Application and analysis of adjustable profile high frequency switchmode transformer having a U-shaped winding structure

This paper introduces a newly developed high frequency switchmode transformer consisting of a U-shaped winding and a multiple toroidal magnetic core element structure. The new transformer with adjustable profile structure exhibits a utilization of the core area which is better than a planar core but worse than a pot core. The coupling efficiency of the transformer is much higher than a planar core structure. The numerical results for the flux density and eddy current density have been compared with those of a planar and pot core transformer structure. The maximum normalized eddy current density of the new structure is 50% less than a pot core or a planar core. The experimental results at low current excitation indicate that the copper loss is lower at high frequency (10 MHz) when using the new winding structure. The core loss is primarily due to hysteresis and increases significantly if a MnZn based material such as TDK PC40 is used at frequencies above 2 MHz.