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Transient Response Tests
Advanced Transient Response Tests (CX450 - Great Wall)
For details on our transient response testing, please click here.
Ιn these tests, we monitored the CX450's response in several scenarios. First, we applied a transient load (10A at +12V, 5A at 5V, 5A at 3.3V and 0.5A at 5VSB) for 200ms as the PSU worked at 20 percent load. In the second scenario, we hit the CPU with the same transient load while operating at 50 percent load.
In the next sets of tests, we increased the transient load on the major rails with a new configuration: 15A at +12V, 6A at 5V, 6A at 3.3V and 0.5A at 5VSB. We also increased the load-changing repetition rate from 5 hertz (Hz) (200ms) to 50Hz (20ms). Again, this runs with the PSU operating at 20 and 50 percent load.
The last tests were even tougher. Although we kept the same loads, we increased the load-changing repetition rate to 1kHz (1ms).
In all of the tests, we used an oscilloscope to measure the voltage drops the transient load caused. The voltages should remain within the ATX specification's regulation limits.
These tests were crucial because they simulated 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 Advanced Transient Response Tests, and they were designed to be very tough to master, especially for a PSU with a capacity of less than 500W.
Advanced Transient Response at 20 Percent – 200ms
| Voltage | Before | After | Change | Pass/Fail |
|---|---|---|---|---|
| 12V | 12.056V | 11.726V | 2.74% | Pass |
| 5V | 5.001V | 4.809V | 3.84% | Pass |
| 3.3V | 3.322V | 3.136V | 5.60% | Fail |
| 5VSB | 5.014V | 4.951V | 1.26% | Pass |
Advanced Transient Response at 20 Percent – 20ms
| Voltage | Before | After | Change | Pass/Fail |
|---|---|---|---|---|
| 12V | 12.056V | 11.560V | 4.11% | Pass |
| 5V | 5.001V | 4.770V | 4.62% | Pass |
| 3.3V | 3.322V | 3.107V | 6.47% | Fail |
| 5VSB | 5.014V | 4.946V | 1.36% | Pass |
Advanced Transient Response at 20 Percent – 1ms
| Voltage | Before | After | Change | Pass/Fail |
|---|---|---|---|---|
| 12V | 12.049V | 11.538V | 4.24% | Pass |
| 5V | 4.999V | 4.8263V | 3.45% | Pass |
| 3.3V | 3.321V | 3.1438V | 5.34% | Pass |
| 5VSB | 5.036V | 4.9351V | 2.00% | Pass |
Advanced Transient Response at 50 Percent – 200ms
| Voltage | Before | After | Change | Pass/Fail |
|---|---|---|---|---|
| 12V | 12.046V | 11.717V | 2.73% | Pass |
| 5V | 4.998V | 4.874V | 2.48% | Pass |
| 3.3V | 3.321V | 3.206V | 3.46% | Pass |
| 5VSB | 5.037V | 4.997V | 0.79% | Pass |
Advanced Transient Response at 50 Percent – 20ms
| Voltage | Before | After | Change | Pass/Fail |
|---|---|---|---|---|
| 12V | 12.040V | 11.748V | 2.43% | Pass |
| 5V | 4.996V | 4.764V | 4.64% | Pass |
| 3.3V | 3.316V | 3.088V | 6.88% | Fail |
| 5VSB | 4.991V | 4.913V | 1.56% | Pass |
Advanced Transient Response at 50 Percent – 1ms
| Voltage | Before | After | Change | Pass/Fail |
|---|---|---|---|---|
| 12V | 12.040V | 11.667V | 3.10% | Pass |
| 5V | 4.996V | 4.750V | 4.92% | Fail |
| 3.3V | 3.316V | 3.062V | 7.66% | Fail |
| 5VSB | 4.991V | 4.902V | 1.78% | Pass |
The Great Wall-based CX450's transient response was not good in these benchmarks. The CWT-manufactured version fared better here hands-down, despite the lower capacity of its caps on the secondary side.
Here are the oscilloscope screenshots we took during Advanced Transient Response Testing:
Transient Response at 20 Percent Load – 200ms
Transient Response at 20 Percent Load – 20ms
Transient Response at 20 Percent Load – 1ms
Transient Response at 50 Percent Load – 200ms
Transient Response at 50 Percent Load – 20ms
Transient Response at 50 Percent Load – 1ms
Turn-On Transient Tests
We measured the response of both CX450s in simpler transient load scenarios during their power-on phase.
For our first measurement, we turned the CX450 off, dialed in the maximum current the 5VSB rail can handle and switched the PSU back on. In the second test, we dialed the maximum load the +12V rail can handle and started the power supply while it was in standby mode. In the last test, while the PSU was completely off (we cut off the power or turned the PSU off through its switch), we dialed the maximum load the +12V rail can handle before restoring power. The ATX specification states that recorded spikes on all rails should not exceed 10 percent of their nominal values (+10 percent for 12V is 13.2V and 5.5 V for 5V).
Corsair CX450 - CWT
There were some minor spikes in the first and third tests, but they didn't worry us much.
Corsair CX450 - Great Wall
The waveforms were smooth in the first two tests. In the last one, we noticed a minor step before the rails settled down.
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