JPS5838033B2 - color television receiver - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a color television receiver that is capable of receiving color television signals of a plurality of different systems and that switches internal circuitry according to each system.

As is well known, the color television systems for broadcasting currently implemented in various countries include the NTSC, PAL, and SECAM systems.

Broadcasting formats are generally determined by region, so there is no particular need to prepare a receiver capable of receiving the multiple formats listed above, but in the case of a VTR, for example, video tapes recorded in the PAL format There are cases where it is necessary to play back a video tape recorded in the SECAM format at the same location.

In such cases, conventionally, a plurality of receivers corresponding to each method have been prepared, or receivers each having an independent demodulation system corresponding to each method have been used.

For this reason, it takes a lot of time to prepare the videotape for playback,
Additionally, the circuit of the receiver was complicated.

The present invention is intended to solve the above-mentioned problems.In a receiver having a plurality of color signal demodulation systems corresponding to each system, the color signal is demodulated from the color television signal of that system using one demodulation system. A discrimination signal for the demodulation system is detected, and the operation of other demodulation systems is stopped using this detection signal.

Embodiments of the present invention will be described below with reference to the drawings.

This embodiment is a case where conventionally known NTSC, PAL, and SECAM systems are applied.

The receiver according to this embodiment basically includes a PAL demodulation system and a SECAM demodulation system, but a part of each demodulation system is used in common.

This not only simplifies the circuit configuration, but also
Set the subcarrier frequency of the NTSC signal to 3. 5 8 MHz
From 4. By converting to 43 MHz using a known method, it becomes possible to demodulate NTSC signals using a PAL demodulation system.

In addition, the subcarrier frequency in each method of this embodiment is PA
In the L method, 4.43MHz.In the 1SECAM method, R-
Y signal is 4.43MHz, B-Y signal is 4.25MHz
, 3 in the NTSC system. 4. Converted from 5 8 MHz. 4 3 MHz.

Furthermore, the vertical synchronization frequency of PAL and SECAM systems is 50Hz, and the vertical synchronization frequency of NTSC system is 60Hz.
shall be.

In FIG. 1, color television signals of various systems are applied to an input terminal 1 from a video detection circuit (not shown).

This signal passes through the first video amplifier 2, the delay circuit 3, the second video amplifier 4, and the contrast control circuit 5, and then the luminance signal Y
is added to each of the matrix circuits (ia, 5b, (ic).

The above path is a luminance signal system common to all systems.

In this signal system, on the output side of the first video amplifier 2,
4 consisting of an inductance and a capacitor C1.
．． 2 5 MHz trap circuit 7a is the switch S1
It is provided through.

Further, on the output side of the delay circuit 3, a 4.43 MHz trap circuit 7b composed of an inductance L2 and a capacitor C2 is provided.

According to the above configuration, when a PAL or NTSC signal is applied to the input terminal 1, the trap circuit 7b detects the 4. A subcarrier frequency fraction of 4 3 MHz can be removed.

Furthermore, when the SECAM signal is applied, the ID signal in the SECAM signal is detected as described later, and this detection signal closes the switch S1, so the trap circuits 7a and 7b ．． 4
3MHz s4. 2 5 MHz and center frequency 4. A subcarrier frequency of 406 MHz can be removed.

In the matrix circuits 6a, 5b, and 6c, the luminance signal Y and the color difference signals R-Y, B-Y from the PAL, NTSC chroma system or SECAM chroma system, which will be described later, are processed.
, G-Y are matrixed to obtain three primary color signals of R, G, and B, and these three primary color signals are passed through amplifiers 8a,
The light is applied to the picture tube 9 via 8b and 8c.

It is also possible to directly add the color difference signal and the luminance signal Y to the cathode of the picture tube 9 and each grid to obtain three primary color signals using a known picture tube matrix, without using the matrix circuits 5a, 6b, 6c. It is possible.

Next, a part of the output signal from the first video amplifier 2 is PAL.
are added to the chroma system 10a and the SECAM chroma system 10b, respectively.

The chroma system 10a constitutes a known PAL chroma system, and includes a color signal band amplifier 11, a killer circuit 12, a subcarrier oscillator 13, a 0°/180' phase switching circuit 14,
90° phase shift circuit 15, flip-flop 16, R-Y,
B-Y, G-Y color difference signal demodulation circuits 17a, 17b,
17c1, each color difference signal amplifier 18a, 18b, 18c, a vector synthesis punch path 19, and the like.

A part of these circuits is also used as an NTSC chroma system.

The chroma system 10b constitutes a known SECAM chroma system, and includes a limiter circuit 20, a killer circuit 21, and an IH
Delay circuit 22, switching circuit 23, R-Y frequency discriminator 24a, B-Y frequency discriminator 24b1 matrix circuit 25, color difference signal amplifiers 26a, 26b, 26
c. Discrimination signal (hereinafter referred to as ID signal).

) It is composed of a detection circuit 27, a DC conversion circuit 28, and the like.

Color difference signal amplifier 18a of the chroma system 10a, 10b,
Each color difference signal from 18b, 18c or 26a, 26b, 26c is switched according to the method by a switching circuit 29 and applied to matrix circuits 5a, 5b, fic, respectively.

On the other hand, a part of the output signal from the second video amplifier 4 is applied to a synchronization separation circuit 30 to separate the synchronization signal.

The separated vertical synchronizing signal (2) is applied to a 50/60 Hz discrimination circuit 31 and a video signal presence/absence discrimination circuit 33 of the display direction path 32, respectively.

This display circuit 32 includes the discrimination circuit 33, the display control circuit 34, switches S2, S3, changeover switches S4, NT
SC display lamp 35a, PAL and black and white display lamp 35
b, a SECAM display lamp 35c1, a +B power supply, etc.

In the SECAM chroma system 10b, the ID detection circuit 27
A color difference signal from the GY color difference signal amplifier 26b is added to the signal, and a known ID signal inserted between 9H of the vertical erasing period in this signal is detected.

This detection signal is applied to the switching circuit 23 and used as a switching signal for switching the color video signal for each IH, and is also applied to the DC conversion circuit 28.

The output of this DC conversion circuit 28 is connected to the input terminal 1 by the SECA
Only when the M signal is applied, the DC voltage becomes a positive number (2), and when PAL, NTSC, and black and white signals are applied, it becomes zero (2).

This output is applied to the killer circuit 21, the switch S4, the switch S1, the killer circuit 12, and the switching circuit 29, respectively, via transmission lines indicated by thick lines in the figure.

Then, when the above output is a positive DC voltage, switch S1
is closed, the movable contact of the switch S4 is closed to the contact a side, each movable contact of each switch S, , S6, S7 of the switching circuit 29 is closed to the contact a side, and the killer circuit 12 is activated, and the chroma system The operation of 10a is stopped.

Further, when the output is zero, the killer circuit 21 operates and the operation of the chroma system 10b is stopped.

In the embodiment, the G-Y color difference signal is added to the D detection circuit 27, but the R-Y or B-Y color difference signal may also be added.

Alternatively, the ID signal may be detected directly from the output of the first video amplifier 2.

In the chroma system 10a, the flip-flop 16 is triggered by a pulse synchronized with the horizontal frequency, and is operated by the discrimination signal at 50Hz from the 50/60Hz discrimination circuit 31, since there is no discrimination signal at 60Hz. It is designed so that the operation is stopped when

Next, the operation of the above configuration will be explained.

When a SECAM signal is applied to the input terminal 1, the color difference signal is demodulated by the operation of the chroma system 10b.

The ID detection circuit 27 detects the ■D signal from this color difference signal, and this ID signal is added to the switching circuit 23 to become a switching signal for switching the color signals line sequentially. is converted into DC voltage.

This DC voltage closes the switch S1 and operates the trap circuit 7a.

This causes 4. 2 5 MHz subcarrier component is removed and 4. 4 3 MH
The subcarrier component of z is removed by the trap circuit 7b to obtain the luminance signal Y.

This luminance signal Y is transmitted to matrix circuits 5a, 6b, 6c.
are added to each.

The PAL chroma system 10a includes a well-known burst signal detection circuit (not shown), which operates the subcarrier oscillator 13, but in this case, no burst signal is detected, so the chroma system The killer circuit 12 should be activated by the color killer signal of 10a itself, and the system should be inactive.

However, the 4.43 MHz subcarrier component in the SECAM signal is detected by the color signal band amplifier 1 of the PAL chroma system 10a.
1 into the subcarrier oscillator 13, the operation of the killer circuit 12 is erroneously canceled.

Therefore, the input SECAM signal is PAL chroma system 1.
Demodulated with 0a, this demodulated meaningless signal (noise)
is generated at terminal b of the switching circuit 29, and this signal is mixed into the regular SECAM demodulated signal due to stray capacitance, etc., resulting in image deterioration.

Therefore, in the present invention, the SECAM chroma system 10b
The DC voltage from the DC exchange circuit 28 provided in the PAL
By also supplying the killer circuit 12 of the chroma system 10a, if the SECAM signal is being received, the P
The AL chroma system is not activated.

The DC voltage is applied to the killer circuit 12 by, for example, ORing the color killer signal with the color killer signal.

As a result, the chroma system 10a can be completely rendered inactive, and the SECAM signal is
Deterioration in image quality due to leakage can be prevented.

The above DC voltage is also applied as a switching signal to the switching circuit 29 to close the movable contacts of each switch S5, S6, S7 to the contact a side.

As a result, the color difference signal amplifiers 26a, 26b, 26
The color difference signals R-Y, G-Y, and B-Y from c are applied to matrix circuits 6a, 6b, and 6c, respectively, and matrixed with the luminance signal Y to obtain three primary color signals of R, G, and H. It will be done.

The DC voltage is further applied to the switch S4, closing its movable contact to the contact a side.

On the other hand, the vertical synchronization signal (2) separated by the synchronization separation circuit 30 is applied to a discrimination circuit 31 and a video signal presence/absence discrimination circuit 33.

The discrimination circuit 31 discriminates that the vertical frequency is 50 Hz, and this discrimination signal is applied to the display control circuit 34 as well as to the flip-flop 16, but since the chroma system 10a is inactive as described above, there is no influence. There isn't.

On the other hand, the discrimination signal determined by the discrimination circuit 33 as to the presence of the synchronization signal is applied to the display control circuit 34 to operate this circuit 34.

When the vertical frequency is 50Hz, the display control circuit 3
The output of 4 closes the switch S2.

By turning on this switch S2 and turning on the contact a side of the switch S4 mentioned above, the SECAM display lamp 35c lights up, indicating that the receiver is receiving the SECAM signal.

Next, the case where a PAL signal is applied to input terminal 1 will be described.

In this case, there is no output from the ID detection circuit 27, and the voltage from the DC conversion circuit 28 is zero.

Therefore, the killer circuit 21 of the chroma system 10b is activated, the chroma system 10b becomes inactive, and the chroma system 10a is activated.

In addition, the switch S1 is turned OFF, and the trap circuit 7b is turned off.
4 of the PAL signal only.

The 43 MHz subcarrier component is removed and the luminance signal Y is applied to matrix circuits 6a, 6b, 6c.

All of the switches 84 to S7 are closed to the contact b side.

The flip-flop 16 is operated by the 50 Hz discrimination signal from the discrimination circuit 31, and this flip-flop 16 is triggered by the horizontal synchronizing signal H to repeat the inversion operation at the horizontal frequency.

The phase switching circuit 14 is switched by the output of the flip-flop 16, and the phase of the oscillation output of the subcarrier oscillator 13 is switched to 07180° in horizontal synchronization.

RY taken out from the chroma system 10a by a known method,
Each color difference signal of B-Y and G-Y is sent to a matrix circuit 6a.
, 6b, and 6c, respectively, and are matrixed with the luminance signal Y to obtain three primary color signals of R, G, and H.

On the other hand, since the PAL signal has a vertical frequency of 50 Hz, the switch S2 is turned on.

Turning on this switch S2 and contact b of the switch S mentioned above
When the PAL display lamp 35b is turned on, the PAL display lamp 35b is turned on, indicating that the receiver is receiving a PAL signal.

Next, input terminal 1 has a subcarrier frequency of 4.4 3 MH.
A case will be explained in which an NTSC signal converted to z is added.

In this case, since the voltage of the DC conversion circuit 28 is zero, the switches 84 to S7 are closed to the contact a side, and the switch S1
becomes OFF.

Further, the chroma system 10b becomes inactive, and the color signal is demodulated by the chroma system 10a.

Also, since the vertical frequency is 60Hz, the display control circuit 3
The output of 4 is applied to switch S3, turning it ON.

Therefore, the NTSC display lamp 35a lights up.

A signal determined to be 60 Hz from the determination circuit 31 is applied to the flip-flop 16 to disable it.

As a result, the switching operation of the phase switching circuit 14 is not performed, and the chroma system 10a operates as a known NTSC signal chroma system, and the demodulated color difference signals are transferred to the matrix circuits 6a and 6.
b and 6c, respectively.

The trap circuit 7b then matrixes the subcarriers along with the removed luminance signal Y to generate R, G, B
Three primary color signals are obtained.

Next, when a black and white signal of each system is applied to the input terminal 1, both the chroma systems 10a and 10b become inactive, and the black and white video signal is applied to the picture tube 9 through the same route as the luminance signal Y. It will be done.

Further, in this case, the switch S4 is closed to the b contact side, so the indicator lamp 35b is lit.

Next, a specific example of the DC conversion circuit 28 will be described.

The purpose of this circuit 28 is to distinguish between color and black and white and to determine whether the switching phase of the switching circuit 23 is normal or not.
ID detection circuit 27 in the chroma system of a general SECAM receiver
Here, one example will be described.

In Figure 2A, 36 is a Tayley monomulti, transistors Q1, Q2, resistors R1, R2, R3, R
It is composed of four capacitors C3 and the like.

A trigger pulse synchronized with the vertical frequency from terminal 37 is connected to the base of the transistor Q, through a backflow prevention diode D.
1, and an output pulse is obtained from the collector (point ■).

An output pulse is also obtained from the collector (point ■) of the transistor Q2.

38 is a flip-flop with transistors Qs, Q4,
It is composed of resistors R5, R6, R7, R8, etc.

The output pulse at the point ■ is differentiated by the capacitor C and the resistor R, and is applied to the base of the transistor Q4 via the diode D2, and the output pulse at the point ■ is differentiated by the capacitor C and the resistor R.
5, differentiated by resistor R1o and applied to the base of transistor Q3 via diode D3.

39 is the ID signal input terminal. A capacitor C is applied to the base of transistor Q4 via diode D4.

D5 is a diode for determining the phase of the ID signal, and 40 is an output terminal.

When the trigger pulse (2) shown in FIG. 2B A is applied to the terminal 37, output pulses of mutually opposite polarities shown in FIG. 2B B and C are obtained at points ■ and ■, respectively.

These output pulses are differentiated and their negative parts are applied to the bases of transistors Q3 and Q4, turning transistor Q3 on and transistor Q4 off.

In this case, when there is no ID signal at the input terminal 39, the output of this transistor Q4, that is, the output of the output terminal 40 is the second
This results in a pulse shown in Figure BD.

Since this pulse is generated during the retrace period, the operation of switches S1, S4, etc. does not affect the screen.

The ID signal detected from the color difference signal by the ID signal detection circuit 27 and applied to the input terminal 39 has a negative polarity waveform as shown in FIG. 2F when the switching circuit 23 performs line sequential switching correctly. is obtained.

If the switching is incorrect, a positive polarity waveform as shown in FIG. 2B is obtained.

Therefore, when the ID signal of Fig. 2B F is applied to the input terminal 39, the transistor Q4 is turned off by the output pulse from point
will be done.

Therefore, from the output terminal 40, a constant DC voltage approximately equal to the power supply voltage as shown in Figure 2B and E is obtained, and as described above, this DC voltage is transmitted to each circuit via the transmission path shown by the thick line in Figure 1. Supplied.

This DC voltage is also used to determine the switching phase of the switching circuit 22, and if the D signal is as shown in Fig. 2B, it can be set to the correct switching phase.

Next, an example of the display circuit 32 will be described.

In FIG. 3, the video signal presence/absence determination circuit 33 is designed to turn off all the lamps 35a, 35b, and 35c when there is no input signal at the input terminal 1 in FIG. QttQetQ7, collector resistance R1
1, R1, R13, emitter resistance R14, resistance R15t
R1 coupling capacitor C7, peak detection diode D
6, D7, capacitor C8, base resistor R17, resistor R
ts, transistor Q8, resistor R19, base resistor R
2 smoothing capacitors C, , C1 emitter resistors R2, ,
R2 and transistor Q resistance R23, base resistance R2
Composed of 4th grade? ing.

The display control circuit 34 has the purpose of selecting lamps 35a, 35b, and 35c to be lit according to the type of input signal, and includes a transistor Q.

,Q. ．． t Q1, Q3yQ14, collector resistance R2
5・R26 J R27 t R28 t R29 r
R42N ”Meter resistor R3o, R3, base resistor R3, R33, bias diode D8, resistor R35
, smoothing capacitor C11, etc.

Switch S2 in FIG. 1 includes a transistor Q15, a collector resistor R3, and an emitter resistor R3. , base resistance 1 {s8J
It is composed of R39 etc.

The switch S3 includes a transistor Q1, a resistor R4, a smoothing capacitor C1, a collector resistor R41, and the like.

Next, the operation of the above configuration will be explained.

First, the case where a PAL signal or a SECAM signal is applied to input terminal 1 will be described.

Vertical and horizontal synchronization signals are applied from the synchronization separation circuit 30 to the base of the transistor Q5, and the output pulse taken out from the emitter is sent to the diodes D6, D7 and the capacitor C8.
The peak voltage is detected by

This peak voltage is applied to the base of transistor Q6 turning it on.

The collector output "0" of this transistor Q6 is applied to the bases of transistors Q7 and Q8, respectively, to turn off these transistors Q7 and Q8, respectively.

When the transistor Q8 is turned off, the transistor Q15 is turned on, that is, the switch S2 is closed.

At this time, the switch S4 is closed to the contact a side or the contact b side according to the SECAM signal or the PAL signal, as described above, and when the switch S2 is turned on, the lamp 35b
Or the lamp 35c is turned on.

Note that a switching element such as a transistor is actually used as the switch S4.

Further, the collector output "1" caused by turning off the transistor Q7 turns off the voltage applied to the base of the transistor Q through the resistor R23.

On the other hand, when the discrimination circuit 31 discriminates that the vertical frequency is 50Hz, this discrimination signal voltage, for example, +8.8
is applied to the base of transistor Qll, turning it on.

The emitter of the transistor Q1 and the emitter of the transistor Q1 are connected through a resistor R29, and when the transistor Qll is turned on, the emitter of the transistor Q12 is turned on. The voltage rises, and at this time, this transistor Q1 is turned off.

This turns off the transistor Q16, so the lamp 35a does not light up.

Further, transistor Q14 is also turned off.

Next, a case will be described in which an NTSC signal with a vertical frequency of 60 Hz is applied to input terminal 1.

In this case, the synchronization signal is applied from the synchronization separation circuit 30 to the transistor Q5, so that the transistors Q5 and Q6 are turned ON1 as described above, and the transistors Q7, Q8, and Q
, becomes OFF.

Further, since the voltage from the discrimination circuit 31 becomes zero, the transistor Q1 is turned off.

This turns on transistors Q, 2, and Q13,
Furthermore, the transistor Q16 is turned on and the lamp 35a
lights up.

Further, the transistor Q14 is also turned on, and the base potential of the transistor Q15, which is connected to its collector through the resistor R29, is lowered to turn off the transistor Q15.

Therefore, the lamps 35b and 35C do not light up. Next, when there is no signal at the input terminal 1, the transistor Q is turned off, so the transistor Q6 is turned off, and the transistors Q7 and Q8 are turned on.

Transistor Q15 turns OFF when transistor Q8 turns ON.
The lamps 35b and 35c do not light up because they are FF.

Further, when the transistor Q7 is turned on, the transistor Q9 is also turned on.

The emitter of this transistor Q9 is the transistor Q12.
Since it is connected to the emitter of transistor Q1 through resistor R4, when transistor Q is turned on, the emitter voltage of transistor Q1 increases, so transistor Q1 is turned off.
becomes.

Therefore, transistors Q13 and Q16 are turned off, and lamp 35a is not lit either.

At this time, transistor Q14 is also turned off.

With the above operation, the lamp 35
One of the lights a, 35b, and 35c can be selected and turned on.

The transistor Q is used to prevent the lamp 35a from being lit when there is no signal, and the transistor Q14 is used to prevent the lamps 35b and 35c from being lit when there is an NTSC signal.

Incidentally, the above-described operation is also performed in the case of a black and white signal, and in this case, the lamp 35b is lit.

FIG. 4 shows an example of the matrix circuit 6a, and the matrix circuits 6b and 6C are also similar circuits. It has the following characteristics.

This connects the emitter of NPN transistor Q1 with collector resistor R44 and the emitter of PNP transistor Q18 to bias resistor R43 and bypass capacitor C13.
are connected through parallel circuits.

A luminance signal Y is applied to the base of transistor Q18,
Also, PAL or NTS is connected to the base of transistor Q17.
By applying the RY signal of the C signal or the RY signal of the SECAM signal through the switch S4, both are matrixed at a predetermined ratio, and the R signal can be obtained from the collector of the transistor Q17.

Although a switching element is used as the switch S5, it is of course possible to switch it manually.

As described above, the circuit shown in FIG.
Each circuit can be switched according to the SC, SECAM, and black and white signals, and the display lamp can be turned on.

In particular, the present invention supplies the output of a SECAM chroma system ID signal detection circuit to a PAL chroma system PAL color killer circuit, so that when a SECAM system color television signal is supplied, the PAL chroma system is forcibly activated. Since the subcarrier component in the SECAM signal mixes with the PAL chroma system, the killer circuit is erroneously deactivated and the input SECAM signal is demodulated in the PAL chroma system. meaningless signal (noise)
However, it is possible to effectively prevent the image from being mixed with the regular SECAM demodulated signal and deteriorating the image.

[Brief explanation of drawings]

Fig. 1 is a circuit diagram of a color television receiver showing an embodiment of the present invention, Fig. 2A is a circuit diagram showing an embodiment of a DC voltage conversion circuit, and Fig. 2B is A, B, C, D, E, F.
, G is an output waveform diagram of each part in FIG. 2A, FIG. 3 is a circuit diagram showing an embodiment of a video signal presence/absence determination circuit and a display control circuit,
FIG. 4 is a circuit diagram showing an embodiment of the matrix circuit. In the symbols used in the drawings, 1 is an input terminal, 7a and 7b are trap circuits, 10a is a PAL chroma system, 10b is a SECAM chroma system, 27 is an ID signal detection circuit, 28 is a DC conversion circuit, and 29 is a switching circuit. circuit, 3
2 is a display circuit.

Claims (1)

[Claims] A common input terminal to which color television signals of the I PAL system or SECAM system are commonly supplied, a PAL demodulation circuit to which the color television signals from this common input terminal are supplied, and a connection between this PAL demodulation circuit and the common input terminal. A PAL color killer circuit is provided in between and detects the absence of a PAL burst signal in the color television signal and stops the operation of the PAL chroma system, and the color television signal is supplied from the common input terminal. A SECAM demodulation circuit; an ID signal detection circuit provided on the output side of the SECAM demodulation circuit to detect the presence or absence of an ID signal included in the vertical erasing period of the SECAM method in the color television signal; and an output of the ID signal detection circuit. In a color television receiver having a SECAM color killer circuit that is controlled by a SECAM color killer circuit and stops the operation of the SECAM chroma system when the ID signal is not present, the ID of the SECAM chroma system is
By supplying the output of the signal detection circuit to the PAL color killer circuit of the PAL chroma system, the PAL chroma system is forced to be inactive when a SECAM system color television signal is supplied. TV receiving duck