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Browse Prior Art Database

Magnetic Amplifier Control Of Logic Voltages In Space Applications

IP.com Disclosure Number: IPCOM000105749D
Original Publication Date: 1993-Sep-01
Included in the Prior Art Database: 2005-Mar-20
Document File: 4 page(s) / 118K

Publishing Venue

IBM

Related People

Carpenter, BA: AUTHOR

Abstract

Disclosed is a method to provide power control of logic voltages in systems where power or fault tolerance requirements dictate partitioning of the power system, such as VLSI spaceborne systems. This method is intended to replace relays currently used in these applications and to provide significant advantages over relays.

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

Magnetic Amplifier Control Of Logic Voltages In Space Applications

      Disclosed is a method to provide power control of logic
voltages in systems where power or fault tolerance requirements
dictate partitioning of the power system, such as VLSI spaceborne
systems.  This method is intended to replace relays currently used in
these applications and to provide significant advantages over relays.

      Relays have several disadvantages which limit their usefulness
in space.  One is their susceptibility to shock and vibration during
launch which requires large shock mounts.  Another is large
transients and contact bounce which occur during switching and limit
their useful life.  Also, at the ratings required for these systems,
the relays are large, massive, and have a significant voltage drop
across the contacts when in the "on" state.  Further, they require
dedicated drive circuitry.  Relay advantages are inherent radiation
hardness and zero "off" state power losses.

      Magnetic amplifiers ("mag amps") are AC switches using
saturable cores.  The cores used in mag amps have a very high
inductance, therefore little current flow, until they saturate.  Upon
saturating, the core has very little impedance, and current flows
freely.  Referring to Fig. 1, the input voltage V(A) is reduced by
the shaded area V(B) by an amount which is controlled by Ibias.  By
making the bias high enough, and with a large enough core, the output
voltage can be reduced to very low levels (<.1V).  This is sufficient
to turn any electronics load off.

      Fig. 2 shows the detailed schematic of the magnetic amplifier
of the present design.  L1 is the saturable reactor.  Several
modifications to the classical mag amp design of Fig. 1 were
necessary to provide the functions required for this application.
The largest problem was getting the mag amp to turn sufficiently
"off."  This required addition of the Shutdown Circuit in Fig. 2,
where switch SW2 takes the place of the logic ON/OFF function.  In
addition, the Current Control Circuit was added to meet the dynamic
performance and current-limiting requirements of the application.

      Magnetic amplifiers, modified for the application, offer
significant improvements over relays, and have manageable
disadvantages.  On the positive side, the magnetic amplifier core is
inherently hard to both radiation and mechanical stresses (shock and
vibration).  Since mag amps are...