Power designers often prefer particular power products or manufacturers. Some designers try to drive these preferences into every application. That’s not surprising. Such choices are usually based on successful relationships with specific manufacturers. The designers already know the products, or they can rely on a level of reliability, on-time delivery, or good prices.
Many suppliers of dc-dc converters offer common input and output voltages, power levels, and features. But the specific ranges or combinations needed to satisfy an application can disqualify some suppliers. Further, each supplier seeks its own niche, such as the highest efficiency, the smallest footprint, or the highest power density. Each of these parameters comes with tradeoffs made somewhere else in the specification.
LOOK AT THE APPLICATION
As a result, the designer’s decision-making process isn’t straightforward. The first and most important place to look for guidance is within the application. Some applications favor a specific architecture or configuration. An application that requires many low-voltage outputs would suggest, for example, that the Intermediate Bus Architecture—with its low-cost, non-isolated converters—should get early consideration.
On the other hand, if the voltages are high and the currents low or if the distances between the power supply and the loads are small, a centralized power architecture (CPA) comes to mind. CPA, of course, generates all system voltages at a central location and distributes them to loads by distribution buses.
Contemporary factors can drive certain solutions in new directions. The processor trends toward lower voltages, higher currents, and higher speeds are forcing power designers to contend with new and different challenges. The dynamic performance of a converter is very critical for applications with a lot of computing power. In fact, dynamic performance is important for other applications as well, such as automated test.
Systems need quick response to current demands. The power supply also often needs to be in the test head, and there’s only so much space left for it. Such requirements suggest using the Factorized Power Architecture. In any case, the power conversion topologies used in the application have to be up to meeting the transient response requirements of today’s fast loads.
Other applications such as transportation and military require rugged power supplies that need to handle harsh environments, such as high or low temperatures. Or, maybe the power supply is on a card with a specified board pitch so there’s limited height above the board. These factors limit your selections and drive specific requirements. Designers need to focus on them to understand the best choice in a power solution.
Price has become such a major factor in so many decisions that designers can lose sight of the other needs of the application. Technical challenges could introduce some flexibility with pricing, but price can be a disqualifier.
Whether it’s an architecture decision or configuration, a building block approach or a complete solution, or thermal management or the mounting or fitting of the power supply within the system, these factors drive the nature of the solution and the selection of the right products and accessories.
WHY START FROM SCRATCH?
Selection ultimately revolves around the needs of the application and deciding what solution makes the most sense. Yet the power designer isn’t starting with a clean slate each time, and there is more help than ever.
New products and accessories—new solutions—are available. Also, power suppliers have competent, experienced applications engineers to help power designers. What’s more, automated design tools can simplify the power designer’s task.
Specialized accessory components are increasingly available. Together with the power components, these matched, compatible accessories—such as filters, holdup capacitors, heatsinks, and ac front ends—allow users to quickly assemble complete power systems by selecting and interconnecting standard, modular parts to meet their design requirements.
Compatible front-end accessories, for example, provide a number of performance features such as input transient protection, electromagnetic interference (EMI) filtering, and inrush current limiting. In addition, they have international agency approvals and can accommodate the wide range of input source voltages necessary to reach worldwide markets.
Web-based systems enable designers to specify online, and verify in real time, the performance and attributes of custom dc-dc converters. An expert system accepts user-specified converter performance requirements and generates an optimal design utilizing an extensive database of prequalified components. The design is downloaded directly into a computer-integrated manufacturing (CIM) system.
By offering a direct link into the mass customization capabilities of an automated design and manufacturing environment, this system frees power specifiers from having to compromise between standard products, which only partially meet their needs, and custom engineered products, with their long cycle times and performance uncertainties.