Digital Power Analyzer
by Jeff Shepard -- EDN, August 6, 2007
Since early 2004, when digital power first burst onto the commercial scene, digital ac-dc power supplies have far outnumbered digital dc-dc converters. When looking at 177 new “digital” product announcements from 14 power suppliers between January 2003 and June 2007, only 21% were dc-dc converters, while 79% were ac-dc power supplies.
The 14 companies in our sample (Emerson/Astec, Emerson/Artesyn, Power-One, Coldwatt, Roal, C&D Technologies, Tyco Power, Delta Products, N2Power, Unipower, Cherokee International, XP Power, Ericsson Power Modules and TDK/Lambda) include both major power supply makers and smaller “niche” suppliers. The results find that only one company introduced more than 10 digital dc-dc converters since 2003 while five companies have introduced over 15 digital ac-dc power supplies during the same period.
The dominance of ac-dc products is also reflected in the use of the various communications buses. The I2C bus is clearly dominant. It is protocol-neutral and is widely used in ac-dc power supplies (but is also found in a few dc-dc converters). Looking at the specific digital communications protocols finds that almost twice as many units use PMBus (10%) as use the Z-Bus (6%). Since the Z-Bus was optimized for use with dc-dc converters in distributed power architectures, and since digital dc-dc converters are far outnumbered by digital ac-dc power supplies, it is not surprising that the more general purpose PMBus outnumbers the Z-Bus. There are 5% of these converters without a communications bus. Those converters employ digital power conversion (loop control), but not digital power management techniques. n
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