Universal input voltage LED driver with dimming capability and reduced DC-link capacitance

This paper presents a digitally controlled Light Emitting Diode (LED) driver with high power factor, universal input voltage, dimming capability and reduced DC-link storage energy capacitance. A two-stage structure composed by the Power Factor Correction and Power Control stages is proposed. The buck-boost DC/DC converter, operating in Discontinuous Conduction Mode is employed for power factor correction, and is responsible for maintain the average bus voltage controlled in 400 V, as function of the input universal voltage (85 - 265 V
_RMS
). The DC/DC Half-Bridge LLC converter composes the power control stage, which is in charged to keep controlled the averaged LED current as function of the required dimming level. Furthermore, the low frequency bus voltage ripple is compensated in this stage through a properly closed loop design. Simulations results are presented with the topology operating under universal input voltage, output dimming, and reduced DC-link capacitance.