Patent ID: 8860384

Claim:
A control method for a buck-boost power converter which includes an inductor, a first switch coupled between a power input terminal of the power converter and a first terminal of the inductor, a diode having an anode coupled to a ground terminal and a cathode coupled to the first terminal of the inductor, a second switch coupled between a second terminal of the inductor and the ground terminal, and a third switch coupled between the second terminal of the inductor and a power output terminal of the power converter, the control method comprising: monitoring an input voltage at the power input terminal, an output voltage at the power output terminal, and a load current at the power output terminal, for determining a voltage ratio between the two terminals of the inductor; selecting one from a buck mode, a first buck-boost mode, a second buck-boost mode, and a boost mode according to the voltage ratio for the power converter; and in the first and second buck-boost modes, switching the first to third switches in a sequence including: turning off the first and second switches, and turning on the third switch; turning on the first switch, keeping the second switch off, and keeping the third switch on; and keeping the first switch on, turning on the second switch, and turning off the third switch.