AN2521 is ST's application note, introducing a 75W wide range input mains and power-factor-corrected ac-dc adapter evaluation board. Its electrical specification is tailored to a typical high-end portable computer power adapter. The distinctive attributes of this design are the very low standby input consumption (< 0.3 W at 265 V), the excellent global efficiency (> 85%) for a two stage architecture and the low cost.
This document details the characteristics and features of a 75 W wide range input mains and power-factor-corrected ac-dc adapter evaluation board. The design utilizes the L6563 for the PFC stage and the L6668 for the flyback converter, achieving a global efficiency greater than 85% and very low standby input consumption of less than 0.3 W at 265 V.
The circuit consists of two stages: a front-end PFC using the L6563 and a flyback converter based on the L6668. The flyback stage acts as the master, controlling circuit operation and switching the PFC stage on and off to optimize efficiency at light loads. The PFC stage reduces harmonic content in accordance with EN61000-3-2 and provides a regulated dc bus.
| Output voltage | 19 V |
|---|---|
| Output current | 4 A |
| Input mains range | 90 - 264 Vac |
| Standby consumption | < 0.3 W |
| Overall efficiency | > 85% |
| Mains harmonics | EN61000-3-2 class-D |
| EMI compliance | EN55022-class B |
| Safety compliance | EN60950 |
The design uses the L6563 for the PFC stage and the L6668 for the flyback converter.
The adapter is rated for 75 W.
Yes, the design implements a tracking boost option (TBO) to maximize overall efficiency.