Note:
As the last EU implementation date has slipped, this is the current situation
as of August 24, 2018. A draft EU
amendment dated 2018 indicates that the legislation may mirror more closely the
DoE Level VI limits effective April, 2020.
External
power supplies (EPS) are widely used in households around the world to charge
phones or operate tablets, laptops, game consoles and a variety of consumer
electronic and electrical items.
Studies
on European energy use of these power supplies indicate that reducing off-load
power consumption and improving product efficiency will save nearly 10TWh of
power a year. A Terawatt hour (TWh) is 1,000,000,000,000
Watts used in an hour. Reducing energy
usage saves money, reduces the requirement to add new power generating capacity
and reduces environmental pollution.
Two
parameters were originally specified to regulate waste energy reduction, which
when multiplied by a billion products becomes very significant:
Maximum off-load power consumption
Many power supplies are left plugged in to the AC supply
and fully operational; even when the device it was charging has been
removed. Although the power supply is
not powering anything, it still consumes power.
The maximum off load power consumption varies with the output power of
the EPS and is stated in the specification.
Minimum average efficiency level
With loads less than the full rating of the EPS, the
efficiency of the power supply can decrease significantly. Low load conditions occur as a battery becomes
partially charged, or when a device goes into an inactive (sleep) mode. External power supplies rarely remain in a 75
to 100% load condition.
First
legislation was announced in 2004, starting with the California Energy
Commission’s (CEC) intent to restrict the sale of non-efficient external power
supplies. The USA, EU, China and a host
of other countries and regions followed over the next ten years with
increasingly tighter legislation.
In
2014, the EU issued a voluntary Code of Conduct (CoC) version 4, running in
parallel with the mandatory Ecodesign Directive 278/2009. Also in 2014, the Department of Energy (DoE) published
their Energy Efficiency Level VI standard.
In
February 2016, the Level VI standard became law in the US. The EU issued the more stringent version 5 CoC
Tier 2 voluntary standard that was supposed to go into effect January 2018. That
has been delayed and mandatory implementation was expected early in 2018.
Table 1: A comparison between the
latest US and EU regulations
Average
efficiency measurements are required at four load conditions; 25, 50, 75 and
100%. These are added together and
divided by four to produce an average efficiency figure.
Note,
the EU has added a minimum efficiency level at 10% load.
The
USA now includes power supplies that are rated at greater than 250W.
The
term external power supply is defined by the US Department of Energy as one
that is used to convert household electric current into DC current or
lower-voltage AC current to operate a consumer product. Currently the US also grants exemptions for
supplies powering FDA approved medical devices.
Modifying
a power supply to meet a decrease in off-load power consumption is not a simple
component change. The control IC often
has to be changed to one that draws less power and energy saving techniques
like pulse skipping implemented. Changes
to primary side circuitry requires resubmitting the products to have the safety
certifications updated. Both the
redesign and submittal process are expensive and older products are often
obsoleted as a result of this. As the
energy standards are directed at the ultra-high volume, short production life
consumer EPSs, this gives some relief to the industrial market which prefers
long production lifecycles.
TDK-Lambda
has a number of external power supplies in the DT series that meet all the latest
requirements, with ratings up to 300W.
