Jul 17, 2018
There is a wide variety of regulations covering energy efficiency around the world, from the California Energy Commission to Energy Star and Energy-related Products (ErP). Specific to external power supplies (wall mount or desktop), the US Department of Energy (DoE) publishes a standard described in levels (Level VI is the most recent and most stringent), while in Europe, the European Union (EU) Code of Conduct (CoC) on External Power Supplies (EPS) is prepared by the Joint Research Centre, the European Commission’s science and knowledge service.
This Code of Conduct identifies its scope as covering single voltage external AC-DC and AC-AC power supplies for electronic and electrical appliances, including among others, AC adapters, battery chargers for mobile phones, domestic appliances, power tools and IT equipment, in the output power range 0.3W to 250W.
Version 5 of this Code of Conduct was published in 2013, with two tiers of increasingly stringent regulations phased in, starting with Tier 1 in January 2014. Tier 2 was planned to come into force in 2016 but was delayed to January 2018. As of the time of writing, the CoC Tier 2 regulations have still not come into force.
Each set of regulations increases the demands on power supply efficiency when it’s in use and reduces the acceptable power consumption when there is no load on the unit.
Efficiency
The EU CoC separates low voltage external power supplies (with a nameplate output voltage of less than 6 volts and a nameplate output current greater than or equal to 550 milliamps) and provides different efficiency criteria for this subcategory. The criteria for both categories are separated by output power according to the tables below.
Table 1: Energy-Efficiency Criteria for Active Mode (excluding Low Voltage external power supplies)
Table 1: Energy-Efficiency Criteria for Active Mode (excluding Low Voltage external power supplies)
What this means is that for a 60 watt external power supply, such as SL Power’s TE60 product family, the minimum efficiency for both Tier 1 and Tier 2 at 25%, 50%, 75% and 100% of full rated output current is greater than 88% for the 5 volt models and greater than 89% for higher voltage models (9, 12, 18, 24 or 48 volt outputs). SL Power’s TE90 and TE150 external power supplies, which also meet the EU CoC Tier 2 specification, fall into the same category.
The CoC states that measurements should be carried out according to the method specified in the ‘Test Method for Calculating the Energy Efficiency of Single-Voltage External AC-DC and AC-AC Power Supplies (August 13, 2004)’, issued by US EPA. Version 5 of the CoC added a 10% measurement point to the existing 25%, 50%, 75% and 100% of full rated output current measurement points.
No-Load Power Consumption
For power supplies in the range 49 W to 250 W, the CoC Tier 1 maximum no-load power consumption was 250 mW (0.250 W) while CoC Tier 2 lowers that threshold to just 150 mW (0.150 W). The requirements for other power outputs are given in this table:
No-Load Power Consumption Conclusion
The impetus behind the EU CoC was to reduce energy consumption across Europe, driven by an impact assessment that calculated that improving the design of external power supplies could save over one terawatt-hour of energy per year by 2020. While the Tier 2 regulation has not become an official regulation as expected, many adapters available today (such as SL Power TE60, TE90, and TE150 Product Families) were designed to comply with these requirements, as this requirement still may become compulsory at some point in the future.
