JP2002335534A - Hue adjusting circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily perform television hue adjustment for the component signal from an outside device such as a DVD player. SOLUTION: This hue adjusting circuit is provided with a chroma signal demodulating circuit 15 for demodulating a chroma signal in a television signal on a carrier wave, and a TINT circuit 19 for phase-shifting the first and second color difference signals outputted from the chroma signal demodulating circuit 15. Thus, the hue adjustment can be operated based on the phase shift quantity of the TINT circuit 19.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hue adjustment circuit used in a television receiver or the like, and more particularly, to a hue adjustment circuit composed of bipolar transistors.

[0002]

2. Description of the Related Art Generally, in a television receiver, a viewer can freely adjust the color tone (TINT) of a chroma signal from the outside using a volume or the like. In order to adjust the color tone, the chroma signal demodulation axes (x axis, y axis) may be shifted in any direction. Add to the demodulator to shift the demodulation axis 3.
What is necessary is just to change the phase of the color carrier of 58MHZ.

FIG. 6 shows a hue adjustment circuit for changing the phase of a 3.58 MHz color carrier. In FIG. 6, it is assumed that a carrier chrominance signal is applied to the input terminal 1 and a horizontal synchronization pulse is applied to the terminal 2.

The burst separation circuit 3 extracts only a burst signal from the carrier chrominance signal input from the input terminal 1 based on the horizontal synchronization pulse. The extracted burst signal is converted by the CW (continuous wave) generation circuit 4 into a continuous wave of a burst.

[0005] The continuous wave is applied to a chroma signal demodulation circuit 6 through a phase shift circuit 5. The chroma signal is applied to the demodulation circuit 6 from the terminal 7, and the BY color difference signal and the RY
Two of the color difference signals are demodulated to terminals 8 and 9. In order to demodulate these two, two types of continuous waves are also required.
Two continuous waves for the BY color difference signal and the RY color difference signal are supplied to the demodulation circuit 6.

If the viewer changes the phase shift amount of the phase shift circuit 5 with the volume or the like, the color tone (TINT) of the chroma signal can be freely adjusted according to the above-described principle.

[0007]

However, in the above-described circuit, the adjustment of the color tone is limited to the signal supplied to the demodulation circuit 6. That is, hue adjustment cannot be performed on a modulated chroma signal, but hue adjustment cannot be performed on a demodulated chroma signal.

By the way, recently, DVD players and TVs
When a receiver is connected, component signals (Y, C
(b, Cr) is applied to the TV receiver, but in such a signal, chroma demodulation has already been performed, and the color tone cannot be adjusted by the above-described conventional circuit.

[0009]

The main features of the invention disclosed in the present application will be described below.

A phase adjusting circuit according to the present invention includes a chroma signal demodulating circuit for demodulating a chroma signal of a television signal according to a carrier wave, and a first color difference signal and a second color difference signal from the chroma signal demodulation circuit. And a phase shift circuit for shifting the phase, wherein the hue adjustment is adjusted based on the phase shift amount of the phase shift circuit.

According to such a configuration, the color tone of the television can be easily adjusted even for a component signal from outside such as a DVD player.

The phase shift circuit is a phase shift circuit that shifts the phase of an input signal represented by (x, y) on a coordinate by θ and converts it into an output signal (X, Y). Output signal according to
A Sinθ generation circuit that generates Sinθ and −Sinθ, and a Cosθ generation circuit that generates an output signal Cosθ corresponding to the input signal θ,
A first multiplication of the input signal x and the output signal Cosθ
A multiplication circuit, a second multiplication circuit that multiplies the input signal y and the output signal Sinθ, a third multiplication circuit that multiplies the input signal x and the output signal Sinθ, and the input signal y
A fourth multiplying circuit for multiplying the output signal Cos θ by
A first addition circuit for adding the output signals of the first and second multiplication circuits; and a second addition circuit for adding the output signals of the third and fourth multiplication circuits, and a hue adjustment voltage as the input signal θ And a color difference signal is given as an input signal represented by (x, y) on the coordinates, and a color difference signal shifted by θ is obtained from the first and second addition circuits. .

According to such a configuration, the phase circuit is composed of Si
A simple configuration can be achieved simply by using an nθ generation circuit, a Cos θ generation circuit, and four multiplication circuits.

[0014]

Next, an embodiment of the present invention will be described with reference to FIG. An ACC (automatic color control) circuit 10 automatically adjusts the level of the composite chroma signal from the input terminal 11. A BPA (bandpass amplifier) 12 separates and extracts a chroma signal and a burst signal from the composite chroma signal output from the ACC circuit 10.

The PLL circuit 13 includes a phase comparison circuit,
A built-in LPF and VCO generate a continuous wave cw synchronized with the burst signal. The phase circuit 14 is the PLL circuit 1
In response to the output signal of No. 3, two types of carrier waves for demodulation are generated (however, variable phase shift is not performed).

The demodulation circuit 15 converts the chroma signal separated and extracted by the BPA 12 into a 2
Demodulation according to one carrier wave to generate a BY signal and an RY signal.

The DVD (Digital Video Disc) 16
A BY signal and an RY signal as a video signal source are generated. Switches 17 and 18 switch the video signal source. TI
The NT circuit 19 (phase circuit for hue adjustment) changes the phases of the BY signal and the RY signal from the switches 17 and 18 according to an external TINT adjustment control voltage controlled by the viewer. There is

Next, the operation of the chroma signal demodulation circuit having the above configuration will be described. The level of the composite chroma signal input from the input terminal 11 is automatically adjusted by the ACC circuit 10. The composite chroma signal whose level has been automatically adjusted is
At 12, the signal is separated into a chroma signal and a burst signal. PL
The L circuit 13 includes a phase comparison circuit, an LPF, and a VCO and generates a continuous wave cw synchronized with the burst signal.

The continuous wave cw is converted into two types of carrier waves for demodulation by the phase circuit 14 and applied to the demodulation circuit 15. Then, in the demodulation circuit 15, a color difference signal BY signal and a RY signal are obtained from the chroma signal and applied to the switches 17 and 18, respectively.

On the other hand, the DVD 16 is
Are applied to the TINT circuit 19 in accordance with the selected state of the switches 17 and 18.

The TINT circuit 19 shifts the phase of the input signal,
This allows hue adjustment. In the system shown in FIG. 1, since the phase of the demodulated signal, that is, the color difference signal is shifted, the hue of the signal from the DVD 16 can be adjusted.

Next, the principle of the TINT circuit 19 will be described. In order to shift the phase of the input signal represented by (x, y) on the coordinate axis by θ and convert it to the output signal (X, Y), the input signal is expressed by the following equation (1) using the coordinate conversion formula What is necessary is just to convert a signal.

[0023]

(Equation 1)

That is, on the circuit, X = x · Cos θ + y · Sin
It suffices if a relational expression between θ and Y = −x · Sin θ + y · Cos θ can be created. By the way, the relationship between the Sin function and the Cos function is expressed as shown in equation (2).

[0025]

(Equation 2)

From the equation (2), the following equations (3) and (4) are derived, so that Cos θ is finally expressed by the equation (5). Therefore, Cosθ is Sin (θ /
If 2) is obtained, it is clear that it can be created.

[0027]

(Equation 3)

[0028]

(Equation 4)

[0029]

(Equation 5)

Therefore, from the input signal θ, the output signal Sin (θ)
Can be obtained, a phase circuit for rotating an input signal represented by (x, y) by θ and converting it into an output signal (X, Y), that is, a TINT circuit can be obtained.

Next, a circuit for generating the output signal Sinθ from the input signal θ will be described. An output substantially equivalent to the output signal Sin θ can be generated from the input signal θ by the differential amplifier shown in FIG. The input terminal 30 in FIG.
31, a constant current I0 of the current source 32 is applied to the current Ic1 and the current Ic according to the input signal θ.
It flows to the collectors of the transistors 33 and 34 as c2.

Then, the current Ic1 and the current Ic2 are obtained from the relationship between the input and output of the general differential amplifier and the relationship between the exponential function and tanh.
Can be expressed as in equations (6) and (7).

[0033]

(Equation 6)

[0034]

(Equation 7)

Here, paying attention to tanh in the equations (6) and (7), it can be seen that Sin and tanh are relatively close values. tan
hθ is expressed by equation (8) when Taylor expansion of mathematics is performed. Sin θ is expressed by Equation (9) when mathematical Taylor expansion is performed. Here, θ is in radians, but actually TI
The amount of phase shift by NT is about 0.7 or 0.8, which is a relatively small value. For this reason, it can be seen that Equations (8) and (9) have slightly different coefficients of the cube of θ, but are very close.

[0036]

(Equation 8)

[0037]

(Equation 9)

Then, the expressions (6) and (7) are replaced by the expression (1)
0) and Equation (11). “1” shown in Expressions (10) and (11) indicates a constant current independent of an input signal, that is, a DC component.

[0039]

(Equation 10)

[0040]

[Equation 11]

Therefore, from equations (10) and (11), FIG.
It can be seen that the differential amplifier can produce an output that is substantially equivalent to the output signal Sin θ from the input signal θ depending on the usage (a small amount of phase shift).

Next, FIG. 3 shows a circuit for shifting the phase of an input signal represented by (x, y) on the coordinate axis by θ using the differential amplifier of FIG. 2 and converting the input signal into an output signal (X, Y). Show. A signal x (corresponding to the color difference signal BY) is applied to the input terminal 40 of FIG. 3, and a signal y (corresponding to the color difference signal RY) is applied to the input terminal 41.
Is applied, and a signal θ for TINT adjustment is applied to the control terminal 42.

The Sinθ generation circuit 43 shown in FIG. 3 can be constituted by the differential amplifier shown in FIG. In order to obtain Cos θ, Equation 5 may be configured as a circuit. The circuit for obtaining Cosθ is
As shown in FIG. 3, the Sin (θ / 2) generation circuit 44, Sin (θ / 2)
Generate Sin ² (θ / 2) by squaring the output signal of the generator 2
Multiplying circuit 45, a multiplying circuit 46 for doubling the output signal of the squaring circuit 45, a subtracting circuit 47 for subtracting the output signal of the multiplying circuit 46 from 1 (the output signal of the DC component generator 48), a positive and negative output signal From the amplifier 49 that generates

The operation will be described later. By these circuits, the terminals 50 to 53 have sinθ, -Sinθ, Cosθ,-
Cos θ is obtained.

Therefore, Cos θ applied to the first multiplier circuit 54 and the fourth multiplier circuit 55 can be obtained from the terminal 52. Sin θ and −Sin θ applied to the second multiplication circuit 56 and the third multiplication circuit 57 can be obtained from the terminals 50 and 51.

As a result, x · Cosθ is obtained at the output terminal of the first multiplication circuit 54, and y is output at the output terminal of the second multiplication circuit 56.
・ Sin θ is obtained. The output terminal of the third multiplying circuit 57 has -x
・ Sin θ is obtained. Further, y · Cosθ is obtained at the output end of the fourth multiplying circuit 55. Then, the first multiplication circuit 54
And the output of the second multiplier 56 are added by the first adder 58, and the output of the third multiplier 57 and the output of the fourth multiplier 55 are added.
Are added by the second adder 59.

Thus, according to the circuit of FIG. 3, X =
Since the relationship x = Cosθ + y ).

FIG. 4 shows the Sinθ generating circuit 43 of FIG.
FIG. 4 is a circuit diagram showing a specific example of a (θ / 2) generation circuit 44. FIG.
, A signal θ is applied between terminals 60 and 61, and a differential amplifier 64 composed of differential transistors 62 and 63 is applied.
And a differential amplifier 67 composed of differential transistors 65 and 66. The operating principle of the differential amplifier 64 is as follows.
It is the same as that of the differential amplifier shown in FIG.
8, 69, Sinθ and −Sinθ can be obtained.

The transistors 65 and 66 of the differential amplifier 67
Are connected to diodes 70 and 71. By the function of the diodes 70 and 71, the terminal 7
Sin (θ / 2) and −Sin (θ / 2) are obtained in 2, 73.

In FIG. 3, the squaring circuit 45 and the first to fourth multiplying circuits 55 to 55 can be constituted by multiplying circuits as shown in FIG. In FIG. 2, the input terminal 8
0 and 81, one input signal is applied to the input terminal 8
The other input signal is applied to 2 and 83, and multiplication of both signals is performed.

A differential amplifier 86 composed of transistors 84 and 85 and a differential amplifier 89 composed of transistors 87 and 88 form a main body of a multiplying circuit. A signal from the base of the transistor and a signal from the emitter side are formed. Is multiplied with the signal of.

Then, a part of the multiplication result is generated as a current at the collector of the transistor 84, and a part of the multiplication result is generated as a current at the collector of the transistor 88.
The collector current of transistor 84 is
The current is inverted at 0 and 91 and transmitted to the output.

The collector current of the transistor 88 is
The current is inverted by transistors 92 and 93 and transistors 94 and 95 and transmitted to the output. As a result, the output terminal 9
6 generates a multiplication result (y · Sin θ) in which the DC component is canceled.

[0054]

According to the present invention, there is provided a phase shift circuit for shifting the first color difference signal and the second color difference signal from the chroma signal demodulation circuit, and the hue adjustment is performed by the phase shift amount of the phase shift circuit. , The color tone of the television can be easily adjusted even for component signals (Y, Cb, Cr) from outside such as a DVD player.

Further, the phase circuit can be easily constructed simply by using a Sin θ generation circuit, a Cos θ generation circuit, and four multiplication circuits.

The Sin θ generation circuit, Cos θ generation circuit, and multiplication circuit can be constituted by bipolar transistors and resistors, so that a phase shift circuit suitable for integration into an integrated circuit can be provided.

[Brief description of the drawings]

FIG. 1 is a block diagram of a chroma signal demodulation circuit according to an embodiment of the present invention.

FIG. 2 is a Sinθ generation circuit diagram according to the embodiment of the present invention.

FIG. 3 is a block diagram of a phase shift circuit according to the embodiment of the present invention.

FIG. 4 is a circuit diagram showing a specific circuit example of a Sinθ generation circuit 43 and a Sin (θ / 2) generation circuit 44 of FIG. 3;

FIG. 5 is a circuit diagram showing specific circuit examples of a squaring circuit 45 and first to fourth multiplying circuits 54 to 55 in FIG. 3;

FIG. 6 is a block diagram of a chroma signal demodulation circuit according to a conventional example.

[Explanation of symbols]

 43 Sinθ generation circuit 44 Sin (θ / 2) generation circuit 45 Square circuit 46 Multiplication circuit 47 Subtraction circuit 54 First multiplication circuit 55 Fourth multiplication circuit 56 Second multiplication circuit 57 Third multiplication circuit

Claims (4)

[Claims] 1. A chroma signal demodulation circuit for demodulating a chroma signal in a television signal according to a carrier wave, and a phase shift of a first color difference signal and a second color difference signal output from the chroma signal demodulation circuit. A hue adjustment circuit comprising: a phase shift circuit, wherein hue adjustment is performed based on a phase shift amount of the phase shift circuit. 2. The hue adjustment circuit according to claim 1, wherein the phase shift circuit shifts an input signal represented by (x, y) on a coordinate by θ and converts it into an output signal (X, Y). A Sinθ generating circuit that generates an output signal Sinθ and −Sinθ according to the input signal θ, a Cosθ generating circuit that generates an output signal Cosθ according to the input signal θ, and the input signal x. A first multiplication with the output signal Cosθ
A second multiplier for multiplying the input signal y and the output signal Sinθ.
A third multiplier for multiplying the input signal x by the output signal Sinθ;
A fourth multiplier for multiplying the input signal y by the output signal Cosθ;
A multiplication circuit, a first addition circuit that adds the output signals of the first and second multiplication circuits, and a second addition circuit that adds the output signals of the third and fourth multiplication circuits, wherein the input signal θ Hue adjustment voltage as
A hue adjustment circuit characterized in that a hue difference signal is provided as an input signal represented by (x, y), and a hue difference signal shifted by θ is obtained from the first and second addition circuits. 3. A chroma signal demodulation circuit for demodulating a chroma signal of a television signal according to a carrier, and output signals Sinθ and -Si according to an input signal θ for hue adjustment.
a Sinθ generation circuit for generating nθ, a Cosθ generation circuit for generating an output signal Cosθ corresponding to an input signal θ for hue adjustment, a first color difference signal x from the chroma signal demodulation circuit and the C signal
a first multiplication circuit that multiplies the output signal Cosθ of the osθ generation circuit by a second color difference signal y from the chroma signal demodulation circuit and the S
a second multiplication circuit that multiplies the output signal Sinθ of the inθ generation circuit; a third multiplication circuit that multiplies the first color difference signal x from the chroma signal demodulation circuit by the output signal Sinθ; A fourth multiplication circuit for multiplying a second color difference signal y from the demodulation circuit by the output signal Cosθ; and adding the output signals of the first and second multiplication circuits to obtain x · Cos
a first adding circuit for obtaining θ + y · Sin θ; and adding the output signals of the third and fourth multiplying circuits to obtain −x · S
and a second adder circuit for obtaining inθ + y · Cosθ.
And a color difference signal shifted by θ from the second adder circuit. 4. The hue adjustment circuit according to claim 2, wherein the Sin θ generation circuit, the Cos θ generation circuit,
The hue adjustment circuit according to claim 1, wherein the first to fourth multiplication circuits use a differential amplifier using a bipolar transistor.