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Fixed Frequency Zero-Current Switching Forward Converter Using Saturable Cores

IP.com Disclosure Number: IPCOM000117717D
Original Publication Date: 1996-May-01
Included in the Prior Art Database: 2005-Mar-31
Document File: 2 page(s) / 42K

Publishing Venue

IBM

Related People

Cleveland, TL: AUTHOR [+2]

Abstract

Disclosed is a circuit which improves the Zero-Current Switching (ZCS) range of Forward converters. This method is also used to "snubber" the output diodes.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 83% of the total text.

Fixed Frequency Zero-Current Switching Forward Converter Using Saturable
Cores

      Disclosed is a circuit which improves the Zero-Current
Switching (ZCS) range of Forward converters.  This method is also
used to "snubber" the output diodes.

      Utilizing saturable cores it is possible to delay the turn on
current of the main switch device and achieve ZCS, thus eliminating
typically half of the main switch device loss.  The saturable cores
are placed in series with the output and free-wheeling diode as shown
in the Figure.  Before the main switch device turns on, saturable
core L2 is saturated and L1 is in a resetted state.  When the switch
turns on, a positive voltage will occur on the secondary of the
transformer.  Saturable core L1 will be in a blocking state for a
period of time and L2 will be saturated.  The output will be in a
free-wheeling mode and Isec will be zero current.  After a period of
time, saturable core L1 will saturate and Isec will increase to the
output inductor current level.  At this time saturable core L2 will
reset.

      ZCS occurs when the main switch device turns on and saturable
core L1 is in a blocking state.  At this time the switch has turned
on but Isw will only be the magnetizing current until core L1
saturates and Isw will then be both the reflected load current and
the magnetizing current.  The net effect of this circuit is that the
load current is delayed through the switch device by saturable core
L1.  This t...