Diodes Incorporated
INPUT VOLTAGE DEPENDENT CONTROL FOR ACTIVE CLAMP FLYBACK

Abstract:

A method for controlling a power converter includes turning on a power switch to maintain a desired output voltage, wherein the power switch is coupled to a primary winding to control a primary current flow and the output voltage is provided by a secondary winding. The method also includes adding a capacitance in parallel to the power switch at a time determined by a magnitude of an input voltage to the power converter. Here, the timing of adding the capacitance depends on the operation mode of the power controller. In a low input voltage mode, the capacitance is added in a demagnetization-time during which the secondary winding discharges. In a high input voltage mode, the capacitance is added in a discontinuous time.