A relatively recent
design concept used in
circuit design, a distributed power
architecture (DPA) uses advances in
power supply efficiencies and power densities to improve
thermal loading in a circuit and increase overall
performance.
A modern circuit, especially one involving microprocessors, requires several voltages to operate. For example, the microprocessor may use 3.3 volts (V), while the fan that cools it may use 12 V. Often, 5 to 7 different voltages are needed for the various chips and devices on the circuit board.
In the past, engineers would use a big power supply that took the wall current and converted it into the multiple voltages needed, carrying them to each device using wires or solder vias (paths) laid down on the board itself. This solution required a big box for the supply, and since all power conversion occurred in the one device, it ran very hot, requiring lots of forced-air cooling.
In the telecom industry, where it is common to have huge racks full of equipment running in the same room, a 48-V "bus voltage" was eventually adopted to remove some of the heat-generating and space-hungry power conversion gear from the individual devices. A single power converter would take the line voltage from the mains and convert it to the lower bus voltage, which would then be routed to all of the equipment. There, smaller power units would take the 48 V and convert it into the muiltiple voltages needed by the circuit.
Advances in planar magnetics and other design aspects used to make power supplies have enabled this paradigm to be extended to the circuit board. Instead of one converter on the board doing all the work, an electrical engineer can now use a board-level bus converter take the incoming voltage (usually 48 or 24 V) and convert it into an intermediate voltage, which then gets sent to point-of-load converters mounted next to the devices that need power, making the final voltage conversion there.
The advantages include a reduced thermal load, as the power conversion work is spread out over the entire board, and a reduced cost, as a smaller single-output bus converter is used for circuit isolation as well as initial conversion, enabling a system designer to use simpler, less expensive non-isolated devices at the point of load. In addition, by spreading the power conversion circuitry across the entire board area, overall system height is decreased, and cooling is easier as the flatter circuit enables a smoother airflow over the board.