JPH0822079B2 - Color television receiver - Google Patents

Description

The present invention relates to a color television receiver, and more particularly to SECA.
The present invention relates to a color television receiver with an M type automatic white adjustment circuit.

[Conventional technology]

Generally, in a color television receiver, a certain standard white signal is the standard for color reproduction.
If the reference white color shifts, it appears as a color shift between the subject and the picture reproduced on the television receiver. Therefore, this reference white color must be adjusted sufficiently, and adjustments are made for each television receiver.However, due to aging, the current ratio of each cathode that determines the RGB output brightness of the cathode ray tube will shift. , The reference white is shifted and the screen becomes reddish or bluish. In order to keep this reference white constant automatically, the conventional technology is:
There is an automatic white adjustment circuit.

The circuit operation will be described below with reference to FIGS. 5 and 6. The output of the Y / C separation circuit 1 with the composite video input 22 is
It is connected to the input of the Y signal processing circuit 2 and its output is connected to the first input of the matrix 5. Y / C separation circuit 1
The second output of is connected to the first input of the chroma SW25,
The second input of chroma SW 25 is connected to the third output of timing generator 12. Chroma SW25 output is BP
It is connected to the input of A (bandpass amplifier) 3, its output is connected to the input of the color demodulation circuit 4, and the output of the color demodulation circuit 4 is connected to the second input of the matrix 5. Here, since the blocks after the matrix 5 have the same system configuration for each of the B, G, and R outputs, only the B output will be described. The B output of the matrix 5 passes through the adders 26 and 27 and drive adjustment is performed. 8 to the first input. The output of drive adjustment 8 is connected to the first input of cutoff adjustment,
Its output is connected to the input of blanking 10 and the output of blanking 10 is connected to the input of CRT amplifier 11. C
The output of the RT amplifier 11 is connected to the base of the PNP transistor 17, its emitter is connected to the cathode of the CRT, and its collector is connected to the GND through the resistor 19 and the first input of each of the comparators 13 and 14. . The second inputs of the comparators 13 and 14 are connected to the reference voltages 15 and 16, respectively, and the output of the comparator 13 is connected to the GND through the hold capacitor 20 and the second input of the drive adjusting circuit 8. The output of the comparator 14 is connected to the GND and the second input of the cutoff adjustment 9 through the hold capacitor 21. The third input of the comparator 13 is
It is connected to the adder 26 through the first output of the timing generator 12 and the reference voltage 6. The third input of the comparator 13 is connected to the adder 27 through the second output of the timing generator 12 and the reference voltage 7. Adder through the second output of timing generator 12 and reference voltage 7
27 connected. The timing generator 12 has a vertical blanking (V, BLK) input 23 and a horizontal blanking (H
BLK) has input 24.

The signal waveform of each part in FIG. 5 is as shown in FIG. That is, the composite video signal input to the Y / C separation circuit 1 has a waveform of only the Y signal at the input of the Y signal processing circuit, and has the waveform of only the chroma signal at the input of the chroma SW 25. Here, the chroma SW pulse shown in FIG. 5 is inputted to the chroma SW 25 during the reference signal period, and during this period, the operation for inhibiting the chroma signal input to the B / P / A in the next stage is performed. Therefore, as shown in FIG. 5, a signal without the chroma signal is input to the B / P / A inputs as shown in FIG.
In the case of the NTSC system, since this chroma signal is directly input to the color demodulation circuit 4 in the next stage, the matrix 5 outputs only the Y signal waveform without the color demodulation signal for the reference signal period. During other periods, a waveform in which the color demodulation signal and the Y signal are combined is output. Hereinafter, since the reference white color is automatically kept constant without any problem in order to perform the operation as shown in Japanese Patent Laid-Open No. 60-18087, as described above, it does not change with time. Automatic white adjustment was done.

[Problems to be Solved by the Invention] In the conventional color television receiver having the automatic white adjustment described above, when the SECAM system is received, the output of the limiter 30 is input to the 1H delay line 28 and the secum SW 29 as shown in FIG. The 1H delay line 28 output is
Since it is input to the color demodulation circuit 4 via 29, the chroma SW25
Even if the pulse for the chroma SW is input to, the chroma signal waveform as shown in FIG. 8 is input during the first 1H period of the reference signal period. Therefore, since the color demodulated signal and the Y signal are output in a combined form in the first 1H period of the reference signal period to the output of the matrix 5, when adding the reference signal of the next stage by the adder, Since the offset of only the demodulated signal is superimposed, the reference white is deviated because the reference white is adjusted using this signal as a reference.

[Means for solving the problem]

The color television receiver of the present invention uses the color demodulation circuit input in the reference signal period so that the chroma signal delayed by 1H by the 1H delay line which causes a malfunction in the automatic white adjustment during SECAM reception is not input to the color demodulation circuit. It has a switch to which a pulse is applied for controlling so as to bypass the ground.

〔Example〕

 Next, the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of the present invention. In the figure, the same components as the conventional color television receiver having automatic white adjustment are designated by the same reference numerals.
As described above, the color signal delayed by the 1H delay line 28 causes the color signal to be output to the output of the secam SW29, but between the input of the color demodulation circuit 4 and the output of the secum SW29,
The first switch formed by the series connection of the first capacitor 33 and the first transistor 35 and the second switch formed by the series connection of the second capacitor 34 and the second transistor 36 are connected, and the switch is turned on. , The bases of the first and second transistors 34, 35 are both driven by the timing generator 12 to determine the off state. The timing generator 22 operates so as to output a high level during the reference signal period, and during the reference signal period, the first and second
The transistors 34 and 35 are turned on, the first and second switches are turned on, the input terminal of the color demodulation circuit 4 is bypassed to the common potential, and the color signal is not input to the color demodulation circuit 4.

The above operation will be further described with reference to FIG. Since the color signal is bypassed to the color demodulation input by the first and second switches during the reference signal period, nothing is input during the reference signal period, and as a result, the output of the CRT amplifier 11 is also the original reference signal. It is output, indicating that the automatic white adjustment works normally.

Although a series of a capacitor and a transistor is used as the first and second switches, it goes without saying that this may be replaced with another switch means.

FIG. 3 is a partial circuit diagram for specifically realizing the present invention. The color signal output from the limiter 30 is
29 and 1H delay line 28 added. The output of the 1H delay line 28 is applied to the secam SW 29, and the secam SW 29 alternately switches the output color signal of the limiter 30 and the output color signal of the 1H delay line 28 by the line discriminating circuit 31 for each 1H and BY. The color demodulation circuit 4 outputs a continuous Y-color signal.
Output to. The two lines of RY and BY color signals between the secum SW 29 and the color demodulation circuit 4 have the first line respectively.
A first switch comprising a capacitor 33 and a first transistor 35 connected in series, and a second switch comprising a second capacitor 34 and a second transistor 36 connected in series are connected between a common ground potential. It The bases of the first transistor 35 and the second transistor 36 are commonly connected to the timing generator 12. In this embodiment, the components other than the two capacitors 33 and 34 and the two transistors 35 and 36 are necessary for the conventional SECAM type color television receiver, and only a few additional parts are required.

FIG. 4 shows another specific circuit. In this example, the circuits of the transistors 35 and 36 and the capacitors 33 and 34 are the secum switch 29.
It is installed in the front stage of.

〔The invention's effect〕

As described above, the present invention has the effect that automatic white adjustment can be performed without malfunction even during SECOM reception.

[Brief description of drawings]

FIG. 1 is a block diagram of a color television receiver of the present invention, FIG. 2 is a diagram for explaining the operation of FIG. 1, FIG. 3 is a circuit diagram of this embodiment, and FIG. 4 is another example. FIG. 5, FIG. 5 and FIG. 7 are block diagrams of an example of a conventional color television receiver, and FIGS. 6 and 8 are diagrams for explaining the operation of FIG. 5 and FIG. 7, respectively. is there. 1 ... Y / C separation circuit, 2 ... Y signal processing circuit, 3 ... band pass amplifier, 4 ... color demodulation circuit, 5 ... R, G, B
Matrix, 8 ... Drive adjustment, 9 ... Cutoff adjustment, 10 ... Blanking circuit, 11 ... CRT amplifier, 12 ...
… Timing generator, 28 …… 1H delay line,
29 …… Secum SW, 30 …… Limiter.

Claims (1)

[Claims] 1. Inserting means for inserting a reference voltage in a reference signal period immediately after vertical blanking, and a CRT in the reference signal period.
The input of the demodulation circuit for the SECAM system color demodulation in the color television receiver in which the white color is automatically adjusted by using the voltage obtained by comparing the voltage proportional to the cathode current with the reference voltage. A color television receiver characterized in that a switch means is provided at an end thereof and the switch means is turned on to bypass the color signal during the reference signal period.