Research on Cross Regulation Rate Control Based on Equivalent Leakage Inductance Constraint of Flyback Multi-Winding Transformer

This paper proposes a cross regulation rate control method based on equivalent leakage inductance constraint of multi-winding transformer, to solve the problem of other output voltages seriously deviating from their rated values caused by changes in one load of Flyback converters. A detailed analysis is conducted on the distribution characteristics of leakage inductance in multi-winding transformers, revealing its inherent connection with the output voltage cross regulation problem. The mathematical relationship that can accurately predict the cross regulation rate through leakage inductance is derived, and the design principles for the leakage ratio of each winding in transformers are explained. A vector called magnetic field intensity area is defined to measure the leakage inductance value, and a multi-winding equivalent leakage inductance model that can be automatically solved is established. The optimal winding arrangement that takes into the requirements of low primary leakage inductance and proportional secondary leakage inductance is selected. An experimental prototype of a 30W six output Flyback converter is built, and the cross regulation rate is tested to be as low as 5%. The correctness and feasibility of the proposed multi-winding equivalent leakage inductance model and cross regulation rate control method are verified.