KR20000000636U - Focus drive circuit of display device - Google Patents

Abstract

The present invention relates to a multi-mode display device, wherein the microcomputer generates a dynamic focus signal corresponding to the display mode with the same gain in response to the input frequency according to the change of the multi-mode. The focus driving circuit outputs the focus signal to the CRT in response to the dynamic focus signal. Accordingly, the focus problem is solved when designing a display device having a wide bandwidth by outputting a constant focus signal to display the screen as precisely as possible in response to the multi-mode change.

Description

FOCUS DRIVING CIRCUIT OF DISPLAY APPARATUS

The present invention relates to a display device, and more particularly, to a focus driving circuit of a multi-mode display device using a CRT.

In general, the size of the electron beam increases toward the corner of the screen. To compensate for this, a compensation signal, that is, a focus signal, is applied to the CRT. This compensation waveform is made by the CRT and the deflection circuit DY. Typically this waveform is parabolic and is synchronized to the deflection signal.

Therefore, the focus function for correcting the difference in focus caused by the difference in driving distance between the center and the corner of the CRT requires a high voltage power source.

Referring to FIG. 1, the focus driving circuit 4 of the conventional multi-mode display apparatus generates a focus signal through a high voltage transformer, that is, a FBT (FlyBack Transformer). It receives the input horizontal frequency from the horizontal deflection circuit (DY: Deflection Yoke) (2) and is input through the resonant capacitor (C1), and generates a focus signal (Focus) corresponding to the horizontal frequency according to the change of the multi-mode .

That is, the focus drive circuit 4 receives the signal which becomes the basis of the focus signal from the horizontal deflection circuit 2. Subsequently, the output voltage induced by the primary coil T1 and the secondary coil T2 through the resonant capacitor C1 is variably output according to the change of frequency. For example, an output voltage between 300 V and 500 V is generated.

Accordingly, the output signal Vpeak-peak of the focus signal is different due to the change of the input frequency, thereby causing a problem in that the focus signal is variably output according to the mode change in the multi mode.

An object of the present invention is to solve the above-described problem, and to provide a focus driving circuit that outputs a constant focus signal according to a display mode of a multi display mode display apparatus.

1 is a circuit diagram showing a focus driving circuit of a display device according to an embodiment of the prior art;

2 is a block diagram showing a configuration of a focus driving circuit according to the present invention; And

FIG. 3 is a circuit diagram illustrating an embodiment of the focus driving circuit shown in FIG. 2.

* Description of symbols on the main parts of the drawings *

10 microcomputer 20 focus driving circuit

30: CRT

According to one aspect of the present invention for achieving the above object, in a multi-mode display device using a CRT: a micro-output for outputting a dynamic focus signal for adjusting the focus of the CRT corresponding to the mode of the multi-mode A computer; And a focus driving circuit that receives and amplifies the dynamic focus signal and outputs the same focus signal to the CRT in response to the corresponding mode regardless of a change in an input frequency. Is output.

In a preferred embodiment of this aspect, the focus driving circuit comprises an amplifying circuit having a constant gain.

In a preferred embodiment of this aspect, the focus drive circuit comprises: a first resistor, one end of which applies a first power supply voltage; A second resistor having one end connected to the other end of the first resistor and the other end grounded; A third resistor, one end of which applies a second power supply voltage; A transistor having a base terminal connected between the first and second resistors and a collector terminal connected to the other end of the third resistor; A fourth resistor, one end of which applies the dynamic focus signal; A capacitor having one end connected to the fourth resistor and the other end connected to an emitter terminal of the transistor; One end is connected to the other end of the capacitor, and the other end includes a fifth resistor that is grounded.

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

2 and 3 show some components of a display device having a CRT according to the present invention.

Referring to FIG. 2, the microcomputer 10 receives horizontal and vertical synchronization signals Hsync and Vsync to determine a corresponding display mode and outputs a corresponding dynamic focus signal Dyn_Focus. It is output with the same gain corresponding to the mode regardless of the frequency change.

The focus driving circuit 20 outputs the same focus signal Focus to the CRT 30 in response to the dynamic focus signal Dyn_Focus regardless of the change in the input frequency. That is, a certain focus signal Focus is output in correspondence with each display mode.

Specifically, as shown in FIG. 3, the focus driving circuit 20 includes first to fifth resistors R1 to R5, a capacitor C2, and a transistor Q.

One end of the first resistor R1 applies a first power supply voltage Vb (eg, 12 V), and one end of the second resistor R2 is connected to the other end thereof.

One end of the second resistor R2 is connected to the other end of the first resistor R1 and the other end is grounded. Accordingly, the first and second resistors R1 and R2 divide the first power supply voltage Vb and input the same to the base terminal of the transistor Q.

One end of the third resistor R3 applies a second power supply voltage Va (for example, 400 V), and the other end thereof is connected to the collector terminal of the transistor Q.

The transistor Q is provided as an NPN type bipolar transistor and is an emitter ground circuit. The base terminal is connected between the first and second resistors R1 and R2, and the collector terminal is connected to the other end of the third resistor R3.

One end of the fourth resistor R4 applies the dynamic focus signal Dyn_Focus from the microcomputer 10.

One end of the capacitor C2 is connected to the fourth resistor R4, and the other end thereof is connected to the emitter terminal of the transistor Q.

One end of the fifth resistor R5 is connected to the other end of the capacitor C2 and the other end is grounded.

Accordingly, the fourth and fifth resistors R4 and R5 and the capacitor C2 are emitter peaking circuits that adjust the gain and impedance of the transistor Q at a high frequency. Correct the bandwidth.

The transistor Q amplifies with a constant gain in response to the dynamic focus signal Dyn_Focus to output the same focus signal Focus to the CRT 30.

As described above, the present invention solves the focus problem of the display device, and the efficient design of the focus circuit and thereby the productivity are improved.

Claims (3)

For multi-mode display devices using CRTs: A microcomputer for outputting a dynamic focus signal for adjusting the focus of the CRT corresponding to the corresponding mode of the multi-mode; And a focus driving circuit that receives and amplifies the dynamic focus signal and outputs the same focus signal to the CRT in response to the corresponding mode regardless of a change in an input frequency. Display device that is output to. The method of claim 1, And the focus driving circuit includes an amplifier circuit having a constant gain. The method of claim 1, The focus driving circuit is: A first resistor, one end of which applies the first power supply voltage; A second resistor having one end connected to the other end of the first resistor and the other end grounded; A third resistor, one end of which applies a second power supply voltage; A transistor having a base terminal connected between the first and second resistors and a collector terminal connected to the other end of the third resistor; A fourth resistor, one end of which applies the dynamic focus signal; A capacitor having one end connected to the fourth resistor and the other end connected to an emitter terminal of the transistor; And a fifth resistor having one end connected to the other end of the capacitor and the other end being grounded.