Energy efficiency for external power supplies (EPS)
By Gary Bocock, Director of Engineering, XP Power
Controlling the power consumed by external power supplies, whether when they are supplying power or when disconnected from the load, is important for continuity of the energy supply and reduction of environmental impacts. Legislation and targets are set for external power supplies because of proliferation, lack of on/off control and because they are commonly left plugged in to the mains supply when not in use.
Many areas around the world have introduced legislation for no load power consumption and active mode efficiency for external power supplies. In the USA there is the California Energy Commission (CEC) and the Energy Independence and Security Act (EISA). In Europe there is the Energy related Products (ErP) Directive, in Canada there is Natural Resources Canada (NRCan) and in Australia the Minimum Energy Performance Standard (MEPS) to name just a few. These are a just a few examples of mandatory requirements written into legislation.
Other organisations setting targets for energy efficiency and no load power consumption are Energy Star in the USA and the EU Code of Conduct (CoC) in Europe. The limits set in these standards are voluntary and are more stringent than those required by legislation. It is anticipated that the mandatory requirements will also become more stringent in the future as newer standards are adopted.
In recent times both Energy star and the EU CoC have set new more demanding standards for both energy efficiency and no load power consumption, the EU CoC has also introduced a new 10% load efficiency requirement reflecting applications which spend a large proportion of time using minimal power from the external power supply such as those with an internal battery and has two tiers to drive future development.
The Energy star level VI and the EU CoC were both introduced in early 2014 with the Energy Star and EU CoC tier 2 requirements coming into force in 2016. While these are voluntary targets, market demand for higher efficiency and reduction of environmental impacts of products drives power supply manufacturers to comply with these latest standards.
These new requirements mean both increased active mode efficiency and reduced no load power consumption. The tables below outline the differences between the existing level V limits previously invoked by Energy star and the ErP, the new Energy Star level VI limits and the EU CoC tier 1 & tier 2 limits with implementation dates . Notably the energy star limits now incorporate external power supplies with an output >250W.
The power market is fast moving and customers are keen to design in products that perform to the latest standards and are future proofed. The first energy efficiency level VI parts are already available and 2015 will see a significant increase in products released to market offering conformance to the very latest energy efficiency requirements.
Figure 1: VER05 and VEL05 series from XP Power
An example of products with energy efficiency level VI already available on the market is XP Power’s VER & VEL series of 5W wall plug adaptors. Believed to be one of the first plug top power supplies to comply with the new Energy Star level VI energy efficiency standard, they are available with either a fixed input plug as required for use in the US, UK, Europe or Australia (VEL05 series), or is supplied with four interchangeable mains (VEL05 series).