BUCK-BOOST CONVERTERS WITH RAMP COMPENSATION

摘要

A control method used in a four-switch buck-boost converter includes: filtering the voltage at the first switching node and generating a first ramp signal; filtering the first ramp signal and generating a first average signal; filtering the voltage at the second switching node and generating a second ramp signal; filtering the second ramp signal and generating a second average signal; generating a set signal based on the first ramp signal, the first average signal, the second ramp signal, the second average signal, a reference signal, and a feedback signal indicative of the output voltage, so as to turn on the first and third transistors, and turn off the second and fourth transistors; turning off the first transistor and turning on the second transistor when the on-time of the first transistor reaches a first time threshold; and turning off the third transistor and turning on the fourth transistor when the on-time of the third transistor reaches a second time threshold.