Digital control of boost PFC converters operating in both continuous and discontinuous conduction mode

Whereas power factor correction (PFC) converters for the lower power range (< 250W) use discontinuous conduction mode (DCM) operation, PFC converters for higher power are commonly designed for continuous conduction mode. Nevertheless, at light load, DCM will appear close to the crossover of the line voltage, causing the converter to switch between both conduction modes. As a result of this switching during a line period, the converter dynamics change abruptly, yielding input current distortion. The control scheme, presented in this paper, exploits the advantages of digital control by employing duty-ratio feedforward, in order to diminish this source of input current distortion.