Abstract: A buck-boost power converter includes a power stage to convert an input voltage to an output voltage, an error amplifier to generate an error signal according to a reference voltage and a feedback signal proportional to the output voltage, a ramp generator to provide two ramp signals, and two comparators to generate two control signals according to the error signal and the two ramp signals to drive the power stage. By using feed-forward technique, one of the two ramp signals has a peak varying with the input voltage and the other ramp signal has a valley varying with the input voltage, so that the power converter has fast line response.