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In this paper, a novel adaptive second-order sliding mode (2-SM) control approach, based on online zero-crossing detection, was proposed to solve the problems of the chattering and fixed control gain for buck converters with multi-disturbances. In modeling, the possible parameter perturbations and external disturbances of the converter system were contained. Instead of the traditional first-order sliding mode (1-SM), the twisting algorithm with 2-SM was adopted for the controller design, which could overcome the chattering problem and realize control continuity. Meanwhile, a novel adaptive mechanism was introduced to replace the conventional fixed control gain by time-varying control gain, the idea of which is to calculate the number of the zero-crossing points of the sliding surface online. As a result, the control magnitude of the improved controller could be reduced to a minimal admissible level, and the steady error of the output voltage could converge to the expected value. Furthermore, the robust stability of the converter system with multi-disturbances wads investigated. Comparative simulations and experiments validated the advantages of this paper as offering better robustness and control performance. [ABSTRACT FROM AUTHOR]

In this paper, a new single-stage power factor correction (PFC) converter is presented. In the input stage of this structure, a buck converter is used to correct the power factor. So, the voltage stress of bulk capacitor reduced, and one of the main problems in the single stage PFC converters is solved. Moreover, by employing a compensator circuit, the input current dead angle which is the main drawback of the existing buck type PFCs is obviated, thus the total harmonic distortion is very low. In converters with buck PFC, input current dead angle results in high THD. In the proposed converter, using an inductor coupled with the main transformer, this problem is solved. A part of input power is transmitted directly to the output that helps to improve efficiency. The proposed converter is analyzed and the validity of the proposed solution is proven in the form of theoretical analysis, simulation and practical results. [ABSTRACT FROM AUTHOR]