CUI INC – External Power Supply Laws are Poised to Change Yet Again

The Current State of External Power Supplies
People today are familiar with the challenges associated with our use of energy, and in particular the need to control greenhouse-gas emissions and use energy efficiently. Anyone placing a hand on a warm notebook power adapter is likely to be thinking of the energy being wasted and its effect on the environment.

Legislators – keen to play their part in preserving the planet – are constantly increasing pressure on equipment suppliers to deliver products that draw less and less power and operate more and more efficiently. In February of 2016, the US Department of Energy (DoE) enacted legislation requiring external power adapters marketed in the USA to comply with international Level VI eco-design specifications. The dust has barely settled, and already the EU is upping the ante by publishing its Code of Conduct (CoC) Tier 2 efficiency standards.

There is some history behind this leapfrog-style progress in environmental legislation. About two years ahead of the US move to Level VI, the EU in 2014 introduced CoC Tier 1 as a voluntary standard. CoC Tier 1 specifies efficiency and power limits that are only slightly less stringent than Level VI, but also requires an extra efficiency measurement to be taken at 10% of full load. This presents a tough challenge to designers, as power supplies are known to exhibit their poorest efficiency at such low loads. CoC Tier 1 is currently under review by EU legislators targeted to become mandatory sometime in 2017, followed in 2018 with CoC Tier 2, which further tightens the no-load power, average-efficiency and 10%-load specifications, effectively setting the bar higher than Level VI.

Efficiency Standards, a Brief History
For the full story, we have to look back to the early 1990s and the US ENERGY STAR initiative. ENERGY STAR began as a voluntary labelling program for products such as computer peripherals and white goods. A short while later, a University of California Berkeley Laboratory study found that stand-by operation of domestic appliances accounted for 5% of the nation’s residential electricity consumption.

At the time, the external power supply (EPS) was considered a prime culprit for this wasted energy and it was estimated that there were more than one billion external power supplies active in the United States alone. The operating efficiency of the linear technology used then was often as low as 50% but worse still, power continued to be drawn even when the end-equipment was turned-off or disconnected. Researchers feared that the growing use of such
external supplies could see this wasted energy grow to as much as 30% of all electrical energy consumption, if nothing was done to reduce the losses. Legislation was considered necessary to require equipment manufacturers to do something about this situation. Accordingly, in 2004, the California Energy Commission became the first to implement mandatory energy efficiency standards.

Since that time, various authorities around the world have introduced a succession of standards, some voluntary and others mandatory, that seek to impose tighter and tighter requirements on the efficiency of external power supplies. The standards timeline on the following page illustrates the progress graphically, and not only brings us to the present date but also shows what we should be anticipating over the next two years.

Challenges Faced by OEMs
While these standards may benefit the consumer and the environment as intended, they present a considerable challenge to both the EPS manufacturer and the OEM. For the power supply manufacturer, the technical challenge of meeting the latest efficiency specifications becomes ever-more complex with each successive regulation. For the OEM, ensuring compliance in the countries where the EPS is used creates a number of logistical and supply chain challenges. These issues are amplified because despite attempts to harmonize standards across the globe, their development and adoption has in reality proved to be a game of leapfrog as countries or regions seek to catch up with and then surpass their neighbors.

In practice this means that OEMs who want to avoid the complexity of having different product configurations for different geographic markets need to ensure their external power supplies meet the latest and most stringent standards worldwide. EPS manufacturers, for their part, must employ leading-edge design techniques to comply with evolving standards and keep their product lines ahead of the game.

CoC Tier 2 Regulations
The CoC Tier 2 standard significantly tightens the limits defined by DoE Level VI. A supply with a nameplate rating between 49W and 250W, which has a maximum no-load power of 210mW under Level VI rules and 250mW under CoC Tier 1, will have to consume less than 150mW to satisfy CoC Tier 2. Tables 1 and 2 on page 24 show a comprehensive list of the Tier 2 specifications, including the requirements for average efficiency (the mean of active efficiency measured at 25%, 50% and 75% of full load), and the low-load efficiency measured at 10%.

Moving Forward
Globally, it is expected that other nations will soon follow suit with the US’ DoE Level VI standard as one has already seen with the EU’s CoC Tier 1 and Tier 2 requirements for external power supplies. It should also be expected that countries with existing efficiency regulations previously in-line with the US, including Canada, will move to harmonize with these newer US and European standards.

The EPA estimates that external power supply efficiency regulations implemented over the past decade have reduced energy consumption by 32 billion kilowatts, saving $2.5 billion annually and reducing CO2 emissions by more than 24 million tons per year. Beyond the mandated government regulations, many OEMs are now starting to demand “greener” power supplies as a way to differentiate their end-products, driving efficiencies continually higher.


CoC Tier 2 Single Voltage External AC-DC Power Supply, Basic Voltage
Nameplate Output Power (POUT)Minimum Average Efficiency in Active Mode (expressed as a decimal)10% Load Average Efficiency in Active Mode (expressed as a decimal)Maximum Power in No-Load Mode (W)
0.3W ≤ POUT ≤ 1W≥0.50 x POUT + 0.169≥0.50 x POUT +0.060≤0.075
1W < POUT ≤ 250W≥0.071 x In (POUT) - 0.00115 x POUT + 0.670≥0.071 x In (POUT) - 0.00115 x POUT + 0570≤0.075
49W < POUT ≤250W≥0.890≥0.790≤0.150

CoC Tier 2 Single Voltage External AC-DC Power Supply, Basic Voltage
Nameplate Output Power (POUT)Minimum Average Efficiency in Active Mode (expressed as a decimal)10% Load Average Efficiency in Active Mode (expressed as a decimal)Maximum Power in No-Load Mode (W)
0.3W ≤ POUT ≤ 1W≥0.517 x POUT + 0.091≥0.517 x POUT≤0.075
1W < POUT ≤ 49W≥0.071 x In (POUT) - 0.0011 x POUT+ 0.609≥0.0834 x In (POUT) - 0.00127 x POUT + 0518≤0.075
49W < POUT ≤250W≥0.880≥0.780≤0.150