Switching Power Supplies A - Z

The best book I've ever read about DC-DC conversion is Switching Power Supplies A - Z by Sanjaya Maniktala (on Amazon here). He starts at a very basic level, even explaining how capacitors and inductors work. Your physics background would help you there. Instead of just throwing equations at you, the book gives you a fundamental understanding of how DC-DC circuits work. If you read this book and understood it, you'd be an expert.