High efficiency, high density MHz magnetic components for a low profile converter

A highly efficient (99.5%) transformer and resonant inductor with very high power density (1500 W/in³) and low profile (height<0.4 in) are described. The design of these components is based on a tradeoff study which establishes the optimum operating frequency to be around 1 MHz. The transformer utilizes highly efficient thin flex circuit windings. The windings are novel folded copper patterns, eliminating the need for vias and resulting in very low DC resistance. The winding arrangements have a high degree of interleaving between the primary and secondary windings, resulting in very low AC conductor losses due to skin and proximity effect. The core is a low profile design with very low core losses. The resonant inductor, instead of using low permeability material, uses highly efficient high permeability material. The desired low permeability is then achieved by introducing a large number (>40) of small gaps to reduce the effect of fringing fields. The high-frequency loss measurements for such highly efficient inductors require a special ring down measurement setup