Power Electronics

Coping With the Challenge of Shrinking Magnetics

As semiconductor geometries shrink into the nanometer range and microprocessor clocks enter multi-GHz speed, the pressure mounts on dc-dc converters powering the new wave of CPUs. Besides employing the right circuit topology and the associated semiconductor ICs, the passives and magnetic components must also be optimal to meet performance, size, and cost requirements of the new generation of VRMs and other dc-dc converters. In fact, the role of magnetics in new generation converters, whether used in PCs or front-end telecom systems, is becoming crucial. Because these components primarily determine the overall footprint and profile of the power supply, in addition to performance and cost, the drive to improve them continues unabated at research centers around the world.

Consequently, rapid changes in the semiconductor world are impacting the magnetics world. Low voltage and high current needs of latest VRMs housed in compact packages with very low profile and high efficiency is creating a challenge for magnetic component suppliers. While they are adept at winding plain old circular wires, they're rapidly revamping their skills to meet future challenges — not to mention core material providers who must keep up to their users demands. Thus, suppliers of magnetic components have become more creative in handling new materials and nontraditional flat wires to achieve high current in low inductance parts in miniature packages. It's not surprising to see IC vendors and magnetic component makers working together to address the problems of power supply designers.

With the ongoing pressure to keep pushing the efficiency bar higher in thinner compact power-hungry bricks and modules of today, the burden seems to have fallen on magnetics. For that extra help, power supply designers are turning to planar magnetic technology. Just a few years ago, it was considered an R&D curiosity. However, recent improvements in core materials, geometries and design techniques have made this innovative technology a reality. In addition to better thermal and heat dissipating characteristics, the benefits of lower leakage inductance and consistent and repeatable characteristics have made planar magnetics an attractive choice for a whole new generation of SMPSs. Concurrently, like other technologies, integration efforts are also underway in this sector to pack more components in a single magnetic package. As indicated by the cover story of this special issue, beginning on page 22, developers are racing to blend high power inductors and transformers of power supply circuits on a single magnetic core structure.

Therefore, at the recent Applied Power Electronics Conference (APEC 2003) in Miami, Fla., it was not surprising to see that majority of dc-dc converter brick and module vendors were using planar magnetics to accomplish their end goals. And key material suppliers were flaunting their ability to supply planar cores for discrete designs, as well as embedding them on printed circuit boards (PCBs). At this rate of progression, it will soon proliferate across a wide variety of general-purpose high frequency, high efficiency dc-dc converter designs.

Despite this progress, planar magnetics remains a custom effort, focused on embedded transformers and inductors on PCBs. Planar magnetics is still a sophisticated part of the power supply design process that requires specialized skills that are not easily available.

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