AC direct multiple-string LED driver with low THD and minimum components

A multiple-string LED driver with low total harmonic distortion (THD) by sinusoid-like reference and minimum components is presented in this paper. The proposed commutating method is able to control the source-coupled-pair by simplest circuitry and without passive components. The reference voltage is divided from rectifier in order to minimize the THD. The simulated 4-strings LED driver is able to achieve high power factor 99.95% and very low THD 3.16% under a 10W/100V AC condition. And the proposed circuit is implemented by differential pair and diodes to replace op-amp and bias voltage.