Digital control for efficiency improvements in interleaved boost PFC rectifiers

This paper presents a simple passive power sharing approach to paralleling power-factor correction (PFC) modules. A digital controller senses only the total inductor current, and drives the modules with matched phase-shifted control signals. Advantages of the approach include simplified current sensing and control, support for arbitrarily large number of paralleled modules, and minimization of conduction losses at heavy loads. Increased current stresses resulting from unequal power sharing are evaluated in terms of parameter mismatches. To maintain high efficiency over very wide range of loads, the digital controller further includes adaptive near-zero-voltage switching and adaptive frequency operation in discontinuous conduction mode (DCM), as well as phase shedding at light loads. Experimental results are shown for a 600W two-phase boost PFC, rectifier.