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An auto-tuning adaptive digital controller with maximum efficiency point tracking to optimize dc-dc converter switching frequency is presented in this paper. The adaptive-frequency-optimization (AFO) controller adjusts the dc-dc converter switching frequency while tracking the converter minimum input power (maximum efficiency) point under variable operation conditions of the power converter. The AFO digital controller continuously finds the optimum switching frequency that will result in minimum total power loss while converter parameters and conditions vary. Moreover, the presented controller addresses the issues that are associated with implementing variable switching frequency in digital controllers, including limit cycle oscillation and possible performance degradation, by using a dynamic algorithm to maintain converter system stability under variable switching frequency operation. In this paper, the proposed controller is discussed, analyzed, and its digital control algorithms and experimental results are presented.