Load Regulation, Line Regulation and Cross-Loading
DC 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 760 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 maximum rated load of 760W. 

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.

PC Power & Cooling Silencer 760W Power Supply Review - Cases and Cooling 33

The following table lists the DC voltage results at five different loads for the PC Power & Cooling Silencer 760 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, one 8-pin CPU, four 6-pin PCI-E, two 4-pin Molex, and two 15-pin SATA).

PC Power & Cooling Silencer 760W Power Supply Review - Cases and Cooling 34

As you can see, the Silencer 760W PSU produced excellent load regulation on all of the outputs across a broad range of loads; pretty much what we have come to expect from PC Power & Cooling – very good!   

PC Power & Cooling Silencer 760W Power Supply Review - Cases and Cooling 35

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.

PC Power & Cooling Silencer 760W Power Supply Review - Cases and Cooling 36

The Line Regulation test was performed with the combined DC loads set to 570W.  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; very good.

Cross-Loading Tests

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 50W (or less) on the combined 3.3V and +5V outputs, the resulting voltage regulation may suffer.

PC Power & Cooling Silencer 760W Power Supply Review - Cases and Cooling 37

The Silencer 760 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 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 on the +3.3V and +5V outputs with a light load (2A/24W) on the +12V rail.  Once again, the Silencer 760 PSU passed this test without problems.


« PreviousNext »