Buck-boost switching power converter, the control circuit and mode switching control unit

Proposed a buck boost switching power converter for buck boost switching power converter mode switching control unit and associated control circuitry. The switching control unit comprises a buck circuit and a comparator detecting a duty ratio boosting duty ratio detection pattern comparison circuit according to embodiments of the present disclosure. Characterization of step-down signal and the duty cycle down the duty ratio threshold comparator circuit for detecting and characterizing the duty ratio comparison step-down mode to provide a first switch control signal to control the step-up step-down switching switch mode power converter and a buck boost - smooth automatic switching between step-down mode. The boosting duty ratio detection circuit and comparator, for characterizing the signal with a threshold value characterizing the boosting duty ratio of the duty ratio of the boost compared to provide a second mode switch control signal to control the boost drop press type switch mode power converter and a boost in the boost - smooth automatic switching between step-down mode.