General concepts for high-efficiency high-frequency 48 V DC/DC converter

A general concept, current steering, is proposed to eliminate the body diode current in various synchronous rectifiers, such as the current-doubler synchronous rectifier and the center-tapped synchronous rectifier, which are widely used in low-output-voltage and large-output-current isolation DC/DC converters. Because of the lack of body diode current, its related losses (body diode conduction loss and reverse-recovery loss) are eliminated successfully. A family of synchronous rectifiers that make use of the transformer leakage inductor to realize this concept has been generalized. To reduce the secondary conduction loss, a small duty cycle concept is also proposed in this paper. The waveforms desired for implementing these concepts are derived. In addition, the soft-switching technique is needed to reduce switching loss. According to these concepts, two novel high-efficiency 48 V DC/DC converters, running at the MHz switching frequency range, are proposed in this paper.