Craig Eaton, Ideal Power
There have been numerous changes to the EU’s directives and regulations concerning the efficiency of electronic devices in recent years, particularly concerning standby power. The Eco Design directive, 2009/125/EC, is the all-embracing directive intended to improve the energy efficiency of all energy related products (ErP). It’s a revision of the directive formerly known as the energy using products (EuP) directive, 2005/32/EC. The goal of this directive is to reduce the energy consumed by ErP by 20%, by 2020; high efficiency external power supplies can help achieve this.
As part of the ErP directive, EC 278/2009 is the regulation that specifically concerns an external power supply connected to electrical or electronic equipment in a household or office. This regulation restricts an external power supply’s maximum no-load power consumption, that is, its power consumption when the power supply is connected to the mains but the output is not connected to any primary load.
The regulation also restricts the average active efficiency of the power supply, which is intended to ensure the efficiency of the supplies while they’re in use. A power supply’s average active efficiency is calculated by measuring its efficiency when it’s at 25%, 50%, 75% and 100% of full load and averaging the four numbers.
New limits for both these criteria were introduced with Stage II of the ErP directive came into effect for anything placed on the market after 27 April 2011. The maximum no-load power consumption was previously 0.5W, but has been reduced to 0.3W for AC-DC power supplies with rated power below 51W. Above 51W output power, the limit is 0.5W.
A summary of the requirements for Stage II for minimum average active efficiency is shown in table 1. Different criteria apply for ‘low voltage external power supplies’, defined as those with a rated DC output below 6V and above 550 mA.
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Table 1. The minimum average active power for Stage II of the EC 278/2009 regulation as they relate to external power supplies. Po is the rated output power of the power supply
Does your system comply?
If you’re designing a piece of electronic equipment that uses an external power supply, it would be wise to consider whether that external power supply is compliant to ErP Stage II. Aside from the technical requirements, the manufacturer of the external power supply must have a conformity system in place to compile a declaration of conformity (DoC). To do this, they must keep technical documentation, including test results showing the product meets the average active efficiency and no-load power consumption requirements, which must be available for ten years after the product was manufactured. They must also mark the product with the CE mark to show that it complies to all the relevant European standards. If the manufacturer is outside the EU, this responsibility falls to whoever imports the product.
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Figure 1. The no-load efficiency of Ideal Power’s 25HK-AB series has been increased to meet ErP II regulations
Part of the reason for introducing the requirements in stages is to allow manufacturers time to redesign their products to meet the new constraints. Ideal Power has done exactly that for all external power supplies, including the 25HK-AB, 25HK-AJ and 25HK-U series, shown in figure 1. Several changes were made in order to meet ErP Stage II.
Firstly, the pulse width modulation (PWM) controller that controls the switching frequency of the components inside the power supply has been upgraded to one with a frequency foldback feature. This feature helps to maximise the power supply’s efficiency at low-load, for example, when the equipment being powered is in standby mode. As the load drops, the PWM controller reduces the switching frequency, which helps reduce switching losses in the power components and therefore increase efficiency.
The PWM controller also has a pulse-skipping mode, which is a way of reducing the switching frequency even further, for maximum efficiency when the load is very low.
Secondly, the cross-sectional area of the output cable has been increased, and for some members of the product range, the output cable length was decreased as well. This helps to reduce the resistance of the cables, meaning less energy is wasted, contributing to the overall efficiency.
The output power for this series is 6-30W with a variety of output voltages and currents to choose from. The units can be supplied in either desktop or plugtop configuration, to suit the application’s requirements. An 8-way DC connector set is supplied with the –CP versions.
In summary, external power supplies must comply with the more stringent Stage II of the ErP directive, under regulation EC 278/2009, in order to qualify for a CE mark. When buying external power supplies, they should come with a statement of compliance for CE marking.
If you’re confused about these requirements, or about EC 1275/2008 (which relates to the power consumed by electrical or electronic household or office equipment) or EC 617/2013 (which specifically relates to computers and computer servers), Ideal Power can help clarify the situation.