Tiny packages, new architectures rock distributed power

Power-One says it is changing the shape of power. Vicor could say something similar. Both companies have introduced small, low-cost, distributed-power products that are radically different—at least in packaging—from almost all others in the market (Picture). In Vicor's case, some products in its FPA (factored-power-architecture) lines differ not only in their size and power density, but also in their electrical architecture. The company calls its new family members PRM (preregulator module) and VTM (voltage-transformation module). A PRM accepts an unregulated input voltage and produces a regulated but nonisolated output voltage approximately equal to the input. A VTM accepts the PRM output, steps it down by a turns ratio to a voltage appropriate for the load, and provides isolation. With the proper connection, which does not affect the isolation, a PRM corrects for the inherently unregulated VTM's internal impedance, thus enabling the VTM to produce a regulated output.

The system achieves efficiencies greater than 95% while operating at a fixed frequency in the neighborhood of 4 MHz. Competitors have been unable to achieve acceptable efficiency at such high frequencies. In addition, FPA represents a break from Vicor's unique tradition of operating its modules at variable frequencies.

The system's apparent Achilles' heel is that designs that use multiple low voltages incur the cost of separate isolation for each voltage, whereas conventional DPAs (distributed-power architectures) provide isolation at one point for multiple outputs. Vicor's pricing suggests, however, that FPA can often produce multiple outputs at lower cost than can conventional DPAs.

For system designers who are still uncomfortable with the unusual electrical architecture but like the new packaging, which Vicor calls VIC (V·I Chip), the company has also introduced a family of isolated, unregulated BCMs (bus-converter modules). The BCMs, which power nonisolated, regulated POL (point-of-load) dc/dc converters, offer small dimensions (21.5×32×6 mm for a 200W unit) and power density of 800W/in.³ maximum. Some BCMs—and other VICs—mount in boards with cutout areas, thus reducing the above-board height to 4 mm. Prices for 200W BCMs are as low as $24 (OEM quantities), or 12 cents/W.

Power-One's X3015P, a 15A regulated-output, nonisolated POL dc/dc converter, the first member of the maXyz family, contains 22 components yet measures just 10×12×1.5 mm. The unit, an MCM (multichip module) packaged in a 20-pin LGA (land-grid array), accepts inputs of 3 to 6V dc, produces outputs of 0.75 to 4V dc, and requires only four external components. When it receives 5V input power and produces 15A at 2.5V, the UL-recognized unit, which operates at a programmable fixed frequency of 300 to 500 kHz, dissipates less than 4W with efficiency of 90.5%. Prices are as low as $5.50 (large OEM quantities). Philips (www.semiconductors.philips.com) and International Rectifier (www.irf.com) also manufacture MCM POL converters, but, according to Power-One, UL does not recognize either competitive unit, neither unit operates from a supply voltage as low as 3.3V, and both units require at least twice the number of external components.

Power-One, 1-805-987-8741, www.power-one.com.

Vicor, 1-978-470-2900, www.vicorpower.com.