JPH0448876A - Cathode ray tube focusing circuit - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a dynamic focus circuit for a cathode ray tube.

[Conventional technology]

In the conventional device, electrode pieces constituting a quadrupole lens as shown in Japanese Unexamined Patent Publication No. 63-203063 are formed. 1st. In a cathode ray tube equipped with an electron gun having a second focusing electrode, the first focusing voltage adjustment variable is used to supply desired DC voltages to the first and second electrodes from the flyback transformer DC voltage generating electrode. A resistor and a second focusing voltage adjustment variable resistor are arranged in parallel, and in series there are a high voltage side DC voltage generating electrode, a low voltage side,
A resistor is connected between the reference voltages, and a parabolic dynamic focus voltage is superimposed on the first focusing electrode via a capacitor. Further, a smoothing capacitor is inserted between the reference voltages to prevent the parabolic voltage superimposed on the first electrode from leaking to the second electrode.

[Problem to be solved by the invention]

In the above conventional technology, when trying to supply a vertically periodic parabolic signal from a parabolic AC voltage source to the first focusing electrode, the impedance time constant of the AC couple capacitor and the DC voltage supply resistor network is Vertical period 4~
Must be 5 times or more.

Otherwise, the vertically periodic parabolic voltage will not be superimposed on the first focusing electrode through the AC coupling capacitor.

On the other hand, when the receiver receives a signal where a part of the screen is bright, it is known that the 7-node voltage decreases in this part.

Generally, the DC component of the first focused voltage is supplied by dividing the anode voltage using the resistor network, but the ripple component correlated to the anode voltage appearing in the first focused voltage is, conversely, It is smoothed out by the voltage dividing resistor network impedance and the AC couple capacitor time constant.

The main electron lens is configured by the potential difference between the first focusing electrode and the anode electrode, and the entire focus is adjusted, but in some bright areas, the focus voltage/anode voltage ratio shifts to a high value, causing focus deterioration. There was a problem.

An object of the present invention is to prevent focus deterioration even in partially bright areas.

[Means to solve the problem]

In order to achieve the above object, a voltage corresponding to a brightness signal corresponding to an anode voltage ripple component is superimposed on the first focusing electrode together with a parabolic voltage for dynamic focusing.

The second focusing electrode is connected to the anode electrode through a capacitor.

[Effect]

The focus voltage/anode voltage ratio is kept constant by the voltage corresponding to the brightness signal superimposed on the first focusing electrode, and focus does not deteriorate.

In addition, by connecting the second focusing electrode and the anode electrode with a capacitor, the anode voltage ripple is superimposed on the second focusing electrode, and the parabolic voltage for dynamic focusing leaking from the first focusing electrode can be removed. An accurate parabolic voltage can be obtained between the first focusing electrode and the second focusing electrode, and no side effects will be caused to the quadrupole lens.

〔Example〕

Fig. 1 shows an embodiment of the present invention, Fig. 2 shows a receiver screen receiving a locally bright picture, Fig. 3 shows the optimum focus voltage characteristics of a cathode ray tube, and Fig. 4 shows the first focusing electrode. , a configuration diagram of a cathode ray tube electron gun equipped with a second focusing electrode, and FIG. 5 is a diagram of voltage waveforms at various parts of the first one.

Fig. 1, 1...Flyback transformer, 2...Resistor, 3...Second focusing voltage adjustment variable resistor, 4...First
Focusing voltage adjustment variable resistor, 5...resistance, 6...resistance,
7... Capacitor, 9... Capacitor for dynamic focus voltage superposition, 10... Amplifier, 11... Resistor for beam current detection, 12.13... Low pass filter, 14... Braun tube.

The operation of the present invention when a locally bright pattern shown in FIG. 2 is received will be explained with reference to FIGS. 1 and 5.

In FIG. 1, a voltage corresponding to the beam current is detected from the resistor 11. The horizontal component is removed by the low-pass filter circuit 12.13, and an envelope voltage waveform with a vertical period corresponding to the brightness is obtained. Figure 5 is already shown.

Further, a dynamic focus parabolic voltage is supplied from point a. After being combined with the brightness signal, it is amplified by 10 amplifiers. The composite waveform is shown in FIG. 5C.

The composite waveform is superimposed on the first focusing electrode through the AC coupling capacitor 9.

On the other hand, the DC component is divided from the center tap electrode voltage of the flyback transformer by 2 resistors, 4 variable resistors, and 5 resistors.
Supplied.

The first focusing electrode waveform is shown in FIG. 5d.

On the other hand, the ripple component of the anode voltage is superimposed on the second focusing electrode through the capacitor 7.

Similar to the first focused voltage, the DC component is supplied after being divided from the center tap electrode voltage of the flyback transformer by two resistors, three variable resistors, and five resistors. The second focusing electrode waveform is shown in FIG. 5f.

Here, capacitor 7 is a component in which the composite waveform of the dynamic focusing parabolic voltage and brightness signal supplied to point d of the first focusing electrode leaks to the second focusing electrode through variable resistors 3 and 4 and resistor 6. It also has the role of smoothing by this resistance impedance and the integral action of the 7 capacitors.

Here, the brightness is newly obtained from the beam current inspection resistor 11 superimposed on the first focusing electrode so that it has the same waveform as the anode voltage ripple component supplied from the anode electrode to the second focusing electrode through the seven capacitors. By approximating the voltage waveform by integrating 12 resistors and 13 capacitors,
Accurately and efficiently between the first focusing electrode and the second focusing electrode,
A parabolic voltage can be obtained and an accurate quadrupole lens can be constructed.

In addition, by superimposing the anode voltage ripple component and an approximate voltage waveform on the first focusing electrode as described above, the focus voltage/anode voltage ratio can be kept constant and the main lens can operate normally. It will not deteriorate.

Also, if the connection of the capacitor 7 is changed from between the second focusing electrode and the anode in the first embodiment to between the second focusing electrode and the reference voltage, this is shown in FIG. 2.

Since focus can be expected to be improved on a locally bright screen, this will be explained using FIGS. 6 and 7.

If the entire screen is dark, such as when receiving text from a computer,
This is a well-known technique because it obtains the dynamic focusing effect of a quadrupole lens without any side effects as in the conventional example, but it will be explained first.

In this case, the ripple voltage of the anode electrode (G4) depending on the screen content is small.

Resistance 2. The ripple voltage corresponding to the screen brightness, which is superimposed on the DC voltage supplied to the first focusing electrode through the first focusing voltage adjustment variable resistor 4, is also reduced by the capacitor 9.
Even if smoothed by , the focus voltage/anode voltage ratio does not change, and there is no focus deterioration due to the main lens.

Furthermore, the almost parabolic voltage (the brightness component is not superimposed on the C voltage because the screen is dark) applied to the first focusing electrode through the capacitor 9 does not appear on the second focusing electrode because it is smoothed by the capacitor 7, and does not appear on the first focusing electrode. By creating a parabolic potential difference between the second focusing electrodes, it is possible to improve focus at the periphery of the screen as in the known example.

When a locally bright screen shown in FIG. 2 is received, a brightness signal is generated at b, and this component is added to the parabolic voltage and is applied to the first focusing electrode.

The second focusing electrode voltage is due to the smoothing effect of the capacitor 7.
There is only a direct current component, and the first focusing electrode.

A voltage corresponding to the parabolic voltage+brightness is applied between the second focusing electrodes.

The relationship between the first focusing voltage and the second focusing voltage is shown in FIG.

In the bright part of the screen, there is a potential difference between the two electrodes.

Compared to the dark case, it becomes larger and the quadrupole lens effect becomes stronger, resulting in more overfocus.

Here, the optimal focus voltage characteristic of a general cathode ray tube is the third
It is generally known that in the high beam current region, it is necessary to lower the focus voltage to achieve overfocus.

In this example, when the screen is dark, the focus ratio is kept constant, and in the high beam current region, the focus deterioration of the main lens consisting of the anode electrode and the first focusing electrode is suppressed, and the quadrupole lens is It can be brought into an overfocused state, and can be used to match the focus characteristics of general cathode ray tubes, and can be expected to improve focus.

〔Effect of the invention〕

According to the present invention, compared to the prior art, the number of parts and cost are hardly increased, and in particular, the connection position of the capacitor connected to the second focusing electrode only needs to be changed, resulting in an inexpensive construction.

[Brief explanation of the drawing]

FIG. 1 is a diagram of an embodiment of the present invention, FIG. 2 is a diagram of a receiver screen that receives a locally bright pattern, FIG. 3 is a diagram of optimum focus voltage characteristics of a cathode ray tube, and FIG. 4 is a diagram of the first focusing electrode, Second
A configuration diagram of a cathode ray tube electron gun equipped with a focusing electrode, FIG. 5 is a voltage waveform diagram of each part of the first electron gun, FIG. 6 is a diagram of a second embodiment of the present invention, and FIG. 7 is a diagram of the first focusing of FIG. It is a voltage and a 2nd focused voltage relationship diagram. 1...Flyback transformer. 3... Second focusing voltage adjustment variable' resistor, 4... First
Focusing voltage adjustment variable resistor, 7... Anode voltage ripple superimposition capacitor, 9... Dynamic focus voltage superimposition capacitor, compilation 3. Compiled diagram

Claims (1)

[Scope of Claims] In a cathode ray tube equipped with an electron gun having first and second focusing electrodes in which electrode pieces constituting first and quadrupole lenses are respectively formed, the first and second electrodes are provided with A first focusing voltage adjusting variable resistor and a second focusing voltage adjusting variable resistor are arranged in parallel to supply desired direct current voltages from the flyback transformer direct current voltage generating electrodes, respectively,
A resistor is connected in series between the high-voltage DC voltage generation electrode and the low-voltage reference voltage, and a parabolic voltage and a voltage depending on the brightness are superimposed on the first focusing electrode via a capacitor. , a cathode ray tube focusing circuit characterized in that the second focusing electrode is connected to a cathode ray tube anode electrode through a capacitor. In a cathode ray tube equipped with an electron gun having first and second focusing electrodes in which electrode pieces constituting a two- and four-pole lens are respectively formed, a flyback transformer direct current is connected to the first and second electrodes. In order to supply desired DC voltages from the voltage generating electrodes, a first focusing voltage adjusting variable resistor and a second focusing voltage adjusting variable resistor are arranged in parallel, and the high voltage side DC voltage is connected in series with the first focusing voltage adjusting variable resistor and the second focusing voltage adjusting variable resistor. A resistor is connected between the generation electrode and the low-voltage reference voltage, and a parabolic voltage and a voltage depending on the brightness are superimposed on the first focusing electrode via a capacitor, and the second focusing electrode is connected to the reference voltage. A cathode ray tube focus circuit characterized by being connected with a capacitor.