The PFE Series combines what previously required two bricks into a single brick. In the past, a separate AC front-end module that included the rectification and PFC functions would be required in addition to a second module that comprised a DC-DC converter that would provide the regulated lower voltage DC output. The diagram above shows the mechanical layout for a typical two-brick solution along with some of the necessary external components.  This once popular solution has been made obsolete by the introduction of the PFE series. The space and cost savings of the PFE series is significant.