From our basic testing we knew already that this power supply had both over current (OCP) and over power (OPP) protections and they were working just fine, as the power supply simply shut down when we tried to pull 460 W from it using our pattern number five, instead of burning.
So the first thing we wanted to see was at what level the over current protection (OCP) circuit was configured. To test this we simply removed the ATX12V cable from the load tester, leaving only cables that were connected to the power supply +12V1 rail installed. Starting from pattern number six we configured +12V1 to pull 20 A and the power supply wouldn’t turn on. We decreased this value to 19 A and the power supply would turn on. So OCP was active and configured to shut down the power supply if we pulled more than 19 A from any rail. This is great, because according to the power supply label each +12 V has a limit of 18 A, so OCP was configured really close to what was printed on the label. Several power supplies on the market have the OCP circuit configured with a value that is so high that it probably will never enter in action, so the power supply isn’t really protected.
Our next move was to discover what was the maximum amount of power this unit could deliver still working inside its specs.
Starting from pattern number six (see previous page) we decreased current on each +12 V rail by 1 A and the power supply would work inside ATX specs. The configuration we used is shown on the table below.
Input
Maximum
+12V1
15 A (180 W)
+12V2
15 A (180 W)
+5V
8 A (40 W)
+3.3 V
8 A (26.4 W)
+5VSB
2.5 A (12.5 W)
-12 V
0.5 A (6 W)
Total
435.8 W
% Max Load
94.7%
Room Temp.
50.0º C
PSU Temp.
49.8º C
AC Power
570 W
Efficiency
76.5%
At this scenario noise and ripple increased a lot, but still inside ATX specs: 83.4 mV at +12V1, 80 mV at +12V2, 32.2 mV at +5 V and 15.6 mV at +3.3 V.
click to enlarge Figure 14: Noise level at +12V1 with this power supply delivering 435.8 W.
click to enlarge Figure 15: Noise level at +12V2 with this power supply delivering 435.8 W.
click to enlarge Figure 16: Noise level at +5V with this power supply delivering 435.8 W.
Short circuit protection (SCP) worked fine for both +5 V and +12 V lines.
The fan used on this power supply is quiet when the power supply isn’t hot, but it starts spinning fast and producing a lot of noise when the power supply temperature is over 30º C.
