JPH06268886A - Dynamic focus circuit - Google Patents

Abstract

(57) [Summary] [Object] The present invention relates to a dynamic focus circuit for supplying a dynamic focus voltage to a cathode ray tube, and it is necessary to always obtain an optimum dynamic focus voltage corresponding to an arbitrary plurality of frequencies. To aim. [Structure] A frequency-voltage (F-V) converter 1, a squaring circuit 2, and an analog multiplier 3 are used to change the amplitude of the sawtooth wave voltage corresponding to an arbitrary frequency, and further, an adding circuit 4 is provided. The configuration of the amplifier circuit 5 is such that an optimum dynamic focus voltage corresponding to a plurality of arbitrary frequencies is always generated and applied to the focusing electrode 7 of the cathode ray tube 6.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dynamic focus circuit for supplying a dynamic focus voltage to a cathode ray tube.

[0002]

2. Description of the Related Art In recent years, dynamic focus circuits have been
Focused images have been improved by applying a parabolic wave voltage synchronized with the deflection pulse to the focusing electrode.

A conventional dynamic focus circuit will be described below. FIG. 4 shows a block circuit configuration of a conventional dynamic focus circuit. In FIG. 4, 4 is an adder circuit and 5 amplifier circuit. Reference numeral 6 is a cathode ray tube, and 7 is a focusing electrode.

The operation of the dynamic focus circuit configured as described above will be described below.
Now, the parabolic wave voltage synchronized with the deflection pulse is amplified by the amplifier circuit 5 and applied to the focusing electrode 7 of the cathode ray tube 6 to improve the focused image. However, at this time, the parabolic wave voltage synchronized with the deflection pulse is amplified by the amplifier circuit 5.
As a result, a phase delay occurs with respect to the actual deflection pulse, so that the voltage applied to the focusing electrode 7 of the cathode ray tube 6 is not an optimum waveform for improving the focus image. Therefore, a sawtooth wave voltage having a constant amplitude synchronized with the deflection pulse is added to the parabolic wave voltage by the adder circuit 4 to improve the phase delay.

[0005]

However, in the sawtooth voltage synchronized with the deflection pulse, the amplitude required to actually improve the phase delay changes depending on an arbitrary frequency and is not constant. Therefore, it is necessary to change the amplitude of the sawtooth voltage according to an arbitrary frequency. Therefore, each time the frequency is changed at an arbitrary frequency, the amplitude of the sawtooth wave voltage synchronized with the deflection pulse must be readjusted by a variable resistor or the like. Also,
This device that cannot be adjusted cannot cope with a plurality of arbitrary frequencies, and has a drawback that an optimum waveform cannot be obtained due to phase delay or phase advance due to frequency change.

In view of the above problems, the present invention makes the amplitude of the sawtooth wave necessary for improving the phase delay variable according to the change of the frequency, and appropriately improves and adjusts the phase delay with respect to arbitrary plural frequencies. The present invention provides a dynamic focus circuit that makes it unnecessary to obtain an optimum waveform.

[0007]

In order to solve the above problems, the dynamic focus circuit of the present invention squares the voltage converted by the frequency-voltage (F-V) converter by the squaring circuit and synchronizes with the deflection pulse. A sawtooth wave voltage having a constant amplitude is multiplied by an analog multiplier, the parabolic wave voltage synchronized with the deflection pulse is added and amplified, and the result is applied to the focusing electrode of the cathode ray tube.

[0008]

According to the present invention, the amplitude of the sawtooth wave voltage synchronized with the deflection pulse is changed corresponding to a plurality of arbitrary frequencies to improve the phase delay according to the frequency, and the dynamic focus of the optimum waveform is always provided. The voltage is obtained.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to screens.

In FIG. 1, 1 is frequency-voltage (F-
V) conversion circuit, 2 is a squaring circuit, and 3 is an analog multiplier. Reference numeral 4 is an adder circuit, and 5 is an amplifier circuit. Reference numeral 6 is a cathode ray tube, and 7 is a focusing electrode.

The circuit of the present invention constructed as above will be described.
The operation will be described with reference to FIG. First, any lap
When the wave number f is input, the F-V conversion circuit 1 outputs V_FAs
Is output. This output V_FSquared by the square circuit 2
The sawtooth wave with a constant amplitude synchronized with the deflection pulse.
Pressure V_SIs multiplied by the analog multiplier 3 and output V_AGot
It This output V_AParabolic wave electric power synchronized with deflection pulse
Pressure V_PAnd output voltage V_KIs generated by the amplifier circuit 5.
Output voltage AV_KAmplify to. This output voltage AV _KThe shade
Dynamic force applied to the focusing electrode 7 of the polar tube 6
Obtain the residue voltage.

At this time, the analog multiplier 3 changes the sawtooth voltage V _S having a constant amplitude into a voltage V _A whose amplitude varies according to the frequency, whereby the output voltage is automatically adjusted for a plurality of arbitrary frequencies. Optimally adjusted.

In the squaring circuit 2, the voltage V _F corresponding to an arbitrary frequency is squared because the voltage for which the phase delay is to be improved is the parabolic wave voltage V _P , and therefore the amplitude required for the improvement is required. This is because has a square characteristic with respect to changes in frequency.

A relational diagram of the output voltage waveform at this time is shown in FIG.
As shown in FIG. 2 shows the case where the frequency is high (for example, the frequency is 65 kHz), and FIG. 3 shows the case where the frequency is low (for example, the frequency is 15.75 kHz).

As is apparent from FIGS. 2 and 3, the sawtooth voltage required to improve the phase delay is variable depending on the frequency, and by controlling the amplitude, there is always no phase delay at any plural frequencies. An optimum voltage waveform can be obtained as the dynamic focus voltage.

As described above, according to this embodiment, by providing the F-V conversion circuit 1, the squaring circuit 2, the analog multiplier 3 and the adding circuit 4, the phase lag corresponding to a plurality of arbitrary frequencies is improved. It is possible to automatically obtain the optimum dynamic focus voltage.

Although the voltage V _F corresponding to the frequency is squared by the squaring circuit 2 in the embodiment, the squaring circuit 2 can be omitted if the change in the amplitude required to improve the phase delay is linear. .

[0018]

As described above, according to the present invention, by providing a circuit for changing the amplitude of a sawtooth wave voltage having a constant amplitude and synchronized with a deflection pulse so as to follow the plurality of arbitrary frequencies, the present invention can be applied to a plurality of arbitrary frequencies. Thus, it is possible to realize an excellent dynamic focus circuit that can always obtain an optimum dynamic focus voltage.

[Brief description of drawings]

FIG. 1 is a block diagram of a dynamic focus circuit according to an embodiment of the present invention.

FIG. 2 is a waveform diagram showing waveforms of respective parts and their relationship when the frequency is high in an embodiment of the present invention.

FIG. 3 is a waveform chart showing waveforms of respective portions and their relationship when the frequency is low in one embodiment of the present invention.

FIG. 4 is a block diagram of a conventional dynamic focus circuit.

[Explanation of symbols]

 1 F-V converter 2 Square circuit 3 Analog multiplier 4 Adder circuit 5 Amplifier circuit 6 Cathode ray tube 7 Focusing electrode

Claims (1)

[Claims] 1. A frequency-voltage converter for converting a frequency into a voltage, a squaring circuit having the output thereof as an input, and an analog multiplier having a sawtooth voltage of constant amplitude synchronized with the output of the squaring circuit and the frequency as an input. A dynamic focus circuit comprising: an adder circuit having an input of a parabolic wave voltage synchronized with an output of the analog multiplier and a frequency; and an amplifier circuit having an output of the adder circuit as an input.