The present invention is directed to a switch mode power converter for supplying an output power to a load, which includes a switching device having a switching input, a switching output, and a control input for enabling or disabling the switching device from conducting current from the switching input to the switching output. The converter also includes a network in which the switching device input, the switching device output, and the load are connected together to form a circuit. The converter also includes a bias winding in the circuit for producing a bias voltage representative of the output power, and a control circuit. The control circuit is for (a) determining the rate of change of the bias voltage, (b) characterizing the rate of change, and (c) controlling the control input as a result of the characterization (b).