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 PSU characteristic since it allows for constant voltage levels even with 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.

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.

10-110% Load Testing

These tests reveal the RM750's load regulation and efficiency levels under high ambient temperatures. They also show how the fan-speed profile behaves under tough operating conditions.

Light Load Testing

The following tests measure the RM750'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 or less capacity. We dial in 2% of the maximum-rated-capacity for stronger units and only run this test with 115 V input.


With close to 77% efficiency with only 15 W load, the RM750 is among the most efficient PSU's at such low loads.

Efficiency

Using the results we gathered so far, we plotted a chart showing the RM750's efficiency at low loads and loads from 10 to 110 percent of its maximum-rated capacity.


High efficiency numbers at both light and normal loads.

5VSB Efficiency

It would be nice to at least have one efficiency reading close to 80%.

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.





Once you push the DC-DC converters, the passive operation stops. This unit apparently needs proper heat sinks on those converters to cope with their thermal load at increased loads. Another solution would be to decrease the maximum combined power at 5V and 3.3V from 150 W to 100 W. After all, no modern system requires that much from the minor rails.