Still on Course, But Miles to Go on Power Road Map

Aug 1, 2007 12:00 PM
David Morrison Editor

Anyone who's ever taken a summer road trip has heard the familiar refrain, “Are we there yet?” Although the question may arise too often, its mere asking reassures us that there's a destination and purpose for the journey. And the question serves as a cue to check the map (or GPS) to gauge our progress.

Perhaps we can ask a similar question when we look at the technology road map published earlier this year by the Power Sources Manufacturers Association (PSMA). The PSMA's power technology road map provides us with a means of charting progress toward specific performance targets in four power-supply categories: ac-dc front-end power supplies, external ac-dc supplies, dc-dc bus converters and nonisolated dc-dc converters.

The PSMA road map contains projections for various performance targets, as well as product and technology trends, showing data for 2006 and then forecasting the expected progress in 2010. In that designers may now be working on power-supply products that will launch in 2008, a midpoint on the road map, this might be a good time for many designers to ask, “Are we there yet, or at least halfway?”

Though vendors may be reluctant to share data on what's coming next year, I thought it would be telling to look at some of the products introduced over the last 12 months and see how they measure up to the PSMA road-map numbers. To make this comparison more manageable, I looked just at the ac-dc front ends. The road map defines these front ends or bulk power supplies as fully enclosed units with a single main output, usually in the 12-V to 48-V range, and rated at 1000 W to 1200 W. These supplies receive input power via a 15-A ac line cord, but are connectorized to plug into a chassis or backplane for delivery of their dc output. They also feature an internal fan or blower for self cooling.

I also limited my comparisons to the parameters of power-conversion density, efficiency and cost/watt. Of course, my survey wasn't comprehensive; I only identified about five new products that closely matched the above criteria. But, I hoped this sampling would help make the road-map numbers more tangible and provide some perspective.

For power-conversion density and efficiency, the road map breaks down its forecasts into three performance classes: most economical, highest practical and bleeding edge. For example, a 1-kW front end in the most economical class is expected to progress from 5 W/in³ in 2006 to 8 W/in³ in 2010. Meanwhile, front ends in the highest-practical class are expected to rise from 10 W/in³ to 15 W/in³, while bleeding-edge supplies are projected to rise from 20 W/in³ to 30 W/in³ over the same time period.

As I looked for new ac-dc front ends, I expected to find any relevant power supplies announced over the past year would fall into the bleeding-edge category for density. To my surprise, most were closer to the highest-practical figure of 10 W/in³.

In the efficiency category, the road map specifies efficiency at 12-V and 48-V output for the same three classes. Here again, I encountered products reaching the highest-practical levels: The road map specifies efficiency at 12 V as 90% in 2006 rising to 92% in 2010. For 48-V output, the road map specifies a range of 92% to 94% efficiency in 2006, and this is not expected to change by 2010.

As for pricing, the road map projects that “carrier class/reliability sensitive” front ends will see prices decrease slightly from a typical cost of $0.15/W in 2006 to $0.13/W in 2010. Although press release pricing may be misleading, the products I found quoted prices as high as $0.20/W or even $0.40/W. Perhaps vendors believe that their unique offerings can command more than the “typical” price.

My takeaway from this exercise is that there are still great opportunities to improve power-supply performance and lower cost. For the highest-performance products, designers still face challenges in improving density and efficiency simultaneously.

And though the performance gap between the highest- and lowest-cost power supplies is expected to narrow, there still will be opportunities for designers to craft products that outperform existing power supplies in a given price/feature class. So, as we look at the PSMA road map and realize that we're not there yet in this one power-supply category, we can take comfort in knowing the road for product development is wide open.

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