Sliding mode-a new way to control series resonant converters

The application of the theory of variable structure control systems for the control of resonant DC-DC converters is illustrated. The full-bridge configuration of series-resonant converters (SRCs) is used. The converter is operated at resonant frequency to obtain both output-to-input voltage characteristics similar to those of the buck converter and high efficiency. To arrive at an exact mathematical model, the SRC is viewed as a piecewise linear system. However, under some approximations and a suitably selected set of state variables, the SRC is characterized by a linear continuous-time model which allows determination of the equivalent control via the sliding mode control (SMC) theory. To obtain a sliding regime, the appropriate sliding surface is selected by assigning poles. This control law constitutes a new approach to the control of resonant DC-DC converters