Increasing power conversion efficiency is an essential topic in recent years. In this way, many topologies and methods have been proposed to reduce conduction losses and switching losses in power devices. CRM and ZVS technique are critical soft-switching techniques to improve efficiency and reduce power devices losses.

A digitally controlled PFC converter is shown in Figure 2-1. For heavy PFC load, inductor current i_L can be continuous-conduction mode (CCM). While, at light load current may become discontinuous (DCM). During DCM operation, the boost inductor L resonates freely with PFC MOSFET output capacitance C_ds. Digital PFC designers can use external components and internal algorithm to detect MOSFET Vds’s ZVS or CRM position cycle by cycle. C2000 type-4 PWM provides internal hardware to realize CRM/ZVS PFC with reduced MCU bandwidth utilization and without using these external components.