DC Load Regulation and AC Ripple
DC Output Load Regulation
To simulate real world and maximum loading conditions, the Seasonic Snow Silent-750 PSU was connected to the load testers and supplied with a constant 115 VAC. In this test we are interested in seeing how well a PSU can maintain the various output voltages while operating under different loads.
The ATX12V V2.2 tolerance for voltages states how much each output (rail) is allowed to fluctuate and has tighter tolerances now for the +12V outputs. I have also included a second table of expanded tolerances (±1% to ±6%) for reference.
The following tables list the DC voltage results for the PSU while operating on 115 VAC, 60 Hz.
Seasonic claims the Snow Silent-750 PSU can provide ultra-tight voltage regulation (+2% and -0% regulation on the +12V output with ±1% on the +3.3V and +5V rails). These are pretty lofty claims and the PSU came very close to meeting them. I’m not going to ding them for -0.02V on the +12V output and the 3.3V and 5V outputs stayed within ±1%.
AC Ripple and Noise on the DC Outputs
The amount of AC ripple and noise present on the DC outputs was checked using a digital oscilloscope. This AC component may be present in the KHz range where most switching power supplies operate or it may be more prevalent at the 60 Hz line frequency. We adjust the O-scope time base to look for AC ripple at both low and high frequencies. The ATX12V V2.2 specification for DC output noise/ripple is defined in the ATX12V Power Supply Design Guide.
Ideally we would like to see no AC ripple (repetitive) or noise (random) on the DC outputs – the cleaner the better! But in reality there will always be some present. I measured the amplitude of the AC signal (in millivolts, peak-to-peak) to see how well the power supply complied with the ATX standard. The following table lists the ripple/noise results during all of the load tests for the main output voltages of interest.
The Snow Silent-750 power supply exhibited excellent AC ripple suppression on all of the outputs and stayed well below the recommended values, even at full load.
The only thing I would like
The only thing I would like to see is 2-4 fan headers for semi-passive case fans.
Also 15-20% passive operation threshold (X-series) makes more sense then 50% as it is kind of hard to dissipate 375W out of the case without a fan.
I’m sure that you’re mistaken
I’m sure that you’re mistaken about the 375 watt dissipation. At 92% efficient, it would be something like 30 watts, before the fan kicks on.
I have had zero issues with any of the Seasonic power supplies that I’ve purchased and have an older 750 watt model in my main rig. I would definitely consider something like this for a future high-end build.
Exactly. The rest of the heat
Exactly. The rest of the heat is energy used by the PC though it would be more than 8% heat dissipated by the PSU since it would suck some heat back into the power supply.
That’s why it is also based on the temperature.
I was talking computer case
I was talking computer case not power supply case. If you deliver 375W to power your computer you need to get rid at least this amount of heat from the computer case.
Would it be easy to swap the
Would it be easy to swap the fan out for something like a Noctua? I believe some of their 140mm fans work in 120mm openings.
Why would you do that when
Why would you do that when one of the main reasons is to get the special fan? Does Noctua even make fans or do they just rebrand too?
Very nice, but why is it
Very nice, but why is it upside down? Everything is oriented as if the fan is expected to be pointing up, but in almost all cases it will be installed with the fan pointing down. Old cases put the PSU above the CPU with the fan down, and modern cases put the PSU at the bottom with the fan pointing down to pull in outside air from underneath. Why would they be expecting the fan to usually point up?
Valid question is why there
Valid question is why there are so few cases where motherboard is turned 90 degrees.
Actually, there might be more
Actually, there might be more people than you think installing the PSU with the fan up (myself included). With a PSU mounted in the bottom of an ATX case with the fan up – it adds to overall case cooling. This can help suck warm case air out of the sometimes stagnant area below the GPU card. The trade-off is causing the PSU to run a little warmer than it would with the fan down (sucking cool, outside air) but good PSUs like the Seasonic, are rated for up to 50 deg C operation. Not for everyone, but a good option for some.
The fan is sucking air in,
The fan is sucking air in, not pushing air out. It’s blowing over the internals of the psu. If it was installed on the top of a case it would act as an exhaust. Which would be optimal as heat rises.
At page 3, I think that fan
At page 3, I think that fan curve hysteresis is actually increased. Reducing hysteresis actually increasing the frequency of fan switching on-off when temperature is near equilibrium at setpoint.