JPS6266789A - Flicker eliminating circuit television receiver - Google Patents

Abstract

PURPOSE:To distinguish vacant channel from VTR input by extracting either of VTR or vacant channel during broadcasting by the presence or absence of synchronizing signals in video signals and a television/VTR switching signal and changing the color of a picture. CONSTITUTION:As synchronizing signals are contained in video signals when selecting a channel in broadcasting, the synchronizing signals are separated and detected by a synchronizing signal separating circuit 2, and these are amplified by an amplifier circuit 3, and no output appears from a switching circuit 4. Then, a color generating circuit for VTR input 17 and a color generating circuit for vacant channel 18 are controlled to an unoperating state, and a normal image is projected in a screen. When the signals of VTR are inputted and synchronizing signals are detected, the video of VTR is projected instead of the color. When a vacant channel is selected, the color generating circuit for he vacant channel 18 is operated, and displayed in color different from VTR input.

Description

Detailed Description of the Invention "Industrial Application Field" The present invention eliminates screen flickering that occurs when selecting an empty channel on a television receiver and displays the screen in a single color, and when VTR input is selected. This invention relates to a flicker erasing circuit that displays a color different from that when an empty channel is selected until a video signal is received.

``Prior Art'' When a vacant channel is selected on a television receiver, an extremely disturbing flicker occurs across the entire screen.
Also, when VTR input is selected and rewinding or fast forwarding operations are performed, a similar noticeable flicker occurs, but conventional devices have not been equipped with a circuit to eliminate this.

``Problem to be Solved by the Invention'' This flickering gives an unpleasant feeling every time you change channels, so when selecting an empty channel or VTR input, this flickering should be immediately erased, and the screen should indicate whether it is just an empty channel or VTR input. There was a desire for something that could be distinguished by color.

"Means for Solving the Problems" The present invention was made in order to solve the above-mentioned problems, and includes a circuit for separating synchronization signals in a video signal, and an amplifier circuit for amplifying the separated synchronization signals. , a switch circuit that is turned on and off depending on the presence or absence of the output of this amplifier circuit, a VTR input color generation circuit that is controlled by this switch circuit, and a color generation circuit that is controlled by the output of the switch circuit and the TV/VTR switching signal. It consists of a channel color generation circuit.

"action" When selecting a channel that is currently being broadcast.

Since the video signal includes a synchronization signal, the synchronization signal (preferably the vertical synchronization signal) is separated and detected by the synchronization signal separation circuit, and is amplified by the amplifier circuit, so that it is not output from the switch circuit. Then, the color generation circuit for VTR input and the color generation circuit for empty channels are controlled to be inactive, and a normal image is displayed on the screen.

When the VTR input is selected and rewinding or fast forwarding, there is no synchronizing signal, so the synchronizing signal separation circuit does not detect the synchronizing signal, and the switch circuit outputs no output.

Then, the VTR input color generation circuit operates and the screen is displayed in a predetermined color.

When a VTR signal is input and a synchronization signal is detected, the VTR image is displayed in place of that color. Further, when an empty channel is selected, the empty channel color generation circuit operates and the color is displayed in a different color from that of the VTR input.

"Example" An embodiment of the present invention will be described below with reference to the drawings.

(1) is a video signal input terminal, this input terminal (1) is coupled to a synchronization signal pre-distributor circuit (2) for separating the vertical synchronization signal, and an amplifier circuit (3) for amplifying the separated synchronization signal. ) and is coupled to a switch circuit (4) which outputs an output when the synchronization signal disappears. This switch circuit (4)
is coupled to a black level generation circuit (5). This black level generation circuit (5) connects the base resistor (9) of the chroma matrix transistor (8) and the base resistor (11) of the video matrix transistor (10) via a transistor (6) and a collector resistor (7). ) is combined with Note that (12) and (13) are input terminals and output terminals for chroma signals, and (14) and (15) are input terminals and output terminals for video signals.

A VTR input color generation circuit (17) and an empty channel color generation circuit (18) are also connected to the switch circuit (4) via a switching circuit (16).

The switching circuit (16) has a transistor ( 20) When this transistor (20) has an output, the VTR input color generation circuit (
17) and disables the operation of the empty channel color generation circuit (
18), a transistor (21) and a resistor (
It consists of 22) (23) (24) (25) (26).

The VTR input color generation circuit (17) is a circuit that outputs one of the 3YK colors of R, G, and B (for example, green (G)) during fast forwarding, rewinding, etc. when the VTR is input. , the collector of the transistor (21) is connected to the transistor (28) via the base resistor (27), and the collector of this transistor (28) is connected to the emitter of the transistor (30) via the resistor (29). There is. Further, the base of the transistor (30) is connected to a color difference signal (
G-Y) input terminal (31) is connected to the emitter, a luminance signal input terminal (35) is connected to the emitter via resistors (32) (33) and a capacitor (34), and the collector is connected to the primary color (G) input terminal (35). An output terminal (36) is coupled thereto.

Similarly, the empty channel color generation circuit (18)
, G, and B, for example, blue (B).
) (40) (41) (42), capacitor (43
), the emitter of the transistor (38) has a brightness input terminal (35), the base has a color difference signal (for example, B-Y) input terminal (44), and the collector has a primary color (B-Y) input terminal (44).
) is coupled to the output terminal (45) of the terminal. In order not only to display colors on the screen but also to eliminate the noise, an audio mute circuit (mainly composed of a transistor (46) and a diode (47)) is installed at the output terminal of the switch circuit (4). 48) are combined. Then, from the volume control terminal (49) to the resistor (50) (51), the volume control transistor (52), and the attenuator (
The audio mute circuit (48) is coupled to the connection point of the resistors (50) and (51) in the volume control line that extends through the audio output terminal (54) via the audio output terminal (53). (5
5) is an audio signal input terminal.

In the above configuration, while a video signal is being sent to the video signal input terminal (1), the vertical synchronization signal is separated and detected in the synchronization signal separation circuit (2), and this is sent to the amplifier circuit (
3), the switch circuit (4) is turned off, and the black level generation circuit (5) and VTR input color generation circuit (17) are amplified.
, the empty channel color generation circuit (18), and the audio mute circuit (48) are all turned off. Therefore, in the black level generation circuit (5), the color signal of the chroma input terminal (12) is outputted to the output terminal (13) via the transistor (8), and the video signal of the video input terminal (14) is outputted to the output terminal (13) through the transistor (8).
0) and is output to the output terminal (15). Further, the VTR input color generation circuit (17) and the empty channel color generation circuit (18) also output the primary colors (G) and (B) to the output terminals (36) and (45) without being affected. Furthermore, the audio signal input to the audio signal input terminal (55) is also sent as is to the output terminal (54) via the attenuator (53).

Next, when VTR input is selected and during rewinding or fast forwarding, there is no video signal at the video signal input terminal (1), so there is no output from the sync signal separation circuit (2), and the amplifier circuit (3) There's no output either. Therefore, the switch circuit (4) is turned on and the output is turned on. The output of this switch circuit (4) causes the transistor (6) of the black level generation circuit (5) to
and the transistor (2) of the VTR input color generation circuit (17).
8) and the transistor (4G) of the audio mute circuit (48)
) turns on. When the transistor (6) of the black level generation circuit (5) is turned on, the bias voltages of the chroma matrix transistor (8) and the video matrix transistor (10) drop, resulting in a black level signal. Also VT
When the transistor (28) of the R input color generation circuit (17) is turned on, the emitter potential of the transistor (30) decreases, but the base potential does not change, so the base-emitter voltage increases, and the collector potential accordingly increases. Also go down.

Therefore, the primary color (G) is emphasized and output to the output terminal (36). Therefore, the screen is displayed in the primary color (G) applied to the output terminal (36).

Further, when the transistor (46) of the audio mute circuit (48) is turned on, the volume control signal passes through the diode (47) and the transistor (46) of the audio mute circuit (48), is released to the ground, and is connected to the attenuator (5).
In step 3), the volume is controlled and noise from the audio signal input terminal (55) is eliminated. When a VTR video signal is input, a synchronizing signal is detected and the video and audio are output normally.

Next, when an empty channel is selected, no video signal is sent, so the output is sent to the switch circuit (4).
In addition, a 12.5V switching signal is input to the TV/VTR input terminal (19) as TVI No. 3, and the transistor (
20) is turned on, the transistor (21) is also turned on, prohibiting the operation of the VTR input color generation circuit (17), and the transistor (3) of the empty channel color generation circuit (18) is turned on.
7) is turned on, and therefore the primary color (B) is output in an emphasized manner to the output terminal (45). Also in this case, the black level generation circuit (5) and the audio mute circuit (48) operate as they are.

In the embodiment, the VTR input color generation circuit (17)
and the color generation circuit (18) for empty channels are R, respectively.
, G, and B, but it is also possible to display intermediate colors that are different from each other.

In the embodiment described above, the vertical synchronizing signal is separated and used in the synchronizing signal separation circuit (2), but it is also possible to separate and use the horizontal synchronizing signal as long as it can be distinguished from noise signals.

In the embodiment, the VTR switching signal input terminal (19)
The TV switching signal No. 43 was set to 12.5V, and the VTR switching signal was set to Ov, but conversely, the VTR switching signal was set to 12.5V.
．． 5V, can also be used as Ov as a TV switching signal,
In this case, (17) becomes a color generation circuit for empty channels, and (18) becomes a color generation circuit for VTR input.

In the embodiment described above, the volume control signal is released to the ground by the audio mute circuit (48), but the present invention is not limited to this. The operation may be stopped.

"Effects of the Invention" As described above, the present invention displays different colors when selecting an empty channel and a VTR input when switching channels. Therefore, it is possible to eliminate the discomfort caused by flickering on one screen, and also to
It is possible to clearly distinguish whether the input is R input or not. Moreover, by using color display, not only will it not be mistaken for a malfunction in the receiver, but it will also give a more pleasant feeling. Furthermore, the circuit configuration is simple and inexpensive.

[Brief explanation of drawings]

The figure is an electrical circuit diagram showing one embodiment of the flicker erasing circuit according to the present invention. (1)...Video signal input terminal, (2)...Sync signal separation circuit, (3)...Amplification circuit, (4)...Switch circuit, (5)...Black level generation circuit, (16)...
Switching circuit, (17)...VTR input color generation circuit, (
18)...Color generation circuit for empty channels, (19).
...TV/VTR switching signal input terminal, (31)...
Color difference signal (G-Y) input terminal, (35)... Luminance signal (Y) input terminal, (36)... (G) output terminal, (
44)...Color difference signal (B-Y) input terminal, (45).
... (B) Output terminal, (48) ... Circuit to audio mu 1, (55) ... Audio signal input terminal.

Claims (6)

[Claims] (1) A synchronization signal separation circuit in a video signal, an amplifier circuit that amplifies this separated synchronization signal, a switch circuit that turns on and off depending on the presence or absence of the output of this amplifier circuit, and a VTR controlled by this switch circuit. 1. A flicker elimination circuit for a television receiver, comprising an input color generation circuit and an empty channel color generation circuit controlled by the output of the switch circuit and a television/VTR switching signal. (2) The VTR input color generation circuit connects a color difference signal input terminal of one of the three primary colors to the base of the transistor, a luminance signal input terminal to the emitter, and an output terminal to the collector, and connects the emitter to the output terminal. 2. A flicker erasing circuit for a television receiver according to claim 1, comprising a transistor that is turned on by the output of a switch circuit. (3) The VTR input color generation circuit connects a color difference signal input terminal of one of the three primary colors to the base of the transistor, a luminance signal input terminal to the emitter, and an output terminal to the collector, and connects the base to the output terminal. 2. The flicker erasing circuit for a television receiver according to claim 1, which combines transistors that are turned on by the output of the switch circuit, and enhances a color difference signal by increasing a base bias voltage. (4) The color generation circuit for empty channels connects the color difference signal input terminal of one of the three primary colors other than that for VTR input to the base of the transistor, the luminance signal input terminal to the emitter, and the output terminal to the collector. 2. A flicker canceling circuit for a television receiver according to claim 1, further comprising a transistor coupled to said emitter, which is turned on by the output of a switch circuit and the output of a television/VTR switching signal. (5) The color generation circuit for empty channels connects the base of the transistor to the color difference signal input terminal of one of the three primary colors other than that for VTR input, the emitter to the luminance signal input terminal, and the collector to the output terminal, and on the base,
Flicker elimination in a television receiver according to claim 1, which combines transistors that are turned on by the output of the switch circuit and the output of the television/VTR switching signal, and increases the base bias voltage to emphasize the color difference signal. circuit. (6) A switching circuit in front of the color generation circuit for VTR input that is activated by the output of the switch circuit and the TV/VTR switching signal to prohibit the operation of the color generation circuit for VTR input and activate the color generation circuit for empty channels. 6. A flicker erasing circuit for a television receiver according to claim 4 or 5, which comprises: