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 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 adaptive output feedback controller, involving online state variable estimation, is designed and shown to ensure quite satisfactory tracking performances. The controller development is performed using the adaptive backstepping control approach combined with the high-gain observer design technique.