The bridgeless boost PFC is similar to the interleaved boost PFC with the exception of the input rectifier bridge (diodes D1, D2, D3 and D4 in Figure 2-2). Removing these diodes eliminates two elements of loss during each switching cycle compared to the interleaved boost topology. The body diode of the FET that is not conducting is subject to losses as the body diode acts as a slow diode in the OFF state of the half cycle. In this topology is EMI because the output voltage ground stays floating in reference to the input AC signal. So, all of the parasitic capacitances contribute to the common-mode noise that can be difficult to filter. Increasing the switching frequency reduces the losses due to the parasitic capacitances.

Therefore, the required sizes of the passive components (the inductor and capacitor) can be reduced which minimizes system size, cost, and EMI. Figure 2-3 shows that the switches in this topology can be driven by a dual channel low-side driver such as the UCC27624.

Figure 2-3 Bridgeless Boost PFC Circuit With UCC27624 Low-Side Dual-Channel Gate Driver