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Amorphous Magnetic Noise Suppressors

Amorphous Magnetic Noise Suppressors
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Amorphous Magnetic Noise Suppressors - 1

Amorphous Magnetic Noise Suppressors How Do They Work? Toshiba’s amorphous magnetic Noise Suppressors are essentially small saturable cores. The square-shaped magnetic hysteresis of these devices is key to their noise suppression ability. They are most effective at suppressing the noise associated with the reverse recovery of diodes. Toshiba offers two types of devices, which have been specifically designed for noise suppression: AMOBEADS® and SPIKE KILLER™. AMOBEADS are smaller than SPIKE KILLERs and have been designed for a single turn. They are simply slipped over the lead of a diode and require no additional circuit board space (also available in a surface mount configuration). SPIKE KILLERs are used when AMOBEADS are insufficient to handle the noise in a particular circuit. They are typically wire wrapped as an inductor. For even larger noise problems, Toshiba’s saturable cores can be used as SPIKE KILLERs. Figure 1: Current Through a Switching Diode www.suppressnoise.toshiba.com To better understand the mechanism by which these devices suppress noise, consider a switching diode, with current as shown in Figure 1, in series with a saturable reactor (i.e. wire wrapped saturable core). Figure 2: Magnetic Behavior of a Saturable Core Figure 2 shows the magnetic hysteresis curve the reactor would follow. The Magnetic Field, H, is proportional to the current flowing in the reactor while the slope of the hysteresis curve is proportional to the inductance of the reactor at the corresponding value of current. When the diode is conducting (Region I in Figure 1), current flows in one direction through the reactor. This situation corresponds to the nearly horizontal region in Figure 2. The slope of the curve in this region is small, therefore a very low inductance is put in series with the diode while it is conducting.

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Amorphous Magnetic Noise Suppressors - 2

CONTACT INFORMATION AMORPHOUS CORES Advanced Materials Division 290 Donald Lynch Blvd. Marlborough, MA 01752 amd@taec.toshiba.com Tel: 508-303-5041 Fax: 508-481-8890 Dexter Magnetic Technologies Tel: 800-775-3829 Fax: 877-221-5052 info@dextermag.com Now suppose the current changes sign (Region II in Figure 1). Only after the current crosses zero will the magnetization be on the inclined portion of Figure 2. This region of the curve has a large slope and so a high inductance is put in series with the diode. The presence of the saturable reactor thus impedes further changes in current. The...

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