KR19990015877U - Monitor electromagnetic wave shield - Google Patents

Abstract

The present invention relates to a circuit for blocking low frequency harmful electromagnetic waves generated from the front side of the monitor. In the past, a method for blocking high frequency electromagnetic waves (EMI) emitted from the monitor tube has been studied in recent years. With the publication of the TCO standard, the need for low frequency electromagnetic shielding is urgent.

Accordingly, the present invention is to install a conductor plate along the outside of the front of the water pipe (CRT) bar, the constant conductor plate is to ensure that the water pipe from the static electricity by insulating coating both sides. In addition, by applying a pulse signal having a frequency opposite to that of the low frequency electromagnetic wave to the conductor plate, the low frequency electromagnetic wave as a positive component and the pulse signal as a negative component are mutually canceled to remove the low frequency electromagnetic wave.

The present invention as described above can pass the TCO standard for regulating low frequency electromagnetic waves, and also has the effect of protecting the human body from low frequency electromagnetic waves.

Description

Device for shielding electromagnetic wave in a monitor

The present invention relates to a circuit for blocking low frequency harmful electromagnetic waves generated in front of the monitor.

In general, a color display device (CRT) used in a monitor focuses and accelerates hot electrons emitted from R, G, and B guns and collides with R, G, and B fluorescent surfaces through a point on a shadow mask to form pixels. The sawtooth current flows through the vertical and horizontal deflection coils to form a two-dimensional screen.

In order to operate the color display device (CRT), a heater voltage of about 6.3V is applied to the heater, a focus grid voltage, a screen grid voltage, etc. are required for focusing the emitted hot electrons, and an anode is used to accelerate the hot electrons. The high pressure of about 25KV will be applied.

As shown in FIG. 1, the power supply circuit of the monitor providing the voltage necessary for the CRT as described above may include a power supply 110, a PWM generator 120, and a B + voltage generator 130. , The oscillator 150, the horizontal driver 160, and the horizontal output unit 170.

Referring to FIG. 1, the DC voltage output from the power supply 110 is converted into a predetermined B + voltage by the PWM generator 120 and the B + voltage generator 130 and applied to the primary winding of the FBT 140. The B + voltage of the primary winding is switched by the horizontal output unit 170 according to the horizontal drive signal (H.drive) to generate a high voltage (HV) on the secondary winding side of the FBT 140.

At this time, the high voltage (HV) generated in the secondary winding of the FBT 140 is applied to the anode of the CRT, divided by the resistors, and then applied to the focus grid FOCUS and the screen grid SCREEN of the CRT, respectively. have.

That is, as the B + voltage applied to the primary winding of the FBT 140 is switched by the horizontal drive signal, the high voltage is induced to the secondary side, and the high voltage remains as an AC noise because a ripple signal of the same frequency as the horizontal drive signal remains. Will work.

In addition, low-frequency electromagnetic waves are emitted from the front of the monitor by the high pressure including the AC noise.

The low frequency electromagnetic waves do not cause serious harm to the human body compared to the high frequency electromagnetic waves (EMI). However, since the TCO standard was published in Sweden in 1991, the TCO standard, also known as MPR III, is a low frequency electromagnetic wave emitted from a monitor. The specification for.

In the TCO standard, a standard for an alternating electric field and a standard for an alternating magnetic field are separately provided, which can be summarized as Table 1 and Table 2 below.

Specification for alternating electric field MPR 2 TCO (MPR 3) Frequency range ELF (5 ㎐ to 2 ㎑) VLF (2㎑ to 400㎑) ELF (5 ㎐ to 2 ㎑) VLF (2㎑ to 400㎑) Limit 25 V / m 2.5 V / m 10 V / m 1 V / m Measuring distance 50 cm 50 cm Front 30 cm Front 30 cm, 50 cm

Specification for alternating magnetic fields MPR 2 TCO (MPR 3) Frequency range ELF (5 ㎐ to 2 ㎑) VLF (2㎑ to 400㎑) ELF (5 ㎐ to 2 ㎑) VLF (2㎑ to 400㎑) Limit 250 nT 25 nT 200 nT 25 nT Measuring distance 50 cm 50 cm Front 30 cm, 50 cm 50 cm

However, there is a problem in that the conventional monitor is unable to cope with the above-described TCO standard because the device for blocking the low frequency electromagnetic waves is not configured.

Accordingly, an object of the present invention is to provide an electromagnetic wave shielding device of a monitor for blocking an electromagnetic wave of low frequency radiated from a power supply system of a monitor, which is devised to solve the problems of the prior art as described above.

Electromagnetic shielding device of the monitor according to the present invention for achieving the above object, the conductive plate is formed integrally along the outer surface of the water tube (CRT), both sides of the insulation coating; And

And a pulse generating means for providing the conductor plate with a low frequency having the same frequency as that of the electromagnetic wave generated from the front side of the water pipe and having the opposite phase.

1 is a configuration diagram showing a power supply circuit of a general monitor,

2 is a configuration diagram showing a power supply circuit including an electromagnetic wave shielding device of a monitor according to the present invention,

Figure 2a is a front configuration diagram of the electromagnetic wave shield,

Figure 2b is a perspective view of the electromagnetic wave shielding device,

3A is a waveform diagram of low frequency electromagnetic waves radiated from the surface of a picture tube,

3B is a waveform diagram of a pulse signal output from the pulse generating means.

* Explanation of symbols for main parts of the drawings

110: power supply 120: PWM generator

130: B + voltage generator 140: FBT

150: oscillation unit 160: horizontal driving unit

170: horizontal output unit 210: water pipe

220: conductor plate 230: pulse generating means

240: anode cap

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

2 is a power supply circuit of the monitor equipped with an electromagnetic wave blocking device according to the present invention, which is a power supply 110, PWM generator 120, B + voltage generator 130, FBT 140, Oscillator 150, the horizontal driving unit 160, the horizontal output unit 170, the conductor plate 220 formed integrally along the outside of the front surface of the water pipe 210 and both sides of the insulation coating, and the water pipe 210 And a pulse generating means 230 for providing the conductor plate 220 with a low frequency having the same frequency as that of the electromagnetic wave generated at the front of the panel.

Here, the pulse generating means 230 is composed of a capacitor (C21) and a resistor (R21) for integrating the negative voltage output from the tertiary side of the FBT 140 to provide to the conductor plate 220, As illustrated in FIG. 2B, the conductor plate 220 includes a metal piece 221 in the center through which the pulse signal output from the pulse generating means flows and an insulating coating layer 222 formed on both sides of the metal piece.

The operation and effects of the present invention configured as described above are as follows.

The AC power flowing from the outside is applied to the primary side of the FBT 140 by the B + voltage through the SMPS 110, the PWM generator 120 and the B + voltage generator 130, the B + voltage of the FBT 140 The high pressure is induced to the secondary side of the FBT 140 while being switched by the horizontal driving signal applied to the other primary side.

The high pressure of the FBT 140 is connected to the anode cap 240 of the water pipe 210 is applied to the surface of the water pipe 210. At this time, the high pressure includes the low frequency ripple, that is, the noise, and the low frequency noise causes the low frequency electromagnetic waves of the positive component as shown in FIG. 3A from the surface of the water pipe 210 by the low frequency noise. .

On the other hand, the negative voltage output from the tertiary side of the FBT 140 is integrated through the pulse generating means 230 is applied to the metal piece 221 of the conductor plate 220, the pulse generating means 230 Since the pulse signal output from is a signal having the same frequency and opposite phase as the low frequency electromagnetic wave of the positive component as shown in FIG. The low frequency electromagnetic waves radiated from the surface of are removed.

At this time, since a negative signal pulse signal is applied to the metal piece 221 of the conductor plate 220, static electricity is generated, and the insulating coating layer 222 insulates the metal piece 221 and the water pipe 210. Because of this, the water pipe 210 is protected from static electricity.

As described above, the present invention forms a conductor plate by insulating coating a metal piece, attaches the conductor plate to the front outer surface of the water pipe, and then radiates from the front surface of the water pipe by applying a negative pulse signal to the metal piece. Since it is offset by the low frequency electromagnetic wave of the positive component, it can pass the TCO standard which regulates the low frequency electromagnetic wave, and also has the effect of protecting a human body from the low frequency electromagnetic wave.

Claims (1)

A conductor plate which is integrally formed along the outer surface of the front surface of the water pipe (CRT) and is coated with both sides thereof; And And a pulse generating means for providing the conductor plate with a low frequency having the same frequency as that of the electromagnetic wave generated in front of the water pipe and having a reverse phase.