With system bus structures changing almost as soon as they're invented, users and vendors of power supplies are again rethinking the longstanding issue of standard vs. custom supplies. Affected by this state of flux in communications and computer architectures are the popular eighth-brick dc/dc converter and the emerging software-based systems that serve the needs of developing distributed power architectures, networked monitoring and 24/7 service.
The arrival of the eighth-brick has brought a twist to the so-called intermediate bus, enabling high-efficiency dc/dc conversion at low output voltages by means of a 12-volt standard input, as opposed to the traditional 48-V input. But even now - with systems called on to deliver a 100-amp, sub-1-V output from a 12-V bus for today's low-voltage ICs, and with buses now on the drawing board that specify operating voltages anywhere from 7 to 12 V - the specs won't likely sit still for long.
The changes seem to call for a custom solution rather than a standard off-the-shelf approach. At the same time, the intense time-to-market and cost pressures now facing the OEM community demand sufficiently inclusive standard or modified-standard product platforms for developing unique products. Thus the line between custom and standard has become finer.
Increasingly, power systems for networked architectures are equipped with communication buses and protocols, such as I²C, that have to deal with basic command/control and monitoring of supplies, intended to streamline on-site servicing and minimize downtime in critical systems. Issuing network commands via the Internet is part of that wide-area control-and-monitoring approach.
Thus, both networks and in their own right, software-based products are poised for a mini revolution, and power designers will likely require more code-writing skills to create customized environments suitable to their applications.
As dynamic control becomes more important, specialty supplies, such as in test and measurement hardware, are also looking to make some gains. From the business side, the market for standard telecom devices is not what it was, and more companies have developed a flexibility of their own.
Most of the recent hardware advances address the server and general datacom markets. In particular, industry opinion diverges widely when it comes to the eighth-brick's practical application in intermediate bus architectures.
Datel Corp. (Mansfield, Mass.) recently launched its LEN D12 eighth-brick. The custom product is a nonisolated eighth-brick working off a 12-V distributed bus that delivers 0.8 to 5 V at up to 25 amps for on-board, point-of-load applications. Amid the contentious debate that addresses the optimum bus voltage and ultimate power capabilities of such architectures, the eighth-brick will likely continue to attract attention. The concept of the nonisolated eighth-brick may indeed catch on, yet there may well be quite a variety of them as bus specs change.
Apart from applying the nonisolated eighth-brick in the intermediate bus, vendors are expected to deliver a broad variety of nonisolated converters in other packages that will provide some of the same capability.
Celestica (Toronto), which was among the first to develop isolated eighth-bricks for telecom, is pursuing the 12-volt distributed power bus with its recently released nonisolated S007 and S016 12-V-input devices, in single-in-line packages. The S007 (measuring 1.2 x 0.39 x 1.1 inches) delivers 8 A and the S016 (1.2 x 0.45 x 1.1 inches) 16 A at 1.2 to 1.5 V.
Indeed, it's more than just the variations on the distributed power bus that are causing headaches for power supply vendors and users. Alternatives to that bus are already making their way into the equation, according to Vicor (Andover, Mass.). Vicor, which was among the first to compete in the brick market, is planning a high-density brick for the second quarter.
At the front end of the bus, Vicor recently introduced its Enmods line for passive harmonic attenuation, targeting use in applications where power factor correction is being addressed via other means. Advantages are said to include low noise and higher efficiency than active topologies, as well as low cost. It also provides a reasonable degree of power factor correction, nominally to the 0.8 level.
In other work, Unipower Telecom (Coral Springs, Fla.) has developed its Power Cassette, an ac/dc supply that uses a so-called virtual-module platform designed to offer high density and configurability, with the emphasis on hot plugging, according to Ed Rodriguez, director of the company's technical center. Unipower's initial entry was a 600-watt supply with up to six outputs, from 1.2 to 24 V. The company has recently released three single-output Power Cassette versions (ac to 12, 24 or 48 V), delivering up to 800 W in a 1U enclosure that's suited to point-of-load applications.
Astec America (Carlsbad, Calif.), meanwhile, is offering configurable, hot-swappable products that include ac-to-12-V and ac-to-48-V HPS racks that deliver 350 to 1,500 W.
Real estate and high-density issues in datacom applications are creating demand for physical as well as electrical changes in offerings. Tyco Electronics' Custom Power division (Mesquite, Texas), historically a major player in telecommunications, has succeeded in deploying new products in the server/storage and enterprise areas. Recent arrivals include the NP series of rectifier front ends in "zero-height" shelves.
Cherokee LLC (Tustin, Calif.), with most of its business in custom and about three-quarters of its activity in datacom, has developed vertically mounted eighth-, quarter- and half-bricks to solve growing space shortages. Other high-density products on the way include a 12-V, 150-W eighth-brick that will be added to the company's Eagle line.
Cherokee is also well along on a 500-W half-brick addition to its Polaris line and 250-W quarter-brick for the Apollo line. The two latter products are 48- to 12-V devices.
Extending the high-density products in Cherokee's ac/dc line will be the CAR series of 2U, 1,500-W switchers (ac to 48 Vdc) and a 1U, 500-watt ac-to-12-V switcher. The company says it's one of the first to use the controller-area network bus for network communications in one of its applications, saying CAN provides all of the inherent advantages of a true digital bus.
Test and measurement calls for yet another speciality: the microprocessor-programmable supply, still a commodity rarely seen in this area of power. "There's two parts to this," said Dorrel Vernon, ac/dc product manager at Lambda (San Diego). "One function is a basic setting of parameters; the other allows the user to write code."
One product, now in sampling, that steps toward such capabilities is Lambda's SmartPlus series of 450- and 650-W switchers, an extension to its Vega line. Microprocessor-based options let the user program most parameters and the supply output via an RS-232 interface using a PC and a graphical user interface. Alternatively, supply functions can be programmed directly via C++, Visual Basic and Labview. The SmartPlus is scheduled for second-quarter release.
Waiting on Web
While software-based products will likely become a bigger part of the custom-supply market, Web tools to aid the designer have hit a snag. "There are two types of Web tools," said Vicor's Andy Hilbert, senior director for product marketing. "One is what we call the configurator type, where the user puts in certain design parameters and gets products out. The second deals with actual simulation of a design." The first, he said, will continue to evolve, but the second won't be practical for some time.
Vicor's VDAC, introduced two years ago, was one of the first configurator-type tools and has been moderately updated to aid user specification.
Advanced simulator-type Web tools suitable for use by designers now seem a long shot. The Virtual Power Lab of Artesyn Technologies (Framingham, Mass.) took a step in that direction a few years ago. In general, though, simulation is best done by the vendor in-house; designing from a distance isn't often practical. Industry consensus sees such Web simulator tools as five years away, at least.
Lambda, an Invensys company
Tyco Electronics Custom Power