The current paper presents the design, analysis, and implementation of a low-profile resonant dc-to-dc converter that utilizes a coreless printed circuit board transformer as a substitute for the conventional magnetic core-based transformer. A prototype series resonant converter, fabricated in a 40 mm80 mm area with a 4 mm thickness while achieving the maximum efficiency of 85% at a 58 W output power, is used as an example to address the theoretical and practical issues involved in the design, analysis, and implementation of a PCB transformer-based low-profile dc-to-dc converter.