PoE and Low-Voltage DC Lighting:
Delivering Power and Data Over a Single Network Cable

In a smart building, the most expensive and troublesome part often isn't the lights themselves but the wiring — one run for power, another for control signals, walls packed full of cable. What if a single network cable, one we already know well, could carry both the power and the data? That's what PoE answers. As its power capability reaches 90W, low-voltage DC lighting has begun to open up new possibilities — though it has boundaries of its own.

In a smart building, the most expensive and troublesome part often isn’t the lights themselves but the wiring.

One run for power, another for control signals, packed densely through walls and ceilings. What if a single network cable, one we already know well, could carry both the power and the data? That’s exactly what PoE sets out to do. As its power capability has grown all the way to 90W, low-voltage DC lighting has begun to open up new possibilities — but it has clear boundaries of its own.

What PoE is: making the network cable carry power too

The core idea of PoE (Power over Ethernet) is simple: since a network cable contains several pairs of copper wires, why not let it carry power while it transmits data? That way, IP cameras, wireless access points, access control, and even LED luminaires can all run on a single network cable, without hunting for an outlet on site.

This is governed by the IEEE 802.3 family of standards, with capability rising version by version:

• IEEE 802.3af-2003 (Type 1): about 15.4W per port at the source, about 12.95W at the powered device^[2].
• IEEE 802.3at-2009 (Type 2, PoE+): about 30W at the source^[2].
• IEEE 802.3bt-2018 (Type 3/4, PoE++): uses all four pairs, with Type 4 delivering up to about 90W at the source and about 71.3W at the powered device^[1].

What 90W can — and can’t — do

IEEE 802.3bt-2018 pushed per-port power up to 90W (at the source, the PSE), leaving about 71.3W usable at the powered device (PD) after line losses^[1]. For lighting, that’s enough to drive quite a few small-to-medium-power LED luminaires, and it makes “lighting as a network node” possible — every light can be addressed, monitored, and scheduled.

But 90W also draws two boundaries:

• Power ceiling: large-area, high-brightness lighting (such as floodlighting or large facades) easily exceeds a single port’s capacity and still needs conventional mains power.
• Distance limit: Ethernet’s cabling distance is about 100 meters; beyond that you need a repeater or a different architecture.

So PoE lighting’s sweet spot is clear: small-to-medium-power indoor scenarios with controllable cabling distances, such as controllable lighting in offices, corridors, and meeting rooms.

The same spirit: less wiring

Seen in a larger context, PoE actually shares its thinking with two-wire power-line carrier — both answer the same question: can one set of conductors carry power and information at once, doing away with that separate control line?

The difference lies in the “level”:

• PoE operates at the building-infrastructure level, using a network cable to deliver power and data “to a light or a zone.”
• Two-wire power-line carrier operates inside the string, using the power line itself to deliver pixel-control commands “to each individual bead.”

One is a merger at the network-node level, the other at the bead level. They address wiring problems at different depths within a lighting system.

A division of labor, not a replacement

Once you understand the difference in level, it becomes clear that the relationship between PoE and bead-level pixel control is a division of labor, not a replacement.

PoE excels at delivering power and coarse-grained control signals cleanly to a luminaire or zone. But it isn’t responsible for the addressing and pixel control among the hundreds or thousands of beads within a decorative string — that’s bead-level work. If a string needs per-bead color changes and animations, it still needs a pixel-control protocol inside the string to handle each bead’s address and brightness.

The common architecture in practice is: upstream, PoE, low-voltage DC, or mains delivers power and overall control to the luminaire; inside the string, a dedicated pixel-control IC handles per-bead addressing over the power line. Each doing its own job is what makes a complete, maintainable lighting system.

Where PowerMOS sits in the low-voltage DC lighting architecture

PowerMOS addressable-control ICs solve addressing and pixel control at the bead level. Whether the upstream is PoE, low-voltage DC, or high-voltage mains (supporting AC110/220V applications), once power reaches the string, the PowerMOS two-wire power-line carrier solution can perform per-bead addressing and brightness control over the same power line — 3.5–7mA indoors and 7–20mA outdoors, supporting a 512-code address depth and in-line addressing, with a single-fault-contained and bead-replaceable repair design. It complements PoE: PoE delivers power and coarse control to the luminaire, PowerMOS builds pixel control into each individual bead. See the product center for the full lineup.

Further reading: for how two-wire carrier works, see Two-Wire Addressable Lighting: How One Power Line Both Powers and Addresses; for signal integrity, see Signal Integrity Engineering for Power-Line Carrier.

Reference Standards and Literature

1. IEEE Std 802.3bt-2018, IEEE Standard for Ethernet — Amendment 2: Physical Layer and Management Parameters for Power over Ethernet over 4 Pairs. IEEE Standards Association.
2. IEEE Std 802.3af-2003 & IEEE Std 802.3at-2009, Data Terminal Equipment (DTE) Power via Media Dependent Interface (MDI). IEEE Standards Association.

This article is an educational overview of lighting power architecture. The names of the standards cited can be verified in the official IEEE Standards Association catalog. PowerMOS addressable-control ICs use a proprietary carrier protocol optimized for LED pixel control, forming a lighting architecture complementary to PoE.

FAQ