Static Regulated Multistage Semiactive LED Drivers for High-Efficiency Applications

Semiactive light-emitting diode (LED) drivers with high efficiency that regulate LED power statically against source voltage variation are proposed. By adopting multistage 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 LC
³
input filter is fully established. A prototype five-stage LED driver of 100-W class was implemented and verified by experiments, which shows LED power variation of 90-110 W with a very high efficiency of 95.1-97.3% for source voltage variation of 200-253 V, meeting power factor and total harmonic distortion regulations.