Two Stage Dimmable PFC LED Driver Digital Controller Design and Analysis for Isolated SEPIC Converter

This study proposes a two-stage power converter with power factor correction (PFC) capability for led dimming applications with a power rating of 200W. The initial stage of the proposed system adopts an isolated single ended primary inductance converter (SEPIC) which aims to ensure the reliability of the PFC operation, eliminate the current harmonics, and maintain the electrical isolation of the digital stage from AC mains. A low-bandwidth compensator for the PFC converter is designed based on the state-space averaged small-signal model of the SEPIC to attenuate the harmonic component at the twice frequency of the mains. A synchronous buck converter is utilized as the second stage to regulate the dynamics of the LED array current. The compensator of the LED driver is designed with a relatively wide bandwidth to achieve fast and robust dimming. The two-stage converter is simulated using PSIM. The simulation results verify that the converter can adjust the LED array's current while ensuring unity power factor operation for the mains input.