Efficiency, Temperature & Noise
Our efficiency testing procedure is detailed here.
Using results from the previous page, we plotted a chart showing the 750 B3's efficiency at low loads, and loads from 10 to 110 percent of its maximum-rated capacity.
Despite the half-bridge topology and LLC resonant converter, EVGA's efficiency levels are quite low under both normal and light loads.
Efficiency At Low Loads
In the following tests, we measure the 750 B3's efficiency at loads significantly lower than 10 percent of its maximum capacity (the lowest load the 80 PLUS standard measures). The loads we dialed were 20, 40, 60, and 80W. This is important for representing when a PC is idle, with power-saving features turned on.
|Test #||12V||5V||3.3V||5VSB||DC/AC (Watts)||Efficiency||Fan Speed||Fan Noise||PF/AC Volts|
|1||1.202A||0.493A||0.479A||0.195A||19.667||62.965%||0 RPM||<6 dB(A)||0.834|
|2||2.430A||0.981A||0.991A||0.391A||39.721||74.065%||0 RPM||<6 dB(A)||0.929|
|3||3.664A||1.478A||1.504A||5.083A||59.893||77.011%||0 RPM||<6 dB(A)||0.941|
|4||4.881A||1.983A||1.985A||0.785A||79.767||78.988%||0 RPM||<6 dB(A)||0.959|
Again, the 750 B3's efficiency levels under light loads are quite low. You cannot expect much in these tests from a PSU with Bronze and ETA-D efficiency certifications.
The ATX specification, along with CEC, ErP Lot 3 2014 and ErP Lot 6 2010/2013, states that 5VSB standby supply efficiency should be as high as possible, recommending 75 percent or higher with 550mA, 1A, and 1.5A of load. The PSU should also achieve higher than 75% efficiency at 5VSB under full load, or with 3A if its max current output on this rail is higher than 3A.
We take six measurements: one each at 100, 250, 550, 1000, and 1500mA, and one with the full load the 5VSB rail can handle.
|Test #||5VSB||DC/AC (Watts)||Efficiency||PF/AC Volts|
The 5VSB rail needs to be upgraded as soon as possible; it suffers very low efficiency across its entire operating range. Unfortunately, Super Flower doesn't pay much attention to this rail, so even its high-end platforms demonstrate low efficiency at 5VSB. This issue was pointed out by Cybenetics, which takes the 5VSB rail's efficiency into account when calculating a final rating. In contrast, 80 PLUS doesn't deal with 5VSB at all. Nonetheless, the ATX spec imposes some fairly strict efficiency requirements on this rail. And there are, of course, other requirements that deal with the 5VSB rail's efficiency (CEC and ErP Lot 6/3).
Power Consumption In Idle And Standby
In the table below, you'll find the power consumption and voltage values of all rails (except -12V) when the PSU is idle (powered on, but without any load on its rails), and the power consumption when the PSU is in standby mode (without any load, at 5VSB).
The phantom power levels we observe are higher than normal.
Fan RPM, Delta Temperature, And Output Noise
Our mixed noise testing is described in detail here.
The first chart below illustrates the cooling fan's speed (in RPM), and the delta between input and output temperature. The results were obtained at 37°C (98.6°F) to 47°C (116.6°F) ambient temperature.
The next chart shows the cooling fan's speed (again, in RPM) and output noise. We measured acoustics from one meter away, inside a hemi-anechoic chamber. Background noise inside the chamber was below 6 dB(A) during testing (it's actually much lower, but our sound meter’s microphone hits its floor), and the results were obtained with the PSU operating at 37°C (98.6°F) to 47°C (116.6°F) ambient temperature.
The following graph illustrates the fan's output noise over the PSU's operating range. The same conditions of the above graph apply to our measurements, though the ambient temperature was between 30°C (86°F) to 32°C (89.6°F).
EVGA's semi-passive mode lasts long enough, given this PSU's low efficiency. Its noise levels exceed 30 dB(A) with over 425W load at +12V; with 100W more, the output noise is within the 35-40 dB(A) range.
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