KR200224874Y1 - Spot elimination circuit of image display device - Google Patents

Abstract

The spot elimination circuit of the disclosed image display device controls a switching operation of a transistor when a power supply of an image display device such as a television receiver and a projection television using a cathode ray tube is turned off to apply a negative high voltage to a first grid that is a control grid. This is to remove spots that appear on the screen.

The spot elimination circuit of the image display device according to the present invention includes a drive amplifier unit for amplifying the R, G and B drive signals of an image signal input to the image display device and supplying them to the cathode of the cathode ray tube, and the image display device operates normally. The control unit charges the voltage output from the first power input terminal when performing the operation, and discharges the charged voltage when the voltage is not output from the first power input terminal, the switching element turned on by the voltage discharged from the switching control unit, and the image. When the display device performs a normal operation, the voltage output from the second power input terminal is charged and distributed at the same time to be applied to the first grid. When the voltage is not applied from the second power input terminal, the charged voltage is discharged. Voltage supply for turning on the discharged voltage directly to the first grid when turned on It is configured.

Therefore, the present invention provides an effect of completely suppressing spots generated when the image display apparatus is turned off, thereby improving product quality and reliability.

Description

Spot elimination circuit of image display device

The present invention relates to a spot killer circuit of an image display device. More particularly, the present invention relates to controlling a switching operation of a transistor when a power supply of an image display device such as a television receiver and a projection television using a cathode ray tube is turned off. The present invention relates to a spot removing circuit of an image display device for applying a negative high voltage to a first grid G1 that is a control grid to remove spots on a screen.

FIG. 1A is a view for explaining a capacitor formed in a cathode ray tube. In general, a cathode ray tube is coated with conductive films 2 and 3 in which graphite and the like are purified on the inner and outer surfaces of the panel 1 as shown. Between the conductive films 2 and 3, a capacitor having a glass of the panel 1 as a dielectric is formed.

FIG. 1B is an equivalent circuit diagram of FIG. 1.

When the cathode ray tube of the image display device operates, a positive high voltage (+ B) is applied to the conductive film 2 inside the panel 1, and the capacitor formed as described above is charged with a positive high voltage (+ B).

In this state, when the power of the image display device is turned off, heat is left in the heater of the cathode ray tube, so that hot electrons are continuously emitted from the cathode, and thus the high voltage charged in the capacitor formed between the above-described conductive films 2 and 3 ( Accelerated by + B).

On the other hand, the deflection current to the horizontal and vertical deflection coils no longer flows due to the interruption of the input of the horizontal and vertical synchronization signals due to the power off. It only collides with the center area, causing spots to appear on the screen.

At this time, if the discharge time of the high voltage charged in the capacitor formed between the conductive films 2 and 3 is long, the time for which the spot remains on the fluorescent screen becomes long, and the strong stimulus is continued to the fluorescent screen. Burst noise is not only generated, but also the fluorescent film itself is deteriorated, which shortens the lifespan.

Such spots are not limited to the case where both the horizontal and vertical synchronization signals are not inputted by turning off the image display device as described above, as well as the display power management system (DPMS) proposed by the video electronics standard association (VESA) of the United States. As the mode of the image display apparatus is changed according to the < RTI ID = 0.0 >

The reason for this is that the horizontal and vertical deflection is also changed even when the mode of the video display device is changed to the stand-by state or the suspend state in order to save power, as the power management system regulations intended. At the same time, the hot electrons due to the heat of the heater are continuously released.

Accordingly, the image display device using the cathode ray tube is provided with a spot removal circuit of the image display device so that the spot as described above does not occur when the power is turned off or the mode is changed.

2 is a circuit diagram illustrating an example of a spot removing circuit of an image display apparatus according to the related art.

As shown, a conventional spot elimination circuit includes a drive amplifier 1 for amplifying R, G and B drive signals of an image signal input to an image display device and supplying them to the cathode of the cathode ray tube 2, and an image display. If the power is turned off during normal operation of the device, it is turned on in accordance with the spot removal control signal output from the microcomputer (not shown) to ground the R, G, and B drive signals, thereby driving the drive amplifier (3) in the cathode ray tube (3). It consists of a spot elimination circuit part 2 which prevents the R, G, and B drive signals amplified through 1) from being supplied.

In the spot elimination circuit 2 described above, the base terminal is connected to the spot elimination control signal output terminal of the microcomputer through the resistor R, the emitter terminal is grounded, and the collector terminal is connected to the drive amplifier through the diode D. It consists of the transistor Q connected to the input terminal of (1).

In the conventional spot elimination circuit configured as described above, the spot elimination control signal of " low " is output from the microcomputer to the base terminal of the transistor Q when the image display apparatus is normally operated.

The transistor Q is turned off by the spot elimination control signal of " low ", whereby the R, G and B drive signals input to the image display apparatus are applied to the drive amplifier 1 as they are.

Therefore, the R, G, and B drive signals input to the drive amplifier 1 are amplified, and the amplified R, G, and B drive signals are applied to the cathode of the cathode ray tube 3, so that the image display device displays the video signal normally. Will be displayed on the screen.

When the power of the image display device is turned off during the normal operation as described above, the spot removal control signal of “high” is output from the microcomputer to the base terminal of the transistor Q.

The transistor Q is turned on by the spot elimination control signal of " high ", so that the R, G, and B drive signals input to the image display device are connected to the diode D of the spot elimination circuit unit 2. The transistor Q is pulled out to ground.

Therefore, since the R, G, and B drive signals are not input to the drive amplification unit 1 and no hot electrons are emitted through the cathode of the cathode ray tube 3, the hot electrons cannot reach the fluorescent film of the cathode ray tube, resulting in an image display. Spots do not appear on the screen of the device.

However, the spot elimination circuit of the conventional image display apparatus described above suppresses the spots generated in the cathode ray tube by grounding the R, G, and B drive signals for a predetermined time when the image display apparatus is powered on / off. Since the output voltage of the drive amplification unit changes when the power is turned on / off, there is a problem in that some spots are not completely eliminated.

Therefore, an object of the present invention is to control the switching operation of the transistor when the power of the video display device such as a television receiver and a projection television using a cathode ray tube is turned off to apply a negative high voltage to the first grid, which is a control grid, to appear on the screen. The present invention provides a spot removing circuit of an image display device for removing spots.

1A is a view for explaining a capacitor formed in the cathode ray tube,

1B is an equivalent circuit diagram of FIG. 1;

2 is a circuit diagram illustrating an example of a spot removing circuit of an image display apparatus according to the prior art;

3 is a circuit diagram illustrating an example of a spot removing circuit of an image display device according to the present invention.

Explanation of symbols on the main parts of the drawings

10: drive amplifier 20: spot removal circuit

21: switching control unit 22: switching element

23: voltage supply unit Q1, Q2: transistor

R1 to R7: resistors C1 and C2: capacitors

D1, D2: Diode G1: First Grid

12V: first power input terminal 220V: second power input terminal

Spot elimination circuit of the image display device according to the present invention for achieving this purpose is a drive amplifier for amplifying the R, G and B drive signal of the video signal input to the image display device to the cathode of the cathode ray tube, and the image, A switching controller which charges the voltage output from the first power input terminal when the display device performs a normal operation, and discharges the charged voltage when the voltage is not output from the first power input terminal, and is turned on by the voltage discharged from the switching controller. When the switching element and the image display device perform a normal operation, the voltage output from the second power input terminal is charged and distributed at the same time to be applied to the first grid, and the charged voltage when no voltage is applied from the second power input terminal. Discharged, the discharged voltage goes directly to the first grid when the switching element is turned on. It is characterized by consisting of a voltage supply such that.

Hereinafter, a spot removing circuit of an image display device of the present invention will be described in detail with reference to the accompanying drawings.

3 is a circuit diagram illustrating an example of a spot removing circuit of an image display device according to the present invention.

As shown, the drive amplifier 10 amplifies the R, G, and B drive signals of the video signal input to the image display device and supplies them to the cathode (not shown) of the cathode ray tube.

The spot removing circuit unit 20 charges a voltage output from the first power input terminal 12V when the image display apparatus performs a normal operation, and discharges the charged voltage when no voltage is output from the first power input terminal 12V. The switching control unit 21, the switching element 22 turned on by the voltage discharged from the switching control unit 21, and the voltage output from the second power input terminal 220V when the image display device performs a normal operation. While charging, it is distributed and applied to the first grid G1. When no voltage is applied from the second power input terminal 220V, the charged voltage is discharged. When the switching element 22 is turned on, the discharged voltage is the first. It consists of a voltage supply part 23 which is applied directly to the grid G1.

When the voltage is input from the first power input terminal 12V, the switching controller 21 divides the voltage into a plurality of resistors R1 and R2 for turning on the transistor Q1 and a voltage from the first power input terminal 12V. If the input is charged to the voltage input through the diode (D1), if the voltage is not input consists of a capacitor (C1) to discharge to the base terminal of the switching transistor (Q2) described later through the resistor (R3) (R4) do.

The switching element 22 has a base terminal connected to the switching controller 21, an emitter terminal connected to a ground, and a collector terminal connected to the voltage supply unit 23 so that the power of the image display device is turned off. And a switching transistor Q2 that is turned on by the voltage discharged from the capacitor C1.

The voltage supply unit 23 is connected between the output terminal of the switching element 22 and the first grid G1 of the cathode ray tube so that a high voltage is input when a high voltage is input from the second power input terminal 220V. R7), a capacitor C2 for charging a high voltage input when a high voltage is input from the second power input terminal 220V, and discharging when a high voltage is not input to apply a negative high voltage to the first grid G1; It consists of a diode D2.

Next, the operation of the spot removing circuit of the image display device according to the present invention configured as described above will be described in detail.

First, when the image display device is powered on and is operating normally, the voltage output through the first power input terminal 12V is distributed by the resistors R5 and R6 and then applied to the base terminal of the transistor Q1. The transistor Q1 is turned on to start charging the capacitor C2 through the diode D1.

When the transistor Q1 is turned on in this way, the switching transistor Q2 of the switching element 22 is turned off.

In addition, the high voltage output from the second power input terminal 220V is divided by the resistors R5 to R7 to supply a voltage of about -60 [V] to the first grid G1 of the cathode ray tube and at the same time, the capacitor C2. Will begin to charge.

Accordingly, the R, G, and B drive signals input to the drive amplifier 10 are amplified, and the amplified R, G, and B drive signals are applied to the cathode of the cathode ray tube so that the image display device normally displays the image signal on the screen. do.

When the power of the image display device is turned off during the normal operation as described above, since the voltage is not output from the first and second power input terminals 12V and 220V, each of the switching control unit 21 and the voltage supply unit 23 may be turned off. The voltage charged in the capacitors C1 and C2 starts to be discharged.

Since no voltage is applied to the base terminal of the transistor Q1, the transistor Q1 is turned off, and the voltage discharged from the capacitor C1 is applied to the base terminal of the switching transistor Q2 so that the switching transistor Q2 is turned on. It is on.

As such, when the switching transistor Q2 is turned on, the positive terminal of the capacitor C2 is rapidly grounded, and a negative high voltage of about -210 [V] is generated at the anode terminal (-) of the diode D2. This negative high voltage is applied to the first grid G1 as it is.

In this case, a voltage of about -210 [V] applied to the first grid G1 transmits a strong negative field to the first grid G1 such that hot electrons emitted from the cathode of the cathode ray tube cannot pass. Since the hot electrons are not able to reach the fluorescent film of the cathode ray tube, the spots do not appear on the screen of the image display device.

As described above, according to the spot elimination circuit of the image display apparatus of the present invention, a high voltage is applied to the first grid according to the switching operation of the switching element when the image display apparatus is powered off, thereby completely suppressing the occurrence of spots. It has the effect of increasing the quality and reliability of the.

Claims (3)

A drive amplifier for amplifying the R, G, and B drive signals of the video signal input to the image display device and supplying the amplified signals to the cathode of the cathode ray tube; When the image display apparatus performs a normal operation, the voltage output from the first power input terminal is charged, and when the voltage is not output from the first power input terminal, the voltage is input from the first power input terminal to discharge the charged voltage. A switching controller comprising: a plurality of resistors for distributing voltage to turn on the transistor; and a capacitor for charging the voltage when the voltage is input from the first power input terminal and discharging when the voltage is not input; A switching device turned on by the voltage discharged from the switching controller; And When the image display apparatus performs a normal operation, the voltage output from the second power input terminal is charged and simultaneously distributed to the first grid. When the voltage is not applied from the second power input terminal, the charged voltage is discharged. And a voltage supply unit for directly applying the discharged voltage to the first grid when the switching element is turned on. The method of claim 1, wherein the switching device; A base terminal connected to the switching control unit, an emitter terminal is grounded, and a collector terminal connected to the voltage supply unit, when the power of the image display device is turned off, the switching turned on by the voltage discharged from the capacitor of the switching control unit A spot removing circuit of a video display device, characterized in that the transistor. The apparatus of claim 1, wherein the voltage supply unit; Charges a diode, a plurality of resistors for distributing a high voltage when a high voltage is input from the second power input terminal, and a high voltage input when a high voltage is input from the second power input terminal, and discharges when the high voltage is not input. A spot elimination circuit of an image display device, characterized by comprising a capacitor for applying a negative high voltage to the grid.