Static Regulated Multi-stage Semi-active LED Drivers for High Efficiency Applications

Semi-active LED drivers with high efficiency that regulate LED power statically against source voltage variation, are proposed. By adopting multi-stage switching circuits in the proposed LED driver, the number of operating LED strings in series is appropriately selected according to the source voltage variation, which results in slow regulation of the LED power. A detailed procedure for selecting hysteresis control of the proposed LED driver with an LC3 input filter is fully established. A prototype 5-stage LED driver of 100 W class was implemented and verified by experiments, which shows LED power variation of 90 W ~ 110 W with a very high efficiency of 95.1 % ~ 97.3 % for source voltage variation of 200 V ~ 253 V, meeting power factor and total harmonic distortion regulations.