KR930000655Y1 - Color signal band compensative circuit - Google Patents

Abstract

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Description

Color signal band correction circuit of color TV with built-in satellite broadcasting

1 is a conventional circuit diagram.

2 is a circuit diagram of one embodiment of the present invention.

* Explanation of symbols for main parts of the drawings

R1-R17: resistor Q1-Q6: transistor

C1-C9: condenser L1, L2, L3: coil

D1, D2, D3: Diode SW: Switch

1: TV / video switching circuit 2: Satellite broadcasting / TV, video switching circuit

3: Y / C separation circuit 4: Chroma demodulation circuit

5: micom 6: emitter amplifier

7: band correction circuit 8: color signal switching circuit

9: bias supply circuit 10: control circuit

The present invention is a color signal band correction circuit of a built-in satellite broadcasting color television, and is a circuit for obtaining a clearer picture by faithfully performing color demodulation by switching a color signal band by switching according to a signal source input to a satellite broadcasting embedded color television.

Generally, in color TV with built-in satellite broadcasting or color TV with many audio and video terminals, chroma signal demodulation is performed by using the color signal separated from the Y / C separation circuit even though the signal source is different from the external color signal source. By inputting into the furnace, color demodulation with good band characteristics could not be performed.

That is, in the conventional color TV with built-in satellite broadcasting, as shown in the circuit diagram of FIG. 1, the color television signal and the video signal are input to the TV / video switching circuit 1, and the control signals of the microcomputer 5 are used to control the television signal and the video signal. One signal is selected and the signal selected by the TV / video switching circuit 1 is inputted again to the satellite broadcasting / TV and video switching circuit 2 so that any one of the satellite broadcasting signals is controlled by the control signal of the microcomputer 5. The signal selected from the satellite broadcasting / TV and video switching circuit 2 (one of the television, video and satellite broadcasting signals) is input to the Y / C separation circuit 3 as a composite video signal, and the luminance signal and the color signal. The color signal separated by and separated by the Y / C separation circuit 3 is directly input to the chroma demodulation circuit 4 to perform color demodulation.

Therefore, since external signal sources (TV, video, satellite broadcasting signal) having different color signal bands are input to the chroma demodulation circuit 4 fixed to one band, faithful color demodulation due to the difference of bands is performed according to each signal source. Since a good color signal could not be obtained, a clear and clear screen could not be obtained.

In order to compensate for these drawbacks of the prior art, the present invention compensates color signals for each input signal source, and inputs color signals having good band characteristics to the chroma demodulation circuit, thereby improving color clarity by faithfully performing color demodulation. have.

The present invention for this purpose will be described in detail with reference to the accompanying drawings.

2 is a circuit diagram of an embodiment of the present invention, which separates a composite video signal selected from a TV / video switching circuit 1, a satellite broadcasting / TV, and a video switching circuit 2 by a microcomputer 5 into a luminance signal and a color signal. A color signal demodulation circuit of a satellite broadcasting built-in color television comprising a / C splitting circuit (3) and a chroma demodulation circuit (4) for color demodulating the color signals separated by the Y / C splitting circuit (3). Emitter amplifier (6) for amplifying the color signal separated by the / C separation circuit (3), and band correction circuit (7) for band correction of the color signal amplified by the emitter amplifier (6) according to each signal source characteristic And a color signal switching circuit 8 for selectively applying the band corrected color signal of the band correction circuit 7 to the chroma demodulation circuit 4 by bias supply according to the switch SW connection of the bias supply circuit 9; ) And the switch S of the bias supply circuit 9 W) consists of a control circuit 10 for controlling the connection with the control signal of the microcomputer.

Here, the emitter amplifier 6 is composed of resistors R1-R3 and transistors Q1, and the band correction circuit 7 includes resistors R4-R6 and capacitors C1- to compensate for the bands corresponding to the respective signal sources. C9) and the bandpass filter in which the time constants of the coils L1-L3 are converted are connected in parallel.

The control circuit 10 is composed of transistors Q5 and Q6 driven by control signals applied from the microcomputer at different levels according to signal source selection, and the bias supply circuit 9 is the transistor Q5. ), And the switch SW is switched according to the driving of Q6 to supply a bias. The color signal switching circuit 8 drives the transistors Q2-Q4 according to the bias supply of the bias supply circuit 9. Is selected to select the output of the color signal passing through the band pass filter of the band correction circuit 7.

When the user selects one of the television, the video, and the satellite broadcasting in the present invention configured as described above, the microcomputer recognizes this and outputs control signals of different levels to the control circuit 10.

That is, when the microcomputer applies a control signal of high or low level to the bases of the transistors Q5 and Q6, the 'turn-on' state of the transistors Q5 and Q6 is selected and the resistor R16 is selected. ), And the voltage applied to the resistor R17 is changed so that the switch SW of the bias supply circuit 9 selects one of the terminals ①②③.

In other words, when a high level control signal is applied to both transistors Q5 and Q6 at the microcomputer, the two transistors Q5 and Q6 are all turned on, and thus the switch SW of the bias supply circuit 9 is switched on. ) Is applied with a voltage almost equal to the ground potential. When a high level control signal is applied to the base of transistor Q5 and a low level control signal is applied to the base of transistor Q6, transistor Q5 is 'turned on' and transistor Q6 is applied. Is turned off so that the switch SW of the bias supply circuit 9 has a voltage drop between the resistors R16 and R17 at the power supply VCC voltage and the voltage between the collector and emitter of the transistor Q5. Voltage is applied except (V _CE ).

When a low-level control signal is applied to the bases of the transistors Q5 and Q6, both the transistors Q5 and Q6 are 'turned off' so that the switch SW of the bias supply circuit 9 supplies power. The power supply voltage other than the voltage drop applied to the resistor R16 in the (VCC) voltage is applied, and a voltage higher than the previous two cases is applied to the bias supply circuit 9.

That is, when the control signals of the microcomputer are all applied at the high level, the voltage applied to the switch SW is the lowest, and when the control signals are all applied at the low level, the voltage applied to the switch SW is the highest and the control signal is When applied at the high level and the low level, the voltage applied to the switch SW is about halfway between the two cases.

Therefore, the bias supply circuit 9 selects one of the terminals (①②③) of the switch SW using the difference in voltage applied from the control circuit 10 described above.

At this time, the terminals (①②③) of the switch SW of the bias supply circuit 9 are band-corrected for the color television signal, the video signal, and the satellite broadcast signal, respectively, and are input to the color signal switching circuit 8 and input transistors Q2, Q3, Q4. ) Bases are connected respectively.

Therefore, when one mode is set in the microcomputer 5 and a control signal is applied, one terminal of the switch SW of the bias supply circuit 9 is selected by driving the transistors Q5 and Q6 in the control circuit 10. In the terminal selected by the switch SW, the power supply Vcc is distributed to the resistors R14 and R15 so that the transistor connected to the terminal selected by the switch SW is 'turned on' and the output of the band correction circuit 7 is applied. Is applied to the chroma demodulation circuit (4).

On the other hand, the signal selected from the color television signal, the satellite broadcasting signal and the video signal is input to the Y / C separation circuit 3 as a composite signal and separated into color signals. The separated color signals are resistors R1, R2, R3 and transistor Q1. Emitter amplifier (6) consisting of amplification to amplify the color signal for band correction, and outputs to one of the color television signal, video signal, satellite broadcasting signal output to the emitter of the transistor (Q1) of the emitter amplifier (6) Each band color signal for is applied to the band correction circuit 7.

At this time, the band correction circuit 7 is composed of a coil (L1-L3), a capacitor (C1-C9), a resistor (R4-R6), such a band correction circuit (7) is only a frequency band required for each signal source As the filter circuit to pass through, the color signal band is well corrected according to each signal source.

Each of the color signals whose bands are corrected in the band correction circuit 7 and each filter is input to the bases of the transistors Q2, Q3, and Q4 of the color signal switching circuit 8, so that the switch SW of the bias supply circuit 9 is applied. By one of the diodes (D1, D2, D3) outputting a color signal to one of the transistors (Q2, Q3, Q4) to prevent mutual interference between the chroma demodulation circuit (4) and the color signal switching circuit (8). After being input through the chroma demodulation circuit 4, the color is demodulated.

As an embodiment of the present invention, the terminal (①) of the switch (SW) in the television mode is selected, the terminal (②) of the switch (SW) in the video mode is selected, and the terminal (③) of the switch (SW) in the satellite broadcasting mode. Assume that) is selected.

First, when the color television mode is set in the control circuit 10 by the microcomputer, the television signal is applied to the Y / C separation circuit 3 while the bias supply circuit 9 is combined with the transistor Q6 of the transistor Q5. Terminal (①) of switch SW.

In other words, when the television signal is selected, when the terminal ① of the switch SW of the bias supply circuit 9 is selected in the control circuit 10, only the transistor Q2 of the color signal switching circuit 8 is turned on and the transistor Q3 is selected. ) And (Q4) remain 'turned off'.

Therefore, the color television signal is separated from the color signal in the Y / C separation circuit 3, and the color signal separated in the Y / C separation circuit 3 is amplified by the emitter amplifier 6 and input to the band correction circuit 7. In the band correction circuit 7, the band is corrected through a filter composed of the capacitors C1-C3, the coil L1, and the resistor R4 according to the television signal band, and then applied to the color signal switching circuit 8.

Here, the color signal band-corrected by the band correction circuit 7 is input to the base of the 'turned on' transistor Q2, and the input color signal is input to the chroma demodulation circuit 4 through the diode D1 at the emitter of the transistor Q2. In this case, the chroma demodulation circuit 4 is capable of sufficiently correcting the color signal band according to the color television signal for good color demodulation.

On the other hand, as the video signal and the satellite broadcast signal are selected, the terminals (2) and (3) of the switch SW are selected and the switching operation of the transistors Q3 and Q4 of the color signal switching circuit 8 changes accordingly, thereby correcting the band. In the circuit 7, the color signals, which are band-corrected differently according to the signal source, are applied to the chroma demodulation circuit 4.

Therefore, since the chroma signal having good band characteristics is applied to the chroma demodulation circuit 4 through the band correction circuit 7 regardless of the signal source, faithful color demodulation can be performed.

As described above, the present invention corrects the color signal band according to the input of the signal of the satellite broadcasting embedded color television, that is, the color television signal and the satellite broadcasting video signal, thereby providing faithful color demodulation by supplying a good color signal to the color demodulation circuit. It is a circuit designed to make it possible to apply to color TV with many audio and video inputs, and to produce a clearer screen.

Claims (3)

A Y / C separation circuit 3 for separating the composite video signal selected by the TV / video switching circuit 1, the satellite broadcasting / TV, and the video switching circuit 2 into a luminance signal and a color signal by the microcomputer 5; A color signal demodulation circuit of a satellite broadcasting built-in color television comprising a color demodulation circuit 4 for color demodulating the color signal separated by the Y / C separation circuit 3, wherein the color signal demodulation circuit is separated from the Y / C separation circuit 3. An emitter amplifier 6 for amplifying the color signals, a band correction circuit 7 for band-correcting the color signals amplified by the emitter amplifier 6 according to the signal source characteristics, and the band correction circuit 7 A color signal switching circuit 8 for selectively applying a band-corrected color signal to the chroma demodulation circuit 4 by bias supply according to the switch SW connection of the bias supply circuit 9, and the bias supply circuit 9; Switch (SW) connection of the microcontroller That consists of the control circuit (10) characterized by a built-in satellite broadcasting color TV band color signal correction circuit in which a. The band pass filter according to claim 1, wherein the band correction circuit 7 converts the time constants of the resistors R4-R6, the capacitors C1-C9, and the coils L1-L3 to compensate for the bands corresponding to the respective signal sources. Color signal band correction circuit of color TV with built-in satellite broadcasting, characterized in that the configuration in parallel. 2. The color signal switching circuit (8) according to claim 1, wherein the color signal switching circuit (8) selects driving of the transistors (Q2-Q4) in accordance with the bias supply of the bias supply circuit (9) to determine the color signal passing through the band pass filter of the band correction circuit (7). A color signal band correction circuit of a color television with built-in satellite broadcasting, configured to select an output.