CM noise reduction in bridgeless PFC converter
Bridgeless PFC is one of the most attractive PFC topologies, which achieves high efficiency by eliminating the line-voltage bridge rectifier. However, this topology emits much higher conducted common mode (CM) EMI noise than conventional boost PFC converters. Significantly larger CM chokes are needed in order to meet the EMC standards. CPES proposed two methods to reduce its CM noise while maintain its high efficiency benefit. One method is to make the topology totally symmetry so that the CM noise is cancelled inside the converter. Accurate model is built and parasitics of the converter are controlled to achieve CM noise reduction from 150 kHz to 30 MHz. The other method is to apply balance technique to the topology. The first method can achieve better CM noise reduction while the second method is simpler in implementation.