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Rectifier With Ringing Suppression

IP.com Disclosure Number: IPCOM000120596D
Original Publication Date: 1991-May-01
Included in the Prior Art Database: 2005-Apr-02
Document File: 2 page(s) / 89K

Publishing Venue

IBM

Related People

Duspiva, WS: AUTHOR [+2]

Abstract

The output rectifiers in power supplies can generate unwanted damped electrical oscillations (ringing) when they switch from a conducting to a non-conducting (blocking) state. It is often necessary to suppress this ringing in order to reduce the peak voltage stress on the rectifiers during the blocking state, and to reduce the electromagnetic interference caused by the ringing.

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This is the abbreviated version, containing approximately 52% of the total text.

Rectifier With Ringing Suppression

      The output rectifiers in power supplies can generate
unwanted damped electrical oscillations (ringing) when they switch
from a conducting to a non-conducting (blocking) state.  It is often
necessary to suppress this ringing in order to reduce the peak
voltage stress on the rectifiers during the blocking state, and to
reduce the electromagnetic interference caused by the ringing.

      One well-known method of suppressing the ringing is to place a
series resistor-capacitor circuit in parallel with a rectifier.
Another method is to place a magnetic toroid or ferrite bead around a
rectifier lead.  Both of these methods require additional components.
In high current supplies, with bus bar conductors and large
connection and mounting hardware, it may be particularly awkward to
incorporate these additional components into the assembly.

      The method described here accomplishes ringing suppression by
using a magnetic metal as part of the contact assembly on the
rectifier chip.  The presence of this metal in the conduction path of
the rectifier current serves to suppress the unwanted high frequency
ringing, with no added components to be accommodated in the assembly.

      The figure shows a top view and a section of a rectifier chip
(not to scale), with dimensions (in mm) typical of a 200 amp Schottky
rectifier chip in "moly tab" or "moly stack" form.  The cathode
connection is to the bottom square of molybdenum, which may be gold
plated for mounting.  The silicon chip is attached to this bottom
moly tab.  Contact to the top anode metallization on the chip is made
through another metal tab, as shown in the figure.  In order to
obtain ringing suppression by the method described in this article,
this metal tab should be a magnetic metal, rather than another moly
tab...