Patent ID: 8536851

Claim:
A system controller for regulating a power conversion system, the system controller comprising: a voltage detector configured to receive an input signal and output a detection signal based on at least information associated with the input signal; and a mode controller configured to receive the detection signal and a feedback signal associated with an output signal of a power conversion system, generate a switch signal based on at least information associated with the detection signal and the feedback signal, and output the switch signal to a switch in order to affect a first current flowing through a primary winding of the power conversion system; wherein the mode controller is further configured to: process information associated with the detection signal and a first threshold; determine whether the detection signal and the first threshold satisfy one or more first predetermined conditions; process information associated with the feedback signal and a second threshold; determine whether the feedback signal and the second threshold satisfy one or more second predetermined conditions; determine whether an operation mode for the power conversion system is a quasi-resonant mode based on at least whether the one or more first predetermined conditions are determined to be satisfied and whether the one or more second predetermined conditions are determined to be satisfied; process information associated with the feedback signal, the second threshold, and a third threshold; determine whether the feedback signal, the second threshold, and the third threshold satisfy one or more third predetermined conditions; and determine whether the operation mode is a quasi-resonant foldback mode based on at least whether the one or more third predetermined conditions are determined to be satisfied, the quasi-resonant foldback mode being different from the quasi-resonant mode; wherein the switch signal corresponds to the operation mode for the power conversion system.