Electric power conversion systems – Current conversion – Including d.c.-a.c.-d.c. converter
Reissue Patent
1999-10-27
2002-10-22
Riley, Shawn (Department: 2838)
Electric power conversion systems
Current conversion
Including d.c.-a.c.-d.c. converter
C363S089000, C363S021140, C363S020000, C327S309000
Reissue Patent
active
RE037889
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to switching type poser converters and in particular to forward and flyback converters having a clamp-mode topology.
BACKGROUND OF THE INVENTION
Self synchronized rectifiers refer to rectifiers using MOSFET rectifying devices having control terminals which are driven by voltages of the windings of the power transformer in order to provide the rectification of the output of the transformer. Use of synchronous rectifiers has been limited however by the inefficiency of these rectifiers in buck derived converter topologies. Efficiency is limited due to the nature of switching of buck derived converters (i.e. buck, buck-boost, boost converters including forward and flyback topologies and due to the variability of the transformer reset voltages in the forward type converters. This variability of reset voltage limits the conduction time of one of the MOSFET rectifiers, diminishing the effectiveness and efficiency of the rectifier. This is because the rectifying devices do not conduct for the full switching period and the gate drive energy of one of the rectifiers is dissipated.
SUMMARY OF THE INVENTION
A synchronous rectifier is combined with a clamped-mode buck derived power converter. In one illustrative embodiment a hybrid rectifier includes a MOSFET rectifying device active in a first cyclic interval of the conduction
onconduction sequence of the power switch. A second rectifying device embodied in one illustrative embodiment as a low forward voltage drop bipolar diode rectifying device is active during an alternative interval to the first conduction
onconduction interval The gate drive to the MOSFET device is maintained continuous at a constant level for substantially the all of the second interval by the clamping action of the clamping circuitry of the converter. This continuous drive enhances the efficiency of the rectifier.
The bipolar rectifier device may also embodied as a MOSFET device in a rectifier using two MOSFET devices. The subject rectifier may be used in both forward and flyback poser converters.
REFERENCES:
patent: 5066900 (1991-11-01), Bassett
patent: 5126931 (1992-06-01), Jitaru
patent: 5303138 (1994-04-01), Rozman
patent: 5872705 (1999-02-01), Loftus, Jr. et al.
patent: 6081432 (2000-06-01), Rinne et al.
patent: 6191964 (2001-02-01), Boylan et al.
Principles of Solid State Power Converstion, Tarter, Ist Ed., pp. 544-547, (1985) (no month).*
Current-Controlled Synchronous Rectification, Acker et al., IEEE, pp. 185-191, (May 1994).*
High Efficiency DC-DC Converter, Jitaru et al., IEEE, pp. 638-644, (May 1994).
Hitt Gaines & Boisbrun
Lucent Technologies - Inc.
Riley Shawn
LandOfFree
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