Browse Prior Art Database

Battery Back-up Unit with Light Emitting Diode Control and Status Indication

IP.com Disclosure Number: IPCOM000106441D
Original Publication Date: 1993-Nov-01
Included in the Prior Art Database: 2005-Mar-21
Document File: 2 page(s) / 63K

Publishing Venue

IBM

Related People

Riggio Jr, SR: AUTHOR

Abstract

Disclosed is a circuit in which a Light Emitting Diode (LED) is used to control the battery charging rate provided within a low cost battery back-up unit. This LED, together with a second LED, also provides a visual indication of whether the battery is being charged or discharged.

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Battery Back-up Unit with Light Emitting Diode Control and Status Indication

      Disclosed is a circuit in which a Light Emitting Diode (LED) is
used to control the battery charging rate provided within a low cost
battery back-up unit.  This LED, together with a second LED, also
provides a visual indication of whether the battery is being charged
or discharged.

      As shown in the Figure, a battery back-up unit 2 provides an
alternate source of power for an electrical load 4 in the event of
the failure of power supplied through an input terminal 6 at an input
voltage V, which may be, for example, the input bulk voltage within a
system using distributed power.  When power is supplied through
terminal 6, it is used to drive load 4 and to provide a trickle
current through a battery 8 for maintaining the proper charge
therein.  When power is not supplied through terminal 6, current from
battery 8 is used to drive load 4.

      When power is supplied through terminal 6, current flows
through a junction field effect transistor (FET) 10 and a green LED
12, which is thereby illuminated, indicating that battery 8 is being
charged.  Since the gate and source of FET 10 are connected, this
device provides a nearly constant current through LED 12.  The
relatively constant voltage drop across LED 12 is therefor suitable
for use as a reference voltage in determining the current flowing to
charge battery 8.  This determination is facilitated by connecting
the base o...