Patent ID: 8730687

Claim:
A switching controller for a power converter, comprising: a PWM circuit, generating a switching signal coupled to switch a transformer of said power converter, wherein a feedback signal is coupled to control and disable said switching signal; a detection circuit, coupled to said transformer via a resistor for generating a valley signal in response to a waveform of said transformer, wherein said valley signal represents a valley number of said waveform; a signal generation circuit, coupled to receive said feedback signal and said valley signal for generating an enabling signal, wherein said enabling signal has a hysteresis characteristic to lock said valley number of said waveform; an oscillation circuit, generating a maximum frequency signal, wherein said maximum frequency signal associated with said enabling signal generates a turning-on signal, said turning-on signal is coupled to enable said switching signal; wherein said feedback signal is correlated to an output load of said power converter, a maximum frequency of said turning-on signal is limited.