KR0144960B1 - A phase sync circuit of television receiver - Google Patents

Abstract

The present invention relates to a phase synchronization circuit of a television receiver for dual scanning.

The phase synchronization circuit of the television receiver determines the channel selection state of the tuner, passes the synchronization signal separation and phase detection circuits in the constant channel, and overcomes the limitations of phase synchronization by the blanking signal in the empty channel or weak electric field. A switching circuit for bypassing and a microcomputer for turning on and off the switching circuit are provided. Also, a digital signal processing unit, a deflection unit, and a color difference matrix circuit which converts the analog composite video signal into a digital signal are provided. Therefore, there is an effect that can effectively prevent the horizontal flow of the screen during the empty channel and the weak electric field.

Description

Phase Synchronization Circuit of Television Receiver

1 is a phase synchronization circuit of a conventional television receiver,

2 is a phase synchronization circuit of a television receiver according to the present invention;

* Explanation of symbols for main parts of the drawings

11: signal processor 12: synchronous separator

13: Phase detector 14,19,26: low pass filter and

Voltage controlled oscillator (LPE / VCO)

15: mono-stabilizer 16: blanking signal generator

17: summer 18: phase detector

20, 21, 22: Divider 23: Digital signal processor

27: Flyback transformer (FBT) 40: deflection part

50, 60: switching part

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a phase synchronization circuit of a television receiver, and more particularly, to a phase locked circuit used in a television receiver adopting a dual scanning function. It relates to a phase synchronization circuit of a television receiver capable of preventing horizontally flowing.

In general, when a composite video signal is input, a synchronization circuit of a television can divide the synchronization signal included in the composite video signal through a synchronization separator and then synchronize the synchronization signal through a deflection circuit. In the electric field, the synchronization cannot be separated or is not separated properly, resulting in a phenomenon that the screen flows. This is particularly common in TV systems that do double scanning.

This phenomenon is described in more detail with reference to FIG. 1, which is a conventional phase synchronization circuit.

As shown in FIG. 1, a conventional phase synchronization circuit is largely divided into a synchronization separation and signal processor 10, a digital processor 30, and a deflector 40. FIG. First, in the sync separation and signal processing section 10, the analog composite image signal input from the front end is sent to the summer 17 after signal processing is performed in the signal processing section 11, and the sync separator 12 for separating the sync signal. Is sent). The phase of the synchronization signal separated by the synchronous separator 12 is detected by the phase detector 13, and this detection operation is output from the integrator low pass filter and the voltage controlled oscillator 14 and then returned via the monostable 15. And comparing the detected signal with the above-described synchronization signal. As described above, the detected phase synchronization signal fh is detected again by the phase detector 18 in the digital processing unit 30. The low pass filter and the control voltage oscillator 19 are similar to those of the synchronous separation and signal processing unit 10 described above. The output signal of is compared with the signal fed back through the divider 20, 21 and detected. In addition, the digital processor 30 generates a clock signal or a horizontal synchronous signal fh by using the output signal of the low pass filter and the control voltage oscillator 19 described above. In addition, the digital signal processing unit 23 in the digital processing unit 30 processes the Y, RY, and BY signals output from the signal processing unit 11 described above as digital signals, and then doubles the color matrix (RGB) matrix unit ( To 24). In addition, the "2fh signal, which has passed through the divider 20, is input to the deflection unit 40, and the" 2fh "signal is a low pass filter and a voltage controlled oscillator 26 as described above in the phase detector 25 therein. ) And the signal and phase feedbacked through the flyback transformer 27 are compared and detected.

In such a situation, in the case of an empty channel or a weak electric field, the synchronization separation and the signal processing unit 10 may not be properly performed. That is, if no synchronization exists in the synchronization separator 12, the synchronization separation and signal processing unit 10 is free running, and as a result, the blanking signal is generated by the blanking signal generator 16. . However, such a blanking signal has a certain degree of accuracy up to the digital processing unit 30 as described above, and performs a synchronization function, but becomes very unstable in the phase synchronization circuit of the deflection unit 40. This instability of synchronization causes the screen to flow horizontally.

SUMMARY OF THE INVENTION The present invention has been devised to solve the above problems, and an object of the present invention is to provide a phase synchronization circuit capable of preventing the flow of a screen due to synchronization instability generated in the case of a co-channel and a weak electric field. A feature of this invention for achieving the above object is a microcomputer for detecting a tuning state of a tuner in a phase-synchronizing circuit of a dual scanning television receiver for synchronizing an analog composite video signal input from a tuner, and At least one switching means is switched by a control signal of a microcomputer, and is switched so that only signal processing is performed without being synchronously separated to prevent horizontal flow of the screen during empty channels and weak electric fields.

DESCRIPTION OF THE PREFERRED EMBODIMENTS A preferred embodiment of a phase synchronization circuit of a television receiver according to the present invention will be described in detail below with reference to the accompanying drawings.

2 is a phase synchronization circuit of a television receiver according to the present invention. The difference from the above-described conventional art 1 is that a switching circuit is added to the front end of the synchronous separator 12 and the digital signal processor 23. Therefore, description of portions overlapping with the above-described prior art columns will be avoided.

As shown in FIG. 2, the analog composite video signal input from a tuner (not shown) includes first and second signals disposed in front of the signal processor 11, the sync separator 12, and the digital signal processor 23.

Input to the second switching unit (50, 60). Referring to FIG. 3, the switching action of the composite image signal is input. The switching transistor Q2 connected to the emitter terminal, which is an output terminal of the amplifying transistor Q1, is connected to the synchronous separator through the capacitor C1. At the same time as the reference numeral 32, the base terminal is connected to operate the control pulse signal of the microcomputer 31, and a fixed bias voltage Vcc2 is applied. Therefore, the switching on / off operation is performed by the control signal of the microcomputer 31 connected to the tuner (not shown). That is, when channel selection is made from the tuner and it is found to be a positive channel, the microcomputer 31 sends a high level signal to the base terminal of the NPN transistor Q2, and the transistor Q2, which is a switching circuit, is switched on. Of course, in the case of the empty channel and vice versa, a low level signal is sent to switch off. On the other hand, the second switching unit 60 is configured in the same structure as the first switching unit 50, but for convenience shown in the symbol switching circuit is shown in detail because it operates in the same manner as the above-described first switching unit. . However, the first switching terminal or the second switching terminal is selected in accordance with the control pulse signal of the microcomputer 31. Therefore, as a whole, when the positive channel is selected and the tuning signal is input, the first switching unit is turned on as the transistor Q2 is switched on, and the second switching unit is adapted to receive a signal from the second terminal, that is, the summer 17. Is selected. On the contrary, in the case of the co-channel or weak electric field, as described above, the first switching unit 50 is switched off, and the second switching unit selects the first terminal. That is, by connecting the first terminal, the composite video signal is bypassed so as not to pass through the above-described sync separation and signal processing unit 10. As a result, when there is no synchronization in the synchronization separator 12, there is no phenomenon in which a blanking signal is generated due to the synchronization separation and the free running of the signal processing unit 10. Therefore, the screen does not flow horizontally. The signal selected appropriately by this switching circuit operation is phase-detected or signal-processed again via the phase detector 18 and the digital signal processor 23 in the synchronous separator 12 and the digital processor 30, respectively. That is, the dual Y, RY, and BY signals, which are output signals of the digital signal processor 23, are periodically sent to the color difference RGB matrix unit 24 by the clock CLK signal generated by dividing the above-described horizontal synchronization signal fh. Or a double synchronization signal 2fh is generated through the low pass filter and voltage control generator 19 and the divider 20 in the digital processing unit 30, and the deflection may be affected by the blanking signal during the empty channel and the weak electric field. Phase detection is again performed by the phase synchronization circuit PLL in the unit 40.

As described above, according to the phase-synchronization circuit of the double-scanning television receiver according to the present invention, there is an effect that can effectively prevent the flow of the screen caused by the horizontal phase synchronization instability generated during the empty channel or weak electric field.

Claims (2)

A signal processor 11 for processing the analog composite video signal input from the tuner to separate the luminance signal Y and the chrominance signal RY, BY, and blanking for generating a blanking signal from the synchronization signal separated from the composite video signal. A summation unit for adding up the signal generation unit 16 and the luminance signal Y and the color difference signals RY and BY generated by the signal processing unit 11 with the blanking signal generated by the blanking signal generation unit 16 ( And a digital processing unit 30 for digitally processing the video signals summed by the adding unit 17 and outputting them to the matrix unit, wherein the tuning of the tuner is performed. A microcomputer 31 which detects a state and outputs a switching and selection control signal: The compounding unit generates the blanking signal generation unit based on a switching control signal output from the microcomputer 31. Switching unit 50 for switching the input of the phase signal; And a selection unit 60 for selectively outputting the composite image signal and the summation unit 17 output to the digital processing unit 30 based on the selection control signal output from the microcomputer 31. A phase synchronization circuit of a television receiver. 2. The phase synchronizing circuit as set forth in claim 1, wherein said microcomputer (31) outputs a switching control signal for turning off said switching unit (50) in the empty channel and the weak electric field.