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Primary Rails And 5VSB Load Regulation
The following charts show the main rails' voltage values recorded between a range of 40W up to the PSU's maximum specified load, along with the deviation (in percent). Tight regulation is an important consideration every time we review a power supply because it facilitates constant voltage levels despite varying loads. Tight load regulation also, among other factors, improves the system’s stability, especially under overclocked conditions and, at the same time, it applies less stress to the DC-DC converters that many system components utilize.
Load regulation is tight at 12V, but not that tight on the minor rails.
Hold-Up Time
Put simply; hold-up time is the amount of time that the system can continue to run without shutting down or rebooting during a power interruption.
The hold-up time is long and the power ok signal is accurate, so everything is good here.
Inrush Current
Inrush current, or switch-on surge, refers to the maximum, instantaneous input current drawn by an electrical device when it is first turned on. A large enough inrush current can cause circuit breakers and fuses to trip. It can also damage switches, relays, and bridge rectifiers. As a result, the lower the inrush current of a PSU right as it is turned on, the better.
The inrush currents stay at low levels, with both voltage inputs.
10-110% Load Tests
These tests reveal the C750's load regulation and efficiency levels under high ambient temperatures. They also show how the fan speed profile behaves under increased operating temperatures.
| Test # | 12V | 5V | 3.3V | 5VSB | DC/AC (Watts) | Efficiency | Fan Speed (RPM) | PSU Noise (dB[A]) | Temps (In/Out) | PF/AC Volts |
| 1 | 4.421A | 1.988A | 1.982A | 0.982A | 74.962 | 86.060% | 0 | <6.0 | 43.25°C | 0.963 |
| 12.070V | 5.030V | 3.331V | 5.091V | 87.104 | 39.63°C | 115.15V | ||||
| 2 | 9.872A | 2.986A | 2.975A | 1.182A | 150.035 | 89.637% | 577 | 10.5 | 40.96°C | 0.979 |
| 12.068V | 5.024V | 3.327V | 5.077V | 167.380 | 45.12°C | 115.13V | ||||
| 3 | 15.662A | 3.489A | 3.477A | 1.383A | 225.038 | 90.437% | 691 | 14.4 | 41.06°C | 0.985 |
| 12.066V | 5.018V | 3.322V | 5.063V | 248.834 | 45.89°C | 115.12V | ||||
| 4 | 21.459A | 3.992A | 3.979A | 1.585A | 300.049 | 90.458% | 903 | 22.2 | 41.78°C | 0.986 |
| 12.062V | 5.011V | 3.318V | 5.050V | 331.699 | 47.22°C | 115.09V | ||||
| 5 | 26.881A | 4.997A | 4.979A | 1.788A | 374.662 | 90.144% | 1087 | 28.1 | 42.03°C | 0.988 |
| 12.059V | 5.004V | 3.313V | 5.036V | 415.624 | 48.10°C | 115.11V | ||||
| 6 | 32.333A | 6.004A | 5.986A | 1.992A | 449.612 | 89.570% | 1316 | 33.7 | 42.29°C | 0.988 |
| 12.056V | 4.997V | 3.308V | 5.021V | 501.965 | 49.25°C | 115.11V | ||||
| 7 | 37.821A | 7.017A | 6.993A | 2.198A | 524.934 | 88.902% | 1654 | 39.3 | 43.06°C | 0.989 |
| 12.052V | 4.989V | 3.304V | 5.006V | 590.462 | 50.69°C | 115.10V | ||||
| 8 | 43.310A | 8.003A | 8.000A | 2.405A | 600.105 | 88.138% | 1988 | 43.6 | 44.27°C | 0.990 |
| 12.049V | 4.981V | 3.300V | 4.990V | 680.873 | 52.28°C | 115.09V | ||||
| 9 | 49.172A | 8.545A | 8.497A | 2.410A | 674.779 | 87.440% | 2081 | 44.6 | 44.37°C | 0.990 |
| 12.045V | 4.973V | 3.296V | 4.980V | 771.705 | 53.74°C | 115.08V | ||||
| 10 | 54.836A | 9.066A | 9.032A | 3.027A | 750.005 | 86.604% | 2094 | 44.7 | 45.22°C | 0.991 |
| 12.041V | 4.965V | 3.289V | 4.957V | 866.012 | 55.17°C | 115.08V | ||||
| 11 | 61.100A | 9.082A | 9.056A | 3.033A | 825.239 | 85.700% | 2104 | 44.9 | 46.51°C | 0.992 |
| 12.038V | 4.956V | 3.280V | 4.947V | 962.936 | 57.17°C | 115.07V | ||||
| CL1 | 0.117A | 12.001A | 12.001A | 0.000A | 101.657 | 84.856% | 794 | 18.4 | 42.21°C | 0.972 |
| 12.079V | 5.017V | 3.336V | 5.088V | 119.799 | 47.85°C | 115.16V | ||||
| CL2 | 62.019A | 1.000A | 1.000A | 1.000A | 759.915 | 87.085% | 2096 | 44.8 | 45.47°C | 0.991 |
| 12.039V | 4.971V | 3.280V | 5.018V | 872.613 | 55.83°C | 115.08V |
The PSU can deliver full power at high operating temperatures without any issues. Naturally, efficiency takes a notable hit under harsh conditions, and it cannot reach 87% at full load, dropping below 86% during the overload test.
20-80W Load Tests
In the following tests, we measure the C750's efficiency at loads significantly lower than 10% of its maximum capacity (the lowest load the 80 Plus standard measures). 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 (RPM) | PSU Noise (dB[A]) | PF/AC Volts |
| 1 | 1.230A | 0.496A | 0.495A | 0.196A | 19.992 | 70.086% | 0 | <6.0 | 0.850 |
| 12.067V | 5.036V | 3.332V | 5.117V | 28.525 | 115.16V | ||||
| 2 | 2.459A | 0.994A | 0.991A | 0.392A | 39.982 | 80.502% | 0 | <6.0 | 0.929 |
| 12.067V | 5.035V | 3.332V | 5.109V | 49.666 | 115.16V | ||||
| 3 | 3.693A | 1.490A | 1.485A | 0.588A | 60.012 | 84.673% | 0 | <6.0 | 0.953 |
| 12.068V | 5.032V | 3.331V | 5.102V | 70.875 | 115.15V | ||||
| 4 | 4.919A | 1.987A | 1.982A | 0.785A | 79.961 | 86.795% | 0 | <6.0 | 0.964 |
| 12.068V | 5.031V | 3.331V | 5.095V | 92.126 | 115.15V |
At light loads, there is no need for the fan to spin if the semi-passive mode is enabled.
2% or 10W Load Test
Intel plans on raising the ante at efficiency levels under ultra-light loads. So from July 2020, the ATX spec will require 70% and higher efficiency with 115V input. The applied load is only 10W for PSUs with 500W and lower capacities, while for stronger units we dial 2% of their max-rated-capacity.
| Test # | 12V | 5V | 3.3V | 5VSB | DC/AC (Watts) | Efficiency | Fan Speed (RPM) | PSU Noise (dB[A]) | PF/AC Volts |
| 1 | 1.080A | 0.212A | 0.208A | 0.052A | 15.053 | 64.017% | 0 | <6.0 | 0.799 |
| 12.062V | 5.038V | 3.330V | 5.121V | 23.514 | 115.16V |
With 2% of its max-rated-capacity load, efficiency is above 60%, but it cannot reach the 70% mark.
Efficiency
Next, we plotted a chart showing the C750’s efficiency at low loads, and loads from 10 to 110% of its maximum-rated capacity. The higher a PSU’s efficiency, the less energy goes wasted, leading to a reduced carbon footprint and lower electricity bills.
The platform performs decently when it comes to efficiency, especially in the 20-80W load range.
5VSB Efficiency
| Test # | 5VSB | DC/AC (Watts) | Efficiency | PF/AC Volts |
| 1 | 0.100A | 0.512 | 74.096% | 0.106 |
| 5.122V | 0.691 | 115.17V | ||
| 2 | 0.250A | 1.280 | 76.647% | 0.219 |
| 5.119V | 1.670 | 115.17V | ||
| 3 | 0.550A | 2.813 | 77.621% | 0.335 |
| 5.112V | 3.624 | 115.17V | ||
| 4 | 1.000A | 5.104 | 77.498% | 0.407 |
| 5.103V | 6.586 | 115.17V | ||
| 5 | 1.500A | 7.639 | 77.846% | 0.442 |
| 5.091V | 9.813 | 115.17V | ||
| 6 | 3.000A | 15.159 | 76.272% | 0.494 |
| 5.053V | 19.875 | 115.17V |
Close enough to the competition, but we would like to see more from Seasonic in this rail.
Power Consumption In Idle And Standby
| Mode | 12V | 5V | 3.3V | 5VSB | Watts | PF/AC Volts |
| Idle | 12.062V | 5.040V | 3.331V | 5.124V | 7.744 | 0.489 |
| 115.2V | ||||||
| Standby | 0.044 | 0.007 | ||||
| 115.2V |
The PSU's energy needs at standby mode are low.
Fan RPM, Delta Temperature, And Output Noise
All results are obtained between an ambient temperature of 37 to 47 degrees Celsius (98.6 to 116.6 degrees Fahrenheit).
The fan speed profile is quite aggressive overall, especially under high operating temperatures.
The following results were obtained at 30 to 32 degrees Celsius (86 to 89.6 degrees Fahrenheit) ambient temperature.
Up to 450W loads, the PSU's noise doesn't exceed 30 dBA, so it is fairly quiet. With higher than 500W loads, it enters the 35-40 dBA zone so it will make its presence felt, while with more than 560W loads, noise output exceeds 40 dBA, which can be annoying.
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