Abstract: An isolated power converter includes: a transformer having primary winding and first and second auxiliary windings on the primary side; a converter stage configured to convert a DC input for driving the primary winding and having a resonant capacitor electrically connected to the primary winding; a controller configured to control switching of the converter stage; and a voltage supply circuit configured to select a first voltage as a supply voltage for the controller if a voltage proportional to a secondary side voltage of the transformer is at a first level or select a second voltage as the supply voltage if the voltage proportional to the secondary side voltage is at a second level greater than the first level. The first voltage corresponds to a summation of voltages across the first auxiliary winding and the resonant capacitor. The second voltage corresponds to a voltage across the second auxiliary winding.

Abstract: In accordance with an embodiment, a power conversion method includes operating a power converter circuit in one of a first operation and a second operation mode based on a feedback signal and a signal level of an output signal at an output. The power converter includes a transformer with a primary winding and a secondary winding, a first electronic switch connected in series with the primary winding, and a rectifier circuit connected between the secondary winding and the output and comprising a second electronic switch.