KR920003022Y1 - Automatic selecting circuit between secam-l and pal-b/g - Google Patents

Abstract

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Description

Automatic selection circuit of SECAM-L and PAL-B / G system in VCR system

1 is a circuit diagram according to the present invention.

* Explanation of symbols for main parts of the drawings

10: Timing control microcomputer D1, D2: Diode

20: tuner 30: oscillator

40: mixer 100: video processing unit

60, 70: first and second surface acoustic filters (SAW)

110: SECAM processing unit 80, 90: first and second demodulation circuit

120: PAL processing unit 130: SECAM detection circuit

140: PAL detection circuit 150: selection enable signal generating means

160: oscillation control means SW1: switch

Q1, Q2: transistor N1: inverter

The present invention relates to an automatic selection circuit that can automatically select the SECAM-L and PAL-B / G methods when recording / reproducing video signals in a video cassette recorder system.

In general, the method of recording and reproducing color television signals includes NTSC method using VHS type VTR (Hitachi's VT-300) and β-pomelt type (Sony's SL series) developed by US RCA. There is a PAL (Phase Altermation) method developed by Telunggen, and a SECAM (Sequential Couleur A Memoire) method developed by France. Here, a schematic description of the recording and reproducing method and technology by the PAL method and the SECAM method of the VHS type is described in detail on pages 158 to 161 of the book "Principle and Service of VTR" published by Garamsa.

As described in the above description of the principle of "VTR" and the contents of the service booklet, in the case of processing both PAL and SECAM in one VCR (Q2 VTR) system in Europe, the mode is operated by hand by external force. Optionally, it has been operated in SECAM-L and PAL-B / G mode.

This is not a problem because PAL-B / G and SECAM-L have the same order of video frequency (PiF) and voice frequency (SIF) in the high band and VHF, but the PIF and low band in the SECAM signal This is because the order of the SIF is changed, and there was no method of automatically selecting the SIF.

Therefore, the purpose of the present invention is to solve the conventional problems by using the latch circuit of the PAL / SECAM detection circuit, when the station is a low-band (VHF low-pass panel), the mixer stage oscillates to automatically select the PAL / SECAM mode in any state. It is to provide a circuit that enables it.

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

FIG. 1 is a circuit diagram according to the present invention, and includes a timing control micom 10 that programmatically generates a tuning control signal, and a tuner that tunes to an intermediate frequency IF according to the control of the timing control microcom 10. 20), a diode D1 for detecting a VHF low channel from the tuner 20, an oscillator 30 for oscillating a predetermined frequency in accordance with the output of the diode D1, and an output of the oscillator 30. And a mixer 40 for mixing intermediate frequencies of the tuner 20, and first and second surface acoustic (SAM) filters 60 and 70 for dividing and filtering the mixed signal through the mixer 40 for each audio and video. And a first demodulation circuit 80 for demodulating the output signal of the first surface acoustic filter 60 into an audio signal, and a second demodulating the output signal of the second surface acoustic filter 70 into a video signal. A demodulation circuit 90, a video processing unit 100 for processing a video signal of the second demodulation circuit 90, and SECAM processing unit 110 for processing a SECAM video signal from the video signal of the second demodulation circuit 90, PAL processing unit 120 for processing a PAL video signal from the video signal of the second demodulation circuit (90) ), A SECAM detection circuit 130 for detecting a SECAM signal at the output of the SECAM processing unit 110, a PAL detection circuit 140 for detecting a PAL signal at the output of the PAL processing unit 120, and the SECAM detection. A select enable signal generating means 150 for generating a control signal for controlling the first and second demodulation circuits 80 and 90 according to an output of the circuit 130 and selecting the PAL / SECAM method, and the SECAM Oscillation control means 160 for generating a control signal for controlling the oscillator 30 in accordance with the output of the detection circuit 130.

Here, in the configuration of FIG. 1, the transistor Q1 corresponds to the select enable signal generating means 150, and a portion composed of the transistor Q2, the diode D2, the resistor R1, and the inverter N1 is formed in the first embodiment. It corresponds to the oscillation control means 160. In addition, the detection circuit (130, 140) of the configuration of the present invention used a "BA7025L" IC of "ROHM" made in Germany.

According to the configuration described above with reference to Figure 1, the effect of the specific embodiment of the present invention as follows.

The input signal is converted into the intermediate frequency IF while passing through the tuner 20 and input to the mixer 40. In this case, the mixer 40 passes through the first and second surface acoustic filters 60 and 70 by mixing with the oscillation signal of the oscillator 30. When the output signal of the tuner 20 is the PAL-B / G band, In I or Band III, the sound frequency (SIF) and the picture frequency (PIF) are spaced at 5.5 MHz. However, in the case of SECAM-L, in the case of band III, the order of SIF and PIF is same as above (SIF occurs at a position lower than PIF on the frequency axis) (stage 6.5 MHz), but in case of band I, SIF The order of and PIF is reversed so that the PIF is generated first and the next SIF is generated because the image and sound carriers are switched when the broadcaster sends out the picture.

This case is called SECAM-L '. In this case (SECAM-L ', that is, band I), the receiver must change the order of PIF and SIF so that SIF is output first and PIF is output later. In the case of L ', the mixer 40 stage oscillates a predetermined frequency in the oscillator 30 to change its order.

Therefore, the mixer 40 functions to subtract the frequencies of the PIF and the SIF from the oscillation frequency of the oscillator 30 in order to correct the SECAM-L 'normally changed in order. That is, for example, when the SECAM-L '(in the case of band I) is received in an out of order state (PIF: 33.4 MHz, SIF: 40.9 MHz), the mixer 40 may determine the oscillator 30. The frequencies of the PIF and the SIF are audited from the frequencies (72.3 MHz), respectively. As a result of this, the SIF is changed to 31.4 MHz, and the PIF is changed to 38.9 MHz (72.3-33.4 = 38.9, 72.3-40.9 = 31.4). Therefore, in the present invention, in the case of the PAL-BG or SECAM-L (Band III), it is necessary not to operate the oscillator 30 and to oscillate the oscillator 30 only in the case of SECAM-L '(Band I). It can be seen that there is.

In order to solve this problem, in case of band I regardless of broadcasting, once the oscillator 30 is operated, the SECAM detection circuit 130 at the rear end finds whether there is a signal or not, and returns to the original mode.

First, in the case of no signal, it operates regardless of whether it is band I or band III. At this time, when band I of PAL or SECAM is tuned, oscillator 30 is oscillated.

When the PAL band I is tuned, the IF signal is changed as described above at the mixer 40 stage, and is recognized as a noise component after passing through the second demodulation circuit 90, so that the SECAM detection circuit 130 is " low " The output comes out. At this time, the transistors Q1 and Q2 are turned on to control the first and second demodulation circuits 80 and 90 to select PAL-B / G, and the oscillator 30 is stopped by the inverter N1.

On the contrary, when the SECAM signal is tuned, the output of the SECAM detection circuit 130 becomes "high", and the transistors Q1 and Q2 are turned off to select SECAM-L and L 'and the oscillator is output by the output of the inverter N1. 30 is oscillated.

Referring to the above operation, first, the output of the inverter M1 has the same input because the output of the SECAM detection circuit 130 is "low" when there is no signal or PAL signal in the state that is tuned to the tuner 20 by the PAL signal means. Receive PAL broadcasts.

At this time, if the SECAM broadcast is tuned by the tuner 20, the output of the SECAM detecting circuit 130 instantly becomes "high" and the output of the inverter N1 becomes "high" from "low".

In this way, the system receives the SECAM broadcast. Initially, the output of the SECAM detection circuit 130 is "low" so that the system receives the SECAM signal so that the PAL / SECAM detection circuits 130 and 140 receive the SECAM "high". The output will change from "low" to "high". Therefore, the output of the inverter N1 continues to be "high" until the PAL / SECAM detection signal is input. At this time, if the tuner 20 tunes to receive the PAL broadcast again, it is enabled by the output of the SECAM detection circuit 130 again, and the system returns to the PAL broadcast reception again.

As described above, the SECAM-L method is not automatically selected until now because the PIF and SIF signals are switched in the band I (VHF low channel), but the conventional problem is solved by using the present invention circuit. The advantage is that automatic selection of the B / G dual system is possible.

Claims (1)

In a PAL and SECAM type selection circuit of a V-CAL system, a timing control micom 10 that programmatically generates a tuning control signal, and an RF signal are tuned according to the control of the timing control microcomputer 10 to obtain an intermediate frequency ( A tuner 20 for converting to IF), a diode D1 for detecting a VHF low channel from the tuner 20, an oscillator 30 for oscillating a predetermined MHz according to the output of the diode D1, Mixer 40 for mixing the output of the oscillator 30 and the intermediate frequency of the tuner 20, and the first and second surface acoustic (SAW) for dividing and filtering the mixed signal through the mixer 40 for each audio and video Filter 60, 70, the first demodulation circuit 80 for demodulating the output signal of the first surface acoustic filter 60 into an audio signal, and the output signal of the second surface acoustic filter 70. A second demodulation circuit 90 that demodulates into a video signal and a video signal of the second demodulation circuit 90 are processed. A video processing unit (100), a SECAM processing unit (110) for processing a SECAM video signal from the video signal of the second demodulation circuit (90), and a PAL video signal from the video signal of the second demodulation circuit (90). A PAL processing unit 120 for processing the PAL processing unit, a SECAM detection circuit 130 for detecting a SECAM signal at the output of the SECAM processing unit 110, and a PAL detection circuit for detecting a PAL signal at the output of the PAL processing unit 120 ( 140 and a select enable signal generating means for generating a control signal for controlling the first and second demodulation circuits 80 and 90 according to the output of the SECAM detection circuit 130 and selecting the PAL / SECAM method. SECAM-L and PAL-B / G characterized in that the oscillation control means 160 for generating a control signal for controlling the oscillator 30 in accordance with the output of the SECAM detection circuit 130 Automatic selection circuit.