PWM CONTROLLER CAPABLE OF CONTROLLING OUTPUT CURRENT RIPPLE VIA A RESISTOR, AND LED DRIVER CIRCUIT USING SAME

摘要

A PWM controller capable of controlling output current ripple via a resistor, and an LED driver circuit using the PWM controller, the PWM controller including: a sawtooth signal generation unit for generating a sawtooth signal, of which a slope of a positive ramp is controlled by a control current, and the control current is determined by an external resistor; an amplifier having a positive input end coupled with a reference voltage, a negative input end coupled with a current sense signal, and an output end coupled with an external capacitor for generating a comparison signal; and a comparator having a positive input end coupled with the sawtooth signal, a negative input end coupled with the comparison signal, and an output end for generating an end-of-conduction signal, wherein the end-of-conduction signal will become active whenever the sawtooth signal reaches the comparison signal.

主权项

1. A PWM controller capable of controlling output current ripple via a resistor, comprising:
a sawtooth signal generation unit, used for generating a sawtooth signal according to a control current, a positive voltage signal, and a constant current, wherein said control current is determined by an external resistor, and said sawtooth signal has a positive ramp, of which a slope is proportional or inversely proportional to said control current; an amplifier having a positive input end coupled with a reference voltage, a negative input end coupled with a current sense signal, and an output end coupled with an external capacitor for providing a comparison signal; and a comparator having a positive input end coupled with said sawtooth signal, a negative input end coupled with said comparison signal, and an output end providing an end-of-conduction signal, wherein said end-of-conduction signal will become active whenever said sawtooth signal reaches said comparison signal.