What Is a Discharge Tube?

A discharge tube is a high-voltage protection element used at the input of a device. If the voltage at both ends is higher than its protection specification value, a short-circuit phenomenon will occur inside it, and the excessive high voltage input will be absorbed.

Discharge tube

Various electrical characteristics of the gas discharge tube, such as DC breakdown voltage, impulse breakdown voltage, surge current resistance, power frequency current capability, and service life, can be adjusted and optimized according to the requirements of the system used. This adjustment is often achieved by changing the type of gas in the discharge tube, the pressure, the composition of the electrode coating material, and the distance between the electrodes.

VICFUSE-Diode

There are two types of gas discharge tubes: bipolar discharge tube and tripolar discharge tube. Some gas discharge tubes have electrode leads, while others do not.

From a structural point of view, the gas discharge tube can be regarded as a symmetric switch with a small capacitance. Under normal operating conditions, it is turned off, and its inter-electrode resistance is above megohm level. When the surge voltage exceeds the withstand voltage of the circuit system, the arc discharge phenomenon occurs when the gas discharge tube is broken down. Because the arc voltage is low, only tens of volts, which can limit the further rise of the surge voltage in a short time. . The gas discharge tube uses the above principle to limit the surge voltage and protects the circuit from overvoltage.

As the overvoltage decreases, the current through the gas discharge tube also decreases accordingly. When the current falls below the minimum current value required to maintain the arc state, the arc discharge stops and the glow of the discharge tube goes out.

VICFUSE-Tripolar discharge tube

Gas discharge tubes are mainly used to protect the safe operation of communication systems, traffic signal systems, computer data systems, and external cables and electronic instruments of various electronic equipment. The gas discharge tube is also a protection element against lightning and transient overvoltage in the circuit.

The gas discharge tube has the characteristics of large current-carrying capacity, fast response time, small capacitance, small size, low cost, stable performance and long life; the disadvantage is that the ignition voltage is high, the cut-off state cannot be restored under DC voltage, and it cannot be used to protect low voltage The performance of the circuit will decrease after each transient voltage.