JPH04250777A - Horizontal synchronizing separator circuit and television receiver - Google Patents

Abstract

PURPOSE:To apply a horizontal synchronizing signal capable of implementing phase control of a horizontal AFC at all times to the television receiver by extracting substantially only the horizontal synchronizing signal even for an equalizing pulse period and a vertical synchronizing signal period from a composite synchronizing signal. CONSTITUTION:A synchronizing separator circuit 3 of a horizontal synchronizing separator circuit 1 separates a composite synchronizing signal (a) from an input video signal from an input terminal 2 and outputs a composite synchronizing signal (b). The signal (b) is delayed via an automatic frequency control circuit 4 by a delay circuit 5 so that the horizontal synchronization position is set within a pulse width of a signal (c). The output signal (c) of the circuit 4 is fed to a clear terminal CLR, a delayed composite synchronizing signal c' from the circuit 5 is fed to a clock terminal CLK and an output (d) from the circuit 6 is only the horizontal synchronizing signal for a period even when an equalization pulse and a vertical synchronizing signal are in existence.

Description

[Detailed description of the invention]

0010

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a television receiver, and more particularly to a horizontal synchronization separation circuit thereof.

[0020]

2. Description of the Related Art In a television receiver, as shown in FIG.
The signal is separated and used for controlling the horizontal AFC circuit 31. The horizontal AFC circuit 31 connects the flyback pulse from the flyback transformer in the horizontal output circuit 34 to the synchronization separation circuit 3.
A phase comparator 32 compares the phase with the horizontal synchronizing signal from 0, and the horizontal oscillation circuit 33 is controlled by the output. The conventional synchronization separation circuit 30 obtains a horizontal synchronization signal by amplitude-separating the input composite video signal, but its output also includes an equalization pulse during the vertical blanking period and a vertical synchronization signal. Therefore, for example, during the vertical synchronization signal period, the phase control of the horizontal AFC circuit 31 is turned off and the horizontal AFC circuit 31 is turned off.
An attempt was made to reduce disturbances in the circuit 31.

[0030]

[Problems to be Solved by the Invention] However, this method does not eliminate the influence of the equalization pulse, causing disturbances in the horizontal AFC circuit. Additionally, relatively wide noise pulses also caused disturbances in the horizontal AFC circuit. On the other hand, since phase control is not performed during the vertical synchronization signal period, when phase control is resumed immediately after this period, the horizontal
There was a problem in that the FC circuit was disturbed and the image was distorted at the top of the screen.

The present invention has been made in view of the above points, and provides a horizontal synchronization separation circuit that supplies a horizontal synchronization signal capable of constantly controlling the phase of horizontal AFC, and a television reception using the same. The purpose is to provide opportunities.

[0050]

[Means for Solving the Problems] In order to achieve the above object, the horizontal synchronization signal separation circuit of the present invention includes a composite synchronization separation means for separating a composite synchronization signal from a composite video signal, and an oscillator that oscillates at a horizontal frequency. and an automatic frequency control circuit that controls the frequency of the oscillator using the composite synchronization signal from the composite synchronization separation means; and extraction means for sequentially extracting the first synchronization signal of the composite synchronization signal.

Further, the horizontal synchronization separation circuit of the present invention has a composite synchronization separation means for separating a composite synchronization signal from a composite video signal, and an oscillator that oscillates at a horizontal frequency, and also includes a composite synchronization signal from the composite synchronization separation means. an automatic frequency control circuit for controlling the frequency of the oscillator using the oscillator, a delay means for delaying the composite synchronization signal output from the composite synchronization separation means for a predetermined time, and outputs of the automatic frequency control circuit and the delay means are inputted. The apparatus may further include gate means for extracting the first signal of the composite synchronization signal from the delay means within each period of the horizontal pulse output from the automatic frequency control circuit. In this case, it is preferable to add a pulse shaping circuit that makes the pulse width of the horizontal synchronizing signal outputted from the extraction means constant.

Further, the television receiver of the present invention includes a composite sync separation means for separating a composite sync signal from a composite video signal, and an oscillator that oscillates at a horizontal frequency, and also includes a composite sync signal from the composite sync separation means. an automatic frequency control circuit that controls the frequency of the oscillator using
Each one of the horizontal signals output from the automatic frequency control circuit
A horizontal AFC circuit that performs horizontal AFC by inputting the horizontal synchronizing signal extracted by the extracting means; and a horizontal AFC circuit that performs horizontal AFC by inputting the horizontal synchronizing signal extracted by the extracting means. composition.

[0080]

[Operation] According to the above-mentioned horizontal synchronization separation circuit of the present invention, the horizontal oscillation signal of the automatic frequency control circuit to which the composite synchronization signal is input is originally affected by the equalization pulse and vertical synchronization signal in the composite synchronization signal. Although it is output with a phase slightly shifted from that of the horizontal signal, each period of the horizontal signal output from the automatic frequency control circuit acts on the horizontal synchronization signal extraction of the composite synchronization signal.

Then, in the portion of the composite synchronization signal where only the horizontal synchronization signal exists, only one signal exists during the one cycle period, so that horizontal synchronization signal is extracted. Next, although there are a plurality of pulses in one period in which one period corresponds to the portion where the equalization pulse exists, only the first one is extracted and the others are not extracted. Similarly, for one cycle period corresponding to the part where the vertical synchronization signal exists, there are multiple pulses in the composite synchronization signal due to cutting pulses, but the first pulse (pulse corresponding to horizontal synchronization)
only are extracted. In this way, the horizontal synchronization signal is substantially obtained during the equalization pulse period and the vertical synchronization signal period as well.

[0100]

Embodiments Hereinafter, embodiments of the present invention will be described with reference to the drawings. In FIG. 1 in which the present invention is implemented, a horizontal synchronization separation circuit 1 includes a composite synchronization separation circuit 3 that separates a composite synchronization signal from an input video signal, an automatic frequency control circuit 4, a delay circuit 5, an extraction circuit 6, It is composed of a monostable multivibrator 7. The composite sync separation circuit 3 separates the amplitude of the composite video signal (a) applied through the input terminal 2 and outputs a composite sync signal (b). This composite synchronization signal (b)
is supplied to an automatic frequency control circuit 4 and a delay circuit 5.

As shown in FIG. 2, the automatic frequency control circuit 4 includes an oscillator 11 that oscillates at a horizontal frequency, and a phase comparator that compares the phase of the output of this oscillator 11 with a composite synchronization signal and controls the oscillator 11 with the comparison output. It has 10. The output of the automatic frequency control circuit 4 (therefore, the output of the oscillator 11) is as shown in FIG. 3(c), but the equalization pulse EP and vertical synchronization signal VD portions are slightly out of phase. This signal (c) is logically received by the extraction circuit 6 at the next stage and the delayed composite synchronization signal (c') from the delay circuit 5. still,
The delay circuit 5 delays the composite synchronization signal so that the horizontal synchronization position is within the pulse width of the signal (c) even if the signal (c) is slightly shifted forward or backward during the equalization pulse or vertical synchronization signal period. . The extraction circuit 6 is composed of a logic circuit as shown in FIG.

In FIG. 4, the output signal (c) of the automatic frequency control circuit 4 is applied to the clear terminal CLR via the terminal 13, and the delayed composite synchronization signal (c') from the delay circuit 5 is applied via the terminal 14. It is applied to the clock terminal CLK. FIG. 5 is a waveform diagram for explaining this circuit, and each signal (
c), (c'), and (d) are all waveforms (c) in FIG.
This corresponds to (c') and (d). In the logic circuit of FIG. 4, when both signals (c) and (c') are at high level, the inverted output (d) of Q falls in synchronization with (c'), and (c)
It rises in synchronization with the fall of . As a result, this logic circuit performs the first (c) in each cycle T of (c).
') will be extracted. As a result, the output (d) of the extraction circuit 6 has a form in which only the horizontal synchronizing signal exists even during the period in which the equalization pulse and the vertical synchronizing signal exist.

As shown in FIG. 3, the pulse width of the output (d) of this extraction circuit is not necessarily constant, so it is processed by the monostable multivibrator 7 to be shaped into a pulse with a constant width. do.

In FIG. 1, the horizontal synchronizing signal (e) thus obtained is supplied to a normal horizontal AFC circuit 8 in a television receiver. In this case, horizontal AFC
The control operation of the circuit 8 can be performed at all times including the vertical synchronization signal period, and moreover, the control operation of the circuit 8 can be performed at all times including the vertical synchronization signal period, and moreover
Since unnecessary pulses and the like during the period are not input, malfunctions such as phase shifts do not occur.

[0150]

As explained above, according to the present invention, since only the horizontal synchronizing signal is substantially obtained during the equalization pulse period and the vertical synchronizing signal period, good control operation can be achieved when performing horizontal AFC. Ru. Therefore, a television receiver that performs horizontal AFC control using the horizontal synchronization separation circuit can form a stable image without distorting the image at the top of the screen.

[Brief explanation of the drawing]

[Fig. 1] Block circuit diagram showing a horizontal synchronization separation circuit implementing the present invention

[Figure 2] Partial configuration diagram of the horizontal synchronization separation circuit

[Figure 3] Signal waveform diagram of each part in Figure 1

[Figure 4] Circuit diagram of the main parts of Figure 1

[Figure 5] Signal waveform diagram of each part in Figure 4

[Figure 6] Block circuit diagram of conventional example

[Explanation of symbols]

1 Horizontal synchronization separation circuit 3 Separation circuit 4 Automatic frequency control circuit 5 Delay circuit 6 Extraction circuit 7 Monostable multivibrator 8 Horizontal AFC circuit

Claims (4)

[Claims] Claims: 1. Composite synchronization separation means for separating a composite synchronization signal from a composite video signal; and an oscillator that oscillates at a horizontal frequency, and controlling the frequency of the oscillator using the composite synchronization signal from the composite synchronization separation means. Horizontal synchronization separation comprising: an automatic frequency control circuit; and extraction means for sequentially extracting the first synchronization signal of the composite synchronization signal existing in each period of the horizontal signal output from the automatic frequency control circuit. circuit. 2. Composite synchronization separation means for separating a composite synchronization signal from a composite video signal, and an oscillator that oscillates at a horizontal frequency, and controlling the frequency of the oscillator using the composite synchronization signal from the composite synchronization separation means. an automatic frequency control circuit; a delay means for delaying the composite synchronization signal outputted from the composite synchronization separation means for a predetermined time; and an output of the automatic frequency control circuit and the delay means that is inputted and outputted from the automatic frequency control circuit. gate means for extracting the first signal of the composite synchronization signal from the delay means within each period of the horizontal pulse. 3. Composite synchronization separation means for separating a composite synchronization signal from a composite video signal, and an oscillator that oscillates at a horizontal frequency, and controlling the frequency of the oscillator using the composite synchronization signal from the composite synchronization separation means. an automatic frequency control circuit; a delay means for delaying the composite synchronization signal outputted from the composite synchronization separation means for a predetermined time; and an output of the automatic frequency control circuit and the delay means that is inputted and outputted from the automatic frequency control circuit. gate means for extracting the first signal of the composite synchronization signal from the delay means within each period of one horizontal pulse; and a pulse shaping circuit for making the pulse width of the horizontal synchronization signal outputted from the extraction means constant. and,
Horizontal sync separation circuit consisting of: 4. Composite synchronization separation means for separating a composite synchronization signal from a composite video signal, and an oscillator that oscillates at a horizontal frequency, and controlling the frequency of the oscillator using the composite synchronization signal from the composite synchronization separation means. an automatic frequency control circuit; an extraction means for sequentially extracting the first synchronization signal of the composite synchronization signal existing in each period of the horizontal signal output from the automatic frequency control circuit; and extraction by the extraction means. Horizontal A
A television receiver comprising a horizontal AFC circuit that performs FC.