JPS635329Y2 - - Google Patents

Description

[Detailed explanation of the invention] (a) Industrial application field This invention is capable of receiving PAL signals, SECAM signals, and NTSC signals (including Mod.NTSC signals).
This invention relates to a color television receiver that shares the 1H delay line necessary for the color demodulation circuit and the SECAM color demodulation circuit.

(B) Prior Art FIG. 1 is a schematic diagram showing an example of a color demodulation circuit of a conventional color television receiver.

In Figure 1, 1 is the first IC that can process PAL chrominance signals and NTSC chrominance signals.
It includes a bandpass amplifier 2, a BY demodulator 3, an RY demodulator 4, and the like. For example, it is an IC manufactured by Mitsubishi Electric Corporation, M51385P. 5 is
A second IC that processes the SECAM chrominance signal, which switches between the limiter amplifier 6, the direct path _l1 , the non-delayed signal given through the direct path _l1 , and the 1H delayed signal given through the external circuit every 1H. Distribute the B-Y component and R-Y component of the chrominance signal to line l ₂ and R-Y line l ₃
SECAM switch 7 and B-Y demodulator 8, R-
A Y demodulator 9 is provided. For example, the IC manufactured by Mitsubishi Electric Corporation, M51398P. 10 is PAL signal,
This is a switching circuit that switches the signal path of an external circuit in response to reception of an NTSC signal or a SECAM signal, and the switching circuit 10 is designed so that the 1H delay line 11 can be shared for receiving PAL signals and SECAM signals.

PAL and NTSC chrominance signals are output from the 1st IC1.
It is output to the 47th pin 47, passes through the switching circuit 10, and is input again through the 46th pin 46 and the 48th pin 48.

The SECAM chrominance signal is output from the first pin of the second IC 5 to the outside via the switching circuit 10 and is input again through the fourth pin.

B ₁ , B ₂ , B ₃ are terminals to which the power supply voltage is applied, P ₁ and P ₂ are terminals to which the power supply voltage is applied when receiving PAL signals, and P ₃ is the terminal to which the power supply voltage is applied when receiving PAL signals.
This is a terminal to which power supply voltage is applied when receiving a signal.
12 is a transformer, and when receiving a PAL signal,
The delayed chrominance signal induced in the secondary coil 12b via the 1H delay line 11 and the primary coil 12a is added and subtracted from the non-delayed chrominance signal applied to the midpoint of the secondary coil 12b to generate the secondary coil. It is output from both ends of the coil 12b.

Next, the operation of the switching circuit 10 will be explained.

(i) When receiving an NTSC signal When receiving an NTSC signal, a killer circuit (not shown) is activated in the second IC 5 and no AC component is output from the No. 1 pin. Since no power supply voltage is applied to the terminals P ₁ and P ₂ , the transistor Q ₁ diodes D ₁ and D ₃ are OFF. At this time, the NTSC chrominance signal output from the 47th pin 47 of the 1st IC1 is supplied to the midpoint of the secondary coil 12b of the transformer 12 via the resistor R ₁ , transistor Q ₂ , diode D ₄ , etc., and then connected to the coupling capacitor. The signal is input to the BY demodulator 3 and the RY demodulator 4 via _C9 , _C10, etc.

(ii) When receiving PAL signals When receiving PAL signals, the power supply voltage is applied to terminal P ₁ , so transistor Q ₁ and diode D ₁
turns on and diode _D2 turns off. Further, since the power supply voltage is also applied to the terminals P ₂ and P ₃ , the diode D ₃ is turned on and the diode D ₄ is turned off. At this time, the output from the 47th pin 47 of the 1st IC1 was
PAL chrominance signal is connected to resistor R ₂ , transistor
Q ₁ , diode D ₁ , resistor R ₆ , R ₇ , capacitor C ₄
The signal is input to the 1H delay line 11 via the 1H delay line 11, etc. Then, the PAL chrominance signal delayed by 1H by the 1H delay line 11 is input to the primary coil 12a of the transformer 12. The middle point of the secondary coil 12b of the transformer 12 is connected to a capacitor C ₂ , a diode D ₃ , and a variable resistor.
It is connected to diode _D1 , which is the PAL chrominance signal path, via _VR1 , etc. Therefore, the transformer 12 adds and subtracts the 1H delayed PAL chrominance signal induced in the secondary coil 12b by the primary coil 12a and the direct PAL chrominance signal applied to the midpoint of the secondary coil 12b. A ±2 (R-Y) chrominance signal and a 2 (B-Y) chrominance signal are output from both ends, and the signals are input to a B-Y demodulator 3 and a R-Y demodulator 4.

(iii) When receiving the SECAM signal When receiving the SECAM signal, the power supply voltage is not applied to the terminals P ₁ and P ₂ and the power supply voltage is applied to the terminal P ₃ , so the transistor Q ₁ diodes D ₁ , D ₃ , and D ₄ are All of them are OFF, and no signal is output from pin 1 of the first IC1 due to a killer circuit (not shown). The diode _D2 is turned on by the output voltage of the No. 1 pin of the second IC5. At this time
The SECAM chrominance signal is input to the SECAM switch 7 after being delayed by 1H via the diode _D2 , capacitor _C4 , 1H delay line 11, capacitor _C6, etc.

As described above, the switching circuit 10 of the conventional color television receiver has a large number of parts, such as requiring two transistors and four diodes.
Furthermore, the number of terminals to which voltage is applied to control the operation of the switching diode is large.

(c) Purpose of the invention The present invention has been made in view of the above points, and is intended to reduce the number of parts in the switching circuit of a color television receiver, and to provide a terminal for supplying control voltage to switching diodes, transistors, etc. It is an object of the present invention to provide a color television receiver in which the cost of the switching circuits can be reduced by reducing the number of switching circuits.

(d) Structure of the invention The invention is based on a system in which the input side of the 1H delay line of the switching circuit of a color television receiver outputs a PAL chrominance signal and an NTSC chrominance signal.
1 IC via a first switching diode, and a second IC that outputs the SECAM chrominance signal via a second switching diode, and the output side of the 1H delay line is connected to the primary coil of the transformer. , a connection point between the first switching diode and the first IC is connected to the middle point of the secondary coil of the transformer via a direct signal path, and when a PAL signal is received, the first switching diode is turned on and the second The switching diode is turned off and the chrominance signal output from the first IC is sent to the first IC of the transformer via the first switching diode and the 1H delay line.
At the same time, a non-delayed chrominance signal is supplied to the midpoint of the secondary coil of the transformer via the direct signal path, and R-Y and B-Y chrominance signals are extracted from both ends of the transformer. , when receiving an NTSC signal, the first switching diode is turned off, and the chrominance signal output from the first IC is supplied to the middle point of the secondary coil of the transformer via the direct signal path. The chrominance signal is extracted as it is from both ends of the chrominance signal, and when receiving the SECAM signal, the first switching diode is turned off.
Turning on the second switching diode,
The chrominance signal output from the second IC is connected to the 1H via the second switching diode.
This color television receiver is characterized in that it supplies a chrominance signal to a delay line and extracts a chrominance signal delayed by 1H from the 1H delay line.

(E) Embodiment FIG. 2 shows an example of a switching circuit for a color television receiver according to the present invention. Incidentally, the same parts as in FIG. 1 are given the same reference numerals and redundant explanation will be omitted.

In FIG. 2, D ₅ is a first switching diode, and D ₆ is a second switching diode, which serve to switch the chrominance signal input to the 1H delay line 11. _B4 is a terminal that supplies power supply voltage, and _P4 is a terminal to which power supply voltage is applied only when receiving a PAL signal. _l5 is a direct signal path for supplying a non-delayed chrominance signal to the middle point of the secondary coil 12b of the transformer 12 when receiving a PAL signal or an NTSC signal, and includes a variable resistor _VR2 and a capacitor _C14 .

The operation of the switching circuit 10 of the color television receiver according to the present invention will be explained below.

(i) When receiving an NTSC signal When receiving an NTSC signal, diode D ₆ is connected to the second IC.
Although it is turned on by the output voltage of IC 5, the second IC 5 does not output an AC signal due to the built-in killer circuit. Also, the bias value of the base of transistor _Q3 is set by a resistor such that the NTSC chrominance signal can pass through transistor _Q3 but does not turn on the first switching diode _D5 .
It is set by R ₂₀ and R ₂₁ . For this reason,
The NTSC chrominance signal output from pin 47 of 1IC1 is connected to capacitor C ₁₁ and transistor
The signal is input to the BY demodulator ₃ and RY demodulator 4 of the first IC 1 via the signal Q 3 , the direct signal path l ₅ , the transformer 12, and the like.

(ii) When receiving a PAL signal When receiving a PAL signal, the power supply voltage is applied to the terminal P ₄ , the base bias value of the transistor Q ₃ becomes high, the transistor Q ₃ and the first switching diode D ₅ turn on, and the second The value of resistor _R19 is determined so that switching diode _D6 is turned off. At this time, the PAL chrominance signal output from the 47th terminal 47 of the 1st IC1 is passed through the 1H delay line through the capacitor C ₁₁ , transistor Q ₃ , first switching diode D ₅ , resistors R ₂₂ , R ₂₅ , capacitor C ₁₂ , etc. 11. Then, the PAL chrominance signal delayed by 1H from the output side of the 1H delay line 11 is input to the primary coil 12a of the transformer 12. Secondary coil 12b of the transformer 12
A non-delayed PAL chrominance signal is fed to the midpoint of the signal via a direct signal path _l5 , etc. Therefore, the transformer 12 has a 1H delay induced in the secondary coil 12b by the primary coil 12a.
A signal obtained by adding and subtracting the PAL chrominance signal and the non-delayed PAL chrominance signal applied to the midpoint of the secondary coil 12b is output from both ends, and the signal is input to the B-Y demodulator 3 and the R-Y demodulator 4. ing.

(iii) When receiving a SECAM signal When receiving a SECAM signal, the first IC 5 does not output a chrominance signal due to the built-in killer circuit. At this time, the second switching diode is activated by the DC output voltage of the first pin of the second IC5.
D ₆ turns on and the first switching diode D ₅
becomes OFF. At this time, the SECAM chrominance signal is connected to the second switching diode _D6 capacitor.
The signal is input to the SECAM switch 7 after being delayed by 1H via the _C12 1H delay line 11 and the capacitor _C16 .

(f) Effects of the invention As described above, according to the invention, the number of components and the number of voltage supply terminals that control switching diodes, etc. are reduced, even though the circuit functions in the same way as a conventional switching circuit. This is useful because it allows cost reduction and the switching circuit can be miniaturized.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing an example of the color demodulation circuit of a conventional color television receiver, and FIG. 2 is a schematic diagram showing an example of the color demodulation circuit of the color television receiver of the present invention. 1...First circuit (1st IC), 5...2nd circuit (2nd IC), _D5 ...1st switching diode,
D ₆ ...Second switching diode, 11...
1H delay line, 12...addition/subtraction circuit (transformer), 1
2a...Primary coil, 12b...Secondary coil, l ₅
...Direct signal path.

Claims (1)

[Scope of Utility Model Registration Claim] (1) In a color television receiver capable of receiving PAL signals, SECAM signals, and NTSC signals,
The input side of the 1H delay line is connected via a first switching diode to a first circuit that outputs a PAL chrominance signal and an NTSC chrominance signal, and is connected via a second switching diode to a second circuit that outputs a SECAM chrominance signal. connected, the output side of the 1H delay line is connected to an addition/subtraction circuit, and a connection point between the first switching diode and the first circuit is also connected to the addition/subtraction circuit via a direct signal path;
When receiving a PAL signal, the first switching diode is turned on, the second switching diode is turned off, and the chrominance signal output from the first circuit is subjected to the addition and subtraction through the first switching diode and the 1H delay line. A 1H delayed chrominance signal is supplied to the circuit, and a non-delayed chrominance signal is supplied to the adder/subtracter circuit via the direct signal path, and R-Y and B-Y chrominance signals are extracted from the adder/subtracter circuit. turning off the first switching diode and supplying the chrominance signal output from the first circuit to the addition/subtraction circuit via the direct signal path;
The chrominance signal is extracted as it is without addition or subtraction from the addition/subtraction circuit, and the first switching diode is switched off when receiving the SECAM signal.
OFF, turn on the second switching diode
A color television characterized in that the chrominance signal output from the second circuit is supplied to the 1H delay line via the second switching diode, and the chrominance signal delayed by 1H from the 1H delay line is extracted. Jiyoung receiver. (2) The addition/subtraction circuit consists of a transformer in which the primary coil is connected to the output side of the 1H delay line, the middle point of the secondary coil is connected to the direct signal path, and the chrominance is connected from both ends of the secondary coil. A color television receiver according to claim 1, characterized in that the color television receiver is adapted to output a signal.