JPS5824991B2 - Tahoushikijiyushinyou TV station Yuzuki - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a multi-system reception television receiver capable of receiving multi-system television broadcasts.

Western European countries, especially countries such as France, Belgium, and Switzerland, are close to each other, so it is possible to receive broadcasts from other countries, but broadcasting methods differ between countries or regions. Therefore, in order to receive broadcasts of different systems with a single receiver, it is necessary to design each circuit in advance according to each system so that reception can be switched as desired.

For example, in certain areas of Europe, in addition to the CCIR standard system, there are three broadcasting systems coexisting: the Belgian system, and the French system, and the signal formats among these systems differ considerably, as shown in Table 1. There is.

Therefore, when receiving broadcasts of such different systems with a single receiver, the bandwidth of the video intermediate frequency amplification circuit and the video amplification circuit, the polarity of the video detection, the audio detection circuit, etc. must be changed according to each system. There must be.

Therefore, in conventional television receivers for multi-system reception of this kind, two detection diodes and a changeover switch are used in the video detection circuit, and the changeover switch is changed according to the reception system to change the detection polarity.

However, in such conventional television receivers, the changeover switch must be manually changed every time the reception method is changed, and if only the reception method is changed without switching, the negative Sometimes, a reversed positive image was displayed.

The present invention has been made in view of these points, and provides a television receiver for multi-system reception in which the polarity of the video signal is automatically switched according to the reception method, regardless of whether the polarity of the video modulation is positive or negative. This is what we provide.

The present invention will be described below according to embodiments shown in the drawings.

FIG. 1 shows one embodiment of the present invention, in which 1 is a video detection circuit consisting of a diode D1, a resistor, a capacitor, etc., 2 is a transistor Ql jQ2 , Q3, a diode D2 . D3, a polarity switching circuit consisting of resistors R1, R2, etc.; 3, a video amplifying circuit consisting of a 4J transistor; 4, a synchronous separation circuit; 5, a phase detection circuit; 6, an AGC amplifier consisting of a transistor Q5, resistors, etc. It is a circuit.

Now, in such a circuit, when a positive polarity modulated video intermediate frequency signal as shown in FIG. A video signal of positive polarity (however, negative polarity in terms of a synchronization signal) is derived, and is supplied to the base of transistor Q1 of polarity switching circuit 2.

The video signal is taken out from the emitter of the transistor Q1 and applied to the sync separation circuit 4.

Although the configuration of the synchronization separation circuit 4 is not specifically specified, a horizontal synchronization signal having a polarity inverted from that of the horizontal synchronization signal included in the video signal is extracted.

Therefore, in this case, a horizontal synchronizing signal of positive polarity as shown in FIG. 2C is obtained from the phase detection circuit 4.

The horizontal synchronization signal is supplied to a phase detection circuit 5, where the polarity of the horizontal synchronization signal is determined based on a flyback pulse having a horizontal oscillation period and a constant polarity.

This phase detection circuit 5 includes, for example, a transistor Q6, a diode D4 . D5 resistor R3, R4t R
52R6 and capacitors C1, C2°C3, a horizontal synchronizing signal is supplied to the base of a transistor Q6, and a diode D4. A negative flyback pulse is supplied to the connection point D.

In the phase detection circuit, when a positive horizontal synchronizing signal is supplied to the base of the transistor Q6, the detection output is e.

When a horizontal synchronizing signal of negative polarity is supplied, a negative output voltage is obtained.

Therefore, in this case, a positive voltage is derived from the phase detection circuit 5, and this is applied to the base of the transistor Q2 of the polarity switching circuit 2, so that the transistor Q2 becomes conductive.

As the transistor Q2 becomes conductive, the transistor Q3 becomes non-conductive, so one end of the resistor R2 becomes open.
Diode D2 becomes conductive and diode D3 becomes non-conductive.

Therefore, at this time, the video signal appearing at the collector of the transistor Q1, that is, the video signal of negative polarity opposite to the video signal shown in FIG. 2, is supplied to the base of the transistor Q4 for video amplification via the diode D2. A video output signal of negative polarity is taken out from the emitter of the transistor Q4.

On the other hand, when the video detection circuit 1 is supplied with a negative polarity modulated video intermediate frequency signal as shown in FIG. A digital video signal is derived from the transistor Q.
1 base.

The video signal is taken out from the emitter and applied to the sync separation circuit 4, from which a horizontal sync signal of negative polarity as shown in FIG. 2f is obtained.

The horizontal synchronization signal is supplied to the phase detection circuit 5, where its polarity is determined from the flyback pulse, and a negative voltage is derived from the phase detection circuit 5.

Therefore, transistor Q2 is non-conductive and transistor Q3 is non-conductive.
becomes conductive, and accordingly, diode D2 becomes conductive and diode D3 becomes non-conductive.

Therefore, at this time, the video signal appearing on the transistor Q1, that is, the video signal of negative polarity as shown in FIG. A sexual video signal is extracted.

In this embodiment, even when a positive polarity modulated video intermediate frequency signal as shown in FIG. 2a is supplied to the video detection circuit 1 as described above, the negative polarity modulated signal as shown in FIG. Even when a video intermediate frequency signal of negative polarity is supplied, a video signal of negative polarity is derived from the emitter of transistor Q4.

In addition, in the above embodiment, the output voltage of the phase detection circuit 5 is AG
The voltage is also supplied to the base of the transistor Q5 for C amplification, and the gain of a video intermediate frequency amplifier (not shown) is controlled based on this output voltage.

FIG. 4 shows another embodiment of the invention.

In the embodiment shown in FIG. 1, the polarity of the horizontal synchronization output of the synchronization separation circuit 4 is different between positive polarity modulation and negative polarity modulation as shown in FIG. Although it is necessary to provide another synchronization separation circuit to obtain a horizontal synchronization signal for controlling the horizontal oscillation stage, in the embodiment shown in FIG. 4, the horizontal synchronization output of the synchronization separation circuit 4 is always of the same polarity.
The horizontal oscillation stage can be controlled based on this output.

Here, the same parts as in the embodiment shown in FIG. D7 and a bistable multi-by-break circuit M are used.

First, the operation when a positive polarity modulated video intermediate frequency signal as shown in FIG. 2a is supplied to the video detection circuit 1 will be explained.
Similar to the operation of the previously described embodiments, the video intermediate frequency signal is detected by the diode D1, and a positive polarity video signal as shown in FIG. 2 is supplied to the base of the transistor Q1.

The video signal is amplified by the transistor Q1, and video signals of positive polarity and negative polarity as shown in FIGS. 2 and 2E are respectively derived from the emitter and collector of the transistor Q1.

By the way, if we assume that the bistable multi-bibreak M is operating in a stable state where the diode D6 is non-conductive, then the diode D2 is now a conductive diode D.
3 is in a non-conducting state, the negative polarity video signal led to the collector side of the transistor Q1 is supplied to the base of the transistor Q4 via the diode D2, and is further amplified by the transistor Q4. A video signal of negative polarity is derived from the emitter of transistor Q4, and is supplied to synchronization separation circuit 4.

Therefore, at this time, a horizontal synchronizing signal of negative polarity as shown in FIG.
The polarity is determined from the flyback pulse of negative polarity, and a negative output voltage is derived from the phase detection circuit 5.

At this time, the diode D7 is in a non-conductive state, so the bistable multi-by-break circuit M maintains the stable operating state up to that point.

Therefore, in such an operating state, the emitter of transistor Q4 outputs a negative-polarity video signal as shown in FIG. 2e, and the synchronization separation circuit 4 outputs a negative-polarity horizontal synchronization signal as shown in FIG. A signal is output.

However, the bistable multi-by-break M is a diode D6.
When the bistable multi-bi-break M is operating in a stable state where it conducts, or when the operation of the bistable multi-bi-break M is reversed due to some reason such as noise and the diode D6 becomes conductive, the diode included becomes non-conductive and the diode D3 becomes conductive. , at this time, the positive polarity video signal led out to the emitter side of the transistor Q1 is supplied to the base of the transistor Q4 via the diode D3,
Video signals of the same polarity are derived from the emitters of 4 and supplied to the sync separation circuit 4.

Therefore, at this time, a positive horizontal synchronization signal as shown in FIG. 2C is derived from the synchronization separation circuit 4, and the phase detection circuit 5
supplied to

Therefore, a positive output voltage is derived from the phase detection circuit 5, which makes the diode D7 conductive and inverts the operation of the bistable multi-bibreak circuit M.

Accordingly, the diode D6 becomes non-conductive, the diode D2 becomes conductive, and the diode D3 becomes non-conductive.

As a result, a video signal of negative polarity is derived from the emitter of transistor Q4.

Next, if the reception method is changed to negative polarity modulation in such an operating state, that is, if the video intermediate frequency signal of negative polarity modulation as shown in FIG. 2d is supplied to the video detection circuit 1,
Due to the detection action of the diode D1, a video signal of negative polarity as shown in FIG. Supplied.

Therefore, at this time, a positive polarity video signal is supplied to the synchronization separation circuit 4 by the same operation as described above, a positive polarity horizontal synchronization signal is derived from the circuit 4, and this is applied to the phase detection circuit 5. A positive output voltage is derived from the circuit 5 and supplied to the bistable multi-bibreak M via the diode D7.

Therefore, the operation of the multi-by-break M is reversed and the diode D6 becomes conductive.

As a result, diode D2 becomes non-conductive, diode D3 becomes conductive, and the second
A video signal of negative polarity as shown in Figure e is derived.

In this way, in this embodiment, regardless of whether a positive polarity modulated video intermediate frequency signal or a negative polarity modulated video intermediate frequency signal is supplied to the video detection circuit 1, the second A video signal of negative polarity as shown in FIG. 2E is derived, and a horizontal synchronization signal of negative polarity as shown in FIG.

In both of the above two embodiments, the horizontal synchronization signal is separated and derived using the synchronization separation circuit 4, and the horizontal synchronization signal is applied to the phase detection circuit 5 to determine the polarity of the synchronization signal. Even when a filter circuit is used instead of 4 and the output signal passing through the filter circuit is applied to the phase detection circuit 5, the output signal has a polarity component almost equivalent to the polarity of the horizontal synchronization signal. , the polarity of the synchronization signal can be determined.

According to the multi-system receiving television receiver of the present invention, even when changing to receiving television broadcasting of another system with a different video modulation system, the video signal can be received by the polarity switching circuit without switching by a manual switch as in the past. The polarity of the image is automatically switched, and an inverted image of negative and positive is not displayed on the screen.

In addition, in the embodiment of the present invention, a case has been described in which the polarity of the video signal is switched according to the reception method, but the present invention can be used to change the bandwidth of the video intermediate frequency amplification circuit and the video amplification circuit and the audio detection circuit according to the reception method. It would also be possible to switch circuits, etc.

[Brief explanation of drawings]

FIG. 1 is a circuit configuration diagram of one embodiment of the present invention, FIG. 2 is a signal waveform diagram for explaining the operation of the same embodiment, FIG. 3 is a circuit configuration diagram of a phase detection circuit in the same embodiment, and FIG. The figure is a circuit configuration diagram of another embodiment of the present invention. 1...Video detection circuit, 2...Polarity switching circuit, 3...Video amplification circuit, 4...Synchronization separation circuit, 5...・Phase detection circuit.

Claims (1)

[Claims] 1. A means for separating and deriving a horizontal synchronizing signal from a video signal after video detection, a means for determining the polarity of the horizontal synchronizing signal obtained by the means, based on a flyback pulse that always has a constant polarity, and the means. means for switching the polarity of the video amplification output based on the polarity discrimination output obtained from the
A television receiver for multi-system reception, characterized by being able to automatically switch and receive multi-system television broadcasts.