BFG LS-550 (New) 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 both were connected to the single +12 V provided by this power supply.
| Input | Test 1 | Test 2 | Test 3 | Test 4 | Test 5 |
| +12V1 | 4 A (48 W) | 8 A (96 W) | 12 A (144 W) | 16 A (192 W) | 20 A (240 W) |
| +12V2 | 4 A (48 W) | 8 A (96 W) | 12 A (144 W) | 16 A (192 W) | 20 A (240 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 | 112.8 W | 215.0 W | 328.5 W | 430.5 W | 531.1 W |
| % Max Load | 20.5% | 39.1% | 59.7% | 78.3% | 96.6% |
| Room Temp. | 45.6° C | 47.2° C | 45.8° C | 48.7° C | 45.9° C |
| PSU Temp. | 47.5° C | 48.1° C | 45.9° C | 48.6° C | 50.1° C |
| Voltage Stability | Fail on -12 V | Pass | Pass | Pass | Pass |
| Ripple and Noise | Pass | Pass | Pass | Pass | Pass |
| AC Power | 133.4 W | 250.8 W | 388.8 W | 520.6 W | 661.0 W |
| Efficiency | 84.6% | 85.7% | 84.5% | 82.7% | 80.3% |
| AC Voltage | 113.1 V | 111.7 V | 110.3 V | 109.5 V | 107.4 V |
| Power Factor | 0.956 | 0.950 | 0.961 | 0.969 | 0.976 |
| Final Result | Pass | Pass | Pass | Pass | Pass |
The new version from BFG LS-550 presents a high efficiency between 84.5% and 85.7% if you pull between 20% and 60% (between 110 W and 330 W) from its labeled wattage. Delivering 80% from its labeled capacity (440 W) efficiency dropped to 82.7%, still a very decent number. At full load (550 W) efficiency dropped to 80.3%, still above the 80% mark.
The only problem we saw was voltage level at -12 V. This output has a higher 10% tolerance, so it can be anywhere between -13.2 V and -10.8 V. During test number one this output was at -10.78 V, passing this limit by 0.02 V. During test two it was touching the limit at -10.87 V, during test three it was at -10.99 V, during test four it was at -11.08 V and during test five it was at -11.19 V. We saw the same thing happening with LS-450.
Ripple and noise stayed inside specs, although they were higher than competing products. 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 531.1 W (86.8 mV).
Figure 16: +12V2 rail with power supply delivering 531.1 W (79.6 mV).
Figure 17: +5V rail with power supply delivering 531.1 W (31.4 mV).
Figure 18: +3.3 V rail with power supply delivering 531.1 W (32.4 mV).
Now let’s see if we could pull more than 550 W from this unit.