Demystifying zero-crossing distortion in single-phase PFC converters

Input current distortion in the vicinity of input voltage zero crossing in single-phase power factor corrected (PFC) AC-DC converters is analyzed in this paper. The key result includes a new model that relates the input current to the input voltage and the reference current. For typical single-phase PFC converter designs employing average current control, this model indicates that the input current response is underdamped and has a leading phase relative to the input voltage, which are largely responsible for the input current zero-crossing distortion. The phase-lead effect is especially prominent in systems with high tine frequencies, such as 400 Hz on commercial aircraft. Additional phase lead may be caused by the filter capacitors on the DC side of the rectifier bridge. Reduction of the zero-crossing distortion through modifications of both control and power stage design is proposed based on the analyses. Numerical simulation and experimental results are presented to validate the analyses.