Mag amp (magnetic amplifier) output regulators have recently become very popular as a means of regulating more than one output of a switching power supply. They offer extremely precise regulation of each independant output, and are efficient, simple and very reliable. Mag amps are particularly well suited for outputs with currents of 1 A to several tens of amps; however, they are also used at lower currents where tight regulation and efficiency are extremely important. The advant of cobalt-based amorphous alloy has made possible the design of mag amps that can operate at higher frequencies than previously possible in output regulation. Cores made from this alloy exhibit: (1) a high squareness ratio, giving rise to low saturated permeability; (2) low coercive force, indicating a small reset current and (3) low core loss, resulting in a smaller temperature rise. Although there are alternatives for post output regulation, mag almp regulation is the most efficient, reliable and low cost design.
This article describes the operation of modern mag amp regulators and guides the reader through the design of the saturable reactor and the control circuitry to achieve a 3.3 V, 20 A output. This mag amp is being developed to power the new generation of ultra-compact integrated circuits such as Intel's new Pentium microprocessor.
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