Feed-forward dynamic compensation control for single-stage PFC LED driver to eliminate flicker to human eyes during AC input voltage variation

The single-stage PFC converters have been well applied to LED drivers due to their simple structure and low cost. However, the slow dynamic response of these topologies causes large variation of output LED current when input voltage varies, which makes human eyes feel obvious flicker. In this paper, a feed-forward control for the single-stage PFC converters has been proposed to improve the dynamic response of the control loop so that the flicker can be eliminated. Essential concept derivation and design principles of the proposed feedforward control have been presented. Furthermore, two types of the altitude detector, which is the key part of the feed-forward control, have been compared. Simulation results show that the predictive-altitude detector has better dynamic response than real-altitude detector when they are applied to the feed-forward control. Experimental results based on a laboratory LED driver prototype have verified the theoretical analysis.