Efficiency, Differential Temperature and Noise


The overall efficiency of a power supply is very important, especially for a fanless unit – the less waste heat generated the better!  Efficiency is defined by the power output divided by the power input and is usually expressed as a percentage.  If a PSU were a 100% efficient (which none are) 460 watts of AC power going in would result in 460 watts of DC power coming out (with no waste heat to dissipate).  In the real world there are always inefficiencies and power is lost in the form of heat during the conversion process. Newer revisions to the ATX12V Power Supply Design Guide V 2.2 have continued to increase the efficiency recommendations for PC switching mode power supplies and now lists both required and recommended minimum efficiencies.

We measured the AC power input to the Seasonic Platinum-460 Fanless PSU with an Extech power analyzer while the total DC load was found by adding all the individual +3.3V, +5V, +12V, -12V and +5VSB loads together. 

The overall efficiency of the Seasonic Platinum-460 Fanless power supply is excellent and easily meets the criteria for 80Plus Platinum certification, even while operating on 115 VAC and at elevated temperatures. 

80 Plus Program

Note 1: Power Factor ≥0.90 (50% to 100% Load)
Note 2: Tests conducted at room temperature (25°C)

Differential Temperature and Noise Levels

To simulate real world operation the Seasonic Platinum-460 Fanless power supply was mounted in a modified mid tower case (Lian Li PC60) during testing.  Since this test environment does not include any case fans I simply removed the top of the case, which allowed hot air to vent out thru the top of the PSU and rise unobstructed via natural convection.

The differential temperature across the power supply was calculated by subtracting the internal case air temperature (T in) from the temperature of the warm exhaust air flowing out the top of the power supply (T out). 

Thermocouples were placed above and below the PSU. The ambient room air temperature was 23ºC (74ºF) +/- 0.5ºC during testing.

T out = temperature of air exhausting from power supply
T in = temperature of air entering power supply
Delta T = T out – T in

Sound pressure level readings were taken 3’ away from the rear of the case in an otherwise quiet room.  The ambient noise level was ~27 dBA.

As expected, the Platinum-460 Fanless was dead silent during operation; no fan – no noise. But remember, just because the X-460 PSU doesn't have a fan does not mean that it doesn't need adequate airflow to dissipate heat.  Ideally, existing case fans should generate a flow of air around and/or through the PSU for cooling.  If you plan to install the X-460 fanless PSU in a case that doesn't have any case fans then it will need to have plenty of open area around the PSU with an opening above to let the hot air out.  Convection cooling relies on being able to draw cool air in through the back and sides with an unrestricted path for hot air to flow out the top.

« PreviousNext »