Multimode Smooth Switching Strategy for Eliminating the Operational Dead Zone in Noninverting Buck-Boost Converter

The existence of operational dead zone during mode switching in noninverting buck-boost converter results in oscillation of the output voltage and instability of the system during high power operation. The mechanism and effect of the operational dead zone are analyzed, the conditions that need to be met when eliminating the operational dead zone are researched, and a multimode smooth switching control strategy which can completely eliminate the operational dead zone is proposed. The converter works with three operating modes, the method of theoretical analysis combined with experimental correction is used to set the mode switching parameters, to ensure that the actual voltage gains of the converter on both sides of the mode switching points are equal. A single-degree-of-freedom buck-boost mode is designed to replace the pass-through mode to maintain the converters stable output. And the converters operating power level and overall power transmission efficiency can be improved, when the control parameters are designed to reduce the interval length of the boost mode and the single-degree-of-freedom buck-boost mode. Finally, a 700-W experimental prototype is built to verify the effectiveness of the proposed solution.