Patent ID: 8031492
Filing Date: 2011-10-04
Classification: H02M

Abstract:
1. A PWM controller for compensating a maximum output power of a power converter, comprising: an oscillator, for generating a pulse signal; a control circuit, coupled to the oscillator for generating a PWM signal in response to the pulse signal, wherein the PWM signal controls a power switch; and a two-level limiter, coupled to the control circuit for generating a two-level limit signal in response to an on-time of the PWM signal, wherein the two-level limit signal is formed by a first-level signal and a second-level signal during a switching period of the PWM signal, and the first-level signal is used to limit the maximum output power of the power converter under a high-line input voltage with a heavy-load condition, and the second-level signal is used to limit the maximum output power of the power converter under a low-line input voltage with the heavy-load condition.