In a switched mode power supply (SMPS) then selectively operates in continuous current mode (CCM) and discontinuous current mode (DCM), the minimum switching frequency of the SMPS is adjusted by setting a minimum duration for DCM operation. A resistance value applied to an external pin of the SMPS controls the duration of a timer that is reset in CCM and activated upon entering DCM. Upon expiration of the variable duration, the SMPS reverts to CCM for at least one switching cycle. This allows the SMPS minimum effective switching frequency to be set, for each application in which the SMPS is deployed, at a level that avoids audible noise (but which may be lower than an ultrasonic frequency), thus taking maximum advantage of the efficiencies of DCM operation under light load conditions.