JPS6246377Y2 - - Google Patents

Description

[Detailed description of the invention] Industrial field of application This invention is suitable for display devices that can be applied to those that obtain high-brightness, high-resolution images, such as word processors, graphic displays, and high-definition color television receivers. Regarding.

BACKGROUND TECHNOLOGY AND PROBLEMS In some display devices that produce high-brightness, high-resolution images, such as word processors, the frequency of the signal handled at the final stage of the video circuit (video output circuit) is approximately 100 MHz. Therefore, for such high frequency signals, as shown in FIG. 1, for example, a line L (L ₁ , _L2 ...) acts as an antenna line, causing unnecessary radiation of high-frequency signals.

This unnecessary radiation will cause noise to adjacent radios, television receivers, etc., and will also interfere with communications if communication equipment is installed.

For this reason, the inner surface of the word processor cabinet 4 is generally treated with metal spraying (Zn spraying) or conductive coating to prevent high frequency signals from leaking to the outside.

However, as mentioned above, if the leakage signal is of high frequency and the leakage level is relatively large,
The light passes through the neck portion 2 of the CRT 1 and the funnel portion coated with a carbon layer. and,
Since the tube surface (front) of the CRT1 is the display surface, it cannot be shielded, so leakage signals that have passed through the tube of the CRT1 cannot be blocked and are unnecessarily radiated to the outside. .

Purpose of the invention Therefore, this invention is designed to prevent high-frequency signals from being unnecessarily radiated to the outside in any configuration using a CRT.

Summary of the invention Therefore, in this invention, the entire CRT drive circuit, including at least the final stage of the video circuit, is housed in a shield case, and some or all of the lines other than the lines connected to the signal line of the video circuit are The above object is achieved by connecting the filter.

Embodiment Next, an example of the application of this invention to a word processor will be described with reference to FIG. 2 and subsequent figures.

In the figure, reference numeral 10 indicates a board mounting device attached to the network part 2. As shown in the figure, this includes a CRT socket 6, a socket board 7 to which this socket 6 is mounted, and a rectangular parallelepiped-shaped shield surrounding this socket board 7. Consists of case 8 and CRT
The socket 6 is inserted into the neck portion 2 of the CRT 1. Therefore, the entire board mounting device 10 is attached to the neck portion 2.
It is inserted and fixed.

The above-mentioned CRT socket 6 is installed on the socket board 7.
In addition to the above, a CRT drive circuit, a white balance adjustment circuit, etc. are provided, and as described above, electronic components of at least the video output circuit, which is the final stage of the video circuit, are mounted. In this example, the entire video circuit is mounted on the socket board 7. In this example, since the wiring part of the socket board 7 is provided on the mounting surface side of the CRT socket 6, the red, green, and blue video output transistors Q _R , which constitute the video output circuit, Q _G and Q _B are installed on the opposite side from the CRT socket 6 as shown in the figure.

The rectangular parallelepiped-shaped shield case 8 is composed of a left half 8A and a right half 8B as shown in the figure, and inside the end surface of the left half 8A there is a stepped portion where the circumferential surface of the socket board 7 abuts. 9 is formed, and as will be described later, when the right half 8B and the left half 8A are combined, the socket board 7 abuts against the step 9 due to the action from the right half 8B and is fixed to the shield case 8. It is done like this. The depth of the left half 8A is selected to cover the CRT socket 6. 11 is the network part 2
This is a through hole for insertion into the

The right half 8B is also constructed in substantially the same manner as the left half 8A, and is attached to the left half 8A by a snap mechanism. This right half 8B is the socket board 7.
It is thermally coupled to the output transistors Q _R to Q B attached to the output transistors Q R to Q _B . Therefore, the transistor Q _R ~
The case of Q _B is made of an insulating layer 12 such as a silicon sheet.
The depth of the right half body 8B is determined so as to be in close contact with the inner surface of the right half body 8B via R to 12B.

In this configuration, the transistor Q _R
~Q Since _B and the right half body 8B and left half body 8A are thermally coupled and act as a heat sink,
The heat generated by the transistors Q _R to Q _B can be effectively radiated by the shield case 8 .

Now, as mentioned above, inside the shield case 8
When a CRT drive circuit, a video circuit, etc. are housed, the circuits inside the shield case 8 and the external circuits are electrically connected with wires. In addition to various power lines, the wire material can be used for video signal lines,
There are bias and control lines (hereinafter referred to as control lines), ground lines, etc. that drive the CRT 1 and control its drive voltage, and these lines act as antenna lines for high-frequency signals, so the shield case 8 is It is not sufficient to shield the video output circuit by providing a video output circuit.

In order to eliminate unnecessary radiation from these multiple lines, a filter F for blocking high frequencies is provided on the lines immediately before they exit the shield case 8.

In the example shown in FIG. 2, the lines inside and outside the shield case 8 are connected by the connector 20.
Connector 20 installed inside shield case 8
A filter F is attached on a line coming out from the male part 20A and close to the male part 20A.

FIG. 3 is an example of a line connecting the inside and outside of the shield case 8, in which two connectors 20 and 21 are used, one connector 20 is related to the power supply line, and the other connector 21 is related to the video signal line and It concerns the control line.
L ₁ is the power line for the heater of CRT1, and L ₂
are the power lines of the video output circuit, L ₃ , L ₄
is a power supply line for driving the TTL or ECL configuration circuit provided in the video circuit.
L ₅ is the ground line.

Low-pass filters F ₁ -F ₄ for blocking high frequency signals, which are constructed of a coil L and a capacitor C as shown in the figure, are connected to the respective power supply lines L ₁ -L ₄ .
The cutoff frequency of filter F is 0 in the video band.
~100MHz, so lower frequencies are preferable, and in this example several MHz, for example 4MHz.
has been selected.

Almost the same configuration is applied to the line connected to the other connector 21. _L6 is a video signal line, and if a color CRT is used as the CRT1, three signal lines for R, G, and B are required, for example. Also, in this example the signal line
Since coaxial cable is used as L ₆ ,
Has ground line _L5 . _L7 is a control line for controlling the fourth grid voltage _G4 of the CRT1, _L8 is a control line for controlling the second grid voltage _G2 , and _L9 is a control line for controlling the first grid voltage G4. This is a control line to control ₁ .

Among these lines, filters F ₇ to _{F 9 having} the same configuration as described above are provided close to the connector 21 on lines L ₇ to L 9 except for the signal line L ₆ and the ground line L ₅ .

Since the filter F is connected to all lines connecting the inside and outside of the shield case 8 except for the signal line and the ground line, even if high frequency signals leaked from the video output circuit jump into these lines, the shield case Therefore, even if the wire connecting the internal circuit of the shield case 8 and the external circuit is long, it acts as an antenna wire and high frequency signals are transmitted through the cabinet 4 and CRT 1. There is no risk of unnecessary radiation outside the set.

Therefore, it is not necessary to create gaps between the contact surfaces of the respective halves of the cabinet 4 to prevent unnecessary radiation from the cabinet 4, or to tighten screws, so that the processing of the cabinet 4 can be simplified. Further, in this case, if the inner surface of the cabinet 4 is shielded as in the conventional manner, unnecessary radiation from the cabinet 4 will be almost eliminated, so that the shielding effect will be even greater.

Filter F may have an RC configuration instead of an LC configuration. In this case, the filter F on the connector 21 side is
Can be completely replaced with RC configuration.

By the way, among the lines connecting the inside and outside of the shield case 8, the one that most easily acts as an antenna wire is
The power line _L1 for the heater of the CRT1, the power line _L2 for the video output circuit, and the control lines _L7 to _L9 , etc., are also connected to the electrodes of the CRT1, but relatively do not act as antenna lines. It is difficult to do. In addition, if only the video output circuit of the video circuit is housed inside the shield case 8, the power supply line for TTL or ECL should be
Since L ₃ and L ₄ become unnecessary, the filter F may be connected only to a line that is likely to act as an antenna line among the plurality of lines connecting the inside and outside of the shield case 8.

In addition, in the example shown in FIG. 2, all the circuit components housed in the shield case 8 are mounted on the socket board 7, but as shown in FIG. Only the circuit is installed on a board (video board) 25 that is separate from the socket board 7.
When installing the board 7, 25 in the shield case 8, the connector 20, 2
A filter F is connected to a line near 1.

Note that the video board 25 is connected to the network part 2 as shown in the figure.
It can be attached and fixed to the shield case 8 in a state where it passes through.

Effects of the invention As explained above, according to this invention, at least the final stage of the video circuit is housed within the shield case 8, so unnecessary radiation can be reduced and
Since the filter F for blocking high frequency signals is connected to all or some of the lines connecting the internal circuit and the external circuit of the shield case 8, high frequency signals leaking to the outside of the shield case 8 through these lines can be blocked. Unnecessary radiation from these lines is also eliminated.

As a result, unnecessary radiation of high-frequency signals through the tube surface of the CRT 1 is prevented, and the influence on electronic equipment adjacent to the set can be reliably avoided.

[Brief explanation of the drawing]

Fig. 1 is a sectional view of a device used to explain this invention, Fig. 2 is a sectional view showing an example of the essential parts of a display device according to this invention, Fig. 3 is an explanatory diagram of a filter, and Fig. 4 is an illustration of this invention. It is a sectional view showing other examples. 1 is a CRT, 3 and 7 are socket boards, L is a wire, 8 is a shield case, 20 and 21 are connectors, and F is a filter.

Claims (1)

[Scope of Utility Model Registration Claim] A CRT, a shield case provided to surround the neck portion of the CRT, and a CRT that is housed within the shield case and includes at least the final stage of a video circuit.
An internal circuit constituted by the drive circuit, an external circuit provided outside the shield case and inside the cabinet to which the CRT is installed, and at least a video signal line connecting the external circuit and the internal circuit. multiple signal lines, including
a filter that blocks high-frequency signals from the signal line, and the filter is provided near the exit of the signal line in the shield case, and also provided on some or all of the signal lines other than the video signal line. A display device characterized by: