Gas Discharge Tubes Abbreviated as GDT

Gas discharge tube is the most widely used switching device in lightning protection equipment. It is connected in series and parallel in the circuit and can be used for lightning protection of AC and DC power supplies and various signal circuits. The lightning current leaked into the earth.

GDT is composed of a pair of discharge gaps encapsulated in a ceramic tube and filled with a discharge medium (inert gas). According to the number of electrodes: There are two types of two-pole discharge tubes and three-pole discharge tubes (connecting two two-pole discharge tubes in series). Its shape is cylindrical, rectangular or two squares and one circle; cylindrical has two structural forms, DIP and SMD.

Basic Structure

Gas Discharge Tubes Principle:

The basic principle of GDT is Gas discharge. The pulse breakdown voltage (Vsi) of the commonly used discharge tube ranges from a few hundred volts to more than one thousand volts. The discharge tube was originally in an open circuit state, with a large impedance and a small capacitance value. Once the surge overvoltage reaches the pulse breakdown voltage value of the GDT, the electric field strength between the two poles of the GDT will exceed the breakdown strength of the gas, causing the gap discharge to ionize the gas in the tube, and the GDT will change from the original open state to the on state. At this time, the overcurrent generated by the surge will be discharged to the ground through the GDT, so that the components of the subsequent circuit will not be damaged by the surge.

Gas Discharge Tubes Application:

Signal lightning protection application:
It is commonly used in the first level of protection, but because its response speed is slower and the breakdown voltage is higher, the second level protection element is also used for voltage limiting protection.

Power supply lightning protection applications:

used in common mode circuits in series with a Varistor to drain overcurrent into the ground, or in differential mode circuits; used in series with a Varistor to block the leakage current of the Varistor to prevent aging.