Improved hybrid rectifier for 1-MHz LLC-based universal AC-DC adapter

Abstract

This paper proposes a 1-MHz single stage LLC converter with improved hybrid full bridge / voltage doubler rectifier for laptop power adapter. Using single stage LLC instead of the two stage configuration is expected to reduce both the size and loss of the existing commercial products. For universal AC input, the hybrid full bridge / voltage doubler rectifier is desired. At 220 V AC input condition, the rectifier operates in full bridge mode, while at 110 V AC input, it operates as voltage doubler rectifier. With this mode switcher, the LLC converter resonant tank design only takes consideration of 220 V AC input case, such that the required operational input voltage range is reduced, and the efficiency of the LLC converter could be optimized. In this paper, two configurations of the improved hybrid full bridge / voltage doubler rectifiers are proposed with reduced cost and improved efficiency. Besides, for the LLC stage, a large magnetizing inductor could be used to significantly reduce the circulating current. To verify the effectiveness of the proposed hybrid full bridge / voltage doubler rectifier and the design of LLC converter, analysis will be carefully explained towards the rectifier and the LLC parameter design in this digest. A 65W prototype is built to demonstrate the feasibility.