JPS6253997B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a landing correction device for a color television receiver that corrects mislanding caused by the earth's magnetism in the color television receiver, and in particular, the present invention relates to a landing correction device for a color television receiver that corrects mislanding caused by the earth's magnetism. This makes it possible to correct mislanding. Generally, color cathode ray tubes in color television receivers emit light in three colors by modulating the current values of three electron beams that stimulate phosphors that emit light in the three primary colors of red, green, and blue in response to signals from broadcasting stations. The brightness is adjusted to reproduce any color contained within the triangle formed by these three colors on the chromaticity diagram. However, due to the influence of the earth's magnetic field, the electron beams are bent depending on the installation location of the color television receiver and the orientation of the screen of the color cathode ray tube, and the electron beams are slightly deviated from a predetermined position on the phosphor surface, resulting in mislanding. That is, FIG. 1 shows the state of mislanding in Tokyo, and as shown in FIG. 1, different mislandings occur depending on the orientation of the screen of the television receiver. The broken line in FIG. 1 indicates the area where the electron beam hits due to the action of the horizontal force of the earth's magnetism, and the difference between the solid line (when the electron beam hits correctly) and this broken line is the amount of mislanding. As is clear from Figure 1, there is a certain regularity to this mislanding caused by the geomagnetic field; when the color cathode ray tube is in the east and west directions, the electron beam has a trapezoidal deviation, and when the color cathode ray tube is in the south and north directions, it is a parallelogram. Also, the positions of the northeast, southeast, northwest, and southwest directions form a composite shape of the shapes of these east and west directions and the south and north directions.
In order to automatically correct such mislanding due to the earth's magnetism, a geomagnetism detection device that accurately detects the amount of earth's magnetism is required. Generally, in a color television receiver, magnetic flux leaks from the horizontal deflection magnetic field, power supply, horizontal output transformer, flyback transformer, etc. Since the magnetic field caused by the Earth's magnetism is stronger than the magnetic field caused by the Earth's magnetism, it has been extremely difficult to accurately detect the magnetic field caused by the Earth's magnetism. In view of this, the present invention is designed to accurately detect the magnetic field caused by the earth's magnetism and automatically correct mislanding caused by the earth's magnetism. Hereinafter, an embodiment of the landing correction device for a color television receiver according to the present invention will be described with reference to the drawings. In this example, as shown in FIG. 2, two magnetic field detection devices S1 and S1 are used to detect magnetic fields in the 45 degree direction and -45 degree direction, respectively, with respect to the horizontal plane in the tube axis direction a of the color cathode ray tube ₁ . Arrange S ₂ . That is, in this case, the magnetic field detection devices S ₁ and S ₂ are installed so as to detect magnetic fields in directions 90 degrees different from each other. This magnetic field detection device S ₁
And as _S2 , a sensor made of magnetic wire as shown in FIG. 3 is used. This sensor has a magnetic material 3 such as permalloy around a 0.1φ copper wire 2 of approximately 20 μm.
A detection coil 4 is wound on this magnetic material 3 in a relationship perpendicular to the copper wire 2. In this sensor, when the excitation current is flowing through the copper wire 2, the magnetic body 3 is saturated and no external magnetic field is detected, but when the excitation current flowing through the copper wire 2 becomes almost zero, the magnetic body 3 A magnetic flux corresponding to the magnetic field H in the parallel direction flows, and a voltage corresponding to the magnetic flux flowing through the magnetic body 3 is generated between both ends of the detection coil 4. In this case, a magnetic body 3 is placed between both ends of the detection coil 4.
A differential waveform corresponding to the magnetic flux flowing through can be obtained. In the present invention, a sine wave current as shown in FIG. 4A of, for example, 35 kHz, which is asynchronous with the frequency of the current flowing through the horizontal deflection coil of the color cathode ray tube 1, for example, 15.75 kHz, is applied to the sensors S ₁ and S ₂ as an exciting current. It is something that is streamed as. In order to correct mislanding caused by earth's magnetism, four correction coils 5a are installed on the panel of the color cathode ray tube 1, as shown in FIG. 5b, 5c and 5d are arranged. In this case, the correction coils 5a and 5b are arranged in a vertical relationship with each other, and the correction coils 5a and 5b are
The correction coils 5a and 5b are connected in series with their winding directions opposite to each other, so that when a current is passed between the terminals 6a and 6b, the correction coils 5a and 5b generate magnetic fields in opposite directions. In addition, correction coils 5c and 5d are arranged in the vertical direction, and the winding directions of the coils are opposite to each other.The correction coils 5c and 5d are connected in series, and the correction is performed by the current flowing between the power supply terminals 6c and 6d. Magnetic fields in opposite directions are generated by the coils 5c and 5d. In this case, the force F exerted on the electron beam by the magnetic field generated by the correction coils 5a and 5c is as shown in FIG. That is, when a current is passed in the positive direction through the correction coils 5a and 5c, a magnetic field perpendicular to the plane of the paper is generated, which applies a force in the direction shown by arrow F to the electron beam, and the electron beam is bent as shown by the broken line to form a color cathode ray. When viewed from the front of the tube, this electron beam will shift to the right. The electron beam can be shifted in the same manner using the correction coils 5b and 5d. FIG. 6 is a top view of the color cathode ray tube 1. In this example, to correct the mislanding of the color cathode ray tube 1 due to horizontal geomagnetism, the current shown in the table below is used.

This mislanding can be corrected by flowing the following signals to the correction coils 5a, 5b, 5c, and 5d, respectively. That is, in this table, Ia is the current flowing through the correction coil 5a, Ib is the current flowing through the correction coil 5b, Ic is the current flowing through the correction coil 5c, and Id is the current flowing through the correction coil 5d. Also, Io indicates a current of a predetermined magnitude. The relationship between the current flowing through the correction coil and the direction is shown in a diagram as shown in FIG. That is, mislanding caused by horizontal geomagnetism occurring in the color cathode ray tube 1 can be corrected by flowing currents having the relationship shown in FIG. 7 through the respective correction coils. In this case, correction coils 5a and 5b
The currents Ia and Ib flowing through the correction coils 5c and 5d, respectively, are in opposite phase with each other, and the correction currents Ic and Id flowing through the correction coils 5c and 5d, respectively.
Since they are in opposite phase to each other, as shown in _FIG . Currents corresponding to the magnetic field obtained in _{step 2} may be made to flow through the correction coils 5c and 5d connected in series in opposite directions.
In FIG. 8, 13a and 13b indicate current drive circuits, respectively. Next, an embodiment of the landing correction device for a color television receiver according to the present invention will be described with reference to FIG. In Figure 9, 7 is the horizontal deflection frequency, e.g.
An excitation signal generation circuit that generates a sine wave current with a frequency asynchronous to 15.75kHz and a frequency between the harmonics of this horizontal deflection frequency, for example 35kHz, is shown, and the excitation signal obtained at the output side of this excitation signal generation circuit 7 is shown. The output signal of the drive circuit 8 is supplied to the sensor drive circuit 8, and the output signal of the drive circuit 8 is connected to the copper wire ₂ of the sensor S1 as shown in FIG.
supply to. The detection signal obtained by the detection coil 4 of this sensor _S1 is supplied to the input side of a tuned amplifier 9 configured to resonate at a double excitation signal, for example, 70kHz. Note that the tuning frequency of the tuning amplifier circuit 9 is set to a value such that detection of earth's magnetism is not hindered by the influence of the horizontal deflection magnetic field. In this case, the sensor _S1 is arranged so as to detect a magnetic field oriented at 45 degrees with respect to the tube axis a of the color cathode ray tube 1, as shown in FIG. A signal with twice the excitation frequency obtained at the output of the tuned amplifier circuit 9 is transmitted to the synchronous detection circuit 10.
is supplied to one input terminal of the Further, the output signal of the excitation signal generation circuit 7 is supplied to a doubling circuit 11 which doubles the frequency, and a signal of twice the excitation signal frequency, for example 70 kHz, is synchronized with the excitation signal obtained from the output of the doubling circuit 11. It is supplied to the other input terminal of the synchronous detection circuit 10 as a reference signal. The DC voltage obtained from the output of this synchronous detection circuit 10 is supplied to a current drive circuit 13 via a DC amplifier 12 (this DC amplifier 12 also serves as an integrating circuit), and the output signal of this current drive circuit 13 is is connected to ground through a series circuit of correction coils 5a and 5b arranged as shown in FIG. 5 and connected in series in an inverse relationship to each other. The circuit shown in FIG. 9 will be explained with reference to FIG. 4. In FIG. 9, since a sine wave current as shown in FIG. 4A is flowing through the copper wire 2 of sensor S ₁ , the detection coil 4 of sensor S ₁ is connected to sensor S as shown in FIG. When the current flowing through the copper wire _{2 of sensor S 1 is} almost zero, the magnetic flux corresponding to the magnetic field parallel to the copper wire 2 of sensor S 1 intersects, and the output of this detection coil 4 is generated by sensor S ₁ as shown in FIG. 4C. A voltage corresponding to a parallel magnetic field is obtained. In FIGS. 4B and 4C, solid lines indicate the case where the magnetic field is in the positive direction, and broken lines indicate the case where the magnetic field is in the opposite direction. Therefore _, as shown in FIG. 4D, the output of the tuned amplifier circuit 9 is a sine wave signal with an excitation signal frequency of, for example, 70kHz, which is twice the level corresponding to the voltage obtained at the detection coil 4 of the sensor S1. . Also in FIG. 4D, the solid line indicates the case where the magnetic field is in the positive direction, and the broken line indicates the case where the magnetic field is in the opposite direction. Also 2
At the output of the multiplier circuit 11, a sine wave signal having twice the frequency of the excitation signal as shown in FIG. According to the output signal of the circuit 9 and the reference signal of the output of the doubler circuit 11, a DC voltage as shown in FIG. 4F is obtained. Fourth
Also in Figure F, the solid line shows the case where the magnetic field is in the positive direction, and the broken line shows the case where the magnetic field is in the opposite direction. The DC voltage obtained by this synchronous detection circuit 10 is converted into a current corresponding to this voltage via an amplifier 12 and a current drive circuit 13, and is supplied to correction coils 5a and 5b.
In this case, since the correction coils 5a and 5b are determined based on the voltage obtained at the detection coil 4 of the sensor _S1 , the currents flowing through the correction coils 5a and 5b can have the relationship shown in FIG. Furthermore, if a circuit similar to that described above is formed corresponding to the magnetic flux detection device _S2 shown in FIG. 2, the correction currents shown in FIG.
It is possible to automatically correct mislanding caused by the earth's magnetic field. Further, in the present invention, the excitation frequency of the sensors S ₁ and S ₂ is asynchronous with the horizontal deflection frequency and is set to a frequency between the harmonics of this horizontal deflection frequency, for example, 35 kHz, and the tuning frequency of the tuned amplifier circuit 9 is set to this harmonic. By setting the frequency, for example 70 kHz, twice the excitation frequency set between the waves, the tuned amplifier circuit 9 does not amplify the horizontal deflection frequency and its harmonics. It is possible to accurately detect the earth's magnetism without detecting the magnetic field due to magnetic flux leaking from a flyback transformer or the like. Furthermore, since the excitation frequency of the sensors S ₁ and S ₂ can be set high, the sensitivity during adjustment can be improved. As described above, according to the present invention, the sensors S ₁ and S ₂
Since the horizontal magnetic field is detected using the frequency of the excitation current supplied to the horizontal deflection frequency as a frequency asynchronous to the horizontal deflection frequency, the earth's magnetism can be detected accurately regardless of the magnetic flux generated by the color television receiver.
According to the present invention, there is an advantage that mislanding caused by the earth's magnetism can be automatically corrected in a good manner. In the above-mentioned embodiment, a sensor as shown in FIG. 3 is used as the magnetic field detection device, but it is of course possible to use other types of magnetic field detection device. Furthermore, it goes without saying that the present invention is not limited to the above-described embodiments, and can take various other configurations without departing from the gist of the present invention.

[Brief explanation of the drawing]

1, 4, and 7 are diagrams for explaining the present invention, FIG. 2 is a diagram showing the relationship between a color cathode ray tube and a magnetic field detection device, and FIG. 3 is an example of a magnetic field detection device. Fig. 5 is a line diagram showing the relationship between the color cathode ray tube and the correction coil, Fig. 6 is a line diagram to explain the correction of the electron beam, and Fig. 8 is a diagram showing the relationship between the magnetic field detection device and the correction coil. FIG. 9 is a connection diagram showing an embodiment of a landing correction device for a color television receiver according to the present invention. 1 is a color cathode ray tube, 5a, 5b, 5c and 5
d is a correction coil, 7 is an excitation signal generation circuit, 9
is a tuned amplifier circuit, 10 is a synchronous detection circuit, 11 is 2
The multiplier circuits, S ₁ and S ₂ are each a sensor.

Claims (1)

[Scope of Claims] 1. A color television receiver that drives a correction coil that performs landing correction of an electron beam based on a detection signal of a geomagnetism detection device that detects geomagnetism in relation to the orientation of a color cathode ray tube. The landing correction device includes an excitation signal generation circuit that generates an excitation signal that is asynchronous with the horizontal deflection frequency of the color television receiver, and a detection element drive circuit that receives the excitation signal and outputs a signal that drives the geomagnetism detection device. and a detection element that constitutes the geomagnetism detection device and detects the geomagnetism by a signal from the detection element drive circuit, and a detection signal obtained from the detection element has a frequency twice that of the excitation signal. a tuned amplifier circuit configured to resonate with the above-mentioned excitation signal generation circuit; and a doubler circuit to which the output signal of the excitation signal generation circuit is supplied.
It has a synchronous detection circuit that inputs the output signal of the doubler and the tunable amplifier, respectively, and the correction coil that is driven by the output signal of the synchronous detection circuit, and the excitation frequency of the excitation signal is The frequency is selected to be higher than the horizontal deflection frequency and between a harmonic of the horizontal deflection frequency and a harmonic of a higher order than the harmonic, and the signal related to the horizontal deflection frequency is amplified by the tuned amplifier circuit. A landing correction device for a color television receiver, characterized in that the landing correction device prevents the landing from occurring.