Efficiency, Differential Temperature and Noise


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) 1300 watts of AC power going in would result in 1300 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 ST1300-TI 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 SilverStone 1300W Titanium Series power supply produced outstanding efficiency, easily exceeding the 80 Plus Organization Titanium criteria, even when operating on 120VAC and at elevated temperatures. These are some of the highest efficiency numbers we have seen to date – very good!

80 Plus Program

    Note: Tests conducted at room temperature (25°C)

In addition to the familiar 80 Plus efficiency testing, SilverStone is now using two other certifications for the Strider Titanium Series PSUs for efficiency and noise.

Cybernetics ETA Efficiency Level A and Cybernetics LAMBDA Noise Level S

Differential Temperature and Noise Levels

To simulate a demanding environment, some of the warm exhaust air from the PSU under test is recirculated back to the intake through a passive air duct, which allows the PSU air inlet temperature to increase with load, up to 40°C.  

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 back of the power supply (T out).  

Thermocouples were placed at the air inlet and exhaust outlet. 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.  

*Fan not spinning

The ST1300-TI Titanium Series power supply starts out silent, in fanless mode. The fan started spinning as soon as we entered test #2 at the 20% load mark but stays relatively quiet through the mid-power range. Above 50% load with an increasing ambient temperature, the cooling fan spun up and the noise became very noticeable but I was not able to take SPL readings because of all the DC load cooling fans running in the background.

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