The following table includes the ripple levels we measured on the SX600-G. The limits are, according to the ATX specification, 120 mV (+12V) and 50 mV (5V, 3.3V and 5VSB).
|Ripple MeasurementsSilverStone SX600-G|
|Test||12V (mV)||5V (mV)||3.3V (mV)||5VSB (mV)||Pass/Fail|
A quick look at the table above suggests the situation is pretty bad. But before you reach a hasty conclusion, let us explain how things really are. First, we followed our normal testing procedure that dictates full load and overload testing at around 45 °C ambient, while SilverStone clearly states that it guarantees good operation under full load at up to 40 °C. We're just following the methodology we use for every sample we receive. In addition, without our sophisticated monitoring and logging software, it would be difficult to catch the spikes that make the PSU fail in the tests shown above. The main issue responsible for these spikes, we believe, is the secondary side's restricted airflow, more specifically in the DC-DC converters area. Fortunately, the ripple problems occur at more than 40 °C ambient. And we're talking about random spikes, not continuous out-of-control ripple suppression. Be that as it may, we have to deduct points in the name of fairness to the other PSUs in our relative performance graph on the next page.
Again, under a 40 °C ambient, ripple suppression is in line with the ATX specification's requirements. Under the extreme conditions we use for testing power supplies is where you'll run into issues. This perfectly illustrates why it's important to test PSUs at high temperatures. An SFX PSU is destined to spend most of its life inside a tiny case with not-so-optimal airflow, so high-ambient testing is necessary.
Ripple - Oscilloscope Screenshots
You can see the AC ripple and noise on the main rails (+12V, 5V, 3.3V and 5VSB) in the following oscilloscope screenshots. The bigger the fluctuations on the instrument's screen, the bigger the ripple/noise. We set 0.01V/Div (each vertical division/box equals 0.01V) as the standard for all measurements.