Traditional power supplies are either AC or DC input. Even so-called universal input power supply units (PSUs) are limited to 85 – 264VAC or 130 – 370VDC. Though supporting a wide range for EITHER an AC or DC input, these ranges are constrained and therefore limit what devices can be supported without extra, costly, intermediary power conversion. AC limits are at least defined to cover all ranges of mains inputs [1], but still constrains the application space because they cannot cope with lower AC or DC supply voltages.
When it comes to DC power, there is a much broader spectrum of needs because most loads ultimately require DC (some motors and inverters are the most prolific exceptions to the rule). Therefore, standards can be specific to a class of products (like the universal serial bus or
Power over Ethernet, USB or PoE) or an application space or market vertical (like the high-voltage data center, HVDC). But standard or no standard, many loads and operating environments will need to support wider, perhaps even unpredictable or unknown, input supply voltage ranges. In general, support for sub-minimal voltages enable the load to operate longer in the case of line voltage sags (a.k.a. – brownout), while support for voltages above maximum ratings enable protections for equipment and users.
Regardless of AC or DC input and if trying to support extended voltage ranges above/below nominal specification, there is also consideration of driving maximum power supply efficiency (e.g. – minimal dissipated power loss) based on the loading condition. In other words, the input voltage level to a power supply or system has an impact on power conversion (a.k.a. - commutation) efficiency, even if the load was to remain static on the output side. But most loads are also dynamic in their current draw [2]. To assess true performance, one must have and study the power solution’s Efficiency vs. Load curve, as demonstrated by the example in the figure below.
Fig. 1: Comparing PSU Efficiency Curves Optimized for Different Load Rangers, Graphic: courtesy of PowerRox [3]
Why should designers limit themselves to the SOUR (Same Old sUpply Range) when there is so much more to be had? The ability to have maximum flexibility for an application in terms of cost, uptime, efficiency, and sustainability in nearly any situation, even where the supply voltage is unpredictable or unknown, is a very powerful tool for any Design Engineer, Factory Manager, or Facilities Architect. For instance, a single power supply (not a product family or options of a common design, but a truly common and universal, single part number) supporting a range from 24V to 240V AC OR DC really opens the door to ACTUAL universal support and unprecedented levels of energy optimization.
RECOM is the first to bring such an advanced product to the market and redefine what is meant to be “universally-wide-input” compliant. How the
RAC15-K/WI will permit SWEET (Super Wide and Effectively EfficienT) solutions to power the facilities and applications of tomorrow is discussed in further detail later on.
