JPS5836094A - Magnetic eraser - Google Patents

Abstract

PURPOSE:To realize automatic magnetic erasure by turning on the gate of a thyristor through a capacitor charged with a main switch in a color TV receiver, and then flowing the charging current of another capacitor to a magnetic erasing coil. CONSTITUTION:When the main switch (not shown in the figure) of equipment is turned on, the charging of a capacitor 10 up to a DC voltage 120V is started through a resistance 9. A DC power source 20V, on the other hand, starts charging a capacitor 14 and when the charged voltage of a Zener diode 15 exceeds its threshold value, a transistor (TR) 17 turns on. Consequently, a TR22 turns off and its collector potential rises to flow a current through the gate of a thyristor 12, which turns on to flow charges, stored in the capacitor 10, to the ground through a magnetic erasing coil 1, thus performing the magnetic erasure by a damping oscillation current.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a degaussing device for color television receivers, color cathode ray tube display devices, etc., and an object thereof is to provide a simple automatic degaussing device using a DC power source.

A method of degaussing a color television receiver, a color cathode ray tube display device, etc. described in , 1, in which a degaussing coil is installed, and when the power switch is turned on, a current that attenuates over time is passed through the degaussing coil automatically or manually. is taken. Automatic degaussing circuits are used in devices that use AC power, but devices that use DC power
Conventionally, only manual degaussing using push button switches or automatic degaussing circuits using expensive relays were available.

Figure 1 shows an automatic degaussing circuit for equipment using an AC power supply.

This is an automatic degaussing method in which a temperature-positive thermistor 2 is connected in series to the degaussing coil 1, and when the power switch 3 is closed, a current that decays over time is supplied to the degaussing coil 1 due to the action of the temperature-positive thermistor 2. It is something to do.

FIG. 2 shows a degaussing device for equipment using a DC power source, which is the object of the present invention. This is connected to the capacitor 6 from the flyback transformer 4 of a color television receiver, etc.
A pulse is taken out through 1- through 1-, the negative direction is clipped through diode 6, the voltage is divided into an appropriate voltage through resistor 7゜8, the capacitor 10 is charged through 1- through resistor 9, and the capacitor 1 Push button switch 1 after ゜ is fully charged.
When 1 is pressed, the charge stored in the capacitor 10 flows into the demagnetizing coil 1, and at this time, the current flowing through the demagnetizing coil 1 is formed by d, the capacitance C2 of the capacitor 10, and the inductance L of the demagnetizing coil 1. Frequency f=1/2π
A) The purpose of demagnetization is achieved by performing damped vibration under the magnetic field. However, with this method, the push button switch 11 must be pressed each time the device is used, which is cumbersome.

The present invention aims to improve this annoying problem by making the demagnetizing current flow automatically when the push button switch is pressed and the main switch of the device is turned on.

FIG. 3 shows an embodiment of the present invention. In the figure, elements that perform the same functions as those in FIG. 2 are designated by the same numbers.

In Fig. 3, the arrangement of the resistor 9 and capacitor 10 for charging 11L and the degaussing coil 3 is the same as in Fig. 2;
By shaping the pulse from the flyback transformer shown in the figure to create a DC voltage, the machine 2 directly uses the DC voltage (in this case 120V) in ÷, and therefore the capacitor 5 in Figure 2 .Diode 6 and resistor 7,
8 can be deleted. - In Fig. 3, other DC voltages 1
13. Connect a charging resistor to the E source (20V here). Capacitor 14 J? J: A charging/discharging circuit is connected to a 1V connection j-1 from a diode 24 for charging and discharging, and one end of this capacitor 14 is connected to a trigger circuit 16 via a Zener diode 15.
The anode and cathode of the Zyristor 12 are connected between the other end of the degaussing coil 1 and the ground, and the gate of this Zyristor 12 is connected to the base of the first transistor 17 constituting the circuit. 16
It is connected to the collector terminal of the second transistor 22 constituting the transistor. Here, in Figure 3, the time constant T, -R1G formed by the resistor 13 and the capacitor 14 is greater than the time constant T, -R1G formed by the resistor 9 and the capacitor 1o.
1,''' constant T2: R2C2 is increased so that the Schmitt trigger is started after the capacitor 10 is sufficiently charged. By doing this, 1: automatic demagnetization is possible, and the Zyristor 12 passes through 5 before the capacitor 10 is sufficiently charged. It can be avoided.

The operation will be explained in detail below. Main switch of equipment (
(not shown), charging of the capacitor 10 via the resistor 9 begins with a DC voltage of 120V. on the other hand,
Charging of the capacitor 14 is started from the DC 20V power supply via the resistor 13, and the cathode voltage of the Zener diode 15 increases.

When the voltage across the capacitor 14 exceeds the avalanche voltage of the Zener diode 16 (approximately 5V in this case), the base current of the transistor 17 begins to flow, turning the transistor 17 ON, and immediately turning the transistor 22 OFF.
It becomes F. Therefore, the collector potential of the transistor 22 rises, and as a result, a current flows through the resistor 23 to the gate of the Zyristor 12, the Zyristor 12 becomes conductive, and the charge that has already been sufficiently stored in the capacitor 10 passes through the degaussing coil 1 to ground. It will flow. At this time, as described above, a damped oscillating current is generated, and since the capacitor 10'l (+) is sufficiently charged, it satisfactorily accomplishes the purpose of demagnetization.

4 and 6 show the interrelationship between the time constant T when charging the capacitor 1o and the time constant T2 when the Schmitt trigger operates.

Further, FIG. 6 shows an outline of the damped oscillating current flowing through the degaussing coil 1. In Figure 73, when the main switch 4 is opened, the charge in the capacitor 14 is instantaneously discharged through the diode 24, and is then stored. 1 8, 19, 20, 21
．． Reference numeral 23 denotes a transistor and a resistor that together with 17 and 22 constitute a Schmitt trigger.

As explained above, the present invention enables automatic degaussing in color television receivers, color cathode ray tube display devices, etc. that operate on DC power, and a push button switch can be added to the conventional degaussing IW. This eliminates the hassle of pressing.

[Brief explanation of drawings]

Figures 1 and 3 are circuit diagrams of the degaussing device according to an embodiment of the present invention. Fig. 6 is a diagram showing charging characteristics, and a diagram showing a damped oscillating current generated in the iJ demagnetizing coil.1... Demagnetizing coil, 9, 13... Charging resistor, 10. 14... Charging capacitor, 1
2...Zyristor, 16...Zener diode, 16...Nyumi, I/trigger circuit.

Claims (1)

[Claims] Full? 1j: Connect one end of the degaussing coil to the connection point of the river resistor and the capacitor, connect the cyrisk to the other end of the degaussing coil, and connect the output terminal of the mitsu trigger circuit to the gate terminal of this cyrisk. Schmitz l-
A charging/discharging circuit is provided to activate the IJ trigger circuit, and a charging time constant of the charging/discharging circuit activated by the Schmitt trigger circuit is made longer than a charging time constant of the charging resistor and capacitor. degaussing device.