Energy Efficiency in AC/DC Power Supplies: Quick Guide to the Essentials

Apr 1, 2020
Energy Efficiency in AC/DC Power Supplies: Quick Guide to the Essentials Blog Post Image
Ten years ago, the European Commission set itself the bold targets of reducing greenhouse gas emissions by 20%, sourcing 20% of its energy from renewables and cutting overall energy consumption by 20%, all by the year 2020. This combined climate and energy package is called the Europe 2020 Strategy.

Table of contents

The Europe 2020 Strategy

As we are now a third of the way through 2020, a good question might be to ask: will the EU meet its own targets? The answer is ‘most of them’. While the reduction of greenhouse gas emissions will probably exceed the plan by 4% and the energy from renewables will hit 21%, the primary energy consumption target will be missed by an estimated 4.9%.

Therefore, the focus is now very definitely on energy consumption as this is a serious missed target. The latest EC Regulation EU2019/1782 becomes law from 1st April 2020 and requires manufacturers of external power supplies to meet new no-load power consumption and averaged efficiency limits and add energy efficiency information to the product instruction manuals in order to comply with the CE marking regulations.

EU Energy Efficiency Limits for External AC/DC Power Supplies (effective 1st April 2020)

No-Load Power Consumption:

High Voltage Output (≥6V) Single Low Voltage (<6V) Multiple Outputs
Pout ≤ 49W 100 mW 100 mW 300 mW
Pout > 49W 210 mW 210 mW 300 mW

Averaged Efficiency:

Output Power Four-point average Efficiency (25%, 50%, 75% and 100% load)
High Voltage Output (≥6V) Single Low Voltage (<6V) Multiple Outputs
≤ 1W ≤ 0.5 x Pout/1 W
+ 160 mW		 ≤ 0.517 x Pout/1 W
+ 87 mW		 ≤ 0.497 x Pout/1 W
+ 67 mW
>1W – ≤ 49 W ≤ 0.071 x ln(Pout/1 W)
– 0.0014 x Pout/1 W
+ 670 mW		 ≤ 0.071 x ln(Pout/1 W)
– 0.0014 x Pout/1 W
+ 670 mW		 ≤ 0.075 x ln(Pout/1 W)
+ 561 mW
> 49 W ≤ 880 mW ≤ 870 mW ≤ 860 mW

EcoDesign, ErPs, DoE VI, EC CoC and Lot6

The legislation requiring EU states to reduce their energy consumption is called the Ecodesign Directive (2009/125/EC). It requires EU countries to make their Energy related Products (ErP) more efficient by phasing out inefficient designs and setting out strict new efficiency standards.

For practical reasons, the implementation of the Ecodesign Directive is split into a number of areas of related products called ”Lots”, each Lot focusing on a different product area with a high potential for energy savings.

Lot 6 concerns ventilation units, a key industry since ventilation, heating and air conditioning represent about 15% of the total energy consumption in the EU. As there is a wide variation in the efficiencies of different ventilation systems, Lot 6 will achieve its targets by setting up minimum performance requirements which will be implemented in steps each year.

In a sleight-of-hand worthy of inclusion in the Dodd-Frank Act, buried deep inside the Lot 6 requirements is a ruling applying to external power supply units in general – even if they have nothing to do with ventilation systems!

Lot 6 standby power consumption limits (applies only to external power supply units):

Mode Old limit (2010) Limit (2013) Limit (2020)
Off Mode (no output) 1 W 500 mW 100 mW
Standby (output on) 1 W 500 mW 100 mW
Standby with display 2 W 1 W 210 mW

There are no regulations regarding standby consumption for internal (built-in) power supplies, but it is a common expectation from customers that power supplies in general also comply with these standby limits, including built-in types. Currently, any power supply that draws less than 0.5W in standby (no load power consumption) can claim to conform to Lot 6 or to the ‘ErP Regulations’.

In addition to the standby power consumption limits there are other standards regarding minimum average efficiencies at intermediate loads and full load. These are currently listed under a European Code of Conduct document (EU CoC on Energy Efficiency of External Power Supplies, Version 5). These requirements are voluntary for now, but they are expected to be incorporated into the EcoDesign Directive in the near future.

The EU CoC energy efficiency limits are split into basic voltage (output ≥6V) and low voltage (output <6V) power supplies. Tier 1 is the current specification and is harmonized with the DoE Level VI limits set by the US Department of the Environment. Efficiencies are measured at a fixed 10% load and also averaged over four load points (25%, 50%, 75% and 100% load). Tier 2 has already been published and adds even harsher limits for the average four-point and 10% load efficiency, although power supplies over 250W and multiple-output power supplies are exempted. The new Ecodesign limits do not match the voluntary CoC limits exactly, but are similar.

EU CoC Limits (Voluntary):

Output Power No Load Power Consumption 10 % Load Four point average Efficiency
Basic Voltage (≥6V) Low Voltage (<6V) Basic Voltage (≥6V) Low Voltage (<6V)
0.3 W – ≤ 1 W ≤ 100 mW ≤ 0.5 x Pout
+ 64 mW		 ≤ 0.5 x Pout ≤ 0.5 x Pout
+ 160 mW		 ≤ 0.517 x Pout
+ 87 mW
≤ 75 mW ≤ 0.5 x Pout
+ + 0.06		 ≤ 0.517 x Pout ≤ 0.5 x Pout
+ 0.169		 ≤ 0.517 x Pout
+ 0.091
1 W –
≤ 49 W		 ≤ 100 mW ≤ 0.0626 x In(Pout)
+ 546 mW		 ≤ 0.072 x In(Pout)
+ 500 mW		 ≤ 0.071 x In(Pout)
- 0.0014 x Pout
+ 670 mW		 ≤ 0.0843 x In(Pout)
- 0.0014 x Pout
+ 609 mW
≤ 75 mW ≤ 0.1 x [0.71 x In(Pout) - 0.0115 x Pout + 5.7] ≤ 0.1 x [0.843 x In(Pout) - 0.0127 x Pout + 5.18] ≤ 0.1 x [0.71 x In(Pout) - 0.0115 x Pout + 6.7] ≤ 0.1 x [0.843 x In(Pout) - 0.011 x Pout + 6.09]
49 W – ≤ 250 W ≤ 210 mW ≤ 790 mW ≤ 780 mW ≤ 880 mW ≤ 870 mW
≤ 150 mW ≤ 0.79 ≤ 0.78 ≤ 0.89 ≤ 0.88
250 W ≤ 500 mW ≤ 875 mW ≤ 875 mW ≤ 875 mW ≤ 875 mW
N/A N/A N/A N/A N/A

In practice, these energy efficiency limits are tough, but realistic for lower power AC/DC power supplies, but the standby power consumption for the higher power units can only be achieved economically by including a second low power auxiliary supply that can be used to independently enable or disable the main power stage (for an example, refer to the RECOM RACM550 datasheet)

We are here to help

RECOM prides itself on designing efficient, compact and cost-effective AC/DC power supplies, whether they be off-board or PCB board mounted. Although the EcoDesign and EU CoC limits apply only to external power supplies, RECOM aims to meet or exceed these efficiency limits for our built-in power supply modules and we also take into account anticipated stricter limits when we design new AC/DC products. For example, some of our low power on-board power supplies have a no-load power consumption of only 75mW max., so they already conform to the harshest Tier 2 limits.

For those interested in the techniques commonly used to achieve these low limits, the RECOM AC/DC Book of Knowledge1 includes a chapter on designing power supplies for the lowest possible no-load power consumption.

An efficient power supply unit, whether it be off-board or on-board, is essential to comply with the energy consumption laws and regulations. Using pre-certified AC/DC power supplies does not remove the need for due diligence in designing an efficient system, but it does make the compliance procedure simpler, faster and cheaper.

RECOM: We Power your Products

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References

1, Please refer to the AC/DC Book of Knowledge,

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