Method and apparatus of providing a biased current limit for limiting maximum output power of power converters

A biased current-limit circuit for limiting a maximum output power of a power converter, comprising:

• an oscillator, generating a pulse signal and an oscillation signal;
• a waveform generator, coupled to the oscillator for generating a waveform signal in response to the oscillation signal;
• a sample-hold circuit, sampling the waveform signal to generate a hold signal in response to a switching signal, the sample-hold circuit further sampling the hold signal to generate a current-limit threshold in response to a second-sampling signal, wherein the switching signal is utilized to switch a transformer of the power converter, and the second-sampling signal is correlated to the pulse signal;
• and
• a current comparator, comparing a current-sensing signal with the current-limit threshold to limit a maximum on-time of the switching signal, wherein the current-sensing signal is correlated to a switching current of the transformer.