JPS58107789A - Automatic magnetism degaussor for video monitor - Google Patents

Abstract

PURPOSE:To attain automatic magnet erasing, by detecting the magnetic state of a monitor with a magnetic field detector, storing the state in a memory, detecting a failure in magnetism through the use of a comparison circuit and flowing a current to a magnet erasing coil. CONSTITUTION:A signal from a magnetism detector 1 is outputted at an amplifier 3 after being divided into three signals; basic signal A, upper limit signal B and lower limit signal C. The three signals A, B, C are applied to the 1st-3rd A/D converters 4-6, and the output of the 2nd and 3rd A/D converters 5, 6 is applied to storage devices 11, 12. An upper limit value EH and a lower limit value EL of the detected signals are compared with a reference signal EA at comparators 7, 8 respectively. The logical sum is taken for the two comparator outputs at a trigger circuit 13, where a trigger pulse 13a is generated only when the logical sum is ''1''. As a result, a pulse having a prescribed time width is generated and a current having a waveform of attenuation oscillation flows to a magnet erase coil 16 via a drive circuit 15.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an automatic demagnetizing device for a video monitor, and in particular, automatically eliminates the costly magnetism that occurs when a shadow mask becomes magnetized due to the influence of earth's magnetism and external magnetism when the monitor is moved. The present invention relates to a magnetic charge detection circuit that detects a signal for erasing.

With conventional magnetic degaussing devices, the monitor was manually demagnetized when the power was turned on, but 1!4311 people often did not notice that there was a difference in convergence due to the movement of the monitor. Convergence could not be obtained.

One object of the present invention is to provide an extremely effective means for promptly eliminating the above-mentioned drawbacks. The structure is such that magnetic abnormalities are stored in a memory and detected using a comparison circuit, and demagnetization is automatically performed by passing current through a degaussing coil.

Hereinafter, preferred embodiments of the automatic demagnetizing device according to the present invention will be described with reference to the drawings.

1 is a magnetic detector, and as shown in FIG.
The part that is not affected by the magnetic field inside (the back corner of monitor 2)
K is provided. The output of this magnetic field detector 1 is transmitted to an amplifier 5.
As shown in FIG. 3, this amplifier 3 is provided with a plurality of dividing resistors R2, R3, and R4 in addition to a series feedback resistor R1 on the emitter side at the collector output of the transistor Tr. A basic signal A, an upper limit signal B, and a lower limit signal C are respectively output from the resistance contacts of the dividing resistors R2, R3, and R4. Among these signals A, B, and C, the reference signal A is sent to the first A/D converter 4, the upper limit signal B is sent to the second A/D converter 5, and the lower limit signal C is sent to the fifth A/D converter 5.
Each is input to an a/n converter 6. This @I A/
The output signal of the D converter 4 is compared with the previous magnetic field and a reference signal 'f! ! The signal A is input to the first comparator 7 and the second comparator 8. A power supply circuit 9 generates an initial pulse when the power is turned on. This initial pulse is passed through the sample clock generator 10 consisting of an OR circuit (logical sum), and then becomes the output signal of the sample clock generator 10f), which is sent to the two memories 11 and 12.
By operating the current position magnetic field information in the second A
The output signal (upper limit value) of the /D converter 5 is input to the first memory 11 , and the output signal (lower limit value) of the fifth a/n converter 6 is input to the second memory 12 . The upper limit value mu of the first memory 11 is sent to the first comparator 7, and the lower limit value KL of the second memory 12 is sent to the first comparator 7.
are respectively input to the second comparator 8 and compared with the subsequent magnetic field. In the first comparator 7, when Z^>E u, the output signal It! of the first comparator 7 is inputted. cu=1 (when it exceeds the upper limit of the previous magnetic field). In the second comparator 8, KA>
The output signal EcL of the second comparator 8 based on KL becomes 1 (when it falls below the previous lower limit value of the magnetic field). These Ecu signals of the first comparator 7 and 1! of the second comparator 8 are combined. tcL signal output line trigger circuit 15Vc input and Ffeu]1j
The logical sum with O1- is 11'' and a trigger pulse 15 is generated just in case.The pulse generator 14 is connected to the trigger circuit 1.
By inputting the trigger pulse 13a generated in No. 3, a pulse of a certain time is generated and is input to the sample clock generator 1o and the drive circuit 15. This sample clock generator 10 generates an input signal when the magnetic field is different from the previous one, but it is generated in the same way as the output signal of the power supply circuit 9. The drive circuit 15 is inputted to the drive circuit 15 by the output signal from the pulp generator 14, and when the pulse generator 14 generates a pulse for a certain period of time, the switch is turned on and the erase coil 16 receives an attenuated current. Monitor 2 like 2nd t+
The bottom of the groove is designed to demagnetize the magnetic field near the shadow mask.

As described above, the self-magnetic demagnetizing attachment for a video monitor according to the present invention includes a magnetic detector, an amplifier that divides the detection output into a plurality of levels, and two memory devices that store the upper and lower limits of these levels. Equipped with a comparison circuit that compares this level with a reference value, it is possible to display a stable color image on the cathode ray tube by automatically demagnetizing the Vζ shadow mask even when affected by the unreal world. can.

[Brief explanation of the drawing]

The drawings are for showing an automatic demagnetizing device for a video monitor according to the present invention. Fig. 1 is an overall block diagram, Fig. 2 is a plan view showing the monitor device, and Fig. 6 is a circuit diagram of the main parts. be. 1... Magnetic field detector 2... Plan view of monitor device 3... Amplifier 4... First A/D converter 5
...Second^/D converter 6...Third A/D converter 7...First comparator 8...Second comparator 9...
Power supply circuit 10...Sample clock generator 11...First memory 12...Second memory 13.
...Trigger circuit 14...Pulse generator 15...
Drive circuit 16...Degaussing coil 2nd sentence 3rd M

Claims (1)

[Claims] An amplifier for inputting the magnetic detector signal, dividing it into multiple levels and outputting it, and a plurality of A/D f converters for outputting all the outputs of different levels from this amplifier.
two memory devices for inputting the outputs of the upper and lower limit A/D converters of the A/D converter, two comparators for inputting the outputs of each memory device, and the plurality of Al1 :
A manual means for inputting the output from the A/Dg converter of the reference value among the l converters to each comparator, a trigger circuit for inputting the output of each comparator, and an input for the output of this trigger circuit. a pulse generator for inputting a signal from a magnetic field detector; input means for inputting the output of the pulse generator to each of the memory devices; and means for transmitting the output of the pulse generator to an erasing coil. A video monitor automatic demagnetizing device configured to control the lover signal to the erasing coil.