A method controls a power switch and senses a primary current through a transformer primary winding coupled to the power switch and deactivates the switch responsive to the sensed primary current reaching a current sensed reference. A demagnetization mode is initiated responsive to deactivating the power switch. During this mode a first capacitance is charged with a first charging current to generate the current sensed reference. The first charging current is based on a bias signal. A second capacitance is charged with a second charging current to generate the bias signal. The second charging current is based on a compensation signal. A third charging current generates a comparison signal, the third charging current based on the current sensed reference. The compensation signal is based on a difference between the comparison signal and an internal reference and the power switch activated based on a secondary current in a secondary transformer winding.