Orthogonally Variable Inductors with Poloidal AC Currents and Axial DC Fields

Prevailing current-actuated variable inductors for power converter applications have a major drawback; the induced ac and actuation dc magnetic fields, are parallel: unwanted field coupling results, which significantly reduces performance. This paper presents the orthogonal-axes variable inductor (OAVI), a means for varying inductance where dc and ac currents and their respective fields are orthogonal. An OAVI variant, OAVI-PM, includes permanent magnets to reduce the dc winding power dissipation for a desired inductance value. Materials and implementation considerations are discussed. Finally, an application to the quasi-square-wave ZVS buck converter in which inductance bounds are determined via the State Plane Diagram with experimental results is presented.