JPH02170776A - Horizontal dynamic focus circuit - Google Patents

Abstract

PURPOSE:To eliminate a trouble and to prevent the generation of artificial miss by automatically adjusting the phase of a current to flow to a focus coil in order that the phase relation of a horizontal pulse voltage and the current to flow to the focus coil can be made into a necessary phase relation. CONSTITUTION:A phase difference between a horizontal synchronizing signal and the current to flow to focus coils LR, LG, and LB is detected, and by changing the capacity of a variable capacitor C2 according to the phase difference, the phase of the current to flow to the focus coils LR, LG and LB is automatically adjusted in order that the phase relation of a horizontal pulse voltage (a) obtained from a horizontal output circuit and the current to flow to the focus coils LR, LG and LB can be made into the necessary phase relation. Consequently, in the manufacturing stage of the product, a necessity for an adjusting person to adjust the phase to flow to the focus coils does not exist. Thus, the trouble can be eliminated, and even the artificial miss such as an adjustment miss cannot be generated.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a projection television that projects an image onto a large screen, and in particular focuses an electron beam in a monochrome projection tube in the horizontal direction on the screen. This invention relates to a horizontal dynamic focus circuit that achieves just focus at any point.

[Conventional technology]

The conventional horizontal dynamic focus circuit is red (R)
A horizontal pulse obtained from a horizontal output circuit is applied to a resonant circuit consisting of a focus coil, a capacitor, and a coil, which are installed in each of the three monochrome projection tubes corresponding to , green (G), and blue (B). A voltage is applied to cause a current (resonant current) to flow through the focus coil, and the intensity of the magnetic field generated by the focus coil is changed according to each point in the horizontal direction on the screen, thereby focusing the electron beam on each monochrome projection tube. It was adjusted so that any point in the horizontal direction on the screen was in just focus.

Incidentally, as such a horizontal dynamic focus circuit, for example, Japanese Patent Laid-Open No. 55-79573 and Japanese Patent Laid-open No. 56
Examples include those described in Japanese Patent Publication No. -98970.

[Problem to be solved by the invention]

By the way, in general, in a horizontal dynamic focus circuit, if the phase relationship between the horizontal pulse voltage obtained from the horizontal output circuit and the current flowing through the focus coil deviates from the desired phase relationship, in the horizontal direction on the screen,
The just focus point shifts between the center and the periphery. In other words, for example, if you focus so that it is in just focus at the center, it will not be in just focus at the periphery, and conversely, if you focus so that it is in just focus at the periphery, it will not be in just focus at the center. Focus and nara (naru).

Therefore, in the conventional horizontal dynamic focus circuit described above, during the product creation stage, the adjuster observes the waveform of the horizontal pulse voltage obtained from the horizontal output circuit and the waveform of the current flowing through the focus coil using a two-phenomenon oscilloscope. At the same time, the phase of the current flowing through the focus coil is adjusted by varying the inductance of the coil that constitutes the above-mentioned resonant circuit so that the phase relationship between the horizontal pulse voltage and the current flowing through the focus coil becomes the desired phase relationship. That's what I was doing.

However, such a method is time-consuming, and the above-mentioned phase relationship may remain deviated from the desired phase relationship due to human error such as an adjustment error. Furthermore, after such adjustments are made and the product is shipped and delivered to the user, the phase relationship described above may deviate from the desired phase relationship due to variations in the values of each element due to temperature changes or changes over time. And there is no way to correct it,
Users had to continue using it as is.

The purpose of the present invention is to solve the problems of the prior art described above,
An object of the present invention is to provide a horizontal dynamic focus circuit capable of automatically adjusting the phase of a current flowing through a focus coil so that the phase relationship between the horizontal pulse voltage and the current flowing through the focus coil is a desired phase relationship. .

[Means to solve the problem]

In order to achieve the above object, the present invention includes a variable capacitor (or variable coil) as the capacitor (or coil) constituting the resonant circuit, and current detection that detects the current (resonant current) flowing through the focus coil. and phase difference detection means for detecting a phase difference between the detection output of the current detection means and the horizontal synchronization signal.

[Effect]

In the present invention, by changing the capacitance (or inductance) of the variable capacitor (or variable coil) according to the phase difference detected by the phase difference detection means, the horizontal pulse voltage obtained from the horizontal output circuit and the focus The phase of the current flowing through the focus coil can be automatically adjusted so that the phase relationship with the current flowing through the coil becomes a desired phase relationship.

Therefore, according to the present invention, there is no need for an adjuster to adjust the phase of the current flowing through the focus coil during the product creation stage, which saves time and effort, and costs can be reduced accordingly. Further, since human errors such as adjustment errors do not occur, the phase relationship between the horizontal pulse voltage and the current flowing through the focus coil does not remain out of the desired phase relationship.

In addition, even if the above-mentioned phase relationship deviates from the desired phase relationship due to variations in each element value due to temperature changes or changes over time after the product is in the hands of the user, it will be automatically corrected. In the horizontal direction on the screen, the just focus point can be partially set at the center and at the periphery.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

Fig. 1 is a circuit diagram showing one embodiment of the present invention, and Fig. 2 is a circuit diagram showing an embodiment of the present invention.
It is a waveform diagram which shows the main part voltage waveform and main part current waveform of a figure.

In Figure 1, 1 is a horizontal synchronizing signal input terminal, 2 is a phase difference detection circuit, 3 is a horizontal pulse voltage input terminal, R1 is a resistor, R2 is a detection resistor, CI is a coupling capacitor, and C2 is a variable capacitor (variable capacitor). ), Ll is a coil, L is a focus coil provided in a monochrome projection tube (not shown) for red (R), and L is a focus provided in a monochrome projection tube (not shown) for green (G). Coyle, L.

is a focus coil provided in a monochrome projection tube (not shown) for blue (B). In FIGS. 1 and 2, a represents a horizontal pulse voltage obtained from a horizontal output circuit (not shown), and b represents each focus coil LI1. LG,
is the resonant current flowing through Ll.

In this embodiment, when the horizontal pulse voltage a is input from the horizontal pulse voltage input terminal 3, the coil is turned on.

and the combined inductance of the focus coils L, La, Lm, and the combined capacitance of the coupling capacitor C1 and the variable capacitor C2, and the resonant current flows through each of the focus coils LR, LG, and Ll+.

At this time, the resonance current is detected by the detection resistor R2, and its detection output is input to one input terminal of the phase difference detection circuit 2. Further, a horizontal synchronizing signal is input to the other input terminal of the phase difference detection circuit 2. Here, the phase difference detection circuit 2 detects the phase difference between the two input signals and outputs the detection result. The detection output is resistor R,
is converted into a DC voltage according to the detected phase difference, and applied to the variable capacitor C2.

As a result, variable capacitor C2
By changing the capacitance of the resonant current A, the phase of the resonant current A is adjusted so that the phase relationship between the horizontal pulse voltage a and the resonant current A becomes as shown in FIG.

In other words, the phase relationship as shown in FIG. 2 is such that the peak of the resonant current S is located in the middle of the pulse of the horizontal pulse voltage a, and the phase of the horizontal pulse voltage a and the resonant current S is When the relationship has such a phase relationship, the just focus points in the center and the periphery coincide in the horizontal direction on the screen, and there is just focus at any point in the horizontal direction on the screen.

Next, FIG. 3 is a circuit diagram showing another embodiment of the present invention.

In FIG. 3, the same components as in FIG. 1 are given the same reference numerals. In addition, C:l is a capacitor, and L2 is a variable coil consisting of a transformer.

In this embodiment, when the horizontal pulse voltage a is input from the horizontal pulse voltage input terminal 3, the combined inductance of the variable coil L and the focus coils L, L, Ls,
It resonates with the capacitance of the capacitor C1, and its resonance current flows through each focus coil LR, LG, and Lm.

At this time, the resonant current S is detected by the detection resistor R2 in the same manner as in the embodiment shown in FIG. Further, a horizontal synchronizing signal is input to the other input terminal of the phase difference detection circuit 2. Here, the phase difference detection circuit 2 detects the phase difference between the two input signals and outputs the detection result.

The detection output is applied to the primary side of the transformer that constitutes the variable coil L1, so that the inductance on the secondary side changes according to the detected phase difference, and the horizontal pulse voltage a
The phase of the resonant current S is adjusted so that the phase relationship between the resonant current S and the resonant current S is as shown in FIG. Therefore, in this embodiment as well, as in the embodiment shown in FIG. becomes.

(Effects of the Invention) According to the present invention, the phase difference between the horizontal synchronization signal and the current flowing through the focus coil is detected, and the capacity it (or inductance) of the variable capacitor (or variable coil) is changed according to the phase difference. By doing this, the phase of the current flowing through the focus coil can be automatically adjusted so that the horizontal pulse voltage obtained from the horizontal output circuit and the current flowing through the focus coil have a desired phase relationship.

Therefore, there is no need for the adjuster to adjust the phase of the current flowing through the focus coil during the product creation stage.
It requires less time and effort, and costs can be reduced accordingly. Further, since human errors such as adjustment errors do not occur, the phase relationship between the horizontal pulse voltage and the current flowing through the focus coil does not remain out of the desired phase relationship.

In addition, even if the above-mentioned phase relationship deviates from the desired phase relationship due to variations in each element value due to temperature changes or changes over time after the product is in the hands of the user, it will be automatically corrected. In the horizontal direction on the screen, the just focus point can be made to match between the center and the periphery.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram showing one embodiment of the present invention, and Fig. 2 is a circuit diagram showing an embodiment of the present invention.
Waveform diagram showing main part voltage waveform and main part current waveform in figure 3.
The figure is a circuit diagram showing another embodiment of the present invention. Explanation of symbols 1...Horizontal synchronization signal input terminal, 2...Phase difference detection circuit, 3...Horizontal pulse voltage input terminal, R2...Detection resistor, Ct...Variable capacitor, Ll... coil,
LRlLc, Lm... Focus coil, Lt...
Variable coil, a...horizontal pulse voltage, b...resonant current. 12m Agent Patent Attorney Akio Namiki

Claims (1)

[Claims] 1. A horizontal pulse voltage synchronized with a horizontal synchronization signal obtained from a horizontal output circuit is applied to a resonant circuit provided at least in a focus coil, a variable capacitor, and a coil provided in the projection tube. A current is applied to the focus coil, and the magnetic field generated by the focus coil focuses the electron beam on the projection tube so that it is in just focus at any point in the horizontal direction on the screen. The dynamic focus circuit includes current detection means for detecting a current flowing through the focus coil, and phase difference detection means for detecting a phase difference between a detection output of the current detection means and the horizontal synchronization signal, By changing the capacitance of the variable capacitor according to the phase difference detected by the detection means, the focus is adjusted such that the phase relationship between the horizontal pulse voltage and the current flowing through the focus coil becomes a desired phase relationship. A horizontal dynamic focus circuit characterized by adjusting the phase of the current flowing through the coil. 2. A horizontal pulse voltage synchronized with a horizontal synchronizing signal obtained from a horizontal output circuit is applied to a resonant circuit provided at least in the projection tube, including a focus coil, a capacitor, and a variable coil. A horizontal dynamic focus circuit that applies a current to a focus coil and uses a magnetic field generated by the focus coil to focus an electron beam on the projection tube so that it is in just focus at any point in the horizontal direction on the screen, Current detecting means for detecting a current flowing through the focus coil; and phase difference detecting means for detecting a phase difference between a detection output of the current detecting means and the horizontal synchronizing signal, By changing the inductance of the variable coil according to the phase difference,
A horizontal dynamic focus circuit, characterized in that the phase of the current flowing through the focus coil is adjusted so that the phase relationship between the horizontal pulse voltage and the current flowing through the focus coil is a desired phase relationship.