JP3011122U - Degaussing circuit - Google Patents

Abstract

(57) [Summary] [Object] The present invention relates to a degaussing circuit for degaussing a picture tube of a television receiver or the like, which automatically operates in response to a stoppage of the operation of the television receiver, and has an optimum waveform for degaussing. The purpose is to reliably demagnetize by supplying the degaussing current of. [Structure] A degaussing circuit including a degaussing coil 5 and a positive temperature coefficient thermistor 6 connected in series to the degaussing coil 5, and a switch 7 for supplying AC power to the degaussing circuit after the power of the image receiving circuit 8 is turned off. .

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a degaussing circuit which is suitable for a television receiver or the like and which is provided to prevent charging of a shadow mask of a picture tube.

[0002]

[Prior art]

 Conventionally, a degaussing coil is provided to prevent the picture tube of a television receiver or the like from being charged, and each time the power of the television receiver is turned off, the degaussing coil is energized to automatically perform degaussing. Such a degaussing device is known (see, for example, Japanese Patent Application Laid-Open No. 5-130628). The degaussing device is configured such that a PTC thermistor is inserted in series with the degaussing coil and a degaussing current is supplied through the PTC thermistor at any time during operation of the display device.

[0003]

[Problems to be solved by the device]

 However, the degaussing device described above has a very small degaussing current after a lapse of a predetermined time (about 10 seconds) from the time of power supply due to the characteristics of the positive temperature coefficient thermistor, which affects the landing of the electron beam of the display device. In many cases, it adversely affected the purity (color purity).

Therefore, the present invention inserts a positive temperature coefficient thermistor in series with the degaussing coil, and supplies a degaussing current to the degaussing coil via the positive temperature coefficient thermistor in conjunction with the power-off of the television receiver. It is an object of the present invention to provide a new degaussing current that can automatically perform a degaussing operation without adversely affecting the tube operation.

[0005]

[Means for Solving the Problems]

 In order to achieve the above object, the present invention provides a degaussing circuit for degaussing a picture tube, the degaussing circuit comprising a degaussing coil and a positive temperature coefficient thermistor connected in series to the degaussing coil, and a degaussing circuit. A switch for connecting the degaussing circuit to the AC power supply after the AC power supply is turned off.

Further, the switch is characterized in that the degaussing circuit and the image receiving circuit can be switched. The switch connected to the degaussing circuit after the AC power supplied to the image receiving circuit is turned off is controlled by a microcomputer.

[0007]

[Action]

 In the present invention, when the power of the television receiver is turned off, current is supplied to the series circuit of the positive temperature coefficient thermistor and the degaussing coil. At this time, due to the characteristics of the positive temperature coefficient thermistor, a degaussing current that is large at the beginning and then gradually attenuates flows in the degaussing coil. As a result, a stable and reliable degaussing effect can be obtained. In particular, since this degaussing operation is performed when the television receiver is not operating, it does not affect the display on the picture tube.

[0008]

【Example】

 Hereinafter, the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing an embodiment of a degaussing circuit according to the present invention. In the figure, reference numeral 1 is a power plug connected to a commercial AC power supply, 2 is a rectifier circuit connected to the power plug 1 via power lines 3 and 4, and the output of the rectifier circuit 2 is a television. Is supplied to the image receiving circuit 8. Further, a degaussing circuit composed of a series circuit of a degaussing coil 5 and a positive temperature coefficient thermistor 6 is connected between the power supply lines 3 and 4 via a changeover switch 7 which also serves as a power supply switch. The changeover switch 7 is a power switch of the television receiver, and operates the degaussing coil 5 when the power is off. FIG. 2 shows the operation timing of the image receiving circuit and the degaussing circuit, and the degaussing current waveform of the degaussing circuit. Next, the operation will be described.

In the degaussing circuit configured as described above, when the changeover switch 7 is on the rectifier circuit 2 side, the AC current supplied through the power plug 1 is rectified by the rectifier circuit 2 and then the image is received. It is supplied to the circuit 8 and the normal image receiving operation is performed. On the other hand, when the changeover switch 7 is switched to the degaussing circuit side to end the image receiving operation, an alternating current flows through the degaussing coil 5 via the positive temperature coefficient thermistor 6. Here, considering the characteristics of the positive temperature coefficient thermistor 6, as shown in FIG. 2, the resistance value is low immediately after energization because the temperature is low, and therefore a large current flows through the degaussing coil 5, but Since the resistance value gradually increases as the temperature rises, the current flowing through the degaussing coil 5 gradually decreases in inverse proportion to this.

Therefore, a stable and reliable degaussing effect can be obtained. Further, since this degaussing operation is performed when the television receiver is not in operation, there is no risk of adversely affecting the display on the picture tube.

FIG. 2 shows a degaussing circuit according to another embodiment of the present invention. In this embodiment, a power relay 11 and a power switch 12 are used in place of the changeover switch used in the embodiment of FIG. 1, and the power relay 11 and the power switch 12 are microcomputers having a predetermined control program. It is controlled by 13. The microcomputer 13 controls on / off of the power switch 12 to operate the image receiving circuit 8 of the television receiver, and after turning off the power switch 12, preferably for a predetermined time after about 10 seconds have passed, The power relay 11 is operated and its contact 14 is turned on.

Therefore, the AC current is supplied to the degaussing circuit including the degaussing circuit 5 and the positive temperature coefficient thermistor to degauss the CRT only while the contact 14 is on. Fig. 4 shows the operation timing of the image receiving circuit and degaussing circuit, and the degaussing current waveform of the degaussing circuit.

[0013]

[Effect of device]

 As described above, according to the present invention, after the power of the television receiver is turned off, the current is automatically supplied to the degaussing circuit composed of the series circuit of the positive temperature coefficient thermistor and the degaussing coil, and Due to the characteristics of the characteristic thermistor, a degaussing current that is initially large and then gradually attenuates flows in the degaussing coil. As a result, a stable and reliable degaussing effect can be obtained. Further, since this degaussing operation is performed when the television receiver is not operating, it does not affect the display on the picture tube.

[Brief description of drawings]

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

FIG. 2 is a diagram showing an operation timing of the degaussing circuit shown in FIG.

FIG. 3 is a circuit diagram showing a configuration of a second embodiment of a degaussing circuit according to the present invention.

FIG. 4 is a diagram showing an operation timing of the degaussing circuit shown in FIG.

[Explanation of symbols]

 1 Power Plug 2 Rectifier Circuit 3, 4 Power Line 5 Degaussing Coil 6 Positive Characteristic Thermistor 7 Changeover Switch 11 Power Relay 12 Power Switch 13 Microcomputer 14 Contact

Claims (3)

[Scope of utility model registration request] 1. A degaussing circuit for degaussing a picture tube, the degaussing circuit comprising a degaussing coil and a positive temperature coefficient thermistor connected in series to the degaussing coil, and after turning off an AC power supply supplied to the image receiving circuit. A degaussing circuit comprising: a switch for connecting the degaussing circuit to an AC power supply. 2. The degaussing circuit according to claim 1, wherein the switch is configured to switch between a degaussing circuit and an image receiving circuit. 3. The switch connected to the degaussing circuit after the AC power supplied to the image receiving circuit is turned off, is controlled by a microcomputer.
Alternatively, the degaussing circuit described in 2.