A novel control strategy to improve the power factor of a Ćuk converter for HBLEDs application

The significant improvements that have been recently achieved in HBLEDs technology in terms of lifetime, luminous efficacy, and power rating, make these devices one the most promising candidates to replace conventional light sources in various residential and industrial applications, despite their high cost. The efficiency requirement should be completed by means of the voltage conversion stage by performing Power Factor Corrector. In this paper we consider the problem of Power Factor Corrector and output current regulation for a group of HBLEDs by using a Ćuk converter under a Sliding-Mode Control which must be ultimately implemented by a hysteretic comparator to limit the switching frequency to practical values. However, with a constant hysteresis width, the system exhibits harmful harmonic distortion in the input line current waveform. Therefore, a variable hysteresis window is used thereby avoiding this distortion near the zero crossing of the input current. Using the Ćuk converter under a Sliding-Mode Control with variable hysteresis window, the converter will be forced to behave as a Loss Free Resistor. Simulation and experimental results are presented in this paper to demonstrate the functionality of the proposed technique.