The RACM30-K/277 Series Powers PoE and PoE+ Applications

Today’s world is teeming with connected devices, including sensors, actuators, and controllers. In many cases, vast amounts of data need to be exchanged between these devices and higher-level systems, ranging from local workstations and servers to cloud-based installations, such as data centers.

While many assume wireless connectivity is the default choice, wired connections often offer critical advantages—particularly in industrial environments. For example, industrial equipment, such as generators, inverters, motors, and welders, can emit strong electromagnetic noise that interferes with wireless signals. In addition, metal structures, such as machinery, shelving, and walls, can reflect or block wireless signals, resulting in multipath distortion and signal dropouts. By comparison, wired connections, such as Ethernet, have a higher tolerance of electromagnetic interference (EMI) and deliver greater reliability, lower latency, and better security. Of particular importance is that wired connections can deliver both data and power over a single cable, as exemplified by “power over Ethernet” technologies.

RECOM’s extensive portfolio of AC/DC converters and power supplies supports a broad spectrum of applications—from compact modules for embedded and IoT systems to high-performance solutions for industrial and automation environments. This diverse product range includes power supply families designed to support Power over Ethernet applications, meeting the demands of everything from compact embedded and IoT systems to robust industrial automation.

Early computer systems in the 1960s and early 1970s relied on a variety of slow, inflexible, and proprietary communication methods. Terminals and printers were typically connected using direct point-to-point links with serial interfaces (e.g., RS-232) or parallel connections (e.g., Centronics). Mainframe terminal networks, which centered around large centralized mainframes connected to hundreds—or even thousands—of dumb terminals, operated on custom bus architectures and proprietary protocols such as IBM’s Systems Network Architecture (SNA).

An alternative to a single large mainframe computer was the deployment of multiple smaller minicomputers. As part of this shift, a variety of local-area network (LAN) architectures and protocols evolved to connect the minicomputers with each other and with devices such as printers and plotters. These solutions faced issues including high cost (due to specialized cabling and hardware), limited scalability, and inefficiency. Furthermore, the lack of standardization meant that systems from different vendors could not communicate, making it difficult for organizations to expand their networks.

The solution to all these problems was Ethernet, invented in 1973 by Robert Metcalfe and David Boggs at Xerox PARC. In 1983, Ethernet became an official IEEE standard (IEEE 802.3), covering 10 Mbps over coaxial cable. Fast Ethernet (100 Mbps), Gigabit Ethernet (1 Gbps), and higher-speed variants (10/40/100 Gbps) followed beginning in 1995. Ethernet’s packet-based protocol is reliable, deterministic, scalable, and flexible—networks can grow by simply adding more nodes without significant changes to the underlying infrastructure. Furthermore, because of standardization and mass adoption, Ethernet’s components (cables, connectors, switches, etc.) quickly became widely available and affordable.

Every connected device requires two key resources: a means to communicate data and a power source. Ethernet addresses the data part of the puzzle, but devices still require power. Batteries are not a viable option in many applications due to limitations in power capacity, reliability, maintenance, safety, and cost. Running separate power cables for each device also increases complexity, expense, and cable clutter—particularly in dense or hard-to-access environments.

The solution is Power over Ethernet (PoE), which allows both electrical power and data to be transmitted over a single, standard Ethernet cable. PoE reduces wiring requirements, simplifies installation, and accelerates the deployment of intelligent systems at scale. Proprietary PoE systems began to emerge in the late 1990s, notably from companies like Cisco. The first official PoE standard, IEEE 802.3af, was introduced in 2003. This standard specifies a minimum of 12.95 watts available at the powered device (PD) and a maximum of 15.40 watts delivered by the power sourcing equipment (PSE).

This was followed in 2009 by an enhanced specification, IEEE 802.3at—commonly known as Power over Ethernet Plus (PoE+). It increases power delivery, specifying 25.50 watts as the minimum available at the powered device (PD) and 30.00 watts as the maximum provided by the power sourcing equipment (PSE). Basic PoE can power a wide variety of low-power network devices, including Internet Protocol (IP) cameras, Voice over Internet Protocol (VoIP) phones, wireless access points (WAPs), and other appliances like access control systems and environmental sensors. With its higher power capacity, PoE+ extends compatibility to more demanding devices, such as pan-tilt-zoom (PTZ) cameras, video IP phones, multi-antenna WAPs and advanced features, alarm systems, and biometric sensors.

The terms “PoE Injection" and “PoE+ Injection” refer to the process of adding (injecting) power to an Ethernet data line so that a connected device (such as a camera or access point) can receive both data and power through the same cable. In a typical setup, an Ethernet switch supplies only data. A PoE injector is placed in line between the switch and the powered device. This injector passes the data signal unchanged while simultaneously delivering PoE or PoE+ compliant power from a suitable source to the end device. PoE generally uses 48VDC, while PoE+ typically employs 54VDC.

The popular RECOM RACM30-K/277 series of cost-effective AC/DC converters is now available with 36, 48, and 54VDC outputs, catering to a broader range of applications, including PoE and PoE+. This augments the existing range of 5, 12, 15, 24, ±12, and ±15VDC outputs. The RACM30-K/277 series supports an ultra-wide input range of 88–305VAC and is available in wired, open-frame, encapsulated PCB, and chassis-mount formats with industry-standard pinouts.

A DIN rail mounting option is also available, featuring push-in wire terminals for simplified installation. Additionally, a fully encapsulated version in an IP65 housing, measuring just 59mm in diameter, features flying wires and fits into flush-mount wall boxes. The footprint for enclosed parts is just 1.5” x 2” for a full 30W rating from 40°C to +60°C ambient and up to 90°C with derating.

Today, Ethernet is ubiquitous: It’s found in office networks, industrial control systems, data centers, home networks, and many other applications. PoE and PoE+ have become critical to many deployments, reducing installation costs and simplifying wiring by eliminating the need for separate power lines. As Ethernet-connected devices become more powerful, PoE+ is becoming an increasingly essential feature. RECOM’s RACM30-K/277 series of AC/DC power converter modules provides a compact, reliable, and standards-compliant power foundation for these applications, delivering what designers need to keep injectors powered and the world’s networks humming.

The RECOM AC/DC, DC/DC, and EMC Books of Knowledge offer an extensive collection of knowledge and experience necessary to implement successful AC/DC power supply designs.

Additionally, RECOM’s Energy Efficiency in AC/DC Power Supplies: Quick Guide to the Essentials blog offers a helpful introduction to eco-design regulations, which are a set of standards and guidelines established by governments or regulatory bodies to ensure that products are designed to minimize their environmental impact throughout their entire life cycle. These regulations primarily focus on improving energy efficiency and promoting sustainability by reducing waste, emissions, and resource consumption.