KR200173615Y1 - Circuit for switching automatically color & black picture by using peak-detector - Google Patents

Abstract

The present invention relates to a black and white or color image automatic switching circuit using a peak director. More specifically, a peak detector is installed in the video signal synchronization unit to select a black and white or color image mode of a video device according to an external video input signal. The present invention relates to an automatic switching circuit of a black and white or color image using a peak detector that automatically switches.

Unlike the conventional method of accurately identifying an external video input signal and manually switching a switch suitable for the method, the method automatically switches and matches the synchronization signal, thereby providing convenience to a video device operator.

Description

Black and white or color image automatic switching circuit using peak detector

1 is a configuration diagram of a conventional manual switching circuit,

2 is a block diagram of a black and white or color image automatic switching circuit using a peak detector according to an embodiment of the present invention,

3 is a waveform diagram of a color sync signal that is externally separated and shaped after an external video signal has passed through a swing amplifier circuit of a band pass filter,

4 is a waveform diagram after the color sync signal separated and shaped by the black and white or color image automatic switching circuit using the peak detector according to the embodiment of the present invention passes through the peak detector.

* Explanation of symbols for main parts of the drawings

a: external video input signal i: phase comparison circuit

b: Horizontal and vertical synchronous separation circuit j: Low pass filter (LPF)

c: Reset pulse generator circuit k: Crystal oscillator control voltage

d: Channel 1 switch 1: Channel 2 switch

e: Reset pulse m: Manual switch

f: Analog switch n: Separately formatted color sync signal

g: Bandpass filter (BPF) o: Peak detector

h: 5-volt amplified swing circuit p: Capacitor discharge holding voltage curve

C1: capacitor R1: resistor

D1: diode Fsc: modulated subcarrier

The present invention relates to an automatic switching circuit of a black and white or color image using a peak detector, and more specifically, a peak of a color image synchronizing signal separated from a swing amplifying circuit output stage of a synchronizing circuit part for an external image signal input. The present invention relates to an automatic switching circuit of a black and white or color image using a peak detector that automatically opens and closes a switch by applying a voltage to an analog switch by maintaining a capacitor voltage of a detector more than a predetermined level.

In general, an external synchronous video device converts an optical signal coming into a camera into an electric signal in a 20-mega frequency band, is transmitted to a receiver such as a monitor, and then modulated into an optical signal. However, in the process of modulating the light into an electric video signal, a synchronization signal having information about the start and end of the signal must also be transmitted so that the receiver can reproduce a clear image in accordance with the synchronization signal.

Therefore, the video signal synchronization circuit unit must detect the video signal input from the outside through a coaxial cable or other transmission medium to accurately match the black and white signal or the color signal.

Looking at the prior art in Figure 1, this diagram is a circuit configuration belonging to a part of the synchronous circuit portion, when the image signal containing the black and white synchronization as an external input, the video device operator determines that the black and white signal is a manual switching switch To open and adjust the operation mode of the video device to the monochrome video signal.

Here, the black-and-white signal is inputted only in the direction of the vertical horizontal synchronous separation circuit (b) which separates the synchronization of the entire screen and the respective scanning lines, that is, the vertical horizontal synchronous, on the image screen, which is inputted to the reset pulse generation circuit (C) A reset pulse (e) is sent out via channel 1 to the output.

On the contrary, when the video signal a including the color sync as a binary input comes in, the manual switching switch m is closed and input to both the vertical horizontal synchronous separation circuit b and the band pass filter g. Of course, the signal input to the vertical horizontal synchronous separation circuit (b) emits the above reset pulse (e).

On the other hand, the color synchronization signal extracts only the frequency component of the 3.58 MHz band from the band pass filter g and amplifies the signal level in the 5 volt switching amplifier circuit h.

This amplified signal is compared with the subcarrier plate (Fsc) of the same 3.58 MHz frequency band in phase inversion (i), and this phase difference becomes the voltage of the DC component after passing the low pass filter (j). Via the channel 2 switch 1, it is output as a crystal balance control voltage k. This control voltage is applied to the oscillator to correct and synchronize by the phase difference.

In particular, the phase comparator (i), the low pass filter (j), and the crystal oscillator are referred to as phase tracking matching circuits (PLL).

In summary, when the monochrome image signal (a) is input to an external input, the manual switching switch (m) is opened to output a reset pulse to the output, and when a color image signal is input, the reset pulse and the crystal oscillator control are performed. Simultaneously emits voltage.

Therefore, in the related art, a user who handles an imaging device having a display synchronization circuit unit, such as a solid-state imaging device (CCD) camera, selects a black and white or color image signal generated from an external circuit and manually selects a black and white image signal to fit the operation mode of the imaging device. Switch (m) must be switched.

The synchronization circuit unit is used for display synchronization circuit units such as an external synchronous solid-state imaging device (CCD) camera, a video camera, and a television.

In almost all cases, an external video input signal including a synchronization signal is generated in the front end circuit of FIG. 1, and the external input video signal may generate both a black and white signal or a color signal, but a signal user may select one of them arbitrarily. .

As can be seen from FIG. 1, in the prior art, in order to select an external video signal in black and white or color, a user who handles this kind of video device each time has to inconvenience the manual switching switch to exactly match the black and white or color signal. You must take. This is because the color image signal has a slightly higher modulation frequency than the black and white image signal.

If the manual changeover switch is accidentally operated and a black-and-white signal is input and the color side is selected, the vertical horizontal synchronization may not be correct, resulting in blurred or blurred images.

On the contrary, when the color synchronization signal is being input and the manual changeover switch is set to black and white, the color and saturation of the image appear distorted.

In the above, problems that occur when using the manual switching switch are the inconvenience of the switch operation, the vibration caused by the vertical and horizontal mismatch of the black and white signal, the color and saturation distortion of the color signal, and other bad phenomena.

In view of the above problems, the present invention aims to provide an automatic switching circuit for monochrome or color images using a peak detector that solves the disadvantages of the prior art by installing a peak detector in the prior art as shown in FIG.

As a means for achieving the above object, the constitution of the present invention is a horizontal vertical synchronizing separation circuit for separating horizontal and vertical synchronizing signals, a reset pulse generating circuit for generating reset pulses, and an analog switch capable of opening and closing two or more channels. A bandpass filter capable of passing 3.58 megahertz frequency components, a 5 volt swing amplifier circuit for amplifying fine, low signal color video signals, and comparing the phases of the amplified color sync signals with subcarriers. A phase comparator, a low pass filter for extracting the DC control voltage, and a peak detector for automatically opening / closing channel 2 of the analog switch according to whether the capacitor maintains a discharge voltage according to a black and white or color image signal. .

The main configuration circuit for realizing the automatic switching operation includes a bandpass filter, a 5-volt swing amplification circuit, a peak detector, and an analog switch capable of opening and closing two or more channels for separating and amplifying an external video input signal. It consists of.

Hereinafter, with reference to the accompanying drawings will be described in detail the most preferred embodiment of this invention.

First, remove the manual changeover switch in FIG. 1, and install a peak detector o between the output terminal of the 5-volt swing amplification circuit h and the channel 2 (1) of the analog switch f. The design is constructed.

If the external video input signal (a) in FIG. 2 includes a color sync signal, it passes through a bandpass filter and a 5 volt swing amplification circuit (h), and at the output stage is separated and shaped as shown in FIG. 3 at 3.58 megahertz. The color synchronizing signal n can be extracted. This color sync signal consists of a high frequency of 3.58 megahertz, consisting of between 9 and 11 wavelengths of the fundamental wave.

Here, when this separate-formed color synchronizing signal n of one cycle is input to the peak detector o, since the waveform voltage is between 0 volts and 5 volts in FIG. 3, the diode D1 is forward current. Will shed.

Therefore, the capacitor C1 constituting the peak detector fills up to 5 volts, and then discharges to 0 volts again through the ground resistor R1 when the next pulse is not present. However, as the capacitor having a large capacity and the large value resistor are disposed in the peak detector, the discharge delay time of the capacitor becomes considerably longer.

Referring to the operation of the peak detector (o) in more detail, the dotted line curve of FIG. 4 of the discharge curve (p) of the condenser is shown when the discretely formatted color sync signal pulses (n) are continuously input for several periods. Create In particular, as the time constants of the resistor R1 and the capacitor C1 are increased, the discharge curve of the capacitor C1 will be kept close to 5 volts.

Therefore, when the 5-volt capacitor discharge holding voltage P is applied to the channel 2 (1) of the analog switch f which is opened and closed at 0 volts and 5 volts, the switch of the channel 2 will be automatically closed.

On the other hand, when the external video input signal a that does not contain the color sync signal (i.e., the black and white sync signal) is input, since the color sync signal is not separately detected, the capacitor C1 is not charged or discharged and remains at 0 volts. The channel 2 switch 1 will then open automatically.

In conclusion, the entire arc part of FIG. 2 outputs a reset pulse (e) to the output by closing only the channel 1 switch (1) while leaving the channel 2 switch (1) open while the monochrome synchronization signal is input to the external input. In contrast, when the color sync signal is input to the external input, the peak detector is operated so that both the channel 1 and 2 switches are operated to output two reset pulses (e) and a crystal oscillator control voltage (k).

As described above, in the prior art, a signal suitable for a video apparatus is selected by manually switching a black and white or color video signal input from the outside, but this design is automatic even if any signal is input from the black and white or color signal. This switch brings about the effect of operating the video equipment related to the signal.

Claims (3)

Horizontal and vertical synchronous separation circuit (b), reset pulse generating circuit (c), analog switch (f) capable of opening and closing two or more channels, and bandpass filter (g) capable of passing frequency components in the 3.58 MHz band (g). ), A 5 volt swing amplification circuit (h) for amplifying a fine, low signal color image signal, a phase comparison circuit (i), a low pass filter (j) for extracting a DC control voltage, And a peak detector (o) for automatically opening / closing channel 2 of the analog switch (f) according to a black and white or color video signal. 2. The peak detector according to claim 1, wherein the peak detector includes a diode D1 for direct current flowing only in the capacitor direction and preventing reverse flow, a value for increasing the time constant, a ground resistance R1, and an analog switch channel 2 ( Black and white or color image automatic switching circuit using a peak detector, characterized in that the capacitor having a large capacity for applying a voltage to 1). 2. The peak detector according to claim 1, wherein in order to automatically open and close channel 2 of the analog switch 1, a separate color sync signal n is used at an output terminal of the 5-volt swing amplification circuit h. Black and white or color image automatic switching circuit.