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Surge protection circuit of video input signal

A video input and surge protection technology, applied in the circuit field, can solve the problem of not being able to effectively protect video AD devices against surges above 2000V, and achieve the effect of avoiding device burnout and simple structure

Inactive Publication Date: 2011-09-14
ZHEJIANG DAHUA TECH CO LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0003] In order to overcome the deficiency that the existing circuit cannot effectively protect the video AD device against the surge impact above 2000V, the present invention provides a surge protection circuit for the video input signal, which protects the surge without affecting the quality of the video signal The surge protection ability is increased from 200V to 4500V, exceeding the highest requirement of the national standard of 4000V

Method used

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Embodiment Construction

[0007] The present invention adds a discharge tube to the ground on the video input line, which is located before the impedance matching resistor, and a current limiting resistor is added after the voltage dividing point of the impedance matching resistor. The position selection of the current limiting resistor is very critical and must be placed After the voltage dividing point, the impedance matching of the line is not affected, and at the same time, the high input impedance of the video AD device is used to limit the current without affecting the signal quality. The video AD device is burned not because of high voltage but high current. When the surge signal arrives, the current limiting resistor limits the current to a very low range, and most of the current is discharged through the discharge tube at the front end, thus achieving protection. The purpose of video AD devices.

[0008] The present invention will be further described below in conjunction with the accompanying...

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Abstract

The invention discloses a surge protection circuit of a video input signal, comprising a capacitor C1, a discharge tube T1 and three resistors R1, R2 and R3, wherein the resistor R1, the resistor R3 and the coupling capacitor C1 are connected to a video input circuit in series; one end of the discharge tube T1 is connected with a video input line at the front end of the resistor R1, and the other end of the discharge tube T1 is grounded; and one end of the resistor R2 is connected with the back end of the resistor R1 and the other end of the resistor R2 is grounded. The surge protection circuit can protect video AD devices at the same time of not influencing signal quality and avoids the devices from being burnt due to surge impact. The surge protection circuit is provided with one discharge tube and four capacitance resistance elements, and the structure is simple.

Description

technical field [0001] The invention relates to a circuit, in particular to a surge protection circuit capable of effectively protecting a rear-end video AD device and preventing video input signals from being damaged by surges. Background technique [0002] At present, the known video input signal surge protection circuit is to add a discharge tube to the ground on the input line, the discharge tube is as close as possible to the position of the external interface, before the impedance matching resistor. When a surge signal appears on the video input line, the voltage of the surge signal is 2000-4000V, and the duration is 10-70us, while the conduction voltage of the discharge tube is 10-150V, and the surge voltage is much higher than the conduction voltage of the discharge tube. The discharge tube is turned on and discharged, and most of the current is discharged to the ground, which protects the video AD device at the back end. However, TechWell's TW28xx series video AD d...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): H02H9/04
Inventor 任耀强楼承恩张兴明傅利泉朱江明吴军吴坚
Owner ZHEJIANG DAHUA TECH CO LTD
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