JP2003284089A - Cathode-ray tube - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress an unwanted magnetic field induced by an electromotive force generated in a demagnetizing coil of a cathode-ray tube by a leakage magnetic field from a deflection yoke, etc. <P>SOLUTION: In the cathode-ray tube provided with the demagnetizing coil 2, the coil 2 is connected to a power supply circuit including a power supply 4 via a selecting switch 9, and the switch 9 is connected between both ends and connection portion 6 of upper and lower portions of the coil 2 via or not via a resistor 10. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cathode ray tube having a degaussing coil.

[0002]

2. Description of the Related Art In a cathode ray tube, when a metal member in the tube, that is, a magnetic material is magnetized by geomagnetism or the like, the orbit of an electron beam is bent and beam landing is adversely affected.

For this reason, as shown in FIGS. 2 and 3, a degaussing coil 2 is arranged outside the cathode ray tube 1 so as to be sandwiched between the degaussing coils 2 from above and below. The magnetic field is degaussed by flowing to prevent adverse effects such as geomagnetism.

The degaussing coil 2 has various shapes. In the illustrated example, the degaussing coil is symmetrically divided into an upper portion and a lower portion. Denoted at 3 is a deflection yoke composed of vertical and horizontal deflection coils.

The degaussing coil 2 is normally connected to the power supply circuit shown in FIG. That is, the degaussing coil 2 has an alternating current of 50
It is connected to a power source (that is, a power line) 4 of about 60 Hz via a positive temperature coefficient thermistor 5. The degaussing current is passed through the degaussing coil 2 and is attenuated by the positive temperature coefficient thermistor 5 as the temperature rises immediately after the power is turned on. After that, the degaussing coil 2 is disconnected from the power supply circuit by the positive temperature coefficient thermistor 5 having a high resistance.

In FIG. 5, a relay switch 7 is further interposed between the degaussing coil 2 and the positive temperature coefficient thermistor 5. Here, after the power is turned on and the degaussing current flows through the degaussing coil 2, the relay switch 7 operates to reliably disconnect the degaussing coil 2 from the power supply circuit.

[0007]

By the way, generally, the degaussing coil 2 is exposed to a magnetic field leaking from the deflection yoke 3 and the deflection current drive circuit located around the degaussing coil, especially from the horizontal deflection coil system of the deflection yoke 3. Induced electromotive force is generated inside.

Since this induced electromotive force has a high frequency of about several tens KHz which is the same as the horizontal deflection frequency, a resonance current flows in the stray capacitance between the inductance of the degaussing coil 2 and the winding of the coil to generate a magnetic field. The induced magnetic field causes deterioration of unnecessary electromagnetic radiation from the cathode ray tube and deterioration of beam landing.

It is also considered to prevent the induction magnetic field from being generated by shielding the degaussing coil with aluminum foil or the like.

In a cathode ray tube for a display or the like,
A so-called cancel coil for canceling the leakage magnetic field from the horizontal deflection coil system of the deflection yoke 3 is further added. However, by picking up the canceling magnetic field from the cancel coil with the degaussing coil 2, the same problem as described above occurs. Occurs.

In view of the above points, the present invention provides a cathode ray tube capable of preventing an unnecessary magnetic field induced by the degaussing coil when the degaussing coil is not used.

[0012]

In order to solve the above problems, a cathode ray tube according to the present invention (Claim 1) is a cathode ray tube having degaussing coils arranged in a vertically divided manner. Except when in use, both ends of the degaussing coil and the upper and lower degaussing coils are effectively short-circuited.

Further, in the cathode ray tube according to the present invention (claim 2), the cathode ray tube is provided with the degaussing coil which is divided into upper and lower parts, and the degaussing coil is connected to the power supply circuit through the selection switch. At the same time, the selection switch is connected between both ends of the degaussing coil and a joining portion between the upper and lower degaussing coils.

Further, a cathode ray tube according to the present invention (claim 3) is a cathode ray tube having a degaussing coil arranged in a vertically divided manner. The selection switch is connected via an impedance circuit.

As described above, when the degaussing coil is not used, that is, after the degaussing current is applied to the degaussing coil, the ends of the degaussing coil in the open state are effectively short-circuited to join the upper and lower degaussing coils, thereby effectively causing resonance. Resonance current induced in the degaussing coil due to the electric field leaking from the deflection yoke and the like can be prevented. Therefore, it is possible to prevent an unnecessary magnetic field that is induced and generated in the degaussing coil by the resonance current.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention relates to a cathode ray tube provided with a degaussing coil which is arranged in a vertically divided manner, except that when the degaussing coil is not used, both ends of the degaussing coil and the joining portion of the degaussing coil divided vertically are It is configured to effectively short-circuit.

According to the present invention, in a cathode ray tube having a degaussing coil arranged in a vertically divided manner, the degaussing coil is connected to a power supply circuit via a selection switch, and both ends of the degaussing coil are joined to the upper and lower degaussing coils. The selection switch is connected between them.

According to the present invention, in a cathode ray tube provided with degaussing coils arranged in a vertically divided manner, the selection switch is connected via a low impedance circuit between both ends of the degaussing coil and the joining portions of the upper and lower degaussing coils. To configure.

Embodiments of the cathode ray tube according to the present invention will be described below with reference to the drawings.

In the cathode ray tube of this example, as shown in FIGS. 2 and 3, the degaussing coil 2 is arranged outside the cathode ray tube body 1 so as to surround the cathode ray tube body from above and below. Various shapes can be applied to the degaussing coil 2, and in the illustrated example, the degaussing coil 2 is symmetrically divided into an upper portion and a lower portion of the cathode ray tube. The present invention is particularly effective when the degaussing coil 2 is arranged so as to approach the deflection yoke 3.

In this example, after the degaussing coil has been used, that is, after the degaussing current has flowed, both ends of the degaussing coil which are in an open state and the joint portions 6 of the upper and lower degaussing coils are short-circuited or a low impedance circuit is formed. A short circuit is made through an appropriate resistor to perform damping to prevent resonance current.

For this reason, as shown in FIG. 1, for example, the degaussing coil 2 is switched through a selection switch, for example, a relay switch 9, to a power supply of about 50 to 60 Hz AC (that is, a power line).
4. The relay switch 9 is connected to the power supply circuit including the positive temperature coefficient thermistor 5, and the relay switch 9 is connected between both ends of the degaussing coil 2 and the joining portions 6 of the upper and lower degaussing coils.

That is, one end of the degaussing coil 2 is connected to the movable contact a of the relay switch 9, and the first fixed contact b1 of the relay switch 9 and the other end of the degaussing coil 2 are connected to the power supply 4. A positive temperature coefficient thermistor 5 is connected between the first fixed contact b1 and the power supply 4.

On the other hand, the other end of the degaussing coil 2 is connected to the second fixed contact b2 of the relay switch 9. The joint portion 6 of the upper and lower degaussing coils is connected to the third fixed contact b of the relay switch 9.
Connect to 3. A suitable resistance element 10 shown by a broken line may be connected between the joint portion 6 between the third fixed contact b3 and the upper and lower degaussing coils of the degaussing coil 2.

According to the configuration of FIG. 1, immediately after the power is turned on, the movable contact a of the relay switch 9 is connected to the first fixed contact b1, and the degaussing current flows into the degaussing coil 2 to magnetize it by the earth magnetism or the like. Degaussing is performed on the magnetic body in the cathode ray tube thus formed.

After the degaussing current flows, the demagnetizing current stops flowing due to the positive temperature coefficient thermistor 5 having a high resistance due to heat generation, so that the movable contact a of the relay switch 9 automatically becomes the second fixed contact b2. Switching to the third fixed contact b3 side, the degaussing current to the degaussing coil 2 is cut off, and at the same time, the ends 6 of the degaussing coil 2 and the joint portions 6 of the upper and lower degaussing coils are short-circuited with or without the resistor 10. It

Although induced electromotive force is generated in the degaussing coil 2 due to a magnetic field leaking from the horizontal deflection coil system of the deflection yoke 3, both ends of the degaussing coil 2 and the upper and lower degaussing coil joints 6 are short-circuited or a resistor 10 is applied. By being short-circuited via, a so-called damping circuit is formed in the upper and lower degaussing coils, and by dividing the degaussing coil into the upper and lower parts,
When the short circuit occurs, the inductance value decreases and the resonance point shifts, so that the resonance current can be prevented.

That is, it is possible to prevent the resonance current generated inside the degaussing coil 2, that is, in each winding, and by dividing the degaussing coil vertically and short-circuiting it, the induced current flowing outside the degaussing coil 2 is extremely small. Become. Therefore, an unnecessary magnetic field induced in the degaussing coil 2 can be suppressed,
It is possible to avoid deterioration of unnecessary electromagnetic radiation from the cathode ray tube and deterioration of beam landing.

[0029]

According to the present invention, when the degaussing coil is not used, both ends of the degaussing coil and the upper and lower degaussing coils are effectively short-circuited, so that the degaussing coil is formed by the leakage magnetic field from the deflection yoke or the like. The unnecessary magnetic field induced can be suppressed, and the deterioration of unnecessary electromagnetic radiation from the cathode ray tube and the deterioration of beam landing can be avoided.

According to the present invention, when the degaussing coil is used, the degaussing coil is connected to the power supply circuit through the selection switch, and the selection switch is connected between both ends of the degaussing coil and the upper and lower degaussing coils. Other than that, the selection switch is switched, and both ends of the degaussing coil and the joining portions of the upper and lower degaussing coils are short-circuited.

As a result, an unnecessary magnetic field induced in the degaussing coil by the leakage magnetic field from the deflection yoke or the like can be suppressed, and it is possible to avoid deterioration of unnecessary electromagnetic radiation from the cathode ray tube and deterioration of beam landing. it can.

According to the present invention, by connecting the selection switch through the low impedance circuit between the ends of the degaussing coil and the junction between the upper and lower degaussing coils, the degaussing coil is induced by the leakage magnetic field from the deflection yoke or the like. It is possible to suppress unnecessary magnetic fields, and it is possible to avoid deterioration of unnecessary electromagnetic radiation from the cathode ray tube and deterioration of beam landing.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an example of a degaussing coil circuit of a cathode ray tube according to the present invention.

FIG. 2 is a side view of a cathode ray tube having a degaussing coil.

FIG. 3 is a rear view of a cathode ray tube having a degaussing coil.

FIG. 4 is a configuration diagram of a degaussing coil circuit of a cathode ray tube according to a conventional example.

FIG. 5 is a configuration diagram of a degaussing coil circuit of a cathode ray tube according to another conventional example.

[Explanation of symbols]

1 Cathode ray tube 2 degaussing coil 3 deflection yoke 4 power supply (light line) 5 Positive Characteristic Thermistor 8 capacitors 9 relay switch 10 resistance

Claims (3)

[Claims] 1. In a cathode ray tube having degaussing coils arranged in a vertically divided manner, both ends of the degaussing coil and the joining portions of the upper and lower degaussing coils are effectively short-circuited except when the degaussing coil is used. A cathode ray tube characterized in that. 2. A cathode ray tube comprising degaussing coils arranged in a vertically divided manner, wherein the degaussing coil is connected to a power supply circuit via a selection switch, and both ends of the degaussing coil are joined to the upper and lower degaussing coils. A cathode ray tube comprising the selection switch connected between the portions. 3. A cathode ray tube comprising degaussing coils arranged in a vertically divided manner, wherein the selection switch is connected through a low impedance circuit between the ends of the degaussing coil and the upper and lower degaussing coils. A cathode ray tube characterized in that.