JPS61117992A - Hue adjusting circuit - Google Patents

Abstract

PURPOSE:To adjust hues of PAL, NTSC and dummy NTSC signals with one common phase shifter circuit by changing the control DC voltage of the phase shifter circuit corresponding to frequency. CONSTITUTION:A switch 31 is switched to a side P at the time of decoding the PAL signal, and its phase shifting angle is decided according to the DC voltage VR2 decided by a semi-fixed variable resistance 35. At the time of decoding the NTSC signal the switch 31 is switched to a side N, while a switch 32 is turned off. The DC voltage VR1 decided by a variable resistance 34 is multiplied by about 1.2 by means of an amplifier 33, and supplied to the control terminal of a phase shifter circuit 30. The variable resistance 34 is adjusted to adjust a hue. At the time of decoding the dummy NTSC signal, the switch 31 is switched to the side N, while the switch 32 is turned on. The DC voltage VR1 decided by the variable resistance 34 is supplied to the control terminal of the phase shifter circuit 30 through the switch 32 instead of the amplifier 33. Accordingly a change in the phase shifting angle can be compensated even if frequency changes, and the variable scope of the hue will not change.

Description

Detailed Description of the Invention [Field of Industrial Application] This invention is applicable to PAL signals, NTSC signals, and signals having a subcarrier frequency of 4.43M although the signal format is an NTSC signal.
Pseudo NTS of Hz (subcarrier frequency of PAL signal)
The present invention relates to a color demodulation circuit, particularly a hue adjustment circuit, which can demodulate C signals using a common circuit.

[Conventional technology]

Due to the similarity between the PAL signal and the NT8C@ carrier color signal,
Color demodulation circuits that can demodulate both types of carrier color signals using a common circuit are conventionally available.

FIG. 3 shows an example of this conventional color demodulation circuit.

In the figure, (1) to (4) are switches which are switched to the N side when demodulating an NTSC signal, and to the @ side when waiting for a PAL signal.

When demodulating NTSC signals and pseudo switches (1) to (4-1jX
Since the carrier color signal of the NrSC signal through the input terminal αυ is switched to N II, the carrier color signal of the NrSC signal is transferred to the carrier color signal amplifier U.
The NTS termination signal is supplied to the demodulation circuit (to) and Q4 through the switch (1).
The APC circuit (to) K is supplied through the C hue adjustment phase shift circuit (2). Then, the burst signal is extracted in this APC circuit (to), and based on this, a continuous wave signal whose phase is locked to the burst signal at a carrier frequency of 3.58 MHz is formed. This continuous wave signal is supplied to a phase shift circuit (c), from which a signal SR with a phase on the RY axis, a signal SR with the opposite phase thereof, and a signal SB with a phase on the BY axis are obtained. During demodulation of this NrSC signal, the switch (5) is switched as shown in the figure, and the signal SR is always obtained from this switch (5), and this signal SR is supplied to the demodulation circuit (to) K and from this The red color difference signal RY is demodulated and derived from the output terminal.The signal SB from the phase shift circuit (to) is supplied to the demodulation circuit α, and from this The color difference signal B-Y is demodulated and obtained, and is delivered to the output terminal (2).

In this case, the NTSC hue adjustment phase shift circuit (c) consists of a coil (211), a capacitor (212), and a variable resistor (2).
13), and by adjusting the variable resistor (213), the phase of the burst signal of 3.58 ME (z) is varied and the hue is adjusted.

Next, when demodulating the PAL signal, switches (1) to (4) are set to p
Since it is switched to @, the input terminal ant- is connected to P.
The carrier color signal of the AL signal is supplied as it is to the subtraction circuit (2) and the addition circuit (g), and is also supplied to the subtraction circuit (to) and the addition circuit (a) through the delay circuit (11) for one horizontal line. .And from subtraction circuit 0, R-
Only the Y component is taken out with the polarity reversed for each horizontal line, and this is supplied to the demodulation circuit (2). Also, only the B-Y component is taken out from the adder αQ, and this is supplied to the demodulation circuit α◆. Supplied.

Also, the PAL carrier color signal through switch (1) is PAL
It is supplied to the APC circuit (goods) through the phase shift circuit (2) for PAL signals, and from this the carrier frequency of the PAL signal is 4.43.
A continuous wave signal of 1Mz is obtained. and phase shift circuit (to)
The signals SR, SR and SB have the same phase as in the case of NTSC and a frequency of 4.43 MHz, and the signal SR is supplied to the demodulation circuit α4. On the other hand, the signals SR and SR are made to correspond to the phase of the R-4 component whose polarity is inverted for each line from the subtraction circuit (to) by switching the switch (5) alternately for each line. The signal from this switch (5) is supplied to the demodulation circuit (to).

Therefore, from the demodulation circuit (to), the red color difference signal R-Y
is demodulated and obtained, which is derived from the output terminal 0,
A blue color difference signal B-Y is demodulated and obtained from the demodulation circuit α◆, and this is led out to an output terminal (2).

In this case, the PAL phase shift circuit (2) is connected to the coil (221)
, capacitor (222), and semi-fixed variable resistor (223)
). PAL signals inherently do not require such a hue adjustment circuit, but if the phase of the burst signal is not adjusted correctly, the performance will deteriorate somewhat, so the phase adjustment is done at the factory for each color television set. Therefore, the phase shift circuit (2) is provided with a K semi-fixed variable resistor (223) for adjustment.

[Problem that the invention seeks to solve]

In the case of the above-mentioned conventional device, phase shift circuits for NTSC and PAL are required separately, such as circuit (2) and phase shift circuit (2).

In addition, when reproducing an NTSC signal on a VTR for the purpose of reproducing the NTSC signal on a PAL color television receiver, a pseudo-N signal with a carrier frequency of 4.43 MHz is used.
In some cases, the signal is reproduced as a TSC signal, but in the conventional device, the hue adjustment of this pseudo NTSC must be performed using a variable resistor (213) (in the phase shift circuit) since the needle can be adjusted by the variable resistor (213). However, since the carrier frequency is different from the normal NTSC signal, the same variable resistor (213
), the variable range of hue is different from that of a normal NTSC signal.

This invention eliminates these drawbacks.

[Means for solving problems]

FIG. 1 shows an example of the present invention. In this example, a switch (1) is not provided, and a common hue adjustment phase shift circuit (G) is provided at the front stage of the APC circuit. A carrier color signal from Anne 7'' (6) is supplied to.

Then, NTS is applied to the control terminal of this phase shift circuit (to).
A first switch 01 is connected which is switched to the N side when demodulating the C signal and to the fip side when demodulating the PAL signal. and,
The N-side contact of this first switch 0η is connected to the second switch (
2) Variable resistance through a parallel circuit with apricot race! S04
It is connected to the movable element. Also, P of the first switch 0 and
The side contact is connected to the movable element of the variable resistor (to). In this case, Anne f(2) increases the input by approximately 1.2 times (4,43MH
z/3.58 Wmz # 1.2) has a ding that is K.

In other words, if the subcarrier frequencies of the pseudo NTSC signal and the NTSC signal are respectively fs, :h, then the gain G is G
= ft/fz relationship (is done.

Further, the phase shift circuit (G) can be controlled by a DC voltage supplied to its control terminal.

[Effect]

During PAL signal demodulation, the 0th switch is switched to the P side, so the phase shift angle is determined according to the DC voltage v'R1 determined by the semi-fixed variable resistor (T).When the NTSC signal is demodulated, the 0th switch is switched to the N side. On the side, the switch (to) is turned off, and the DC/voltage VRt determined by the variable resistor (b)
is multiplied by approximately 1.2 times by the amplifier (2), and the phase shift circuit (7)
), and the hue is adjusted by adjusting the variable resistor (b).

Also, when demodulating a pseudo NTSC signal, switch 0 is switched to the N side and switch (to) is turned on, and the DC voltage VRs: bE determined by the variable resistor (b)
.

The phase shift circuit (
1) is supplied to the control terminal.

In other words, when the subcarrier frequency is 4.43 MH$, the DC voltage from the variable resistor (b) or (to) is
The subcarrier frequency is 358M.
When the frequency is Hz, Din's amplifier (
The DC voltage from the variable resistor (b) is supplied to the phase shift circuit through the variable resistor (b). Therefore, even if the frequency changes, changes in the phase shift angle can be compensated for, and the hue variable range will be different.

[Example] Figure 2 shows a phase shift circuit for hue adjustment, first and second switches 01 (to), amplifier (to), variable resistor ■ and (to)
6 in one embodiment of the part.

In the same figure, the right side of the dotted line is the phase shift circuit 00t, where (301) is the input terminal for the carrier color signal from the amplifier (2), (302) is the output terminal, and (303) is the control terminal. @And the transistor (304) (305
) (306), resistor (307), capacitor (3
The circuit consisting of 08) constitutes a variable range phase shifter with a phase shift angle of ±45°, and the pace potential of the transistors (304) and (305) changes depending on the DC voltage supplied to the control terminal (303). The input signal is phase-shifted by the phase shift amount determined by this, and an output terminal (302) K is obtained.

In addition, the part to the left of the dotted line in Figure 2 is the circuit part connected to the phase shift circuit 00 such as a switch 0, and the transistor (3
11) and (312) constitute the first switch 0),
The transistor (320) constitutes the second switch. In addition, the transistor (331) and the transistor (332),
The resistors (333) and (334) constitute a 77m (31), and when the transistor switch (320) is turned on during demodulation of the N'rSC signal by the signal SWN'K from the switching signal input terminal (321), the resistor ( 335
) is connected in parallel with the resistor (334), and DIN is made approximately 1.2 times as large as when this resistor (335) is not inserted.

In addition, transistors (361) (362) and resistors (
An amplifier is constructed from 363) and 364. This amplifier (to) is a switching transistor (320)
When is off, the gain will be the same as the amplifier (to).5:
When demodulating the PAL signal, the transistor (311
) The signal SwP supplied by K becomes rlJ, and the signal SwN supplied to the transistor (312) through the switching signal input terminal (31N) becomes "O", so the transistor (311) is turned on and the transistor (31
2) is turned off, the amplifier (to) is in operation, and the amp! (
2) becomes inactive. For this reason, the variable resistor (c)
The voltage corresponding to the DC voltage set by the phase shift circuit (1
) is supplied to the control terminal of

During demodulation of the NTSC signal, the signal swp becomes "0" and the signal amplitude becomes rlJ, so the transistor (311) is turned off and the transistor (312) is turned on, so that anf@ is inactive and an f01 is in an operating state. . At this time, the signal SWN' through the input terminal (321) is rlJ and the transistor (320) is on, so the amplifier (to)
DIN is approximately 1.2 times that when this transistor (320) is off, and the voltage corresponding to the DC voltage set by the variable resistor (B) K is multiplied by 1.2 times, and the phase shift circuit - is supplied to the control terminal (303) of.

Next, when demodulating the pseudo NTSC signal, from this state, the signal source' passing through the input terminal (321) becomes rOJ, and the transistor (320) is turned off. For this reason, the amplifier (
The dyne of (to) is the same as that of an f (to).

Therefore, the control voltage supplied to the phase shift circuit (G) is changed from that for a pure NTSC signal, and the variable phase shift range is such that the difference in carrier frequency of the running input signal is compensated for through the input terminal (301). Become.

〔Effect of the invention〕

When input signals with different frequencies are phase-shifted using a single common phase-shifting circuit, the phase-shifting angle changes depending on the frequency, but in this invention, the control DC voltage of the phase-shifting circuit is changed according to the frequency. As a result, hue adjustment of PAL signals, NTSC signals, and pseudo-NTSC signals can be performed using one common phase shift circuit. Therefore, since only one phase shift circuit is required, the configuration is simplified.

[Brief explanation of the drawing]

FIG. 1 is a system diagram of an embodiment of the inventive device, FIG. 2 is a diagram showing a specific circuit example of the main part thereof, and FIG. 3 is a system diagram of an example of a conventional device. (2) and a4 are demodulation circuits, ■ and ■ are APC circuits and phase shift circuits for forming demodulation reference signals, (to) is a common phase shift circuit, 0 is the first switch, (2) is the second switch. Figure 1 Figure 3

Claims (1)

[Claims] In a device that can demodulate carrier color signals of PAL signals, NTSC signals, and pseudo-NTSC signals, one phase shift circuit for hue adjustment common to the above three types of signals is installed before the circuit that forms the reference signal for demodulation. is provided and the first
and a second switch, the output of the first switch is supplied as a control input of the phase shift circuit, one input of the first switch is supplied with a first control voltage, and the other input is supplied with a first control voltage. As inputs, the subcarrier frequency of the NTSC signal and the pseudo NT are input by the second switch.
A second control voltage whose gain is switched in accordance with the ratio to the subcarrier frequency of the SC signal is supplied, and during PAL signal demodulation, the first switch is switched to one input side, and the NTSC signal and pseudo-NTSC The hue adjustment circuit is configured such that the first switch is switched to the other input side during signal demodulation, and the second switch is switched between NTSC signal demodulation and pseudo-NTSC signal demodulation.