JP2000217012A - Image quality correction device for television receiver - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain stable image quality independently of a tracking error of a tuner circuit. SOLUTION: The subject image quality correction device is provided with a burst signal extract means consisting of a synchronization separator circuit 31, a waveform shaping circuit 32, a band amplifier circuit 33, and a burst separation circuit 34 i order to extract a burst signal from a video signal amplified by a video amplifier circuit 24 of the television receiver and with a level conversion means consisting of an ACC detection and amplifier circuit 35 to convert a fluctuation component of the burst signal into a DC voltage. The DC voltage is fed back to a frequency characteristic correction circuit of the video amplifier circuit 24 via a control circuit 36.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a video signal processing circuit of a television receiver, and more particularly, to an image quality correction device for correcting a band frequency characteristic of a video signal.

[0002]

2. Description of the Related Art FIG. 11 shows a circuit configuration of a conventional television receiver. An input tuning circuit 11, a high-frequency amplifier circuit 12, an interstage tuning circuit 13, a PLL circuit 14, a local oscillation circuit 15,
Tuner circuit 1 including mixing circuit 16 and intermediate frequency tuning circuit 17, SAW filter 21, video intermediate frequency amplifier circuit 22, video detection circuit 23, video amplifier circuit 24, AGC
The image signal processing circuit 2 includes a detection circuit 25, an AGC circuit 26, an audio detection circuit 27, an audio intermediate frequency amplification circuit 28, and an FM detection circuit 29.

That is, a received high-frequency signal is selected for a predetermined channel by an input tuning circuit 11, amplified by a next-stage high-frequency amplifier circuit 12, further removed by an inter-stage tuning circuit 13, and then mixed. Input to the circuit 16. Then, in the mixing circuit 16, the signal is mixed with the local oscillation signal oscillated by the local oscillation circuit 15, converted into an intermediate frequency signal, and the intermediate frequency tuning circuit 17 removes extra signal components. To enter. PLL circuit 14
Is a circuit for controlling the local oscillation frequency oscillated by the local oscillation circuit 15 to be constant.

In the video signal processing circuit 2, the input intermediate frequency signal is passed through a SAW filter 21 to remove excess signal components first, and then amplified by a video intermediate frequency amplifier circuit 22. Thereafter, the amplified video signal is supplied to a video detection circuit 23.
, And input to the video amplification circuit 24. The video signal amplified by the video amplification circuit 24 is converted to an AGC detection circuit 25.
The AGC circuit 26 determines the strength of the input radio wave using the detected video signal, and inputs a control signal for controlling the output level to be constant to the video intermediate frequency amplification circuit 22.

On the other hand, the audio signal is detected by an audio detection circuit 27 to be an audio intermediate frequency signal, amplified by an audio intermediate frequency amplifier circuit 28, and then detected by an FM detection circuit 29.

[0006]

By the way, recent tuner circuits employ an electronic tuning system in which a variable capacitance diode, whose capacitance changes when a reverse applied voltage (tuning voltage) is changed, is used for each tuning circuit. . Therefore, there is a problem that a tracking error due to a variation in components such as a capacitor and a diode is likely to occur, and the frequency characteristic of a video signal varies between reception channels.

[0007] In particular, with the recent increase in the number of channels, when restrictions on adjacent channel interference and various types of interference become strict, the amount of change in the tuning frequency of each tuning circuit with respect to the amount of change in the tuning voltage increases. Need to be higher. Therefore, tracking errors are an unavoidable problem.

In other words, when the frequency characteristics of the video signal are reduced such that the level of the high frequency band is lower than that of the low frequency band due to the variation in the frequency characteristics of the video signal due to the tracking error, the coloring of the image quality becomes soft. Further, if the frequency characteristics are such that the level of the high band is higher than that of the low band, the coloring of the image quality becomes hard. As described above, the variation in image quality between channels due to the tracking error of the tuner circuit has been a problem in television receivers and video devices that require high image quality.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and has as its object to provide an image quality correcting device for a television receiver capable of obtaining a stable image quality irrespective of a tracking error of a tuner circuit. It is in.

[0010]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, a first aspect of the present invention is a burst signal extracting means for extracting a burst signal from a video signal amplified by a video amplifier circuit of a television receiver. A level converting means for converting the fluctuation level of the burst signal extracted by the burst signal extracting means into a DC voltage, and feeding back the DC voltage converted by the level converting means to a frequency characteristic correction circuit of the video amplifier circuit,
And a control means for controlling the level of the high frequency band relative to the low frequency level of the video signal to be constant.

That is, as shown in FIGS. 8 (a) and 8 (b), the frequency characteristic F of the video signal output from the video amplifying circuit is such that the high level is higher than the low level (FIG. 8). 8 (a)) or lower (see FIG. 8).
Then, the level EB of the burst signal included in the video signal which is the output signal of the video amplification circuit is also
In response to this, the size increases (see EB1 in FIG. 8A) or decreases (see EB2 in FIG. 8B). The present invention focuses on the correlation between the change in the frequency characteristic F of the video signal and the change in the level EB of the burst signal. Therefore, in order to extract a burst signal from the video signal output from the video amplification circuit, a burst signal extraction unit including a synchronization separation circuit, a waveform shaping circuit, a band amplification circuit, and a burst separation circuit is provided. In order to convert the DC voltage into a signal, a level conversion means including an ACC detection / amplification circuit is provided, and the DC voltage is fed back to the frequency characteristic correction circuit of the video amplification circuit via the control means. Thus, the level of the high frequency range is controlled to be constant with respect to the low level level of the frequency characteristic of the video signal. That is, since the burst level (color level) is controlled to be constant, it is possible to eliminate the variation in the image quality between the channels.

According to a second aspect of the present invention, in the above configuration, the frequency characteristic correction circuit is provided between a coil inserted on a signal line of the video amplifier circuit and an output side of the coil and ground. The capacitor comprises a connected capacitor and a variable capacitance diode connected in parallel to the capacitor, and the DC voltage is supplied to the cathode side of the variable capacitance diode via a resistor. The essential part of the present invention is an LPF (low-pass filter) including a coil, a capacitor, and a variable capacitance diode including a resistor. The capacitor is a correction capacitance capacitor of the variable capacitance diode, and the resistor is a bias resistance of the variable capacitance diode. is there. That is, by forming an LPF with a coil, a capacitor, and a variable capacitance diode, and applying a DC voltage that has passed through a control circuit to the cathode side of the variable capacitance diode,
The resonance frequency is controlled.

According to a third aspect of the present invention, in the above configuration, the frequency characteristic correction circuit is provided between a coil inserted on a signal line of the video amplifier circuit and an output side of the coil and ground. It comprises a capacitor and a variable capacitance diode connected in series, and the DC voltage is supplied to the cathode side of the variable capacitance diode via a resistor. The essential part of the present invention is that a coil, a capacitor, and a variable capacitance diode include a resistor including a resistor.
PF (Low Pass Filter), the capacitor is a tuning capacitor, and the resistor is a bias resistor of a variable capacitance diode. That is, the resonance frequency is controlled by forming an LPF with a coil, a capacitor, and a variable capacitance diode and applying a DC voltage passed through a control circuit to the cathode side of the variable capacitance diode.

According to a fourth aspect of the present invention, in the above configuration, the frequency characteristic correction circuit includes a coil connected between a signal line and a ground of the video amplifier circuit and a coil connected between the signal line and the ground. And a variable capacitance diode connected in series, and the DC voltage is supplied to the cathode side of the variable capacitance diode via a resistor. The basic part of the present invention is a peaking circuit including a coil, a capacitor, and a variable capacitance diode including a resistor. The capacitor is a tuning capacitor, and the resistance is a bias resistance of the variable capacitance diode.
That is, by forming peaking with a coil, a capacitor and a variable capacitance diode, and applying a DC voltage that has passed through a control circuit to the cathode side of the variable capacitance diode,
The resonance frequency is controlled.

According to a fifth aspect of the present invention, in the above-mentioned configuration, the frequency characteristic correction circuit includes a coil connected between the signal line and the ground of the video amplifier circuit and a coil connected between the signal line and the ground. And a second capacitor connected in parallel with the variable capacitor diode, and the DC voltage is supplied to the cathode side of the variable capacitor diode via a resistor. Is what is done. The basic part of the present invention is a peaking circuit including a coil, a first capacitor, a second capacitor, and a variable capacitance diode including a resistor, wherein the first capacitor is a tuning capacitor,
The second capacitor is a correction capacitance capacitor of the variable capacitance diode, and the resistance is a bias resistance of the variable capacitance diode. That is, peaking is formed by the coil, the first capacitor, the second capacitor, and the variable capacitance diode,
The resonance frequency is controlled by applying a DC voltage that has passed through the control circuit to the cathode side of the variable capacitance diode.

According to a sixth aspect of the present invention, in the above configuration, the video amplifier circuit has a frequency control terminal,
The frequency characteristic correction circuit includes a coil and a variable capacitance diode connected in series between the frequency control terminal and the ground, and a capacitor connected in parallel with the variable capacitance diode, and the cathode side of the variable capacitance diode. The DC voltage is supplied via a resistor. The basic part of the present invention is a peaking circuit including a coil, a capacitor, and a variable capacitance diode including a resistor. The capacitor is a correction capacitance capacitor of the variable capacitance diode, and the resistor is a bias resistance of the variable capacitance diode. That is, the resonance frequency is controlled by forming peaking with a coil, a capacitor, and a variable capacitance diode and applying a DC voltage passed through a control circuit to the cathode side of the variable capacitance diode.

According to a seventh aspect of the present invention, in the above configuration, the video amplifier circuit has a frequency control terminal,
The frequency characteristic correction circuit includes a coil, a capacitor, and a variable capacitance diode connected in series between the frequency control terminal and the ground, and the DC voltage is supplied to a cathode of the variable capacitance diode via a resistor. Things. The basic part of the present invention is a peaking circuit including a coil, a capacitor, and a variable capacitance diode including a resistor. The capacitor is a tuning capacitor, and the resistance is a bias resistance of the variable capacitance diode. That is, the resonance frequency is controlled by forming peaking with a coil, a capacitor, and a variable capacitance diode and applying a DC voltage passed through a control circuit to the cathode side of the variable capacitance diode.

[0018]

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

FIG. 1 is a block diagram showing a circuit configuration of a television receiver including an image quality correcting apparatus according to the present invention. In the figure, reference numeral 11 denotes an input tuning circuit, 12 denotes a high frequency amplifier circuit, and 13 denotes an interstage tuning circuit. , 14 is a PLL circuit, 15 is a local oscillator circuit, 16 is a mixing circuit, 17 is an intermediate frequency tuning circuit, 21 is a SAW filter, 22 is a video intermediate frequency amplifier circuit, 23
Is a video detection circuit, 24 is a video amplification circuit, 25 is an AGC detection circuit, 26 is an AGC circuit, 27 is an audio detection circuit, 28
Denotes an audio intermediate frequency amplification circuit, and 29 denotes an FM detection circuit.
Since these configurations are the same as the circuit configuration of the conventional television receiver shown in FIG. 11, detailed description is omitted here.

In the present invention, in addition to the above-described circuit configuration, in order to extract a burst signal from a video signal output from the video amplification circuit 24, a synchronization separation circuit 31, a waveform shaping circuit 32,
Burst signal extracting means including a band amplification circuit 33 and a burst separation circuit 34 is provided.
In order to convert the fluctuation of the burst signal separated in step 4 into a DC voltage, a level conversion means including an ACC detection / amplification circuit 35 is provided, and the DC voltage is corrected via the control circuit 36 by a frequency characteristic correction circuit (not shown) of the video amplification circuit 24. It is configured to feed back to the circuit.

That is, a video signal which is an output signal of the video amplification circuit 24 is input to the synchronization separation circuit 31 and the band amplification circuit 33. The synchronization separation circuit 31 extracts only the synchronization signal from the input video signal and outputs the synchronization signal to the next waveform shaping circuit 32.
To enter. The waveform shaping circuit 32 generates a gate pulse for extracting a burst signal from the synchronization signal based on the input synchronization signal.

On the other hand, the band amplification circuit 33 extracts only the carrier chrominance signal from the input video signal and inputs it to the next burst separation circuit 34. The burst separation circuit 34 extracts only a burst signal from the input carrier chrominance signal according to the gate pulse given from the waveform shaping circuit 32. Then, the extracted burst signal is input to the ACC detection / amplification circuit 35, where it is converted into a DC voltage corresponding to the fluctuation level of the burst signal.
By feeding back to the frequency characteristic correction circuit of the video amplifier circuit 24 via the control circuit 6, the frequency characteristic correction circuit is controlled so that the high-frequency level of the video signal relative to the low-frequency level is constant.

Thus, even if the band frequency characteristics vary due to the tracking error of the tuner circuit, the burst level (color level) can be kept constant, and the high frequency band of the video signal frequency characteristic between the low band and the low band can be maintained between the channels. Level variation can be suppressed.

Next, various embodiments of the frequency characteristic correction circuit for realizing the image quality correction apparatus of the present invention will be described with reference to the circuit diagrams of FIGS. 2 to 7 and the characteristic diagrams of FIGS. 9 and 10. It will be described with reference to FIG.

FIG. 2 is a circuit diagram of a frequency characteristic correction circuit according to a second aspect. The frequency characteristic correction circuit is connected to a coil L1 inserted on a signal line of the video amplifier circuit 24, a capacitor C1 connected between the output side of the coil L1 and the ground, and connected in parallel to the capacitor C1. And a control circuit 36 is connected to the cathode side of the variable capacitance diode D1 via a resistor R1. In addition, a sync separation circuit 31 and a band amplification circuit 33 are connected to the cathode side of the variable capacitance diode D1.

The main part of this embodiment is a coil L1,
A resistor R is connected to the capacitor C1 and the variable capacitance diode D1.
1 is an LPF (low-pass filter) that is configured to include 1. The capacitor C1 is a variable capacitance diode D1
And the resistor R1 are bias resistors of the variable capacitance diode. That is, an LPF is formed by the coil L1, the capacitor C1, and the variable capacitance diode D1, and the control circuit 3 is connected to the cathode of the variable capacitance diode D1.
The resonance frequency is controlled by applying a DC voltage that has passed through 6.

Thus, for example, when the frequency characteristic of the video signal is the same as the low-frequency level in the high-frequency level, the frequency characteristic becomes as shown by the solid line in FIG.
The level of the burst signal included in the output signal is EB3
Becomes On the other hand, when the level of the high frequency band relative to the low frequency band of the video signal is reduced due to the variation between the channels, the frequency characteristic becomes as shown by the solid line in FIG. The signal level EB4 satisfies EB3> EB4. Therefore, the level of this burst signal is converted into a DC voltage, and this is fed back to the frequency characteristic correction circuit via the control circuit 36,
By changing the resonance frequency as shown in FIG.
By controlling the frequency characteristic correction circuit so that = EB4, the burst level (color level) can be kept constant. Note that FIG. 9 shows only the case where the level of the high frequency band relative to the low frequency band of the video signal is reduced (FIG. 9B). Even when the level of the area increases, the burst level (color level) can be kept constant by the same control.

FIG. 3 is a circuit diagram of a frequency characteristic correction circuit according to the third aspect. This frequency characteristic correction circuit includes a coil L1 inserted on a signal line of the video amplifier circuit 24, and a capacitor C1 and a variable capacitance diode D1 connected in series between the output side of the coil L1 and the ground. The control circuit 36 is connected to the cathode side of the variable capacitance diode D1 via the resistor R1. Also, at the connection point between the coil L1 and the capacitor C1,
The synchronization separation circuit 31 and the band amplification circuit 33 are connected.

The main part of this embodiment is a coil L1,
A resistor R is connected to the capacitor C1 and the variable capacitance diode D1.
1 is a LPF (low-pass filter) including a tuning capacitor and a resistor R
1 is a bias resistance of the variable capacitance diode D1. That is, an LPF is formed by the coil L1, the capacitor C1, and the variable capacitance diode D1, and the variable capacitance diode D1
The resonance frequency is controlled by applying a DC voltage that has passed through the control circuit 36 to the cathode side of.

Thus, for example, when the frequency characteristic of the video signal is the same as the low-frequency level in the high frequency level, the frequency characteristic becomes as shown by the solid line in FIG.
The level of the burst signal included in the output signal is EB3
Becomes On the other hand, when the level of the high frequency band relative to the low frequency band of the video signal is reduced due to the variation between the channels, the frequency characteristic becomes as shown by the solid line in FIG. The signal level EB4 satisfies EB3> EB4. Therefore, the level of this burst signal is converted into a DC voltage, and this is fed back to the frequency characteristic correction circuit via the control circuit 36,
By changing the resonance frequency as shown in FIG.
By controlling the frequency characteristic correction circuit so that = EB4, the burst level (color level) can be kept constant.

FIG. 4 is a circuit diagram of a frequency characteristic correction circuit according to a fourth aspect. This frequency characteristic correction circuit includes a coil L1 connected between the signal line of the video amplifier circuit 24 and the ground, and a capacitor C1 and a variable capacitance diode D1 connected in series between the signal line and the ground. The control circuit 36 is connected to the cathode side of the variable capacitance diode D1 via the resistor R1. Also, at the connection point between the coil L1 and the capacitor C1,
The synchronization separation circuit 31 and the band amplification circuit 33 are connected.

The main part of this embodiment is a coil L1,
A resistor R is connected to the capacitor C1 and the variable capacitance diode D1.
1 is a peaking circuit, wherein the capacitor C1 is a tuning capacitor, and the resistor R1 is a bias resistor of the variable capacitance diode D1. That is, peaking is formed by the coil L1, the capacitor C1, and the variable capacitance diode D1, and a DC voltage passed through the control circuit 36 is applied to the cathode side of the variable capacitance diode D1, thereby controlling the resonance frequency.

Thus, for example, when the frequency characteristic of the video signal is the same as the low-frequency level in the high-frequency level, the frequency characteristic becomes as shown by the solid line in FIG. The level of the included burst signal is E
B5. On the other hand, when the level of the high frequency band relative to the low frequency band of the video signal is reduced due to the variation between the channels, the frequency characteristics shown by the solid line in FIG. The signal level EB6 satisfies EB5> EB6. Therefore, the level of the burst signal is converted into a DC voltage, and the DC voltage is fed back to the frequency characteristic correction circuit via the control circuit 36, and the resonance frequency is changed as shown in FIG. 10 (c) so that EB5 = EB6. By controlling the frequency characteristic correction circuit in this manner, the burst level (color level) can be kept constant. Note that FIG. 10 only shows a case where the level of the high frequency range of the frequency characteristic of the video signal is lower than the low frequency range (FIG. 10B).
Even when the level of the frequency characteristic of the video signal in the high frequency range relative to the low frequency range is increased, the burst level (color level) can be kept constant by the same control.

FIG. 5 is a circuit diagram of a frequency characteristic correction circuit according to the fifth aspect. This frequency correction circuit
A coil L1 connected between the signal line of the video amplifier circuit 24 and the ground, a first capacitor C1 and a variable capacitance diode D1 connected in series between the signal line and the ground, and the variable capacitance diode D1 , And a control circuit 36 is connected to the cathode side of the variable capacitance diode D1 via a resistor R1. Further, a synchronization separation circuit 31 and a band amplification circuit 33 are connected to a connection point between the coil L1 and the first capacitor C1.

The main part of this embodiment is a coil L1,
A peaking circuit including a first capacitor C1, a second capacitor C2, and a variable capacitance diode D1 including a resistor R1, wherein the first capacitor C1 is a tuning capacitor, and the second capacitor C2 is a variable capacitor. The correction capacitance capacitor of the capacitance diode D1 and the resistor R1 are bias resistors of the variable capacitance diode D1. That is, the coil L1, the first capacitor C1, and the second capacitor C2
The peaking is formed by the variable capacitance diode D1 and a DC voltage passed through the control circuit 36 is applied to the cathode side of the variable capacitance diode D1 to control the resonance frequency.

Thus, for example, when the frequency characteristic of the video signal is the same as the low-frequency level in the high-frequency level, the frequency characteristic becomes as shown by the solid line in FIG. The level of the included burst signal is E
B5. On the other hand, when the level of the high frequency band relative to the low frequency band of the video signal is reduced due to the variation between the channels, the frequency characteristics shown by the solid line in FIG. The signal level EB6 satisfies EB5> EB6. Therefore, the level of the burst signal is converted into a DC voltage, and the DC voltage is fed back to the frequency characteristic correction circuit via the control circuit 36, and the resonance frequency is changed as shown in FIG. 10 (c) so that EB5 = EB6. By controlling the frequency characteristic correction circuit in this manner, the burst level (color level) can be kept constant.

FIG. 6 is a circuit diagram of a frequency characteristic correction circuit according to the sixth aspect. In the present embodiment, the video amplification circuit 24 has a frequency control terminal, and the frequency characteristic correction circuit includes a coil L1 and a variable capacitance diode D1 connected in series between the frequency control terminal and the ground. The variable capacitance diode D1 comprises a capacitor C1 connected in parallel with the variable capacitance diode D1.
The control circuit 36 is connected to the cathode side of the transistor via a resistor R1. Further, a synchronization separation circuit 31 and a band amplification circuit 33 are connected to a connection point between the coil L1 and the first capacitor C1.

The main part of this embodiment is a coil L1,
A resistor R is connected to the capacitor C1 and the variable capacitance diode D1.
The capacitor C1 is a correction capacitor for the variable capacitance diode D1, and the resistor R1 is a bias resistor for the variable capacitance diode D1. That is, the coil L1, the capacitor C1
The peaking is formed by the variable capacitance diode D1 and a DC voltage passed through the control circuit 36 is applied to the cathode side of the variable capacitance diode D1 to control the resonance frequency.

Thus, for example, when the frequency characteristic of the video signal is the same as the low-frequency level in the high-frequency level, the frequency characteristic becomes as shown by the solid line in FIG. The level of the included burst signal is E
B5. On the other hand, when the level of the high frequency band relative to the low frequency band of the video signal is reduced due to the variation between the channels, the frequency characteristics shown by the solid line in FIG. The signal level EB6 satisfies EB5> EB6. Therefore, the level of the burst signal is converted into a DC voltage, and the DC voltage is fed back to the frequency characteristic correction circuit via the control circuit 36, and the resonance frequency is changed as shown in FIG. 10 (c) so that EB5 = EB6. By controlling the frequency characteristic correction circuit in this manner, the burst level (color level) can be kept constant.

FIG. 7 is a circuit diagram of a frequency characteristic correction circuit according to the seventh aspect. In the present embodiment, the video amplification circuit 24 has a frequency control terminal, and the frequency characteristic correction circuit includes a coil L1, a capacitor C1, and a variable capacitance diode connected in series between the frequency control terminal and the ground. D1 and a variable capacitance diode D
The control circuit 36 is connected to the cathode side of 1 via a resistor R1. Further, the coil L1 and the first capacitor C1
Is connected to the synchronization separation circuit 31 and the band amplification circuit 33.

The main part of this embodiment is a coil L1,
A resistor R is connected to the capacitor C1 and the variable capacitance diode D1.
1 is a peaking circuit, wherein the capacitor C1 is a tuning capacitor, and the resistor R1 is a bias resistor of the variable capacitance diode D1. That is, peaking is formed by the coil L1, the capacitor C1, and the variable capacitance diode D1, and a DC voltage passed through the control circuit 36 is applied to the cathode side of the variable capacitance diode D1, thereby controlling the resonance frequency.

Thus, for example, when the frequency characteristic of the video signal is the same as the low-frequency level in the high-frequency level, the frequency characteristic becomes as shown by the solid line in FIG. The level of the included burst signal is E
B5. On the other hand, when the level of the high frequency band relative to the low frequency band of the video signal is reduced due to the variation between the channels, the frequency characteristics shown by the solid line in FIG. The signal level EB6 satisfies EB5> EB6. Therefore, the level of the burst signal is converted into a DC voltage, and the DC voltage is fed back to the frequency characteristic correction circuit via the control circuit 36, and the resonance frequency is changed as shown in FIG. 10 (c) so that EB5 = EB6. By controlling the frequency characteristic correction circuit in this manner, the burst level (color level) can be kept constant.

[0043]

According to the picture quality correcting apparatus for a television receiver of the present invention, when the band frequency characteristics vary due to the tracking error of the tuner circuit, the level of the video signal frequency characteristics between channels is higher than the lower frequency range. Can be suppressed, so that a change in image quality between channels can be eliminated.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a circuit configuration of a television receiver including an image quality correction device of the present invention.

FIG. 2 is a circuit diagram of a frequency characteristic correction circuit according to claim 2 of the present invention.

FIG. 3 is a circuit diagram of a frequency characteristic correction circuit according to claim 3 of the present invention.

FIG. 4 is a circuit diagram of a frequency characteristic correction circuit according to claim 4 of the present invention.

FIG. 5 is a circuit diagram of a frequency characteristic correction circuit according to claim 5 of the present invention.

FIG. 6 is a circuit diagram of a frequency characteristic correction circuit according to claim 6 of the present invention.

FIG. 7 is a circuit diagram of a frequency characteristic correction circuit according to claim 7 of the present invention.

FIGS. 8A and 8B are explanatory diagrams showing a difference in burst signal due to a difference in level of a high frequency band with respect to a low frequency band of a video signal frequency characteristic.

9A is an explanatory diagram showing a standard video signal frequency characteristic and a pass characteristic of the circuit of the present invention, and a burst signal level at that time. FIG. FIG. 4 is an explanatory view showing the pass characteristics of the circuit of the present invention and the burst signal level at that time. FIG. 9 is an explanatory diagram showing levels.

10A is an explanatory diagram showing a standard video signal frequency characteristic and a pass characteristic of the circuit of the present invention, and a burst signal level at that time. FIG. 10B is a diagram showing a video signal frequency characteristic at the time of a tracking error and the present invention. FIG. 4 is an explanatory view showing the pass characteristics of the circuit of the present invention and the burst signal level at that time. FIG. 9 is an explanatory diagram showing levels.

FIG. 11 is a block diagram illustrating a circuit configuration of a conventional television receiver.

[Explanation of symbols]

 24 Video amplification circuit 31 Synchronization separation circuit 32 Waveform shaping circuit 33 Band amplification circuit 34 Burst separation circuit 35 ACC detection / amplification circuit 36 Control circuit

Claims (7)

[Claims] 1. A burst signal extracting means for extracting a burst signal from a video signal amplified by a video amplifier circuit of a television receiver, and a level for converting a fluctuation level of the burst signal extracted by the burst signal extracting means into a DC voltage. Converting means, and feeding back the DC voltage converted by the level converting means to the frequency characteristic correction circuit of the video amplifier circuit, so that the level of the high frequency band relative to the low frequency level of the frequency characteristics of the video signal becomes constant. Control means for controlling the image quality in a television receiver. 2. A frequency characteristic correction circuit, comprising: a coil inserted on a signal line of a video amplification circuit; a capacitor connected between an output side of the coil and ground; and a capacitor connected in parallel to the capacitor. The image quality correction device for a television receiver according to claim 1, comprising a variable capacitance diode, wherein the DC voltage is supplied to a cathode side of the variable capacitance diode via a resistor. 3. The frequency characteristic correction circuit includes a coil inserted on a signal line of a video amplifier circuit, and a capacitor and a variable capacitance diode connected in series between an output side of the coil and ground. 2. The image quality correction device according to claim 1, wherein the DC voltage is supplied to a cathode side of the variable capacitance diode via a resistor. 4. A coil connected between a signal line of a video amplification circuit and ground, wherein the frequency characteristic correction circuit includes:
The television receiver according to claim 1, comprising a capacitor and a variable capacitance diode connected in series between the signal line and the ground, wherein the DC voltage is supplied to a cathode side of the variable capacitance diode via a resistor. Image quality correction device. 5. A coil connected between a signal line of a video amplifier circuit and ground, wherein the frequency characteristic correction circuit comprises:
The first connected in series between the signal line and ground
2. The capacitor according to claim 1, comprising a capacitor and a variable capacitance diode, and a second capacitor connected in parallel to the variable capacitance diode, wherein the DC voltage is supplied to the cathode side of the variable capacitance diode via a resistor. An image quality correction device for a television receiver. 6. The image amplification circuit has a frequency control terminal, and the frequency characteristic correction circuit is a series connection of a coil and a variable capacitance diode between the frequency control terminal and ground, and the variable capacitance diode. 2. The image quality correction device for a television receiver according to claim 1, wherein the DC voltage is supplied via a resistor to a cathode side of the variable capacitance diode. 7. The image amplification circuit has a frequency control terminal, and the frequency characteristic correction circuit includes a coil, a capacitor, and a variable capacitance diode connected in series between the frequency control terminal and ground, and is variable. The image quality correction device according to claim 1, wherein the DC voltage is supplied to a cathode side of a capacitance diode via a resistor.