Designing and Analyzing a Single-stage Soft-switching Power Factor Correction Converter for Dual-string LED Driver with Auto Current Sharing and Low DC-Bus Voltage

In this paper, a single-stage soft-switching power-factor-correction (PFC) converter is proposed for driving two strings of LEDs. In the proposed driver, a transformer is added to an asymmetric series resonant half bridge converter to shape the input current. Also, zero-current-switching condition (ZCS) and zero-voltage-zero-current-switching (ZVZCS) condition are provided for switches at turn-on and turn-off, respectively, and near-unity power-factor is achieved for the converter. Moreover, the output currents are equal and independent of the output voltages which eliminates the need for current feedback or active current sharing method. Besides, the proposed driver provides minimum voltage for DC-bus capacitor and also switches voltage stress, while attaining low THD. Therefore, low voltage rating semiconductors with low on resistance and lower voltage capacitors with lower volume can be used. To validate the proposed driver features, operating principle of the proposed LED driver is presented, design considerations are discussed and experimental results of a laboratory prototype for supplying two 50 W/70 V strings of LED modules from 220 Vrms/50 Hz ac main is reported in this paper.