JPH0353671A - Dynamic focus circuit - Google Patents

Abstract

PURPOSE:To obtain an inexpensive dynamic focus circuit by employing a side pin cushion distortion correction circuit applying vertical parabolic modulation to a capacitor voltage for S-shape correction. CONSTITUTION:A side pin cushion distortion correction circuit 6 arranged in parallel with a horizontal output circuit 25 side by side is employed for a large sized television receiver and the circuit 6 uses a vertical parabolic wave voltage generating circuit 18 to apply vertical parabolic modulation to a voltage of a resonance capacitor 15 to apply vertical parabolic modulation similarly to a voltage of an S-shape correction capacitor 12 being a power supply for horizontal deflection current thereby applying side pin cushion distortion correction. The voltage of the resonance capacitor 15 is a horizontal blanking pulse subject to vertical parabolic modulation and the voltage is fed to a horizontal parabolic wave voltage forming circuit 7 where the voltage is subject to horizontal parabolic modulation to obtain a horizontal.vertical dynamic focus voltage. Thus, an inexpensive dynamic focus circuit is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a focus circuit used in a cathode ray tube, and particularly to a dynamic focus circuit for obtaining just focus over the entire screen of a cathode ray tube. [Prior art] The optimal focus voltage for a cathode ray tube needs to be higher at the periphery than at the center of the screen. For this reason, in the past, optimal focus was obtained by superimposing horizontal and vertical periodic parabolic wave voltages on the DC focus voltage. As a conventional example using such a method, for example, in Japanese Patent Application Laid-open No. 60267/1983, as shown in FIG.
A horizontal deflection pulse generation circuit 2 solely for forming horizontal retrace pulses is provided in parallel with the first horizontal deflection circuit 1 having the horizontal deflection coil 6, and the obtained horizontal retrace pulses are transmitted to the vertical parabolic wave voltage generation circuit. The vertical period parabola wave generated by 3 is amplitude-modulated via the power supply voltage control circuit 4. Then, the horizontal retrace pulse amplitude-modulated by the parabolic wave with the vertical period is converted into two pulses by the focus correction voltage forming circuit 5.
A dynamic focus voltage in both the horizontal and vertical directions was obtained by integrating the two consecutive times, and this voltage was superimposed on the DC focus voltage and applied to the focus electrode of the cathode ray tube (not shown) to obtain the optimal focus. ．． [Problems to be Solved by the Invention] In the above conventional example, in addition to the normal horizontal deflection circuit, there is also a horizontal deflection pulse generation circuit 2 for generating a new horizontal retrace pulse; Since a vertical parabolic wave generating circuit 3 and a generating circuit 5 are required for parabolic modulation, the entire circuit becomes expensive. In addition, in the conventional example, the voltage of the S-shaped correction capacitor, which is the power source of the horizontal deflection current that has become mainstream in recent large TVs, is vertically parabola modulated and applied to the side pin distortion correction circuit that corrects the side pin distortion. , is not considered. An object of the present invention is to provide a dynamic focus circuit that is inexpensive and can be applied to a side pin distortion correction circuit.

[Means to solve the problem]

The above object is achieved by connecting a horizontal parabolic modulation circuit to the side pin distortion correction circuit.

[Effect]

The second resonant capacitor voltage of the side pin distortion correction circuit arranged in parallel with the horizontal output circuit is
This is a horizontal retrace pulse with vertical parabola modulation. By using the above voltage and performing horizontal parabolic modulation with a horizontal parabolic wave voltage forming circuit, dynamic focus voltages in both horizontal and vertical directions can be obtained. [Example] Hereinafter, an example of the present invention will be explained based on the figures. FIG. 1 is a circuit diagram showing one embodiment of the present invention. In the figure, the side pin distortion correction circuit 6 arranged in parallel with the horizontal output circuit 25 is
This is a well-known circuit that is generally used in large-sized televisions. This circuit 6 is a vertical parabola wave voltage generation circuit 18 that vertically parabola modulates the voltage of the resonant capacitor 15, and similarly vertically parabola modulates the voltage of the S-shaped correction capacitor 12, which is the power source of the horizontal deflection current. Side pin distortion correction is performed. Here, the voltage of this resonant capacitor 15 is a horizontal retrace pulse that has been subjected to vertical parabola modulation, and by horizontally parabola modulating this voltage in the horizontal parabola wave voltage forming circuit 7, horizontal and vertical dynamic focus can be achieved. You can get the voltage. Note that the diode 19 is for rectification, and sets the resonance wave number of the capacitor 20, the primary inductance of the transformer 22, and the resistor 21 to a horizontal frequency,
The turns ratio of the transformer 22 may be set so that the secondary voltage of the transformer 22 becomes 500 to 600 Vp-p, which is the required focus voltage. The obtained dynamic focus voltage is superimposed on the DC focus voltage via the superposition capacitor 23 and applied to the focus electrode of the cathode ray tube 24.

In this embodiment, the transistor 13 is provided in the side pin distortion correction circuit 6, but it does not need to be provided separately, and the horizontal parabolic wave voltage forming circuit 7 also includes a transistor amplification after two stages of integration in addition to the LC resonance circuit. Needless to say, this is also possible with circuits. [Effects of the Invention] As described above, according to the present invention, an inexpensive dynamic focus circuit can be realized by using a side pin distortion correction circuit in which the S-curve correction capacitor voltage is vertically parabola modulated. It can be done.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing an embodiment of the present invention, and the diagram showing the second focus circuit is a conventional dynamic circuit diagram. 1...Horizontal deflection circuit 2...Horizontal deflection pulse generation circuit 3...Vertical parabolic wave voltage generation circuit 4...Power supply voltage control circuit 5...Focus correction voltage formation circuit 6...Side pin distortion Correction circuit 7...Horizontal parabolic wave voltage generation circuit 18...Vertical parabolic wave voltage generation circuit 2

Claims (1)

[Claims] 1. A first series circuit comprising a horizontal deflection coil and a first capacitor connected in series between a cathode ray tube, a first connection point and a second connection point; a horizontal output circuit comprising a resonant capacitor, a first damper diode, and a horizontal output transistor connected in parallel with each other;
A second series circuit formed by connecting a coil and a second capacitor in series, a second resonant capacitor, a second damper diode, and a switching element are connected in parallel to each other between the connection point and the ground point. and a side pin distortion correction circuit that corrects side pin distortion in the cathode ray tube by vertically parabola modulating the voltage of the second resonant capacitor. The horizontal retrace pulse voltage, which is the voltage of the resonant capacitor No. 2, is parabolically modulated with a horizontal period to obtain a dynamic focus voltage in both horizontal and vertical directions, and the dynamic focus voltage is superimposed on the DC focus voltage to A dynamic focus circuit characterized by the addition of a focus electrode.