KR20000013385A - Brightness correction circuit of display apparatus - Google Patents

Abstract

PURPOSE: An brightness correction circuit of display apparatus is provided to maintain a brightness of a back raster. CONSTITUTION: The circuit comprises a microcomputer for discriminating whether current operation mode is normal mode or video mute mode and outputting a video mute control signal corresponding to the current operation mode and a mute circuit for supplying a DC voltage generated by a second winding of flyback transformer as a DC bias voltage of a first grid when the current operation mode is the video mute mode and supplying a constant voltage as a DC bias voltage of the first grid when the current operation mode is normal mode.

Description

Brightness Correction Circuit of Display Device

The present invention relates to a brightness correction circuit of a display device, and more particularly, to provide a negative voltage supplied to a first grid provided in a cathode ray tube to a constant voltage regardless of the beam amount of the cathode ray tube. The present invention relates to a brightness correction circuit of a display device that maintains a constant brightness.

In general, a back raster, which is a picture drawn with a scanning line on a fluorescent surface of a display device such as a television receiver and a computer monitor, is displayed even when an image signal is not supplied in a normal operation state.

In most monitors, the voltage output from the flyback transformer is used as the first grid voltage to adjust the brightness of the back raster, and the screen voltage output from the flyback transformer is used to adjust the speed of the electron beam. I use it.

That is, the voltage derived from the flyback transformer is supplied to the electron gun of the cathode ray tube, and the electron gun emits hot electrons to collide with the fluorescent surface with a thin electron beam to display an image.

The electron gun arbitrarily controlling the amount of electrons impinging on the fluorescent surface is composed of a cylindrical cathode, a grid, and an anode, and the first grid G1 of the grid controls the amount of electrons emitted from the cathode as a control grid to adjust brightness. .

1 is a circuit diagram for supplying a dish bias voltage to a first grid provided in a cathode ray tube of a display device according to the prior art.

As shown in the drawing, the microcomputer 10 receives a horizontal synchronization signal and a vertical synchronization signal output from a video card, outputs a reference oscillation signal, and outputs a video mute control signal by a power on / off signal input from the outside. do.

The horizontal and vertical processing unit 20 receives a reference oscillation signal output from the microcomputer 10 and a horizontal / vertical synchronization signal output from the video card and supplies a signal to the high voltage circuit and the deflection circuit.

The flyback transformer 30 receives the horizontal power supply voltage and generates a high pressure to supply the cathode ray tube.

The mute circuit and the DC voltage supply unit 40 are connected to the output terminals of the microcomputer 10 and the flyback transformer 30 to mute the video signal when the mode is changed to supply the adjusted voltage of the first grid G1 to the cathode ray tube. do.

The video preamplifier 50 processes the R, G and B color signals output from the video card according to the contrast control signal output from the automatic current limiting circuit ABL and supplies them to the cathode ray tube through the video output amplifier 60. .

The operation of the circuit for supplying the dish bias voltage of the first grid G1 provided in the cathode ray tube of the display device having the above-described configuration will be described below.

First, when the user turns on / off the power of the display device or changes the mode while the display device is in use, the microcomputer 10 recognizes the power on / off state by the input power state, and inputs from the computer main body. You will notice the mode changed to the horizontal / vertical frequency.

As described above, when the microcomputer 10 detects the OFF state and the mode change of the power supply, the mute circuit and the clock voltage supply unit 40 output a high level video mute control signal for muting the video signal displayed on the cathode ray tube. Will output

Therefore, the mute circuit and the dish voltage supply part 40 are turned off, and the negative voltage generated by the secondary winding of the flyback transformer 40 is supplied with the voltage of the first grid G1 of the cathode ray tube. The video mute circuit and the vertical blanking circuit were implemented by supplying a negative voltage to the first grid G1.

However, as described above, in the related art, the amount of beams radiated to the cathode ray tube, that is, the beams radiated to the cathode ray tube is low beam and high beam by supplying the dish voltage of the first grid G1 by the secondary winding of the flyback transformer. In this case, since the difference in the dish voltage supplied to the first grid increases, there is a problem that the difference in the brightness of the back raster is increased.

Accordingly, an object of the present invention is to maintain the brightness of the backlight device of the display device by supplying the negative voltage supplied to the first grid provided in the cathode ray tube at a constant voltage regardless of the beam amount of the cathode ray tube so as to solve the above problems. It is to provide a brightness correction circuit of the display device to maintain it.

1 is a circuit diagram for supplying a dish bias voltage to a first grid provided in a cathode ray tube of a display device according to the prior art;

2 is a circuit diagram illustrating a configuration of a brightness correction circuit of the display device according to the present invention.

* Description of Signs of Main Parts of Drawings *

100: microcomputer

400: mute circuit and brightness correction circuit

In the display device in which the voltage generated by the secondary winding of the flyback transformer according to the present invention is supplied to the dish bias voltage of the first grid, the device of the present invention is currently operating. A microcomputer that determines whether the mode is a normal mode or a video mute mode and outputs a video mute control signal having an opposite level, and the display device operates in a video mute mode in response to a video mute control signal input from the microcomputer. When the display device is in operation to supply the dish voltage generated by the secondary winding of the flyback transformer to the dish bias voltage of the first grid, and to supply the set constant voltage to the dish bias voltage of the first grid when the display device is operating in the normal mode Composed of mute circuit and brightness correction circuit The features.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

2 is a circuit diagram illustrating a configuration of a brightness correction circuit of the display device according to the present invention.

The detailed description of the horizontal / vertical processing unit 200, the flyback transformer 300, the video preamplifier 500, and the video output amplifier 600, which are the same parts as in the prior art, will be omitted. The microcomputer 100 determines whether the current operating mode is normal mode or the video mute mode and outputs a video mute control signal whose levels are opposite to each other, and the video mute control signal input from the microcomputer 100. In response, when the display device is operating in the video mute mode, the DC voltage generated by the secondary winding of the flyback transformer 300 is supplied to the dish bias voltage of the first grid, and the display device is set when the display device is operating in the normal mode. And a mute circuit and a brightness correction circuit unit 400 for supplying a constant voltage to the dish bias voltage of the first grid.

The mute circuit and the brightness correction circuit unit 400 are turned on when the display apparatus is operated in the normal mode, and output the constant voltage set to the first grid G1, and turned off when the display apparatus is operated in the video mute mode. A switching element Q1 for switching a negative voltage generated by the secondary winding of the flyback transformer 300 to the first grid G1 and a first grid G1 when the switching element Q1 is turned on. And a constant voltage generating element ZD1 for outputting a constant voltage.

The above-described constant voltage generating element ZD1 is a zener diode.

The voltage generated by the above-described constant voltage generating element ZD1 is set to be larger than the voltage generated by the secondary winding of the flyback transformer 300.

The operation of the brightness compensating circuit of the display device according to the present invention configured as described above will be described in more detail with reference to the accompanying drawings.

First, when the display apparatus operates in the normal mode, the microcomputer 100 outputs a low level video mute control signal to the mute circuit and the brightness correction circuit 400, and thus the transistor Q1, which is a switching element, is turned on.

When the transistor Q1 is turned on, it is correlated with the voltage V2 generated by the secondary winding of the flyback transformer 300 that changes according to the beam amount of the cathode ray tube with the dish voltage of the first grid G1 provided in the cathode ray tube. The predetermined voltages Vcc to Vz generated by the zener diode ZD1, which is a constant voltage generating element, are supplied without.

In addition, when a power on / off control signal is input from the outside or the mode of the display device is changed, the microcomputer 100 switches the display device to the video mute mode. That is, the microcomputer 100 converts the low level video mute control signal into a high level video mute control signal and outputs it to the mute circuit and the brightness correction circuit unit 400 so that the transistor Q1 which is a switching element is turned off.

When the transistor Q1 is turned off, the voltage V2 generated by the secondary winding of the flyback transformer 300 is supplied to the clock voltage of the first grid G1 provided in the cathode ray tube to implement the video mute function. do.

Therefore, as described above, the present invention is a constant voltage generated by the zener diode instead of the voltage generated by the secondary winding of the flyback transformer, which is a DC voltage of the first grid provided in the cathode ray tube, which changes according to the beam amount of the cathode ray tube. This output is provided so that the brightness of the backlight of the screen can be kept constant.

Claims (4)

In the display device in which the voltage generated by the secondary winding of the flyback transformer is supplied to the dish bias voltage of the first grid, A microcomputer that determines whether the current operating mode of the display device is a normal mode or a video mute mode and outputs a video mute control signal whose levels are opposite to each other; In response to the video mute control signal input from the microcomputer, when the display device is operating in the video mute mode, the display device generates a dish voltage generated by the secondary winding of the flyback transformer as a dish bias voltage of the first grid. And a brightness correction circuit unit configured to supply a set constant voltage to the dish bias voltage of the first grid when the device is operating in the normal mode. According to claim 1, wherein the brightness correction circuit unit; When the display device is operating in normal mode, it is turned on to output a constant voltage set to the first grid, and when the display device is operating in video mute mode, it is turned off and generated by the secondary winding of the flyback transformer to the first grid. A switching element for switching a negative voltage to be output; And And a constant voltage generating device configured to output a constant voltage to the first grid when the switching device is turned on. The method of claim 1, wherein the constant voltage generating device; A brightness correction circuit of a display device, characterized in that the zener diode. The brightness compensating circuit of claim 1, wherein the voltage generated by the constant voltage generator is set to be greater than the voltage generated by the secondary winding of the flyback transformer.