Multi-phase adaptive on-time PFC for better light load efficiency and EMI performance

With the fast growing information technologies, high efficiency and high power density become the two major challenges for AC-DC front-end power supplies in all kinds of distributed power system applications. For the power factor correction (PFC) stage, the adaptive on-time control was proposed to achieve high efficiency over the whole load range. The EMI performance of single phase adaptive on time controlled PFC is tested in this paper, and multi-phase approach is used to improve the EMI performance. Since the switching frequency of the adaptive on time control is a variable, the novel adaptive phase angle control is proposed to achieve the best noise cancellation effect, leading to significant EMI filter size reduction. The experiment results show that both high efficiency and high power density can be achieved by the multi-phase adaptive on-time PFC approach.