Patent ID: 7663351

Claim:
A controller for power converter comprising: a first voltage rail; a pin that is adapted to receive a synchronization signal; a synchronization circuit including: a first switch that is coupled to the first voltage rail, wherein the first switch includes a control electrode; a first resistive element that is coupled between the first switch and the pin; a second switch that is coupled to ground, wherein the second switch includes a control electrode; and a second resistive element that is coupled between the second switch and the pin; a pulse generator that is coupled to the pin; a logic circuit that is coupled to the pulse generator; an oscillator including: a latch having a set input, a reset input, and an output, wherein the set input is coupled to the logic; an RC network having a third switch and an RC node, wherein the third switch is coupled to the output of the latch at its control electrode; a first comparator having a first input, a second input, and an output, wherein the first input of the first comparator is coupled to the RC node, and wherein the output of the first comparator is coupled to the logic circuit and to the control electrodes of the first and second switches, and wherein the first comparator compares the voltage at the RC node to a first threshold voltage; a second comparator having a first input, a second input, and an output, wherein the first input of the second comparator is coupled to the RC node, and wherein the output of the second comparator is coupled to the reset input of the latch, and wherein the second comparator compares the voltage at the RC node to a second threshold voltage.