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Browse Prior Art Database

Battery Charging Circuit

IP.com Disclosure Number: IPCOM000091742D
Original Publication Date: 1968-May-01
Included in the Prior Art Database: 2005-Mar-05
Document File: 2 page(s) / 25K

Publishing Venue

IBM

Related People

Dyar, JR: AUTHOR [+3]

Abstract

The circuit charges a rechargeable battery from commercial AC power. A constant battery charging current over a wide range of line voltages and frequencies is realized.

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Battery Charging Circuit

The circuit charges a rechargeable battery from commercial AC power. A constant battery charging current over a wide range of line voltages and frequencies is realized.

Capacitor C1 limits AC current flow through the full-wave rectifier bridge formed by diodes D1...D4. Thus, point A is at a positive DC potential. This potential is greater than the voltage on battery B. The charging current is controlled by transistor Q1. Zener diode D5 is biased by resistor R4 and controls the collector current through Q1. With a constant voltage on the base of Q1, the collector current, which is approximately equal to the emitter current, is constant and a constant charging current is supplied to battery B. The value of C1 is such that its impedance at the desired line frequencies provides a sufficient DC voltage at point A to operate the circuit under all line voltage conditions.

Resistor R1 is a current-limiting resistor for neon indicator lamp N1. Resistor R2 serves as a bleed-off resistor for capacitor C1 when the unit is unplugged. Diode D6 serves to block current from discharging battery B when the unit is unplugged. This circuit can be used in apparatus such as dictation equipment, except that the DC voltage at point A is derived from the secondary of the main power transformer rather than from line voltage.

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