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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.
We should note that the ATX spec requires capacitive loading during the transient rests, but in our methodology we choose to apply the worst case scenario with no extra capacitance on the rails.
Advanced Transient Response at 20% – 200ms
| Voltage | Before | After | Change | Pass/Fail |
|---|---|---|---|---|
| 12V | 12.125V | 11.893V | 1.91% | Pass |
| 5V | 5.010V | 4.829V | 3.61% | Pass |
| 3.3V | 3.365V | 3.111V | 7.55% | Fail |
| 5VSB | 4.979V | 4.901V | 1.57% | Pass |
Advanced Transient Response at 20% – 20ms
| Voltage | Before | After | Change | Pass/Fail |
|---|---|---|---|---|
| 12V | 12.125V | 11.834V | 2.40% | Pass |
| 5V | 5.005V | 4.855V | 3.00% | Pass |
| 3.3V | 3.364V | 3.075V | 8.59% | Fail |
| 5VSB | 4.981V | 4.911V | 1.41% | Pass |
Advanced Transient Response at 20% – 1ms
| Voltage | Before | After | Change | Pass/Fail |
|---|---|---|---|---|
| 12V | 12.127V | 11.903V | 1.85% | Pass |
| 5V | 5.002V | 4.812V | 3.80% | Pass |
| 3.3V | 3.364V | 3.073V | 8.65% | Fail |
| 5VSB | 4.981V | 4.920V | 1.22% | Pass |
Advanced Transient Response at 50% – 200ms
| Voltage | Before | After | Change | Pass/Fail |
|---|---|---|---|---|
| 12V | 12.084V | 11.882V | 1.67% | Pass |
| 5V | 5.011V | 4.828V | 3.65% | Pass |
| 3.3V | 3.341V | 3.077V | 7.90% | Fail |
| 5VSB | 4.945V | 4.865V | 1.62% | Pass |
Advanced Transient Response at 50% – 20ms
| Voltage | Before | After | Change | Pass/Fail |
|---|---|---|---|---|
| 12V | 12.084V | 11.866V | 1.80% | Pass |
| 5V | 5.005V | 4.770V | 4.70% | Pass |
| 3.3V | 3.340V | 3.038V | 9.04% | Fail |
| 5VSB | 4.947V | 4.872V | 1.52% | Pass |
Advanced Transient Response at 50% – 1ms
| Voltage | Before | After | Change | Pass/Fail |
|---|---|---|---|---|
| 12V | 12.083V | 11.732V | 2.90% | Pass |
| 5V | 5.005V | 4.823V | 3.64% | Pass |
| 3.3V | 3.340V | 3.044V | 8.86% | Fail |
| 5VSB | 4.947V | 4.879V | 1.37% | Pass |
The 3.3V rail has a very hard time during these tests. The other rails perform much better, but still there is room for improvement, especially at 5V and 5VSB.
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 measure a spike (5.232V) at 5VSB which is below the upper limit. Lastly, the waveform during the last test is not so smooth, especially during the time that it reaches the nominal voltage.
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 | 12.2 mV | 6.5 mV | 8.7 mV | 12.3 mV | Pass |
| 20% Load | 13.4 mV | 7.5 mV | 9.6 mV | 16.4 mV | Pass |
| 30% Load | 15.4 mV | 8.9 mV | 10.3 mV | 15.1 mV | Pass |
| 40% Load | 19.0 mV | 10.0 mV | 11.0 mV | 17.6 mV | Pass |
| 50% Load | 23.1 mV | 11.8 mV | 12.5 mV | 18.7 mV | Pass |
| 60% Load | 34.7 mV | 15.9 mV | 14.4 mV | 19.4 mV | Pass |
| 70% Load | 35.6 mV | 15.3 mV | 15.4 mV | 19.7 mV | Pass |
| 80% Load | 38.3 mV | 16.1 mV | 18.7 mV | 22.2 mV | Pass |
| 90% Load | 46.3 mV | 18.2 mV | 20.3 mV | 22.1 mV | Pass |
| 100% Load | 53.2 mV | 19.9 mV | 21.6 mV | 25.5 mV | Pass |
| 110% Load | 58.7 mV | 21.0 mV | 23.2 mV | 26.1 mV | Pass |
| Crossload 1 | 21.6 mV | 37.6 mV | 17.5 mV | 14.2 mV | Pass |
| Crossload 2 | 60.7 mV | 18.3 mV | 19.0 mV | 21.7 mV | Pass |
The ripple suppression is satisfactory for a power supply in this price range. If you need lower ripple, especially at +12V, you will have to look at a higher (and more expensive) PSU category.
Ripple At Full Load
Ripple At 110% Load
Ripple At Cross-Load 1
Ripple At Cross-Load 2
EMC Pre-Compliance Testing – Average and 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 lower frequencies (<1MHz) which are much lower than the corresponding limits though.
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