A method comprises providing a buck-boost converter comprising a first high-side switch and a first low-side switch connected in series across an input capacitor, a second high-side switch and a second low-side switch connected in series across an output capacitor and an inductor coupled between a common node of the first high-side switch and the first low-side switch, and a common node of the second high-side switch and the second low-side switch, detecting a first voltage resonance waveform across a switch of the buck-boost converter and turning on the switch of the buck-boost converter when the first voltage resonance waveform falls to zero.