Nowadays, lightning and the instantaneous overvoltage of large electrical equipment are more and more frequently intruding into indoor electrical equipment and network equipment through lines such as power supplies, antennas, radio signal transceiver equipment, etc.

This causes damage to equipment or components, casualties, interference with or loss of transmitted or stored data, and even causes electronic equipment to malfunction or temporarily paralyze, system shutdown.

Data transmission terminals, local area networks and even wide area networks can also be damaged. 

Therefore, we need to pay more attention to power supply lightning protection. Once the outdoor base station power supply is damaged, it may affect the surrounding communication transmission, so it is necessary to design a lightning protection solution for the base station power supply.

With the increase of thunderstorm weather in summer, the power cable of the DC48 base station is pulled from the equipment room to the RRU of the radio frequency unit. The cable is long and easily disturbed by lightning.

When designing the lightning protection solution for the communication power supply, high surge protection of 20KA differential mode and 20KA common mode is required.The gas discharge tube with large flow rate is widely used in the lightning protection of power supply.It can release the current to the ground in the common mode circuit.In the power supply lightning protection differential mode circuit, it can be well blocked leakage current by connecting in series with a varistor.In addition, it can also form an anti-lightning surge circuit with varistors to achieve full protection in common mode and differential mode.The following will introduce the lightning protection solution of DC48 base station power supply realized by Socay using GDT discharge tube and varistor:

Gas Discharge Tubes(GDTs)

GDT1【SC2E8-600H5SMD】DC Spark-over Voltage：600V±20%，Nominal Impulse Discharge Current（8/20μS）：20kA，Maximum Capacitance＜1.0pF，Minimum Insulation Resistance >1GΩ; 

GDT2【SC2E8-90HSMD】DC Spark-over Voltage：90V±20%，Nominal Impulse Discharge Current（8/20μS）：20kA，Maximum Capacitance＜1.0pF，Minimum Insulation Resistance >1GΩ; 

Varistor(MOV)

Part No【14D820K】Varistor Voltage（at1mA）：74V-90V，Withstanding Surge Current（8/20μS）：4500A，Maximum Clamping Voltage（at5A）：135V

Solution Note

1.The back end of this solution use MOV with fast response time and low residual voltage

2.The front end used smd GDT with  high current-handling capability.

3.Use 6μH~10μH inductors L1 and L2 for decoupling, and drive GDT1 to leak the amplified current in the middle

4.The solution meets surge test standards such as IEC61000-4-5, GBT17626.5

In the lightning protection of the power supply, due to the isolation effect of the discharge tube, almost no leakage current flows through the varistor, which greatly slows down the aging phenomenon of the varistor caused by the long-term leakage current.At the same time, on the premise of ensuring that the Power-flow current of the gas discharge tube is cut off, we can choose a varistor with a lower voltage to reduce its residual voltage and clamping level.

For more power lightning protection solutions, please directly enter the Socay Electronics website to consult the online customer service http://www.socay.com/.