Analysis And Optimization Of High Efficiency ZVS Totem-pole PFC Interleaving Control

Switching power supply has the advantages of high efficiency,light weight,wide voltage regulation range,etc.,and has been widely used in the field of communication power supply.The traditional communication power supply is composed of a front-end PFC and a back-end DC/DC.The most important specifications of PFC are high power factor and high efficiency.In many cases,it is also necessary to ensure high reliability and low cost.Efficiency,reliability,and cost largely depend on device and topology.The research object of this paper is the interleaving CRM totem pole PFC based on Si devices.Totem Pole PFC has simple topology and low conduction loss.It is often used in high-efficiency AC/DC communication power supply.The interleaving technology can reduce the input current ripple,increase the power level,and improve the light load efficiency.The Si MOSFET has mature technology and low on-resistance,which is more conducive to achieving high efficiency,high reliability and low cost.The changing switching frequency brings challenges to the interleaving control in CRM mode.This article summarizes the open-loop and closed-loop interleaving control strategies,analyzes the limitations of the interleaving control strategy in digital control,adopts the closedloop interleaving control strategy to ensure the stable interleaving,and analyzes the digital control strategy of CRM Totem Pole PFC in detail.In CRM closed-loop interleaving control strategy,whether the master-slave phase can realize soft switching depends on whether the ZCD strategy is reliable.In this scheme,the synchronous rectifier freewheeling is adopted,and ZCD must be realized by sampling inductor current.The current sampling may be affected by disturbances,leading to ZCD leading or lagging,making the switch has the risk of hard turn-on.This article introduces the existing ZCD strategy in detail,analyzes the reliability of the soft switch control when the ZCD signal is affected by disturbances,and proposes an improved dual ZCD strategy to ensure soft switching.Finally,a 3k W highefficiency CRM totem pole PFC prototype based on Si devices with 98.9% peak efficiency is built,which verifies the reliability of the closed-loop interleaving control and the dual ZCD strategy.