This paper presents state-of-the-art application of Sliding Mode Control theory, to improve the performance and to integrate the modulator and control electronics design of power converters. This approach eliminates conventional PWM modulators and loop linear PI regulators, reducing the converter complexity, weight and volume, which increases its power density figure. Sliding Mode Control techniques are used to obtain, from the controllability canonical system model, the control law, a linear combination of state variable errors and its derivatives, whose implementation is a simple circuit, that directly generates the drive pulses for the semiconductors. The commutation strategy implements a power converter with better performances than conventional PWM controlled ones, faster response and robustness concerning circuit parameter variations and operating conditions. This non linear control approach provides zero steady-state error and, by the subtle use of limiters, short circuit ouput current limitation. Using a simple 3 level clock, it is also shown how to obtain a sliding mode controller with constant switching frequency and zero steady-state error.
Design of practical sliding-mode controllers with constant switching frequency for power converters