Efficiency, Differential Temperature and Noise

Efficiency

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) 1,000 watts of AC power going in would result in 1,000 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 Dark Power Power Pro 11 1,000W CM 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 Dark Power Power Pro 11 1,000W CM power supply is again excellent and easily meets the criteria for 80 Plus Platinum certification, even while operating on 115 VAC and at elevated, real world temperatures. Note that efficiency peeks out at around the 60~70% range and stays well above 90% even at 100% load.

80 Plus Program

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

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, just like it would in a real PC.  

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.  

The Dark Power Power Pro 11 1,000W CM PSU cooling fan starts out spinning very slowly and is virtually silent up through mid-power. As the power supply approaches full output the fan ramps up and at the 1,000W mark the fan noise has become very noticeable. Quiet operation is one of the Dark Power Pro 11 Series’ main features and it delivers!

Note: I was not able to take a SPL measurement at the highest load due to the background noise created by all the programmable DC load cooling fans running. At the low to mid power test loads I am able to catch a moment when all of the load fans have cycled off to take a SPL reading of just the PSU fan.

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