Power converters employing extrapolative conductance mode (ECM) control utilize periodic current sampling and employ an extrapolation method to determine charge pulse duration. In preferred embodiments, the operating frequency of the converter is altered in response to current sample perturbations to dissipate sub-harmonic oscillations associated with duty cycles of 50% or greater without the use of slope correction. High current monitor signal-to-noise ratios may be achieved in conjunction with low power losses, and a first order output filter response may be obtained for duty cycles greater than 50%.