Why designers are moving to distributed power architecture
Original article date: June 1998
Time-to-market, fault tolerance and system flexibility are all key concerns for electronics equipment manufactures and OEMs. Many companies are now adopting a distributed power architecture (DPA) for their latest products and systems.
Most electrical and electronic systems employ a power distribution strategy based on centralised AC-DC supplies. The convert the incoming line voltage to multiple regulated DC outputs, which are then fed individually to every point of use within the equipment.
This approach suffers from many disadvantages, including lengthy design timescales, significant distribution losses, susceptibility to noise pick-up and lack of expansion flexibility.
A distributed power architecture provides an alternative approach, in which an intermediate level DC voltage is generated and bussed around. In this inherently modular approach, DC-DC converters on each board or sub-system, then convert this to the required level, placing tightly-regulated sources exactly where they are needed.
Use of off-the-shelf DC-DC converters lowers development costs and shortens design cycles significantly. Once the supply requirements of a particular function or PCB are known, its power sub-system can be completed simply by specifying the appropriate module. The converters can be pre-approved, accelerating the overall system qualification time of the project.
The inherent modularity of DPA means that additional features, functions or boards can easily be added to the system without necessitating a complete re-design. It is also much easier to optimise DPA-based systems by keeping excess power capacity to a minimum and only expanding on this when necessary – a pay-as-you grow approach.
Multiple power distribution buses and cable harnesses are completely eliminated by DPAs. The use of an intermediate voltage – typically 4V – also means less current needs to be bussed around the equipment to create high power, low voltage rails, such as 3.3V and 5V sources for digital logic circuits. This minimises distribution losses, obviates the need for remote sensing and enables smaller, less expensive conductors to be used.
Since each element in a DPA has its own power supply, failure of a DC-DC converter will only affect a single function or PCB, making the design of fault-tolerant systems much easier. Further, thermal stresses are reduced, because the heat-generating components are decentralised, leading to reduced cooling requirements.
Computer Products has launched a series of low cost front-end AC/DC power supplies for systems using distributed power architectures. The DPF family contains three models with power capabilities of 600W, 950W and 1500W. Each unit features an universal input that accommodates a wide range of AC supply voltages and produces a high current 48Vdc output for distribution to the system’s locally placed DC/DC converters.
Each DPF power supply features automatic power factor corrections and complies with the new European Harmonic Standard EN 61000-3-2, due to come into force in June 1998. The standard specifies stringent limits for harmonic current emissions on 230Vac 50Hz mains supplies.
- Computer Products
June 1998