Issue link: https://resources.mouser.com/i/1442796
Surge Protection for Exposed DC Power Supplies By Tim Howell, for Bourns, Inc. It is common for certain types of communication equipment, like Remote Radio Units (RRUs) and Small Cell Radios, to be placed outdoors, on towers, poles, and rooftops. The equipment can be powered by a -48V DC power supply that is connected using long copper wires. Large voltages can be induced on these exposed wires due to lightning strikes (direct and indirect) and other transient events. These large voltages pose a threat to the sensitive electronic devices in the equipment. Surge protection must be included in the design to avoid damage and to eliminate expensive equipment downtime. Standards and Surge Requirements The providers of communication systems rely on a number of national and international standards (Table 1) to determine the protection requirements for their equipment so that equipment is not damaged by certain transient events including lightning. Although these systems are commonly protected by external Surge Protective Devices (SPDs), additional protection must be built-in. Leveraging the company's extensive knowledge of communication applications, Bourns has developed a proven line of circuit protection components for these applications. The most common surge requirement for these DC power supply inputs is an 8/20µS surge waveform, typically with a peak current of 10kA to 20kA. Today, some communication equipment makers are adding a 10/350µS surge waveform requirement, with a peak current of 1kA to 4kA. IEC 61643-1 introduced a test that specified the 10/350µS surge waveform to test SPDs. At the time, it was accepted that the 10/350µS waveform was a better representation of surges that occur due to direct lightning strikes. Today, some communication equipment makers are adopting the 10/350µS test waveform and applying it to their equipment's DC power supply input. | 12 |