APEC papers examine DC distribution to LED fixtures and PLC
LED lighting can potentially offer greater efficiency when driver from a DC distribution system, and Power Line Control can add remote management.
At the recent APEC (Applied Power Electronic Conference) event, two papers addressed DC-driven LED lighting. The technology offers potential power savings and perhaps a more flexible wiring scheme. Those papers seem especially relevant given the launch of Redwood Systems and their DC approach to commercial office lighting that also includes Power Line Control (PLC) of fictures.
At APEC, a researcher from Carnegie Mellon University presented a paper that modeled the potential of DC power distribution for both fluorescent and LED lighting and found that DC offered efficiency advantages for LEDs. Meanwhile, a team from Zhejiang University in China authored both a paper and a poster session describing a low-voltage DC bus for powering and controlling LED lights via a PLC scheme.
Brinda Thomas of Carnegie Mellon evaluated fluorescent and LED fixtures powered by a 277-VAC line and then similar fixtures powered from 250 VDC. DC power distribution has been widely considered in the past few years as an energy savings measure. For instance, the IT industry is evaluating DC distribution in computer data centers. DC distribution eliminates the AC/DC stage of a power supply and the associated efficiency hit in the power supply.
Note that the DC scheme studied by Carnegie Mellon is still quite different from the Redwood Systems technology. The Carnegie scheme would still rely on a DC/DC converter in the light fixture, whereas the Redwood technology does all power conversion in a central system and provides the precise DC power needed to drive LEDs in the remote fixture.
The choice of a 250-VDC distribution scheme matches the typical DC/DC converter topologies on the market in IC form. Those converters are typically designed to operate globally where AC line voltage can vary from the 110V line in the US to 240V lines in other regions. So most power supplies include an AC/DC stage that outputs DC voltage in the range of 250V.
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