Overview

Gas discharge tube is an electronic component used for overvoltage protection. It is commonly used in electrical equipment to provide transient voltage suppression function, especially suitable for protection against transient overvoltages such as lightning, switching surges, electromagnetic interference, etc. The working principle of GDT is based on the gas breakdown phenomenon, and its working process involves the gas breaking down and conducting electricity under high voltage, thereby limiting the overvoltage.

Working Principle

1.Structure

  • The ceramic gas discharge tube consists of two electrodes (usually metal) and an inert gas (such as argon, nitrogen, etc.) filled between the electrodes. The electrodes are isolated by ceramic materials (insulating materials). Ceramics usually play an insulating and protective role, preventing the current between the electrodes from short-circuiting and providing physical strength.
  • GDT is usually in the shape of a tube (or similar shape), with electrodes at both ends and a gas-filled space in the middle.

2.Normal working state

  • In the absence of overvoltage, the gas discharge tube is in an open circuit state. The gas inside is an inert gas and is not conductive, so when the circuit is working normally, the current will not flow through the gas discharge tube.


3.When overvoltage arrives

  • When a transient overvoltage occurs in the circuit (such as lightning strikes, power surges, electromagnetic pulses, etc.), the voltage rises rapidly and exceeds the breakdown voltage (also called "discharge voltage") of the GDT. When the voltage reaches a certain value, the molecules in the gas are excited by the electric field, the gas begins to ionize, and the gas becomes conductive. At this time, the current can flow through the gas discharge tube.


4.Breakdown and conduction

  • Gas breakdown: The working principle of the gas discharge tube is based on gas breakdown. When the voltage exceeds the breakdown voltage, the degree of ionization of the gas increases sharply, forming free electrons and ions, and the resistance of the gas drops significantly, and it begins to conduct electricity, forming a low-impedance channel.
  • Gas conduction: Once the gas breaks down and conducts electricity, the current of the GDT flows through the gas tube, and the current quickly "absorbs" the overvoltage after passing through, thereby protecting other sensitive components in the circuit from overvoltage damage.

5.Recovery state

  • Once the instantaneous overvoltage pulse passes, the voltage returns to the normal working voltage, and the conductivity of the gas discharge tube also returns to the original state. The gas no longer conducts electricity, and the gas discharge tube returns to an open circuit state. At this time, the gas discharge tube no longer affects the normal operation of the circuit.
  • During the recovery process, the gas discharge tube will not produce a persistent conductive path, and it will only conduct at the moment of overvoltage, thereby avoiding the circuit from being affected permanently.

More Information

For more product details, please visit the website:

https://en.semiware.com/product-line/gas-discharge-tube

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