LINE RIPPLE COMPENSATION FOR SHIMMERLESS LED DRIVER

摘要

A power converter controller includes an oscillator, a drive circuit, and a frequency modulator. The drive circuit receives a clock signal from the oscillator and generates a drive signal in response thereto to control switching of a switch of the power converter. The frequency modulator controls the frequency of the clock signal in response to an inductor voltage across an inductor of the energy transfer element to reduce a peak-to-peak ripple value in an output current of the power converter. The frequency modulator controls the frequency of the clock signal during each line half cycle to be a fixed frequency when the inductor voltage is less than or equal to a threshold voltage. When the inductor voltage is greater than the threshold voltage the frequency modulator varies the frequency to be less than the fixed frequency to adjust a shape of an input current of the power converter.