JPH01174072A - Synchronizing signal separator - Google Patents

Abstract

PURPOSE:To avoid malfunction even if a synchronizing signal portion of a luminance signal is shrinked by comparing a 2nd luminance signal outputted from a low pass filter cutting off the high frequency component of a 1st luminance signal with a 3rd potential at a comparator and outputting a signal being the result of separating the synchronizing signal of the luminance signal. CONSTITUTION:The luminance signal inputted from an input terminal 1 is fed to an inverse amplifier 3. A peak detection circuit 4 detects the potential or the tip of a synchronizing signal being a peak potential or the signal to be inputted. A detection circuit 5 detects the potential of the pedestal portion of the inputted signal. A low pass filter 6 eliminates the high frequency component such as noise from the input signal and gives the result to a comparator 8. The comparator 8 compares the output signal of the low pass filter 6 with the potential at the tip of the synchronizing signal of the luminance signal and the potential of the pedestal portion and outputs a signal being the result or separating the synchronizing signal of the luminance signal to the output terminal 9. Thus, even if the synchronizing signal portion of the input luminance signal is shrinked, a correct synchronizing signal separation output is obtained and the time delay of the output synchronizing signal is decreased.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a synchronization signal separation device for separating a synchronization signal of a video signal in a magnetic recording and reproducing device for recording and reproducing video signals.

2. Description of the Related Art Hereinafter, a conventional synchronization signal separation device will be described with reference to the drawings.

FIG. 2 shows a block diagram of a conventional synchronization signal separation device. In Fig. 2, 1 is a luminance signal input terminal;
3 is a clamp circuit, 3 is an inverting amplifier, 4 is a peak detection circuit 6 is a low-pass filter, 8 is a comparator, and 9 is a synchronization signal output terminal.

FIG. 3 shows waveforms at various parts.

First, a luminance signal is input from the input terminal 1 and supplied to the clamp circuit 2. The clamp circuit 2 outputs to the inverting amplifier 3 a signal as shown in FIG. The inverting amplifier 3 outputs a signal as shown in FIG. 3 to the low-pass filter 6. The low-pass filter 6 removes high-frequency components such as noise and supplies a signal to the peak detection circuit 4 and the comparator 8. The peak detection circuit 4 detects the potential at the leading end of the synchronization signal, which is the peak value of the input signal, and supplies it to the level shift circuit 10. The level shift circuit 10 shifts the potential at the tip of the input manually input synchronization signal by a constant voltage V1 and supplies it to the comparator 8.

As shown in FIG. 3C, the comparator 8 receives and compares the output signal of the low-pass filter 6 and the potential obtained by shifting the potential at the tip of the synchronizing signal outputted from the level shift circuit 10 by Vl. A signal obtained by separating the synchronization signal of the luminance signal as shown in the third diagram is output to the synchronization signal output terminal 9.

Problems to be Solved by the Invention However, in the above configuration, the third output signal of the synchronizing signal separation device is delayed by a time T1 due to the shadow τ of the low-pass filter for noise removal. Also, in order to reduce the delay time T1 at this time, the level shift amount V of the level shift circuit 10 is adjusted.

When V is set such that V<V2, for example, when a signal in which the synchronization signal portion of the luminance signal is compressed is input from the input terminal 1, the input signal of the comparator 8 is as shown in FIG. 3e, The potential of the output signal of the level shift circuit 10 becomes lower than the level of the output signal of the low-pass filter 6, and the signal output from the comparator 8 becomes
This has the problem that a signal with a wider width than the actual synchronization signal is output.

Means for Solving the Problems In order to solve the above problems, the synchronization signal separation device of the present invention includes a clamp circuit that clamps the potential at the tip of the synchronization signal of the luminance signal to a constant potential, and a a first detection circuit that detects the potential at the tip of the synchronization signal of the first luminance signal; a second detection circuit that detects the potential at the pedestal portion of the first luminance signal; and an output from the first detection circuit. the first potential output from the second detection circuit and the second potential output from the second detection circuit.
a potential generating circuit that inputs the potential of the t-th luminance signal and generates a third potential; a low-pass filter that cuts off the high frequency component of the t-th luminance signal; and a second potential that is output from the low-pass filter.
The third potential includes a comparator that compares the luminance signal of the second potential with the third potential.

Effect of the Invention With the above-described configuration, the present invention prevents the synchronization signal separating device from malfunctioning so that the width of the output synchronization signal becomes wider even when the synchronization signal portion of the luminance signal is shortened, and also prevents the output synchronization signal from widening. The delay time is also small, and the operation is stable even at that time.

Embodiment Hereinafter, an embodiment of the synchronization signal separation device of the present invention will be described with reference to the drawings.

FIG. 1 shows a block diagram of a synchronization signal separation device according to an embodiment of the present invention. In FIG. 1, parts with the same reference numerals as those in FIG. 2 are the same or corresponding parts. 5
7 is a detection circuit that detects the potential of the pedestal portion of the luminance signal, and 7 is a potential generator that generates a new potential from two different DC potentials. The operation of the synchronization signal separation device configured as described above will be explained below.

The luminance signal input from input terminal 1 is sent to clamp circuit 2.
As shown in FIG. 3a, the synchronizing signal is supplied to the inverting amplifier 3 whose leading end is clamped to a certain clamp potential. The inverting amplifier 3 inverts and amplifies the input signal, and
The signal shown in the figure is detected by the peak detection circuit 4 and the detection circuit 5.
, and supplied to the low-pass filter 6. The peak detection circuit 4 detects the tip of the synchronizing signal 1) 6, which is the peak potential of the human input signal.
Detects the potential of The detection circuit 5 detects the potential of the pedestal portion of the input signal. The borrow pass filter 6 removes high frequency components such as noise from the input signal and outputs it to the comparator 8. The potential generator 7 generates a potential that internally divides the potential of the synchronizing signal tip portion of the input luminance signal and the potential of the pedestal portion by a certain ratio x: 1-x, (x, < 1). and outputs it to the comparator 8. As shown in FIG. 3q, the comparator 8 converts the output signal of the low-pass filter 6, the potential at the tip of the synchronization signal of the luminance signal, and the potential at the pedestal section into x:
(1-x,), x, is compared with the potential internally divided at a ratio of <1, and a signal obtained by separating the synchronization signal of the luminance signal as shown in the third diagram is outputted to the output terminal 9. At this time, in order to reduce the delay time T2 of the third output synchronizing signal of the present synchronizing signal device, the internal ratio X of the potential generator 7 is set to
For example, even when the synchronization signal part of the luminance signal input to input terminal 1 is shrunk,
The signal input to the comparator 8 is as shown in Figure 3i,
A correct synchronizing signal is obtained from the comparator 8 as shown in FIG. 3j, and no setting operation occurs. Further, the time delay T3 is also T3 minus T2.

Effects of the Invention As described above, the synchronization signal separation device of the present invention can correctly obtain a synchronization signal separated output even when the synchronization signal portion of the input luminance signal is shrunk, and can reduce the time delay of the output synchronization signal. An excellent effect can be obtained in that the size can also be made smaller.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an embodiment of the sync signal separation device of the present invention, FIG. 2 is a block diagram of a conventional sync signal separation device, and FIG. 3 is a waveform diagram of each part. 1...Input terminal, 2...Clamp circuit, 3...Inverting amplifier, 4...Peak detection circuit, 5...Detection circuit , 6...Low pass filter, 7...Potential generator, 8...
... Comparator, 9... Output terminal. Name of agent: Patent attorney Toshio Nakao and one other person Figure 1 Figure 2 Figure 3

Claims (1)

[Claims] a clamp circuit that clamps to a constant potential the potential of the synchronization signal tip of the luminance signal component of the video signal; and a first detection circuit that detects the potential of the synchronization signal tip of the first luminance signal output from the clamp circuit. and a second detection circuit that detects the potential of the pedestal portion of the first luminance signal, and a first potential output from the first detection circuit and a second potential output from the second detection circuit. a potential generation circuit that inputs and generates a third potential; a low-pass filter that cuts off high frequency components of the first luminance signal; and a second luminance signal and a third potential that are output from the low-pass filter. A synchronous signal separation device comprising: a comparator for comparing the signals.