JPS60160775A - Cathode-ray tube device - Google Patents

Abstract

PURPOSE:To obtain a deflection characteristic the same as that when no external magnetic field exists by providing a detector detecting the external magnetic field, and controlling a deflection current in response to the detected output. CONSTITUTION:Magnetic field detectors 7, 8 detect the external magnetic field in X and Y directions around a cathode-ray tube and the detected output amplified by amplifiers 9, 10 controls respectively a horizontal deflection amplifier 3 and a vertical deflection amplifier 4. The deflection is corrected to a value subtracting the effect of the external magnetic field so as to obtain an object deflection after the said external magnetic field is superimposed on the magnetic field due to the said deflection current in advance in both X and Y directions. Thus, the effect of the external magnetic field is cancelled substantially and the deflection characteristic as designed is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a cathode ray tube device such as a color television.

[Prior art]

Display devices using such cathode ray tubes have the disadvantage that display quality tends to deteriorate due to the influence of external magnetic fields.

To prevent this, conventional magnetic shielding using iron plates has been used, but in order to obtain a sufficient shielding effect (C), it is necessary to surround the cathode ray tube with a considerably thick iron plate, which poses problems in terms of weight and workability. It was small.

[Object and structure of the invention]

The present invention has been made in view of the above circumstances, and its object is to provide a cathode ray tube device that eliminates the influence of external magnetic fields without using a thick iron plate for shielding.

In order to achieve such an object, the present invention provides a detector that detects an external magnetic field, and detects a deflection current according to the detected force, and only when the external magnetic field is affected by the external magnetic field. The same deflection characteristics as without it can be obtained! This is corrected to a value that is

The present invention will be explained in detail using "Practice 1" below.
Embodiment] FIG. 1 is a configuration diagram showing an embodiment of the present invention.

In the figure, 1 is a horizontal synchronization circuit that constitutes a normal television circuit, 2 is also a vertical synchronization circuit, 3 is a horizontal deflection amplifier, and 4 is a vertical 3'fI width amplifier. A current is supplied to the deflection coil 5 and the vertical deflection coil 6 to generate a deflection magnetic field.

In addition to this, 7 is an X-direction magnetic field detector that detects the magnetic field strength and direction in the X direction, that is, the horizontal direction, which is parallel to the screen around the cathode ray tube (not shown), and 8 also detects the magnetic field strength and direction in the Y direction. This is a Y-direction magnetic field detector.

Both detectors I and 8 are magnetic field detectors using electromagnetic coils, Hall elements, magnetoresistive elements, etc.
placed around the cathode ray tube.

Therefore, these two magnetic field detectors 7 and g detect the external magnetic fields in the X and Y directions around the cathode ray tube, and the amplified detection outputs are sent to the horizontal deflection amplifiers 3 and 10, respectively. Controls the vertical deflection amplifier 4. For example, when not affected by an external magnetic field, the output of the vertical deflection amplifier 4, that is, the vertical deflection current is as shown in FIG.
), and when there is an external magnetic field in the Y direction as shown in (b) of the same figure, the vertical deflection current shown in (a) of the same figure is applied. In this case, the actual vertical deflection magnetic field is a superposition of the magnetic field generated by the deflection iC6 flow and the external magnetic field, and therefore good deflection characteristics cannot be obtained. Therefore, each of the above-mentioned detectors 7 and g detects this external magnetic field, and in anticipation of its influence, a vertical deflection current is generated as shown in FIG. Then, the effect of the external magnetic field is subtracted so that the desired amount of deflection is obtained. The same goes for the X direction.
When the detected external magnetic field exists on the positive side of the X direction, it is corrected to the negative side according to its magnitude to cancel it out, and when it exists on the negative side of the X direction, it is corrected to the negative side according to the magnitude. Correct to the positive side accordingly.

This substantially cancels out the influence of the external magnetic field and allows the deflection characteristics as designed to be obtained.

FIG. 3 shows a specific configuration example when the present invention is applied to an actual television circuit. In the figure, reference numeral 100 denotes a normal television circuit, and the synchronizing signal SY, although omitted in the figure, is extracted from the received signal that has been converted to an intermediate frequency and subjected to image detection in the video receiving circuit by 11 frequency separation. It is input to the synchronization separation circuit 11, where the horizontal synchronization signal -gsyH and the vertical synchronization signal syv are separated by frequency separation.
and are input to a horizontal deflection circuit 101 and a vertical deflection circuit 102, respectively. Each synchronization circuit supplies a sawtooth current for generating a deflection magnetic field to the horizontal deflection coil LH and the vertical deflection coil LV in synchronization with the synchronization signal. The vertical deflection circuit 102 includes a vertical oscillation circuit 12 that generates a sawtooth current, a vertical drive circuit 13 that increases its output 11a, and a vertical output circuit 14 that supplies the sawtooth current to the deflection coil LV. While the vertical synchronizing signal extracted through an integrating circuit, which is a type of low-pass filter, does not contain pulse noise and can therefore directly control the vertical oscillation circuit 12, the horizontal synchronizing signal extracted through a type of bypass filter does not contain any pulse noise. Pulse noise etc. are mixed in. For this reason, a synchronous AFC is used that synchronizes with the average of several synchronous signals with the same t+; A phase detection circuit 18 and an integration circuit 19 are provided. In addition, FBT
is a fly bank transformer for anode high voltage generation, CI,
Cm is a capacitor.

On the other hand, 200 is an X-direction correction circuit that corrects the horizontal deflection current in consideration of the contribution of an external magnetic field in the X-direction, that is, the horizontal direction. The X-direction external magnetic field is detected by the X-direction magnetic field detector 21, amplified by the amplifier 22, and the amplified detection output is applied to the primary coil of the transformer TI by the X-direction correction output port w524. X direction gain adjustment circuit 23
Due to the non-uniformity of the external magnetic field, the X-direction magnetic field detector 21,
This is to compensate for the amount that cannot be completely captured by the amplifier 22 and the X-direction correction output circuit 24 by manually adjusting the gain of the correction circuit. One end of the secondary coil of the transformer TI is connected to the horizontal deflection coil LH which is connected to the horizontal output circuit 1T, and when the input to the primary coil increases, the horizontal deflection current flowing through the horizontal deflection coil LH increases. decreases, and if the above input decreases, the horizontal deflection current increases.

, 300 is a Y-direction correction circuit that corrects the deflection current by considering the contribution of the external magnetic field in the Y-direction, that is, the vertical direction; Gain opening circuit 33, Y direction correction output port [334:I
, - and the output of this Y-direction correction output circuit 34 are input to the primary coil, and the secondary coil is constituted by a transformer T3 connected to the other end of the vertical deflection coil LV. If the detection output of the Y-direction magnetic field detector 31 increases, the vertical deflection current flowing through the vertical deflection coil decreases, and if the detection output decreases, the vertical deflection current increases.

〔Effect of the invention〕

As described above, according to the present invention, a detector for detecting an external magnetic field is provided, and the supine current is corrected to a value obtained by subtracting the contribution of the external magnetic field according to the detection output of the detector. By doing so, it is possible to always obtain a constant good display quality regardless of the presence of an external magnetic field or its variation ωl. Further, it can be realized by adding a breakout υ-output device and extremely simple circuit construction, and problems such as an increase in fJ:Ifi and difficulty in processing that occur when using a thick iron plate for shielding do not occur.

[Brief explanation of the drawing]

Fig. 1 is a configuration diagram showing an embodiment of the present invention, Fig. 2(a)
~(C) is a waveform diagram for detailed explanation of the present invention, the third
The figure shows an actual example of applying the present invention to a television circuit #IIi! , is a diagram. 5. LH/Fist: Horizontal deflection coil, 6. LV...
Vertical deflection coil, 7, 21-...-X direction magnetic field detector,
8, 31...Y-direction magnetic field detector, 14...Vertical output circuit, 17゛・Φ--Horizontal output circuit, 23...11
-X direction gain adjustment circuit, 24...X direction correction output circuit, 33...Y direction gain adjustment circuit, 34...
ψY direction correction output circuit. Patent applicant Yamatake Honeywell Co., Ltd. Agent Masaki Yamakawa (and 2 others) Figure 1 Figure 2 Figure 3 Z[J[J

Claims (1)

[Claims] A detector that detects the magnetic field around the cathode ray tube in horizontal and vertical directions parallel to the screen, and a horizontal and vertical deflection current according to the detection output of each detector, and a current in the absence of an external magnetic field detected by the detector. 1. A cathode ray tube device comprising: a correction circuit that corrects the value by subtracting the influence of the external magnetic field on the amount of deflection.