PoE: How to Design A Reliable PoE Power Supply Solution?

The widespread adoption of PoE technology has brought significant convenience to powering and transmitting data to network devices. When designing a reliable PoE power supply, ensuring stable and efficient power delivery is essential, particularly for critical applications like IP cameras, VoIP phones, and wireless access points. This article will focus on the key factors to consider when designing a PoE power system and how to choose high-performance PoE switches and cables.

PoE Technology

PoE (Power over Ethernet) refers to the technology that allows power to be delivered to IP-based devices, such as IP phones, wireless access points (APs), and network cameras, while transmitting data over the existing Ethernet cabling infrastructure without modification. PoE is also known as Power over LAN (PoL) or Active Ethernet. In some cases, it is simply referred to as Ethernet power. This technology is the latest standard that enables the transmission of both data and power over standard Ethernet cables, while maintaining compatibility with existing Ethernet systems and users. PoE technology allows both power and data signals to be delivered through a single network cable, eliminating the need for additional power cables.

Components of a PoE Power Supply System

PoE Power Supply: The PoE power supply provides power for the entire PoE system. The number of PDs (Powered Devices) connected to a PSE (Power-Sourcing Equipment) depends on the power capacity of the PoE power supply. PoE power supplies can be either internal or external, depending on whether they are plug-in or built-in.

Power-Sourcing Equipment (PSE): PSEs are PoE devices that provide power to PDs via Ethernet. They offer features such as detection, analysis, and intelligent power management. PSEs are classified as either standard or non-standard, depending on compliance with IEEE standards. Examples include standard PoE switches and non-standard PoE switches.

Powered Devices (PD): PDs are IP terminal devices that receive power from PSEs. Examples include IP phones, wireless access points (APs), and network cameras. PDs are classified as either standard or non-standard based on IEEE standards. Standard PDs must support two powering methods (Alternative A and Alternative B), but PSEs may support only one of these methods.

PoE Power Standards

Before designing a PoE power supply system, it's crucial to understand the different PoE standards. The most widely used standards are:

IEEE 802.3af (PoE)

IEEE 802.3af, the first PoE standard, was officially released in 2003. It allows the Power Sourcing Equipment (PSE) to deliver up to 15.4W of power through an Ethernet cable to a PD. However, due to power loss in the cable, the actual power available to the PD is 12.95W. This standard is suitable for low-power devices such as VoIP phones and basic network cameras.

IEEE 802.3at (PoE+)

As the demand for higher power increased, the IEEE introduced the 802.3at standard, also known as PoE+, in 2009. This standard raised the power delivery capacity to 30W, with a minimum of 25.5W available to the PD. PoE+ is backwards compatible with 802.3af, meaning it can support higher-power devices like wireless access points (WAPs) and PTZ network cameras, while still powering older, lower-demand devices.

IEEE 802.3bt (PoE++)

IEEE 802.3bt is the latest PoE standard and supports two power modes: Type 3 and Type 4. Type 3 (PoE++) can deliver up to 60W of power, with a minimum of 51W available to the PD, while Type 4 can supply up to 100W, with at least 71W reaching the PD. PoE++ transmits power over all four pairs of Ethernet cables, accommodating high-power devices like video conferencing systems and LED lighting.

All PoE standards are backwards compatible, meaning that newer PSEs can power older PDs, and vice versa. Devices use an intelligent detection mechanism to automatically adjust the power to ensure safe operation, preventing overload or insufficient power.

Managing Power Distribution in a PoE Power Supply

In larger PoE networks, efficient power distribution is vital to ensure all devices function properly. Most modern PoE switches feature intelligent power management systems that dynamically allocate power, avoiding overloads. When necessary, administrators can also manually adjust power distribution through the switch’s management interface.

Some advanced switches allow you to set port priority. For example, if the total power demand exceeds the switch’s capacity, lower-priority ports will stop receiving power first, ensuring that critical devices continue to operate. This mechanism plays a key role in maintaining network stability and ensuring the proper functioning of essential equipment.

Additionally, many enterprise networks regularly add or update devices, making dynamic power management essential. This feature automatically detects the power requirements of new devices and allocates power resources accordingly, simplifying network maintenance and expansion.

Choosing the Right FS PoE Switch and Cables

Selecting the right PoE switch is crucial for a reliable PoE power supply. The S5810-48TS-P, FS next-generation switch, is equipped with 48 10/100/1000Mbps PoE ports and 4 1G/10G uplink ports. It comes pre-installed with PicOS®, offering comprehensive SDN functionality and compatibility with AmpCon™ management software, delivering more efficient network operations at a lower total cost of ownership (TCO).

This switch provides a maximum power budget of 740W across all PoE ports, with up to 30W available per port. It utilises state-of-the-art Broadcom chips and is fitted with redundant hot-swappable power supplies and variable-speed axial fans, ensuring exceptional processing performance.

FS also offers a range of high-performance Cat5e, Cat6, Cat6a, Cat7 and Cat8 PoE cables, available in both shielded and unshielded versions to meet diverse application needs. All Ethernet cables undergo rigorous Fluke testing, including patch cord, channel, and permanent link tests, to ensure superior performance.

Conclusion

A reliable PoE power supply system is built on careful planning and consideration of various factors, including PoE standards, power requirements, switch capabilities, and proper cabling. By focusing on these elements, businesses can ensure efficient and stable power delivery to their network devices, helping maintain uninterrupted services and support for critical applications. FS offers comprehensive, high-quality PoE solutions that provide complete coverage for your networking needs.