A close-loop PWM controller for a primary-side controlled power converter is provided. A voltage-waveform detector produces a voltage-feedback signal and a discharge-time signal. A current-waveform detector generates a current-waveform signal by measuring a primary-side switching current. An integrator generates a current-feedback signal by integrating the current-waveform signal with the discharge-time signal. A time constant of the integrator is correlated with a switching period of the switching signal, therefore the current-feedback signal is proportional to the output current of the power converter. The close-loop PWM controller further including a voltage-loop error amplifier and a current-loop error amplifier. A PWM circuit and comparators control the pulse width of the switching signal in response to the outputs of the voltage-loop error amplifier and the current-loop error amplifier. The output voltage and the maximum output current of the power converter are therefore regulated.