KR0158325B1 - Image signal mute circuit in tv power on-off - Google Patents

Abstract

The present invention provides a television receiver capable of preventing output of a noise screen through a CRT screen and preventing damage to the CRT by muting a video output of a CRT (Cathode-ray Tube) when the power is turned on or off. An image muting circuit for power on / off of an image, comprising: image processing means for processing a composite video signal to output a color difference signal and a luminance signal, and a CRT driving unit for receiving a color difference signal and a luminance signal and driving a CRT based thereon; 1. A television receiver equipped with means, comprising: switching means for cutting off a luminance signal applied to said CRT driving means, control means for outputting a signal of a first level when the television is turned on and a second level when the television is turned off; First switching driving means for driving the switching means for a predetermined time at the time of outputting the level signal, and for the predetermined time at the time of outputting the second level signal; And a second switching driving means for driving the switching means.

Description

Video mute circuit at the time of power supply ON / OFF of television receiver

1 is a block diagram of a general television receiver.

2 is a block diagram showing an image muting circuit at the time of power on / off of a television receiver according to one embodiment of the present invention.

* Explanation of symbols for main parts of the drawings

1: antenna 2: tuner

3: IF amplification part 4: P / S separation part

5: voice detector 6: image detector

7: Remote controller 8: Receiver

11; Voice processor 12: voice amplifier

13 image processing unit 14 CRT driving unit

15: Buffer 16: Power plug

17: main power supply unit 18: flyback transformer (FBT)

19: relay driver 31: microprocessor

41: Video Mute Circuit RY: Relay

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a television receiver, and in particular, by muting the video output of a cat hode-ray tube (CRT) when the power is turned on or off, it is possible to prevent output of a noise screen through the CRT screen and to prevent damage to the CRT. The present invention relates to an image muting circuit at the time of power on / off of a television receiver.

FIG. 1 is a block diagram schematically illustrating a general configuration of a television (hereinafter, referred to as a TV) which is widely used as a broadcast receiver.

In the drawing, reference numeral 1 denotes an antenna, 2 denotes a tuner for amplifying a radio frequency (RF) signal received by the antenna 1 and generating an intermediate frequency signal IF for a tuned broadcast signal, and 3 denotes the tuner 2 Is an IF amplifying part for amplifying the IF signal outputted from the?, And 4 is a surface acoustic wave for separating the video intermediate frequency signal PIF and the voice intermediate frequency signal SIF from the IF signal output from the IF amplifier 3, for example. P / S separation unit such as a filter, 5 is an audio detector for detecting an audio signal from the SIF signal, and 6 is an image detector for detecting a video signal from the PIF signal and outputting a composite video signal.

Further, reference numeral 7 denotes a remote control device for performing a channel selection or the like for the viewer to turn on / off the power of the television, and 8 denotes an electric signal for converting an infrared signal from the remote control device 7 into a code signal. The receiver 31 is a microprocessor for controlling the entire apparatus.

Further, reference numeral 11 is not shown for the voice signal output from the voice detector 5, but the base, treble, volume, etc. according to the control signal from the microprocessor 31 12 is a voice amplifier which amplifies the voice signal processed by the voice processor 11 and outputs it to the speaker.

Although reference number 13 is not shown for the image signal output from the image detector 6, the color, tint, and brightness are in accordance with a control signal from the microprocessor 31. ), And outputs a color difference signal (RY, BY, GY) and a luminance signal (-Y) of R (Red), G (Green), and B (Blue) signals corresponding to the video signal. 14 is a CRT driver for driving the CRT based on the color difference signals (RY, BY, GY) and the luminance signal (-Y) output from the image processor 14.

In addition, the image processor 13 may include, for example, a video chroma IC, and the luminance signal (-Y) output from the image processor 13 is applied to the CRT driver 14 through the buffer 15. Will be.

Although not shown in the drawing, a deflection circuit is provided to deflect the electron beam emitted from the cathode side of the CRT in the horizontal and vertical directions based on the synchronization signal detected in the composite video signal.

Meanwhile, in FIG. 1, reference numeral 16 denotes a power plug, 17 denotes a main power supply composed of SMPS (Switching Mode Power Supply), and 18 denotes a CRT based on a voltage of, for example, 123 V applied from the main power supply 17. B) a flyback transformer (FBT) for generating a high voltage required in various circuit parts, RY is a relay for intermittent input power applied to the main power supply 17, 19 is a microprocessor 31 Is a relay driver for driving the relay RY on / off under the control of the "

That is, in the above configuration, when the viewer operates the remote control device 7 to turn on the TV, the microprocessor 31 controls the relay driver 19 to turn on the relay RY to input the main power supply 17. When the power is supplied and the viewer operates the remote control unit 7 to input operation signals such as channel selection, volume, and color, the viewer controls the tuner 2, the audio processing unit 11, and the image processing unit 13 accordingly. As a result, the viewer can control TV operation in a desired state. When the viewer operates the remote control device 7 after watching a TV, the microprocessor 31 controls the relay driver 19 to turn off the relay RY to turn off the relay RY. The TV will be turned off by cutting off the input power supply.

By the way, in the above-described TV, the following problem occurs when the TV is turned on / off by the viewer.

That is, when the viewer turns on the TV using the remote controller 7, the microprocessor 31 controls the relay driver 19 to turn on the relay RY to supply the operating power to the entire apparatus and to tune the tuner ( 2) By controlling the audio processing unit 11 and the image processing unit 13, the video and audio signals corresponding to a predetermined broadcast channel are output through the CRT and the speaker. In the initial operation of the TV, the CRT is not sufficiently preheated. In this case, the amount of electron beams output from the cathode of the CRT becomes insufficient, resulting in a blooming phenomenon in which the output image of the CRT becomes cloudy.

In addition, when the viewer turns off the TV by using the remote controller 7, the microprocessor 31 controls the relay drive unit 19 to turn off the relay RY, whereby the operation of the FBT 18 stops. The horizontal and resin deflection circuits are momentarily stopped. At this time, on the CRT side, a residual image signal supplied through the image processing unit 13 and the CRT driving unit 14 or a charge remaining on the cathode side of the CRT is applied to the heater. The emitted electrons are emitted onto the fluorescent surface of the CRT. Therefore, in this case, the electrons emitted from the heater go straight as they are without deflection to generate white spots, that is, spots, in the center portion of the CRT, thereby causing a problem that the CRT is damaged.

Accordingly, the present invention has been made in view of the above circumstances, and the blooming caused by not being supplied with sufficient electron beams when the TV is turned on by muting the video signal output on the CRT when the TV is turned on / off. It provides a video mute circuit when the TV is powered on / off to prevent the phenomenon that occurs due to the phenomenon and the sudden power cut when the TV is turned off. The purpose is.

According to the present invention for realizing the above object, the video mute circuit when the television receiver is turned on / off is configured to process a composite video signal and output a color difference signal and a luminance signal, and receive the color difference signal and the luminance signal. A television having CRT driving means for driving a CRT on the basis of: a switching means for cutting off a luminance signal applied to the CRT driving means, and a first level signal when the television is turned on and a second level signal when the television is turned off; A first switching driving means for driving the switching means for a predetermined time when the first level signal is output, and a second switching driving the switching means for a predetermined time when the second level signal is output. It comprises a drive means.

According to the present invention having the above-described configuration, the output of the video signal on the CRT for a predetermined time when the TV is on / off is prevented. Therefore, it is possible to prevent the blooming phenomenon occurring at power on and the spot phenomenon occurring at power off.

Hereinafter, another embodiment of the present invention will be described with reference to the drawings.

FIG. 2 is a block diagram showing an image muting circuit at the time of power on / off of a TV according to an embodiment of the present invention. The same reference numerals are assigned to the same parts as those in FIG. 1, and detailed description thereof will be omitted.

In FIG. 2, a transistor as a switching means for setting the buffer 15 for buffering and outputting the luminance signal (-Y) output from the image processor 13 to the CRT driver 14 in a driving or non-driven state. Q2) is equipped.

That is, the transistor Q2 is connected to the base of the PNP transistor Q1 constituting the buffer 15 and the collector is coupled to the power supply voltage through the reverse current prevention diode D1. When Q2) is turned on, the power supply voltage Vcc is applied to the base of the transistor Q1 through a current path between the diode D1 and the collector-emitter of the transistor Q2. Therefore, in this case, since the transistor Q1 is turned off, the luminance signal (-Y) output from the image processor 13 is blocked from being applied to the CRT driver 14, so that the CRT is in a black screen state, that is, image mute. Will be in a state.

In FIG. 2, reference numeral 20 denotes a microprocessor for outputting a high level signal when the TV is turned on and a low level signal when the TV is turned off, and 30 is composed of resistors R2 and R3 and an NPN transistor Q3. The buffer circuit 40 which inverts the output signal of the output signal 20, outputs a transistor as the switching means for a predetermined time when a low level signal, that is, a high level signal from the microprocessor 20, is output from the buffer circuit 30 ( The first switching driver 50 for driving Q2) is configured to turn on the transistor Q2 for a predetermined time when a high level signal from the buffer circuit 30, that is, a low level signal from the microprocessor 20 is output. 2 switching drive.

In addition, the first switching driver 40 has a first time constant circuit 45 coupled to the output of the buffer 30, the base is coupled to the time constant circuit 45, and the collector is for preventing reverse current. The transistor Q4 is coupled to the base of the above-described transistor Q2 through the diode D2 and the current limiting resistor R5.

In addition, the second switching driver 50 is coupled to the output of the buffer 30, and is composed of a resistor (R7, R8) and a transistor (Q5) and inverting the output of the buffer 30, and The base is coupled to the second time constant circuit 55 and the time constant circuit 55 coupled to the inverter, and the collector is connected to the transistor described above through the reverse current prevention diode D3 and the current limiting resistor R11 ( And a transistor Q6 coupled to the base of Q2).

That is, the first switching driving unit 400 and the second switching driving unit 50 are different from each other in that the second switching driving unit 50 has an inverter circuit at an input terminal, and is substantially the same configuration. The second switching driver 50 switches and drives the transistor Q2 in a signal input state opposite to that of the first switching driver 40.

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

In FIG. 2, the resistor R3 is set to have a lower resistance value than the resistor R4, and likewise, the value of the resistor R8 is set to be lower than the resistor R9. Accordingly, when the transistors Q3 and Q5 are turned on, the capacitors C2 and C3 are charged to voltages applied through the resistors R4 and R9, respectively, and then the transistors Q3 and Q5 are turned off. The capacitors C2 and C3 are respectively charged with the voltage applied through the resistors R3 and R8.

First, when the TV is in the off state, the output of the microprocessor 20 is in the low level state, so the transistor Q3 of the buffer circuit 30 is in the off state while the transistor Q5 is kept in the on state. Will be. Therefore, in this case, the capacitor C2 of the first time constant circuit 45 is charged with the collector side of the transistor Q3 at a high level by a predetermined voltage, and the capacitor C3 of the second time constant circuit 55 is charged. ) Is charged with the base side of the transistor Q6 high. In addition, the transistors Q4 and Q6 of the first and second switching drivers 40 and 50 are kept on by the voltage applied through the resistors R4 and R9, respectively, so that the first and second switching devices are turned on. The low level switching signal is output from the driving units Q40 and 50. Therefore, at this time, the transistor Q2 is kept in the off state.

In the above state, when the viewer inputs the on signal of the TV using the remote controller 7, the output of the microprocessor 20 rises from the low level to the high level, thereby turning on the transistor Q3. In addition, transistor Q5 is turned off.

Therefore, in the first switching driver 40, when the voltage charged in the capacitor C2 through the resistor R3 is CV, the transistor Q3 is turned on and the transistor is instantaneously at the ground level. As the base side of Q4 becomes -CV and the transistor Q4 is turned off, the charging voltage of the capacitor C2 is discharged to the ground side through the transistor Q30.

That is, in this state, the transistor Q4 is turned off, and the power supply voltage Vcc is applied to the base side of the transistor Q2 through the resistor R5, the diode D2, and the resistor R6, so that the transistor Q2 is turned on. As a result, the transistor Q1 of the buffer circuit 15 is turned off, so that the luminance signal -Y applied from the image processor 13 to the CRT driver 14 is blocked.

Subsequently, as described above, as the discharge current flows from the power supply voltage Vcc through the resistor R4, the capacitor C2, and the transistor Q3, the capacitor C2 is gradually charged. In this way, when the capacitor C2 is charged and the charging voltage becomes higher than the threshold of the transistor Q4, that is, 0.7V or more, the transistor Q4 is turned on. In addition, when the transistor Q4 is turned on as described above, the transistor Q2 is turned off and the transistor Q1 of the buffer circuit 15 is turned on so that the luminance signal (-Y) output from the image processor 13 is The CRT driving unit 14 is applied.

On the other hand, in the second switching driver 50, when the transistor Q3 of the buffer circuit 30 is turned on and the transistor Q5 is turned off, the capacitor C3 is rapidly caused by the power supply voltage applied through the resistor R8. When the capacitor C3 is recharged and the capacity of the capacitor C3 is equal to the capacitor C2 of the first switching driver 40, the collector side of the transistor Q5 is charged as high as CV, and the transistor Q6 is still turned on. Will remain in the state.

On the other hand, when the viewer inputs the TV off signal by using the remote controller 7 while the TV is on, the output of the microprocessor 20 is lowered from the high level to the low level, so that the first switching driver 40 And the second switching driver 50 are operated opposite to the above-described operation when the TV is turned on.

That is, when the output of the microprocessor 20 drops to the low level, the transistor Q3 is turned off and the transistor Q5 is turned on. Accordingly, while the capacitor C3 of the second switching driver 50 is discharged through the transistor Q5 and set by the resistor R9 and the capacitor R3, the transistor Q6 is turned off for a predetermined time while the transistor Q2 is turned off. The luminance signal (-Y) which is turned on and applied to the CRT driver 14 from the image processor 13 is blocked, and the transistor Q3 is turned off in the first switching driver 40 through the resistor R3. The capacitor C2 is recharged by the applied power supply voltage Vcc and the transistor Q4 is kept in the on state.

That is, in the above configuration, when the viewer turns on the TV by using the remote controller 7, when the output of the microprocessor 20 rises from the low level to the high level, the transistor Q2 is turned on by the first switching driver 40. Is turned on for a predetermined time, and when the viewer turns off the TV by using the remote controller 7, the output of the microprocessor 20 decreases from the high level to the low level. Q2) is turned on for a predetermined time. Therefore, when the TV is turned on or off, the luminance signal applied from the image processor 13 to the CRT driver 14 is cut off, and the CRT is in a black screen state for a predetermined time, thereby causing a blooming phenomenon or spot generated when the TV is turned on or off. It becomes possible to prevent the phenomenon.

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.

That is, for example, in the above embodiment, the case in which the output screen of the CRT is set to the black screen state at the time of TV on / off is explained, but this is changed to the black screen state at the time of TV on or off. In this case, only one first switching driving unit 40 and second switching driving unit 50 may be provided as necessary.

As described above, according to the present invention, the CRT is brought to a black screen state when the television power is turned on / off by controlling the luminance signal output from the image processor. Therefore, the output of the noise screen generated when the television receiver is turned on or off can be prevented, thereby making it possible to solve the anxiety of the viewer. In addition, the blurring phenomenon of blurring the image is eliminated due to the lack of the electron beam emitted on the CRT when the power is turned on, and the operation of the horizontal and vertical deflection circuits (not shown) that deflects the electron beam when the power is turned off is stopped. As the electrons emitted from the laser beam go straight, the spot phenomenon that only the central portion of the CRT fluorescent surface shines brightly can be suppressed reliably, thereby preventing damage to the CRT.

Claims (1)

A television receiver having image processing means for processing a composite video signal and outputting a color difference signal and a luminance signal, and a CRT driving means for receiving the color difference signal and the luminance signal and driving the CRT based thereon. Switching means for controlling an applied luminance signal, control means for outputting a signal of a first level when the television is on, and a second level when the television is turned off, and the switching means for a predetermined time when the first level signal is output. A first switching driving means for driving the switch on, and a second switching driving means for driving the switching means on for a predetermined time when the second level signal is output. City mute circuit.