Method and apparatus to limit maximum switch current in a switching power supply

摘要

An example integrated circuit for use in a power supply includes a switch, a terminal and a controller. The controller is coupled to control switching of the switch to regulate the output of the power supply in response to a feedback signal received at the terminal. The controller includes a comparator and an oscillator. The comparator is coupled to detect when a switch current through the switch exceeds a current limit and the oscillator is coupled to extend an off time of the switch in response to the comparator detecting that the switch current exceeds a current limit and if an on time of the switch is substantially equal to a sum of a leading edge blanking period and a current limit delay time period. The oscillator extends the off time of the switch independent of the feedback signal.