Efficiency, Differential Temperature and Noise
The overall efficiency of a power supply is very important, especially when it’s designed to deliver 1,350W. 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.
The latest 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.
I measured the AC power input to the Toughpower 1350W PSU with the 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 Toughpower 1350W power supply is very good and easily meets the 80 PLUS Silver certification criteria (see table below) even while operating at higher, real-world temperatures.
Note that efficiency will almost always be higher at the 240 VAC line voltage versus 115 VAC (as the voltage goes up the current goes down, and since line/component loses are proportional to current, less current means lower loses.
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 Toughpower 135W power supply was mounted in a modified mid tower case (Lian Li PC60) during testing. Some of the warm exhaust air from the PSU under test is recirculated back into the case, which allows the internal case air temperature to increase with load, just like it would in a real PC. The internal case air temperature is allowed to increase up to 40ºC and then held constant from then on at 40ºC.
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 ~28 dBA.
Let’s face it; if you are in the market for a 1350W power supply, you probably are not too concerned about how super-quiet the unit is. It’s nice to have minimal fan noise at lower power levels but when the gaming begins, keeping the hardware from overheating takes priority. The Toughpower 1350W PSU was relatively quiet at the lower to mid power levels but I was not able to take SPL readings at the higher loads due to all the programmable DC load cooling fans running in the background.
(Courtesy of Thermaltake)