Digitally controlled improved THD and power factor single-stage flyback LED driver with active input-current wave-shaping

This paper presents single-stage constant-current high-brightness light-emitting-diode (HB LED) driver with flyback topology based power-factor-corrector (PFC) section operating in transition-mode or boundary conduction-mode. Active input-current shaping technique is employed to improve total-harmonic-distortion (THD) and power-factor (PF). A digital output-current regulator and a digital phase-locked-loop (PLL) algorithm is developed using an 8-bit microcontroller to achieve the stated goal. Mathematical analysis and experimental results are presented to demonstrate the proposed scheme.