A class of easy-to-implement sliding-mode controllers with constant switching frequency for power converters

Generally, sliding-mode controllers have to be modified to achieve a constant switching frequency or at least to have an upper limit for it. A family of sliding-mode controllers easy to implement is proposed in this paper. If a controller has the form specified in this paper then it can be implemented using a pulse-width modulator assuring a constant switching frequency, without requiring the control to be modified. The control structure proposed is shown to be feasible by presenting a controller for the boost converter as an example. Simulations and experimental results show that the controller structure proposed has the usual high performance and robustness of sliding-mode controllers. In addition, it has the very convenient features of constant switching frequency and easy implementation.