KR0122114B1 - Screen voltage auto-controlling circuit - Google Patents

Abstract

A screen voltage automatic regulation circuit automatically adjusts a grid voltage at the outside, includes a circuit(20) under the control of the microcomputer(30) inside of a monitor, and automatically adjusts a magnitude of the screen grid voltage applied to a cathode ray tube. The circuit includes: first and second resistors(R11,R12) for fixing a magnitude of a screen grid voltage according to a reference brightness sensor value of a cathode ray tube; a transistor(Q1) connected to the second resistor(R112); and a load resistor(R13) for preventing a load of the transistor(Q1).

Description

Screen voltage automatic regulation circuit

1 is a conventional screen voltage regulation circuit diagram.

2 is a screen voltage automatic adjustment circuit of the present invention.

3 is a configuration diagram of the voltage automatic regulation device of the present invention.

* Explanation of symbols for main parts of the drawings

1: High pressure generating transformer 10: Monitor CRT

20: automatic screen voltage adjustment circuit 30: microcomputer

40: luminance sensor unit 50: interface unit

R1, R2, R14: resistors R11, R12: first and second fixed resistors

R13: Load Resistance VR: Variable Resistance

Q1: transistor

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a screen voltage automatic adjustment circuit which enables the outside to automatically adjust the grid voltage supplied to a cathode ray tube (hereinafter referred to as a cathode ray tube) used for a monitor and a TV receiver.

Conventionally, the screen grid voltage supplied to the CRT is supplied from a high voltage generating transformer (FBT) and the voltage is adjusted using a variable resistor.

This can be represented as shown in FIG.

That is, the screen grid voltage supplied to the CRT is supplied from the high voltage generating transformer 1, and the magnitude of the voltage should be changed with respect to the reference luminance value according to the luminance change of the CRT. This may change the magnitude of the voltage by the variable resistor VR which is connected in series between the resistors R1 and R2 so that the screen grid voltage is applied to the CRT. However, since the screen grid voltage supplied to the CRT is a high voltage ranging from 300V to 800V, an expensive variable resistor must be used to control the high voltage with a variable resistor (VR). In addition, the voltage must be adjusted manually, so accurate adjustment is not possible.

In view of the above, the present invention is characterized in that a circuit is configured to automatically adjust the size of the screen grid voltage applied to the CRT using a microcomputer inside the monitor.

That is, first and second fixed resistors for fixing the magnitude of the screen grid voltage applied from the high voltage generating transformer to the CRT according to the reference luminance sensor value of the CRT, a transistor connected to the second fixed resistor and controlled by the microcomputer; It is made of a load resistor to prevent the load of the transistor.

In addition, by using a circuit as described above, the microcomputer inside the monitor detects the brightness change of the brightness sensor unit mounted in front of the monitor CRT and controls the screen automatic voltage circuit unit to adjust the screen grid voltage.

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

2 is a voltage automatic adjustment circuit diagram of the present invention.

Connect the CRT screen grid voltage to be applied between the first and second fixed resistors R11 and R12 for fixing the magnitude of the screen grid voltage applied from the high-voltage generating transformer 1 to the CRT according to the CRT value. The second fixed resistor R12 is connected to a transistor Q1 for controlling the screen grid voltage applied to the CRT by switching the voltage generated from the high voltage generating transformer 1 under the control of the microcomputer 30. At this time, a load resistor R13 that prevents the load of the transistor Q1 is connected in parallel between the collector terminal of the transistor Q1 and the second fixed resistor R12. R14 is a resistor connected in series between the microcomputer 30 and the emitter terminal of the transistor Q1.

The control operation of the screen grid voltage by the voltage automatic adjustment circuit is performed as follows.

The voltage generated by the high voltage generating transformer 1 is divided by the second fixed resistor R12, the transistor Q1, and the resistor R14 while being transmitted through the first fixed resistor R11. In this case, the sizes of the first and second fixed resistors R11 and R12 are determined such that voltages necessary for the screen grid are applied. At this time, when it is necessary to adjust the size of the screen grid voltage so that the value of the brightness sensor becomes a reference value according to the brightness change of the CRT, the microcomputer 30 detects the change in brightness and adjusts the magnitude of the voltage delivered to the screen grid. This is done by changing the voltage at the microcomputer terminal. That is, since the output terminal of the microcomputer is a D / A converter terminal, it is possible to convert from 0V to 12V. According to the voltage conversion of the microcomputer output terminal, the screen grid voltage is adjusted by switching a part of the voltage applied to the screen grid through the transistor Q1.

As shown in FIG. 3, the configuration of the automatic voltage regulator for adjusting the size of the screen grid voltage by detecting the change in luminance of the CRT is shown in FIG.

That is, the voltage applied from the screen voltage automatic adjustment circuit unit 20 is connected to the monitor CRT 10 through the screen grid, and the brightness sensor unit 40 for detecting the brightness of the CRT 10 in front of the monitor CRT 10. To be fitted. At this time, the microcomputer 30 mounted inside the monitor for adjusting the magnitude of the screen grid voltage applied from the screen voltage automatic adjustment circuit unit 20 to the CRT 10 according to the change in the brightness of the CRT 10 is a luminance sensor unit ( The interface unit 50 is provided outside between the luminance sensor unit 40 so as to detect the change in luminance of the 40.

Due to this, the microcomputer recognizes the brightness change detected by the brightness sensor unit 40 through the interface unit 50, and accordingly, changes the voltage size of the output terminal, thereby applying the magnitude of the screen grid voltage applied to the CRT 10 of the monitor. Will be adjusted. Therefore, when the luminance sensor value is smaller or larger than the reference luminance sensor value, the microcomputer changes the value of the luminance sensor to be equal to the reference value by changing the voltage size of the output terminal.

As described above, according to the present invention, the screen grid voltage is automatically adjusted according to the luminance change by implementing the screen voltage automatic adjustment circuit using the transistor so that the screen grid voltage applied to the CRT can be automatically adjusted by the microcomputer. Accurate adjustment is possible.

Claims (4)

In constructing the screen voltage adjusting circuit for adjusting the magnitude of the screen grid voltage applied from the high voltage generating transformer, fixing the magnitude of the screen grid voltage applied from the high voltage generating transformer 1 to the CRT according to the reference luminance sensor value of the CRT. A first and second fixed resistors R11 and R12, a transistor Q1 connected to the second fixed resistor R12 and controlled by the microcomputer 30, and a load resistor to prevent a load of the transistor Q1. And (R13) a screen voltage automatic regulation circuit. 2. The transistor Q1 of claim 1, wherein the transistor Q1 is connected to an output terminal of the microcomputer 30, which is a D / A converter terminal capable of converting the voltage through the resistor R14, and is controlled by the microcomputer 30. Screen voltage automatic regulation circuit. The automatic screen voltage adjusting circuit according to claim 1, wherein the screen grid is applied with a voltage of the high voltage generating transformer (1) through a first fixed resistor (R11). The transistor Q1 of claim 1, wherein an external interface unit is provided to allow the microcomputer 30 to recognize a change in the luminance sensor value of the CRT of the monitor. The screen voltage automatic regulation circuit, characterized in that for changing the magnitude of the switching voltage of.