Nonlinear adaptive output feedback control of series resonant dc-dc converters

The problem of regulating the output voltage of DC-to-DC series resonant converters (SRC) is addressed. The difficulty is threefold: (i) the converter model involves discontinuous and highly nonlinear terms and is, further, controlled through a modulating frequency signal; (ii) all state variables are not accessible to measurements; (iii) the load is uncertain and may even be varying. An output feedback controller, not necessitating the measurement of the converter state variables, is proposed and shown to ensure semi-global stabilization of the closed-loop system and perfect output reference asymptotic tracking. The controller is developed using the backstepping control approach and the high-gain observer design technique.