Patent ID: 7518346

Claim:
A buck-boost DC-DC converter with an inductor and a power stage having a set of switches selectively connecting the inductor between a voltage input, a voltage output and a reference level in accordance with buck or boost mode, comprising: a switch control providing control signals to the set of switches: a comparator providing a first pulse width modulation signal to the switch control in buck mode and a second pulse width modulation signal to the switch control in boost mode; a ramp generator providing a first ramp signal to the comparator for buck mode and a second ramp signal to the comparator for boost mode; and an overlap control providing a ramp shift signal to the ramp generator in response to a detection signal that indicates activity of the set of switches in the power stage, wherein the ramp shift signal adjusts the first and second ramp signals relative to each other so as to minimize gap and overlap between the first and second ramp signals.