It is shown that the model of the boost DC-DC converter is minimum phase for operation on the left-hand side of the extremum of the steady state characteristic and nonminimum phase - on the right-hand side. For operation on the left-hand side a simple proportional controller is proposed which gives significantly better quality of control than many other controllers appearing in literature. However, it is noted that efficiency of the converter during operation on the left-hand side is smaller, therefore another original proposal of the controller based on nonlinear transformation and state feedback, designed for operation on the right-hand side, is proposed.