JPH0398393A - Degaussing circuit - Google Patents

Abstract

PURPOSE:To make a current of a circuit completely zero after degaussing without generation of a residual current in a degaussing coil by providing a current control means interrupting a current flowing to the degaussing coil when a temperature of a positive characteristic thermister reaches a prescribed temperature. CONSTITUTION:When a temperature of a positive characteristic thermister 11 reaches a prescribed temperature after a prescribed time elapses and a residual current flows, the temperature of a moving piece 4a in contact with a lead wire 6 is selected to by the prescribed temperature value and the temperature is set. When the temperature of the positive characteristic thermister 11 reaches the prescribed temperature, the moving contact 4a is parted from the contact point of the lead wire 5 and contacts the contact of a lead wire 6 connected to a bypass wire 2, then a current flowing to a degaussing coil 14 is interrupted and the current flows to the bypass wiring 2 through the lead wire 6. Thus, no residual current is caused in the degaussing coil and the current at the circuit equilibrium point after degaussing is made completely zero.

Description

Detailed Description of the Invention [Objective of the Invention] (Industrial Application Field) The present invention relates to a degaussing coil installed near the picture tube of a color television receiver as an object to be demagnetized, and The present invention relates to a degaussing circuit including a positive temperature coefficient thermistor having a function of allowing a current that attenuates to flow through the degaussing coil.

(Prior Art) One of the conventional degaussing circuits is disclosed in Japanese Utility Model Application Laid-Open No. 52-28113, and its circuit structure is shown in FIG.

This degaussing circuit includes a positive temperature coefficient thermistor 11 connected to a power supply 13 via a switch 12;
1 and a bimetal 15 connected in parallel with the degaussing coil 14. Further, the thermistor 11 and the bimetal 15 are thermally connected to each other, and the bimetal 15 is operated by the self-heating temperature of the positive temperature coefficient thermistor 11, and the switching part of the bimetal 15 is turned on. The resistance values of the degaussing coil 14 and the bimetal 15 are set so that the former is higher than the latter.

In the degaussing circuit configured as described above, when the switch 12 is first turned on, current flows from the positive temperature coefficient thermistor l1 to the degaussing coil 14, but as the energization time elapses, the temperature increases between the positive temperature coefficient thermistor 11 and the degaussing coil 14. The bimetal 15, which is connected to
It is possible to limit the current flowing to 4.

That is, the bimetal is operated by the self-heating temperature of the positive temperature coefficient thermistor, and the current of the degaussing circuit is limited.

(Problem to be Solved by the Invention) However, in the above degaussing circuit, the bimetal 15 operates due to the self-heating temperature of the positive temperature coefficient thermistor 11.
Even if a short circuit composed of the power supply 13, the switch 12, the positive temperature coefficient thermistor 11, and the bimetal 15 is formed, the impedance Zs of this short circuit does not actually become zero, and the bimetal 15 of the short circuit Due to the relationship between the impedance Zc of the degaussing circuit replaced by the degaussing coil 14 and the impedance Zs of this short circuit, a residual current of Zs/(Zc+Zs) is generated in the degaussing coil.

As a result, the current flowing through the demagnetizing coil 14 shown in FIG. 4 does not become zero, so there is a problem that a sufficient demagnetizing effect cannot be obtained.

Therefore, an object of the present invention is to provide a degaussing circuit in which no residual current is generated in the degaussing coil and the current in the circuit after degaussing becomes completely zero.

[Structure of the Invention] (Means for Solving the Problems) In order to achieve the above-mentioned object, the present invention has a degaussing circuit in which when the temperature of a positive temperature coefficient thermistor reaches a predetermined temperature value 3, a current flows through the degaussing coil. A current control means capable of interrupting the current is provided.

(Function) The function of the present invention is that when the temperature of the positive temperature coefficient thermistor reaches a predetermined temperature value, a residual current is generated in the degaussing coil itself by cutting off the current flowing through the degaussing coil by the current control means. This is done so that the current in the circuit after demagnetization becomes completely zero.

(Embodiment) An embodiment of the degaussing circuit of the present invention will be described below from Figs. 1 to 3.
This will be explained in detail with reference to the figures.

FIG. 1 is a circuit diagram of a degaussing circuit showing an embodiment of the present invention.

The difference between the degaussing circuit 1 shown in FIG. 1 and the degaussing circuit 10 shown in FIG. 4 described above is that the degaussing circuit 10 shown in FIG. When the temperature value is reached, the degaussing coil l4
current control means 3 capable of interrupting the current flowing through the degaussing coil 1;
Bypass wiring 2 to bypass the current flowing into 4
This is because we have established the following. Here, the above-mentioned predetermined temperature value is a temperature value at which the maximum demagnetizing effect is obtained after a predetermined energization time has elapsed. The current control means 3 includes:
It is composed of a bimetal 4, and has a mechanism that can switch and control the degaussing coil 14 and the bypass wiring 2.

As shown in FIG. 2, the bimetal 4 is enclosed in a synthetic resin case 12 together with a positive temperature coefficient thermistor 11, and one end of the bimetal 4 is connected to one end surface of the element body 7 so as to be electrically conductive. Connected and fixed, one open end is
It consists of a movable piece 4a that comes into contact with the contact point of either one of the lead wires 5, 6 depending on the temperature of the positive temperature coefficient thermistor 11 between the lead wires 5 and 6.

In this embodiment, when the positive temperature coefficient thermistor 11 does not reach a predetermined temperature, the movable piece 4a contacts the contact point of the lead wire 5. Furthermore, since the lead wire 6 is connected to the bypass wiring 2, when no current is passed through the 5 6 degaussing coil 14, the current is passed through the bypass wiring 21.

Note that 8 in FIG. 2 is a lead wire connected to the other end surface of the element body 7.

In the degaussing circuit 1 configured as described above, when the power switch 12 is turned on (on), a current corresponding to the temperature flows through the degaussing coil 14 due to the action of the positive temperature coefficient thermistor 11. Next, due to this energized state, the temperature of the positive temperature coefficient thermistor 11 itself rises, and the resistance value also rises accordingly, and the flowing current value decreases as shown in FIG. 3.

In FIG. 3, the horizontal axis indicates time t1, and the vertical axis indicates current value i.

Here, if the temperature of the PTC thermistor 11 itself reaches a predetermined temperature value after a predetermined time t1 has elapsed, and a residual current flows, the temperature when the movable piece 4a contacts the lead wire 6 is set to the predetermined temperature value. Set this value as the temperature value. When the temperature of the positive temperature coefficient thermistor 11 reaches the set temperature, the movable piece 4a separates from the contact point of the lead wire 5 and comes into contact with the contact point of the lead wire 6 connected to the bypass wiring 2, so that the current flows to the degaussing coil 14. The current that was flowing is cut off, and the current starts to flow to the bypass wiring 2 via the lead wire 6. From this, a current always flows through the current control means 3, and after the current flows through the bypass wiring 2, the temperature of the positive temperature coefficient thermistor 11 itself becomes stable at a certain stable temperature point, so that the movable piece 4a is turned off again. It does not come into contact with the contacts of the lead wire 5.

In FIG. 1, the state of the bimetal 4 after displacement is shown by dotted lines.

As described above, in this embodiment, when the positive temperature coefficient thermistor reaches a predetermined temperature, the residual current flowing through the degaussing coil is completely cut off, so that no current flows through the degaussing coil.

Therefore, when a degaussing coil is installed near the picture tube of a color television receiver as the object to be degaussed, although the decay characteristic of the initial current is slow, no residual current is generated in the degaussing coil. It is possible to solve the problem that the picture tube screen flickers, which is caused by the oscillating magnetic field caused by the current giving "fluctuations" to the electron beam in the picture tube. Here, the oscillating magnetic field acting on the electron beam is defined as AxT, where A is the residual current flowing through the degaussing coil 14, and T is the number of turns of the degaussing coil 14.
It is expressed as Furthermore, since no residual current is generated in the degaussing coil, there is no need to consider residual current, so it is possible to set an arbitrary initial current attenuation characteristic depending on the object to be demagnetized. In addition, in this embodiment, a bimetal is used as the current control means, but it is not limited to the above-mentioned bimetal.
For example, a temperature-sensitive reed switch or any device that can cut off current at a predetermined temperature value can be applied.

[Effects of the Invention] As detailed above, the present invention provides a degaussing circuit in which no residual current is generated in the degaussing coil and the current at the equilibrium point of the circuit after demagnetization is completely zero. be able to.

[Brief explanation of drawings]

Fig. 1 is a configuration circuit diagram of a degaussing circuit as an embodiment of the present invention, Fig. 2 is a schematic configuration diagram of the positive temperature coefficient thermistor shown in Fig. 1, and Fig. 3 is a current diagram of the degaussing circuit shown in Fig. 1. The attenuation characteristic diagram, FIG. 4, is a configuration circuit diagram of a conventional degaussing circuit. 3... Current control means, 11... Positive characteristic thermistor,
14... Demagnetizing coil. 9 10 JP-A-3 98393 (4) Figure 3

Claims (3)

[Claims] (1) A demagnetizing coil installed near the object to be demagnetized,
In a degaussing circuit having a positive temperature coefficient thermistor having a function of allowing a current that decays over time to flow through the degaussing coil, when the temperature of the positive temperature coefficient thermistor reaches a predetermined temperature value, the degaussing coil is activated. A degaussing circuit comprising current control means capable of interrupting the flowing current. (2) The degaussing circuit is provided with bypass wiring for bypassing the current flowing through the degaussing coil, and the current control means switches and controls the degaussing coil and the bypass wiring. degaussing circuit. (3) The degaussing circuit according to claim 1, wherein a bimetal is installed in the degaussing circuit at a location where switching control is performed between the degaussing coil and the bypass wiring, and the switching control is performed using the bimetal.