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Transient Response Tests, Ripple Measurements and EMC Pre-Compliance Testing
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.
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% – 200ms
| Voltage | Before | After | Change | Pass/Fail |
|---|---|---|---|---|
| 12V | 12.067V | 11.889V | 1.48% | Pass |
| 5V | 5.005V | 4.827V | 3.56% | Pass |
| 3.3V | 3.317V | 3.122V | 5.88% | Fail |
| 5VSB | 5.050V | 4.989V | 1.21% | Pass |
Advanced Transient Response at 20% – 20ms
| Voltage | Before | After | Change | Pass/Fail |
|---|---|---|---|---|
| 12V | 12.068V | 11.817V | 2.08% | Pass |
| 5V | 5.004V | 4.794V | 4.20% | Pass |
| 3.3V | 3.317V | 3.088V | 6.90% | Fail |
| 5VSB | 5.050V | 5.000V | 0.99% | Pass |
Advanced Transient Response at 20% – 1ms
| Voltage | Before | After | Change | Pass/Fail |
|---|---|---|---|---|
| 12V | 12.067V | 11.900V | 1.38% | Pass |
| 5V | 5.004V | 4.800V | 4.08% | Pass |
| 3.3V | 3.317V | 3.089V | 6.87% | Fail |
| 5VSB | 5.050V | 4.991V | 1.17% | Pass |
Advanced Transient Response at 50% – 200ms
| Voltage | Before | After | Change | Pass/Fail |
|---|---|---|---|---|
| 12V | 12.044V | 11.869V | 1.45% | Pass |
| 5V | 4.997V | 4.821V | 3.52% | Pass |
| 3.3V | 3.310V | 3.116V | 5.86% | Fail |
| 5VSB | 5.002V | 4.940V | 1.24% | Pass |
Advanced Transient Response at 50% – 20ms
| Voltage | Before | After | Change | Pass/Fail |
|---|---|---|---|---|
| 12V | 12.044V | 11.788V | 2.13% | Pass |
| 5V | 4.997V | 4.787V | 4.20% | Pass |
| 3.3V | 3.310V | 3.082V | 6.89% | Fail |
| 5VSB | 5.002V | 4.952V | 1.00% | Pass |
Advanced Transient Response at 50% – 1ms
| Voltage | Before | After | Change | Pass/Fail |
|---|---|---|---|---|
| 12V | 12.043V | 11.864V | 1.49% | Pass |
| 5V | 4.997V | 4.791V | 4.12% | Pass |
| 3.3V | 3.309V | 3.089V | 6.65% | Fail |
| 5VSB | 5.002V | 4.956V | 0.92% | Pass |
The problem with the ACRF topology is the bad performance in transient loads. The charts and tables above clearly show this. The 3.3V rail in particular is getting hammered in these 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.
We notice a small voltage overshoot at 5VSB, which is nothing to worry about.
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 degrees 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 | 35.6 mV | 16.6 mV | 19.1 mV | 19.3 mV | Pass |
| 20% Load | 41.3 mV | 14.8 mV | 19.4 mV | 21.0 mV | Pass |
| 30% Load | 27.7 mV | 15.7 mV | 19.9 mV | 22.0 mV | Pass |
| 40% Load | 43.1 mV | 20.0 mV | 24.4 mV | 23.7 mV | Pass |
| 50% Load | 31.0 mV | 20.3 mV | 23.1 mV | 24.7 mV | Pass |
| 60% Load | 34.3 mV | 17.2 mV | 17.2 mV | 23.3 mV | Pass |
| 70% Load | 36.7 mV | 18.7 mV | 18.9 mV | 25.6 mV | Pass |
| 80% Load | 41.5 mV | 20.5 mV | 19.7 mV | 28.1 mV | Pass |
| 90% Load | 47.1 mV | 22.4 mV | 21.3 mV | 29.9 mV | Pass |
| 100% Load | 60.4 mV | 25.1 mV | 22.9 mV | 32.1 mV | Pass |
| 110% Load | 68.6 mV | 28.0 mV | 24.2 mV | 35.1 mV | Pass |
| Crossload 1 | 49.5 mV | 29.1 mV | 29.4 mV | 23.9 mV | Pass |
| Crossload 2 | 53.0 mV | 23.5 mV | 21.2 mV | 33.6 mV | Pass |
The ripple suppression at +12V should be better. For today's standards 60-70mV of ripple on this rail, even under tough conditions, is mediocre performance. The ripple on the minor rails is low, while at 5VSB it's a little higher than the average but still not high enough to raise any concerns.
Ripple At Full Load
Ripple At 110% Load
Ripple At Cross-Load 1
Ripple At Cross-Load 2
EMC Pre-Compliance Testing – Average & 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 close-by devices.
Electromagnetic Interference (EMI) stands for the electromagnetic energy a device emits, and it can cause problems in other close-by devices if too high. For example, it can be the cause of increased static noise in your headphones or/and speakers.
There are some spurs at low frequencies here, but none of them goes above accepatable limits.
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