A DC-DC converter has a Step-Up stage connected to a Step-Down stage. A common Step-Down controller is designed and configured such that a single reference voltage is compared to the output voltage of the Step-Down stage by a single comparator, producing a single error signal. The error signal is then compared to two different saw signals to generate first and second pulse-width modulated signals respectively. The first and second pulse-width modulated signals are inputted to a control unit that generates a first pair of control signals and a second pair of control signals, which control switching of the Step-Up stage and of the Step-Down stage.