KR900008277Y1 - Audio and video input circuit for hot-power - Google Patents

Abstract

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Description

Hot Power Audio and Video Input Circuitry

The accompanying drawings are circuit diagrams of the present invention.

* Explanation of symbols for main parts of the drawings

PC ₁ , PC ₂ : Photocoupler Q _1- Q ₇ : Transistor

R ₁ -R ₂₇ : Resistor C ₁ -C ₁₃ : Capacitor

The present invention relates to a circuit capable of switching television signals, audio and video signals when adding an audio video input function in a television set employing a hot power supply (90-260V).

Most of the hot power circuits for Free Volt use Switching Mode Power Supply, and since the ground and the signal ground are in common without being separated, When there is some potential difference with the ground of other equipment and it is grounded at the same time, it gives a large output to the equipment due to the short circuit of the potential.

Therefore, unlike a television that uses a single power source, that is, a power transformer to separate the power ground and the signal ground, it is necessary to separate the ground of the video circuit, the switching circuit for switching the audio signal and the television signal, and the ground of the signal circuit. Difficulties made it impossible to add audio and video inputs to the hot chassis itself.

The present invention has been made to solve the above problems, and to provide a circuit that can add video and audio input functions in common without separating power ground and signal ground in a TV adopting a hot power system. The purpose.

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

The accompanying drawings are circuit diagrams of the present invention, wherein the audio signal input unit includes a transistor Q ₁ , a resistor R _1- R ₄ , and a capacitor C ₁ operating the port coupler PC ₁ by an input audio signal ( 10) and an audio signal amplifier 20 composed of a transistor Q ₂ for amplifying the signal transmitted by the photocoupler PC ₁ , resistors R ₅ -R ₇ , and capacitors C ₂ , C ₃ . And a video signal input unit including a transistor (Q ₃ ), a resistor (R ₈ -R ₁₂ ), a capacitor (C ₄ ), and a diode (D ₁ ) for operating the photocoupler PC ₂ by an input video signal ( 30) and a video signal amplification comprising a transistor (Q ₁ , Q ₅ ), a resistor (R ₁₄ , R ₁₉ ), and a capacitor (C ₉ -C ₁₁ ), which amplify the signal transmitted by the photocoupler (PC ₂ ). section 40, and a diode that by switching the audio and video signal (D _3, D ₄₎ and a resistor (R ₂₀ -R ₂₇₎ and a transistor (Q _6, Q ₇₎ and a capacitor (C _12, C ₁₃₎ and Amplification And a power switching section 50 composed of a signal switching section 50 driven as a switching element, a transformer TRS, a capacitor C ₅ -C ₈ , a resistor R ₁₃ , and a diode D ₂ . .

Referring to the operation of the inventive circuit having the above configuration, the audio signal is applied to the base of the transistor Q ₁ biased by the resistors R ₂ and R ₃ to turn on and off the transistor Q ₁ . The photodiode emits light from the coupler PC ₁ and transmits light. The input signal is transmitted to the base of the transistor Q _{2 as it} is, and the output amplified by the emitter appears in phase.

The video signal has an impedance junction by the resistor R ₈ , the photodiode of the photocoupler PC ₂ emits light by turning on and off the transistor Q ₃ , and the reverse current is caused by light in the depletion layer of the PN junction. By increasing the video input signal to the base of the transistor Q ₄ is delivered in reverse phase. At this time, the variable resistor (R ₁₂ ) is to control the current flowing in the light emitting diode due to the error of the photo coupler (PC ₂ ).

Transistor appears on the collector of the waveforms of the transistors (Q ₄₎ in inverted (Q _4), the waveform is input to the base of the transistor (Q ₅₎ and output a signal amplified by the emitter. At this time, the capacitor C ₉ grounded from the base of the transistor Q ₄ is for removing noise of a higher frequency than the video input signal, and also from the photocoupler PC ₂ to the emitter of the transistor Q ₄ . The connected resistor (R ₁₉ ) is set to prevent the base current from flowing due to the charge accumulated inside the transistor even though there is no light in the transistor inside the photocoupler (PC ₂ ). It is to reduce the accumulation time.

With regard to the switching of video and television signals, the TV / video switching signal applies 12V when video and maintains OV when television, so that in the television signal, the diode D ₃ is turned off so that the audio signal is diode D _3. ), The FM signal detected as the sound output of the television is input through the diode (D ₄ ) through the condenser (C ₈ ) to the sound amplifier to output the television sound, and the television signal is output transistor (Q _7). From the emitter to the video input inside the set to output television sound and video.

On the other hand, in the video signal, 12V is applied to the switching diode to turn on the diode (D ₃ ) and turn off the diode (D ₄ ) so that the television sound is cut off, and the audio signal from the emitter of the transistor (Q ₂ ) to the sound amplifier stage. Is entered.

In addition, the video input signal transmitted to the emitter stage of the transistor Q ₅ is amplified twice in the amplifier AMP and output as 2V _P - _P to the emitter of the output transistor Q ₇ , and the audio input signal is displayed on the speaker. The video input signal appears in the display, and during video switching, the voltage of 12V is distributed and applied to the base of the transistor Q ₆ by the resistors R ₂₂ and R ₂₃ so that the transistor Q ₆ is turned on and the AGC voltage of the television is turned on. The TV signal was cut off so that the TV signal was not transmitted during the video.

On the other hand, as a power source, the FBT16.5V line is insulated from the primary and secondary coils using a pulse transformer (TRS), and the pulse of the secondary coil is rectified and smoothed from the diode (D ₂ ) and the capacitor (D ₈ ) to a voltage of 12V. This is to be applied to the video and audio input circuit separated from the power ground, and the capacitor (C ₅ ) connected in parallel with the diode (D ₄ ) is to remove noise, and the resistor (R ₁₃ ) is For pulse transformer (TRS) protection due to short circuit on the secondary side.

By using this power supply, the effect on the screen caused by power supply ripple can be eliminated.

As described above, according to the present invention, a video and audio input function can be added in common without separating power ground and signal ground in a television adopting a hot power system.

Claims (1)

In the television circuit of the hot-powered, that are common to the power ground and the signal ground, delivered by an audio signal input unit 10 for operating the photo coupler (PC _1), by an audio input signal, a photo coupler (PC ₁₎ An audio signal amplification unit 20 for amplifying the audio signal, a video signal input unit 30 for operating the photocoupler PC ₂ by the video input signal, and a video signal transmitted by the photo coupler PC ₂ . A video signal amplifying unit 40 for inverting and amplifying, a signal switching unit 50 for separating and outputting a television and a video signal based on a television and a video switching signal, and for separating a power ground, an audio, and a video ground. Hot power audio and video input circuit comprising a power supply unit 60 for supplying a power of 12V from the FBT to the circuit of the present invention.