Distributed Power Architecture: What’s the Problem?

March 1, 2012
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Since the 1980s the bricks of distributed power architecture (DPA) have delivered the classic functions of DC-DC converters (isolation, voltage transformation and regulation) to the point of load.

But …at a price in terms of premium space and cost.

Electronics power suppliers have long recognized these problems. One of the earliest responses was the introduction of DPA, in which the silver box AC-DC power supply was used to serve DC-DC converters distributed near the system’s points of load, typically using an intermediate DC voltage such as 48 V. The AC-DC supply handled rectification, regulation, isolation, noise suppression and power factor correction. The DC-DC converters, implemented using high density bricks, each provided an isolated output voltage at a level suitable for the load they were serving. Compared with the previous centralised power approach, DPA reduced the I²R losses associated with transmitting low voltage around the system and improved dynamic response. It also moved heat generation away from a single source, greatly reducing or eliminating the need for heat sinks or high velocity airflow. Elimination of hotspots improved system reliability.

DPA, however, increased costs and board space consumption because each PoL brick had to provide every DC-DC function – isolation, regulation, transformation, EMI filtering and input protection. This problem grew steadily as onboard voltage requirements proliferated. Additionally, as devices continually became faster, their transient response requirements exceeded the capabilities of typical DPA brick topologies.

Furthermore, if a single DC-DC converter could not provide adequate power or fault tolerance for a particular output voltage, multiple DC-DC converters had to be paralleled.  This creates additional complexity because remote sense leads were required from each paralleled converter to a single, common point, and additional circuitry was needed within each paralleled converter to force power sharing among the units. 

Distributed power put DC-DC converter “bricks” on system boards… but, with expanding voltage requirements, DPA began to take up too much precious real estate and cost.

To learn more about the next step in the evolution of power architectures you should listen to our recent web seminar, “The Three Approaches to Power”, which is now available as a rebroadcast.  Tom Curatolo, our director of applications engineering, discusses the challenges faced by today’s power system designers and the architecture approaches  available.

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