JPH0591526A - Video signal processor - Google Patents

Abstract

PURPOSE:To change a television(TV) screen to a required color at the time of nonsignal by providing this video signal processing circuit with plural status detecting means, a control circuit, an output circuit, and a signal generating means. CONSTITUTION:The video signal processing circuit is provided with the 1st detection means for detecting that a video signal to be displayed is a signal outputted from an external video apparatus, the 2nd detection means 10 for detecting that a video signal to be displayed is in a signal-free state, the control circuit 11 for generating a control signal in accordance with a detection output, the output circuit for driving the cathode electrode of a CRT 16 in accordance with an input signal, and the signal generating means for impressing a display signal to the output circuit in accordance with the control signal outputted from the circuit 11 so as to display a required color on the CRT 16. Namely when a TV image receiver selects a video signal from the external and detects that the video signal is in the signal-free state, a signal for forming a required color is impressed to the output circuit. Thus the TV screen can automatically be turned to a required color.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a video signal processing circuit for a television receiver, and more particularly to a video signal processing circuit capable of displaying a desired color on a television screen when there is no signal.

[0002]

2. Description of the Related Art Generally, when a TV receiver is used as a monitor screen of a VTR or the like, when the video input terminal of the TV receiver is opened, the TV screen should be black (the color of the cathode ray tube itself). Was there. However, if the TV screen is made black with an inexpensive TV receiver that does not include a power pilot lamp, the viewer may mistakenly think that the TV receiver is powered off. Therefore, some TV sets are set to an appropriate brightness (gray) when there is no signal. Such a material is disclosed, for example, in JP-A-60-59.
No. 879.

[0003]

However, the method described in the above publication can only make the television screen black or gray, which has a low recognizability and may cause misjudgment.

[0004]

The present invention has been made in view of the above points, and is a video signal processing circuit incorporated in a television receiver for displaying a video signal from an external video device on a cathode ray tube. And first detecting means for detecting that the video signal to be displayed is from an external video device, and second detecting means for detecting that the video signal to be displayed is in a non-signal state. A control circuit for generating a control signal according to the detection output of the first and second detection means, an output circuit for driving a cathode electrode of the cathode ray tube according to the input signal, and a desired color being displayed on the cathode ray tube. And a signal generating means for applying a display signal to the output circuit according to a control signal from the control circuit.

[0005]

According to the present invention, when the TV receiver selects an external video signal and detects that the video signal is in a non-signal state, a signal forming a desired color is applied to the output circuit. is doing.

[0006]

FIG. 1 is a circuit diagram showing an embodiment of the present invention.
(1) is the terminal of the IC (2) to which the composite video signal generated inside the TV receiver (INT) is applied, (3)
Is a terminal to which a composite video signal from an external (EXT) video device such as a VTR or a laser disk is applied,
(4) is composed of a microcomputer, etc., and is an IC
A control circuit for applying control signals and R, G, and B primary color signals for OSD (abbreviation of on-screen display indicates channel display or volume display), and (5) control based on a command from a viewer. It is switched according to the control signal from the circuit (4), and the image on the INT side or EXT is displayed on the TV screen.
Switch for selectively displaying the side image, (6) is TR
A video signal processing circuit for processing a video (luminance) signal from an AP (trap) circuit (7), (8) a chroma signal processing circuit for processing a chroma signal from a BPF (band pass filter) (9), (10) ) Is a no-signal detection circuit for detecting a no-signal state of the video signal, (11) is a control circuit for selecting the EXT-side video signal and generating a control signal when detecting the no-signal state, (12) Selects and outputs R-Y, G-Y, B-Y and -Y signals from the INT side or R, G, B signals from the EXT side according to the BL (blanking) signal from the control circuit (4). In addition, switching circuits that generate primary color signals for screen display according to control signals from the control circuit (11), and (13) to (15) are transistors that drive the cathode electrode of the cathode ray tube (16).

First, the path of the composite video signal from the INT side or the EXT side will be described. A control signal is applied to the switch (5) from the control circuit (4) via the terminal (17), and the switch (5) is switched. Then,
The selected video signal is the video signal processing circuit (6),
The chroma signal is processed by the chroma signal processing circuit (8). The chrominance signal processing circuit (8) generates color difference signals R-Y, G-Y and B-Y signals, and the switching circuit (1
2) is applied. The video signal processing circuit (6) generates a -Y signal which is an inversion signal of the video signal.

On the other hand, from the control circuit (4), the R for OSD, which is displayed in synchronization with the above-mentioned composite video signal,
G and B signals are generated and applied to the switching circuit (12) via the terminals (18) to (20). In this state, if the BL signal is not generated from the control circuit (4), the switching circuit (1
2) outputs RY, GY and BY signals to terminals (21) to (23) and -Y signal to terminal (24). or,
When the BL signal is generated, the switching circuit (12) supplies the R, G and B signals to the terminals (21) to (23) and the terminal (2).
A constant voltage is generated at 4). Since the BL signal is generated when any one of the R, G and B signals is generated, the OSD image signal can be inserted into the image signal from the terminal (1) or (3). ..

When a color difference signal is generated from the terminals (21) to (23), the -Y signal is applied to the base of the transistor (25), and therefore the transistor (13).
Subtraction is carried out at through (15), and primary color signals are generated at the collectors of the transistors (13) through (15). When primary color signals are generated from the terminals (21) to (23), level-shifted primary color signals are generated in the transistors (13) to (15).

Now, it is assumed that the EXT side composite video signal from the terminal (3) is selected, and the signal becomes a non-signal state for some reason. Then, the no-signal detection circuit (10) detects no signal and applies the detection output to the control circuit (11). The terminal (26) is for applying the detection output to another utilization circuit (for example, a horizontal AFC circuit). Further, a control signal indicating that the EXT side is currently selected is applied from the control circuit (4) to the control circuit (11). Then, a control signal is applied from the control circuit (11) to the switching circuit (12). Then, the switching circuit (12) generates a DC voltage signal for displaying a desired color at the terminals (21) to (23) and the terminal (24). Various kinds of signals can be considered depending on the color.

Therefore, according to the circuit of FIG. 1, when the video signal from the external device is cut off, the cathode ray tube can be automatically colored, and the risk of erroneous determination is eliminated.
FIG. 2 shows a specific circuit of the switching circuit (12) shown in FIG. 1, and switches (2) by the BL signal applied to the terminal (27).
8) to (31) are switched to select the EXT side and the INT side. When a control signal is applied from the control circuit (11), the switches (32) and (33) are closed. Then, the output of the comparator (34) causes the switch (2
8) to 30) select the primary color signal side, and switch (3
1) is switched to the 2.8 [V] DC power supply (35) side.
Further, the comparator (36) switches the switch (37) in the opposite manner to that shown in the figure, and a DC voltage of 4 [V] is applied to the level shift circuit (38). Then, a DC voltage of 6 [V] is generated from the −6 dB amplifier (39) and is led to the terminal (23) via the switch (37).

Therefore, the 2.8 obtained at the terminal (24).
The B primary color signal can be created by the signal of [V] and the signal of 6 [V] obtained at the terminal (23).
The control circuit (11) of FIG. 2 may be housed in the IC (2).

[0013]

As described above, according to the present invention, a television screen can be automatically set to a desired color when a video signal coming from an external device goes into a non-signal state. In particular, according to the present invention, since it can be carried out only by providing a simple circuit inside the integrated circuit, it is suitable for an IC.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a video signal processing circuit of the present invention.

FIG. 2 is a specific circuit diagram of a switching circuit (12) shown in FIG.

[Explanation of symbols]

 (2) IC (5) Switch (10) No signal detection circuit (11) Control circuit (12) Switching circuit (16) CRT

Claims (2)

[Claims] 1. A video signal processing circuit built in a television receiver for displaying a video signal from an external video device on a cathode ray tube, wherein the video signal to be displayed is from the external video device. A first detection means for detecting that the video signal to be displayed is in a non-signal state, and a control signal is generated according to detection outputs of the first and second detection means. Control circuit, an output circuit that drives the cathode electrode of the cathode ray tube according to the input signal, and a display circuit for the output circuit according to the control signal from the control circuit so that the desired color is displayed on the cathode ray tube. A video signal processing circuit comprising: a signal generating means for applying a signal. 2. The first detecting means, the second detecting means,
2. The video signal processing circuit according to claim 1, wherein the control circuit and the signal generating means are built in a single integrated circuit.