Patent ID: 8717785

Claim:
An integrated circuit controller for a power converter, the controller comprising: a track and hold circuit to be coupled to receive a signal from a single terminal of the controller, the signal to represent an output voltage of the power converter during at least a portion of an off time of a first switch, wherein the track and hold circuit includes a first capacitor coupled to provide a first voltage that tracks the signal during the portion of the off time of the first switch and holds the first voltage at an end of the portion of the off time; a sample and hold circuit coupled to the track and hold circuit to sample the first voltage when the first voltage is held on the first capacitor, wherein the sample and hold circuit includes a second capacitor coupled to integrate an output of the first capacitor over a sample period that ends before a next on time of the first switch and to hold a second voltage representative of the first voltage after the sample period, wherein the second capacitor has a capacitance value larger than that of the first capacitor; and drive logic coupled to the sample and hold circuit and coupled to control the first switch to regulate an output of the power converter in response to the second voltage, wherein the drive logic includes: a current limit generator coupled to the second capacitor to generate a variable current limit threshold in response to the second voltage; and a comparator coupled to disable the first switch during the on time of the first switch in response to comparing a current sense signal that is representative of a switch current in the first switch with the variable current limit threshold.