JPH1042224A - Radiation electric field reduction device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To surely reduce the radiation electric field of the face of CRT by detecting a radiation electric field from the front face of CRT, inversely amplifying it and generating a signal for canceling a radiation electric field from electrodes provided at the upper/lower sides of the peripheral edge part of CRT. SOLUTION: A deflection circuit 5 applies deflection pulse voltage to the deflection yoke 3 of CRT 1. A high voltage generation circuit 4 comprises a fly back transformer and the like, and it supplies high voltage to an anode 2. A video circuit 6 gives a video signal to the anode 2. Electrodes 11 for detecting a radiation electric field detecting the radiation electric field from the front face of CRT are provided for the two upper/lower sides of the peripheral part of CRTR 1. Electrodes 12a and 12b for cancel electric field generation generating the electric field for canceling the radiation electric field from the face of CRT are provided on the two upper/lower sides of the peripheral part of CRT 1. An inversion amplification circuit 13 inversely amplifies a voltage signal induced by the detection electrode 11, generates the signal for radiation electric field cancel for canceling the radiation electric field from the face of CRT and applies it to the electrodes 12a and 12b. Thus, the radiation electric field on the face of CRT is reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a radiated electric field reducing apparatus for reducing a radiated electric field radiated from the front of a CRT used for a display device of a computer or a TV receiver to the outside.

[0002]

2. Description of the Related Art Conventionally, users of CRT display devices,
Considering the effect on the health of workers nearby,
Measures have been taken so that the intensity of the electric field radiated from the front surface (radiated electric field intensity) does not exceed a certain standard.

The main cause of the electric field radiating from the front surface of the CRT is a deflection yoke and a flyback transformer. Various components are used to prevent electromagnetic waves radiated from these components from radiating (leaking) to the outside of the CRT display device. Shield is applied. However, since the front surface (display surface) of the CRT cannot be covered with a metal plate or the like, it is particularly important to reduce the radiated electric field radiated from the front surface of the CRT.

As a method of reducing the radiation electric field on the front surface of the CRT, a method of attaching a transparent and high-conductivity film (a so-called AR panel) to the display surface of the CRT, a method of attaching a metal plate or an antenna lead to the inside of the bezel. Aperture grill (shadow mask) by applying a pulse voltage of opposite polarity to the radiated electric field, or by connecting a large-capacity capacitor between the anode and the ground of the CRT
A method of increasing the electric field shielding effect of the device has been adopted. However, these methods require expensive and special CRTs.
Or the CRT display device becomes complicated as a whole, resulting in an increase in cost as a whole. In order to solve this problem, Japanese Patent Application Laid-Open No. 6-289801 discloses a circuit for generating a pulse voltage for canceling an electric field radiated from a high voltage generating circuit and a deflection circuit in a CRT display device, and an output voltage of the high voltage generating circuit. There has been proposed a device in which a circuit for superimposing a canceling pulse is provided.

[0005]

However, in Japanese Patent Application Laid-Open No. Hei 6-289801, a pulse for canceling a radiation electric field is taken from a winding provided in a flyback transformer or a horizontal output transformer, and the phase is adjusted. Since it is merely superimposed on the output voltage of the high-voltage generating circuit, there is a problem that the radiation electric field does not cancel out well for the following reasons, and the radiation electric field on the front surface of the CRT is not accurately reduced. .

For example, if the luminance of the display screen changes, the anode current changes accordingly. In the case where the anode voltage stabilizing circuit is provided, a pulse generated on the secondary side of the flyback transformer according to the change in luminance. The peak value of the pulse changes, and the voltage / current of the pulse generated on the secondary side of the flyback transformer fluctuates due to these interactions. Also, since the anode voltage generation circuit using a flyback transformer is a peak rectifier, it is well-smoothed at low luminance and the ripple of the horizontal scanning frequency included in the anode voltage is small, but at high luminance, the anode current becomes large and the smoothness is increased. And the ripple of the horizontal scanning frequency included in the anode voltage increases. Therefore, for example, if an image like vertical stripes is displayed, a change in ripple occurs during horizontal scanning, and if an image like horizontal stripes is displayed, the amount of the ripple changes with vertical scanning, Further, for example, when a blinking image or the like is displayed, the amount of the ripple varies according to the blinking. For this reason, the pulse-like voltage superimposed on the anode voltage changes according to the display content and the brightness of the screen, and the radiated electric field changes due to the influence of the flyback transformer. Furthermore, the pulse voltage applied to the deflection yoke for deflection is not always constant, but changes due to, for example, the operation of the distortion correction circuit. Therefore, the intensity of the electric field radiated from the deflection yoke or the conductor capacitively coupled to the deflection yoke changes.

Therefore, the radiated electric field canceling pulse is taken from the winding provided in the flyback transformer or the horizontal output transformer, and the phase is adjusted to be superimposed on the output voltage of the high voltage generating circuit. The electric fields are not canceled out well, and the radiated electric field cannot be reduced accurately.

SUMMARY OF THE INVENTION An object of the present invention is to provide a radiated electric field reducing device capable of accurately reducing a radiated electric field radiated from the front surface of a CRT display device even in response to a change in luminance without using a special and expensive CRT. It is in.

[0009]

According to the present invention, in order to reduce a radiated electric field at the front surface of a CRT, an electrode for detecting a radiated electric field and an electrode for generating a canceling electric field are provided on the periphery of the CRT. A voltage signal induced in the electrode is inverted and amplified to generate a radiated electric field canceling signal, and a means for applying the radiated electric field canceling signal to the canceling electric field generating electrode is provided.

With this configuration, a voltage signal having a waveform similar to the radiated electric field radiated from the front surface of the CRT is induced in the radiated electric field detecting electrode. Then, by inverting and amplifying the voltage signal induced at the radiation electric field detection electrode, a voltage signal (radiation electric field canceling signal) having a waveform similar to the waveform obtained by inverting the radiation electric field radiated from the front surface of the CRT is obtained. generate. The radiated electric field canceling signal is applied to the canceling electric field generating electrode, and an electric field substantially equal to the inverted electric field generated inside the CRT display device and radiated from the display surface is generated. The electric field on the front surface of the CRT is a composite of the electric field radiated from the display surface and the electric field generated by applying the radiated electric field canceling signal to the canceling electric field generating electrode. Is ideally 0
Becomes In reality, the positions where the radiation electric field detection electrode and the canceling electric field generation electrode are provided are different. Therefore, the radiation electric field does not always become 0 over the entire area in front of the CRT display device. The electric field will be greatly reduced.

In addition, the CRT is controlled by a change in screen brightness or the like.
Even if the electric field radiated from the device changes, the radiated electric field canceling signal changes following the change.
The radiated electric field at the front of T is reduced.

Further, if the radiation field detecting electrode and the canceling field generating electrode are provided on different sides of the periphery of the CRT, the direct connection between the radiation field detecting electrode and the canceling field generating electrode can be achieved. Since the electromagnetic field coupling is reduced, the intensity of the radiated electric field to be canceled can be reliably detected without the radiation electric field detecting electrode being affected by the canceling electric field generated by the canceling electric field generating electrode.

Further, by providing the canceling electric field generating electrodes on at least three sides of the periphery of the CRT, an electric field for canceling the electric field radiated from the front surface of the CRT can be generated in various directions. And the radiation electric field at the front surface of the CRT can be reduced more effectively.

Further, the radiated electric field detecting electrode may be a CRT.
Is provided on two opposite sides of the periphery of the CRT.
Electric field radiated from the front of
The effect of reducing the radiation electric field on the front surface of T can be further increased.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a block diagram showing the overall configuration of a CRT display device having a radiated electric field reducing device according to an embodiment of the present invention. In FIG. 1, an interior graphite film and a shadow mask (aperture grill) are provided on the inner surface of the CRT 1, and an exterior graphite film is provided on the surface. The deflection yoke 3 is attached to the neck of the CRT 1. The high voltage generating circuit 4 includes a flyback transformer or the like, and the anode 2 of the CRT 1 is connected through an anode lead.
Supply high voltage to The deflection circuit 5 applies a deflection pulse voltage to the deflection yoke 3. The video circuit 6 supplies a video signal to the cathode of the CRT 1. Further, a radiation field detection electrode (hereinafter, referred to as a “detection electrode”) 11 for detecting a radiation field from the front surface of the CRT is provided on two left and right sides (side surfaces) of the periphery of the CRT 1. On two upper and lower sides (upper and lower surfaces), canceling electric field generating electrodes 12 (12a, 12b) for generating an electric field for canceling a radiation electric field from the CRT surface are provided. The inverting amplification circuit 13 inverts and amplifies the voltage signal induced at the detection electrode 11 to generate a radiated electric field canceling signal for canceling the electric field radiated from the front of the CRT. An electric field canceling signal is applied. Detection electrode 11 and electrode 12 for generating a canceling electric field
Is composed of a copper plate, a printed wiring board, a lead wire or the like. In addition, both electrodes are not limited to a quadrangle or a linear shape, but may have an arbitrary shape such as a circle. In the above configuration,
The radiated electric field reduction device according to the present invention includes a detection electrode 11, an offset signal injection electrode 12, and an inverting amplifier circuit 13.

FIG. 2 is a diagram showing the configuration of the radiated electric field reducing device according to the embodiment of the present invention. The detection electrode 11 has a CR
A voltage is generated in the T display device and is induced according to a radiation electric field radiated from the front of the CRT. General CRT
In the display device, a voltage (anode voltage) as shown in FIG. 3 is applied to the anode 2 of the CRT 1. The waveform of the anode voltage is different between low luminance and high luminance (broken line) as shown in FIG. Further, the radiated electric field radiated from the display surface of the CRT 1 is similar to the waveform of the anode voltage, and the waveform of the electric field radiated from the front surface of the CRT 1 is also different between low luminance and high luminance. Here, for example, assuming that the radiated electric field radiated from the front surface of the CRT 1 has a waveform shown in FIG. 4A, a voltage signal having a waveform shown in FIG. Becomes Here, the waveform of the voltage signal induced in the detection electrode 11 is similar to the waveform of the radiated electric field intensity. The inverting amplifier circuit 13 non-inverts and amplifies the voltage induced on the detection electrode 11 by the operational amplifier OP at a predetermined amplification factor. And
By inputting the output of the operational amplifier OP to the base of the transistor Q, a voltage signal obtained by inverting and amplifying the voltage signal induced at the detection electrode 11 is generated between the collector and the emitter of the transistor Q. The waveform shown in FIG. 4C is applied between the collector and the emitter of the transistor Q (FIG. 4A).
And a waveform similar to the inverted waveform of (B). Although the amplification factor will be described later, it is set to a value at which the radiated electric field at the center of the front surface of the CRT becomes substantially zero. The voltage signal generated between the collector and the emitter of the transistor Q is the radiated electric field canceling signal according to the present invention. By applying this signal to the canceling electric field generating electrode 12, radiated from the display surface on the front surface of the CRT. And a canceling electric field having a polarity opposite to that of the radiated electric field.

The intensity of the radiated electric field on the front surface of the CRT 1 is generated inside the CRT display as shown in FIG.
Is a combination of a radiated electric field radiated from the front surface and a canceling electric field. Therefore, the amplification factor of the inverting amplifier circuit 13 is set such that a canceling electric field having substantially the same waveform as the waveform obtained by inverting the radiation electric field at a predetermined position at a predetermined distance from the front surface of the CRT is obtained at the predetermined position. Thereby, CRT1
The radiated electric field at the front surface of the device is accurately reduced. For this reason, the influence on the health of the user of the CRT display device and the workers near the CRT display device can be reduced. Further, as described above, the voltage induced on the detection electrode 11 provided on the side surface of the CRT 1 is inverted and amplified, and the voltage is applied to the canceling electric field generating electrode 12 to generate the radiation radiated from the front surface by the canceling electric field generated. Since the configuration cancels out the electric field, even if the radiated electric field radiated from the display surface of the CRT 1 due to a change in the brightness of the screen or the like changes, the canceling electric field also changes according to this change. Therefore, a canceling electric field having an appropriate intensity is always generated with respect to the radiation electric field radiated from the front surface of the CRT, and the radiation electric field at the front surface of the CRT display device can always be kept low.

In the above-described embodiment, an example is shown in which the canceling electric field generating electrodes 12 are provided on the upper and lower surfaces of the CRT 1, but they may be provided on only one of the surfaces. Alternatively, the detection electrode 11 may be provided on either the upper surface or the lower surface of the CRT 1, and the canceling electric field generating electrodes 12 may be provided on both left and right sides.

As shown in FIG. 6, a detection electrode 11 is arranged on an arbitrary side of the periphery of the CRT (right side in the figure), and the canceling electric field generating electrodes 1 are provided on all three other sides.
2 (12a, 12b, 12c). With such a configuration, a canceling electric field can be generated from multiple directions, and the radiated electric field radiated from the display surface of the CRT 1 can be more efficiently reduced.

Further, as shown in FIG. 7, detection electrodes 1 are provided on two opposite sides (left and right side surfaces in FIG. 7) of the peripheral portion of the CRT.
1 (11a, 11b) are arranged, and the offset signal injection electrodes 12 (12a, 1b) are arranged on the other two sides (upper and lower surfaces in FIG. 7).
2b) may be provided. With such a configuration, it is possible to improve the detection accuracy of the radiated electric field radiated from the front surface of the CRT 1, and it is possible to more reliably reduce the radiated electric field at the front surface of the CRT 1.

[0021]

According to the first aspect of the present invention, the radiated electric field radiated from the front surface of the CRT is canceled by the electric field generated by applying the radiated electric field canceling signal to the canceling electric field generating electrode. Thereby, the radiation electric field on the front surface of the CRT can be accurately reduced. Moreover, the radiated electric field canceling signal is controlled based on the voltage signal induced by the electric field radiated from the front of the CRT.
Even if the radiated electric field radiated from the front of T changes due to a change in the brightness of the screen or the like, the radiated electric field on the front of the CRT can always be accurately reduced.

According to the second aspect of the present invention, since the direct electromagnetic coupling between the radiated electric field detecting electrode and the canceling electric field generating electrode is reduced, the radiated electric field detecting electrode is replaced with the canceling electric field generating electrode. The intensity of the radiated electric field to be canceled can be reliably detected without being greatly affected by the generated canceling electric field.

According to the third aspect of the present invention, an electric field for canceling the electric field radiated from the front surface of the CRT can be generated from multiple directions, and the radiated electric field on the front surface of the CRT can be reduced more effectively. can do.

According to the fourth aspect of the present invention, C
The electric field radiated from the front of the RT can be detected more accurately,
The effect of reducing the radiation electric field on the front surface of the CRT can be further increased.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a configuration of an entire CRT display device to which a radiation field reducing device according to an embodiment of the present invention is applied.

FIG. 2 is a diagram showing a configuration of a radiated electric field reducing device according to an embodiment of the present invention.

FIG. 3 is a diagram showing a waveform of an anode voltage applied to an anode lead.

FIG. 4 is a diagram showing waveforms of a radiation electric field, a voltage signal induced in a detection electrode, and a radiation electric field canceling signal.

FIG. 5 is a diagram showing a concept in which a radiated electric field on the front surface of a CRT is canceled.

FIG. 6 is a diagram showing a configuration of another radiated electric field reduction device.

FIG. 7 is a diagram showing a configuration of another radiated electric field reduction device.

[Explanation of symbols]

 1-CRT 2-anode 3-deflection yoke 4-high voltage generation circuit 5-deflection circuit 6-video circuit 11 (11a, 11b) -detection electrode 12 (12a, 12b, 12c) -cancellation electric field generation electrode 13- Inverting amplifier circuit

Claims (4)

[Claims] 1. A radiated electric field reducing device for reducing a radiated electric field on a front surface of a CRT, comprising: a radiated electric field detecting electrode and a canceling electric field generating electrode provided on a peripheral portion of the CRT; A radiated electric field canceling device which inverts and amplifies the applied voltage signal to generate a radiated electric field canceling signal, and applies the radiated electric field canceling signal to the canceling electric field generating electrode. 2. The radiated electric field reducing device according to claim 1, wherein the radiated electric field detecting electrode and the canceling electric field generating electrode are provided on different sides of a peripheral portion of a CRT. 3. The CRT according to claim 2, wherein said canceling electric field generating electrodes are provided on at least three sides of a periphery of the CRT.
3. The radiation electric field reduction device according to 1. 4. The radiated electric field reducing device according to claim 2, wherein the radiated electric field detection electrodes are provided on two opposing sides of the periphery of the CRT.