A Nonlinear State Machine for Dead Zone Avoidance and Mitigation in a Synchronous Noninverting Buck–Boost Converter

A new nonlinear state machine is proposed as the solution to an operational dead zone near the buck/boost interface of the noninverting buck-boost converter. This dead zone avoidance and mitigation (DZAM) state machine transforms the sequence of buck and boost duty cycles applied to the converter to a new sequence which completely avoids the dead zone while largely shielding the rest of the converter from its presence. The state machine contains one of several possible embedded nonlinearities, the choice of which determines the exact characteristics of the DZAM algorithm and is application specific. Previously published attempts to deal with the noninverting buck-boost dead zone either double switching loss or apply only to systems with slowly changing input/output conditions. By contrast, the high-speed DZAM technique proposed here does not increase switching loss and operates autonomously, independent of external conditions, thereby allowing its use in all applications.