Improved COT control strategy for CRM Boost-PFC circuits applied to marine integrated power systems

This study addresses the problems of critical conduction mode (CRM) Boost-PFC circuit switch tubes(switch tubes are semiconductor devices like MOSFET that control electric current on/off states) with large opening voltages that lead to high opening loss and high dv/dt, which result in poor electromagnetic interference (EMI). This study also proposes an improved soft-switching constant on time (COT) control method that adaptively realizes ZVS at low instantaneous input voltage values and valley conduction at high instantaneous input voltage values. The EMI performance of the circuit was improved by reducing the switching voltage, switching loss, and the dv/dt of the switch tube. This study discusses the Boost-PFC circuit of the CRM mode, the principle and working process of the proposed control method, analyzes the impact of the proposed control method on the EMI characteristics of the circuit, and designs key parameters. Finally, the simulation and experimental results demonstrate the input and output characteristics, efficiency curves, and EMI curves of the prototype with a power of 20-40 W, an input of 176-277Vac, and an output constant voltage of 430Vdc, which verify the effectiveness of the proposed control method.