JP2005057636A - Crt display apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent an electronic circuit from malfunctioning or destroying caused by the influence of surge due to in-pipe electric discharge at a display apparatus using a CRT as an display device. <P>SOLUTION: The CRT display apparatus comprises a CRT 101, a CRT socket 108 with a discharge gap, an external circuit 110, and two kinds of CRT grounding conductors 104 and 105. Apart from a conventional CRT grounding conductor for connecting a first grid (control grid) 107 and a GND of the external circuit 110 and being connected to an external conductive film serving as the GND of the CRT 101, the apparatus employs a configuration in which the GND of the discharge gap 109 is connected to the external conductive film of the CRT 101 with a separate CRT grounding conductor independently without being connected with other GNDs at all. By the configuration, a surge current of in-pipe electric discharge can be returned to a CRTGND, while the surge current does not affect practically the external circuit. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a display device using a cathode ray tube (hereinafter referred to as CRT) as a display device.

  In particular, the present invention relates to a method for preventing an electronic circuit from malfunctioning or being destroyed by an in-tube discharge caused by a high voltage peculiar to a CRT.

  Since a CRT applies a high voltage of several tens of kV to the anode, discharge may occur to an electrode disposed near the anode in an electron gun such as a focus or a screen grid. At that time, discharge is usually caused by a discharge gap in the CRT socket, and a discharge current flows to the CRT through the CRT ground line, which affects an external circuit including a circuit for processing a video signal or a circuit for driving the CRT. In reality, however, the discharge current does not flow only in the 100% CRT ground line, and the discharge current also flows in the external circuit. As a result, the external circuit may malfunction or break down.

  On the other hand, conventionally, as disclosed in Patent Document 1 and Patent Document 2, it is detected that the discharge in the tube has occurred, and the operation is stopped or the power is turned off so that the apparatus is protected from malfunction or destruction. Measures were taken.

  Further, as a technique for fundamentally preventing the surge current due to the discharge in the tube from affecting the external circuit, a discharge gap is provided in the CRT socket as shown in FIG. A method of flowing through a conductive film has been performed. Here, the conventional technique will be described in detail with reference to FIG.

  The conventional CRT display device includes a CRT 201, a CRT socket 208, an external circuit 210, and a ground line 204. The CRT 201 is a grid other than the anode 202, the external conductive film 203, the first grid 207, and the first grid 207 ( Hereinafter, the CRT socket 208 has a discharge gap 209. The first grid 207, the external circuit 210, and the discharge gap 209 are connected to the external conductive film, which is CRTGND, by the ground line 204.

Next, the operation will be described. The high voltage charged in the capacity between the external conductive film 203 of the CRT 201 and the anode 202 is discharged from the anode 202 to the second grid 206, and the current is discharged in the discharge gap 209 of the CRT socket 208, and then grounded. It flows through the line 204 to the external conductive film 203 of the CRT 201. The surge current generated by the discharge is thus quickly returned to the discharge source CRT 201. However, since the impedance of the ground line 204 is not 0, the first grid 207, the discharge gap 209, and the external In some cases, the GND voltage of the circuit 210 fluctuates, causing the external circuit 210 to malfunction or break down.
JP 2000-350051 A JP-A-11-284875

  Since the protection circuit starts operating after detection according to the conventional method, it is unavoidable that the surge due to discharge must be delayed, and the circuit protection effect commensurate with the cost increase due to the addition of the circuit cannot be obtained. Almost never have a CRT display installed.

  In addition, if the power is turned off or the display is turned off each time a discharge occurs in the tube, the user may be suspected of malfunction, and hopefully there will be no damage or malfunction when the discharge occurs in the screen. There was a problem of wanting to make sure there was no abnormality.

  As a means for preventing the surge current due to the discharge from affecting the external circuit fundamentally, as described above, the discharge is caused by the gap of the CRT socket and the surge current is released to the external conductive film of the CRT by the ground line. However, there is a problem that the GND of the external circuit can be changed by the impedance of the ground line.

  Therefore, the method for protecting a CRT display device from breakdown / malfunction due to in-tube discharge according to the present invention does not detect the in-tube discharge and operate the protection circuit, but prevents the discharge current generated by the in-tube discharge from flowing to other circuits. In the first place, it does not affect the external circuit.

  In addition, the influence on the external circuit is made extremely small rather than the conventional surge countermeasure method using the CRT ground line.

  Specifically, it is composed of a CRT and a CRT socket with a discharge gap, an external circuit, and two types of CRT ground wires, and connects the conventional first grid (control grid) and the GND of the external circuit, and is the external of the CRT GND In addition to the CRT ground line connected to the conductive film, the GND of the discharge gap is connected to the external conductive film of the CRT by another CRT ground line alone without connecting to the other GND.

  When the in-tube discharge countermeasure according to the present invention is used, it is possible to configure a CRT display device in which no abnormality occurs on the screen without destruction or malfunction of an external circuit even when in-tube discharge occurs.

(Embodiment 1)
An embodiment of the present invention will be described with reference to FIG.

  The display device includes a CRT 101, a CRT socket 108, an external circuit 120, a first ground line 104, and a second ground line 105. The CRT 101 includes an anode 102, an external conductive film 103, a first grid 107, and a first grid. The CRT socket 108 includes a discharge gap 109, which is composed of a grid 106 (hereinafter, referred to as a second grid) 106 other than 107. The external circuit 120 also includes a signal processing circuit that processes an input video signal or audio signal, and a drive circuit for displaying video on the CRT 201.

  The GND of the second grid 107 and the external circuit 110 is connected to the external conductive film which is CRTGND by the first ground line 104, and the discharge gap 109 is connected to the CRT external conductive film by the second ground line 105 alone. Is done.

  As shown in the figure, an in-tube discharge is generated from the anode 102 to the second grid 106, and the current is discharged in the discharge gap 109 of the CRT socket 108, and then immediately passes through the second ground line 105 to conduct external conduction. The film 103 flows. As a result, the external circuit 110 can extremely reduce the influence of the surge current caused by the discharge.

  The CRT display device according to the present invention has an effect that the electronic circuit is prevented from malfunctioning or being destroyed due to the in-tube discharge due to the high voltage peculiar to the CRT, and is hardly affected even if the internal discharge occurs. It can be applied to uses such as a television receiver using the TV.

The figure which shows the structure of the CRT display apparatus in Embodiment 1 of this invention. The figure which shows the structure of the conventional CRT display apparatus.

Explanation of symbols

101 CRT
102 Anode 103 External conductive film (CRTGND)
104 First ground line 105 Second ground line 106 Second grid 107 First grid 108 CRT socket 109 Discharge gap GND
110 External circuit

Claims (1)

A display device using a CRT as a display device, comprising the CRT, a CRT socket with a discharge gap, an external circuit, and two types of CRT ground lines, and connecting the conventional first grid (control grid) and GND of the external circuit In addition to the CRT ground line connected to the external conductive film which is the GND of the CRT, the GND of the discharge gap is connected to the external conductive film of the CRT alone by another CRT ground line without connecting to the other GND at all. A display device characterized by that.

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