JPS63146662A - Dynamic focus circuit - Google Patents

Abstract

PURPOSE:To generate a proper focus voltage in horizontal direction depending on the horizontal amplitude by utilizing a horizontal pulse generated in a horizontal deflection coil so as to generate a horizontal parabolic waveform. CONSTITUTION:A horizontal pulse is fed across a series circuit comprising the series connection consisting of an inductance element L3 and a capacitive element C6 to generate a horizontal parabolic voltage synchronously with the horizontal pulse across the capacitive element C6. In modulating a focus voltage of a CRT 2 by the horizontal parabolic wave obtained in this way, a dynamic focus effect is obtained. That is, the amplitude of the said horizontal parabolic wave is nearly proportional to the raster horizontal amplitude and an optimum correction waveform is obtained in the dynamic focus.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a dynamic focus circuit for always maintaining an optimal focus level, particularly in the center and peripheral areas in the horizontal direction, of a raster of a cathode ray tube (hereinafter abbreviated as CRT). It is something.

2. Description of the Related Art A conventional dynamic focus circuit has a structure as shown in FIG. 7, which is a cascade connection of transistors. The horizontal parabolic waveform is input to the base of the transistor TR2 in the first stage of the cascade, is amplified by the cascade output transistor TR1, and the G3 electrode (focus electrode) of the CRT is modulated with the amplified horizontal parabolic waveform. The horizontal parabon waveform that modulates is
The waveform was as shown in FIG. 8, in which the amplitude did not change in the vertical period.

Problems to be Solved by the Invention Therefore, in this conventional circuit, it is fine if the raster on the CRT screen is a sister as shown in Fig. 4, where the horizontal amplitude is constant with the vertical period, but In a case like the one shown in Fig. M5, in which the horizontal parabolic wave (Fig. 2) whose amplitude is constant in the vertical period is not the optimal correction waveform.

If the raster on the CRT screen is modulated with a vertical period as shown in Figure 5, the amplitude of the horizontal parabolic waveform modulating the G3 electrode must be a waveform modulated with a vertical period as shown in Figure 6. No.

In view of such conventional problems, the present invention provides a circuit that can perform optimal dynamic focus correction by modulating the amplitude of a horizontal parabolic waveform used in a dynamic focus circuit according to the magnitude of horizontal vibration 1@. The purpose is to

Means for Solving the Problems In the present invention, a horizontal parabolic waveform is created using a horizontal pulse generated in a horizontal deflection coil that matches the magnitude relationship of horizontal amplitudes, and is supplied to a CRT.

Operation In the present invention, a reduced or increased pressure of the horizontal pulse generated at both ends of the horizontal deflection coil is received by a circuit in which an inductance element and a capacitance element are connected in series. A sawtooth current that is approximately proportional to the horizontal pulse wave flows through this inductance element, and a horizontal parabolic wave is generated at both ends of the capacitive element. The amplitude of this horizontal parabolic wave is approximately proportional to the raster horizontal amplitude, and becomes an optimal correction waveform in dynamic focus.

Example An embodiment of the present invention is shown in FIGS. 1 and 2. FIG.

FIG. 2 shows an embodiment of the main part, which is a circuit consisting of an inductance element L3 and a capacitance element C6 connected in series. A horizontal pulse is applied to both ends of this series circuit, and a horizontal parabolic voltage (
(Fig. 3) can be generated. By modulating the focus voltage terminal of ωT2 with this horizontal parabola wave, a focus effect is obtained.

A horizontal pulse generated in the horizontal deflection coil L2 is input to the transformer T2 in order to step up or step down the voltage. By receiving the horizontal pulse generated on the secondary side of the transformer T2 by the Chigok coil L3 and the capacitive element C6, a horizontal parabolic voltage can be obtained across the capacitive element Ce. This horizontal parabolic wave modulates the focus voltage of the CRT 2 through the waveform transmission capacitive element C7.

Note that in FIG. 1, TR3 is a horizontal output transistor TR.
4 is a transistor for horizontal amplitude modulation, Dl is a damper diode, C3 is a horizontal resonance capacitor, C4 is a figure-of-eight correction capacitor, T1 is a flyback transformer, and Cs is a DC cut capacitor.

Effects of the Invention As described above, according to the dynamic focus circuit of the present invention, it is possible to provide an appropriate focus voltage in the horizontal direction according to the horizontal amplitude.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram of a dynamics focus circuit in an embodiment of the present invention, Fig. 2 is a circuit diagram showing main parts of an embodiment of the invention, and Fig. 3 is a diagram for explaining the operation of Fig. 2. Waveform diagrams, Figures 4 and 5 are front views showing the raster shape on the CRT tube surface, and Figure 6 is a waveform diagram showing the dynamic focus correction wave necessary for the raster shape as shown in Figure 6. 7
The figure is a circuit diagram of a conventional dynamic focus circuit, and FIG. 8 is its output waveform diagram. C6...Capacitor, C7...Capacitor, L2...Horizontal deflection coil, L3...
...Coil, T1...FBT%T2...
・Horizontal Hals transfer transformer, TR3...Horizontal deflection output transistor, TR4...Transistor for horizontal amplitude modulation. M I E
Figure 2 @ Figure 3 Figure 4 Figure 5 Figure 6

Claims (1)

[Claims] A horizontal pulse generated in the horizontal deflection coil is supplied to a series connection circuit of an inductance element and a first capacitance element, and the first
A dynamic focus circuit characterized in that one end of the capacitive element and a cathode ray tube electrode are connected by a second capacitive element.