Minimisation of power losses in PFC flyback converters operating in the continuous conduction mode

The wide use of PFC converters as DC supplies for electrical and electronic applications over the last few years, in order to comply with EMC directives, has highlighted the issue of efficiency improvement in these converters. This paper presents a detailed study of the switching and power loss behaviour under any line and load conditions, for the case of PFC flyback converters operating in the continuous conduction mode (CCM). The whole analysis is based on the analytical calculation of the power factor (which drastically affects the conduction losses) and its variation in relation to the nop-solution that minimises the switching losses. As is proved theoretically, as well as by the use of simulation and experimental results, the operation of PFC flyback converters in the nop-area not only minimises the switching losses and limits the voltage stresses on the semiconductive elements, but also produces a high power-factor regulation. These facts, along with the simplicity of the flyback topology, establish the nop-solution for PFC flyback converters operating in the CCM as an optimal way to achieve high power-factor regulation, high efficiency and high power density