This Small Business Innovation Research (SBIR) Phase I project develops coreless transformers in switching power supplies for Mhz and greater frequencies. The miniaturization of integrated circuits has not been accompanied by a similar reduction in the size of their power supplies. Although high-frequency operation has always been associated with smaller energy storage components, smaller power transformers are limited by increasing core and ohmic losses and by parasitic effects at higher frequencies. A new concept is a transformer without ferrite core and consisting of a cascade of printed striplines on multilayer structures. The idea is to store and transfer energy by electromagnetic waves through waveguiding structures (transmission lines). Important features of these transformer structures are stripline lengths on the order of the guide wavelength and a turns-ratio determined by the stripline characteristic impedance. Phase constants and line impedance of the striplines, as a function of various parameters, will be determined by Computer Aided Design (CAD) methods. Practical design issues will be addressed including maximum possible voltage ratio obtainable with the constraint of the device's dimensions, possible low-loss materials with high permitivity or permeability for wavelength reduction, a bandwidth enhancement method, and the geometrical shape of the stripline for the best use of the planar surface. Other design issues will include power handling and heat dissipation capabilities. Transformers are important in power processing circuits, which are required in all common electric appliances, cellular phones, television sets, VCRs, computers, etc. Size and weight reduction and speed enhancements require new power converters with switching frequencies in the Mhz and greater range. An absence of satisfactory electronics power transformers in this range may be worthwhile commercially.
