JPH05153606A - Degaussing circuit - Google Patents

Abstract

PURPOSE:To make a degaussing coil small, to reduce the cost and to improve the degaussing effect. CONSTITUTION:A positive characteristic thermister 13 and a switch 19 are connected in series with a degaussing coil 17. Moreover, a positive characteristic thermister 15 and a switch 21 are connected in series with a degaussing coil 23. When a voltage of a commercial AC power supply 1 is 120V, the degaussing coils 17, 23 are connected in parallel. When a voltage of a commercial AC power supply 1 is 240V, the degaussing coils 17, 23 are connected in series. Through the constitution above, the degaussing effect is improved and the diameter of the degaussing coils is reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a degaussing circuit, and more particularly to a degaussing circuit for a color television.

[0002]

2. Description of the Related Art When a color television is turned on, a high voltage power source is applied to a picture tube to generate magnetism and an external magnetic field due to the earth's magnetism. These magnetism remains in the shadow mask of the picture tube and peripheral parts. In order to eliminate the influence of the magnetic field due to the earth's magnetism, it is necessary to demagnetize the shadow mask and magnetically shield the electron beam. Further, once the magnetism remains in the shadow mask, the color purity may decrease. Therefore, a degaussing circuit is provided to remove this magnetism. The degaussing circuit automatically degausses by passing an alternating current that decays with time through a degaussing coil.

FIG. 4 shows a block diagram of the degaussing circuit described above. In FIG. 4, the commercial AC power supply 101 includes degaussing coils 103 and 10 via a positive temperature coefficient thermistor 102.
4 is connected. The degaussing coil 104 is a commercial AC power supply 1
01 is connected. The resistance value of the positive temperature coefficient thermistor 102 increases as the temperature rises. Commercial AC power supply 1
When 01 is turned on, a large current flows through the degaussing coils 103 and 104, and the thermistor 102 self-heats, so that the current flowing through the entire circuit decreases. FIG. 5 shows a waveform diagram of the current flowing through the degaussing coils 103 and 104. As is clear from FIG. 5, the current flowing through the degaussing coils 103 and 104 is gradually reduced and degaussed.

By the way, worldwide televisions have been put into practical use. This is a television that can be used even in areas where the power supply voltage, frequency, etc. are different. That is, the voltage at which the television is driven varies from region to region and is, for example, 100 to 240 volts. Therefore,
The voltage applied to the television receiver also varies from region to region. For this reason, it is inappropriate to use the degaussing circuit described above in a worldwide television. Here, the degaussing coil used in the degaussing circuit of the television corresponding to the whole world is devised so as to cope with magnetism generated by different voltages.

[0005]

That is, with respect to the maximum voltage, it is necessary to increase the number of windings of the degaussing coil to increase the impedance in order to prevent the fuse from being blown by the over-discharge of the current. There is. For this reason, the amount of coils used increases, and the cost increases. Further, for the minimum voltage, it is necessary to increase the wire diameter of the degaussing coil and lower the impedance in order to allow the current to flow through the degaussing coil. In this case, since the wire diameter of the degaussing coil is large, the coil becomes heavy and the workability deteriorates.

Therefore, an object of the present invention is to provide a degaussing circuit capable of improving the degaussing effect and reducing the cost by reducing the size of the degaussing coil.

[0007]

According to the present invention, first and second degaussing coils are provided, a switch network is provided in series with the first and second degaussing coils, and a positive temperature coefficient thermistor is inserted. The first and second degaussing coils are connected in series at the power supply voltage of 1, and the first and second degaussing coils are connected at the second power supply voltage.
And a second degaussing coil connected in parallel, which is a degaussing circuit for a color television.

[0008]

The input voltage is detected by the voltage detection circuit. The connection of the degaussing coil is switched based on the detection result.

By switching the connection of the degaussing coil and utilizing the voltage doubler circuit, a constant voltage is supplied to the power supply circuit regardless of the input voltage.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a block diagram of a degaussing circuit according to the present invention. In FIG. 1, the commercial AC power supply 1 may have a voltage of 120 V or 240 V, for example, depending on the area. One end of the commercial AC power supply 1 detects how much voltage is used as a power supply 120/240
It is connected to the V detection circuit 3 and also to a connection point 7 via a switch 5 for on / off control of the entire circuit. The delay circuit 9 is connected to the switch 5. An on / off switch 11 for controlling on / off of the television is connected to the delay circuit 9. The on / off switch 11 is connected to the 120 / 240V detection circuit 3.

The connection point 7 is a degaussing coil 17 and 2 which will be described later.
3 is connected to one end of positive temperature coefficient thermistors 13 and 15 for supplying an attenuation current to the positive temperature coefficient thermistor 13. The other end of the positive temperature coefficient thermistor 13 is connected to the terminal 19a of the switch 19 via the degaussing coil 17.
And a terminal 21b of the switch 21. The switch 19 has a terminal 19c and a terminal 19a.
9b is switched. The other end of the positive temperature coefficient thermistor 15 is connected to the terminal 21 a of the switch 21. The terminal 21c of the switch 21 is connected to one end of the degaussing coil 23. The switches 19 and 21 are controlled in conjunction with the output of the 120 / 240V detection circuit 3. Degaussing coil 2
The other end of 3 and the terminal 19c of the switch 19 are connected to the connection point 25.
Respectively connected to. Connection point 25 is 120/240
It is connected to the V detection circuit 3 and the other end of the commercial AC power supply 1.

When the on / off switch 11 is turned on,
120 / 240V detection circuit 3 as commercial AC power supply 12
It is detected whether 0V or 240V is used. Based on this detection result, the switches 19 and 2
1 is controlled. That is, when the commercial AC power used is detected to be 120V by the 120 / 240V detection circuit 3, the terminal 19c of the switch 19 and the terminal 21c of the switch 21 are connected to the terminals 19a and 21a, respectively. .. Therefore, the degaussing coils 17 and 2
3 are connected in parallel. On the other hand, when 240V is detected, the terminal 19c of the switch 19 and the terminal 21c of the switch 21 are connected to the terminals 19b and 21b, respectively. Therefore, the degaussing coils 17 and 23 are connected in series.

After controlling the switches 19 and 21, a control signal is supplied to the switch 5 by the delay circuit 9 and the switch 5 is turned on. This turns on the entire circuit. Attenuated currents are supplied to the terminals 19a and 21a by the positive temperature coefficient thermistors 13 and 15. Commercial A
When the C power source 1 is 120 V, the degaussing coils are connected in parallel, and the impedances of the degaussing coils 17 and 23 are reduced. This facilitates the degaussing current to flow. Further, when the commercial AC power source 1 is 240 V, the impedance of the degaussing coils 17 and 23 is increased by connecting the degaussing coils in series. This makes it difficult for the degaussing current to flow. The power consumption of the degaussing coils 17 and 23 is the same between the series connection and the parallel connection. In this way, different power supply voltages can be accommodated simply by switching the connection relationship between the degaussing coils 17 and 23.

FIG. 2 shows a block diagram of a degaussing circuit according to a second embodiment of the present invention. One end of the commercial AC power supply 31 is connected to a 120 / 240V detection circuit 33 that detects how much voltage is used as a power supply, and
Two positive temperature coefficient thermistors 3 housed in one case via a switch 35 for on / off control of the entire circuit.
7 (37a and 37b). The positive temperature coefficient thermistor 37 is for supplying an attenuation current to the degaussing coils 43 and 45 described later. A delay circuit 39 is connected to the switch 35. An on / off switch 41 for controlling on / off of the television is connected to the delay circuit 39. This on / off switch 41 is 1
It is connected to the 20 / 240V detection circuit 33.

The positive temperature coefficient thermistor 37a includes a switch 47.
Connected to the terminal 47a. In addition, the positive temperature coefficient thermistor 3
7b is a terminal 4 of the switch 47 via the degaussing coil 45.
7b and the terminal 49a of the switch 49. The switch 49 is switched between the terminal 49a and the terminal 49b by the terminal 49c. The terminal 47c of the switch 47 is connected to one end of the degaussing coil 43. In addition,
The switches 47 and 49 are controlled in conjunction with the output of the 120 / 240V detection circuit 33. The other end of the degaussing coil 43 and the terminal 49c of the switch 49 are connected to the connection point 51, respectively. The connection point 51 is connected to the other end of the 120 / 240V detection circuit 33 and the commercial AC power supply 31.

When the on / off switch 41 is turned on,
The 120 / 240V detection circuit 33 detects whether 120V or 240V is used as the commercial AC power supply. The switches 47 and 49 are controlled based on the detection result. That is, the 120 / 240V detection circuit 33 causes the commercial AC power source used to
When it is detected as V, the terminal 47c of the switch 47 and the terminal 49c of the switch 49 are the terminals 47a and 4
9a, respectively. Therefore, the degaussing coil 43
And 45 are connected in parallel. On the other hand, when 240V is detected, the terminal 47c of the switch 47 and the terminal 49c of the switch 49 are connected to the terminals 47b and 49b, respectively. Therefore, the degaussing coils 43 and 45 are connected in series.

After controlling the switches 47 and 49, a control signal is supplied to the switch 35 by the delay circuit 39, and the switch 35 is turned on. This turns on the entire circuit. In this way, by switching the switches 47 and 49 before the switch 35 is turned on, safe operation of the circuit is ensured. Attenuated current is supplied to the terminals 47a, 47b, and 49a by the positive temperature coefficient thermistor 37. When the commercial AC power source 31 is 120 V, the degaussing coils 43 and 45 are connected in parallel,
The impedance of the degaussing coils 43 and 45 is reduced. This facilitates the degaussing current to flow. Further, when the commercial AC power source 31 is 240V, the degaussing coil 43
And 45 in series, the impedance of the degaussing coils 43 and 45 is increased. This makes it difficult for the degaussing current to flow. The degaussing coils 43 and 4
The power consumption in 5 is the same in the case of series connection and the case of parallel connection. Thus, the circuit can be simplified by using a single thermistor having two positive temperature coefficient thermistors.

FIG. 3 shows a block diagram of a degaussing circuit according to a third embodiment of the present invention. In FIG. 3, one end of the commercial AC power supply 61 is connected to a switch 63 for on / off control of the entire circuit and a connection point 65a of a diode bridge 65 that performs full-wave rectification. An on / off switch 69 for controlling on / off of the television is connected to the switch 63. This on / off switch 1
1 is connected to the power supply circuit 71.

The switch 63 is connected to two positive temperature coefficient thermistors 73 (73a and 73b) housed in one case. The PTC thermistor 73 operates similarly to the second embodiment. The positive temperature coefficient thermistor 73a is
It is connected to the terminal 75a of the switch 75. Further, the positive temperature coefficient thermistor 73b is connected to the terminal 75b of the switch 75 and the terminal 79a of the switch 79 via the degaussing coil 77. The switch 79 can be switched between the terminal 79a and the terminal 79b by the terminal 79c.

The terminal 75c of the switch 75 is connected to one end of the degaussing coil 81. The other end of the degaussing coil 81 and the terminal 79c of the switch 79 are connected to the connection point 83, respectively. The connection point 83 is the connection point 65 b of the diode bridge 65 and the terminal 8 of the switch 87 via the connection point 85.
7a. It is a switch that is set according to the voltage of the commercial AC power supply. When the commercial AC power source is 120V, the switch 87 is turned on, and when the commercial AC power source is 240V, the switch 87 is turned off. The switch 87 is switched in association with the switches 75 and 79. The connection point 65c of the diode bridge 65 is connected to one ends of the power supply circuit 71 and the capacitor 89. The other end of the capacitor 89 is connected to the terminal 87b of the switch 87 and the capacitor 91.
Connected to one end of. The other end of the capacitor 91 is connected to the connection point 65d of the power supply circuit 71 and the diode bridge 65. The connection point 85 is connected to the other end of the commercial AC power supply 61.

When the on / off switch 69 is turned on,
The drive signal is supplied to the power supply circuit 71, and the switch 63 is turned on. Here, it is assumed that the commercial AC power source 61 is, for example, a 120V power source. In this case, the switch 87 is turned on in advance, and the terminal 75c of the switch 75 and the terminal 79c of the switch 79 are switched to the terminals 75a and 79a, respectively. As a result, the degaussing coils 77 and 81 are connected in parallel. The commercial AC power source is voltage-doubled and rectified by a voltage doubler rectifier circuit including a diode bridge 65 and capacitors 89 and 91. As a result, the voltage supplied to the power supply circuit 71 becomes 240V.

In addition, the commercial AC power source 61 is, for example, 240
When the power source of V is applied, the switch 87 is turned off in advance, and the terminal 75c of the switch 75 and the terminal 79c of the switch 79 are the terminals 75b and 79b.
Have been switched to. As a result, the degaussing coils 77 and 81 are connected in series. Also, switch 8
Since 7 is turned off, bridge rectification is performed and the power supply circuit 7
The voltage supplied to 1 is 240V. In this circuit,
It is possible to supply a constant voltage to the power supply circuit 71 even when the input voltage is different.

As described above, when a low voltage is input, the degaussing coils 77 and 81 can be connected in parallel to reduce the impedance of the degaussing coil so that the degaussing current can easily flow. Further, when a high voltage is input, by connecting the above-described degaussing coils in series, it is possible to increase the impedance of the degaussing coil and prevent the degaussing current from flowing too much. Further, in the third embodiment, by using the voltage doubler rectifier circuit of the power supply circuit, the voltage detection circuit used in the first and second embodiments can be eliminated and the circuit can be simplified. Can be measured.

[0024]

According to the present invention, the degaussing effect can be improved by switching the connection of the degaussing coil according to different input voltages. Further, the winding of the degaussing coil can be reduced to reduce the cost. Further, since the diameter of the degaussing coil is reduced, the set can be easily designed and the workability can be improved.

[Brief description of drawings]

FIG. 1 is a block diagram of a degaussing circuit according to a first embodiment of the present invention.

FIG. 2 is a block diagram of a degaussing circuit according to a second embodiment of the present invention.

FIG. 3 is a block diagram of a degaussing circuit according to a third embodiment of the present invention.

FIG. 4 shows a block diagram of a prior art degaussing circuit.

FIG. 5 is a waveform diagram showing a current flowing through the degaussing coil.

[Explanation of symbols]

 3, 33 120 / 240V detection circuit 17, 23, 43, 45, 77, 81 Degaussing coil 19, 21, 45, 49 Switch 65 Diode bridge 71 Power supply circuit

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[Procedure amendment]

[Submission date] March 27, 1992

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0018

[Correction method] Change

[Correction content]

In FIG . 3, one end of the commercial AC power source 61 is
The degaussing circuit on / off control is performed via the main switch 69.
Switch 63 and a diode for rectifying the power supply
It is connected to the bridge 65a. Double voltage for switch 63
/ Bridge rectification automatic switching circuit 87 through delay circuit 92
And then connected.

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0020

[Correction method] Change

[Correction content]

The terminal 75c of the switch 75 is connected to one end of the degaussing coil 81. The other end of the degaussing coil 81 and the terminal 79c of the switch 79 are connected to the connection point 83, respectively. The connection point 83 is connected to the connection point 65b of the diode bridge 65 and the double voltage / bridge rectification via the connection point 85.
It is connected to the terminal 87a of the automatic switching circuit 87 . Commercial AC
It is a circuit that switches the rectification method according to the voltage of the power supply.
If the commercial AC power source is 120V, double voltage / bridge
The rectification automatic switching circuit is turned on, and when the commercial AC power source is 240 V, the voltage doubler / bridge rectification automatic switching circuit is turned off. Switch 7 by switching signal of voltage doubler / bridge rectification circuit
5 and 79 are switched. Diode bridge 65
The connection point 65c is connected to one ends of the power supply circuit 71 and the capacitor 89. The other end of the capacitor 89 is connected to the terminal 87b of the switch 87 and one end of the capacitor 91. The other end of the capacitor 91 is connected to the connection point 65d of the power supply circuit 71 and the diode bridge 65. The connection point 85 is connected to the other end of the commercial AC power supply 61.

[Procedure 3]

[Document name to be amended] Statement

[Correction target item name] 0021

[Correction method] Change

[Correction content]

When the on / off switch 69 is turned on,
The switch 63 has switches 75 and 79 depending on the input voltage.
After switching, it is turned on by the delay circuit and becomes a degaussing circuit.
Degaussing current flows. Double voltage / bridge rectification automatic switching circuit
Voltage is applied to. Here, it is assumed that the commercial AC power source 61 is, for example, a 120V power source. In this case,
When the voltage doubler / bridge rectifier automatic switching circuit 87 is turned on to co <br/>, terminal 79c of the terminal 75c and the switch 79 of the switch 75 is switched to terminals 75a and the terminal 79a. As a result, the degaussing coils 77 and 81 are connected in parallel. The commercial AC power supply is a diode bridge 6
5 and a voltage doubler rectifier circuit composed of capacitors 89 and 91. As a result, the voltage supplied to the power supply circuit 71 becomes 240V.

[Procedure amendment 4]

[Document name to be amended] Statement

[Name of item to be corrected] 0022

[Correction method] Change

[Correction content]

In addition, the commercial AC power source 61 is, for example, 240
Double voltage / bridge rectification when V power source is applied
With automatic switching circuit 87 is turned off, the terminal 79c of the terminal 75c and the switch 79 of the switch 75, terminal 75b
And the terminal 79b. As a result, the degaussing coils 77 and 81 are connected in series. Further, since the voltage doubler / bridge rectification automatic switching circuit 87 is turned off, bridge rectification is performed, and the voltage supplied to the power supply circuit 71 is 240V. In this circuit, a constant voltage can be supplied to the power supply circuit 71 even when different input voltages are used.

[Procedure Amendment 5]

[Document name to be corrected] Drawing

[Name of item to be corrected] Figure 1

[Correction method] Change

[Correction content]

[Figure 1]

[Procedure correction 6]

[Document name to be corrected] Drawing

[Name of item to be corrected] Figure 2

[Correction method] Change

[Correction content]

[Fig. 2]

[Procedure Amendment 7]

[Document name to be corrected] Drawing

[Name of item to be corrected] Figure 3

[Correction method] Change

[Correction content]

[Figure 3]

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yasuyuki Yamazaki 6-7-35 Kitashinagawa, Shinagawa-ku, Tokyo Sony Corporation

Claims (1)

[Claims] 1. A first and a second degaussing coil are provided, a switch circuit network is provided in series with the first and the second degaussing coil, and a positive temperature coefficient thermistor is inserted. A degaussing circuit for a color television, wherein the first and second degaussing coils are connected in series, and the first and second degaussing coils are connected in parallel when a second power supply voltage is applied.