KR200165529Y1 - Crt focus circuit - Google Patents

Abstract

The present invention relates to a focus circuit of a CRT, and in particular, a breather resistor connected between the first node and the anode voltage output terminal of the high voltage rectifier connected to the secondary side of the flyback transformer to generate an anode voltage. A first resistor connected between ground to provide a discharge path of the anode voltage when the power is off, and a first voltage connected between the first node and the ground to divide the anode voltage to generate a focus voltage, and to discharge the focus voltage when the power is turned off. Focus voltage generating means for providing a path. Therefore, in the present invention, by providing the discharge path of the anode voltage and the discharge path of the focus voltage when the power is off, the stray emission can be prevented by preventing the influence of the anode high voltage on the focus.

Description

CALTI's focus circuit {CRT FOCUS CIRCUIT}

The present invention relates to a focus circuit of a CRT. In particular, the discharge path of the high voltage anode voltage and the focus voltage are separately configured to eliminate the effect of the high voltage on the discharge voltage of the focus voltage, thereby causing the stray emission problem. The focus circuit can be solved.

The CRT applies a high pressure between the cathode and the anode and accelerates the hot electrons emitted from the cathode by the electromagnetic field formed thereon and emits the phosphor by causing the accelerated electrons to collide on the screen to display a black and white or color image.

A focus electrode is included to focus the electron beam emitted from the cathode at a point on the screen.

As shown in FIG. 1, the anode back electrode 14 formed on the screen 12 of the CRT 10 is half-wave rectified by the high-voltage rectifier 30 by half-wave rectification of the flyback pulse provided from the flyback transformer 20. A high voltage anode voltage of is applied. The focus voltage provided from the focus circuit unit 40 is applied to the focus electrode 16. The video signal is applied to the cathode electrode 18.

The conventional focus circuit unit 40 has one end connected to the anode voltage output terminal of the high voltage rectifying unit 30 through a bleeder resistor Rb, and the other end is formed of an adjustment resistor Rv connected to ground, and the bleeder resistor The divided voltage of the anode voltage by the resistance ratio of the control resistor and the output resistor is output as the focus voltage.

In such a structure, when the power supply is turned off, the anode voltage is discharged to ground through the bleeder resistor and the adjusting resistor, so that the high voltage anode voltage affects the focus voltage during this discharge. This effect causes Stray Emission (SE).

Stray emission refers to an unwanted emission phenomenon caused by the barium component evaporated from the cathode during the long time use of the CRT is induced to the screen by a large potential difference between the cathode and the focus electrode and the barium is thus adsorbed on the phosphor.

Improving the CRT itself in order to prevent such a stray emission requires a lot of cost and effort.

The purpose of the present invention is to solve the problem of stray emission by dividing the anode voltage discharge path and the focus voltage discharge path separately to prevent the anode voltage from affecting the focus voltage when the power is turned off. It is to provide a focus circuit that can be prevented.

1 is a diagram showing a configuration of a focus circuit of a conventional CRT.

2 is a diagram illustrating a configuration of a focus circuit of a CRT according to the present invention.

≪ Description of Codes for Major Parts of Drawings>

10: CRT 12: Screen

14 anode electrode 16 focus electrode

18: cathode electrode 20, 50: focus circuit portion

30: high voltage rectifier 40: focus circuit

In order to achieve the above object of the present invention, the device of the present invention is connected to the secondary side of the flyback transformer and the bleeder resistor connected between the first node and the anode voltage output terminal of the high voltage rectifier for generating an anode voltage; And a first resistor providing an anode voltage discharge path connected between the first node and ground, and a focus voltage generating means connected between the first node and ground.

Hereinafter, with reference to the accompanying drawings, it will be described in detail the present invention through an embodiment of the present invention.

2 shows a focus circuit of a CRT according to the present invention. In FIG. 2, one end of the secondary coil of the flyback transformer FBT is connected to the high voltage rectifier 30 including the diode D1 and the resistor R2, and the other end is connected in parallel with the capacitor C1 and the resistor R1. It is grounded through. The voltage across the resistor R1 is provided as an auto luminance limit signal ABL. The RGB image signal is applied to the cathode electrode 18.

The high-voltage anode voltage half-wave rectified by the high-voltage rectifier 30 is applied to the anode electrode 14 of the CRT 10. The focus circuit unit 50 is connected between the output terminal of the high voltage rectifying unit 30 and the ground. The output of the focus circuit section 50 is connected to the focus electrode 16 of the CRT 10.

The focus circuit unit 50 is connected to the secondary side of the flyback transformer to generate an anode voltage, and a bleeder resistor Rb connected between the anode voltage output terminal of the high voltage rectifying unit and the first node N1 and the first node. A focus including a first resistor R4 providing an anode voltage discharge path connected between N1 and ground, and a regulating resistor Rv and a resistor R3 connected in series between the first node N1 and ground. And a voltage generating means. The resistance value of the resistor R4 is set to a value smaller than the series synthesis resistance value of the resistor Rv and the resistor R3.

Therefore, in the present invention, the high voltage anode voltage is discharged through the bleed resistor and the resistor R4 and the focus voltage is discharged through the resistor Rv and the resistor R3 when the power is turned off. Therefore, the influence on the focus voltage at the time of discharge of the high voltage anode voltage can be eliminated.

As described above, in the present invention, the discharge path of the anode voltage and the focus voltage of the focus voltage are configured separately when the power is turned off, thereby eliminating the effect of the anode voltage on the focus electrode during discharge, thereby preventing stray emission. Can be. In addition, the present invention can prevent the stray emission phenomenon by improving the focus circuit, it is possible to solve the stray emission problem at a very low cost compared to the method of improving the CRT itself.

Although the above has been described with reference to a preferred embodiment of the present invention, those skilled in the art various modifications and changes of the present invention without departing from the spirit and scope of the present invention described in the claims below. I can understand that you can.

Claims (1)

A breather resistor connected between the first node and an anode voltage output terminal of the high voltage rectifying unit connected to the secondary side of the flyback transformer to generate an anode voltage; A first resistor providing an anode voltage discharge path coupled between the first node and ground; And And a focus voltage generating means connected between the first node and ground.