Patent ID: 6958920

Claim:
A control circuit for controlling a switching power converter, wherein said switching power converter includes a power magnetic element having at least one power winding, a second winding, a switching circuit for periodically energizing said at least one power winding, wherein said control circuit controls said switching circuit, and wherein said control circuit comprises: an integrator having an input coupled to said second winding for providing an output representing an amount of magnetic energy storage in said power magnetic element; a comparison circuit for detecting when said output of said integrator indicates that said amount of magnetic energy storage has reached a level substantially equal to zero; a sampling circuit having a signal input coupled to said second winding and a control input coupled to an output of said comparison circuit for sampling a voltage of said second winding in conformity with said integrator indicating that said amount of magnetic energy storage has reached said substantially zero level; and a switch control circuit having an output coupled to said switching circuit and having an input coupled to an output of said sampling circuit, whereby said switching circuit is controlled in conformity with said sampled voltage.