Patent ID: 7804282

Claim:
A method to achieve a constant output voltage with a buck-boost converter is comprising: (1) providing a buck-boost converter, converting a DC input voltage to a DC output voltage, comprising a mode control block, a buck control block, an inductor, a precharge-boost control block, and an output capacitor; (2) checking, if the input voltage is significantly higher than the output voltage required, if positive go to step 3 else go to step 5; (3) performing buck control of said inductor to convert input voltage down to output voltage; (4) go to step 2; (5) pre-charging of the inductor during a part of a buck period which is dependent upon the level of input voltage during a first phase of buck period, wherein a monitoring of the input voltage is performed by an analog-to-digital converter and a length of a pre-charge pulse is generated in discrete steps; and (6) go to step (3).