A PFC rectifier for telecommunications high power applications

This paper presents a new power factor corrected rectifier for telecommunications applications, where main switches support only half of the DC bus voltage at both preregulator and DC-DC converter. The power factor correction is performed by a three-level boost pre-regulator that produces a half-shared DC bus. This DC bus supplies an isolated dc-dc converter, which is composed of two half-bridge converters connected in series. The DC-DC converter is phase-shift modulated and operates with ZVS in full-load range. The main features of the DC-DC isolated converter are: (i) each switch is designed to support only half of the maximum dc voltage; (ii) the current stresses are equally distributed among the switches, allowing conduction losses reduction; (iii) the use of two high frequency transformers connected in series makes this converter appropriate for high-power applications; (iv) the voltage ratings of input capacitors of the DC-DC converter is one-quarter of the bus voltage; (v) there is no low frequency dynamics on input capacitors voltage, associate to duty-cycle variations. Experimental results for 1.5W/60V/25A, design procedures and comparisons between the use of phase-shift-modulation and pulse-width-modulation are presented.