Test Setup

Primary Rails Load Regulation

The following charts show the voltage values of the main rails, recorded over a range from 60 W to the maximum specified load, and the deviation (in percent) for the same load range. Tight load regulation is an important characteristic for every power supply since it allows for constant voltage levels despite changes in load.

5VSB Regulation

Hold-up Time

Hold-up time represents the amount of time, usually measured in milliseconds, a PSU can maintain output regulations as defined by the ATX specification without input power. Hold-up time is the amount of time the system can continue to run without shutting down or rebooting during a power interruption. In the following screenshots, the blue line is the mains signal and the green line is the "Power Good" signal, while the yellow line represents the +12V rail.







The hold-up time is very low. It should at least be 17 ms.

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. Large enough inrush current can cause the tripping of circuit breakers and fuses and may 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.


Inrush current is on the high side, but not high enough to create problems.

10-110% Load Testing

These tests reveal the PS-750SP's load regulation and efficiency levels under high ambient temperatures. They also show how the fan-speed profile behaves under tough operating conditions.


Load regulation is tight enough with +12 V, but quite loose on the minor rails. The fan profile should also have more fan-speed points. If you take a look at the table above, you will notice that the difference in fan speed and noise between the 70% and 80% load tests is enormous.

Light Load Testing

In the following tests, we measure the PS-750SP'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 its power-saving features turned on.

Ultra-Light Load Testing

The applied load in this test is only 10 W for PSUs with 500 W and lower capacities. We dial in 2% of the maximum-rated-capacity with stronger PSUs. This test is only run with 115 V input.


Efficiency with 2% load is very high since it exceeds 70%. Starting in July 2020, 70% or more efficiency with such a light load will also be requirement by the ATX specification.

Efficiency

Using the results we gathered so far, we plotted a chart showing the PS-750SP's efficiency at low loads and loads from 10 to 110 percent of its maximum-rated capacity.



I measured high efficiency levels under both light and normal loads. That having been said, efficiency would also take a hit with a properly sized bulk cap for a longer hold-up time.

5VSB Efficiency

The 5VSB rail's efficiency is decent.

Power Consumption in Idle and Standby

Fan RPM, Delta Temperature and Output Noise

The following results were obtained at 37–47 °C ambient.





The following results were obtained at 30–32 °C ambient.