signals are extracted from the switches 26R, 26G, and 26B.
[0005]
These cathode currents are fed back to the level shift circuits 23R, 23G, and 23B through the detection circuits 27R, 27G, and 27B, and control is performed so that, for example, the black level of the three primary color video signals is equal to the height of the reference pulse. Thereby, for example, automatic cut-off adjustment is performed. That is, in the apparatus of FIG. 2, for example, a reference pulse inserted outside the effective screen of the video signal is detected, so that compensation for individual differences in the cathode ray tubes, secular change, and the like is performed.
[0006]
[Problems to be solved by the invention]
Incidentally, in the above-described apparatus, the reference pulse inserted into the video signal is a pulse signal having a predetermined luminance level. Therefore, if such a reference pulse is inserted into the effective screen, it may be displayed as a bright line in the horizontal direction and disturb the viewing of the video signal. Therefore, as described above, the reference pulse is inserted, for example, outside the effective screen of the video signal. However, the insertion position is likely to fluctuate due to disturbance of the synchronization signal, phase change, or the like.
[0007]
That is, in the above-described apparatus, for example, vertical deflection in the cathode ray tube (CRT) 25 is performed as shown in FIG. In FIG. 3, for example, a video signal from a demodulation circuit (not shown) is supplied to a vertical synchronization separation circuit 31, and a vertical synchronization signal in the video signal is separated. The separated vertical sync separation signal is supplied to the V countdown circuit 32. In the V countdown circuit 32, for example, interpolation is performed for the lack of the signal separated by the vertical synchronization separation circuit 31.
[0008]
Further, the vertical synchronizing pulse from the V countdown circuit 32 is supplied to the deflection circuit 33 to form a so-called sawtooth vertical deflection signal (voltage). That is, in FIG. 4, for example, a vertical synchronization separation signal as shown in FIG. 4A from the vertical synchronization separation circuit 31 is supplied to the V countdown circuit 32 to form a vertical synchronization pulse as shown in FIG. 4B. . Then, a sawtooth vertical deflection signal (voltage = VD) as shown in FIG. 4C is formed from this vertical synchronizing pulse.
[0009]
This vertical deflection signal (voltage) is supplied to the deflection drive circuit 34, and for example, the voltage signal is converted into a current. The vertical deflection signal converted into this current is supplied to the vertical deflection coil (not shown) of the cathode ray tube 25 to perform vertical deflection. Thus, vertical deflection of the electron beam formed by the video signal supplied to the cathode electrode of the cathode ray tube 25 is performed, and an image is displayed. Horizontal deflection is performed separately.
[0010]
In this case, for example, when the reception channel is switched at time t1 in FIG. 4 and the vertical synchronization phase changes significantly, the V countdown circuit 32 initially lacks the vertical synchronization signal of the previous video signal. As a result, the vertical synchronization signal of the new video signal is ignored and interpolation is performed. However, if the vertical synchronizing signal does not recover within a predetermined time, for example, at time t2, the V countdown circuit 32 starts to form a vertical synchronizing signal in accordance with the vertical synchronizing signal of the new video signal.
[0011]
Therefore, in this case, two vertical synchronizing signals (pulses) are generated at a short interval as shown in FIG. 4B, for example, at a time near time t2 immediately after the vertical synchronizing signal of the new video signal. It is formed (a) continuously. Then, by forming a vertical deflection signal (voltage) from such a vertical synchronizing signal (pulse), the vertical deflection signal (voltage) thus formed has a sawtooth apex of 2 as shown in FIG. One continuous shape (b) is obtained.
[0012]
However, in the above-described apparatus, for example, an integration effect generally works in a vertical deflection system of a cathode ray tube (CRT) 25. Therefore, a waveform of a deflection current actually acting on an electron beam is a waveform as shown in D of FIG. Will be dull (c). In particular, in a deflection system using a charge pump type circuit, when the vertical synchronization signal (pulse) continues at a short interval as described above, the synchronization pulse is supplied while the pump-up is not sufficient. As a result, the peak of the waveform drops.
[0013]
When the deflection is performed with the vertical deflection signal (voltage) as shown in FIG. 4D, the vertical deflection is temporarily stopped at the dull portion of the waveform. On the other hand, when the reference pulse is formed with reference to the vertical synchronization pulse shown in FIG. 4B, the reference pulse (d) is generated even when the vertical deflection is stopped as shown in E of FIG. . For this reason, in the above-described apparatus, a horizontal bright line by the reference pulse is displayed in the effective screen of the cathode ray tube (CRT) 25.
[0014]
That is, in FIG. 5, for example, when the deflection is performed with a normal deflection current (left side) as shown in A of FIG. 5, the reference pulse is inserted in the portion outside the effective screen of the cathode ray tube 25 (right side). The display is hidden. On the other hand, if the waveform of the deflection current (left side) is dull as shown in B of the figure, a reference pulse inserted at a predetermined timing from the second vertical synchronization signal (pulse) is displayed in the effective screen. It will be displayed.
[0015]
This application has been made in view of the above points, and the problem to be solved is that in the conventional apparatus, a cathode ray tube is caused by a disturbance of a synchronization signal or a phase change at the time of switching of a reception channel. In some cases, a reference pulse is formed in the effective screen, and a horizontal bright line due to the reference pulse is displayed in the effective screen, which may interfere with the viewing of the video signal.
[0016]
[Means for Solving the Problems]
For this reason, in the present invention, the generation of the reference pulse related to the first vertical synchronization drawn after the vertical synchronization of the video signal is disturbed is stopped. Reference pulses are prevented from being formed in the effective screen of the cathode ray tube due to disturbance of the sync signal or phase change at the time of switching, etc., and horizontal bright lines are displayed in the effective screen to allow viewing of the video signal. It can be prevented from being disturbed.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
That is, in the present invention, in a television receiver having means for providing a predetermined reference pulse outside the effective screen of the video signal and detecting a signal by the reference pulse outside the effective screen of the picture tube and performing a predetermined adjustment. Means are provided for stopping the generation of a reference pulse related to the first vertical synchronization that is pulled in after the vertical synchronization of the signal is disturbed.
[0018]
【Example】
Hereinafter, the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing a configuration of a main part of an example of a television receiver to which the present invention is applied.
[0019]
That is, in FIG. 1, a set-reset type flip-flop 1 is provided. The first vertical sync separation signal ((a) pulse indicated by B in FIG. 4) that is drawn after the vertical synchronization of the video signal detected in the V countdown circuit is disturbed is flip-flops through the control terminal 2. 1 to the set terminal (S). Further, a control signal of a reference pulse formed at a predetermined timing from the above vertical synchronization signal (pulse) is supplied to the control terminal 3, and this control signal is supplied to the reset terminal (R) of the flip-flop 1 through the inverter 4. .
[0020]
Then, the signal obtained at the output terminal (QX) of the flip-flop 1 is supplied to the AND circuit 5 and synthesized with the control signal from the control terminal 3 described above. As a result, the AND circuit 5 normally detects the control signal from the control terminal 3 and, for example, pulls in the vertical sync signal (the vertical sync pulse is reset by the vertical sync separation signal of the input signal). Thus, only the first control signal after detection has been performed is masked.
[0021]
Further, in FIG. 1, video signals of three primary colors (R, G, B) from a demodulation circuit (not shown) are supplied to input terminals 11R, 11G, 11B. These video signals are supplied to the switch circuits 12R, 12G, and 12B. The switch circuit 12R, 12G, 12B is supplied with a control signal formed by the above-described AND circuit 5, for example, masked only for the first signal after detection is performed, and the effective signal is out of the effective screen according to this control signal. A reference pulse of a predetermined level is inserted at an arbitrary position.
[0022]
The video signals of the three primary colors with the reference pulses inserted are supplied to the drive circuits 14R, 14G, and 14B through the level shift circuits 13R, 13G, and 13B, respectively. Here, for example, in the drive circuit 14R, the supplied video signal is amplified by the transistor Q and supplied to the cathode electrode of the cathode ray tube (CRT) 15 through the transistor P. Since the drive circuits 14G and 14B have the same configuration as the drive circuit 14R, detailed illustration is omitted.
[0023]
Further, currents flowing through the transistors P of these drive circuits 14R, 14G, and 14B are taken out through the switches 16R, 16G, and 16B, respectively. Here, the switches 16R, 16G, and 16B are turned on, for example, at the timing when the reference pulse from the AND circuit 5 is inserted. As a result, cathode currents corresponding to the respective reference pulses inserted into the three primary color video signals are extracted from the switches 16R, 16G, and 16B.
[0024]
These cathode currents are fed back to the level shift circuits 13R, 13G, and 13B through the detection circuits 17R, 17G, and 17B, and control is performed so that, for example, the black level of the three primary color video signals is equal to the height of the reference pulse. Thereby, for example, automatic cut-off adjustment is performed. That is, also in the apparatus of FIG. 1, for example, by detecting a reference pulse inserted outside the effective screen of the video signal, compensation for individual differences and secular change of the cathode ray tube is performed.
[0025]
In this apparatus, for example, only the first control signal after detecting that the vertical synchronization signal is drawn (the vertical synchronization pulse is reset by the vertical synchronization separation signal of the input signal) is masked, for example, The reference pulse (d) formed while the vertical deflection is stopped at E of 4 can be eliminated, and the horizontal bright line by this reference pulse is displayed in the effective screen of the cathode ray tube (CRT). The fear can be resolved.
[0026]
In the above-described apparatus, for example, all the reference pulses during a period in which the vertical synchronization separated signal and the vertical synchronization pulse of the input signal do not match can be masked. In this case, the level shift circuit 13R that is feedback-controlled, The levels of 13G and 13B become unstable, and for example, the video signal level may be controlled to the maximum or minimum limit value.
[0027]
Further, in the above-described apparatus, the reference pulse is formed at a predetermined timing from, for example, the vertical synchronization pulse. Therefore, for example, even during a period in which the vertical synchronization separation signal of the input signal and the vertical synchronization pulse do not coincide with each other, The reference pulse formed at this timing is always inserted outside the effective screen of the cathode ray tube (CRT).
[0028]
Therefore, in this device, by stopping the generation of the reference pulse related to the first vertical synchronization that is pulled in after the vertical synchronization of the video signal is disturbed, the synchronization signal is disturbed or the phase is changed when the receiving channel is switched. Thus, it is possible to prevent the reference pulse from being formed in the effective screen of the cathode ray tube, and to prevent the horizontal bright line from being displayed in the effective screen and obstructing the viewing of the video signal. .
[0029]
As a result, in the conventional apparatus, a reference pulse may be formed in the effective screen of the cathode ray tube due to a disturbance of the synchronization signal or a phase change at the time of switching the reception channel. However, according to the present invention, these problems can be easily solved.
[0030]
Thus, according to the above-described television receiver, in a device having means for providing a predetermined reference pulse outside the effective screen of the video signal and detecting a signal by the reference pulse outside the effective screen of the picture tube and performing a predetermined adjustment Prevents the formation of reference pulses in the effective screen of the cathode ray tube by providing means to stop the generation of reference pulses related to the first vertical synchronization that is pulled in after the vertical synchronization of the video signal is disturbed In addition, the horizontal bright line is displayed in the effective screen so that the viewing of the video signal is not hindered.
[0031]
【The invention's effect】
Therefore, according to the first aspect of the present invention, the generation of the reference signal related to the first vertical synchronization drawn after the vertical synchronization of the video signal is disturbed is stopped, so that Reference pulses are not formed in the effective screen of the cathode ray tube due to disturbances or phase changes, and horizontal bright lines are displayed in the effective screen so that viewing of the video signal is not hindered. It can be made.
[0032]
As a result, in the conventional apparatus, a reference pulse may be formed in the effective screen of the cathode ray tube due to a disturbance of the synchronization signal or a phase change at the time of switching the reception channel. However, according to the present invention, these problems can be easily solved.
[Brief description of the drawings]
FIG. 1 is a configuration diagram of a main part of an example of a television receiver to which the present invention is applied.
FIG. 2 is a configuration diagram of a main part of a conventional television receiver.
FIG. 3 is a configuration diagram of a vertical deflection system.
FIG. 4 is a diagram for explaining a reference pulse.
FIG. 5 is a diagram for explaining the operation;
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Set-reset type flip-flop, 2, 3 ... Control terminal, 4 ... Inverter, 5 ... AND circuit, 11R, 11G, 11B ... Input terminal of video signal of 3 primary colors (R, G, B), 12R, 12G, 12B ... switch circuit, 13R, 13G, 13B ... level shift circuit, 14R, 14G, 14B ... drive circuit, 15 ... cathode ray tube (CRT), 16R, 16G, 16B ... switch, 17R, 17G, 17B ... detection circuit

Claims (2)

Provide a predetermined reference pulse outside the effective screen of the video signal,
In a television receiver having means for detecting a signal by the reference pulse outside the effective screen of the picture tube and performing a predetermined adjustment,
A television receiver comprising means for stopping the generation of the reference pulse related to the first vertical synchronization drawn after the vertical synchronization of the video signal is disturbed. The television receiver according to claim 1.
A television receiver comprising means for stopping the generation of the reference pulse related to the first vertical synchronization drawn after the phase of the vertical synchronization of the video signal has changed significantly.

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