check out ti.com for seminars on switch mode power supplies and related techniques -- this might be under the old name of "unitrode power supply seminars"
Another information that may help you- - BPB Publication, New Delhi publishes a good book on Transformer designing(all type). DESIGNING COILS AND TRANSFORMERS By M.C. Sharma ISBN : 81-7656-796-5
also
PRACTICAL TRANSFORMER DESIGN HANDBOOOK By Eric Lowdon
ISBN : 81-8333-303-0