JPH0583721A - Display device - Google Patents

Abstract

PURPOSE:To attain excellent display by preventing the deviation of landing due to demagnetization of a shadow mask or the like due to the earth magnetism in the display device employing a cathode ray tube and a degaussing coil. CONSTITUTION:A synchronizing signal detection circuit 201 connecting to a deflection circuit 101 detects the presence of a synchronizing signal and a timer circuit 202 discriminates the absence of the synchronizing signal for a long time and a current required for degaussing is supplied to a degaussing coil, in which the degaussing is implemented and the degaussing device implements the automatic degaussing automatically when no synchronizing signal is in existence. Thus, even when color slurring takes place in the cathode ray tube in operation due to demagnetization, since the degaussing is implemented automatically in the absence of the synchronizing signal, an excellent display state is always obtained by eliminating the synchronizing signal at proper time in operation.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a display device such as a computer display.

[0002]

2. Description of the Related Art In televisions and computer displays using cathode ray tubes, a demagnetizing coil provided around the cathode ray tube is provided with a positive temperature coefficient thermistor or the like in order to prevent the landing from being displaced due to the magnetism of the shadow mask due to the magnetism. , A degaussing current that decays with time when the power of the device is turned on is used to degauss, or an independent degaussing switch is provided to degauss as necessary.

FIG. 3 is a block diagram of a conventional display device.
Reference numeral 01 is a deflection circuit, 102 is a display cathode ray tube, 103 is a degaussing coil, 104 is a positive temperature coefficient thermistor, and 105 is a manual degaussing switch. A conventional display device will be described below with reference to FIG. PTC thermistor 104 and cathode ray tube 1
A degaussing coil 103 provided in the vicinity of 02 is connected in series to a power supply circuit (not shown) via a degaussing switch 105 so that the degaussing switch 105 is turned on when the device is turned on. Or degauss switch 105
The degaussing current that decays with time by turning on the degaussing coil 1 as needed is degaussed by the positive characteristic thermistor 104.
Degaussing is performed on the shadow mask etc.

[0004]

However, in the above-described conventional configuration, when a system in which a positive temperature coefficient thermistor and a degaussing coil are connected in series is connected to a power supply circuit and degaussing is performed when the power of the device is turned on, , The usage time becomes long, and in the computer display etc., the installation direction is often changed by the twist and swivel device attached to the device after turning on the power, once when changing the setting direction Degaussing and good landing may cause deterioration and uneven color may occur.At this time, even if the power switch is turned off and then turned on again, the power off time is short. If
Since the PTC thermistor is not sufficiently cooled, the temperature of the PTC thermistor is high, and the resistance value is large, a sufficient degaussing current does not flow to the degaussing coil, so that the magnetization cannot be canceled and a problem occurs.

As a countermeasure against this, a dedicated independent degaussing switch is provided. However, the operation becomes complicated, it may hinder the design of the device, and the display device may not be operated when placed at a distance. ..

In order to solve the above problems, the present invention provides a display device which has good operability and can always obtain good landing.

[0007]

SUMMARY OF THE INVENTION In order to solve the above problems, the present invention provides a sync signal detecting means for detecting a sync signal and a current flowing through a degaussing coil when the sync signal detecting means does not detect the sync signal. The degaussing means for degaussing the shadow mask of the cathode ray tube is provided.

[0008]

According to the present invention, the degaussing operation is performed in the absence of the sync signal due to the above-described structure.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of the present invention will be described below with reference to FIGS.
Will be described with reference to.

FIG. 1 is a block diagram of a display device according to an embodiment of the present invention. 101 is a deflection circuit, 102 is a display cathode ray tube, 103 is a degaussing coil, 104 is a positive temperature coefficient thermistor, and 105 is a manual degaussing switch. , 201 is a sync signal detection circuit, 202 is a timer circuit, 203 is a one-shot multivibrator circuit, 204 is a relay drive circuit, 205 is a relay, 1 in FIG. 2 is a pull-up resistor, 2 is a discharge resistor, 3 is an integrating capacitor. Reference numeral 4 is a diode, and 5 is an inverter IC.

A display device according to an embodiment of the present invention will be described below. For example, a synchronization signal detection circuit 2 as shown in FIG. 2B connected to the deflection circuit 101 in FIG.
At 01, the presence or absence of a sync signal is detected, it is determined that there is no sync signal, and a signal is output to the timer circuit 202. The operation of the sync signal detection circuit 201 of FIG. 2B will now be described. First, from point A, a negative-polarity synchronizing signal of TTL level shown in FIG. 2B is input, and after being inverted by the inverter of the integrated circuit 5, peak holding is performed by the diode 4 and the capacitor 3. When there is a synchronizing signal, the diode 4 A voltage is generated in the peak hold circuit composed of the capacitor 3 and the capacitor 3, and the presence or absence of the synchronizing signal can be detected. Here, the resistor 2 is for setting the peak hold time. Figure 1
When the timer circuit 202 detects that the synchronization signal does not have a time signal of about several seconds, it supplies a trigger voltage to the one-shot multivibrator circuit 203 to generate a voltage for the time required for the degaussing operation and drive the drive circuit 204. When the relay 205 is turned on and a current is passed through the positive temperature coefficient thermistor 104 and the degaussing coil 103 to perform the degaussing operation, the degaussing operation can be automatically performed when there is no synchronizing signal.

Here, the timer circuit 202 is provided to prevent the degaussing operation from being performed when the synchronization signal is lost for a short time when the software is simply switched.

In the present embodiment, the description has been made by using the relay, but the electronic circuit is formed by using a triac or the like,
It is also clear that the same effect can be obtained even if the demagnetizing current is obtained by using the self-resonant current without using the positive temperature coefficient thermistor.

[0014]

As described above, according to the present invention, the synchronizing signal detecting means for detecting the synchronizing signal, and when the synchronizing signal detecting means does not detect the synchronizing signal, a current is passed through the degaussing coil to degauss the shadow mask of the cathode ray tube. By providing a degaussing means, it is possible to perform a degaussing operation when there is no sync signal, and a sync signal from a computer or the like during use disappears, thereby providing a display device that can always obtain a good display state. You can

[Brief description of drawings]

FIG. 1 is a block diagram of a display device according to an embodiment of the present invention.

FIG. 2 is a circuit diagram of a sync signal detection circuit according to an embodiment of the present invention.

FIG. 3 is a block diagram of a conventional display device.

[Explanation of symbols]

 101 Deflection circuit 102 Display cathode ray tube 103 Degaussing coil 104 Positive characteristic thermistor 105 Manual degaussing switch 201 Synchronous signal detection circuit 202 Timer circuit 203 One-shot multivibrator circuit 204 Relay drive circuit 205 Relay

Claims (3)

[Claims] 1. A display device having a cathode ray tube and a degaussing coil, wherein a degaussing current is passed through the degaussing coil when the synchronizing signal detecting means detects a synchronizing signal and the synchronizing signal detecting means does not detect the synchronizing signal. A degaussing device comprising degaussing means for performing an operation. 2. The demagnetizing means degausses when the synchronizing signal detecting means includes a timer circuit for detecting a time during which the synchronizing signal is not detected, and when the timer circuit reaches a predetermined time. 1. Display device. 3. A display device according to claim 1, wherein degaussing is performed by the degaussing means when the power of the device is turned on.