KR920005314B1 - Video signal switching circuit - Google Patents

Abstract

The video signal switching circuit is for selecting television signal transmitted from a tuner or line signal transmitted through a video jack to record. The circuit comprises a bias circuit (1) for setting reference voltages of respective subcircuits, a first input circuit (2) for inputting video signal (A) transmitted from a tuner, a second input circuit (3) for inputting line signal (B) transmitted through a video jack, a control circuit (4) for controlling the first and the second input circuits (213), and a buffer/output circuit (5) for outputting selected video signal.

Description

Video signal switching circuit

1 is a block diagram of a video signal switching circuit of the present invention.

2 is a detailed circuit diagram of a video signal switching circuit of the present invention.

FIG. 3 is a signal waveform diagram of each part of the video signal switching circuit shown in FIG.

* Explanation of symbols for the main parts of the drawings

1: bias circuit part 2: first input circuit part

3: second input circuit section 4: control circuit section

5: Buffer / Output Q ₁ ~ Q ₂₃ : Transistor

D ₁ : Diode

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a video signal switching circuit in a VCR system. In particular, the present invention relates to a video signal switching circuit for switching an input video signal such that a TV broadcast signal through a tuner and a line signal through a video jack can be arbitrarily selected for recording a video screen. It relates to a signal switching circuit.

In general, the conventional VCR system does not have a function of switching between video signals and video signals of video cameras or other video systems according to TV broadcasting. That is, when the TV broadcast receiving antenna is connected, only the TV broadcast image can be recorded, other images cannot be recorded, and the video jack is connected to the antenna terminal. When this connection is established, only video from a video camera or other video system through this video jack can be recorded, and other TV video cannot be recorded. Therefore, if a user wants to record a video other than a TV broadcast when the TV broadcast signal is input to the VCR system, the user must remove the TV broadcast receiving antenna, connect the video jack to the antenna terminal, and record there. There was a hassle of inputting a line signal, and having to connect and record a TV broadcast receiving antenna while the line signal is being input to the VCR system. Moreover, the selection of the recorded video signal is very difficult for beginners who handle the VCR for the first time, and causes the breakdown of the VCR product due to careless handling.

The present invention has been made to solve the above-mentioned drawbacks of the conventional VCR system, and an object thereof is to provide a video signal switching circuit capable of simply selecting and recording a video signal with a simple switch operation. With reference to the accompanying drawings, the configuration, operation, and effects of the present invention will be described in detail.

The video signal switching circuit of the present invention for achieving the above object is composed of a resistor (R ₁ ~ R ₇ ) and transistors (Q ₁ ~ Q ₅ ) to set the reference potential of each circuit portion bias circuit section 1, and (R ₈ ~ R ₁₃₎ and the transistor (Q ₆ ~ Q ₁ 0) is composed of outputting a video signal (a) input from the tuner into the buffer / output unit 5 under the control of the control circuit (4) a first input circuit (2), the resistance (Q ₁₆ ~ R ₁₉₎ is composed of the first and second input circuit (2, 3) control circuit 4 and, for controlling the operation of the resistor (R ₂₀ ~ R ₂₃₎ and consists of a diode (D ₁₎ and a transistor (Q ₂₀ ~ Q _26), the buffer / output portion (5) constituting the input video signal to be stably output to.

FIG. 2 is a detailed circuit diagram of the video signal switching circuit of the present invention, and FIG. 3 is a signal waveform diagram of each part of the video signal switching circuit shown in FIG. 2, and the video signal of TV broadcasting shown in FIG. The first input circuit unit 2 is applied as a video signal A to the first input circuit unit 2 through a tuner, and the other video signal unit is connected to the first input circuit unit 2 as the line signal B shown in FIG. (3) is applied. At this time, if the user wants to record the image of the TV broadcast, the user operates the TV broadcast selection switch installed on the front panel of the VCR set. Then, the signal C shown in Fig. 3 (3-3) becomes the base of the transistor Q ₁₇ in the control circuit section 4 in response to the user's switch operation. Accordingly, since the transistor Q ₁₇ is turned off and the transistor Q ₁₆ is turned on, the video signal A of the TV broadcast shown in FIG. 3-1 applied to the first input circuit unit 2 is It is output through the transistor Q ₉ of the first input circuit section 2 and applied to the buffer / output section 5. Therefore, from the buffer / output unit 5, the output signal E shown in FIG. 3-3, which is the video signal A of the TV broadcast, is output and recorded.

On the other hand, when the user wants to record the line signal (B) shown in FIG. 3 (3-2) input through the video jack instead of the TV broadcast, operate the line signal selection switch provided on the front panel of the VCR set. Done. Then, the signal D shown in Fig. 3-3 (3-3) turns on the transistor Q ₁₇ in the control circuit section 4, and the transistor Q ₁₆ turns off, so that the signal D shown in FIG. Line signal B through the video jack shown in FIG. 3-2 is output through transistor Q ₁₂ of second input circuit section 3 to buffer / output section 5 Is approved. Therefore, the line signal B shown in FIG. 3 (3-2) is output from the buffer / output section 5 as the output signal E shown in FIG. 3 (3-4) and recorded. Here, the transistor Q ₁₈ of the control circuit part 4 is the second input circuit part when the transistor Q ₁₇ is saturated when the high level voltage of the signal D input to the control circuit part 4 is higher than the supply voltage Vcc. In order to prevent distortion of the line signal B inputted to (3), the signal D which can be used by the use of this transistor Q ₁₈ is up to about Vcc + 0.3V, and the bias circuit section 1 The reference potential of the circuit portion is set, and the buffer / output 5 functions to stably output the input video signal.

The present invention, which operates as described above, can select and record a video signal to be recorded by simple switch operation, which is not only very convenient in use, but also minimizes the failure rate due to careless handling, and improves VCR products. There is an effect that can be high quality.

Claims (1)

A bias circuit section 1 composed of resistors R ₁ to R ₇ and transistors Q ₁ to Q ₅ to set the reference potential of each circuit section, resistors R ₈ to R ₁₃ , and transistors Q ₆ to Q ₁₀ ) is composed of a first input circuit section (2) for inputting / outputting a video signal (A) input through the tuner, resistors (R ₁₄ ~ R ₁₉ ) and transistors (Q ₁₁ ~ Q ₁₅ ) The second input circuit part 3 and the transistors Q ₁₆ to Q _{19 for} inputting / outputting the line signal B inputted through the control part control the operation of the first and second input circuit parts 2 and 3. And a buffer / output section 5 composed of a control circuit section 4 and resistors R ₂₀ to R ₂₃ , diodes D ₁ and transistors Q ₂₀ to Q ₂₆ to stably output an input signal. Video signal switching circuit.

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