JPH0413892Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to a color signal processing circuit of a color television receiver. Measures have been taken to prevent this from happening.

[Technical background of the invention] Generally, in a color television receiver, a reference color subcarrier is required to demodulate the color signal, and by adding this to the color demodulator along with the carrier color signal sent, the demodulated output can be increased. can get. Figure 2 shows
This shows the configuration of a circuit that demodulates color signals,
FIG. 2 is a block diagram that also includes specific external terminals as an integrated circuit.

In the figure, a carrier color signal is supplied to a terminal 1, and this signal is input to a burst amplifier 3 and a second band amplifier 4 via a first band amplifier 2. The burst amplifier 3 has a hue adjustment terminal 5 and branches its output into two systems.One output is introduced into a detector for automatic saturation control (hereinafter referred to as an ACC detector) 6, and its detection output is The signal is applied to the first band amplifier 2, thereby controlling the amplitude of the carrier color signal. The other output of the burst amplifier 3 is led out to the terminal 7 together with the signal from the second band amplifier 4, and is again introduced to the terminal 8 of the integrated circuit via a predetermined external signal path (not shown).
The signal led to this terminal 8 is supplied to a color killer detector 9, a detector for automatic phase control (hereinafter referred to as an APC detector) 10, and a demodulator 11, respectively. The signal input to the APC detector 10 is
The burst signal serves as a reference signal to phase-detect the signal from the voltage-controlled oscillator (hereinafter referred to as VCO) 12, and the phase of the reference color subcarriers CW ₁ and CW ₂ generated by the VCO 12 can be controlled using this detection output. can. The subcarrier whose phase has been controlled in this manner and the carrier color signal from the terminal 8 are supplied to the demodulator 11, and color demodulated outputs of a predetermined phase are output from the output terminal 1, respectively.
2, 13, and 14. In addition, the signal input to the color killer detector 9 is compared in level with the signal from the VCO 12, and the color killer voltage is applied to the second band amplifier 4 during black and white broadcasting without a burst signal and during a weak electric field where the burst level is small. The amplifier 4 is cut off by applying this voltage. In addition, the terminal 1 drawn out from the ACC detector 6, the color killer detector 9, and the APC detector 10
5, 16, and 17 are connected to external filters for integrating the output of each detector, and the terminals 18 and 19 drawn out from the second band amplifier 4 are used to adjust the level of the chromaticity signal. voltage feed end,
The terminal 19 is a so-called unicolor adjustment voltage feeding end. Further, the VCO 12 has terminals 20 and 21 for connecting an oscillation frequency setting element such as a crystal.

On the other hand, FIG. 3 shows a typical example of a practical circuit of the burst amplifier 3. In FIG. This circuit extracts a burst signal from a carrier color signal using a circuit consisting of transistors _Q1 to _Q6 , and varies the burst phase using a circuit consisting of transistors _Q7 to _Q14 . That is, the transistors Q ₁ to Q ₄ form a differential amplifier, the base of the transistor Q ₁ is supplied with the carrier color signal from the first band amplifier 2 via the resistor R ₁ , and the base of the transistor Q ₄ is supplied with the carrier color signal from the first band amplifier 2 via the resistor R 1. A carrier color signal is fed through a phase shifter consisting of a resistor R ₂ and a capacitor C ₁ . In the differential amplifier, the collectors and emitters of transistors Q ₁ and Q ₂ are connected to each other, the collectors and emitters of transistors Q ₃ and Q ₄ are connected to each other, and the bases of transistors Q ₂ and Q ₃ are connected to each other. . This base end has a burst gate pulse
_GP is applied, and with this pulse _GP , transistors Q ₁ ,
One differential burst output is led to the collector of Q ₂ , and a burst signal to the ACC detector 6 is led from the collector of transistor Q ₅ cascade-connected to this collector. Also, transistor
The collectors of Q ₃ and Q ₄ are connected to the band amplification output line 7a via the emitter-collector path of transistor Q ₆ .
and is combined with the chromaticity signal from the second band amplifier 4 on this line 7a. Note that these transistors Q ₅ and Q ₆ have a fixed bias B ₁ applied to their bases, and have load resistances R ₃ and R ₄ between the voltage source line V _CC and the collector, and the load resistance of transistor Q _{6 R4} is shared with the load resistance of the next stage transistor _Q11 . Also transistor
The emitters of Q ₁ and Q ₂ and the transistor Q ₃ ,
The emitters of Q ₄ are connected to the ground line through resistors R ₅ and R ₆ and a common current source I ₁ .

On the other hand, the next stage circuit consists of transistor _Q7 or
Q ₁₀ forms the lower stage differential amplifier, transistor Q _11
Q14 forms an upper stage differential amplifier. The carrier color signal from the phase shifter is supplied to the base of the transistor Q ₇ in the lower stage, a fixed bias of B ₂ is applied to the base of the transistor Q ₁₀ , and the transistors Q ₇ and Q ₁₀ are connected to the transistor Q ₈ respectively. ，
The collector and emitter of Q ₉ are connected together. The bases of these transistors Q ₈ and Q ₉ are connected together, and a burst gate pulse G _P is applied to this connection end. Also, transistors Q ₇ and Q ₈
The collectors of are connected to the emitters of upper stage transistors Q ₁₁ and Q ₁₂ , and the collectors of transistors Q ₉ and Q ₁₀ are connected to the emitters of upper stage transistors Q ₁₃ and Q ₁₄ . Of these upper stage differential amplification elements, the bases of transistors Q ₁₁ and Q ₁₄ and the bases of transistors Q ₁₂ and Q ₁₃ are commonly connected,
A fixed bias _B1 is applied to each connection point via resistors _R7 and _R8 , and a transistor
A voltage from the hue adjustment terminal 5 is applied to the bases of Q ₁₁ and Q ₁₄ via a resistor R ₉ . Note that the emitters of the lower transistors Q ₇ and Q ₈ and the transistors Q ₉ and Q ₁₀ are connected to the ground line via resistors R ₁₀ and R ₁₁ and a common current source I ₂ , respectively. Further, the collectors of the upper stage transistors Q ₁₂ and Q ₁₄ are directly connected to the voltage source line V _CC , while the collector outputs of the transistors Q ₁₁ and Q ₁₃ are led to the band amplification output line 7a,
It joins the differential burst signal from Q ₆ and the chromaticity signal from second band amplifier 4 and is supplied together with these signals to color demodulator 11 , APC detector 10 and color killer detector 9 .

In the above circuit, when performing hue adjustment, the voltage applied to the hue adjustment terminal 5 is varied between the positive side and the negative side around the base voltage of the transistors Q ₁₂ and Q ₁₃ .
For each differential component of the delayed burst signal that passes through the phase shifter derived from Q ₇ and Q ₁₀ , make the negative phase component more on the positive side, the in-phase component more on the negative side, and the same amount at the center position. I can do it. This results in
The delayed burst component of the burst signal from transistor Q ₆ can be adjusted, and as a result, the phase of the burst signal to APC detector 10 can be varied. Therefore, due to this change in the burst signal phase, VCO1
The phases of the subcarriers CW ₁ and CW 2 outputted by the subcarriers CW ₂ are varied, and the hue can be adjusted.

[Problems with Background Art] Conventional circuits have a problem in that the screen background changes depending on the value of the hue adjustment voltage when receiving monochrome broadcasting or when operating a color killer. The reason for this is that when receiving black and white broadcasting and during color killer operation, the second band amplifier 4 is cut off by the color killer voltage, so the color signal component is not normally supplied to the color demodulator 11 etc. VCO12 is oscillating in a free oscillation state,
This is because the oscillation center frequency component and its harmonic components leak from inside and outside the integrated circuit to the input side of the first band amplifier 2, burst amplifier 3, or color demodulator 11. And like this
If there is a leak from VCO12, APC detector 1
0 performs a phase detection operation using this leakage component to generate an output of several mV at the output terminals 12, 13, and 14 of the demodulator 11 according to the hue adjustment position to change the black and white screen or to prevent variations when adjusting the white balance. It was meant to be made bigger.

[Purpose of the invention] This invention was made in view of the above points,
It is an object of the present invention to provide a color signal processing circuit in which the screen background is not affected by the hue adjustment position when receiving monochrome broadcasting or during color killer operation and can accurately adjust white balance.

[Summary of the invention] In order to achieve the above object, the present invention fixes the hue adjustment position when receiving monochrome broadcasting or when operating a color killer, and a carrier color signal including a burst signal and a color signal is supplied. , a first circuit for extracting a burst signal from the carrier color signal; a second circuit for generating a burst signal phase-shifted with respect to the burst signal extracted by the first circuit; first circuit and second circuit
a third circuit which synthesizes the burst signals from the circuits and generates a phase-controlled burst signal, the amount of synthesis being determined by the hue adjustment voltage; a circuit that generates control signals exhibiting different potentials; and a circuit that is coupled to the third circuit and responsive to the control signal, and that generates a burst signal from the third circuit regardless of the value of the hue adjustment voltage during black and white broadcasting. The color signal processing circuit includes a phase locking means for locking the phase.

[Embodiments of the invention] Hereinafter, the present invention will be described in detail with reference to illustrated embodiments.

FIG. 1 is a circuit diagram showing an embodiment of a color signal processing circuit according to the present invention. The explanation will be made with reference to FIG. 2 as well.

In the same figure, _the same parts as those in _FIG . transistor
Q ₇ , Q ₈ and the collectors of transistors Q ₉ , Q ₁₀
In parallel between the transistors, transistors Q ₁₅ and Q ₁₆
The collector and emitter of transistors Q ₁₅ and Q ₁₆ are connected to each other, and a bias power supply B ₃ and the collector of transistor Q ₁₇ are connected to the bases of these transistors Q 15 and Q 16 .

The transistor _Q17 is configured such that, for example, a color killer voltage _VK from the color killer detector 9 shown in FIG. 2 is applied to its base,
The emitter is grounded. This color killer voltage
V _K is a voltage that is at a high level when receiving a color broadcast, and is at a low level when receiving a monochrome broadcast and when operating a color killer.

The operation of the circuit configured as above is as follows.

(1) When receiving a color broadcast When a color broadcast is received, a carrier color signal of a predetermined phase is supplied to the base of the transistor _Q1 through the resistor _R1 , and this signal is transmitted during the gate period of the burst gate pulse _GP (this implementation In the example, the pulse G _P is a negative polarity pulse), the burst signal a is extracted, and the negative phase component -a of the input from the transistor Q ₁ and the in-phase component of the input from the transistor Q ₄ are derived to the respective collectors. On the other hand, since the color killer voltage V _K is at a high level and turns on the transistor Q ₁₇ in the saturation region, for example, it turns off the transistors Q ₁₅ and Q ₁₆ . Therefore, the burst signal b in the delayed carrier color signal that has passed through the phase shifter is transferred to the transistor Q ₇
The input negative phase component -b is derived from the collector of the transistor _Q10 , and the in-phase component b of the input is derived from the collector of the transistor Q10. Therefore, the a-b signal is introduced into the band amplification output line 7a via the emitter-collector path of the transistor _Q6 , and the second band amplifier 4
It joins the chromaticity signal from. Next, when the voltage from the hue adjustment terminal 5 is higher (on the positive side) than the base voltage of the transistors Q ₁₂ and Q ₁₃ , -b becomes larger in absolute value than b according to that value, and the difference is The negative phase component is the transistor Q ₁₁
is combined into an a-b signal via an emitter-collector path, and the hue is adjusted by changing the burst phase by a predetermined amount. On the other hand, when the hue adjustment voltage is lower than the base potential (minus side), b is -b
The signal becomes larger in absolute value and is combined into the a-b signal, making it possible to vary the burst phase by a predetermined amount. Also, when the phase adjustment voltage is equal to the base potential, the absolute values of -b and b are equal,
No signals from transistors Q ₁₁ and Q ₁₃ appear on signal line 7a. At this time, the hue adjustment position is the center position. Therefore, when the hue adjustment voltage is at the maximum level on the positive side, the burst phase is
The phase can be changed from a-b phase at the center position to a-2b phase at the maximum level on the negative side.

(2) When color killer is activated or when receiving black and white broadcasting,
At this time, since the color killer voltage _VK is at a low level, the transistor _Q17 is turned off. As a result, the bias voltage B ₃ is applied to the bases of the transistors Q ₁₅ and Q ₁₆ via the resistor R ₁₂ , and the transistors Q ₁₅ and Q ₁₆ are turned on. When these are turned on, the collector-emitter voltage of transistors Q ₇ and Q ₁₀ is limited by the collector-emitter voltage of transistors Q ₁₅ and Q ₁₆ , and -b and b are kept at the same level during the burst gate period. Output. Therefore, this state is equivalent to setting the hue adjustment position to the center position, and the burst phase is a-
It is fixed at b.

In this way, the present invention has no relation to the hue adjustment position.
The burst signal for phase variation is canceled out, so that the background does not change when a black and white screen is displayed, and no direct current is superimposed on the demodulated output when white balance is adjusted.

[Effects of the invention] As explained above, according to the invention, the hue adjustment position is fixed when receiving black and white broadcasting and during color killer operation, so that the screen background does not change depending on the hue adjustment position. Alternatively, there is an effect that it is possible to suppress misalignment of white balance adjustment.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram showing a color signal processing circuit according to an embodiment of the present invention, Fig. 2 is a block diagram showing an example of the configuration of a color demodulation processing circuit related to the present invention, and Fig. 3 is a circuit diagram showing a conventional color signal processing circuit. FIG. 2 is a circuit diagram showing a signal processing circuit. Q ₁ ~ _{Q 17} ... Transistor, C ₁ ... Capacitor, R ₁ - R ₁₂ ... Resistor, B ₃ ... Bias voltage,
V _K ...Color killer voltage.

Claims (1)

[Claims for Utility Model Registration] A carrier color signal including a burst signal and a chromaticity signal is supplied, and a first circuit for extracting the burst signal from the carrier color signal; and a carrier color signal is extracted by the first circuit. a second circuit that generates a burst signal that is phase-shifted with respect to the burst signal that is phase-controlled; and a circuit that synthesizes the burst signals from the first circuit and the second circuit to generate a phase-controlled burst signal. a third circuit in which the amount of synthesis is determined by the hue adjustment voltage; a circuit that generates a control signal that exhibits different potentials during color broadcasting and monochrome broadcasting; and coupled to the third circuit; and a phase fixing means responsive to the control signal to fix the phase of the burst signal from the third circuit regardless of the value of the hue adjustment voltage during monochrome broadcasting.