| Distributed vs. Centralized: power systems |
Originally, power supplies were located near the bottom of any electronic systems structure because of their weight. Heavy gauge wire was run up to the various chassis or rack drawers, supplying power to them. This centralized architecture, popular since vacuum tube days, does not account for small voltage drops in the power wires. Also created by this architecture is the probability of one chassis feeding noise to another, and causing inter-chassis problems. Digital circuits are especially prone to these headaches. However, before microcircuits, this was the only practical architecture to be used.
A newer way of piping power around is this: have a centralized bulk power supply that provides power to individual chassis. Then, on each p.c. board, attach this power buss to a regulator sized appropriately for the card. Inter-chassis noise is eliminated, and the centralized bulk supply can still be heavy and on the bottom of the structure. This is called a distributive architecture.
The on-board regulators will not be affected by raw power line voltage drops. A simple three terminal linear regulator should suffice.
The bulk supply can have minimal or no regulators on its output, depending on the system design, which allows it to be lower cost than when used alone. The dollars saved here could counteract the additional expense of on-board regulators.