A Pulse Width Modulation-Based Sliding Mode Controller for Phase-Shifted Full-Bridge Converter With Diodes in Series on the Lagging Leg

Abstract

The typical strategy for the phase-shifted full-bridge (PSFB) converter is to design a linear compensator based on a small-signal model. However, this approach cannot provide a strongly robust output under changing operating conditions or with perturbations in the converter parameters. In this article, a fixed-frequency pulse width modulation (PWM) based full-order sliding mode controller is proposed to improve the performance of a PSFB converter with diodes in series on the lagging leg. Firstly, to facilitate the application of sliding control laws, we construct a simplified equivalent control model by analyzing the phase-shifted modulation and operating waveforms of the converter. Secondly, we derive strict existence conditions for the sliding phases to ensure that the state trajectories fulfill the requirements. Thirdly, the perturbations of both the external and internal variables are considered in the equivalent control function to improve the stability of the controller. Finally, simulation and experimental results verify that the proposed sliding mode controller provides better dynamic regulation performance and robustness than does a linear controller.

Keywords

• Phase-shifted full-bridge
• sliding mode control
• pulse-width modulation
• equivalent control law
• robustness