Power conversion chain
Beginner
The steps that bring electricity from the power lines down to the gentle 1 volt a chip needs. A little is lost as heat at each step.
Novice
The sequence from the utility’s high voltage down to about 1 volt at the chip: transformers, a backup system (UPS), distribution units (PDUs), the server’s power supply (PSU) and the voltage regulators beside each chip. Each stage’s efficiency multiplies with the others.
Expert
Typically medium-voltage AC → low-voltage AC (transformer) → UPS → PDU → PSU (AC to a 48 V-class DC bus in modern racks) → intermediate bus converter → multiphase point-of-load regulators. End-to-end efficiency is the product of stage efficiencies, and losses upstream scale with every watt lost downstream.
Explained in Power and cooling (Systems).
See also: UPS (uninterruptible power supply), PDU (power distribution unit), PSU (power supply unit), VRM (voltage regulator module).