Load Regulation, Line Regulation and Cross-LoadingDC Output Load Regulation
Of course one of the first things we want to see is how well this PSU can regulate the DC outputs and maintain rock-solid voltages. To simulate real world and maximum loading conditions, the Silencer Mk II 950W PSU was connected to the load testers and supplied with a constant 115 VAC. In this test we are interested in seeing how well a PSU can maintain the various output voltages while operating under different loads; all the way up to 950W.
The ATX12V V2.2 tolerance for voltages states how much each output (rail) is allowed to fluctuate and has tighter tolerances now for the +12V outputs. I have also included a second table of expanded tolerances (±1% to ±6%) for reference.
The following table lists the DC voltage results at five different loads for the PC Power & Cooling Silencer Mk II 950W PSU while operating on 115 VAC, 60 Hz. To help minimize the voltage drop induced by the distribution wires and connectors, I used as many cables/connectors as my test setup would allow (one 24-pin ATX, two 8-pin CPU, five 6-pin PCI-E, two 4-pin Molex, and two 15-pin SATA).
As you can see, the Silencer Mk II 950W PSU produced excellent load regulation on all of the outputs across a broad range of loads; just what we have come to expect from PC Power & Cooling – very good!
DC Output Line Regulation
In this test we are interested in seeing how well a PSU can maintain the various output voltages while the AC input line voltage changes. In the previous Load Regulation test, the AC line voltage was held constant at 115 VAC. Now we will look at how much the DC outputs change as the AC line voltage is changed from 120 VAC down to 90 VAC.
The Line Regulation test was performed with the combined DC loads set to 712W. The AC input voltage to the power supply (via the Extech power analyzer) was adjusted using a Powerstat variable autotransformer.
No measurable change in the DC outputs… like a rock.
PC switching mode power supplies provide multiple DC output voltages. Ideally, the total load should be distributed across all the main outputs (+3.3V, +5V, +12V). This means that the combined +3.3V and +5V load should be proportional to the combined +12V load – as one increases, so should the other. Unfortunately, this is not always the case, especially in newer PCs that predominately use +12V and may put only minimal loads on the +3.3V and/or +5V rails.
Cross-loading refers to imbalanced loads. If a PC pulls 500W on the +12V outputs and only 20W (or less) on the combined 3.3V and +5V outputs, the resulting voltage regulation may suffer.
The Silencer Mk II 950W PSU had no problems handling our cross-loading tests, thanks in large part to the DC to DC converters used to generate the +3.3V and +5V outputs from +12V. In the first test we put a heavy load (78A) on the +12V output and a light load on the remaining outputs. Even with this large imbalance, the voltages are near perfect!
In the second test we reversed the cross-load and placed a heavy load (166W) on the +3.3V and +5V outputs with a light load (2A/24W) on the +12V rail. Once again, the Silencer Mk II 950 PSU passed this test without problems. I think we’re on a roll here… 🙂