Elimination of Leakage Effects Related to the Use of Windings with Fractions of Turns

Obtaining exact output voltages from transformers is a difficult task due to discrete turn ratios. This becomes even more difficult in modern switching power supplies operating above 100 kHz because the number of turns per winding is reduced. For multichannel applications different methods of postregulation have been employed, resulting in increased power dissipation and power supply cost. A new method of dealing with this problem has been developed, offering a higher degree of flexibility. This technique allows the use of fractions of turns, while maintaining low leakage inductances. Theoretical analysis of leakage effects related to fractional turn windings has been derived and tests on an experimental transformer have been performed.