Design of a sliding mode controller based on local averaged technique and applied to the buck converter

A modeling methodology applied to PWM DC-DC converters is presented in this paper. Parasitic resistors have been considered in inductor and power supply. A generalised equivalent circuit based on averaged variables is obtained for the basic structures of DC-DC converters. This circuit and the associated model are valid for continuous conduction mode and discontinuous conduction mode. This contribution contains expressions to detect changes of the converter operation made and to estimate the value of the diode duty cycle operating under discontinuous conduction mode. A sliding mode controller for the regulation of the output voltage has been designed in terms of averaged state variables and converter parameters. The procedure is applied to a 100W Buck converter prototype. Simulations and experimental results are presented.