Power Electronics

Data Points

EPA Revises Energy Star Specification for External Power Supplies

The U.S. Environmental Protection Agency (EPA) recently issued Final Draft Version 2.0 of its ENERGY STAR external power-supply (EPS) specification and solicited input from interested parties. This document outlines the proposed new energy-efficiency requirements that EPS models would need to meet to earn the ENERGY STAR certification. It is intended that once final, this document will replace the current Version 1.1 specification. The EPA plans to finalize the Version 2.0 specification this month, allowing industry approximately nine months transition time prior to the new specification taking effect.

While the EPA was reviewing stakeholder comments on the Draft 1 specification, the Energy Independence and Security Act of 2007 was signed into law with new federal mandatory standards for EPSs to take effect on July 1, 2008. In the wake of that action, some stakeholders suggested that an ENERGY STAR Version 2.0 specification was not needed, while others encouraged the EPA to align ENERGY STAR requirements with these new standards.

Based on the performance of currently available EPSs, the EPA has concluded that sufficient differentiation remains among products such that an ENERGY STAR level more stringent than the pending federal standard could be established, offering a cost-effective, more-efficient alternative. Thus, the EPA has proposed new efficiency levels in its Final Draft specification where 25% of the units in the EPA's data set would qualify as ENERGY STAR, taking into account the proposed active mode and no-load mode requirements.

In addition, a few stakeholders requested an increase in the maximum allowed no-load power for ac-ac models. The EPA did not implement this change because it would have made ENERGY STAR's voluntary levels less stringent than the new U.S. mandatory standards. The proposed Final Draft ENERGY STAR no-load specification for ac-ac models is identical to the 0.5-W limit in the Energy Independence and Security Act of 2007.

The EPA was encouraged by some stakeholders to postpone the effective date for the Version 2.0 specification to allow more transition time for products such as telephony, whose ENERGY STAR specifications reference the EPS specification. However, because the EPS federal mandatory standard that goes into effect on July 1, 2008, is more stringent than the current ENERGY STAR specification for EPSs, it is important, in order for ENERGY STAR to remain relevant in the market, for the new specification to go into effect as soon after that date as possible. Accordingly, the EPA has proposed to extend the date until Nov. 1, 2008, which allows approximately nine months transition.

Significant feedback was received on many elements of the Draft 1 Version 2.0 specification and, in response, the EPA has made the following key adjustments to the proposed Version 2.0 energy-efficiency criteria:

  • Added a definition and separate active-mode requirements for low-voltage EPS models in recognition of design constraints that limit the efficiency of low-voltage, high-current products

  • Adjusted the active-mode equations for EPS models at or below 49-W output power to ensure more consistent qualification rates across various wattage ranges

  • Revised the higher-wattage EPS threshold for active-mode calculations from 36 W to 49 W. As such, active-mode efficiency is based on three equations that relate to output power and cover 0 W to less than or equal to 1 W, greater than 1 W to less than or equal to 49 W, and greater than 49 W

  • Changed the power factor requirement to apply to power supplies where input power is 100 W or greater (and included a second power factor option for review and comment)

  • Added new language to clarify that the effective date is based on the EPS unit's date of manufacture

  • Inserted a new Section 6 “Effective Date for ENERGY STAR Product Specifications” to formally and concisely outline the EPA's intentions with regard to EPS requirements in other ENERGY STAR end-use product specifications.

Finally, the EPA has maintained its requirement of testing and qualification at 115 V and 230 V for EPSs capable of operating at multiple voltages and frequencies. At stakeholder request, when developing the Final Draft specification levels, the EPA made sure to analyze the data set in a way that is consistent with this approach — that is, models with both 115-V and 230-V data must meet all levels at both voltages.

A masked version of the data set used by the EPA to determine the proposed energy-efficiency requirements in this Final Draft Version 2.0 EPS specification is available, as are summary charts and graphs depicting the EPS data and the proposed levels.

For more information, see the U.S. Department of Energy Web site at www.eere.energy.gov/buildings/appliance_standards/schedule_setting.html and click on the “Report to Congress on Appliance Energy Efficiency Rulemakings — Implementation Report: Energy Conservation Standards Activities,” February 2008.

PSMA Launches Comprehensive Database of Energy-Efficiency Standards, Regulations

An online database containing the ever-evolving standards and regulations for energy efficiency is now available from the Power Sources Manufacturers Association (PSMA).

The global database includes the various organizations that are active in establishing energy-efficiency standards and regulations for power supplies used in commercial applications. This information resource is currently available to the entire industry for a limited time through the Energy Efficiency Forum on the PSMA Web site (www.psma.com). In the future, the database will be available only from the members-only portion of the association's Web site.

Users can search by agency, by country and state, by application (such as battery chargers and lighting) or by region. When searching by agency, for each organization, the database includes the most recent status of the standards and the specific applications affected by the standards; identifies critical documents, meetings and milestones; and provides a link to the organization's Web site. PSMA has contracted with Anagenesis, a technical marketing company in the power semiconductor industry, to update and maintain the database.

“The ongoing activities worldwide in establishing new and sometimes conflicting energy-efficiency standards and regulations are affecting all companies as they design their new products for global markets,” says Dusty Becker, cochair of the PSMA Energy-Efficiency Committee. “This database is a valuable resource for engineers and product planners to keep abreast of ongoing activities and to access the latest version of the standards.”

Tim Cassidy, the other cochair of the PSMA Energy-Efficiency Committee, adds, “The PSMA Energy-Efficiency Committee is acting in an advisory role and industry resource for a number of state and federal organizations involved in developing new energy-efficiency standards and regulations for a variety of applications. The committee is also closely monitoring similar activities in major industrial nations and encouraging the harmonization of standards on a global basis.”

PETech Columnist Ponders Impact of Liquid Cooling

This month at www.powerelectronics.com, online columnist Lou Pechi argues that the now-popular techniques for cooling chips and pc boards are becoming inadequate as levels of power dissipation continue to rise. In addition to discussing why forced-air cooling, heatsinks and vias won't be able to cope with the heat generated by future ICs, Pechi looks at an emerging technology for liquid cooling and discusses its implications for chip developers and board designers.

In “Liquid Cooling is Coming to Chips and Boards,” Pechi writes, “As the power density of high-performance ICs increases, cooling the devices is becoming a more-significant concern. Conventional forced-air-cooling techniques will be unable to meet the needs of future power-hungry devices — especially 3-D multichip modules that pack more processing power into less space. Cooling high-power electronic devices dissipating more than 300 W/cm2 at the die is beyond the capability of most conventional air- or liquid-cooling solutions.

“A new technique for fabricating liquid-cooling channels onto the backs of high-performance ICs could allow denser packaging of chips, while providing better temperature control and improved reliability,” writes Pechi. This type of cooling technique will require new design skills in terms of pc-board design and new ICs that “can interface with the on-board pc fluid distribution systems to provide fluid circulation inside IC devices.”

APEC Presentations Posted Online

Slide presentations given at the recent Applied Power Electronics Conference in Austin, Texas, in the plenary session and in the special presentation sessions are now posted online at the APEC 2008 conference site. The plenary sessions, which were discussed in this month's editorial, are posted at www.apec-conf.org/content/view/159/215/, while the special sessions are posted at www.apec-conf.org/content/view/155/216/.

In the latter group are the sessions on market trends, business, system design, power electronics for a greener world and current topics in power electronics research.

Power Electronics Web Site Enables Browsing of Archive

Readers interested in browsing the titles of the more than 2000 design articles in the Power Electronics Technology archive can now do so on the magazine's Web site. The site provides links to the archive's three indexes, which list articles by title, by issue and by subject for all of the articles on the 30 Years of Power Electronics Technology DVD.

In the subject index, readers can search within the following major subject headings: power semiconductors, power management, portable power management, power systems, thermal management and passives/packaging. Within these headings, readers can drill down into subcategories to find design articles on specific topics.

For example, under the power management heading, there are subcategory listings for PWM controllers, digital power control, high-voltage devices and motor power management, just to name a few. Under the power semiconductors heading, subcategories such as IGBTs, power MOSFETs, power modules and thyristors appear. Other popular subcategories such as EMI show up under power systems, while magnetics appears under passives/packaging. Most of the design articles in the archive are cross listed in multiple subject headings and subcategories.

The archive contents span the first 30 years of Power Electronics Technology's publication from 1975 to 2005. During this time, the magazine appeared initially under the title Solid-State Power Conversion, but was subsequently known as Power Conversion International, Power Conversion & Intelligent Motion, PCIM Power Electronic Systems, and under its current title, Power Electronics Technology.

To browse the articles, go to powerelectronics.com/cd/, and click on article index, subject index and issue ind

Hybrids Integrate Control and Power Handling

TT electronics BITechnologies has combined its small signal and power hybrid technologies to develop custom hybrid modules that integrate control and power handling functions. Typical applications for these products include motor drives, power supplies and power amplifiers.

The custom modules combine thermally conductive ceramic substrates with packaged discrete components or bare die through the use of vacuum low-flow die attach. According to the company, this approach results in a smaller design than comparable products.

An example product might combine two types of substrate stacked in layers. For instance, power stage components could be mounted to a direct-bonded-copper (DBC) board for the desired thermal and electrical performance, while control components could be mounted to a daughterboard that sits on the DBC substrate. The daughterboard could use thick-film-on-ceramic technology to achieve finer pitch than the DBC. Wirebonding could then be used to connect the substrates.

A hybrid module can handle up to 100 A with a voltage rating of 1000 V. The latter limit is actually determined by the component selection. Another limiting factor is substrate size. The ceramic substrate is manufactured in 4-in. × 4-in. plates, which sets the limit on maximum board area.

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