Phase Compensation Driving Scheme for Synchronous Rectifiers

The necessity of developing highpower density, low output voltage converters with very high efficiency for distributed power supply systems, leads to the substitution of the rectifier diodes of the output stage by synchronous rectifiers (SR). The most suitable device as synchronous rectifier in high switching frequency converters is the power MOSFET. The use of SR in PWM converters has been widely studied. However, synchronous rectification techniques applied to resonant converters have been hardly investigated. Generally, SR driving methods for PWM converters can not be directly applied to resonant converters. For resonant converters, the SR can be driven by obtaining drain to source voltage of SR. The sensed Vds of SR is processed by control circuit to determine the level of the current. The SR can be switched in close proximity of the zero current transition. However, due to inevitable package inductance, the sensed terminal drain to source voltage of SR is
actually the sum of MOSFET resistive voltage drop and package inductive voltage drop. The SR drive signal is much shorter than expected value. In order to overcome the issue of SR driving methods, a novel phase compensation driving scheme is proposed. With the proposed driving scheme, the adverse effect of the package inductance can be eliminated. Body diode conduction of SR is almost eliminated. The reverse recovery problem of body diode is omitted. Voltage stress of SR is effectively reduced. The high efficiency operation of SR can be achieved.

Patent Information:
Title App Type Country Serial No. Patent No. File Date Issued Date Expire Date
Phase Compensation Driving Scheme for Synchronous Rectifiers US Utility *United States 11/749,405 7,602,154 5/16/2007 10/13/2009 1/26/2028
For Information, Contact:
Li Chen
Licensing Associate
Virginia Tech Intellectual Properties, Inc.
(540) 443-9217
Dianbo Fu
Fred Lee
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