Cross-Load Tests And Infrared Images
Our cross-load tests are described in detail here.
To generate the following charts, we set our loaders to auto mode through our custom-made software before trying more than 25,000 possible load combinations with the +12V, 5V and 3.3V rails. The load regulation deviations in each of the charts below were calculated by taking the nominal values of the rails (12V, 5V and 3.3V) as point zero.
Load Regulation Charts
As you can see, the 850 BQ's efficiency is greater than 85% during much of our testing. Above 650W loads it drops to the 80-85% range, but this isn't an issue. The cooling fan's noise is what should worry you under higher loads.
We took some IR photos of the PSU with its top cover, along with the fan, missing and around 400W of load applied for several minutes. We used our modified FLIR E4 camera that delivers 320x240 IR resolution (76,800 pixels).
The SBRs on the secondary side get hot quickly without a fan pushing lots of air above them. Even with a fan, under tough conditions the thermal loads on those SBRs will be high. This is why HEC uses a large secondary heat sink.
Also worth mentioning is the NTC thermistor's very high operating temperature, which reaches 97°C in a matter of minutes. The higher its temperature, however, the less energy is wasted, since its resistance gets lower as the temperature rises. The only potential issue is that it'll take some time for the thermistor to cool down once the PSU turns off before it's ready to do its job during the start-up phase.