ETA

We call our new efficiency measurements program ETA, deriving from the Greek letter “η” which is widely used to represent efficiency.

Contrary to existing methodologies we plan to apply more than 1450 different load combinations in the DUT (Device Under Test), which with the interpolation of results, can provide up to 25,000 measurement points, while current methodologies only take three to four measurements. The overall efficiency will be the average of all measurements, which cover the PSU’s entire operational range. This way it is impossible for a manufacturer to tune its products to meet some specified load levels, since, in essence, we take under consideration the efficiency levels under a higher number of different load combinations, evenly spread throughout the full load range. Besides efficiency, we also take voltage, ripple, power factor, noise, and temperature measurements. For the moment we will use the power factor and noise results, while in the future we can use some of the remaining factors (or all of them) should we want to enrich our methodology.

Furthermore, the massive load of data that our methodology provides allows us to quickly modify our efficiency certification program, in case this is required. Finally, we start our tests at close to 30 °C with the PSU inside a hot-box, which simulates a case environment. At the end of the test, the ambient temperature inside the box reaches up to 32-34 °C, so it is close to real-life conditions.  

Vampire power (power consumption with no load on the 5VSB rail) is of high importance since all this amount of energy goes wasted and most PC systems aren’t kept in operation 24/7, meaning that for a significant part of the day the PSUs just consume energy without doing anything useful. We will evaluate each PSU by following closely the EN 50564:2011 and IEC 62301 measurement guidelines. In case the DUT doesn’t meet our standards, it will be automatically downgraded to the next lower efficiency certification level. 

Besides all the above ETA will also take into account the overall efficiency of the 5VSB rail. We will measure efficiency on this rail per 0.05 A steps up to its max current output and the average of all measurements will be the final efficiency result. We expect all PSUs to deliver over 70% overall efficiency output on this rail, with this threshold set even higher for units that fall into the top categories of the ETA program.
                                                          
Table (1)
Efficiency  Levels 
(115V Input)
Efficiency  (1) (2)PF  (3)5VSB Efficiency  (1) (3) (4)Vampire Power  (3)
DIAMOND≥93 overall efficiency≥0.985 >79%<0.10W
TITANIUM≥91% & <93% overall efficiency≥0.980>77%<0.13W
PLATINUM≥89% & <91% overall efficiency≥0.975>76%<0.16W
GOLD≥87% & <89% overall efficiency≥0.970>75%<0.19W
SILVER≥85% & <87% overall efficiency≥0.960>73%<0.22W
BRONZE≥82% & <85% overall efficiency≥0.950>71%<0.25W

Table (2)
Efficiency  Levels 
(230V Input)
Efficiency  (1) (2)PF  (3)5VSB Efficiency  (1) (3) (4)Vampire Power  (3)
DIAMOND≥95 overall efficiency≥0.945 >78%<0.12W
TITANIUM≥93% & <95% overall efficiency≥0.940>76%<0.15W
PLATINUM≥91% & <93% overall efficiency≥0.935>75%<0.18W
GOLD≥89% & <91% overall efficiency≥0.930>74%<0.20W
SILVER≥87% & <89% overall efficiency≥0.920>72%<0.23W
BRONZE≥84% & <87% overall efficiency≥0.910>70%<0.25W

(1) In case the PSU is close enough to the limits (0.1%), we will ask its manufacturer if it is willing to send a second sample for re-evaluation. If the second sample registers a significant performance difference compared to the first one (>0.5%), we will ask for a third one, to verify the test results. Moreover, in case the difference with the upper limit is <= 0.05% (e.g., 91.95%), we will round the number to the second digit and the PSU will be taxed to the higher category. 

(2) We conduct a number of load tests with 230V input in order to make sure that the under evaluation PSUs meet all requirements mentioned in the (EU) No 617/2013 regulation:

(a) 85% efficiency at 50% of rated output power;
(b) 82% efficiency at 20% and 100% of rated output power;
(c) power factor >= 0.9 at 100% of rated output power.

(3) If the PSU fails in any of those requirements, it will lose one class and will drop to the lower one (especially for the PF it will drop to the class that meets the corresponding requirements), despite its efficiency performance. The same applies for the requirements listed in Table (3) except for the first test (2013 ErP Lot 6 requirement), where we allow for a 5% deviation (40-45% range) due to the very low applied load and the 0.55 A to 1.5 A load tests where we also allow for the same 5% deviation (70-75% range). In any case, vampire power must be lower than 0.25 W, even with 230 V input. 

(4) The 5VSB rail should also achieve the required efficiency levels listed in Table (3), to meet various requirements including the CEC and ErP Lot 6/3 ones. Those requirements are also listed and recommended by the Power Supply Design Guide for Desktop Platform Form Factors, v.2.53 (June 2020). 

  Table (3)
5VSB LoadEfficiency Target (115V & 230V)Notes
3 Ampere or Full Load75%Recommended
1.50 Ampere75%Required - ASM for CEC & ErP Lot 3 2014
1.00 Ampere75%Recommended
0.55 Ampere75%Required - ASM for CEC & ErP Lot 3 2014
90 Milliampere45%Required - ErP Lot 6 2010
45 Milliampere45%Required - ErP Lot 6 2013
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