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Advanced Transient Response Tests
For details about our transient response testing, please click here.
In the real world, power supplies are always working with loads that change. It's of immense importance, then, for the PSU to keep its rails within the ATX specification's defined ranges. The smaller the deviations, the more stable your PC will be with less stress applied to its components.
We should note that the ATX spec requires capacitive loading during the transient rests, but in our methodology, we also choose to apply a worst case scenario with no additional capacitance on the rails.
Advanced Transient Response at 20% – 20ms
| Voltage | Before | After | Change | Pass/Fail |
|---|---|---|---|---|
| 12V | 12.214V | 11.867V | 2.84% | Pass |
| 5V | 5.040V | 4.896V | 2.86% | Pass |
| 3.3V | 3.309V | 3.120V | 5.71% | Fail |
| 5VSB | 5.049V | 4.988V | 1.21% | Pass |
Advanced Transient Response at 20% – 10ms
| Voltage | Before | After | Change | Pass/Fail |
|---|---|---|---|---|
| 12V | 12.214V | 11.861V | 2.89% | Pass |
| 5V | 5.041V | 4.903V | 2.74% | Pass |
| 3.3V | 3.309V | 3.121V | 5.68% | Fail |
| 5VSB | 5.049V | 4.987V | 1.23% | Pass |
Advanced Transient Response at 20% – 1ms
| Voltage | Before | After | Change | Pass/Fail |
|---|---|---|---|---|
| 12V | 12.214V | 11.900V | 2.57% | Pass |
| 5V | 5.041V | 4.897V | 2.86% | Pass |
| 3.3V | 3.309V | 3.116V | 5.83% | Fail |
| 5VSB | 5.049V | 4.942V | 2.12% | Pass |
Advanced Transient Response at 50% – 20ms
| Voltage | Before | After | Change | Pass/Fail |
|---|---|---|---|---|
| 12V | 12.174V | 11.829V | 2.83% | Pass |
| 5V | 5.029V | 4.884V | 2.88% | Pass |
| 3.3V | 3.302V | 3.101V | 6.09% | Fail |
| 5VSB | 5.017V | 4.951V | 1.32% | Pass |
Advanced Transient Response at 50% – 10ms
| Voltage | Before | After | Change | Pass/Fail |
|---|---|---|---|---|
| 12V | 12.174V | 11.848V | 2.68% | Pass |
| 5V | 5.030V | 4.878V | 3.02% | Pass |
| 3.3V | 3.302V | 3.103V | 6.03% | Fail |
| 5VSB | 5.016V | 4.931V | 1.69% | Pass |
Advanced Transient Response at 50% – 1ms
| Voltage | Before | After | Change | Pass/Fail |
|---|---|---|---|---|
| 12V | 12.175V | 11.855V | 2.63% | Pass |
| 5V | 5.031V | 4.873V | 3.14% | Pass |
| 3.3V | 3.302V | 3.108V | 5.88% | Fail |
| 5VSB | 5.016V | 4.917V | 1.97% | Pass |
The transient response at 12V is, politely, not so good. The same goes for 3.3V, which failed in all of our tests.
Turn-On Transient Tests
In the next set of tests, we measure the PSU's response in simpler transient load scenarios—during its power-on phase. Ideally, we don't want to see any voltage overshoots or spikes since those put a lot of stress on the DC-DC converters of installed components.
There are no high spikes or voltage overshoots in these tests—only a small step in the 12V waveform. This won't have any affect on your system, so there's no need to worry about it.
Power Supply Timing Tests
There are several signals generated by the power supply, which need to be within new ATX spec ranges. If they are not, there can be compatibility issues with other system parts, especially mainboards.
Starting last year, PSUs now need to have a Power-on time (T1) lower than 150ms. The PWR_OK delay (T3) also now has to be from 100 to 150ms, to be compatible with the Alternative Sleep Mode.
| T1 (Power-on time) & T3 (PWR_OK delay) | ||
|---|---|---|
| Load | T1 | T3 |
| 20% | 30ms | 134ms |
| 100% | 30ms | 134.5ms |
Luckily, the XPG Pylon 550W's PWR_OK delay is within the 100-150ms region, so the PSU supports the alternative sleep mode. This is per ATX spec recommendations.
Ripple Measurements
Ripple represents the AC fluctuations (periodic) and noise (random) found in the PSU's DC rails. This phenomenon significantly decreases the capacitors' lifespan because it causes them to run hotter. A 10-degree Celsius increase can cut into a cap's useful life by 50%. Ripple also plays an important role in overall system stability, especially when overclocking is involved.
The ripple limits, according to the ATX specification, are 120mV (+12V) and 50mV (5V, 3.3V, and 5VSB).
| Test | 12V | 5V | 3.3V | 5VSB | Pass/Fail |
| 10% Load | 7.0 mV | 5.7 mV | 5.3 mV | 8.9 mV | Pass |
| 20% Load | 8.3 mV | 6.0 mV | 5.2 mV | 9.1 mV | Pass |
| 30% Load | 8.8 mV | 5.8 mV | 5.3 mV | 10.3 mV | Pass |
| 40% Load | 9.3 mV | 6.3 mV | 5.7 mV | 9.8 mV | Pass |
| 50% Load | 11.3 mV | 6.9 mV | 6.6 mV | 10.7 mV | Pass |
| 60% Load | 14.3 mV | 7.0 mV | 6.7 mV | 21.6 mV | Pass |
| 70% Load | 17.4 mV | 6.9 mV | 6.0 mV | 13.8 mV | Pass |
| 80% Load | 23.1 mV | 8.6 mV | 12.8 mV | 18.5 mV | Pass |
| 90% Load | 26.6 mV | 8.3 mV | 13.3 mV | 17.8 mV | Pass |
| 100% Load | 40.9 mV | 9.3 mV | 14.3 mV | 18.4 mV | Pass |
| 110% Load | 52.7 mV | 10.5 mV | 15.6 mV | 17.5 mV | Pass |
| Crossload 1 | 9.1 mV | 7.6 mV | 15.6 mV | 8.0 mV | Pass |
| Crossload 2 | 45.5 mV | 7.8 mV | 7.3 mV | 12.4 mV | Pass |
Ripple suppression on the XPG Pylon 550W is satisfactory at 12V and well above averaged on all other rails.
Ripple At Full Load
Ripple At 110% Load
Ripple At Cross-Load 1
Ripple At Cross-Load 2
EMC Pre-Compliance Testing – Average & Quasi-Peak EMI Detector Results
Electromagnetic Compatibility (EMC) is the ability of a device to operate properly in its environment without disrupting the proper operation of other nearby devices.
Electromagnetic Interference (EMI) stands for the electromagnetic energy a device emits, and it can cause problems in other nearby devices if too high. For example, it can be the cause of increased static noise in your headphones or speakers.
Thankfully, the XPG Pylon 550W's conducted EMI emissions are kept low.
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