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Improvement in Zero-Volt Switching Range for Resonant Topologies Using Current Doublers

IP.com Disclosure Number: IPCOM000117671D
Original Publication Date: 1996-May-01
Included in the Prior Art Database: 2005-Mar-31
Document File: 2 page(s) / 43K

Publishing Venue

IBM

Related People

Roden, GG: AUTHOR [+2]

Abstract

Disclosed is a circuit modification to Current Doublers used to extend the zero-volt switching range of ZVS converters and dampens the "ringing" on the output diodes, D1 and D2. This modification uses a saturable core such as W material from Magnetics Inc. in series with the output diodes. They are denoted as LSAT1 and LSAT2. This circuit only works with ZVS converters such as the ZVS Fullbridge, phase-shifted Fullbridge, half-bridge running at 50% duty-cycle or any topology that uses resonant soft-switching technology.

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Improvement in Zero-Volt Switching Range for Resonant Topologies
Using Current Doublers

      Disclosed is a circuit modification to Current Doublers used to
extend the zero-volt switching range of ZVS converters and dampens
the "ringing" on the output diodes, D1 and D2.  This modification
uses a saturable core such as W material from Magnetics Inc. in
series with the  output diodes.  They are denoted as LSAT1 and LSAT2.
This circuit only  works with ZVS converters such as the ZVS
Fullbridge, phase-shifted Fullbridge, half-bridge running at 50%
duty-cycle or any topology that  uses resonant soft-switching
technology.

      The circuit works as follows.  When the secondary transformer
voltage goes positive, LSAT1 will be in a blocking state and LSAT2
will be in a saturated state for a period of time.  During this time,
the output current continues to flow through D2.  After a period of
time (after the blocking-time) LSAT1 saturates and LSAT2 resets.  At
this point, D2 turns off and D1 turns on.  When D2 turns off, the
capacitance of the diode will resonant with any secondary leakage
inductance and load inductance.  However, LSAT2 behaves as a high
inductance in parallel with a resistance which represents the core
loss.  This dampens any ringing that occurs.

      When the secondary voltage of the transformer drops to zero
volts.  LSAT1 remains saturated and LSAT2 in a reset state.  At this
time diode D1 is on and D2 is off.  The output inductors,...