JPS6030291A - Color reproducing circuit - Google Patents

Abstract

PURPOSE:To specify the relation between the relative phase of demodulation and the input relative phase of a color difference signal componet securely by supplying the oscillation signal of chrominance subcarrier frequency to a CR phase shifting means and two differential amplifying means. CONSTITUTION:The signal (a) of the chrominance subcarrier frequency impressed to an input terminal 31 is supplied to the CR phase shifting circuit 32 which has a 45 deg. phase dalay and the positive-side input terminal of the 1st differential amplifier circuit 33. The output signal (b) of the CR phase shifting circuit 32 is impressed to the load input terminal of the 1st differential amplifier circuit 33 and the positive-side input terminal of the 2nd differential amplifier circuit 34. This constitution allows four 90 deg. out-of-phase signals (b), (a-b), (-b), and (b-a) to be obtained from the differential amplifier circuits 33 and 34; the 90 deg. out-of-phase signals (b) and (b-a) are supplied to the 1st resistance matrix circuit 35, and the remaining signals are supplied to the 2nd matrix circuit 36, so that two relative-phase signals (c) and (d) are led out of the matrix circuits.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a color reproduction circuit in, for example, a color television (color television) or television receiver.

[Technical background of the invention]

In NTSC-based broadcast systems, chromaticity information (hue and saturation information) is transmitted in a narrowband manner with bandwidth limited to match visual resolution. Further, the chromaticity information is expressed as two color difference signals ER-EY and EB-EY. The chromaticity information includes two color subcarriers having a phase difference of 90° from each other as the two color difference signals ER-EY,
Each signal is amplitude-modulated by EB-EY, and the sidebands generated at that time are added together and sent as a carrier color signal.

Below is the relative phase (90°) of the two color subcarrier numbers for modulation.
is called the modulation relative phase. In addition, each color difference signal ER-EY obtained by amplitude modulation.

The sideband wave of EB-EY is converted into color difference signal component [:ER-EYIC
.

(EB-EY)C.

On the receiving side, the carrier color signal is demodulated to obtain two color difference signals ER-EY and EB-EY, and from this, three primary color signals (EB, (EG, (EB)) or three color difference signals ER- EY, EG-EY.

The system obtains EB-EY and supplies them to a picture tube to reproduce colors. In this case, two color subcarriers (ER-, EY) CW for demodulation.

There is a difference between the relative phase of [EB-EY] CW (hereinafter referred to as post-tone relative phase) and the input relative phase of the two color difference signal components [ER-EYIC and [EB-EYIC] for the de-94 circuit. It is designed to have a phase difference of several degrees.

This is due to the fact that the luminous chromaticity and white chromaticity of the phosphor in the picture tube of a color television receiver are different from the standard three primary colors and standard white in the NTSC system, and also that there is a phase shift in the reproduced colors. This is because

The following method is available as a method for setting a phase difference of several degrees between the demodulation relative phase and the input relative phase.

(1) Two color difference signal components [ER-EY]C, (EB-
Method 0: Leave the input relative phase of EYIC as the modulation relative phase, and set the demodulation relative phase to 90' Doshi degrees. (2) Set the demodulation relative phase to 90', and set the input relative phase to 90.
°How to set the Satoshi number degree.

(3) A method of setting a phase difference of 10 times by shifting both the demodulation relative phase and the input relative phase from 90°.

FIG. 1 is a circuit diagram showing a conventional color reproduction circuit. In FIG. 1, reference numeral 11 is an input terminal for a composite video signal output from a sandwich amplifier circuit (not shown).

12 and 13 each have a selection band in the frequency band of the carrier color signal. The second band amplification circuit 014 is a demodulation circuit, 15 is a CR phase shift circuit, 16 is a picture tube, 17 is a burst signal amplification circuit, and 18 is an automatic phase control circuit (hereinafter referred to as AP-C circuit). , 19 is a voltage controlled oscillation circuit (hereinafter referred to as v
(referred to as CO). The above circuit constitutes a so-called color synchronization circuit for generating a color subcarrier synchronized with a color burst signal.

20 is an automatic color control circuit (hereinafter referred to as ACC circuit), and 2 is a color killer circuit. 22 is a saturation adjustment volume, and 23 is a hue adjustment volume. 24 is a dirt pulse input terminal for extracting a carrier color signal from a composite color signal (a composite signal of a carrier color signal and a color burst signal); 25 is a color input terminal from the composite color signal;
This is the dart pulse input terminal for extracting the 4-stroke signal.

The color reproducing circuit shown in the figure is designed to provide a phase difference of a few degrees between the demodulated relative phase and the input relative phase, in addition to setting the input relative phase to 90 ± a few degrees as explained in section 2 above. This purpose is achieved by the CR phase shift circuit 15. In other words, the CR phase shift circuit 15 converts, for example, a color difference signal component (ER-g
When Y]c is delayed or advanced by a few degrees, the input relative phase is set to 90-10 degrees or 9o-10 degrees. As a result, a phase of several degrees is set between the demodulation relative phase and the input relative phase.

FIG. 2 is a vector diagram showing the color vectors of FIG. 1.

If the modulation axes of the color difference signals ER-EY and EB-EY are the RY axis and the BY axis, respectively, the color subcarrier for demodulation (E
The phases of R-EY)CW and (EB-EY)CW coincide with the R-Y axis and the B-Y axis, respectively. In addition, the color difference signal component (
The phase of EB-EY)C coincides with the BY axis. On the other hand, it has a phase shifted by ffa degrees with respect to the ff1aaR-y axis of the color difference signal component [R-Ey)c. The figure shows the case of more than 10 degrees.

Note that the phase of the force 2-burst signal Bu is 180° different from the color subcarrier (EB-EY'3cW).

[Problems with background technology]

However, the above configuration has the following problems.

That is, when the CR phase shift circuit 15 is integrated into an integrated circuit, the time constant CR based on the capacitance value of the capacitor and the resistance value of the resistor varies around the designed value. As a result, the phase shift lid of the CR phase shift circuit 15 varies, making it impossible to set a predetermined phase difference between the demodulated relative phase and the input relative phase.

Therefore, when the color reproduction circuit shown in FIG. 1 is integrated into an integrated circuit, the CR cedar phase circuit 15 must be designed as an external circuit, which is unfavorable in terms of circuit manufacturing cost and number of parts. .

The above has explained the color reproduction circuit based on the method (2) above, but even in the case of color reproduction circuits based on the methods (1) and (3), conventionally when integrating the circuit, the demodulation relative phase and the input There was no technology that could reliably set the phase difference from the relative phase to a value close to the design value.

[Purpose of the invention]

The present invention has been made to address the above-mentioned circumstances, and it is possible to reliably set a predetermined phase between the demodulation relative phase and the input relative phase of the color difference signal component even in an integrated circuit.
Furthermore, the color difference signals ER-EY and EB obtained by the demodulation circuit
-It is possible to match the luminescence and chromaticity of EY, and
It is an object of the present invention to provide a color reproduction circuit in which variations in the phase of color subcarriers due to integrated circuits have almost no effect on color reproduction.

[Summary of the invention]

This invention provides a CR phase shift means and two differential amplification means,
By supplying an oscillation signal having a color subcarrier frequency to these circuit means, four signals having phases different by 90 degrees can be obtained. By suitably combining these signals with a resistance matrix means, a signal having a phase can be obtained. Two signals are obtained, one having a phase delayed by 1 (1-90°) and the other having a phase delayed by 1. Then, these two signals having a relative phase of θ are used as color subcarriers for demodulation.

Furthermore, one of the four signals is used as a comparison signal for synchronizing the oscillation operation of the oscillation means that outputs the oscillation signal with the color burst signal.

Supplied through a series circuit with.

Further, when the color burst signal is supplied to a phase comparison means that performs a phase comparison with the comparison signal, it is supplied.

[Embodiments of the invention]

Hereinafter, one embodiment of the present invention will be described in detail with reference to the drawings.

First, the configuration and operation of the part that obtains the color subcarrier for demodulation will be explained using FIGS. 3 and 4. In FIG. 3, 31 is an input terminal, and the signal applied to this input terminal 31 is connected to the positive terminal of the CR phase shift circuit 32 and the first differential amplifier circuit 33, which have a delay phase shift amount of 45 degrees. Supplied to the side input terminal.

The output signal of the CR phase shift circuit 32 is sent to the first differential amplifier circuit 33.
and the positive input terminal of the second differential amplifier circuit 34. A DC voltage E at a predetermined level is applied to the negative input terminal of the second differential amplifier circuit 34. One output signal of the first differential amplifier circuit 33 is supplied to one input terminal of the first resistance matrix circuit 35, and the other output signal is supplied to one input terminal of the second resistance matrix circuit 36. Ru. One output signal of the second differential amplifier circuit 34 is supplied to one input terminal of the first resistance matrix circuit 35, and the other output signal is supplied to the other input terminal of the second resistance matrix circuit 36. Ru. The output signals of the first and second resistance matrix circuits 35, 36 are respectively led to output terminals 37, 38.

The operation of the above configuration will be explained with reference to the vector diagram in FIG. Let the signal applied to input terminal 3 be expressed as a vector. It is also assumed that the signal output from the CR phase shift circuit 32 is represented by a vector. Further, it is assumed that the relative phase of the two Shingetsu guided to the output terminals 37° and 38 is θ larger than 90°, for example.

2 and 6 have a phase difference of 45°, and form a semicircular chord whose diameter is the amplitude of 2, b t . First differential amplifier circuit 3
3, a signal -1, which is the difference between the two vectors, and a signal, which has a phase difference of 180 degrees, are obtained. The signal knees are 90 degrees ahead in phase with the signal beam, and the signal beams are 90 degrees behind the signal beam. The second differential amplifier circuit 34 obtains signals having a phase difference of 180° from the signals.

Among the four signals, λ-, -ra, and -2, which have phases different by 90° obtained in this way, two signals with 90° different phases, for example, signals et al. and 6--, are n-series. 1 resistor matrix circuit 3sK4Jt is supplied. Similarly, the remaining two signals M-ra and -b with a 90° phase difference are the second
It is supplied to the resistor matrixless circuit 36 of. The first resistance matrix circuit 35 performs a vector combination θ-900 of the two signals C and -λ, and obtains only a signal whose phase is advanced by, for example, the vectors C and -λ. The resistance value of the matrix resistor is set so that υ, 1, 2, and 2 are set to '147. Similarly, the second resistor matrix circuit 36 receives two signals - and λ.
- and the like are synthesized by vector θ-90° to obtain a vector a whose phase is advanced by vector ray □. Therefore, two signals d and h having the desired relative phase θ can be derived at the output terminals 37 and 38.

According to the above configuration, even if the time constant CR varies around the design value due to the integration of the CR phase shift circuit 32, and the phase difference between the signal λ and the signal λ becomes a value different from 45°. , the signals change in phase and wivJ so as to form a chord on a semicircle whose diameter is the amplitude of the signal. Therefore, the first
The differential amplifier circuit 33 can always output signals -1 and -2 having a phase difference of 90° with respect to the signals, regardless of the variation in the time constant CR. In other words, 1. From the second differential amplifier circuits 33 and 34, four signals, -1, -mo, and ra-2, whose phases differ by 90 degrees can always be obtained regardless of the variation in the time constant C-R. . Therefore, these signals baa~ et al.

The relative phase θ of the signals c and d obtained by combining b+b a with the resistance matrix circuits 35 and 36 does not vary due to the variation in the time constant C−H.

In addition, 1. If the second resistance matrix circuits 35 and 36 are integrated, the resistance values of the matrix resistors will vary, but the relative phase θ of the signals and h will not be affected by this variation in resistance values. In other words, it is not the resistance value but the resistance ratio that affects the relative phase θ.
This is because even if the resistance values of the matrix resistors vary due to integrated circuits, they vary in the same way, so the resistance ratio will hardly vary. We have explained the case where the phase of the signal ++er d is determined based on the two signals -b and b-λ, but if the reference signals have a phase difference of 90°, the signals -la and la −
Of course, it is not limited to λ.

Furthermore, it goes without saying that θ may also be selected to a value smaller than 90°.

By the way, in Fig. 3, a frequency of 3.58 MH synchronized with the color burst signal 13u is input to input terminal 3.
Before applying the signal z (hereinafter referred to as fsc),
Color subcarrier for demodulation (ER-E
Y) CW, [EB-EY] CW can be extracted. In this case, as mentioned in (1) above, by setting the demodulation relative phase to 90 degrees, there is a method of creating a phase difference of several degrees between the demodulation relative phase and the input relative phase. If this is done, the phase difference of a few degrees can always be ensured even if the circuits related to this are integrated circuits.

FIG. 5 is a circuit diagram showing an embodiment of the color reproduction circuit of the present invention, which is configured to generate color subcarriers using the circuit shown in FIG. 3. In the figure, 41 is an input terminal for a composite video signal output from a video amplification circuit (not shown).

42 and 43 each have a selection band in the frequency band of the carrier color signal. This is a second band amplification circuit. 44°45
is a CR phase shift circuit. These CR phase shift circuits 44.45
The amount of phase shift is the same, but the direction of phase shift is different. That is,
The CR phase shift circuit 44 advances the phase of the input signal, whereas the CR phase shift circuit 45 delays the phase of the input signal. The amount of phase shift of these CR phase shift circuits 44 and 45 will be described later. A demodulation circuit 46 demodulates the carrier color signal to obtain, for example, primary color signals ER, EC, and EB for supply to the picture tube 47.

48 is a composite color signal (
This is a pulse amplifying circuit which extracts and amplifies the 12-burst signal Bu from the carrier color signal and the color pulse (combined signal of the M bus).

49 is a CR phase shift circuit that advances the phase of the color burst signal Bu output from the burst signal amplification circuit 48. The amount of phase shift of this CR phase shift circuit 49 will be described later.

50 is an APC circuit, 51 is a color subcarrier frequency (fsc
) is a VCO that outputs an oscillation signal of the same frequency. A
The PC circuit 50 is designed to synchronize the output phase of the VCO 51 with the color burst signal Bu in a predetermined phase relationship.

52 is a CR phase shift circuit that delays the oscillation signal of the VCO 51. The phase shift amount of this CR phase shift circuit 52 is set to 45°. 53 and 54 are a hue circuit and a hue adjustment volume for adjusting the hue, respectively. The output signal of this hue circuit 53 is supplied to the circuit shown in FIG. 3 (circuit surrounded by a broken line). 1st. Second resistance matrix circuit 3
The output signals of 5.36;, :1 are the color subcarriers for demodulation (ER-EY, ICW, r-
EB-EY] is supplied to the demodulation circuit 46 as CW.

56 is an ACC circuit. The ACC circuit 56 controls the gain of the first band amplification circuit 42 using a detection voltage proportional to the amplitude of the color burst signal from the burst signal amplification circuit 48. As a result, the first band amplification circuit 42
The amplitude of the composite color signal output from is kept constant. 5
Reference numeral 7 denotes a color killer circuit, which turns off the second band amplification circuit 43 during monochrome broadcasting, etc., and prevents the generation of color noise.

Signal 'a ([ER-EY]
CW), a([EB-EY)CW) is t;hlt Furthermore, the comparison signal CAPCICW for APC detection, the comparison signal [K11ler] for killer detection, and the APC circuit 5 as CW.
0. The signal is supplied to a color killer circuit 57.

Note that 58 is a color saturation adjustment volume.

Further, 59 is a terminal to which a dart pulse G for extracting the carrier color signal from the composite color signal is applied, and 60 is a terminal for extracting the color burst signal Bu from the composite color signal.
This is the terminal to which the signal G2 is applied.

FIG. 6 is a circuit diagram showing a specific circuit configuration of FIG. 5.

The CR phase shift circuit 44 for leading phase shift and the CR phase shift circuit 45 for lagging phase shift are connected to capacitor C11mC1! , resistance R11~R
111, and a transistor QllllQ12. Of these, the capacitor C1l and the resistor R11 are used to set the leading phase shift amount, and the resistor Rss and the capacitor C□ are used to set the lagging phase shift amount. Also, transistor Q
t t ld Forms an emitter follower that supplies a bias voltage to the double HA circuit 46.

The CR phase shift circuit 49 for the advance phase shift consists of a capacitor (11% resistor gty to Rtos) and a range meter 9 plates 8°Q14.The capacitor C1 and the resistor RIT are for setting the amount of advance phase shift. Transistor Q14 is Ap
It forms an emitter follower that supplies bias voltage to the C circuit 50 and color killer circuit 5.

The CR phase shift circuit 52 with a delay phase shift amount of 45° includes a capacitor C141C1, a resistor R□ to RIW, and a transistor Q.
Consists of 1s*QCs. Resistor R2m and capacitor C
Il+ is for setting a delay phase shift amount of 45°. Further, the transistor Qrs forms an emitter follower that supplies a bias voltage to the hue circuit 53.

Is the CR phase shift circuit 32 with a delay phase shift amount of 45° the capacitor C16#01? , resistors Rta to R34, and transistors Q□ and Q18. The resistor R8° and the capacitor C0 are used to set a delay phase shift amount of 45°. The transistor Q1g is the first. Second (7) differential amplifier circuit 33.3
It forms an emitter follower for supplying bias voltage to 4.

1st. The second difference, dynamic amplification circuit 33.34 includes transistors Q11. ~Qta, consisting of resistors R0 to R46.

The transistors QIll#Q20 forming the differential pair constitute the first differential amplifier circuit 33, and the transistors Q211Q2 forming the differential pair! constitutes the second differential amplifier circuit 34. The transistor Qzs is the first transistor. O 1. which is a transistor for supplying a bias voltage to the second resistance matrix circuits 35 and 36. The second resistance matrix circuits 35 and 36 are composed of transistors Q□ to Q,8 and resistors n4y to RIll crab. Resistor R4? # R4@ is the matrix resistor of the first resistor matrix circuit 35, resistor R4 + 1sR1
+. is a matrix resistor of the second resistor matrix circuit 36. Also, transistor Q! @ forms an emitter follower that supplies the limiter 55 with a negative voltage.

The limiter 55 includes transistors Q2 to Q36 and a resistor gs.
It consists of y~aSS. Transistor Q! 9 is demodulation circuit 4
6. APC circuit 50. This is a transistor that supplies a bias voltage to the color killer circuit 51.

The operation in the above configuration will be explained. The first band amplification circuit 42 extracts a composite color signal from the composite video signal applied to the input terminal 41 and amplifies it.

At this time, the composite color signal is set to a constant amplitude by the gain control operation of the ACC circuit 56. Second band amplifier circuit 4
3 is goo) NoJ? According to the signal G, only the carrier color signal is extracted from the output signal of the first A1 band amplification circuit 42,
Amplify this. The amplified carrier color signal is once advanced by one predetermined phase shift amount by the CR phase shift circuit 44, and then
By being delayed by the same amount of phase shift by the CR phase shift circuit 45, the signal is returned to its original phase and is supplied to the demodulation circuit 46. Then, the demodulation circuit 46 demodulates the color subcarrier supplied from the limiter 55, and the color difference signal ER-
It is output as EY, EB-EY. The demodulation circuit 46 further reproduces the color difference signal EG-EY from the color difference signals ER-EY and EB-EY, and reproduces the color difference signal EG-EY from these three color difference signals ER-EY.
, EB-EY, EG-EY and the luminance signal EY to the primary color signal ER.

EG and EB are produced and supplied to the picture tube 47. Note that during black and white broadcasting, the second band amplification circuit 43 is turned off by the color killer circuit 57, thereby preventing the generation of color noise.

Next, a carrier color signal (ER-EY) CW for demodulation.

[EB-EY] CW-? Comparison signal for phase detection in the APC circuit 50 (APCICWs color key 2-circuit 57
Comparison signal (Killer) CW for killer detection in
The color synchronization circuit that generates .

The color burst signal Bu output from the burst signal amplification circuit 48 is delayed by a predetermined phase shift amount in the CR phase shift circuit 49 and then supplied to the APC circuit 50 . The APC circuit 50 uses the color burst signal Bu as a reference signal, and compares this with the signal (APC) CW from the limiter 59, ! Compare the phase of −. Then, according to the comparison result, VCO5
The oscillation phase of this VCO 51 is synchronized with the color burst signal Bu in a predetermined phase relationship. As mentioned above, the oscillation frequency of vC051 is 3.58MHz, which is the same as the color subcarrier frequency fsc.
The delayed signal is supplied to the hue circuit 53. Now, C
Assuming that the signal not delayed by the R phase shift circuit 52 is λ and the delayed signal is λ, the hue circuit 53 is as shown in FIG.
Outputs the difference signal -1 between the two signals. This signal -1 has a phase lead of 45 degrees with respect to signal -2. The reason why the phase shift amount of the CR phase shift circuit 52 is selected to be 45 degrees is to set the hue variable range by the hue adjustment volume 54 to 90'. The signal knees are the output signals of the hue circuit 53 when the hue adjustment volume 54 is set at the center. On the other hand, when adjusting the hue and setting the Q-mu 54 to the MAX state,
When the output signal of the hue circuit ε4 is set to the MIN state, the output signal becomes a-26. Well, the hue is 45
It is possible to view within a range of ±45° centered on °. Resistor R0 and capacitor C1, (
The resistance value R and the capacitance value C (see FIG. 6) are set to satisfy 45=tan2-πφfsc-c·R (1). Examples of such values include R=8.9, Ω, and C=5 pF.

If the time constant C-R determined in this way varies from the designed value, the phase and amplitude of each signal 26, knee 26, etc. will also change. In diagram M7, the solid lines indicate each signal when the time constant C-R has a designed value. The broken lines indicate each signal when the time constant C-R varies in the positive direction and becomes the largest. The single point @ line is 4! when the time constant C-R varies in the negative direction and becomes the smallest! Indicates the r@ number. Even if the time constant C-R varies, the relative phase of the signals λ and nee remains unchanged at approximately 900, but since the phase of the signal λ is fixed, the time constant C-R
If there is a large variation in the hue, the hue variable range will be 90%.
If the C-R varies in the smaller direction, the hue variable range becomes larger than 90°.

Note that in FIG. 7, the numbers attached to each signal vector indicate the phase and amplitude. Further, a dirt pulse G is supplied to the hue circuit 53, and the hue can be adjusted during the period of the carrier color signal, but the hue cannot be adjusted during the period of the black burst signal Bu.

The output signal of the hue circuit 53 is supplied to the first differential amplifier circuit 33 and is passed through the CR phase shift circuit 32 having a delay phase shift amount of 145° to the first differential amplifier circuit 33. Second differential amplifier circuit 33.34
supplied to Resistor R8 to obtain a delay phase shift amount of 45°
The resistance value and capacitance value of the capacitor C17 (see FIG. 6) are also determined according to the above equation (1), and are set to, for example, 89Ω and 5 pF, respectively.

As explained above with reference to FIGS. 3 and 4, if the undelayed signals are the signals delayed by 2.45 degrees, these signals are expressed as shown in FIG. In FIG. 6, a transistor forming the l-th inverse amplifier circuit 33. +o+Q2° takes the signal 2 as one input and the signals . The signals form a semicircular chord whose diameter is the amplitude of the signal b, and the signal b −; h
, a-1) have a phase difference of ±90° with respect to Im et al.

In addition, the transistor Qz which forms the second differential amplifier circuit
z Q22 closes the signals to one input, and the transistor Q
, with a constant DC voltage E given from the emitter of , as the other input, and a load resistor R3,.

Signals are also obtained from both ends of the 8 ports.

Therefore, the first. As shown in FIG. 8, the second differential amplifier circuits 33 and 34 produce four signals having a phase difference of 90' from each other, ``&-LA, -RA, LA-λ.

In FIG. 6, signals L and R are respectively supplied to the base of the transistor Qty*Qt4, and are combined by the matrix resistors R4, , R, of the first resistor matrix circuit 35, and the color difference signal component ( A signal used as a color subcarrier (ER-FiY) CW for demodulating ER-EY)C is obtained.This signal alone is also used as a comparison signal (APC) CW for APC detection.Also, The signals are the transistors Q211 and Q, respectively.
ts and the second resistor matrix circuit 3
The signal a is synthesized by the matrix resistors R49 and *R110 of No. 6, and is used as a color subcarrier (ER-EY) CW for demodulating the color difference signal component (EB-EY) C. This signal a is further used as a comparison signal (Killer CW) for killer detection.Signal; is O as explained in Figs. 3 and 4 above and has a relative phase of θ. If the values are respectively Rax Rb, the amplitude large 11 phase l of the signal only is expressed by the following formula (
2) is given by (3).

...(2) Similarly, the resistance values of resistor R4g + R5o are Rc,
If Rd, amplitude +L11+, phase L' of signal a
a is given by the following equations (4) and (5), respectively.

(4) Now, if the demodulation relative phase θ is set to 109°, for example, the color difference signal component (
ER-EY)C and [:EB-EY:If the phase difference between the IC input relative phase and the demodulation relative phase θ is set to 19°, the resistance values Ra and Rb are the right-hand side of equation (3). It is sufficient if the two vertices are determined to satisfy 9.5°. The resistance value Ra e Rb determined in this way is, for example, 2
0 is Ω, and 3.35 is Ω. The resistance value Rcl Rd can also be calculated in the same way, and as an example, Rc
=3.35 kΩ.

Ω can be listed as Rd=20. In this case, the phases L e , L d Id, sotL (' h 27
9.5° and 170.5°. Further, the amplitude 1;1 or +a+ can be determined by substituting the above-mentioned resistance value into equation (2) or (4), and in this case, both become 0.434.

FIG. 8 shows the state of change in each signal λ, λ, λ, and λ due to variations in the time constants CH of the resistors B50z and TC in the CR phase shift circuit 32 from the designed values. is also shown. In this case, the solid line shows each signal when the time constant C-R is the design value, the broken line shows each signal when the time constant c-rt varies in the positive direction and becomes the largest, and the dashed-dotted line shows the time constant Each signal is shown when the constant CR varies in the negative direction and becomes the smallest.

Even if the time constant C-R varies, the signals always form a semicircular chord whose diameter is the amplitude of signal D, as explained in FIGS. They also always have a phase difference of ±90° with respect to each other. therefore,
Look at the signal.

The phase difference of 9, demodulation relative phase 0, is also 110.8° when the time constant C-R is maximum and 111.9° when it is minimum.
and 109° can maintain consistent values. Note that in general integrated circuits, the resistance value is ±20-20% of the design value.
It varies within the range of. In addition, the capacitance value is ±3 relative to the design value.
C wobbles in the 0% range.

In this way, when integrating the circuit, the CR phase circuit 3
Even if the time constant C-R of 2 varies, the color subcarrier (ER-
EY)CW, [:EB-EY''ICW) Since the relative phase does not vary, good color reproduction can be achieved.

FIG. 9 shows variations in the relative phases θ of signals c and d due to variations in the resistance values of the IJ box resistors.

When integrating circuits, even if the resistance value of each resistor varies within a range of ±20 inches, the resistance ratio will hardly vary.
Even in a general integrated circuit, it can be suppressed within the range of ±5%.

Therefore, even if the resistance value varies, the demodulated relative phase θ hardly varies as shown in FIG. 9, and the variation can be suppressed within the range of ±1%.

FIG. 8 shows the case where the hue adjustment circuit 54 is in the center state and the delayed signal is not delayed by the OR phase shift circuit 32, the delayed signal is input, and the signals a-b, -b, b-2 are output. ,
This shows a. In addition, FIG. 11 and FIG. 10 show each signal when the hue adjustment goream 54 is set to the MAX state.

Further, FIG. 11 is a diagram showing each of the above-mentioned signals when the hue adjustment brings the volume 54 to the MIN state. In addition, the 10th
In FIG. 11, solid lines indicate each signal when the time constant C-R of the OR phase shift circuit 32 is the design value, and broken lines indicate each signal when the time constant C-R is the maximum. , and the dashed-dotted lines indicate each signal when the time constant CR becomes the minimum.

The signal is supplied to the base of one transistor Qso of the differential pair of transistors Qso+Qsl in the limiter 55. The base of the other transistor Qsx is supplied with a constant DC voltage as is the emitter of the transistor Q2B. Therefore, these transistors Qso
+ After being subjected to the amplitude limiting effect by Qal, the color difference signal component [ER-EY:] is output from the collector of the transistor Qso connected to the load resistor R6o. [AP
C] is supplied to the demodulation circuit 46 and the APC circuit 50 as CW. Similarly, the signal a is also subjected to an amplitude limiting action by the transistor Q32*Qas forming a differential pair in the limiter 55, and then the color difference signal component (EB-gy
) Color subcarrier for demodulation of c [ER-EY] Comparison signal for CW and killer detection [K11ler] CW is supplied to the demodulation circuit 46 and color killer circuit 57.

Here, the reason for providing the OR phase shift circuits 44, 45, and 49 will be explained. Now, considering the case where the OR phase shift circuit 44, 45, 49 is not provided, the color difference signal component (ER-EY)
C and [EB-EYI C have the same phase as the signal r-a (comparison signal for APC detection>+-1;<comparison signal for killer detection) shown in FIG. 8, respectively. However, in such a configuration, the color difference signal component [ER-EYI C
, (EB-EY) C as a color subcarrier for demodulation (ER-E
YI CW, (EB-EY) If only the CW signal is demodulated with a, the color difference signal ER-EY,
The hue adjustment of the EB-EY light emitting dichromaticity does not match when the lume 54 is in the center state.

The OR phase shift circuit 49 is provided to solve this problem. That is, the resistance value of the capacitor 3 and the resistance value of the resistor R17 are set so that the lead phase shift amount of the OR phase shift circuit 49 is 1109'-90' (=19°). By setting the advance phase shift amount to such a value, the color difference signal components (ER-EY) C and (FB-E
Y) C is the color subcarrier for demodulation (ER-EYI CW
, (EB-EY) is delayed by 19 degrees relative to CW, and the above problem is solved.

Also, by providing this CR phase shift circuit 4g, the time constant C of the OR phase shift circuit 52 and 32 of the color synchronization circuit [1111]
-OR phase shift circuit 4 on the color synchronization circuit input side even if R varies
Since the time constant C·R of 9 also varies in the same way, the color subcarrier [ER-EY,] CW.

[EB-EYI CW and detection comparison signal (APC)
C.W.

[Ki l Ier] CW phase variation is APC
This is canceled out by variations in the phase of the color burst signal Bu supplied to the circuit 5° and the color killer circuit 51.

Therefore, the color subcarrier [:ER-EY] C always synchronized with a predetermined phase relationship with respect to the force 2-burst signal Bu.
W, (EB-EY) CW-? Comparison signal (APC) CW for APC detection and killer detection.

(Ki l 1er), CW is obtained,
It is possible to almost eliminate the phase shift between the two chromaticities of the light emission of the color difference signals ER-EY and EB-EY due to variations in the time constant C-H on the color synchronization circuit side. Specifically, the time constant C-
Color difference signal ER when R varies the most in the positive direction
-EY, EB-EY emission 1 chromaticity phase shift is 7.
4° (hue variable range 65.2°), and the phase shift of the emission dichromaticity is 11° when the largest variation is in the negative direction.
(hue variable range 121.4°).

In this case, there is a shift due to hue adjustment, but the above value was considered with the time constant C-R having the largest variation, and it will be reduced a little more in actual manufacturing.

Considering the killer sensitivity, when the time constant C-R is the design value, the detection efficiency is 0.49 dB, and the time constant ac-
The maximum variation in R is 0.2 dB, and the killer performance is hardly affected by the variation in the time constant C-R.

As mentioned above, the OR phase shift circuit 49 receives the color burst signal B.
This is provided to eliminate the influence of variations in the time constant C-H on the color synchronization circuit side in the relationship between u and the color subcarrier for demodulation and the comparison signal for detection. On the other hand, the OR phase shift circuits 44 and 45 convert the carrier color signal (color difference signal component (ER
-EY) C.

(EB-EY) C composite signal) and the color subcarrier for demodulation (FAR-EY) CW, (EB-EY) CW, the variation in the time constant C-R on the color synchronization circuit side This was designed to eliminate the impact. That is, the time constant C- of the OR phase shift circuit 52.32 on the color synchronization circuit side
Even if R varies, the time constant C-R of the OR phase shift circuit 44.45 on the input side of the demodulation circuit 46 also varies in the same way. As a result, the demodulation color subcarrier (ER-EY) CW, (
EB-EY) CW phase variations are offset by phase variations of the carrier color signal due to variations in the time constant C-H of the OR phase shift circuits 44 and 45. In this case, the reason why two CRs phase circuits 44 and 45 are provided, and they have the same phase shift amount and sound volume but different directions is that the OR phase shift circuit is provided between the second band amplification circuit 43 and the demodulation circuit 46. This is to prevent the phase relationship between the carrier color signal and demodulation color subcarrier from changing due to the provision of the circuit. Further, by doing so, even if the time constant C-R of the OR phase shift circuits 44, 45 varies, the amplitude of the carrier color signal hardly varies and the degree of saturation remains constant. Role, OR phase shift circuit 44
．． An example of the phase shift amount of 45 is ±19°.

In the OR phase shift circuits 44, 45, and 49, the resistance values of the resistors R11 and R17 and the capacitance values of the capacitors C11+C1B to obtain a phase shift amount of 19° are, for example, 1, respectively.
7.7 can include Ω and 15 PF. Further, the resistance value of the resistor R11l and the capacitance value of the capacitor C12 are 5.1 Ω and 3PF, respectively.

FIG. 12 shows variations in the input phases of the color burst signals B and u to the APC circuit 50 and color killer circuit 51 due to variations in the time constant C-H of the OR phase shift circuit 49, and the variation in the input phase of the OR phase shift circuit 44 and 45. Color difference signal component [ER-B
Y]C, [EB-EY: It is a diagram showing the degree of variation in the input phase of the IC. In the figure, the solid line shows each signal when the time constant C-R is the design value, the dashed line shows the signal when the time constant C-R varies in the positive direction and becomes the largest, and the dashed line shows the time constant This shows a signal when CR varies in the negative direction and becomes the smallest.

In FIG. 12, the color burst signal Bu output from the burst signal amplification circuit 48 is designated as Bu2,
What is supplied to the APC circuit 50 and the color 4-color circuit 57 is shown as BU3.

FIG. 13 shows the color subcarrier (ER-EY) CW for demodulation due to variations in the time constant C-R of the OR phase shift circuit.

(EB-EY) CW, comparison signal for APC detection and killer detection (APC) CW, (Kller
) CW, color burst signal Bu, color difference signal component [
ER-EY)C.

(EB-EV) It is a diagram showing the degree of variation in the phase of C.

Note that during actual demodulation, the demodulation circuit 46 performs synchronous detection by inverting the phases of the input color subcarriers [:ER-EY:] CW and [EB-X) CW. Therefore, FIG. 13 shows the phase-inverted color subcarrier (ER-E
Y]CW, [EB-EY] Indicates CW.

FIG. 14 shows color subcarriers (ER-EY) CW and (EB-EY) CW for demodulation when the output signal of the VCO 51 is synchronized with the color burst signal Bu in a predetermined phase relationship.

Comparison signal for detection [:APC:] CW, [:K1
1ler] CW.

In addition, color difference signal components (ER-EY) C, [EB-EY
EC is shown.

〔Effect of the invention〕

As described above, according to the present invention, even in an integrated circuit, a predetermined phase can be reliably set between the demodulation relative phase and the input relative phase of the color difference signal component, and further, the color difference gain obtained by the demodulation circuit can be set reliably. No. ER-EY, EB-EY light emission 2
It is possible to provide a color reproduction circuit that can match chromaticity and in which variations in the phase of color subcarriers caused by integrated circuits have little effect on color reproduction.

[Brief explanation of drawings]

Figure 1 is a circuit diagram showing a conventional color reproduction circuit, and Figure 2 is a circuit diagram showing a conventional color reproduction circuit.
FIG. 3 is a signal vector diagram for explaining the operation of the circuit shown in the figure. FIG. 3 is a circuit diagram showing an embodiment of the color reproducing circuit according to the present invention, and in particular a circuit diagram showing a part that generates a color subcarrier for demodulation. , FIG. 4 is a signal vector diagram for explaining the operation of the circuit shown in FIG. 3, FIG. 5 is a circuit diagram showing the overall configuration of the color reproduction circuit of one embodiment, and FIG. A circuit diagram showing an example of a specific configuration of the circuit shown in FIG.
FIG. 7 is a signal vector diagram showing signals of each part in FIG. 7 and FIG. 6; , V 2.44 , 45 , 49 , 52... CR phase shift circuit, 33... First differential amplifier circuit, 34... Second differential amplifier circuit, 35... First differential amplifier circuit Resistance matrix circuit, 36... Second resistance matrix circuit, 41...
Input terminal, 42... first band amplifier circuit, 43...
Second band amplification circuit, 46... Demodulation circuit, 47...
Picture tube, 48... Perst 1 word amplification circuit, 50...
・APC circuit, 51 =-VCo, 5 j-... Hue circuit, 54... Hue adjustment volume, 55... Limiter, 56... ACC circuit, 57... Color killer circuit, 58... Saturation adjustment volume, 69.60・
...Terminal. Applicant's agent: Patent attorney Takehiko Suzue. Figure 2 Figure 3 Figure 4

Claims (1)

[Scope of Claims] A band amplifying means for extracting the carrier color signal from a composite color signal consisting of a color burst signal and a carrier color signal, and a relative phase of the two color subcarriers of the carrier color extracted by the band amplifying means. 2 with leading phase shift amount and lagging phase shift amount
a first CR phase shifter inserted between the output terminal of the band amplification means and the input terminal of the demodulation means; oscillation at the same frequency as the color subcarrier frequency; oscillating means for outputting a signal; second CR phase shifting means having an input terminal connected to the output terminal side of the oscillating means and shifting the phase of the input signal by a predetermined amount; and this second CR phase shifting 6-track input signal. a first differential amplification means for synthesizing an output signal and outputting two signals having a phase difference of 180 degrees from each other and a phase difference of 90 degrees with respect to the output signal; and an output signal of the second OCR phase shift means. 20th differential amplification means for synthesizing DC voltages of a predetermined level and outputting two signals, one in phase and the other in phase with the output signal of the second CR phase shift means; The first . resistance matrix means for obtaining two color subcarriers for demodulating the carrier color signal with a relative phase of θ by suitably combining the output signals of the second differential amplification means; burst signal extraction means for extracting the color burst signal from the composite color signal; and a third OR of the output signal of the burst signal extraction means.
The output signal of the phase shifting means is phase-compared with one of the four signals output from the first and second differential amplifying means, and the oscillation operation of the oscillating means is controlled according to the comparison result. A color reproduction circuit comprising phase control means for synchronizing an oscillation signal of the oscillation means with the color burst signal.