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Automatic Battery Switching and Monitoring Subsystem for Power Supplies

IP.com Disclosure Number: IPCOM000101913D
Original Publication Date: 1990-Sep-01
Included in the Prior Art Database: 2005-Mar-17
Document File: 5 page(s) / 211K

Publishing Venue

IBM

Related People

Ballou, RV: AUTHOR [+3]

Abstract

A power supply design is described whereby an automatic battery switching and monitoring subsystem provides a means of enabling battery operated systems to continue to supply voltage to circuitry from a primary battery when the system is turned off, as opposed to running the circuitry from a secondary battery.

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This is the abbreviated version, containing approximately 31% of the total text.

Automatic Battery Switching and Monitoring Subsystem for Power Supplies

       A power supply design is described whereby an automatic
battery switching and monitoring subsystem provides a means of
enabling battery operated systems to continue to supply voltage to
circuitry from a primary battery when the system is turned off, as
opposed to running the circuitry from a secondary battery.

      The primary intent of the concept is to increase the life of a
secondary battery, such as a lithium battery, since the secondary
battery will not be used while the primary battery is charged.  The
subsystem has low battery-monitoring capabilities to allow a system
to protect itself from a low primary battery condition.  The
subsystem allows monitoring of the primary battery and provides for
switching to a secondary battery when the primary battery is in a
discharged state.

      The design incorporates multiple power rails and "keep-alive"
voltage generation.  The "keep-alive" voltage is maintained at a
specified voltage whenever the primary battery is charged.  The
"keep-alive" voltage drops to a lower specified voltage whenever the
primary battery is in a discharged state or cannot be used.  Since
the "keep-alive" voltage is generated by the a primary battery, more
current can be sourced by the "keep-alive" voltage.  When the
"keep-alive" voltage is generated from a secondary battery, then only
the minimal required components are powered up. This enables certain
components to be powered OFF while the system is OFF and the primary
battery is being used as the "keep-alive" source.  Also, more
components can be powered OFF when the primary battery is discharged,
as when the secondary battery is being used as the "keep-alive"
source when the system is off.

      A power control logic (PCL) section is incorporated to allow
orderly management of power so as to avoid latch-up conditions and to
guarantee that components do not attempt to turn-on when the primary
battery can no longer provide the required current.  A momentary
switch allows system turn-on, while a digital control line allows for
system turn-off.

      The block diagram shown in the drawing illustrates how the
subsystem in interconnected.  The subsystem consists of the
following:
   Primary battery unit (PBU) 10 is the source of DC power for
everyday use.  It contains the primary battery which produces a fully
charged output.  It connects to voltage regulators 11, 12 and 13.
Two other lines coming from the PBU 10 are connected to the trigger
input of voltage regulator 12 and battery switch-over controller
(BSC) 14.  They are fixed voltage divider outputs from PBU 10.  As
the primary battery voltage decreases, the trigger voltages also
decrease.
        Secondary battery unit (SBU) 15 contains a "keep-alive"
battery for the subsystem.  It is used to maintain power to those
components that need to always be ON.  In a normal system, the
components...