Load testing the PSU
Load Testing The PSU
Testing a power supply is challenging, and you need professional load testers to correctly check the PSU’s behavior.
The first basic test is performed with a simple power supply tester. It doesn’t load the PSU with more than a couple of Watts, but it helps determine if the power supply unit is operational. There’s a self-check indicating if the voltages are at the proper levels. As you can see, there have been no issues with the Lian Li SP850 unit.
The following setup was used for the remainder of the testing:
- Voltcraft VC-870 Digital Multimeter - voltage measurement (+ Fluke 97 scope meter)
- Oscilloscope - GW INSTEK GDS 3154
- DC load - original solution
- Fluke 97 Scope meter (a measurement of voltage and ripple),
- Voltcraft SL-451 decibel meter (volume measurement)
- ACUVIM-IIRF – for measuring active power (input from the socket).
- PCE Instruments PCE-DT 50 tachometer – for the measurement of the rotational speed of the fan.
Measurements are taken only using 230 V input voltage.
Efficiency
Older components require more power, but there has been some progress in this area. In our power supply reviews, we emulate real-world usage by creating such loads as a power-hungry, multi-GPU setup with a powerful CPU would generate. In a typical configuration, reaching over 500-600 Watts of power draw is difficult. Checking efficiency is a relatively easy thing to accomplish. Let’s take a look at the SP850’s efficiency first.
It does look great even at low loads (e.g., 10%, equaling 85 W), which is quite typical of the idle state in modern PCs.
Maximum load
Next is the maximum wattage this unit can hold before switching off.
|
Maximum Load |
Efficiency (in %) |
|
915 W |
90.03 % |
Efficiency looks excellent, even above 100% load. Watts is a good value, but you wouldn’t want to come close to that for very long.
ErP Lot 6 Power Off wattage
We looked at the powered-off status (ErP/EuP), productivity mode (when we stress the CPU), and gaming. The lower the wattage, the more efficient the PSU. It is that simple.
|
ErP Lot 6 Power Off |
value in Watts |
|
850 W |
0.08 |
This is well below the 0.5 W requirement.
Ripple testing
First up is the ATX12V V2.2 specification for DC output ripple:
|
ATX12V Ver 2.2 Noise/Ripple Tolerance |
|
|
Output |
Ripple (mV p-p) |
|
+3.3 V |
50 |
|
+5 V |
50 |
|
+12 V |
120 |
The Lian Li SP850 achieved the following results:
| AC Ripple (mV p-p) | +3.3 V | +5 V | +12 V |
| 85 W (10%) | 8 | 15 | 10 |
| 212.5 W (25%) | 7 | 13 | 12 |
| 425 W (50%) | 8 | 16 | 15 |
| 637.5 W (75%) | 10 | 15 | 18 |
| 850 W (100%) | 15 | 20 | 23 |
The values are very well within tolerance. Even in the worst-case scenario (100% load), it is not worrying.
