Power Electronics Technology July 2008 www.powerelectronics.com14 High-Frequency Inductors By Weyman Lundquist, President and Engineering Manager, West Coast Magnetics, Stockton,Calif.

ower electronics are rapidly expanding into new applications as high-power semiconductor devices increase their rated operating current and frequencies to higher and higher levels. As a basic building block of virtu-ally all power electronics equipment, inductors have a unique potential for improvement. That’s because inductors are usually the largest, most expensive and volumetrically inefficient items in a power system. Consequently, improvements in inductor design can have a great impact on the size and cost of the inductor, which can have a significant impact on the rest of the power electronics design. One way to help shrink a power inductor is to reduce its losses at high frequencies, so that a lower value of inductance may be specified and, therefore, a smaller inductor may be used in the system. To lower an inductor’s power losses at high frequencies, designers must understand the role of winding losses and the options available for reducing those losses. Those op-tions include a new foil-winding technique that achieves low losses for inductors operating at high ripple current and high power levels. For designers looking to optimize inductor designs using Litz wire, there’s also a new tool to aid the design process. This tool takes the form of a freeware program that allows the user to optimize the stranding and positioning of the winding inside of the available winding window