Patent ID: 7061780

Claim:
A switching control circuit for a primary-side-controlled power converter, comprising: a switch for switching a transformer; wherein said transformer is coupled to an input voltage of the power converter; a sense device, which is coupled to said transformer for sensing current or/and voltage of said transformer; a switching signal, coupled to said switch for regulating an output voltage and a maximum output current of the power converter; and a controller, coupled to said transformer to generate a first feedback signal and a discharge-time signal by multi-sampling a voltage signal and a discharge time of said transformer during an off-time of said switching signal, said controller further coupled to said sense device to generate a second feedback signal in response to said discharge-time signal and a current signal of said transformer, wherein said controller generates said switching signal in response to said first feedback signal, said controller controlling a switching frequency of said switching signal in response to said second feedback signal.