Akasa Paxpower 500 W 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 the +12V1 input was connected to the power supply +12V1 (main motherboard connector and peripheral power connectors) while the +12V2 input was connected to the power supply +12V1 and +12V2 rails (EPS12V connector), except on test number five, where we had to remove the ATX12V connector that was connected to +12V1 from the +12V2 input from our load tester, as we will explain below.
| Input | Test 1 | Test 2 | Test 3 | Test 4 | Test 5 |
| +12V1 | 4 A (48 W) | 7 A (84 W) | 11 A (132 W) | 14.5 A (174 W) | 18 A (216 W) |
| +12V2 | 3 A (36 W) | 7 A (84 W) | 10 A (120 W) | 14 A (168 W) | 18 A (216 W) |
| +5V | 1 A (5 W) | 2 A (10 W) | 4 A (20 W) | 5 A (25 W) | 6 A (30 W) |
| +3.3 V | 1 A (3.3 W) | 2 A (6.6 W) | 4 A (13.2 W) | 5 A (16.5 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) | 2.5 A (12.5 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 | 101.9 W | 192.6 W | 294.4 W | 391.4 W | 484.6 W |
| % Max Load | 20.4% | 38.5% | 58.9% | 78.3% | 96.9% |
| Room Temp. | 46.6° C | 46.3° C | 46.6° C | 46.7° C | 46.6° C |
| PSU Temp. | 49.8° C | 49.3° C | 50.2° C | 50.4° C | 51.6° C |
| Voltage Stability | Pass | Pass | Pass | Pass | Pass |
| Ripple and Noise | Pass | Pass | Pass | Pass | Pass |
| AC Power (1) | 122 W | 226 W | 351 W | 474 W | 612 W |
| Efficiency (1) | 83.5% | 85.2% | 83.9% | 82.6% | 79.2% |
| AC Power (2) | 129 W | 238 W | 367 W | 497 W | 636 W |
| Efficiency (2) | 78.7% | 81.0% | 80.3% | 78.7% | 76.2% |
| AC Voltage | 113.6 V | 112.1 V | 111.6 V | 110.4 V | 108.7 V |
| Power Factor | 0.958 | 0.986 | 0.994 | 0.996 | 0.997 |
| Final Result | Pass | Pass | Pass | Pass | Pass |
Updated 06/24/2009: We re-tested this power supply using our new GWInstek 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. Under light load (20% load, i.e., 100 W), the active PFC circuit from this unit isn’t as good as when operating under higher loads.
Efficiency was above 80% only when we pulled between 40% and 60% from this power supply labeled power (between 200 W and 300 W). On all other load patterns efficiency was below 80%.
Another problem we had with Akasa Paxpower 500 W was during test five: using the two ATX12V connectors at the same time connected to the load tester’s +12V2 input the power supply wouldn’t turn on. By removing the plug that was connected to the power supply’s +12V1 rail from the machine, the unit would turn on.
Ripple and noise was the highlight from this product, very low levels all the time. Below you see the waveforms during test number five. Just to remember, the maximum allowed is 120 mV at +12 V and 50 mV at +5 V and +3.3 V. All values are peak-to-peak.
Figure 15: +12V1 rail with power supply delivering 484.6 W (36.4 mV).
Figure 16: +12V2 rail with power supply delivering 484.6 W (35.4 mV).
Figure 17: +5V rail with power supply delivering 484.6 W (14.4 mV).
Figure 18: +3.3 V rail with power supply delivering 484.6 W (13.2 mV).
Now let’s see if we could pull more than 500 W from this unit.