Two-stage configuration for 60W universal-line AC-DC adapter

Universal-line (90-264V_ac) AC-DC adapter poses a major challenge to maintain a high efficiency across the entire line. At the same time, the reduction of its weight and size is required. Usually, low-power AC-DC adapter is implemented with a single-stage AC-DC flyback converter. To further improve the efficiency, valley switching technique and secondary synchronous rectifier is applied to it. However, it still has low efficiency. Therefore, two-stage adapters are required to have higher efficiency under the entire line. Therefore, this paper presents the comparative evaluation for the 60W two-stage adapter with the same size as the conventional single-stage adapter. In two-stage adapter, PFC stage consists of boost converter or buck converter and DC-DC stage consists of LLC converter. Experimental results obtained on a 60W(16.5V/3.65A) notebook adapter are provided,