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Abstract
This paper presents an approach to efficiency optimization in digitally controlled flyback dc–dc converters over wide ranges of operating conditions. Efficiency is characterized and optimized based on power loss modeling and multivariable nonlinear constrained optimization over power-stage and controller parameters. A valley switching technique is adopted to reduce MOSFET turn-on switching loss in discontinuous conduction mode. An optimization procedure is formulated to minimize power loss weighted over a range of operating points, under a cost constraint. A lookup table-based digital controller is applied to achieve on-line efficiency optimization by programming switching frequencies and operating modes based on the efficiency optimization processes. The proposed on-line efficiency optimization approach is verified by experimental results on a low cost 65 W flyback dc–dc prototype.