KR900008166Y1 - Focusing tube for brown tube - Google Patents

Abstract

No content.

Description

CRT focus circuit

1 is a circuit diagram showing a conventional horizontal dynamic focus circuit.

2 is a circuit diagram showing an embodiment of the present invention.

FIG. 3 is a waveform diagram showing voltage waveforms of important parts in the circuit of FIG. 2. FIG.

* Explanation of symbols for main parts of the drawings

1: horizontal drive transistor 2: horizontal output transistor

3: damper diode 4,5: resonant capacitor

6: horizontal deflection yoke 7: S-shaped correction capacitor

8: power supply 9: flyback transformer

10: CRT 11: resistance

12: focus VR 13,20: resistance

14,15,18 Condenser 16: Amplifier

17: trance 19: coil

21: diode

The present invention relates to a CRT focus circuit in a television receiver.

In CRTs such as television receivers, the most suitable focus voltage is usually increased as it moves from the center of the screen to the periphery. For this reason, a technique has been devised to obtain the most suitable focus over the entire CRT by superimposing a parabolic voltage such as a horizontal period and a vertical period on a DC focus voltage. This technique is called dynamic focus here.

Since the CRT has a ratio of 3 to 4 in the vertical and horizontal dimensions, a circuit for compensating for this is particularly known since the deterioration of the focus in the horizontal direction is particularly severe.

1 shows a conventional horizontal dynamic focus circuit.

1, (1) is a horizontal drive transistor, (2) is a horizontal output transistor, (3) is a damper diode, (4) and (5) are respective resonant capacitors, (6) is a horizontal deflection yoke, (7) is an S-shaped correction capacitor, (8) is a power supply, (9) is a flyback transformer, (10) is a CRT, (11) is a resistor, (12) is a focusing variable resistor, (13) is a resistor, Reference numerals 14 and 15 denote capacitors, 16 amplifiers and 17 transformers, respectively.

In FIG. 1, only the parabolic voltage of a horizontal period is taken out from the condenser 15 from the S-shaped correction capacitor 7. In FIG. This is amplified by the amplifier 16 and sent to the primary side of the transformer 17.

In the transformer 17, amplification and polarity are reversed. This signal is superimposed on the direct current focus voltage through the condenser 14.

In the conventional focus circuit which requires such an amplifier 16 or a transformer 17, a high voltage semiconductor element is required for the amplifier 16, and the transformer 17 must also be a high voltage insulation type, resulting in an expensive circuit.

An object of the present invention is to provide an inexpensive horizontal dynamic focus circuit.

In order to achieve the above object, according to the present invention, a vibration circuit made of a capacitor, a coil, and a resistor is made, and a horizontal retrace period pulse is introduced into the circuit to generate a vibration voltage of a horizontal period, and this is superimposed on a DC focus voltage to provide horizontal dynamics. This is the focus voltage.

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

2 is a view showing an embodiment of the present invention.

In FIG. 2, the same reference numerals are used for the first and the same parts, and detailed description thereof will be omitted. In the same figure, the circuit shown in the dotted line is the dynamic focus voltage generating portion according to the present invention.

3 shows the voltage waveforms of the respective portions in the second dotted line.

Next, a detailed description will be given with reference to FIGS. 2 and 3.

The horizontal retrace period pulse ⓐ taken between the resonant capacitors 4 and 5 is supplied to the capacitor 18 via the diode 21. By this signal, the capacitor 18 is charged up to the peak of the pulse. Thereafter, the diode 21 is cut off between the syringes. Charge of the charged capacitor 18 begins to discharge through the coil 19 and the resistor 20.

The time constant of the closed circuit composed of the capacitor 18, the coil 19, and the resistor 20 is set so as to satisfy (resistance 20 < 2 > < 4 (coil 19 / capacitor 18), and the vibration frequency is almost It should be 15.734KHz.

The waveform thus obtained is shown in FIG. 3B.

This driving voltage is regarded as a pseudo parabola voltage and is superimposed on the focus voltage through the condenser 14.

According to the present invention, if the horizontal retrace period pulse voltage is increased, a large pseudo parabola voltage can be obtained simply, thereby eliminating the need for expensive semiconductor devices and transformers, and making the dynamic focus circuit inexpensive.

Claims (1)

Resistance division circuits 11, 12, and 13 for generating the focus voltage of the CRT 10 flyback pulse generators 1 through 9 for generating horizontal flyback pulses, having a resonant frequency equal to the horizontal frequency, and the coil 19 And a resonant circuit (18, 19, 20) in which a series connection circuit consisting of a resistor (20) and a first capacitor (18) are connected in parallel, and the first capacitor (18) is charged with a peak voltage of a horizontal flyback pulse. And a second capacitor 14 for supplying the diode 21 which cuts off during the horizontal scanning period and the resonance voltage generated in the resonance circuit to the resistance splitting circuits 11, 12 and 13 so as to superimpose the resonance voltage on the focus voltage. Focus circuit of CRT including).