JPS63252069A - Dynamic focus correction circuit for flat picture tube - Google Patents

Abstract

PURPOSE:To attain the correction of dynamic focus over the entire fluorescent screen with a simple circuit constitution by constituting a dynamic focus correction circuit of a flat picture tube by a signal inverting amplifier circuit. CONSTITUTION:The level of an intermediate voltage of a horizontal deflection coil 1 and a DC blocking capacitor 2 is set by a variable resistor 3 and the result is fed to a signal inverting amplifier circuit 4. The output of the signal inverting amplifier circuit 4 is superimposed on a focus power supply 7 and the result is fed to a focus electrode G3.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a dynamic focus correction circuit for a flat picture tube in which the central axis of an electron gun is not perpendicular to the phosphor screen.

2. Description of the Related Art Conventionally, picture tubes have generally been constructed such that the center of the phosphor screen is located on the same axis as the central axis of the electron gun, and is perpendicular to the phosphor screen. In picture tubes with such a configuration, the distance from the electron gun to the phosphor screen does not vary greatly;
In the case of a flat picture tube, the phosphor screen 15 is arranged approximately parallel to the electron gun 14, as shown in the plan view in Figure 4 and the cross-sectional view in Figure 5. , the electron beam is in the range B from the person, and the dynamic focus correction signal is a in FIG. 6. Further, in horizontal scanning, since the positions at the same distance from the electron gun are broken lines C and D, the dynamic focus correction signal for obtaining the optimum focus on the phosphor screen is b. Therefore, the dynamic focus correction signal shown in FIG. 6C, which is obtained by superimposing the correction signal a for the horizontal scan on the correction signal a for the vertical scan, is used as the dynamic focus correction signal.

FIG. 7 shows a block diagram of a conventional dynamic focus correction circuit. The horizontal deflection pulse signal from the horizontal deflection pulse generator 14 is shown in FIG.
If the horizontal deflection angle has a certain angle, the horizontal deflection angle changes with the vertical scanning period, so keystone correction is performed and the result is as shown in the figure. This horizontal deflection pulse is passed through a Q-secondary integrating circuit 168, where it is second-order integrated and outputted as a waveform output as shown in FIG. The level of this signal is set using a variable resistor 16, and the signal is inputted to a signal inversion circuit 17, and the output of the signal inversion circuit as shown in FIG. Focus correction was being performed.

Problems to be Solved by the Invention However, in such a configuration, the horizontal and vertical directions of the phosphor screen! In order to correct dynamic focus in all 100 directions, a quadratic integration circuit and a signal inversion circuit are required.
There was a problem that the circuit became complicated and the cost increased.

SUMMARY OF THE INVENTION The present invention overcomes the above problems and provides a dynamic focus correction circuit that can correct dynamic focus over the entire area of a phosphor screen with a simple circuit configuration.

Means for Solving the Problems The dynamic focus correction circuit of the present invention that solves the above problems utilizes the midpoint voltage between the horizontal deflection coil and the DC blocking capacitor of the horizontal deflection circuit, and uses this midpoint voltage to invert and amplify the signal. The purpose is to obtain a dynamic focus correction signal by inverting and amplifying the signal in the circuit.

In the present invention, the midpoint voltage between the horizontal deflection coil and the DC blocking capacitor of the horizontal deflection circuit is a parabolic wave with a horizontal deflection period, and the signal is keystone-corrected with the vertical deflection period. This is approximately similar to the output waveform of the quadratic integration circuit in . Therefore, dynamic focus correction can be performed by supplying this midpoint voltage waveform to a signal inversion amplifier circuit and superimposing the output signal of the signal inversion amplifier circuit on the focus electric image of the flat picture tube.

Embodiment Hereinafter, one embodiment of the present invention will be described based on the accompanying drawings.

FIG. 1 shows a block diagram of a dynamic focus correction circuit according to the present invention. 1 in the diagram is horizontal deflection Koinope 2
is a DC blocking capacitor, and the voltage at the midpoint of its connection point P is set in level by a variable resistor 3 and is supplied to a signal inversion amplifier circuit 4.

Then, the output of the signal inversion amplifier circuit 4 is superimposed on the focus power supply 7 via the capacitor 6, and the focus electrode G3
is applied to.

FIG. 2 shows a circuit diagram of the dynamic focus correction circuit of the present invention. In the figure, 10 is a transistor for signal inversion and amplification, and 8 and 9 are bias resistors. A resistor 13 is connected between the collector of the transistor 1o and the power supply, and a resistor 11 is connected between the emitter and ground of the transistor 1o.

Since the waveforms of each part overlap with those of the conventional example, they will be explained with reference to FIG.

The horizontal deflection pulse output from the horizontal deflection pulse generator 14 is shown in FIG. 3a, and is a keystone corrected pulse. As a result, when a horizontal deflection current is passed through the horizontal deflection coil 1, a voltage as shown in FIG. 3 is generated at the midpoint P.

When this midpoint voltage wave is supplied to the signal inversion amplifier circuit 4 through the variable resistor 3, the signal is inverted and a signal amplified by the ratio of the resistors 11 and 13 is generated at the collector of the transistor 1o. . This output signal is shown in Figure 3C,
This is connected via a capacitor 5 to a power source 7 for the focus electrode.
The dynamic focus is corrected by superimposing it on the current and applying it to the focus electrode G3, thereby obtaining the optimum focus over the entire phosphor screen of the flat picture tube.

By the way, in this embodiment, the dynamic focus correction signal uses the midpoint voltage of the horizontal deflection circuit, so the ratio of the amplitude of the keystone correction signal in the vertical period to the amplitude of the parabolic wave in the horizontal period is as desired. There may be cases where it does not match the dynamic focus correction signal. In that case,
This problem can be overcome by adjusting the amplification degree of the horizontally periodic parabolic wave using a capacitor 12 inserted in parallel with the resistor 11 to generate an optimal dynamic focus correction signal.

Effects of the Invention As described above, the present invention allows the dynamic focus correction circuit of a flat picture tube to be configured only with a signal inverting amplifier circuit, and inverts and increases the midpoint voltage between the horizontal deflection coil and the DC blocking capacitor of the horizontal deflection circuit: p By superimposing the crystal on the focus electrode of the picture tube, dynamic focus correction is performed over the entire area of the phosphor screen, and uniform focus can be obtained. There is a practical effect called a dog.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an embodiment of a dynamic focus correction circuit for a flat picture tube according to the present invention, FIG. 2 is a specific circuit diagram of the same, FIG. 3 is an operational waveform diagram in a conventional example and an embodiment of the present invention, and 4 is a plan view of a flat bridge (quadrant), FIG. 6 is a sectional view of the same, FIG. 6 is a waveform diagram showing the concept of dynamic focus, and FIG. 7 is a block diagram of a conventional dynamic focus correction circuit. 1... Horizontal deflection Koinope 2... DC blocking capacitor, 3... Variable resistor, 4... Signal inversion amplification circuit 9.5.12...・Capacitor, A... Focus voltage, 8, 9, 11, 13...
・Resistor, 10... Transistor, 14... Electron gun, 16... Fluorescent screen. Name of agent: Patent attorney Toshio Nakao and 1 other person
1 Figure 2 Figure 3 (C) Figure 4 Figure 6 --- Figure 7! 5/7

Claims (1)

[Claims] The present invention is characterized in that an inverted amplified output obtained by inverting and amplifying the midpoint voltage between the horizontal deflection coil and the DC blocking capacitor of the horizontal deflection coil to which the horizontal deflection pulse is applied via the DC blocking capacitor is superimposed on the focus electrode of the picture tube. Dynamic focus correction circuit for flat picture tubes.