KR960004258Y1 - Auto tuner converting apparatus of pip tv - Google Patents

Abstract

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Description

Automatic Synchro Switch for Picture-in-Picture Television Receiver

1 is a block diagram of a conventional PIP television receiver.

2 is a circuit diagram of a PIP television receiver to which an automatic synchronous switching device according to an embodiment of the present invention is applied.

* Explanation of symbols for main parts of the drawings

30: video signal switching unit 32: main screen processing unit

34: luminance detector 36: color difference signal demodulator

38, 50: first and second synchronous signal separator 40: A / D conversion unit

42: screen compression unit 44: mixer

46: CRT drive unit 48: CRT

52: synchronization signal switching unit 54: microcomputer

The present invention relates to a picture-in-picture television receiver having a function of displaying a sub-picture of another video inside the main screen, and in particular, a sub-picture video signal is supplied. If not, the present invention relates to an automatic synchronization switching device of a PIP television receiver capable of stabilizing an auxiliary image by switching a vertical synchronization signal for a main screen as a vertical synchronization signal for an auxiliary screen.

In order to display an auxiliary screen having a certain size of image inside the main screen, a conventional PIP television receiver has to compress the video signal for the auxiliary screen to a certain size. A screen compression circuit is provided. The screen compression circuit stores the sub-screen video signal in a frame memory and reads it at a speed several times faster than the storage speed to compress the sub-screen video signal to a predetermined size. The screen compression circuit synchronizes the storage operation of the frame memory to a vertical synchronization signal for the sub picture separated from the sub picture video signal in order to prevent loss of the image information during screen compression. The conventional PIP television receiver is used for the sub picture. It has a synchronization signal separator which separates the vertical synchronization signal from the video signal and supplies it to the screen compression circuit. Due to this circuit configuration, the conventional PIP television receiver cannot update the video signal stored in the frame memory when the video signal for the sub picture is not supplied, and repeatedly displays the video signal finally stored in the frame memory. It caused a screen anxiety condition in which an image was displayed. As described above, the conventional PIP television receiver displays a still image when the video signal for the sub picture is not supplied so that the user cannot know the broadcast state and the input of the video signal and further mistaken for a malfunction of the TV receiver. I had a problem. The problem of the conventional PIP television receiver will be described in detail with reference to FIG.

Referring to FIG. 1, a conventional PIP television receiver is inputted via a broadcast composite video signal and second through fourth input terminals 13, 15, and 17 that are introduced through the first input terminal 11. One of the two composite video signals selected by selecting two composite video signals from the reproduction composite video signals from the video reproducing apparatus is the luminance detector 14, the color difference signal demodulator 16, The video signal switching unit 10 is supplied to the synchronization signal separator 20 while the other is supplied to the main screen processing unit 12 as a composite video signal for the main screen. The main screen processor 12 demodulates a color difference signal and a luminance signal including a red-luminance (hereinafter referred to as "RY") signal and a blue-luminance (hereinafter referred to as "BY") signal from the main image composite video signal. The demodulated chrominance signal and the luminance signal are supplied to the mixer 24. The luminance detector 14 detects a luminance signal distributed in a low frequency band (that is, a frequency band of 0 to 3 MHz) by removing a color signal component in the vicinity of 3.58 MHz of the sub picture composite video signal. The signal is supplied to an analog-digital (hereinafter, referred to as "A / D") conversion section 18. The color difference signal demodulator 16 demodulates the composite video signal for the sub-screen and generates a color difference signal including an R-Y signal and a B-Y signal, and supplies the generated color difference signal to the A / D converter 18. Then, the A / D converter 18 converts the luminance signal from the luminance detector 14 and the color difference signal from the color difference signal into digital luminance and digital color difference signals to convert the converted digital luminance and color difference signals. It is supplied to the screen compression part 42. On the other hand, the synchronization signal separator 20 separates the vertical synchronization signal from the composite video signal for the sub-screen and supplies the separated vertical synchronization signal to the screen compressor 22 through the resistance dividers R1 and R2. . The resistor voltage dividers R1 and R2 divide the vertical synchronization signal from the synchronization signal separator 20 so as to have a voltage level required by the screen compressor 22. The screen compression unit 22 compresses the screen luminance of the digital luminance and the color difference signal from the A / D converter 18 to have a constant size, and converts the compressed digital luminance and color difference signals into the form of analog luminance and color difference signals. A frame memory (not shown) and a digital-analog (hereinafter, referred to as "D / A") converter (not shown) are provided to convert the circuit into. In addition, the screen compression unit 22 receives the digital luminance and color difference signals from the A / D conversion unit 18 during the injection of the vertical synchronization signal from the synchronization signal separator 20 to compress the screen size. The digital luminance and color difference signals stored in the frame memory are read out in a much shorter period than the interval between the syringes of the vertical synchronization signal. In addition, the D / A converter included in the screen compressor 22 converts the digital luminance and color difference signals read from the frame memory into analog luminance and color difference signals, and converts the converted analog luminance and color difference signals into the mixer ( 24). Then, the mixer 24 mixes the main screen luminance and chrominance signal from the main screen processing unit 12 and the screen compressed sub-screen luminance and chrominance signal from the screen compression unit 22, thereby partially mixing the internal parts. PIP luminance and color difference signals having different images in the screen area are generated, and the generated PIP luminance and color difference signals are supplied to a cathode ray tube (hereinafter referred to as "CRT") driver 26. The CRT driving unit 26 combines the luminance and the color difference signal from the mixer 24 to red (hereinafter referred to as "R"), blue (hereinafter referred to as "B") and green (hereinafter referred to as "R"). Generates a signal, and amplifies the R, G, and B signals to supply the amplified R, G, and B signals to the CRT 28. Driven by the R, G, and B signals from the CRT driving section 26, a PIP image having an image of another program is displayed in a part of the screen area.

As described above, the conventional PIP television receiver is configured to control the storage operation of the frame memory in the screen compression circuit for compressing the screen size of the video signal for the sub picture by a vertical synchronization signal separated from the video signal for the sub picture. When the composite video signal for the sub picture is not supplied, the image anxiety cannot be updated and the image data finally stored in the frame memory is repeatedly displayed in the sub picture area (ie, the still picture display phenomenon). ). As a result, the conventional PIP television receiver has a problem that makes it impossible for a user to know whether or not to supply a composite video signal for an auxiliary screen and a broadcast state of a video program, and further doubts the reliability of the PIP television receiver.

Accordingly, an object of the present invention is to provide an automatic synchronization switching device of a PIP television receiver which can prevent anxiety of an auxiliary picture screen of a PIP television receiver and enhance reliability.

In order to achieve the above object, the automatic synchronization switching device of the PIP television receiver of the present invention includes a first synchronization signal separating means for separating the vertical synchronization signal from the composite video signal for sub-screen, and vertical synchronization from the composite video signal for main screen. Second synchronous signal separation means for separating the signal, switching means for selecting and sending out a vertical synchronous signal from the first and second synchronous signal separation means and outputting it through an output terminal, and vertical from the first synchronous signal separation means And detecting the presence or absence of a supply of the composite video signal for the sub-screen according to whether the synchronization signal is input and controlling the switching means according to the detected result.

Other objects and advantages of the present invention in addition to the above objects will become apparent from the detailed description of the following embodiments with reference to the accompanying drawings.

Hereinafter, with reference to the accompanying Figure 2 an embodiment of the present invention will be described in detail.

Referring to FIG. 2, the broadcast composite video signal flowing through the first input terminal 31 and the external video reproducing apparatus input through the second to fourth input terminals 33, 35, and 37 are input. One of the two composite video signals selected by selecting two composite video signals among the reproduced composite video signals is a composite video signal for an auxiliary picture, and includes a luminance detector 34, a color difference signal demodulator 36, and a first synchronous signal separator ( 38) PIP to which the automatic synchronous switching device according to the embodiment of the present invention, which has a video signal switching unit 30 for supplying to the main screen processing unit 32 as a main image composite video signal, is provided. A television receiver is described. The main picture processor 32 demodulates the color difference signal and the luminance signal including the R-Y signal and the B-Y signal from the main picture composite video signal and supplies the demodulated color difference signal and the luminance signal to the mixer 44. The luminance detector 34 detects a luminance signal distributed in a low frequency band (that is, a frequency band of 0 to 3 MHz) by removing a color signal component in the vicinity of 3.58 MHz of the sub-picture composite video signal. The signal is supplied to the A / D converter 40. The color difference signal demodulator 36 demodulates the composite image signal for the sub-screen to generate a color difference signal including an R-Y signal and a B-Y signal, and supplies the generated color difference signal to the A / D converter 40. Then, the A / D converter 40 converts the luminance signal from the luminance detector 34 and the color difference signal from the color difference signal demodulator 36 into digital luminance and digital color difference signals. And a color difference signal to the screen compression unit 42. On the other hand, the brake signal separator 38 separates the vertical synchronization signal from the composite video signal for the sub-screen and supplies the separated vertical synchronization signal to the screen compressor 22 via the resistance dividers R1 and R2. . The resistor voltage dividers R1 and R2 divide the vertical synchronization signal from the brake signal separator 38 so as to have a voltage level required by the screen compressor 42. The screen compression unit 42 compresses the screen luminance of the digital luminance and the color difference signal from the A / D converter 40 to have a constant size, and converts the compressed digital luminance and color difference signals into the form of analog luminance and color difference signals. A frame memory (not shown) and a D / A converter (not shown) are provided for converting to. In addition, the screen compression unit 42 receives the digital luminance and color difference signals from the A / D conversion unit 40 during the injection of the vertical synchronization signal from the brake signal separator 38 to compress the screen size. The digital luminance and color difference signals stored in the frame memory are read out in a much shorter period than the interval between the syringes of the vertical synchronization signal. The D / A converter included in the screen compression unit 42 converts the digital luminance and color difference signals read from the frame memory into analog luminance and color difference signals, and converts the converted analog luminance and color difference signals into the mixer ( 44). Then, the mixer 44 mixes the main screen luminance and color difference signals from the main screen processing unit 32 and the screen compressed sub-screen luminance and color difference signals from the screen compression unit 42 to form a part of the interior. PIP luminance and chrominance signals having different images in the screen area are generated and the generated PIP luminance and chrominance signals are supplied to the CRT driver 48. The CRT driver 48 generates R, B, and G signals by combining luminance and color difference signals from the mixer 44, and amplifies the R, G, and B signals to amplify the R, G, and B signals. It is supplied to 48. The CRT 48 is driven by the R, G, and B signals from the CRT driving section 46 to display a PIP image having an image of another program in a portion of the screen area therein.

The PIP television receiver to which the automatic synchronous switching device is applied is provided with a second synchronous signal separator (50) for inputting a composite video signal for main screen transmitted from the image signal switching unit (30) to the main screen processing unit (32). A microcomputer 54 for introducing a vertical synchronizing signal transmitted from the one synchronizing signal separator 38 to the resistance voltage dividers R1 and R2 is further provided. The second synchronizing signal separator 54 separates the vertical synchronizing signal from the main picture composite video signal from the image signal switching unit 30 and supplies the separated vertical synchronizing signal to the synchronizing signal switching unit 52. The microcomputer 54 monitors the logic state of the output signal from the output terminal 39 of the first synchronous signal separator 38 to determine the vertical synchronous signal separated by the first synchronous signal separator 38. It is generated by detecting the presence or absence of the composite video signal supplied to the first synchronous signal separator 38 and generating a switching control signal having a logic state of high or low according to the detected result. The switching control signal is applied to the synchronization signal switching unit 52. The composite synchronous signal is supplied to the first synchronous signal separator 38 of the switching control signal generated by the microcomputer 54 and the first synchronous signal separator 38 outputs a vertical synchronous signal to its output terminal 39. In the case of transmitting through a), the low synchronous state, on the contrary, when the composite synchronous signal is not supplied to the first synchronous signal separator 38 and the first synchronous signal separator 38 does not generate a vertical synchronous signal, It has a high logic state. The synchronous signal switching unit 52 is connected between the first and second synchronous signal separators 38 and 50 and the resistance voltage dividers R1 and R2 to form a logic state of a switching control signal from the microcomputer 54. According to the selection, the vertical synchronous signal from the first synchronous signal separator 38 or the vertical synchronous signal from the second synchronous signal separator 50 is selected to switch the selected vertical synchronous signal to the resistance voltage dividers R1 and R2. . In other words, when the switching control signal has a high logic state, that is, the composite image signal for the sub picture is the luminance detector 34, the color difference signal demodulator 36, and the first signal. When not supplied to the first synchronous signal separator 38, the vertical synchronous signal from the second synchronous signal separator 50 is selected and the vertical synchronous signal from the selected second synchronous signal separator 38 is selected. It supplies to the screen compression part 42 via R1 and R2. On the contrary, when the switching control signal has a low logic state, that is, when the switching control signal is supplied to the luminance detector 34, the color difference signal demodulator 36, and the first synchronous signal separator 38, the synchronization signal switching unit 52 is used. ) Selects a vertical synchronous signal from the first synchronous signal separator 38 and transmits the vertical synchronous signal to the resistance voltage dividers R1 and R2. Then, the screen compressor 42 is configured to supply the second synchronization signal when the composite image signal for the auxiliary screen is not supplied to the luminance detector 34, the color difference signal demodulator 36, and the first synchronization signal separator 38. The image data stored in the frame memory in the self is updated by the image data without image information from the A / D converter 40 by the vertical synchronization signal for the main screen separated by the separator 50, and the image stored in the frame memory. By initializing the data, an auxiliary image having white snow noise is displayed on the CRT 48. Due to the auxiliary image having the snow noise, the user determines whether to supply the playback composite video signal for the sub picture and the broadcast state of the composite video signal for the sub picture.

In addition, the synchronization signal switching unit 52 may selectively transmit the vertical synchronization signals from the first and second synchronization signal separators 38 and 50 to the resistance dividers R1 and R2. The resistor R3 is connected from the diode D1 and the second synchronous signal separator 50 connected between the output terminal 39 of the separator 38 and the input terminal 41 of the resistor voltage dividers R1 and R2. And a transistor Q1 for introducing a vertical synchronization signal into its base. The transistor Q1 is vertically applied from the second synchronous signal separator 50 to the switching control signal supplied from the microcomputer 54 to its emitter via the diode D2 and the line 43. In the period of the logical state of the synchronization signal, it mutes toward the ground potential GND through its collector to generate the same pulse signal on the line 43 as the vertical synchronization signal from the second synchronization signal separator 50. The transistor Q1 is supplied from the microcomputer 54 to the line 43 when a switching control signal in a high logic state is supplied to the line 43, i.e., a composite image signal for an auxiliary screen is applied to the luminance detector 34 and the color difference signal demodulator ( 36) and when not supplied to the first synchronous signal separator 38, the same pulse signal as the vertical synchronous signal generated by the second synchronous signal separator 50 is generated in the line 43. The vertical synchronizing signal generated on the line 43 is supplied to the input terminal 41 of the resistor voltage dividers R1 and R2 via the diode D1. In addition, the capacitor C1 connected between the line 43 and the ground potential GND is turned on when the transistor Q1 is turned on / off or turned off. This function removes the impulsive noise signal generated in. The diode D1 is configured so that the output signal of the first synchronous signal separator 38 is not affected by the vertical synchronous signal supplied to the input terminals 41 of the resistor voltage dividers R1 and R2. The output signal of the microcomputer 54 has a function of buffering the output signal of the separator 38, and the diode D2 is affected by the same pulse signal as the vertical synchronization signal generated in the line 43. The output signal of the microcomputer 54 is buffered so as not to be received, and the diode D3 is connected to the line 43 by a vertical synchronization signal supplied to the input terminal 41 of the resistor voltage dividers R1 and R2. The signal generated in the line 43 is buffered so that the generated signal is not affected.

As described above, the automatic synchronization switching device of the PIP television receiver of the present invention provides a screen compression circuit by supplying a vertical synchronous signal separated from the composite video signal for the main screen to the screen compression circuit when the auxiliary video composite video signal is not supplied. By allowing the video data stored in the frame memory to be initialized in itself, it provides the advantage of displaying an auxiliary picture in the state of snow noise without image information. In addition, the automatic synchronization switching device of the PIP television receiver of the present invention allows the user to determine whether to supply the playback composite video signal for the sub picture and the broadcast composite video signal for the sub picture by the auxiliary image in the snow noise state. It also provides the advantage of improving the user's trust in the product.

Claims (1)

First synchronous signal separating means for separating the vertical synchronous signal from the composite video signal for sub-screens, second synchronous signal separating means for separating the vertical synchronous signal from the composite video signal for main screen, and the first and the second Switching means for selecting a vertical synchronous signal from the synchronous signal separating means and sending it through an output terminal; and whether to supply the composite video signal for the sub-screen according to whether the vertical synchronous signal is inputted from the first synchronous signal separating means. And an image presence detecting means for controlling the switching means according to the detected and detected result.