Active clamp forward converter with simple gate control strategy for high light-load efficiency

Abstract

Recently, as the demand for fast charging increases, a new charging standard called USB Power Delivery (USB PD) has been developed. Adapters that support the USB Power Delivery specification need to be able to provide variable charging profiles. Because of this, high efficiency is required not only in heavy-load but also in light-load. This paper proposes a new gate control method for improving the light-load efficiency of active clamp forward converters (ACFC) suitable for adapter applications. The conventional ACFC has high conduction losses due to excessive freewheeling current under light-load conditions, which makes it difficult to expect high efficiency. The proposed control method can obtain higher light-load efficiency with reduced conduction loss without additional complex circuits. The feasibility of a proposed control method is verified by the experimental results with the prototype under the universal AC input and 65W output.