A Novel Valley-Fill Single-Stage Boost-Forward Converter With Optimized Performance in Universal-Line Range for Dimmable LED Lighting

In this paper, a novel valley-fill single-stage boost-forward LED driver is presented, where the valley-fill circuit is modified by adding a range-selection switch. The switch is manually closed under low input line and opened under high line to achieve an optimal performance in universal-line range. And the voltage stress of the high-frequency switch under high line range is also reduced. On the other hand, pulse width modulation (PWM) dimming is employed to overcome the inherent voltage stress problem in light load and make the proposed converter a good choice for medium power in engineering practices. The operation principle, design process, and control strategy are presented. And finally the feasibility of the proposed converter is verified by a prototype with 30-V, 2.0-A output.