Corsair CX400W Power Supply Review
Load Tests
Contents
We conducted several tests with this power supply, as described in the article Hardware Secrets Power Supply Test Methodology.
First we tested this power supply with five different load patterns, trying to pull around 20%, 40%, 60%, 80%, and 100% of its labeled maximum capacity (actual percentage used listed under “% Max Load”), watching how the reviewed unit behaved under each load. In the table below we list the load patterns we used and the results for each load.
If you add all the power listed for each test, you may find a different value than what is posted under “Total” below. Since each output can vary slightly (e.g., the +5 V output working at +5.10 V), the actual total amount of power being delivered is slightly different than the calculated value. On the “Total” row we are using the real amount of power being delivered, as measured by our load tester.
+12V1 and +12V2 are the two independent +12V inputs from our load tester and during our tests they were connected to the single +12 V rail available on the tested power supply.
| Input | Test 1 | Test 2 | Test 3 | Test 4 | Test 5 |
| +12V1 | 2.5 A (30 W) | 5.5 A (66 W) | 8 A (96 W) | 10.5 A (126 W) | 14 A (168 W) |
| +12V2 | 2.5 A (30 W) | 5.5 A (66 W) | 8 A (96 W) | 10.5 A (126 W) | 13 A (156 W) |
| +5V | 1 A (5 W) | 2 A (10 W) | 4 A (20 W ) |
6 A (30 W) | 8 A (40 W) |
| +3.3 V | 1 A (3.3 W) | 2 A (6.6 W) | 4 A (13.2 W) | 6 A (19.8 W) | 8 A (26.4 W) |
| +5VSB | 1 A (5 W) | 1 A (5 W) | 1.5 A (7.5 W) | 2 A (10 W) | 2 A (10 W) |
| -12 V | 0.5 A (6 W) | 0.5 A (6 W) | 0.5 A (6 W) | 0.5 A (6 W) | 0.5 A (6 W) |
| Total | 79.3 W | 159.6 W | 238.5 W | 317.0 W | 402.9 W |
| % Max Load | 19.8% | 39.9% | 59.6% | 79.3% | 100.7% |
| Room Temp. | 45.8° C | 45.5° C | 45.2° C | 45.9° C | 49.0° C |
| PSU Temp. | 48.3° C | 48.0° C | 48.3° C | 48.8° C | 54.5° C |
| Voltage Stability | Pass | Pass | Pass | Pass | Pass |
| Ripple and Noise | Pass | Pass | Pass | Pass | Pass |
| AC Power | 97.6 W | 190.3 W | 285.0 W | 383.8 W | 500.2 W |
| Efficiency | 81.3% | 83.9% | 83.7% | 82.6% | 80.5% |
| AC Voltage | 112.4 V | 111.6 V | 111.7 V | 110.6 V | 109.2 V |
| Power Factor | 0.983 | 0.990 | 0.994 | 0.996 | 0.996 |
| Final Result | Pass | Pass | Pass | Pass | Pass |
Corsair CX400W presents a very good efficiency for an entry-level product. If you pull between 40% and 60% from its labeled capacity (between 160 W and 240 W) you will see efficiency of almost 84%. Pulling around 80% from its maximum (320 W) efficiency was 82.6%. At light load (20%, i.e., 80 W) and full load (400 W) efficiency dropped, but still above the 80% mark.
Voltage stability is another highlight from this product. All voltages (except -12 V) were within 3% from their nominal value, whereas the ATX specification says they must be within 5%. Translation: voltages were closer to their nominal values than needed.
Ripple and noise were extremely low. With this power supply delivering 400 W noise level at +12 V outputs were less than a quarter of the maximum allowed. You can see the results for test number five below. All numbers are peak-to-peak figures and the maximum allowed is 120 mV for the +12 V outputs and 50 mV for the +3.3 V and +5 V outputs.
Figure 15: +12V1 input from load tester at 402.9 W (26.6 mV).
Figure 16: +12V2 input from load tester at 402.9 W (29.6 mV).
Figure 17: +5V rail with power supply delivering 402.9 W (18.2 mV).
Figure 18: +3.3 V rail with power supply delivering 402.9 W (16.4 mV).
Let’s see if we could pull more than 400 W from this unit.