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Switching Power Supplies A - Z, Second Edition
Switching Power Supplies A - Z, Second Edition, by Sanjaya Maniktala (Newnes), starting at $55.25
Home » Power
Can We Trust the 80 Plus Certification?
Author: Gabriel Torres 60,859 views
Type: Articles Last Updated: November 10, 2010
Page: 1 of 2

The 80 Plus certification was an important step to change the scenario from the power supply industry: now the savvy consumer knows that he or she should buy a power supply with at least 80% efficiency. New certification levels (Bronze, Silver, Gold, and Platinum) raised the bar even more. But maybe it is time for a change on the 80 Plus certification methodology. Let’s see why.

For a background on efficiency and the 80 Plus certification, please read our tutorial Understanding the 80 Plus Certification.

The main flaw with the methodology used on the 80 Plus certification process is room temperature. Ecos Consulting, the company behind 80 Plus, tests power supplies at a room temperature of only 23° C (73.4° F).

We always wondered why they chose this value, because in engineering the standard room temperature for data collection is 25° C (77° F). Not that collecting data at 25° C instead of 23° C would make a big difference on the overall picture, but we always wonder why this value.

Our conspiracy minds keep thinking that this could be done to help manufacturers to achieve the 80 Plus certification on power supplies that wouldn’t be able to get the certification if they set temperature at a higher value, because the lower the temperature, the higher efficiency is. So when they were trying to market the idea of the 80 Plus certification and getting customers, this lower temperature probably helped them to please their first customers.

The problem is that unless you have a very low-power PC, temperature inside the computer case is never that low, especially if you have a gaming-grade machine.

In our reviews we test power supplies with a room temperature between 45° C and 50° C (between 113° F and 122° F), because we like to test power supplies under the worst case scenario and not under the best scenario like Ecos Consulting does.

The reason we complain so much about temperature comes to the fact that all semiconductors have an effect called de-rating. Their ability to deliver current (and thus, power) drops with temperature. To illustrate this phenomenon, consider the specifications of the SPP20N60C3 MOSFET, one of the most widely used transistors in PC power supplies. Its current limit at 25° C (77° F) is of 20.7 A, but at 100° C (212° F) the maximum current this transistor can deliver drops to 13.1 A, a huge 37% drop. The resistance of FET/MOSFET transistors, a parameter called RDS(on), increases with temperature, meaning that transistors consume more for its own operation when temperature increases, reducing efficiency. Other parameters change with temperature as well.

Is there anything wrong of using a lower temperature to test power supplies? No. It is just our personal preference to test power supplies at real-world temperatures.

The “problem” is that during our reviews we’ve seen several power supplies that received a certain 80 Plus certification not being able to achieve the same efficiency level at high temperatures. For example, some power supplies labeled as “80 Plus Silver” would need to be labeled as “80 Plus Bronze” if they tested the unit at a higher temperature range. And we’ve seen some power supplies that wouldn’t be even able to get the standard 80 Plus certification. So far we've seen only two power supply companies labeling a power supply with an 80 Plus certification level inferior from the one they got because of this phenomenon: Corsair and Thermaltake.

Thus consumers must be advised that the 80 Plus certification is achieved at a “lab environment” temperature and not at a real-world temperature, and power supplies may not achieve the advertised efficiency at high temperatures. It is our opinion that Ecos Consulting should revamp their certification program and start testing power supplies at real-world temperatures. A short-term solution would be the power supply manufacturer guaranteeing that their products can achieve the 80 Plus certification at a higher temperature, just like some manufacturers advertise that their power supplies can deliver their labeled wattage at a higher temperatures like 40° C, 45° C or 50° C (104° F, 113° F or 122° F).

Another potential problem with the 80 Plus certification is that they don't re-test rebranded power supplies. We will explore this subject in the next page.

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