JPH0544875B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (A) Field of Industrial Application The present invention relates to a color television receiver capable of receiving PAL signals, NTSC signals, and SECAM signals.

(b) Prior Art As a color signal processing unit for a television receiver as mentioned above, the applicant previously proposed a circuit configuration as shown in FIG. 3 in Utility Model Application No. 59-3972. That is,
In Figure 3, 1 is the first IC for PAL/NTSC color signal processing (M51385P manufactured by Mitsubishi Electric Corporation).
etc.), in addition to a band amplification circuit 2 for amplifying PAL and NTSC carrier color signals (PAL: 4.43MHz, NTSC: 3.58MHz), B-Y, R-Y demodulation circuits 3 and 4, APC, ACC, associated with
It is equipped with a color killer circuit, an ID circuit for PAL, a PAL switch circuit, etc. 5 is the second IC for SECAM color signal processing (manufactured by Mitsubishi Electric Corporation)
M51398P, etc.), and a limiter amplifier circuit 6 for amplifying the SECAM carrier color signal, and a direct path from the amplifier circuit.
The non-delayed carrier color signal given via _L1 and the carrier color signal input from the outside via terminal _T7 are distributed to two output paths _L2 and _L3 every 1H (one horizontal period). SECAM switch circuit 7 to be derived, the switching operation of this switch circuit is expressed by horizontal pulse (HP) and
It is provided with a switch control circuit 8 for obtaining and controlling an ID signal (ID), demodulation circuits 9 and 10 for BY and RY, and the like.

On the other hand, 11 is PAL signal, NTSC signal, SECAM
This is a signal path selection circuit that switches a signal path for a carrier color signal in response to each reception of a signal, and is configured as follows. That is, the terminal T ₁ of the first IC 1
A normally active buffer transistor TR, into which the carrier color signal derived from the second IC 5 is input via the coupling capacitor _C1 , the PAL carrier color signal appearing at its emitter and the SECAM carrier color signal derived from the terminal _T6 of the second IC 5 . Switching diodes D ₁ and D ₂ for selectively switching and outputting signals, each of which carries color signals passes through a coupling capacitor C ₂ and is input by a resistor R ₁ for impedance matching and a coil LC with a 1H delay. line 12, the carrier color signal passed through this delay line and the carrier color signal applied from the voltage division midpoint A on the emitter side of the transistor TR via the coupling capacitor _C3 are added and subtracted to produce a B-Y carrier color signal. and R-Y
A transformer 13 that distributes the carrier color signals to the carrier color signals, lines L ₅ and L ₄ that lead the respective signals to the color demodulation circuits 3 and 4 in the first IC 1 , and the carrier color signals that have passed through the delay line 12 are transferred to the terminals of the second IC 5. It is equipped with a coupling capacitor C ₄ etc. leading to T ₇ .

14 is each demodulation circuit 3, 4 or 9, 1.
This is a switching circuit for guiding the B-Y signal and R-Y signal output from 0 to the color matrix circuit, and this switching circuit is the above-mentioned IC:
Although it is built in, it is shown here as an external circuit for convenience.

Note that switching of the passband of the band amplifier circuit 2 in the first IC 1 between PAL reception and NTSC reception is performed by switching constants of an external tuning circuit. Further, the frequency switching of the subcarrier signal applied to the demodulation circuits 3 and 4 within this IC is performed by switching an external crystal oscillator. Further, when receiving NTSC, the switching operation of the PAL switch circuit in this IC is stopped, and a constant phase subcarrier signal for NTSC is given to the demodulation circuits 3 and 4. Since the configuration inside the first IC 1 is already known, further explanation will be omitted.

Now, in the circuit shown in Figure 3, a high level (H) voltage is applied to the first switching terminal _P1 only when receiving PAL, and a low level (L) voltage is applied during other receptions. , on the other hand, the second switching terminal P ₂ has a
L level is applied when receiving PAL, and H level is applied when receiving other signals. Therefore, when receiving PAL, diodes D ₁ and D ₃ are turned on and diode D ₂ is turned off, thereby causing the terminal of the first IC 1 to
The carrier color signal of PAL outputted from T ₁ is applied to the primary side of the transformer 13 through the path of emitter of transistor TR → diode D ₁ → capacitor C ₂ → 1H delay line 12 on the one hand, and is applied to the primary side of transformer 13 on the other hand. It is applied to the intermediate tap on the secondary side of the transformer 13 through the line of TR → point A → capacitor C ₃ , so that both the 1H delayed and non-delayed signals are applied on the secondary side.
The PAL carrier color signals are added and subtracted, resulting in
The B-Y carrier color signal is distributed to line _L5 , and the RY carrier color signal is distributed to line _L4 . At this time, since the diode _D3 is on, the resistance value of the variable resistor VR1 with respect to the carrier color signal becomes equivalently small, and the non-delayed signal given to the intermediate tap on the secondary side of the transformer 13 becomes The voltage is stepped down from the primary side and 2
It is designed to be adjusted to approximately the same magnitude as the 1H delayed signal that appears on the next side.

Furthermore, since the diodes D ₁ and D ₃ are turned off during NTSC reception, the NTSC carrier color signal appearing at the point A is applied to the intermediate tap on the secondary side of the transformer 13 through only the path of the capacitor C ₃ . is equally derived from each of the lines L ₄ and L ₅ . At this time, the resistance value of the variable resistor VR is equivalently increased by turning off the diode _D3 , and the signal at point A is adjusted to approximately twice the size when receiving PAL.
This makes it possible to derive a carrier color signal of approximately the same magnitude as that during PAL reception onto the lines L ₄ and L ₅ .

Next, when receiving SECAM, diode D ₂ is turned on and diodes D ₁ and D ₃ are turned off, so
The SECAM carrier color signal output from terminal T ₆ of the second IC 5 passes through the path of diode D ₂ → capacitor C ₂ → 1H delay line 12 → capacitor C ₄ → terminal T ₇ .
The signal is input to the SECAM switch circuit 7 of the 2IC 5 , from which it is distributed and derived into B-Y and RY carrier color signals.

By the way, in this conventional circuit, the 1H delay line 12
can be used for both PAL and SECAM, and
One of the carrier color signal paths for (i.e. capacitor C ₃ )
It has the advantage that it can be shared for NTSC, but it requires a transformer 13, a buffer transistor TR, three switching diodes _D1 , _D2 , _D5, etc., and the external circuit of the IC is complicated. The drawback was that it could not be realized inexpensively.

(c) Purpose of the invention The present invention has been made in view of the above points,
In realizing a television receiver capable of receiving color television signals of each of the above-mentioned systems, the objective is to realize it at a low cost by simplifying the external circuit of the color signal processing IC as much as possible. do.

(d) Structure of the invention In the color television receiver of the present invention,
PAL in the 1st IC for PAL/NTSC color signal processing
and a first output transistor to which each NTSC carrier color signal is input is turned on only when receiving PAL.
a switching circuit, and a carrier color in which each of the carrier color signals is given as one input via a direct path in the first IC, and the other carrier color signal input is input from the outside via an input terminal of the first IC. A signal distribution circuit is provided, and the second IC for SECAM color signal processing includes a
a second switching circuit that turns on a second output transistor into which the SECAN carrier color signal is input only when SECAM is received; A SECAM switch circuit is provided to which a carrier signal input is externally applied via the input terminal of the second IC, and the commonly connected output terminal of the first and second output transistors and each of the input terminals of the first and second IC are provided. A 1H delay circuit is connected between the and,
The output signals of the color demodulation circuit in the first IC to which the output signal of the carrier color signal distribution circuit is applied and the color demodulation circuit in the second IC to which the output signal from the SECAM switch circuit is applied are selectively taken out. There is.

(e) Embodiment FIG. 1 shows a schematic configuration of the main parts of an embodiment of the present invention. Corresponding parts to those in FIG. explain. That is, in this embodiment, first,
In the first IC 1 for PAL/NTSC color signal processing, in addition to the band amplification circuit 2 and demodulation circuits 3 and 4 similar to those shown in FIG.
Output transistor TR ₁ , carrier color signal distribution circuit 16
It is equipped with The first switching circuit 15 is connected to a first killer voltage K1 and an NTSC switch signal NS, which will be described later.
It operates in response to switching the magnitude (gain) of the output signal of the band amplification circuit 2, and turns on and off the first output transistor _TR1 for deriving this output signal. Further, the carrier color signal distribution circuit 16 has an addition circuit and a subtraction circuit, and the PAL or NTSC carrier color signal from the first switching circuit 15 is directly inputted to one of the two circuits via a path _L6 . and each other carrier color signal input is provided from outside the IC via terminal _T12 . Then, the output signal of the adder circuit is input to the BY demodulation circuit 3 via the line _L4 in the IC,
The output signal of the subtraction circuit is input to the RY demodulation circuit 4 via line _L8 .

Here, the first killer voltage K1 is the PAL or
Generated by detecting the presence or absence of a burst signal in an NTSC signal. Further, the NTSC switch signal NS is a signal indicating whether or not the received signal is an NTS signal.
Manual selection switch installed outside the IC or horizontal
The signal is supplied from a vertical scanning frequency detection circuit or the like. Note that the first IC 1 is of course provided with circuits such as an ID circuit and a PAL switch circuit as in the conventional one.

Next, the second IC 5 of SECAM color signal station processing is
The second output transistor TR ₂ for deriving the output signal of the limiter amplifier circuit 6 is connected to a second killer voltage K2.
The configuration is similar to that of FIG. 3, except that a second switching circuit 17 that turns on and off in response to is added.

In this embodiment, the first and second ICs 1 and 5 are configured as described above, and the first and second ICs have an emitter follower configuration.
The output terminals T ₁₁ and T ₁₅ connected to the respective emitters of the second output transistors TR ₁ and TR ₂ are connected, and the impedance matching resistor R ₁ and the coil are connected to the connection midpoint B via the coupling capacitor C ₂ . 1H with LC
The input terminal of the delay line 12 is connected, the output terminal of this delay line is connected to the input terminal _T16 of the second IC 5 via the coupling capacitor _C4 , and the delay output terminal connected to the output side of the delay line 12 is connected. Variable resistor VR ₂ for amplitude adjustment
The slider is connected to the input terminal _T12 of the first IC1 via a coupling capacitor _C6 . Note that LC is a coil for adjusting delay time.

In this embodiment, when receiving PAL, the first killer voltage K1 is at H level and the NTSC switch signal NS is at L level, as shown in FIG.
As a result, the first switching circuit 15
The gain of the PAL carrier color signal from the PAL carrier color signal is attenuated to approximately 1/2, and the first output transistor _TR1 is turned on to lead out the attenuated PAL carrier color signal to the output terminal _T11 . At this time, the second killer voltage K2 becomes L level, and the second switching circuit 17 turns off the second output transistor _TR2 , but in this state, both transistors _TR1 and _TR2 are connected with a common emitter. This will definitely be achieved.
As a result, the PAL carrier color signal derived from the output terminal _T11 passes through the 1H delay line 12, and then passes through the input terminal _T12 and is input to the carrier color signal distribution circuit 16 in the first IC, and is directly connected to this circuit by the path _L6. By addition and subtraction with the non-delayed carrier color signal inputted through the B-Y and R-Y carrier color signals, they are supplied to the corresponding demodulation circuits 3 and 4, respectively.

Next, when receiving NTSC, the first killer voltage K1 and the NTSC switch signal NS are both high as shown in Figure 2.
become the level. As a result, the first switching circuit 15 does not attenuate the gain of the NTSC carrier signal from the band amplifier circuit 2, and moreover turns off the first output transistor _TR1 . At this time, the second killer voltage K2 becomes L level, and the second output transistor _TR2 also becomes PAL.
It is turned off as it was when I received it. As a result, only the NTSC carrier color signal passing directly from the first switching circuit 15 through the path _L6 is input to the distribution circuit 16, and thus:
The same NTSC carrier color signal is input to the demodulation circuits 3 and 4 in the first IC 1 at substantially the same magnitude as when receiving PAL.

Furthermore, when receiving SECA, the first killer voltage K1 and the NTSC switch signal NS go to L level, turning off the first output transistor _TR1 , and conversely, the second killer voltage K2 goes to H level, and the second output transistor TR1 turns off. Since the output transistor TR ₂ is turned on, the first
The SECAM carrier color signal appearing at the output terminal _T15 of the 2IC5 passes through the 1H delay line 12 and is then input to the SECAM switch circuit 7 in the 2nd IC5 via the input terminal _T16 . Similarly, B-Y
It is divided into a carrier color signal and an R-Y carrier color signal,
The respective signals are given to demodulation circuits 9 and 10, respectively.

The first and second killer voltages K1 and K2 are also inputted to the carrier color signal distribution circuit 16 and the switch control circuit 8, respectively, so that the operations of the respective circuits 16 and 8 are stopped when they are at L level. It's summery.

(F) Effects of the Invention According to the present invention, in realizing a television receiver capable of receiving television signals of PAL, NTSC, and SECAM formats, color signal processing
This has the advantage that the external circuit of the IC can have a very simple configuration with a small number of parts, and can be realized at low cost.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing a schematic configuration of main parts of an embodiment of the present invention, FIG. 2 is a diagram used to explain its operation,
FIG. 3 is a circuit diagram showing a schematic configuration of the main parts of a conventional color television receiver. 1 : 1st IC, 5 : 2nd IC, TR ₁ : 1st output transistor, TR ₂ : 2nd output transistor, 12:
1H delay circuit.

Claims (1)

[Claims] 1. A television receiver capable of receiving PAL signals, NTSC signals, and SECA signals, wherein the first IC 1 for PAL/NTSC color signal processing includes a PAL and NTSC carrier color signal amplification device. a band amplification circuit 2, a first switching circuit 15 that turns on the first output transistor TR1, into which the output signal of the amplification circuit 2 is input, only when receiving PAL, and an addition circuit and a subtraction circuit. A carrier color signal, one input end of which is connected to the output side of the band amplification circuit 2 via a direct path in the first IC, and the other input end of which is connected to the carrier color signal input terminal _T12 of the first IC. A distribution circuit 16 and color demodulation circuits 3 and 4 for demodulating each carrier color signal from the distribution circuit are provided, and a second IC 5 for SECAM color signal processing includes:
Limiter amplifier circuit 6 for SECAM carrier color signal amplification
and a second switching circuit 17 that turns on the second output transistor TR ₂ to which the output signal of the amplifier circuit 6 is input only when SECAM is received; A SECAM switch circuit 7 connected to the output side of the limiter amplifier circuit 6 and whose other input terminal is connected to the carrier color signal input terminal _T16 of the second IC, and demodulates each carrier color signal from the switch circuit 7. Color demodulation circuits 9 and 10 are provided, and a 1H delay circuit is provided between the commonly connected output terminal B of the first and second output transistors and each of the carrier color signal input terminals T ₁₂ and T ₁₆ of the first and second ICs. 12 are connected to each other, and the output signals of the respective color demodulation circuits in the first and second ICs are switched and extracted by a selection circuit 14. 2. The collar according to claim 1, wherein each of the first and second output transistors is configured as an emitter follower type, and each emitter thereof is commonly connected to the input terminal of the 1H delay circuit. television receiver. 3. The color device according to claim 1, wherein the first switching circuit switches to cause the direct path to derive a carrier color signal having approximately twice the size as when receiving PAL when receiving NTSC. television receiver.