KR100393794B1 - Dynamic focus waveform-shaping circuit - Google Patents

Abstract

The dynamic focus waveform shaping circuit according to the present invention is a parabola wave (secondary curve waveform) in order to generate a bath tub-shaped drive waveform, particularly in a horizontal (wide) or flat CRT having an aspect ratio of 16: 9. In addition, since the circuit becomes complicated and the number of components increases by generating drive waveforms having higher order components such as 4th, 6th or higher order components, the present invention solves the horizontal and vertical synchronization signals. First and second input terminals for inputting a triangular wave synchronous to the first and second multipliers for generating first and second parabola waves from the input triangular wave, and an output voltage of the first multiplier A nonlinear amplifier for nonlinear amplifying the amplitude of the first and second amplifiers for amplifying the output of the nonlinear amplifier and the output of the second multiplier, An adder for adding the outputs of the first and second amplifiers, and a high voltage amplifier for amplifying the output of the adder at a high voltage up to an amplitude required for the focus electrode of the CRT, and forming the bath tub by only generating a secondary component. Generate waveforms.

Description

Dynamic focus waveform shaping circuit {DYNAMIC FOCUS WAVEFORM-SHAPING CIRCUIT}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dynamic focus waveform shaping circuit in a TV or other display device using a cathode ray tube, and more particularly, to a dynamic focus waveform shaping circuit suitable for a horizontal (wide) tube or a flat cathode tube having an aspect ratio of 16: 9.

In a display device using a CRT, a dynamic focus circuit is used to obtain good focus through the central portion and the entire peripheral portion of the screen. The dynamic focus circuit is a circuit for forming a focus voltage applied to the focus electrode of the CRT. In particular, the dynamic focus circuit generates a parabola waveform voltage such that a high voltage is applied to the CRT.

1 shows a conventional general dynamic focus circuit. The dynamic focus circuit is a circuit for producing a parabola wave for dynamic focus from a triangle wave synchronized with horizontal and vertical synchronization signals. The multiplier 1 inputs a triangular wave synchronized by a horizontal synchronizing signal, and the multiplier 2 inputs a triangular wave synchronized by a vertical synchronizing signal, and the multiplier 1 and the multiplier 2 input the input triangular wave. Is converted into a parabola wave (secondary curve waveform) as shown in the figure. The converted parabola waves are amplified again by the amplifier 3 and the amplifier 4, and the horizontal and vertical components are added in the adder 5. The added horizontal and vertical components are then amplified at high voltage to the amplitude required for the focus electrode of the CRT in the high pressure amplifier 16 and applied to the focus electrode.

However, in recent CRTs, the aspect ratio becomes wider from 4: 3 to 16: 9, and the screen tends to be flattened. Thus, in order to obtain focus around the CRT, in particular, a horizontal dynamic focus waveform is used. It needs to be shaped like a bath tub.

FIG. 2 shows an example of a conventional circuit for generating such bath tub-shaped parabola waves. The conventional circuit is a circuit for inputting a triangular wave synchronized by a horizontal synchronizing signal, using a first multiplier 1a for generating a secondary parabola wave and an output of the multiplier 1a as inputs. A second multiplier 1b for generating a parabolic wave, a third multiplier 1c for generating a sixth-order parabola wave using the output of the multiplier 1b, and the first to third multipliers 1a. , 1b, 1c consists of three amplifiers 3a, 3b, 3c for properly amplifying the respective outputs.

Accordingly, a drive waveform having not only a secondary waveform but also a fourth and sixth order higher order components is generated from the input triangular wave, and the waveform is added to the adder 5 to obtain a bath tub-like waveform. have.

However, since the dynamic focus circuit of the system shown in FIG. 2 forms a drive waveform having a higher order component having a fourth order, sixth order, or more, the circuit becomes complicated and the number of parts increases.

The present invention provides a dynamic focus waveform shaping circuit capable of generating, with a simple circuit configuration, an optimal bath tub-shaped correction waveform required by a long-length CRT tube or a flat CRT tube having an aspect ratio of 16: 9. It aims to do it.

MEANS TO SOLVE THE PROBLEM In order to solve the said subject, the dynamic focus waveform shaping circuit of this invention is the 1st and 2nd input terminal for inputting the triangular wave synchronized by the horizontal and vertical synchronizing signal, and the 1st and 2nd from the input triangular wave. First and second multipliers for generating parabola waves, nonlinear amplifiers for nonlinear amplifying the amplitude of the output voltage of the first multiplier, first and second amplifiers for amplifying the output of the nonlinear amplifier and the output of the second multiplier A second amplifier, an adder for adding the outputs of the first and second amplifiers, and a high voltage amplifier for amplifying the output of the adder at a high voltage to an amplitude required for the focus electrode of the CRT.

Here, the nonlinear amplifier operates to reduce the amplification factor of the amplitude below a predetermined voltage.

With the above configuration, the dynamic focus waveform shaping circuit of the present invention does not require multiple multipliers for generating higher order components, such as fourth order and sixth order, and the basb stub only needs to be used with one multiplier for generating second order components. It is possible to form a focus voltage having a bath tub shaped waveform.

The nonlinear amplifier may further include a bias circuit for providing a predetermined direct current (DC) bias voltage to the output of the multiplier, a buffer circuit for current amplification, a voltage divider and a rectifier for providing a nonlinear amplification rate, and an operation of the rectifier device. It consists of a simple circuit including a second bias circuit for setting points.

1 shows a conventional dynamic focus circuit.

FIG. 2 shows a conventional dynamic focus circuit for obtaining a bath tub shaped waveform. FIG.

3 is a block diagram showing the configuration of the dynamic focus circuit of the present invention.

4A and 4B are diagrams illustrating the operation of the circuit of FIG. 3.

FIG. 5 is a circuit diagram illustrating a first embodiment of the nonlinear amplifier of FIG. 3.

6A and 6B are diagrams illustrating the operation of the circuit of FIG. 5.

**** Explanation of symbols for the main parts of the drawing ****

1, 2: multiplier 3, 4: amplifier

5: adder 6: high voltage amplifier

7: nonlinear amplifier

Fig. 3 is a block diagram showing the basic configuration of the dynamic focus waveform shaping circuit of the present invention. As shown here, in the circuit for processing triangular waves synchronized by the horizontal synchronizing signal, a nonlinear amplifier 7 is inserted between the multiplier 1 and the amplifier 3. The horizontally and vertically synchronized triangular waves are parabolic waves by being squared by their respective multipliers, but the horizontal component is further manipulated by the nonlinear amplifier 7 after the rate of change of the waveform is further amplified, respectively. , It is added.

4A and 4B schematically show the input / output characteristics regarding the amplitude (voltage) of the nonlinear amplifier 7. 4A shows the input / output characteristic (solid line) in the case of inputting the DC wave, and FIG. 4B shows the input / output characteristic (solid line) in the case of inputting the 2nd wave (parabola wave). As shown in Figs. 4A and 4B above, the nonlinear amplifier 7 of the present invention is an amplifier which operates to reduce the amplification factor below a certain voltage. Therefore, when parabola waves are input to the nonlinear amplifier 7 as shown in Fig. 4B, when the voltage value becomes lower than the change point A, the amplification factor decreases, so that the amplitude is compressed and consequently the floor is flat. A bath tub shaped waveform is obtained.

FIG. 5 is a circuit diagram showing one embodiment of the nonlinear amplifier 7 shown in FIG. The circuit consists of a capacitor (C), a resistor (R1), a power supply (V1), a bias circuit for applying a suitable direct current (DC) bias voltage to the transistor (Q1), the transistor (Q1), the resistor (R5) A buffer circuit comprising: a resistor (R2), a resistor (R3) (voltage divider circuit) for providing a nonlinear amplification factor, a diode (D) (rectifier), and a direct current (DC) for setting an operating point of the diode (D). It consists of the power supply V2 (2nd bias circuit). In addition, transistor Q2 is an output buffer transistor.

The operation of the circuit will be described below using the waveform diagrams of FIGS. 6A and 6B.

The horizontal parabola wave input to the circuit shown in FIG. 5 is biased by the capacitor C, the resistor R1 and the voltage source V1, and is buffered by the transistor Ql and the resistor R5. And is input to the base of the transistor Q2 via the resistor R2. FIG. 6A shows the waveform of point a (a ') in the circuit of FIG.

On the other hand, since the voltage divider circuit consisting of the voltage source V2, the diode D and the two resistors R2 and R3 is provided between the point a 'and the base of the transistor Q2, the transistor In response to the instantaneous voltage of the emitter waveform of Q1, the rectifying action of the diode occurs. That is, because of the partial pressure by the resistor R2 and the resistor R3 while the diode is conducting. The base voltage of the transistor Q2, that is, the voltage waveform at point b, is as shown by the solid line in FIG. 6B. In other words, the amplification factor is decreased in the portion below the voltage V2, whereby a flat bottom waveform is obtained.

As shown in FIG. 6B, the flatness is B as the amplitude width between the minimum amplitude when the nonlinear amplification is not performed and the voltage V2, and the amplitude width between the voltage V2 as the minimum amplitude when the linear amplitude is nonlinearly amplified and B. In the case of ', the amplitude width B' is represented by the following equation.

B '= BR3 / (R2 + R3)

Therefore, as the resistance R3 decreases, the flatness increases, and when the resistance R3 becomes zero, the amplitude becomes constant at the voltage V2 value. In addition, the change point A shown in FIG. 4 may be arbitrarily set by the voltage V1 and the voltage V2.

As described above, by using the nonlinear amplifier having the configuration shown in Fig. 5, the change point A of the bath tub shape can be arbitrarily selected by setting the voltage source, and the flatness below the waveform is determined by the resistor ( R2) and the partial pressure of the resistor R3. Thus, the circuit can generate a dynamic focus drive waveform suitable for a planar CRT having a 16: 9 aspect ratio from parabola waves having only secondary components.

Conventional dynamic focus waveform shaping circuits use not only parabola waves (secondary curve waveforms) but also 4 to generate a bath tub-shaped drive waveform in a wide CRT or flat CRT having a 16: 9 aspect ratio. It was necessary to produce tea, 6th order and more higher order components. In contrast, the dynamic focus waveform shaping circuit of the present invention can generate the bath tub-shaped drive waveform only by generating a secondary component, and also adds a small nonlinear circuit to a good basstub. The bath tub waveform can be obtained, contributing to the improvement of the peripheral focus.

Claims (3)

First and second input terminals for inputting triangular waves synchronized by horizontal and vertical synchronization signals, First and second multipliers for generating first and second parabola waves from the input triangular wave, A nonlinear amplifier for nonlinear amplifying the amplitude of the output voltage of the first multiplier; First and second amplifiers for amplifying an output of the nonlinear amplifier and an output of the second multiplier; An adder for adding outputs of the first and second amplifiers, A dynamic focus waveform shaping circuit comprising a high voltage amplifier that amplifies the output of the adder to a required voltage at a focus electrode of a CRT with a high voltage. 2. The dynamic focus waveform shaping circuit of claim 1, wherein the nonlinear amplifier operates to reduce an amplification factor of an amplitude below a predetermined voltage. 3. The nonlinear amplifier according to claim 1 or 2, wherein the nonlinear amplifier comprises a bias circuit for applying a predetermined direct current (DC) bias voltage to the output of the first multiplier, a buffer circuit for current amplification, and a voltage divider for providing a nonlinear amplification factor. And a rectifying element and a second bias circuit for setting an operating point of the rectifying element.