Posted on 17 July 2019

New Tool Easily Navigates the Efficiency Standards Landscape

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Platform to use Worldwide Energy-Efficiency Specs and Standards

Since discovering that approximately 10% of the electricity generated for residential use is being wasted by devices that are turned off but actually continue consuming power, government agencies have been developing programs to improve the efficiency of Energy-using Products (EuPs). This focus on reduced power consumption has moved energy efficiency from being a secondary concern to the top tier of a new product’s design objectives.

By Rich Fassler, Manager, Energy-Efficiency Programs, Power Integrations, Inc. (San Jose, CA)


Today´s designers must fully understand whether their product will comply with current and pending energy-efficiency specifications and standards. Further, they must take into consideration the operating mode requirements of the systems in which their products will be used.

The energy-efficiency regulation landscape is constantly changing. Finding time to keep up-to-date with those changes, to make sure current and future products comply, has become a daunting task for design engineers. In the beginning, it was easy because regulations were relatively uncomplicated, targeting only standby or no-load power consumption. Over the years, however, energyefficiency programs have evolved, becoming more complicated and covering multiple operating modes in order to capture as much energy loss as possible.

A prime example of this is the evolution of External Power Supply (EPS) efficiency programs. Beginning in 2001, the European Commission´s Code of Conduct (CoC) for EPS simply specified the maximum no-load power consumption. Today´s CoC EPS (version 4) includes two minimum average active-mode efficiency specifications (one for low-voltage models <6V and 550 mA, and one for all other EPS under 250 W), as well as three sets of no-load power consumption limits (one for mobile phone chargers <8 W, one for AC-AC EPS, and one for AC-DC EPS). Other government EPS efficiency regulations have also emerged that target both active-mode and no-load efficiency, including the ENERGY STAR EPS specifications, the U.S. EISA 2007 EPS standard, and both tiers of the European Commission´s Ecodesign Directive for EuPs. Figure 1 illustrates the efficiency specifications of these four programs.

Comparison of major EPS efficiency regulations

To further complicate matters for power supply designers, new application-driven EPS efficiency requirements have recently begun surfacing. China´s Communication Industrial Standard of PRC (YD/T 1591-2006), mandates a USB connector and power output with a minimum active-mode efficiency of 50% and a no-load power consumption of 300 mW for mobile telecommunication terminal equipment EPS. In 2008, a group of leading mobile phone manufacturers, through the European Commission IPP process, developed a "five-star rating" for mobile phone adapters / chargers, specifying no-load power consumption down to 30 mW (five stars) . well below any current or proposed government programs. In early 2009, the Open Mobile Terminal Platform group adopted this star rating, proposing standardization of mobile phone chargers and specifying that chargers meet a four-star rating minimum (150 mW no-load).

There is a ray of sunshine in this regulation maze in that all of the current major EPS efficiency programs have harmonized around the same test method, Test Method for Calculating the Energy Efficiency of Single-Voltage External AC-DC and AC-AC Power Supplies, found at Also, the mathematics used in calculating the average active-mode efficiency of an EPS (the arithmetic average of measured efficiency at 25%, 50%, 75%, and 100% of load) and the minimum efficiency level allowed by the spec (based on nameplate output power) are simple and straightforward. However, while there has been an effort by worldwide agencies to harmonize EPS specifications to simplify design, recent revisions have caused differences to appear, making it necessary for design engineers to research agency requirements on a regular basis.

There are many ways an engineer can keep abreast of new efficiency programs and pending changes to current specs. These include becoming an active stakeholder and attending (worldwide) government agency meetings, subscribing to efficiency newsletters, blogs, and databases (which may not always be up-to-date or include information relevant to an EPS), or regularly searching the internet for news on EPS efficiency programs. Unfortunately, all of these tasks can be very time consuming and may not provide a clear picture of whether the designer’s product will comply.

In an effort to assist power supply designers, Power Integrations has developed a web-based tool to determine compliance to major worldwide EPS regulations. The EPS Efficiency Compliance Calculator covers all major EPS efficiency programs, is simple to use, and applies to all types of EPS designs. The tool quickly calculates the average efficiency (based on the user’s measurements), compares the user’s EPS performance to the major efficiency regulations (showing both sets of data), and displays a pass/fail status. Figure 2 shows a screen shot of the calculator.

Power Integrations’ web-based EPS Efficiency Compliance Calculator

Designers begin by inputting the EPS output voltage, output current, and input voltage. The drop-down menu offers single input voltages (115 VAC and 230 VAC), as well as the universal input voltage range, important for determining compliance to ENERGY STAR EPS (version 2.0). The EPS measured no-load power consumption and the four active-mode efficiency levels can then be input. The tool calculates the average active-mode efficiency in real-time. After the user inputs are completed, the calculator displays compliance (green cell) or non-compliance (red cell) to the following efficiency programs:

ENERGY STAR EPS (version 2.0)
• US Energy Independence and Security Act 2007
• European Commission Code of Conduct (version 4)
• European Commission Ecodesign Directive for EuPs (tier 1 - 2010)
• European Commission Ecodesign Directive for EuPs (tier 2 - 2011)
• China USB Charger Spec (YD/T 1591-2006)

The calculator also determines the EPS no-load power consumption “star rating” as described in the European Commission Integrated Product Policy Program (IPP) for mobile phone adapters. An adapter can earn from one star (no-load ≤500 mW) to five stars (no-load ≤30 mW) based on its no-load consumption. When the user inputs the measured no-load power consumption, stars appear (or disappear) according to the IPP specification.

The calculator is also adept at helping avoid embarrassing non-compliance moments due to the subtleties of some areas of the regulations. For example, a 3 W EPS with a 5 V, 0.6 A output and a 65% average active-mode efficiency will easily pass all six of the regulations. However, a similarly rated 3 W EPS with a 6 V, 0.5 A output and the exact same average efficiency will fail ENERGY STAR, EC Code of Conduct, and tier 2 of the EC Ecodesign Directive because those programs have tighter efficiency requirements for a standard voltage EPS compared to those designated as low-voltage models (<6 V and ≥550 mA), even with the same output power.

EPS energy-efficiency regulations will continue to evolve, as device efficiency and design methods improve. The EPS Efficiency Compliance Calculator provides power supply designers with a single resource for verifying and calculating compliance to all major EPS specs and standards. Try it now at:



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