CUI INC – Understanding the latest changes to the laws governing external power supplies

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People today are familiar with the challenges associated with our use of energy, and in particular the need to control greenhouse gas emissions and to use energy efficiently. Anyone placing a hand on a notebook computer’s warm power adapter will immediately be aware of the effect of wasted energy: such power losses have a direct impact on the environment.

In line with government policies aimed at minimizing the harm to the planet caused by greenhouse gas emissions, legislators have been constantly increasing pressure on equipment suppliers to deliver products which use less and less power and which operate more and more efficiently. In February 2016, the US Department of Energy (DoE) enacted legislation requiring external power adapters marketed in the US to comply with international Level VI eco-design specifications. The dust has barely settled, and yet already the European Union (EU) is now tightening the screw by publishing its new Code of Conduct (CoC) Tier 2 efficiency standards.

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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, with the expectation that it will become mandatory during 2017. In 2018 CoC Tier 2 is expected to come into force, further tightening the no-load power, average efficiency and 10% load specifications, and effectively setting the bar higher than Level VI.

Efficiency standards: a brief history
For the full story of the regulations governing external power supplies, it is necessary to look back to the early 1990s and the US ENERGY STAR initiative. ENERGY STAR began as a voluntary labelling programme 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 was considered a prime culprit, and it was estimated that there were more than one billion external power supplies active in the US alone. The operating efficiency of the linear technology used then was often as low as 50%. 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 wasteful power use account for 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 respond adequately. 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, which impose tighter and tighter requirements on the efficiency of external power supplies. Figure 1 illustrates the sequence of events. It not only brings us to the present but also shows what OEMs should be expecting in 2017 and 2018.

Challenges faced by OEMs
While these standards might benefit the consumer and the environment, they present a considerable challenge to both the manufacturer of the external power supply and the OEM which pairs it with its end-product. 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, the compliance effort in the countries where the power supply is used involves a number of logistical and supply-chain challenges. These difficulties are amplified because, despite attempts to harmonise 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 neighbours.

In practice this means that OEMs which want to avoid the complexity of maintaining 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 wave of changes.

CoC Tier 2 regulations
The CoC Tier 2 standard significantly lowers the already tight limits set by the DoE’s Level VI standards. 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 the requirements of CoC Tier 2. Figures 2 and 3 present a comprehensive list of the Tier 2 specifications. Here, average efficiency is the mean of active efficiency measured at 25%, 50% and 75% of full load; low-load efficiency is measured at 10% of full load.

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Changes to be expected in future
Globally, it is expected that other nations will soon follow the lead set by the DoE Level VI standard. It should also be expected that countries with existing efficiency regulations previously in line with the US, such as Canada, will move to harmonise with the newer US and European standards.

The US Environmental Protection Agency estimates that external power-supply efficiency regulations implemented over the past decade have reduced energy consumption by 32 billion kilowatts, saving $2.5bn annually and reducing CO2 emissions by more than 24 million tonnes per year. Furthermore, many OEMs are now starting to demand greener power supplies as a way to differentiate their end-products, pushing efficiencies continually higher.

OEMs therefore need to future-proof their power supplies to ensure that they meet these new CoC Tier 2 standards. CUI has already done everything needed to adapt its circuit topologies to meet efficiency requirements at all load levels, using advanced devices, high- efficiency topologies and reduced switching frequencies under light and no-load conditions.

The company has further qualified the majority of its Level VI line to also conform to the more stringent CoC Tier 2 standards. In the future, CUI will continue to implement the latest energy-saving technologies into its external power supplies in order to comply with current and future standards as the regulatory landscape continues to evolve.

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)Minimum 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 ≤ 49W≥ 0.071 x In (Pout ) – 0.00115 x Pout + 0.670≥ 0.071 x In (Pout ) – 0.00115 x Pout + 0.570≥ 0.075
49W < Pout ≤ 250W≥ 0.890≥ 0.790≥ 0.150
Pout > 250WN/AN/AN/A

CoC Tier 2 Single-voltage External AC-DC Power Supply, Low 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)Minimum 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≥ 0.0834 x In (Pout ) – 0.0011 x Pout + 0.609≥ 0.0834 x In (Pout ) – 0.00127 x Pout + 0.518≥ 0.075
49W < Pout ≤ 250W≥ 0.880≥ 0.780≥ 0.150
Pout > 250WN/AN/AN/A

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