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Battery Charger

IP.com Disclosure Number: IPCOM000095987D
Original Publication Date: 1964-Nov-01
Included in the Prior Art Database: 2005-Mar-07
Document File: 2 page(s) / 23K

Publishing Venue

IBM

Related People

Abramson, P: AUTHOR

Abstract

The above drawing is a circuit for charging battery 10. An AC input signal is rectified by diode 12 and applied through transistor 14, when transistor 14 is conducting, to charge battery 10. The potential at the base of transistor 14 is primarily determined by fully-charged reference battery 16. Battery 16 is of the same type as battery 10 being charged.

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Battery Charger

The above drawing is a circuit for charging battery 10. An AC input signal is rectified by diode 12 and applied through transistor 14, when transistor 14 is conducting, to charge battery 10. The potential at the base of transistor 14 is primarily determined by fully-charged reference battery 16. Battery 16 is of the same type as battery 10 being charged.

Since batteries 10 and 16 are of the same type, when battery 10 is fully charged the same potential is applied to the emitter and the base of transistor 14. This causes 14 to be cut off and prevents charging current from being applied to battery 10. Battery 10 can, therefore, not be overcharged. Also, as battery 10 approaches a fully-charged condition, the resistance applied by transistor 14 to the charging current increases, thus reducing the charging rate.

Diode 18 performs two functions in the circuit. First, it protects battery 16 by preventing it from discharging through transistor 14 when no AC input signal is applied to the circuit. Second, the potential drop across diode 18 is substantially equal to the base-emitter drop in transistor 14, thus assuring that battery 10 is fully charged when equal potentials appear at the base and emitter of transistor 14, cutting this transistor off. To adapt the circuit to charge a different type of battery, a reference battery of the new type is substituted.

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