KR19980050200A - Color bleed elimination circuit at power-on of television receiver - Google Patents

Abstract

The present invention relates to a color bleeding elimination circuit at power-on of a television receiver that can eliminate color bleeding of an output image appearing on a cathode-ray tube (CRT) when the power of the television receiver is turned on.

In the present invention, a television receiver having a chroma IC for processing a composite video signal and outputting a corresponding luminance signal and a color difference signal, and a CRT driver for driving a CRT based on the luminance and color difference signals applied from the chroma IC. And a luminance signal blocking means for blocking a luminance signal applied from the chroma IC to the CRT driver for a predetermined time when the power-on signal is output.

That is, in the present invention, the luminance signal is not applied from the chroma IC to the CRT driver for a predetermined time while the viewer turns on the television receiver, thereby preventing the video signal from being generated in the CRT during the initial operation of the television receiver. The blooming phenomenon and the color bleeding phenomenon are removed beforehand.

Description

Color bleed elimination circuit at power-on of television receiver

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a television receiver, and more particularly, to a color bleed removal circuit when power is turned on of a television receiver, which is capable of eliminating color bleeding of an output image appearing on a cathode-ray tube (CRT) at power on.

1 is a configuration diagram showing the main components of a general television receiver.

In Fig. 1, reference numeral 1 denotes a chroma IC which outputs a luminance signal (-Y) and a color difference signal (RY, BY, GY) corresponding to the composite video signal detected from the broadcast signal. The CRT driver outputs R (Red), G (Green), and B (Blue) signals for CRT driving based on latitude and color difference signals applied from the chroma IC 1. In addition, reference numeral 3 denotes a buffer for buffering the luminance signal (-Y) applied from the chroma IC 1 to the CRT driver 2, which is based on the luminance signal (-Y) applied from the chroma IC 1. Is coupled to the collector, and the emitter is coupled to the power supply voltage through a pull-up resistor (R1), while the connection node of the emitter and resistor (R1) is coupled to the luminance input terminal of the CRT driver (2). ) Is configured to include.

In the drawing, reference numeral 4 denotes a CRT that receives a RGB signal applied from the CRT driving unit 2 to generate a predetermined video screen, and the high voltage from the flyback transformer 7 which will be described later on its anode end. It is intended to be authorized.

In the drawing, reference numeral 5 denotes a power plug, and 6 denotes a main power supply such as a switching mode power supply (SMPS) that generates operating power required by each circuit part based on an input power applied from the power plug 5. The power supply unit 7 is a flyback transformer (FBT) for generating various high voltages required for the CRT by receiving an operating voltage of, for example, 123 V (Volt) applied from the main power supply unit 6.

In addition, reference numeral 8 is a relay for controlling the operating power applied to the flyback transformer 7 from the main power supply 6, 9 is a relay driver for driving the relay 8 in accordance with a predetermined control signal, 10 is a remote control device for the user to operate the television receiver, 11 is a receiving unit for converting an infrared signal applied from the remote control device 10 into an electrical code signal corresponding thereto, 12 is applied from the remote control device 10 In addition to controlling the entire apparatus according to the operation signal, in particular, the relay driver 9 is controlled to control the television receiver on / off.

That is, in the above configuration, when the viewer operates the remote controller device 10 to turn on the television receiver, the microprocessor 12 outputs, for example, a high level drive signal to the relay driver 9 to drive the relay driver 9. This turns on the relay 8.

Therefore, the operating power is applied from the main power supply unit 6 to the flyback transformer 7 so that a high voltage is applied from the flyback transformer 7 to the CRT 4 so that the CRT 4 is driven.

That is, the electron beam according to the RGB signal applied from the CRT driving section 2 is scanned onto the fluorescent film of the CRT by the high voltage applied to the anode terminal of the CRT 4 so that a predetermined image is formed on the CRT 4.

When the viewer turns off the television when using the remote controller 10 again, the microprocessor 12 controls the relay driver 9 to turn off the relay 8 to be applied to the flyback transformer 7. The operating power is cut off, and thus the driving of the CRT 4 is stopped, so that the television receiver is turned off.

By the way, in the above-described television receiver, the viewer turns on the television receiver and at the same time the high voltage output from the flyback transformer 7 is applied to the anode of the CRT 4 so that the beam is high from the anode side of the CRT 4 to the tank gun. An electric current flows, in which an image detection circuit (not shown) or a chroma IC (1) and a deflection circuit (not shown) that detect a composite video signal are momentarily disabled so that the output image appears on the CRT (4). This blurring blooming or color bleeding occurs.

Accordingly, the present invention has been made in view of the above circumstances, and an object thereof is to provide a color bleeding elimination circuit during power-on of a television set which can eliminate blooming or color bleeding caused when the television set is turned on. .

1 is a block diagram showing a main portion of a general television receiver.

Figure 2 is a block diagram showing a color blur removal circuit of a television receiver according to an embodiment of the present invention.

* Brief description of the main parts of the drawing

1: chroma IC, 2: CRT driver,

3: buffer, 4: CRT,

5: power plug, 6: main power supply,

7: flyback transformer, 8: relay,

9: relay driving unit, 10: remote control device,

11: receiver, 12: microprocessor,

13: luminance signal blocking unit.

In order to achieve the above object, a color bleeding elimination circuit at power-on of a television receiver according to the present invention comprises a chroma IC for processing a composite video signal and outputting a corresponding luminance signal and a chrominance signal, and a luminance applied from the chroma IC. A television receiver having a CRT driver for driving a CRT based on a color difference signal, comprising: a luminance signal blocking means for blocking a luminance signal applied from the chroma IC to the CRT driver for a predetermined time when a power-on signal is output; It is characterized by.

According to the present invention having the above-described configuration, the application of the luminance signal from the chroma IC to the CRT driving unit for a predetermined time when the viewer turns on the television receiver is blocked.

Therefore, since the video signal is not generated in the CRT during the initial operation of the television receiver, blooming or color bleeding occurring on the CRT can be eliminated in advance.

Hereinafter, an embodiment according to the present invention will be described with reference to the drawings.

FIG. 2 is a block diagram illustrating a color bleeding elimination circuit at power-on of a television receiver according to an embodiment of the present invention. In FIG. 2, the same reference numerals are given to the same parts as those of FIG.

In FIG. 2, reference numeral 21 denotes a luminance blocking unit that blocks the luminance signal -Y applied from the chroma IC 1 to the CRT driving unit 2 for a predetermined time when the television receiver is powered on.

The luminance blocking unit 21 is coupled to the base and the control signal applied from the microprocessor 12 to the relay driver 9, the emitter is grounded, the collector is connected to the power supply voltage (Vcc) through the bias resistor (R2) NPN transistor Q2 connected to the resistor, a resistor R3 connected in series between the connection node of the transistor Q2, the collector of the transistor Q2, and the ground, a reverse current prevention diode D1, and a charge / discharge capacitor (C1), a PNP transistor Q3 having a base coupled to the connection node of the collector of the transistor Q2 and the resistor R2, and an emitter coupled to the connection node of the diode D1 and the capacitor C1. ), The base is coupled to the collector of the transistor Q3 through the resistor R4, and the collector is coupled to the power supply voltage Vcc through the smoothing capacitor C3 and the reverse current prevention diode D2, and the emitter Transistors constituting the buffer 3 It is configured to include the NPN-type transistor (Q4) coupled to the base of (Q1).

Next, the operation of the circuit having the above configuration will be described.

First, in a state where the television receiver is turned off, the control signal output from the microprocessor 12 to the relay driver 9 is at a low level, so that the transistor Q2 is turned off and through the resistor R3 and the diode D1. The capacitor C1 is charged.

At this time, the transistor Q3 is turned off as the transistor Q2 is turned off, and the transistor Q4 is turned off accordingly, so that the transistor Q1 constituting the buffer 3 is kept in a normal on state. .

On the other hand, when the viewer turns on the television receiver and outputs a high level power-on signal from the microprocessor 12, the transistor Q1 is turned on by the high level signal and the base of the transistor Q2 is turned on. The potential of the stage is lowered to the ground level, whereby the emitter-base voltage of the transistor Q3 is set to a predetermined value or more by the voltage charged by the capacitor C1 so that the transistor Q3 is turned on. do.

Subsequently, when the transistor Q3 is turned on, the charge charged in the capacitor C1 is applied to the base side of the transistor Q4 through the current path between the emitter and the collector of the transistor Q3. As the transistor Q4 is turned on, the power supply voltage Vcc is applied to the base of the transistor Q1 constituting the buffer 3 so that the transistor Q1 is turned off.

When all the charges charged in the capacitor C1 are discharged by the above operation and the transistor Q3 is turned off, the transistor Q4 is turned off accordingly, so that the transistor Q1 constituting the buffer 3 is It will be set to on again.

That is, in the above embodiment, the application of the luminance signal -Y from the chroma IC 1 to the CRT driving unit 2 is blocked for a predetermined time when the viewer turns on the television receiver.

Therefore, the generation of the video signal to the CRT 4 during the initial operation of the television receiver is cut off, so that the blooming or color bleeding occurring on the CRT 4 can be eliminated in advance.

In addition, the present invention is not limited to the above embodiments, and various modifications can be made without departing from the technical scope of the present invention.

As described above, according to the present invention, it is possible to realize a color bleed removal circuit at the time of power-on of the television receiver, which can eliminate the blooming phenomenon and the color bleeding phenomenon generated when the television receiver is turned on.

Claims (2)

A television receiver comprising a chroma IC for processing a composite video signal and outputting a corresponding luminance signal and a chrominance signal, and a CRT driver for driving the CRT based on the luminance and chrominance signal applied from the chroma IC. And a luminance signal blocking means for blocking a luminance signal applied from the chroma IC to the CRT driving unit for a predetermined time when a signal is outputted. The television set according to claim 1, wherein a buffer means is provided between the luminance signal output terminal of the chroma IC and the luminance signal input terminal of the CRT driving section, and the luminance signal blocking means sets the buffer means in an inoperative state. Color bleed elimination circuit at power-on of the receiver.