JPS63148792A - Color signal processing circuit - Google Patents

Abstract

PURPOSE:To always attain an accurate discrimination by varying discrimination functions respectively automatically depending on the intensive strong electric field small level input state of a burst signal, an intensive electric field large level input state and a weak electric field input state. CONSTITUTION:The output of an ACC circuit 15 is fed to a killer control circuit 28 and the output of the circuit 28 controls the discriminating state of a killer detection circuit 22. Through the constitution above, in case of the intensive electric field small level input state (black/white mode) of the burst signal, the base potential of a transistor Q12 is increased to improve the discrimination accuracy, and in case of the intensive electric field large level input state (color mode) of the burst signal or a weak electric field reception state, the base potential of a TR Q12 is lowered to lower the discrimination accuracy. Since the output of a sample/hold circuit 25 and the reference level to be compared are changed in this way, the accurate discrimination is always attained.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to a color signal processing circuit used in a television receiver, etc., and in particular, to a color signal processing circuit used in a television receiver, etc. Regarding what you tried to improve.

(Prior Art) As is well known, the color signal processing circuit of a television receiver has conventionally been configured as shown in FIG. That is, the carrier color signal supplied to the input terminal 11 is amplified by the first chroma amplification circuit 12 and then supplied to the second chroma amplification circuit 13 and the burst amplification circuit 14.

Of these, the burst amplification circuit 14 extracts a burst signal from the input signal and outputs the burst signal to an automatic color control (ACC) circuit 15. This ACC
The circuit 15 is an unspecified AC connected to the connection terminal 16.
The input cover burst signal is level-detected using a C filter circuit, and a control signal (A
CC signal) and uses the ACC signal to control the gain of the first chroma amplifier circuit 12, whereby the output signal level of the first chroma amplifier circuit 12 is controlled to be constant. It is.

Further, the second chroma amplification circuit 13 separates and amplifies the chroma signal component from the input signal. The chroma signal outputted from this second chroma amplification circuit 13 is supplied to the demodulation circuit 17, and (RY), (G
-Y) and (B-Y) color signals.

In this case, in the demodulation circuit 11, the (RY) demodulation carrier (R-Y) generated by the carrier generation circuit 18 is
CW) and carrier for (B-Y) demodulation (B-YCW)
Demodulation processing is performed using Then, the carrier phase of the carrier generation circuit 18 is controlled by automatic phase control ll (
APC) circuit 19. The phase is controlled to be synchronized with the burst signal by a loop formed by a voltage controlled oscillation circuit (VCO) 20, a carrier hue adjustment circuit 21, and the like.

That is, the APC circuit 19 is the burst amplifier circuit 1
Phase detection is performed between the burst signal output from VCO 4 and the oscillation signal output from VCO 20, and the phase of the oscillation signal from VCO 20 is synchronized with the burst signal based on the phase error.

The carrier generation circuit 18 uses the output of -vCO 20 to generate various carriers by phase synthesis.

Further, the burst signal output from the burst amplification circuit 14 is also supplied to the killer detection circuit 22. This killer detection circuit 22 performs multiplicative detection of the carrier from the carrier generation circuit 18 and the burst signal, and determines whether the mode is a color mode or a black-and-white mode depending on whether the burst signal level is above a certain value. Yes(
A discrimination signal which is at H) level and becomes low (L) level in black and white mode is generated in the second chroma amplifier circuit 13.

In this case, the second chroma amplification circuit 13 derives the chroma signal to the demodulation circuit 17 when the H level discrimination signal is supplied, and the chroma signal demodulation circuit 17 when the L level discrimination signal is supplied. It operates to stop output to.

Here, FIG. 4 shows a specific configuration of the first chroma amplification circuit 12 and the killer detection circuit 22.

First, a circuit including transistors Q1 to Q8 and resistors R1 to R10 constitutes a first chroma amplifier circuit 12. That is, the carrier color signal supplied to the input terminal 11 is
After being amplified by a differential amplifier circuit consisting of transistors Ql and Q2, it is synthesized by a double-balanced differential amplifier circuit consisting of transistors 04 to Q7, and then connected to resistors R6 and R.
7, the second chroma amplification circuit 13 and the burst amplification circuit 1 are
4 respectively.

At this time, for example, if the burst signal level of the chroma signal input to the first chroma amplifier circuit 12 becomes high, the AC
Since the burst signal level supplied to the C circuit 15 also becomes high, the ACC circuit 15 generates a detection current Qi in the direction shown in the figure. Therefore, the base potentials of the transistors Q5 and Q6 rise, and as a result, the output signal level generated from the output terminals 23 and 24 falls, and the output level is controlled to be constant.

On the other hand, in FIG. 4, transistors Q9 to Q18. Resistance R1
1 to R15 and a sample/hold circuit 25 constitute a killer detection circuit 22.

Here, the sample and hold circuit 25 samples and holds the input burst signal level every horizontal scanning period. In this case, the sample-and-hold circuit 25 generates an H-level signal when there is a color mode, that is, a burst signal, by the action of a killer filter circuit (not shown) connected to its output terminal via a connection terminal 26, and when a burst signal is present, the sample-and-hold circuit 25 generates an H level signal, In other words, when there is no burst signal, an L level signal is generated.

This killer detection circuit 22 uses the output level of the sample/hold circuit 25 and a transistor.

The reference level ■r generated by a circuit consisting of Q9 to Q11 and resistors R11 to R14 is connected to transistors Q12 to Q
A differential amplifier circuit consisting of transistors Q17 . Q1
This signal is generated in the second chroma amplification circuit 13 via the current mirror circuit 8 and the output terminal 27.

In this case, if the output of the sample/hold circuit 25 is at H level, it becomes higher than the reference level Vr, transistor Q13 is turned off, and an L level discrimination signal corresponding to the color mode is output from the output terminal 27. generated. Furthermore, if the output of the sample/hold circuit 25 is at L level, it becomes lower than the reference level Vr, transistor Q13 is turned on, and an H level discrimination signal corresponding to the black and white mode is generated from the output terminal 27. However, with the conventional means of discriminating between color mode and black and white mode as described above, if the reference level vr is set low so that accurate discrimination can be performed when a weak electric field is input, then when a strong electric field is input A problem arises in that a malfunction occurs when determining the black and white mode.

(Problems to be Solved by the Invention) As described above, with conventional discrimination means, it is difficult to design a circuit that can perform accurate discrimination operations both when a weak electric field is input and when a strong electric field is input. The problem is that

Therefore, the present invention has been made in consideration of the above circumstances, and the discrimination function is automatically changed depending on the strong electric field low level input state of the burst signal, the strong electric field large level input state, and the weak electric field input state. It is an object of the present invention to provide an extremely good color signal processing circuit that can always perform accurate discrimination operations and has a simple configuration.

[Structure of the invention], (Means for solving the problem) That is,
A color signal processing circuit according to the present invention detects a burst signal from the output of a chroma amplification circuit that amplifies a chroma signal in a carrier color signal, and controls a 0ma amplification circuit so that the level of the burst signal is constant. an automatic color control circuit that generates a control signal for the automatic color control circuit; and a killer detection circuit that compares the burst signal, which has been made to a constant level by the automatic color control circuit, with a reference level and generates a signal for discriminating between color mode and monochrome mode. The target is a color signal processing circuit equipped with the following.

Then, according to the llll1l signal output from the automatic color control circuit, the input state of the burst signal is determined, and the determination accuracy of the killer detection circuit is increased in the strong electric field low level input state, and the strong electric field large level input state and the weak The reference level is automatically changed so as to reduce the discrimination accuracy of the killer detection circuit in the electric field input state.

(Function) According to the above configuration, the input state of the burst signal in a strong electric field and the input state in a weak electric field are determined according to the IIJIII signal output from the automatic color control circuit, and the determination result is The reference level is automatically changed based on the , and the discrimination accuracy of the killer detection circuit is changed.
It is now possible to perform accurate discrimination operations in the first state of strong electric field low level input of the burst signal, and the second state of strong electric field large level input and weak electric field input, and the configuration is also simplified. This is something that can be realized.

(Example) Hereinafter, an example of the present invention will be described in detail with reference to the drawings. In FIG. 1, the same parts as in FIG. 3 are indicated by the same symbols, and only the different parts will be described here. That is, the difference from the conventional method is that the output of the ACC circuit 15 is supplied to the killer control circuit 28, and the output of the killer control circuit 28 is used to control the discrimination operation of the killer detection circuit 22.

Then, the killer control circuit 28 discriminates between a strong electric field low level input state, a strong electric field large level input state, or a (very weak electric field input state) of the burst signal according to the control signal output from the ACC circuit 15, The reference level Vr is set such that the discrimination accuracy of the killer detection circuit 22 is increased in a strong electric field low level input state, and the discrimination IIr!1 of the killer detection circuit 22 is reduced in a strong electric field large level input state or a weak electric field input state.
It has the effect of changing the

Here, as shown in FIG. 2, the killer control circuit 28 includes transistors Q19 to Q23 and resistors R16 and R1.
It consists of 7 and more. Then, the ACC circuit 15
By connecting the connection terminal 16 to the output terminal to the killer control circuit 28 side, the output terminal outputs an H level signal when the burst signal is in a strong electric field low level input state, that is, in black and white mode. is generated, and a level signal is generated when a strong electric field is input at a large level, that is, in a color mode or when a weak electric field is input.

Therefore, when a strong electric field of a burst signal is input at a small level, the transistor Q21 is turned on, and a current flows in the direction of the arrow a in FIG. 2, flowing into the resistor RIB, and the base potential of the transistor Q12 rises. Therefore, transistor Q12. Q13 is turned on, and an H level discrimination signal corresponding to the black and white mode is generated from the output terminal 27.

Furthermore, when the burst signal is in a strong electric field high level input state, that is, in color mode, the transistor Q20 is turned on, and a current flows in the direction indicated by the arrow in FIG. . Therefore, transistor Q12. Q13 is turned off, and a level discrimination signal corresponding to the color mode is generated from the output terminal 27.

Further, in the weak electric field input state, the transistor 020 is turned on as in the color mode, and current flows in the direction indicated by the arrow in FIG. 2, and the current flows out from the resistor R16, and the base potential of the transistor Q12 decreases. Here, in a weak electric field input state, the output of the sample-and-hold circuit 25 deteriorates to an intermediate potential between H level and L level, but since the base potential of transistor Q12 is lowered as described above, the discrimination operation is done accurately.

Therefore, according to the configuration of the above embodiment, when the strong electric field level of the burst signal is input in a low level input state, that is, in the monochrome mode, the base potential of the transistor Q12 is increased to improve the discrimination accuracy, and the strong electric field level of the burst signal is increased. In the input state, that is, in color mode or in the weak electric field reception state,
Since the reference level to be compared with the output of the sample-and-hold circuit 25 is changed so as to lower the base potential of the transistor Q12 and lower the discrimination accuracy, accurate discrimination can be performed at all times.

In addition, the determination between the strong electric field low level input state and the strong electric field large level input state or weak electric field reception state of the burst signal is as follows:
Since the output of the CC circuit 15 is used, there is no need to provide a separate determination means, and the configuration can be simplified.

It should be noted that the present invention is not limited to the above-mentioned embodiments, and can be implemented with various modifications without departing from the gist thereof.

[Effects of the Invention] Therefore, as detailed above, according to the present invention, the discrimination function is automatically performed in the strong electric field low level input state of the burst signal, the strong electric field large level input state, and the weak electric field input state. It is possible to provide an extremely good color signal processing circuit that can always perform an accurate discrimination operation by changing the color signal to 1, and can have a simple configuration.

[Brief explanation of the drawing]

FIG. 1 is a block configuration diagram showing an embodiment of a color signal processing circuit according to the present invention, FIG. 2 is a circuit configuration diagram specifically showing the main parts of the same embodiment, and FIG. 3 is a block diagram showing a conventional color signal processing circuit. FIG. 4 is a block configuration diagram showing a processing circuit. FIG. 4 is a circuit configuration diagram showing a specific configuration of a first chroma amplifier circuit and a killer detection circuit of the conventional color signal processing circuit. DESCRIPTION OF SYMBOLS 11... Input terminal, 12... First chroma amplification circuit, 13... Second chroma amplification circuit, 14... Burst amplification circuit, 15... Automatic color control circuit, 16... Connection terminal, 17... Demodulation circuit, 18... Carrier generation circuit, 19... Automatic phase control circuit, 20... Voltage controlled oscillation circuit, 21... Carrier hue adjustment circuit, 22...
... Killer detection circuit, 23.24 ... Output terminal, 25
...sample/hold circuit, 26...connection terminal,
27... Output terminal, 28... Killer iI1wa circuit.

Claims (1)

[Claims] A chroma amplification circuit that amplifies a chroma signal in a carrier color signal, and a control signal that detects a burst signal from the output of this chroma amplification circuit and controls the chroma amplification circuit so that the level of the burst signal is constant. and a killer detection circuit that compares the level of the burst signal, which has been made to a constant level by the automatic color control circuit, with a reference level and generates a signal for discriminating between color mode and monochrome mode. The color signal processing circuit determines the input state of the burst signal according to the control signal output from the automatic color control circuit, increases the discrimination accuracy of the killer detection circuit in the strong electric field low level input state, and A color signal processing circuit comprising a control circuit that changes the reference level so as to reduce the discrimination accuracy of the killer detection circuit in a large electric field input state and a weak electric field input state.