Switching Analysis of Synchronous Rectifier MOSFETs With Phase-Shifted Full-Bridge Converter and Current Doubler
by Mark Hu, Product Application Manager, Vishay Siliconix
This application note analyzes the switching behavior of synchronous rectifier MOSFETs in a phase-shifted full-bridge converter topology with a current doubler. The first figure shows the basic circuit of this application. An overview describes the timing diagram of a phase-shifted full-bridge converter for achieving zero voltage switching (ZVS). Two topologies are introduced for gate driving of synchronous rectifier (SR) MOSFETs. The timing diagrams introduces the SR MOSFET operations during every stage for both topologies. The body diode is highlighted and the operational phenomena that occur when the SR MOSFET turns off is described. The power dissipation of SR MOSFETs are presented as equations to assist in designs, while test results of waveforms help in understanding the application. A summary includes the advantages of SR MOSFETs, an efficiency comparison, and other design considerations.
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