by Henry Martel
Field Application Engineer, Antaira Technologies
Power over Ethernet (PoE) switches have fundamentally transformed how devices are powered and connected to industrial networks. By transmitting both power and data through a single Ethernet cable, industrial PoE switches enable the deployment of Powered Devices (PD), such as IP cameras, wireless access points, VoIP phones, and sensors.
Standard PoE Ethernet switches supply PDs with clean, stable DC power compliant with the IEEE’s 802.3af/at/bt PoE specifications. In order to do this, they usually require 48VDC (Direct Current Voltage) input, and are unable to properly supply PoE to devices in settings where this voltage is not accessible.
This article explores a new generation of low-voltage PoE switches able to operate on input voltages below 48VDC. Internal DC-to-DC power-boosting technology enables these switches to convert 12-36VDC input to 48-56VDC output, ensuring seamless power delivery for PDs in compliance with IEEE 802.3 PoE standards.
IEEE Specifies 48VDC Input on Devices
Due to its stability, virtually all communication devices utilize direct current (DC) sourced from a power supply, converting alternating current (AC) into DC or a DC battery. IEEE specified 48VDC in its PoE standards because it balances efficient power transmission, voltage drop considerations over long Ethernet cable runs, and electrical safety thresholds. While many PoE devices can operate on battery power, the vast majority of enterprise and industrial PoE networks derive power from AC-to-DC power supplies converting grid electricity. PoE operates within a flexible voltage range rather than a fixed 48VDC. The IEEE’s original PoE standard, 802.3af, along with subsequent standards 802.3at and 802.bt, specify a voltage range requirement of 44 to 57 volts.
Industrial networks continuously change and expand into new areas, unlocking opportunities even in locations without 48VDC input to power standard PoE switches. Low voltage input switches represent an innovative new solution, eliminating the need for complex setups like connecting four 12V batteries in series to achieve 48VDC. By simplifying power requirements, low voltage input Ethernet switches save space, reduce complexity, and enhance reliability by removing the need for additional voltage converters for lower-voltage devices. Below are some applications where low-voltage PoE switches excel, particularly in remote sites without readily available power outlets.
Smart Buses: These vehicles are networked to improve transportation efficiency and the passenger experience. Smart buses can be frequently equipped with IP cameras, WAPs, GPS, and VoIP, yet have only DC12V input for a PoE switch to draw power. Similar power challenges arise in RVs, mobile command centers, trucks, and ships.
Remote Sites: Off-grid industrial sites use solar-powered battery systems featuring DC12V, DC18V, and DC36V inputs. Depending on the size of the panel and the sunlight conditions, different types of high-capacity batteries can be charged to power a low-voltage industrial PoE switch, greatly simplifying connectivity for multiple PDs. These PDs can include standalone roadside devices, access control/VoIP, agricultural monitoring, surveillance trailers, and Intelligent Transportation Systems. Besides solar, batteries can be charged by a backup generator or connected to the grid during off-peak hours, when available. Though far less common, wind, hydroelectrical, and geothermal power are power options.
Factory Automation: Although these electrical systems can range from 12VDC to 36VDC, the de facto voltage for industrial automation and control systems is 24VDC. Relays, industrial sensors, actuators, and PLCs use 24VDC, for instance. A low-voltage PoE switch will operate on various 24VDC power supplies in industrial automation systems. The low voltage PoE switch will power network devices directly from a properly specified 24VDC power supply without needing a separate high-voltage wall outlet.
Mobile Trailers: Solar-powered mobile security trailers allow for quick deployment in various scenarios, such as construction sites, live events, parking lots, schools, and general crowd control. Trailers provide a security presence by being equipped with multiple IP cameras, speakers, wireless radios, lights, and other hardware to identify, find, and deter criminals and capture incidents 24/7, day or night. Solar-powered mobile security trailers offer a solution for where reducing the use of long electrical cables improves safety.
In these situations, a low-voltage PoE switch with an internal DC boost is required to convert 12-36VDC input into the necessary 48-56VDC PoE output for connected PDs.
Antaira Power Boost
Antaira’s “power boost” technology utilizes the switch’s integrated circuitry, typically a boost converter, to efficiently store energy in an inductor during the switch-on phase and release it during the switch-off phase. This process results in a higher output voltage than the input, ensuring reliable power delivery. This way, PDs operate on a standard 48VDC PoE output even when the industrial type of switch is supplied with a lower voltage input. It also eliminates the need for a separate step-up transformer and, in turn, saves space in an enclosure using only one device.
CAPTION: Antaira’s LMP-1002G-10G-SFP-24 is a 10-port industrial Gigabit PoE+ (30W) managed Ethernet switch embedded with Ethernet ports and SFP+ slots that runs on an input voltage of 12-55 VDC
CAPTION: Diagram shows bt switch powering surveillance cameras that use 60 watts or more. It has the ability to power from a 12VDC solar battery and still inject 802.3bt compliant power to the cameras and other devices.
About Antaira Technologies
Antaira Technologies is a leading developer and manufacturer that provides high-quality industrial networking and communication product solutions. Since 2005, Antaira has offered a full spectrum of product lines that feature reliable Ethernet infrastructures, extended temperature tolerance, and rugged enclosure designs. Our product lines range from industrial Ethernet switches, industrial wireless devices, Ethernet media converters, and serial communication devices. Our vast professional experience allows us to deploy a wide array of products worldwide in mission-critical applications across various markets, such as automation, transportation, security, oil & gas, power/utility, and medical. Antaira is ISO9001 certified. Learn more at antaira.com
Source: antaira.com