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High power inductors stay cool in high frequency apps

Posted: 09 Aug 2004 ?? ?Print Version ?Bookmark and Share

Keywords:j.w. miller? toroid inductor? magnetic? kool mu? powder core?

J.W. Miller's new low loss series of high power toroid inductors is the company's first standard product offering to incorporate Magnetic Inc.'s Kool M? ferrous alloy powder core. Although typically more expensive than powder iron cores, they offer a key advantage over these lower cost materials by preventing the distributed air gap cores from getting too hot in high frequency applications.

Typically, core losses as a result of using powder iron in high frequency applications can result in temperature rises which contribute to poor performance, and in some cases, component failures, in power supplies including dc-dc converters, switching power supplies or voltage regulators, said Andy Chow, chief design engineer for J.W. Miller. The new 2100LL, 2200LL and 2300LL devices address these issues and allow the component to maintain a low temperature rise, which makes it suitable for low losses at high frequencies.

Key factors to remember in choosing the right inductor for an application is that core materials do impact an inductor's frequency range and core losses heat the inductor. Chow said iron powder cores will absorb a lot of power and turn that into heat at high frequencies. By switching to a low core loss material such as Sendust, or what's more commonly known as Kool M?, in high frequency environments the core won't produce as much heat as generated in iron powder, he said.

Several power solution manufacturers have recommended in their application notes the use of either Magnetics Inc.'s Molypermalloy or Kool M? cores for use in high switching frequencies primarily because high efficiency converters generally can't withstand the core loss associated with low cost powdered iron cores. Ultimately, it could lead to a fast rise in inductor ripple current and thus output voltage ripple, they reported.

Available in horizontal and vertical mounting configurations, the LL series offers an inductance range from 1?H to 1,000?H with a 34A maximum rated current. Custom inductance ranges are available. Featuring a self-shielding design, the inductors offer an operating temperature range of -55C to 125C.

It's also possible to achieve smaller core sizes with the Kool M? powder cores as compared with powder iron cores in similar high-frequency applications. This is a result of the 10,500 gauss saturation level of the Kool M? core, which provides a higher energy storage capability in comparison with gapped ferrite E cores.

The core size can be smaller with the Kool M? material for the same amount of energy storage, Chow said. However, the company selected a similar core size as the powder iron version in order to maintain the same footprint as in the original series.

- Gina Roos

eeProductCenter





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