A dimmable LED driver with partial power regulation

A dimmable light-emitting-diode (LED) driver circuit with partial power regulation is proposed in this paper. A string of LEDs is driven by a dc source in series with a flyback converter. The LED current is regulated by the flyback converter by processing only a fractional power while the major power is directly supplied from the dc source. To dim the LEDs with a pulsed current with constant amplitude, the flyback converter is operated with double pulse-width modulation (DPWM). Experimental results on a laboratory circuit designed for a 48 W LED lamp have demonstrated the excellent efficiency of the driver with the proposed approach.