Why you can trust Tom's Hardware Our expert reviewers spend hours testing and comparing products and services so you can choose the best for you. Find out more about how we test.
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% – 200ms
| Voltage | Before | After | Change | Pass/Fail |
|---|---|---|---|---|
| 12V | 12.037V | 11.932V | 0.87% | Pass |
| 5V | 5.022V | 4.960V | 1.23% | Pass |
| 3.3V | 3.282V | 3.180V | 3.11% | Pass |
| 5VSB | 5.029V | 4.984V | 0.89% | Pass |
Advanced Transient Response at 20% – 20ms
| Voltage | Before | After | Change | Pass/Fail |
|---|---|---|---|---|
| 12V | 12.037V | 11.901V | 1.13% | Pass |
| 5V | 5.024V | 4.953V | 1.41% | Pass |
| 3.3V | 3.284V | 3.165V | 3.62% | Pass |
| 5VSB | 5.029V | 4.985V | 0.87% | Pass |
Advanced Transient Response at 20% – 1ms
| Voltage | Before | After | Change | Pass/Fail |
|---|---|---|---|---|
| 12V | 12.037V | 11.841V | 1.63% | Pass |
| 5V | 5.025V | 4.944V | 1.61% | Pass |
| 3.3V | 3.285V | 3.159V | 3.84% | Pass |
| 5VSB | 5.029V | 4.972V | 1.13% | Pass |
Advanced Transient Response at 50% – 200ms
| Voltage | Before | After | Change | Pass/Fail |
|---|---|---|---|---|
| 12V | 12.017V | 11.947V | 0.58% | Pass |
| 5V | 5.015V | 4.949V | 1.32% | Pass |
| 3.3V | 3.279V | 3.170V | 3.32% | Pass |
| 5VSB | 5.009V | 4.964V | 0.90% | Pass |
Advanced Transient Response at 50% – 20ms
| Voltage | Before | After | Change | Pass/Fail |
|---|---|---|---|---|
| 12V | 12.017V | 11.917V | 0.83% | Pass |
| 5V | 5.016V | 4.939V | 1.54% | Pass |
| 3.3V | 3.280V | 3.151V | 3.93% | Pass |
| 5VSB | 5.009V | 4.965V | 0.88% | Pass |
Advanced Transient Response at 50% – 1ms
| Voltage | Before | After | Change | Pass/Fail |
|---|---|---|---|---|
| 12V | 12.017V | 11.914V | 0.86% | Pass |
| 5V | 5.017V | 4.938V | 1.57% | Pass |
| 3.3V | 3.280V | 3.142V | 4.21% | Pass |
| 5VSB | 5.009V | 4.948V | 1.22% | Pass |
Results 25-29: Transient Response
View Original
View Original
View Original
View Original
View Original
View Original
View Original
View Original
The voltage deviations are kept low in all rails. Nonetheless, because of the low nominal voltage of 3.3V, the voltage levels drop lower than 3.2V once we apply the transient load.
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.
Turn-On Transient Response Scope Shots
The performance is close to perfect, in these tests.
Ripple Measurements
Ripple represent 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.
Get Tom's Hardware's best news and in-depth reviews, straight to your inbox.
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 | 6.9 mV | 10.8 mV | 15.6 mV | 9.2 mV | Pass |
| 20% Load | 8.6 mV | 11.1 mV | 16.3 mV | 8.1 mV | Pass |
| 30% Load | 8.5 mV | 10.9 mV | 15.6 mV | 7.8 mV | Pass |
| 40% Load | 8.4 mV | 11.2 mV | 15.9 mV | 8.4 mV | Pass |
| 50% Load | 8.9 mV | 11.1 mV | 16.1 mV | 10.3 mV | Pass |
| 60% Load | 9.3 mV | 12.1 mV | 17.1 mV | 12.4 mV | Pass |
| 70% Load | 8.8 mV | 12.0 mV | 17.2 mV | 12.0 mV | Pass |
| 80% Load | 11.9 mV | 30.4 mV | 19.2 mV | 14.9 mV | Pass |
| 90% Load | 11.3 mV | 31.9 mV | 19.1 mV | 14.0 mV | Pass |
| 100% Load | 13.9 mV | 13.4 mV | 21.3 mV | 16.0 mV | Pass |
| 110% Load | 14.9 mV | 13.1 mV | 20.1 mV | 20.7 mV | Pass |
| Crossload 1 | 12.8 mV | 11.3 mV | 19.8 mV | 8.5 mV | Pass |
| Crossload 2 | 13.5 mV | 13.6 mV | 19.9 mV | 15.4 mV | Pass |
Results 30-33: Ripple Suppression
View Original
View Original
View Original
View Original
The ripple suppression is good in all rails, despite the lack of in-line capacitors on the modular cables.
Ripple At Full Load
Ripple Full Load Scope Shots
View Original
View Original
View Original
View Original
Ripple At 110% Load
Ripple 110% Load Scope Shots
View Original
View Original
View Original
View Original
Ripple At Cross-Load 1
Ripple CL1 Load Scope Shots
View Original
View Original
View Original
View Original
Ripple At Cross-Load 2
Ripple CL2 Load Scope Shots
View Original
View Original
View Original
View Original
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 several high spurs with no of them, though, exceeding the limits.
MORE: Best Power Supplies
MORE: How We Test Power Supplies
MORE: All Power Supply Content
Current page: Transient Response Tests, Ripple Measurements and EMC Pre-Compliance Testing
Prev Page Protection Features, DC Power Sequencing, Cross-Load Tests and Infrared Images Next Page Performance, Noise and Efficiency
Aris Mpitziopoulos is a contributing editor at Tom's Hardware, covering PSUs.