Discrete-time sliding mode control of SEPIC and Ćuk converters supplying HBLEDs

In this work, a digital control for a High-Brightness LEDs based lightning system connected to the grid is proposed. The digital control law is obtained by means of the application of the discrete-time sliding mode control theory in which the use of the discrete-time model of the converter is necessary. Two fourth order power converters have been analyzed for this application: SEPIC and Ćuk converter. In contrast to analogue sliding mode controllers, the calculated digital control law allows the operation at a constant switching frequency. This difference makes possible a comparative study between the power factor and total harmonic distortion parameters for different controllers: a conventional sliding mode control, an average current mode control in PWM and the proposed digital control.