Patent ID: 7443700
Filing Date: 2008-10-28
Classification: H02M

Abstract:
1. A method for limiting an output current of a power supply over multiple switching cycles in a constant current mode using pulse width modulation, said power supply having a primary side and a secondary side wherein an inductor, having a magnetizing inductance, electrically separates said primary and secondary sides, the method comprising the steps of: generating a sense voltage signal on the primary side that is proportional to an output voltage signal on the secondary side; measuring a reset time on the primary side using said sense voltage signal, said reset time representing a duration of a current pulse on the secondary side; and generating a digital feedback voltage signal on the primary side that is used to maintain a substantially constant current on the secondary side, said digital feedback voltage signal representing the on-time for a subsequent switching cycle, wherein said digital feedback voltage signal is generated without any representation of the input voltage or any representation of the magnetizing inductance.