This study presents an approach to system identification and adaptive control of a non-inverting buck-boost converter in the presence of large signal changes, uncertainty of converter components and effects of imperfect modelling. Feedback loops of DC-DC converters are typically designed conservatively so that the closed-loop regulation and stability margins are maintained over a pre-determined range of operating conditions. The proposed approach is able to keep a high-performance response without the instability issue of dynamic change of the converter. In the presence of uncertainty on the parameters of a DC-DC converter, a digital adaptive controller based on system identification and minimum degree pole placement is proposed. To verify the validity of the proposed digital controller, an experimental setup is constructed for a non-inverting buck-boost converter and the fully digital adaptive control is implemented by a micro controller. The experimental results show the capability of an adaptive controller during different operating points.