JPH02238790A - Magnetic field correction device - Google Patents

Abstract

PURPOSE:To use one coil for a correction coil and a degaussing coil in common by applying a voltage whose amplitude is being attenuated to one terminal of the magnetic field correction coil and applying a voltage in response to the detection of a magnetism azimuth sensor at the other end. CONSTITUTION:A voltage whose amplitude is being decreased is applied to one terminal of a magnetic field correction coil 13 and a voltage in response to a magnetic field detected by a magnetism azimuth sensor 24 is applied to the other terminal of the magnetic field correction coil 13. Since the AC degaussing current whose amplitude is decreased flows to the magnetic field correction coil 13 while being superimposed onto the DC earth magnetism correction current in response to the horizontal component of the earth magnetism to cancel the earth magnetism acting on a CRT thereby eliminating magnetization. Thus, the magnetic field correction device using the correction coil and the degaussing coil in common is used.

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention is a color cathode! The present invention relates to a magnetic field correction device for correcting the effects of external magnetic fields such as earth's magnetism (hereinafter referred to as CRT) acting on KRT and magnetization of CRT.

[Conventional technology]

FIG. 6 is a circuit diagram showing a conventional magnetic field correction device. In the figure, 25 is a correction coil for canceling earth's magnetism, 26
is a switch that changes the current flowing through the correction coil 25, and is configured to change the voltage divided by the resistance. a
+b indicates the direction of the current flowing through the correction coil 25, BH, . ．． BH is a magnetic field generated in the correction coil 25. 29 is a degauss coil for canceling the magnetization of the CRT, 28 is a vojistor connected in series with the degauss coil 29, and 27 is an AC power source for driving the degauss coil 29.

Figure 7 shows a display monitor using a CRT.
0 indicates a display monitor, 31 indicates a CRT tube surface, BH indicates a horizontal component of geomagnetism, and BY indicates a vertical component of geomagnetism.

Next, the operation will be explained. Earth's magnetism exists on the earth, and this earth's magnetism can usually be considered to be divided into a horizontal component (hereinafter referred to as BH component) and a vertical component (hereinafter referred to as BV component).

In FIG. 7(A), a display monitor 30 displays an image by electromagnetically deflecting an electron beam emitted from an electron gun (not shown) to scan the tube surface 31 of a CRT.

The CRT tube surface 31 is easily influenced by the earth's magnetism because it is located at a long distance from the electron gun and is in direct contact with the atmosphere. Here, as shown in FIGS. 7(A) and (B), the display monitor 3
Suppose we change the direction of 0. At the position shown in FIG. 2A, the BH component of the earth's magnetism acts perpendicularly to the CRT tube surface 31, and the BV component acts on the CRT tube surface 31 from below to above. In this state, according to Fleming's left-hand rule, the screen rotates to the left due to p and the BH component, and BV
Depending on the ingredient, the screen will shift to the right.

Next, at the position shown in Figure (B), the BH component of the geomagnetic field is
acts in the horizontal direction, while the BY component is the same as in (A), a! K Works from bottom to top. That is, at positions (A) and (B), both BV components have the same effect on the CRT.

However, since the BH component coincides with the beam deflection magnetic field in the state (B), it does not have a slight effect on the beam, but it has a large effect on the state (A).

As mentioned above, due to the displacement of the beam due to the BH component, the CRT beam does not correctly hit the phosphor on the tube surface 31, which generally results in a symptom of "poor one-color purity."

In order to eliminate the influence of the BH component, a magnetic field equivalent to the BH component may be applied from the opposite direction. A method often used for this purpose is to wind a correction coil 25 around the CRT as shown in FIG. 6, and to flow a direct current through the correction coil 25.

In FIG. 6, when a direct current in direction a is passed through the correction coil 25, a magnetic field is generated in the direction indicated by BH in the figure. On the other hand, when a direct current is passed in the b direction, a magnetic field is generated in the direction indicated by BH in the figure. In other words, the strength of the BH component can be canceled by changing the direction of the DC current. The direction and magnitude of this direct current are selected by a changeover switch 26.

On the other hand, in order to demagnetize the magnetism that is magnetized in the iron material of the CRT, an AC current is applied to the Side-Gauss coil 29 from the AC power supply 27. Since the POSISTOR 28 is initially cold, its resistance value is low, and most of the current flows to the degauss coil 29.
As time passes, the heat generation of the resistor 28 increases and the resistance value increases, and the current converges and the magnetization is demagnetized.

FIG. 8 shows the state of demagnetization by the degaussing current IC flowing through the degauss coil 29 and the relationship between the BH component of the earth's magnetism, etc. The degaussing current Icl gradually attenuates as described above, and as a result A hysteresis loop starts, gradually becomes smaller, and converges at a convergence point, thereby demagnetizing the magnetized portion of the CRT. In that case, the magnetic force H, at the start point and convergence point of the hysteresis loop remains, but this magnetic force H1 is due to the above-mentioned BH component, and this magnetic force H, is caused by the DC current flowing through the correction coil 25. Canceled.

[Problem to be solved by the invention]

Since the conventional magnetic field correction device is configured as described above, it requires two coils: a correction coil 25 for correcting the earth's magnetism and a degauss coil 29 for demagnetizing the magnetism of the CRT K. This has led to problems such as increased costs.

This invention was made to solve the above-mentioned problems, and an object thereof is to obtain a magnetic field correction device that can share the correction coil and the degauss coil.

[Means to solve the problem]

The magnetic field correction device according to the present invention applies a voltage whose amplitude is reduced to one end of one magnetic field correction coil, and applies a voltage corresponding to the magnetic field detected by the magnetic orientation sensor to the other end of the magnetic field correction coil. K.

[Effect]

In the magnetic field correction coil of the present invention, an alternating current demagnetizing current whose amplitude decreases is superimposed with a direct current geomagnetic correction current K corresponding to the horizontal component of the geomagnetism and flows into the magnetic field correction coil. )． ．．
It is possible to cancel the earth's magnetism and magnetization of CRT.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. 1st
In the figure, 1 is a DC power supply, 2 is a power switch that supplies the power supply voltage of DC power supply 1 to the device, 3 is a pulse oscillator, 3
3 is a switch for obtaining the output of the pulse oscillator 3; 4 is a transistor in which the pulse oscillator 3 is connected to the pace via the switch 33; 34 is a pace bias resistor for the transistor 4; 6 is a posistor serving as a load for the transistor 4;
A resistor 45 serving as a load together with the resistor 6 is a smoothing capacitor connected to the connection point between the resistor 6 and the resistor 7, a coupling capacitor 8 is connected to the collector of the transistor 4, and 11 and 12 are Transistors that are complementary connected and constitute a push-pull amplifier, 9.10 is a pace bias resistor of the transistor 1112, v1 is a first signal applied to the base of the transistor 11.12,
A magnetic field correction coil 13 (hereinafter referred to as coil 13) has one end connected to the emitter connection point b of the transistors 11 and 12, and is wound around the CRT in the same way as a conventional degauss coil.

24 is a magnetic direction sensor (hereinafter referred to as sensor 24) that detects the BH component acting on the CRT, and a coil 24a
It is composed of a ring-shaped core 24b around which is wound, and a conductor g 2 4c passing through the core 24b. 32 is an AC power supply that supplies current to the coil 24a, IB is a detection signal as a current detected by the sensor 24, 23 is a current-to-voltage converter using an operational amplifier for converting the detection signal In into voltage, and V3 is 22 is an operational amplifier for amplifying the correction voltage V and adding it to the detection signal IB;
0.21 is a transistor constituting a pushable amplifier to which the output voltage of the current-to-voltage converter 23 is applied; 18 is a transistor 20 . 21 is a transistor whose output is added to the pace; 19 is the emitter resistor of the transistor 18; 14.15 is a transistor constituting a push-pull amplifier; the other end of the coil 13 is connected to the emitter connection point e. 16.17 is the pace bias resistor of the transistor 14.15, and 2 is the second signal applied from the collector of the transistor 18 to the base of the transistor 14.15. IC is a current for magnetic field correction flowing through the coil 13.

35 in the figure, 3 to 10. 33. A first signal output circuit configured with 34 elements and outputting a first signal V, 3
Reference numeral 6 denotes a coil control circuit of the first type, which is constituted by transistors 11.12, 37 is a second coil control circuit constituted by transistors 14.15, and 38 is a coil control circuit of 16 to 21.2.
3, which is a second signal output circuit that outputs a second signal V,.

FIG. 2 is a block diagram of the circuit shown in FIG. 1 into functional blocks, and shows the magnetic direction sensor 24 in FIG. Operational amplifier 22, second signal output circuit 38, second coil control circuit 37, first signal output circuit 35. The first coil control circuit 36, coil 13, etc. are shown. The coil 13 is wound around the curved surface of the tube surface 31 of the CRT.

Next, the operation will be explained. When the switch 33 is turned on with the power switch 2 turned on, the pulse oscillator 3
The transistor 4 performs a switching operation based on the output pulse. This causes a current to flow through the syposistor 6 and the resistor 7. Initially, the resistor 6 has a small resistance value because it is cold, but as the resistance value increases due to heat generation, the voltage drop increases, and as a result, the amplitude gradually increases at the collector of the transistor 4, as shown in FIG. A pulse is output for a predetermined period of time. This pulse is connected to capacitor 8
After being DC-cut by the resistor 9.10, the first signal V is applied to the transistor 11.
Entered into 12 paces.

As a result, a voltage corresponding to the first signal VI is output at point b.

On the other hand, the detection signal IB corresponding to the BH component obtained from the sensor 24 is converted into a voltage by the current-to-voltage converter 23. This voltage is power amplified by a push-pull amplifier consisting of transistors 20 and 21 and applied to the transistor 18 pace. As a result, a second signal V, which corresponds to the detection signal IB and is biased by the resistor 16.17, is obtained at the collector of the transistor 18.

This second signal V changes depending on whether the detection signal IB is a positive current or a negative current K, and depending on the magnitude thereof.

Now, if the potential at point g (first signal V+) in FIG. As a pulse waveform, a
It flows from point → point b → point e → point f.

Also, if the potential at point g is lower than the potential at point h, the electric current is applied. As the negative direction pulse waveform shown in Fig. 4, point d →
Flows from point e to point b to point C. Also, due to the difference in DC potential between point g and point h, a DC component shown in FIG. 4 is generated in the coil 13 due to geomagnetic correction. It is running as 1.

The alternating current component of the current Ic flowing through the coil 13 is the demagnetizing current Ic.
Acts as y. That is, by gradually attenuating as shown by ICt in FIG. 5, the hysteresis harp is converged to the origin, the residual magnetic flux density becomes <L, and the CRT is demagnetized. Furthermore, the above DC geomagnetic correction current IC+
In this case, the coil 13 can be used as the correction coil to cancel out the earth's magnetic field.

On the other hand, since a display monitor using a CRT is surrounded by an iron plate or the like, the magnetic field acting on the sensor 24 is no longer equivalent to the earth's magnetism. In order to correct this, the corrected voltage V3 is passed through an operational amplifier 22 to a current-to-voltage converter 2.
3, the correction voltage V is added to the voltage converted from the detection signal IB.

According to the above, as is clear from FIG. 5, the magnetic force H due to the earth's magnetism is canceled by the earth's magnetic correction current ICt, and the CRT is demagnetized by the demagnetizing current Icy, so the hysteresis loop is The convergence point can be set as the origin and complete magnetic field correction can be performed.

In the above embodiment, the transistor 18 is used to determine the potential at point h in FIG. 1, but a resistor may be used in place of the transistor 18 and the same effect can be achieved.

〔Effect of the invention〕

As described above, according to the present invention, a voltage whose amplitude is attenuated is applied to one end of one magnetic field correction coil, and a voltage corresponding to the detection of the magnetic direction sensor is applied to the other end. This has the advantage that one coil can be used in common as a coil and a degauss coil.

[Brief explanation of drawings]

Fig. 1 is a circuit diagram showing a magnetic field correction device according to an embodiment of the present invention, Fig. 2 is a block diagram of the device, Fig. 3 is a waveform diagram of pulses obtained by the device, and Fig. 4 is a diagram of the device. A waveform diagram of the current flowing through the coil, Fig. 5 is a hysteresis characteristic diagram showing the magnetic field correction effect of the device, Fig. 6 is a circuit diagram showing a conventional magnetic field correction device, and Fig. 7 is a perspective view of a display monitor using a CRT. The figure, side view, and FIG. 8 are hysteresis characteristic diagrams showing the magnetic field correction effect of the conventional device. 3 is a pulse oscillator, 4 is a transistor, 5 is a capacitor, T is a resistor, 8 is a capacitor, 9.10 is a pace bias resistor, 11.12 is a transistor, 13 is a magnetic field correction coil, 14.15 is a transistor, 16.17 is a pace bias resistor, 18 is a transistor, 19 is an emitter resistor, 20.21 is a transistor, 23 is a current-to-voltage converter, 24 is a magnetic orientation sensor, vI is a first signal, ■, is a second signal, 35 3 is a first signal output circuit, 36 is a first coil control circuit, 37 is a second coil control circuit, and 38 is a second signal output circuit. In addition, in the figures, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Claims] a first signal output circuit that outputs a first signal whose amplitude gradually attenuates over a predetermined period; a first coil control circuit that outputs a voltage corresponding to the first signal to its output terminal; a magnetic orientation sensor that detects a magnetic field; a second signal output circuit that outputs a second signal according to the detection signal of the magnetic orientation sensor; and a second signal output circuit that outputs a voltage according to the second signal to its output terminal. and a magnetic field correction coil having both ends connected to an output end of the first coil control circuit and an output end of the second coil control circuit.