This paper explores a new application field of power electronics. A soft-switching quasiresonant flyback converter is designed for transdermal drug delivery (TDD) applications with the processes of electroporation and phonophoresis. The converter can generate a constant DC voltage output for a pulsed generator in electroporation processing and can generate a variable DC voltage to drive a radial type of piezoelectric device in axial vibration mode for phonophoresis processing. Weight and size of the system can be reduced significantly, and its efficiency can be correspondingly improved, which is suitable for designing a portable TDD system. Experimental results have verified the feasibility and effectiveness of the proposed ideas.