An isolated switched-mode power converter converts power from an input source into power for an output load. Power switches within a primary-side power stage control the amount of power input to the power converter and, ultimately, provided to the output load. A digital controller on the secondary side of the power converter generates signals to control the power switches. This generation is based upon closed-loop (feedback) control as well as feedforward control. The feedforward control compensates for variations in the voltage of the input source. The input voltage is estimated by sensing a rectified voltage at a node between a secondary winding of the isolation transformer and an output filter. The feedforward compensation modifies the generated switch control signals based upon the sensed rectified voltage.