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Switching Circuit for a Personal Computer System Using a Power Supply With a Battery Backup

IP.com Disclosure Number: IPCOM000100036D
Original Publication Date: 1990-Mar-01
Included in the Prior Art Database: 2005-Mar-15
Document File: 2 page(s) / 73K

Publishing Venue

IBM

Related People

Betor, TM: AUTHOR [+3]

Abstract

This article describes a circuit arrangement which pro- vides short duration power capability to a personal computer (PC) system to prevent the system from initial program load (IPL) in the case of short power outages. If an outage occurs, power is automatically switched to the backup battery until such time as the main power supply is functioning properly.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 54% of the total text.

Switching Circuit for a Personal Computer System Using a Power Supply With a Battery Backup

       This article describes a circuit arrangement which pro-
vides short duration power capability to a personal computer (PC)
system to prevent the system from initial program load (IPL) in the
case of short power outages.  If an outage occurs, power is
automatically switched to the backup battery until such time as the
main power supply is functioning properly.

      The circuit arrangement is shown in the drawing.  It is
different from a conventional battery backup in the sense that
programs that are executing when there is a power failure will
continue to do so with the assistance of the battery pack shown.  The
battery pack provides a nominal voltage of 8.4V (up to 9.6V when
fully charged).  It can be discharged to 7V and the 4.9V linear
voltage regulator will still operate properly, providing a stable +5V
output.  The on/off switch is a three-pole single-throw switch.  When
the system is powered on, the switch allows the 120V AC line to
activate the power supply and the battery to power the linear voltage
regulator.  The power supply will, at this time, provide the system
board with the required voltages (+12V, -12V, +5V).  The linear
voltage regulator, which is diode isolated, will be in an idle state
during AC operation because the 5V coming from the power supply
voltage will dominate.  During a power failure, the power supply will
turn off and the linear...