Dynex 400 W Power Supply Review
Overload Tests
Contents
We conducted several tests with this power supply, as described in the article Hardware Secrets Power Supply Test Methodology.
Usually we test power supplies with five different load patterns, trying to pull around 20%, 40%, 60%, 80%, and 100% of its maximum capacity (actual percentage used listed under “% Max Load”), watching how the reviewed unit behaved under each load.
But since we had a bad experience with Huntkey Green Star 450 W (that we now know that internally is identical to this 400 W model), we decided to add one additional load patterns to our methodology, trying to pull around 350 W from this power supply. We also included two load patterns for the 100% load test, one pulling more current from +5 V and +3.3 V outputs than we liked to see (test 6), but respecting more the old project used by this power supply, which uses rectifiers with greater capacity on these outputs, and another representing the current usage of a typical PC (test 7), where we pulled more current from the +12 V outputs.
We broke the results down into two tables. On the first table you see the results for loads between 20% and 80%, and on the second table you see the results for loads between 80% and 100%. Below we will explain more about this second table.
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.
+12V2 is the second +12V input from our load tester and during our tests it was connected to the power supply ATX12V connector, which is the only thing connected to the unit’s +12V2 rail. So this time +12V1 and +12V2 inputs from our load tester were really connected to the +12V1 and +12V2 rails from the reviewed power supply.
| Input | Test 1 | Test 2 | Test 3 | Test 4 |
| +12V1 | 3 A (36 W) | 6 A (72 W) | 9 A (108 W) | 11 A (132 W) |
| +12V2 | 2.5 A (30 W) | 6 A (72 W) | 8 A (96 W) | 11 A (132 W) |
| +5V | 1 A (5 W) | 2 A (10 W) | 4 A (20 W) | 6 A (30 W) |
| +3.3 V | 1 A (3.3 W) | 2 A (6.6 W) | 4 A (13.2 W) | 6 A (19.8 W) |
| +5VSB | 1 A (5 W) | 1 A (5 W) | 1.5 A (7.5 W) | 2 A (10 W) |
| -12 V | 0.3 A (3.6 W) | 0.3 A (3.6 W) | 0.3 A (3.6 W) | 0.3 A (3.6 W) |
| Total | 82.5 W | 167.5 W | 246.3 W | 325.3 W |
| % Max Load | 20.6% | 41.9% | 61.6% | 81.3% |
| Room Temp. | 45.9° C | 46.6° C | 46.3° C | 44.3° C |
| PSU Temp. | 53.9° C | 55.4° C | 55.2° C | 52.1° C |
| Load Test | Pass | Pass | Pass | Pass |
| Voltage Stability | Pass | Pass | Pass | Pass |
| Ripple and Noise | Pass | Pass | Pass | Pass |
| AC Power (1) | 102 W | 200 W | 298 W | 402 W |
| Efficiency (1) | 80.9% | 83.8% | 82.7% | 80.9% |
| AC Power (2) | 104.5 W | 205.9 W | 306.2 W | 413.6 W |
| Efficiency (2) | 78.9% | 81.4% | 80.4% | 78.7% |
| AC Voltage | 111.5 V | 110.7 V | 109.9 V | 109.1 V |
| Power Factor | 0.575 | 0.637 | 0.676 | 0.701 |
| Final Result | Pass | Pass | Pass | Pass |
| Input | Test 5 | Test 6 | Test 7 |
| +12V1 | 11 A (132 W) | 12 A (144 W) | 14 A (168 W) |
| +12V2 | 11 A (132 W) | 12 A (144 W) | 14 A (168 W) |
| +5V | 10 A (50 W) | 12 A (60 W) | 8 A (40 W) |
| +3.3 V | 10 A (33 W) | 12 A (39.6 W) | 8 A (26.4 W) |
| +5VSB | 2.5 A (12.5 W) | 2.5 A (12.5 W) | 2.5 A (12.5 W) |
| -12 V | 0.3 A (3.6 W) | 0.3 A (3.6 W) | 0.3 A (3.6 W) |
| Total | 364.3 W | 406.9 W | 402.8 W |
| % Max Load | 91.1% | 101.7% | 100.7% |
| Room Temp. | 48.1° C | 50.1° C | 45.5° C |
| PSU Temp. | 58.9° C | 62.4° C | 54.4° C |
| Load Test | Pass | Pass | Pass |
| Voltage Stability | Pass | Pass | Pass |
| Ripple and Noise | Pass | Pass | Pass |
| AC Power (1) | 465 W | 536 W | 523 W |
| Efficiency (1) | 78.3% | 75.9% | 77.0% |
| AC Power (2) | 477.0 W | 548.0 W | 560.0 W |
| Efficiency (2) | 76.4% | 74.3% | 71.9% |
| AC Voltage | 107.9 V | 107.4 V | 107.2 V |
| Power Factor | 0.708 | 0.715 | 0.718 |
| Final Result | Pass | Pass | Pass |
Updated 07/03/2009: We re-tested this power supply using our new GWInsteak GPM-8212 power meter, which is a precision instrument and provides accuracy of 0.2% and thus presenting the correct readings for AC power and efficiency (results marked as “2” on the table above; results marked as “1” were measured with our previous power meter from Brand Electronics, which isn’t so precise as you can see). We also added the numbers for AC voltage during our tests, an important number as efficiency is directly proportional to AC voltage (the higher AC voltage is, the higher efficiency is). Also, manufacturers usually announce efficiency at 230 V, which usually inflates efficiency numbers. We added power factor (PF) numbers as well. These numbers measure the efficiency of the power supply active PFC circuit. This number should be as close to 1 as possible. Since this power supply does not feature a PFC circuit, which is in charge of “fixing” the power factor, numbers for this parameter were very low. Units with active PFC achieve numbers above 0.97 here.
The main problem with this power supply is efficiency. You will only see efficiency slightly above 80% when pulling between 40% and 60% from its nominal capacity (between 160 W and 240 W). On all other load patterns efficiency stays below 80%, hitting a hard bottom during test seven, at 71.9%. That is really bad.
Voltage stability, on the other hand, was the highlight of this product, with all outputs between 3% of their nominal voltage in almost all tests, which is excellent (ATX standard allows voltages to be up to 5% from their nominal values – 10% in the case of the -12 V output). We only saw voltages outside this 3% range on tests one and six on -12 V output, but it was still inside the maximum allowed.
Noise level was far higher than we wanted to see, but still inside ATX specs – actually touching it during test number six, where could see a 113.2 mV noise level at +12V1. Under other patterns – including test seven – noise wasn’t that high, but still at a level far higher than the one achieved by good power supplies. On the other hand, noise level at +3.3 V was always below 15 mV, which is excellent.
We wouldn’t be complaining about noise and efficiency if it was a power supply costing less than USD 40, but for a product that costs the double of that this is simply unacceptable.
The results below are for test number seven.
Figure 16: Noise level at +12V1 with power supply delivering 400 W (81 mV).
Figure 17: Noise level at +12V2 with power supply delivering 400 W (72 mV).
Figure 18: Noise level at +5 V with power supply delivering 400 W (22 mV).
Figure 19: Noise level at +3.3 V with power supply delivering 400 W (12.2 mV).
Now let’s see if we could pull even more power from this unit and our tests of the power supply protections.