JPH0617391Y2 - Television receiver - Google Patents

Description

TECHNICAL FIELD The present invention relates to a television receiver, and more particularly to an RGB signal of a video source such as a television broadcast or an external input image and an RGB signal for multiple display (for superimpose). The present invention relates to a television receiver including an RGB switching circuit that switches between and by a switching signal (Ys signal).

<Prior Art> In recent years, in television receivers, there is a demand for removing a so-called noise screen without a video signal when a vacant channel is tuned in or after the end of TV broadcasting so as to be a screen that is visually easy to see. is there.

<Object of the Invention> The present invention has been made in view of the above points, and an object of the present invention is to provide a television receiver capable of eliminating a noise screen with a relatively simple configuration. .

<Configuration of Device> In order to achieve the above-mentioned object, the present invention provides a television image receiving device including an RGB switching circuit for switching and outputting an RGB signal of a video source such as a television broadcast and an RGB signal for multiple display by a switching signal. In the machine, a sync signal detection circuit that detects a sync signal included in the composite video signal of the video source and provides a corresponding output is provided, while an RGB contrast circuit that controls the contrast of the RGB signal for multiple display is provided in the RGB The output of the synchronization signal detection circuit is provided in the preceding stage of the switching circuit, and the output of the synchronization signal detection circuit is given to the RGB switching circuit as a switching signal, and a multiple display positioning horizontal pulse based on a flyback pulse is supplied to the multiple display R.
When each signal of GB is given to at least one of the input parts input to the RGB contrast circuit, and the sync signal is not detected by the sync signal detection circuit,
The horizontal pulse is output from the RGB switching circuit.

<Example> Hereinafter, an example of the present invention will be described in detail with reference to the drawings. FIG. 1 is a circuit diagram of an essential part of an embodiment of the present invention. The television receiver of this embodiment uses a switching signal (Ys signal) between an RGB signal of an image source such as a television broadcast and an external input image and an RGB signal for multiple display to perform a CRT.
The RGB switching circuit 1 for switching and outputting to the drive circuit.

The RGB changeover circuit 1 includes three first to third changeover switches 2 to 4 individually corresponding to RGB primary color signals, and each changeover switch 2 to 4 is an RGB source image signal.
First individual contacts 2a to 4a to which signals are respectively applied,
It is composed of second individual contacts 2b to 4b to which RGB signals for multiple display are respectively applied, and movable contacts 2c to 4c controlled by a switching signal from the input terminal 8. This RGB
The switching circuit 1 outputs the RGB signal for multiple display when the switching signal is at the high level, and outputs the RGB signal of the video source when the switching signal is at the low level.

In front of the RGB switching circuit 1, an RGB contrast circuit 5 for controlling the contrast of RGB signals for multiple display,
A clamp circuit 6 for setting the black level of the RGB signals is provided.

Therefore, in the television receiver of the present invention, the RGB contrast circuit 5 is adjusted by the viewer adjusting an adjusting volume or the like (not shown) in accordance with the surrounding environment and preferences.
It is possible to control the contrast of RGB signals for multiple display via.

The RGB switching circuit 1, the RGB contrast circuit 5, and the clamp circuit 6 are integrated into an IC as an RGB processing circuit 9.

In this embodiment, a video source, such as television broadcast or V
A sync signal detection circuit 7 for detecting a sync signal included in an externally input composite video signal such as TR is provided. The sync signal detection circuit 7 basically has a sync separation circuit for separating the sync signal from the input composite video signal, an integration circuit for integrating the output of the sync separation circuit, and an output of the integration circuit as a reference. It is composed of a comparison circuit for comparing with the level, and when a sync signal is detected, a low level output is given,
It is configured to provide a high level output when the sync signal is not detected.

The output of the sync signal detection circuit 7 is applied as a switching signal to the input terminal 8 of the RGB switching circuit 1 via the resistor R8 and the diode D4. That is, the RGB switching circuit 1 is switched according to the presence / absence of the synchronization signal. A switching signal (Ys signal) is applied to the input terminal 8 via the diode D3 as in the conventional case.

First to third input terminals 10 to 12 of the RGB processing circuit 9
Is an RGB signal for multiple display of volume, channel sign, etc. or RG for multiple display from a personal computer, etc.
B signals are provided respectively.

In this embodiment, a positioning horizontal pulse for multiple display formed by a flyback pulse is given to the third input terminal 12 of B signal among the input terminals 10 to 12 of RGB signal for multiple display. The horizontal pulse is input to the RGB switching circuit 1 via the clamp circuit 6 and the RGB contrast circuit 5.

That is, the flyback pulse is sliced at a predetermined level by the resistors R1 and R2, and waveform-shaped by the transistor TR1 to form a positioning horizontal pulse for multiple display, and the resistor R4, the transistor TR2, the resistor R5, the diode D1, and the capacitor C1 are connected. Through the third input terminal 1
Given to 2. Further, the B signal for multiple display is given to the third input terminal 12 via the diode D2 and the capacitor C1 as in the conventional case.

The multiple display positioning horizontal pulse from the transistor TR1 is also used for positioning as in the conventional case.

FIG. 2 is a signal waveform diagram of each part of the embodiment of FIG.
2 (A) is a flyback pulse, FIG. 2 (B) is the collector output of the transistor TR1, that is, a positioning horizontal pulse for multiple display, and FIG. 2 (C) is the output of the RGB switching circuit 1, FIG. (D) shows switching signals, respectively.

For example, if a television broadcast is currently being received, the second
The switching signal shown in FIG. 6D is at a low level, and therefore the movable contacts 2c to 4c of the changeover switches 2 to 3 of the RGB switching circuit 1 are on the first individual contact 2a to 4a side and the second As shown by A in FIG.
The GB signal is output from the RGB switching circuit 1.

While receiving this TV broadcast, for example,
When the synchronization signal is no longer detected by the channel selection, the output of the synchronization signal detection circuit 7 becomes high level, the switching signal to the RGB switching circuit 1 becomes high level as shown in FIG. 2-4 movable contacts 2c-
4c switches to the side of the second individual contacts 2b-4b. As a result, the RGB switching circuit 1 is provided with the positioning horizontal pulse for multiple display shown in FIG. 2B via the clamp circuit 6 and the RGB contrast circuit 5, and the RGB switching circuit 1 outputs the horizontal pulse shown in FIG. The horizontal pulse shown in C) will be output, and in this embodiment, a blue screen will be displayed.

Therefore, when there is no synchronization signal such as when a vacant channel is selected, a blue screen is displayed instead of a noise screen, and the screen is visually easy to see.

Moreover, since the horizontal pulse is given to the RGB switching circuit 1 via the RGB contrast circuit 5, the viewer is RG
By performing an adjustment operation on the B contrast circuit 5 with a volume not shown, the blue screen when there is no signal can be adjusted to the brightness (contrast) according to the taste of the viewer.

In the above embodiment, when the sync signal is not detected,
Although the screen is blue, it is of course possible to use a screen of another color.

<Effects of the Invention> As described above, according to the present invention, while the sync signal detection circuit is provided, the RGB contrast circuit for controlling the contrast of the RGB signal for multiple display is provided, and the output of the sync signal detection circuit is switched to the RGB switch. A multiple display positioning horizontal pulse based on a flyback pulse is provided to the circuit as a switching signal, and is provided to at least one input unit of the input units of the RGB signals for multiple display, and when a synchronization signal is not detected, Since the horizontal pulse is output from the RGB switching circuit, a single-color screen, which is not a noise screen, is displayed with a relatively simple structure, which is easy to see.

Moreover, since the horizontal pulse is applied to the RGB switching circuit via the RGB contrast circuit, it is possible to obtain a single-color screen having brightness (contrast) according to the viewer's preference by adjusting the RGB contrast circuit.

[Brief description of drawings]

FIG. 1 is a circuit diagram of an essential part of an embodiment of the present invention, and FIG. 2 is a signal waveform diagram used for explaining the operation of FIG. 1 ... RGB switching circuit, 7 ... Sync signal detection circuit.

Claims (1)

[Scope of utility model registration request] 1. A television receiver including an RGB switching circuit for switching and outputting an RGB signal of a video source such as a television broadcast and an RGB signal for multiple display according to a switching signal, which is included in a composite video signal of the video source. A sync signal detection circuit that detects a sync signal and provides a corresponding output is provided, while an RGB contrast circuit that controls the contrast of the RGB signal for multiple display is provided in the preceding stage of the RGB switching circuit. The output is given to the RGB switching circuit as a switching signal, and a positioning horizontal pulse for multiple display based on a flyback pulse is input to each of the RGB contrast circuits. To at least one of the input sections, and the sync signal is not detected by the sync signal detection circuit. In some cases, the horizontal pulse is output from the RGB switching circuit.