A digitally controlled four-switch buck-boost converter (4SBB) that has a wide input voltage range, high power density and efficiency is designed with new smooth mode transition. The problems encountered during mode changes under varying input voltage have been investigated and thoroughly identified via simulations and the tests obtained from an experimental converter. The instabilities at the control signal, the appearing of input voltage at the output without any regulation during the intervals called the dead-zone, the fluctuations and harmonics at the output voltage, the pulse skipping of switches can be listed as the major problems encountered during mode transitions. These problems negatively affect the efficiency of the converter, regulation and controller stability. A new smooth transition method is proposed with many advantages over the well know methods. The negative effects of these problems are all minimized with the proposed method. The superiority of the developed technology and transition method is demonstrated by comparing the results with the state-of-the-art methods.
