Seasonic SS-350TGM 80 Plus Gold TFX

TESTING

For a fuller understanding of ATX power supplies, please read the reference article Power Supply Fundamentals. Those who seek source materials can find Intel's various PSU design guides at Form Factors.

SPCR's PSU Test Platform V4.1. is the basic setup for the testing. It is a close simulation of a moderate airflow mid-tower PC optimized for low noise. There is one major change: The primary testing is done with the PSU NOT inside the hotbox but atop it, out of the heat path. This is in recognition of several realities that prevail today:

• In SPCR's test platform, the internal temperature varied proportionately with output load. The tested PSU was subject to this heat, and operating ambient temperature rose with increased load, reaching >40°C and often much higher at full power. This was a realistic simulation of a mid-tower PC case where the PSU is mounted conventionally at the top back portion of the case.
• The vast majority of "serious" PC cases for the home builder place no longer position the PSU at the top back corner. They put the PSU at the bottom/back corner, mostly out of the path of heat from the other components in the case. This design concept took root with the Antec P180 going back over 5 years, and dominates the DIY case arena. This means the PSU generally has to dissipate only its own heat.

With the current test, we're reversing our approach: The PSU will be tested briefly in the hotbox only to check on what happens to noise, fan speed and temperatures when it is used in an outmoded case design

Acoustic measurements are performed in our own anechoic chamber with ambient level of 11dBA or lower, with a PC-based spectrum analyzer comprised of SpectraPLUS software with an ACO Pacific microphone and M-Audio digital audio interfaces.

REAL SYSTEM POWER NEEDS: While we test the PSU to full output in order to verify the manufacturer's claims, real desktop PCs simply do not require anywhere near this level of power. The most pertinent range of DC output power is between about 30W and 300W, because it is the power range where most systems will be working most of the time. With virtually no power demand at idle from some CPUs and GPUs, some PCs can idle at <20W. It is true that a very elaborate system with two of the most power hungry video cards today might draw as much as another 150~400W at maximum, but the total should remain under 700W in most cases.

TEST RESULTS

The ambient temperature was 22-23°C, and the ambient noise level was ~10.5dBA.

1. EFFICIENCY — This is a measure of AC-to-DC conversion efficiency. The ATX12V Power Supply Design Guide recommends 80% efficiency or better at all output power loads. 80% efficiency means that to deliver 80W DC output, a PSU draws 100W AC input, and 20W is lost as heat within the PSU. Higher efficiency is preferred for reduced energy consumption and cooler operation. It allows reduced cooling airflow, which translates to lower noise. The 80 Plus Gold standard requires 87% efficiency at 20% load, 90% efficiency at 50% of rated load, and 87% at full rated load.

At the super low 20W load, efficiency was excellent at over 77%. Efficiency rose quickly as the load was increased. 87% efficiency was reached around the 65W mark (lower than the required 70W load), broke 92% by 150W, and stayed above 90% all the way to 350W load. This is better than required by 80 Plus Gold, approaching Platinum at higher power loads.

2. VOLTAGE REGULATION refers to how stable the output voltages are under various load conditions. The ATX12V Power Supply Design Guide calls for the +12, +5V and +3.3V lines to be maintained within ±5%.

At all load levels, the critical 12V line was within +0.22V (1.8%) and -0.18V (1.5%) of 12V. It started high, at 12.22V, and dropped with increased load to 11.82V (-1.5%) at full load. The 5V line was dead on almost all the way to maximum power, where it dropped marginally to 4.98V. The 3.3V ranged from 3.38V to 3.35V. These are excellent results, better than voltage regulation needs to be for any PC.

3. AC RIPPLE refers to unwanted "noise" artifacts in the DC output of a switching power supply. It's usually very high in frequency (in the order of 100s of kHz). The peak-to-peak value is measured. The ATX12V Guide allows up to 120mV (peak-to-peak) of AC ripple on the +12V line and 50mV on the +5V and +3.3V lines. Ripple on all the lines was excellent at all power levels, generally staying under 15mV through the lower half of the power range. Even at maximum power, the 12V ripple stayed at just 45mV. This is very good, though not excellent, performance.

4. POWER FACTOR is ideal when it measures 1.0. In the most practical sense, PF is a measure of how "difficult" it is for the electric utility to deliver the AC power into your power supply. High PF reduces the AC current draw, which reduces stress on the electric wiring in your home (and elsewhere up the line). It also means you can do with a smaller, cheaper UPS backup; they are priced according to their VA (volt-ampere) rating. Power factor was very good for this model, running at or close to 1.0 through most of the loads and no lower than 0.89 even at just 20W load.

5. LOW LOAD TESTING revealed no problems starting at very low loads. Our sample had no issue starting up with no load, either, and the power draw was low. The 0.4W power draw in standby (power switch on but computer off) is excellent.

6. LOW & 240VAC PERFORMANCE

The power supply was set to 200W load at various AC input voltages. Most full-range input power supplies achieve higher efficiency with higher AC input voltage. SPCR's lab is equipped with a 240VAC line, which was used to check power supply efficiency for the benefit of those who live in higher mains voltage regions. We also used a hefty variac to check the stability of the PSU under brownout conditions where the AC line voltage drops from the 120V norm.

Efficiency improved to over 94% at the higher voltage. This is higher than the minimum 92% required by the 80 Plus Gold standard for 230VAC operation. The sample passed the 100VAC minimum input at 200W load without any issues. Neither voltage regulation nor ripple changed appreciably during these tests.

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