There’s absolutely no reason for having to endure a loud power supply unit anymore, as was quite the standard about 15 years ago. Our approach to PSUs is to equip them with high-grade components and put a very silent fan on top. But there are two developments in that field that cropped up in the last few years and warrant a closer look: passive and semi-passive power supply units.
“passive” means that the PSU comes completely without a fan, the heat dissipation is completely being taken care of by a big heat sink – which means that the system is pretty much noiseless. Sounds super, but has one major drawback: This only works up to a certain performance limit as crossing that threshold bears the very real risk of overheating the system. This means that from this point on you simply need something actively dissipating the heat thus preventing overheating and shutdown.
This brings “semi-passive power supplies” into view. By and large they are built like regular active PSUs but with the major difference that their fan is usually dormant and only springs into action when the system crosses a pre-defined performance limit, usually something between 40% and 50%, or a certain temperature threshold.