A Novel Adaptive Synchronous Rectification System for Low Output Voltage Isolated Converters

Abstract

The design of efficient, isolated low output voltage converters is a major concern due to their widespread use. One of the preferred methods used to maximize their efficiency is synchronous rectification, i.e. the replacement of the secondary side diodes with MOSFETs to decrease conduction losses. However, depending on the topology being used, synchronous rectification might not provide the required efficiency improvement or even be easily implemented. This paper presents a novel synchronous rectification system that can be applied to converters with symmetrically-driven transformers and to converters from the Flyback family; in both cases, the proposed system adaptively generates a control signal that controls a synchronous rectifier MOSFET placed in paralell with each diode, turning it on during the conduction intervals of the diodes. The proposed system uses only information from the secondary side, thus avoiding breaking the isolation barrier; it can be built using a few low cost analog components, it is reliable and simple, and could be easily implemented in an integrated circuit. Up to a 3 % improvement is demonstrated in a 3.3-5 V, 120 W Push-Pull converter and up to a 2.5 % improvement is obtained in a 5 V, 50 W Flyback converter, both of them designed for telecom applications.

Bidirectional DC–DC soft‐switching converter for stand‐alone photovoltaic power generation systems

“…The specifications of a bidirectional buck-boost soft-switching converter designed according to (2), and the measurement specifications, are listed in Table 2. The measurement results for the boost and buck modes are explained below.…”

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“…6(a), it is confirmed that the overshoot of the output current of the unit with a larger inductance become larger than one using a smaller inductance. Then, the damping factor and the overshoot normalized to the output current can be expressed by (6) and (7).…”

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