KR960010488B1 - Caption signal generating circuit of tv receiver - Google Patents

Abstract

The circuit produces caption signals having specified range of signal level. The circuit includes: an image signal output (100) for amplifying an image signal of 2V(P-P); the third buffer (24) for outputting the video signal 2VP-P generated from the video signal output (100) and a video signal of 0.7-1.4 V(P-P); and a caption IC (25) for receiving the video signal of 0.7-1.4 V(P-P) from the third buffer (24) to generate a caption signal.

Description

Caption signal generation circuit of television receiver

1 is a block diagram showing the configuration of a caption signal generating circuit of a general television receiver.

2 is a block diagram showing the concept of a caption signal generating circuit of a television receiver of the present invention.

* Explanation of symbols for main parts of the drawings

1: Chroma Integrated Circuit (IC) 2: Buffer

3, 25: caption integrated circuit (IC) 20: first buffer

21: main integrated circuit (IC) 22: amplifier

23: second buffer 24: third buffer

26: voltage divider circuit

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a television receiver, and more particularly to a caption signal generating circuit of a television receiver for outputting a certain level of caption signal to a caption integrated circuit (Caption IC).

Recently, a TV receiver with a function of providing subtitle data for an audio signal and a so-called caption function has been developed and released.

FIG. 1 is a block diagram showing the configuration of a caption signal generating circuit of such a television receiver. FIG. 1 is a chroma IC which outputs a composite video signal, and 2 is a first NPN transistor Q1 and a first resistor. A buffer configured to R1 to buffer the composite video signal output from the chroma integrated circuit 1, and 3 is caption data from the composite video signal applied from the buffer 2 through the first coupling capacitor C1. It is a caption integrated circuit for generating a.

That is, in the above configuration, the composite video signal output from the chroma integrated circuit 1 is buffered and set to a predetermined level using the buffer 2, and then applied to the caption integrated circuit 3 to generate caption data. have.

On the other hand, the purpose of using the buffer 2 is to set the level of the composite video signal to the input level of the caption integrated circuit 3, that is, 0.7-1.4 VP-P as described above. This is to prevent the caption integrated circuit 3 from malfunctioning when the level of the composite video signal is out of the above range.

In general, the level of the composite video signal output through the chroma integrated circuit 1 is varied by the degree of modulation of the intermediate frequency and the level of the audio / video signal. If it becomes small, the caption integrated circuit 3 will malfunction.

Accordingly, the present invention has been made in view of the above circumstances, and an object thereof is to provide a caption signal generating circuit of a television receiver capable of generating a caption signal of a constant level.

The present invention for realizing the above object is based on the following matters.

The television receiver has a monitor output terminal for outputting a video signal and an audio signal to the outside. The level of the video signal output through the monitor output terminal is normally set to about 2V _{PP according} to the specification of the apparatus.

Accordingly, when the composite video signal output through the monitor output terminal of the television receiver is applied as the caption signal, it is possible to ensure stable operation of the caption integrated circuit.

The present invention for achieving the above object is characterized in that the video signal output unit, the third buffer, the caption integrated circuit.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

2 is a circuit diagram showing the configuration of the caption signal generating circuit of the television receiver according to the first embodiment of the present invention.

In FIG. 2, reference numeral 21 denotes a main integrated circuit (IC) for outputting a video signal, and 22 denotes an amplifier for amplifying the video signal output from the main integrated circuit 21, and is configured of, for example, a two stage amplifier. .

A first buffer 20 including a second NPN transistor Q2 and a second resistor R2 is provided between the main integrated circuit 21 and the amplifier 22.

In addition, a second buffer 23 including a third NPN transistor Q3 and a third resistor R3 is provided at an output terminal of the amplifier 22, a second coupling capacitor C2, and fourth and fifth resistors R4. , The monitor output terminal is connected via a voltage divider circuit according to R5).

On the other hand, in the above configuration, at the connection point of the amplifier 22 and the second buffer 23, the third buffer 24 and the third coupling including the sixth-eighth resistors R6-R8 and the fourth NPN transistor Q4 are connected. The caption integrated circuit 25 is connected through the capacitor C3 and the ripple canceling capacitor C4. The third buffer 24 receives the 2V _PP video signal output from the amplifier 22. This is to set the caption signal of the level of 0.7-1.4V _PP required in 25).

As shown in FIG. 2, the present invention provides a 2V _PP video signal output from the video signal output unit 100 on the video signal output unit 100 to amplify and output the 2V _PP video signal. The third buffer 24 which sets and outputs the video signal of V _PP , and the caption integrated circuit 25 which generates and outputs a caption signal by receiving the 0.7-1.4 _PP video signal output from the third buffer 24. It consists of

Meanwhile, the video signal output unit 100 includes a main integrated circuit 21, a first buffer 20, and an amplifier 22.

Referring to the operation of the present invention configured as described above in detail. First, the video signal output unit 100 amplifies and outputs an input video signal, and the amplified video signal is output to the monitor output terminal through the second buffer 23 and the voltage dividing circuit 26.

Meanwhile, the 2V _PP video signal output from the amplifier 22 of the video signal output unit 100 is also output to the third buffer 24 and set as a 0.7-1.4V _PP video signal so that the caption integrated circuit ( 25).

The 0.7-1.4V _PP video signal thus input is set as a caption signal and output.

That is, according to the above embodiment, the caption signal generating circuit of the television receiver of the present invention is based on the constant voltage of 2V _PP output from the amplifier 22 through the second buffer 23, and the caption integrated circuit 25 Since it generates the caption signal of 0.7-1.4V _PP required by the it is possible to prevent the malfunction of the caption integrated circuit 25.

As described above, according to the present invention, there is an effect that a caption signal generating circuit of a television receiver capable of generating caption signals having a certain range of levels can be realized.

Claims (2)

A third buffer for setting and outputting a video signal output means for amplifying and outputting a video signal of 2V _PP 100, a video signal of the video signal of 2V _{PP PP} 0.7-1.4V output from the image signal outputting means (100) (24) A caption signal generating circuit of a television receiver comprising a caption integrated circuit (25) for receiving a 0.7-1.4V _PP video signal output from the third buffer (24) to generate and output a caption signal. The television receiver according to claim 1, wherein a third coupling capacitor (C3) and a grounded ripple canceling capacitor (C4) are connected in series between the third buffer (24) and the caption integrated circuit (25). Caption signal generator circuit.