KR19990002540U - Spot elimination circuit on power off in television receiver - Google Patents

Abstract

The present invention relates to a television receiver, and more particularly, to a spot removal circuit during power-off for eliminating a spot phenomenon that occurs when a time period when the high voltage of the water pipe driving unit is discharged is long. In the present invention, in the medium of the luminance signal (Y) output from the image processor circuit 100 to the water pipe display unit 200 to the transistor (Q3), the luminance signal (Y) is input to the base of the transistor, The emitter of the transistor is input to the water pipe display 200 and at the same time the standby power ( In a television receiver circuit connected to 2):

A capacitor charged while the power is on to supply a cut-off voltage to the base of the transistor Q3 so that the luminance signal Y is not input to the water pipe display 200 when the power is turned off ( C1) and a supply circuit of a predetermined cut-off voltage composed of the first transistor Q1 for switching charging and discharging (at power off) of the capacitor C1.

Description

Spot elimination circuit on power off in television receiver

The present invention relates to a television receiver, and more particularly, to a spot removal circuit during power-off for eliminating a spot phenomenon that occurs when a time period when the high voltage of the water pipe driving unit is discharged is long. It is about.

A television displaying an image using a CRT (water tube) is supplied with high pressure to the water tube. This is because high pressure is applied to the anode to accelerate hot electrons emitted from the cathode of the electron gun to reach the fluorescent surface. The voltage across the anode is 20–30 mA, and in addition to the screen grid is relatively high, 200–700 V.

When the power of the television set is turned off, the high pressure applied to the water pipe is also turned off (discharged) as described above. However, when the high voltages, which determine the amount of current reaching the fluorescent surface, are discharged relatively slowly, a phenomenon in which the central portion of the picture tube screen is brightly shined, that is, a spot phenomenon occurs. This bright spot increases as the use of the product increases, resulting in a problem of shortening the life of the product.

Conventional methods for solving the above problems include a method of rapidly discharging a high voltage applied to an anode of a water pipe or a high voltage applied to a flyback transformer (FBT) (above 123 V), which controls relatively high voltage. In view of this, many circuit elements are required, and since the characteristics of the object are high voltage, it is difficult to miniaturize. In particular, the method of controlling the high voltage does not fundamentally eliminate the temporary bright point phenomenon at power off.

The present invention for solving the above-described problems, the luminance signal at the time of power off to remove the bright point phenomenon that occurs when the time when the high voltage of the water pipe driving unit is discharged during the turn off of the water pipe power is long, It is an object of the present invention to provide a cut-off voltage supply circuit that cuts off the input of the correlator.

1 is a circuit diagram showing a video signal transfer process from a video processor circuit to a water pipe display in a conventional television.

2 is a circuit diagram showing a video signal transfer process with a spot removal circuit added when the power off according to the present invention.

Explanation of symbols on the main parts of the drawings

100: image processor circuit 200: water pipe display

One, 2: standby power supply C1, C2: capacitor

D1, D2: Diode R1, R2: Resistance

Q1, Q2, Q3: transistor Y: luminance signal

In order to achieve the above object, a feature of the present invention is that the luminance signal (Y) outputted from the image processor circuit (100) to the water pipe display unit (200) by the transistor (Q3), the luminance signal (Y) Is inputted to the base of the transistor, and the emitter of the transistor is inputted to the water pipe display 200 and at the same time the standby power ( In a television receiver circuit connected to 2):

A capacitor charged while the power is on to supply a cut-off voltage to the base of the transistor Q3 so that the luminance signal Y is not input to the water pipe display 200 when the power is turned off ( C1) and supply means for supplying a predetermined cut-off voltage composed of the first transistor Q1 for switching the charge and discharge (when power off) of the capacitor C1.

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

The accompanying drawings are circuit diagrams showing a video signal transmission process from a video processor circuit to a water pipe display unit in a television. FIG. 1 is a conventional circuit diagram, and FIG. 2 is a diagram for removing bright spots during power turn-off according to the present invention. It is a circuit diagram to which the supply means of a cut-off voltage was added.

The supply means of the cut-off voltage provided by the present invention is largely composed of a charging means and a switching means, and the connection relationship between the means will be described in detail as follows.

With the charging means, a standby power source ( One end of a resistor R1 for a voltage drop of a predetermined level is connected to 1) in series. An anode of a predetermined diode D1 is connected to the other end of the drop resistor R1, and one end of a predetermined capacitor C1 is connected to the cathode thereof. When the other end of the capacitor C1 is grounded, the power source ( It will be charged while 1) is on.

Since the switching means supplies the charged electricity (voltage) to the base of the transistor Q3 of the conventional circuit diagram as a cut-off voltage, it uses the n-type transistor Q1, and in some cases, a more reliable switching role. The second transistor Q2 of p type may be added to the collector terminal of the n-type transistor Q1 as the first transistor.

The base of the first transistor Q1 is connected to supply an on / off voltage state according to a power state. It may be connected to a microcomputer that outputs a high / low control signal, and the standby power source ( Since 1) is the same, it may be simultaneously connected between the drop resistance R1 and the diode D1. The emitter is connected, in parallel, at the point where the cathode of the diode D1 and the capacitor C1 are connected.

When the second transistor Q2 is not added, the collector of the first transistor Q1 is connected to the base of the conventional transistor Q3, and when the second transistor Q2 is also added, Connect to the base Thus, the emitter terminal of the second transistor Q2 is connected to the base of the intermediate transistor Q3 which mediates the luminance signal so that the cut-off voltage is conducted when the second transistor Q2 is turned on.

A predetermined second capacitor C2 and a predetermined second diode D2 are connected in parallel to the collector of the second transistor Q2, and the anode of the second diode D2 is connected to the conventional resistor R2. Power in parallel with 2) is connected. The other terminal of the second capacitor C2 is grounded for charging at power-on.

Hereinafter, the operation relationship of the cut-off voltage supply circuit for interrupting the transmission of the luminance signal provided by the present invention to eliminate the bright point phenomenon at power off will be described.

In the conventional video signal transfer circuit diagram of FIG. 1, when the luminance signal Y output from the video / chroma circuit 100 is input to the base of the intermediate transistor Q3, the standby signal is connected to the emitter of the intermediate transistor Q3. power( 2), the magnitude of the current (that is, the voltage) input to the picture tube display unit 200 changes according to the current change between the base and the collector of the transistor Q3.

Similarly, in FIG. 2, when the power of the water pipe is turned on, the luminance signal Y is input to the base of the transistor Q3, and the standby power source ( One, 2) is also turned on. Thus, the first and second capacitors C1 and C2 are charged by the power supply. At this time, the cut-off voltage for turning off the intermediate transistor Q3 is not supplied to the base. The detailed description is as follows.

When the first transistor Q1 or the second transistor Q2 is in an off state (a state in which no electricity is applied), since a low voltage is supplied to the base of the intermediate transistor Q3, the luminance signal ( Y) is not cut off. The standby power supply ( Since 1) is in the ON state or the control signal of the microcomputer is Hi, the high voltage is applied to the base of the first transistor Q1. Since the first transistor is n-type, it is turned off. Since the collector of the first transistor becomes a low voltage, the p-type second transistor Q2 is also turned off.

Now, let's say that the power of the Prime Minister is turned off. The standby power supply ( The control signal of 1) and microcomputer are all low voltage. Accordingly, the first transistor Q1 is turned into a turned-on state and becomes a conductive state. Then, the electricity (voltage) charged in the first capacitor C1 is discharged from the emitter of the first transistor Q1 to the collector. . This is because the first diode D1 is present.

When the collector of the first transistor Q1 is directly connected to the base of the intermediate transistor Q3, the above discharge voltage acts as a cut-off voltage to block the luminance signal Y, thereby eliminating the bright spot phenomenon. It becomes possible. The capacity of the first capacitor C1 should be sufficient to shut off for a sufficient time.

When the collector of the first transistor Q1 is connected to the base of the second transistor Q2, since the second transistor Q2 is p-type, since the discharge voltage is a high voltage, the second transistor Q2 is turned on. Thus, the electricity (voltage) charged in the second capacitor C2 becomes the cut-off voltage as the discharge voltage.

As another embodiment of the present invention, as a means for supplying a cut-off voltage to the collector of the second transistor (Q2), instead of the second capacitor (C2) to give a discharge voltage for a predetermined time or more during power-off (Hi) It can be connected to the place that maintains the voltage state.

In addition, since the cut-off voltage is only supplied for about 2 to 3 seconds to remove the bright spot as the predetermined time, in order to save power, in the present invention, only while the charging electricity of the first capacitor C1 is discharged. It is preferable that the second transistor Q2 is turned on. The supply of the cut-off voltage desired by the present invention may be sufficient as the first capacitor C1, the first diode D1, and the first transistor Q1. Those skilled in the art will readily be able to make modifications.

The present invention, which operates as described above, supplies a cut-off voltage for turning off the transistor that mediates the transmission of the luminance signal so that the luminance signal does not reach the receiving tube display unit when the tube power is turned off. There is an effect that can be removed. Thus, there is an effect that can extend the life of the product.

Claims (3)

In the medium of the luminance signal Y output from the image processor circuit 100 to the water pipe display unit 200 as the transistor Q3, the luminance signal Y is input to the base of the transistor, The emitter is input to the water pipe display 200 and at the same time the power ( In a television receiver circuit connected to In order to prevent the luminance signal Y from being input to the water pipe display 200 when the power is turned off, a supply means for supplying a cutoff voltage for supplying a cutoff voltage to the base of the transistor Q3 is added. Spot elimination circuit at power off. The power supply means according to claim 1, wherein the supply means for supplying the cut-off voltage comprises: predetermined power storage means charged by a power supply while the power is on; And a predetermined switching means for switching such that the charging voltage of said power storage means is discharged to a cut-off voltage at the time of power-off. 3. The power storage device according to claim 2, wherein the power storage means has one side grounded and the other end thereof connected in series with a predetermined resistor R1. ) Is connected to capacitor (C1), The switching means is a predetermined n-type transistor Q1. In this connection of the transistor Q1, a predetermined power on / off voltage is connected to a base thereof, and the capacitor C1 is connected to the emitter. Is connected, and the collector is connected so that the voltage as cut-off is output and at the same time, In order to conduct only the emitter of the transistor Q1 when the capacitor C1 is discharged, a predetermined diode D1 is connected so that its cathode is connected to the emitter. Spot removal circuit upon power off, characterized in that it is inserted in series with 1).