Corsair AX850 PSU Review: Top Performer and Dead Silent

Load Regulation, Hold-Up Time, Inrush Current, Efficiency and Noise

To learn more about our PSU tests and methodology, please check out How We Test Power Supply Units. 

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, 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.

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The load regulation is tight overall. Nonetheless, the SSR-850TR performs even better here in all rails, but 5VSB.

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.

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The hold-up time is much longer than 17ms, the minimum that the ATX spec requires, while the power-ok signal is accurate.

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.

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The registered inrush currents are at normal levels.

10-110% Load Tests

These tests reveal the AX850’s load regulation and efficiency levels under high ambient temperatures. They also show how the fan speed profile behaves under increased operating temperatures.

The fan profile is relaxed even under extremely tough conditions. Moreover, the unit's efficiency is high and strangely enough it peaks with 30% of the platform's max-rated-capacity load. Normally we measure the peak efficiency at the 40-50% load tests.

20-80W Load Tests

In the following tests, we measure the AX850's efficiency at loads significantly lower than 10 percent 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.

Unlder light loads the unit's fan is not employed at all, even under >36°C ambient, and the efficiency levels are amazing! With 80W load the 90% mark is easily reached, while with 20W we measure close to 78% efficiency while other units in the same test struggle to stay above 70%.

Efficiency

Next, we plotted a chart showing the AX850’s efficiency at low loads, and loads from 10 to 110 percent of its maximum-rated capacity. The higher a PSU’s efficiency the less energy goes wasted leading to a reduced carbon footprint, besides lower electricity bills.

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With normal loads the AX850 conquers first place, while with light loads it is second behind Seasonic's original platform.

5VSB Efficiency

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The 5VSB rail besides tight load regulation is also highly efficient.

Power Consumption In Idle And Standby

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Fan RPM, Delta Temperature, And Output Noise

All results are obtained between an ambient temperature of 37°C (98.6°F) to 47°C (116.6°F).   

As we already mentioned, the fan profile is highly relaxed under any operating condition.

The following results were obtained at 30°C (86°F) to 32°C (89.6°F) ambient temperature.   

The semi-passive operation lasts for quite long (up to 300W) and the fan's speed is kept low when it is engaged. 

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