JP4538287B2 - Color demodulation circuit - Google Patents

Description

  The present invention relates to an ACC (Automatic Chroma Control) circuit and chroma killer control in a color demodulation circuit for television signal processing.

  A conventional color demodulation circuit detects a burst portion of a digital carrier color signal of a television signal and automatically controls the amplitude level of the detected burst portion to be a preset color signal amplitude level (hereinafter referred to as an ACC circuit, For example, a circuit such as Patent Document 1) and a circuit for detecting a phase shift or amplitude level of a burst signal after output from the ACC circuit and applying a chroma killer are shown. It is shown in FIG.

  The color demodulation circuit shown in FIG. 6 includes a band-pass filter 1, an ACC circuit 2, a multiplier 3, a phase killer detection circuit 4, an amplitude killer detection circuit 5, a chroma killer control circuit 6, and a color difference output demodulation circuit 7. is there.

The band pass filter 1 extracts color components from the digital carrier color signal.
The ACC circuit 2 automatically controls the signal amplitude of the burst portion of the carrier color signal so as to become the level set by the color level setting signal.
The multiplier 3 multiplies the bandpass filter 1 output and the ACC circuit 2 output.

  The phase killer detection circuit 4 outputs a phase killer detection signal based on the phase shift of the burst portion of the carrier color signal whose amplitude is adjusted from the output of the multiplier 3.

  The amplitude killer detection circuit 5 outputs an amplitude killer detection signal based on the amplitude level of the burst portion of the carrier color signal whose amplitude is adjusted from the output of the ACC circuit 2.

  The chroma killer control circuit 6 outputs a chroma killer signal based on the phase killer detection signal output from the phase killer detection circuit 4 and the amplitude killer detection signal output from the amplitude killer detection circuit 5.

  The color difference output demodulating circuit 7 demodulates and outputs a color difference signal (RY signal, BY signal) from the output of the multiplier 3 based on the chroma killer signal.

Next, the operation of the conventional color demodulation circuit will be described.
In the band pass filter 1, the color component is extracted from the input carrier color signal and is multiplied by the output of the ACC circuit 2 by the multiplier 3. In this ACC circuit 2, a value linked to the amplitude of the band-pass filter 1 output is fed back while feeding back the result of the multiplier 3 output so that the color signal amplitude (color level) preset by the color level setting signal is always maintained. Output. That is, the carrier color signal whose amplitude is always adjusted to the color level set by the color level setting signal by the ACC circuit 2 and the multiplier 3 is output to the phase killer detection circuit 4 and the color difference output demodulation circuit 7.

  The phase killer detection circuit 4 detects the phase state of the burst portion of the carrier color signal whose amplitude is adjusted from the output of the multiplier 3, and outputs a phase killer detection signal if the burst phase does not maintain a constant phase state. . The amplitude killer detection circuit 5 detects the amplitude of the burst portion of the carrier color signal whose amplitude has been adjusted from the output of the ACC circuit 2 and outputs an amplitude killer detection signal if the burst amplitude does not reach a certain level. To do.

  The chroma killer control circuit 6 outputs a chroma killer signal to the color difference output demodulation circuit 7 based on the phase killer detection signal output from the phase killer detection circuit 4 and the amplitude killer detection signal output from the amplitude killer detection circuit 5. .

The color difference output demodulating circuit 7 detects the burst signal state of the input carrier color signal based on the chroma killer signal output from the chroma killer control circuit 6, and based on the burst signal state, outputs the RY signal from the multiplier 3 output. , And the BY signal.
Japanese Patent Application Laid-Open No. 08-107549

  However, in the conventional ACC circuit 2, when the burst signal input to the ACC circuit 2 is fluctuated instantaneously, for example, there is a state where there is a burst signal as shown in FIG. When a carrier color signal that changes over time is input to the color demodulation circuit, the multiplier of the multiplier 3 is determined based on the signal amplitude state of the burst portion of the input carrier color signal and the output state of the multiplier 3. Since time is required until the calculation result in the ACC circuit 2 is stabilized, the output state of the ACC circuit 2 becomes an unstable state when the burst signal is present or absent, or when there is no burst signal.

  In addition, when the carrier color signal without the burst signal is input to the color demodulation circuit, the operation of the ACC circuit 2 that automatically controls the burst signal amplitude level to the preset color signal amplitude is impossible. Two outputs are in an unstable state. Therefore, when the output state of the ACC circuit 2 is in an unstable state, the RY signal and the BY signal output from the color difference output demodulation circuit 7 are also confirmed as noise on the television screen due to a sudden change, and the ACC circuit Since the two outputs are directly connected to the amplitude killer detection circuit 5, an erroneous detection of the amplitude killer may occur.

  Furthermore, in the conventional color demodulation circuit, the ACC circuit 2 always outputs a carrier color signal having a constant amplitude level regardless of the input amplitude level. However, the input signal strength of the carrier color signal is a minute input such as a weak electric field. Is supplied to the multiplier 3, the output of the ACC circuit 2 becomes large due to the automatic color control function of the ACC circuit 2, and when the further minute input is given to the multiplier 3, the output of the ACC circuit 2 is saturated. As a result, the carrier color signal cannot be maintained at a constant amplitude level. Further, when the input to the multiplier 3 becomes too small, the amplitude level is attenuated. When phase killer detection is performed in this state, in the conventional configuration in which phase killer detection is performed based on the burst amplitude, a phase killer is erroneously detected that the phase killer is detected even though the phase is correct. It was.

  As described above, the conventional color demodulation circuit cannot cope with the temporal change of the burst signal and the change of the electric field state of the carrier color signal, and it is difficult to perform stable killer detection and color difference output.

  The present invention has been made to solve the above-described conventional problems, and an object thereof is to provide a color demodulation circuit capable of performing stable color difference demodulation regardless of the state of the ACC circuit output.

In order to solve the above-mentioned problem, a color demodulation circuit according to claim 1 of the present invention is a color demodulation circuit that demodulates a color difference signal from a carrier color signal, and that amplifies the amplitude of the carrier color signal. An amplification circuit, an ACC circuit that variably controls the amplification degree of the first amplification circuit in accordance with the input carrier color signal, and detection of the amplitude level of the burst portion of the carrier color signal from the ACC circuit output Detecting a phase shift of the burst portion of the carrier color signal from the output of the first amplifier circuit and generating a chroma killer signal based on the detection result; and a first amplifying the amplitude of the carrier color signal. 2 amplifier circuits, a selector for selecting the first amplifier circuit output or the second amplifier circuit output, and an output of the first amplifier circuit when the chroma killer signal is OFF. Switches the so that the selector when said chroma killer signal is OFF, the switching of the selector to select the output of the first amplifier circuit, when said chroma killer signal is ON, the above immediately before the chroma killer signal is turned ON When the output of the ACC circuit is set as the amplification factor of the second amplifier circuit, the selector is switched to select the output of the second amplifier circuit, and the ACC is changed when the chroma killer signal changes from ON to OFF. A control circuit that switches the selector so as to select the output of the first amplifier circuit after a lapse of a predetermined time until the output state of the circuit becomes stable; and a color difference output demodulation circuit that demodulates a color difference signal from the selector output; , Provided.

According to a second aspect of the present invention, there is provided the color demodulation circuit according to the first aspect, wherein the control circuit is configured such that when the chroma killer signal changes from OFF to ON, the second amplification circuit. the amplification degree After the output of the ACC circuit, is characterized in that the switch between the selector to select the second amplifier circuit output.

According to the color demodulation circuit of the first aspect of the present invention, the color demodulation circuit that demodulates the color difference signal from the carrier color signal, which is input to the first amplification circuit that amplifies the amplitude of the carrier color signal. An ACC circuit that variably controls the amplification degree of the first amplifier circuit in accordance with the carrier color signal, and detecting the amplitude level of the burst portion of the carrier color signal from the output of the ACC circuit, and the first amplification. Detecting a phase shift of a burst portion of the carrier color signal from a circuit output, and generating a chroma killer signal based on the detection result; a second amplifier circuit for amplifying the amplitude of the carrier color signal; a selector for selecting the first amplifier circuit output or said second amplifying circuit output, when the chroma killer signal is OFF, the selector to select the output of the first amplifier circuit When the chroma killer signal is ON, the output of the ACC circuit immediately before the chroma killer signal is turned on is set as the amplification degree of the second amplifier circuit, and the output of the second amplifier circuit is selected. The selector is switched so that, when the chroma killer signal changes from ON to OFF, the output of the first amplifier circuit is selected after a predetermined time until the output state of the ACC circuit becomes stable. And a color difference output demodulating circuit for demodulating the color difference signal from the selector output, the amplitude is adjusted by the amplifier circuit depending on the output of the ACC circuit while detecting a sudden change in the burst signal. The carrier color signal, or the carrier color signal whose amplitude is adjusted by the amplifier circuit independent of the ACC circuit output, can be selected. CC circuit output makes it possible to prevent transient noise, and amplitude killer erroneous detection on the television screen that occurs when the non-stable state.

According to a color demodulation circuit of a second aspect of the present invention, in the color demodulation circuit according to the first aspect of the present invention, the control circuit is configured such that when the chroma killer signal changes from OFF to ON, After the amplification degree of the amplifier circuit and the output of the ACC circuit, the one in which switch between the selector to select the second amplifier circuit output, when the chroma killer signal is oN, depending on the ACC circuit output The color difference output can be demodulated from the carrier color signal whose amplitude has been adjusted by the amplifier circuit that does not, and a more stable color difference output can be obtained.

Embodiments according to the present invention will be described below with reference to the drawings.
(Embodiment 1)
FIG. 1 is a diagram showing a schematic configuration of a color demodulation circuit according to the first embodiment of the present invention.

  1 includes a band-pass filter 10, an ACC circuit 11, a first amplifier (multiplier) 12, a control circuit (CPU) 13, a second amplifier (multiplier) 14, a selector 15, and a chroma killer generation. A circuit 100 and a color difference output demodulation circuit 19 are provided.

The band pass filter 10 extracts color components from the digital carrier color signal.
The ACC circuit 11 detects the signal amplitude of the burst portion of the digital carrier color signal, and automatically controls the detected burst signal amplitude to be a level set in advance by the level setting signal.

  The multiplier 12 multiplies the output of the band pass filter 10 and the output of the ACC circuit 11.

  The CPU 13 monitors the output of the ACC circuit 11 and the chroma killer signal, and outputs an ACC monitor signal and a switching signal. The ACC monitor signal indicates a multiplier input to the multiplier 14, and this multiplier satisfies the relationship of color level setting signal = output of the ACC circuit 11 (multiplier of the multiplier 12) × output of the band pass filter 10. Is to be determined.

The multiplier 14 multiplies the output of the bandpass filter 10 and the ACC monitor signal.
The selector 15 selects the multiplier 12 output or the multiplier 14 output based on a switching signal output from the CPU 13.

  The chroma killer generation circuit 100 generates and outputs a chroma killer signal, and includes a phase killer detection circuit 16, an amplitude killer detection circuit 17, and a chroma killer control circuit 18. The phase killer detection circuit 16 detects the phase state of the burst portion of the output of the multiplier 12 (amplified carrier color signal). If the burst phase does not maintain a constant phase state, the phase killer detection signal is output. Output. The amplitude killer detection circuit 17 detects the amplitude of the burst portion of the carrier color signal whose amplitude has been adjusted from the output of the ACC circuit 11, and outputs an amplitude killer detection signal if the burst amplitude does not reach a certain level. The chroma killer control circuit 18 determines a burst signal state based on the phase killer detection signal and the amplitude killer detection signal, and outputs a chroma killer signal.

  The color difference output demodulation circuit 19 demodulates and outputs a color difference signal (R−Y signal, B−Y signal) from the signal selected by the selector 15 based on the chroma killer signal generated by the chroma killer generation circuit 100.

Next, the operation of the color demodulation circuit according to the first embodiment will be described.
The carrier color signal input to the color demodulation circuit is extracted by the band pass filter 10. The extracted color component is amplitude-adjusted by the ACC circuit 11 and the multiplier 12. The amplitude-adjusted signal (multiplier 12 output) is input to the phase killer detection circuit 16 and the selector 15. Further, the output of the ACC circuit 11 is input to the amplitude killer detection circuit 17.

  The phase killer detection circuit 16 performs phase killer detection on the output of the multiplier 12 (amplified carrier color signal), and the amplitude killer detection circuit 17 performs amplitude killer detection on the output of the ACC circuit 11. Then, the chroma killer control circuit 18 generates a chroma killer signal based on the results of the phase killer detection and the amplitude killer detection.

  When the chroma killer signal output from the chroma killer control circuit 18 is OFF, the CPU 13 outputs a switching signal to the selector 15 so as to select the multiplier 12 output. When the chroma killer signal output from the chroma killer control circuit 18 is ON, the output of the ACC circuit 11 immediately before the chroma killer signal is turned ON is output to the multiplier 14 as an ACC monitor signal, and the output of the multiplier 14 is output. A switching signal is output to the selector 15 for selection.

  The color difference output demodulation circuit 19 demodulates and outputs a color difference signal (RY signal, BY signal) from the selector 15 output.

  Next, the operation of the CPU 13 in the color demodulation circuit according to the first embodiment will be described with reference to FIGS. FIG. 2 is a flowchart for explaining the operation of the CPU 13. 3A and 3B are signal waveform diagrams in the color demodulation circuit according to the first embodiment, where FIG. 3A is a carrier color signal, FIG. 3B is a chroma killer signal, FIG. 3C is an output state of the ACC circuit 11, and FIG. The state of the switching signal is shown.

  First, the output value of the ACC circuit 11 is read and set (step S101). Further, a chroma killer signal is read from the chroma killer generation circuit 100 (step S102), and the chroma killer signal is monitored (step S103).

  In step S103, when the chroma killer signal remains OFF and no state change is detected, that is, when a normal carrier color signal is input to the color demodulation circuit, the output of the ACC circuit 11 is stable, so the multiplier 12 A switching signal is output to the selector 15 so as to select the output (step S104).

  On the other hand, when a change in the state of the chroma killer signal is detected in step S103, that is, as shown in FIG. If it is input, it is confirmed whether the change in the chroma killer signal is from OFF to ON or from ON to OFF (step S105).

  When a change from OFF to ON of the chroma killer signal is detected in step S105, that is, when the burst portion of the carrier color signal is changed from the presence to the absence, the value set in step 101 is set as a multiplier (ACC monitor). Signal) is output to the multiplier 14 (step S106), and a switching signal is output to the selector 15 so as to select the output of the multiplier 14 (step S107).

  In step S105, when the change of the chroma killer signal from ON to OFF is detected, that is, when the burst portion of the carrier color signal changes from absent to present, the state of the output of the ACC circuit 11 is the burst signal. Since it takes time to stabilize due to an abrupt change in time, a predetermined time from when the chroma killer signal changes from ON to OFF until the output state of the ACC circuit 11 becomes stable (step S108) is multiplied. A switching signal is output to the selector 15 so as to select the output of the device 12 (step S109).

  In the first embodiment, another multiplier 14 that does not depend on the output of the ACC circuit 11 is provided, and the output of the bandpass filter 10 and the ACC monitor signal are connected to the input of the multiplier 14, and the state of the output of the ACC circuit 11 For example, when the output of the ACC circuit 11 is in an unstable state with respect to the temporal change of the input carrier color signal with or without the burst signal, the ACC is switched between the multiplier 12 and the multiplier 14. The output of the multiplier 14 that does not depend on the output of the circuit 11 is input to the color difference output demodulation circuit 19 and demodulated into a color difference signal, and the carrier color signal having a constant amplitude is supplied to the color difference output demodulation circuit 19 regardless of the state of the output of the ACC circuit 11. As a result, stable outputs can be obtained for the RY signal and the BY signal, and the output generated when the output of the ACC circuit 11 is in an unstable state can be obtained. It makes it possible to prevent the transient noise on the bi screen.

  In the first embodiment, when the chroma killer signal output from the chroma killer control circuit 18 is ON, the selector 15 is switched and the output of the multiplier 14 is selected and demodulated. However, the signal state of the chroma killer is described. The operation of the color difference output demodulating circuit 19 can be changed according to the usage of the user. For example, when the chroma killer signal is ON, the output of the RY signal and the BY signal is stopped as before. May be.

(Embodiment 2)
FIG. 4 is a diagram showing a schematic configuration of a color demodulation circuit according to the second embodiment of the present invention.
4 includes a band-pass filter 20, an ACC circuit 21, a first amplifier (multiplier) 22, an electric field strength detection circuit 30, a weak electric field detection signal generation circuit 31, a control circuit (CPU) 23, 2, an amplifier (multiplier) 24, a selector 25, a chroma killer generating circuit 200, and a color difference output demodulating circuit 29.

The band pass filter 20 extracts the color component of the digital carrier color signal.
The ACC circuit 21 detects the signal amplitude of the burst portion of the digital carrier color signal, and automatically controls the detected burst signal amplitude to be a level set in advance by the color level setting signal.

The multiplier 22 multiplies the output of the band pass filter 20 and the output of the ACC circuit 21.
The electric field strength detection circuit 30 detects the electric field strength of the television signal.

  The weak electric field detection signal generation circuit 31 turns on the weak electric field detection signal if the electric field intensity detection signal output from the electric field intensity detection circuit 30 has not reached the level set in advance by the weak electric field level setting signal. Output.

  The CPU 23 monitors the color level setting signal, the electric field strength detection signal, and the weak electric field detection signal, and outputs them as a weak electric field state monitor signal. The weak electric field state monitor signal indicates a multiplier input to the multiplier 24. The multiplier has a relationship of color level setting signal = weak electric field state monitor signal (multiplier of the multiplier 24) × bandpass filter 20 output. It is determined to hold.

The multiplier 24 multiplies the output of the bandpass filter 20 and the weak electric field state monitor signal.
The selector 25 selects the multiplier 22 output or the multiplier 24 output based on the weak electric field detection signal.

  The chroma killer generation circuit 200 generates and outputs a chroma killer signal, and includes a phase killer detection circuit 26, an amplitude killer detection circuit 27, and a chroma killer control circuit 28. The phase killer detection circuit 26 detects the phase state of the carrier color signal whose amplitude has been adjusted by the multiplier 22 or the burst portion of the carrier color signal whose amplitude has been adjusted by the multiplier 24, and this burst phase is a constant phase state. If not maintained, a phase killer detection signal is output. The amplitude killer detection circuit 27 detects the amplitude of the burst portion of the carrier color signal whose amplitude is adjusted from the output of the ACC circuit 21, and outputs an amplitude killer detection signal if the burst amplitude does not reach a certain level. The chroma killer control circuit 28 determines a burst signal state based on the phase killer detection signal and the amplitude killer detection signal, and outputs a chroma killer signal.

  The color difference output demodulation circuit 29 demodulates the output of the multiplier 22 into a color difference signal (R−Y signal, B−Y signal) based on the chroma killer signal generated by the chroma killer generation circuit 200 and outputs it.

Next, the operation of the color demodulation circuit according to the second embodiment will be described.
The carrier color signal input to the color demodulation circuit is extracted by the band pass filter 20. The amplitude of the extracted color component is adjusted by the ACC circuit 21 and the multiplier 22. The amplitude-adjusted signal (multiplier 22 output) is input to the selector 25 and the color difference output demodulation circuit 29. Further, the output of the ACC circuit 21 is input to the amplitude killer detection circuit 27.

  The CPU 23 monitors the color level setting signal and the weak electric field detection signal output from the weak electric field detection signal generation circuit 31. When the weak electric field detection signal is ON, the color level setting signal and the electric field strength detection circuit 30 Based on the output electric field strength detection signal, a weak electric field state monitor signal is output to the multiplier 24.

  When the weak electric field detection signal output from the weak electric field detection signal generation circuit 31 is OFF, the output of the multiplier 22 is selected by the selector 25, and when the weak electric field detection signal is ON, the multiplier 24 outputs the multiplier 24. The output is selected and input to the phase killer detection circuit 26.

  The phase killer detection circuit 26 performs phase killer detection on the output of the selector 25, and the amplitude killer detection circuit 27 performs amplitude killer detection on the output of the ACC circuit 21. Then, the chroma killer control circuit 28 generates a chroma killer signal based on the results of the phase killer detection and the amplitude killer detection.

  The color difference output demodulation circuit 29 demodulates the color difference signal from the output of the multiplier 22 when the chroma killer signal is OFF, and stops outputting the color difference signal when the chroma killer signal is ON.

  Next, operations of the CPU 23 and the selector 25 in the color demodulation circuit according to the second embodiment will be described with reference to FIG. Steps S201 to S205 show the operation of the CPU 23, and steps S206 to S207 show the operation of the selector 25.

  First, the CPU 23 reads a color level setting signal (step S201). Further, the weak electric field detection signal is read from the weak electric field detection signal generation circuit 31 (step S202), and the electric field strength of the television signal is monitored (step S203).

  In step S203, when it is detected that the television signal is in the weak electric field state (the electric field strength is weak), that is, when the weak electric field detection signal is ON, the CPU 23 determines the electric field strength from the electric field strength detection circuit 30. The detection signal is read and set (step S204), and a value calculated based on the color level setting signal and the electric field strength detection signal is output to the multiplier 24 as a weak electric field state monitor signal (step S205). The selector 25 selects the output of the multiplier 24 and inputs it to the phase killer detection circuit 26 (step S206).

  On the other hand, when it is detected in step S203 that the television signal is in the normal electric field state, that is, when the weak electric field detection signal is OFF, the selector 25 selects the output of the multiplier 22 and the phase killer. It inputs into the detection circuit 26 (step S207).

  In this way, by switching the output signal to the phase killer detection circuit 26 by the selector 25, it is possible to prevent erroneous detection of the phase killer resulting from the instability of the output of the ACC circuit 21 in a weak electric field state.

  In the second embodiment, since the multiplier 24 independent of the output of the ACC circuit 21 is provided and the input to the phase killer detection circuit 26 is controlled according to the electric field state of the carrier color signal, the ACC circuit 21 When the output state is an unstable state, the multiplier 24 output that does not depend on the output of the ACC circuit 21 is input to the phase killer detection circuit 26, and the carrier color signal having a constant amplitude is phase-shifted regardless of the state of the ACC circuit 21 output. The killer detection circuit 26 can be stably supplied, and as a result, erroneous detection of the phase killer can be prevented.

  In the second embodiment, the case where the color difference output by the color difference output demodulation circuit 29 is stopped when the chroma killer signal output from the chroma killer control circuit 28 is ON has been described. However, the signal state of the chroma killer and the color difference output demodulation circuit 29 are described. The function of can be changed according to the usage of the user. For example, only the chroma killer detection may be performed, and the color difference output may be directly output from the color difference output demodulation circuit 29.

  The color demodulation circuit according to the present invention enables stable color difference demodulation output and killer detection irrespective of the burst signal of the input carrier color signal, and is useful for a color demodulation circuit in television signal processing.

It is a figure which shows the structure of the color demodulation circuit of Embodiment 1 of this invention. FIG. 5 is a flowchart for explaining the operation of a CPU in the color demodulation circuit of the first embodiment. It is a figure for demonstrating the chroma killer control by the color demodulation circuit of the said Embodiment 1. FIG. It is a figure which shows the structure of the color demodulation circuit of Embodiment 2 of this invention. FIG. 10 is a flowchart for explaining the operation of a CPU in the color demodulation circuit of the second embodiment. It is a figure which shows the structure of the conventional color demodulation circuit.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Band pass filter 2 ACC circuit 3 Multiplier 4 Phase killer detection circuit 5 Amplitude killer detection circuit 6 Chroma killer control circuit 7 Color difference output demodulation circuit 10 Band pass filter 11 ACC circuit 12 Multiplier 13 CPU
14 Multiplier 15 Selector 16 Phase Killer Detection Circuit 17 Amplitude Killer Detection Circuit 18 Chroma Killer Control Circuit 19 Color Difference Output Demodulation Circuit 20 Band Pass Filter 21 ACC Circuit 22 Multiplier 23 CPU
24 multiplier 25 selector 26 phase killer detection circuit 27 amplitude killer detection circuit 28 chroma killer control circuit 29 color difference output demodulation circuit 30 electric field strength detection circuit 31 weak electric field detection signal generation circuit 100 chroma killer generation circuit 200 chroma killer generation circuit

Claims (2)

A color demodulation circuit that demodulates a color difference signal from a carrier color signal,
A first amplifier circuit for amplifying the amplitude of the carrier color signal;
An ACC circuit that variably controls the degree of amplification of the first amplifier circuit in accordance with an input carrier color signal;
Based on the detection result, the amplitude level of the burst portion of the carrier color signal is detected from the output of the ACC circuit, and the phase shift of the burst portion of the carrier color signal is detected from the output of the first amplifier circuit. A chroma killer generating circuit for generating a chroma killer signal;
A second amplifier circuit for amplifying the amplitude of the carrier color signal;
A selector for selecting the first amplifier circuit output or the second amplifier circuit output;
When the chroma killer signal is OFF, the selector is switched to select the output of the first amplifier circuit. When the chroma killer signal is ON, the output of the ACC circuit immediately before the chroma killer signal is turned ON 2 is set as the amplification degree of the second amplifier circuit, and the selector is switched to select the output of the second amplifier circuit, and when the chroma killer signal changes from ON to OFF, the output state of the ACC circuit is stable. A control circuit that switches the selector so as to select the output of the first amplifier circuit after a predetermined time has elapsed ;
A color difference output demodulation circuit for demodulating a color difference signal from the selector output,
A color demodulation circuit. The color demodulation circuit according to claim 1,
The control circuit is
After when the chroma killer signal is changed from OFF to ON with the amplification degree of the second amplifier circuit and the output of the ACC circuit, toggle between the selector to select the second amplifier circuit output,
A color demodulation circuit.

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