Peak power limitation and overpower protection for switched-mode power supplies

摘要

A method of cycle-by-cycle operation of a switched-mode power converter includes converting an input voltage at the primary side to an output voltage at the secondary side by switching a transistor connected to the primary side from an on-state to an off-state during the present cycle, detecting valleys in a voltage across the transistor in the off-state, determining which valley at which the transistor is to be switched from the off-state to the on-state in the next switching cycle, and determining a maximum peak current limit for the primary side above which the transistor is switched from the on-state to the off-state in the next switching cycle. The maximum peak current limit is determined as a function of the input voltage and the valley at which the transistor is to be switched from the off-state to the on-state in the next switching cycle. Forced valley switching techniques are also disclosed.