Tiny, Silent and Efficient: The picoPSU

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To illustrate just how efficient the picoPSU / EDac power bricks are, one need only look at the best of the best that we've previously tested. Take careful note of where the peak efficiency is reached, and keep in mind that a system without an external graphics card typically requires between 65~90W under load. Toss in a mid-powered graphics card, and that number jumps to 90W~120W.

Efficiency Comparison: picoPSU vs. Past Efficiency Champs
Target Output Power
Peak Efficiency
Load @ Peak
picoPSU + 80W power brick
picoPSU + 120W power brick
Seasonic SS-300SFD 80 Plus
Seasonic 400HT Active PFC F3 80 Plus
FSP Zen FSP300-60GNF
Silentmaxx Fanless 400 Watt MX460-PFL01

Only one of the conventional power supplies manages to match the efficiency of the picoPSU anywhere: The Seasonic SS-300SFD and the picoPSU / 80W brick both reach 84.6% efficiency at 90W. The 120W brick is unchallenged; its peak efficiency higher than any other power supply and it is right where most systems hover.


The picoPSU needs to prove itself outside the test conditions in an actual system. Things tend to go wrong in less controlled circumstances — temperatures are higher, the loads are dynamic, and there's always the risk that a stray peak might burn something out. In addition, using the picoPSU removes both a source of heat and a source of airflow, so some real-world thermal data could be very useful.

The picoPSU was installed in a low-powered HTPC setup, and we ran a basic before/after test to check for differences in temperatures, stability, and power consumption. The following components were used:

  • Zalman HD160 HTPC case
  • AMD A64 3000+, Venice Rev. JH8-E3. TDP is 44.1W, and TCaseMax is 57°C
  • DFI RS482 motherboard
  • Onboard Video w/ ATI 200 chipset
  • 512 MB OCZ PC4000 DDR RAM, one stick
  • Zalman 7700CU heatsink modded with a Nexus 120mm fan @ 12V
  • 2 x 80mm Zalman case fans @ 5V
  • Samsung Spinpoint P120 250GB hard drive
  • Samsung CD-RW drive

Baseline results were measured using a recently-reviewed Seasonic S12-330 Rev. A3 power supply.

CPU Load
CPU Load
Seasonic S-12 330
picoPSU +
120W Power Brick

The system remained perfectly stable throughout the test; there was never any reason to suspect that it might be overheating or overloading. However, we did run out of connectors to power everything: The need to use one of the Molex connectors to power the +12V AUX cable meant we did not have a spare connector for the optical drive. We also used an adapter for our SATA drive, as it did not accept the older IDE-style connector.

The most significant difference with the picoPSU was a drop in power consumption. The AC power consumption dropped by approximately 8W both at idle and under load. At idle, that difference was nearly 20% — a huge amount considering that the electrical load did not change. Even under load, the difference was still 10%.

On top of that, the ambient temperature in the system also dropped slightly, no doubt because the power supply had no thermal impact at all. Any power lost in the AC-to-DC conversion was lost outside of the case, where it could not affect the system temperature. In other words, the use of the picoPSU actually improved the thermal environment inside the case.

Finally, the picoPSU made the system a bit quieter, as the 120mm fan in the PSU was eliminated as a source of noise. With the exhaust and heatsink fans, and the HDD still making noise, the drop in noise was subtle, not much more than 1 dBA, but it was audible.


It's hard not to be delighted with the picoPSU. It's quiet (fanless, in fact), efficient, small, cool... the list goes on. Although it is targeted at systems using VIA's embedded EPIA technology, it can easily be used in a desktop system with a low-powered Athlon 64, to say nothing of a laptop processor such as a Core Duo or a Turion 64.

Its only real disadvantage is its size: 120W isn't quite enough for a system with a decent (read: power-hungry) graphics card. Its limited cable length and connectors may also cause difficulties. But these are small gripes about what is otherwise an excellent power supply.

With the right power brick, the picoPSU has proved itself to be the most efficient power supply that you can buy right now. This isn't just a couple of percent at a power level that your system will never even reach. The benefits of the efficiency were seen in an actual system against a known good contender. The net decrease in power draw of 20% at idle is amazing considering that the load did not change.

Of course, with the right power brick is a key part of the efficiency results. +12V power bricks that can output 120W capacity are hard to come by, and their efficiency is virtually unknown. Until (and if) detailed information about other models on the market can be found, it's probably safest to stick with the EDac bricks that we tested. Unfortunately, the 120W brick has its own drawback: The cooling fan that comes on at 90W load. Hopefully, there are other 12VDC power bricks of this capacity that don't have a cooling fan.

Andrei Bulucea, the creator of the picoPSU, says that sales are about evenly split between companies and individual end users. The companies that buy the picoATX use it for specialized commercial and industrial applications where miniaturization and low power consumption are absolutely critical — digital display signs, PoS systems, digital video & sSecurity, and so on. Individual end users are generally hobbyists (like many SPCR forum readers) who use the picoPSU for special projects such as tiny mini-ITX PCs. We think it could quickly become a SPCR modder's weapon of choice.

All in all, the picoPSU is inventive, practical, and even affordable. (Why do those things so rarely go together?) In time, we hope to see many similar products — or perhaps an industry-wide shift to using single-rail power supplies.

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Much thanks to Mini-box.com for the opportunity to examine this power supply.


SPCR Articles of Related Interest:
Power Supply Fundamentals & Recommended Units
Power Distribution within Six PCs
Seasonic SS-400HT power supply, 80 Plus version
Seasonic SS-300SFD 80 Plus: Little Big PSU

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Discuss this article in the SPCR Forums.

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