JP2001103501A - Display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce mis-landing by improving landing correction even when degaussing by a degaussing coil such as just after the end of the degaussing is insufficient. SOLUTION: The display device is provided with a landing correction control circuit 5 that controls a correction current supplied to a landing correction coil 7 conducting the landing correction in response to a current able to be supplied to a degaussing circuit to degauss a cathode ray tube 2. Since the landing correction control circuit 5 has an insufficient degaussing capability when the current able to be supplied to the degaussing circuit 4 is small, the correction current applied to the landing correction coil 7 is increased by the share so as to compensate deficient degaussing by the degaussing circuit 4.

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 (CR) for displaying a video signal from a computer terminal (for example, a personal computer or a workstation).
The present invention relates to a display device having T), and more particularly, to a display device capable of satisfactorily correcting a landing error caused by the influence of geomagnetism or the like.

[0002]

2. Description of the Related Art In order to prevent deterioration of color purity due to terrestrial magnetism, environmental temperature, and expansion of a shadow mask due to an electron beam in a cathode ray tube display, an electron beam landing correction technique has been conventionally studied.

FIG. 9 is a block diagram showing a configuration example of a landing control circuit conventionally applied to a display device. In the figure, reference numeral 511 denotes a geomagnetic sensor 51
2 is a temperature sensor, 513 is a memory, 523 is a shadow mask temperature model, 53x, 53y, 532, 533, and 5
34 is an A / D converter, 3 is a CPU, 551 and 55
2,553,554,555 are D / A converters, 56
1, 562, 563, 564, and 565 are amplification circuits;
1, 72, 73, 74 and 75 are landing correction coils. Hereinafter, the operation will be described.

The CPU 3 obtains the state of the display device from the terrestrial magnetism sensor 511, the temperature sensor 512, and the shadow mask temperature model 523, and calculates the difference between the reference data stored in the memory and the rear corner of the CRT 4 and the outer periphery of the CRT. Landing correction coil 7 placed
1, 72, 73, 74, and 75 are generated, and the landing deviation is corrected by driving each of the landing correction coils, so that the image is always displayed in a just-landing state. As a display device having such a landing control circuit, for example, a display device described in JP-A-10-164612 is known.

[0005]

In the above prior art, no consideration has been given to landing correction when the degaussing operation cannot be performed sufficiently. In other words, the degaussing operation of the display device uses the self-heating phenomenon of the thermistor to control the current flowing through the degaussing coil, so once the degaussing operation is performed, sufficient current is degaussed until the thermistor cools naturally. The current cannot be passed through the coil, resulting in insufficient demagnetization. For example, if the geomagnetism incident on the display device changes by rotating the display device immediately after performing the degaussing operation, the degaussing operation by the degaussing coil cannot be performed sufficiently. Therefore, in such a case, a landing correction amount larger than usual is required. However, in the related art, the landing correction in such a case becomes insufficient, and there is a possibility that mislanding may occur.

An object of the present invention has been made in view of the above-mentioned problems, and an object of the present invention is to improve landing correction and reduce mislanding even when the degaussing coil cannot perform a sufficient degaussing operation. It is an object of the present invention to provide a display device which is enabled.

[0007]

In order to achieve the above object, a display device according to the present invention controls a landing correction amount in accordance with information indicating a physical state of a degaussing means for degaussing a CRT. It is characterized by the following.

More specifically, a degaussing circuit for degaussing a cathode ray tube, a landing correction coil for performing landing correction, and information indicating the physical state of the degaussing circuit
A control circuit for controlling a correction current supplied to the landing correction coil.

The information indicating the physical state of the degaussing circuit is:
This information relates to the magnitude of demagnetization that can be performed by the degaussing circuit, and is information relating to the magnitude of current that can be supplied to the degaussing circuit. This information may be obtained by using a model representing a time-dependent change characteristic of a current that can be supplied to the degaussing circuit. This model may be composed of a time constant circuit having a resistor and a capacitor, or a clock generation circuit for generating a clock, and counting the clock output from the clock generation circuit to calculate the elapsed time from the end of the degaussing operation. , And the correction current may be controlled using the elapsed time obtained by the counter and the previously stored characteristic of the physical state of the demagnetizing circuit with time. Also, the control circuit has a CPU, and the CP
The characteristics may be stored in U in advance.

[0010] The control circuit may control the correction current to a first level when the current that can be supplied to the degaussing circuit is at a first level.
When the current that can be supplied to the degaussing circuit is at a second level smaller than the first level, the correction current is set to a second value larger than the first value. That is, when the current that can be supplied to the degaussing circuit changes in a small direction, the control circuit controls the correction current supplied to the landing correction coil in a large direction.

According to such a configuration, when the temperature of the thermistor in the degaussing circuit is high and the internal resistance thereof is large, for example, immediately after the degaussing operation is completed, that is, since the current supplied to the degaussing circuit cannot be increased, the degaussing is sufficiently performed. Even when the correction cannot be performed, the correction current supplied to the correction coil for performing the landing correction by the correction circuit can be increased. That is, according to the present invention, even when the degaussing circuit cannot sufficiently perform degaussing just after the end of the degaussing operation or the like, it is possible to sufficiently perform landing correction even when it is desired to compensate for the influence of terrestrial magnetism or the like again. Can be reduced.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of a display device according to the present invention. In the figure, 1 is a display control circuit, 2 is a cathode ray tube, 3 is a CPU,
4 is a degaussing circuit, 5 is a landing control circuit, 6 is a degaussing coil, 7 is a landing correction coil, 8 is a deflection circuit, 9
Is a deflection yoke. First, the operations of the display control circuit 1, the cathode ray tube 2, the CPU 3, the deflection circuit 8, and the deflection yoke 9 will be described below.

The display control circuit 1 performs signal processing such as amplification, amplitude adjustment and black level adjustment on the input video signal based on the control from the CPU 3, and applies the processed video signal to the cathode electrode of the cathode ray tube 2. To drive the cathode. The deflection circuit 8 deflects the electron beam generated in the CRT 2 by driving a deflection yoke 9 mounted on the CRT 2 based on the horizontal synchronization signal and the vertical synchronization signal input together with the video signal. The input image signal is displayed on the screen of the CRT 2.

The degaussing circuit 4 drives the degaussing coil 6 under the control of the CPU 3 to prevent the color purity from deteriorating due to the magnetization of the shadow mask provided inside the cathode ray tube 2.

The CPU 3 receives the input horizontal synchronizing signal and
The input signal is specified by detecting the frequency and polarity of the vertical synchronization signal, and the display control circuit 1 and the deflection circuit 8 are controlled so that an optimal image display can be performed. Further, when the power is turned on or when there is a request from the user, the degaussing circuit 4 is controlled to perform degaussing. Further, the landing control circuit 5 is controlled based on the outputs of various sensors provided inside the display device to correct mislanding.

Hereinafter, a specific example of the landing control circuit 5 will be described with reference to FIG. In the figure, 511 is a geomagnetic sensor 512 is a temperature sensor, 513 is a memory, 52
3) Shadow mask temperature model, 524: demagnetizing coil drive current model, 53x, 53y, 532, 533, 53
4 is an A / D converter, 551, 552, 553, 55
4,555 are D / A converters, 561,562,56
3,564,565 are amplifier circuits, 71,72,73,7
4 and 75 are landing correction coils. Hereinafter, the operation of each unit will be described.

The geomagnetic sensor 511 detects a magnetic field (x
(First axis) for detecting a magnetic field (y-axis) and a second element for detecting a magnetic field (y-axis) in a direction horizontal to the tube axis. Each element detects terrestrial magnetism in each direction and outputs x data and y data. For example, a Hall element, a magnetoresistive element, a magnetic impedance element, a flux gate sensor, and the like can be used for each element.

The temperature sensor comprises a thermistor, and outputs a voltage value corresponding to the temperature of the environment where the display device is installed.

A configuration example of the shadow mask temperature model 523 is shown in FIG. 3 and will be described. In the figure, 5231 is a diode, 5232 is a capacitor, 5233 is a resistor,
A voltage source 234 changes its voltage value based on the ABL voltage from the flyback transformer. Hereinafter, the operation of the shadow mask temperature model 523 will be described. The temperature of the shadow mask rises due to the irradiation of the electron beam. Therefore, the temperature of the shadow mask starts to rise from the time when an image is displayed on the display device, and saturates when the temperature reaches the temperature equilibrium point. Further, since the magnitude of the beam current varies depending on the content of the displayed image, the saturation temperature also varies.

Therefore, the shadow mask temperature model 523 of the display device of this embodiment is
And the time constant of the resistor 5233 are set so as to match the temperature change characteristic of the shadow mask of the cathode-ray tube 2 by the electron beam, and the ABL changes according to the amount of the electron beam.
The temperature of the shadow mask is modeled by using a voltage source 5234 corresponding to the saturation temperature based on the voltage.

The diodes 5231 and 5235 serve to prevent the charge stored in the capacitor 5232 from flowing out when the power of the display device is turned off.

Next, a specific example of the degaussing circuit 4 and the degaussing coil driving current model 524 is shown in FIG. In FIG.
41 is a switch, 42 is a thermistor, 5241 is a diode, 5242 is a capacitor, and 5243 is a resistor.
Hereinafter, the degaussing circuit 4 and the degaussing coil drive current model 524
The operation of will be described. A control signal for driving the degaussing circuit 4 from the CPU 3 is supplied to the switch 41,
The opening / closing operation of the switch 41 is controlled. This switch 4
1 is composed of, for example, a transistor and a relay.
When the control signal from the CPU 3 is, for example, “H”, the switch 41 is closed, and a voltage of, for example, 100 V from the power supply is applied via the switch 41 and the thermistor 42 to the demagnetizing coil 6.
Supplied to The degaussing circuit 4 configured in this way controls the current flowing through the degaussing coil using the self-heating effect of the thermistor 42. Therefore, even if the degaussing operation is performed again immediately after the degaussing operation is performed, the resistance value is high and the sufficient degaussing current cannot flow because the thermistor 42 is in a high temperature state. Accordingly, the degaussing coil driving current model 524 of the present embodiment represents the time constant of the capacitor 5242 and the resistor 5243 as a natural cooling characteristic after the demagnetizing operation of the thermistor 42 (a characteristic of a temperature change of the thermistor 42 with the passage of time). Yes, equivalent to the time characteristic of the degaussing current level that can be supplied to the degaussing coil).
, A control signal for the degaussing circuit 4 is input via a diode 5241. That is, a time constant circuit having the capacitor 5242 and the resistor 5243 constitutes a model of the natural cooling characteristic of the degaussing coil. By using such a model, the temperature (natural cooling characteristic) of the thermistor 42, which is difficult to directly detect, is virtually detected.

With this configuration, the voltage at the connection point between the diode 5241 and the capacitor 5242 ends the degaussing operation.
The discharge of the electric charge stored in the capacitor 5242 is started by the resistor 5243 from the moment when the control signal of the degaussing circuit 4 becomes Low level. As described above, the temporal change characteristic of the voltage at the connection point between the diode 5241 and the capacitor 5242 matches the natural cooling characteristic of the thermistor. Therefore, the diode 5241 and the capacitor 52
By converting the voltage at the connection point with the A / D converter 534 into a digital signal by the A / D converter 534 and supplying the digital signal to the CPU 3, the CPU 3 can virtually detect the temperature of the thermistor 42. As a result, the CPU 3 can predict how much degaussing current flows before performing the degaussing operation. That is, when the voltage at the connection point is high (when the amount of electric charge discharged from the capacitor 5242 is small), the current that can be supplied to the degaussing circuit 4 (the degaussing coil 6) because the thermistor 42 is at a high temperature and in a high resistance state. Can not be increased by the CPU 3. On the other hand, when the voltage at the connection point is low (when the amount of electric charge discharged from the capacitor 5242 is large), the current that can be supplied to the degaussing circuit 4 (the degaussing coil 6) because the thermistor 42 is in a low temperature and low resistance state. Can be predicted by the CPU 3.

Note that the diode 5241 functions to prevent the electric charge stored in the capacitor 5242 from flowing out when the power supply of the display device is turned off.

The memory 513 stores reference values for the geomagnetic sensor 511, the temperature sensor 512, the shadow mask temperature model 523, and the degaussing coil drive current model 524.

FIG. 5 shows the positions of the landing correction coils 71 to 75. FIG. 3 is a rear view of the CRT 2, in which a landing correction coil 71 is disposed at the upper left of the CRT, a landing correction coil 72 is disposed at the upper right of the CRT, and a landing correction coil 73 is disposed at the lower right of the CRT.
And a landing correction coil 7 at the lower left of the CRT.
4 and a landing correction coil 75 on the outer periphery of the cathode ray tube. Hereinafter, the role of each coil will be described.

The landing correction coil 71 is shown in FIG.
The electron beam is controlled in the direction from the upper left of the screen toward the center of the screen as shown in FIG. The landing correction coil 72 is shown in FIG.
The electron beam is controlled in the direction from the upper right of the screen toward the center of the screen as shown in FIG. Landing correction coil 73
Controls the electron beam in the direction from the lower right of the screen toward the center of the screen as shown in FIG. The landing correction coil 74 controls the electron beam in a direction from the lower left of the screen toward the center of the screen as shown in FIG. The landing correction coil 75 controls the electron beam in a direction in which the entire screen is rotated around the center of the screen as shown in FIG.

The CPU 3 fetches data obtained by A / D conversion of the output voltage of the terrestrial magnetism sensor 511, the temperature sensor 512, the shadow mask temperature model 523, and the degaussing coil drive current model 524 at a predetermined cycle, for example, and stores the data in the memory 513. Correction data that determines the amount of landing correction to be output to the landing correction coils 71 to 75 is calculated from the difference from the reference value. Here, according to the output value of the degaussing coil driving current model 524, when sufficient degaussing current cannot be supplied to the degaussing coil, a large correction data for the terrestrial magnetism is output to perform sufficient degaussing. The compensation amount is compensated to prevent landing deviation.

That is, the degaussing coil driving current model 52
4 is large (the degaussing coil drive current model 52
4 when the voltage at the connection point between the diode 5241 and the capacitor 5242 is high), the thermistor 42 is in a high resistance state, and the current supplied to the thermistor 42 cannot be increased. Calculates and outputs correction data that increases the landing correction amount (as compared with the normal case). Conversely, when the output of the degaussing coil drive current model 524 is small, the thermistor 42 is in a low resistance state and the current supplied to the thermistor 42 can be increased, that is, the demagnetization can be sufficiently performed. The correction data to be reduced (or set to the normal level) is calculated and output. This correction data is calculated for each of the landing correction coils 71 to 75.

The correction data output from the CPU 3 and corresponding to the respective landing correction coils 71 to 75 are converted into analog signals by D / A converters 551 to 555, respectively, and further amplified by amplifier circuits 561 to 565.
The current is supplied to each of the landing correction coils 71 to 75 as a correction current for the landing correction.

As described above, by operating the respective components, the display device of the present embodiment can correct a landing deviation due to terrestrial magnetism, environmental temperature, and beam current, and can always display an image in a just landing state.

In this embodiment, an example in which a shadow mask type cathode ray tube is used has been described. However, the present invention is not limited to this, and an aperture grill type cathode ray tube may be used. Further, in the present embodiment, an example has been described in which the correction data for the terrestrial magnetism is amplified and output when the sufficient degaussing current cannot be passed through the degaussing coil.However, the present invention is not limited to this. Conversely, the correction data may be attenuated and output. In addition, whether to amplify or attenuate each correction coil may be controlled. In the present embodiment,
Information indicating the physical state of the degaussing circuit 4 when the landing correction is performed (magnitude of current that can be supplied to the degaussing circuit 4 such as temperature and resistance of the thermistor 42 (magnitude of degaussing that can be executed by the degaussing circuit 4)) Is detected virtually using a model, but the detection result may be used as long as it can be directly detected. Further, in the present embodiment, the landing correction amount (the level of the correction current supplied to the landing correction coils 71 to 75) is controlled by increasing or decreasing the correction data in the CPU 3 according to the physical state of the degaussing circuit 4. , Amplifier circuits 561 to 56
5 is constituted by a variable gain amplifying circuit,
The CPU 3 may generate a control signal corresponding to the physical state of, and supply the control signal to the amplifier circuits 561 to 565 to control the gain to control the landing correction amount. Absent.

Another embodiment of the present invention will be described with reference to the drawings. FIG. 7 is a block diagram showing another configuration example of the degaussing coil drive current model 524 according to another embodiment of the display device according to the present invention. The above-described embodiment according to the present invention uses the degaussing coil driving current model 524 as a resistor,
This embodiment is different from the above-described embodiment in that the present embodiment is an example in which the degaussing coil driving current model 524 is realized by a digital circuit, whereas the embodiment is realized by an analog circuit such as a capacitor. In FIG. 7, 5245 is a counter, 5246
Is a crystal oscillation circuit. Here, the CPU 3 has a characteristic indicating the relationship between the time characteristic of the current that can be supplied to the degaussing circuit 4 in advance, that is, the number of clocks after the execution of the degaussing operation is completed, and the natural cooling characteristic of the thermistor of the degaussing circuit 4. Is stored. Hereinafter, the operation will be described in detail with reference to FIG. In addition, the same reference numerals are given to the same portions, and duplicate description will be omitted.

The counter 5245 has a crystal oscillation circuit 5246
And supplies the count result to the CPU 3. After executing the degaussing operation, the CPU 3
A reset signal is issued to the counter 5245 to count the number of clocks after the execution of the degaussing operation is completed, and the result is obtained. When there is a request for degaussing from the user, the count obtained from the counter 5245 is determined by the number of clocks after the execution of the degaussing operation stored in the CPU 3 in advance and the natural cooling characteristic of the thermistor of the degaussing circuit 4. It is determined whether or not the thermistor is sufficiently cooled by applying the relationship to the above relationship. If the thermistor is not sufficiently cooled, the landing correction coils 71 to 7 are determined.
5 is amplified and output.

As described above, even if the degaussing coil driving current model 524 is constituted by a digital circuit, the display device of this embodiment corrects a landing deviation due to terrestrial magnetism, environmental temperature, and beam current, and is always in a just-landing state. Image display can be performed. Note that a general-purpose logic IC such as 74AC161 and 74AC163 may be used for the counter 5245, and a plurality of stages may be used if a large number of counts are required, or an ASIC such as a gate array may be used. In the present embodiment, an example in which the crystal oscillation circuit 5246 is used as a means for generating a clock has been described. However, the present invention is not limited to this, and the input synchronizing signal is generated by multiplying using a PLL. May be.

Another embodiment of the present invention will be described with reference to FIG. FIG. 8 shows still another embodiment of the display device according to the present invention, and is a block diagram showing still another configuration of the degaussing coil drive current model 524.
While the above-described embodiment according to the present invention is an example in which the degaussing coil driving current model 524 is realized by a digital circuit such as a crystal oscillation circuit and a counter, the present embodiment realizes the degaussing coil driving current model 524 by software of the CPU 3. This embodiment differs from the above-described embodiment in that this is an example. In FIG. 8, reference numeral 524 denotes a timer counter built in the CPU 3. Here, it is assumed that the relationship between the timer count number after the execution of the degaussing operation is completed and the natural cooling characteristic of the thermistor of the degaussing circuit 4 is stored in the CPU 3 in advance. Hereinafter, the operation will be described in detail with reference to FIG. In addition, the same reference numerals are given to the same portions, and duplicate description will be omitted.

After executing the degaussing operation, the CPU 3 starts counting by the built-in timer counter 5247 and counts the number of counts after the execution of the degaussing operation is completed. And
When there is a demagnetization request from the user, the count number of the built-in timer counter 5247 and the CPU
3 to determine whether or not the thermistor is sufficiently cooled by applying to the relationship between the count number after the execution of the degaussing operation recorded inside and the natural cooling characteristic of the thermistor of the degaussing circuit 4. If it is not cooled, the correction data to be output to the landing correction coils 71 to 75 is amplified and output.

As described above, even if the degaussing coil driving current model 524 is configured, the display device of this embodiment corrects a landing deviation due to terrestrial magnetism, environmental temperature, and beam current, and always displays an image in a just-landing state. be able to. Note that the timer counter 5247
May be used as the clock obtained by dividing the system clock of the CPU 3, and even if supplied externally, it does not depart from the scope of the present invention.

[0040]

As described above, according to the present invention, even when demagnetization is not sufficiently performed, a landing deviation due to a change in the surrounding environment such as terrestrial magnetism can be satisfactorily corrected. Therefore, it is possible to display an image with high image quality while reducing the influence of a change in the surrounding environment.

[Brief description of the drawings]

FIG. 1 is a view showing one embodiment of a display device according to the present invention.

FIG. 2 is a diagram showing an example of a specific configuration of a landing control circuit 5 shown in FIG.

FIG. 3 is a shadow mask temperature model 523 shown in FIG. 2;
The figure which shows an example of the specific structure of.

FIG. 4 is a diagram showing an example of a specific configuration of a degaussing circuit 4 and a degaussing coil drive current model 524 shown in FIG.

FIG. 5 is a view showing an arrangement position of a landing correction coil of the display device according to the present invention.

FIG. 6 is a diagram showing a function of a landing correction coil of the display device according to the present invention.

FIG. 7 is another embodiment of the display device according to the present invention, and is a view showing another example of the specific configuration of the degaussing coil drive current model 524.

FIG. 8 is a view showing still another embodiment of the display device according to the present invention, showing still another example of the specific configuration of the degaussing coil drive current model 524.

FIG. 9 is a diagram showing a configuration of a conventional landing control circuit.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Display control circuit, 2 ... CRT, 3 ... CPU, 4 ... Degaussing circuit, 5 ... Landing control circuit, 6 ... Degaussing coil,
7 Landing correction coil, 8 Deflection circuit, 9 Deflection yoke, 41 Switch, 42 Thermistor, 511
Geomagnetic sensor, 512 temperature sensor, 513 memory
523: shadow mask temperature model, 524: degaussing coil drive model, 53x, 53y, 532, 533, 53
4 A / D converter, 551 to 555 D / A converter, 5
61 to 565: an amplifier circuit, 71 to 75: a landing correction coil.

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Akira Sawada 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Prefecture F-term in Hitachi Digital Media System Division (Reference) 5C060 BD02 BD06 BE02 CM01 CP04 HA07 HA08 HA14 HB04 HB24 HB27

Claims (14)

[Claims] 1. A display device wherein a landing correction amount is controlled in accordance with information representing a physical state of a degaussing means for degaussing a cathode ray tube. 2. A degaussing circuit for degaussing a cathode ray tube, a landing correction coil for performing landing correction, and a correction current supplied to the landing correction coil in accordance with information representing a physical state of the degaussing circuit. A display device, comprising: a control circuit. 3. The information indicating the physical state of the degaussing circuit is:
The display device according to claim 3, wherein the display device is obtained by using a model representing a temporal change characteristic of the physical state. 4. The information indicating the physical state of the degaussing circuit includes:
4. The display device according to claim 3, wherein the information is related to the magnitude of demagnetization that can be performed by the degaussing circuit, and the information is related to the magnitude of current that can be supplied to the degaussing circuit. 5. The display device according to claim 3, wherein said model is constituted by a time constant circuit having a resistor and a capacitor. 6. A control circuit comprising: a clock generation circuit for generating a clock; and a counter for counting a clock output from the clock generation circuit to obtain an elapsed time from the end of the degaussing operation. 4. The display device according to claim 3, wherein the control device controls the correction current using an elapsed time obtained by the counter and a temporal change characteristic of a physical state of the degaussing circuit stored in advance. 7. The display device according to claim 6, wherein said control circuit includes a CPU, and said characteristics are stored in said CPU in advance. 8. The control circuit sets the correction current to a first value when the current that can be supplied to the degaussing circuit is at a first level, and sets the current that can be supplied to the degaussing circuit to the first level. 5. The display device according to claim 4, wherein when the second level is smaller than the first value, the correction current is set to a second value larger than the first value. 9. A video processing circuit to which R, G, B video signals are input, a cathode ray tube for displaying based on an output of the video processing circuit, and a horizontal and vertical synchronization pulse input together with the video signal. A deflection circuit for deflecting the electron beam of the CRT, a degaussing coil for degaussing the CRT, a degaussing coil driving circuit for driving the degaussing coil, and changing the trajectory of the electron beam of the CRT to perform landing correction. In a display device having at least one correction coil and a control circuit for controlling a correction current supplied to the correction coil, the control circuit supplies the correction current to the correction coil according to a magnitude of a current flowing through the degaussing coil. A display device for controlling a correction current to be applied. 10. A video processing circuit to which R, G, B video signals are input, a cathode ray tube for displaying based on an output of said video processing circuit, and a horizontal and vertical synchronizing pulse input together with said video signal. A deflection circuit for deflecting the electron beam of the CRT, a degaussing coil for degaussing the CRT, a degaussing coil driving circuit for driving the degaussing coil, and changing the trajectory of the electron beam of the CRT to perform landing correction. A display device having at least one correction coil and a control circuit for controlling a correction current supplied to the correction coil,
The control circuit has a degaussing coil driving current model that models a current level that can be supplied to the degaussing coil, and controls a correction current supplied to the correction coil according to an output of the degaussing coil driving current model. A display device characterized by the above-mentioned. 11. The display device according to claim 10, wherein said degaussing coil driving current model is constituted by a time constant circuit having a resistor and a capacitor. 12. The degaussing coil driving current model has a clock generating circuit for generating a clock, and a counter for counting clocks output from the clock generating circuit to obtain an elapsed time from the end of the degaussing operation. 11. The control circuit according to claim 10, wherein the control circuit controls the correction current using an elapsed time obtained by the counter and a time-dependent characteristic of a current level which can be supplied to the degaussing coil and stored in advance. A display device according to claim 1. 13. The control circuit includes a CPU.
The display device according to claim 15, wherein the characteristic is stored in the display device. 14. The display device according to claim 16, wherein said counter is a timer counter inside said CPU.