Load 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 constant voltages. To simulate real world and maximum loading conditions, the Toughpower 1,500W PSU was connected to the load testers and supplied with 240 VAC. In this test we are interested in seeing how well the PSU can maintain the various output voltages while operating under different loads.
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.
The following table lists the DC voltage results at the different loads for the Toughpower 1,500W PSU while operating on 240 VAC, 60 Hz.
Note: The +12V outputs were distributed evenly up until the final 1,250W and 1,500W tests, at which point +12V1 and +12V2 were held at 20.0A and +12V3 and +12V4 were pushed to 34.5A each.
The PSU produced very good load regulation on all of the outputs across a broad range of loads; all the way up to 1,500 watts of DC power. The +12V rails are particularly strong. All the major outputs remained well within the specified ATX12V limits.
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.
In the first test we put a heavy combined load (90A/1,080W) on the +12V outputs and a light load on the remaining outputs. The Toughpower 1,500W power supply had no problems delivering well over 1,000W on the +12V rails with only a light load on +3.3V and +5V. Even with this large imbalance, the voltages all look very good.
In the second test we reversed the cross-load and placed a heavy load (186W) on the +3.3V and +5V outputs with a light load (4A/48W) on the +12V rail. Once again, the Toughpower PSU passed this test without problems.
In both tests the measured AC ripple remained consistent with the values observed during the other tests and stayed within spec.