KR19990052757A - Monitor's geometry distortion correction circuit - Google Patents

Abstract

The present invention relates to a geometric distortion correction circuit for correcting geometric distortion of a screen generated from a color display tube (CDT), the circuit of the present invention comprises: a push-pull amplifier for amplifying a horizontal size control signal output from a microcomputer; A first transistor biased to decrease the emitter current from the driving power supply when the signal level of the amplified horizontal scale control signal output from the push-pull amplifier increases; When the emitter current of the first transistor decreases, the emitter current from the driving power source increases and the DC voltage of the collector stage is increased, and the pincushion signal input to the base stage is inverted and amplified and output through the collector stage. A second transistor; And a third transistor for inverting and amplifying the collector terminal output voltage of the second transistor and outputting the amplified voltage to the horizontal deflection unit.

Therefore, the present invention generates an geometry distortion correction signal by using a plurality of transistors, thereby making it possible to implement a circuit at a lower cost.

Description

Circuit for compensating geometry distortion in a monitor

The present invention relates to a geometry distortion correction circuit for correcting geometric distortion (hereinafter referred to as geometry distortion GD) of a screen generated in a color display tube (CDT).

In general, a color display device focuses and accelerates hot electrons emitted from R, G and B electron guns, and collides with R, G and B fluorescent surfaces through a point on a shadow mask to form pixels, and sawtooth currents are applied to vertical and horizontal deflection coils. Flowing to form a two-dimensional screen.

Since the color display device requires very precise operation in order to form a high density pixel on a narrow screen, various correction devices such as a purity magnet, a convergence magnet, and the like are mounted on the neck portion of the CRT. In order to prevent image quality deterioration by magnetism, element coils are provided in the panel portion of the CRT.

Geometry Distortion (GD), as described above, is a CRT-specific geometric distortion. For monitors, the geometry of the screen is set up so that the edges of the image appear straight when viewed from a distance (typically 50 cm). To this end, most monitors allow you to adjust the screen's geometry distortion through pincushion control and trapezoidal control.

Here, pincushion control changes the entire bow-in or bow-out on the vertical edge of the screen, while trapper-dial control is used between the top and bottom of the screen. Convert the Width Ratio.

On the other hand, in the CRT, the size of the screen depends on the amount of deflection (the larger the deflection amount, the larger the screen, and the smaller the deflection amount, the smaller the screen), and the deflection amount is roughly expressed as in Equation 1 below.

Here, 'B' is the magnitude of the magnetic field, which is proportional to the product of the number of turns of the deflection coil and the current (i _dy ) flowing in the coil, l 'Is the length of the deflection coil, and' L 'is the distance from the deflection point to the fluorescent surface. 'Va' is also the anode voltage of the water tube. In the above equation 1, when the voltage of the anode is constant, 1 l Since L and L are fixed constants, the amount of deflection varies according to 'B', and since the number of turns of the deflection coil has a fixed constant value, the amount of deflection is usually determined according to the current i _dy flowing in the deflection coil.

Therefore, the geometrical structure of the monitor screen can be corrected by adjusting the current flowing in the deflection coil. A conventional circuit for performing pincushion control is applied to a user's key input as shown in FIG. Therefore, the current flowing through the deflection coil is adjusted.

Referring to FIG. 1, the horizontal output transistor Q1 is turned on and off according to the horizontal drive signal H. drive to switch the B + voltage applied through the FBT primary winding, and at the same time, the damping diode Dd and the retrace capacitor. A sawtooth current flows through the horizontal deflection coil by the action of (Cr), the horizontal deflection coil (HY), and the like. At this time, the S-shaped correction capacitor Cs and the linearity correction coil Lin are connected to the horizontal deflection coil H.Y to correct the horizontal linearity.

That is, the S-shaped correction capacitor and the linearity correction coil correct the sawtooth current to be S-shaped to prevent the peripheral portion of the screen from appearing longer than the center portion of the screen. When the S-corrected sawtooth current flows through the horizontal deflection coil, As the deflection angular velocity at the periphery of is smaller than the deflection angular velocity at the center, the amount of deflection at the periphery and the center of the screen becomes equal.

In addition, the horizontal size control signal (H.size ') output from the microcomputer 170 is amplified by the first op amp (OP1), the pincushion signal output from the pincushion signal generator 160 is the second op The buffer is buffered in the amplifier OP2, and the DC level is blocked by the DC voltage blocking capacitor C2 and then loaded on the constant DC voltage V _DC in the third op amp OP3. That is, a parabola waveform having a DC voltage of 0 V is applied to node A as shown in FIG. _2A , and a parabola waveform having a DC voltage of V _DC is applied to node B as shown in FIG. Is approved.

The generated parabolic waveform and the horizontal size control signal are combined in the fourth op amp OP4, and the parabola waveform loaded on the DC voltage V _DC is applied to the horizontal size control signal H.size '. The summation is applied to the geometric distortion correction signal as shown in FIG. The geometric distortion correction signal generated as described above varies the sawtooth wave current flowing in the horizontal deflection coil HY so that the size of the horizontal screen is constant and the screen size is constant at the top, bottom, and center.

However, the geometry distortion correction circuit as described above uses a plurality of op amps, which are integrated circuits, which causes a problem of increasing the price of the monitor.

Accordingly, the present invention has been made to solve the problems of the prior art as described above, by implementing a circuit using a transistor instead of an op amp to provide a geometry distortion correction circuit of the monitor that can be used to compensate for the geometric distortion at a low price Its purpose is to.

In order to achieve the above object, the circuit of the present invention loads the pincushion signal output from the pincushion signal generator to the horizontal size control signal output from the microcomputer to generate a geometry distortion correction signal, and horizontally corrects the correction signal. A geometry distortion correction circuit of a monitor for outputting a deflection unit to a sawtooth wave current flowing through a horizontal deflection coil, the monitor comprising: a push-pull amplifier for amplifying a horizontal scale control signal output from the micom; A first transistor biased to decrease the emitter current from the driving power supply when the signal level of the amplified horizontal scale control signal output from the push-pull amplifier increases; When the emitter current of the first transistor decreases, the emitter current from the driving power source increases and the DC voltage of the collector stage is increased, and the pincushion signal input to the base stage is inverted and amplified and output through the collector stage. A second transistor; And a third transistor inverting and amplifying the collector terminal output voltage of the second transistor and outputting the amplified voltage to the horizontal deflection unit.

1 is a circuit diagram showing a circuit for compensating for geometric distortion (GD) in the related art.

2 is a waveform diagram of each sub-signal of FIG. 1;

3 is a circuit diagram illustrating a circuit for correcting geometry distortion GD according to the present invention.

* Explanation of symbols for the main parts of the drawings

110: main power supply 120: DC-DC converter

130: FBT 140: horizontal drive unit

150: horizontal deflection unit 160: pincushion signal generation unit

170: microcomputer 180: video preamplifier

190: video power amplifier Q31, Q32: push-pull amplifier

Q33, Q34, Q35: transistor

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

3 is a diagram illustrating a geometry distortion correction circuit of a monitor according to the present invention, in which a geometry distortion correction circuit carries a pincushion signal output from a pincushion signal generator to a horizontal size control signal output from a microcomputer to correct geometry distortion. A signal is generated and the correction signal is output to the horizontal deflection unit 150 so that the sawtooth current flowing through the horizontal deflection coil is varied.

Referring to FIG. 3, the geometry distortion correction circuit includes push-pull amplifiers Q31 and Q32 that amplify the horizontal size control signal output from the microcomputer, and an amplified horizontal size control signal output from the push-pull amplifiers Q31 and Q32. The first transistor Q33 is biased so that the emitter current from the driving power supply Vcc decreases when the signal level increases, and when the emitter current of the first transistor Q33 decreases, the driving power supply Vcc decreases. As the emitter current increases, the second transistor Q34 which is biased to increase the DC voltage of the collector stage and inverts and amplifies the pincushion signal input to the base stage and outputs through the collector stage, and the second transistor Q34 And a third transistor Q35 for inverting and amplifying the collector stage output voltage and outputting the amplified voltage to the horizontal deflection unit 150.

In addition, a resistor R31 is connected between the push-pull amplifiers Q31 and Q32 and the base terminal of the first transistor Q33, and the resistor R33 is connected between the base terminal of the first transistor Q33 and the driving power supply Vcc. Connect The emitter terminal of the first transistor Q33 and the emitter terminal of the second transistor Q34 are connected to each other. A resistor R34 is connected between the common contact point and the driving power supply Vcc. A resistor R35 is connected between the base end of the second transistor Q34 and the driving power supply Vcc, and a capacitor C31 is connected between this common contact and the ground line. The pincushion signal is applied to the base terminal of the second transistor Q34 through the resistor R36.

The collector end of the second transistor Q34 and the base end of the third transistor Q35 are connected. A capacitor C32 is connected and fed back between the base end and the collector end of the third transistor Q35, and the first transistor is connected. A resistor R32 is connected between the base end of Q33 and the collector end of the third transistor Q35. The collector terminal voltage of the third transistor Q35 is input to the horizontal deflection unit 150.

Here, the first transistor Q33 and the second transistor Q34 are pnp type transistors constituting a current mirror circuit, and the third transistor Q35 is an emitter ground npn type transistor for amplification.

Referring to the operation of the present invention configured as described above are as follows.

When the user adjusts the horizontal size of the screen to a large size, the horizontal size control signal (H.size) output from the microcomputer increases, which is amplified by the push-pull amplifiers Q31 and Q32 and then passed through the resistor R31 to the first transistor. It is applied to the base end of Q33. That is, the base terminal voltage of the first transistor Q33 increases, and the emitter current of the first transistor Q33 flowing from the emitter terminal of the first transistor Q33 to the collector terminal through the resistor R34 decreases. The emitter current of the second transistor Q34 flowing from the emitter end of the second transistor Q34 to the collector end through the resistor R34 is increased.

As such, when the emitter current of the first transistor Q33 is increased, the DC voltage applied to the collector terminal is increased, and the pincushion signal of the parabola waveform is loaded on the DC voltage. That is, the pincushion signal output from the pincushion signal generator is applied to the base terminal of the second transistor Q34 through the resistor R36 to vary the base current of the second transistor Q34, and the second transistor ( As the collector current is varied according to the base current of Q34), the collector voltage of the second transistor Q34 is loaded with a parabolic waveform pincushion signal on a DC voltage according to the horizontal size control signal.

The collector terminal voltage of the second transistor Q34 is amplified by the third transistor Q35 and a geometry distortion correction signal is output through the collector terminal of the third transistor Q35. It is inputted to change the sawtooth wave current flowing in the horizontal deflection coil. That is, as the amount of deflection increases, the horizontal size of the screen increases, and pincushion distortion of the screen is corrected.

On the other hand, if the user adjusts the horizontal size of the screen smaller, the microcomputer outputs a horizontal voltage adjustment signal of a low voltage. That is, the base voltage of the first transistor Q33 output from the push-pull amplifiers Q31 and Q32 is lowered. At this time, the emitter current of the first transistor Q33 is increased and the emitter of the second transistor Q34 is increased. The current decreases so that the DC voltage at the collector end of the second transistor Q34 is lowered.

The pincushion signal of the parabola waveform is loaded on the DC voltage and output to the collector terminal of the second transistor Q34. The signal is amplified by the third transistor Q35 and then applied to the horizontal deflection unit 150. The geometry distortion correction signal output from the collector terminal of the third transistor Q35 becomes a pincushion signal having a low DC voltage according to the horizontal size control signal (H.size). It becomes smaller and the pincushion distortion is corrected.

As described above, the circuit of the present invention generates an geometry distortion correction signal by using a plurality of transistors, so that a circuit at a lower cost can be realized.

Claims (1)

The pincushion signal output from the pincushion signal generator is loaded on the horizontal size control signal output from the microcomputer to generate the geometry distortion correction signal, and the correction signal is output to the horizontal deflection unit so that the sawtooth wave current flowing in the horizontal deflection coil is varied. In the monitor's geometry distortion correction circuit, A push-pull amplifier for amplifying the horizontal scale control signal output from the microcomputer; A first transistor biased to decrease the emitter current from the driving power supply when the signal level of the amplified horizontal scale control signal output from the push-pull amplifier increases; When the emitter current of the first transistor decreases, the emitter current from the driving power source increases and the DC voltage of the collector stage is increased, and the pincushion signal input to the base stage is inverted and amplified and output through the collector stage. A second transistor; And And a third transistor for inverting and amplifying the collector terminal output voltage of the second transistor and outputting the same to the horizontal deflection unit.