Temperature-robust LC3 LED driver with low THD, high efficiency, and long life

A new type of passive LED driver that can reduce total harmonic distortion (THD) significantly by LC parallel resonance is proposed in this paper. Using an inductor and three capacitors, called LC³, novel characteristics such as high efficiency and power factor (PF) with extremely long life time are achieved. The proposed LED driver has a temperature-robust characteristic because its power is hardly changed by temperature, selecting the number of LED in series n_s appropriately so that the LED power variation due to temperature change in LED can be zero. For analyzing LED power of the proposed LED driver, the phasor transformation technique is applied, which is firstly applied to a non-linear diode rectifier modeling. Nevertheless this non-linear switching, the proposed analyses agreed well with simulation and experiment results. A prototype LED driver showed very high power efficiency of 96.7 % at 60 W, meeting high PF of 0.95 and low THD of 10.1 %, though a reasonably small filter was used.