EnergyStar or no, power supplies deliver

How much efficiency can be gained by dropping phases with a multiphase power supply? This graph from Linear Technology Corp. provides an idea of the possible gains. The two curves illustrate the gains for the state-of-the-art and previous generation product.
Select figure to enlarge.

Industry is abuzz over the Environmental Protection Agency's recent decision to “sunset” the Energy Star programs for external power supplies at the end of the year (Dec. 31, 2010). But make no mistake -- developers are still hot on delivering the lowest-loss designs across the board. The intent of all standards, declared and otherwise, remains the same: maximize efficiency and minimize standby requirements.

Power supply design is still about getting the most power out, but it's also increasingly about energy conservation. IC makers in particular have, in a sense, recast the power conversion issue. The goal today has as much to do with cutting wasted energy and dealing with heat dissipation as with delivering more raw power to the load. The principle plays out particularly in portables as the industry searches for better ways to economize on energy while charging a battery.

EPA's July announcement at the top of the news has the industry somewhat confused as to the future of some energy standards, but nothing has been lost. “We're confident that the effect of the Energy Star EPS (external power supply) standard will be sustained because many of the other standards remain in place,” said Ann Bailey, Chief of the Energy Star Labeling Branch, citing the existence of federal minimum efficiency standards for EPSs. “It's not quite as stringent as Energy Star, but it establishes a floor, which is very important. We also have product-specific performance specs for a long list of products that use external power supplies and those will continue to require EPSs that are as efficient as (directed in) our old specification.”

EPA's intent is that so-called Level V EPSs as designated under the International Efficiency Marking Protocol will become the de-facto substitute for those supplies qualifying under the old Energy Star 2.0 EPS spec. “Levels I through V corresponds to a different level of energy efficiency and our Energy Star requires an equivalent of Level V. This marking system will remain,” says Bailey. With the major efficiency issues aside, specific other details with respect to such parameters as the 0.5-W standby power proposal for the larger supplies are not yet clear. But Energy Star v. 2.0 EPS is a voluntary spec and thus no contentious issues are foreseen.

It won't be the first time a major voluntary spec has been withdrawn. “It doesn't happen very often,” says Bailey, “but as we get to a point where it doesn't appear there are additional efficiency issues to be gained, then we “sunset” it. We did that, for example, with LED traffic signals and transformers, not your average consumer products. We actually “sunset” the specification for cable boxes at one point, but we're revisiting that now.”

But it doesn't mean the old standard is obsolete. “It's because its mission was accomplished,” says Bailey, “and we don't expect anything to fall back to what it was because this spec has gone away. This is a great story about how two agencies can work together and government sort of functions ideally. We had an initial impact on the voluntary side. Because of that impact, DoE was able to establish a standard and then we were able to further move the market and the standard stayed in place. Once there's a minimum efficiency standard, there's no backslide.”

Meanwhile, there's a move afoot to appoint third-party organizations to confirm claims for compliance with various existing standards by supply manufacturers. Amid some contentious issues — including a study in 2007 of EU and U.S. customers as to their trust in claims from both business and government -- UL Environment (ULE, Northbrook Illinois) has recently been certified as the newest third party to confirm Energy Star claims.

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