KR940003409Y1 - Color sub-carrier automatic transfer circuit - Google Patents

Abstract

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Description

Color carrier automatic switching circuit

Circuit diagram of FIG.

* Explanation of symbols for main parts of the drawings

1: image 2: burst detector

3: oscillator 4: frequency-to-voltage converter

CP1: Comparator Q1-Q3: Transistor

X1, X2: Crystal R1-R7: Resistance

The present invention relates to a color carrier automatic switching circuit which detects a color burst signal and automatically switches a color carrier suitable for a broadcast method in a television receiving different broadcast methods. This is to allow automatic selection.

Especially in Europe, where various broadcasting systems are scattered, if you have a multi-system TV that can watch two or more broadcasting methods, and want to watch different broadcasting methods, you want to watch the color carrier selection switch exposed to the outside of the set. Viewing was possible only by selecting manually according to the broadcasting method.

In other words, whenever viewing a different broadcast system, the user can view the broadcast only by switching the color carrier selection switch exposed to the outside.

In view of the above, the present invention detects the frequency of the color burst signal and uses the same to automatically switch the color carrier so that the broadcast method can be automatically selected without the operation of the external color carrier selection switch.

This will be described in detail with reference to the accompanying drawings.

In a multi-system television in which a color carrier output is selected in accordance with the selective driving of crystals X1 and X2 in an image processing unit 1 to which a broadcasting signal is applied, the broadcasting signal is applied to the image processing unit 1 while The burst signal detected by the burst detector 2 is configured to be applied to the burst detector 2, and the burst signal detected by the burst detector 2 is applied to the oscillator 3 so that the oscillator 3 oscillates in synchronization with the burst signal. .

The oscillation frequency of the oscillator 3 is applied to the frequency-voltage converter 4 to be converted into a constant voltage, and the output voltage of the frequency-voltage converter 4 is configured to be applied to the inverting terminal (-) of the comparator CP1. The reference voltage Vr is applied to the non-inverting terminal + of the comparator CP1.

The output of the comparator CP1 is connected to control the driving of the transistors Q1-Q3, and the driving of the crystals X1 and X2 is selected according to the driving of the transistors Q1-Q3.

That is, the driving of the transistors Q1 to Q3 is controlled in accordance with the output of the comparator CP1, and the driving of the crystals X1 and X2 is selected in accordance with the driving of the transistors Q1 to Q3.

The operation effect of the present invention configured as described above will be described by taking an example of the operation when viewing by selecting the NTSC method and the PAL method.

First, the composite image signal is applied to the image processor 1 and to the burst detector 2, and the burst detector 2 detects the burst signal contained in the composite image signal and applies it to the oscillator 3. do.

At this time, the oscillator 3 oscillates in synchronization with the burst signal detected and applied by the burst detector 2, and the oscillation frequency is oscillated at the oscillation frequency of the burst signal to be oscillated at the oscillation frequency in the frequency-voltage converter 4. Will change accordingly.

Accordingly, 3.58MHZ is oscillated in the oscillator 3 in the case of an NTSC broadcast signal, and 4,43MHZ is oscillated in the PAL method and applied to the frequency-voltage converter 4.

The frequency-to-voltage converter 4 outputs a voltage corresponding to the generated frequency applied by the generator 3, and the output voltage of the frequency-to-voltage converter 4 is the inverting terminal (-) of the comparator CP1. ) Is compared with the reference voltage (Vr) applied to the non-inverting terminal (+).

At this time, assuming that the frequency-voltage converter 4 outputs a voltage V1 when 3.58 MHZ is applied and outputs a voltage V2 when 4.43 MHZ is applied, the voltage magnitudes of the two voltages V1 and V2 become V1 <V2.

In other words, the higher the frequency, the higher the voltage output.

As such, the voltages V1 and V2 output from the frequency-voltage converter 4 are compared with the reference voltage Vr in the comparator CP1. In this case, the reference voltage Vr is measured by measuring the voltage V1 and V2 rather than the voltage V1. Set it higher and lower than the V2 voltage.

That is, the relationship between the reference overtime Vr of the comparator CP1 and the voltages V1 and V2 output from the frequency-voltage converter 4 is set to V1 <Vr <V2.

Accordingly, the comparator CP1 compares the reference overtime Vr and the output voltages V1 and V2 of the frequency-voltage converter 4. When the voltage V1 is applied, the output of the comparator CP1 becomes a high level voltage and V2. When voltage is applied, it is a low level output.

That is, when the NTSC type 3.58MHZ is applied, the voltage V1 is applied to the inverting terminal (-) of the comparator CP1. When the PAL type 4.43MHZ is applied, the voltage V2 is applied to the inverting terminal (-) of the comparator CP1. As a result, the output of the comparator CP1 becomes high level when the NTSC broadcast method is used, and the output of the comparator CP1 becomes low level when the PAL broadcast method is used.

At this time, when the output of the comparator CP1 becomes a high level state, the transistor Q1 connected to the resistor R2 is "turned on" to operate the crystal X1, while the transistor Q3 is "turned on" and the transistor Q2 ) Is " turned off " so that crystal X2 is inoperative.

When the output of the comparator CP1 is at a low level, the transistor Q1 is "turned off" so that the crystal X1 is not operated, but the transistor Q3 is "turned off" and the transistor Q2 is "turned on". Crystal (X2) is to operate.

That is, when the output of the comparator CP1 is at a high level, the crystal X1 is operated. When the output of the comparator CP1 is at a low level, the crystal X2 is operated.

In other words, the output of the comparator CP1 is high level in the case of NTSC broadcasting, and the output of the comparator CP1 is low level in the case of PAL broadcasting. As a result, the crystal X1 operates in the case of NTSC broadcasting. In the PAL broadcast method, the crystal X2 is operated.

Therefore, the image processor 1 to which the broadcast signal is applied divides the resonant frequency of the crystal (X1) (X2), which is selectively operated according to the broadcasting method, in half and uses a color carrier suitable for each broadcasting method. You can switch to.

As described above, the present invention can automatically select a broadcast method based on a burst signal, thereby eliminating the conventional color carrier selection switch exposed to the outside, thereby making the appearance beautiful, and also not selecting the broadcast method manually. It can be selected automatically, which has a convenient effect.

Claims (1)

In a multi-system television in which the color processor carrier output is selected by the image processing unit 1 to which a broadcast signal is applied according to the drive selection of the crystals X1 and X2, a burst detector 2 for detecting a burst signal in the broadcast signal and An oscillator 3 oscillating in synchronization with the burst signal of the burst detector 2, a frequency-to-voltage converter 4 for converting the oscillation frequency of the oscillator 3 into a voltage, and the frequency-to-voltage converter ( Comparator CP1 for comparing the output voltage of 4) with reference voltage Vr, and transistors Q1-Q3 for which driving is selected by the output of the comparator CP1 and controlling the operation of crystals X1 and X2. Color carrier carrier switching circuit, characterized in that consisting of).