Efficiency

Using the efficiency results from the previous page, we plotted a chart showing efficiency of the XTR-650 at low loads and at loads equal to 20% -100% of the PSU's maximum-rated load.



It performed very well at low loads and closely trailed the Gold competition with normal loads. We should note that this is Seasonic's budget platform. While it does exploit an LLC converter to minimize energy losses, its secondary side utilizes a few SBRs, which are less efficient than mosfets at, especially, higher loads.

Efficiency at Low Loads

In the next tests, we measured the efficiency of the XTR-650 at loads much lower than 20% of its maximum-rated load (the lowest load the 80 Plus Standard measures). The loads we dialed were 40 W, 60 W, 80 W, and 100 W (for PSUs with over 500 W of capacity). This is important for settings where the PC is in idle mode with Power Saving turned on.

The fan spun at very low RPM despite the high ambient inside our hot-box in the tests above, which had the PSU operate silently. As you can see by looking at the corresponding column in the above table, the PSU performed incredibly well in terms of efficiency.

5VSB Efficiency

The ATX specification states that 5VSB standby supply efficiency should be as high as possible and recommends 50% or higher efficiency with 100 mA of load, 60% or higher with 250 mA of load, and 70% or higher with 1 A or more of load.

We will take four measurements: one at 100, 250, and 1000 mA, each, and one with the full load the 5VSB rail can handle.

Efficiency at 5VSB was satisfactory, but definitely not exceptional since it didn't crack the magic 80% mark at even full load.

Power Consumption in Idle & Standby

In the table below, you will find the power consumption and the voltage values of all rails (except -12V) when the PSU is in idle mode (powered on but without any load on its rails) and the power consumption when the PSU is in standby mode (without any load at 5VSB).

Vampire power was very low, which is often the case with modern PSUs that utilize good standby PWM controllers.

Fan RPM, Delta Temperature & Output Noise

The cooling fan's speed (RPMs) and the delta difference between input and output temperature are illustrated in the following chart. The following results were obtained at 37°C-46°C ambient.



A chart that shows the cooling fan's speed (RPMs) and the output noise follows. We measure the fan's noise from 1 meter away, inside a small custom-made anechoic chamber whose internals are completely covered in specialized soundproofing material (Be Quiet! Noise Absorber Kit). Background noise inside the anechoic chamber was below 20 dBA during testing, and the results were obtained with the PSU operating at 37°C-46°C ambient.



The following graph illustrates the fan's output noise throughout the PSU's entire operating range. The same conditions of the above graph apply to our measurements, but the ambient temperature was in-between 28°C and 30°C.



At normal ambient, the PSU operates quietly with low-middle loads, but higher loads have the fan speed up, which produces significant amounts of noise.