JPH11261912A - Television receiver - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a television receiver that can automatically discriminate a state of displaying a sand storm image and a state of displaying an image in black. SOLUTION: This television receiver is provided with a comparator 9 that compares a beam information signal Sb obtained from a deflection processing circuit 7 with a prescribed threshold level, and with an OR circuit 10 that ORs a video detection signal Sv obtained from the comparator 9 and a synchronization detection signal Sh obtained from a horizontal AFC circuit 8 to generate signal detection information Sd. So that a state of displaying a sand storm image and a state of displaying an image in black are discriminated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a television receiver for displaying an image on a CRT screen in response to an input of an image signal.

[0002]

2. Description of the Related Art Generally, in a TV (television) receiver, a VTR (video tape recorder) is connected to a video input terminal.
In a state where the video signal received by the tuner is displayed on the CRT screen as a video, and a video input mode for displaying the video signal reproduced from the VTR as a video on the CRT screen is connected to the user. Switching is performed by a selection operation, and a desired image is viewed. Here, when the TV receiver and the VTR are of the same manufacturer, the mode switching can be performed automatically.

If the power of the game machine is turned off while the game machine is connected to the video input terminal of the TV set, the screen becomes solid black because no video signal is input to the TV set. , While the power of the TV receiver is turned on, the state may be left. Therefore, recent TV receivers have a built-in circuit that determines the presence or absence of a video signal input by detecting the presence or absence of a horizontal synchronization signal to be included in the video signal. When the machine is turned off,
Switch the TV set to the channel reception mode,
It is possible to notify the screen that the TV power supply remains ON, or to automatically turn off the power of the TV receiver.

[0004]

However, when a VTR is connected to a TV receiver, a video input mode is set,
In the state where the magnetic tape is being reproduced, when a transition is made to the connection of the two programs on the magnetic tape, that is, the reproduction of the non-recording part, the non-recording part does not include the horizontal synchronization signal. The screen display operation is not performed, and a so-called sandstorm screen is displayed. Then, the above-described video signal presence / absence determination circuit detects the disappearance of the synchronization signal and switches the TV receiver to the channel reception mode. Therefore, when the user continues to watch the next program recorded after the non-recording portion, the user needs to perform an operation of returning the TV receiver to the video input mode.

As described above, in the conventional TV receiver,
For example, a state in which a sandstorm screen is displayed as when a non-recorded portion of a magnetic tape is reproduced, for example, when the power of the game machine is turned off.
There is a problem that it is not possible to automatically discriminate a state in which a black screen is displayed as in the case of FF. Therefore, an object of the present invention is to provide a TV receiver capable of reliably discriminating between the two states.

[0006]

A TV receiver according to the present invention is supplied to a synchronization detection means for detecting the presence or absence of a horizontal synchronization signal to be included in a video signal, and to an anode (15) of a CRT (6). A beam detecting means for detecting a beam information signal corresponding to the magnitude of the beam current, and comparing the beam information signal detected by the beam detecting means with a predetermined threshold to determine whether or not a video signal including an AC component has been input. The horizontal synchronizing signal is detected by the video detecting means for detecting and the synchronous detecting means,
Or a logic operation unit that outputs signal detection information when an input of a video signal containing an AC component is detected by the video detection unit, and a control unit that executes a predetermined control operation based on the signal detection information. I have.

In the TV receiver according to the present invention, for example, when a VTR is connected and the video input mode is set, when the reproduction of the non-recording portion of the magnetic tape is started, the reproduction signal from the non-recording portion is output. Does not include the horizontal synchronizing signal, the synchronization detecting means cannot detect the horizontal synchronizing signal. However, since a signal containing an AC component is reproduced from the non-recording portion and a screen display operation is performed based on the reproduced signal, a certain amount of beam current is applied to the anode (15) of the CRT (6). Will flow. On the other hand, when the game machine is connected to the TV receiver and the video input mode is set, the power of the game machine is turned off.
In the case of F, the video signal is not supplied to the TV receiver, so that the synchronization detecting means cannot detect the horizontal synchronization signal, and the beam current is supplied to the anode (15) of the CRT (6). Does not flow.

[0008] Therefore, by using the beam information signal when the beam current is zero as a predetermined threshold value and comparing the actually detected beam information signal with the predetermined threshold value, the presence or absence of input of a video signal containing an AC component can be determined. Can be detected. Therefore,
When the input of a video signal containing an AC component is detected in a state where the horizontal synchronization signal is not detected, it is possible to determine that the sandstorm screen is displayed based on the output of the signal detection information, and the video signal containing the AC component is detected. Is not detected, it can be determined based on the disappearance of the signal detection information that the display state is a black one-color screen.

When a normal black image signal is included in a normal image signal, the beam information signal temporarily becomes equal to a predetermined threshold. However, the image signal includes a horizontal synchronizing signal. Therefore, the logical operation means maintains the output of the signal detection information.

More specifically, the apparatus further comprises signal switching means for switching between the first video signal received by the tuner and the second video signal input from the external input terminal, and comprises an input mode (video) for the second video signal. When the signal detection information is lost in (input mode), the control means automatically switches from the input mode of the second video signal to the input mode (channel reception mode) of the first video signal.

In the specific configuration, for example, when the game machine is connected to the TV set and the video input mode is set and the game machine is turned off, the signal detection information is lost. Accordingly, the input mode of the second video signal (video input mode) is automatically switched to the input mode of the first video signal (channel reception mode). On the other hand, even if the VTR is connected to the TV set and the video input mode is set and the reproduction of the non-recorded portion of the magnetic tape is started, the signal detection information remains output and does not disappear. 2 video signal input mode
(Video input mode) is maintained.

[0012]

According to the TV receiver of the present invention, the display state of a so-called sandstorm screen and the display state of a black-and-white screen based on the disappearance of an input video signal can be automatically determined.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be specifically described below with reference to the drawings. FIG. 1 shows a configuration of a TV receiver according to the present invention. A radio wave received by an antenna is demodulated into a video signal by a tuner / intermediate frequency amplifier circuit (1) and input to an AV switching circuit (2). Is done.

The AV switching circuit (2) receives a video signal from the tuner / intermediate frequency amplifier circuit (1) and a video signal from the video input terminal under the control of a control circuit (3) comprising a microcomputer. Can be switched between. The video signal selected in this way is supplied to the video processing circuit (4) and the synchronization separation circuit (5). Video processing circuit (4)
In, after the video signal is decoded into an RGB signal, and the image quality is optimally corrected by the control of the control circuit (3),
It is amplified and supplied to the CRT (6). by this,
The cathode of the CRT (6) is driven.

On the other hand, the video signal input to the synchronization separation circuit (5) is separated into a horizontal synchronization signal Hs and a vertical synchronization signal Vs, and the two synchronization signals Hs and Vs are supplied to a deflection processing circuit (7). The deflection processing circuit (7) includes a horizontal drive circuit, a vertical drive circuit, a horizontal output circuit, and a vertical output circuit. A horizontal drive pulse and a vertical drive pulse are generated by the horizontal drive circuit and the vertical drive circuit. The output circuit and the vertical output circuit generate a horizontal deflection current Ih and a vertical deflection current Iv for scanning the electron beam, and supply them to the CRT (6).

The horizontal synchronization signal Hs obtained from the synchronization separation circuit 5 and the horizontal drive pulse Hd obtained from the deflection processing circuit 7 are supplied to a horizontal AFC circuit 8.
In response to this, the horizontal AFC circuit (8) compares the phase of the horizontal synchronization signal Hs with the phase of the horizontal drive pulse Hd, generates a control signal D for minimizing the phase difference between them, and generates a deflection processing circuit (7). Supply to The horizontal AFC circuit (8) determines the presence or absence of the horizontal synchronization signal Hs based on the phase comparison between the horizontal synchronization signal Hs and the horizontal drive pulse Hd. When it is not determined that the synchronization detection signal Sh is present, a synchronization detection signal Sh which becomes low is generated and output to the subsequent circuit.

The horizontal output circuit of the deflection processing circuit (7) has a function of generating a horizontal deflection current as described above and a function of supplying a high voltage to the anode of the CRT (6).
It shows a circuit for realizing the latter function of the horizontal output circuit (16). The horizontal drive pulse Hd is converted into a flyback pulse of about 1000 Vp-p by a resonance circuit including the primary winding (12) of the flyback transformer (11) and the capacitor C, and the secondary winding of the flyback transformer (11) is formed. 13)
Generates a rectified high voltage of about 25 kV,
The voltage is applied to the anode (15) of (6).

Here, a beam information signal output terminal (14) extracted from one end of the secondary winding (13) of the flyback transformer (11) is connected to the CRT (6) from the secondary winding (13). Anode (1
A DC voltage corresponding to the magnitude of the beam current flowing to 5) is generated. That is, when the beam current increases, the DC voltage decreases, and when the beam current decreases, the DC voltage increases. This DC voltage is extracted as a beam information signal Sb.

The beam information signal Sb is supplied to an inverting input terminal of a comparator (9) as shown in FIG. 1, and the DC voltage when the beam current is zero is supplied to a non-inverting input terminal of the comparator (9). Supply. As a result, the comparator (9) obtains a high image detection signal Sv when the beam current is flowing, and a low image detection signal Sv when the beam current is not flowing.

The video detection signal Sv output from the comparator (9) and the synchronization detection signal Sh output from the horizontal AFC circuit (8) are supplied to both input terminals of an OR circuit (10), and the logic of both signals is obtained. By taking the sum, signal detection information Sd that becomes high when one or both of the signals are high and low when both signals are low is created. The signal detection information Sd is sent to the control circuit (3),
Various control operations are provided. For example, when the signal detection information Sd changes from high to low in the video input mode, the control circuit (3) switches from the video input mode to the channel reception mode.

Therefore, the game machine is connected to the TV receiver,
The game machine is turned off with the video input mode set.
When it becomes FF, the mode is automatically switched from the video input mode to the channel reception mode, and returns to, for example, the reception state of the channel set immediately before. On the other hand, when the VTR is connected to the TV set and the video input mode is set, and when the reproduction of the unrecorded portion of the magnetic tape is started, the signal detection information Sd remains high. Is maintained.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a circuit configuration of a TV receiver according to the present invention.

FIG. 2 is a block diagram illustrating a main part of a horizontal output circuit.

[Explanation of symbols]

 (1) Tuner / intermediate frequency amplifier circuit (2) AV switching circuit (3) Control circuit (4) Video processing circuit (5) Sync separation circuit (7) Deflection processing circuit (8) Horizontal AFC circuit (9) Comparator (10 ) OR circuit

Claims (2)

[Claims] 1. A television receiver for displaying an image on a screen of a CRT (6) in response to an input of an image signal, comprising: a synchronization detecting means for detecting the presence or absence of a horizontal synchronization signal to be included in the image signal; 6) comparing a beam information signal detected by the beam detection means with a predetermined threshold value, and a beam detection means for detecting a beam information signal corresponding to the magnitude of the beam current supplied to the anode (15); Video detection means for detecting the presence or absence of input of a video signal containing an AC component, and signal detection when a horizontal synchronization signal is detected by the synchronization detection means or when a video signal containing an AC component is detected by the video detection means. A television receiver comprising: a logical operation unit that outputs information; and a control unit that executes a predetermined control operation based on signal detection information. 2. The apparatus according to claim 1, further comprising signal switching means for switching between a first video signal received by a tuner and a second video signal input from an external input terminal, wherein said signal is input in a second video signal input mode. 2. The television receiver according to claim 1, wherein the control unit automatically switches from the input mode of the second video signal to the input mode of the first video signal when the detection information is lost.