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.
Transient Response Tests
Advanced Transient Response Tests
Ιn these tests, we monitor the PSU's response in two different scenarios. First, a transient load (10 A at +12V, 5 A at 5V, 5 A at 3.3V and 0.5 A at 5VSB) is applied for 200 ms while the TPG-1500D-T works at 20 percent load. In the second scenario, the PSU is hit by the same transient load while operating at 50 percent load. In both tests, we use our oscilloscope to measure the voltage drops caused by the transient load. The voltages should remain within the ATX specification's regulation limits.
These tests are crucial because they simulate the transient loads a PSU is likely to handle (such as booting a RAID array or an instant 100 percent load of CPU/GPUs). We call these tests "Advanced Transient Response Tests," and they are designed to be very tough to master, especially for power supplies with a capacity of less than 500 W.
Advanced Transient Response at 20 Percent
| Voltage | Before | After | Change | Pass/Fail |
|---|---|---|---|---|
| 12V | 12.043V | 11.957V | 0.71% | Pass |
| 5V | 5.013V | 4.914V | 1.97% | Pass |
| 3.3V | 3.340V | 3.165V | 5.24% | Pass |
| 5VSB | 4.994V | 4.922V | 1.44% | Pass |
Advanced Transient Response at 50 Percent
| Voltage | Before | After | Change | Pass/Fail |
|---|---|---|---|---|
| 12V | 11.992V | 11.930V | 0.52% | Pass |
| 5V | 4.984V | 4.881V | 2.07% | Pass |
| 3.3V | 3.313V | 3.141V | 5.19% | Pass |
| 5VSB | 4.957V | 4.883V | 1.49% | Pass |
The +12V rail demonstrates small deviations, which comes naturally for such a strong PSU, while the deviations on the 5V and 5VSB rails are low as well. On the contrary, the 3.3V rail doesn't respond well in transient loads, registering significant deviations and very high voltage drops.
Here are the oscilloscope screenshots we took during Advanced Transient Response Testing:
Transient Response At 20 Percent Load
Transient Response At 50 Percent Load
Turn-On Transient Tests
In the next set of tests, we measured the TPG-1500D-T's response in simpler transient load scenarios—during its power-on phase.
For the first measurement, we turned off the PSU, dialed in the maximum current the 5VSB could output and switched the TPG-1500D-T on. In the second test, we dialed the maximum load the +12V could handle and started the PSU while it was in standby mode. In the last test, while the TPG-1500D-T was completely switched off (we cut off the power or switched it off by flipping its on/off switch), we dialed the maximum load the +12V rail could handle before switching the PSU back on from the loader and restoring power. The ATX specification states that recorded spikes on all rails should not exceed 10 percent of their nominal values (+10 percent for 12 V is 13.2 V, and 5.5 V for 5 V).
The 5VSB test results are fine, and the same goes for the second test. Only in the last test we do notice a small wave before the rails settle down, though this is nothing to worry about. Overall, we observe very good performance.
