KR930007187Y1 - Automatic selection receiver between secam-l and pal television system - Google Patents

Abstract

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Description

SECAM-L / PAL Automatic Receiving Circuit

1 is a conventional SECAM-L / PAL scheme receiving circuit diagram.

2 is a SECAM-L / PAL method receiving circuit diagram of the present invention.

* Explanation of symbols for main parts of the drawings

10: tuner 20: video detection circuit

30: phase inversion switch inversion 40: FM detection circuit

50: AM detection circuit 60: FM / AM switch circuit

70: synchronization detection circuit SW1: broadcast mode selection switch

The present invention relates to a SECAM-L / PAL type automatic receiving circuit for automatically receiving two types of broadcasting in a video receiver receiving SECAM-L type and PAL type broadcasting.

When a user receives a broadcast using a video receiver capable of receiving SECAM-L and a PAL method, the user memorizes the broadcast method for each channel, and then switches manually. You can watch the broadcast you want to give.

In other words, the two signals are broadcast because the AMAM video signal of the SECAM-L broadcast method is positively modulated, the AM signal is modulated and the audio signal is AM-modulated, and the PAL broadcast video signal is negative AM-modulated and the audio signal is FM-modulated. When the video signal phases of the methods are reversed and received by the receiver as they are, they appear in opposite phases.

Therefore, the user may feel uncomfortable in switching between the broadcasting method memory and the broadcasting mode selection switch because the user can watch the normal screen only after the broadcasting method is switched and the broadcasting mode selection switch is matched to match the broadcasting method.

In view of the above, the present invention does not know the broadcasting method for each channel, but when the channel is selected, the broadcasting method is automatically selected. Therefore, the phase of the video signal of the SECAM-L method and the PAL method is different, and thus the synchronization signal can be detected. In this case, since only one broadcast method is detected, the broadcast reception system of the receiver is automatically switched by using the same.

Hereinafter, the configuration and operation effects of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is a conventional circuit diagram. An image intermediate frequency signal tuned by the tuner 10 is detected as a composite image signal by an image detection circuit 20, and an audio intermediate frequency signal is an FM detection circuit 40 and an AM detection circuit 50. ) Is detected as an audio signal, and the composite video signal of the video detection circuit 20 is output as it is or is phase-inverted from the phase inversion switch circuit 30 according to the switching state of the broadcast mode selection switch SW1.

The audio signal of the FM detection circuit 40 and the AM detection circuit 50 is selected and output by the FM / AM switch circuit 60 according to the switching state of the broadcast mode selection switch SW1.

2 is a circuit diagram of the present invention, and the composite video signal of the image detection circuit 20 is selectively output through the phase reversal switch circuit 30, and the audio signal of the FM detection circuit 40 and the AM detection circuit 50 is shown. Is a circuit selectively outputted through the FM / AM switch circuit 60, wherein the synchronization signal included in the composite video signal of the image detection circuit 20 is detected and integrated by the synchronization detection circuit 70 and output. The switching operation of the phase inversion switch 30 and the FM / AM switch circuit 60 is selected as the output of the synchronous detection circuit 70.

Here, the image detection circuit 20 is positively falsified and applied when the input signal is a PAL method, but detects and outputs a negative composite video signal, and is negatively modulated and applied when the input signal is a SECAM-L method. The composite video signal is output.

The synchronization detection circuit 70 is composed of a clamping circuit for detecting a synchronization signal in the positive image signal and an integration circuit for integrating the detected synchronization signal. When the positive composite video signal is applied from the image detection circuit 20, the synchronization is performed. Since the signal is detected and integrated, the high level switching signal is output. When the negative composite video signal is applied, the synchronization signal cannot be detected, and the low level switching signal is output.

The phase reversal switch circuit 30 is composed of a switch for switching the signal flow and a phase reversal element. If the switching signal output of the synchronous detection circuit 70 is high, the phase reversal switch circuit 30 outputs the composite video signal output of the image detection circuit 20 as it is. When the switching signal output of the synchronous detection circuit 70 is at a low level, the composite video signal output of the image detection circuit 20 is phase-inverted and output by the phase inversion element.

In addition, the FM / AM switch circuit 60 is composed of a switch selected for switching operation by an external switching signal. If the switching signal output of the synchronous detection circuit 70 is high level, the output of the M detection circuit 40 is selected and output. If the output of the switching signal of the synchronous detection circuit 50 is at a low level, the output of the AM detection circuit 50 is selected and output.

The case where the channel selected in the present invention is the PAL method will be described. The intermediate frequency signal tuned by the tuner 10 is negatively modulated because it is a PAL method and is applied to the image detection circuit 20 to detect the image. It is output as a video signal and applied to the phase inversion switch circuit 30 and the synchronization detection circuit 70.

Here, the synchronization detecting circuit 70 detects a horizontal synchronization signal among the input composite video signals. At this time, since a positive video signal is applied, a synchronization signal is detected, and when the detected synchronization signal is integrated, the output of the synchronization detection circuit 70 is output. Becomes the high level.

The high level switching signal of the synchronous detection circuit 70 is applied to the phase inversion switch circuit 30 and the FM / AM switch circuit 60.

Therefore, since the high level switching signal is applied to the phase inversion switch circuit 30 by the synchronization detection circuit 70, the positive image signal is output by outputting the positive image signal applied from the image detection circuit 20 as it is. .

If the switching signal of the synchronous detection circuit 70 is at a high level, the FM / AM switch circuit 60 selects and outputs the output of the FM detection circuit 40 so that the audio output is the FM demodulated by the FM detection circuit 40. The signal is output.

Next, the case where the selected channel is the SECAM-L method will be described.

The intermediate frequency signal tuned by the tuner 10 (which is positively modulated since it is a SECAM-L method) is applied to the image detection circuit 20 to detect the image. At this time, the detection output of the image detection circuit 20 is positively modulated. The negative composite video signal is output to the phase inversion switch circuit 30 and the synchronization detection circuit 70.

Here, the sync detection circuit 70 detects a horizontal sync signal among the input video signals, but in the SECAM-L method, since a negative video signal is applied, the sync detection circuit 70 cannot detect the horizontal sync signal, thereby outputting a switching signal of the sync detection circuit 70. Is applied to the phase inversion switch 30 and the FM / AM switch circuit 60 at a low level.

Therefore, since the low level switching signal is applied from the synchronous detection circuit 70, the phase inversion switch circuit 30 outputs the negative video signal applied by the image detection circuit 20 by inverting the phase, thereby outputting the positive video signal. Will be.

In addition, when the synchronous detection circuit 70 is at a low level, the FM / AM switch circuit 60 selects and outputs the output of the AM detection circuit 50 so that the audio output is output by the AM signal demodulated by the AM detection circuit 50. It is done.

As described above, the present invention outputs the same phase and is automatically selected as an audio signal regardless of PAL broadcasting and SECAM-L method, so that PAL broadcasting and SECAM-L broadcasting can be viewed on a normal screen without a separate switch operation. do.

Claims (1)

The composite image signal detected by the image detection circuit 20 is inverted or output as it is by an external switching signal in the phase reversal switch circuit 30 composed of a switch and a phase reversal device, and the FM detection circuit 40 and the AM detection circuit. A circuit in which an audio signal of 50 is selectively outputted by an external switching signal from an FM / AM switch circuit 60 constituted by a switch, wherein the synchronization signal of the composite video signal detected by the image detection circuit 20 is received. A synchronous detection circuit 70 for detecting by the clamp circuit and integrating it in the integrating circuit and outputting the switching signal, and converting the switching signal of the synchronous detection circuit 70 into a phase inversion switch circuit 30 and an FM / AM switch circuit ( SECAM-L / PAN automatic receiving circuit, characterized in that configured to be applied to the external switching signal of 60).